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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

The Effect of Geometrical Contact Input to Wheel-Rail Contact Model

Martin, Michael January 2018 (has links)
Wheel-rail contact is an important aspect of railway, the forces transferred between the wheel and rail are the one that guide, brake, or accelerate the train, and that is why the understanding of the contact between wheel and rail is an interesting research topic. In this master thesis wheel-rail contact model named ANALYN is used to see the effect of the different geometrical input, like undeformed distance, relative longitudinal curvature, and relative lateral curvature calculation affect the contact patch estimation formed at the wheel-rail contact.  In the process, a geometrical contact search code is made to find the contact point between wheel and rail for certain lateral displacement, yaw angle, and roll angle of the wheelset. The codes used to calculate the three geometrical inputs are also prepared, with two methods are prepared for each input. The results that generated from combination of the geometrical contact search and geometrical input preparation are used as the input to ANALYN. The results showed that different geometrical input calculations do affect the shape of the contact patch, with the calculation of lateral curvature being the most important since it affects the shape of the contact patch greater than other geometrical inputs. It is also shown that taking yaw angle into account in the contact search will affect the shape of the contact patch.
2

Algorithm for Estimation of Wheel-Rail Friction Coefficient from Vehicle-Track Forces

Petrov, Vladislav January 2012 (has links)
In order to ensure safe travel, railway vehicles must be stable under every condition along the track. Thus, a vehicle can be certified for operation only when it can fulfil certain criteria related to the ride stability. The stability of the vehicle is highly dependent on the wheel-rail friction coefficient: higher friction results in worse ride. So, to ensure a good evaluation of the stability, the friction should be high enough during tests. The same applies to the risk of wheel flange climbing. At the present time, the wheel-rail friction can not be measured directly but there are different procedures utilized to ensure that the conditions are suitable for testing the stability of the vehicle. In this study an algorithm is proposed to estimate the wheel-rail friction coefficient by using quantities which can be measured in reality. The algorithm is tried out in computer simulations. The algorithm has two parts: in Part 1 the friction coefficient is proposed to be equal to the ratio of the total creep force divided by the normal force; in Part 2 the total creep and spin creep are estimated to observe their correlation to the estimated friction. The contact angle in Part 1 is estimated by a contact point function. In the simulations, different conditions are tried. There are four horizontal radii: tangent track, R1300m, R1000m, and R400m. Three friction coefficients are used: 0.5, 0.4 and 0.3. In addition to this, track irregularities are included. A single vehicle is simulated in two modes: capable and incapable of passive radial steering. The track irregularities caused high values of the proposed estimated friction coefficient. The values in some instances were close or equal to the input friction coefficient of the simulation. Thus, if the highest values of the estimated friction were taken over a certain distance or time, the friction of the simulation could be approximated. In most cases, the total creep was following the trend of the estimated friction. The total creep and spin creep were used as a quality factor to determine how close the estimated friction was to the simulation’s friction. In this study when the total creep was greater than 0.006 and the spin creep was less than 1.0 m-1, the estimated friction was close to the input friction. The closeness was dependent on the simulation’s friction. Higher input friction resulted in larger deviation compared to lower friction. A sensitivity analysis has been performed by deliberately introducing errors in the position of the contact point and the angle of attack. The analysis shows that the errors are not critical when the contact point is close to the tread circle. When the contact point is close to the flange, a good measurement of the wheel profile and the contact point position required to obtain accurate results. On the other hand, the errors affect the friction estimate for high spin and low total creepage. These results are discarded by the algorithm, the influence of the errors is minimized.
3

Simulação numérica de escoamentos bidimensionais com superfícies livres e linhas de contato dinâmicas / An arbitrary lagrangian-eulerian method for surface-tension dominated flows with contact lines

Silva, Alysson Alexander Naves 26 April 2010 (has links)
Um método lagrangeano-euleriano arbitrário para a resolução de escoamentos dominados por tensão superficial é apresentado neste trabalho. Tais escoamentos são importantes em muitas aplicações, especialmente em canais capilares que frequentemente aparecem em escoamentos em microescala. A resolução deste tipo de escoamento apresenta vários desafios que são abordados neste trabalho. O escoamento é resolvido somente para a fase líquida, com condições de contorno apropriadas para a superfície livre que delimita o líquido e o gás, que é representada por arestas e vértices da malha computacional. Esta se move e se deforma, sendo que sua qualidade é mantida sob controle para não degradar a solução numérica. As equações de Navier-Stokes são discretizadas pelo método de elementos finitos em um referencial arbitrário. O método de incorporação dos efeitos de tensão superficial e linha de contato é explicado em detalhes. Validações comprovam a precisão do método proposto, com comparações através de soluções pseudo-analíticas para casos simples. Finalmente alguns resultados sobre escoamentos em capilares são apresentados / An arbitrary lagrangian-eulerian finite element method to solve surface tension dominated flows is presented. Such flows are important in many applications, particularly in capillary channels, that appear in microscale flows. The resolution of such flows presents several challenges that are addressed in this work. The flow is solved only in the liquid phase, and proper boundary conditions are applied on the free-surface, bounding the liquid and gas, which is explicitly represented by vertices and edges of the computational mesh. The mesh is moved and deformed, but its quality is kept under control in order to control errors in the numerical solution. The Navier-Stokes equations are discretized by standard Galerkin finite element method in an arbitrary reference. Details of the computation of surface tension and contact line effects are presented. The methodology is validated for a number of simple test cases against known pseudo-analytical solutions, and numerical results are presented, showing the robustness and accuracy of the methodology. Finally, some results about surface-tension-driven flows in capillaries are presented
4

Simulação numérica de escoamentos bidimensionais com superfícies livres e linhas de contato dinâmicas / An arbitrary lagrangian-eulerian method for surface-tension dominated flows with contact lines

Alysson Alexander Naves Silva 26 April 2010 (has links)
Um método lagrangeano-euleriano arbitrário para a resolução de escoamentos dominados por tensão superficial é apresentado neste trabalho. Tais escoamentos são importantes em muitas aplicações, especialmente em canais capilares que frequentemente aparecem em escoamentos em microescala. A resolução deste tipo de escoamento apresenta vários desafios que são abordados neste trabalho. O escoamento é resolvido somente para a fase líquida, com condições de contorno apropriadas para a superfície livre que delimita o líquido e o gás, que é representada por arestas e vértices da malha computacional. Esta se move e se deforma, sendo que sua qualidade é mantida sob controle para não degradar a solução numérica. As equações de Navier-Stokes são discretizadas pelo método de elementos finitos em um referencial arbitrário. O método de incorporação dos efeitos de tensão superficial e linha de contato é explicado em detalhes. Validações comprovam a precisão do método proposto, com comparações através de soluções pseudo-analíticas para casos simples. Finalmente alguns resultados sobre escoamentos em capilares são apresentados / An arbitrary lagrangian-eulerian finite element method to solve surface tension dominated flows is presented. Such flows are important in many applications, particularly in capillary channels, that appear in microscale flows. The resolution of such flows presents several challenges that are addressed in this work. The flow is solved only in the liquid phase, and proper boundary conditions are applied on the free-surface, bounding the liquid and gas, which is explicitly represented by vertices and edges of the computational mesh. The mesh is moved and deformed, but its quality is kept under control in order to control errors in the numerical solution. The Navier-Stokes equations are discretized by standard Galerkin finite element method in an arbitrary reference. Details of the computation of surface tension and contact line effects are presented. The methodology is validated for a number of simple test cases against known pseudo-analytical solutions, and numerical results are presented, showing the robustness and accuracy of the methodology. Finally, some results about surface-tension-driven flows in capillaries are presented
5

An Algorithm To Resolve The Optimal Locomotion Problem Of Modular Robots

Mencek, Hakan 01 December 2007 (has links) (PDF)
In this study, a novel optimal motion planning algorithm is developed for the locomotion of modular robots. The total energy consumption of the robot is considered to be the optimization criteria. In order to determine the energy consumption of the system, the kinematic and dynamic analyses of the system are performed. Due to the variable number of modules in the system, a recursive formulation is developed for both kinematic and dynamic analyses. Coulomb&#039 / s static and dynamic friction models are used to model the frictional forces at the contact points. In modular robot locomotion, the number of contact points and the positions of the contact points vary with time. As a result, the structure of the dynamic equilibrium equations changes. Depending upon the number and type of contacts (i.e., contact with static or dynamic friction), the dynamic equilibrium equations may lead to an overdetermined, regular or underdetermined system of equations. The last case implies that the system is statically indeterminate. A novel solution method, which takes into account the deflections of the flexible links in the modular robot, is introduced to resolve this statical indeterminacy problem. Another important contribution is the identification of the singularities associated with the dynamic equilibrium equations. It is shown that these equations become singular when all tangential contact point velocities are in the same direction. The developed optimal motion planning algorithm ensures that such singularities are avoided. The procedure is illustrated via a modular, self reconfigurable robot called MTRAN. However, the method may be easily extended to other modular robots by changing the structural parameters. In order to display the resulting motion, a visual simulation program is developed for MTRAN using the commercial software Mathematica.
6

Součinnost traumacentra Nemocnice České Budějovice, a.s. a Zdravotnického operačního střediska Zdravotnické záchranné služby Jihočeského kraje při hromadném neštěstí. / Cooperation of the Trauma Centre of the Hospital České Budějovice and Medical Operation Center of the Emergency Medical Service of the South Bohemian Region in the Event of Mass-Casualty Incident

URBANOVÁ, Alena January 2014 (has links)
In 2011 and 2012, dramatic changes were made to the health care reform in the Czech Republic. As a consequence, almost the complete legislation related to traumatological planning was changed. This reform primarily introduced two new types of operating divisions; a department of emergency preparedness, as for the emergency medical service providers, and a contact point, from the aspect of emergency inpatient care providers. Emergency preparedness primarily processes a concept of the traumatological plan for the emergency medical service and introduces potential changes. The contact point, as a department of the emergency inpatient care with continuous operation, receives calls from the emergency medical service, especially in the event of emergencies and crisis situations. The given Master's Diploma Thesis entitled "Cooperation of the Trauma Centre of the Hospital České Budějovice and Medical Operation Center of the Emergency Medical Service of the South Bohemian Region in the Event of Mass-Casualty Incident" develops a key issue of the interconnection of traumatological plans established by health service providers within the South Bohemian Region and the level of their cooperation. Then the work analyses three mass-casualty incidents which happened in the past within the area and the level of involvement and cooperation of the aforementioned departments, i.e. the Hospital's trauma centre and Medical Operation Centre upon the Medical Emergency Centre of the Region of South Bohemia. The Diploma Thesis proceeds from the qualitative research which is divided into two parts. The first one defines the V1 research question specifying the role of the Traumatological Plan of the South Bohemian health care during the cooperation with the trauma centre under the Hospital České Budějovice and medical operation centre of the Medical Emergency Service of the South Bohemian Region in the event of a mass-casualty incident. By using a comparative method, which assessed the three traumatological plans, the level of cooperation did not exceed more than 20 % owing to the fact that the Traumatological Plan of the South Bohemian health care is out-dated. As a consequence, the answer to the V1 research question was following: The role of the Traumatological Plan of the South Bohemian health care with the cooperation of the trauma centre under the Hospital České Budějovice and Medical operation centre of the Medical Emergency Service of the South Bohemian Region in the event of a mass-casualty incident is insignificant. The second part develops the V2 research question: whether the failure in communication between the aforementioned trauma centre and medical operation centre could have any impact on the injured in the event of a mass-casualty incident. The qualitative research with the use of a method of analysis implemented during the previous mass-casualty incidents and interviews with four operators working for the medical operation centre and four doctors working at the accident, emergency and plastic surgery department provided the second answer to the V2 research question: Failure in communication between the two aforementioned departments could have a significant impact on the injured in the event of a mass-casualty incident. In the end, the thesis refers to the dramatic difference between the ideal traumatological planning and the current situation pointing out the Traumatological Plan of the South Bohemian healthcare which has not been updated for three and a half years since the reform. The given work also describes the issue of the ideal solution to the establishment of contact points in hospitals and compares it with the current situation at the Hospital České Budějovice where the contact point was established only in order to comply with the legislation, i.e. the contact point is based in the operating centre of medical transport.
7

e-Government: Czech POINT - role a přínosy elektronizace kontaktních míst veřejné správy s občany a s jinými formami subjektů naší společnosti / e-Government: Czech POINT: Roles and benefits of digitalization of New Public Management contact points with citizens and other forms of entities in our country

Pávek, Václav January 2015 (has links)
The thesis "Czech Point - roles and benefits of digitalization of New Public Management contact points with citizens and other forms of entities in our society" deals with the problem of insufficient and ineffective availability for Governments electronic services for use of private and public sector with a focus on electronical services contact points in the Czech Republic - Czech POINT. Powered by TCPDF (www.tcpdf.org)
8

Modified train wheel wear calculation for fast calculation / Modifierad tåghjulsförslitning för snabb beräkning

Chen, Shaoyao January 2021 (has links)
In this thesis, a modified wear calculation method is developed to calculate the train wheel wear, which can give less precise but faster results compared to the classic wear calculation method. This modified method is developed based on the classic wear calculation method developed by Jendel, which uses Hertz theory and Kalker’s simplified theory to calculate the contact variables and uses Achard theory to calculate the wear volume in an iterative manner. Compared with the classic method, this modified wear calculation method does not execute the multibody simulation (MBS) at each wear step, instead, it executes MBS by different strategies, for example, does MBS only at the first wear step or does it at every several wear steps. This way, a look-up table is utilised to store the contact variables from MBS and when no MBS is executed, the variables stored in the look-up table would be used to calculate the wear.In order to make the implementation of the modified wear calculation method possible, a contact point detection program is developed in this research. Significantly, this contact point detection program considers the material flexibility and can detect multiple contact points, which makes it very precise. It uses the pressure distribution calculated by Winkler theory as a weighting function to consider the material flexibility. In terms of multiple contact points detection, the gap between wheel and rail is regarded as a function, and the derivative relationship of the function is used to detect multiple contact points. Results from the modified wear calculation method are compared with results from the classic wear calculation method. The effects of different strategies are discussed, and the analysis of the error source is carried out in this work.This modified wear calculation method could be used for predicting the wear condition of the wheel when a quick result with only moderate precision is needed. / I den här avhandlingen utvecklas en modifierad beräkningsmetod för slitage av spårfordons hjul, som ger mindre exakta men snabbare resultat jämfört med den klassiska beräkningsmetoden för hjulslitage. Den modifierade beräkningsmetoden är utvecklad baserat på den klassiska beräkningsmetoden för slitage som utvecklats av Tomas Jendel, som använder Hertz-teorin och Kalkers förenklade teori för att beräkna kontaktvariablerna och använder Achard-teorin för att beräkna volymen av materialet som har slitits bort med en iterativ metod. Jämfört med den klassiska metoden utför inte denna modifierade beräkningsmetod flerkroppssimulering (MBS) vid varje steg där normal hjulprofilen uppdateras, utan använder sig av olika strategier. Till exempel genomförs gör MBS bara vid första slitagesteget eller vid några av slitagestegen. Därför används en uppslagstabell för att lagra kontaktvariablerna från MBS och när ingen MBS exekveras, användas variablerna lagrade i uppslagstabellen för att beräkna slitage.För att möjliggöra implementeringen av den modifierade beräkningsmetoden för slitage utvecklas ett kontaktpunktdetekteringsprogram i denna examensarbete.. Det är viktigt att detekteringsprogrammet tar hänsyn till materialflexibiliteten och att det kan detektera flera kontaktpunkter, med hög precision. Programmet använder Winkler-metoden och den tryckfördelning som beräknas enligt Winkler-teorin som en viktning för att beakta materialets flexibilitet. När det gäller detektering av flera kontaktpunkter betraktas gapet mellan hjul och räls som en funktion, och derivatan av den funktionen används används för att detektera flera kontaktpunkter.Resultat från den modifierade beräkningsmetoden för slitage jämförs med resultaten från den klassiska beräkningsmetoden. Effekterna av olika strategier diskuteras och felkällor analyseras.Denna modifierade beräkningsmetod för slitage kan användas för att förutsäga hjulets slitagetillstånd när ett snabbt resultat med endast måttlig precision behövs.
9

Sociétés minières canadiennes et violations des droits de l’homme à l’étranger : le Canada respecte-t-il les prescriptions internationales en la matière?

Cournier, Marine 08 1900 (has links)
La présente étude a pour objectif de vérifier si le Canada respecte les prescriptions internationales en matière de droits de l’homme et d’entreprises vis-à-vis de l’encadrement qu’il exerce sur les sociétés minières canadiennes évoluant à l’étranger. En 2011, le Conseil des droits de l’homme de l’ONU a adopté des «Principes directeurs» afin de mettre en oeuvre le cadre de référence « Protéger, Respecter, Réparer » du Représentant spécial chargé de la question des droits de l’homme et des sociétés transnationales et autres entreprises. Selon ce cadre de référence, les États ont des obligations de protection et de réparation alors que les entreprises ont seulement la responsabilité de respecter les droits humains. Après six années de travail, le Représentant spécial John Ruggie, a fait le choix de formuler dans ses «Principes directeurs» des directives non contraignantes à l’égard des États et des entreprises afin de les aider à remplir leurs obligations et responsabilités vis-à-vis des droits de l’homme. Selon, l’ONU, cet instrument de portée universelle est le plus élaboré en la matière, si bien qu’il est recommandé aux entreprises et plus particulièrement aux États de s’y conformer lors de l’élaboration de leurs politiques respectives en matière d'activité économique et de droits humains. Il convient donc de vérifier d’une part si l’encadrement exercé par l’appareil législatif et gouvernemental vis-à-vis des sociétés minières canadiennes évoluant à l’étranger est conforme au principe directeur «Protéger». D’autres part, il convient de vérifier si les recours judiciaires et extrajudiciaires disponibles au Canada remplissent les exigences du principe directeur «Réparer». Cette double analyse permettra de conclure que le Canada respecte dans les grandes lignes ces «Principes directeurs» mais qu’il pourrait faire bien plus notamment en terme d’accès à des réparations effectives pour les victimes étrangères de minières canadiennes. / This study propose to assess whether Canada meets the international requirements of business and human rights in relation to the supervision it has on Canadian mining companies operating abroad. In 2011, the Human rights Council adopted the Special Representative’s Guiding Principles on Business and Human Rights in order to implement the United Nations “Protect, Respect and Remedy” Framework. According to this framework, States have obligations to protect and remedy while companies only have responsibilities to respect human rights. After six years of work, the Special Representative on Business and Human rights, John Ruggie, has chosen to give in its Guiding Principles non- binding recommendations in order to help States and businesses to encounter their obligations and responsibilities towards human rights. According to the UN, this universal instrument is the most developed in the field. Thus, it is strongly recommended that companies and especially States, comply those «guiding principles» when they elaborate their respective policies on economic activity and human rights. It is therefore necessary to check first if the supervision exercised by the legislature and the government on Canadian mining companies operating abroad succeeds to comply with the "Protect" principles. On the other hand, it must be checked whether the judicial and extrajudicial remedies available in Canada meet the requirements of the «Remedy" principles. This dual analysis will led to conclude that Canada meets broadly the "Guiding Principles" but could do much more, especially in terms of access to effective remedies for foreign victims of Canadian mining companies.
10

Sociétés minières canadiennes et violations des droits de l’homme à l’étranger : le Canada respecte-t-il les prescriptions internationales en la matière?

Cournier, Marine 08 1900 (has links)
La présente étude a pour objectif de vérifier si le Canada respecte les prescriptions internationales en matière de droits de l’homme et d’entreprises vis-à-vis de l’encadrement qu’il exerce sur les sociétés minières canadiennes évoluant à l’étranger. En 2011, le Conseil des droits de l’homme de l’ONU a adopté des «Principes directeurs» afin de mettre en oeuvre le cadre de référence « Protéger, Respecter, Réparer » du Représentant spécial chargé de la question des droits de l’homme et des sociétés transnationales et autres entreprises. Selon ce cadre de référence, les États ont des obligations de protection et de réparation alors que les entreprises ont seulement la responsabilité de respecter les droits humains. Après six années de travail, le Représentant spécial John Ruggie, a fait le choix de formuler dans ses «Principes directeurs» des directives non contraignantes à l’égard des États et des entreprises afin de les aider à remplir leurs obligations et responsabilités vis-à-vis des droits de l’homme. Selon, l’ONU, cet instrument de portée universelle est le plus élaboré en la matière, si bien qu’il est recommandé aux entreprises et plus particulièrement aux États de s’y conformer lors de l’élaboration de leurs politiques respectives en matière d'activité économique et de droits humains. Il convient donc de vérifier d’une part si l’encadrement exercé par l’appareil législatif et gouvernemental vis-à-vis des sociétés minières canadiennes évoluant à l’étranger est conforme au principe directeur «Protéger». D’autres part, il convient de vérifier si les recours judiciaires et extrajudiciaires disponibles au Canada remplissent les exigences du principe directeur «Réparer». Cette double analyse permettra de conclure que le Canada respecte dans les grandes lignes ces «Principes directeurs» mais qu’il pourrait faire bien plus notamment en terme d’accès à des réparations effectives pour les victimes étrangères de minières canadiennes. / This study propose to assess whether Canada meets the international requirements of business and human rights in relation to the supervision it has on Canadian mining companies operating abroad. In 2011, the Human rights Council adopted the Special Representative’s Guiding Principles on Business and Human Rights in order to implement the United Nations “Protect, Respect and Remedy” Framework. According to this framework, States have obligations to protect and remedy while companies only have responsibilities to respect human rights. After six years of work, the Special Representative on Business and Human rights, John Ruggie, has chosen to give in its Guiding Principles non- binding recommendations in order to help States and businesses to encounter their obligations and responsibilities towards human rights. According to the UN, this universal instrument is the most developed in the field. Thus, it is strongly recommended that companies and especially States, comply those «guiding principles» when they elaborate their respective policies on economic activity and human rights. It is therefore necessary to check first if the supervision exercised by the legislature and the government on Canadian mining companies operating abroad succeeds to comply with the "Protect" principles. On the other hand, it must be checked whether the judicial and extrajudicial remedies available in Canada meet the requirements of the «Remedy" principles. This dual analysis will led to conclude that Canada meets broadly the "Guiding Principles" but could do much more, especially in terms of access to effective remedies for foreign victims of Canadian mining companies.

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