• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 7
  • 2
  • 2
  • 1
  • 1
  • Tagged with
  • 16
  • 16
  • 6
  • 3
  • 3
  • 3
  • 3
  • 3
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 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

Computational Models for Design and Analysis of Compliant Mechanisms

Lan, Chao-Chieh 22 November 2005 (has links)
We consider here a class of mechanisms consisting of one or more compliant members, the manipulation of which relies on the deflection of those members. Compared with traditional rigid-body mechanisms, compliant mechanisms have the advantages of no relative moving parts and thus involve no wear, backlash, noises and lubrication. Motivated by the need in food processing industry, this paper presents the Global Coordinate Model (GCM) and the generalized shooting method (GSM) as a numerical solver for analyzing compliant mechanisms consisting of members that may be initially straight or curved. As the name suggests, the advantage of global coordinate model is that all the members share the same reference frame, and hence, greatly simplifies the formulation for multi-link and multi-axis compliant mechanisms. The GCM presents a systematic procedure with forward/inverse models for analyzing generic compliant mechanisms. Dynamic and static examples will be given and verified experimentally. We also develop the Generalized Shooting Method (GSM) to efficiently solve the equations given by the GCM. Unlike FD or FE methods that rely on fine discretization of beam members to improve its accuracy, the generalized SM that treats the boundary value problem (BVP) as an initial value problem can achieve higher-order accuracy relatively easily. Using the GCM, we also presents a formulation based on the Nonlinear Constrained Optimization (NCO) techniques to analyze contact problems of compliant grippers. For a planar problem it essentially reduces the domain of discretization by one dimension. Hence it requires simpler formulation and is computationally more efficient than other methods such as finite element analysis. An immediate application for this research is the automated live-bird transfer system developed at Georgia Tech. Success to this development is the design of compliant mechanisms that can accommodate different sizes of birds without damage to them. The feature to be monolithic also makes complaint mechanisms attracting in harsh environments such as food processing plants. Compliant mechanisms can also be easily miniaturized and show great promise in microelectromechanical systems (MEMS). It is expected that the model presented here will have a wide spectrum of applications and will effectively facilitate the process of design and optimization of compliant mechanisms.
2

A Study in the Frequency Warping of Time-Domain Methods

Gao, Kai January 2015 (has links)
This thesis develops a study for the frequency warping introduced by time-domain methods. The work in this study focuses first on the time-domain methods used in the classical SPICE engine, that is the Backward Euler, the Trapezoidal Rule and the Gear's methods. Next, the thesis considers the newly developed high-order method based on the Obreshkov formula. This latter method was proved to have the A-stability and L-stability properties, and is therefore robust in circuit simulation. However, to the best of the author's knowledge, a mathematical study for the frequency warping introduced by this method has not been developed yet. The thesis therefore develops the mathematical derivation for the frequency warping of the Obreshkov-based method. The derivations produced reveal that those methods introduce much smaller warping errors than the traditional methods used by SPICE. In order to take advantage of the small warping error, the thesis develops a shooting method framework based on the Obreshkov-based method to compute the steady-state response of nonlinear circuits excited by periodical sources. The new method demonstrates that the steady-state response can be constructed with much smaller number of time points than what is typically required by the classical methods.
3

Shooting Method for Two-Point Boundary Value Problems

Baumann, John D. 01 May 1976 (has links)
The purpose of this paper is to develop the shooting method as a technique for approximating the solution to the two-point boundary value problem on the interval [a,b] with the even order differential equation {i.e. n is even) u(n)(t) + f(t, u(t), u(i)(t, ),..., u(n-1)(t)) = 0 and boundary conditions u(a) = A u(b) = B and with at most n-2 other boundary conditions specified at either a or b. The basic proceedure will be illustrated by the following example. Consider the two-point boundary value problem (0.1) (0.2) (0.3) with the additional boundary conditions u(i)(a) = mi for i = 1, ... ,k-1,k+l, ... ,n-1. The first step is to find values m1 and m2 such that the solutions or "shots", u1(t) and u2(t), to (0.1) that satisfy the initial conditions u(a) = A u(k-1)(a)= mk-1 u(k)(a) = m1 u(k+1)(a) = mk+l u(n-1)(a) = mn-1 with 1 = 1,2, respectively, with the property that u1(b) < B < u2(b). The interval [m1,m2] is then searched by seccussive bisection to find the value, m, such that the solution or "shot", u(t), to the initial value problem with (0.1) and initial conditions u(a) = A u(k-1)(a)= mk-1 u(k)(a) = m1 u(k+1)(a) = mk+l u(n-1)(a) = mn-1 has the property that u(b) = B.
4

Ground states in Gross-Pitaevskii theory

Sobieszek, Szymon January 2023 (has links)
We study ground states in the nonlinear Schrödinger equation (NLS) with an isotropic harmonic potential, in energy-critical and energy-supercritical cases. In both cases, we prove existence of a family of ground states parametrized by their amplitude, together with the corresponding values of the spectral parameter. Moreover, we derive asymptotic behavior of the spectral parameter when the amplitude of ground states tends to infinity. We show that in the energy-supercritical case the family of ground states converges to a limiting singular solution and the spectral parameter converges to a nonzero limit, where the convergence is oscillatory for smaller dimensions, and monotone for larger dimensions. In the energy-critical case, we show that the spectral parameter converges to zero, with a specific leading-order term behavior depending on the spatial dimension. Furthermore, we study the Morse index of the ground states in the energy-supercritical case. We show that in the case of monotone behavior of the spectral parameter, that is for large values of the dimension, the Morse index of the ground state is finite and independent of its amplitude. Moreover, we show that it asymptotically equals to the Morse index of the limiting singular solution. This result suggests how to estimate the Morse index of the ground state numerically. / Dissertation / Doctor of Philosophy (PhD)
5

Improvements to the design methodology and control of semicontinuous distillation

Madabhushi, Pranav Bhaswanth January 2020 (has links)
Distillation technology has been evolving for many decades for a variety of reasons, with the most important ones being energy efficiency and cost. As a part of the evolution, semicontinuous distillation was conceived, which has the advantages of both batch and continuous distillation. The economic benefits of this intensified process compared to batch and continuous distillation were expounded in many of the previous studies. Semicontinuous distillation of ternary mixtures, which is the main focus of this thesis, is carried out in a single distillation column with a tightly integrated external middle vessel and the operation is driven by a control system. The system operation does not include any start-up or shut-down phases of the column and has three periodically repeating operating modes. In the status quo design procedure, called the ‘sequential design methodology,’ an imaginary continuous distillation system design was used to design the semicontinuous distillation system. In this methodology, dynamic simulations of the process were used to find the values of the controller tuning parameters based on the design of the continuous system. Afterwards, black-box optimization was used to find better controller tuning parameter values that minimized cost. However, after analyzing the dynamics of the system for different cases, it was found that the heuristics used in this design methodology yielded suboptimal designs. Therefore, the primary goal of the thesis is to improve these heuristics by incorporating more knowledge of the system and thereby develop a better design methodology. Firstly, the setpoint trajectories generated by the ideal side draw recovery arrangement for side stream flowrate control, which was standard in most semicontinuous distillation studies, was modified. In this thesis, the performance of the status quo as compared to the modified version, based on the criteria, cycle time and cost for different case studies, was presented. Results showed that the modified-ideal side draw recovery arrangement for side stream flowrate control performed better with a 10-20% lower separating cost while maintaining product purities. Furthermore, to reap more cost benefits, dynamic optimization was used to seek the flow rate trajectory that minimized cost. However, it was found that the additional cost savings, which is in addition to the benefits gained by using the modified version, were at the most 2% from different case studies. Subsequently, the impact of changing the imaginary continuous distillation system design on the nature of the semicontinuous distillation limit cycle, specifically, its period was studied. Results revealed the necessity for a new design procedure, and thus the back-stepping design methodology was proposed. This design methodology was used to find better limit cycles of zeotropic ternary semicontinuous distillation using the aspenONE Engineering suite. The proposed methodology was applied to three different case studies using feed mixtures with different chemical components. A comparison with the sequential design methodology for the two case studies indicates that the new method outperforms the state-of-the-art by finding limit cycles that were 4% to 57% lower in terms of cost. Furthermore, the designs obtained from this procedure were guaranteed to have feasible column operation with stable periodic steady-state behaviour. Semicontinuous distillation design using the design methodology with heuristic components involves guessing, checking and then using black-box optimization to find the values of the design variables to meet some performance criteria. Furthermore, mathematical guarantees of either local or global optimality of the designs obtained from the design procedure do not exist. Therefore, to address these issues, in this thesis, the application of using the shooting method for designing the semicontinuous distillation process was demonstrated using two case studies, which involve the separation of hexane, heptane and octane. This method has the potential to be combined with gradient-based optimization algorithms for optimization of the process design in the future. / Thesis / Doctor of Philosophy (PhD)
6

Face Transformation by Finite Volume Method with Delaunay Triangulation

Fang, Yu-Sun 13 July 2004 (has links)
This thesis presents the numerical algorithms to carry out the face transformation. The main efforts are denoted to the finite volume method (FVM) with the Delaunay triangulation to solve the Laplace equations in the harmonic transformation undergone in face images. The advantages of the FVM with the Delaunay triangulation are: (1) Easy to formulate the linear algebraic equations, (2) Good to retain the geometric and physical properties, (3) less CPU time needed. The numerical and graphical experiments are reported for the face transformations from a female to a male, and vice versa. The computed sequential and absolute errors are and , where N is division number of a pixel into subpixels. Such computed errors coincide with the analysis on the splitting-shooting method (SSM) with piecewise constant interpolation in [Li and Bui, 1998c].
7

Úspěšnost střelby v české házenkářské extralize v sezoně 2010/2011. / The success of shooting in the Czech Extraleague Handball in season 2010/2011.

MĚCHURA, Matěj January 2011 (has links)
This thesis analyses the successful of shooting in the highest Czech handball competition - Extraleague Men, in season 2010/2011. The analysis was realized by watching video recordings which were taken during the basic part of the competition. Besides the monitoring of the total success of these teams, we focused on components of the attack on the overall success and, for example, on shooting from the perspective of post player or shooting methods. The data were processed into graphs and commented.
8

Existência e multiplicidade de soluções de problemas de autovalor não lineares elípticos / Existence and multiplicity of solutions of nonlinear elliptic eigenvalue problems

Silva, Kaye Oliveira da 03 July 2015 (has links)
Submitted by Marlene Santos (marlene.bc.ufg@gmail.com) on 2018-06-29T19:43:37Z No. of bitstreams: 2 Tese - Kaye Oliveira da Silva - 2015.pdf: 3763230 bytes, checksum: 2a51ab65a386fdff2c014712b4f5a7fd (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2018-07-03T15:21:01Z (GMT) No. of bitstreams: 2 Tese - Kaye Oliveira da Silva - 2015.pdf: 3763230 bytes, checksum: 2a51ab65a386fdff2c014712b4f5a7fd (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2018-07-03T15:21:01Z (GMT). No. of bitstreams: 2 Tese - Kaye Oliveira da Silva - 2015.pdf: 3763230 bytes, checksum: 2a51ab65a386fdff2c014712b4f5a7fd (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2015-07-03 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / In this work, we study two problems in partial differential equations. The first one is a nonlinear eigenvalue problem given by: ( 􀀀div( (jruj)ru) = f(x; u) em , u = 0 em @ , where the nonlinearity f is oscilatory. By using Orlicz-Sobolev spaces and techniques of minimization, degree theory, lower and upper solutions and regularization of solutions, we show that for each sufficiently big, there is a family of solutions, which is finite when f oscillates a finite number of times (with respect to the second variable) and it is infinite when f oscillates infinitely many times. On the second problem, we use the shooting method, to show that the problem: ( 􀀀(r (ju0(r)j)u0(r))0 = r f(u(r)); 0 < r < R; u(R) = u0(0) = 0; has for each sufficiently small, a family fukg1k =1 of solutions, where for each positive integer k, uk has exactly k roots in the interval (0;R). / Neste trabalho estudamos dois problemas de equações diferenciais parciais. O primeiro é um problema não linear de autovalores da forma: ( 􀀀div( (jruj)ru) = f(x; u) em , u = 0 em @ , cuja não linearidade f é oscilatória. Utilizando os espaços de Orlicz-Sobolev e técnicas de minimização, teoria do grau, sub e super soluções e regularização de soluções, mostramos que para cada suficientemente grande, existe uma família de soluções, que é finita no caso de f oscilar um número finito de vezes (com relação a segunda variável) e infinita no caso de f oscilar um número infinito de vezes. No segundo problema, usamos o método de shooting, para mostrar que o problema ( 􀀀(r (ju0(r)j)u0(r))0 = r f(u(r)); 0 < r < R; u(R) = u0(0) = 0; possui para cada > 0 suficientemente pequeno, uma família fukg1k =1 de soluções, onde para cada k inteiro positivo, uk tem exatamente k raízes no intervalo (0;R).
9

Numerical methods for analyzing nonstationary dynamic economic models and their applications

Tsener, Inna 15 May 2015 (has links)
No description available.
10

Contrôle optimal géométrique et numérique appliqué au problème de transfert Terre-Lune / Numerical and geometric control methods and applications to the Earth - Moon transfert problem

Picot, Gautier 29 November 2010 (has links)
L'objet de cette thèse est de proposer une étude numérique, fondée sur l'application de résultats de la théorie du contrôle optimal géométrique, des trajectoires spatiales du système Terre-Lune dans un contexte de poussée faible. Le mouvement du satellite est décrit par les équations du problème restreint des trois corps controlé. Nous nous concentrons sur la minimisation de la consommation énergétique et du temps de transfert. Les trajectoires optimales sont recherchées parmi les projections des courbes extrémales solutions du principe du maximum de Pontryagin et peuvent être calculées grâce à une méthode de tir. Ce procédé fait intervenir l'algorithme de Newton dont la convergence nécessite une initialisation précise. Nous surmontons cette difficulté au moyen de techniques homotopiques ou d'études géométriques du système de contrôle linéarisé. L'optimalité locale des trajectoires extrémales est ensuite vérifée en utilisant les conditions du second ordre liées au concept de point conjugué. Dans le cas du problème de minimisation de l'énergie, une technique de "recollement" de trajectoires optimales kepleriennes autour de la Terre et La Lune et d'une solution optimale de l'équation du mouvement linéarisée au voisinage du point d'équilibre L1 est également proposée pour approximer les transferts Terre-Lune à énergie minimale. / This PhD thesis provides a numerical study of space trajectories in the Earth-Moon system when low-thrust is applied. Our computations are based on fundamental results from geometric control theory. The spacecraft's motion is modelled by the equations of the controlled restricted three-body problem. We focus on minimizing energy cost and transfer time. Optimal trajectories are found among a set of extremal curves, solutions of the Pontryagin's maximum principle, which can be computed solving a shooting equation thanks to a Newton algorithm. In this framework, initial conditions are found using homotopic methods or studying the linearized control system. We check local optimality of the trajectories using the second order optimality conditions related to the concept of conjugate points. In the case of the energy minimization problem, we also describe the principle of approximating Earth-Moon optimal transfers by concatening optimal keplerian trajectories around The Earth and the Moon and an energy-minimal solution of the linearized system in the neighbourhood of the equilibrium point L1.

Page generated in 0.0553 seconds