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Reeves, Ahmad John. "Modelling participation in virtual environments." Thesis, Queen Mary, University of London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.414476.
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Rajper, Noor Jehan. "VOML : virtual organization modelling language." Thesis, University of Leicester, 2012. http://hdl.handle.net/2381/10942.
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Virtual organizations (VOs) and their breeding environments are an emerging approach for developing systems as a consortium of autonomous entities formed to share costs and resources, better respond to opportunities, achieve shorter time-to-market and exploit fast changing market opportunities. VOs cater for those demands by incorporating reconfigurations making VOs highly resilient and agile by design. Reconfiguration of systems is an active research area. Many policy and specification languages have been dedicated for the purpose. However, all these approaches consider reconfiguration of a system as somewhat isolated from its business and operational model; it is usually assumed that the latter two remain unaffected through such reconfigurations and the reconfiguration is usually limited to dynamic binding of components the system consists of. However the demands of VO reconfiguration go beyond dynamic binding and reach the level where it becomes crucial to keep changing the organizational structure (process model) of the system as well, which leads to changes of the operational/functional model. This continuous reconfiguration of the operational model emphasizes the need of a modelling language that allows specification and validation of such systems. This thesis approaches the problem of formal specification of VOs through the Virtual Organization Modelling Language (VOML) framework. The core of this framework are three languages each capturing a specific aspect. The first language named Virtual Organization Structural modelling language (VO-S), focuses on structural aspects and many of the characteristics particular to VOs such as relationship between the members expressed in domain terminology. The second language named VO Reconfiguration (VO-R for short), permits different reconfigurations on the structure of the VO. This language is an extension of APPEL for the domain of VOs. The third language named VO Operational modelling language (VO-O) describes the operational model of a VO in more details. This language is an adaptation and extension of the Sensoria Reference Modelling Language for service oriented architecture (SRML). Our framework models VOs using the VO-S and the VO-R which are at a high level of abstraction and independent of a specific computational model. Mapping rules provide guidelines to generate operational models, thus ensuring that the two models conform to each other. The usability and applicability of VOML is validated through two cases studies one of which offers travel itineraries as a VO service and is a running example. The other case study is an adaptation of a case study on developing a chemical plant from [14].
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Wikström, Patrik. "Reluctantly Virtual : Modelling Copyright Industry Dynamics." Doctoral thesis, Karlstad University, Faculty of Economic Sciences, Communication and IT, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-478.
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<p>During the evolution of the music industry, developments in the media environment have required music firms to adapt in order to survive. Changes in broadcast radio programming during the 1950s; the Compact Cassette during the 1970s; and the deregulation of media ownership during the 1990s are all examples of changes which have heavily affected the music industry. This study explores similar contemporary dynamics, examines how decision makers in the music industry perceive and make sense of the developments, and reveals how they revise their business strategies, based on their mental models of the media environment.</p><p>A qualitative system dynamics model is developed in order to support the reasoning brought forward by the study. The model is empirically grounded, but is also based on previous music industry research and a theoretical platform constituted by concepts from evolutionary economics and sociology of culture. The empirical data primarily consist of 36 personal interviews with decision makers in the American, British and Swedish music industrial ecosystems. The study argues that the model which is proposed, more effectively explains contemporary music industry dynamics than music industry models presented by previous research initiatives.</p><p>Supported by the model, the study is able to show how “new” media outlets make old music business models obsolete and challenge the industry’s traditional power structures. It is no longer possible to expose music at one outlet (usually broadcast radio) in the hope that it will lead to sales of the same music at another (e.g. a compact disc).</p><p>The study shows that many music industry decision makers still have not embraced the new logic, and have not yet challenged their traditional mental models of the media environment. Rather, they remain focused on preserving the pivotal role held by the CD and other physical distribution technologies.</p><p>Further, the study shows that while many music firms remain attached to the old models, other firms, primarily music publishers, have accepted the transformation, and have reluctantly recognised the realities of a virtualised environment.</p>
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Oxnard, Stephen. "Efficient hybrid virtual room acoustic modelling." Thesis, University of York, 2016. http://etheses.whiterose.ac.uk/17459/.
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This thesis investigates approaches to virtual room acoustic modelling and auralisation in order to a develop hybrid modelling solution that is capable of efficient and accurate simulation of enclosed sound propagation. Emphasis is placed on the advantages and disadvantages of state of the art numerical and geometric acoustic modelling methods. Numerical methods have been shown to preserve important sound wave characteristics such as diffraction and room modes, and are considered more accurate for low frequency acoustic modelling than geometric techniques which fail to preserve such wave effects. However, the implementation of numerical acoustic models inherently requires large computational effort compared to more efficient geometric techniques such as ray-tracing. This is particularly problematic for simulations of large-scale 3D acoustic environments and for high spatio-temporal sampling rates. A novel acoustic modelling solution is presented, which seeks to circumvent the disadvantageous computational requirements of 3D numerical models while producing a suitable approximation to low frequency sound behaviour. This modelling technique incorporates multiple planar cross-sectional 2D Finite Difference schemes that are utilised in combination to synthesise low frequency wave propagation throughout the target acoustic field. In this way a subset of prominent low frequency sound wave characteristics may be emulated with low computational cost compared to 3D numerical schemes. These low-frequency results can then be combined with the high-frequency output from efficient geometric simulations to create a hybrid model providing accurate broadband results at a relatively low computational cost. Investigation of room impulse response rendering for a series of theoretic and real spaces demonstrates advantages of this new hybrid acoustic modelling technique over purely ray-based methods in terms of low frequency accuracy, and over 3D numerical methods in terms of computational efficiency. Conclusions are drawn from objective measurements obtained from simulation results of the virtual models produced. Results demonstrate the applicability of the novel hybrid approach to the enhancement of purely ray-based room impulse response rendering by which a more realistic representation of low frequency wave phenomena may be simulated in an efficient manner, improving the theoretical accuracy of objective and audible results. This study contributes towards research and design of high-speed, interactive virtual acoustic simulations appropriate for industrial and creative virtual reality applications.
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Johansson, Anja. "Modelling Expectations and Trust in Virtual Agents." Thesis, Linköping University, Department of Science and Technology, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-9704.
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<p>Computer graphics has long been the foremost area of advancement in both the gaming and the motion picture industry. Nowadays, as computer graphics is getting difficult to advance any further, other areas begin to interest the developers. One of these areas is artificial intelligence. The gaming industry has begun to create far more intelligent virtual characters that no longer are as predictable as they used to be. Mixing character animation with intelligent agents techniques results in a vastly more interesting experience for the gamer as well as for the developer.</p><p>This project focuses on introducing expectational behaviour and trust in intelligent virtual characters. The area is highly interesting as it enables a vastly more complex emotional structure for virtual agents than that of reactive, rational behaviour. Although expectations can indeed be rational, often they are not when it comes to humans. This project studies the effects of expectations on the emotional state of agents and the effect that the emotions have on the reasoning abilities and the action selection mechanism. It also examines how trust influences emotions and vice versa and how trust influences the action selection mechanism.</p><p>One of the requirements of this work is that the computations concerning the triggering of emotions have to be done in real-time. While it is possible to do off-line computations for simulations (such as is often done for the movie industry), it is not what we desire here. It is our goal to create interesting virtual characters that can be interacted with in real-time. Therefore, also expectations and trust must be calculated and managed in real-time.</p>
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Zhao, Yue. "Investigation of an emotional virtual human modelling method." Thesis, Brunel University, 2008. http://bura.brunel.ac.uk/handle/2438/5808.
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In order to simulate virtual humans more realistically and enable them life-like behaviours, several exploration research on emotion calculation, synthetic perception, and decision making process have been discussed. A series of sub-modules have been designed and simulation results have been presented with discussion. A visual based synthetic perception system has been proposed in this thesis, which allows virtual humans to detect the surrounding virtual environment through a collision-based synthetic vision system. It enables autonomous virtual humans to change their emotion states according to stimuli in real time. The synthetic perception system also allows virtual humans to remember limited information within their own First-in-first-out short-term virtual memory. The new emotion generation method includes a novel hierarchical emotion structure and a group of emotion calculation equations, which enables virtual humans to perform emotionally in real-time according to their internal and external factors. Emotion calculation equations used in this research were derived from psychologic emotion measurements. Virtual humans can utilise the information in virtual memory and emotion calculation equations to generate their own numerical emotion states within the hierarchical emotion structure. Those emotion states are important internal references for virtual humans to adopt appropriate behaviours and also key cues for their decision making. The work introduces a dynamic emotional motion database structure for virtual human modelling. When developing realistic virtual human behaviours, lots of subjects were motion-captured whilst performing emotional motions with or without intent. The captured motions were endowed to virtual characters and implemented in different virtual scenarios to help evoke and verify design ideas, possible consequences of simulation (such as fire evacuation). This work also introduced simple heuristics theory into decision making process in order to make the virtual human’s decision making more like real human. Emotion values are proposed as a group of the key cues for decision making under the simple heuristic structures. A data interface which connects the emotion calculation and the decision making structure together has also been designed for the simulation system.
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Bayliss, Gary M. "Design by manufacturing an interactive virtual factory." Thesis, University of Bath, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362156.
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鄧興汎 and Hing-fan Anthony Tang. "A hybrid relational data structure for virtual reality modelling." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2001. http://hub.hku.hk/bib/B31225184.
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Tang, Hing-fan Anthony. "A hybrid relational data structure for virtual reality modelling /." Hong Kong : University of Hong Kong, 2001. http://sunzi.lib.hku.hk/hkuto/record.jsp?B25101249.
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Nyman, Jonas. "Faster Environment Modelling and Integration into Virtual Reality Simulations." Thesis, Högskolan i Skövde, Institutionen för ingenjörsvetenskap, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:his:diva-19800.
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The use of virtual reality in engineering tasks, such as in virtual commissioning, has increased steadily in recent years, where a robot, machine or object of interest can be simulated and visualized. Yet, for a more immerse experience, an environment for the object in question needs to be constructed. However, the process for creatingan accurate environment, for a virtual simulation have remained a costly and a long endeavour. Because of this, many digital simulations are performed, either with no environment at all, or present a very basic and abstract representation of an intended environment.The aim of this thesis is to investigate if technologies such as LiDAR and digital photogrammetry could shorten the environment creation process. Therefore, a demonstrative virtual environment was created and analysed, in which the different technologies was investigated and presented in the form of a comprehensive review of the current state of the technologies with in digital recreation. Lastly, a technique specific evaluation of the time requirement, cost and user difficulty was conducted. As the field of LiDAR and digital photogrammetry is too vast to investigate all forms thereof within one project, this thesis is limited to the investigation of static laser scanners and wide lens camera photogrammetry. A semi industrious locale was chosen for digital replication, which through static laser scans and photographs would generate semi-automated 3D models.The resulting 3D models leave much to be desired, as large holes were present throughout the 3D models, sincecertain surfaces are not suitable for neither replication processes. Transparent and reflective surfaces lead to ripple effects within the 3D models geometry and textures. Moreover, certain surfaces, as blank areas for photogrammetry or black coloration for laser scanners led to missing features and model distortions.Yet despite the abnormalities, the majority of the test environment was successfully re-created. An evaluation of the created environments was performed, which list and illustrate with tables and figures the attributes, strengths and weaknesses of each technique. Moreover, technique specific limitations and a spatial analysis was carried out. With the result, seemingly illustrating that photogrammetry creates more visually accurate 3D models in comparison to the laser scanner, yet the laser scanner produces a more spatially accurate result. As such, a selective combination of the techniques can be suggested.Observations and interviews seem to point towards the full scale application, in which an accurate 3D model is re-created without much effort, to currently not exist. As both photogrammetry and static laser scanning require great effort, skill and time in order to create a seemingly perfect solid model. Yet, utilizing either, or both techniques as a template for 3D object creation could reduce the time to create an environment significantly.Furthermore, methods such as digital 3D sculpting could be used in order to remove imperfections and create what is missing from the digitally constructed 3D models. Thereby achieving an accurate result.
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Newman, Guy. "Characterisation of virtual power plants." Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/characterisation-of-virtual-power-plants(5e647750-5a44-40f0-8a33-763361d3a50b).html.
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The growing number of micro generation devices in the electrical network is leading many to consider that these devices can no longer be considered as fit and forget, but should instead be considered as having a demonstrable network impact which should be predicted and utilised. One of the techniques for considering the impacts of these devices is the Virtual Power Plant (VPP). The VPP is the aggregation of all the Distributed Generation (DG) connected into the network up to and including the connection voltage of the VPP, such that the cumulative power up the voltage levels can be seen in the single VPP unit, rather than across a broad spread of devices. One of the crucial tasks in characterising the VPP, developed in this work, is the ability to correctly predict and then aggregate the behaviour of several technology types which are weather driven, as a large proportion of DG is weather driven. Of this weather driven DG, some can only typically be dispatched with modification and the rest cannot be dispatched at all. The aggregation of the VPP as part of the electrical network is also developed, as the constraints of the network and the reliability of the network cannot be overlooked when considering the aggregation of the VPP. From a distribution network operator's (DNO) perspective, these characterisation models can be used to highlight problems in the network introduced by the addition of DG, but are also generally utilitarian in their role of predicting the power output (or negative load) found throughout the network due to DG. For a commercial agent interested in selling energy, these models allow for accurate predictions of energy to be determined for the trading period. A VPP agent would also be adversely affected by line failure in the network, leading to the development of an N-1 analysis based upon reliability rates of the network, which is used as the basis for a discussion on the impacts of single line failure and the mitigation available through feedback from the DNO.
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Weng, Ng Giap. "Modelling skill learning for augmented and virtual reality learning environments." Thesis, University of Salford, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.502807.
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Wright, A. "Tyre/soil interaction modelling within a virtual proving ground environment." Thesis, Cranfield University, 2012. http://dspace.lib.cranfield.ac.uk/handle/1826/7904.
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Off-road mobility defines the ability of land-based vehicles to accelerate, pull loads and climb gradients. Historically, much of the work completed to relate mobility to vehicle and terrain characteristics has been empirical in nature, and has therefore been susceptible to errors caused by the inherent variability of naturally occurring soils. This thesis addresses the off-road mobility of wheeled vehicles, and in particular the use of a finite element (FE) based approach to predict performance metrics such as rolling resistance, drawbar pull and tractive efficiency. Tools to predict these measures of performance have a wide range of applications, including military, agricultural and leisure vehicles, aircraft operating from temporary airfields and planetary landing craft. The current study extends the virtual proving ground (VPG) concept, where a single vehicle model can be subjected to a series of virtual test conditions, to include the assessment of off-road mobility. Throughout, modelling has been carried out using LS-DYNA, a commercially available non-linear dynamic analysis code. Unlike previous studies using FE techniques to investigate wheel / soil interaction, an Eulerian representation of the soil has been employed, which permits a consistent approach to be applied to both purely cohesive and purely frictional soils, as well as those displaying a combination of cohesive and frictional behaviour. At each stage of the research, the validity of the FE-based modelling approach has been assessed using data from controlled experimental testing at Cranfield University’s off-road dynamics facility. A key finding of the work completed is that rate sensitivity in moisture containing soils can significantly affect the accuracy of (empirical, analytical and numerical) model predictions, even at low translational speeds (less than 0.1m/s). This finding highights the adverse impact of simplifications in many previous experimental and modelling studies, which have assumed that rate effects may be ignored providing the translational speed of the vehicle is low.
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Webb, Craig Jonathan. "Parallel computation techniques for virtual acoustics and physical modelling synthesis." Thesis, University of Edinburgh, 2014. http://hdl.handle.net/1842/15779.
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The numerical simulation of large-scale virtual acoustics and physical modelling synthesis is a computationally expensive process. Time stepping methods, such as finite difference time domain, can be used to simulate wave behaviour in models of three-dimensional room acoustics and virtual instruments. In the absence of any form of simplifying assumptions, and at high audio sample rates, this can lead to simulations that require many hours of computation on a standard Central Processing Unit (CPU). In recent years the video game industry has driven the development of Graphics Processing Units (GPUs) that are now capable of multi-teraflop performance using highly parallel architectures. Whilst these devices are primarily designed for graphics calculations, they can also be used for general purpose computing. This thesis explores the use of such hardware to accelerate simulations of three-dimensional acoustic wave propagation, and embedded systems that create physical models for the synthesis of sound. Test case simulations of virtual acoustics are used to compare the performance of workstation CPUs to that of Nvidia’s Tesla GPU hardware. Using representative multicore CPU benchmarks, such simulations can be accelerated in the order of 5X for single precision and 3X for double precision floating-point arithmetic. Optimisation strategies are examined for maximising GPU performance when using single devices, as well as for multiple device codes that can compute simulations using billions of grid points. This allows the simulation of room models of several thousand cubic metres at audio rates such as 44.1kHz, all within a useable time scale. The performance of alternative finite difference schemes is explored, as well as strategies for the efficient implementation of boundary conditions. Creating physical models of acoustic instruments requires embedded systems that often rely on sparse linear algebra operations. The performance efficiency of various sparse matrix storage formats is detailed in terms of the fundamental operations that are required to compute complex models, with an optimised storage system achieving substantial performance gains over more generalised formats. An integrated instrument model of the timpani drum is used to demonstrate the performance gains that are possible using the optimisation strategies developed through this thesis.
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Burkitt, Mark. "Computational modelling of sperm behaviour in a 3D virtual oviduct." Thesis, University of Sheffield, 2011. http://etheses.whiterose.ac.uk/2246/.
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The processes by which individual sperm cells navigate the length and complexity of the female reproductive tract and then reach and fertilise the oocyte are fascinating. Numerous complex processes potentially influence the movement of spermatozoa within the tract, resulting in a regulated supply of spermatozoa to the oocytes at the site of fertilisation. Despite significant differences between species, breeds and individuals, these processes converge to ensure that an optimal number of high quality spermatozoa reach the oocytes, resulting in successful fertilisation without a significant risk of polyspermy. Computational modelling provides a useful method for combining knowledge about the individual processes in complex systems to help understand the relative significance of each factor. In this thesis, the first agent based computational model of sperm behaviour within the oviductal environment has been created. First, a generic conceptual model of sperm behaviour within the 3D oviduct is presented. Sperm are modelled as individual cells with a set of behavioural rules defining how they interact with their local environment and regulate their internal state. Secondly, a set of 3D models of the mammalian oviduct were constructed. Histology images of the mouse oviduct were obtained and the path that the oviductal tube follows through the tissue was identified using CUDA based image analysis. This was used to determine cross-sectional topology, and measurements from the cross sections were used to generate a set of accurately scaled 3D models of the oviduct. The process of constructing and validating the agent-based computational model of sperm movement and transport within the oviductal environment is described. The model is grounded in reality, with accurate space and time scales used throughout, and parameters and mechanisms from literature where available. Sensitivity analysis is performed on all parameters, and those which are most sensitive to variation have been identified. The model has been validated against literature were possible, and the limitations of the model, validation and assumptions made are clearly stated. The model has been used to investigate the significance of the oviductal environment on the regulation of sperm distribution and progression to the site of fertilisation, and how changes to that environment alter the distribution. Finally, the potential use for the model and how more complex mechanisms could be integrated in the future are discussed.
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Wang, Lulu. "Virtual imaging system." Click here to access this resource online, 2009. http://hdl.handle.net/10292/668.
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The main purpose of this research project was to implement a combination of computer graphics and processing to generate displays that will aid in the visualization of the colour rendering properties of a range of light sources, including the new generation of high-output LEDs (light emitting diodes) that are becoming widely adopted in general lighting service. The CIE (International Commission on Illumination) has developed a colour appearance model CIECAM02 for use in colour imaging and colour management, and this model is utilized in this work. This thesis describes the design and construction of a computer-based model that can be used as a research tool for the simulation and demonstration of the colour rendering properties of various artificial light sources. It is a comprehensive study of the colour models and measurement procedures currently in use in the lighting industry, as recommended by the CIE. This research project focused on the display of a set of surface colour patches as if they were illuminated by a specific light source, and the simultaneous display of two such sets to demonstrate the surface colour differences arising from the use of the two different light sources. A VIS (virtual imaging system) has been developed to display the colour properties of a series of test colour samples under different light sources. This thesis describes the computer models developed for the representation and display of surface colours in general, and colour rendering in particular. The designed system computes and displays the colour of each sample from a knowledge of the light-source spectrum and the spectral reflectance of each surface. It can simultaneously display the colours resulting from illumination by two different sources. In addition, the system computes the colour appearance differences for two sets of colours using the CIECAM02 colour appearance model. Subjective and objective tests were taken to validate the computed results. The VIS has been designed and implemented. It also has been tested by 21 observers and we believe that it will be a powerful research tool for the lighting industry, especially in relation to colour rendering.
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Piliego, Hadrien, and Koorosh Salari. "Virtual testing of articulated haulers." Thesis, Linnéuniversitetet, Institutionen för maskinteknik (MT), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-35247.
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Multi-body system dynamics is one of the most important theoretical achievementsin mechanics. With the development of the theory, corresponding commercialsoftware packages have been developed and are used for modellingand simulation of complicated large systems, such as air planes and vehicles.This kind of virtual prototypes can be used for studies and assessments ofreal systems even before the real systems are built. As a result, the high costprototype building and prototype testing can be saved, so as the time can bereduced. This is just the demand of modern industry. This theory can beapplied on the vehicle-virtual road interaction study which has been used inthis thesis.This thesis suggests a target velocity prole for a heavy vehicle which driveson tough road. Having uneven and hilly road, actual driving conditions arechanged as the driver runs the vehicle. Drivers can perceive the road conditionwith their visual organ and sense of balance and then they control theirvehicles more safely by re ecting various conditions of this target velocityprole. Without this process, the driving-stabilization on slope and twistingroads would fall considerably, and the problem could be directly connected tooverturning. This thesis, moreover, will show how to acquire the road data,extract the velocity prole, and verify the performance of the suggested velocityprole through virtual road test.In vehicle-virtual road interaction simulation, multi body system (MBS) dynamicswith software Adams has been employed to model an articulatedhauler. The simulation has been validated by velocity prole test data andcompared to the former velocity prole. This method can be used for estimatingthe eects of dynamic forces on the frame so that the load design canbe assessed in vehicle design process.This project is in collaboration with Volvo Construction Equipment AB,Braas, Sweden.
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Kahana, Yuvi. "Numerical modelling of the head-related transfer function." Thesis, University of Southampton, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326799.
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Zhang, Yinghui. "Multi-asperity based friction modelling and haptic rendering in virtual environments." Thesis, University of Hull, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.440138.
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Logan, Ivan Paul. "Soft tissue modelling and a virtual environment for knee arthroscopy training." Thesis, University of Hull, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267034.
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Alekhtyar, Mumena. "Building Information Modelling and Virtual Design and Construction : Differentiations and interaction." Thesis, KTH, Fastigheter och byggande, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-231602.
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Within the last decade BIM technology products have been providing the construction industry with various tools that can be used in all construction phases and aspects with a wide set of potentials that range from visualization to simulation, scheduling and cost estimation (Kam , et al., 2016). As a result, the term BIM started to have new interpretation from a process- oriented perspective beside the product-oriented interpretation. These different interpretations and definitions of BIM creates an ambiguity regarding BIM. The ambiguity about what is BIM takes another direction when the term “Virtual Design and Constructions” VDC is used as synonym of BIM as well in many situations. VDC is defined as the use of integrated multi-disciplinary performance models of design-construction projects to support explicit and public business objectives (Kunz & Fischer, 2012). This study is an attempt to answer the following questions: What are the differences between BIM and VDC and how BIM and VDC interact and affect each other. As a result, a timeline for both terms was created based on a historical analysis for the emergence of both terms. Furthermore, more differences between VDC and BIM were located through literature reviews and empirics and this mapping was used to find how each term affects the other. The study was conducted in Tyréns Swedish consultancy company and it covered two infrastructure projects where VDC is used.
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Van, Wyk Desmond Eustin. "Virtual human modelling and animation for real-time sign language visualisation." University of the Western Cape, 2008. http://hdl.handle.net/11394/2998.
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>Magister Scientiae - MSc<br>This thesis investigates the modelling and animation of virtual humans for real-time sign language visualisation. Sign languages are fully developed natural languages used by Deaf communities all over the world. These languages are communicated in a visual-gestural modality by the use of manual and non-manual gestures and are completely di erent from spoken languages. Manual gestures include the use of hand shapes, hand movements, hand locations and orientations of the palm in space. Non-manual gestures include the use of facial expressions, eye-gazes, head and upper body movements. Both manual and nonmanual gestures must be performed for sign languages to be correctly understood and interpreted. To e ectively visualise sign languages, a virtual human system must have models of adequate quality and be able to perform both manual and non-manual gesture animations in real-time. Our goal was to develop a methodology and establish an open framework by using various standards and open technologies to model and animate virtual humans of adequate quality to e ectively visualise sign languages. This open framework is to be used in a Machine Translation system that translates from a verbal language such as
English to any sign language. Standards and technologies we employed include H-Anim, MakeHuman, Blender, Python and SignWriting. We found it necessary to adapt and extend H-Anim to e ectively visualise sign languages. The adaptations and extensions we made to H-Anim include imposing joint rotational limits, developing exible hands and the addition of facial bones based on the MPEG-4 Facial De nition Parameters facial feature points for facial animation. By using these standards and technologies, we found
that we could circumvent a few di cult problems, such as: modelling high quality virtual humans; adapting and extending H-Anim; creating a sign language animation action vocabulary; blending between animations in an action vocabulary; sharing animation action data between our virtual humans; and e ectively visualising South African Sign Language.<br>South Africa
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Yu, Hui. "An investigation on the framework of dressing virtual humans." Thesis, Brunel University, 2010. http://bura.brunel.ac.uk/handle/2438/4412.
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Realistic human models are widely used in variety of applications. Much research has been carried out on improving realism of virtual humans from various aspects, such as body shapes, hair, and facial expressions and so on. In most occasions, these virtual humans need to wear garments. However, it is time-consuming and tedious to dress a human model using current software packages [Maya2004]. Several methods for dressing virtual humans have been proposed recently [Bourguignon2001, Turquin2004, Turquin2007 and Wang2003B]. The method proposed by Bourguignon et al [Bourguignon2001] can only generate 3D garment contour instead of 3D surface. The method presented by Turquin et al. [Turquin2004, Turquin2007] could generate various kinds of garments from sketches but their garments followed the shape of the body and the side of a garment looked not convincing because of using simple linear interpolation. The method proposed by Wang et al. [Wang2003B] lacked interactivity from users, so users had very limited control on the garment shape.This thesis proposes a framework for dressing virtual humans to obtain convincing dressing results, which overcomes problems existing in previous papers mentioned above by using nonlinear interpolation, level set-based shape modification, feature constraints and so on. Human models used in this thesis are reconstructed from real human body data obtained using a body scanning system. Semantic information is then extracted from human models to assist in generation of 3 dimensional (3D) garments. The proposed framework allows users to dress virtual humans using garment patterns and sketches. The proposed dressing method is based on semantic virtual humans. A semantic human model is a human body with semantic information represented by certain of structure and body features. The semantic human body is reconstructed from body scanned data from a real human body. After segmenting the human model into six parts some key features are extracted. These key features are used as constraints for garment construction.Simple 3D garment patterns are generated using the techniques of sweep and offset. To dress a virtual human, users just choose a garment pattern, which is put on the human body at the default position with a default size automatically. Users are allowed to change simple parameters to specify some sizes of a garment by sketching the desired position on the human body.To enable users to dress virtual humans by their own design styles in an intuitive way, this thesis proposes an approach for garment generation from user-drawn sketches. Users can directly draw sketches around reconstructed human bodies and then generates 3D garments based on user-drawn strokes. Some techniques for generating 3D garments and dressing virtual humans are proposed. The specific focus of the research lies in generation of 3D geometric garments, garment shape modification, local shape modification, garment surface processing and decoration creation. A sketch-based interface has been developed allowing users to draw garment contour representing the front-view shape of a garment, and the system can generate a 3D geometric garment surface accordingly. To improve realism of a garment surface, this thesis presents three methods as follows. Firstly, the procedure of garment vertices generation takes key body features as constraints. Secondly, an optimisation algorithm is carried out after generation of garment vertices to optimise positions of garment vertices. Finally, some mesh processing schemes are applied to further process the garment surface. Then, an elaborate 3D geometric garment surface can be obtained through this series of processing. Finally, this thesis proposes some modification and editing methods. The user-drawn sketches are processed into spline curves, which allow users to modify the existing garment shape by dragging the control points into desired positions. This makes it easy for users to obtain a more satisfactory garment shape compared with the existing one. Three decoration tools including a 3D pen, a brush and an embroidery tool, are provided letting users decorate the garment surface by adding some small 3D details such as brand names, symbols and so on. The prototype of the framework is developed using Microsoft Visual Studio C++,OpenGL and GPU programming.
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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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Bangay, Shaun Douglas. "Modelling parallel and distributed virtual reality systems for performance analysis and comparison." Thesis, Rhodes University, 1997. http://hdl.handle.net/10962/d1006656.
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Most Virtual Reality systems employ some form of parallel processing, making use of multiple processors which are often distributed over large areas geographically, and which communicate via various forms of message passing. The approaches to parallel decomposition differ for each system, as do the performance implications of each approach. Previous comparisons have only identified and categorized the different approaches. None have examined the performance issues involved in the different parallel decompositions. Performance measurement for a Virtual Reality system differs from that of other parallel systems in that some measure of the delays involved with the interaction of the separate components is required, in addition to the measure of the throughput of the system. Existing performance analysis approaches are typically not well suited to providing both these measures. This thesis describes the development of a performance analysis technique that is able to provide measures of both interaction latency and cycle time for a model of a Virtual Reality system. This technique allows performance measures to be generated as symbolic expressions describing the relationships between the delays in the model. It automatically generates constraint regions, specifying the values of the system parameters for which performance characteristics change. The performance analysis technique shows strong agreement with values measured from implementation of three common decomposition strategies on two message passing architectures. The technique is successfully applied to a range of parallel decomposition strategies found in Parallel and Distributed Virtual Reality systems. For each system, the primary decomposition techniques are isolated and analysed to determine their performance characteristics. This analysis allows a comparison of the various decomposition techniques, and in many cases reveals trends in their behaviour that would have gone unnoticed with alternative analysis techniques. The work described in this thesis supports the Performance Analysis and Comparison of Parallel and Distributed Virtual Reality systems. In addition it acts as a reference, describing the performance characteristics of decomposition strategies used in Virtual Reality systems.
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Trinh, Thanh-Hai. "A constraint-based approach to modelling spatial semantics of vitual environments." Phd thesis, Université de Bretagne occidentale - Brest, 2012. http://tel.archives-ouvertes.fr/tel-00817685.
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Within Virtual Reality Environments (VREs), spatial relationships among objects convey fundamental knowledge about the environment, namely direction ("left", "right", "front of"), distance ("near", "far"), topology ("inside", "disjoint"), and projection ("between", "surrounded by"). Modelling spatial relationships is critical in a variety of applications of VREs, such as human learning environments, virtual museums, or navigation-aids systems. However, spatial relationships have been considered as abstract information and thus, difficult to specify. Addressing this issue, this thesis proposes an approach to model spatial relationships among virtual objects in VREs. First, we formalise a formal model of spatial relationships dedicated to VREs. Second, we provide a language and a framework to specify spatial relationships at a conceptual level. Finally, we apply our model to specify spatial relations in two real applications: Virtual Physics Laboratory -- a VRE for learning physics, and BrestCoz -- an application for visiting Brest harbour in the 18th century. We claim that the proposed language is a relevant basis to specify spatial constraints related to activities of agents and users within VREs.
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Athanasopoulos, Michael. "Modelling and Animation using Partial Differential Equations. Geometric modelling and computer animation of virtual characters using elliptic partial differential equations." Thesis, University of Bradford, 2011. http://hdl.handle.net/10454/5437.
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This work addresses various applications pertaining to the design, modelling and animation of parametric surfaces using elliptic Partial Differential Equations (PDE) which are produced via the PDE method. Compared with traditional surface generation techniques, the PDE method is an effective technique that can represent complex three-dimensional (3D) geometries in terms of a relatively small set of parameters. A PDE-based surface can be produced from a set of pre-configured curves that are used as the boundary conditions to solve a number of PDE. An important advantage of using this method is that most of the information required to define a surface is contained at its boundary. Thus, complex surfaces can be computed using only a small set of design parameters. In order to exploit the advantages of this methodology various applications were developed that vary from the interactive design of aircraft configurations to the animation of facial expressions in a computer-human interaction system that utilizes an artificial intelligence (AI) bot for real time conversation. Additional applications of generating cyclic motions for PDE based human character integrated in a Computer-Aided Design (CAD) package as well as developing techniques to describe a given mesh geometry by a set of boundary conditions, required to evaluate the PDE method, are presented. Each methodology presents a novel approach for interacting with parametric surfaces obtained by the PDE method. This is due to the several advantages this surface generation technique has to offer. Additionally, each application developed in this thesis focuses on a specific target that delivers efficiently various operations in the design, modelling and animation of such surfaces.
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Percival, Graham Keith. "Physical modelling meets machine learning : performing music with a virtual string ensemble." Thesis, University of Glasgow, 2013. http://theses.gla.ac.uk/4253/.
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This dissertation describes a new method of computer performance of bowed string instruments (violin, viola, cello) using physical simulations and intelligent feedback control. Computer synthesis of music performed by bowed string instruments is a challenging problem. Unlike instruments whose notes originate with a single discrete excitation (e.g., piano, guitar, drum), bowed string instruments are controlled with a continuous stream of excitations (i.e. the bow scraping against the string). Most existing synthesis methods utilize recorded audio samples, which perform quite well for single-excitation instruments but not continuous-excitation instruments. This work improves the realism of synthesis of violin, viola, and cello sound by generating audio through modelling the physical behaviour of the instruments. A string's wave equation is decomposed into 40 modes of vibration, which can be acted upon by three forms of external force: A bow scraping against the string, a left-hand finger pressing down, and/or a right-hand finger plucking. The vibration of each string exerts force against the instrument bridge; these forces are summed and convolved with the instrument body impulse response to create the final audio output. In addition, right-hand haptic output is created from the force of the bow against the string. Physical constants from ten real instruments (five violins, two violas, and three cellos) were measured and used in these simulations. The physical modelling was implemented in a high-performance library capable of simulating audio on a desktop computer one hundred times faster than real-time. The program also generates animated video of the instruments being performed. To perform music with the physical models, a virtual musician interprets the musical score and generates actions which are then fed into the physical model. The resulting audio and haptic signals are examined with a support vector machine, which adjusts the bow force in order to establish and maintain a good timbre. This intelligent feedback control is trained with human input, but after the initial training is completed the virtual musician performs autonomously. A PID controller is used to adjust the position of the left-hand finger to correct any flaws in the pitch. Some performance parameters (initial bow force, force correction, and lifting factors) require an initial value for each string and musical dynamic; these are calibrated automatically using the previously-trained support vector machines. The timbre judgements are retained after each performance and are used to pre-emptively adjust bowing parameters to avoid or mitigate problematic timbre for future performances of the same music. The system is capable of playing sheet music with approximately the same ability level as a human music student after two years of training. Due to the number of instruments measured and the generality of the machine learning, music can be performed with ensembles of up to ten stringed instruments, each with a distinct timbre. This provides a baseline for future work in computer control and expressive music performance of virtual bowed string instruments.
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Chang, Jaewoong. "A modelling and networking architecture for distributed virtual environments with multiple servers." Thesis, University of Hull, 1999. http://hydra.hull.ac.uk/resources/hull:8383.
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Virtual Environments (VEs) attempt to give people the illusion of immersion that they are in a computer generated world. VEs allow people to actively participate in a synthetic environment. They range from a single-person running on a single computer, to multiple-people running on several computers connected through a network. When VEs are distributed on multiple computers across a network, we call this a Distributed Virtual Environment (DVE). Virtual Environments can benefit greatly from distributed strategies. A networked VE system based on the Client-Server model is the most commonly used paradigm in constructing DVE systems. In a Client-Server model, data can be distributed on several server computers. The server computers provide services to their own clients via networks. In some client-server models, however, a powerful server is required, or it will become a bottleneck. To reduce the amount of data and traffic maintained by a single server, the servers themselves can be distributed, and the virtual environment can be divided over a network of servers. The system described in this thesis, therefore, is based on the client-server model with multiple servers. This grouping is called a Distributed Virtual Environment System with Multiple- Servers (DVM). A DVM system shows a new paradigm of distributed virtual environments based on shared 3D synthetic environments. A variety of network elements are required to support large scale DVM systems. The network is currently the most constrained resource of the DVM system. Development of networking architectures is the key to solving the DVM challenge. Therefore, a networking architecture for implementing a DVM model is proposed. Finally, a DVM prototype system is described to demonstrate the validity of the modelling and network architecture of a DVM model.
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CHEVITARESE, DANIEL SALLES. "NEURONAL CIRCUIT SPECIFICATION LANGUAGE AND TOOLS FOR MODELLING THE VIRTUAL FLY BRAIN." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2015. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=29820@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO<br>COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR<br>PROGRAMA DE EXCELENCIA ACADEMICA<br>PROGRAMA DE DOUTORADO SANDUÍCHE NO EXTERIOR<br>O cérebro da Drosophila é um sistema atrativo para o estudo da lógica do circuito neural, porque implementa o comportamento sensorial complexo com um sistema nervoso que compreende um número de componentes neurais que é de cinco ordens de grandeza menor do que o de vertebrados. A análise do conectoma da mosca, revelou que o seu cérebro compreende cerca de 40 subdivisões distintas chamadas unidades de processamento local (LPUs), cada uma das quais é caracterizada por circuitos de processamento
únicos. As LPUs podem ser consideradas os blocos de construção funcionais da cérebro, uma vez que quase todas LPUs identificadas correspondem a regiões anatômicas do cérebro associadas com subsistemas funcionais específicos tais como a sensação e locomoção. Podemos, portanto, emular todo o cérebro da mosca, integrando suas LPUs constituintes. Embora o nosso conhecimento do circuito interno de muitas LPUs está longe de ser completa, análises dessas LPUs compostas pelos sistemas olfativos e visuais da mosca sugerem a existência de repetidos sub-circuitos que são essenciais para as funções de processamento de informações fornecidas por cada LPU. O desenvolvimento de modelos LPU plaussíveis, portanto, requer
a habilidade de especificar e instanciar sub-circuitos, sem referência explícita a seus neurônios constituintes ou ligações internas. Para este fim, este trabalho apresenta um arcabouço para modelar e especificar circuitos do cérebro, proporcionando uma linguagem de especificação neural chamada CircuitML, uma API Python para melhor manipular arquivos CircuitML e um conector otimizado para neurokernel para a simulação desses LPUs em GPU. A CircuitML foi concebida como uma extensão para NeuroML (NML), que é uma linguagem para de descrição de redes neurais biológicas baseada em XML que fornece primitivas para a definição de sub-circuitos neurais. Sub-circuitos são dotados de portas de interface que permitem a sua ligação a outros sub-circuitos através de padrões de conectividade neural.<br>The brain of the fruit y Drosophila Melanogaster is an attractive model system for studying the logic of neural circuit function because it implements complex sensory-driven behavior with a nervous system comprising a
number of neural components that is five orders of magnitude smaller than that of vertebrates. Analysis of the fly s connectome, or neural connectivity map, using the extensive toolbox of genetic manipulation techniques developed for Drosophila, has revealed that its brain comprises about 40 distinct modular subdivisions called Local Processing Units (LPUs), each of which is characterized by a unique internal information processing circuitry. LPUs can be regarded as the functional building blocks of the y, since almost all identified LPUs have been found to correspond to anatomical regions of the y brain associated with specific functional subsystems such as sensation and locomotion. We can therefore emulate the entire
y brain by integrating its constituent LPUs. Although our knowledge of the internal circuitry of many LPUs is far from complete, analyses of those LPUs comprised by the fly s olfactory and vision systems suggest the existence of repeated canonical sub-circuits that are integral to the information processing functions provided by each LPU. The development of plausible LPU models therefore requires the ability to specify and instantiate sub-circuits without explicit reference to their constituent neurons and internal connections. To this end, this work presents a framework to model and specify the circuit of the brain, providing a neural circuit specification language called CircuitML, a Python API to better handler CircuitML files and an optimized connector to neurokernel for the simulation of those LPUs on GPU. CircuitML has been designed as an extension to NeuroML (NML), which is an XML-based neural model description language that
provides constructs for defining sub-circuits that comprise neural primitives. Sub-circuits are endowed with interface ports that enable their connection to other sub-circuits via neural connectivity patterns.
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Dumbuya, Abdulai Don. "Visual perception modelling for intelligent virtual driver agents in synthetic driving simulation." Thesis, Loughborough University, 2003. https://dspace.lboro.ac.uk/2134/34591.
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This thesis documents new research into the modelling of driver vision and the integration of a new vision model into a microscopic traffic simulation tool. It is proposed and demonstrated that modelling of driver vision enhances the realism of simulated driver decision-making and behaviour, in turn, leading to improved simulation of driver interactions and traffic flow. Driving and traffic related research has traditionally fallen into the three distinct areas of driver psychology, traffic and highway engineering and vehicle dynamics, with modelling or experimentation in any of these areas supported by significant approximation in the others. In contrast to this, the vision research discussed here has been carried out in a context that aims to integrate all of these areas equally. This has been realised through the implementation of a new modelling environment, Synthetic Driving SIMulation, SD-SIM.
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Alrashdan, Khaled Rasheed. "A virtual environment for the modelling, simulation and manufacturing of orthopaedic devices." Thesis, Brunel University, 2011. http://bura.brunel.ac.uk/handle/2438/8840.
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The objective of this work is to investigate whether the game physics based modelling is accurate enough to be used in modelling the motion of the human body, in particular musculoskeletal motion. Hitherto, the implementation of game physics in the medical field focused only on anatomical representation for education and training purposes. Introducing gaming platforms and physics engines into orthopaedics applications will help to overcome several difficulties encountered in the modelling of articular joints. Implementing a physics engine (PhysX), which is mainly designed for video games, handles intensive computations in optimized ways at an interactive speed. In this study, the capabilities of the physics engine (PhysX) and gaming platform for modelling and simulating articular joints are evaluated. First, a preliminary validation is carried out for mechanical systems with analytical solutions, before constructing the musculoskeletal model to evaluate the consistency of gaming platforms. The developed musculoskeletal model deals with the human joint as an unconstrained system with 6 DOF which is not available with other joint modeller. The model articulation is driven by contact surfaces and the stiffness of surrounding tissues. A number of contributions, such as contact modelling and muscle wrapping, have been made in this research to overcome some existing challenges in joint modelling. Using muscle segmentation, the proposed technique effectively handles the problem of muscle wrapping, a major concern for many; thus the shortest path and line of action are no longer problematic. Collision behaviour has also shown a stable response for colliding as well as resting objects, provided that it is based on the principles of surface properties and the conservation of linear and angular momentums. The precision of collision detection and response are within an acceptable tolerance controllable by varying the mesh density. An image based analysis system is developed in this thesis, mainly in order to validate the proposed physics based modelling solution. This minimally invasive method is based on the analysis of marker positions located at bony positions with minimal skin movement. The image based system overcomes several challenges associated with the currently existing methods, such as inaccuracy, complication, impracticability and cost. The analysis part of this research has considered the elbow joint as a case study to investigate and validate the proposed physics based model. Beside the interactive 3D simulation, the obtained results are validated by comparing them with the image based system developed within the current research to investigate joint kinematics and laxity and also with published material, MJM and results from experiments performed at the Brunel Orthopaedic Research and Learning Centre. The proposed modelling shows the advantageous speed, reliability and flexibility of the proposed model. It is shown that the gaming platform and physics engine provide a viable solution to human musculoskeletal modelling. Finally, this thesis considers an extended implementation of the proposed platform for testing and assessing the design of custom-made implants, to enhance joint performance. The developed simulation software is expected to give indicative results as well as testing different types of prosthetic implant. Design parameterization and sensitivity analysis for geometrical features are discussed. Thus, an integrated environment is proposed to link the real-time simulation software with a manufacturing environment so as to assist the production of patient specific implants by rapid manufacturing.
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Cortes, Ciriano Isidro. "Applications of proteochemometrics (PCM) : from species extrapolation to cell-line sensitivity modelling." Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066176/document.
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Proteochemometrics (PCM) est une bioactivité prophétique la méthode posante de simultanément modeler la bioactivité de ligands multiple contre des objectifs multiples<br>Proteochemometrics (PCM) is a predictive bioactivity modelling method to simultaneously model the bioactivity of multiple ligands against multiple targets. Therefore, PCM permits to explore the selectivity and promiscuity of ligands on biomolecular systems of different complexity, such proteins or even cell-line models. In practice, each ligand-target interaction is encoded by the concatenation of ligand and target descriptors. These descriptors are then used to train a single machine learning model. This simultaneous inclusion of both chemical and target information enables the extra- and interpolation to predict the bioactivity of compounds on targets, which can be not present in the training set. In this thesis, a methodological advance in the field is firstly introduced, namely how Bayesian inference (Gaussian Processes) can be successfully applied in the context of PCM for (i) the prediction of compounds bioactivity along with the error estimation of the prediction; (ii) the determination of the applicability domain of a PCM model; and (iii) the inclusion of experimental uncertainty of the bioactivity measurements. Additionally, the influence of noise in bioactivity models is benchmarked across a panel of 12 machine learning algorithms, showing that the noise in the input data has a marked and different influence on the predictive power of the considered algorithms. Subsequently, two R packages are presented. The first one, Chemically Aware Model Builder (camb), constitues an open source platform for the generation of predictive bioactivity models. The functionalities of camb include : (i) normalized chemical structure representation, (ii) calculation of 905 one- and two-dimensional physicochemical descriptors, and of 14 fingerprints for small molecules, (iii) 8 types of amino acid descriptors, (iv) 13 whole protein sequence descriptors, and (iv) training, validation and visualization of predictive models. The second package, conformal, permits the calculation of confidence intervals for individual predictions in the case of regression, and P values for classification settings. The usefulness of PCM to concomitantly optimize compounds selectivity and potency is subsequently illustrated in the context of two application scenarios, which are: (a) modelling isoform-selective cyclooxygenase inhibition; and (b) large-scale cancer cell-line drug sensitivity prediction, where the predictive signal of several cell-line profiling data is benchmarked (among others): basal gene expression, gene copy-number variation, exome sequencing, and protein abundance data. Overall, the application of PCM in these two case scenarios let us conclude that PCM is a suitable technique to model the activity of ligands exhibiting uncorrelated bioactivity profiles across a panel of targets, which can range from protein binding sites (a), to cancer cell-lines (b)
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Pezouvanis, Antonios. "Engine modelling for virtual mapping : development of a physics based cycle-by-cycle virtual engine that can be used for cyclic engine mapping applications, engine flow modelling, ECU calibration, real-time engine control or vehicle simulation studies." Thesis, University of Bradford, 2009. http://hdl.handle.net/10454/4419.
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After undergoing a study about current engine modelling and mapping approaches as well as the engine modelling requirements for different applications, a major problem found to be present is the extensive and time consuming mapping procedure that every engine has to go through so that all control parameters can be derived from experimental data. To improve this, a cycle-by-cycle modelling approach has been chosen to mathematically represent reciprocating engines starting by a complete dynamics crankshaft mechanism model which forms the base of the complete engine model. This system is modelled taking into account the possibility of a piston pin offset on the mechanism. The derived Valvetrain model is capable of representing a variable valve lift and phasing Valvetrain which can be used while modelling most modern engines. A butterfly type throttle area model is derived as well as its rate of change which is believed to be a key variable for transient engine control. In addition, an approximation throttle model is formulated aiming at real-time applications. Furthermore, the engine inertia is presented as a mathematical model able to be used for any engine. A spark ignition engine simulation (SIES) framework was developed in MATLAB SIMULINK to form the base of a complete high fidelity cycle-by-cycle simulation model with its major target to provide an environment for virtual engine mapping procedures. Some experimental measurements from an actual engine are still required to parameterise the model, which is the reason an engine mapping (EngMap) framework has been developed in LabVIEW, It is shown that all the moving engine components can be represented by a single cyclic variable which can be used for flow model development.
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Spranger, Katerina. "Computational modelling of vascular interventions : endovascular device deployment." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:2c052e1f-3a8c-4d82-9907-ce17677b0c05.
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Minimally invasive vascular interventions with stent deployment have become a popular alternative to conventional open surgery in the treatment of many vascular disorders. However, the high initial success rates of endovascular repairs have been overshadowed by reported complications that cause re-interventions and, in the worst case, morbidity and mortality. The dangerous complications could be mitigated by better choice of device design and by the appropriate positioning of the implant inside the vessel. However, there is currently no possibility for the interventionist to predict the resulting position and the expanded shape of the device for a given patient, before the actual procedure, within the clinical setting. Motivated by this unmet clinical need and the lack of suitable methods, this thesis develops a methodology for modelling virtual deployment of implantable devices inside patient vessels, that features fast computational execution times and can be used in clinical practice. This novel deployment method was developed based on a spring-mass model and was tested in different deployment scenarios, expanding stents inside vessels in the order of seconds. Further, the performance of the novel method was optimised by calibrating a set of parameters with the help of a genetic algorithm, which utilises the outcomes of a finite element analysis as a learning reference. After the calibration, the developed stenting method demonstrated acceptable accuracy as compared to the "gold standard" of the finite element simulation. Finally, on a real patient case, 4 alternative stenting scenarios were investigated by comparing the subsequent blood flow conditions, via computational haemodynamics. The obtained results suggested that device design, dimensions, stiffness and positioning have important implications on the post-procedural haemodynamics of the vessel. Ultimately, the presented results can play a transformative role in aiding clinical decision-making and also give rise to overall improvements in implant design and deployment procedure.
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Alzamil, Ibrahim Ali M. "Energy-aware profiling and prediction modelling of virtual machines in cloud computing environments." Thesis, University of Leeds, 2017. http://etheses.whiterose.ac.uk/17243/.
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Cloud Computing has changed the way in which individuals and businesses use IT resources. Instead of buying their own IT resources, they can use the Cloud services offered by Cloud providers with reasonable costs based on a “pay-per-use” model. With the wide adoption of Cloud Computing, the costs for maintaining the Cloud infrastructure have become a vital issue for the providers, especially with the large amount of energy being consumed to operate these resources. Hence, the excessive use of energy consumption in Cloud infrastructures has become one of the major cost factors for Cloud providers. In order to reduce the energy consumption and enhance the energy efficiency of Cloud resources, proactive and reactive management tools are used with consideration of physical resources’ energy consumption. However, these tools need to be supported with energy-awareness not only at the physical machine (PM) level but also at virtual machine (VM) level in order to make enhanced energy-aware decisions. As the VMs do not have physical interface, identifying the energy consumption at the VM level is difficult and not directly measured. This thesis introduces an energy-aware Cloud system architecture that aims to enable energy-awareness at the deployment and operational levels of a Cloud environment. At the operational level, an energy-aware profiling model is introduced to identify energy consumption for heterogeneous and homogeneous VMs running on the same PM based on the size and CPU utilisation of each VM. At the deployment level, an energy-aware prediction framework is introduced to forecast future VMs’ energy consumption. This framework first predicts the VMs’ workload based on historical workload patterns, particularly static and periodic, using Auto-regressive Integrated Moving Average (ARIMA) model. The predicted VM workload is then correlated to the physical resources within this framework in order to get the predicted VM energy consumption. The evaluation of the proposed work on a real Cloud testbed reveals that the proposed energy-aware profiling model is capable of fairly attributing the physical energy consumption to homogeneous and heterogeneous VMs, therefore enabling energy-awareness at the VM level. Compared with actual results obtained in this testbed, the predicted results show that the proposed energy-aware prediction framework is capable of forecasting the energy consumption for the VMs with a good prediction accuracy for static and periodic Cloud application workload patterns. The application of the proposed work is providing energy-awareness which can be used and incorporated by other reactive and proactive management tools to make enhanced energy-aware decisions and efficiently manage the Cloud resources. This can lead towards a reduction of energy consumption, and therefore lowering the cost of operational expenditure (OPEX) for Cloud providers and having less impact on the environment.
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Haag, Zsolt. "Deontic logic based process modelling for co-ordination support in virtual software corporations." Thesis, Glasgow Caledonian University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322220.
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Virtual Software Corporations (VSCs) are a novel and important organisational form for large-scale software development. The increased complexity of this development environment requires the use of tools to support human actors in undertaking their tasks, which in turn require modelling solutions able to capture the VSC specific issues. One of the key aspects identified for software development in a VSC setting is the need to support co-ordination. One approach in the development of support for coordination in heterogeneous environments in respect to processes and support tools, such as VSCs, is the use of commitment management. The purpose of this thesis is to define a formalism suitable for capturing and managing commitments, as a means to support co-ordination. This is done by first analysing existing VSCs, and determining the requirements for co-ordination support. Consequently a formalism is defined to address the requirements. The formalism is based on a commitment modelling approach and deontic logic, a modal logic, which is used to manage the commitments. The defined formalism is the basis of a prototype support system, which is used for testing and evaluating. The evaluation has focused on identifying the level of support provided for the initial requirements. To this end three process examples have been used: the initial case study, the study of an independent VSC and the example of a desired process for software configuration management.The results indicate that the formalism, through the use of the prototype system, is able to represent and to manage commitments, as the most important issues in coordinating VSC software development. Thus it has a significant contribution as a modelling approach and it was shown to be applicable to realistic process scenarios.
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Butters, Timothy Daniel. "Development of a virtual 3D sheep atria for the study of clinical atrial fibrillation." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/development-of-a-virtual-3d-sheep-atria-for-the-study-of-clinical-atrial-fibrillation(d462efa3-19d0-4c1f-bede-a00a4190b678).html.
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Cardiovascular disease remains the leading cause of death in the developed world. In this thesis computational modelling techniques were used to study the mechanisms and genesis of atrial arrhythmias. It is separated into 2 parts: (1) The mechanistic links between mutations of the fast Na+ channel (INa) and the ability of the sinoatrial node to pace the surrounding atrial muscle were investigated. The mutations were separated into two groups, one for the mutations affecting the steady-state activation, and the other for those affecting steady-state inactivation. On the single cell level it was found that all mutations slowed the pacing rate of the sinoatrial node in a similar way, but at the 2D level the two mutation groups modulated the excitation of the tissue differently. One caused a conduction block between the sinoatrial node and atrium, where the other abolished pacemaking all together. (2) A new set of mathematical models were then developed for the sheep atria. This was incorporated into an anatomically detailed 3D geometry of the whole sheep atria to form a platform suitable for the study of clinical atrial fibrillation, and other atrial arrhythmias. Due to the lack of single cell electrophysiology data available, a method of cross-species modelling was utilised. A biophysically detailed model of the 3D sheep atria was created, and used in a preliminary study into the susceptibility of tissue to atrial fibrillation from the rapid pacing of the pulmonary vein area. It was found that both electrical heterogeneity and the complex fibre structure of the atria need to be considered for sustained atrial fibrillation to be seen.
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Demoucron, Matthias. "On the control of virtual violins - Physical modelling and control of bowed string instruments." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2008. http://tel.archives-ouvertes.fr/tel-00349920.
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Cette thèse porte sur le contrôle de la synthèse sonore par modélisation physique des instruments à corde frottée. Elle se base, d'une part, sur l'exploration systématique de l'influence des paramètres de contrôle (pression d'archet, vitesse de l'archet et distance au chevalet) sur le comportement du modèle, et d'autre part, sur la mesure du contrôle effectif qu'exerce l'instrumentiste afin d'obtenir un contrôle réaliste du modèle physique. Un modèle physique basé sur la résolution modale de l'équation de la corde est d'abord présenté et implémenté pour la synthèse sonore du violon. Le comportement du modèle physique est ensuite examiné en effectuant des simulations et se concentre sur deux aspects: la ``jouabilité", c'est-à-dire l'espace des paramètres de contrôle dans lequel un mouvement de Helmholtz périodique est obtenu, et les variations des propriétés du son synthétisé (fréquence d'oscillation, niveau sonore et centroïde spectral) à l'intérieur de cet espace de paramètres. La deuxième partie de ce travail concerne la mise au point d'un capteur pour mesurer la force d'appui de l'archet sur la corde dans un contexte de jeu réel. Le capteur est ensuite combiné avec un système optique de capture du mouvement afin de mesurer l'ensemble complet des paramètres de jeu du violoniste. La dernière partie présente l'analyse des mesures de ces paramètres de contrôle pour des modes de jeu typiques (sautillé, spiccato, martelé, tremolo, détaché). Ces mesures permettent de décrire certaines propriétés du geste instrumental et de proposer un contrôle réaliste de la synthèse sonore pour différents modes de jeu et différentes tâches musicales.
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Southey, Finnegan. "OSSA, a modelling system for virtual realities based on conceptual graphs and production systems." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ35935.pdf.
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Kulkarni, Davendu Yashwant. "The feature-based computational geometry and secondary air system modelling for virtual gas turbines." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/56959.
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This dissertation presents a novel method for generating the computational geometry of three spool aero engine for the Virtual Engine (VE) design environment, which is capable of carrying out full integration of preliminary and detailed design and analysis activities. The multi-fidelity and multi-disciplinary analysis of complex gas-turbine assemblies is the prime requirement of industrial design. The present challenges for gas-turbine industry, namely excessive design times, lack of decisive information till the late design stages, mismatching of databases and high costs associated with testing etc. necessitate creation of an integrated design framework such as VE. This thesis presents the work on selected parts of VE design environment. The present work initially focuses on the development of an integrated geometry modelling system for VE. The architecture of geometry module is derived from the requirements of VE design environment and Computer Aided Design (CAD) geometry systems. A dedicated geometry modeller is developed to represent gas turbine components. The building blocks of this modeller, known as features, are constructed as object-oriented data structures. A taxonomy of turbomachinery design features is defined to generate 2D axisymmetric geometry model of three-spool aero-engine. Such system supports intra-analysis information augmentation, data updating and automated data transformation for any kind of analysis. In the next phase, the Computer Aided Engineering (CAE) capabilities of VE are demonstrated by carrying out flow network analysis of Secondary Air System (SAS). Particular attention is devoted to the automated extraction of SAS network from the geometry. The generation of SAS network involves interrogation of component models, automatic identification of flow links and pre-processing of network elements. A library of physics-based linearized pressure loss models is prepared, validated and incorporated in VE. A new loss model for straight-through labyrinth seal is developed from numerical experiments and it is validated against those in the literature. A linearized flow solver for the whole engine SAS network model is also developed. Finally, low fidelity steady-state flow analysis is demonstrated on a limited domain of SAS network model. This work meets its objectives by showing a way of constructing important modules of VE design framework. It bridges the gap in current features technology by creating the design features that represent turbomachinery components. The work demonstrates quick generation of low-fidelity geometry model for whole aero-engine assembly, thus endorsing its utility for the analysis in early stages of design. A methodology for performing automated CAE analysis of secondary air system (SAS) of aero engine has also been developed. The development of new loss model for labyrinth seal and the demonstration of low-fidelity steady-state SAS analysis confirm the successful implementation of selected part of VE project.
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Korzeniowski, Przemyslaw. "Modelling and simulation of flexible instruments for minimally invasive surgical training in virtual reality." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/58344.
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Improvements in quality and safety standards in surgical training, reduction in training hours and constant technological advances have challenged the traditional apprenticeship model to create a competent surgeon in a patient-safe way. As a result, pressure on training outside the operating room has increased. Interactive, computer based Virtual Reality (VR) simulators offer a safe, cost-effective, controllable and configurable training environment free from ethical and patient safety issues. Two prototype, yet fully-functional VR simulator systems for minimally invasive procedures relying on flexible instruments were developed and validated. NOViSE is the first force-feedback enabled VR simulator for Natural Orifice Transluminal Endoscopic Surgery (NOTES) training supporting a flexible endoscope. VCSim3 is a VR simulator for cardiovascular interventions using catheters and guidewires. The underlying mathematical model of flexible instruments in both simulator prototypes is based on an established theoretical framework – the Cosserat Theory of Elastic Rods. The efficient implementation of the Cosserat Rod model allows for an accurate, real-time simulation of instruments at haptic-interactive rates on an off-the-shelf computer. The behaviour of the virtual tools and its computational performance was evaluated using quantitative and qualitative measures. The instruments exhibited near sub-millimetre accuracy compared to their real counterparts. The proposed GPU implementation further accelerated their simulation performance by approximately an order of magnitude. The realism of the simulators was assessed by face, content and, in the case of NOViSE, construct validity studies. The results indicate good overall face and content validity of both simulators and of virtual instruments. NOViSE also demonstrated early signs of construct validity. VR simulation of flexible instruments in NOViSE and VCSim3 can contribute to surgical training and improve the educational experience without putting patients at risk, raising ethical issues or requiring expensive animal or cadaver facilities. Moreover, in the context of an innovative and experimental technique such as NOTES, NOViSE could potentially facilitate its development and contribute to its popularization by keeping practitioners up to date with this new minimally invasive technique.
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Demoucron, Matthias. "On the control of virtual violins : physical modelling and control of bowed string instrument." Paris 6, 2008. http://www.theses.fr/2008PA066430.
Full textAbstract:
Cette thèse porte sur le contrôle de la synthèse sonore par modélisation physique des instruments à corde frottée. Un modèle physique basé sur la résolution modale de l'équation de la corde est d'abord présenté et implémenté pour la synthèse sonore du violon. L’exploration systématique de l'influence des paramètres de contrôle sur le comportement du modèle permet ensuite de définir des régions optimales pour le jeu et d’en décrire les propriétés sonores. D’autre part, un capteur est mis au point pour mesurer la force d'appui de l'archet sur la corde, et combiné avec un système de capture du mouvement afin de mesurer les paramètres de jeu du violoniste dans un contexte de jeu réel. L’analyse du contrôle effectif qu'exerce l'instrumentiste permet finalement de décrire les propriétés de son geste et de proposer un contrôle réaliste de la synthèse sonore pour différents modes de jeu et différentes tâches musicales.
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Gwynn, Timothy. "A user interface for terrain modelling in virtual reality using a head mounted display." Master's thesis, Faculty of Science, 2021. http://hdl.handle.net/11427/33707.
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The increased commercial availability of virtual reality (VR) devices has resulted in more content being created for virtual environments (VEs). This content creation has mainly taken place using traditional desktop systems but certain applications are now integrating VR into the creation pipeline. Therefore we look at the effectiveness of creating content, specifically designing terrains, for use in immersive environments using VR technology. To do this, we develop a VR interface for terrain creation based on an existing desktop application. The interface incorporates a head-mounted display and 6 degree of freedom controllers. This allows the mapping of user controls to more natural movements compared to the abstract controls in mouse and keyboard based systems. It also means that users can view the terrain in full 3D due to the inherent stereoscopy of the VR display. The interface goes through three iterations of user centred design and testing. This results in paper and low fidelity prototypes being created before the final interface is developed. The performance of this final VR interface is then compared to the desktop interface on which it was based. We carry out user tests to assess the performance of each interface in terms of speed, accuracy and usability. From our results we find that there is no significant difference between the interfaces when it comes to accuracy but that the desktop interface is superior in terms of speed while the VR interface was rated as having higher usability. Some of the possible reasons for these results, such as users preferring the natural interactions offered by the VR interface but not having sufficient training to fully take advantage of it, are discussed. Finally, we conclude that while it was not shown that either interface is clearly superior, there is certainly room for further exploration of this research area. Recommendations for how to incorporate lessons learned during the creation of this dissertation into any further research are also made.
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Chi, Ying. "Segmentation and deformable modelling techniques for a virtual reality surgical simulator in hepatic oncology." Thesis, Imperial College London, 2008. http://hdl.handle.net/10044/1/4350.
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Liver surgical resection is one of the most frequently used curative therapies. However, resectability is problematic. There is a need for a computer-assisted surgical planning and simulation system which can accurately and efficiently simulate the liver, vessels and tumours in actual patients. The present project describes the development of these core segmentation and deformable modelling techniques. For precise detection of irregularly shaped areas with indistinct boundaries, the segmentation incorporated active contours - gradient vector flow (GVF) snakes and level sets. To improve efficiency, a chessboard distance transform was used to replace part of the GVF effort. To automatically initialize the liver volume detection process, a rotating template was introduced to locate the starting slice. For shape maintenance during the segmentation process, a simplified object shape learning step was introduced to avoid occasional significant errors. Skeletonization with fuzzy connectedness was used for vessel segmentation. To achieve real-time interactivity, the deformation regime of this system was based on a single-organ mass-spring system (MSS), which introduced an on-the-fly local mesh refinement to raise the deformation accuracy and the mesh control quality. This method was now extended to a multiple soft-tissue constraint system, by supplementing it with an adaptive constraint mesh generation. A mesh quality measure was tailored based on a wide comparison of classic measures. Adjustable feature and parameter settings were thus provided, to make tissues of interest distinct from adjacent structures, keeping the mesh suitable for on-line topological transformation and deformation. More than 20 actual patient CT and 2 magnetic resonance imaging (MRI) liver datasets were tested to evaluate the performance of the segmentation method. Instrument manipulations of probing, grasping, and simple cutting were successfully simulated on deformable constraint liver tissue models. This project was implemented in conjunction with the Division of Surgery, Hammersmith Hospital, London; the preliminary reality effect was judged satisfactory by the consultant hepatic surgeon.
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Oqielat, Moa'ath Nasser. "Modelling water droplet movement on a leaf surface." Queensland University of Technology, 2009. http://eprints.qut.edu.au/30232/.
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The central aim for the research undertaken in this PhD thesis is the development of a model for simulating water droplet movement on a leaf surface and to compare the model behavior with experimental observations. A series of five papers has been presented to explain systematically the way in which this droplet modelling work has been realised. Knowing the path of the droplet on the leaf surface is important for understanding how a droplet of water, pesticide, or nutrient will be absorbed through the leaf surface. An important aspect of the research is the generation of a leaf surface representation that acts as the foundation of the droplet model. Initially a laser scanner is used to capture the surface characteristics for two types of leaves in the form of a large scattered data set. After the identification of the leaf surface boundary, a set of internal points is chosen over which a triangulation of the surface is constructed. We present a novel hybrid approach for leaf surface fitting on this triangulation that combines Clough-Tocher (CT) and radial basis function (RBF) methods to achieve a surface with a continuously turning normal. The accuracy of the hybrid technique is assessed using numerical experimentation. The hybrid CT-RBF method is shown to give good representations of Frangipani and Anthurium leaves. Such leaf models facilitate an understanding of plant development and permit the modelling of the interaction of plants with their environment. The motion of a droplet traversing this virtual leaf surface is affected by various forces including gravity, friction and resistance between the surface and the droplet. The innovation of our model is the use of thin-film theory in the context of droplet movement to determine the thickness of the droplet as it moves on the surface. Experimental verification shows that the droplet model captures reality quite well and produces realistic droplet motion on the leaf surface. Most importantly, we observed that the simulated droplet motion follows the contours of the surface and spreads as a thin film. In the future, the model may be applied to determine the path of a droplet of pesticide along a leaf surface before it falls from or comes to a standstill on the surface. It will also be used to study the paths of many droplets of water or pesticide moving and colliding on the surface.
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Jones, Christian Martyn. "Automated lip synchronisation for human computer interaction, animation, and communications : the MATRTI Project." Thesis, University of Newcastle Upon Tyne, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.285325.
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Wang, Yang. "Virtual testing of post-buckling behaviour of metallic stiffened panel." Thesis, Cranfield University, 2011. http://dspace.lib.cranfield.ac.uk/handle/1826/7291.
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The aim of the project presented in this thesis is to demonstrate a modelling method for predicting the variability in the ultimate load of stiffened panel under axial compression due to manufacturing variability.
Bulking is sensitive to imperfections. In the case of a post-buckled panel, manu-facturing variability produces a scatter in the ultimate load. Thus, reasonable leeway for imperfections and inherent variability must be allowed in their design.
Firstly, a finite element model of a particular stiffened panel was developed, and all nonlinearities within the material, boundary condition and geometry were considered. Verification and validation were performed to examine the accuracy of the buckling behaviour prediction, especially ultimate load.
Experiments on 5 identical panels in design were performed to determine the level of panel-panel variation in geometry and collapse load. A data reduction programme based on the practical geometry scanning was developed, in addi-tion to which, the procedure of importing measured imperfection into Finite Ele-ment model was introduced.
To identify and apply representative imperfections to the panel model, a double Fourier series representation of the random geometric distributions is attempt-ed, and was used thereby to derive a series of shapes representing random ge-ometry scatters.
With these newly generated geometric imperfections, the variation in collapse load was determined, using the validated FE analysis. And also, the probability of these predicted loads was generalized.
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Vyshnavi, Bandaru. "Virtual VPN in the Cloud : Design and Modelling of an IPSec VPN in Virtualized Environment." Thesis, Blekinge Tekniska Högskola, Institutionen för kommunikationssystem, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-10801.
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Jeffrey, Stuart. "Three dimensional modelling of Scottish early medieval sculpted stones." Thesis, Connect to electronic version, 2003. http://ads.ahds.ac.uk/catalogue/library/theses/jeffrey%5F2004/index.cfm.
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Thesis (Ph. D.)--University of Glasgow, 2003.<br>Accompanied by CD-ROM. Ph. D. thesis submitted to the Department of Archaeology, University of Glasgow, 2003. Includes bibliographical references. Print version also available.