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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.
271

Antény na flexibilním substrátu / Flexible substrate antennas

Sedlák, Jakub January 2020 (has links)
This diploma thesis deals with a design of antennas based on a flexible substrate. There is also a design of a transmission line between a flexible and rigid substrate with FLEX- RIGID technology. In the first part of thesis, there is the technology, advantages and disadvantages of using this technology in design of antennas mentioned. There are also basic antenna parameters mentioned. In second part, the design of a transmission line and four antennas is presented. Two of these antennas are manufactured and measured. Finally, the measured parameters are compared with the simulated results.
272

Biomechanical Comparison of Wire Circlage and Rigid Plate Fixation for Median Sternotomy Closure in Human Cadaver Specimens

Wong, Mark Steven 01 April 2010 (has links)
Background: Over 700,000 patients per year undergo open-heart surgery. Healing complication rates can be up to 5% of patients who undergo this procedure, with a morbidity rate of 50% if mediastinitis supervenes. A secure and rigid fixation of surgically divided sternum is critical to avoid healing complications. The purpose of this study was to compare the yield load, construct stiffness, ultimate load, displacement at ultimate load, and post-yield behavior of three sternotomy closure methods (Peristernal wires or Sternalock titanium plates) when stressed in each of three directions: lateral distraction, rostro-caudal (longitudinal) shear distraction, and anterior-posterior (transverse) shear in a cadaveric model. Methods: Forty-two fresh cadaver models were divided into three test groups: group A, B, and C. A cardiothoracic surgeon divided each cadaveric sternum longitudinally and repaired peristernal wires or one of two Sternalock configurations. Tests were performed using a materials testing system that applied force at a constant displacement rate in a uniaxial direction until the construct catastrophically failed. Mechanical behavior was monitored using a 3D texture correlation system to create a real-time three-dimensional representation of strain directions. The resulting displacement pattern is analogous to a finite element contour plot of displacements, Lagrange Strain, or velocity. Statistical analysis was used to show the different mechanical properties of each closure method. Results: When loaded in lateral distraction, both Sternalock configurations surpassed the rigidity of peristernal wires by 600%. Some evidence was also found linking Sternalock with stiffer behavior in the rostro-caudal direction. Though not statistically significant, a trend was observed showing that constructs using the Sternalock also had higher yield loads, as well as, less post-yield displacement when compared to peristernal wires. Conclusions: Data gathered showed the superior performance of the Sternalock system in stiffness in both longitudinal distraction and rostro-caudal shear. Implications for use of the Sternalock system are faster healing times, lower complication rates, and success of the procedure.
273

Fyzikální simulace na GPU / Physics Simulation on GPU

Janošík, Ondřej January 2016 (has links)
This thesis addresses the issue of rigid body simulation and possibilities of paralellization using GPU. It describes the basics necessary for implementation of basic physics engine for blocks and technologies which can be used for acceleration. In my thesis, I describe approach which allowed me to gradually accellerate physics simulation using OpenCL. Each significant change is described in its own section and includes measurement results with short summary.
274

Planetary Rover Wheel and Lower Leg Structural Design to Reduce Rock Entanglements

Lawton, Natalie January 2020 (has links)
This thesis looks at the SherpaTT planetary rover. The rover is a hybrid walking and driving rover that has been developed and built by DFKI and has already been deployed on several Mars analogue field studies. The SherpaTT rover wheels were found to become entangled in rocks during the last field deployment in Morocco. As human intervention would be impossible on Mars the aim is to reduce the possibility of rock entanglements by performing a mechanical redesign of the wheels. During this redesign care is taken to ensure the current traction, slip-resistance, weight and strength are not adversely affected. In addition, the durability of the wheels is investigated in terms of materials to review whether the current wheels are suitable for a mars deployment. An investigation into the grousers design results in a changed design that aims to both reduce rock entanglements and increase wheel performance by optimising the grouser height and number over several different wheel and terrain cases. Wheels are produced for four scenarios, a rigid wheel on hard ground, a rigid wheel on soft ground, a flexible wheel on hard ground and a flexible wheel on soft ground. A conceptual investigation into the wheel fork design is carried out to examine the effects of changing three properties of the wheel fork. The magnitude and location of the stress is compared for each. Materials are investigated resulting in the recommendation of several potential material choices which provide an increase in the overall strength and hardness. While SherpaTT is still in development the 6000 class of aluminium is recommended due to the relative ease with which it can be worked with. Once SherpaTT moves onto the final stages it is recommended that at least the grousers are made from the 7000 class of aluminium, which have higher levels of strength and hardness.
275

Transient Stress and Strain Assessment of Marine Boiler : Fully Rigid Body Dynamics Coupled Finite Element Analyses

Anwar, Sohail January 2020 (has links)
Operationally, marine components and structures such as boiler in a Ship, are exposed to varying mechanically and thermally induced forces. High-frequency mechanical loading arises from the cyclic pressure, temperature transients, and six directional Rapid Amplitude Operator (RAOs). These types of loadings are mainly in the elastic region usually denoted as high cycle fatigue (HCF), most pronounced during the start-up, and the shut-down sequence of operation, which are responsible for an astronomically  reduction in Marine Boiler’s lifetime as compared to land boiler with same designed operating condition. Therefore, there is a need to determine the limitations of the engineering variables of the boiler with respect to Pressure, temperature, RAOs, and best locational point for the optimization of its designed lifetime during Operation. Detailed knowledge of this interaction between varying temperatures, RAOs and load cases is of considerable importance for precise lifetime calculations.  In order to understand and analyze the material behavior under contentious stress exposure, a general-purpose linear Finite Element (FE) code, LS-DYNA software is used as a pre-processor and solver during the simulation and data are post-processed using stress-based analysis method.
276

Vizuálně realistické modelování deformací dynamických objektů / Visually realistic modeling of dynamic objects deformations

Bulušek, Petr January 2013 (has links)
The present work deals with simulation methods for rigid bodies and deformable bodies. In the first chapter you can find research of some methods for simulation of rigid body physics with emphasis on method used in open source physics engine Bullet. In second chapter you can find methods for simulation of deformable bodies, again with emphasis on Bullet physics engine. In last chapter model order reduction technique is presented. This method enables to reduce system of ordinary differential equations. These equations come for example from applying finite element method to partial differential equations describing motion of elastic body. The technique is studied on bar truss systems. Powered by TCPDF (www.tcpdf.org)
277

Simulating Destruction Effects in SideFX Houdini

Elkins, Ethan B 01 May 2020 (has links)
As movies, television shows, and other forms of media have progressed over the last century, the use of destruction sequences as a form of entertainment have seemingly grown exponentially. From ginormous explosions to cities collapsing, more destruction sequences have drawn people’s attention in ways that are quite captivating. However, as content producers continue to push the limit of what is possible, the reliance on practical effects starts to dwindle in comparison to the usage of computer generated scenes. This thesis acknowledges the trend and dissects the entire process of how a general destruction sequence is made, from the research and planning process to the actual simulation of the effects. Various methods are discussed in how to attempt the creation of destruction with a singular project in mind. The goal is to not only to complete the sequence, but to do so in an efficient manner that can rival a professional workflow.
278

Investigation of the behaviour of return collectors on Paris’ subway MP05 (Line 1)

Le Bars, Theo January 2014 (has links)
Return collectors are predominant organs for rubber-tyred subways to operatesince they ensure both the track circuit shunt and the traction current return. Po- sitioned at the interface between the track and the rolling stock, they are subjected to the disruptions linked to the train movement and the track irregularities. One of the most critical steps is the crossing of a switch nose.This study aims at determining the collector position during this crossing by means of a quasi-static analysis of the system. Two approaches are investigated. The first one brings into play a rigid contact and geometrical angles. It enables to model the crossing until the contact with the crossing nose. The diving capability of the collector is also taken into account. The second one is a standard  approach of the contact. A slight penetration is considered, which allows to grasp the contact with  the crossing nose. The second advantage  is to prepare the ground for a complete dynamical analysis. Both approaches are then implemented on Matlab to solve the equations. Finally the study of the switch crossing in nominal conditionsand a parametric analysis are achieved for a specified switch.
279

Implementation of multiple design procedures into MULTI-PAVE.

Gebrehiwot, Nahusenay K January 2011 (has links)
One particular challenge in pavement design is comparing the results of the different design methods. Some methods, such as the AASHTO (American Association of State Highway and Transportation Officials) Flexible design method and the AASHTO Rigid method were developed in the US, and use US units, as well as typical design loads and specifications. The same can be said for the Florida Cracking method. Other methods, such as the Swedish PMS-Object use SI units and different design axle load. This thesis describes the development of a MATLAB based unified Graphical design interface, called MULTI-PAVE, which implements all the aforementioned design methods using a unified input, to achieve comparable design pavement thicknesses. The program is validated by comparing its output against independently written modules.
280

Propuesta de diseño estructural del pavimento rígido convencional y fibroreforzado de la Av. Sánchez Cerro en Piura usando la tecnología del reciclado mecánico / Structural design proposal for the conventional and fiber-reinforced rigid pavement of Sánchez Cerro avenue in Piura using mechanical recycling technology

Espinoza Gonzáles, Alvaro Javier, Vargas Guevara, Jessica Jeanette 31 August 2020 (has links)
Debido al incremento tránsito, el poco o nulo mantenimiento de la vía, la falta de drenaje pluvial y los estragos ocasionados por el fenómeno de “El Niño Costero”, la infraestructura vial de la Av. Sánchez Cerro se ha deteriorado a tal punto de presentar fallas estructurales y nulos niveles de serviciabilidad que no permiten un tránsito adecuado de los vehículos y peatones que circulan por la zona, afectando el confort del ciudadano y el paisajismo de la ciudad. Ante ello, y debido a que la zona es altamente comercial, con muchas interferencias producidas por los servicios públicos, las tendencias de sostenibilidad a nivel global y los niveles existentes en el proyecto, se ha realizado optado por realizar una propuesta de rehabilitación del pavimento mediante una base reciclada de asfalto con colocación de una losa de pavimento rígido que permita cumplir con los objetivos del proyecto. El objetivo principal del estudio es realizar el diseño del reciclado mecánico, también conocido como RAP, y el diseño de la losa de concreto del pavimento rígido mediante las metodologías AASHTO 1993, PCA 1984 y la “Yield Line Theory” (basada en Technical Report N° 34 del Eurocódigo) utilizada para el diseño de losas reforzadas con fibras que permita verificar las condiciones de diseño, brindando soluciones tradicionales y alternativas que permitan mantener los niveles de la vía. / Due to the increase in traffic, the lack of maintenance and drainage of the road and the damage caused by "El Niño Costero", the infrastructure of Sánchez Cerro avenue has deteriorated to the point of presenting structural failures and zero levels of serviceability that do not allow the transit of vehicles and pedestrians, affecting the comfort of the citizen and the landscape of the city. Given this, and because the area is highly commercial, with many interferences produced by public services, the global sustainability trends and existing levels in the project, it has been decided to carry out a proposal for the rehabilitation of the pavement through a recycled asphalt pavement (RAP) with the placement of a concrete slab that allows reach the objectives of the project. The main objective is to carry out the mechanical recycling design and the design of the rigid pavement concrete slab using the AASHTO 1993, PCA 1984 and “Yield Line Theory” methodologies (based on Technical Report No. 34 of the Eurocode) used for the design of slabs reinforced with fibers that allows to verify the design conditions, providing traditional and alternative solutions that allow maintaining the levels of the road. / Tesis

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