• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 56
  • 11
  • 8
  • 7
  • 6
  • 4
  • 4
  • 1
  • 1
  • 1
  • Tagged with
  • 256
  • 256
  • 256
  • 175
  • 66
  • 60
  • 52
  • 49
  • 48
  • 47
  • 44
  • 44
  • 43
  • 43
  • 40
  • 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.

Image feature matching using polynomial representation of chain codes

Houghton, Michael Kevin January 1993 (has links)
In this thesis the development of a novel descriptor for boundary images represented in a chain code format is reported. This descriptor is based on a truncated series of orthogonal polynomials used to represent a piecewise continuous function derived from a chain code. This piecewise continuous function is generated from a chain code by mapping individual chain links onto real numbers. A variety of alternative mappings of chain links onto real numbers are evaluated, along with two specific orthogonal polynomials; namely Legendre polynomials and Chebychev polynomials. The performance of this series descriptor for chain codes is evaluated initially by applying it to the problem of locating short chains within a long chain; and then extending the application and critically evaluating the descriptor when attempting to match features from pairs of similar images. In addition, a formal algebra is developed that provides the rule base that enables the transformation and manipulation of chain encoded boundary images. The foundation of this algebra is based on the notion that the labelling of the directions of an 8-connected chain code is essentially arbitrary and 7 other, different and consistent labellings can be distinguished.

Projeto de um manipulador com tres juntas revolutas : concepção, construção e testes preliminares

Pellissari, João Orestes, 1960- 07 February 1994 (has links)
Orientador: Douglas Eduardo Zampieri / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-07-19T08:06:00Z (GMT). No. of bitstreams: 1 Pellissari_JoaoOrestes_M.pdf: 15764176 bytes, checksum: d7724dd0944624f1b02863d766f9e68d (MD5) Previous issue date: 1994 / Resumo: Neste trabalho o protótipo de um manipulador com três graus de liberdade é apresentado e as fases de projeto, execução e desenvolvimento básico do controle são detalhadas. Os conceitos fundamentais de robótica são revistos, visando a obtenção dos modelos geométricos (direto e inverso) e dinâmico (recursivo). Finalmente, propõe-se, também um método simples para a verificação de repetibilidade dos movimentos da base, braço e ante-braço. Em outras palavras, o trabalho aborda a metodologia de projeto em engenharia, comentando em seu final os problemas surgidos e propondo algumas correções no protótipo, adaptando as especificações de projeto as limitações de manufatura / Abstract: In this work, a prototype of a three-degrees-of-freedom manipulator is presented. The manipulator design stages, its construction, and the basic control development are detailed. The fundamental concepts of robotics are reviewed, aiming the establishment of the geometric models (direct and inverse) and the dynamic model (recursive). Finally, a simple method for the verification of the repetibility of the mouvements of the base, the arm, and the forearm is proposed. In other words, the work is concerned with the methodology of projects in engneering. It covers some problems and proposes some corrections in the prototype, adapting the specifications of the project to the limitations of manufacture / Mestrado / Mestre em Engenharia Mecânica

Computer program development for the analysis of inelastic beam and soil behaviour in geotechnical design

Howie, C T January 1992 (has links)
Computer-aided engineering requires the correct implementation of design methods in computer programs so as to play a beneficial role in engineering practice. This thesis describes the development of a computer program to analyse geotechnical engineering problems based on the principles of beam-soil interaction where the beam is supported by a single or two-layer soil system. In 1867, a foundation model was proposed by Winkler in which the elastic foundation beneath a horizontal beam could be viewed as a series of independent springs. Foundation reaction to beam deflection is, therefore, linear. A stiffness matrix, for use in matrix methods of structural analysis, has been developed to define this beam-soil interaction, and such a method can be incorporated into a computer program. Furthermore, an iterative technique was created to allow for inelastic soil response when using the elastic stiffness matrix. However, such a technique did not consider realistic soil behaviour, and has limitations is used for practical design. This research' work describes how use can be made of the pressure-displacement response relationship for a soil to bring greater realism to beam-soil modelling and analysis. Such a relationship is commonly determined in geotechnical design procedures through a plate load test in the field. In addition, the iterative technique is extended to include non-linear beam behaviour as well, and plastic hinging of the beam material is incorporated to enable limitation of inelastic response. While previous research has only considered foundations of a single soil only, a procedure to model a two-layered system is developed. Two-layered foundations are required for proper modelling of soldier pile support systems, an area of structural design in geotechnics chosen to demonstrate realistic design potential for the computer program. The two-layered principle is based on the derivation of a control parameter to differentiate between response from just the upper soil layer, and a combined response from both soil layers. The procedure is relatively simple, and no extra information is required other than the two pressure displacement relationships for the individual soil layers. A desktop computer program is described which incorporates the inelastic analysis features, as well as the two-layered soil system. The program makes use of a graphical user interface to offer the user an easy, interactive environment for analysing beam-on-soil foundation problems. As such, the program can be used directly, or for further research into beam-soil interaction. The program is applied in the analysis of both field and laboratory tests to ascertain its accuracy in predicting beam-soil interaction. The laboratory test measures the deflection of a horizontal beam on a single soil foundation medium, where the beam is loaded by a single jack at approximately mid-span. Computer predictions for such a test were in very close agreement with the laboratory observations, despite the small magnitude of beam displacements, and the fact the beam-soil system suffered a bearing capacity failure which affected the beam deflection. The field test was performed to investigate the performance of a flexible soldier pile under high anchor loading. Results of the computer analyses again show the program's predictions to be in very close agreement with the field measurements. Currently, the program does not include the facility to model soil layers behind a soldier pile, but the method developed in this thesis can easily incorporate multiple pressure-displacement curves for different soils. Final conclusions drawn express a need for more research into soldier pile systems before the techniques of this work can be used for routine design. Nevertheless, the development of the program has made a significant contribution to advancing the use of computer-aided design in this field of geotechnical engineering.

Development of a Finite Element Model for Predicting the Impact Energy Absorbing Performance of a Composite Structure

Roberts, Matthew Lowell 01 June 2014 (has links)
Because of their high strength-to-weight ratio, Fiber Reinforced Composite (FRC) materials are well suited for use in high performance racing applications where weight must be kept to a minimum. Formula SAE (FSAE) race cars are designed and built by college students, roughly following the model of a scaled down Formula One car. Strict regulations are placed on specific components of the car in the interest of equalizing competition and ensuring the safety of the drivers. Students are required to construct a survival cell (the chassis), which can resist large amounts of energy in the event of a crash, with an energy absorbing device at the front of the vehicle. The nose cone of the Cal Poly FSAE car is constructed as a carbon fiber shell designed to act as this sacrificial energy absorbing device. One difficulty associated with using FRC materials is that the anisotropic properties can lead to a variety of complex failure modes such as buckling, delamination, matrix cracking, and fiber breakage, all of which absorb different amounts of energy. In order to accurately predict the behavior of the nose cone so that it meets the requirements set forth by SAE, an initial finite element model has been constructed. This model uses the test results from another paper to construct an explicit non-linear dynamic analysis in Abaqus which simulates the axial crushing of a thin walled composite tube between two rigid plates. The modeling techniques discussed in this paper will be used as the basis for a future thesis dedicated to designing the nose cone for the Cal Poly FSAE car.

Structure Climbing Monkey Robot

Bessent, Paul 01 June 2011 (has links)
This report describes the design, building, and testing of the Structure Climbing Monkey Robot (SCMR). It is composed of seven successive joints and linkages with two grippers at the two ends. Each gripper can act as the base or the end of the robot. The SCMR has the ability to climb any structure. The gripper plates can be changed to grab different kinds of structures, but this one is made to grab 2x4‘s. A program was written to assist the user to grab four non-coplanar, non-orthogonal points. The SCMR is actuated by a total of nine motors: two to open and close the two grippers and seven to control the movement of the SCMR. Planetary gear motors are used with a worm gear to control the motion of each joint. The worm gear increases the torque of the motor and reduces the rotational speed to a usable value. The SCMR is just over 45 inches long and weighs about 30 pounds. The motion of the SCMR is controlled by the microcontroller Arduino Mega 2560, Vex Robotic quadrature encoders, and Pololu 18v15 motor driver chips. Code was written in the languages Arduino and Processing to actuate the motors and create the GUI, respectively. The motors can be controlled individually or run simultaneously while incrementing a specified angle.


El-Achwah, Ahmad, Mr. 01 January 2019 (has links)
Aerosolized medications can potentially be delivered to the lungs of infants through a nasal cannula interface. However, nose-to-lung delivery technologies currently allow for ~1% of the loaded dose to reach an infant’s lungs. Conventional dry powder inhalers (DPI) are superior to other types of inhalers in many ways. However, passive DPIs that operate based on user inhalation and require large volumes of airflow are not applicable to infants. To overcome this challenge, positive pressure DPIs have been developed that enable aerosol delivery to infants. Unless an adequate nasal interface is used with these devices, a significant amount of drug will still be lost. Computational fluid dynamics (CFD) provide a method to assess the performance of a nasal cannula interface and optimize its performance. In this study, a CFD model was first experimentally validated using the low-Reynolds number k-ω turbulence model, then used to assess and optimize several conical diffuser cannula designs for infants. The performance of a cannula depends primarily on two requirements: the amount deposited particles and the cannula’s volume. It was found that 90 and 100 mm long simple diffusers achieved the necessary deposition and volume requirements when operated at 3 and 5 liters per minute, respectively. Additionally, including clean sheath co-flow air with the 70 mm long diffuser achieved the targeted performance requirements. Inclusion of recent advancements in the field with the recommended cannula designs is likely to improve pharmaceutical aerosol delivery to infants using the nose-to-lung approach.

Towards a Semantic Knowledge Management Framework for Laminated Composites

Premkumar, Vivek 23 November 2015 (has links)
The engineering of laminated composite structures is a complex task for design engineers and manufacturers, requiring significant management of manufacturing process and materials information. Ontologies are becoming increasingly commonplace for semantically representing knowledge in a formal manner that facilitates sharing of rich information between people and applications. Moreover, ontologies can support first-order logic and reasoning by rule engines that enhance automation. To support the engineering of laminated composite structures, this work developed a novel Semantic LAminated Composites Knowledge management System (SLACKS) that is based on a suite of ontologies for laminated composites materials and design for manufacturing (DFM) and their integration into a previously developed engineering design framework. By leveraging information from CAD/FEA tools and materials data from online public databases, SLACKS uniquely enables software tools and people to interoperate, to improve communication and automate reasoning during the design process. With SLACKS, this research shows the power of integrating relevant domains of the product lifecycle, such as design, analysis, manufacturing and materials selection through the engineering case study of a wind turbine blade. The integration reveals a usable product lifecycle knowledge tool that can facilitate efficient knowledge creation, retrieval and reuse, from design inception to manufacturing of the product.

A Prediction of the Acoustical Output of a Golf Driver Head Using Finite Elements

Sharpe, Roger 01 March 2010 (has links) (PDF)
A simulation was created using LS-DYNA® to determine the acoustical properties of a golf ball and golf driver head impact. LS-DYNA® has a coupled finite element analysis (FEA) and boundary element method (BEM) solver that uses the integral form of Helmholtz’s acoustic wave equation to deliver predicted sound pressure levels at predetermined acoustic points. Validation of the modeling was done on a simple plate donated by Titleist Golf. The plate was modeled and meshed using TrueGrid and impacted by a three layer golf ball model derived from “Tanka’s” paper on multilayered golf balls. The final converging model consisted of 10,900 solid fully integrated elements between the ball, plate, and plate support structure. The result was compared to experimental data taken by an air cannon and anechoic chamber that housed strain and acoustical measurement equipment. The sound level predictions from the model showed a promising correlation with experimental data and the focus switched to a golf driver head response during impact. The same ball developed from Tanaka’s paper was used to impact a 350cc generic golf driver head. The driver head consisted of 3300 fully integrated shell elements throughout the model. The top of the hosel was fixed during the simulation to simulate the connection to the golf shaft. The ball was fired at the center of the driver’s face and the predicted sound was determined for a point two feet behind the driver head. The BEM prediction of the driver head model showed little correlation with actual recorded impact sounds provided by Cleveland Golf when comparing frequency response functions. These differences could arise from assumptions and simplifications made to speed up the impact simulation. The sound produced from the golf ball after impact was one such factor was not included. Due to the complex shape of the driver head and the total number of elements involved, the numerical solution took upwards of 100 hours to finish. Adding the golf ball sound would greatly increase computational time and not contribute significantly to the overall predicted sound. Although the BEM solution can be used to characterize different driver heads, the impact is too complicated to efficiently and accurately predict the true impact sounds.


Chan, KC Thomas 27 July 2014 (has links)
<p>Computer simulation is widely used to predict the fatigue life of engine oil coolers that fail under pressure cycles. The objective of this study is to develop a practical simulation methodology to accurately predict the fatigue life of an engine oil cooler undergoing pressure cycle testing. The study focuses on two key areas of the simulation process. First, it investigates the effect of using linear and nonlinear FEA to provide stress or strain results for subsequent fatigue analysis. Second, due to lack of fatigue material properties for the aluminum coreplate material, approximate material models derived from tensile properties are used in fatigue life calculation. The study has attempted to find out the material model that gives the best correlation in life prediction. The life prediction correlation based on the Seeger, the Modified Universal Slopes and the Modified Mitchell models, together with the Modified Universal Slopes-Al model, are evaluated.</p> <p>It is concluded that the Modified Universal Slopes-Al model, which is a re-assessment of the Modified Universal Slopes model based on the fatigue data of 16 wrought aluminum alloys, gives the best life prediction for simulations using either linear or nonlinear approaches. Life prediction using nonlinear finite element results together with this approximate material model is recommended to be the best approach. On the other hand, a simple and quick linear analysis, followed by fatigue life calculation using this material model still gives life estimates with an acceptable level of confidence.</p> <p>In the last part of the study, the life prediction performance using different strain-life criteria, together with either Morrow or Smith-Watson-Topper (SWT) mean stress correction, are evaluated. It is found that SWT mean stress correction method is worse than that of Morrow in EOC fatigue life prediction in both linear and nonlinear approaches. Using the principal strain criterion with SWT mean stress correction gives conservative life prediction in both approaches. On the other hand, there are no significant differences in life prediction correlations using the principal strain, the Brown-Miller combined strain and the maximum shear strain strain-life criteria, with Morrow mean stress correction. As such, the Brown-Miller combined strain criterion with Morrow mean stress correction is the recommended strain-life model used in fatigue life calculation.</p> / Master of Applied Science (MASc)

Numerical Analysis of Fluid Flow and Heat Transfer in Atria Geometries

Kitagawa, Aaron T. 04 1900 (has links)
<p>The design, simulation, and analysis of a reference atrium using ComputationalFluid Dynamics (CFD) are presented. Atria geometries can be observed in manybuildings but their understanding from an energy perspective is not fully understood.Due to the many physical phenomena occurring within these atria, it is often difficult toassess the thermal comfort, energy consumption, and functionality of an atrium's design.The scale of an atrium’s structure coupled with dynamic physical phenomena creates acomplex problem to solve. One particular tool that is useful in solving for detailedenergy quantities is CFD. Validation studies have been conducted using previousexperimental atria data to ensure confidence in the predictions. These validation studieswere successful and also provided further insight on turbulence models, glazing systems,HVAC systems, thermal mass, and fluid flow and heat transfer behavior in atriageometries. A design for a reference atrium located in Toronto, Canada was thensimulated for typical summer and winter conditions using various configurations forglazing, solar heat flux, wall materials, occupant load, and HVAC. These simulationsprovide a realistic analysis of the reference atria and conclusions for the behavior of thereference atria are made.</p> / Master of Applied Science (MASc)

Page generated in 0.0295 seconds