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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.
1121

Engineering design optimization using species-conserving genetic algorithms.

Li, Jian-Ping, Balazs, M.E., Parks, G.T. January 2007 (has links)
No / A species conservation technique takes inspiration from the field of ecology, in which the population is divided into several species according to their similarity. Based on this technique, a Species Conservation Genetic Algorithms (SCGA) was established and had been proved to be very effective in finding multiple solutions of multimodal optimisation problems, including some problems known to be deceptive for genetic algorithms (GAs). In this paper, the SCGA is introduced to engineering structure design, and two structure designs are used to demonstrate the performances of the SCGA and how the choice of a meaningful measure of similarity will help in exploration of significant designs.
1122

Effect of different platforms on coupling compensation matrices in AOA estimation algorithms using small size UCA

Ghazaany, Tahereh S., Zhu, Shaozhen (Sharon), Jones, Steven M.R., Abd-Alhameed, Raed, Noras, James M., Van Buren, T., Marker, S. January 2014 (has links)
No / In this paper the sensitivity of the decoupling matrix used for mutual coupling compensation in small size uniform circular arrays has been studied. The compensation matrix is calculated using the receiving mode technique for a 5-element uniform circular array and applied to two groups of direction finding algorithms, namely phase comparison-based (interferometry) and subspace-based algorithms. In the tracking application considered the receiver array is deployed on a car roof or aircraft, so the geometry of the platform influences the compensation results. In this work, the effect of different ground plane geometries in terms of the standard deviation of angular error for each estimation algorithm using simulation results is investigated. The results show that the calibration conditions used to determine the compensation matrix affect the AOA estimation accuracy.
1123

Investigating the impact of discomfort in load scheduling using genetic algorithm

Anuebunwa, U.R., Rajamani, Haile S., Pillai, Prashant, Okpako, O. 24 November 2016 (has links)
Yes / Energy consumers oftentimes suffer some element of discomfort associated with the implementation of demand response programs as they aim to follow a suggested energy consumption profile generated from scheduling algorithms for the purpose of optimizing grid performance. This is because people naturally do not like to be told what to do or when to use their appliances. Although advances in renewable energy have made the consumer to also become energy supplier, who can actively cash in at times of the day when energy cost is high to either sell excess energy generated or consume it internally if required, thereby nullifying the adverse effect of this discomfort. But a majority of consumers still rely wholly on the supply from the grid. This impact on users' comfort who are active participants in demand response programs was investigated and ways to minimizing load scheduling discomfort was sought in order to encourage user participation.
1124

A k-nearest neighbour technique for experience-based adaptation of assembly stations

Scrimieri, Daniele, Ratchev, S.M. 04 March 2020 (has links)
Yes / We present a technique for automatically acquiring operational knowledge on how to adapt assembly systems to new production demands or recover from disruptions. Dealing with changes and disruptions affecting an assembly station is a complex process which requires deep knowledge of the assembly process, the product being assembled and the adopted technologies. Shop-floor operators typically perform a series of adjustments by trial and error until the expected results in terms of performance and quality are achieved. With the proposed approach, such adjustments are captured and their effect on the station is measured. Adaptation knowledge is then derived by generalising from individual cases using a variant of the k-nearest neighbour algorithm. The operator is informed about potential adaptations whenever the station enters a state similar to one contained in the experience base, that is, a state on which adaptation information has been captured. A case study is presented, showing how the technique enables to reduce adaptation times. The general system architecture in which the technique has been implemented is described, including the role of the different software components and their interactions.
1125

Screen-based Watermarking and Color Screen Design Based on Aperiodic Clustered-dot Halftoning

Jiayin Liu (5930726) 11 October 2024 (has links)
<p dir="ltr">FM (Frequency modulation) halftoning (aperiodic, dispersed-dot) is widely used with inkjet printers in both low-end and high-end devices. There is a desire from customers in the commercial market to use this capability with high-end digital presses based on electrophotographic printing (EP) technologies. However, the inherent instability of the EP process challenges the achievement of satisfactory print quality with dispersed-dot, aperiodic halftoning. The direct binary search (DBS) algorithm is widely considered to represent the gold standard of dispersed-dot, aperiodic halftone image quality.</p><p dir="ltr">In this thesis, we adapt DBS from dispersed-dots to clustered-dots to use with the Indigo liquid EP printing technology. We present a new screen design algorithm for aperiodic, clustered-dot halftoning based on Direct Binary Search. Our screen design has a very good detail rendering capability and a very stable halftone frequency</p><p dir="ltr">overall. In the next part of the thesis, we introduce a new microscreen design algorithm that allows the embedding of binary metadata in an aperiodic, clustered-dot halftone image with no loss of visual quality. We describe a simple method for decoding the embedded meta-data with only a knowledge of the two microscreens used to halftone the continuous-tone image. Our results with one image demonstrate 100% recovery of the embedded metadata. In the last part of the thesis, we introduce a method for joint design of three-color CMY screen sets, which is the continuation of the work from monochrome screen design. The method we developed was deemed to be satisfactory in all aspects of halftone texture quality as a 3-screen CMY solution.</p>
1126

Contention resolution with collision cost

Biswas, Umesh Chandra 13 August 2024 (has links) (PDF)
Contention resolution coordinates access to a shared communication channel divided into synchronized slots. For any fixed slot, a packet can be sent, leading to three outcomes: empty (no packet sent), successful (one packet sent), or collision (multiple packets sent). Each slot provides ternary feedback: empty, successful, or collision. Much of the prior work has mainly focused on optimizing the makespan, the number of slots needed for all packets to succeed. However, in many modern systems, collisions also incur time costs, which existing algorithms do not address. In this thesis, we design and analyze a randomized contention-resolution algorithm, Collision-Evasion Backoff, that optimizes both the makespan and the cost of collisions. In our research, �� ≥ 2 packets are initially present in the system, and each collision has a known cost C, where 1 ≤ C ≤ ���� for a known ��. With error probability polynomially small in ��, Collision-Evasion Backoff guarantees that all packets succeed with makespan �� (��√C log(��)) and a total expected collision cost of �� (��√C log2 (��)).
1127

Algorithm development in computational electrochemistry

Cutress, Ian James January 2011 (has links)
This thesis presents algorithm development in computational chemistry, and applies new computer science concepts to voltammetric simulation. To begin, this thesis discusses why algorithm development is necessary, and inherent problems found in commercial simulation solvers. As a result of this discussion, this thesis describes the need for simulators to keep abreast of recent computational developments. Algorithm development in this thesis is taken through stages. Chapter 3 applies known theory relating to the stripping voltammetry at a macroelectrode to the diffusional model of a microdisk, using finite difference and alternating direction implicit simulation techniques. Chapter 4 introduces the concept of parallel computing, and how computational hardware has developed recently to take advantage of out-of-order calculations, by processing them in parallel to reduce simulation time. The novel area of graphics card simulation for highly parallel algorithms is also explained in detail. Chapter 5 discusses the adaptation of voltammetric finite difference algorithms to a purely parallel format for simulation by explicit solution. Through explicit solution, finite difference algorithms are applied to electrode geometries which necessitate a three-dimensional solution – elliptical electrodes; square, rectangular, and microband electrodes; and dual microdisk electrodes in collector-generator mode. Chapter 6 introduces 'Random Walk' simulations, whereby individual particles in the simulation are modelled and their trajectories over time are calculated. The random walk technique in this thesis is improved for pure three-dimensional diffusion, and adapted to graphics cards, allowing up to a factor 4000 increase in speed over previous computational methods. This method is adapted to various systems of low concentration confined voltammetry (chapter 6.4) and single molecule detection, ultra low concentration cyclic voltammetry (chapter 6.5), and underpotential deposition of thallium on mobile silver nanoparticles (chapter 6.6). Overall, this thesis presents, and applies, a series of algorithm development concepts in computational electrochemistry.
1128

Problém plnění palet a využití jedné z jeho heuristik při rozmístění zboží ve skladu / Pallet loading problem and using one of its heuristics for box placement on pallets in a warehouse

Rybka, Ondřej January 2009 (has links)
This work concerns new borders, heuristics, algoritms and mathematic models of pallet loading problem (PLP). We try to describe these computational methods and find out if we can use them in real. We maximalize number of boxes placed on rectangular pallets in a particular warehouse by using chosen heuristics. Every box has a rectangular form with the same lenght and width and is fully placed on the pallet. We can rotate with the box by 90% degree until it is fixed as we want and its side lies parallelly with side of the pallet. All instances are setted in model (X, Y, a, b), where X is lenght, Y width of the pallet, a lenght and b width of the box.
1129

Algoritmos evolutivos como estimadores de frequência e fase de sinais elétricos: métodos multiobjetivos e paralelização em FPGAs / Evolutionary algorithm as estimators of frequency and phase of electrical signal: multi objective methods and FPGA parallelization

Silva, Tiago Vieira da 19 September 2013 (has links)
Este trabalho propõe o desenvolvimento de Algoritmos Evolutivos (AEs) para estimação dos parâmetros que modelam sinais elétricos (frequência, fase e amplitude) em tempo-real. A abordagem proposta deve ser robusta a ruídos e harmônicos em sinais distorcidos, por exemplo devido à presença de faltas na rede elétrica. AEs mostram vantagens para lidar com tais tipos de sinais. Por outro lado, esses algoritmos quando implementados em software não possibilitam respostas em tempo-real para uso da estimação como relé de frequência ou Unidade de Medição Fasorial. O desenvolvimento em FPGA apresentado nesse trabalho torna possível paralelizar o cálculo da estimação em hardware, viabilizando AEs para análise de sinal elétrico em tempo real. Além disso, mostra-se que AEs multiobjetivos podem extrair informações não evidentes das três fases do sistema e estimar os parâmetros adequadamente mesmo em casos em que as estimativas por fase divirjam entre si. Em outras palavras, as duas principais contribuições computacionais são: a paralelização do AE em hardware por meio de seu desenvolvimento em um circuito de FPGA otimizado a nível de operações lógicas básicas e a modelagem multiobjetiva do problema possibilitando análises dos sinais de cada fase, tanto independentemente quanto de forma agregada. Resultados experimentais mostram superioridade do método proposto em relação ao estimador baseado em transformada de Fourier para determinação de frequência e fase / This work proposes the development of Evolutionary Algorithms (EAs) for the estimation of the basic parameters from electrical signals (frequency, phase and amplitude) in real time. The proposed approach must be robust to noise and harmonics in signals distorted, for example, due to the presence of faults in the electrical network. EAs show advantages for dealing with these types of signals. On the other hand, these algorithms when implemented in software cant produce real-time responses in order to use their estimations as frequency relay or Phasor Measurement Unit. The approach developed on FPGA proposed in this work parallelizes in hardware the process of estimation, enabling analyses of electrical signals in real time. Furthermore, it is shown that multi-objective EAs can extract non-evident information from the three phases of the system and properly estimate parameters even when the phase estimates diverge from each other. This research proposes: the parallelization of an EA in hardware through its design on FPGA circuit optimized at level of basic logic operations and the modeling of the problem enabling multi-objective analyses of the signals from each phase in both independent and aggregate ways. Experimental results show the superiority of the proposed method compared to an estimator based on Fourier transform for determining frequency and phase
1130

Ambiente para avaliação de algoritmos de processamento de imagens médicas. / Environment for medical image processing algorithms assessment.

Santos, Marcelo dos 20 December 2006 (has links)
Constantemente, uma variedade de novos métodos de processamento de imagens é apresentada à comunidade. Porém poucos têm provado sua utilidade na rotina clínica. A análise e comparação de diferentes abordagens por meio de uma mesma metodologia são essenciais para a qualificação do projeto de um algoritmo. Porém, é difícil comparar o desempenho e adequabilidade de diferentes algoritmos de uma mesma maneira. A principal razão deve-se à dificuldade para avaliar exaustivamente um software, ou pelo menos, testá-lo num conjunto abrangente e diversificado de casos clínicos. Muitas áreas - como o desenvolvimento de software e treinamentos em Medicina - necessitam de um conjunto diverso e abrangente de dados sobre imagens e informações associadas. Tais conjuntos podem ser utilizados para desenvolver, testar e avaliar novos softwares clínicos, utilizando dados públicos. Este trabalho propõe o desenvolvimento de um ambiente de base de imagens médicas de diferentes modalidades para uso livre em diferentes propósitos. Este ambiente - implementado como uma arquitetura de base distribuída de imagens - armazena imagens médicas com informações de aquisição, laudos, algoritmos de processamento de imagens, gold standards e imagens pós-processadas. O ambiente também possui um modelo de revisão de documentos que garante a qualidade dos conjuntos de dados. Como exemplo da facilidade e praticidade de uso, são apresentadas as avaliações de duas categorias de métodos de processamento de imagens médicas: segmentação e compressão. Em adição, a utilização do ambiente em outras atividades, como no projeto do arquivo didático digital do HC-FMUSP, demonstra a robustez da arquitetura proposta e sua aplicação em diferentes propósitos. / Constantly, a variety of new image processing methods are presented to the community. However, few of them have proved to be useful when used in clinical routine. The task of analyzing and comparing different algorithms, methods and applications through a sound testing is an essential qualification of algorithm design. However, it is usually very difficult to compare the performance and adequacy of different algorithms in the same way. The main reason is due to the difficulty to assess exhaustively the software, or at least using a comprehensive and diverse number of clinical cases for comparison. Several areas such as software development, image processing and medical training need a diverse and comprehensive dataset of images and related information. Such datasets could be used to develop, test and evaluate new medical software, using public data. This work presents the development of a free, online, multipurpose and multimodality medical image database environment. The environment, implemented such as a distributed medical image database, stores medical images, reports, image processing softwares, gold standards and post-processed images. Also, this environment implements a peer review model which assures the quality of all datasets. As an example of feasibility and easyness of use, it is shown the evaluation in two categories of medical image processing methods: segmentation and compression. In addition, the use of the set of applications proposed in this work in other activities, such as the HC-FMUSP digital teaching file, shows the robustness of the proposed architecture and its applicability on different purposes.

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