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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.
151

Multibody model vozidla - hodnocení jízdního komfortu / Vehicle Multibody Model - Ride Comfort Evaluation

Friedl, Michal Unknown Date (has links)
This master’s thesis is concerned of ride comfort. It uses MBS simulation software MSC Adams, especially its Car module. It contains simulations of ride over the road with obstacles that represent the everyday conditions in real traffic. The main area of focus is to find acceleration data that are present on the driver’s seat and co-driver’s seat in relation on specific suspension settings which affect the ride comfort.
152

Fältövning som undervisningsmetod ur ett krigsvetenskapligt perspektiv

Perkola, Jarmo January 2017 (has links)
This essay analyses how students translate theoretical warfare into practical action during a staff ride. Through case studies, at the actual location, in a real or fictitious scenario, students can apply theoretical knowledge about principles of warfare to practical situations. Discussion of the outcomes of different examples on the actual terrain allows a comparison of contemporary tactics and contemporary technology. The terrain is still there, albeit perhaps altered and, although the military geography’s character shifts, it is consistent. Therefore, one can compare the contemporary tactical and technical conditions with the practical conditions of the present, and draw conclusions that are relevant to modern tactics. Thus, one can learn from the historical context through staff rides as a teaching method. The essay is about the teaching situation and the method that students are exposed to during a staff ride, and how theories of warfare relate to and are used in the practical implementation of a staff ride.
153

Enregistrements stratigraphiques des cycles glacio-eustatiques et de la déformation durant le Pléistocène le long de la marge centrale d’Équateur : exploitation des données de la campagne ATACAMES / Stratigraphic record of the glacio-eustatic cycles and the deformation during the Pleistocene along the central Ecuadorian margin : using the ATACAMES data campaign

Martillo Bustamante, Carlos 11 May 2016 (has links)
L’objectif de cette étude est de contraindre les déformations au cours du Pléistocène d'une marge active à partir de l’analyse sismo-stratigraphique des sédiments conservés sur la plate-forme et la pente supérieure, le long de la marge centrale d’Equateur. A partir les données de sismique haute résolution et de carottage collectées pendant l'expédition Atacames (2012), plusieurs bassins ont été identifiés. La répartition latérale et de la succession des séquences T-R dans ces bassins montrent une distribution complexe des sédiments dans le temps et l'espace. Ce travail montre que, le long des marges actives, l’analyse sismo-stratigraphique de l’enregistrement des séquences liées aux cycles eustatiques du Pléistocène est un outil très puissant. A l'échelle locale, la subduction de seamounts perturbe et renforce l'effet de déformation régionale de la ride de Carnegie. / The aim of this study is to constrain recent deformation and stratigraphic evolution of an active margin, using sismo-stratigraphic analysis of Pleistocene sediment preserved on the margin shelf and upper slope along of the Central Ecuadorian margin. From the extensive geophysical and sedimentological investigations carried out during the ATACAMES expedition (2012), we are identified serveral basins in the Ecuadorian margin. A detailed analysis of the thickness, the lateral distribution and stacking patterns in these basins show a complex distribution of sediments in time and space. The seismic-sequence stratigraphy analysis related to eustatic cycles of the Pleistocene shows a regional regional unconformity at the base (1782-Ka as minimum age), which can correspond to the signature of the beginning of the Carnegie ridge collision.
154

Design and Analysis of a Shock Absorber with a Variable Moment of Inertia Flywheel for Passive Vehicle Suspension

Xu, Tongyi January 2013 (has links)
Conventional vehicle suspensions consist of a spring and a damper, while mass is rarely used. A mass, if properly used, can also create a damping-like effect. However, a mass has only one terminal which makes it difficult to be incorporated into a suspension. In order to use a mass to achieve the damping-like effect, a two-terminal mass (TTM) has to be designed. However, most of the reported TTMs are of fixed moment of inertia (TTM-CMI), which limits the further improvement of the suspension performance and responsiveness to changes in environment and driving conditions. In this study, a TTM-based vibration absorber with variable moment of inertia (TTM-VMI) is proposed. The main component of the proposed TTM absorber contains a hydraulic-driven flywheel with sliders. The moment of inertia changes with the positions of the sliders in response to the driving conditions. The performance of the proposed TTM-VMI absorber has been analyzed via dynamics modeling and simulation and further examined by experiments. The analysis results indicate that the TTM-VMI absorber outperforms the TTM-CMI design in terms of body displacement; and ride comfort, tire grip and suspension deflection for zero and impulse inputs with comparable performance for sinusoidal input.
155

Doubly-fed induction generator wind turbine modelling, control and reliability

Lei, Ting January 2014 (has links)
The trend of future wind farms moving further offshore requires much higher reliability for each wind turbine in order to reduce maintenance cost. The drive-train system and power electronic converter system have been identified as critical sub-assemblies that are subject to higher failure rates than the other sub-assemblies in a wind turbine. Modern condition monitoring techniques may help schedule the maintenance and reduce downtime. However, when it comes to offshore wind turbines, it is more crucial to reduce the failure rates (or reduce the stresses) for the wind turbines during operation since the harsh weather and a frequently inaccessible environment will dramatically reduce their availability once a failure happens. This research examines the mechanical, electrical and thermal stresses in the sub-assemblies of a doubly-fed induction generator (DFIG) wind turbine and how to reduce them by improved control strategies. The DFIG control system (the rotor-side and the grid-side converter control) as well as the wind turbine control system are well established. The interactions of these control systems have been investigated. This research examines several further strategies to reduce the mechanical and electrical stresses. The control system's coordination with the protection schemes (crowbar and dc-chopper) during a grid fault is presented as well. An electro-thermal model of the power converter has been developed to integrate with the DFIG wind turbine model, for the evaluation of the thermal stresses under different operating states and control schemes. The main contributions of this thesis are twofold. A first contribution is made by providing all the control loops with well-tuned controllers in a more integrated methodology. The dynamics of these controllers are determined from their mathematical models to minimize the interference between different control-loops and also to reduce the electrical transients. This thesis proposes a coordination strategy for the damping control, pitch control and crowbar protection which significantly reduces the mechanical oscillations. On the other hand, an integrated model of the wind turbine and converter electro-thermal system is established that can illustrate the performance integration with different control strategies.
156

Vliv zápisu kulturních statků na Reprezentativní seznam nemateriálního kulturního dědictví lidstva UNESCO v regionu Slovácko / The influence of the inscription of cultural assets on the Representative List of the Intangible Cultural Heritage of Humanity by UNESCO in the region of Slovácko

Vávrová, Ivana January 2014 (has links)
The thesis aims to determine the influence on the development and preservation of traditional folk culture which had the inscription of two cultural assets, The Ride of kings and The Slovácko verbuňk, on the Representative List of the Intangible Cultural Heritage of Humanity by UNESCO in the region of Slovácko. In general the thesis also introduces applicable regulations of UNESCO in the field of intangible cultural heritage and their application in the Czech Republic. In more detail, the thesis devotes to the process of inscription of both cultural assets on the Representative List of UNESCO, particularly to the safeguarding measures and obligations arising from it for the Czech Republic. In conclusion the thesis explains how these safeguarding measures are met, and analyzes the impact of the entry to the UNESCO for assets themselves and their recipients and for general public.
157

Analýza vybraných manévrů cyklistů / Analysis of Selected Manoeuvres of Bicyclists

Špačková, Kateřina January 2021 (has links)
This diploma thesis Analysis of selected manoeuvres of bicyclists deals with the history and development of the bicycles, further their division of, construction, analysis accident and national legislation in the theoretical part. The practical part of the master thesis is devoted to the measurements of the bicycles. Specifically, it is about acceleration, deceleration, transverse movement, ride in the curve and looking back before changing the direction. For measuring are selected different type of bikes with different construction. The results of individual measurements are evaluated in the end of the diploma thesis.
158

Analýza jízdních dat vozidla / Vehicle data analysis

Starý, Přemysl January 2016 (has links)
The diploma thesis deals with a data analysis of the Formula Student race car. An attention is given for both, vehicle and driver. Processes of braking, turning and balance of car are analysed. Special attention is given to the dampers positions while driving and their settings. Dampers velocity histograms and ride frequencies graph are put together. Algorithms in MATLAB are suggested to reduce requested time for analysis. Scripts for displaying important channels are made. Analyzed data are used to create events which accelerate orientation in record and tell the most important information.
159

Finite Element Modelling of Off-Road Tyres

Conradie, Johan January 2014 (has links)
Most tyre models developed to date require a fair amount of data before an accurate representation of the tyre can be obtained. This study entails the development of a simplified, yet accurate, non-linear Finite Element (FE) model of an “off-road” tyre to study the behaviour of the tyre due to radial loading conditions. The study aims to develop a FE tyre model that can solve fast and be accurate enough to be used in multibody dynamic vehicle simulations. A model that is less complex than conventional detailed FE models is developed. The work explores the use of superimposed finite elements to model the varying stiffness in the respective orthogonal directions of the sidewall and tread of the tyre. Non-linear elements defined by Neo-Hookean or Ogden models and elements with different linear orthogonal stiffnesses are superimposed onto each other to simulate the global material properties of the tread and the sidewall of the tyre investigated. The geometry of the tyre studied was measured experimentally using laser displacement transducers and digital image correlation techniques. Material properties of segments of the tyre were obtained by performing tensile tests on samples. Since the rubber slipped against the clamps during the experiment, deformation of the segments was also measured using digital image correlation. These geometrical and material properties were used as input to develop a finite element model of an “off-road” tyre. Measurements were conducted using laser displacement transducers, load cells mounted to actuators, etc. to obtain accurate sidewall deformation profiles and global radial load vs. displacement curves for different radial loading conditions. The data obtained from the results was used to validate the tyre model developed. Numerous analyses are performed with different combinations of moduli of elasticity in the respective orthogonal directions of the sidewall stiffness and the tread to investigate its influence on the global behaviour of the tyre model. The main focus of the project was to develop a tyre model from data obtained from laser and photogrammetry measurements in a laboratory that accurately represents tyre behaviour due to radial forces. A finite element model that can simulate the effect of radial forced and obstacles on a tyre was developed. The use of two subsets of elements, superimposed onto each other to simulate global material properties of the rubbers, steel wires, polyester and nylon threads, was investigated. The combination of material properties that gave the best fit for all the load cases investigated were determined. The finite element model correlated well with the load vs. displacement graphs and sidewall displacement profiles determined experimentally. The solving time is still fairly high and is still not quite suitable for real-time dynamic simulation. However, it solves faster than more complex tyre models where details of steel wires, etc. are included in the model. For future studies it is recommended that different element types be investigated in the tyre model. The study proves that equivalent material properties can be used to simulate the composite properties of the materials in tyres. Most tyres can be divided into a few regions that each has its own material structure right through the region. These regions can be characterized by simple tests and the input can be used as a first estimation of the tyre’s material properties for the model. Accurate validation criteria should be used to validate the tyre model if time does not allow for excessive testing of the material properties of all the rubber, steel wires, polyester threads, etc. Geometric displacement data at various loading conditions can be used for validation of the tyre model. The model developed can be used to investigate the effect of different stiffnesses and other material changes in the sidewall or tread of a tyre. Useful insight can be obtained from the finite element model developed for dynamic simulation where the force vs. global displacement data is important. / Dissertation (MEng)--University of Pretoria, 2014. / tm2015 / Mechanical and Aeronautical Engineering / MEng / Unrestricted
160

Information flows in Demand Responsive Public Transport : Interactivity, information, and flexibility in a modern ridesharing service

Hamnebo, Karl, Askfelt, Oscar January 2021 (has links)
The focus of this thesis is to study what and how information flows can be used to improve Demand responsive transport (DRT) systems by understanding potential users and how they could be willing to participate in DRT to a higher degree. The viewpoint of this thesis tends to lean towards a DRT service of a public transport type. This thesis studies users in relation to what interaction and information they perceive to be needed in dealing with a DRT service and the different pros and cons with various approaches. The study gathers information by performing adapted qualitative interviews with a select number of users between the ages of 20-35. The participants give their views on three DRT scenarios and reflect on DRT in general as a concept presented to them through a tangible mocked-up interactive prototype.  The thesis makes several distinct findings. The importance of pricing a DRT service correctly is vital to the users, as several participants in the study relied on pricing for decision-making. It also finds that the usage of zones as nomenclature is confusing to many users. The services must be dependable and punctual to both attract users, keep users, and build trust among the general populace. This study shows that DRT services could be a difficult concept to introduce to users. DRT could be introduced as a complement or as an alternative to conventional public transport. An important factor is a well-designed flow of information in the application to keep the user engaged and involved. It is shown that the usability of the application is a cornerstone for a theoretical DRT service to excel. Context is important where DRT and ridesharing would have a higher success rate. Nighttime in urban areas could be a niche market, due to the irregularity, delay, or interruption of regular public transport services at these hours.

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