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Loucký, Vojtěch. "Model Li-ion akumulátoru." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2021. http://www.nusl.cz/ntk/nusl-442783.
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This diploma thesis deals with description of the principle of Li-ion cells, literature search on the topic of mathematical models of Li-ion cells and the creation of a selected mathematical model in MATLAB, which is able to simulate the course of voltage and state of charge as a function of time for different ambient conditions, such as various aging of battery .The creation of both the model and the procedure of identification of parameters necessary for the creation of the model are described here as well as different options of identification of parameters. The selected Thevenin model is then compared with the real course and the accuracy of the model is evaluated with respect to the measured course.
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Bornitz, Matthias, Thomas Zahnert, Hans-Jürgen Hardtke, and Karl-Bernd Hüttenbrink. "Identification of Parameters for the Middle Ear Model." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-135790.
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This paper presents a method of parameter identification for a finite-element model of the human middle ear. The parameter values are estimated using a characterization of the difference in natural frequencies and mode shapes of the tympanic membrane between the model and the specimens. Experimental results were obtained from temporal bone specimens under sound excitation (300–3,000 Hz). The first 3 modes of the tympanic membrane could be observed with a laser scanning vibrometer and were used to estimate the stiffness parameters for the orthotropic finite-element model of the eardrum. A further point of discussion is the parameter sensitivity and its implication for the identification processDieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich
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Bornitz, Matthias, Thomas Zahnert, Hans-Jürgen Hardtke, and Karl-Bernd Hüttenbrink. "Identification of Parameters for the Middle Ear Model." Karger, 1999. https://tud.qucosa.de/id/qucosa%3A27677.
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This paper presents a method of parameter identification for a finite-element model of the human middle ear. The parameter values are estimated using a characterization of the difference in natural frequencies and mode shapes of the tympanic membrane between the model and the specimens. Experimental results were obtained from temporal bone specimens under sound excitation (300–3,000 Hz). The first 3 modes of the tympanic membrane could be observed with a laser scanning vibrometer and were used to estimate the stiffness parameters for the orthotropic finite-element model of the eardrum. A further point of discussion is the parameter sensitivity and its implication for the identification process.Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
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Kučerová, Anna. "Identification of nonlinear mechanical model parameters based on softcomputing methods." Cachan, Ecole normale supérieure, 2007. http://tel.archives-ouvertes.fr/tel-00256025/fr/.
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Le problème d'identification des paramètres apparaît dans beaucoup de problèmes en génie civil sous formes différentes et il peut être résolu par beaucoup de méthodes distinctes. Cette thèse présente deux philosophies principales d'identification avec orientation vers les méthodes basées sur intelligence artificielle. Les aspects pratiques sont montrés sur plusieurs problèmes d'identification, où les paramètres des modèles mécaniques non linéaires sont à déterminerThe problem of parameters identification occurs in many engineering tasks and, as such, attains several différent forms and can bc solved by many very distinct methods. An overview of two basic philosophies of thé identification is presented in this thesis with an emphasis put on thé area of sort computing methods. Practical aspects are shown on several identification tasks, where parameters of highly non linear mechanical models are to be determined
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Temeltas, H. "Real-time identification of robot dynamic model parameters using parallel processing." Thesis, University of Nottingham, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357973.
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Karameh, Fadi Nabih. "On-line identification and control algorithm for system model with jump parameters using wavelets." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/11019.
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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1996.Includes bibliographical references (leaves 73-75).
by Fadi Nabih Karameh.
M.S.
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Zhou, Haiyan. "Stochastic Inverse Methods to Identify non-Gaussian Model Parameters in Heterogeneous Aquifers." Doctoral thesis, Universitat Politècnica de València, 2011. http://hdl.handle.net/10251/12267.
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La modelación numérica del flujo de agua subterránea y del transporte de masa se está convirtiendo en un criterio de referencia en la actualidad para la evaluación de recursos hídricos y la protección del medio ambiente. Para que las predicciones de los modelos sean fiables, estos deben de estar lo más próximo a la realidad que sea posible. Esta proximidad se adquiere con los métodos inversos, que persiguen la integración de los parámetros medidos y de los estados del sistema observados en la caracterización del acuífero. Se han propuesto varios métodos para resolver el problema inverso en las últimas décadas que se discuten en la tesis. El punto principal de esta tesis es proponer
dos métodos inversos estocásticos para la estimación de los parámetros del modelo, cuando estos no se puede describir con una distribución gausiana, por ejemplo, las conductividades hidráulicas mediante la integración de observaciones del estado del sistema, que, en general, tendrán una relación no lineal con los parámetros, por ejemplo, las alturas piezométricas.
El primer método es el filtro de Kalman de conjuntos con transformación normal (NS-EnKF) construido sobre la base del filtro de Kalman de conjuntos estándar (EnKF). El EnKF es muy utilizado como una técnica de asimilación de datos en tiempo real debido a sus ventajas, como son la eficiencia y la capacidad de cómputo para evaluar la incertidumbre del modelo. Sin embargo, se sabe que este filtro sólo trabaja de manera óptima cuándo los parámetros del modelo y las variables de estado siguen distribuciones multigausianas. Para ampliar la aplicación del EnKF a vectores de estado no gausianos, tales como los de los acuíferos en formaciones fluvio-deltaicas, el NSEnKF propone aplicar una transformación gausiana univariada. El vector de estado aumentado formado por los parámetros del modelo y las variables de estado se transforman en variables con una distribución marginal gausiana.Zhou ., H. (2011). Stochastic Inverse Methods to Identify non-Gaussian Model Parameters in Heterogeneous Aquifers [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/12267
Palancia
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Benedetti, Lorenzo. "Substructuring approache in state space models for dynamic system parameters identification." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amslaurea.unibo.it/2325/.
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In the recent decade, the request for structural health monitoring expertise increased exponentially in the United States. The aging issues that most of the transportation structures are experiencing can put in serious jeopardy the
economic system of a region as well as of a country. At the same time, the monitoring of structures is a central topic of discussion in Europe, where the preservation of historical buildings has been addressed over the last four
centuries. More recently, various concerns arose about security performance of civil structures after tragic events such the 9/11 or the 2011 Japan earthquake: engineers looks for a design able to resist exceptional loadings due to
earthquakes, hurricanes and terrorist attacks. After events of such a kind, the assessment of the remaining life of the structure is at least as important as the initial performance design. Consequently, it appears very clear that the introduction of reliable and accessible damage assessment techniques is crucial for the localization of issues and for a correct and immediate rehabilitation.
The System Identification is a branch of the more general Control Theory. In Civil Engineering, this field addresses the techniques needed to find mechanical characteristics as the stiffness or the mass starting from the signals captured by sensors.
The objective of the Dynamic Structural Identification (DSI) is to define, starting from experimental measurements, the modal fundamental parameters of a generic structure in order to characterize, via a mathematical model, the dynamic behavior.
The knowledge of these parameters is helpful in the Model Updating procedure, that permits to define corrected theoretical models through experimental validation. The main aim of this technique is to minimize the differences between the theoretical model results and in situ measurements of
dynamic data.
Therefore, the new model becomes a very effective control practice when it comes to rehabilitation of structures or damage assessment.
The instrumentation of a whole structure is an unfeasible procedure sometimes because of the high cost involved or, sometimes, because it’s not possible to physically reach each point of the structure. Therefore, numerous scholars
have been trying to address this problem. In general two are the main involved methods.
Since the limited number of sensors, in a first case, it’s possible to gather time histories only for some locations, then to move the instruments to another location and replay the procedure. Otherwise, if the number of sensors is
enough and the structure does not present a complicate geometry, it’s usually sufficient to detect only the principal first modes. This two problems are well presented in the works of Balsamo [1] for the application to a simple system and Jun [2] for the analysis of system with a
limited number of sensors.
Once the system identification has been carried, it is possible to access the actual system characteristics. A frequent practice is to create an updated FEM model and assess whether the structure fulfills or not the requested functions.
Once again the objective of this work is to present a general methodology to analyze big structure using a limited number of instrumentation and at the same time, obtaining the most information about an identified structure without
recalling methodologies of difficult interpretation. A general framework of the state space identification procedure via OKID/ERA algorithm is developed and
implemented in Matlab. Then, some simple examples are proposed to highlight the principal characteristics and advantage of this methodology. A new algebraic manipulation for a prolific use of substructuring results is developed
and implemented.
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Huang, Changwu. "Kriging-assisted evolution strategy for optimization and application in material parameters identification." Thesis, Normandie, 2017. http://www.theses.fr/2017NORMIR05.
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Afin de réduire le coût de calcul pour des problèmes d'optimisation coûteuse, cette thèse a été consacrée à la Stratégie d'Evolution avec Adaptation de Matrice de Covariance assistée par modèle de Krigeage (KA-CMA-ES). Plusieurs algorithmes de KA-CMA-ES ont été développés et étudiés. Une application de ces algorithmes KA-CMA-ES développés est réalisée par l'identification des paramètres matériels avec un modèle constitutif d'endommagement élastoplastique. Les résultats expérimentaux démontrent que les algorithmes KA-CMA-ES développés sont plus efficaces que le CMA-ES standard. Ils justifient autant que le KA-CMA-ES couplé avec ARP-EI est le plus performant par rapport aux autres algorithmes étudiés dans ce travail. Les résultats obtenus par l'algorithme ARP-EI dans l'identification des paramètres matériels montrent que le modèle d'endommagement élastoplastique utilisé est suffisant pour décrire le comportement d'endommage plastique et ductile. Ils prouvent également que la KA-CMA-ES proposée améliore l'efficace de la CMA-ES. Par conséquent, le KA-CMA-ES est plus puissant et efficace que CMA-ES pour des problèmes d'optimisation coûteuseIn order to reduce the cost of solving expensive optimization problems, this thesis devoted to Kriging-Assisted Covariance Matrix Adaptation Evolution Strategy (KA-CMA-ES). Several algorithms of KA-CMA-ES were developed and a comprehensive investigation on KA-CMA-ES was performed. Then applications of the developed KA-CMA-ES algorithm were carried out in material parameter identification of an elastic-plastic damage constitutive model. The results of experimental studies demonstrated that the developed KA-CMA-ES algorithms generally are more efficient than the standard CMA-ES and that the KA-CMA-ES using ARP-EI has the best performance among all the investigated KA-CMA-ES algorithms in this work. The results of engineering applications of the algorithm ARP-EI in material parameter identification show that the presented elastic-plastic damage model is adequate to describe the plastic and ductile damage behavior and also prove that the proposed KA-CMA-ES algorithm apparently improve the efficiency of the standard CMA-ES. Therefore, the KA-CMA-ES is more powerful and efficient than CMA-ES for expensive optimization problems
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Spohrer, Klaus. "The water regime in a lychee orchard of Northern Thailand : identification of model parameters for water balance modelling /." Stuttgart : Univ. Hohenheim, Inst. für Bodenkunde und Standortlehre, 2007. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=016421055&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
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Usu, Kerem. "Identification Of Soft Tissue Mechanical Material Model And Corresponding Parameters From In Vivo Experimental Data By Using Inverse Finite Element Method." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609885/index.pdf.
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The purpose of this thesis is to search for the best material model for soft biological tissues in general. Different sections of human body exhibit different responses like stress relaxation, creep, hysteresis and preconditioning to external loading conditions. These body sections can be assumed as viscoelastic, poroelastic or pseudoelastic. After making the choice of the material model from one of these for the current study, the finite element model and the material code to be used with this model have been created. The material code has also been tried on a simple finite element model before implementing to the real model to prove the fact that it is
working properly. Then, the constants in the code which simulates the in vivo experimental data that was obtained by indenting the elliptic indenter tip into the forearm, medial part as close as possible, have been derived by inverse finite element method. Consequently, the characteristic behaviors of the soft tissue could be simulated. Despite the big size of the finite element model and very long submission times (up to one day for preconditioning simulation), relaxation and creep behaviors could be simulated with the maximum normalized sum of square errors of 0.74 % and 0.43 %, respectively. The number of square errors for the hysteresis and preconditioning behaviors appeared as 2.56 % and 3.89 % which are also acceptable values. These values prove that these material models are well suited for the simulation of the behavior of soft biological tissues. By using different experimental data obtained from other sections of human body, simulation of the behavior of different soft tissues can be achieved by using these material models.
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Krashanitsa, Roman Yurievich. "An Inverse Computational Approach for the Identification of the Parameters of the Constitutive Model for Damaged Ceramics Subjected to Impact Loading." Diss., Tucson, Arizona : University of Arizona, 2005. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu%5Fetd%5F1390%5F1%5Fm.pdf&type=application/pdf.
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Tran, Thanh Binh. "A Bayesian Network framework for probabilistic identification of model parameters from normal and accelerated tests : application to chloride ingress into conrete." Nantes, 2015. https://archive.bu.univ-nantes.fr/pollux/show/show?id=1bd3c7d5-c357-43f1-b430-bb5e97e9ef3c.
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La pénétration des chlorures dans le béton est l'une des causes principales de dégradation des ouvrages en béton armé. Sous l’attaque des chlorures des dégradations importantes auront lieu après 10 à 20 ans. Par conséquent, ces ouvrages devraient être périodiquement inspectés et réparés afin d’assurer des niveaux optimaux de capacité de service et de sécurité pendant leur durée de vie. Des paramètres matériels et environnementaux pertinents peuvent être déterminés à partir des données d’inspection. En raison de la cinétique longue des mécanismes de pénétration de chlorures et des difficultés pour mettre en place des techniques d'inspection, il est difficile d'obtenir des données d'inspection suffisantes pour caractériser le comportement à moyen et à long-terme de ce phénomène. L'objectif principal de cette thèse est de développer une méthodologie basée sur la mise à jour du réseau bayésien pour améliorer l'identification des incertitudes liées aux paramètres matériels et environnementaux des modèles en cas de quantité limitée de mesures. Le processus d'identification est appuyé sur des résultats provenant de tests normaux et accélérées effectués en laboratoire qui simulent les conditions de marée. Sur la base de ces données, plusieurs procédures sont proposées pour : (1) identifier des variables aléatoires d'entrée à partir de tests normaux ou naturels; (2) déterminer un temps équivalent d'exposition (et un facteur d'échelle) pour les tests accélérés; et (3) caractériser les paramètres en dépendants du temps. Les résultats indiquent que le cadre proposé peut être un outil utile pour identifier les paramètres du modèle, même à partir d’une base de données limitéeChloride ingress into concrete is one of the major causes leading to the degradation of reinforced concrete (RC) structures. Under chloride attack important damages are generated after 10 to 20 years. Consequently, they should be periodically inspected and repaired to ensure an optimal level of serviceability and safety during its lifecycle. Relevant material and environmental parameters for reliability analysis could be determined from inspection data. In natural conditions, chloride ingress involves a large number of uncertainties related to material properties and exposure conditions. However, due to the slow process of chloride ingress and the difficulties for implementing the inspection techniques, it is difficult to obtain sufficient inspection data to characterise the mid- and long-term behaviour of this phenomenon. The main objective of this thesis is to develop a framework based on Bayesian Network updating for improving the identification of uncertainties related to material and environmental model parameters in case of limited amount of measurements in time and space. The identification process is based on results coming from in-lab normal and accelerated tests that simulate tidal conditions. Based on these data, several procedures are proposed to: (1) identify input random variables from normal or natural tests; (2) determine an equivalent exposure time (and a scale factor) for accelerated tests; and (3) characterise time-dependent parameters combining information from normal and accelerated tests. The results indicate that the proposed framework could be a useful tool to identify model parameters even from limited
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Hesham, Abdelwahed Ahmed Youssef Elshazly. "A NEW APPROACH TO IDENTIFICATION OF MODEL PARAMETERS OF STRUCTURES AND PREDICTION OF THEIR RESPONSE TO FUTURE EARTHQUAKES BY INVERSE ANALYSIS." Kyoto University, 1997. http://hdl.handle.net/2433/202379.
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Kyoto University (京都大学)0048
新制・課程博士
博士(農学)
甲第6895号
農博第913号
新制||農||738(附属図書館)
学位論文||H9||N3019(農学部図書室)
16012
UT51-97-H279
京都大学大学院農学研究科農業工学専攻
(主査)教授 長谷川 高士, 教授 河地 利彦, 教授 水山 高久
学位規則第4条第1項該当
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Lourens, Alexandra Susanna Maritz. "Air quality in the Johannesburg-Pretoria megacity: its regional influence and identification of parameters that could mitigate pollution / A.S.M. Lourens." Thesis, North-West University, 2012. http://hdl.handle.net/10394/8760.
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A megacity is generally defined as a city that, together with its suburbs or recognised metropolitan area, has a total population of more than 10 million people. Air pollution in megacities is a major concern due to large increases of populations over the past decades. Increases of air pollution result from more anthropogenic emission sources in megacities, which include energy production, transportation, industrial activities and domestic fuel burning. In the developing parts of Africa, urbanisation is increasing rapidly, with growth rates of populations in cities of up to 5% per annum. The major driving forces for these population increases in African countries can be attributed to population growth, natural disasters and armed ethnic conflicts. In South Africa, 62% of the total population lived in cities in 2010. The rate of urbanisation growth is predicted to be 1.2% per annum.
The largest urbanised city in South Africa is the Johannesburg-Pretoria conurbation (referred to as Jhb-Pta megacity) that has more than 10 million inhabitants. Johannesburg is considered to be the central hub of economic activities and -growth in South Africa. The larger conurbation includes all the suburbs of Johannesburg and Pretoria. In South Africa, household combustion and traffic emissions are major sources of pollutants in urbanised areas. The major pollutants emitted from these activities include nitrogen oxide (NO), nitrogen dioxide (NO 2 ), sulphur dioxide (SO2 ), carbon monoxide (CO), particular matter (PM) and various organic compounds. The Jhb-Pta megacity is also located relatively close to large industrialised regions in South Africa, i.e. the Mpumalanga Highveld and the Vaal Triangle.
Very few air quality modelling studies have been conducted for the Jhb-Pta megacity. According to the knowledge of the author, no literature existed in peer-reviewed publications at the time of the study. An in-depth modelling study was therefore conducted to assess the current state of air quality within the Jhb-Pta megacity. The main objectives were to optimise an existing photochemical box model for the Jhb-Pta megacity and to utilise the model to investigate the photochemical processes in the Jhb-Pta megacity and surrounding areas. In this investigation, ground-based measurements of criteria atmospheric pollutant species representative of the Jhb- Pta megacity were obtained to utilise as input data in the model, as well as to compare to results determined with the model. From the ground-based measurements, the possible contribution of the Jhb-Pta megacity to the NO2 hotspot observed over the South African Highveld from satellite retrievals was also contextualised.
Five ground-based monitoring sites were situated strategically within the boundaries of the Jhb- Pta megacity to measure the direct influences of urban air pollution, e.g. traffic emissions, biomass burning and residential pollution. One measurement site was situated outside the modelling domain in order to collect rural background data in close proximity to the Jhb-Pta megacity. All the air quality stations continuously measured the criteria pollutants NOx, SO2 and O3. In addition, benzene, toluene, ethylbenzene and xylene (BTEX) were measured at four sites. Passive sampling of NOx, SO2 , O3 and BTEX was also conducted in March and April
2010. Active data was obtained for March to May 2009, since no active measurements were available for the same year that passive sampling was performed due to logistical reasons. Meteorological parameters that included temperature, pressure and relative humidity were also measured at the monitoring stations
Ground-based measurements provided a good indication of the state of the air quality in the Jhb-Pta megacity. The air quality levels of NO2 , SO2 , O3 and BTEX could be compared to other cities in the world. A distinct diurnal cycle was observed for NO2 at most of the stations. An early morning peak between 6:00 and 9:00 coincided with the time that commuters travel to work, whereas an evening peak between 18:00 and 21:00 could be attributed to traffic emissions and household combustion. Levels of O3, which is a secondary pollutant, peaked between 13:00 and 15:00. This diurnal pattern could be attributed to the photochemical formation of O3 from precursor species NO and VOCs. Toluene was predominantly higher than the other BTEX species. Benzene and xylene concentrations were in the same order, while the lowest levels were measured for ethyl benzene
Ground-based measurements also indicated that the NO2 Highveld hotspot, which is well known in the international science community due to its prominence in satellite images, is accompanied by a second hotspot over the Jhb-Pta megacity. Peak NO2 pollution levels in the Jhb-Pta megacity exceeded the maximum daily Highveld values during the morning and evening rush hours. This result is significant for the more than 10 million people living in the Jhb-Pta megacity. Although satellite instruments have been extremely valuable in pointing out global hotspots, a limitation of satellite retrievals due to their specific overpass times has been presented.
Chemical processes in the Jhb-Pta megacity were investigated by utilising an existing photochemical box model, i.e. MECCA-MCM. This model was further developed in this study and was termed the MECCA-MCM-UPWIND model. This model included horizontal and vertical mixing processes in the atmosphere. These processes were included to simulate the advection of upwind air masses into the modelling domain, as well as the entrainment from the troposphere resulting from the diurnal mixing layer (ML) height variation. Three processes, i.e. horizontal mixing, vertical mixing and ML height variation, were built into the MECCA-MCM- UPWIND model. The model was tested and evaluated to determine the efficiency of the model to represent atmospheric mixing processes. MECCA-MCM-UPWIND simulated horizontal mixing, vertical entrainment and ML height variations as expected.
The input data for the model runs for the Jhb-Pta megacity modelling runs were either obtained from ground-based measurements or literature. Input data included meteorology, emission inventory, ML height and mixing ratios of the atmospheric chemical species. The chemical composition of the air mass entering the Jhb-Pta megacity was determined with MECCA-MCM- UPWIND. The concentrations and diurnal variability of criteria pollutant species were well predicted with the MECCA-MCM-UPWIND model. The day-time chemistry, especially, compared well, while slight under-predictions were observed for the night-time chemistry for most of the species. The differences observed between modelled and measured data could partially be ascribed to uncertainties associated with some of the input data obtained from literature used.
The MECCA-MCM-UPWIND model was used to perform sensitivity studies on the influence of different parameters on O3 levels in the Jhb-Pta megacity. Possible scenarios to alter or mitigate pollution were also investigated. The results from the sensitivity analyses showed that O3 mixing ratios decreased within the Jhb-Pta megacity with increasing wind speeds. The contribution of local emissions to the change in the concentration of pollutants is reduced at higher wind speeds. It also indicated that the Mpumalanga Highveld can potentially be a source of NOx in the Jhb-Pta megacity that can lead to the titration of O3 . This also implies that if the air quality of the surrounding area improves, the concentration of the secondary pollutant O 3 will increase in the Jhb-Pta megacity due to the decrease in the titration of O3 . Sensitivity analyses also indicated that the Jhb-Pta megacity is a VOC-limited (or NOx-saturated) regime. Therefore, O3 reduction in the Jhb-Pta megacity will mostly be effective if VOC emissions are reduced. The same effect was observed in various cities world-wide where O3 increased when NOx emissions the Jhb-Pta megacity on the instantaneous production of O 3 was also investigated. A significant increase of approximately 23ppb O3 production was observed when changing from Euro-0 to Euro-3 vehicles with lower emissions of VOCs, NOx and CO. This compares with other modelled sensitivity studies of traffic emissions that also predict that future urban O 3 concentrations will increase in many cities by 2050 due to the reduction in the NOx titration of O3 despite the implementation of O3 control regulationsThesis (PhD (Environmental Sciences))--North-West University, Potchefstroom Campus, 2013
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Karavelić, Emir. "Stochastic Galerkin finite element method in application to identification problems for failure models parameters in heterogeneous materials." Thesis, Compiègne, 2019. http://www.theses.fr/2019COMP2501.
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Cette thèse traite de rupture localisée de structures construites en matériau composite hétérogène, comme le béton, à deux échelles différentes. Ces deux échelles sont connectées par le biais de la mise à l'échelle stochastique, où toute information obtenue à l'échelle méso est utilisée comme connaissance préalable à l'échelle macro. À l'échelle méso, le modèle de réseau est utilisé pour représenter la structure multiphasique du béton, à savoir le ciment et les granulats. L'élément de poutre représenté par une poutre Timoshenko 3D intégrée avec de fortes discontinuités assure un maillage complet indépendance de la propagation des fissures. La géométrie de la taille des agrégats est prise en accord avec la courbe EMPA et Fuller tandis que la distribution de Poisson est utilisée pour la distribution spatiale. Les propriétés des matériaux de chaque phase sont obtenues avec une distribution gaussienne qui prend en compte la zone de transition d'interface (ITZ) par l'affaiblissement du béton. À l'échelle macro, un modèle de plasticité multisurface est choisi qui prend en compte à la fois la contribution d'un écrouissage sous contrainte avec une règle d'écoulement non associative ainsi que des composants d'un modèle d'adoucissement de déformation pour un ensemble complet de différents modes de défaillance 3D. Le modèle de plasticité est représenté par le critère de rendement Drucker-Prager, avec une fonction potentielle plastique similaire régissant le comportement de durcissement tandis que le comportement de ramollissement des contraintes est représenté par le critère de St. Venant. La procédure d'identification du modèle macro-échelle est réalisée de manière séquentielle. En raison du fait que tous les ingrédients du modèle à l'échelle macro ont une interprétation physique, nous avons fait l'étalonnage des paramètres du matériau en fonction de l'étape particulière. Cette approche est utilisée pour la réduction du modèle du modèle méso-échelle au modèle macro-échelle où toutes les échelles sont considérées comme incertaines et un calcul de probabilité est effectué. Lorsque nous modélisons un matériau homogène, chaque paramètre inconnu du modèle réduit est modélisé comme une variable aléatoire tandis que pour un matériau hétérogène, ces paramètres de matériau sont décrits comme des champs aléatoires. Afin de faire des discrétisations appropriées, nous choisissons le raffinement du maillage de méthode p sur le domaine de probabilité et la méthode h sur le domaine spatial. Les sorties du modèle avancé sont construites en utilisant la méthode de Galerkin stochastique fournissant des sorties plus rapidement le modèle avancé complet. La procédure probabiliste d'identification est réalisée avec deux méthodes différentes basées sur le théorème de Bayes qui permet d'incorporer de nouvelles bservations générées dans un programme de chargement particulier. La première méthode Markov Chain Monte Carlo (MCMC) est identifiée comme mettant à jour la mesure, tandis que la deuxième méthode Polynomial Chaos Kalman Filter (PceKF) met à jour la fonction mesurable. Les aspects de mise en œuvre des modèles présentés sont donnés en détail ainsi que leur validation à travers les exemples numériques par rapport aux résultats expérimentaux ou par rapport aux références disponibles dans la littératureThis thesis deals with the localized failure for structures built of heterogeneous composite material, such as concrete, at two different scale. These two scale are latter connected through the stochastic upscaling, where any information obtained at meso-scale are used as prior knowledge at macro-scale. At meso scale, lattice model is used to represent the multi-phase structure of concrete, namely cement and aggregates. The beam element represented by 3D Timoshenko beam embedded with strong discontinuities ensures complete mesh independency of crack propagation. Geometry of aggregate size is taken in agreement with EMPA and Fuller curve while Poisson distribution is used for spatial distribution. Material properties of each phase is obtained with Gaussian distribution which takes into account the Interface Transition Zone (ITZ) through the weakening of concrete. At macro scale multisurface plasticity model is chosen that takes into account both the contribution of a strain hardening with non-associative flow rule as well as a strain softening model components for full set of different 3D failure modes. The plasticity model is represented with Drucker-Prager yield criterion, with similar plastic potential function governing hardening behavior while strain softening behavior is represented with St. Venant criterion. The identification procedure for macro-scale model is perfomed in sequential way. Due to the fact that all ingredients of macro-scale model have physical interpretation we made calibration of material parameters relevant to particular stage. This approach is latter used for model reduction from meso-scale model to macro-scale model where all scales are considered as uncertain and probability computation is performed. When we are modeling homogeneous material each unknown parameter of reduced model is modeled as a random variable while for heterogeneous material, these material parameters are described as random fields. In order to make appropriate discretizations we choose p-method mesh refinement over probability domain and h-method over spatial domain. The forward model outputs are constructed by using Stochastic Galerkin method providing outputs more quickly the the full forward model. The probabilistic procedure of identification is performed with two different methods based on Bayes’s theorem that allows incorporating new observation generated in a particular loading program. The first method Markov Chain Monte Carlo (MCMC) is identified as updating the measure, whereas the second method Polynomial Chaos Kalman Filter (PceKF) is updating the measurable function. The implementation aspects of presented models are given in full detail as well as their validation throughthe numerical examples against the experimental results or against the benchmarks available from literature
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Piroti, Shwana, and Jesper Eriksson. "Friction Modeling in FE Simulation : Identification of Friction Model Parameters in Airbag and Crash Dummy Head Contact through Simulation and Experimental Data Response Correlation." Thesis, KTH, Hållfasthetslära (Avd.), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-232473.
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Motor vehicle-traffic accidents are a common cause of traumatic brain injuries, resulting in severe and sustaining disabilities, or even fatality. In an effort to mitigate injuries related to vehicle crashes, various safety systems such as the occupant airbag has been implemented. In angled impacts, occupant interaction with the airbags can lead to head rotation, and during recent years head rotation has been emphasized as an important contributor to head injury risk. Therefore, for prediction of head injury risk in crash simulations it is important to correctly model the friction force which arises in the contact between occupants and the car interior. The aim of this thesis is therefore to study the friction within such a system. More specifically, the analysis is focusing on dummy head to airbag interaction and to correlate a three parameter friction model for this contact pair, as well as a one parameter model currently used by Volvo Car Group, with measured laboratory test data in the software LS-DYNA.A preliminary study in LS-DYNA was conducted to determine the configuration of the laboratory setup consisting of a statically inflated customized driver airbag and a crash dummy head being launched to impact the airbag. The laboratory test data was analyzed using linear regression and Students T-test to identify the influence of parameters on the measured responses. The simulation model was then modified to represent the laboratory setup, prior to an optimization study performed to correlate simulation and laboratory test data responses. Lastly, an evaluation study was made to test whether or not the proposed friction model could improve occupant crash simulations.It was found in the thesis study that the friction force had a large effect on the rotation of the head around the vertical axis (z−axis in the anatomical coordinate system of the head). The experimental data showed that the internal pressure of the airbag had little effect on the response. This was likely due to the studied pressures being large enough for the airbag to be so stiff that no plowing effect of the dummy head moving through the airbag fabric could be seen. Furthermore, results from the optimization study indicated that the model correlation was improved when a three parameter friction model with velocity dependence was used. This implies that the friction coefficient is dependent on the velocity. It was also shown that material properties affecting friction behavior vary between different crash dummy heads, as well as different surface coating. Both dummy T-shirt fabric and grease paint resulted in significantly lower surface friction.Due to the difference in friction for different dummy heads, a single set of friction model parameter values that describes the friction behavior of all crash dummy heads does not exist. The study finds that when sliding is present in a contact, a three parameter model for describing the friction improves the correlation, as it can account for the velocity dependence of the friction in the contact. In contrast, when sliding is not present the one parameter and the three parameter model give similar results.Keywords: friction, velocity dependent friction coefficient, finite element analysis, car crash simulation, Volvo Cars, crash test dummy head, driver airbag, LS-DYNA, laboratory testing, optimization study.
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Djimli, Lynda. "Analyse du phénomène de rochet : essais et modélisation." Phd thesis, INSA de Rouen, 2010. http://tel.archives-ouvertes.fr/tel-00583729.
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Cette thèse s'inscrit dans le contexte de l'étude de l'effet de l'identification des paramètres matériau sur la prévision du comportement cyclique. Une étude de l'effet de la pré-déformation sur la réponse du matériau vis à vis le rochet est aussi présentée. Pour cela deux types d'expériences ont été menés au sein de l'équipe Mécanique du Groupe de Physique des Matériaux (GPM, UMR 6634) à l'INSA de Rouen sur un acier inoxydable de type 304L : Les essais EXP1 contenant des essais à déformation imposée axiale et multiaxiale et des essais de rochet en une et deux phases. Ces essais sont tirés de la littérature et nous ont servi de base de donnée pour la réalisation des différentes étapes de l'identification. Les essais EXP2 contenant des essais de rochet après déformation imposée.Ils sont réalisés dans le cadre de cette étude et permettent l'étude de l'effet de la pré déformation sur le phénomène de rochet. L'identification des paramètres est faite''automatiquement'' avec une méthode d'optimisation en utilisant des bases de données à complexité croissante. Les paramètres identifiés sont ensuite injectés dans des simulations qui seront superposées avec les courbes expérimentales. L'ensemble des simulations est fait avec le code de calcul Zébulon avec le choix du modèle de Chaboche. Les résultats obtenus montrent l'effet de la pré déformation sur le rochet selon les histoires, les mêmes conditions à contraintes imposées peuvent mener à différents comportements cycliques : Elastique et adaptation plastique dans d'autre cas. La pré-déformation précédente peut également mener à l'anisotropie du matériau conduisant à un faible rochet sous traction compression avec une contrainte moyenne nulle !L'étude précise également l'importance de la base de données expérimentale utilisée pour l'identification de paramètres. Le choix des essais devrait étroitement être lié aux équations constitutives du modèle choisis . À savoir, la présence des essais à déformation imposée non proportionnelle peut être non appropriée si le modèle ne peut pas tenir compte explicitement d'un tel caractère.
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Huang, Renke. "Seamless design of energy management systems." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/53518.
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The contributions of the research are (a) an infrastructure of data acquisition systems that provides the necessary information for an automated EMS system enabling autonomous distributed state estimation, model validation, simplified protection, and seamless integration of other EMS applications, (b) an object-oriented, interoperable, and unified component model that can be seamlessly integrated with a variety of applications of the EMS, (c) a distributed dynamic state estimator (DDSE) based on the proposed data acquisition system and the object-oriented, interoperable, and unified component model, (d) a physically-based synchronous machine model, which is expressed in terms of the actual self and mutual inductances of the synchronous machine windings as a function of rotor position, for the purpose of synchronous machine parameters identification, and (e) a robust and highly efficient algorithm for the optimal power flow (OPF) problem, one of the most important applications of the EMS, based on the validated states and models of the power system provided by the proposed DDSE.
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Cottanceau, Emmanuel. "Simulation numérique du processus d’assemblage de câbles flexibles en grands déplacements." Thesis, Paris, ENSAM, 2018. http://www.theses.fr/2018ENAM0011/document.
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Avec l’essor de l’électronique embarquée, les câbles électriques constituentune part importante des pièces automobiles tandis que l’espace à bord n’a cessé de diminuer. Leur flexibilité requiert la prédiction de leur déformation durant leur montage afin d’éviter le contact avec d’autres pièces du véhicule et leur endommagement. Les outils actuels ne permettent pas une prédiction assez réaliste et précise de leur comportement, nécessaire dans un volume de travail très restreint. Les étapes de montage sont donc validées via la réalisation de maquettes réelles coûteuses. Cette thèsea pour but d’améliorer la simulation numérique de ces pièces souples. Nous proposonsici un code de simulation 3D basé sur un modèle de poutre géométriquement exact résolu par la méthode des éléments finis. Son originalité tient dans le couplage des quaternions pour modéliser les rotations 3D et de la méthode asymptotique numérique pour la continuation du système non linéaire qui lui confère une grande robustesse. Un banc d’essai permettant l’identification des paramètres homogénéisés nécessaires au modèle numérique et sa validation par comparaison de la géométrie finale et du chemin d’équilibre est présenté. Combinés à des développements analytiques sur les modèles de poutres avec cisaillement, les essais mènent à une évaluation critique du modèle deTimoshenko 3D pour la représentation des torons de câblesWith on-board electronics expansion, electrical cables are an essential partof automotive pieces and the space on board has plummeted. Their flexibility requires to predict their deformation during vehicle assembly in order to avoid the contact with other pieces and damaging. Current numerical tools do not allow a realistic and accurate prediction, which is necessary in the obstructed car space. Assembly steps thus are validated on costly physical mock-ups. This thesis aims at improving numerical simulation of these flexible pieces. We herein propose a 3D algorithm based on a geometrically exact beam model solved by the finite element method. This work’s originality stands in coupling quaternions as rotational parameters and the asymptotic numerical method as nonlinear solver which results in a very robust algorithm. A test bench designed to identify the homogenized beam parameters of the numerical model and to validate it by offering a comparison on the final geometry and the equilibrium path is presented. Analytical developments on shear beams and the results of these experimental tests lead to a critical evaluation of the 3D Timoshenko model for representing stranded cables
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La, Delfa Salvatore. "SECAAC : Système d'Eco-Conduite Auto-Adaptatif au Conducteur." Thesis, Valenciennes, 2017. http://www.theses.fr/2017VALE0002.
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Yang, Yanfeng. "Étude des effets des changements de trajet en emboutissage." Thesis, Paris, HESAM, 2020. http://www.theses.fr/2020HESAE001.
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Dans le processus de formage de tôle, le matériau subit généralement de grandes déformations, des historiques de chargement complexes et son comportement mécanique peut être modélisé par des équations constitutives. Malgré les efforts considérables déployés pour développer des modèles d’écrouissage avancés tenant compte de l'effet de Bauschinger, la fiabilité et l'applicabilité des modèles d’écrouissage développés doivent encore être étudiés, à la fois expérimentalement et théoriquement. Plusieurs types de modèles d’écrouissage sont implantés numériquement dans cette thèse. Ils sont utilisés pour étudier la prévision de l'évolution de la surface de plasticité, ce qui montre qu'une certaine violation apparente de la condition de normalité peut être simulés modèles basés sur la plasticité associée. La deuxième partie porte principalement sur la caractérisation et la discrimination pour la sélection de modèles de matériaux. Premièrement, certains tests de caractérisation, y compris les trajets de chargement complexes, sont effectués pour identifier les paramètres des matériaux, puis le test discriminant de pliage sous tension est conçu pour l’investissement d’un comportement de retour élastique capable de déterminer le meilleur modèleIn sheet metal forming process, the material usually undergoes large deformations, complex loading histories and its mechanical behavior can be modeled by constitutive equations. Despite the great efforts paid to develop advanced hardening models considering the Bauschinger effect, the reliability and applicability of the developed hardening models still needs to be investigated, both experimentally and theoretically. In the first part, based on the developed hardening models, some classical and advanced models are selected are implemented by using Euler explicit implementation method. After that, the developed numerical instruments in current work are applied to investigate the prediction of the yield surface evolution, which show that some apparent violation of the normality condition can be simulated using models based on associated plasticity. The second part mainly focuses on characterizing and discriminating for selecting material models. Firstly some characterizations tests including complex loading path are performed to identify material parameters and bending-under-tension discriminant test is built to investing springback behavior that can sort out the best model
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Yang, Junqing. "Assimilation de données variationnelles pour les problèmes de transport des sédiments en rivière." Université Joseph Fourier (Grenoble), 1999. http://tel.archives-ouvertes.fr/tel-00004863.
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La prévision de la sédimentation d'une rivière requiert l'utilisation d'un modèle mathématique régissant l'écoulement et de données d'observation. Le but de ce travail est de proposer une méthode d'assimilation de données qui permet de reconstituer les champs en tenant en compte du modèle et des données d'observation. La méthode qui est proposée est fondée sur les techniques de contrôle optimal. On présente les problèmes de sédimentation et leurs approximations numériques, un algorithme de décomposition est introduit et sa convergence est étudiée. En préalable à l'exploitation à des problèmes réels, on a vérifié la faisabilité de la méthode variationnelle d'assimilation de données pour trois types de problèmes de transport des sédiments : 1) la détermination de la condition initiale, 2) l'identification des paramètres, 3) l'estimation de l'erreur de la modélisation. Les études de sédimentation sur le terrain conduisent à des problèmes numériques de très grande dimension, dans une dernière partie on s'est intéressé à des techniques permettant la réduction de l'espace de contrôle pour obtenir des problèmes d'une taille raisonnable
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Dittrich, Petr. "Odhad Letových Parametrů Malého Letounu." Doctoral thesis, Vysoké učení technické v Brně. Fakulta informačních technologií, 2017. http://www.nusl.cz/ntk/nusl-412582.
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Tato práce je zaměřena na odhad letových parametrů malého letounu, konkrétně letounu Evektor SportStar RTC. Pro odhad letových parametrů jsou použity metody "Equation Error Method", "Output Error Method" a metody rekurzivních nejmenších čtverců. Práce je zaměřena na zkoumání charakteristik aerodynamických parametrů podélného pohybu a ověření, zda takto odhadnuté letové parametry odpovídají naměřeným datům a tudíž vytvářejí předpoklad pro realizaci dostatečně přesného modelu letadla. Odhadnuté letové parametry jsou dále porovnávány s a-priorními hodnotami získanými s využitím programů Tornado, AVL a softwarovéverze sbírky Datcom. Rozdíly mezi a-priorními hodnotami a odhadnutými letovými paramatery jsou porovnány s korekcemi publikovanými pro subsonické letové podmínky modelu letounu F-18 Hornet.
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Imamovic, Ismar. "Ultimate load limit analysis of steel structures accounting for nonlinear behaviour of connections." Thesis, Compiègne, 2017. http://www.theses.fr/2017COMP2373/document.
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Cette thèse traite de l'analyse limite des structures de châssis en acier, qui s'utilise souvent comme la structure principale de support des bâtiments. La structure du cadre en acier est caractérisée par une réponse très ductile et un grand potentiel pour dissiper l'énergie, ce qui est crucial pour la résistance par rapport aux tremblements de terre. La ductilité dans la réponse de la structure est la cause du comportement du matériau lui-même et du comportement des connexions entre les éléments de la structure. Les connexions entre les poutres et les poteaux peuvent influencer de manière significative la réponse de la structure du cadre en acier, parfois jusqu'à 30%. L'idée est de intégrer le comportement des connexions par les éléments de poutres qui seront situés dans les coins du cadre et la modélisation du reste serra fait avec des éléments de poutres non-linéaires qui décrirons le comportement des poutres en acier. Cette recherche est composée de deux parties. La première partie est consacrée au comportement des connexions structurelles, la deuxième partie présente le développement de l'élément fini du faisceau non linéaire capable de représenter le comportement ductile d'un élément de la structure en acier. Dans la première partie de la thèse, nous définissons la procédure d'identification des paramètres constitutifs pour le modèle couplé de plasticité-dégâts avec dix-huit inconnus. Ce modèle constitutif est très robuste et capable de représenter une large gamme de problèmes. La procédure définie a été utilisée dans la préparation de tests expérimentaux pour trois types de connexions en acier structuré. Les tests expérimentaux ont été effectués pour deux cas de charge. Pour la première, la charge a été appliquée dans un sens avec les cycles de chargement et de déchargement. À partir des mesures expérimentales, nous avons conclu que le modèle de plasticité peut bien représentée le comportement de la connexion structurale. Paramètres constitutifs ont été déterminés à partir des résultats de l'expérimentation, on a utilisé une poutre géométriquement exacte avec la loi bilinéaires renforcement du matériel et la loi linéaire pour le ramollissement. Également, on a effectué des essais expérimentaux de deux types de raccords en acier en cas de chargement cyclique. Les données mesurées montrent que le modèle de la plasticité n'est pas assez bon pour décrire le comportement de connexion pour ce type de charge. A savoir, en raison de changements du sens de l'application du chargement, les connexions montrent moins de rigidité, qui peut être décrite avec un modèle constitutif de dommages. Pour cette raison, nous avons développé un nouveau modèle plasticité-dommages qui est capable d'inclure le phénomène mentionné ci-dessus. A la fin de cette section est faite l'identification des paramètres constitutifs. La deuxième partie de la thèse de doctorat est composé de formulations théoriques et la mise en œuvre numérique des faisceaux géométriquement exacte. La réponse de durcissement de la poutre comprend l'interaction entre les forces de la section résultant du stress (N, T et M), et la réponse de ramollissement est définit par la loi non linéaire. Ce type d'élément fini de poutre est capable de décrire le comportement ductile des structures en acier et inclure les effets du second ordre, qui sont très importantes pour l'analyse ultime des structures de cadre en acier. L'élément fini développé de poutre géométriquement exacte et les lois définies de liaison de comportement dans la construction en acier, offrant la possibilité d'une analyse de haute qualité des structures en acier. En utilisant les modèles de poutre proposé et la méthodologie de modélisation des structures de châssis en acier, il est possible de déterminer une distribution réaliste des forces de section transversale , y compris la redistribution due à la formation de rotules plastiquesThis thesis deals with the ultimate load limit analysis of steel frame structures. The steel frame structure has a very ductile response and a large potential to dissipate energy, which is crucial in the case of earthquakes. The ductility in the response of the structure comes from the behavior of the material itself and the behavior of the semi-rigid structural connections. The semi-rigid connections between beams and columns can significantly influence the response of the structure, sometimes up to 30%. In this thesis, we propose a methodology for modeling steel frame structures with included connection behavior. The idea is to model the behavior of the structural connections by the beam elements positioned in the corners of the steel frame structure. Other members of the steel frame structure, steel beams, and columns, will be modeled with nonlinear beam elements. This research consists of two parts. The first part deals with the behavior of the structural steel connections. In the second part, we present the development of the nonlinear beam element capable of representing the ductile behavior of steel structural elements, beams and columns. In the first part of the thesis, we define constitutive parameters identification procedure for the coupled plasticity-damage model with eighteen unknowns. This constitutive model is very robust and capable of representing a wide range of problems. The identification procedure was used in the preparation of experimental tests for three different types of structural steel connections. The experimental tests have been performed for two load cases. In the first, the load was applied in one direction with both the loading and unloading cycles. From the experimental measurements, we have concluded that the response of the experimental structure can be represented by the plasticity model only because no significant change in the elastic response throughout the loading program was observed. Therefore, we have chosen an elastoplastic geometrically exact beam to describe connection behavior. The hardening response of the beam is governed by bilinear law, and the softening response is governed by nonlinear exponential law. The identification of the parameters has been successfully done with fifteen unknown parameters identified. The two types of the experimental structures were also exposed to the cyclic loading. Measured experimental data shows complex connection behavior that cannot be described by the plasticity model alone. Namely, after changing load direction stiffness of the connection decreases. This suggests that the damage model should be incorporated in the constitutive law for the connections behavior as well. Therefore, we propose a new coupled plasticity-damage model capable of representing the loss in the stiffness of the connection with the changing of the load direction. At the end of this part, we also give the constitutive parameters identification for the proposed model. The second part of the thesis deals with the theoretical formulation and numerical implementation of the elastoplastic geometrically exact beam. The hardening response of the beam includes interaction between stress resultant section forces (N, T and M), and the softening response of the beam, which is governed by the nonlinear law. This type of the beam element is capable of representing the ductile behavior of a steel frame structure, and it takes into account second order theory effects. Performed numerical simulations show that the proposed geometrically nonlinear beam element is very robust and is able to provide a more precise limit load analysis of steel frame structures. By using proposed methodology for modeling steel structures, we are able to obtain the real distribution of section forces, including their redistribution caused by forming of the hinges and the connections behavior
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Teissier, Yoann. "Metapopulation dynamics of dengue epidemics in French Polynesia." Thesis, Sorbonne Paris Cité, 2017. http://www.theses.fr/2017USPCB008.
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La dengue circule en Polynésie française sur un mode épidémique depuis plus de 35 ans. Néanmoins, en dépit de la taille relativement faible de la population de Polynésie française, la circulation de la dengue peut persister à de faibles niveaux pendant de nombreuses années. L’objectif de ce travail de thèse est de déterminer si l'épidémiologie de la dengue dans le système insulaire de la Polynésie française répond aux critères d’un contexte de métapopulation. Après avoir constitué une base de données regroupant les cas de dengue répertoriés sur les 35 dernières années, nous avons réalisé des analyses épidémiologiques descriptives et statistiques. Celles-ci ont révélé des disparités spatio-temporelles distinctes pour l’incidence de la dengue des archipels et des îles, mais la structure de l'épidémie globale à l’échelle de la Polynésie française pour un même sérotype ne semble pas être affectée. Les analyses de la métapopulation ont révélé l'incidence asynchrone de la dengue dans un grand nombre d’îles. Celle-ci s’observe plus particulièrement par la différence de dynamique de l’incidence entre les îles plus peuplées et celles ayant une population plus faible. La taille critique de la communauté nécessaire à la persistance de la dengue n’est même pas atteinte par la plus grande île de Polynésie Française, Tahiti. Ce résultat suggère que la dengue peut uniquement persister grâce à sa propagation d’île en île. L'incorporation de la connectivité des îles à travers des modèles de migration humaine dans un modèle mathématique a produit une dynamique de la dengue davantage en adéquation avec les données observées, que les tentatives de modélisation traitant la population dans son ensemble. Le modèle de la métapopulation a été capable de simuler la même dynamique que les cas de dengue observés pour l'épidémie et la transmission endémique qui a suivi pour la période de 2001 à 2008. Des analyses complémentaires sur la différenciation de l'incidence de la maladie et de l'infection seront probablement instructives pour affiner le modèle de métapopulation de l'épidémiologie de la dengue en Polynésie françaiseDengue has been epidemic in French Polynesia for the past 35 years. Despite the relatively small population size in French Polynesia, dengue does not disappear and can persist at low levels for many years. In light of the large number of islands comprising French Polynesia, this thesis addresses the extent to which a metapopulation context may be the most appropriate to describe the epidemiology and persistence of dengue in this case. After compiling a database of dengue cases over the last 35 years, we used a number of descriptive and statistical epidemiological analyses that revealed distinct spatio-temporal disparity in dengue incidence for archipelago and islands. But the global structure of the epidemics of the same serotype were not affected. Metapopulation analyses revealed asynchronous dengue incidence among many of the islands and most notably larger islands lagged behind the smaller islands. The critical community size, which determines dengue persistence, was found to exceed even the largest island of Tahiti, suggesting that dengue can only exist by island-hopping. Incorporation of island connectedness through patterns of human migration into a mathematical model enabled a much better fit to the observed data than treating the population as a whole. The metapopulation model was able to capture to some extent the epidemic and low level transmission dynamics observed for the period of 2001-2008. Further analyses on differentiating incidence of disease and infection will likely prove informative for the metapopulation model of dengue epidemiology in French Polynesia
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Litwhiler, Dale H. "Identification of the nonlinear internal variable model parameters /." Diss., 2000. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:9982871.
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Chen, Wei-Chi, and 陳韋圻. "Automatic Parameters Identification of Groundwater Model using Expert System." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/91961603798405589532.
Full textAbstract:
碩士國立交通大學
土木工程系所
97
Conventionally, parameters identification of groundwater model can be classified into manual parameters identification and automatic parameters identification using optimization method. Parameter searching in manual parameters identification requires heavily interaction with the modeler. Therefore, the identified parameters value is interpretable by the modeler. However, manual method is a complicated and time-consuming work and requires groundwater modeling practice and parameters identification experiences to performing the task. Optimization-based identification is more efficient and convenient comparing to the manual one. Nevertheless, the parameters search in the optimization approach can not directly interactive with modeler and one can only examine the final results. Moreover, because of the simplification of the optimization model, the parameters value obtained by optimization-based identification may not be feasible in reality. In light of previous discussion, this study integrates a rule-based expert system and a groundwater simulation model, MODFLOW 96, to develop an automatic groundwater parameters identification system. The hydraulic conductivity and specific yield are the parameters to be calibrated in the system. Since the parameter value is automatic searched according the rules that are specified by modeler, it is efficient and the identified parameters value is more interpretable than that by optimized based approach. Beside, since the rules are easy to modify and adding, the system is flexible and can accumulate the expertise experiences. Several hypothesized cases were used to examine the system validity and capability. The result shows a good agreement between the identified and given parameter values and also demonstrates a great potential for extending the system to a fully function and practical field application system.
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Zhang, Xiaoqin. "Identification of model and grid parameters for incompressible turbulent flows." Doctoral thesis, 2007. http://hdl.handle.net/11858/00-1735-0000-0006-B39C-1.
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Tai, Chih-Hao, and 戴志豪. "The Identification of Structural Dynamic Parameters by Auto- Regressive Model." Thesis, 1997. http://ndltd.ncl.edu.tw/handle/08227556726875958047.
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碩士國立臺灣大學
造船工程學系
85
Abstract In this paper we develop an identification system of dynamical parameters, which are determined by the measured data from multiple I/O channels of structures. The modal parameters, natural frequency, damping ratio, mode shape and frequency response function (FRF) can be estimated by a Vector Auto-Regressive model (VAR model). The VAR simultaneous equations are set up in a time discrete state equations, which are consisted of measured points with q-time steps, in which q is the order of AR model. The classical modal testing approach based on fast Fourier transformation is used to compare the working procedure and the difference of results from both approaches. Finally we selected the identification of modal parameters for analysis of a numerical 3 dof numerical dynamic system and experiment of a cantilever beam as study cases. Results show that the VAR model has following advantages: (1)VAR model has better ability to filter out the noise. (2)The FRF curves from VAR model are more smooth. (3)The modal parameters determined from VAR model are in a more convenient way. (4)The calculated results from VAR model are more accurate.
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Lee, Min-Hsien, and 李旻憲. "Identification and Calibration of Complex Model Parameters via Multiple Performance Deviations." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/2maf8p.
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碩士國立臺灣大學
機械工程學研究所
106
Parameter uncertainty plays an important role in system performance and robustness. This research builds up a procedure for calibrating deviated parameters. However, there may be difficulties applying parameter calibration in complex system, namely (1) computation inefficiency due to a large number of parameters, (2) inaccuracy in parameter calibration, and (3) low confidence in calibration result. This research selects important parameters by main effect analysis and uses the neural network to calibrate parameters via performance deviation. After getting calibration results via different performance deviation, we use the decision tree to increase the accuracy of calibration and evaluate the result by applying confidence interval. The method is demonstrated in an engineering case: vehicle dynamic test, the minimum mean square error of calibration is 0.136%.
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Bo-WenLin and 林博文. "Validation of Model-based Identification Methods for Estimating Individual Hemodynamic Parameters." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/65003485109997737993.
Full textAbstract:
博士國立成功大學
航空太空工程學系
102
A reliable, non-invasive diagnostic tool for assessing cardiovascular characteristics and/or the connected end organ health state is still lacking. The present work aims at developing an identification procedure for estimating individual hemodynamic parameters based on a one-dimensional (1-D) tree-like vascular flow model. With the use of clinically available measurements, the proposed identification methods solve the hemodynamic inverse problem associated with the modeled vascular system, yielding the estimates of the unknown model parameters that are of clinical interest. For the present vascular diagnostic method, the arterial stiffness and stress-free lumen radius as well as the terminal lumped resistances and compliance that reflect the health state of the connected end organs were estimated. The present parameter estimation procedure uses measurable clinic data as system input and observation functions. Sensor data errors and measurement uncertainties are not considered. The measurements obtained at sites of interest are assumed noise-free and mutually compatible. The present identification procedure consists of a 1-D flow state estimator and a genetic parameter search algorithm, and thus both physical parameters and state estimation are included simultaneously in the identification procedure. Differential evolution (DE), a global genetic search algorithm, has been employed as the parameter optimizer. Parallel computing was applied to accelerate the speed of DE optimization. To cope with different data measurements obtained in vivo, identification methods that use pressure-flow rate (pq), pressure-velocity (pU), and diameter-velocity (DU) waveforms as system input/measurement pair were proposed and constructed. The present model-based identification algorithm was constructed and validated using a numerical 1-D hemodynamic simulation code which simulates pulsatile blood flow circulating in human arterial system with high-fidelity. In this simulation code, a high-resolution Roe’s scheme augmented by characteristics-based boundary condition treatments were developed to solve the complex wave reflection and re-reflection phenomena prevailing in the tree-like vascular network. Validations were performed on estimating regional vascular and terminal end-organ parameters, respectively, using both numerical and clinical data pairs to assess the feasibility and accuracy of the proposed identifier. The results show that all the three pq, pU and DU identification methods are accurate and feasible. For point-wise vascular diagnosis, the DU method has been particularly accurate, which may potentially extend the current usability of vascular ultrasonography onto a new horizon of evaluating local arterial stiffness non-invasively. For identifying individual parameters pertaining to a segmental arterial network of an arm, agreed hemodynamic waveforms reconstructed by the pq method were compared favorably to the in vivo measurements. Furthermore, the feasibility of identifying end-organ hemodynamic parameters using brachial (peripheral) pressure/wall distension waveforms was demonstrated. These preliminary successes indicate that, with the aid of model-based identification, a non-invasive, individual-based diagnosis of the organ health states using measurable observations at peripheral arteries is theoretically possible.
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Chang, Wei Chi, and 張韋棋. "Identification of system with friction and model parameters on multi-axis platform." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/57509818581109055139.
Full textAbstract:
碩士清雲科技大學
機械工程研究所
94
The multi-axis platform is a common mechanism in the servo mechanisms. Friction is an inevitable physical phenomenon present in mechanisms which produces undesirable behaviors in control systems such as position and tracking errors, and limit cycles. It also involves static, viscous, coulomb friction etc. The effects of system with friction are considered by the multi-axis platform. Then we develop a general estimation method for the identification of equivalent inertia and damping of systems with friction. Furthermore, the first and second order characteristics are going to be considered to estimate the parameters respectively by the experiment.
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Mulia, Andri, and 木安利. "Identification of Soil Constitutive Soil Model Parameters Using Multi-Objective Particle Swarming Optimization." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/t5v47r.
Full textAbstract:
碩士國立臺灣科技大學
營建工程系
100
This thesis presents a study that uses an evolutionary method called the particle swarming optimization (PSO) for identifying soil constitutive model parameters. Three constitutive models, namely Modified Cam-Clay (MCC), SClay-1, and MIT-S1, have been implemented in this study. These models have respectively 4, 6, and 16 parameters that need to be identified, giving increasing difficulty in the identification process. The identification is done using standard laboratory testing data and tries to minimize the difference between model calculations and measured data. This difference is defined by objective-function or fitness function. Furthermore, this thesis pursues the use of multi-objective optimization to deal with multiple testing data. It is a common practice to have multiple tests done on a soil in order to measure various properties of soils, and multiple tests can generate multiple evidences to help better identify parameters used in soil models. Finally, the algorithm chosen for optimization is PSO for its easiness of implementation and its effectiveness. Each implemented soil constitutive model, SO-PSO and MO-PSO are validated. Parameter identification of soil model parameters are presented and discussed in this thesis. In addition, a discussion regarding parameters controlling PSO, iteration count, particle number, and objective function selection is discussed in order to know their effect to PSO performance related to the parameters identification. Finally, a case-study for Taipei Silty Clay has been carried out to prove the developed procedure can be used successfully for real measured data.
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Zhang, Xiaoqin [Verfasser]. "Identification of model and grid parameters for incompressible turbulent flows / vorgelegt von Xiaoqin Zhang." 2007. http://d-nb.info/988352818/34.
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Chen, Yan-Ren, and 陳彥任. "Parameters Identification of Growth Model and Prediction of Production for Batch Culture of Rotifer." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/80576935131667611183.
Full textAbstract:
碩士國立臺灣大學
農業機械工程學系研究所
87
This thesis identified the parameters of growth model and predicted the production for the batch culture of rotifers. The growth rate of rotifers was modeled by a first-order linear stochastic model with the densities of rotifers carrying multiple, single or no egg as state variables. The parameters of the growth model for rotifers were estimated by real-time recursive least-squares (RLS) algorithm. Parameters were identified and production was predicted for the cases of time interval 1, 12, and 24 hours. The effects of forgetting factorsλwere also investigated. Better results were obtained with forgetting factorλbetween 0.97 and 1.00 in the cases of 1-hour time interval prediction. During the beginning and fore post-exponential phase, forgetting factorλranging between 0.97 and 1.00 was better in 12 or 24-hour time interval prediction. For more fluctuant cases such as processes throughout 4 phases, λ=0.91 to 0.93 was more adequate in 12-hour time interval andλ=0.91 in 24-hour time interval. Parameters obtained from the foregoing experiment could be applied to predict the result of another experiment. Prediction errors could remain between 4.42% and 11.47% within 96 hours.
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Liu, Jing-Yu, and 劉靖俞. "Identification of Instantaneous Model Parameters of A Time Varying Structure via Recursive Least Square Techniques." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/87348030627038004725.
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碩士國立交通大學
土木工程系所
97
This study applies various recursive least squares (RLS) algorithms to establish the time varying autoregressive with exogenous input (TVARX) model for a structure from its dynamic displacement responses and further estimates the instantaneous modal parameters of the structure from the time varying coefficients of TVARX model. The RLS algorithms under study include a forgetting factor approach, a Kalman filter approach and a weighted polynomial basis function expansion approach. The RLS algorithms under consideration are utilized to process numerically simulated responses of single-degree-of-freedom (SDOF) systems with different instantaneous natural frequencies and modal damping ratios. The advantages and shortcomings of these RLS algorithms are investigated through comprehensively studying the effects of main parameters in each approach on accurately identifying the instantaneous modal parameters of the SDOF systems. The parameters under investigation include the order of TVARX model, forgetting factor, control factor in Kalman filter, order of polynomial basis, and noise. It is found that the identified results obtained by the weighted polynomial basis function expansion approach are very sensitive to the values of forgetting factor. Although the instantaneous parameters are poorly identified by all the approaches considered herein in processing the noisy responses with 2% noise-to-signal ratio, the general trends of instantaneous modal parameters varying with time are reasonably found. The approaches under consideration are further applied to process measured dynamic displacement responses of a single-story RC frame and a three-story steel frame in shaking table tests. The specimens were damaged during testing. The identified trends of instantaneous modal parameters varying with time are consistent with the observed physical phenomena.
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Wang, Yun-Chih, and 王雲直. "Automatic Parameters Identification of Groundwater Model using Expert System - Case Study of Choshuihsi Alluvial Fan." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/93886479198334176424.
Full textAbstract:
碩士國立交通大學
土木工程學系
98
Conventional parameter identification for groundwater models can be classified into manual parameter identification and automatic parameter identification. Manual parameter identification requires manual decisions to define parameter values. The resulting parameter values can be interpreted, and this process is flexible. However, this method is time consuming and requires expert analysis. Conversely, automatic parameter identification is based on the optimization method, and is computationally efficient. This method represents concepts and experiences as objective functions and constraints. This correlation is complicated and abstract; the application of this method is often limited to complicated field problems. The computational loading of the optimization method increases significantly when the parameters dimension is large. Based on previous discussion, this study integrates a rule-based expert system and a groundwater simulation model, MODFLOW 2000, to develop an automatic groundwater parameter identification system. The proposed model has the manual identification advantages of interpretability and flexibility as and the automatic identification advantage of efficiency. To demonstrate the capability of solving a large field problem, this study proposes a model to identify the parameters for a simulation of the Choshuihsi Alluvial Fan. This study develops a steady state simulation model and estimates steady recharge rates. Results indicate that the total recharge of the Choshuihsi Alluvial Fan from rain and rivers is 1.241 billion metric tons, and its total pumping rate is 1.275 billion metric tons. These results are comparable to previous studies. Moreover, the spatial distribution of the pumping rate is consistent with the potential water use, or land use. An in-depth analysis shows that the upstream of the fan is the main recharge area, and affects the groundwater of whole alluvial fan. Hence, in the initial stages of identification, the system mainly modifies the parameters in the upstream area. Due to the interaction between upstream and midstream areas, the model required more iterations to obtain reasonable values for those areas. The downstream, coastal area has a Dirichlet boundary in the surface layer. The downstream aquiclude has greater coverage in lower layers, making it easier for the parameters to converge. This field case study demonstrates the feasibility and capability of the proposed model. The expert system is the kernel to modify the parameters. Therefore, the model can increase its parameter identification capacity by adding new rules to the system.
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Chien, Shao-Chun, and 簡劭純. "Determine the Optimal Model Parameters Using SRIM、SSI and RLS Methods on Structural System Identification." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/19096816303197345530.
Full textAbstract:
碩士國立臺灣大學
土木工程學研究所
96
System identification is a procedure to determine the system characteristics of structure and the parameters of mathematical model for structural mechanics from measured input and output data.. The purpose of this paper is to identify ways in various systems of unknown parameters required to seek a systematic planning,so that different users can have a detailed process and the definition of reference. Here, we introduced three identification methods, respectively are System Realization using Information Matrix (SRIM)、Stochastic Subspace Identification method(SSI) and Recursive Least Squares with ARX model (RLS), Were in accordance with the parameters in the way for a complete selection criteria, to modal physical parameters (natural frequency, damping ratio and the mode shape) as the basis for comparison between the methods. In order to verify the steps proposed in this paper to identify the feasibility and effectiveness, first of all, we choose a simulated three floors of the structure as a test and description. Application of this technology but also to all kinds of shaking table and the real test of the structure - the central Bai-shin building can have good results of the identification.
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Huang, Jun, and 黃俊. "Study on Polynomial Identification System Parameters Comparison of DC Servo Motor and Application of System Model Prediction." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/22082571826583998093.
Full textAbstract:
碩士健行科技大學
機械工程系碩士班
104
The study uses the polynomial identification system to explore transfer function of the DC servo motor system. The system is formed by DC servo motor and electronic circuits. The system use unit-impulse function for input signal to detect the motor rotor angular velocity. The parameters of the transfer function are estimated by the relationship between unit-impulse input and rotor angular velocity output. A polynomial predictor is connected with DC motor system to forecast output signal by MATLAB and Simulink software. The output signal of transfer function and predicted waveform are compared to verify actual system model.
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Xie, Chen. "Statistical Estimation of Two-Body Hydrodynamic Properties Using System Identification." 2009. http://hdl.handle.net/1969.1/ETD-TAMU-2009-08-7062.
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A basic understanding of the hydrodynamic response behavior of the two-body system is
important for a wide variety of offshore operations. This is a complex problem and
model tests can provide data that in turn can be used to retrieve key information
concerning the response characteristics of such systems. The current study demonstrates
that the analysis of these data using a combination of statistical tools and system
identification techniques can efficiently recover the main hydrodynamic parameters
useful in design.
The computation of the statistical parameters, spectral densities and coherence functions
provides an overview of the general response behavior of the system. The statistical
analysis also guides the selection of the nonlinear terms that will be used in the reverse
multi-input / single-output (R-MI/SO) system identification method in this study. With
appropriate linear and nonlinear terms included in the equation of motion, the R-MISO
technique is able to estimate the main hydrodynamic parameters that characterize the
offshore system. In the past, the R-MISO method was primarily applied to single body
systems, while in the current study a ship moored to a fixed barge was investigated. The formulation included frequency-dependant hydrodynamic parameters which were
evaluated from the experimental measurements. Several issues specific to this extension
were addressed including the computation load, the interpretation of the results and the
validation of the model. Only the most important cross-coupling terms were chosen to
be kept based on the estimation of their energy. It is shown that both the heading and the
loading condition can influence system motion behavior and that the impact of the wave
in the gap between the two vessels is important. The coherence was computed to verify
goodness-of-fit of the model, the results were overall satisfying.
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Bélaise, Colombe. "Estimation des forces musculaires du membre supérieur humain par optimisation dynamique en utilisant une méthode directe de tir multiple." Thèse, 2018. http://hdl.handle.net/1866/21856.
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