Dissertations / Theses on the topic 'Optimization'
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Pieume, Calice Olivier. "Multiobjective optimization approaches in bilevel optimization." Phd thesis, Université Paris-Est, 2011. http://tel.archives-ouvertes.fr/tel-00665605.
Full textRuan, Ning. "Global optimization for nonconvex optimization problems." Thesis, Curtin University, 2012. http://hdl.handle.net/20.500.11937/1936.
Full textGedin, Sebastian. "Securities settlement optimization using an optimization software solution." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-279295.
Full textMånga har bedrivit handel med aktier eller andra värdepapper, men få är medvetna om hur transaktionerna genomförs. Processen där ägandet av värdepapper överförs, ofta i utbyte mot kontanter, kallas värdepappersavveckling. Om parterna som är involverade i transaktionen har de tillgångar som de är skyldiga att leverera vid tidpunkten för avvecklingen är värdepappersavvecklingen enkel. Men om värdepappersavvecklingssystemet står inför en uppsättning transaktioner, där någon part saknar den tillgång som hon är skyldig att leverera, kommer avvecklandet att misslyckas. Eftersom den mottagande parten av en transaktion som inte genomförs kan ha varit beroende av tillgångarna från den transaktionen för att uppfylla sina egna förpliktelser, kan en misslyckad avveckling leda till att många andra transaktioner inte kan genomföras. Värdepappersavveckling bör därmed optimeras för att minimera skadan i en situation där en eller flera transaktioner inta kan genomföras. I det här examensarbetet modellerar vi optimering av värdepappersavveckling som ett linjärprogrammeringsproblem med heltalsvillkor och utvärderar hur en optimeringsprogramvara presterar i jämförelse med en girig heuristisk algoritm på probleminstanser härledda från verklig avvecklingsdata. Vi finner att programvaran erbjuder en betydande fördel jämfört med den heuristiska algoritmen när det gäller att minimera antalet transaktioner som misslyckas, men att det görs till kostnaden av längre exekveringstid. Dessutom upptäcker vi att även om programvaran bara får köra i några minuter ger den en betydande fördel jämfört med den heuristiska algoritmen. Vår slutsats är att användningen av denna typ av programvara för optimering av värdepappersavveckling verkar vara en genomförbar strategi, men att ytterligare experiment med andra dataset behövs.
Sim, Melvyn 1971. "Robust optimization." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/17725.
Full textIncludes bibliographical references (p. 169-171).
We propose new methodologies in robust optimization that promise greater tractability, both theoretically and practically than the classical robust framework. We cover a broad range of mathematical optimization problems, including linear optimization (LP), quadratic constrained quadratic optimization (QCQP), general conic optimization including second order cone programming (SOCP) and semidefinite optimization (SDP), mixed integer optimization (MIP), network flows and 0 - 1 discrete optimization. Our approach allows the modeler to vary the level of conservatism of the robust solutions in terms of probabilistic bounds of constraint violations, while keeping the problem tractable. Specifically, for LP, MIP, SOCP, SDP, our approaches retain the same complexity class as the original model. The robust QCQP becomes a SOCP, which is computationally as attractive as the nominal problem. In network flows, we propose an algorithm for solving the robust minimum cost flow problem in polynomial number of nominal minimum cost flow problems in a modified network. For 0 - 1 discrete optimization problem with cost uncertainty, the robust counterpart of a polynomially solvable 0 - 1 discrete optimization problem remains polynomially solvable and the robust counterpart of an NP-hard o-approximable 0-1 discrete optimization problem, remains a-approximable.
(cont.) Under an ellipsoidal uncertainty set, we show that the robust problem retains the complexity of the nominal problem when the data is uncorrelated and identically distributed. For uncorrelated, but not identically distributed data, we propose an approximation method that solves the robust problem within arbitrary accuracy. We also propose a Frank-Wolfe type algorithm for this case, which we prove converges to a locally optimal solution, and in computational experiments is remarkably effective.
by Melvyn Sim.
Ph.D.
Lopes, David Granja. "Collections Optimization." Master's thesis, Instituto Superior de Economia e Gestão, 2013. http://hdl.handle.net/10400.5/6505.
Full textEste trabalho debruça-se sobre a otimização do transporte de componentes automóveis. Começa-se por fazer uma revisão bibliográfica e de seguida um enquadramento da situação a estudar, bem como da empresa onde será aplicado (Volkswagen Autoeuropa). É desenvolvido um modelo matemático que permite identificar as rotas ótimas. O objetivo principal deste trabalho é a identificação de rotas otimizadas que permitam o aumento da eficiência, económica e operacional, da cadeia de abastecimento da Volkswagen Autoeuropa. Os resultados foram bastantes promissores, pois foi possível obter uma poupança média de 37% nas rotas identificadas.
This work focuses on optimizing the transport of automotive components. Starts by a literature review and then a framework of the situation being studied, as well as the company where it will be applied (Volkswagen Autoeuropa). A mathematical model that identifies the optimal routes is developed. The main objective of this work is the identification of optimal routes which can increase efficiency, economic and operational, of the supply chain of Wolkswagen Autoeuropa. The results were very promising as it was achieved an average saving of 37% on the identified routes.
Bylund, Johanna. "Collateral Optimization." Thesis, Umeå universitet, Institutionen för fysik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-148006.
Full textYu, Hao. "Run-time optimization of adaptive irregular applications." Diss., Texas A&M University, 2004. http://hdl.handle.net/1969.1/1285.
Full textArayapan, Khanittha, and Piyanut Warunyuwong. "Logistics Optimization: Application of Optimization Modeling in Inbound Logistics." Thesis, Mälardalen University, School of Innovation, Design and Engineering, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-6213.
Full textTo be a market leader, low cost and responsiveness are the key success factors. Logistics activities create high cost reducing competitiveness of the company, especially for the remote production base. Thus, logistics activities which are delivery planning, freight forwarder and delivery mode selection must be optimized. The focusing area of this paper is inbound logistics due to its big proportion in the total cost and involvement with several stakeholders. The optimization theory and Microsoft Excel’s Solver is used to create the standard optimization tools since it is an efficient and user friendly program. The models are developed based on the supply chain management theory in order to achieve the lowest cost, responsiveness and shared objectives. 2 delivery planning optimization models, container loading for fixed slitting and loading pattern and container loading for pallet loaded material, are formulated. Also, delivery mode selection is constructed by using optimization concept to determine the best alternative. Furthermore, freight forwarder selection process is created by extending the use of the delivery mode selection model. The results express that safety stock, loading pattern, transport mode, and minimum order quantity (MOQ) significantly affect the total logistics cost. Including hidden costs, long transit time and delay penalties, leads freight forwarder selection process to become more realistic and reliable. Shorter processing time, ensured optimal solution, transparency increase and better communication are gained by using these optimization models. However, the proper boundaries must be defined carefully to gain the feasible solution.
GOUCHER, DANIEL. "Database optimization : An investigation of code-based optimization techniques." Thesis, KTH, Skolan för datavetenskap och kommunikation (CSC), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-153754.
Full textDatabasoptimering - En utredning av kodbaseradeoptimeringstekniker. I den här rapporten utreds databasoptimering med en inriktning på området som kan implementeras med mjukvara. Anledningen till denna inriktning är att mjukvaruoptimering är att område som alla utvecklare har resurserna att implementera.För att undersöka dessa optimeringstekniker så har jag först presenterat teorin bakom olika optimeringstekniker så som index, cachning och materialiserade vyer. En kort beskrivning på hur dessa tekniker kan implementeras i MySQL och PHP ges sedan. Med hjälp av dessa teorier så har en mängd tester skapats för att se hur olika optimeringstekniker reagerar på olika databasfrågor och storlekar. Resultatet av dessa tester presenteras sedan tillsammans med en diskussion på hur de sammanhänger med teorierna som presenterades och hur de kan användas i ett specifikt system.
Aggarwal, Varun. "Analog circuit optimization using evolutionary algorithms and convex optimization." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/40525.
Full textIncludes bibliographical references (p. 83-88).
In this thesis, we analyze state-of-art techniques for analog circuit sizing and compare them on various metrics. We ascertain that a methodology which improves the accuracy of sizing without increasing the run time or the designer effort is a contribution. We argue that the accuracy of geometric programming can be improved without adversely influencing the run time or increasing the designer's effort. This is facilitated by decomposition of geometric programming modeling into two steps, which decouples accuracy of models and run-time of geometric programming. We design a new algorithm for producing accurate posynomial models for MOS transistor parameters, which is the first step of the decomposition. The new algorithm can generate posynomial models with variable number of terms and real-valued exponents. The algorithm is a hybrid of a genetic algorithm and a convex optimization technique. We study the performance of the algorithm on artificially created benchmark problems. We show that the accuracy of posynomial models of MOS parameters is improved by a considerable amount by using the new algorithm. The new posynomial modeling algorithm can be used in any application of geometric programming and is not limited to MOS parameter modeling. In the last chapter, we discuss various ideas to improve the state-of-art in circuit sizing.
by Varun Aggarwal.
S.M.
Olsson, Per-Magnus. "Methods for Network Optimization and Parallel Derivative-free Optimization." Doctoral thesis, Linköpings universitet, Optimeringslära, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-104110.
Full textSheehan, Shane P. "Spacecraft Trajectory Optimization Suite (STOPS): Optimization of Low-Thrust Interplanetary Spacecraft Trajectories Using Modern Optimization Techniques." DigitalCommons@CalPoly, 2017. https://digitalcommons.calpoly.edu/theses/1901.
Full textFitzgerald, Timothy J. "Spacecraft Trajectory Optimization Suite (STOpS): Optimization of Multiple Gravity Assist Spacecraft Trajectories Using Modern Optimization Techniques." DigitalCommons@CalPoly, 2015. https://digitalcommons.calpoly.edu/theses/1503.
Full textZhou, Fangjun. "Nonmonotone methods in optimization and DC optimization of location problems." Diss., Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/21777.
Full textBoissier, Mathilde. "Coupling structural optimization and trajectory optimization methods in additive manufacturing." Thesis, Institut polytechnique de Paris, 2020. http://www.theses.fr/2020IPPAX084.
Full textThis work investigates path planning optimization for powder bed fusion additive manufacturing processes, and relates them to the design of the built part. The state of the art mainly studies trajectories based on existing patterns and, besides their mechanical evaluation, their relevance has not been related to the object’s shape. We propose in this work a systematic approach to optimize the path without any a priori restriction. The typical optimization problem is to melt the desired structure, without over-heating (to avoid thermally induced residual stresses) and possibly with a minimal path length. The state equation is the heat equation with a source term depending on the scanning path. Two physical 2-d models are proposed, involving temperature constraint: a transient and a steady state one (in which time dependence is removed). Based on shape optimization for the steady state model and control for the transient model, path optimization algorithms are developed. Numerical results are then performed allowing a critical assessment of the choices we made. To increase the path design freedom, we modify the steady state algorithm to introduce path splits. Two methods are compared. In the first one, the source power is added to the optimization variables and an algorithm mixing relaxation-penalization techniques and the control of the total variation is set. In a second method, notion of topological derivative are applied to the path to cleverly remove and add pieces. eventually, in the steady state, we conduct a concurrent optimization of the part’s shape and of the scanning path. This multiphysics optimization problem raises perspectives gathering direct applications and future generalizations
Sghir, Inès. "A Multi-Agent based Optimization Method for Combinatorial Optimization Problems." Thesis, Angers, 2016. http://www.theses.fr/2016ANGE0009/document.
Full textWe elaborate a multi-agent based optimization method for combinatorial optimization problems named MAOM-COP. It combines metaheuristics, multiagent systems and reinforcement learning. Although the existing heuristics contain several techniques to escape local optimum, they do not have an entire vision of the evolution of optimization search. Our main objective consists in using the multi-agent system to create intelligent cooperative methods of search. These methods explore several existing metaheuristics. MAOMCOP is composed of the following agents: the decisionmaker agent, the intensification agents and the diversification agents which are composed of the perturbation agent and the crossover agents. Based on learning techniques, the decision-maker agent decides dynamically which agent to activate between intensification agents and crossover agents. If the intensifications agents are activated, they apply local search algorithms. During their searches, they can exchange information, as they can trigger the perturbation agent. If the crossover agents are activated, they perform recombination operations. We applied MAOMCOP to the following problems: quadratic assignment, graph coloring, winner determination and multidimensional knapsack. MAOM-COP shows competitive performances compared with the approaches of the literature
Yu, Feng. "Constructing Accurate Synopses for Database Query Optimization and Re-optimization." OpenSIUC, 2013. https://opensiuc.lib.siu.edu/dissertations/709.
Full textJensen, Marina. "Conversion Rate Optimization : A Qualitative Approach to Identifying Optimization Barriers." Thesis, Tekniska Högskolan, Högskolan i Jönköping, JTH, Datateknik och informatik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-44487.
Full textDenna uppsats har undersökt frågan "Vilka hinder hindrar svenska företag från att genomföra en strukturerad konverteringsoptimerings process?". Med syfte att få en förståelse för vad som hindrar företagen att utföra konverteringsoptimering (CRO). Då CRO är en viktig del i de flesta digitala marknadsaktiviteter. Och trots ökad budget och kunskap inom marknadsföring är resursbegränsningen fortfarande det största hindret. Metoden som användes för att undersöka denna fråga var kvalitativa intervjuer med deltagare som arbetade med webbplatser inom sju olika företag. En analys genomfördes, som tog upp företags kunskapsnivå, övergripande struktur, prioriteringar och nuvarande hinder. Det fastställdes att intervjuarna hade flera olika problemområden med avseende om konverteringsoptimering. Begränsad tid, budget, prioriteringar, kunskap, ägandeskap, strukturerat abetsflöde och tolkning av data, behandlades alla i analysen. En diskussion gjordes för att argumentera för definitionen av "största" barriären, eftersom vissa hinder var vanligare än andra men lättare att övervinna. Sammantaget kan dessa hinder alltså spåras tillbaka till hinder som prioritering, struktur och ägande. Slutsatsen var att företagen måste ha en mer strukturerad arbetsprocess inom området för konverteringsoptimering för att denna disciplin ska prioriteras som en väsentlig del av företagets marknadsföringsaktiviteter online.
Müller, Stephan. "Constrained portfolio optimization /." [S.l.] : [s.n.], 2005. http://aleph.unisg.ch/hsgscan/hm00133325.pdf.
Full textJayaraman, Shankar. "Dynamic cutback optimization." Thesis, Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/33812.
Full textLi, Zhuo. "Fast interconnect optimization." Texas A&M University, 2005. http://hdl.handle.net/1969.1/3250.
Full textGopinath, Varun. "Industrial Silo Optimization." Thesis, Linköpings universitet, Maskinkonstruktion, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-67645.
Full textAndersson, Joakim, and Jimmy Bertilsson. "SETUP TIME OPTIMIZATION." Thesis, Örebro universitet, Institutionen för naturvetenskap och teknik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:oru:diva-23661.
Full textAbstract Emhart Glass Ltd is a world leader in glass bottle manufacturing. They design automated machines that shape glass bottles. In Sweden there are two factories, one in Örebro and one in Sundsvall. In Örebro they manufacture primarily spare parts and new parts for the machines while they in Sundsvall assemble the machines. There are a total of 15 factories and offices around the world with the headquarter located in Swiss Cham.Since Emhart Glass Örebro has long setup times on some of their machines. This is why we want to identify the current setup process and how the setup process differs between operators. We will also look at whether there are any opportunities for improvement to be made and if they have a standardized way to work. A document that describes how to setup work should be done will also be developed.An excellent tool to shorten the setup time in a production is the SMED method. The philosophy behind SMED is that you should analyze and separate the inner and outer activities. Inner and outer activities mean those activities which can only be performed when the machine is turned off, respectively those activities that can be performed when the machine is in operation. In order to standardize the adjustment process so that all operators are working in a similar way it's required that you make a documentation about how the work should be done. Therefore, checklists been developed to the operator. "Checklista - Omställning.xls" is a checklist with the purpose to be able to check which parts of the preparations they have made before the next setup work. It has been designed to be easy to keep track of what parts you have done if you had to work with the machine between the trial or if you quit your shift and leaving parts of the work to the next operator. If all of these improvements are implemented, we expect a set-up time reduction of 20.5% which corresponds to about 35min per set-up. By ignoring the running time and only check on the setup times, one can see an improvement of 36.4%.
Puhle, Michael. "Bond portfolio optimization." Berlin Heidelberg Springer, 2007. http://d-nb.info/985928115/04.
Full textRuziyeva, Alina. "Fuzzy Bilevel Optimization." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2013. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-106378.
Full textSogand, Yousefbeigi. "Wind Farm Optimization." Master's thesis, METU, 2013. http://etd.lib.metu.edu.tr/upload/12615685/index.pdf.
Full textGenetic Algorithm and Lingo, were used to solve the MILP optimization formula and results were compared for different cases in the conclusion part.
Stettner, Martin. "Tiltrotor multidisciplinary optimization." Diss., Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/12996.
Full textVan, Rooyen Marchand. "Stable parametric optimization." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=70259.
Full textLaw, S. L. "Financial optimization problems." Thesis, University of Oxford, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.426391.
Full textAbdi, Mohammad Javad. "Cardinality optimization problems." Thesis, University of Birmingham, 2013. http://etheses.bham.ac.uk//id/eprint/4620/.
Full textFaramarzi, Oghani Sohrab. "Clinical laboratory optimization." Thesis, Lille 1, 2018. http://www.theses.fr/2018LIL1I072.
Full textThis thesis focuses on the optimization of clinical laboratory design and operating decisions. In this thesis, a decision support tool including mathematical models, a heuristic algorithm and a customized simulation model is developed to aid decision makers for the main strategic, tactical and operational problems in clinical laboratory design and operations management. In this thesis, machine selection and facility layout are studied as the main strategic problems, analyzer configuration problem as the tactical problem, and assignment, aliquoting, and scheduling as the principal operational problems. A customized and flexible simulation model is developed in FlexSim to study the clinical laboratory designed through the outputs of developed mathematical models and layout algorithm. The simulation model helps the designer to construct and analyze a complete clinical laboratory taking into account all major features of the system. This simulation attribute provides the ability to scrutinize the system behaviour and to find out whether the designed system is efficient. Furthermore, simulation model can be fruitful to decide on scheduling, aliquoting and staffing problems through the evaluation of various scenarios proposed by decision maker for each of these problems. To verify the validity of the proposed framework, data extracted from a real case is used. The output results seal on the applicability and the efficiency of the proposed framework as well as competency of proposed techniques to deal with each optimization problem. To the best of our knowledge, this thesis is one of the leading studies on the optimization of clinical laboratories
Singer, Adam B. "Global dynamic optimization." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/28662.
Full textIncludes bibliographical references (p. 247-256).
(cont.) on a set composed of the Cartesian product between the parameter bounds and the state bounds. Furthermore, I show that the solution of the differential equations is affine in the parameters. Because the feasible set is convex pointwise in time, the standard result that a convex function composed with an affine function remains convex yields the desired result that the integrand is convex under composition. Additionally, methods are developed using interval arithmetic to derive the exact state bounds for the solution of a linear dynamic system. Given a nonzero tolerance, the method is rigorously shown to converge to the global solution in a finite time. An implementation is developed, and via a collection of case studies, the technique is shown to be very efficient in computing the global solutions. For problems with embedded nonlinear dynamic systems, the analysis requires a more sophisticated composition technique attributed to McCormick. McCormick's composition technique provides a method for computing a convex underestimator for for the integrand given an arbitrary nonlinear dynamic system provided that convex underestimators and concave overestimators can be given for the states. Because the states are known only implicitly via the solution of the nonlinear differential equations, deriving these convex underestimators and concave overestimators is a highly nontrivial task. Based on standard optimization results, outer approximation, the affine solution to linear dynamic systems, and differential inequalities, I present a novel method for constructing convex underestimators and concave overestimators for arbitrary nonlinear dynamic systems ...
My thesis focuses on global optimization of nonconvex integral objective functions subject to parameter dependent ordinary differential equations. In particular, efficient, deterministic algorithms are developed for solving problems with both linear and nonlinear dynamics embedded. The techniques utilized for each problem classification are unified by an underlying composition principle transferring the nonconvexity of the embedded dynamics into the integral objective function. This composition, in conjunction with control parameterization, effectively transforms the problem into a finite dimensional optimization problem where the objective function is given implicitly via the solution of a dynamic system. A standard branch-and-bound algorithm is employed to converge to the global solution by systematically eliminating portions of the feasible space by solving an upper bounding problem and convex lower bounding problem at each node. The novel contributions of this work lie in the derivation and solution of these convex lower bounding relaxations. Separate algorithms exist for deriving convex relaxations for problems with linear dynamic systems embedded and problems with nonlinear dynamic systems embedded. However, the two techniques are unified by the method for relaxing the integral in the objective function. I show that integrating a pointwise in time convex relaxation of the original integrand yields a convex underestimator for the integral. Separate composition techniques, however, are required to derive relaxations for the integrand depending upon the nature of the embedded dynamics; each case is addressed separately. For problems with embedded linear dynamic systems, the nonconvex integrand is relaxed pointwise in time
by Adam Benjamin Singer.
Ph.D.
Xiong, Ying S. M. Massachusetts Institute of Technology. "Racing line optimization." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/64669.
Full textThis electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (p. 112-113).
Although most racers are good at controlling their cars, world champions are always talented at choosing the right racing line while others mostly fail to do that. Optimal racing line selection is a critical problem in car racing. However, currently it is strongly based on the intuition of experienced racers after they conduct repeated real-time experiments. It will be very useful to have a method which can generate the optimal racing line based on the given racing track and the car. This paper explains four methods to generate optimal racing lines: the Euler spiral method, artificial intelligence method, nonlinear programming solver method and integrated method. Firstly we study the problem and obtain the objective functions and constraints for both 2-D and 3-D situations. The mathematical and physical features of the racing tracks are studied. Then we try different ways of solving this complicated nonlinear programming problem. The Euler spiral method generates Euler spiral curve turns at corners and it gives optimal results fast and accurately for 2-D corners with no banking. The nonlinear programming solver method is based on the MINOS solver on AMPL and the MATLAB Optimization Toolbox and it only needs the input of the objective function and constraints. A heavy emphasis is placed on the artificial intelligence method. It works well for any 2-D or 3-D track shapes. It uses intelligent algorithms including branch-cutting and forward-looking to give optimal racing lines for both 2-D and 3-D tracks. And the integrated method combines methods and their advantages so that it is fast and practical for all situations. Different methods are compared, and their evolutions towards the optimum are described in detail. Convenient display software is developed to show the tracks and racing lines for observation. The approach to finding optimal racing lines for cars will be also helpful for finding optimal racing lines for bicycle racing, ice skating and skiing.
by Ying Xiong.
S.M.
Lu, Xin Ph D. Massachusetts Institute of Technology Operations Research Center. "Online optimization problems." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/82724.
Full textThis electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 149-153).
In this thesis, we study online optimization problems in routing and allocation applications. Online problems are problems where information is revealed incrementally, and decisions must be made before all information is available. We design and analyze algorithms for a variety of online problems, including traveling salesman problems with rejection options, generalized assignment problems, stochastic matching problems, and resource allocation problems. We use worst case competitive ratios to analyze the performance of proposed algorithms. We begin our study with online traveling salesman problems with rejection options where acceptance/rejection decisions are not required to be explicitly made. We propose an online algorithm in arbitrary metric spaces, and show that it is the best possible. We then consider problems where acceptance/rejection decisions must be made at the time when requests arrive. For dierent metric spaces, we propose dierent online algorithms, some of which are asymptotically optimal. We then consider generalized online assignment problems with budget constraints and resource constraints. We first prove that all online algorithms are arbitrarily bad for general cases. Then, under some assumptions, we propose, analyze, and empirically compare two online algorithms, a greedy algorithm and a primal dual algorithm. We study online stochastic matching problems. Instances with a fixed number of arrivals are studied first. A novel algorithm based on discretization is proposed and analyzed for unweighted problems. The same algorithm is modified to accommodate vertex-weighted cases. Finally, we consider cases where arrivals follow a Poisson Process. Finally, we consider online resource allocation problems. We first consider the problems with free but fixed inventory under certain assumptions, and present near optimal algorithms. We then relax some unrealistic assumptions. Finally, we generalize the technique to problems with flexible inventory with non-decreasing marginal costs.
by Xin Lu.
Ph.D.
Teo, Kwong Meng. "Nonconvex robust optimization." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/40303.
Full textThis electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 133-138).
We propose a novel robust optimization technique, which is applicable to nonconvex and simulation-based problems. Robust optimization finds decisions with the best worst-case performance under uncertainty. If constraints are present, decisions should also be feasible under perturbations. In the real-world, many problems are nonconvex and involve computer-based simulations. In these applications, the relationship between decision and outcome is not defined through algebraic functions. Instead, that relationship is embedded within complex numerical models. Since current robust optimization methods are limited to explicitly given convex problems, they cannot be applied to many practical problems. Our proposed method, however, operates on arbitrary objective functions. Thus, it is generic and applicable to most real-world problems. It iteratively moves along descent directions for the robust problem, and terminates at a robust local minimum. Because the concepts of descent directions and local minima form the building blocks of powerful optimization techniques, our proposed framework shares the same potential, but for the richer, and more realistic, robust problem.
(cont.) To admit additional considerations including parameter uncertainties and nonconvex constraints, we generalized the basic robust local search. In each case, only minor modifications are required - a testimony to the generic nature of the method, and its potential to be a component of future robust optimization techniques. We demonstrated the practicability of the robust local search technique in two realworld applications: nanophotonic design and Intensity Modulated Radiation Therapy (IMRT) for cancer treatment. In both cases, the numerical models are verified by actual experiments. The method significantly improved the robustness for both designs, showcasing the relevance of robust optimization to real-world problems.
by Kwong Meng Teo.
Ph.D.
Sadownick, Ronald 1960. "Helicopter configuration optimization." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/82683.
Full textThis electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (leaf 102).
by Ronald Sadownick.
S.M.
Bailey, Drake (William Drake), and Daniel Skempton. "Communicating optimization results." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/81092.
Full textCataloged from PDF version of thesis.
Includes bibliographical references (p. 76-79).
With global supply chains becoming increasingly complex, leading companies are embracing optimization software tools to help them structure and coordinate their supply chains. With an array of choices available, many organizations opt for one of the numerous off-the-shelf products. Others choose instead to create their own bespoke optimization tools. While this custom approach affords greater versatility than a commercially available product, it also presents significant challenges to both the creators and users of the tool in terms of complexity. It can often be time-consuming and difficult for the users of the tool to understand and verify the results that are generated. If a decision-maker has difficulty understanding or trusting the output of a model, then the value of the tool is seriously diminished. This paper examines the challenges between the creators, or operational research engineers, and the end-users when deploying and executing complex optimization software in supply chain management. We examine the field of optimization modeling, communication methods involved, and relevant data visualization techniques. Then, we survey a group of users from our sponsoring company to gain insight to their experience using their tool. The general responses and associated crosstab analysis reveals that training and visualization are areas that have potential to improve the user's understanding of the tool, which in turn would lead to better communication between the end-users and the experts who build and maintain the tool. Finally, we present a section on current, cutting edge visualization techniques that can be adapted to influence the way a user visualizes the optimization results.
by Drake Bailey and Daniel Skempton.
M.Eng.in Logistics
Simmen, Martin Walter. "Neural network optimization." Thesis, University of Edinburgh, 1992. http://hdl.handle.net/1842/12942.
Full textSpeicher, Maximilian. "Search Interaction Optimization." Doctoral thesis, Universitätsbibliothek Chemnitz, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-208102.
Full textIm Laufe der vergangenen 25 Jahre haben sich Suchmaschinen zu einem der wichtigsten, wenn nicht gar dem wichtigsten Zugangspunkt zum World Wide Web (WWW) entwickelt. Diese Entwicklung resultiert vor allem aus der kontinuierlich steigenden Zahl an Dokumenten, welche im WWW verfügbar, jedoch sehr unstrukturiert organisiert sind. Überdies werden Suchergebnisse immer häufiger in Kategorien klassifiziert und in Form semantischer Informationen bereitgestellt, die direkt in der Suchmaschine konsumiert werden können. Dies spiegelt einen allgemeinen Trend wider. Durch die wachsende Zahl an Dokumenten und technologischen Neuerungen wandeln sich die Bedürfnisse von sowohl Nutzern als auch Suchmaschinen ständig. Nutzer wollen mit immer besseren Suchergebnissen und Interfaces versorgt werden, während Suchmaschinen-Unternehmen Werbung platzieren und Gewinn machen müssen, um ihre Dienste kostenlos anbieten zu können. Damit geht die Notwendigkeit einher, in hohem Maße benutzbare und optimierte Suchergebnisseiten – sogenannte SERPs (search engine results pages) – für Nutzer bereitzustellen. Gängige Methoden zur Evaluierung und Optimierung von Usability sind jedoch größtenteils kostspielig oder zeitaufwändig und basieren meist auf explizitem Feedback. Sie sind somit entweder nicht effizient oder nicht effektiv, weshalb Optimierungen an Suchmaschinen-Schnittstellen häufig primär aus dem Unternehmensblickwinkel heraus durchgeführt werden. Des Weiteren sind bestehende Methoden zur Vorhersage der Relevanz von Suchergebnissen, welche größtenteils auf der Auswertung von Klicks basieren, nicht auf neuartige SERPs zugeschnitten. Zum Beispiel versagen diese, wenn Suchanfragen direkt auf der Suchergebnisseite beantwortet werden und der Nutzer nicht klicken muss. Basierend auf den Prinzipien des nutzerzentrierten Designs entwickeln wir eine Lösung in Form eines ganzheitlichen Ansatzes für die oben beschriebenen Probleme. Dieser Ansatz orientiert sich sowohl an Nutzern als auch an Entwicklern. Unsere Lösung stellt automatische Methoden bereit, um unternehmenszentriertem Design entgegenzuwirken und implizites Nutzerfeedback für die effizienteund effektive Evaluierung und Optimierung von Usability und insbesondere Ergebnisrelevanz nutzen zu können. Wir definieren Personas und Szenarien, aus denen wir ungelöste Probleme und konkrete Anforderungen ableiten. Basierend auf diesen Anforderungen entwickeln wir einen entsprechenden Werkzeugkasten, das Search Interaction Optimization Toolkit. Mittels eines Bottom-up-Ansatzes definieren wir zudem eine gleichnamige Methodik auf einem höheren Abstraktionsniveau. Das Search Interaction Optimization Toolkit besteht aus insgesamt sechs Komponenten. Zunächst präsentieren wir INUIT [1], ein neuartiges, minimales Instrument zur Bestimmung von Usability, welches speziell auf sinnvolle Korrelationen mit implizitem Nutzerfeedback in Form Client-seitiger Interaktionen abzielt. Aus diesem Grund dient es als Basis für die direkte Herleitung quantitativer Usability-Bewertungen aus dem Verhalten von Nutzern. Das Instrument wurde basierend auf Untersuchungen etablierter Usability-Standards und -Richtlinien sowie Experteninterviews entworfen. Die Machbarkeit und Effektivität der Benutzung von INUIT wurden in einer Nutzerstudie untersucht und darüber hinaus durch eine konfirmatorische Faktorenanalyse bestätigt. Im Anschluss beschreiben wir WaPPU [2], welches ein kontextsensitives, auf INUIT basierendes Tool zur Durchführung von A/B-Tests ist. Es implementiert das neuartige Konzept des Usability-based Split Testing und ermöglicht die automatische Evaluierung der Usability beliebiger SERPs basierend auf den bereits zuvor angesprochenen quantitativen Bewertungen, welche direkt aus Nutzerinteraktionen abgeleitet werden. Hierzu werden Techniken des maschinellen Lernens angewendet, um automatisch entsprechende Usability-Modelle generieren und anwenden zu können. WaPPU ist insbesondere nicht auf die Evaluierung von Suchergebnisseiten beschränkt, sondern kann auf jede beliebige Web-Schnittstelle in Form einer Webseite angewendet werden. Darauf aufbauend beschreiben wir S.O.S., die SERP Optimization Suite [3], welche das Tool WaPPU sowie einen neuartigen Katalog von „Best Practices“ [4] umfasst. Sobald eine durch WaPPU gemessene, suboptimale Usability-Bewertung festgestellt wird, werden – basierend auf dem Katalog von „Best Practices“ – automatisch entsprechende Gegenmaßnahmen und Optimierungen für die untersuchte Suchergebnisseite vorgeschlagen. Der Katalog wurde in einem dreistufigen Prozess erarbeitet, welcher die Untersuchung bestehender Suchergebnisseiten sowie eine Anpassung und Verifikation durch 20 Usability-Experten beinhaltete. Die bisher angesprochenen Tools fokussieren auf die generelle Usability von SERPs, jedoch ist insbesondere die Darstellung der für den Nutzer relevantesten Ergebnisse eminent wichtig für eine Suchmaschine. Da Relevanz eine Untermenge von Usability ist, beinhaltet unser Werkzeugkasten daher das Tool TellMyRelevance! (TMR) [5], die erste End-to-End-Lösung zur Vorhersage von Suchergebnisrelevanz basierend auf Client-seitigen Nutzerinteraktionen. TMR ist einvollautomatischer Ansatz, welcher die benötigten Daten auf dem Client abgreift, sie auf dem Server verarbeitet und entsprechende Relevanzmodelle bereitstellt. Die von diesen Modellen getroffenen Vorhersagen können wiederum in den Ranking-Prozess der Suchmaschine eingepflegt werden, was schlussendlich zu einer Verbesserung der Usability führt. StreamMyRelevance! (SMR) [6] erweitert das Konzept von TMR, indem es einen Streaming-basierten Ansatz bereitstellt. Hierbei geschieht die Sammlung und Verarbeitung der Daten sowie die Bereitstellung der Relevanzmodelle in Nahe-Echtzeit. Basierend auf umfangreichen Nutzerstudien mit echten Suchmaschinen haben wir den entwickelten Werkzeugkasten als Ganzes evaluiert, auch, um das Zusammenspiel der einzelnen Komponenten zu demonstrieren. S.O.S., WaPPU und INUIT wurden zur Evaluierung und Optimierung einer realen Suchergebnisseite herangezogen. Die Ergebnisse zeigen, dass unsere Tools in der Lage sind, auch kleine Abweichungen in der Usability korrekt zu identifizieren. Zudem haben die von S.O.S.vorgeschlagenen Optimierungen zu einer signifikanten Verbesserung der Usability der untersuchten und überarbeiteten Suchergebnisseite geführt. TMR und SMR wurden mit Datenmengen im zweistelligen Gigabyte-Bereich evaluiert, welche von zwei realen Hotelbuchungsportalen stammen. Beide zeigen das Potential, bessere Vorhersagen zu liefern als konkurrierende Systeme, welche lediglich Klicks auf Ergebnissen betrachten. SMR zeigt gegenüber allen anderen untersuchten Systemen zudem deutliche Vorteile bei Effizienz, Robustheit und Skalierbarkeit. Die Dissertation schließt mit einer Diskussion des Potentials und der Limitierungen der erarbeiteten Forschungsbeiträge und gibt einen Überblick über potentielle weiterführende und zukünftige Forschungsarbeiten
Li, Xing-Si. "Entropy and optimization." Thesis, University of Liverpool, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.235500.
Full textElsayed, M. A. N. "Aircraft trajectory optimization." Thesis, Loughborough University, 1985. https://dspace.lboro.ac.uk/2134/32873.
Full textHillberg, Alexander, and Marcus Olmarker. "Optimization of Flexplate." Thesis, Högskolan i Halmstad, Akademin för ekonomi, teknik och naturvetenskap, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-37051.
Full textFrån 2019 kommer alla nya drivlinor från Volvo att elektrifieras, även inkluderat förbränningsmotorbaserade drivlinor. I de förbränningsmotorbaserade drivlinorna med automatisk växellåda så fäster en medbringarplåt samman vevaxeln med den automatiska växellådan för att överföra kraften. Medbringarplåten måste hantera vridmomentstoppar från vevaxeln vid förbränningen, vevaxelrotation och axiella krafter generade av momentöverföraren. Vridmomentslasten vid förbränningen är maximerad vid varje tändning, men lasten är även beroende på motorns hastighet/last och på växlingar. Alla dessa laster som medbringarplåten utsätts för innebär att plåten kommer påverkas av höga spänningsnivåer. Dessa höga spänningsnivåer gör det mer sannolikt att medbringarplåten går sönder och därav förkortas livslängden. Därför var målet med denna avhandling att generera nya optimerade designkoncept på plåten med minimerade spänningsnivåer genom att använda metoden Simulation Driven Design. För att förstå resultatet, genomfördes även en parameterstudie med hjälp av Design of Experiments. Genom att använda Simulation Driven Design så kunde flera designkoncept tas fram, men endast två visade på hållbara resultat, och de optimerades med parametrisk optimering samt Design of Experiments i Catia V5. En topologisk optimering i programmet Inspire försöktes även, men modellen var för komplicerad och kunde inte återskapas på ett noggrant sätt i programmet, vilket gjorde att optimeringen var omöjlig att göra. Med en kombination av parametrisk optimering och Design of Experiments visade de två koncepten en minskning i spänning på 16,4% och 11,1% jämfört med originaldesignen. De visade även en ökning i deformation samt en liten minskning i vikt. Resultatet visar att det är möjligt att dra slutsatsen att Simulation Driven Design är en fantastisk metod att använda i produktutveckling. Resultatet visar även att kombinationen av parametrisk optimering och Design of Experiments kan användas effektivt under optimeringsprocessen i produktutveckling
Mesgarpour, Mohammad. "Airport runway optimization." Thesis, University of Southampton, 2012. https://eprints.soton.ac.uk/366012/.
Full textFlach, Guilherme Augusto. "Clock mesh optimization." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2010. http://hdl.handle.net/10183/34773.
Full textClock meshes are a suitable clock network architecture for reliably distributing the clock signal under process and environmental variations. This property becomes very important in the deep sub-micron technology where variations play a main role. The clock mesh reliability is due to redundant paths connecting clock buffers to clock sinks, so that variations affecting one path can be compensated by other paths. This comes at cost of more power consumption and wiring resources. Therefore it is clear the tradeoff between reliably distributing the clock signal (more redundancy) and the power and resource consumption. The clock skew is defined as the difference in the arrival time of clock signal at clock sinks. The higher is the clock skew, the slower is the circuit. Besides slowing down the circuit operation, a high clock skew increases the probability of circuit malfunction due to variations. In this work we focus on the clock skew problem. We first extract some useful information on how the clock wirelength and capacitance change as the mesh size changes. We present analytical formulas to find the optimum mesh size for both goals and study how the clock skew varies as we move further away from the optimum mesh size. We also present a method for reducing the clock mesh skew by sliding buffers from the position where they are traditionally placed. This improvement comes at no increasing cost of power consumption since the buffer size and the mesh capacitance are not changed.
Devarakonda, SaiPrasanth. "Particle Swarm Optimization." University of Dayton / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1335827032.
Full textCheng, Jianqiang. "Stochastic Combinatorial Optimization." Thesis, Paris 11, 2013. http://www.theses.fr/2013PA112261.
Full textIn this thesis, we studied three types of stochastic problems: chance constrained problems, distributionally robust problems as well as the simple recourse problems. For the stochastic programming problems, there are two main difficulties. One is that feasible sets of stochastic problems is not convex in general. The other main challenge arises from the need to calculate conditional expectation or probability both of which are involving multi-dimensional integrations. Due to the two major difficulties, for all three studied problems, we solved them with approximation approaches.We first study two types of chance constrained problems: linear program with joint chance constraints problem (LPPC) as well as maximum probability problem (MPP). For both problems, we assume that the random matrix is normally distributed and its vector rows are independent. We first dealt with LPPC which is generally not convex. We approximate it with two second-order cone programming (SOCP) problems. Furthermore under mild conditions, the optimal values of the two SOCP problems are a lower and upper bounds of the original problem respectively. For the second problem, we studied a variant of stochastic resource constrained shortest path problem (called SRCSP for short), which is to maximize probability of resource constraints. To solve the problem, we proposed to use a branch-and-bound framework to come up with the optimal solution. As its corresponding linear relaxation is generally not convex, we give a convex approximation. Finally, numerical tests on the random instances were conducted for both problems. With respect to LPPC, the numerical results showed that the approach we proposed outperforms Bonferroni and Jagannathan approximations. While for the MPP, the numerical results on generated instances substantiated that the convex approximation outperforms the individual approximation method.Then we study a distributionally robust stochastic quadratic knapsack problems, where we only know part of information about the random variables, such as its first and second moments. We proved that the single knapsack problem (SKP) is a semedefinite problem (SDP) after applying the SDP relaxation scheme to the binary constraints. Despite the fact that it is not the case for the multidimensional knapsack problem (MKP), two good approximations of the relaxed version of the problem are provided which obtain upper and lower bounds that appear numerically close to each other for a range of problem instances. Our numerical experiments also indicated that our proposed lower bounding approximation outperforms the approximations that are based on Bonferroni's inequality and the work by Zymler et al.. Besides, an extensive set of experiments were conducted to illustrate how the conservativeness of the robust solutions does pay off in terms of ensuring the chance constraint is satisfied (or nearly satisfied) under a wide range of distribution fluctuations. Moreover, our approach can be applied to a large number of stochastic optimization problems with binary variables.Finally, a stochastic version of the shortest path problem is studied. We proved that in some cases the stochastic shortest path problem can be greatly simplified by reformulating it as the classic shortest path problem, which can be solved in polynomial time. To solve the general problem, we proposed to use a branch-and-bound framework to search the set of feasible paths. Lower bounds are obtained by solving the corresponding linear relaxation which in turn is done using a Stochastic Projected Gradient algorithm involving an active set method. Meanwhile, numerical examples were conducted to illustrate the effectiveness of the obtained algorithm. Concerning the resolution of the continuous relaxation, our Stochastic Projected Gradient algorithm clearly outperforms Matlab optimization toolbox on large graphs
Cha, Kyungduck. "Cancer treatment optimization." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/22604.
Full textCommittee Chair: Lee, Eva K.; Committee Member: Barnes, Earl; Committee Member: Hertel, Nolan E.; Committee Member: Johnson, Ellis; Committee Member: Monteiro, Renato D.C.
Allan, John S. Nekimken Kyle J. Weills Spencer B. "Pump sequencing optimization /." Click here to view, 2009. http://digitalcommons.calpoly.edu/mesp/7.
Full textProject advisor: Tom Mase. Title from PDF title page; viewed on Jan. 13, 2010. Includes bibliographical references. Also available on microfiche.
Nasiri, Faranak. "Ambulance Optimization Allocation." OpenSIUC, 2014. https://opensiuc.lib.siu.edu/theses/1462.
Full textRamachandran, Selvaraj. "Hypoid gear optimization." PDXScholar, 1992. https://pdxscholar.library.pdx.edu/open_access_etds/4419.
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