Thèses : « Object Modelling System »

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Garvey, Mary. « An object-oriented database system for geographic data modelling ». Thesis, University of Wolverhampton, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.413469.

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Underwood, Jason. « Integrating design and construction to improve constructability through an effective usage of it ». Thesis, University of Salford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308260.

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Hew, Ken Ping. « A knowledge-based electronic prototype system (KEPS) for building and services design integration ». Thesis, University of Reading, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.242336.

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de, la Vara González José Luis. « Business process-based requirements specification and object-oriented conceptual modelling of information systems ». Doctoral thesis, Universitat Politècnica de València, 2011. http://hdl.handle.net/10251/11445.

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Two of the main needs when developing an information system for an organization are that system analysts know and understand the application domain and that the system properly supports the business processes of the organization. Consequently, elicitation of system requirements from business process models has been acknowledged as a suitable activity to deal with that needs. In addition, system requirements must be linked to subsequent development stages. However, system analysts can face many challenges when performing these activities. They may have problems communicating with customer stakeholders and may need to analyse and operationalize the purpose of the information system. Furthermore, system analysts must bridge the gap between business and system domains for specification of system requirements, specify different types of system requirements and guarantee that their specification is precise, consistent and homogeneous. In relation to object-oriented conceptual modelling-based information system development, system analysts must also avoid potential problems that may arise when a conceptual schema is created from system requirements as part of their link with subsequent development stages. For example, a conceptual schema can be incomplete and/or inconsistent if it is not properly managed. As a solution, this thesis presents a methodological approach for business process-based requirements specification and object-oriented conceptual modelling of information systems. The approach consists of four stages: organizational modelling, purpose analysis, specification of system requirements and derivation of object-oriented diagrams. By following the design research methodology for performing research in information systems, the methodological approach has been designed on the basis of many existing ideas and principles in academia and industry and provides new principles, mechanisms and guidance to address the challenges presented above.
De La Vara González, JL. (2011). Business process-based requirements specification and object-oriented conceptual modelling of information systems [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/11445
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Poudel, Sabin. « Modelling of a Generic Aircraft Environmental Control System in Modelica ». Thesis, Linköpings universitet, Fluida och mekatroniska system, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-156675.

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This thesis documents the modelling of generic Environmental Control System(ECS) of an aircraft in Modelica by utilizing components from free version of theTTECCS (Technical Thermodynamic Environmental Control and Cooling Systems) library. In doing so, components used for developing ECS from the TTECCS library are mathematically verified with theoretical formula in MATLAB. Selected components are investigated with valid input data to initialize the simulation and verify its behaviors with corresponding available data. Hereinafter, the object-oriented modelling method is used to integrate ECS components to develop a functional system. The main function of ECS is to regulate the pressure and temperature inside the cabin to accepted physiology flight safetylevels. Different types of ECS architecture are presented in this document. An ECS developed here is based on the bootstrap system and consists only one cooling unit comprised with the source, pipes, two heat exchanger, compressor, turbine, temper-ature control valve, pressure control valve, and sinks. Dry air(Ideal gas) is used as a medium in the system. Temperature drop along each component corresponds to available A320 cruise flight data in order to calculate the top level parameter and to initialize the components, subsequently an ECS system. Several systematized methods for Object-oriented modelling and system design were studied and steps are extracted accordingly that suits to initiate the procedurefor this project, which is also presented. Time domain simulation is performed inModelica and Dymola. A simplified control system is built to regulate the system, therefore restrained it as a future work to develop real in-flight condition control system of an ECS.Top level parameters were selected within valid customized ranges for developing a performance map of the components. After generating the map, optimal data from the map were taken to initialize final ECS. The simulation results of the final model is then compared to A320 flight data which is comparable in behavior; this was expected. Above all, simulation environment Modelica and free version of TTECCS library components are reliable to develop ECS in order to investigate ECS components behavior and predict cabin conditions before developing a prototype.

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Hewings, D. B. « Probabilistic modelling of load and harmonic distortion in an A.C. traction system using an object-oriented approach ». Thesis, Swansea University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.637271.

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As a means of reducing over-design and gaining greater insight into the operation of dynamic systems, probabilistic methods have evolved as a extremely important design tool. This has been true of power system design in general over the past thirty years, and probabilistic methods are now used in the design of overhead line supports, fault-clearing plant and the assessment of load demands. However, the application of probabilistic methods to the design and analysis of traction power systems has been relatively limited. These systems involve not only the electrical characteristics of the power system, but also the mechanical aspects of an electric railway, and produce moving, frequently changing electrical loads. The electrical system itself is not easily analysed, since modern locomotives incorporate power electronic switching drives, conventionally analysed in the time domain, whilst the supply is analysed in the frequency domain. This study details the development of an object-oriented traction system model, which can incorporate both the time and frequency representations into a single integrated model. This integrated model is then used as the basis of investigation into the probabilistic characteristics of the electrical load and harmonic distortion produced by the traction system. The study shows that an object-oriented approach may be applied to switching-circuit analysis, and that a combined frequency- and time- domain analysis may be easily implemented with this type of system. The probabilistic simulations show for the first time that the load and harmonic characteristics of an a.c. traction system do not fit known parametric models, and are in fact highly dependent upon the operational characteristics of the traction system, e.g. route profile and timetable.

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Rudolph, Melanie M. « National freight transport planning : towards a Strategic Planning Extranet Decision Support System (SPEDSS) ». Thesis, Loughborough University, 1998. https://dspace.lboro.ac.uk/2134/7080.

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This thesis provides a `proof-of-concept' prototype and a design architecture for a Object Oriented (00) database towards the development of a Decision Support System (DSS) for the national freight transport planning problem. Both governments and industry require a Strategic Planning Extranet Decision Support System (SPEDSS) for their effective management of the national Freight Transport Networks (FTN). This thesis addresses the three key problems for the development of a SPEDSS to facilitate national strategic freight planning: 1) scope and scale of data available and required; 2) scope and scale of existing models; and 3) construction of the software. The research approach taken embodies systems thinking and includes the use of: Object Oriented Analysis and Design (OOA/D) for problem encapsulation and database design; artificial neural network (and proposed rule extraction) for knowledge acquisition of the United States FTN data set; and an iterative Object Oriented (00) software design for the development of a `proof-of-concept' prototype. The research findings demonstrate that an 00 approach along with the use of 00 methodologies and technologies coupled with artificial neural networks (ANNs) offers a robust and flexible methodology for the analysis of the FTN problem domain and the design architecture of an Extranet based SPEDSS. The objectives of this research were to: 1) identify and analyse current problems and proposed solutions facing industry and governments in strategic transportation planning; 2) determine the functional requirements of an FTN SPEDSS; 3) perform a feasibility analysis for building a FTN SPEDSS `proof-of-concept' prototype and (00) database design; 4) develop a methodology for a national `internet-enabled' SPEDSS model and database; 5) construct a `proof-of-concept' prototype for a SPEDSS encapsulating identified user requirements; 6) develop a methodology to resolve the issue of the scale of data and data knowledge acquisition which would act as the `intelligence' within a SPDSS; 7) implement the data methodology using Artificial Neural Networks (ANNs) towards the validation of it; and 8) make recommendations for national freight transportation strategic planning and further research required to fulfil the needs of governments and industry. This thesis includes: an 00 database design for encapsulation of the FTN; an `internet-enabled' Dynamic Modelling Methodology (DMM) for the virtual modelling of the FTNs; a Unified Modelling Language (UML) `proof-of-concept' prototype; and conclusions and recommendations for further collaborative research are identified.

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Baghaei, Nilufar. « A collaborative constraint-based intelligent system for learning object-oriented analysis and design using UML ». Thesis, University of Canterbury. Computer Science and Software Engineering, 2007. http://hdl.handle.net/10092/1204.

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Web-based collaborative learning is becoming an increasingly popular educational paradigm as more individuals who are geographically isolated seek higher education. As such students do not meet face to face with their peers and teachers, support for collaboration becomes extremely important. Successful collaboration means asking questions to gain a better understanding of the main concepts, elaborating and justifying opinions and sharing and explaining ideas. When group members' combined skills are sufficient to complete the learning task, effective group work can result in greater overall achievement than individual learning. Intelligent Tutoring Systems (ITS) have been shown to be highly effective at increasing students' performance and motivation. They achieve their intelligence by representing pedagogical decisions about how to teach as well as information about the learner. Constraint based tutors are a class of ITSs that use Constraint-based Modelling(CBM) to represent student and domain models. Proposed by Ohlsson, CBM is based on learning from performance errors, and focuses on correct knowledge. In this thesis, we present COLLECT-UML, a collaborative constraint-based ITS that teaches object-oriented analysis and design using Unified Modelling Language (UML). While teaching how to design UML class diagrams, COLLECT-UML also provides feedback on collaboration. Being a constraint-based tutor, COLLECT-UML represents the domain knowledge as a set of syntax and semantic constraints. However, it is the first system to also represent a higher-level skill such as collaboration using the same formalism. We started by developing a single-user ITS that supported students in learning UML class diagrams. The system was evaluated in a real classroom, and the results showed that students' performance increased significantly. We then extended the system to provide support for collaboration as well as domain-level support. The enhancement process included implementation of the shared workspace, modification of the pedagogical module to support groups of users, designing and implementing a group-modelling component, and developing a set of meta-constraints which are used to represent an ideal model of collaboration. The effectiveness of the system was evaluated in two studies. In addition to improved problem-solving skills, the participants both acquired declarative knowledge about effective collaboration and did collaborate more effectively. The participants enjoyed working with the system and found it a valuable asset to their learning. The results, therefore, show that CBM is an effective technique for modelling and supporting collaboration in computer-supported collaborative learning environments.

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Černiauskaitė, Agnė. « Aplinkos apsaugos inspekcijos informacinės sistemos posistemių projektavimas ir programinė realizacija ». Master's thesis, Lithuanian Academic Libraries Network (LABT), 2005. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2005~D_20050527_112439-60844.

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Nowadays the complexity and size of business systems is growing steadily and, as practise shows, the situation is not going to change in the nearest future. This necessitates difficulties not only for lifecycle of programmes’ development but for maintenance and expansibility also. That’s why, solving them, requires a broader perspective that views the system as consisting of other systems. This work looks what kind of methods can be applied in this context. The analysis of modern technologies (Java programming language) and modelling methods (functional decomposition and object-oriented system engineering) are presented. Suggested system decomposition approach is the synthesis of already existing ones. In this work new method has been applied for the development of experimental Information System of Territorial Departments of Environmental Inspection. The prototype of the mentioned system has been realized by using J2EE (Java 2, Enterprise Edition) technologies. Developed software implements the requirements for usage and maintenance (large number of the users, security rights, compatibility, centralised administration, etc.) of large distributed systems. Suggested approach may be used while expanding the existing software or developing similar applications.

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Liu, Quan. « Modélisation bayésienne des interactions multidimensionnelles dans un système complexe : application à la gestion des risques de crues ». Thesis, Toulouse, INPT, 2018. http://www.theses.fr/2018INPT0038/document.

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Le travail aborde la modélisation et l’analyse de systèmes complexes, caractérisés, dans un cadre incertain et évolutif, par de nombreuses interactions entre composants. Dans un cadre de gestion des risques, le travail vise à créer un modèle causal spatio-temporel pour l’explication et la probabilisation de certains événements redoutés à des fins de diagnostic et de pronostic. Le travail de modélisation est basé sur l’approche bayésienne et, plus particulièrement, sur les Réseaux Bayésiens (RB). Dans l’optique de considérer des systèmes de grande taille et de représenter leur complexité spatio-temporelle, leur caractère multiéchelles et incertain dans un cadre dynamique, l’idée de ce travail est alors d’étendre le concept des Réseaux Bayesiens Dynamiques (RBD) et d’utiliser le paradigme Orienté Objet pour l’appliquer aux réseaux bayésiens. Dans leur forme actuelle, les réseaux bayésiens orientés objet permettent de créer des instances réutilisables mais non instanciables. En d’autres termes, cela implique que l’objet généré est susceptible d’être appelé plusieurs fois dans la construction d’un modèle mais sans pour autant que ces paramètres (tables de probabilités marginales ou conditionnelles) ne soient modifiés. Ce travail de thèse vise à combler cette lacune en proposant une approche structurée permettant de construire des grands systèmes à base d’objets (caractérisés par des réseaux bayésiens simples) dont les paramètres peuvent être actualisés en fonction de l’instant ou du contexte de leur appel et de leur utilisation. Ce concept est concrétisé sous la forme de Réseaux Bayésiens Multidimensionnels par leur propension à combiner plusieurs dimensions qu’elles soient spatiales ou temporelles
The work addresses the modelling and analysis of complex systems, characterized, in an uncertain and evolving framework, by numerous interactions between components. Within a risk management framework, the work aims to create a spatio-temporal causal model for the explanation and probability of certain feared events for diagnostic and prognostic purposes. The modelling work is based on the Bayesian approach and, more specifically, on the Bayesian Networks (BN). In an attempt to consider large-scale systems and represent their spatio-temporal complexity, their multi-scale and uncertain character in a dynamic framework, the idea of this work is then to extend the concept of Dynamic Bayesian Networks (DBN) and use the Object Oriented paradigm to apply it to Bayesian networks. In their current form, object-oriented Bayesian networks can create reusable but not instantiable instances. In other words, this implies that the generated object is likely to be called several times in the construction of a model, but without these parameters (marginal or conditional probabilities tables) being modified. This thesis aims to fill this gap by proposing a structured approach to construct large object-based systems (characterized by simple Bayesian networks) whose parameters can be updated according to the moment or context of their call and use. This concept is embodied in the form of Bayesian Multidimensional Networks by their propensity to combine several dimensions, whether spatial or temporal

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Bakker, Harm. « Object-oriented modelling of information systems the INCA conceptual object model / ». Maastricht : Maastricht : Rijksuniversiteit Limburg ; University Library, Maastricht University [Host], 1995. http://arno.unimaas.nl/show.cgi?fid=6561.

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Jankowfsky, Sonja. « Compréhension et modélisation des processus hydrologique dans un petit bassin versant périurbain à l'aide d'une approche spatialisée orientée objet et modulaire. Application aux sous-basins de la chaudanne et du mercier (bassin de l'Yzeron, France) ». Phd thesis, Université de Grenoble, 2011. http://tel.archives-ouvertes.fr/tel-00721988.

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La densification actuelle de l'urbanisation conduit à un changement d'occupation du sol et du réseau de drainage en zone péri-urbaine. L'écoulement est concentré dans des fossés ou des réseaux d'assainissement et ainsi accéléré. Ces phénomènes peuvent avoir des conséquences importantes pour les nappes et les cours d'eau, comme par exemple l'aggravation des crues et des sécheresses et l'altération de la qualité chimique et/ou biologique du milieu. Sous la pression réglementaire (Directive Cadre Européenne sur l'Eau) et la demande sociale, les gestionnaires sont donc confrontés à des choix complexes en terme d'aménagement. Ainsi, il est nécessaire de mettre au point des méthodes et des modèles capables de quantifier l'impact de l'augmentation de l'urbanisation sur la vulnérabilité des hydro-systèmes péri-urbains. Dans ce travail, nous formulons l'hypothèse qu'une modélisation hydrologique spatialisée continue, prenant explicitement en compte les objets des paysages périurbains (parcelles urbaines, agricoles, forestières, haies,..) et les éléments déterminant les chemins de l'eau (topographie, mais aussi réseaux d'assainissement ou de routes) peut aider à comprendre et hiérarchiser le rôle des différents objets du paysage sur la réponse hydrologique. Pour ce faire, le modèle distribué PUMMA (Peri-Urban Model for landscape Management) adapté aux bassins versants péri-urbains, a été développé dans le cadre de cette thèse. Il consiste en une intégration du modèle existant URBS, décrivant des processus hydrologiques urbains à l'échelle d'une parcelle cadastrale, dans la plate-forme de modélisation LIQUID, qui contient déjà des modules représentants des processus hydrologiques en zone rurale. PUMMA a également été complété par de nouveaux modules simulant les déversoirs d'orage, les bassins de rétention et le transfert du ruissellement de surface. Le modèle suit une approche orientée objet dans laquelle le paysage est divisé en mailles irrégualières, correspondant aux parcelles cadastrales en zone urbaine et aux unités de réponse hydrologiques (HRUs) en zone rurale. Afin de pouvoir appliquer le modèle à l'échelle d'un bassin versant, des méthodes automatiques pour la préparation des données géographiques ont été mises au point. De plus, une méthode a été développée pour déterminer les contours de bassins versants péri-urbains, en distinguant les surfaces contributives de temps sec et humide. Le modèle a été appliqué au bassin versant de la Chaudanne, un sous-bassin de l'Yzeron, situé en zone péri-urbaine lyonnaise pour deux années en conditions contrastées (sèche et humide). Les paramètres du modèle ont été spécifiés à partir des observations disponibles et des données de la littérature. Les résultats montrent un comportement du modèle réaliste et une aptitude à représenter les comportements différents en période sèche et humide, en lien avec des degrés de saturation des sols différents, même si les pics de débits d'été sont en général surestimés. Différents tests de sensibilité sur certains processus/paramètres montrent l'importance des processus urbains sur la réponse hydrologique du bassin, comme en particulier la génération de ruissellement de surface par les surfaces imperméables et naturelles urbaines, le drainage de l'eau du sol par les réseaux d'assainissement et les connexions entre les îlots urbains et le réseau hydrographique naturel et artificiel. L'épaisseur des sols et la conductivité hydraulique à saturation latérale jouent aussi un rôle important sur la dynamique du débit de base. Nous montrons aussi le potentiel du modèle pour tester différents scenarii d'aménagement ou de gestion des eaux pluviales.

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Rogers, Paul. « Object-oriented modelling of flexible manufacturing cells ». Thesis, University of Cambridge, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.276540.

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Lavery, Eamonn. « Object oriented modelling and simulation of manufacturing systems ». Thesis, Queen's University Belfast, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361254.

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Ambrus, Rares. « Unsupervised construction of 4D semantic maps in a long-term autonomy scenario ». Doctoral thesis, KTH, Centrum för Autonoma System, CAS, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-215323.

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Robots are operating for longer times and collecting much more data than just a few years ago. In this setting we are interested in exploring ways of modeling the environment, segmenting out areas of interest and keeping track of the segmentations over time, with the purpose of building 4D models (i.e. space and time) of the relevant parts of the environment. Our approach relies on repeatedly observing the environment and creating local maps at specific locations. The first question we address is how to choose where to build these local maps. Traditionally, an operator defines a set of waypoints on a pre-built map of the environment which the robot visits autonomously. Instead, we propose a method to automatically extract semantically meaningful regions from a point cloud representation of the environment. The resulting segmentation is purely geometric, and in the context of mobile robots operating in human environments, the semantic label associated with each segment (i.e. kitchen, office) can be of interest for a variety of applications. We therefore also look at how to obtain per-pixel semantic labels given the geometric segmentation, by fusing probabilistic distributions over scene and object types in a Conditional Random Field. For most robotic systems, the elements of interest in the environment are the ones which exhibit some dynamic properties (such as people, chairs, cups, etc.), and the ability to detect and segment such elements provides a very useful initial segmentation of the scene. We propose a method to iteratively build a static map from observations of the same scene acquired at different points in time. Dynamic elements are obtained by computing the difference between the static map and new observations. We address the problem of clustering together dynamic elements which correspond to the same physical object, observed at different points in time and in significantly different circumstances. To address some of the inherent limitations in the sensors used, we autonomously plan, navigate around and obtain additional views of the segmented dynamic elements. We look at methods of fusing the additional data and we show that both a combined point cloud model and a fused mesh representation can be used to more robustly recognize the dynamic object in future observations. In the case of the mesh representation, we also show how a Convolutional Neural Network can be trained for recognition by using mesh renderings. Finally, we present a number of methods to analyse the data acquired by the mobile robot autonomously and over extended time periods. First, we look at how the dynamic segmentations can be used to derive a probabilistic prior which can be used in the mapping process to further improve and reinforce the segmentation accuracy. We also investigate how to leverage spatial-temporal constraints in order to cluster dynamic elements observed at different points in time and under different circumstances. We show that by making a few simple assumptions we can increase the clustering accuracy even when the object appearance varies significantly between observations. The result of the clustering is a spatial-temporal footprint of the dynamic object, defining an area where the object is likely to be observed spatially as well as a set of time stamps corresponding to when the object was previously observed. Using this data, predictive models can be created and used to infer future times when the object is more likely to be observed. In an object search scenario, this model can be used to decrease the search time when looking for specific objects.

QC 20171009

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Bofakos, Petros. « An object-oriented approach to geo-referenced data modelling ». Thesis, Keele University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386632.

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Tubini, Niccolò. « Theoretical and numerical tools for studying the Critical Zone from plot to catchments ». Doctoral thesis, Università degli studi di Trento, 2021. http://hdl.handle.net/11572/319821.

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After the seminal works by Freeze and Harlan (1969), the scientific community realized that groundwater and vadose zone equation were breaking up. Hydrologists split into three communities following the motto “you are my boundary condition”: groundwater people, vadose zone scientists and surface water hydrologists. This compartmentalization of the scientific community fostered a deepening of knowledge in single branches, allowing to break things down into simple parts. However, this division represented an obstacle to the comprehension of the complexity that characterises the interactions between them. Eventually, this separation of the communities continued into software code. As a matter of fact, the boundary conditions were hard-wired, but they offered a poor representation of the physics in the interaction between different domains. Recently, there has been a renewed interest in studying the big picture, the interactions between different domains. This it is evident in the development of a new research field named the Earth’s Critical Zone (CZ). It is defined as the “ heterogeneous, near surface environment in which complex interactions involving rock, soil, water, air, and living organism regulate the natural habitat and determine the availability of life-sustaining resources” (National Research Council, 2001). Further interest in the studying the CZ is given by the ever-increasing pressure due to the growth in human population, wealth, and climatic changes. This thesis focuses on the CZ while recognising the central role of having a solid set of tools for modeling the water movements in all conditions. Recently, Prentice et al. (2015) identified Reliable, Robust, and Realistic, the three R’s, as the three characteristics that numerical models should have. Soil moisture is one of the key components to simulate the processes in the critical zone. The governing equation to describe the water flow in a porous material is know as the Richards equation and it dates back to 1931.The numerical solution of the Richards equation is far from trivial because of its mildly nonlinearity and it is often discarded in favour of more empirical models. After the pioneering work by Celia et al. (1990), a lot of work has been done in this direction and several model, for instance Hydrus, GEOtop, Cathy, Parflow adopted variants of the Newton algorithm to allows global convergence. Since Casulli and Zanolli (2010), anticipated by Brugnano and Casulli (2008), a new method called nested Newton has been found to guarantee convergence in any situation, even under the use of large time steps and grid sizes. The research presented in this thesis used this integration algorithm. Besides the numerical aspect, another issue was the correct definition of the boundary condition at the soil surface. As a matter of fact, the definition of the surface boundary condition is necessary to capture the generation of surface run-off. In the literature several approaches were proposed to couple surface and subsurface flow, and in this work the approach presented by Gugole (2016) has been used. The novelty regarded the discretization of the shallow water equation and the Richards equation in an unique algebraic system that was solved in a conservative manner. Richards equation was criticized from many points of view, but it is difficult to criticize its core mass conservation. The definition of the hydraulic properties of the soil, including both the soil water retention function (SWRC) and the hydraulic conductivity models, often uses simplified representation of the pore system describing it as bundle of cylindrical capillaries where the largest ones drain first and are filled last. As pointed out by Bachmann et al. (2002), “physical effects, like surface water film adsorption, capillary condensation and surface flow in liquid films, as well as volumetric changes of the pore space are often ignored”. Thus, the capillary bundle concept is a rough, even if still useful approximation of soil reality. From these observations, during the research the code has been designed to offer the opportunity to easily implement new soil water hydraulic models that might be proposed in the future. The Richards’ equation alone is not anymore sufficient to model the water flow in soils. In fact, soil temperature affects the water flow in soils. This is evident in cold regions where soil water is subject to freezing and thawing processes, but also in unfrozen soil, where temperature modifies water properties such as viscosity, the surface tension, and the contact angle. These microscopic variations of the water physical properties have significant impacts in the mass and energy budget within the CZ. For instance, it has been observed that the infiltration rates between the stream and the vadose zone show a clear diurnal pattern: infiltration rates are highest in late afternoon, when stream temperature is greatest, and they are lowest in early morning when stream temperature is least. In cold regions the run-off production is strongly affected by the presence of ice with the soil. Nonetheless, soil moisture modifies the thermal properties of the soil: water is characterised by a high thermal inertia and the thermal conductivity of ice is almost four times larger than that of liquid water, and water flow carries a significant amount of sensible heat. These aspects come under one the R of realistic. Hence, the Richards’ equation has been coupled with the energy equation for the unfrozen case. Moreover, the research developed a model to study the heat transfer considering the phase change of water. In both cases robust numerical schemes have been used. There are few models that already coupled the equations. One of these models is GEOtop that was conceived and built in the research group where this work was carried out. Such models have some limitations. One of the main limitations regards their implementations. In fact, these models were built as a monolithic code and this turns in difficulties in maintaining and developing existing codes. In this work the codes have been developed by using Design Patterns. As a result, the codes are easy to maintain, to extend, and to reuse. Considering the CZ, these aspects are of crucial importance. Researchers should have a model that can be extended to include more processes, i.e. increase its complexity and avoiding the code to become too complicated. The models were integrated in the Object Modelling System v3 (OMS3) framework. The system provides various components for precipitation treatment, radiation estimation in complex terrain, evaporation and transpiration that can be connected to each other’s for generating inputs and outputs. Due to the modularity of the system, whilst the components were developed and can be enhanced independently, they can be seamlessly used at run time by connecting them with the OMS3 DSL language based on Groovy. OMS3 provides the basic services and, among them, tools for calibration and implicit parallelization of component runs. In sum, the thesis analyses the relevant literature to date. It presents a detailed description of the physical processes related to the water flow and the energy budget within the soil. Then, it describes the numerical method used to solve and coupled the equations. It also provides the informatics behind WHETGEO 1D (Water HEat Tracers in GEOframe). Finally, the work focuses on the WHETGEO extension for the bidimensional case by showing how the code can be designed to store grid information.

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Adamu, Abdul T. « Object modelling of temporal changes in Geographical Information Systems ». Thesis, Kingston University, 2003. http://eprints.kingston.ac.uk/20707/.

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Changes in current temporally enabled GIS systems, thàt have been successfully implemented, are based on the snapshot approach which consist of sequences of discrete images. This approach does not allow either the pattern of changes to be shown or the complexities within the changes to be examined. Also the existing GIS database models cannot represent effectively the history of geographical phenomena. The aim of this research is to develop an object-oriented GIS model (OOGIS) that will represent detailed changes of geographical objects and track the evolution of objects. The detailed changes include spatial, thematic, temporal, events and processes that are involved in the changes. Those have been addressed, but not implemented, by a number of previous GIS projects. Object tracking and evolution includes not only attributes changes to homogenous objects, but also major changes that lead to transforming/destroying existing objects and creating new ones. This will allow the pattern of changes of - geographical phenomena to be examined by tracking the evolution of geographical objects. The OOGIS model was designed using an object-oriented visual modelling tool and was implemented using an object-oriented programming environment (OOPE), an object-oriented database system (OODBS). The visual modelling tool for designing the OOGIS model was Unified Modelling Language (UML), OOPE for implementing the OOGIS model was Microsoft Visual C++ and the OODBS was Objectivity/DB. The prototype of the investigation has been successfully implemented using a Case Study of Royal Borough of Kingston-Upon-Thames, in the United Kingdom. This research is addressing in particular the deficiencies in two existing GIS models that are related to this work. The fust model, the triad model, represents the spatial, thematic and temporal but fails to represent events and processes connected to the changes. The second model, the event-oriented model, though it represents the events (or processes) related to the changes, it stores the changes as attributes of the object. This model is.limited to temporal stable (static) changes and can not be applied to the evolution of geographical phenomena or changes that involve several objects sharing common . .propertíes and temporal relationships. Moreover, the model does not take into account the evolution (e.g. splitting, transformation etc) of a specific object which can involve more than changes to its attributes. Both models are not able to tackle, for instance, in situation when an object such as a park is disappearing to make way for new objects (i.e. roads and new buildings) or in situation where an agriculture piece of land becomes an industrial lot or village becomes a city. In this work the construction of a new approach which overcomes these deficiencies is presented. Also the approach take into account associations and relationships between objects such as inheritance which would be reflected in the object oriented database. For example a road can be regarded a base class from which other classes can be derived such as motorways, streets, dual roads etc which might reflect the evolution of objects ,in non-homogenous ways. The object versioning technique in this work will allow the versions of a geographical object to be related, thereby creating temporal relationships between them. It requires less data storage, since only the changes are recorded. The association between the versions allows continuous forward and backward movement within the versions, and promotes optimum query mechanisms.

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Anderson, Alison Mary. « The object-oriented modelling of information systems security risk ». Thesis, Queensland University of Technology, 1997.

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20

Harris, S. J. « A graph-based framework for dynamic process systems modelling ». Thesis, University of Newcastle Upon Tyne, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263127.

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Dupuy-Chessa, Sophie. « Couplage de notations semi-formelles et formelles pour la spécification des systèmes d'information ». Université Joseph Fourier (Grenoble), 2000. http://tel.archives-ouvertes.fr/tel-00006742.

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Les notations semi-formelles et formelles semblant complémentaires, leur couplage semble un cadre intéressant pour pouvoir bénéficier de leurs avantages respectifs tout en diminuant leurs points faibles. En effet, d'une part, les notations semi-formelles qui pêchent par leur précision sont de bons vecteurs de communication dont le coût de formation est raisonnable ; d'autre part, les langages formels apportent la précision et le potentiel de raisonnement manquant aux notations semi-formelles. Dans ce travail, nous proposons une approche de traduction de modèles semi-formels objet en des spécifications formelles en Z ou en Object-Z afin de fournir un couplage bénéfique de ces deux types de spécifications. Nous cherchons à rendre nos propositions les plus utilisables possible en en montrant trois bénéfices avérés : un guide méthodologique pour l'expression des contraintes annotant un modèle objet, une aide à la vérification des modèles et de leurs contraintes et des raisonnements informels sur la sémantique de modèles simples. Nous avons aussi développé un outil de support à notre approche, RoZ qui permet de faire cohabiter les notations semi-formelles et formelles. Enfin nous étudions une autre approche de couplage, la vérification de cohérence par méta-modélisation pour laquelle nous proposons des règles de cohérence entre le modèle objet et Z. Ce travail nous permet de comparer cette approche avec notre stratégie de traduction afin de mieux comprendre leurs avantages et leurs inconvénients
Semi-formal and formal notations being complementary, their joint use could define an interesting framework in order to take advantage of their good points by reducing their drawbacks. On the one hand, semi-formal notations which are imprecise are good communication vectors with affordable training cost ; on the other hand, formal languages bring precision and their reasoning abilities which miss to semi-formal notations. In this work, we propose a translation approach from semi-formal object models to formal specifications in Z and Object-Z so as to offer a powerful integration of these two kinds of specifications. We want to make our proposals the most useful possible by showing three established advantages : a methodological guidance to express constraints annotating an object model ; an help to check the models and their constraints and informal reasoning about the semantics of simple models. We also have developed a tool, RoZ that supports our approach by making semi-formal and formal notations live together. Finally, we study another integration approach, the consistency checking by meta-modelling for which we propose consistency rules between the object model and Z. This work enables us to compare this approach with our translation strategy to understand their advantages and drawbacks

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Tripathy, Shakti Ranjan. « A study of the modelling and storage of objects for materials selection ». Thesis, Queen's University Belfast, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359127.

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Münch, Manfred. « Generic modelling with graph rewriting systems paramateric polymorphism and object-oriented modelling with Progress / ». [S.l.] : [s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=970711239.

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Yi, Choong-ho. « Modelling object-oriented dynamic systems using a logic-based framework / ». Linköping : Univ, 2002. http://www.bibl.liu.se/liupubl/disp/disp2002/tek774s.pdf.

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Goldsworthy, David Richard. « An object oriented approach to the modelling of parallel systems ». Thesis, University of Reading, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.280461.

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Hollands, Robin. « Modelling and visualisation of systems with mixed-mode dynamics ». Thesis, University of Sheffield, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319415.

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Retonda-Modiya, John-Charly. « Development of an embedded system actuator node for intergration into an IEC 61850 based substation automation application ». Thesis, Cape Peninsula University of Technology, 2012. http://hdl.handle.net/20.500.11838/1162.

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Thesis submitted in fulfilment of the requirements for the degree Master of Technology: Electrical Engineering in the Faculty of Engineering at the Cape Peninsula University of Technology, 2012
The introduction of the IEC 61850 standard in substations for communication networks and systems by the International Electrotechnical Commission (IEC) in 2003 provided the possibility for communication between devices of different manufacturers. However, the advent of this standard also brought about many challenges associated with it. The challenges introduced by this fairly recent standard of communications in Substation Automation Systems (SAS), and the need for the development of cost effective IEC 61850- compliant devices, motivated the decision of the Centre for Substation and Energy Management Systems within the Electrical Engineering Department of the Cape Peninsula University of Technology to focus on the implementation of the IEC 61850 standard using an embedded hardware platform. The development of an IEC 61850 embedded application requires substantial knowledge in multiple domains such as data networking, software modelling and development of Intelligent Electronic Devices (IEDs), protection of the electrical system, system simulation and testing methods, etc. Currently knowledge about the implementation of the IEC 61850 standard usually resides with vendors and is not in the public domain. The IEC 61850 standard allows for two groups of communication services between entities within the substation automation system. One group utilizes a client-server model accommodating services such as Reporting and Remote Switching. The second group utilizes a peer-to-peer model for Generic Substation Event (GSE) services associated with time-critical activities such as fast and reliable communication between Intelligent Electronic Devices (IEDs) used for protection of the power network. The messages associated with the GSE services are the Generic Object Oriented Substation Event (GOOSE) messages. The use of GOOSE messages for protection of the electrical system is very important in modern substations. Detailed knowledge of the structure of these messages is important in instances requiring fault diagnosis to determine the cause of mal– operation or to address interoperability concerns or when developing custom IEC 61850- compliant devices with limited functionality. A practical protection application (overcurrent) case study is presented where GOOSE messages are exchanged between a commercial IED and an IEC 61850-compliant controller based on an embedded platform. The basic data model and software development of an actuator node for a circuit breaker is proposed using an IEC 61850 communication stack on an embedded platform. The performance of the GOOSE messages is confirmed to be as per the functional behaviour specified, and per the IEC 68150 standard in terms of the temporal behaviour required. This thesis document tables the methods, software programs, hardware interfacing and system integration techniques that allow for the development and implementation of a low cost IEC 61850-compliant controller unit on an embedded systems platform for the substation automation system. The overcurrent case study distributed between a commercial IED (SIEMENS Siprotec device) and the actuator application developed on an embedded platform for this project (DK60 board) is in compliance with the IEC 61850 standard and utilizing GOOSE messaging is successfully completed both in terms of functional and temporal behaviour. This novel research work contributes not only to the academic community, but to the international Power Systems community as a whole. Keywords: IEC 61850 standard, IEDs, GOOSE message, software modelling, software development, substation automation systems, communication stack, embedded systems, actuator.

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Konstas, Nikolaos-Kyriakos. « Object oriented petri net modelling and analysis of large production systems ». Thesis, University of Sussex, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.298734.

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Millham, Richard C. « Evolution of batch-oriented COBOL systems into object-oriented systems through unified modelling language ». Thesis, De Montfort University, 2006. http://hdl.handle.net/2086/4961.

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Throughout the world, there are many legacy systems that fulfil critical business functions but often require new functionality to comply with new business rules or require redeployment to another platform. Legacy systems vary tremendously in size, functionality, type (such as batch-oriented or real-time), programming language source code, and many other factors. Furthermore, many of these legacy systems have missing or obsolete documentation which makes it difficult for developers to re-develop the system to meet any new functionality. Moreover, the high cost of whole scale redevelopment and high switchover costs preclude any replacement systems for these legacy systems. Reengineering is often proposed as a solution to this dilemma of high re-development and switchover costs. However, reengineering a legacy system often entails restructuring and re-documenting a system. Once these restructuring and re-documentation processes have been completed, the developers are better able to redevelop the parts of the systems that are required to meet any new functionality. This thesis introduces a number of methods to restructure a procedurally-structured, batch-oriented COBOL system into an object-oriented, event-driven system through the use of an intermediate mathematical language, the Wide Spectrum Language (WSL), using system source code as the only documentation artefact. This restructuring process is accomplished through the application of several algorithms of object identification, independent task evaluation, and event identification that are provided in the thesis. Once these transformations are complete, method(s) are specified to extract a series of UML diagrams from this code in order to provide documentation of this system. This thesis outlines which of the UML diagrams, as specified in the UML Specifications version 1.5, can be extracted using the specified methods and under what conditions this extraction, using system source code only, can occur in a batch-oriented system. These UML diagrams are first expressed through a WSL-UML notation; a notation which follows the semantics and structure of UML Specifications version 1.5 in order to ensure compatibility with UML but is written as an extension of WSL in order to enable WSL to represent abstract modelling concepts and diagrams. This WSL-UML notation is then imported into a visual UML diagramming tool for the generation of UML diagrams to represent this system. The variety of legacy systems precludes any universal approach to reengineering. Even if a legacy system shares a common programming language, such as COBOL, the large number of COBOL constructs and the huge number of possible dialects prevents any universal translator of the original program code to another. It is hoped that by focusing on one particular type of legacy system with constraints, in this case a batch-oriented COBOL system with its source code its only surviving artefact, and by providing validated algorithms to restructure and re-document these legacy systems in the Unified Modelling Language, an industry system modelling standard, and by determining which of these Unified Modelling Language can be extracted practically from such a system, some of the parameters and uncertainties, such as program understanding of an undocumented system, in reengineering this type of system can be reduced.

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Watson, Christopher. « Requirements-driven modelling as a means of controlling change in object-oriented systems ». Thesis, University of Hull, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342868.

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Ahranjani, Nayrah Khandani. « Modelling of a Suspended Floc in Wastewater Treatment Systems using Object-Oriented Programming ». Thesis, University of Newcastle Upon Tyne, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.519487.

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Johansen, Valdemar. « Object serialization vs relational data modelling in Apache Cassandra : a performance evaluation ». Thesis, Blekinge Tekniska Högskola, Institutionen för datalogi och datorsystemteknik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-10391.

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Context. In newer database solutions designed for large-scale, cloud-based services, database performance is of particular concern as these services face scalability challenges due to I/O bottlenecks. These issues can be alleviated through various data model optimizations that reduce I/O loads. Object serialization is one such approach. Objectives. This study investigates the performance of serialization using the Apache Avro library in the Cassandra database. Two different serialized data models are compared with a traditional relational database model. Methods. This study uses an experimental approach that compares read and write latency using Twitter data in JSON format. Results. Avro serialization is found to improve performance. However, the extent of the performance benefit is found to be highly dependent on the serialization granularity defined by the data model. Conclusions. The study concludes that developers seeking to improve database throughput in Cassandra through serialization should prioritize data model optimization as serialization by itself will not outperform relational modelling in all use cases. The study also recommends that further work is done to investigate additional use cases, as there are potential performance issues with serialization that are not covered in this study.

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Lu, Tung-Wu. « Geometric and mechanical modelling of the human locomotor system ». Thesis, University of Oxford, 1997. https://ora.ox.ac.uk/objects/uuid:789d619c-f32e-4efa-9935-6ec8ce82ece4.

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A critical review of studies related to the modelling of the human locomotor system is given. Kinematic and dynamic modelling and analysis of the pelvis-leg apparatus as an ensemble of four rigid body segments are described. Experiments were performed on two patients with custom-made instrumented massive proximal femoral prostheses implanted after tumour resection. Telemetered axial forces transmitted along the prostheses, together with kinematic, force plate and electromyographic data, were recorded synchronously during level walking, single and double leg stance, and isometric tests of the hip muscles. A sagittal plane model of the locomotor system, with an anatomical model of the knee joint, was developed from an existing model and used for a comparative study of methods for the calculation of the internal forces. A three-dimensional computer graphics-based animated model of the locomotor system was developed, with the hip as a ball-and-socket joint, the knee as a parallel spatial mechanism and the ankle as a two-hinge complex. Thirty-four muscles or muscle groups were included. A method for the determination of the orientation of multi-joint systems from surface markers was developed to take account of measurement errors including skin movement artefacts. Both the 2D and 3D models of the locomotor system were evaluated and validated quantitatively with the telemetered femoral axial forces. It is concluded that (a) a significant part of the bending moments along limbs are transmitted by a combination of tensile forces in muscles and compressive forces in bones so that moments transmitted by the bones are much less than the limb moments, (b) bi-articular muscles play a major role in modulating forces in bones, (c) appropriate simulation of muscle forces is important in experimental or theoretical studies of load transmission along bones, (d) computer graphics-based modelling and animation are important tools in bridging the gap between clinical users and biomechanists.

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Franz, Benjamin. « Recent modelling frameworks for systems of interacting particles ». Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:ac76d159-4cdd-40c9-b378-6ea1faf48aed.

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In this thesis we study three different modelling frameworks for biological systems of dispersal and combinations thereof. The three frameworks involved are individual-based models, group-level models in the form of partial differential equations (PDEs) and robot swarms. In the first two chapters of the thesis, we present ways of coupling individual based models with PDEs in so-called hybrid models, with the aim of achieving improved performance of simulations. Two classes of such hybrid models are discussed that allow an efficient simulation of multi-species systems of dispersal with reactions, but involve individual resolution for certain species and in certain parts of a computational domain if desired. We generally consider two types of example systems: bacterial chemotaxis and reaction-diffusion systems, and present results in the respective application area as well as general methods. The third chapter of this thesis introduces swarm robotic experiments as an additional tool to study systems of dispersal. In general, those experiments can be used to mimic animal behaviour and to study the impact of local interactions on the group-level dynamics. We concentrate on a target finding problem for groups of robots. We present how PDE descriptions can be adjusted to incorporate the finite turning times observed in the robotic system and that the adjusted models match well with experimental data. In the fourth and last chapter, we consider interactions between robots in the form of hard-sphere collisions and again derive adjusted PDE descriptions. We show that collisions have a significant impact on the speed with which the group spreads across a domain. Throughout these two chapters, we apply a combination of experiments, individual-based simulations and PDE descriptions to improve our understanding of interactions in systems of dispersal.

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Rata, Scott. « Mathematical modelling of mitotic controls ». Thesis, University of Oxford, 2018. https://ora.ox.ac.uk/objects/uuid:7bef862c-2025-4494-a2bb-4fe93584d92a.

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The mitotic cell cycle is fundamental to eukaryotic life. In mitosis, replicated chromosomes are segregated to form two new nuclei. This is essential to ensure the maintenance of chromosome number between parent and daughter cells. In higher eukaryotes, numerous cytological changes occur to facilitate the separation of the genetic material: the nuclear envelope breaks down, the mitotic spindle assembles, and the cell rounds-up. There is a well-conserved control network that regulates these processes to bring about the entry into mitosis, the separation of the genetic material, and the reversal of these processes during mitotic exit. To build a coherent model of these regulatory networks requires us to write the biochemical reactions in mathematical form. The work in this Thesis pertains to three fundamental switches: entry into mitosis, the metaphase-to-anaphase transition, and exit from mitosis. I present three studies from a systems-level perspective. The first investigates a novel bistable mechanism controlling mitotic entry/exit in vitro using purified proteins. Dephosphorylation of Greatwall kinase by the phosphatase PP2A-B55 creates a double negative feedback loop that gives a bistable system response with respect to cyclin-dependent kinase 1 (Cdk1) activity. The second looks at hysteresis between mitotic entry and mitotic exit in HeLa cells. Hysteresis persists when either of the regulatory loops of Cdk1 or its counter-acting phosphatase PP2A-B55 is removed, but is diminished when they are both removed. Finally, the regulation of separase in the metaphase-to-anaphase transition is analysed. Separase that is liberated from securin inhibition is isomerised by Pin1 into a conformation that can bind to cyclin B1. This binding peaks after separase has cleaved cohesin and initiated anaphase.

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Al-Rowaihi, Salem F. K. « An object-oriented approach to the modelling of real-time computer systems and communication protocols ». Thesis, Cardiff Metropolitan University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.304801.

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Pitcher, Ashley Brooke. « Mathematical modelling and optimal control of constrained systems ». Thesis, University of Oxford, 2009. http://ora.ox.ac.uk/objects/uuid:044a26ab-99dc-4b34-b4a3-04e5c0d61ba0.

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This thesis is concerned with mathematical modelling and optimal control of constrained systems. Each of the systems under consideration is a system that can be controlled by one of the variables, and this control is subject to constraints. First, we consider middle-distance running where a runner's horizontal propulsive force is the control which is constrained to be within a given range. Middle-distance running is typically a strategy-intensive race as slipstreaming effects come into play since speeds are still relatively fast and runners can leave their starting lane. We formulate a two-runner coupled model and determine optimal strategies using optimal control theory. Second, we consider two applications of control systems with delay related to R&D expenditure. The first of these applications relates to the defence industry. The second relates to the pharmaceutical industry. Both applications are characterised by a long delay between initial investment in R&D and seeing the benefits of R&D realised. We formulate models tailored to each application and use optimal control theory to determine the optimal proportion of available funds to invest in R&D over a given time horizon. Third, we consider a mathematical model of urban burglary based on the Short model. We make some modifications to this model including the addition of deterrence due to police officer presence. Police officer density is the control variable, which is constrained due to a finite number of police officers. We look at different control strategies for the police and their effect on burglary hot-spot formation.

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Tran, Martino. « Modelling innovation diffusion in complex energy-transport systems ». Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:30ab651b-7c5a-4a4b-a905-6d86b5507042.

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Global sustainable energy and environmental policies have increased the need to understand how new energy innovations diffuse into the market. The transport sector is currently a major source of unsustainable energy use contributing ~20-25% global CO2 emissions. Although the potential benefits of alternative fuel vehicle (AFV) technologies to reduce CO2 emissions and fossil fuel dependency have been demonstrated, many uncertainties exist in their market diffusion. It is also not well understood how policy can influence rapid diffusion of AFVs. To transition to a more sustainable energy-transport system, we need to understand the market conditions and factors necessary for triggering widespread adoption of new energy innovations such as AFVs. Modelling the diffusion of innovations is one way to explain why some ideas and technologies spread through society successfully, while others do not. These diffusion processes are characterized by non-linear interactions between heterogeneous agents in complex networked systems. Diffusion theory has typically been applied to consumer durable goods but has found less application to new energy and environmental innovations. There is much scope for advanced diffusion methods to inform energy policy. This depends upon understanding how consumer behaviour and technologies interact and can influence each other over time. There is also need to understand the underlying mechanisms that influence adoption behaviour among heterogeneous agents. This thesis tackles the above issues using a combination of empirical data analysis, scenarios, and simulation modelling as follows: 1) We first develop the empirical basis for assessing innovation diffusion from a technology-behavioural perspective, where we explicitly account for interactions between consumer preferences and technological performance across different spatial and temporal scales; 2) Scenarios are then used to disaggregate consumer markets and analyze the technological and behavioural factors that might trigger large-scale adoption of AFVs; 3) We then case-analyze the UK transport sector and develop a model of the dynamics between how vehicle technologies and consumer preferences can change and influence the diffusion process; 4) Finally, we develop exploratory simulations to assess how social network effects can influence individual adoption behaviour; 5) We close with policy implications of our findings, contributions and limitations of the thesis, and possible avenues for taking the research forward.

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Boughton, Nicholas J. « Modelling manufacturing planning and control systems : the application of object-oriented principles and discrete-event simulation ». Thesis, Aston University, 1995. http://publications.aston.ac.uk/15285/.

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This thesis argues that the fit between the planning and control system and the manufacturing organisation is a crucial element of success. The design of appropriate control systems is, therefore, important. The different approaches to the design of manufacturing planning and control systems are investigated. It is concluded that there is no provision within these design methodologies to properly assess the impact of a proposed design on the manufacturing facility. Consequently, an understanding of how a new (or modified) planning and control system will perform in the context of the complete manufacturing system is unlikely to be gained until after the system has been implemented and is running. There are many modelling techniques available, however discrete-event simulation is unique in its ability to model the complex dynamics inherent in manufacturing systems, of which the planning and control system is an integral component. The existing application of simulation to manufacturing control system issues is limited: although operational issues are addressed, application to the more fundamental design of control systems is rarely, if at all, considered. The lack of a suitable simulation-based modelling tool does not help matters. The requirements of a simulation tool capable of modelling a host of different planning and control systems is presented. It is argued that only through the application of object-oriented principles can these extensive requirements be achieved. This thesis reports on the development of an extensible class library called WBS/Control, which is based on object-oriented principles and discrete-event simulation. The functionality, both current and future, offered by WBS/Control means that different planning and control systems can be modelled: not only the more standard implementations but also hybrid systems and new designs. The flexibility implicit in the development of WBS/Control supports its application to design and operational issues. WBS/Control wholly integrates with an existing manufacturing simulator to provide a more complete modelling environment.

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Jin, Lei. « Particle systems and SPDEs with application to credit modelling ». Thesis, University of Oxford, 2010. http://ora.ox.ac.uk/objects/uuid:07b29609-6941-4aa9-b4bc-29e7b4821b82.

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Turnbull, Michael Stuart. « The numerical modelling of steep waves interacting with structures ». Thesis, University of Oxford, 1999. http://ora.ox.ac.uk/objects/uuid:9341dc08-29c1-4752-ad92-ef74d2b5e038.

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The interaction of steep waves with structures is a complex problem which is still not fully understood, and is of great importance for the design of offshore structures. A particular problem of interest is the phenomenon of ringing which is highly nonlinear. In this thesis a number of inviscid free surface flow problems are simulated using a finite element model. The free surface boundary condition is fully nonlinear, meaning nonlinear effects up to very high order can be simulated, depending on mesh resolution. The model uses a fully automatic unstructured mesh generator; this allows the mesh to change its shape and structure as the free surface deforms. Two unstructured mesh generators have been developed, one based on the advancing front method, the other on the Voronoi technique. Variations of each method are examined. Both methods give good quality meshes. The advancing front technique is found to be faster, but the Voronoi method is more robust and reliable. In addition to the standard finite element method, a sigma transformed version of the finite element formulation has been developed as an alternative. Both techniques have been used for the numerical simulations. The sigma transformation involves stretching of the mesh between the bed and free surface, and so has the advantage that remeshing is avoided. The standard finite element method is straightforward to apply to problems involving submerged arbitrary shaped bodies. Simulations have been performed of a number of test cases, such as a standing wave of large amplitude, a base excited tank and steep travelling waves. Convergence tests were carried out and results found to be in close agreement with analytical and alternative numerical solutions of Wu and Eatock Taylor (1994), Wu et al. (1998) and Chern et al. (1999). The force on a submerged horizontal cylinder due a travelling wave has been calculated. First and second order components have been obtained by Fourier analysis. The results have been compared with the theoretical predictions of Ogilvie (1963), Vada (1987) and Wu and Eatock Taylor (1990) and the experimental results of Chaplin (1984).

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Kuan, Kam-sing. « CoBlocks using objects to improve voxel modelling to support group work in early design phases / ». Click to view the E-thesis via HKUTO, 2006. http://sunzi.lib.hku.hk/hkuto/record/B36212519.

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Perantoni, Giacomo. « Optimal control of vehicle systems ». Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:b75fa69c-ebe0-4812-98e9-984d93476d37.

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This thesis studies the optimal control of vehicular systems, focusing on the solution of minimum-lap-time problems for a Formula 1 car. The basic optimal control theory is summarised as an infinite-dimensional extension of optimisation theory. The relevant numerical techniques for optimisation and integral approximation are compared in view of the application to vehicle systems. The classical brachistochrone problem is revisited from an optimal control perspective, with two vehicle-relevant generalisations. Closed-form solutions are derived for both the optimal trajectory and transit time. Problems involving a steerable disc rolling on the interior surface of a hemisphere are studied. For three-dimensional problems of this type, which involve rolling bodies and nonholonomic constraints, numerical solutions are used. The identification of 3D race track models from measured GPS data is treated as a problem in the differential geometry of curves and surfaces. Curvilinear coordinates are adopted to facilitate optimal control solutions. The track is specified in terms of three displacement-dependent curvatures and two edge variables. The differential model is smoothed using numerical optimal control techniques. The Barcelona track is considered as an illustrative example. The minimum-lap-time problem for a Formula 1 car on a flat track is solved using direct transcription. The driven line and multiple car setup parameters are optimised simultaneously. It is shown that significant lap-time reductions can be obtained from track-specific setup parameter optimisation. Reduced computing times are achieved using a combination of analytical derivatives, model non-dimensionalisation and problem scaling. The optimal control of the car on a 3D track is studied; the results are compared with flat-track solutions. Contemporary kinetic energy-recovery systems are studied and compared with future hybrid kinetic-thermal energy-recovery systems. It is demonstrated that these systems can produce contemporary lap time using approximately two-thirds of the fuel required by present-day vehicles.

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Poeti, Leonardo. « An Object-Oriented Modelling Method for Evolving the Hybrid Vehicle Design Space in a Systems Engineering Environment ». Thesis, Cranfield University, 2011. http://dspace.lib.cranfield.ac.uk/handle/1826/6861.

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A combination of environmental awareness, consumer demands and pressure from legislators has led automotive manufacturers to seek for more environmentally friendly alternatives while still meeting the quality, performance and price demands of their customers. This has led to many complex powertrain designs being developed in order to produce vehicles with reduced carbon emissions. In particular, within the last decade most of the major automotive manufactures have either developed or announced plans to develop one or more hybrid vehicle models. This means that to be competitive and o er the best HEV solutions to customers, manufacturers have to assess a multitude of complex design choices in the most e cient way possible. Even though the automotive industry is adept at dealing with the many complexities of modern vehicle development; the magnitude of design choices, the cross coupling of multiple domains, the evolving technologies and the relative lack of experience with respect to conventional vehicle development compounds the complexities within the HEV design space. In order to meet the needs of e cient and exible HEV powertrain modelling within this design space, a parallel is drawn with the development of complex software systems. This parallel is both from a programmatic viewpoint where object-oriented techniques can be used for physical model development with new equation oriented modelling environments, and from a systems methodology perspective where the development approach encourages incremental development in order to minimize risk. This Thesis proposes a modelling method that makes use of these new tools to apply OOM principles to the design and development of HEV powertrain models. Furthermore, it is argued that together with an appropriate systems engineering approach within which the model development activities will occur, the proposed method can provide a more exible and manageable manner of exploring the HEV design space.The exibility of the modelling method is shown by means of two separate case studies, where a hierarchical library of extendable and replaceable models is developed in order to model the di erent powertrains. Ultimately the proposed method leads to an intuitive manner of developing a complex system model through abstraction and incremental development of the abstracted subsystems. Having said this, the correct management of such an e ort within the automotive industry is key for ensuring the reusability of models through enforced procedures for structuring, maintaining, controlling, documenting and protecting the model development. Further, in order to integrate the new methodology into the existing systems and practices it is imperative to develop an e cient means of sharing information between all stakeholders involved. In this respect it is proposed that together with an overall systems modelling activity for tracking stakeholder involvement and providing a central point for sharing data, CAE methods can be employed in order to automate the integration of data.

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Lu, Qiong. « Modelling of pesticides and POPS in the River Thames system : potential impacts of changes in climate and management ». Thesis, University of Oxford, 2017. https://ora.ox.ac.uk/objects/uuid:e8c8bf1e-6cf3-4de8-b189-1b89abfee4e3.

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Due to environmental concerns, most of persistent organic pollutants (POPs) have been eliminated or reduced in production and use; however, due to their great persistency, POPs are expected still to be found in the environment long after their use has ceased. Although, in recent years, POPs have rarely been detected in river water in the United Kingdom (UK), their concentrations in fish (biota) and sediment are expected to be notable due to their lipophilicity and bioaccumulation; however, there is a lack of information and data to understand the current contamination of POPs in catchments and evaluate their potential risk to the environment and ecosystem. This thesis describes the application of mathematical modelling approaches to (i) predict the current distribution and concentration of POPs in catchments, (ii) evaluate the influence of climate change and extreme weather conditions on the fate of POPs, and (iii) provide guidelines to inform decision-making on managing the potential risks of POPs in river basins. The modelling studies have mainly focused on polychlorinated biphenyls (PCBs). The River Thames catchment was chosen as the study area. The Fugacity level III model was initially used to describe the general distribution of PCBs between different compartments; it was predicted that the greatest mass of PCBs remain in the soil, but the fish and sediments represent compartments with the highest PCB concentrations. The contamination of PCBs in Thames fish was estimated to exceed the unrestricted consumption thresholds of 5.9 μg/kg for ∑PCBs set by the U.S. Environmental Protection Agency (EPA); no current EU Environmental Quality Standards (EQS) are available for PCBs in fish. It was indicated that the PCBs in fish could be linked to PCB contamination in sediment, which was predicted to be about three times higher than the fish concentrations, but insufficient observed data of PCBs in Thames fish and sediment are available to validate the results. In order to address this limitation in observed data, fish and sediment sampling and chemical analysis were carried out for the presence of POPs. In addition to PCBs, the measured results for hexachlorobenzene (HCB) and polybrominated diphenyl ethers (PBDEs) in Thames fish and sediment were assessed. Although the observed fish- and sediment concentrations of the chemicals appear quite variable, when normalised to organic carbon the levels in sediment, they were comparable to the fish lipid normalised concentrations. Using the temperature and rainfall data forecasts in the UK Climate Projections 2009 (UKCP09), climate change scenarios were established and assessed in the fugacity modelling. The modelling results suggested a modest influence of climate change on PCB fate over the next 80 years. The most significant result was a tendency, in the Thames catchment, for climate change to enhance the evaporation of PCBs from soil to air. While the fugacity model successfully simulated the distribution and fate of PCBs, we used greatly simplified representations of climate, hydrology and biogeochemical processes of the catchment: to have a deeper understanding, a newly developed dynamic hydrobiogeochemical transport model - the Integrated Catchment Contaminants model (INCAContaminants) was applied. Using additional information about weather, river flows and water chemistry, the INCA-Contaminants model provided new insights into the behaviour of contaminants in the catchment; this led to a better representation of PCB contamination in sediment. In addition, INCA demonstrated the important impact of short-term weather variation on PCB movement through the environment. It was shown that PCBs contamination in Thames sediment was greatly disturbed by the severe flooding that occurred in early 2014. This thesis presents the application of the INCA model to assess - in addition to POPs - the behaviour of metaldehyde in the River Thames catchment. Metaldehyde is a type of pesticide used mainly to kill snails and slugs. Its application in agricultural areas within the catchment area has in recent years caused severe problems with drinking water supply. The INCA model has proved to be an effective tool for simulating the transport of metaldehyde in the catchment, predicting observed metaldehyde concentrations at multiple locations in the River Thames; this is the first time that a dynamic modelling approach has been used to predict the behaviour of metaldehyde in river basins. Modelling results showed that high concentrations of metaldehyde in the river system are a direct consequence of excessive application rates. In this thesis, a simple decision-support tool was derived from modelling results, based on variable application rates and application areas. This decision-support tool is now being used by Thames Water to help control peak concentrations of metaldehyde at key water supply locations.

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Chou, Dean. « Computational modelling of brain transport phenomena : application of multicompartmental poroelasticity ». Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:8ad5cf12-e20c-4944-b27f-b3fd2951faca.

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The global population is predicted to increase to around 11 billion by 2100. By 2050, the average age in the most populous age group will be over sixty. The ageing population (over sixty-five) is projected to exceed the number of children by 2047. These demographics imply that as the ageing population section increases, there will be a greater need for long-term care services. In order to adequately prepare against this trend, medical experts and evidence-driven policymakers are realising that personalised healthcare can help alleviate the burden related to the planning and commissioning of services allied to long-term care. Central to this picture is conditions that affect the brain - the most important organ of the human body. Dementia, stroke, and other conditions have a tremendous impact on loss of life, quality of life and healthcare cost. The challenge regarding brain disease is exacerbated further due to the difficulty regarding accessibility of this organ, but also due to the immense complexity regarding its morphology and functionality. In this context, advanced biophysical modelling is considered a promising option for studying brain pathophysiology and becomes a priority investment regarding routes for brain research. Simulations offer the promise of improved, clinically relevant, predictive information, acceleration for the pipeline of drug discovery/design and better planning of long-term care for patients. Within this paradigm, a particular model of water transport in the cerebral environment is essential. Numerous brain disorders arise from water imbalance in the cerebral environment, such as hydrocephalus (HCP), oedema and Chiari malformations to name a few. In this research, a novel multiscale model of fluid regulation and tissue displacement in the cerebral environment is developed, arising from the use of Multiple-network Poroelastic Theory (MPET). Characteristics of a four-network poroelastic model (4MPET) are first explored. Then, this model is extended to a fully dynamic (transient) six-network model (6MPET) via the addition of two new compartments, namely the glial cells compartment and the glymphatic system compartment. The introduction of these two compartments in the MPET paradigm reflects recent seminal findings in cerebral physiology, namely the extent and importance regarding transport/clearance of the perivascular spaces of the brain vasculature. We develop and present a numerical implementation of the 6MPET model, and we utilise this framework to analyse acute HCP and cerebral oedema in a variety of settings, in order to show the enhanced capability of the proposed 6MPET model compared to the classical 4MPET. Investigations of acute hydrocephalus through the fully dynamic 6MPET reveal compensatory trans-ependymal pressure behaviour in the glymphatic compartment. It was also shown that aquaporin-4 (AQP4) deficient expression exaggerates ventriculomegaly, and this too is demonstrated in acute hydrocephalus. Additionally, using the 6MPET model, one is able to witness three mitigating factors for cytotoxic oedema. Specifically, these are: reducing water mobility in the glial cells compartment, increasing the compliance of the glial cells compartment and finally AQP4-deficient expression.

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Black, Jonathan Paul. « Mathematical modelling of electronic contact mechanisms in silicon photovoltaic cells ». Thesis, University of Oxford, 2015. https://ora.ox.ac.uk/objects/uuid:ff671215-5f05-4ef0-a876-3f474a8450c9.

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In screen-printed silicon-crystalline solar cells, the contact resistance of a thin interfacial glass layer between the silicon and the silver electrode plays a limiting role for electron transport. The motivation of this project is to gain increased understanding of the transport mechanisms of the electrons across this layer, which can be exploited to provide higher performance crystalline silicon solar cells. Our methodology throughout is to formulate and analyse mathematical models for the electron transport, based on the drift diffusion equations. In the first chapter we outline the problem and provide a summary of relevant theory. In Chapter 2 we formulate a one-dimensional model for electron transport across the glass layer, that we solve both numerically and by employing asymptotic techniques. Chapter 3 extends the model presented in Chapter 2 to two dimensions. To solve the two-dimensional model numerically we devise and validate a new spectral method. The short circuiting of current through thinner regions of the glass layer enables us to find limiting asymptotic expressions for the average current density for two different canonical glass layer profiles. In Chapter 4 we include quantum mechanical effects into the one-dimensional model outlined in Chapter 2 and find that they have a negligible effect on the contact resistance of the glass layer. We model the boundary effects present at the silicon emitter-glass interface in Chapter 5. Finally, in Chapter 6 we summarise our key results, suggest possible future work, and outline the implications of our work to crystalline silicon solar cell manufacturers.

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Kuan, Kam-sing, et 關錦盛. « CoBlocks : using objects to improve voxel modelling to support group work in early design phases ». Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2006. http://hub.hku.hk/bib/B36212519.

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Pearce, Helen Elizabeth. « East African rainfall : classification of rain producing systems : a modelling and observation study ». Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:d5bb4c4c-6e5e-40d4-8a65-b3002277b550.

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The study of anthropogenic climate change is a research area of vital importance for the coming decades, with rainfall change and variability expected to be keenly felt in vulnerable regions of the world, including Africa. The focus of this study is daily rainfall during the short rains season over East Africa from October to December, which has one of the most coherent increasing rainfall projections in the Coupled Model Intercomparison Project (CMIP) dataset. This thesis aims to examine the fidelity of coupled climate models over an East African domain, with the question approached through focus on the daily (rather than monthly) rainfall field. The self-organising map is used as a clustering tool to establish contemporary characteristics of daily rainfall events in reanalysis (ERA-40) and satellite (TRMM) rainfall datasets between 1971-2000 and 1998-2010 respectively for the East African short rains. Moisture flux divergence is found to be the circulation parameter that is most closely related to the presence of rainfall events or dry conditions over East Africa. Coupled climate models are poor at replicating the daily rainfall field over the domain. A key result of the analysis is the consistent overestimation of daily rainfall by climate models for days where dry conditions of suppressed convection should prevail. In contrast, the moisture flux divergence field maps well to dry nodes for days of the self-organising map array for the models. Dry days are associated with widespread anomalous moisture flux divergence and rainfall events with co-located anomalous moisture flux convergence. This is in agreement with the moisture flux divergence field in the ERA-40 dataset; it is the rainfall field where there is disagreement for days of suppressed convection. Twenty to thirty-five percent of the projected rainfall increase towards the end of the twenty-first century results from an increase in the proportion of days assigned to nodes of suppressed convection in six of the seven models and the ensemble mean. There is an accompanying projected rainfall increase associated with days assigned to these nodes. Such days in the 2090s are characterised by projected increased strength moisture flux divergence over East Africa. Given that the moisture flux field was more successfully simulated in the coupled models under contemporary conditions than the daily rainfall field, this suggests that rainfall projections under a high emissions scenario at the end of the twenty-first century are overestimated and that an important part of the key increase in the projected rainfall may not be real.

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Luo, James L. H. « An object-oriented generic approach to process planning ». Thesis, Queensland University of Technology, 1998.

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Thèses sur le sujet « Object Modelling System »

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