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1
England, Dean. "Operational planning of discrete component manufacturing lines". Thesis, Loughborough University, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.416182.
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Smith, Justin Wesley. "Points and Lines in the Plane". University of Cincinnati / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1282052825.
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Cayan, Fatma Nihan. "The Method Of Lines Solution Of Discrete Ordinates Method For Nongray Media". Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/3/12607401/index.pdf.
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A radiation code based on method of lines (MOL) solution of discrete ordinates method (DOM) for the prediction of radiative heat transfer in nongray absorbing-emitting media was developed by incorporation of two different gas spectral radiative property models, namely wide band correlated-k (WBCK) and spectral line-based weighted sum of gray gases (SLW) models.
Predictive accuracy and computational efficiency of the developed code were assessed by applying it to the predictions of source term distributions and net wall radiative heat fluxes in several one- and two-dimensional test problems including isothermal/non-isothermal and homogeneous/non-homogeneous media of water vapor, carbon dioxide or mixture of both, and benchmarking its steady-state predictions against line-by-line (LBL) solutions and measurements available in the literature. In order to demonstrate the improvements brought about by these two spectral models over and above the ones obtained by gray gas approximation, predictions obtained by these spectral models were also compared with those of gray gas model. Comparisons reveal that MOL solution of DOM with SLW model produces the most accurate results for radiative heat fluxes and source terms at the expense of computation time when compared with MOL solution of DOM with WBCK and gray gas models.
In an attempt to gain an insight into the conditions under which the source term predictions obtained with gray gas model produce acceptable accuracy for engineering applications when compared with those of gas spectral radiative property models, a parametric study was also performed. Comparisons reveal reasonable agreement for problems containing low concentration of absorbing-emitting media at low temperatures.
Overall evaluation of the performance of the radiation code developed in this study points out that it provides accurate solutions with SLW model and can be used with confidence in conjunction with computational fluid dynamics (CFD) codes based on the same approach.
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Sotomayor, Polar Manuel Gustavo. "Analysis of Microstrip Lines on Substrates Composed of Several Dielectric Layers under the Application of the Discrete Mode Matching". Thesis, University of Gävle, University of Gävle, University of Gävle, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-3106.
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Microstrip structures became very attractive with the development of cost-effective dielectric materials. Among several techniques suitable to the analysis of such structures, the discrete mode matching method (DMM) is a full-wave approach that allows a fast solution to Helmholz equation. Combined with a full-wave equivalent circuit, the DMM allows fast and accurate analysis of microstrips lines on multilayered substrates.
The knowledge of properties like dispersion and electromagnetic fields is essential in the implementation of such transmission lines. For this objective a MATLAB computer code was developed based on the discrete mode matching method (DMM) to perform this analysis.
The principal parameter for the analysis is the utilization of different dielectric profiles with the aim of a reduction in the dispersion in comparison with one-layer cylindrical microstrip line, showing a reduction of almost 50%. The analysis also includes current density distribution and electromagnetic fields representation. Finally, the data is compared with Ansoft HFSS to validate the results.
The German Aerospace Center has rights over the thesis work
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Yesilgul, Mustafa, e Firas Nasser. "Discrete event modelling and Simulation of an Assembly Line at GKN Driveline Köping AB". Thesis, Mälardalens högskola, Akademin för innovation, design och teknik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-20266.
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Today’s economic conditions force companies and organizations to work more effectively in their processes due to different reasons. Especially; after the Second World War, owing to the changing business perception and strong competition between companies, new terms such as productivity, flexible systems, efficiency, and lean came into industrial engineering discipline. However, these kinds of terms also brought a new question. How are they reached? At that point, discrete event simulation has been used as an effective method to give an answer to this question. From this perspective; this project focuses on discrete event simulation and its role in real industrial processes. The main interest of this paper is discrete event simulation, but in this study we also tried to give some detailed information about other types of simulations such as continuous and discrete rate. Basically, we can say that this paper consists of several parts. In the beginning of this paper, the reader can find some theoretical information about simulation itself and the requirements for implementing it on real processes. Secondly, we tried to explain different types of simulations and the reason why we used discrete event simulation instead of continuous or discrete rate in our case study. Furthermore, one of the main areas of this research is to inform the reader about how computer support is used as a simulation tool by today’s companies. To do this, a powerful software, Extendsim8, is described in detail. The reader is able to find all the information about how to create discrete event models in this software. In case study part, we are able to find the results of the five months work that we did between February and June at GKNDriveline Köping AB in Sweden. In these five months, we had been busy with analyzing an assembly line, collecting data, creating a simulation model, discussion with workers and engineers and doing some tests such as validation & verification. In this part, the reader can find all the information about the production line and the simulation model. In conclusion, reader can find the results of the project at the end with the visualization of future state. As it will be discussed repeatedly in the paper, validation is one of the important steps in a simulation project. Therefore, in order to see the reliability of our simulation model, different calculations and tests were made. Last of all, some of results will be shown by graphs and tables in order to give better insight to reader.
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Cetinay, Hande. "Models Of Synchronous Production Lines With No Intermediate Buffers". Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612227/index.pdf.
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Production lines with unreliable machines have received a great amount of attention
in the literature. Especially, two-station systems have mostly been studied because
such systems are easier to handle when compared to the longer lines. In literature,
longer lines are usually evaluated by a decomposition algorithm, whereby the long
line is partitioned into chunks of two-station lines. Decomposition algorithms require
intermediate buffer storages of capacity at least two or three. The trends in modern
manufacturing practices, on the other hand, such as the Toyota Production System,
dictate that intermediate storages be eliminated. Our work studies multi-station lines
with no intermediate storage. We develop software to automate the generation of
transition probability matrices to allow the analysis of system behavior.
The algorithm allows the use of software packages to handle computations and to
solve for exact solutions. Long-run behavior is obtained via the algorithm developed
in the computational environment MATLAB. The purpose is to analyze the system
performance measures such as starvation and blockage times of stations, production
rate and work-in-process.
In addition, the production rate and the work-in-process measures over failure and
repair probabilities are curve-fit to establish simple and useful empirical formulas for
lines consisting three, four and five identical stations. Numerical analyses show that
the proposed algorithm is effective for exact solutions and the suggested formulas are
valid for approximate solutions.
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Uscka-Wehlou, Hanna. "Digital lines, Sturmian words, and continued fractions". Doctoral thesis, Uppsala : Matematiska institutionen, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-107274.
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López, De La Cova Trujillo Miguel Angel, e Niklas Bertilsson. "Investigation of the workforce effect of an assembly line using multi-objective optimization". Thesis, Högskolan i Skövde, Institutionen för ingenjörsvetenskap, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:his:diva-13134.
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ABSTRACT The aim of industrial production changed from mass production at the beginning of the 20th century. Today, production flexibility determines manufacturing companies' course of action. In this sense, Volvo Group Trucks Operations is interested in meeting customer demand in their assembly lines by adjusting manpower. Thus, this investigation attempts to analyze the effect of manning on the main final assembly line for thirteen-liter heavy-duty diesel engines at Volvo Group Trucks Operations in Skövde by means of discrete-event simulation. This project presents a simulation model that simulates the assembly line. With the purpose of building the model data were required. One the one hand, qualitative data were collected to improve the knowledge in the fields related to the project topic, as well as to solve the lack of information in certain points of the project. On the other hand, simulation model programming requires quantitative data. Once the model was completed, simulation results were obtained through simulation-based optimization. This optimization process tested 50,000 different workforce scenarios to find the most efficient solutions for three different sequences. Among all results, the most interesting one for Volvo is the one which render 80% of today’s throughput with the minimum number of workers. Consequently, as a case study, a bottleneck analysis and worker performance analysis was performed for this scenario. Finally, a flexible and fully functional model that delivers the desired results was developed. These results provide a comparison among different manning scenarios considering throughput as main measurement of the main final assembly line performance. After analyzing the results, system output behavior was revealed. This behavior allows predicting optimal system output for a given number of operators.
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Altrabulsy, Osama. "A Simulation-based Optimization Approach for Automated Vehicle Scheduling at Production Lines". Thesis, Högskolan i Skövde, Institutionen för ingenjörsvetenskap, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:his:diva-18454.
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The world becomes more integrated and sophisticated, especially in the birth of advanced technologies, which have influenced all life aspects. Automated systems could be considered an example of those aspects, which have been affected by recent changes in today’s life. The competition in the market is putting increasing pressure on different manufacturing organizations to find the best methods that enable them to stay up to date with the latest technologies in the industrial field. One of the most famous dilemmas that exist in this field is designing an efficient and flexible material handling system. This issue draws the attention of both decision-makers in different companies and software developers who put considerable effort into making that desired system real. Inclusive research needs to be performed to obtain such a system, and the most significant part of the research that requires special attention is the applied methodology.The approach to be adapted determines the degree of stability of a particular material handling system to function effectively in the case studied. Several methods are available and could be implemented to design that effective system such as meta-heuristic algorithms, and approaches that depend on simulation software tools. The latter approach, which is the simulation approach, seems to get increasing attention from developers of the industrial system since it plays a vital role in reducing the cost and preserving available resources. Besides, it helps predict future changes and scenarios of the system to be analyzed.In this project, a discrete-event simulation model was built for the proposed layout of the main shop floor owned by a Swedish manufacturing company. The corporation located in the south of Sweden, and it produces a vast range of manufacture of goods. The chosen methodology is a combination of lean, simulation, and optimization approaches. It has been implemented on the proposed layout in which material is handled into production lines by using automated guided vehicles (AGVs) as a means of transportation. The analysis of results shows potential benefits, where the production process became more efficient and organized since the operational cost has been reduced by decreasing the number of required vehicles. Moreover, the simulation approach facilitated testing new ideas and designing improved scenarios without the necessity to change the current state of the factory layout or disturbing the regular activities.
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Khoshnoudirad, Daniel. "Aspects combinatoires des motifs linéaires en géométrie discrète". Thesis, Paris Est, 2016. http://www.theses.fr/2016PESC1046.
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La Géométrie Discrète, comme Science de l'Informatique Théorique, étudie notamment les motifs linéaires tels que les primitives discrètes apparaissant dans les images : les droites discrètes, les segments discrets, les plans discrets, les morceaux de plans discrets par exemple. Dans ce travail, je me concentre tout particulièrement sur les diagrammes de Farey qui apparaissent lors de l'étude des primitives discrètes que sont les (m,n)-cubes, autrement dit les morceaux de plans discrets. J’étudie notamment la Combinatoire des droites formant les diagrammes de Farey, en établissant des formules exactes. Je montre alors que certaines méthodes utilisées auparavant ne permettront pas d'optimiser la Combinatoire des (m,n)-cubes. J'obtiens aussi une estimation asymptotique en utilisant la Théorie des Nombres Combinatoire. Puis, concernant les sommets apparaissant dans les diagrammes de Farey, j'obtiens une borne inférieure. J'analyse alors les stratégies déjà mises en place pour l'étude des $(m,n)$-cubes par les seuls diagrammes de Farey en deux dimensions. Afin d'obtenir de nouvelles bornes plus précises pour les $(m,n)$-cubes, une des seules méthodes actuellement existantes, est de proposer une généralisation de la notion de pré image d'un segment discret, à celle de pré image d'un $(m,n)$-cube, avec pour conséquence une nouvelle inégalité combinatoire sur le cardinal des (m,n)-cubes (inégalité qui pourrait même s'avérer être une égalité). Ainsi, nous introduisons la notion de diagramme de Farey en trois dimensionsDiscrete Geometry, as Theoretical Computer Science, studies in particular linear patterns such as discrete primitives in images: the discrete lines, discrete segments, the discrete planes, pieces of discrete planes, for example. In this work, I particularly focused on Farey diagrams that appear in the study of the $ (m, n) $ - cubes, ie the pieces of discrete planes. Among others, I study the Combinatorics of the Farey lines forming diagram Farey, establishing exact formulas. I also get an asymptotic estimate using Combinatorial Number Theory. Then, I get a lower bound for the cardinality of the Farey vertices. After that, we analyze the strategies used in the literature for the study of (m, n)- cubes only by Farey diagrams in two dimensions. In order to get new and more accurate bounds for (m, n)- cubes, one of the few available methods, is to propose a generalization for the concept of preimage of a discrete segment for (m, n) - cube, resulting in a new combinatorial inequality. Thus, we introduce the notion Farey diagram in three dimensions
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Aboutaleb, Adam. "Empirical study of the effect of stochastic variability on the performance of human-dependent flexible flow lines". Thesis, De Montfort University, 2015. http://hdl.handle.net/2086/12103.
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Manufacturing systems have developed both physically and technologically, allowing production of innovative new products in a shorter lead time, to meet the 21st century market demand. Flexible flow lines for instance use flexible entities to generate multiple product variants using the same routing. However, the variability within the flow line is asynchronous and stochastic, causing disruptions to the throughput rate. Current autonomous variability control approaches decentralise the autonomous decision allowing quick response in a dynamic environment. However, they have limitations, e.g., uncertainty that the decision is globally optimal and applicability to limited decisions. This research presents a novel formula-based autonomous control method centered on an empirical study of the effect of stochastic variability on the performance of flexible human-dependent serial flow lines. At the process level, normal distribution was used and generic nonlinear terms were then derived to represent the asynchronous variability at the flow line level. These terms were shortlisted based on their impact on the throughput rate and used to develop the formula using data mining techniques. The developed standalone formulas for the throughput rate of synchronous and asynchronous human-dependent flow lines gave steady and accurate results, higher than closest rivals, across a wide range of test data sets. Validation with continuous data from a real-world case study gave a mean absolute percentage error of 5%. The formula-based autonomous control method quantifies the impact of changes in decision variables, e.g., routing, arrival rate, etc., on the global delivery performance target, i.e., throughput, and recommends the optimal decisions independent of the performance measures of the current state. This approach gives robust decisions using pre-identified relationships and targets a wider range of decision variables. The performance of the developed autonomous control method was successfully validated for process, routing and product decisions using a standard 3x3 flexible flow line model and the real-world case study. The method was able to consistently reach the optimal decisions that improve local and global performance targets, i.e., throughput, queues and utilisation efficiency, for static and dynamic situations. For the case of parallel processing which the formula cannot handle, a hybrid autonomous control method, integrating the formula-based and an existing autonomous control method, i.e., QLE, was developed and validated.
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Amini, Malaki Afshin. "A Study of the Effects of Operational Time Variability in Assembly Lines with Linear Walking Workers". Thesis, Tekniska Högskolan, Högskolan i Jönköping, JTH, Industriell organisation och produktion, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-17877.
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In the present fierce global competition, poor responsiveness, low flexibility to meet the uncertainty of demand, and the low efficiency of traditional assembly lines are adequate motives to persuade manufacturers to adopt highly flexible production tools such as cross-trained workers who move along the assembly line while carrying out their planned jobs at different stations [1]. Cross-trained workers can be applied in various models in assembly lines. A novel model which taken into consideration in many industries nowadays is called the linear walking worker assembly line and employs workers who travel along the line and fully assemble the product from beginning to end [2]. However, these flexible assembly lines consistently endure imbalance in their stations which causes a significant loss in the efficiency of the lines. The operational time variability is one of the main sources of this imbalance [3] and is the focus of this study which investigated the possibility of decreasing the mentioned loss by arranging workers with different variability in a special order in walking worker assembly lines. The problem motivation comes from the literature of unbalanced lines which is focused on bowl phenomenon. Hillier and Boling [4] indicated that unbalancing a line in a bowl shape could reach the optimal production rate and called it bowl phenomenon. This study chose a conceptual design proposed by a local automotive company as a case study and a discrete event simulation study as the research method to inspect the questions and hypotheses of this research. The results showed an improvement of about 2.4% in the throughput due to arranging workers in a specific order, which is significant compared to the fixed line one which had 1 to 2 percent improvement. In addition, analysis of the results concluded that having the most improvement requires grouping all low skill workers together. However, the pattern of imbalance is significantly effective in this improvement concerning validity and magnitude.
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Schanzenbächer, Florian. "Max-plus modeling of traffic on passenger railway lines with a junction : fundamental diagram and dynamic control". Thesis, Paris Est, 2020. http://www.theses.fr/2020PESC2098.
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La thèse a pour objectif principal de contribuer à la méthodologie de régulation du trafic sur une ligne ferroviaire, dans la configuration typique d’une ligne à tronc et branches en milieu urbain ou régional. L'ambition est d’apporter une modélisation plus fine du trafic des voyageurs et des trains en interaction, qui permette à la fois d’évaluer finement la qualité du service rendu aux voyageurs et différentes décisions de l’opérateur de la ligne. Se basant sur cette modélisation, nous développerons une méthode de contrôle du trafic (stratégique/ tactique et opérationnel) spécialement adaptée au problème de ligne avec embranchement. L'objectif industriel est l'implémentation d'un système de régulation dynamique intelligent pour une ligne à fourcheThe aim of the doctoral thesis is to contribute on the developpement of real-time traffic control algorithms for mass transit railway systems with junctions, located in urban areas. The scientific ambition of the doctoral thesis is to develop a traffic model with a finer modelisation of the train-passengers interaction. The model will allow a more precise evaluation of the level of service offered to the passengers and of the decisions taken by the operator of the line. Basing on this modeling, we will develop a control algorithm (strategic/ tactical and operational) in order to enhance the service quality on the line. The objective of the Paris metro system operator, financing this thesis, is to have a ready-to-implement control system for a railway line with a junction
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Laboureix, Bastien. "Hyperplans arithmétiques : connexité, reconnaissance et transformations". Electronic Thesis or Diss., Université de Lorraine, 2024. http://www.theses.fr/2024LORR0040.
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Le monde numérique est parsemé de structures mathématiques discrètes, destinées à être facilement manipulables par un ordinateur tout en donnant à notre cerveau l'impression d'être de belles formes réelles continues. Les images numériques peuvent ainsi être vues comme des sous-ensembles de Z^2. En géométrie discrète, nous nous intéressons aux structures de Z^d et cherchons à établir des propriétés géométriques ou topologiques sur ces objets. Si les questions que nous nous posons sont relativement simples en géométrie euclidienne, elles deviennent beaucoup plus difficiles en géométrie discrète : plus de division, adieu les limites, tout n'est plus qu'arithmétique. Cette thèse est également l'occasion de jongler avec de nombreuses notions élémentaires de mathématiques et d'informatique (algèbre linéaire, anneaux, automates, analyse réelle, arithmétique, combinatoire) pour résoudre des questions de géométrie discrète. Nous nous intéressons à des structures fondamentales de cette géométrie : les hyperplans arithmétiques. Ceux-ci ont en effet une définition très simple et purement arithmétique : un hyperplan arithmétique est l'ensemble des points entiers situés entre deux hyperplans (réels) affines parallèles. Nous parlons dans cette thèse de trois problèmes portant sur les hyperplans arithmétiques : - la connexité : un hyperplan arithmétique est-il composé d'un seul morceau ou de plusieurs ? Apport principal de ce manuscrit, nous étendons des résultats déjà connus pour la connexité par faces pour des voisinages quelconques. Si certains phénomènes demeurent dans le cas général, l'explosion combinatoire rend difficile l'adaptation des algorithmes connus pour résoudre le problème. Nous adoptons donc une approche analytique et prouvons des propriétés de connexité en étudiant la régularité d'une fonction. - la reconnaissance : comment connaître les caractéristiques d'un hyperplan arithmétique ? Problème plus classique de géométrie discrète, avec une littérature très riche, nous proposons pour le résoudre un algorithme de reconnaissance reposant sur l'arbre de Stern-Brocot généralisé. Nous introduisons notamment la notion de corde séparante qui caractérise géométriquement les zones auxquelles appartiennent les paramètres d'un hyperplan arithmétique. - les transformations douces : comment transformer continûment un hyperplan arithmétique via des translations ou rotations ? Approche discrète des transformations homotopiques, nous caractérisons les mouvements de pixels possibles dans une structure discrète tout en préservant ses propriétés géométriques. Au-delà de l'étude de ces problèmes et des résultats que nous avons pu obtenir, cette thèse montre l'intérêt d'utiliser des réels, et notamment de l'analyse réelle, pour mieux comprendre les hyperplans arithmétiques. Ces derniers sont en effet caractérisés en grande partie par leur vecteur normal, souvent considéré entier pour obtenir des propriétés de périodicité. Considérer des vecteurs normaux réels quelconques permet de gagner en souplesse, et de faire disparaître les phénomènes de bruit induits par les relations arithmétiques du vecteur. S'ouvrir de nouveau au réel est enfin un moyen de créer des ponts vers d'autres branches des mathématiques, comme la combinatoire des mots ou les systèmes de numérationThe digital world is littered with discrete mathematical structures, designed to be easily manipulated by a computer while giving our brains the impression of beautiful continuous real shapes. Digital images can thus be seen as subsets of Z^2. In discrete geometry, we are interested in the structures of Z^d and seek to establish geometric or topological properties on these objects. While the questions we ask are relatively simple in Euclidean geometry, they become much more difficult in discrete geometry: no more division, goodbye to limits, everything is just arithmetic. This thesis is also an opportunity to juggle many elementary notions of mathematics and computer science (linear algebra, rings, automata, real analysis, arithmetic, combinatorics) to solve discrete geometry questions. We are interested in the fundamental structures of this geometry: arithmetic hyperplanes. These have a very simple and purely arithmetical definition: an arithmetical hyperplane is the set of integer points lying between two parallel (real) affine hyperplanes. In this thesis, we discuss three problems involving arithmetic hyperplanes:- connectedness: is an arithmetic hyperplane composed of a single piece or of several pieces? The main contribution of this manuscript is to extend results already known for facewise connectedness for any neighbourhood. While certain phenomena remain in the general case, the combinatorial explosion makes it difficult to adapt known algorithms to solve the problem. We therefore adopt an analytical approach and prove connectivity properties by studying the regularity of a function. - recognition: how can we find out the characteristics of an arithmetic hyperplane? This is a more traditional problem in discrete geometry, with a very rich literature. To solve it, we propose a recognition algorithm based on the generalised Stern-Brocot tree. In particular, we introduce the notion of separating chord, which geometrically characterises the zones to which the parameters of an arithmetic hyperplane belong. - soft transformations: how can an arithmetic hyperplane be continuously transformed using translations or rotations? A discrete approach to homotopic transformations, we characterise the possible pixel movements in a discrete structure while preserving its geometric properties. Beyond the study of these problems and the results we were able to obtain, this thesis shows the interest of using the reals, and in particular real analysis, to better understand arithmetic hyperplanes. Arithmetic hyperplanes are largely characterised by their normal vector, which is often considered integer to obtain periodicity properties. Considering any real normal vectors provides greater flexibility and eliminates the noise induced by the arithmetic relationships of the vector. Finally, opening up to the real again is a way of building bridges to other branches of mathematics, such as word combinatorics or numbering systems
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Aydin, Guzide. "Radiative-convective Model For One-dimensional Longwave Clear Sky Atmosphere". Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/2/12609826/index.pdf.
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Climate models are the primary tools used for understanding past climate variations and for future projections. The atmospheric radiation is the key component of these models. Accurate modeling of atmosphere necessitates reliable evaluation of the medium radiative properties and accurate solution of the radiative transfer equation in conjunction with the time-dependent multi-dimensional governing equations of atmospheric models. Due to difficulty in solving the equations of atmospheric and radiation models simultaneously, radiation equations have been solved when input data such as concentration, temperature etc. were made available upon solution of equations of atmospheric models. Generally, time step of conservation equations are 10-30 minutes but radiative transfer equation is called only once every 1-3 hours. However, there is inaccuracy due to the fixed radiation fluxes over the intervening time steps. To overcome this problem, the equations of atmospheric and radiation models have to be solved simultaneously and the solution methods have to be compatible. For this purpose, a radiative-convective model with radiation model based on method of lines (MOL) solution of discrete ordinate method (DOM) with wide band correlated-k (WBCK) was developed. To achieve this objective, a previously developed MOL solution of DOM with WBCK model was adapted to 1-D longwave clear sky atmosphere and its predictive accuracy and computational efficiency was examined on the test problem by using benchmark solution obtained from Line-by-line Radiative Transfer Model (LBLRTM). The radiation code was then coupled with radiative-convective model and the predictive accuracy of this model was examined for several coupling intervals. Comparisons reveal that as coupling interval increases, although the computation time of the model decreases, the predicted temperature profiles diverge from the one obtained when equations of radiative-convective model and the radiation model are solved simultaneously and percentage relative error in temperature increases an order of magnitude when coupling time between radiative-convective model and the radiation model increases from 2 to 10 hours. Therefore, it can be concluded that the equations of the radiation model have to be solved simultaneously with the equations of the climate model.
Overall evaluation of the performance of the radiation model used in this study points out that it provides accurate and computationally efficient solutions and can be used with confidence in conjunction with the climate models for simultaneous solution of governing equations with radiation transfer equation.
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Maldonado, Lopez Juan Pablo. "Some links between discrete and continuous aspects in dynamic games". Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066271/document.
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Cette thèse étudie les liens entre a) les jeux en temps discret et continu, et b) les jeux à très grand nombre de joueurs identiques et les jeux avec un continuum de joueurs. Une motivation pour ces sujets ainsi que les contributions principales de cette thèse sont présentées dans le Chapitre 1. Le reste de la thèse est organisé en trois parties. La Partie I étudie les jeux différentiels à somme nulle et à deux joueurs. Nous décrivons dans le Chapitre 3 trois approches qui ont été proposées dans la littérature pour établir l’existence de la valeur dans les jeux différentiels à deux joueurs et à somme nulle, en soulignant les liens qui existent entre elles. Nous fournissons dans le Chapitre 4 une démonstration de l’existence de la valeur à l’aide d’une description explicite des stratégies ε optimales. Le Chapitre 5 établit l’équivalence entre les solutions de minimax et les solutions de viscosité pour les équations de Hamilton-Jacobi-Isaacs. La Partie II porte sur les jeux à champ moyen en temps discret. L’espace d’action est supposé compact dans le Chapitre 6, et fini dans le Chapitre 7. Dans les deux cas, nous obtenons l’existence d’un ε- équilibre de Nash pour un jeu stochastique avec un nombre fini de joueurs identiques, où le terme d’approximation tend vers zéro lorsque le nombre de joueurs augmente. Nous obtenons dans le Chapitre 7 des bornes d’erreur explicites, ainsi que l’existence d’un ε-équilibre de Nash pour un jeu stochastique à durée d’étape évanescente et à un nombre fini de joueurs identiques. Dans ce cas, le terme d’approximation est fonction à la fois du nombre de joueurs et de la durée d’étape. Enfin, la Partie III porte sur les jeux stochastiques à durée d’étape évanescente, qui sont décrits dans le Chapitre 8. Il s’agit de jeux où un paramètre évolue selon une chaîne de Markov en temps continu, tandis que les joueurs choisissent leurs actions à des dates discrètes. La dynamique en temps continu dépend des actions des joueurs. Nous considérons trois évaluations différentes pour le paiement et deux structures d’information : dans un cas, les joueurs observent les actions passées et le paramètre, et dans l’autre, seules les actions passées sont observéesIn this thesis we describe some links between a) discrete and continuous time games and b) games with finitely many players and games with a continuum of players. A motivation to the subject and the main contributions are outlined in Chapter 2. The rest of the thesis is organized in three parts: Part I is devoted to differential games, describing the different approaches for establishing the existence of the value of two player, zero sum differential games in Chapter 3 and pointing out connections between them. In Chapter 4 we provide a proof of the existence of the value using an explicit description of ε-optimal strategies and a proof of the equivalence of minimax solutions and viscosity solutions for Hamilton-Jacobi-Isaacs equations in Chapter 5. Part II concerns discrete time mean field games. We study two models with different assumptions, in particular, in Chapter 6 we consider a compact action space while in Chapter 7 the action space is finite. In both cases we derive the existence of an ε-Nash equilibrium for a stochastic game with finitely many identical players, where the approximation error vanishes as the number of players increases. We obtain explicit error bounds in Chapter 7 where we also obtain the existence of an ε-Nash equilibrium for a stochastic game with short stage duration and finitely many identical players, with the approximation error depending both on the number of players and the duration of the stage. Part III is concerned with two player, zero sum stochastic games with short stage duration, described in Chapter 8. These are games where a parameter evolves following a continuous time Markov chain, while the players choose their actions at the nodes of a given partition of the positive real axis. The continuous time dynamics of the parameter depends on the actions of the players. We consider three different evaluations for the payoff and two different information structures: when players observe the past actions and the parameter and when players observe past actions but not the parameter
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Silva, Murilo da. "Implementação de um localizador de faltas híbrido para linhas de transmissão com três terminais baseado na transformada wavelet". Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/18/18154/tde-11042008-110740/.
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Este trabalho apresenta o estudo e o desenvolvimento de um algoritmo híbrido para detecção, classificação e localização de faltas em sistemas com três terminais utilizando como principal ferramenta a transformada wavelet (TW) em suas versões discreta (TWD) e estacionária (TWE). O algoritmo é dito híbrido, pois alia duas metodologias para localizar a falta. A primeira baseada na análise de componentes de alta freqüência (ondas viajantes) e a segunda, baseada na extração dos componentes fundamentais para o cálculo da impedância aparente. A metodologia proposta foi concebida de maneira a trabalhar com dados sincronizados dos três terminais ou apenas dados locais para estimar a localização da falta. O localizador híbrido escolhe automaticamente qual a melhor técnica de localização ser utilizada para alcançar uma localização confiável e precisa. Deste modo, um método pode suprir as dificuldades do outro, ou, no mínimo, fornecer mais informações para que, junto ao conhecimento do operador, uma localização próxima da ótima possa ser alcançada. Com o objetivo de testar e validar a aplicabilidade do algoritmo de localização de faltas híbrido para linhas com três terminais, utilizou-se de dados de sinais faltosos obtidos através de simulações do software ATP (Altenative Transients Program), levando-se em conta a variação de diversos parâmetros que poderiam influenciar o desempenho do algoritmo proposto. Os resultados alcançados pelo algoritmo frente às situações avaliadas são bastante animadores, apontando a uma promissora aplicabilidade do mesmo.This work presents a study and development of a hybrid algorithm for fault detection, classification and location in tree terminal lines based on wavelet transform (WT). It will be presented in two versions: discrete wavelet transform (DWT) and stationary wavelet transform (SWT). The algorithm is called hybrid because it uses two fault location methodologies: one based on fundamental components and other based on traveling waves. The proposed methodology works either with synchronized tree terminal data or only local data. The hybrid fault locator chooses automatically which location technique to be used in order to reach a reliable and accurate fault location. In this manner, this technique can avoid some difficulties present in other techniques, aiming to reach an optimized fault location. The proposed hybrid fault location was evaluated by simulated fault signals obtained by alternative transient program (ATP). In the tests, several parameters, which would influence the performance of the hybrid algorithm, were varied, such as: fault inception angle, fault resistance, fault type, etc. The results obtained by the proposed methodology are very encouraging and it points out to a very promising application.
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Manceaux, Antoine. "Contribution au rééquilibrage dynamique des lignes d'assemblage : modélisation, résolutions et applications". Thesis, Université de Lorraine, 2015. http://www.theses.fr/2015LORR0279/document.
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Si le problème d'équilibrage lors de la conception de lignes d'assemblage est largement étudié dans la littérature sous le nom d’ALBP (Assembly Line Balancing Problems), peu de travaux concernent leur rééquilibrage dans un horizon court terme et en-ligne. Les travaux présentés dans ce mémoire portent donc sur le rééquilibrage dynamique des lignes d’assemblage en réaction aux événements court terme perturbants la production. L’objectif étant de changer l’allocation des taches sur les postes de travail afin de lisser la charge induite par la perturbation. Le délai court sans arrêt de production étant plus important que l'optimalité de la solution, le temps de résolution rapide des méthodes de résolution approchées nous a intéressé. Deux approches ont été étudiées pour leur simplicité et leur nouveauté dans le domaine du ALBP : la méthode ILS (Iterated Local Search) et la recherche d’atteignabilité sur un réseau d’automates communicants. Cela nous a montré qu'elles peuvent répondre au besoin de réactivité imposé par notre problème mais qu’elles sont difficilement adaptables lorsque les leviers d’action pour rééquilibrer la ligne sont modifiés. Notre proposition pour répondre à ce besoin d’adaptabilité est une méthodologie de modélisation et de résolution des problèmes de rééquilibrage des lignes d’assemblage s’appuyant sur un réseau d’automates communicants et une recherche d’atteignabilité sur celui-ci. Pour assurer la généricité, la méthodologie est décomposée en deux niveaux d’abstraction : l'étude de la classe du problème ALBP considéré et al résolution du problème spécifique. Les travaux ont été validés sur des exemples industriels issus de la société TraneAssembly lines are flow-oriented production systems. They are still typical in industrial production systems despite the evolution from mass-production to more personalized and fluctuating production. In order to meet customer demand (quantity, time, etc.) and to reduce manufacturing costs, the lines must be well balanced. In other words, the products need to move from one workstation to another with the same pace, usually called takt time. This assembly line design problem is widely studied in the literature under the name of ALBP (Assembly Line Balancing Problems). Nonetheless, few studies concern the on-line reconfiguration and in particular, the dynamic rebalancing. The work presented in this thesis focuses on the dynamic rebalancing of assembly lines in response to short-term events disturbing production. Two approaches have been studied for their simplicity, speed of implementation and innovation in the field of ALBP: the ILS approach (Iterated Local Search) and the reachability analysis approach based on a network of communicating automata. This study showed that both approaches can address the need for a quick resolution required by dynamic rebalancing problem but lacked for adaptation when model constraints or objectives are changed. A methodological approach for assembly line balancing problems modeling and resolution is proposed to bridge the gap of adaptability. To ensure the genericity of obtained models., the methodology is composed of two levels of abstraction: a study of the class of the considered problem and a focus on the specific problem to solve. Studies have been validated on industrial examples from Trane factories
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Karri, Senanayak Sesh Kumar. "On the Links between Probabilistic Graphical Models and Submodular Optimisation". Thesis, Paris Sciences et Lettres (ComUE), 2016. http://www.theses.fr/2016PSLEE047/document.
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L’entropie d’une distribution sur un ensemble de variables aléatoires discrètes est toujours bornée par l’entropie de la distribution factorisée correspondante. Cette propriété est due à la sous-modularité de l’entropie. Par ailleurs, les fonctions sous-modulaires sont une généralisation des fonctions de rang des matroïdes ; ainsi, les fonctions linéaires sur les polytopes associés peuvent être minimisées exactement par un algorithme glouton. Dans ce manuscrit, nous exploitons ces liens entre les structures des modèles graphiques et les fonctions sous-modulaires. Nous utilisons des algorithmes gloutons pour optimiser des fonctions linéaires sur des polytopes liés aux matroïdes graphiques et hypergraphiques pour apprendre la structure de modèles graphiques, tandis que nous utilisons des algorithmes d’inférence sur les graphes pour optimiser des fonctions sous-modulaires. La première contribution de cette thèse consiste à approcher par maximum de vraisemblance une distribution de probabilité par une distribution factorisable et de complexité algorithmique contrôlée. Comme cette complexité est exponentielle dans la largeur arborescente du graphe, notre but est d’apprendre un graphe décomposable avec une largeur arborescente bornée, ce qui est connu pour être NP-difficile. Nous posons ce problème comme un problème d’optimisation combinatoire et nous proposons une relaxation convexe basée sur les matroïdes graphiques et hypergraphiques. Ceci donne lieu à une solution approchée avec une bonne performance pratique. Pour la seconde contribution principale, nous utilisons le fait que l’entropie d’une distribution est toujours bornée par l’entropie de sa distribution factorisée associée, comme conséquence principale de la sous-modularité, permettant une généralisation à toutes les fonctions sous-modulaires de bornes basées sur les concepts de modèles graphiques. Un algorithme est développé pour maximiser les fonctions sous-modulaires, un autre problème NP-difficile, en maximisant ces bornes en utilisant des algorithmes d’inférence vibrationnels sur les graphes. En troisième contribution, nous proposons et analysons des algorithmes visant à minimiser des fonctions sous-modulaires pouvant s’écrire comme somme de fonctions plus simples. Nos algorithmes n’utilisent que des oracles de ces fonctions simple basés sur minimisation sous-modulaires et de variation totale de telle fonctionsThe entropy of a probability distribution on a set of discrete random variables is always bounded by the entropy of its factorisable counterpart. This is due to the submodularity of entropy on the set of discrete random variables. Submodular functions are also generalisation of matroid rank function; therefore, linear functions may be optimised on the associated polytopes exactly using a greedy algorithm. In this manuscript, we exploit these links between the structures of graphical models and submodular functions: we use greedy algorithms to optimise linear functions on the polytopes related to graphic and hypergraphic matroids for learning the structures of graphical models, while we use inference algorithms on graphs to optimise submodular functions.The first main contribution of the thesis aims at approximating a probabilistic distribution with a factorisable tractable distribution under the maximum likelihood framework. Since the tractability of exact inference is exponential in the treewidth of the decomposable graph, our goal is to learn bounded treewidth decomposable graphs, which is known to be NP-hard. We pose this as a combinatorial optimisation problem and provide convex relaxations based on graphic and hypergraphic matroids. This leads to an approximate solution with good empirical performance. In the second main contribution, we use the fact that the entropy of a probability distribution is always bounded by the entropy of its factorisable counterpart mainly as a consequence of submodularity. This property of entropy is generalised to all submodular functions and bounds based on graphical models are proposed. We refer to them as graph-based bounds. An algorithm is developped to maximise submodular functions, which is NPhard, by maximising the graph-based bound using variational inference algorithms on graphs. As third contribution, we propose and analyse algorithms aiming at minimizing submodular functions that can be written as sum of simple functions. Our algorithms only make use of submodular function minimisation and total variation oracles of simple functions
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Maciel, Lucio Flore [UNESP]. "Aplicação da simulação a eventos discretos no balanceamento de linha de montagem". Universidade Estadual Paulista (UNESP), 2016. http://hdl.handle.net/11449/148830.
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O objetivo geral da pesquisa foi desenvolver um modelo de simulação a eventos discretos para ser aplicado ao balanceamento de uma linha de montagem de componentes numa empresa do setor automotivo, buscando aumentar a produtividade da linha e utilizando menores quantidades de insumos. Na situação estudada há muitos elementos com comportamento estocástico, que podem influenciar na produtividade da linha, além da diversidade de insumos que abastecem a montagem, o que torna o balanceamento da linha uma tarefa complexa e favorece o uso da Simulação como procedimento de solução. Na modelagem conceitual do problema estudado adotou-se o método IDEF-SIM e para a simulação foi utilizado o software ProModel®. Como resultados tem-se um modelo conceitual e implementado para uma linha de montagem que possibilitou informações interessantes sobre o problema, tais como: juntar funções de dois postos de trabalhos, eliminar excesso de movimentação e eliminar gargalos.
The overall objective of the research was to develop a simulation model discrete event to be applied to balancing an assembly line components in automotive company, seeking to increase line productivity and using lower amounts of inputs. In the situation studied for many elements with stochastic behavior, which may influence the productivity of the line beyond the range of products that supply assembly, which makes the balancing line a complex task and promotes the use of the simulation procedure as a solution. In conceptual modeling of the studied problem adopted the IDEF-SIM method and for the simulation we used the ProModel® software. As results has a conceptual model and implemented for an assembly line that has enabled interesting information about the problem, such as joining functions of two posts jobs, eliminate excess movement and eliminate bottlenecks.
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Cremer-Schulte, Dominik Clemens. "On the links between natural amenities, residential processes and urban planning : lessons from an Alpine urban region". Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAE002/document.
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Les régions urbaines alpines et en proximité des Alpes présentent des caractéristiques spécifiques: elles combinent une ressource foncière limitée pour l'urbanisation et une qualité environnementale particulière dans l'arrière-pays. Cette combinaison les rend particulièrement propices à la péri-urbanisation, et potentiellement à la ségrégation sociale. Dans le contexte d'une métropolisation croissante, ces deux processus entravent des objectifs centraux de la planification urbaine, à savoir la compacité des formes urbaines, la mixité fonctionnelle, l'égalité territoriale et la cohésion sociale. Dans les régions urbaines alpines, les liens entre l'environnement montagnard, les politiques de planification et les processus résidentiels à l’œuvre restent toutefois peu connus.Cette thèse analyse la planification urbaine et des choix de localisation résidentielle en région urbaine alpine. Elle cherche à comprendre les liens entre l'environnement montagnard, les politiques de planification urbaine et deux processus résidentiels: la péri-urbanisation et la ségrégation sociale. Son objectif général est de mettre en lumière comment et dans quelle mesure ces processus résidentiels sont influencés par (i) l'environnement montagnard et (ii) les politiques de planification pour ainsi fournir des recommandations pour la planification territoriale en région urbaine. Pour cela, nous nous appuyons sur trois contributions distinctes en utilisant la région urbaine de Grenoble comme zone d'étude centrale.La première contribution porte sur les changements dans la pratique de la planification urbaine contemporaine dans la région d'étude. Basée sur une recherche qualitative, elle se concentre sur l'émergence d'une planification territoriale stratégique et sa montée en échelle vers des périmètres de planification plus larges intégrants les espaces péri-urbains. Le chapitre montre la création de nouvelles arènes de gouvernance qui remettent en question les cultures de planification locale.La deuxième contribution analyse les liens entre les préférences pour l'environnement naturel, les choix de localisation résidentielle et la ségrégation sociale. En utilisant des modèles de choix de localisation pour la région d'étude et la région métropolitaine de Marseille, cette partie présente une analyse de ségrégation contrefactuelle qui compare les résultats de ségrégation og avec fg{} et og sans fg{} les préférences pour l'environnement naturel entre les deux régions. Le principal résultat est que la recherche des milieux naturels par les ménages a des effets significatifs sur la ségrégation sociale. Cette recherche a le plus souvent tendance à renforcer la ségrégation, mais peut également être un facteur d'atténuation.La dernière contribution étudie les liens entre les politiques de planification urbaine et les processus résidentiels. Le chapitre développe un modèle de choix discrets pour créer et analyser des simulations de demande résidentielle pour différents scénarios de politique de planification. Les résultats illustrent que les scénarios tendanciels de planification soutiennent et potentiellement renforcent la périurbanisation dans la région d'étude. Des politiques de planification plus contraignantes semblent capables de freiner et potentiellement d'inverser la dispersion de la demande. Les politiques visant à ré-centraliser la demande tendent à maintenir, voire accroître les niveaux de ségrégation sociale.Les résultats de cette thèse suggèrent l'importance d'une prise en compte plus grande de l'environnement naturel dans la planification urbaine et territoriale. Si les disparités spatiales dans la qualité environnementale contribuent aux processus résidentiels qui portent atteintes aux objectifs du développement urbain, les politiques de planification devraient rendre compte de ces disparités afin de limiter l'étalement urbain, la ségrégation sociale et l'inégalité environnementale, non seulement dans un contexte de région urbaine alpineUrban regions in and close to the Alps have specific characteristics: they combine a limited land resource for urban development with particular environmental quality in their mountainous hinterland. This combination makes them particularly prone to peri-urbanisation, and potentially social segregation. In the context of continued metropolisation, both of these processes work against central objectives of urban planning, notably compactness of settlement patterns, functional mix, social equity and cohesion. In Alpine urban regions, the links between the mountain environment, urban planning policies and residential processes remain, however, not well understood.This thesis analyses urban planning and residential moves in an Alpine urban region. It seeks to understand the links between the mountain environment, urban planning and notably two residential processes: peri-urbanisation and social segregation. Its general objective is to investigate how and to what extent these residential processes are influenced by (i) the mountain environment and (ii) urban planning policies and to develop recommendations for urban and regional planning. The thesis does this via three distinct contributions which use the urban region of Grenoble in the French Alps as a central study area.The first contribution addresses changes in contemporary urban planning practice in the study region. Based on qualitative research, it focuses on the shift towards strategic spatial planning and on territorial re-scaling towards large urban-peri-urban planning perimeters. The chapter shows the creation of new governance arenas which call into question local planning cultures.The second contribution investigates the links between preferences for the natural environment, residential moves and social segregation. Using location choice models for the study region and the Marseille metropolitan area, this chapter presents a counterfactual segregation analysis that compares segregation outcomes ``with'' and ``without'' preferences for the natural environment. The main result is that households' search for natural environments has significant impacts on social segregation. It most often contributes to reinforcing segregation, but can also be an attenuating factor.The last contribution investigates the links between urban planning policies and residential processes. The chapter develops a residential location choice model in order to predict and analyse residential demand patterns for different planning policy scenarios in terms of concentration and segregation. The scenario results show that continued trends in urban planning policies would sustain and potentially reinforce peri-urbanisation in the region. Confining planning policies are found to be capable of curbing and potentially reversing demand dispersion. Policies that aim at re-centralising demand sustain and potentially increase social segregation levels.The results of this thesis call for a stronger integration of the natural environment in urban and regional planning. If spatial disparities in environmental qualities contribute to residential processes that are detrimental to compact urban forms and an equitable access to environmental quality, then planning should incorporate and account for these disparities in order to prevent further loss of land resources, socio-spatial fragmentation and environmental inequality, not only in an Alpine urban region context
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Taylor, Paul Geoffrey. "Quantifying the functional role of discrete movement variability: Links to adaptation and learning". Thesis, Australian Catholic University, 2016. https://acuresearchbank.acu.edu.au/download/8e0b296509df6f9f48db9492f39d38c680ddcdb87c3446055b5a993dfd8361e0/3760378/Taylor_2016_Quantifying_the_functional_role_of_discrete.pdf.
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Introduction: Movement variability can be defined as the variance in human movement from one trial or cycle to the next, often when attempting to maintain dynamic equilibrium (in the case of continuous skills) or achieve consistent movement outcome (for discrete skills). Some theoretical perspectives of motor control consider movement variability to be deleterious. However, the dynamical systems perspective proposes beneficial and functional roles for movement variability. Within this view variability has developed as an independent theme of research that has gained momentum over the past 25 years, attracting focus from various sub-disciplines within the field with a major contribution from sports biomechanics. The previous research within the field of movement variability has proposed that these functional roles include reducing the risk of injury, enabling coordination change and facilitating adaptation to varying task or environmental constraints. This thesis is primarily constituted of four sequential studies designed to further the method-related approach to, and theoretical understanding of, the interaction between variability in discrete movement and adaptation.
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Manceaux, Antoine. "Contribution au rééquilibrage dynamique des lignes d'assemblage : modélisation, résolutions et applications". Electronic Thesis or Diss., Université de Lorraine, 2015. http://www.theses.fr/2015LORR0279.
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Si le problème d'équilibrage lors de la conception de lignes d'assemblage est largement étudié dans la littérature sous le nom d’ALBP (Assembly Line Balancing Problems), peu de travaux concernent leur rééquilibrage dans un horizon court terme et en-ligne. Les travaux présentés dans ce mémoire portent donc sur le rééquilibrage dynamique des lignes d’assemblage en réaction aux événements court terme perturbants la production. L’objectif étant de changer l’allocation des taches sur les postes de travail afin de lisser la charge induite par la perturbation. Le délai court sans arrêt de production étant plus important que l'optimalité de la solution, le temps de résolution rapide des méthodes de résolution approchées nous a intéressé. Deux approches ont été étudiées pour leur simplicité et leur nouveauté dans le domaine du ALBP : la méthode ILS (Iterated Local Search) et la recherche d’atteignabilité sur un réseau d’automates communicants. Cela nous a montré qu'elles peuvent répondre au besoin de réactivité imposé par notre problème mais qu’elles sont difficilement adaptables lorsque les leviers d’action pour rééquilibrer la ligne sont modifiés. Notre proposition pour répondre à ce besoin d’adaptabilité est une méthodologie de modélisation et de résolution des problèmes de rééquilibrage des lignes d’assemblage s’appuyant sur un réseau d’automates communicants et une recherche d’atteignabilité sur celui-ci. Pour assurer la généricité, la méthodologie est décomposée en deux niveaux d’abstraction : l'étude de la classe du problème ALBP considéré et al résolution du problème spécifique. Les travaux ont été validés sur des exemples industriels issus de la société TraneAssembly lines are flow-oriented production systems. They are still typical in industrial production systems despite the evolution from mass-production to more personalized and fluctuating production. In order to meet customer demand (quantity, time, etc.) and to reduce manufacturing costs, the lines must be well balanced. In other words, the products need to move from one workstation to another with the same pace, usually called takt time. This assembly line design problem is widely studied in the literature under the name of ALBP (Assembly Line Balancing Problems). Nonetheless, few studies concern the on-line reconfiguration and in particular, the dynamic rebalancing. The work presented in this thesis focuses on the dynamic rebalancing of assembly lines in response to short-term events disturbing production. Two approaches have been studied for their simplicity, speed of implementation and innovation in the field of ALBP: the ILS approach (Iterated Local Search) and the reachability analysis approach based on a network of communicating automata. This study showed that both approaches can address the need for a quick resolution required by dynamic rebalancing problem but lacked for adaptation when model constraints or objectives are changed. A methodological approach for assembly line balancing problems modeling and resolution is proposed to bridge the gap of adaptability. To ensure the genericity of obtained models., the methodology is composed of two levels of abstraction: a study of the class of the considered problem and a focus on the specific problem to solve. Studies have been validated on industrial examples from Trane factories
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Bettersworth, Zachary S. "Nullification of Torus Knots and Links". TopSCHOLAR®, 2016. http://digitalcommons.wku.edu/theses/1626.
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Knot nullification is an unknotting operation performed on knots and links that can be used to model DNA recombination moves of circular DNA molecules in the laboratory. Thus nullification is a biologically relevant operation that should be studied.
Nullification moves can be naturally grouped into two classes: coherent nullification, which preserves the orientation of the knot, and incoherent nullification, which changes the orientation of the knot. We define the coherent (incoherent) nullification number of a knot or link as the minimal number of coherent (incoherent) nullification moves needed to unknot any knot or link. This thesis concentrates on the study of such nullification numbers. In more detail, coherent nullification moves have already been studied at quite some length. This is because the preservation of the previous orientation of the knot, or link, makes the coherent operation easier to study. In particular, a complete solution of coherent nullification numbers has been obtained for the torus knot family, (the solution of the torus link family is still an open question). In this thesis, we concentrate on incoherent nullification numbers, and place an emphasis on calculating the incoherent nullification number for the torus knot and link family. Unfortunately, we were unable to compute the exact incoherent nullification numbers for most torus knots. Instead, our main results are upper and lower bounds on the incoherent nullification number of torus knots and links. In addition we conjecture what the actual incoherent nullification number of a torus knot will be.
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Chao, Daphne (Yu Fen). "MDRIP: A Hybrid Approach to Parallelisation of Discrete Event Simulation". Thesis, University of Canterbury. Computer Science and Software Engineering, 2006. http://hdl.handle.net/10092/1076.
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The research project reported in this thesis considers Multiple Distributed Replications in Parallel (MDRIP), a hybrid approach to parallelisation of quantitative stochastic discrete-event simulation. Parallel Discrete-Event Simulation (PDES) generally covers distributed simulation or simulation with replicated trials. Distributed simulation requires model partitioning and synchronisation among submodels. Simulation with replicated trials can be executed on-line by applying Multiple Replications in Parallel (MRIP). MDRIP has been proposed for overcoming problems related to the large size of simulated models and their complexity, as well as with the problem of controlling the accuracy of the final simulation results. A survey of PDES investigates several primary issues which are directly related to the parallelisation of DES. A secondary issue related to implementation efficiency is also covered. Statistical analysis as a supporting issue is described. The AKAROA2 package is an implementation of making such supporting issue effortless. Existing solutions proposed for PDES have exclusively focused on collecting of output data during simulation and conducting analysis of these data when simulation is finished. Such off-line statistical analysis of output data offers no control of statistical errors of the final estimates. On-line control of statistical errors during simulation has been successfully implemented in AKAROA2, an automated controller of output data analysis during simulation executed in MRIP. However, AKAROA2 cannot be applied directly to distributed simulation. This thesis reports results of a research project aimed at employing AKAROA2 for launching multiple replications of distributed simulation models and for on-line sequential control of statistical errors associated with a distributed performance measure; i.e. with a performance measure which depends on output data being generated by a number of submodels of distributed simulation. We report changes required in the architecture of AKAROA2 to make MDRIP possible. A new MDRIP-related component of AKAROA2, a distributed simulation engine mdrip engine, is introduced. Stochastic simulation in its MDRIP version, as implemented in AKAROA2, has been tested in a number of simulation scenarios. We discuss two specific simulation models employed in our tests: (i) a model consisting of independent queues, and (ii) a queueing network consisting of tandem connection of queueing systems. In the first case, we look at the correctness of message orderings from the distributed messages. In the second case, we look at the correctness of output data analysis when the analysed performance measures require data from all submodels of a given (distributed) simulation model. Our tests confirm correctness of our mdrip engine design in the cases considered; i.e. in models in which causality errors do not occur. However, we argue that the same design principles should be applicable in the case of distributed simulation models with (potential) causality errors.
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Agunlejika, Oluwafunmilayo. "Efficient discrete modelling of axisymmetric radiating structures". Thesis, Loughborough University, 2016. https://dspace.lboro.ac.uk/2134/21714.
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This thesis describes research on Efficient Discrete Modelling of Axisymmetric Radiating Structures . Investigating the possibilities of surmounting the inherent limitation in the Cartesian rectangular Transmission Line Modelling (TLM) method due to staircase approximation by efficiently implementing the 3D cylindrical TLM mesh led to the development of a numerical model for simulating axisymmetric radiating structures such as cylindrical and conical monopole antennas. Following a brief introduction to the TLM method, potential applications of the method are presented. Cubic and cylindrical TLM models have been implemented in MATLAB and the code has been validated against microwave cavity benchmark problems. The results are compared to analytical results and the results obtained from the use of commercial cubic model (CST) in order to highlight the benefit of using a cylindrical model over its cubic counterpart. A cylindrical TLM mesh has not previously been used in the modelling of axisymmetric 3D radiating structures. In this thesis, it has been applied to the modelling of both cylindrical monopole and the conical monopole. The technique can also be applied to any radiating structure with axisymmetric cylindrical shape. The application of the method also led to the development of a novel conical antenna with periodic slot loading. Prototype antennas have been fabricated and measured to validate the simulated results for the antennas.
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Janius, Camilla, e Sahel Mir. "Using discrete event simulation : Improving efficiency and eliminating nonvalue added work". Thesis, Mälardalens högskola, Akademin för innovation, design och teknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-35065.
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Process improvement is one of the challenging tasks within manufacturing companies. This study has been focused on analysing a packaging station by using a discrete event simulation tool. Packaging is an important part of the production and logistics process, but it is seldom considered when analysing non-value added activities. Discrete event simulation has been used in the analysis of non-value added activities in production systems, but noted by the low number of articles related to the usage of discrete event simulation within packaging, there exists a limited understanding of discrete event simulation use in this area. The authors divided the scope of the research into the following research questions, which are presented below: RQ1: How can discrete event simulation be used as a tool to identify time wastes and create efficiency in a packaging station? RQ2: What method is suitable when creating a simulation project? These questions were to be answered by performing a literature review and a case study in ABB AB Control Products Vasteras, mentioned as ABB in later in the thesis, where the packaging station were in need of improvements. The results from theoretical and empirical finding were analysed, they highlight the importance of packaging and its impact on logistics and supply chain management performance. By creating discrete event simulation models for both current and future stage, the authors were able to provide analysed improvements of the packaging station. The result of the models illustrated by implementing the improvements it could generate in less pressure on the operators as well as an approximated improvement of 125% more packed product. The improvements of the model involve a better material handling and a more optimized packaging station in order to create a more efficient workstation. The conclusion of the study is that the company should develop the product simultaneously as the production, were every activity and process should be included. They should also consider what impacts the development has on the entire supply chain. This could be a way to eliminate non-value activities from the start. Discrete event simulation is a tool that could be of help when visualizing the process and it allows the developers to see the impact of a change or improvement on the other processes.
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Samieinia, Shiva. "Digital Geometry, Combinatorics, and Discrete Optimization". Doctoral thesis, Stockholms universitet, Matematiska institutionen, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-47399.
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This thesis consists of two parts: digital geometry and discrete optimization. In the first part we study the structure of digital straight line segments. We also study digital curves from a combinatorial point of view. In Paper I we study the straightness in the 8-connected plane and in the Khalimsky plane by considering vertical distances and unions of two segments. We show that we can investigate the straightness of Khalimsky arcs by using our knowledge from the 8-connected plane. In Paper II we determine the number of Khalimsky-continuous functions with 2, 3 and 4 points in their codomain. These enumerations yield examples of known sequences as well as new ones. We also study the asymptotic behavior of each of them. In Paper III we study the number of Khalimsky-continuous functions with codomain Z and N. This gives us examples of Schröder and Delannoy numbers. As a byproduct we get some relations between these numbers. In Paper IV we study the number of Khalimsky-continuous functions between two points in a rectangle. Using a generating function we get a recurrence formula yielding this numbers. In the second part we study an analogue of discrete convexity, namely lateral convexity. In Paper V we define by means of difference operators the class of lateral convexity. The functions have plus infinity in their codomain. For the real-valued functions we need to check the difference operators for a smaller number of points. We study the relation between this class and integral convexity. In Paper VI we study the marginal function of real-valued functions in this class and its generalization. We show that for two points with a certain distance we have a Lipschitz property for the points where the infimum is attained. We show that if a function is in this class, the marginal function is also in the same class.At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Submitted. Paper 5: Manuscript. Paper 6: Manuscript.
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Tribess, Andrea. "Liens discrets : processus historiques dans le milieu agricole d'un village sarde, 1950-1990". Paris, EHESS, 2000. http://www.theses.fr/2000EHES0060.
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Kalpokas, Justas. "Discrete moments of the Riemann zeta function and Dirichlet L-functions". Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2012. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2012~D_20121119_130728-97328.
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In mathematics, analytic number theory is a branch of number theory that uses methods from mathematical analysis to solve problems that concern the integers. It is often said to have begun with Dirichlet's introduction of Dirichlet L-functions. In analytic number theory one of the main investigation objects is the Riemann zeta function. The Riemann hypothesis states that all non-trivial zeros of the Riemann zeta function lie on the critical line. In the thesis we investigate value distribution of the Riemann zeta function on the critical line. To do so we use the curve of the Riemann zeta function on the critical line. A problem connected to the curve asks the question whether the curve is dense in the complex plane. We prove that the curve expands to all directions on the complex plane. A separete case of the main result can be stated as follows Riemann zeta function has infinetly many negative values on the critical line and they are unbounded.Analizinė skaičių teorija yra skaičių teorijos dalis, kuri, naudodama matematinės analizės ir kompleksinio kintamojo funkcijų tyrimo metodus, sprendžia uždavinius susijusius su sveikaisiais skaičiais. Manoma, kad analizinės skaičių teorijos pradžią žymi Dirichlet eilučių ir Dirichlet L-funkcijų taikymai. Vienas iš pagrindinių analizinės skaičių teorijos tyrimo objektų yra Riemann’o dzeta funkcija. Riemann’o hipotezė teigia, kad visi netrivialieji nuliai yra ant kritinės tiesės. Disertacijoje nagrinėjamas Riemann’o dzeta funckijos reikšmių pasiskirstymas ant kritinės tiesės. Tam pasitelkiama Riemann’o dzeta funkcijos kreivė. Svarbus klausimas susijęs su kreive yra ar ši kreivė yra visur tiršta kompleksinių skaičių plokštumoje. Disertacijoje įrodoma, kad kreivė plečiasi į visas puse kompleksinių skaičių plokštumoje. Atskiras disertacijos pagrindinio rezultato atvejis gali būti formuluojamas taip – Riemann’o dzeta funkcija ant kritinės tiesės įgyja be galo daug neigiamų reikšmių, kurios yra neaprėžtos.
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Le, Floc'h Laurence. "Cristaux électromagnétiques bidimensionnels discrets de taille finie : une étude théorique et expérimentale". Brest, 2005. http://www.theses.fr/2005BRES2022.
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Cette thèse est consacrée à l'étude théorique et au développement de Cristaux Photoniques (CP) originaux : les Cristaux Discrets (CPD) constitués d'un empilement fini périodique de multipôles interconnectés par des zones homogènes de propagation. Facilement réalisables aux fréquences micro-ondes, les CPD ont aussi l'avantage de se décrire par l'algèbre linéaire de façon rigoureuse et exacte. Après quelques généralités sur les CP, nous traitons les CP unidimensionnels (1D) de façon inédite. Au moyen d'une description " quadripolaire ", nous mettons en place une procédure de normalisation. Ceci permet de mener une étude paramétrique universelle des réponses des CP 1D (paramètres S). Une structure expérimentale est conçue (ligne de transmission structurée micro-ruban) et analysée à l'aide de cet outil. Ensuite, la procédure est étendue aux CPD 2D. Nous exprimons les réponses en coordonnées normalisées sous une forme analytique à l'aide d'une méthode exploitant les symétries. Nous proposons une analyse des comportements en fonction d'un nombre réduit de paramètres et indépendamment de la nature des ondes. Une attention particulière est apportée au contrôle des largeur, position et niveau des bandes interdites. Puis, nous développons une méthode de synthèse simple et rapide des CPD 2D. Les démonstrateurs à motifs annulaires sont fabriqués en technologie micro-ruban dans la plage 0-7 GHz afin d'en minimiser le coût. Enfin, nous menons une étude théorique et expérimentale de l'influence des conditions aux limites sur les réponses d'un CPD 2D. L'optimisation des conditions permet d'envisager des fonctions intéressantes en termes d'application tels le filtrage et la commutationThis thesis is devoted to the theoretical study and development of a novel class of Photonic Crystals (PCs) so-called Discrete Photonic Crystals (DPCs). DPCs are arrangements of multi-port networks interconnected by wave guides. Easily manufactured in the microwave domain, CPDs can be described exactly using a classical linear algebra. After a general introduction on several types of PC, an original study on one-dimensional PCs (1D PCs) is proposed. By considering these PCs as two-port networks, we develop a process of normalization. This tool allows us to perform a universal parametric study of the responses (scattering parameters). The theory is experimentally illustrated with a microstrip periodic transmission line. The concept is then extended to the 2D-type DPCs. Symmetries have been exploited to give the responses of the structure in analytical form and in normalised units. We propose an analysis of PC spectra behaviour by means of a reduced set of parameters whatever the characteristics of the waves. Special care has been with respect to the control of width frequency position and reflectivity of the Photonic Band-gap. A simple and fast design method applied to these “2D”-type DPC has been developed. Low-cost ring-shaped prototypes are fabricated using microstrip technology in the 0-7 GHz band. We finally conduct a theroretical and an experimental study on the effects of boundary conditions on 2D DPCs responses. The optimization of theses conditions enables us to envisage specific functions for applications such as filtering or switching devices
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Rosenbaum, Leah F. "Exploring the On-line Partitioning of Posets Problem". Scholarship @ Claremont, 2012. http://scholarship.claremont.edu/scripps_theses/53.
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One question relating to partially ordered sets (posets) is that of partitioning or dividing the poset's elements into the fewest number of chains that span the poset. In 1950, Dilworth established that the width of the poset - the size of the largest set composed only of incomparable elements - is the minimum number of chains needed to partition that poset. Such a bound in on-line partitioning has been harder to establish, and work has evalutated classes of posets based on their width. This paper reviews the theorems that established val(2)=5 and illustrates them with examples. It also covers some of the work on establishing bounds for on-line partitioning with the Greedy Algorithm. The paper concludes by contributing a bound on incomparable elements in graded, (t+t)-free, finite width posets.
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Silva, Rodrigo Cleber da [UNESP]. "Representação de linhas de transmissão, utilizando elementos discretos de circuitos, no domínio das fases". Universidade Estadual Paulista (UNESP), 2012. http://hdl.handle.net/11449/87151.
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Neste trabalho será mostrado o desenvolvimento de dois modelos de linhas de transmissão, baseados em elementos discretos de circuitos, que fornecem respostas diretamente no domínio do tempo e nas fases. Os dois modelos propostos partem da hipótese de que um pequeno segmento de linha de transmissão pode ser representado por um circuito . Hipótese esta já validada para linhas monofásicas por diversos autores, e que neste trabalho será utilizada para representar pequenos segmentos de linhas bifásicas e trifásicas. Deste modo, tais linhas serão representadas por uma grande quantidade de blocos (constituídos de elementos discretos de circuitos que representam um pequeno segmento de linha) conectados em cascata. No primeiro modelo proposto, válido para representar linhas idealmente transpostas, as fases de cada um dos pequenos segmentos de linha são separados em seus modos de propagação, e as correntes e tensões são calculadas no domínio modal. No entanto a conversão fase-modo-fase está inserida nas equações de estado que descrevem as correntes e tensões ao longo da linha, sendo que não há a necessidade do usuário do modelo conhecer a teoria de representação de linhas no domínio modal. Uma vez que o modelo não usa explicitamente o processo de decomposição modal, neste trabalho o mesmo será considerado como sendo um modelo desenvolvido no domínio das fases sem o uso explícito da teoria de decomposição modal. Este modelo pode ser utilizado para representar linhas que podem ter suas fases desacopladas por matrizes reais e invariáveis em relação à frequência. A representação de pequenos segmentos de linhas por elementos discretos de circuitos também foi aplicada em linhas bifásicas e trifásicas sem plano de simetria vertical. Neste caso, devido ao fato de que as matrizes...
This paper will show the development of two models of transmission lines, based on discrete circuit elements, which provide answers directly in the time domain and phase. The two proposed models start from the assumption that a small segment of transmission line can be represented by a -circuit, this hypothesis has already been validated for single-phase by several authors and this work will be used to represent small segments of lines biphasic and triphasic. Thus, these lines will be represented by a large number of blocks (consisting of discrete circuit elements that represent a small segment of the line) in cascade. In the first model, valid for ideally transposed lines represent the phases of each small line segments are separated into their modes of propagation and the currents and voltages are calculated in the modal domain. However the conversion phase-mode-phase is inserted into the state equations describing the currents and voltages along the line being that there is no need for the user the model to know representation theory of modal lines. Since the model does not explicitly use modal decomposition process, this paper it will be considered to be a model developed in the field of the phases without the explicit use of modal decomposition theory. This model can be used to represent lines that may have decoupled phases for real matrices and invariant with respect to frequency. The representation of small line segments by discrete circuit elements has also been applied in biphasic and triphasic lines without vertical symmetry plane. In this case, due to the fact that the matrices that separate line in their modes of propagation are not real and invariant with respect to frequency, the model was developed directly in the field of the phases without the use of modal decomposition matrices
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Coupat, Raphaël. "Méthodologie pour les études d’automatisation et la génération automatique de programmes Automates Programmables Industrielssûrs de fonctionnement. Application aux Equipements d’Alimentation des Lignes Électrifiées". Thesis, Reims, 2014. http://www.theses.fr/2014REIMS019/document.
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Le projet de recherche présenté dans cette thèse a été réalisé avec la collaboration de la Direction de l'Ingénierie SNCF et le CReSTIC de l'Université de Reims Champagne-Ardenne (URCA). L'objectif de ce projet est de contribuer à l'amélioration des études de conception du contrôle/commande des projets d'électrification menées par les chargés d'études. Ce projet doit répondre à des objectifs humains, économiques et techniques exprimés par la SNCF, notamment appliqué au domaine des Equipements d'Alimentation des Lignes Electrifiées (EALE). Pour répondre à ces problématiques, une méthodologie pour les études d'automatisation est proposée. Elle intègre deux axes de recherche. Le premier axe est la génération automatique de livrables (codes, documents, schémas…). Celle-ci repose nécessairement sur une standardisation et une modélisation du « métier ». L'approche MDD (Model Driven Development) du génie logiciel et l'approche DSM (Domain Specific Modeling), apporte des éléments de solution reposant sur l'utilisation de « templates métiers ». Toutefois, il est fondamental de générer des livrables de qualité et du code API (Automates Programmables Industriels) sûr de fonctionnement. Le second axe de recherche s'intéresse à la commande sûre de fonctionnement. Trois approches de synthèse de la commande (la Supervisory Control Theory (SCT), la synthèse algébrique, la commande par contraintes logiques) permettant a priori de répondre à ces objectifs de sûreté sont présentées et discutées. La commande par contraintes logiques présente l'avantage majeur de séparer la sécurité (qui est vérifiée formellement hors ligne par model-checking) et le fonctionnel, et de pouvoir être utilisée avec des programmes API existants, ne remettant pas ainsi en cause la méthodologie de travail des chargés d'étudesThe research project presented in this thesis has been realized with the collaboration of the Engineer Department of the SNCF and the CReSTIC of the University of Reims Champagne-Ardenne. The goal of this project is to contribute to the improvement of the control studies of the electrification projects realized by the design engineers. This project must meet human, economic and technical aims expressed by the SNCF applied to the field of the Power Supply Equipments of the Electrified Lines (EALE in french). To answer these problems, a methodology for the automation studies is proposed. It integrates two research orientations were studied. The first axis is the automatic generation the deliverables (codes, documents, diagrams…). This axis is based on standardization and modeling of the “work”. MDD (Model Driven Development) and DSM (Domain Specific Modeling) approaches, brings suggestions for solution based on the use of “work templates”. However, it is fundamental to generate quality deliverables and safe PLC (Programmable Logic Controller) code. The second research orientation is interested in safe control. Three approaches of control synthesis (Supervisory Control Theory (SCT), the algebraic synthesis, the control by logical constraints) permitting a priori to reach these aims of safety are presented and discussed. The major advantage of the control by logical constraints is to separate the safety (which is checked formally off line by model-checking) and the functional parts. It can be used with existing PLC programs, which doesn't change thus the working methodology of the design engineers
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Ubertosi, Fabrice. "Chenalisation de l'écoulement et du transport dans les milieux fracturés : approche discrète par réseaux de liens". Poitiers, 2008. http://www.theses.fr/2008POIT2257.
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La complexité des réservoirs fracturés fait qu'aujourd'hui, aucune approche conceptuelle n’est capable de proposer un modèle à la fois simple et précis. L'approche continue simple milieu est certainement la plus facile à appréhender mais reste imprécise en raison de son incapacité à homogénéiser toute l'information locale. Les approches multi-continuums et les approches discrètes du réseau de fractures s'avèrent plus judicieuses mais supposent des efforts numériques conséquents et une paramétrisation importante souvent non conditionnable sur les données disponibles. Le travail consigné dans ce manuscrit emprunte une modalité de représentation discrète du milieu avec ajout éventuel de continuums "stagnants" pour le transport de solutés. Le modèle se veut pour autant simple mais cependant moins précis. La perte de précision est le fait d'une prise en compte uniquement des flux majeurs (chenaux). La simplification est le fait d'une homogénéisation sur un lien 1D de l'hétérogénéité locale d'un chenal d'écoulement. Un réseau 3D de liens est créé dynamiquement sur la base préliminaire d'un semis de noeuds invariants puis en prenant en compte à la fois la direction du gradient hydraulique général et la géométrie des principales familles de fractures simulées. Le modèle peut ensuite calculer les écoulements en régime permanent et transitoire ainsi que le transport de soluté avec quelques effets réactifs. Plus spécifiquement, le transport utilise une méthode Lagrangienne dans le domaine des temps qui se révèle rapide et efficace sur un réseau de liens 1D. Au final, le modèle proposé s'avère intéressant car il génère un réseau simplifié et évolutif (déformable sur des points d'appui fixes, les noeuds) en fonction des conditions d'écoulement tout en préservant le comportement moyen d'un réseau de fractures. Les capacités de déformation du réseau de liens et la relative facilité de manipulation devraient, à terme, permettre d'aborder l'inversion de scénarios de transport à la fois sur les paramètres locaux des liens et la géomètrie du réseauThe complexity of fractured reservoirs makes that for the moment there is not any conceptual approach to these media either simple and accurate. The continuous simple-medium approach is probably the easier-one to handle but remains imprecise because unable to homogenize the local information. Multicontinuum approaches and discrete approaches to the fracture network are more relevant but induce some numerical efforts as well as a huge parameterization often unaffordable in terms of conditioning on available data. The work in this manuscript is on the side of a discrete representation of the medium with the eventual addition of stagnant continuums for simulating solute transport. The model claims to be but simple and thus slightly less accurate. The loss of precision is the consequence of accounting for main water fluxes (channels) only. The simplification comes from a 1D single bond homogenized representation of the local heterogeneity within each flowing channel. A 3D network of 1D bonds can be built dynamically by accounting for both the general head gradient and the geometry of the principal families of fractures. This network of bonds rests however on an invariant bombing of nodes representing bond intersections. The model can then calculate steady-state and transient flow as well as solute transport with a few additional retention and reaction mechanisms. Incidentally, solving transport is based on a Time Domain Random Walk method (TDRW) which is worth and rapid when handled over a network of 1D bonds. Finally, the model reveals interesting since it generates an evolutionary simplified network (the network can be deformed, or more exactly redistributed, while keeping invariant seed nodes) according to flow conditions and it is able to mimic correctly the mean behavior of a fracture network. The deformation capacity of the bond network and its relative ease of handling should allow in the end to tackle with the inversion of transport scenarios by optimizing both the local parameters of the bonds and the network geometry
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Silva, Rodrigo Cleber da. "Representação de linhas de transmissão, utilizando elementos discretos de circuitos, no domínio das fases /". Ilha Solteira : [s.n.], 2012. http://hdl.handle.net/11449/87151.
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Orientador: Sérgio KurokawaBanca: Luiz Fernando Bovolato
Banca: Marcos de Araujo Paz
Resumo: Neste trabalho será mostrado o desenvolvimento de dois modelos de linhas de transmissão, baseados em elementos discretos de circuitos, que fornecem respostas diretamente no domínio do tempo e nas fases. Os dois modelos propostos partem da hipótese de que um pequeno segmento de linha de transmissão pode ser representado por um circuito . Hipótese esta já validada para linhas monofásicas por diversos autores, e que neste trabalho será utilizada para representar pequenos segmentos de linhas bifásicas e trifásicas. Deste modo, tais linhas serão representadas por uma grande quantidade de blocos (constituídos de elementos discretos de circuitos que representam um pequeno segmento de linha) conectados em cascata. No primeiro modelo proposto, válido para representar linhas idealmente transpostas, as fases de cada um dos pequenos segmentos de linha são separados em seus modos de propagação, e as correntes e tensões são calculadas no domínio modal. No entanto a conversão fase-modo-fase está inserida nas equações de estado que descrevem as correntes e tensões ao longo da linha, sendo que não há a necessidade do usuário do modelo conhecer a teoria de representação de linhas no domínio modal. Uma vez que o modelo não usa explicitamente o processo de decomposição modal, neste trabalho o mesmo será considerado como sendo um modelo desenvolvido no domínio das fases sem o uso explícito da teoria de decomposição modal. Este modelo pode ser utilizado para representar linhas que podem ter suas fases desacopladas por matrizes reais e invariáveis em relação à frequência. A representação de pequenos segmentos de linhas por elementos discretos de circuitos também foi aplicada em linhas bifásicas e trifásicas sem plano de simetria vertical. Neste caso, devido ao fato de que as matrizes... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: This paper will show the development of two models of transmission lines, based on discrete circuit elements, which provide answers directly in the time domain and phase. The two proposed models start from the assumption that a small segment of transmission line can be represented by a -circuit, this hypothesis has already been validated for single-phase by several authors and this work will be used to represent small segments of lines biphasic and triphasic. Thus, these lines will be represented by a large number of blocks (consisting of discrete circuit elements that represent a small segment of the line) in cascade. In the first model, valid for ideally transposed lines represent the phases of each small line segments are separated into their modes of propagation and the currents and voltages are calculated in the modal domain. However the conversion phase-mode-phase is inserted into the state equations describing the currents and voltages along the line being that there is no need for the user the model to know representation theory of modal lines. Since the model does not explicitly use modal decomposition process, this paper it will be considered to be a model developed in the field of the phases without the explicit use of modal decomposition theory. This model can be used to represent lines that may have decoupled phases for real matrices and invariant with respect to frequency. The representation of small line segments by discrete circuit elements has also been applied in biphasic and triphasic lines without vertical symmetry plane. In this case, due to the fact that the matrices that separate line in their modes of propagation are not real and invariant with respect to frequency, the model was developed directly in the field of the phases without the use of modal decomposition matrices
Mestre
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Cousty, Jean. "Lignes de partage des eaux discrètes : théorie et application à la segmentation d'images cardiaques". Phd thesis, Université de Marne la Vallée, 2007. http://tel.archives-ouvertes.fr/tel-00321885.
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La notion de clivage formalise l'idée d'ensemble frontiére dans un graphe. Fusionner deux régions, comme le requièrent certaines méthodes de segmentation d'images, pose des diffIcultés. Nous introduisons quatre classes de graphes (de fusion) dans lesquels ces diffIcultés sont progressivement supprimées. Nous montrons que l'une de ces classes est celle pour laquelle tout clivage est mince. Nous introduisons une relation d'adjacence, appelée grille de fusion parfaite, dans laquelle deux régions voisines peuvent être fusionnées, en préservant toutes les autres régions.La ligne de partage des eaux topologique (LPE) étend la notion de clivage aux graphes dont les sommets sont valués et permet de segmenter une image. Nous étendons les propriétés des clivages dans les graphes de fusion aux cas des fonctions et proposons un algorithme de LPE
monotone et linéaire dans les grilles de fusion parfaites. Grâce à la notion de graphe d'arêtes, les propriétés des LPE dans les grilles de fusion parfaites s'étendent aux graphes à arêtes valuées.
Nous étudions en profondeur les LPE dans les graphes à arêtes valuées. Les LPE peuvent y être définies en suivant l'idée intuitive de gouttes d'eau s'écoulant sur un relief topographique. Nous établissons aussi bien la consistance que l'optimalité de cette définition. De plus, nous proposons deux algorithmes linéaires qui, à notre connaissance, sont les plus efficaces pour le calcul des LPE.
En nous reposant sur ces résultats théoriques, nous proposons une méthode et développons un logiciel pour la segmentation du ventricule gauche dans des images cardiaques 3D+t par résonance magnétique. La méthode est quantitativement et qualitativement validée par comparaison avec des segmentations manuelles tracées par deux experts cardiologues.
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Ragavan, Prasanna Kumar. "Adaptive Sampling Line Search for Simulation Optimization". Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/84938.
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This thesis is concerned with the development of algorithms for simulation optimization (SO), a special case of stochastic optimization where the objective function can only be evaluated through noisy observations from a simulation. Deterministic techniques, when directly applied to simulation optimization problems fail to converge due to their inability to handle randomness thus requiring sophisticated algorithms. However, many existing algorithms dedicated for simulation optimization often show poor performance on implementation as they require extensive parameter tuning.
To overcome these shortfalls with existing SO algorithms, we develop ADALINE, a line search based algorithm that eliminates the need for any user defined parameters. ADALINE is designed to identify a local minimum on continuous and integer ordered feasible sets. ADALINE on a continuous feasible set mimics deterministic line search algorithms, while it iterates between a line search and an enumeration procedure on integer ordered feasible sets in its quest to identify a local minimum. ADALINE improves upon many of the existing SO algorithms by determining the sample size adaptively as a trade-off between the error due to estimation and the optimization error, that is, the algorithm expends simulation effort proportional to the quality of the incumbent solution. We also show that ADALINE converges ``almost surely'' to the set of local minima. Finally, our numerical results suggest that ADALINE converges to a local minimum faster, outperforming other advanced SO algorithms that utilize variable sampling strategies.
To demonstrate the performance of our algorithm on a practical problem, we apply ADALINE in solving a surgery rescheduling problem. In the rescheduling problem, the objective is to minimize the cost of disruptions to an existing schedule shared between multiple surgical specialties while accommodating semi-urgent surgeries that require expedited intervention. The disruptions to the schedule are determined using a threshold based heuristic and ADALINE identifies the best threshold levels for various surgical specialties that minimizes the expected total cost of disruption. A comparison of the solutions obtained using a Sample Average Approximation (SAA) approach, and ADALINE is provided. We find that the adaptive sampling strategy in ADALINE identifies a better solution quickly than SAA.Ph. D.
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Osty, Guillaume. "Extraction de particularités sur données discrètes issues de numérisation 3D : partitionnement de grands nuages de points". Cachan, Ecole normale supérieure, 2002. http://www.theses.fr/2002DENS0003.
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Les systèmes de numérisation 3D permettent l'acquisition, en un temps relativement court de la peau d'un objet sous forme de grands nuages de points. Quelle que soit son exploitation, il se pose le problème du traitement de cette grande quantité de données discrètes : rapidité de traitement, non structuration des données, perte de continuité,. . . Ainsi pour être directement exploitable en rétro-conception, métrologie ou encore copiage de forme, le nuage de points doit subir une opération de partitionnement divisant l'ensemble de points issus d'une numérisation 3D en sous-ensembles de points cohérents. Ce travail doctoral présente des méthodes et outils associés au partitionnement de grands nuages de points basés sur l'extraction à partir des données discrètes et bruitées des contours 3D caractéristiques de singularités géométriques. L'approche développée s'appuie sur une représentation par espace -voxels permettant d'identifier les points caractéristiques des contours et d'en assurer la continuité. Une fois les contours fermés, ils délimitent des sous-ensembles de points pouvant être traités indépendamment.
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Spacek, Pavel. "Modélisation, analyse et commande des systèmes à événements discrets par l’algèbre des dioides : application aux lignes de galvanoplastie". Besançon, 1998. http://www.theses.fr/1998BESA2011.
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Ce travail porte sur la modélisation, l'analyse et la commande des systèmes à événements discrets par l’algèbre des dioides. Une application aux lignes de galvanoplastie est ensuite développée. Les systèmes à événements discrets sont des systèmes non-linéaires et complexes. Il existe peu d'outils mathématiques de modélisation et d'analyse systématique. Parmi ces outils, l’algèbre des dioides, avec entre autres les algèbres (max,+) et (min,+), peuvent nous donner des résultats importants. Une description sous forme d'une équation d’état et une autre sous forme d'une équation récurrente sont développées. A partir de ces descriptions, les propriétés structurelles et comportementales d’observabilité et de commandabilité, l'ordre minimal d'une équation récurrente et le réglage sous l'aspect d'une structure en boucle fermée sont étudiés. Nous développons ensuite une application choisie parmi les nombreux systèmes de production : ce sont les lignes de galvanoplastie. Le traitement de surface est souvent une étape obligatoire et critique dans la fabrication de produits manufacturiers. Dans ce domaine, nous voyons apparaître des problèmes d'ordonnancement de taches liés au contrôle d'un système de manutention dans une ligne de galvanoplastie. Nous avons analysé une ligne mono-produit. Des résultats encourageants sont obtenus. Ces résultats sont appliqués à un exemple industriel. Certains résultats et perspectives sont aussi donnés pour le cas multi-produits.
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Arekar, Chaitanya. "Real time analysis with development, simulation and validation of discrete element method models for tumbling mill charge motion and liner wear". Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=81524.
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Tumbling mills, which consume around 6% of world's electric power, though inefficient (use 1% of the supplied energy) have been used in mineral processing industry for over a century. Harsh internal mill environments have prevented the access to in-mill dynamics. This situation has led researchers to develop models based on the Discrete Element Method (DEM) to predict internal mill dynamics. But before DEM models can be used in the mineral processing industry, their rigorous validation is essential.In this thesis, we have carried out real time analysis of the DEM model to enable online availability of the mill parameters for the mill operators. We have completed rigorous validation of a DEM model based on nine mill parameters by comparing the predicted parameters under varying operating conditions of a 30" pilot mill and some simulated industrial mills. Further, we have also developed a simulator to predict the wear on the tumbling mill liner profile.
Results show that the charge motion simulator used is faster than real time. The validation exercise showed that improvements to charge motion are possible, liner wear prediction is feasible but affects real-time simulator behaviour. Based on these results, it is recommended to continue the improvement of the charge motion model as well as the liner wear model.
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Mazauric, Dorian. "Optimisation discrète dans les réseaux de télécommunication : reconfiguration du routage, routage efficace en énergie, ordonnancement de liens et placement de données". Phd thesis, Université de Nice Sophia-Antipolis, 2011. http://tel.archives-ouvertes.fr/tel-00643513.
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Nous nous intéressons dans cette thèse à différents types de réseaux (optiques, sans-fil, pair-à-pair) ayant chacun leurs spécificités mais partageant des problématiques communes : assurer la meilleure qualité de services possible, garantir la stabilité du système, minimiser les ressources et donc le coût de fonctionnement. Tout d'abord, nous étudions le problème de la reconfiguration du routage dans les réseaux optiques consistant à rerouter les requêtes de connexion en minimisant les perturbations pour les utilisateurs. Puis, nous nous intéressons au problème de la détermination de routages efficaces en énergie dans les réseaux coeur. Pour ce faire, nous étudions le problème de trouver des routages minimisant le nombre d'équipements utilisés. Ensuite, nous nous intéressons aux algorithmes d'ordonnancement des liens dans les réseaux sans-fil en présence d'interférence. Enfin, nous considérons le problème de stockage de données dans les réseaux pair-à-pair. Nous étudions l'impact de différentes politiques de placement sur la durée de vie des données et nous déterminons un choix de placement optimal. Pour résoudre ces problèmes, nous utilisons les outils théoriques des mathématiques discrètes (graphes, configurations, optimisation combinatoire), d'algorithmique (complexité, algorithmique distribuée) et de probabilités.
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Han, Junyu. "Fault location on mixed overhead line and cable network". Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/fault-location-on-mixed-overhead-line-and-cable-network(1a911a42-ddfa-4592-8365-badc8d5c45f3).html.
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Society is increasingly concerned about the environmental impact of energy systems, and prefers to locate power lines underground. In future, certain socially/environmentally sensitive overhead transmission feeders will need to include underground cable sections. Fault location, especially when using travelling waves, become complicated when the combined transmission line includes a number of discontinuities, such as junction points, teed points and fault points. Consequently, a diverse range of fault locators were developed in this thesis, and the performance of the proposed fault locators investigated. For a combined transmission line (CTL), consisting of one or more overhead line sections and one or more underground cable sections, a hybrid fault location scheme is proposed. This utilises the robustness of an impedance based distance algorithm and the accuracy, but stability concerns, of a travelling wave based fault locator, to determine the faulted section. The distance algorithm can determine the approximate fault location, but if the fault is located near an “underground-overhead” junction point, the accuracy is not sufficient to decide whether the fault is located on the overhead or the underground section. This thesis proposes utilizing a single end travelling wave fault locator to improve the accuracy of the fault location decision. The single end travelling wave fault locator can determine the fault section according to the permutation of the polarity of the “special surges”, which is especially important when the fault is close to a junction point. However, this single end fault locator fails in certain “blind” areas, wand these require the use of a distance relay to help determine fault section. Simulation results demonstrated that this hybrid fault locator can reliably determine which section of the feeder is faulty. For all types of CTL, including teed networks, the multiple-end travelling wave fault locator, utilising the arrival time at the feeder ends of the first fault instigated surges, can estimate the fault location. One of the main features of the proposed fault locator is the classification of the time difference between the arrivals of a fault instigated surge at the feeder ends as standard values, when the fault is located at each of the junction points or teed points. Comparing the time differences measured during an actual fault with these standard values allows the faulted feeder section to be estimated. The simulation results show this multiple-end travelling wave fault locator is highly reliable and suitable for application on combined overhead and underground transmission lines.
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Said, Mouhammad. "Géométrie multi-résolution des objets discrets bruités". Grenoble, 2010. http://www.theses.fr/2010GRENM084.
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Les courbes frontières définissent les régions ou les formes du plan de manière compacte et descriptive. Il est bien connu que les formes doivent être étudiées à différentes échelles. Ceci a conduit au développement des pyramides régulières et irrégulières pour l'analyse des formes et la compréhension des scènes. Cependant, il n'existe pas une description analytique de la multi-résolution d'une forme numérique, contrairement au célèbre espace-échelle (scale-space) dans le monde continu. En outre, les primitives géométriques telles que les lignes, les cercles ou les polynômes ont une grande importance dans le contexte de la géométrie numérique. Les morceaux des droites numériques sont un bon moyen pour estimer les tangentes et les arcs discrets approchent la courbure. Il est donc nécessaire de les garder dans l'analyse multi-échelle des frontières numériques. Un des objectifs de cette thèse est de donner des nouveaux résultats analytiques sur la multi-résolution des droites 4-connexes et des segments de droites 4-connexes. Figueiredo est le premier qui a étudié le comportement des droites 8-connexes lors du changement de la résolution de la grille. Dans le présent travail, nous considérons une droite 4-connexe pour laquelle une description analytique est fournie lorsque la résolution de la grille est modifiée par un facteur arbitraire. En plus, nous montrons que leurs couvertures sont des droites 4-connexes. Comme les formules analytiques des segments de droite sont un problème beaucoup plus difficile, nous proposons un parcours indirect pour la multi-résolution d'un DSS en utilisant le fait qu'un segment est un morceau fin d'une droite discrète. Etant donné un DSS, nous construisons deux droites dont l'intersection le contient et dont la partie connexe principale a les mêmes caractéristiques arithmétiques, ainsi que le même nombre de motifs. Notons que nous proposons de nouveaux résultats combinatoires des intersections de droites. Nous déterminons la multi-résolution du segment en examinant la multi-résolution de l'intersection de ces deux droites. Nous donnons une nouvelle description analytique de cet ensemble avec des inégalités arithmétiques. Nous abordons également le problème du calcul des caractéristiques exactes d'un sous-segment d'une droite 4-connexe qui a des caractéristiques connues. Nous présentons deux nouveaux algorithmes SmartDSS et ReversedSmartDSS qui résolvent ce problème. Leur principe est de se déplacer dans l'arbre de Stern-Brocot de la fraction soit de manière haut-bas ou bas-haut. Dans le pire cas, leur complexité est meilleure que l'algorithme de reconnaissance DSS classique. Les deux algorithmes peuvent dès lors servir à calculer efficacement la multi-résolution d'un segment. Les bruits tout au long des contours numériques ne sont pas vraiment détectés, mais plutôt annulés par l'épaississement des segments de droites 4-connexes. De plus, l'épaisseur est réglée par un utilisateur et aussi définie globalement pour le contour. Pour surmonter ce problème, nous proposons une stratégie originale pour détecter localement à la fois la quantité de bruit et les épaisseurs significatives de chaque point de contour. Ce travail se base sur les propriétés asymptotiques de segments flous d'épaisseurs différentes, et forme une alternative à l'approche multi-résolution de la détection du bruitBoundary curves are compact and descriptive means for defining regions or shapes in the plane. It is well known that shapes should be studied at different scales. This has led to the development of regular and irregular pyramids for shape analysis and scene understanding. However there exists no analytical description of the multiresolution of a digital shape, contrary to the famous scale-space analysis in the continuous world. Moreover, in the context of digital geometry, geometric primitives such as lines, circles or polynomials are of a great importance. For instance, pieces of digital lines are excellent tangent estimators, circular arcs estimate curvature. It is thus fundamental to keep them in the multiscale analysis of digital boundaries. One of the contribution of this thesis is to give new analytical results on the multiresolution of Digital Straight Line (DSL) and Digital Straight Segment (DSS). Figueiredo is the first one who studied the behavior of 8-connected lines when changing the resolution of the grid [41]. In this work, we consider a standard digital line. The objective is to provide an analytic description of digital straight line DSL when the resolution of the grid is changed by an arbitrary factor. We also prove that their subsampling is a standard digital line. As analytical formulae for DSS appear to be a much harder problem and DSS are finite parts of DSL, we propose an indirect path to DSS multiresolution. Given a DSS, we build two DSL whose intersection contains it and whose main connected part has the same arithmetic characteristics as well as the same number of patterns. We note here that we propose new results about the combinatorics of such digital line intersections. We determine the multiresolution of DSS by examining the multiresolution of the intersection of these two DSL. We give a new analytical description of this set with arithmetic inequalities. We also address the problem of computing the exact characteristics of any subsegment of digital straight line with known characteristics. We present two new algorithms SmartDSS and ReversedSmartDSS that solve this problem. Their principle is to climb the Stern-Brocot tree of fraction either in a top-down or bottom-up way. Their worst-time complexity are better than the classical DSS recognition algorithm. Both algorithms are useful to compute efficiently the multiresolution of a DSS. The noise along digital contours is not really detected but is rather canceled out by thickening digital straight segments. The thickness is tuned by a user and set globally for the contour. To overcome this issue, we propose an original strategy to detect locally both the amount of noise and the meaningful thickness of each point of a digital contour. This work is based on the asymptotic properties of blurred segments with different thicknesses and forms an alternative to the multiscale approach to noise detection
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Maciel, Lucio Flore. "Aplicação da simulação a eventos discretos no balanceamento de linha de montagem /". Guaratinguetá, 2016. http://hdl.handle.net/11449/148830.
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Orientador: Fernando Augusto Silva MarinsBanca: José Roberto Dale Luche
Banca: Roberto Campos Leoni
Resumo: O objetivo geral da pesquisa foi desenvolver um modelo de simulação a eventos discretos para ser aplicado ao balanceamento de uma linha de montagem de componentes numa empresa do setor automotivo, buscando aumentar a produtividade da linha e utilizando menores quantidades de insumos. Na situação estudada há muitos elementos com comportamento estocástico, que podem influenciar na produtividade da linha, além da diversidade de insumos que abastecem a montagem, o que torna o balanceamento da linha uma tarefa complexa e favorece o uso da Simulação como procedimento de solução. Na modelagem conceitual do problema estudado adotou-se o método IDEF-SIM e para a simulação foi utilizado o software ProModel®. Como resultados tem-se um modelo conceitual e implementado para uma linha de montagem que possibilitou informações interessantes sobre o problema, tais como: juntar funções de dois postos de trabalhos, eliminar excesso de movimentação e eliminar gargalos
Abstract: The overall objective of the research was to develop a simulation model discrete event to be applied to balancing an assembly line components in automotive company, seeking to increase line productivity and using lower amounts of inputs. In the situation studied for many elements with stochastic behavior, which may influence the productivity of the line beyond the range of products that supply assembly, which makes the balancing line a complex task and promotes the use of the simulation procedure as a solution. In conceptual modeling of the studied problem adopted the IDEF-SIM method and for the simulation we used the ProModel® software. As results has a conceptual model and implemented for an assembly line that has enabled interesting information about the problem, such as joining functions of two posts jobs, eliminate excess movement and eliminate bottlenecks
Mestre
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Lopez, Paola Johana Saboya. "Uma contribuição ao problema de detecção de ruídos impulsivos para power line communication". Universidade Federal de Juiz de Fora (UFJF), 2013. https://repositorio.ufjf.br/jspui/handle/ufjf/4155.
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A presente dissertação tem por objetivo propor e avaliar cinco técnicas de detecção de ruídos impulsivos para a melhoria da transmissão digital de dados via redes de energia elétrica (do inglês, Power Line Communications) (PLC). As técnicas propostas contemplam a detecção de ruídos impulsivos no domínio do tempo discreto, no domínio da transformada wavelet discreta (do inglês, Discrete Wavelet Transform) (DWT) e no domínio da transformada discreta de Fourier (do inglês, Discrete Fourier Transform) (DFT). Tais técnicas fazem uso de métodos de extração e seleção de características, assim como métodos de detecção de sinais baseados na teoria de Bayes e redes neurais. Análises comparativas explicitam as vantagens e desvantagens de cada uma das técnicas propostas para o problema em questão, e ainda indicam que estas são bastante adequadas para a solução do mesmo.
This dissertation aims to propose and evaluate five techniques for impulsive noise detection in order to improve digital communications through power line channels. The imput signals for the proposed detection techniques are impulsive noise signals on discrete-time domain, on the Discrete Wavelet Transform domain and on the Discrete Fourier Transform domain and it makes use of feature extraction and selection techniques, as well as detection techniques supported on Bayes Theory and Multi-layer Perceptron Neural Networks. Comparative analysis show some advantages and disadvantages of each proposed technique and the relevance of them to solve the impulsive noise detection problem.
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Albaba, Adel. "Modélisation par éléments discrets de l’impact des laves torrentielles granulaires sur des structures rigides et flexibles". Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAI111/document.
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Les risques naturels tels que les laves torrentielles constituent des menaces réelles pourles zones urbanisées de montagne. Les bâtiments et infrastructures peuvent être exposésà de grandes forces d’impact en cas d’évènement extrême. La réduction de cette menace,par des ouvrages de protection, impose de quantifier l’impact de ces écoulements sur lesstructures, qu’elles soient flexibles ou rigides.Tout d’abord, un écoulement granulaire sec, composé de particules non-sphériquesglissant sur un plan incliné, est modélisé en utilisant une loi de contact visco-élastiqueavec critère de rupture de Mohr-Coulomb. Des données expérimentales de la littératureont été utilisé pour calibrer et valider le modèle. À cette fin, la forme de la particule,l’épaisseur de l’écoulement et la forme finale du dépôt sur le mur sont considerés. Lavalidation est basée sur l’impact sur un mur rigide divisé en six segments. La principalecontribution de la force totale normale appliquée sur le mur est due à la composantedynamiques. La distribution hétérogène de la force normale sur chaque partie du murest due au développement des chaînes de force différent pour chaque arrangement desparticules.Ensuite, un filet est modélisé en utilisant des éléments cylindriques. L’impact sur lefilet est modélisé en utilisant le même modèle d’écoulement que précédemment. Le rôledes dissipateurs d’énergie apparaît essentiel pour réduire la force d’impact sur le filet etlimiter la force appliquée sur les points d’ancrage latéraux.Pour la première fois, des simulations montrent que pour un même écoulementgranulaire la force d’impact est plus élevée pour un obstacle rigide, avec une différencede 50% par rapport à un obstacle flexible. les simulations permettent de définir quelquesrecommandation pour le dimensionnement des filets. Il est constaté que l’utilisationviiid’un maillage de filet plus petit que D90 de l’écoulement est acceptable en termes decapacité à retenir les matériaux en écoulement. En plus, si le câble en bas du filet n’estpas fixé, le filet pourrait perdre totalement sa capacité de retenueNatural hazards such as debris flows are real threat to the urbanization of mountainousareas. Local communities and infrastructures can be exposed to large impact forces inextreme debris events. Mitigation of such threats requires, along other measures, theestimation of the impact of such flows on protection structures (rigid walls and flexiblebarriers). In this thesis, Discrete Element Method (DEM) is used to model the granularflow, the rigid walls and flexible barriers.First, a dry granular flow made of non-spherical particles flowing in inclined plane ismodeled using a visco-elastic contact law with Mohr-Coulomb failure criterion. Experimentaldata from the literature is used to calibrate and validate the model. The modelis calibrated based on the shape of the particle, the flow thickness and the final shapeof the deposit on the wall. Validation procedure is based on the impact on a rigid walldivided into six segments. The main contribution of total normal force applied on thewall is found to be due to the dynamic component. On the micro-scale, development offorce chains is believed to cause heterogeneous distribution of normal force on each partof the wall, for multiple same-test conditions.Next, a flexible barrier is modeled using cylindrical elements. The impact on thebarrier is modeled using the same flow model used for wall-impact problem. The use ofenergy dissipators is found to be essential for minimizing the impact force on the barrier,and thus controlling the force applied on the lateral anchors.By comparing a rigid wall and a flexible barrier for the same flow, we found thatthe rigid wall is exposed to higher impact force, due its high global stiffness comparedwith the flexible barrier. Next, different simulations are carried out to recommend designguidelines for the flexible barrier. It is found that using a mesh size as large as D90 of theviflow is acceptable in terms of mass retaining capacity. In addition, not fixing the bottomcable of flexible barriers might lead to the total loss of its retaining capacity in extremeevents
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Nader, François. "Modélisation de la rupture 3D des grains polyédriques par éléments discrets". Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEI082/document.
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Les structures en enrochements sont parmi les ouvrages les plus usuels de génie civil (barrages, murs de soutènement,. . . ). Des tassements importants peuvent apparaître tout au long de leur durée de vie et sont principalement dus à la rupture des blocs rocheux. Cette thèse propose un modèle numérique permettant de simuler le comportement de matériaux granulaires présentant des ruptures de grains. Afin de prendre en compte la nature discontinue de ces milieux, la méthode des éléments discrets est utilisée. La modélisation adoptée est de type "Non-Smooth Contact Dynamics", où les grains et particules sont supposés rigides. Afin de générer des blocs ayant des formes complexes, un modèle de grain 3D est proposé. Ce modèle de grain est ensuite discrétisé en sous-éléments de forme tétraédrique liés par des liaisons cohésives afin de pouvoir représenter la rupture. Un critère de rupture de Mohr-Coulomb est utilisé. Le modèle est implémenté sur la plateforme logicielle LMGC90. Le modèle est d’abord éprouvé lors de simulations d’écrasement de blocs cassables entre deux plaques. Plusieurs paramètres contrôlant la résistance du grain sont étudiés : cohésion intergranulaire, taille, discrétisation, forme et orientation du grain. L’effet d’échelle observé sur ce type de matériau est vérifié. Le modèle est ensuite testé lors de simulations numériques de compression œdométrique d’enrochements. L’effet des paramètres du modèle et de l’assemblage du milieu granulaire est également étudié. Les simulations œdométriques sont confrontées à des résultats expérimentaux et présentent une bonne concordance. Enfin, des expérimentations numériques sont menées afin d’étudier les énergies mises en jeu dans ces essais. L’énergie de création de surface est estimée pour ce type de matériau. Les résultats sont proches des données de la littératureRockfill structures are very popular among civil engineering structures (dams, retaining walls, . . . ). Important settlements can take place during the lifetime of these structures, settlements mainly caused by the breakage of rockfill grains. This thesis proposes a numerical model that allows the simulation of the behavior of granular materials exhibiting grain breakage. To take into account the discrete nature of these media, the discrete element method is chosen. The adopted strategy is the Non-Smooth Contact Dynamics method, where grains are considered to be rigid. To generate blocks having complex shapes, a 3D grain model is suggested. This grain model is then discretized into tetrahedral subgrains, joined together using cohesive bonds so that breakage can be simulated. A Mohr-Coulomb failure criterion is used for the cohesive bonds. The model is implemented into the LMGC90 software platform. At first, the model is tested in single grain crushing simulations between two plates. Multiple parameters controling the strength of the grain are studied : the intra-granular cohesion, the size, the discretization and the orientation of the grain. The scale effect that characterizes this type of material is verified. Then the model is tested in numerical simulations of œdometric compression of rockfill. The influence of the parameters of the model and of those of the granular medium are studied. The results of œdometric simulations are compared to experimental results, and present a good agreement. Lastly, numerical experimentations are conducted in order to study the energies that are brought into play in the simulations. The surface creation energy is estimated for this type of material. Results are close to the data provided in the literature
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Ferrari, Sandro Mauro. "Identificação on-line de motores de indução através de modelo discreto para sinais senoidais". Universidade do Estado de Santa Catarina, 2006. http://tede.udesc.br/handle/handle/1882.
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Previous issue date: 2006-07-20Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
In this work are developed two on-line identification methods for three-phase induction motors based on discrete models obtained when we consider continuous systems excited by sinusoidal signals. The first method uses the discrete model of the homopolar machine in the stationary frame to estimate the stator resistance and the stator dispersion inductance and the discrete model of the linear system existent among the stator flux and current in the rotor frame to estimate all the electric parameters of the motor. The second method, besides this last model, presupposes to estimate the stator resistance with DC excitation added to the supply voltage of the motor and the knowledge of the motor class, in order to estimate the other electric parameters through classical methods of least squares parameters estimation. The two methods presuppose the estimate of the rotor frame signals from measurements of stator currents in the stationary frame and measurement of the rotor angular velocity. Simulation and experimental results illustrate the proposed methods.
Neste trabalho são desenvolvidos dois métodos on-line para identificação do motor de indução trifásico baseados em modelos discretos obtidos ao se considerar sistemas contínuos excitados por sinais senoidais. O primeiro método utiliza o modelo discreto da máquina homopolar no referencial estacionário para estimar a resistência estatórica e a indutância de dispersão de estator e o modelo discreto da relação linear existente entre o fluxo estatórico e a corrente estatórica no referencial que gira com o rotor para a obtenção dos demais parâmetros elétricos. No segundo método, além deste último modelo, pressupõe-se a estimação da resistência de estator através do acréscimo de excitação C.C. à tensão bifásica de alimentação do motor. A obtenção dos demais parâmetros elétricos é realizada através de métodos clássicos de Mínimos Quadrados, sendo necessário o conhecimento da classe do motor. Os dois métodos pressupõem a estimação dos sinais no referencial que gira com o rotor a partir das medidas de correntes de estator no referencial estacionário e da medição da rotação do motor. Resultados de simulação e experimentais ilustram a metodologia proposta.
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Xia, Johnny. "A NEW STUDY OF UNBALANCED PRODUCTION LINE WITH OPTIMIZATION". Thesis, Högskolan i Skövde, Institutionen för ingenjörsvetenskap, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:his:diva-15149.
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This project is a continuous research of a topic well-known in the literature, namely, the performance study of unbalanced unpaced production system. In the literature, there were many studies that investigated the statistical outputs of an unbalanced production line using simulation. This project focuses on researching the outputs like average buffer level and idle time that are rarely studied in previous research by using optimization tools from discrete event simulation software FACTS.The models used in the article (Shaaban & McNamara, 2009) have been used as a guideline during the development of the simulation models for this project. Two simulation models were created, each using different discrete event simulation software, namely FACTS analyzer and Plant simulation. Those simulation models fulfills its role in verification & validation stage, with their statistical outputs compared to each other and with Shaaban and McNamara’s results. After verification & validation comes optimization of those simulation models, by using optimization tools from FACTS.The research area expanded during the optimization phase. Originally Shaaban et.al analyzed unbalanced production line with one fixed value of coefficient of variation. In order to expand the view on the properties of an unbalanced production line, three more coefficient variation were added with total of four in this project. As a result, 12 optimization results were created at the end of this project. Each optimization has 30 000 iterations to ensure its convergence.The first step of analysis is done by locating all Pareto-optimal solutions with optimization tools in FACTS. The raw data of all solutions are later transferred and converted into EXCEL files. Using scatter graph and putting all outputs against each other in EXCEL, it creates visual graph that can be used to analyze and to investigate interesting behavior in an unbalanced production line.The analysis on the optimization results showed several interesting behaviors from production line with different settings. One being that if a production line possess worse coefficient of variation than its competition. By raising the inter-stage buffer level of the production line with inferior coefficient of variation, it can achieve the same level, if not greater outputs than its competitor who possess better coefficient of variation. The other interesting behavior are optimization results with highest outputs in regard of either idle time or average buffer level, with deep analyzation using optimization tools from FACTS. Certain operation time pattern and inter-stage buffer pattern could be observed from those results.