Spelling suggestions: "subject:"[een] DECOUPLING"" "subject:"[enn] DECOUPLING""
201 |
Study of Tied-up Capital Level in Supply Chain in Vehicle SectorKiani, Amirkiarash January 2012 (has links)
In vehicle industry, it has been trends towards focusing on pull-basedsystems and elimination of waste (Lean), which decrease the tied-up capitallevel in the focal factory. Research by Holweg & Miemczyk (2002)showed that the relevant supply chain has low inventory level in the focalfactory, but at upstream and especially downstream; the tied-up capitallevel is dramatically higher in comparison to the focal factory.By conducting research and extensive literature reviews, this volatilityof tied-up capital level has been studied and analysed with regard topush and pull systems. As the three main causes of this unevenness; bullwhipeffect, CODP position in supply chain and intensity level of supplierrelationship have been identified and explained.As a practical solution for decreasing the tied-up capital level of finishedvehicles, implementation of centralised warehouse structure hasbeen suggested and discussed.Moreover, as an application of game theory in logistics, iterated prisoners’dilemma has been discussed as the base for a progressive relationshipwith suppliers (upgrading to win-win game) which is requisite for the successof pull-based supply chains. / Program: BSc in Industrial Engineering - International Business Engineering
|
202 |
Analysis and coordination of mixed-criticality cyber-physical systemsMaurer, Simon January 2018 (has links)
A Cyber-physical System (CPS) can be described as a network of interlinked, concurrent computational components that interact with the physical world. Such a system is usually of reactive nature and must satisfy strict timing requirements to guarantee a correct behaviour. The components can be of mixed-criticality which implies different progress models and communication models, depending whether the focus of a component lies on predictability or resource efficiency. In this dissertation I present a novel approach that bridges the gap between stream processing models and Labelled Transition Systems (LTSs). The former offer powerful tools to describe concurrent systems of, usually simple, components while the latter allow to describe complex, reactive, components and their mutual interaction. In order to achieve the bridge between the two domains I introduce the novel LTS Synchronous Interface Automaton (SIA) that allows to model the interaction protocol of a process via its interface and to incrementally compose simple processes into more complex ones while preserving the system properties. Exploiting these properties I introduce an analysis to identify permanent blocking situations in a network of composed processes. SIAs are wrapped by the novel component-based coordination model Process Network with Synchronous Communication (PNSC) that allows to describe a network of concurrent processes where multiple communication models and the co-existence and interaction of heterogeneous processes is supported due to well defined interfaces. The work presented in this dissertation follows a holistic approach which spans from the theory of the underlying model to an instantiation of the model as a novel coordination language, called Streamix. The language uses network operators to compose networks of concurrent processes in a structured and hierarchical way. The work is validated by a prototype implementation of a compiler and a Run-time System (RTS) that allows to compile a Streamix program and execute it on a platform with support for ISO C, POSIX threads, and a Linux operating system.
|
203 |
Kundorderstyrd tillverkning – Påverkande faktorer, förutsättningar och problem : En övergripande studie om hur små och medelstora företag flyttar kundorderpunkten och går mot mer kundanpassning.Eriksson, Malin January 2011 (has links)
This study presents a holistic view of which factors small and medium-sized enterprises (SMEs) have to consider, in moving their customer order decoupling point (CODP) further from the customer, thereby becoming more customized. The study also investigate whether SMEs and larger enterprises differ in the strategic questions relating to what influences an enterprise to become more customized, which prerequisites are required and which problems enterprises should anticipate and prepare for. These questions are important, given that strategic change is challenging, and can take considerable time to accomplish; it therefore needs to be based on the right decisions. This study is motivated by the fact that the markets SMEs are selling to tend to become more and more complex and harder to anticipate. Increased globalisation and use of IT and ICT have lead to greater uncertainty in customer demand. At the same time customers have ever more demanding needs and specifications; if these are not met, they will go elsewhere rather than reducing or adapting them. This complexity requires a more customized production and is a way to gain commercial advantages. Customised production includes many benefits such as reduced uncertainty, by producing totally customized products less capital bound is tied up. But meanwhile many challenges such as reduced production efficiency, furthermore flexibility must be increased and higher demands on communications and IT systems are often necessary. The study starts with a wide and thorough theoretical overhaul around the movement of the CODP, but also addresses other parts of the organization to get the all-important big picture. This theoretical work is leading to a work-model which is used in six interviews within SMEs. In order to get a thorough picture, the enterprises that take part in the study are from different line of business and have from 18 to 235 employees. During these interviews, conducted on a single occasion per company, the model and related questions are discussed. Thereby an analysis of the interviews and the theory is done, with the model as the starting-point. The result of this study is a basic model, which SMEs can use as an analytical tool, and a checklist, to facilitate a move towards a make-to-order manufacturing strategy, thereby gaining more flexibility. The study provides a basic generic framework which can be adapted and tailored by the company in question to see which parts are relevant to specific circumstances.
|
204 |
Om reformer : En studie av Kvalitetsreformen, Politireform 2000 og Kunnskapsløftet / On Reforms : A study of the Quality Reform, Police Reform 2000 and theKnowledge Reform.Moren, Jan January 2011 (has links)
This thesis studies three major reforms in the public sector of Norway. The sectors studied are the police, higher education, and primary schools. The main motive for studying these reforms are of a theoretical nature, the reason to study them is to produce general knowledge about reforms. The study aims to answer two main questions. One is about the possibilities and limitations contained in using reforms to change organizations. The second is about how organizations can promote the ideals of representative democracy. In its efforts to attain answers to these questions the thesis blends empirically-oriented research with aspects of organization theory and political theory. The thesis is divided into four different parts. First, there is a descriptive presentation of the three reforms. Secondly, there is a discussion of various theories of reforms and organizations. The primary aim of this analysis is to illuminate and explain the empirical data, but this discussion should also provide its own answers to the main questions asked in the thesis. Thirdly, these theories are applied to analyze data from the three reforms. And finally, the study concludes with a summary of what general insights about the reforms we are left with after studying the Quality Reform, The Police Reform 2000, and the Knowledge Reform. The study shows that reforms have both policy and content aspects, and that it is important to distinguish between the two in order to analyse and understand them. The policy aspect is that reforms are a strategy for change - they are tools for implementing change in organizations. The content aspect is that reforms have a specific content - they have certain objectives that they want to realize. The study concludes that in order to understand this complex and fascinating phenomenon, we need to understand reforms both as instrumental tools, institutional adaptations and symbols.
|
205 |
Pour l'optimisation de la commande des machines synchrones à aimants permanents en régime de haute vitesse pour véhicule électrique / For the optimization of the control of permanent magnet synchronous motors in high speed mode for electric vehiclesSepulchre, Leopold 28 March 2017 (has links)
Dans ce travail nous cherchons à développer des algorithmes de commande adaptés au fonctionnement à haute vitesse d’une machine synchrone à aimants permanents (MSAP) et de son onduleur en optimisant l’efficacité énergétique de l’ensemble. Bien que la vocation soit très large, le domaine de la traction électrique est priorisé. Les MSAP tournant à haute vitesse sont de plus en plus utilisées dans les véhicules électriques en raison de leur forte densité de puissance. La haute vitesse implique une force électromotrice élevée et requiert la réduction du flux (défluxage) dans l’entrefer. Lors d’un fonctionnement de la machine en régime défluxé, si la contribution de l’aimant peut-être totalement compensée alors nous pouvons utiliser une stratégie Maximum Torque Per Volt (MTPV) pour générer les consignes de courant qui respectent les limites électriques théoriques quelle que soit la vitesse de rotation de la machine. En l’absence de boucle de vitesse, le couple de référence doit être limité aux points de fonctionnement atteignables, calculés en fonction des limites de courant (limites onduleur et machine), tension (batterie) et puissance (batterie et partie mécanique). Nous proposons ainsi dans cette thèse de calculer les références de courant avec une stratégie MTPA (Maximum Torque Per Ampere) à basse vitesse et d’utiliser un algorithme de défluxage basé sur une régulation de la norme de la tension associée à une stratégie MTPV à haute vitesse sans commutation d’algorithme mais par une action continue sur la valeur de la saturation de courant. Concernant la boucle de courant nous réalisons une commande numérique dans le repère d-q qui tient compte de la discrétisation, du retard (dû au temps de calcul), et du fort couplage inter-axes à haute vitesse sous des critères de précision, stabilité et rapidité. Nous étudions les stratégies de découplage minimal et de découplage discret avec prédiction de la variation du courant. Les approches par régulateurs avec structure RST et par commande prédictive-optimale sont développées. Une prédiction de la position réelle du rotor est incluse afin de conserver la stabilité à haute vitesse. Finalement nous réalisons une maquette avec une MSAP à échelle réduite sur laquelle nous testons ces stratégies de commande. Nous validons par expérience que l’algorithme proposé dans la thèse est capable de piloter la machine à haute vitesse en respectant les limites électriques et nous vérifions qu’il améliore les performances (couple, vitesse maximale, pertes) obtenues à haute vitesse. / In this work we search to develop control algorithms adapted to the high speed operation of a permanent magnet synchronous motor (PMSM) and its inverter by optimizing the energy efficiency of the set. Although the vocation is very broad, the field of electric traction is prioritized. High speed PMSMs are increasingly used in electrical vehicles because of their high power density. The high speed implies a high electromotive force and requires the reduction of the flux (fluxweakening) in the air gap. When the motor is running in flux-weakening mode, if the contribution of the magnet can be fully compensated then we can use a Maximum Torque Per Volt (MPTV) strategy to generate the current references that meet the theoretical limits regardless of the machine rotation speed. In the absence of a speed loop the reference torque must be limited to the achievable operating points, calculated according to the current limits (inverter and machine limits), voltage (battery) and power (battery and mechanical part). We propose in this thesis to calculate the current reference with Maximum Torque Per Ampere (MTPA) strategy at low speed and to use a flux-weakening algorithm based on a regulation of the voltage norm associated with a MTPV strategy at high speed without switching algorithms but by a continuous action on the value of the current saturation. Concerning the current loop, we carry out a numerical control in the d-q frame which takes into account the discretization, the delay (due to the computation time), and the high inter-axis coupling at high speed under criteria of precision, stability and speed. We study the strategies of minimal decoupling and discrete decoupling with prediction of the variation of the current. The approaches by regulators with RST structure and predictive-optimal control are developed. A prediction of the actual rotor position is included to maintain the stability at high speed. Finally a real model with a reduced scale PMSM is realized on which these control strategies are tested. We validate by experiment that the algorithm proposed in the thesis is able to control the machine at high speed respecting the electrical limits and verify that it improves the performances (torque, maximum speed, losses) obtained at high speed.
|
206 |
Desacoplamento de um gerador s?ncrono atrav?s de um controle adaptativo por modelo de refer?ncia baseado em fun??es de Base radialOliveira, Odailson Cavalcante de 28 July 2011 (has links)
Made available in DSpace on 2014-12-17T14:55:56Z (GMT). No. of bitstreams: 1
OdailsonCO_DISSERT.pdf: 807518 bytes, checksum: 6b1541fcc8435e2f642b214f2496487c (MD5)
Previous issue date: 2011-07-28 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / An alternative nonlinear technique for decoupling and control is presented. This technique
is based on a RBF (Radial Basis Functions) neural network and it is applied to the
synchronous generator model. The synchronous generator is a coupled system, in other
words, a change at one input variable of the system, changes more than one output. The
RBF network will perform the decoupling, separating the control of the following outputs
variables: the load angle and flux linkage in the field winding. This technique does not
require knowledge of the system parameters and, due the nature of radial basis functions,
it shows itself stable to parametric uncertainties, disturbances and simpler when it is applied
in control. The RBF decoupler is designed in this work for decouple a nonlinear
MIMO system with two inputs and two outputs. The weights between hidden and output
layer are modified online, using an adaptive law in real time. The adaptive law is developed
by Lyapunov s Method. A decoupling adaptive controller uses the errors between
system outputs and model outputs, and filtered outputs of the system to produce control
signals. The RBF network forces each outputs of generator to behave like reference
model. When the RBF approaches adequately control signals, the system decoupling is
achieved. A mathematical proof and analysis are showed. Simulations are presented to
show the performance and robustness of the RBF network / Neste trabalho, ser? apresentada uma t?cnica alternativa para o desacoplamento e controle
de sistemas n?o lineares. A estrat?gia de desacoplamento proposta est? baseada
numa rede neural RBF (Radial Basis Functions) combinada com o controle adaptativo
por modelo de refer?ncia. A t?cnica ? aplicada no controle do modelo de um gerador
s?ncrono, cujas vari?veis de sa?da s?o o ?ngulo de carga e o fluxo concatenado no enrolamento
de campo. O sistema do gerador s?ncrono ? acoplado, ou seja, a mudan?a
numa das vari?veis de entrada do sistema altera mais de uma vari?vel de sa?da. A rede
RBF realizar? o desacoplamento do sistema, fazendo o controle de forma independente
de cada uma das sa?das. Tal estrat?gia n?o exige conhecimento dos par?metros do sistema
e observa-se um comportamento est?vel da rede RBF, tanto na presen?a de incertezas na
modelagem, como de perturba??es no sistema. Ser? mostrada a simplicidade da aplica??o
da t?cnica e do projeto da rede RBF. Os pesos, que interligam as camadas oculta
e de sa?da da rede, s?o ajustados utilizando uma lei adaptativa em tempo real. Essa lei
adaptativa foi desenvolvida pelo m?todo de fun??es de energia de Lyapunov. O sistema
de controle e desacoplamento faz uso dos sinais filtrados da sa?da do gerador e dos sinais
dos erros entre as sa?das do gerador e as sa?das do modelo refer?ncia. Assim, atrav?s dos
sinais de controle aplicados pela rede RBF, cada sa?da do sistema do gerador ? for?ada a
se comportar conforme uma din?mica desejada, dada pelo modelo de refer?ncia. Quando
a rede RBF aproxima adequadamente os sinais de controle, o desacoplamento do sistema
? alcan?ado. Os resultados do desempenho da estrat?gia ser?o apresentados atrav?s de
simula??es. Tamb?m ser? mostrada a prova matem?tica de estabilidade do sistema em
malha fechada para o caso escalar
|
207 |
Geometria do desacoplamento e integração numérica de equações diferenciais não lineares implícitas. / Decoupling geometry and numerical integration of differential equations implicit nonlinear systems.Iderval Silva de Souza 24 November 2006 (has links)
Existem métodos de integração de equações algébrico diferenciais não lineares (DAEs) considerados clássicos pela literatura. Porém, neste trabalho, através uma abordagem geométrica, apresenta-se um método de integração de DAEs. Tal método é inspirado na teoria de desacoplamento de sistemas não lineares explícitos, quando se considera que as saídas são restrições algébricas. Neste caso, a DAE pode ser identificada como dinâmica zero. O resultado principal desta abordagem é que, dada uma DAE, sob certas condições, é possível a construção de um sistema explícito, de tal maneira, que as soluções desse sistema explícito convergem para as soluções da DAE. / Classical methods for numerical integration of diferential algebraic equations (DAEs) can be formal in the literature. In this work, using a diferential geometric approach, a numerical method of integration of DAEs is established. This method is inspired in the decoupling theory of nonlinear explicit systems, when one considers that the outputs are algebraic constraints. The main result is the construction of an explicit system, whose solutions converge to the solutions of the DAE.
|
208 |
Développement de capteurs optimisés pour l'IRM à champ magnétique faible (0.2T) : application à l'imagerie de l'animal / Coil design and optimization for low field MRI : implementation for animal imagingFeuillet, Thomas 16 December 2014 (has links)
L'imagerie par résonance magnétique (IRM) appliquée au domaine vétérinaire exploite des systèmes à bas champ magnétostatique qui ont de nombreux avantages, notamment leur faible coût d'achat et d'entretien. Mais sur ces machines, les capteurs radiofréquence (RF) sont initialement dédiées à l'homme et ne permettent pas une qualité d'image optimale. Dans le cadre de cette thèse, des méthodes simples d'optimisation de capteurs à 0,2 T ont été développées, puis exploitées pour des applications de recherche et préclinique. Le travail d'optimisation a été partagé en deux axes. Dans un premier temps, un modèle analytique a été développé sous MATLAB pour l'estimation du rapport signal sur bruit intrinsèque à un capteur paramétré par ses dimensions et les propriétés de l'objet imagé. La validation du modèle a été obtenue par la comparaison entre mesures et simulations du facteur de qualité. Cette méthode d'optimisation a été appliquée pour deux études spécifiques qui ont fait l'objet d'une publication. Dans un second temps, un travail sur le découplage actif a été mené. En effet, sur l'IRM 0,2 T à notre disposition, le découplage passif est la méthode retenue par le constructeur. Mais pour certaines applications des artefacts d'imagerie sont inévitables et le facteur de qualité réduit. Des moyens de découplage actif ont donc été développés. Les performances des capteurs ainsi équipés se sont avérées meilleures qu'en découplage passif. Ce système de découplage associé à un dispositif de connexion par couplage inductif du signal de résonance magnétique a été également démontré à 3 T comme une preuve de concept d'un dispositif de connexion universelle. Ce dispositif a fait l'objet d'un article récemment soumis pour publication / Magnetic resonance imaging {MRl) in veterinary practice employs low magnetostatic field devices which have numerous advantages such as their low maintenance and initial cost. Yet, the radiofrequency {RF) coils commercially provided with these devices are dedicated to human morphology, therefore reducing image quality. ln this work, simple optimization methods for 0.2 T RF coils were developed for an implementation in research and preclinical studies. Optimization protocol was subdivided into two main steps. First, an analytical model was developed using MATLAB in order to estimate the intrinsic signal to noise ratio variations with coil and imaged sample characteristics. Validation of the model was assessed thanks to quality factor comparison between simulated and measured values. The use of the analytical model for two specific studies was described in a recently accepted publication. Second, active decoupling was investigated. lndeed, passive decoupling is the decoupling method implemented on the 0.2 T MR device at our disposal. However, this technique can lack of efficiency in some experiments, inducing imaging artifacts and reduced quality factor. Active decoupling method was therefore implemented. The electronic performances of the coils equipped this way were better than in passive decoupling. This active decoupling device combined with an inductive coupling connecting system was tested at 3 T to demonstrate the technical feasibility of a new universal connecting device, for which an article was recently submitted
|
209 |
Computing free energies of protein-ligand associationDonnini, S. (Serena) 09 October 2007 (has links)
Abstract
Spontaneous changes in protein systems, such as the binding of a ligand to an enzyme or receptor, are characterized by a decrease of free energy. Despite the recent developments in computing power and methodology, it remains challenging to accurately estimate free energy changes. Major issues are still concerned with the accuracy of the underlying model to describe the protein system and how well the calculation in fact emulates the behaviour of the system.
This thesis is largely concerned with the quality of current free energy calculation methods as applied to protein-ligand systems. Several methodologies were employed to calculate Gibbs standard free energies of binding for a collection of protein-ligand complexes, for which experimental affinities were available. Calculations were performed using system description with different levels of accuracy and included a continuum approach, which considers the protein and the ligand at the atomic level but includes solvent as a polarizable continuum, and an all-atom approach that relies on molecular dynamics simulations.
In most such applications, the effects of ionic strength are neglected. However, the severity of this approximation, in particular when calculating free energies of charged ligands, is not very clear. The issue of incorporating ionic strength in free energy calculations by means of explicit ions was investigated in greater detail and considerable attention was given to the affinities of charged peptides in the presence of explicit counter-ions. A second common approximation is concerned with the description of ligands that exhibit multiple protonation states. Because most of current methods do not model changes in the acid dissociation constants of titrating groups upon binding, protonation equilibria of such ligands are not taken into account in free energy calculations. The implications of this approximation when predicting affinities were analysed.
Finally, when calculating free energies of binding, a correct description of the interactions between the protein and the ligand is of fundamental importance. However, active sites of enzymes, where strained conformations may hold a functional role, are not always accurately modelled by molecular mechanics force fields. The case of a strained planar proline in the active site of triosephosphate isomerase was investigated using an hybrid quantum mechanics/molecular mechanics method, which implies a higher level of accuracy.
|
210 |
Vem bryr sig om mångfald? : En studie av mångfaldsbegreppet inom Polismyndigheten / Who cares about diversity? : A study of the diversity concept within the Swedish Police AuthorityPereira, Sara January 2021 (has links)
The Swedish Police Authority aims to increase diversity among employees within the authority. This is asserted in the Swedish Police Authority's own policies and action plans, which together with other internal documents are the subject of my qualitative study. The focus of this study is to look at how the use of the concept of diversity has changed within the Swedish Police Authority by using qualitative analysis of ideas and ideological context, the perspective of discursive psychology and neo-institutional theory. The aim is also to find out what is missing out in the current diversity discourse. My study reveals through an examination of a selection of The Swedish Police Authority’s document that there is a discrepancy between the external discourses on diversity and the internal norms that are to be found within the Swedish Police Authority.
|
Page generated in 0.0571 seconds