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European conference on Power Electronics and Applications

作者： Asma Merdassi Laurent Gerbaud Seddik Bacha UMR 5269 INPG/UJF-CNRS ENSE3 G2e Laboratory (Grenoble Electrical Engineering) Saint Martin d'Heres France

ISBN: (纸本)9781424444328

The paper deals with the automatic generation of global model of static converters without the description of their environment. The considered models are average and exact models (i.e. with ideal switches). These models are obtained by using a software tool named AMG (for Average Model Generator) with a priori on the control mode and behaviour of the static converter. In this paper, an extension of this tool is developed and allows to gather together the generated models with the models of their environment without considering the equations of the loads and sources of the static converter. It proposes to use the causality between models, then non causual modelling languages as Modelica [9] or VHDL-AMS [30]. This is useful for loads such electrical machines described by a Park model. The generated models are in text file, VHDL-AMS and Modelica forms. This modelling method has been applied to several applications, among them a three-phase voltage inverter coupled with a three-phase machine simply modelled by a three-phase resistor-inductor load, presented in the paper to illustrate the approach. This generated model has been implemented in Matlab/Simulink reg (C-Sfunction) [11], VHDL-AMS (Cadence [28], Portunus [17], Mentor [29], Saber [24], Simplorer[20], Smash [27]) and Modelica (Amesim [21], Dymola [25], Scilab-Scicos [31]).

关键词： Power system modeling Static power converters Power electronics mathematical model Switches Software tools Automatic generation control Equations Voltage Inverters

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Grid connection oriented modelling of wind turbines with full converters

Grid connection oriented modelling of wind turbines with ful...

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International Universities Power engineering conference (UPEC)

作者： D. D. Banham-Hall G. A. Taylor C. A. Smith M. R. Irving Brunei University UK Converteam UK Ltd. UK

ISBN: (纸本)9781424468232;9780947649449

Wind power represents a growing proportion of generation capacity around the world. As wind power has increased, it has been important to accurately model the behaviour of wind turbines in order to understand their impact on the power system. This paper presents a model of a multi-megawatt induction machine wind turbine equipped with a full power converter. This model is implemented in Matlab-Simulink and is designed to be appropriate for power system studies whilst including representation of all major electrical, mechanical and aerodynamic subsystems. The increasing proportion of wind power in the power system has led to concern over frequency regulation and how wind plants will regulate active power. The model presented here is used to simulate both high and low frequency excursions and to demonstrate that wind turbines can be controlled to provide rapid response. Alternative approaches to providing system reserve, in the presence of a fluctuating resource, are discussed and consideration is given to the firmness of response and the level of the spilt wind.

关键词： Wind turbines Power system modeling mathematical model Wind energy Power system simulation Induction generators Power generation Wind energy generation Induction machines Computer languages

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Climate change influence on diatoms bio-diversity in Lake Prespa

Climate change influence on diatoms bio-diversity in Lake Pr...

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作者： Naumoski, Andreja Mitreski, Kosta Faculty of Electrical Engineering and Information Technology Skopje Macedonia

ISBN: (纸本)9789604741366

A diversity index (DI) is a mathematical measure of species diversity in a community. Diversity indices provide more information about community composition than simply species richness (i.e., the number of species present);they also take the relative abundances of different species into account. This paper presents DI models obtained from the diatoms abundance in Lake Prespa and correlated with physical-chemical parameters of the environment. Diversity indices have been widely used in ecology to gain better understanding of the biodiversity of an ecosystem. These indices intend to assess the diversity of any population in which each member in a part of unique spices, in our case the diatoms. For modelling of the DIs models we use the raw;as measured, values of the concentrations for the physical-chemical parameters and the diversity indices of the diatoms. The DIs are divided along two dimensions: time and space. The well known machine learning techniques are used to express this relationship: regression trees (RTs). The results from the models express high correlation between the two diversity indices and the temperature. Because these species depends on the temperature, which is expected to rise in the next decades according the climate change models, important decision policy should be implement. More strongly correlation is made with the nutrient loading and this is quite vital, because pressure from the human activities could jeopardize diatoms environmental conditions. This conclusion is important because the diatoms are spices which are known to live in water with low temperature and low level of nutrients. The models have captured this information with correlation between 0.6 and 0.7 for lake measurements, while the models from river stations didn't show any correlation. In future we plan to investigate the relationship between all DIs and physical-chemical parameters together with multi-objective regression trees.

关键词： Climate change

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A Software Agent Based Simulation Model for Systems with Decision Units

A Software Agent Based Simulation Model for Systems with Dec...

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IEEE International Symposium on Dependable, Autonomic and Secure Computing (DASC)

作者： Yuan Miao School of Engineering and Science Victoria University Australia

This paper proposes a software agent based simulation model for studying the behavior of complex, highly nonlinear, non-continuous, concurrent systems, especially those involving intelligent units or human factors. Such a system is normally very difficult, if at all possible, to be modeled with well formed differential equations or statistical models. The normal system modelling and analysis methods were not designed for such systems and could not handle them well. This paper attempts to provide insights into such systems through a software agent based simulation model. The model represents each important factors or units in the system as a software agent. One agent can have impacts on other agents. Each agent independently makes its own decision on the impacts from other agents, and/or observations of other agents. The hidden patterns of the complex system are then revealed through simulations. An simulation economic problem is used to illustrate the model.

关键词： Software agents Analytical models Power generation economics Pattern analysis humans Computational modeling Fuzzy cognitive maps Fuzzy systems mathematical model Concurrent computing

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Hierarchical learning of dimensional biases in human categorization 09

Hierarchical learning of dimensional biases in human categor...

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Proceedings of the 23rd International conference on Neural Information Processing Systems

作者： Katherine Heller Adam Sanborn Nick Chater Department of Engineering University of Cambridge Cambridge Gatsby Computational Neuroscience Unit University College London London Cognitive Perceptual and Brain Sciences University College London London

ISBN: (纸本)9781615679119

Existing models of categorization typically represent to-be-classified items as points in a multidimensional space. While from a mathematical point of view, an infinite number of basis sets can be used to represent points in this space, the choice of basis set is psychologically crucial. People generally choose the same basis dimensions - and have a strong preference to generalize along the axes of these dimensions, but not "diagonally". What makes some choices of dimension special? We explore the idea that the dimensions used by people echo the natural variation in the environment. Specifically, we present a rational model that does not assume dimensions, but learns the same type of dimensional generalizations that people display. This bias is shaped by exposing the model to many categories with a structure hypothesized to be like those which children encounter. The learning behaviour of the model captures the developmental shift from roughly "isotropic" for children to the axis-aligned generalization that adults show.

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Melt flow behaviour of poly-ε-caprolactone in fused deposition modelling

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JOURNAL OF MATERIALS SCIENCE-MATERIALS IN MEDICINE 2008年第7期19卷 2541-2550页

作者： Ramanath, H. S. Chua, C. K. Leong, K. F. Shah, K. D. Singapore Inst Mfg Technol Singapore 638075 Singapore Nanyang Technol Univ Sch Mech & Aerosp Engn Singapore 639798 Singapore Vellore Inst Technol Sch Mech & Bldg Engn Vellore Tamil Nadu India

Fused deposition modelling (FDM) is an extrusion based Rapid prototyping (RP) technique which can be used to fabricate tissue engineering scaffolds. The present work focuses on the study of the melt flow behaviour (MFB) of Poly-epsilon-caprolactone (PCL) as a representative biomaterial, on the FDM. The MFB significantly affects the quality of the scaffold which depends not only on the pressure gradient, its velocity, and the temperature gradients but also physical properties like the melt temperature and rheology. The MFB is studied using two methods: mathematical modelling and finite element analysis (FEA) using Ansys (R). The MFB is studied using accurate channel geometry by varying filament velocity at the entry and by varying nozzle diameters and angles at the exit. The comparative results of both mathematical modelling and FEA suggest that the pressure drop and the velocities of the melt flow depend on the flow channel parameters. One inference of particular interest is the temperature gradient of the PCL melt, which shows that it liquefies within 35% of the channel length. These results are invaluable to better understand the MFB of biomaterials that affects the quality of the scaffold built via FDM and can also be used to predict the MFB of other biomaterials.

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3D fuel cracking modelling in pellet cladding mechanical interaction

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engineering FRACTURE MECHANICS 2008年第11期75卷 3581-3598页

作者： Michel, B. Sercombe, J. Thouvenin, G. Chatelet, R. CEN Cadarache DEC SESC F-13108 St Paul Les Durance France

This study is concerned with the modelling of fuel behaviour and of pellet-cladding interaction (PCI). A new fuel software (PLEIADES) is currently co-developed by the Atomic Energy Commission (CEA) and Electricite de France (EDF). This software includes a multi-dimensional FE program (ALCYONE) devoted to Pressure Water Reactors (PWR) fuel rods. PCI studies are mainly undertaken with the 3D model of ALCYONE. The objectives of this work are twofold: first, to propose a constitutive model for the fuel pellet which accounts for the stress relaxation of the material resulting from cracking and creep, second, to estimate the impact of the pellet cracking oil PCI. In this paper, a mathematical formulation which couples a viscoplastic law for creep with a multi-surface plastic softening law for cracking is detailed, leading a two inelastic strains model. Mesh dependency is overcome thanks to a material parameter related to the finite element size. The 3D calculations of PCI presented in this paper show that the considered modelling of fuel cracking is consistent with the experimental knowledge available on crack development under irradiation. A parametric study is then presented which leads to the conclusion that the tangential stresses at the pellet cladding interface and hence the risk of PCI failure are significantly reduced when the fuel tensile strength is divided by two. (C) 2006 Elsevier Ltd. All rights reserved.

关键词： PWR pellet-cladding interaction (PCI) failure behaviour

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Diagrammatic Models in the engineering Sciences

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FOUNDATIONS OF SCIENCE 2008年第2期13卷 127-142页

作者： Boon, Mieke Univ Twente Dept Philosophy NL-7500 AE Enschede Netherlands

This paper is concerned with scientific reasoning in the engineering sciences. engineering sciences aim at explaining, predicting and describing physical phenomena occurring in technological devices. The focus of this paper is on mathematical description. These mathematical descriptions are important to computer-aided engineering or design programs (CAE and CAD). The first part of this paper explains why a traditional view, according to which scientific laws explain and predict phenomena and processes, is problematic. In the second part, the reasons of these methodological difficulties are analyzed. Ludwig Prandtl's method of integrating a theoretical and empirical approach is used as an example of good scientific practice. Based on this analysis, a distinction is made between different types of laws that play a role in constructing mathematical descriptions of phenomena. A central assumption in understanding research methodology is that, instead of scientific laws, knowledge of capacities and mechanisms are primary in the engineering sciences. Another important aspect in methodology of the engineering sciences is that in explaining a phenomenon or process spatial regions are distinguished in which distinct physical behaviour occur. The mechanisms in distinct spatial regions are represented in a so-called diagrammatic model. The construction of a mathematical description of the phenomenon or process is based on this diagrammatic model.

关键词： engineering science Diagrammatic models Methodology Prandtl mathematical modelling Scientific practice Experiments

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Mitral valve finite-element modelling from ultrasound data: a pilot study for a new approach to understand mitral function and clinical scenarios

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PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A-mathematical PHYSICAL AND engineering SCIENCES 2008年第1879期366卷 3411-3434页

作者： Votta, Emiliano Caiani, Enrico Veronesi, Federico Soncini, Monica Montevecchi, Franco Maria Redaelli, Alberto Politecn Milan Dept Bioengn I-20133 Milan Italy Politecn Torino Dept Mech I-10129 Turin Italy

In the current scientific literature, particular attention is dedicated to the study of the mitral valve and to comprehension of the mechanisms that lead to its normal function, as well as those that trigger possible pathological conditions. One of the adopted approaches consists of computational modelling, which allows quantitative analysis of the mechanical behaviour of the valve by means of continuum mechanics theory and numerical techniques. However, none of the currently available models realistically accounts for all of the aspects that characterize the function of the mitral valve. Here, a new computational model of the mitral valve has been developed from in vivo data, as a first step towards the development of patient-specific models for the evaluation of annuloplasty procedures. A structural finite-element model of the mitral valve has been developed to account for all of the main valvular substructures. In particular, it includes the real geometry and the movement of the annulus and papillary muscles, reconstructed from four-dimensional ultrasound data from a healthy human subject, and a realistic description of the complex mechanical properties of mitral tissues. Preliminary simulations allowed mitral valve closure to be realistically mimicked and the role of annulus and papillary muscle dynamics to be quantified.

关键词： mitral valve finite-element modelling three-dimensional real-time echocardiography

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Accurate robot simulation through system identification

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ROBOTICS AND AUTONOMOUS SYSTEMS 2008年第12期56卷 1082-1093页

作者： Kyriacou, T. Nehmzow, U. Iglesias, R. Billings, S. A. Univ Ulster Sch Comp & Intelligent Syst Coleraine BT48 7JL Londonderry North Ireland Univ Keele Sch Comp & Math Keele ST5 5BG Staffs England Univ Santiago de Compostela Dept Elect & Comp Sci Santiago De Compostela Spain Univ Sheffield Dept Automat Control & Syst Engn Sheffield S1 3JD S Yorkshire England

Robot simulators are useful tools for developing robot behaviour. They provide a fast and efficient means for testing robot control code at the convenience of the office desk. In all but the simplest cases though, due to complexities of physical systems modelled in the simulator, there are considerable differences between the behaviour of the robot in the simulator and that in the real world environment. In this paper we present a novel method to create a robot Simulator using real sensor data. Logged sensor data are used to construct a mathematically explicit model (in the form of a NARMAX polynomial) of the robot's environment. The advantage Of Such a transparent model in contrast to opaque modelling methods such as artificial neural networks-is that it can be analysed to characterise the modelled system, using established mathematical methods. In this paper we compare the behaviour of the robot running a particular task in both the simulator and the real-world using qualitative and quantitative measures including statistical methods to investigate the faithfulness of the simulator. (C) 2008 Elsevier B.V. All rights reserved.

关键词： Robot simulation System identification for simulation Robot modelling Quantitative assessment of computer simulations

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