Dissertations / Theses on the topic 'Problem Solver'
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1
Hoessen, Benoît. "Solving the Boolean satisfiability problem using the parallel paradigm." Thesis, Artois, 2014. http://www.theses.fr/2014ARTO0406/document.
Full textAbstract:
Cette thèse présente différentes techniques permettant de résoudre le problème de satisfaction de formule booléenes utilisant le parallélisme et du calcul distribué. Dans le but de fournir une explication la plus complète possible, une présentation détaillée de l'algorithme CDCL est effectuée, suivi d'un état de l'art. De ce point de départ, deux pistes sont explorées. La première est une amélioration d'un algorithme de type portfolio, permettant d'échanger plus d'informations sans perte d'efficacité. La seconde est une bibliothèque de fonctions avec son interface de programmation permettant de créer facilement des solveurs SAT distribuésThis thesis presents different technique to solve the Boolean satisfiability problem using parallel and distributed architectures. In order to provide a complete explanation, a careful presentation of the CDCL algorithm is made, followed by the state of the art in this domain. Once presented, two propositions are made. The first one is an improvement on a portfolio algorithm, allowing to exchange more data without loosing efficiency. The second is a complete library with its API allowing to easily create distributed SAT solver
2
Danieli, Adrian B. (Adrian Brian) 1975. "A Tsume-Go life & death problem solver." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/50434.
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Thesis (S.B. and M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1998.Includes bibliographical references (p. 61-62).
by Adrian B. Danieli.
S.B.and M.Eng.
3
Geary, John Michael. "Social work skills : roles of the problem solver /." The Ohio State University, 1989. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487598303841346.
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Lampl, Damian. "Smart Grid Optimization Using a Capacitated Transshipment Problem Solver." Thesis, North Dakota State University, 2013. https://hdl.handle.net/10365/27120.
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A network flow model known as the capacitated transshipment problem, or CTP, can represent key aspects of a smart grid test network with the goal of finding minimum cost electric power flows using multiple different cost performance metrics. A custom CTP Solver was developed and implemented as an ASP.NET web application in an effort to study these various minimum cost smart grid problems and provide their optimal solutions. The CTP Solver modifies traditional linear programming concepts by introducing object oriented software development practices, as well as an insightful innovation for handling bidirectional arcs, which effectively halves the required disk and memory allocation of fully bidirectional networks. As an initial step toward smart grid optimization problem solutions, the CTP Solver provides a glimpse of how self-healing and possibly other key components of smart grid architecture might be handled in the future.
5
Ahmadi, Ehsan. "SOLVING INCREMENTAL SPECIFICATIONS USING Z3 SMT SOLVER." OpenSIUC, 2016. https://opensiuc.lib.siu.edu/theses/2036.
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Many problems in nature can be represented as some kind of a satisfiability problem. Several SAT solvers and SMT solvers have been developed in the last decade with the goal of checking the satisfiability of different SAT problems. An all-solution satisfiability modulo theories on top of the Z3 SMT solver is presented that uses the clause blocking algorithm to find all the solution sets of a SAT problem. Then, an incremental All-SMT solver has been presented based on the all-SMT solver which is able to find the satisfiable answers of an incremental SMT problem based on the solution set of the original problem.
6
Bain, Stuart, and n/a. "Evolving Algorithms for Over-Constrained and Satisfaction Problems." Griffith University. School of Information and Communication Technology, 2007. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20071126.080227.
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The notion that a universally effective problem solver may still exist, and is simply waiting to be found, is slowly being abandoned in the light of a growing body of work reporting on the narrow applicability of individual heuristics. As the formalism of the constraint satisfaction problem remains a popular choice for the representation of problems to be solved algorithmically, there exists an ongoing need for new algorithms to effciently handle the disparate range of problems that have been posed in this representation. Given the costs associated with manually applying human algorithm development and problem solving expertise, methods that can automatically adapt to the particular features of a specific class of problem have begun to attract more attention. Whilst a number of authors have developed adaptive systems, the field, and particularly with respect to their application to constraint satisfaction problems, has seen only limited discussion as to what features are desirable for an adaptive constraint system. This may well have been a limiting factor with previous implementations, which have exhibited only subsets of the five features identified in this work as important to the utility of an adaptive constraint satisfaction system. Whether an adaptive system exhibits these features depends on both the chosen represen-tation and the method of adaptation. In this thesis, a three-part representation for constraint algorithms is introduced, which defines an algorithm in terms of contention, preference and selection functions. An adaptive system based on genetic programming is presented that adapts constraint algorithms described using the mentioned three-part representation. This is believed to be the first use of standard genetic programming for learning constraint algo-rithms. Finally, to further demonstrate the efficacy of this adaptive system, its performance in learning specialised algorithms for hard, real-world problem instances is thoroughly evaluated. These instances include random as well as structured instances from known-hard benchmark distributions, industrial problems (specifically, SAT-translated planning and cryptographic problems) as well as over-constrained problem instances. The outcome of this evaluation is a set of new algorithms - valuable in their own right - specifically tailored to these problem classes. Partial results of this work have appeared in the following publications: [1] Stuart Bain, John Thornton, and Abdul Sattar (2004) Evolving algorithms for constraint satisfaction. In Proc. of the 2004 Congress on Evolutionary Computation, pages 265-272. [2] Stuart Bain, John Thornton, and Abdul Sattar (2004) Methods of automatic algorithm generation. In Proc. of the 9th Pacific Rim Conference on AI, pages 144-153. [3] Stuart Bain, John Thornton, and Abdul Sattar. (2005) A comparison of evolutionary methods for the discovery of local search heuristics. In Australian Conference on Artificial Intelligence: AI'05, pages 1068-1074. [4] Stuart Bain, John Thornton, and Abdul Sattar (2005) Evolving variable-ordering heuristics for constrained optimisation. In Principles and Practice of Constraint Programming: CP'05, pages 732-736.
7
Bain, Stuart. "Evolving Algorithms for Over-Constrained and Satisfaction Problems." Thesis, Griffith University, 2007. http://hdl.handle.net/10072/365848.
Full textAbstract:
The notion that a universally effective problem solver may still exist, and is simply waiting to be found, is slowly being abandoned in the light of a growing body of work reporting on the narrow applicability of individual heuristics. As the formalism of the constraint satisfaction problem remains a popular choice for the representation of problems to be solved algorithmically, there exists an ongoing need for new algorithms to effciently handle the disparate range of problems that have been posed in this representation. Given the costs associated with manually applying human algorithm development and problem solving expertise, methods that can automatically adapt to the particular features of a specific class of problem have begun to attract more attention. Whilst a number of authors have developed adaptive systems, the field, and particularly with respect to their application to constraint satisfaction problems, has seen only limited discussion as to what features are desirable for an adaptive constraint system. This may well have been a limiting factor with previous implementations, which have exhibited only subsets of the five features identified in this work as important to the utility of an adaptive constraint satisfaction system. Whether an adaptive system exhibits these features depends on both the chosen represen-tation and the method of adaptation. In this thesis, a three-part representation for constraint algorithms is introduced, which defines an algorithm in terms of contention, preference and selection functions. An adaptive system based on genetic programming is presented that adapts constraint algorithms described using the mentioned three-part representation. This is believed to be the first use of standard genetic programming for learning constraint algo-rithms. Finally, to further demonstrate the efficacy of this adaptive system, its performance in learning specialised algorithms for hard, real-world problem instances is thoroughly evaluated. These instances include random as well as structured instances from known-hard benchmark distributions, industrial problems (specifically, SAT-translated planning and cryptographic problems) as well as over-constrained problem instances. The outcome of this evaluation is a set of new algorithms - valuable in their own right - specifically tailored to these problem classes. Partial results of this work have appeared in the following publications: [1] Stuart Bain, John Thornton, and Abdul Sattar (2004) Evolving algorithms for constraint satisfaction. In Proc. of the 2004 Congress on Evolutionary Computation, pages 265-272. [2] Stuart Bain, John Thornton, and Abdul Sattar (2004) Methods of automatic algorithm generation. In Proc. of the 9th Pacific Rim Conference on AI, pages 144-153. [3] Stuart Bain, John Thornton, and Abdul Sattar. (2005) A comparison of evolutionary methods for the discovery of local search heuristics. In Australian Conference on Artificial Intelligence: AI'05, pages 1068-1074. [4] Stuart Bain, John Thornton, and Abdul Sattar (2005) Evolving variable-ordering heuristics for constrained optimisation. In Principles and Practice of Constraint Programming: CP'05, pages 732-736.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Information and Communication Technology
Faculty of Engineering and Information Technology
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Li, Changqing. "Wave Diffraction and Refraction Problem and a Block-Wise Band Matrix Solver." W&M ScholarWorks, 1995. https://scholarworks.wm.edu/etd/1539617698.
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Molari, Luca. "Algoritmi di ottimizzazione per il bus touring problem." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amslaurea.unibo.it/9275/.
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Nel campo della Ricerca Operativa e dei problemi di ottimizzazione viene presentato un problema, denominato Bus Touring Problem (BTP), che modella una problematica
riguardante il carico e l’instradamento di veicoli nella presenza di di vincoli temporali e topologici sui percorsi.
Nel BTP, ci si pone il problema di stabilire una serie di rotte per la visita di punti di interesse dislocati geograficamente da parte di un insieme di comitive turistiche, ciascuna delle quali stabilisce preferenze riguardo le visite. Per gli spostamenti sono disponibili
un numero limitato di mezzi di trasporto, in generale eterogenei, e di capacitá limitata.
Le visite devono essere effettuate rispettando finestre temporali che indicano i periodi di apertura dei punti di interesse; per questi, inoltre, é specificato un numero massimo di visite ammesse. L’obiettivo é di organizzare il carico dei mezzi di trasporto e le rotte intraprese
in modo da massimizzare la soddisfazione complessiva dei gruppi di turisti nel rispetto dei vincoli imposti.
Viene presentato un algoritmo euristico basato su Tabu Search appositamente ideato e progettato per la risoluzione del BTP.
Vengono presentati gli esperimenti effettuati riguardo la messa appunto dei parametri dell'algoritmo su un insieme di problemi di benchmark.
Vengono presentati risultati estesi riguardo le soluzioni dei problemi.
Infine, vengono presentate considerazioni ed indicazioni di sviluppo futuro in materia.
10
Thi, Thanh Truc Vu. "Testing and optimization of Unicorn Fluid-Structure Interaction solver for simulating an industrial problem." Thesis, KTH, Numerisk analys, NA, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-139104.
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In industry applications, such as power supply plants, the issue of interaction between fluid and structure is always presented. More precisely, the fluid flow affects the structure by applying force(s) on it and vice versa. As a result, the structure can move (vibrate) or deform. A good understanding of this problem can help to design the system in term of safety, stability and efficiency. This project aims to optimize and test the Unicorn FSI solver from the FEniCS project [1] to simulate the interaction of fluid and structure in an experiment, which was carried out at Vattenfall Research and Development. The target is to improve the Unicorn FSI solver to cope with a real industrial problem. Moreover, some results of the simulation can be used as a tool to predict the behavior of a system under the effect of fluid flowI industriapplikationer, såsom kraftverk, är frågan om samspelet mellan fluid och struktur alltid närvarande. Närmare bestämt påverkar fluiden kraftverkets struktur genom att applicera en kraft på det och vice versa. Som ett resultat av fluidens kraftpåverkan, kan kraftverkets struktur vibrera eller deformeras. En god förståelse för detta FSI problem kan bidra till att utforma system ifråga om säkerhet, stabilitet och effektivitet. Detta projekt syftar till att optimera och testa Unicorn FSI lösaren från FEniCS projektet. Denna FSI lösare ska därefter användas till att simulera samspelet mellan vätska och struktur i ett experiment, som utförts på Vattenfalls forsknings och utvecklingsavdeling. Målet är att förbättra Unicorn FSI-lösaren för att klara av ett verkligt industriellt problem. Dessutom kan vissa resultaten av simuleringen användas som ett verktyg för att förutsäga beteendet hos ett system under inverkan av en fluid.
11
Hunt, John. "A task specific integration architecture for multiple problem solver, model-based, diagnostic expert systems." Thesis, Aberystwyth University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308391.
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Punch, William F. "A diagnosis system using a task integrated problem solver architecture (TIPS), including causal reasoning /." The Ohio State University, 1989. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487599963589822.
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Suzuki, Atsushi. "A Parallel Finite Element Solver for Large-Scale 3-D Stokes Problem and its Application to Earth's Mantle Convection Problem." 京都大学 (Kyoto University), 2003. http://hdl.handle.net/2433/148278.
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Huang, Shuo. "A New Multidomain Approach and Fast Direct Solver for the Boundary Element Method." University of Cincinnati / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1505125721346283.
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Ada, Ketchie, Nehe Meret, and Shapira Hila. "For the Creative Problem-Solver : An Integrated Process of Design Thinking and Strategic Sustainable Development." Thesis, Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-4208.
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Since the dawn of humanity design has influenced human life. Today, facing the depletion of the socio-ecological system, increasing complex problems threaten humanity’s existence. Design has been a contributor to creating such problems, yet with appropriate tools can become a source for solutions. Design Thinking (DT) was identified as a possible approach that could contribute to Strategic Sustainable Development (SSD). The purpose of this thesis is to examine potential contributors and hindrances of the DT process with regards to SSD, and create a prototype for an integrated process that could help achieve more strategic and sustainable outcomes. With the use of the Framework for Strategic Sustainable Development (FSSD) as a lens to examine the above, along with interviews, Action Research and expert feedback, an integrated process was created. Results of the interviews and FSSD analysis helped shape two prototypes that were examined through the mentioned methods. It was indicated by participants of the Action Research and by experts that the prototype could help reach a strategic and sustainable outcome, and further refinement should be pursued. The final prototype is presented as part of the discussion, suggesting additional tools and actions that if included could create a possible Sustainable DT (SDT) process.
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Genc, Balkan Ziya. "Implementation And Comparison Of Turbulence Models On A Flat Plate Problem Using A Navier-stokes Solver." Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/1096668/index.pdf.
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For turbulent flow calculations, some of the well-known turbulence models in the literature are applied on a previously developed Navier-Stokes solver designed to handle laminar flows. A finite volume formulation, which is cell-based for inviscid terms and cell-vertex for viscous terms, is used for numerical discretization of the Navier-Stokes equations in conservative form. This formulation is combined with one-step, explicit time marching Lax-Wendroff numerical scheme that is second order accurate in space. To minimize non-physical oscillations resulting from the numerical scheme, second and fourth order artificial smoothing terms are added. To increase the convergence rate of the solver, local time stepping technique is applied.
Before applying turbulence models, Navier-Stokes solver is tested for a case of subsonic, laminar flow over a flat plate. The results are in close agreement with Blasius similarity solutions.
To calculate turbulent flows, Boussinesq eddy-viscosity approach is utilized. The eddy viscosity (also called turbulent viscosity), which arises as a consequence of this approach, is calculated using Cebeci-Smith, Michel et. al., Baldwin-Lomax, Chien&rsquos k-epsilon and Wilcox&rsquo
s k-omega turbulence models. To evaluate the performances of these turbulence models and to compare them with each other, the solver has been tested for a case of subsonic, laminar - transition fixed - turbulent flow over a flat plate. The results are verified by analytical solutions and empirical correlations.
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Talal, Khan Muhammad. "Formulation of the power flow problem in human readable form for translation into an efficient solver." Thesis, KTH, Skolan för elektro- och systemteknik (EES), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-201090.
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Power systems are complex systems that need supervision and control to operatereliably and safely. Energy Management Systems (EMS)/SCADA provides the necessary aids formonitoring and control of power systems. Since power ow forms the basis of power system analysis,power ow solvers (PFS) are an integral part of EMS/SCADA systems. With the evolving powersystems new challenges appear which force new functionalities and requirements on EMS/SCADA,these in turn are translated into requirements on the PFS. Current EMS/SCADA utilize PFS thatwere developed in the 1970's and 1980's. Maintaining and upgrading these PFS to meet currentrequirements is ever more dicult. The development of an advanced, ecient and easier to maintainPFS is therefore necessary. This thesis focuses on the development of a power ow solver that iseasier to maintain, ecient and scalable. To achieve this a programming language that can meet theperformance requirements of a PFS and formulate the power ow problem at a higher abstractionlevel is required. Several programming languages are reviewed while they fulll some aspects theyare decient on other requirements. Therefore the open EMS programming language (OPL) isdeveloped, which can describe the power ow problem at a higher programming level. OPL is usedto model a small power system network, which is solved to obtain the power ow solution. Theexisting model is extended to include ratio tap changers and switched shunts, to proof the conceptthat additional equipment is added with relative ease.Elkraftsystem är komplexa system som kräver övervakning och styrningför att fungera pålitlighet och säkert. Energy Management Systems (EMS)/SCADA används förövervakning och styrning av systemet. Eftersom effektflöden utgör basen för analys av elkraftsystemfinns beräkningsverktyg (power ow solvers, PFS) integrerat i EMS/SCADA. I och med attelkraftsystemet utvecklas uppstår nya utmaningar, som kräver nya funktionaliteter och krav påEMS/SCADA. Detta resulterar i krav på även PFS. PFS som anvands i EMS/SCADA idag utveckladespå 1970- och 80-talet. Att underhålla och utveckla dessa för att uppfylla de nya kraven blirallt svårare. Detta examensarbete syftar till att utveckla en PFS som är lättare att underhållaoch som är effektiv och anpassningsbar. För att uppnå detta behövs ett programmeringsspråk somuppfyller prestandan som krävs för PFS, och ödesproblemet behöver formuleras om på en högrenivå. I detta examensarbete har era programmeringsspråk granskats, och samtliga uppfyller vissaav kraven men brister i andra. Därför har ett öppet programmeringsspråk (OPL). Detta beskrivereffektödesproblemet på en högre abstraktionsnivå. OPL har utvarderats genom användning förmodellering av ett litet elkraftsystem, för att lösa effektödesproblemet. Modellen inkluderar ävenlindningskopplare och shuntar, vilket visar att konceptet relativt lätt tillåter utökning med flerapparater i systemet.
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Oriani, Mattia. "A mixed hybrid finite volumes solver for robust primal and adjoint CFD." Thesis, Queen Mary, University of London, 2018. http://qmro.qmul.ac.uk/xmlui/handle/123456789/39760.
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In the context of gradient-based numerical optimisation, the adjoint method is an e cient way of computing the gradient of the cost function at a computational cost independent of the number of design parameters, which makes it a captivating option for industrial CFD applications involving costly primal solves. The method is however a ected by instabilities, some of which are inherited from the primal solver, notably if the latter does not fully converge. The present work is an attempt at curbing primal solver limitations with the goal of indirectly alleviating adjoint robustness issues. To that end, a novel discretisation scheme for the steady-state incompressible Navier- Stokes problem is proposed: Mixed Hybrid Finite Volumes (MHFV). The scheme draws inspiration from the family of Mimetic Finite Di erences and Mixed Virtual Elements strategies, rid of some limitations and numerical artefacts typical of classical Finite Volumes which may hinder convergence properties. Derivation of MHFV operators is illustrated and each scheme is validated via manufactured solutions: rst for pure anisotropic di usion problems, then convection-di usion-reaction and nally Navier-Stokes. Traditional and novel Navier-Stokes solution algorithms are also investigated, adapted to MHFV and compared in terms of performance. The attention is then turned to the discrete adjoint Navier-Stokes system, which is assembled in an automated way following the principles of Equational Di erentiation, i.e. the di erentiation of the primal discrete equations themselves rather than the algorithm used to solve them. Practical/computational aspects of the assembly are discussed, then the adjoint gradient is validated and a few solution algorithms for the MHFV adjoint Navier-Stokes are proposed and tested. Finally, two examples of full shape optimisation procedures on internal ow test cases (S-bend and U-bend) are reported.
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Serédi, Silvester. "Evoluční algoritmy v úloze booleovské splnitelnosti." Master's thesis, Vysoké učení technické v Brně. Fakulta informačních technologií, 2013. http://www.nusl.cz/ntk/nusl-236224.
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The goal of this Master's Thesis is finding a SAT solving heuristic by the application of an evolutionary algorithm. This thesis surveys various approaches used in SAT solving and some variants of evolutionary algorithms that are relevant to this topic. Afterwards the implementation of a linear genetic programming system that searches for a suitable heuristic for SAT problem instances is described, together with the implementation of a custom SAT solver which expoloits the output of the genetic program. Finally, the achieved results are summarized.
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Immler, Fabian [Verfasser], Tobias [Akademischer Betreuer] Nipkow, Tobias [Gutachter] Nipkow, and Warwick [Gutachter] Tucker. "A Verified ODE Solver and Smale's 14th Problem / Fabian Immler ; Gutachter: Tobias Nipkow, Warwick Tucker ; Betreuer: Tobias Nipkow." München : Universitätsbibliothek der TU München, 2018. http://d-nb.info/1163013404/34.
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Pham, Duc Nghia, and n/a. "Modelling and Exploiting Structures in Solving Propositional Satisfiability Problems." Griffith University. Institute for Integrated and Intelligent Systems, 2006. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20070216.143447.
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Recent research has shown that it is often preferable to encode real-world problems as propositional satisfiability (SAT) problems and then solve using a general purpose SAT solver. However, much of the valuable information and structure of these realistic problems is flattened out and hidden inside the corresponding Conjunctive Normal Form (CNF) encodings of the SAT domain. Recently, systematic SAT solvers have been progressively improved and are now able to solve many highly structured practical problems containing millions of clauses. In contrast, state-of-the-art Stochastic Local Search (SLS) solvers still have difficulty in solving structured problems, apparently because they are unable to exploit hidden structure as well as the systematic solvers. In this thesis, we study and evaluate different ways to effectively recognise, model and efficiently exploit useful structures hidden in realistic problems. A summary of the main contributions is as follows: 1. We first investigate an off-line processing phase that applies resolution-based pre-processors to input formulas before running SLS solvers on these problems. We report an extensive empirical examination of the impact of SAT pre-processing on the performance of contemporary SLS techniques. It emerges that while all the solvers examined do indeed benefit from pre-processing, the effects of different pre-processors are far from uniform across solvers and across problems. Our results suggest that SLS solvers need to be equipped with multiple pre-processors if they are ever to match the performance of systematic solvers on highly structured problems. [Part of this study was published at the AAAI-05 conference]. 2. We then look at potential approaches to bridging the gap between SAT and constraint satisfaction problem (CSP) formalisms. One approach has been to develop a many-valued SAT formalism (MV-SAT) as an intermediate paradigm between SAT and CSP, and then to translate existing highly efficient SAT solvers to the MV-SAT domain. In this study, we follow a different route, developing SAT solvers that can automatically recognise CSP structure hidden in SAT encodings. This allows us to look more closely at how constraint weighting can be implemented in the SAT and CSP domains. Our experimental results show that a SAT-based mechanism to handle weights, together with a CSP-based method to instantiate variables, is superior to other combinations of SAT and CSP-based approaches. In addition, SLS solvers based on this many-valued weighting approach outperform other existing approaches to handle many-valued CSP structures. [Part of this study was published at the AAAI-05 conference]. 3. Finally, we propose and evaluate six different schemes to encode temporal reasoning problems, in particular the Interval Algebra (IA) networks, into SAT CNF formulas. We then empirically examine the performance of local search as well as systematic solvers on the new temporal SAT representations, in comparison with solvers that operate on native IA representations. Our empirical results show that zChaff (a state-of-the-art complete SAT solver) together with the best IA-to-SAT encoding scheme, can solve temporal problems significantly faster than existing IA solvers working on the equivalent native IA networks. [Part of this study was published at the CP-05 workshop].
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Pham, Duc Nghia. "Modelling and Exploiting Structures in Solving Propositional Satisfiability Problems." Thesis, Griffith University, 2006. http://hdl.handle.net/10072/365503.
Full textAbstract:
Recent research has shown that it is often preferable to encode real-world problems as propositional satisfiability (SAT) problems and then solve using a general purpose SAT solver. However, much of the valuable information and structure of these realistic problems is flattened out and hidden inside the corresponding Conjunctive Normal Form (CNF) encodings of the SAT domain. Recently, systematic SAT solvers have been progressively improved and are now able to solve many highly structured practical problems containing millions of clauses. In contrast, state-of-the-art Stochastic Local Search (SLS) solvers still have difficulty in solving structured problems, apparently because they are unable to exploit hidden structure as well as the systematic solvers. In this thesis, we study and evaluate different ways to effectively recognise, model and efficiently exploit useful structures hidden in realistic problems. A summary of the main contributions is as follows: 1. We first investigate an off-line processing phase that applies resolution-based pre-processors to input formulas before running SLS solvers on these problems. We report an extensive empirical examination of the impact of SAT pre-processing on the performance of contemporary SLS techniques. It emerges that while all the solvers examined do indeed benefit from pre-processing, the effects of different pre-processors are far from uniform across solvers and across problems. Our results suggest that SLS solvers need to be equipped with multiple pre-processors if they are ever to match the performance of systematic solvers on highly structured problems. [Part of this study was published at the AAAI-05 conference]. 2. We then look at potential approaches to bridging the gap between SAT and constraint satisfaction problem (CSP) formalisms. One approach has been to develop a many-valued SAT formalism (MV-SAT) as an intermediate paradigm between SAT and CSP, and then to translate existing highly efficient SAT solvers to the MV-SAT domain. In this study, we follow a different route, developing SAT solvers that can automatically recognise CSP structure hidden in SAT encodings. This allows us to look more closely at how constraint weighting can be implemented in the SAT and CSP domains. Our experimental results show that a SAT-based mechanism to handle weights, together with a CSP-based method to instantiate variables, is superior to other combinations of SAT and CSP-based approaches. In addition, SLS solvers based on this many-valued weighting approach outperform other existing approaches to handle many-valued CSP structures. [Part of this study was published at the AAAI-05 conference]. 3. Finally, we propose and evaluate six different schemes to encode temporal reasoning problems, in particular the Interval Algebra (IA) networks, into SAT CNF formulas. We then empirically examine the performance of local search as well as systematic solvers on the new temporal SAT representations, in comparison with solvers that operate on native IA representations. Our empirical results show that zChaff (a state-of-the-art complete SAT solver) together with the best IA-to-SAT encoding scheme, can solve temporal problems significantly faster than existing IA solvers working on the equivalent native IA networks. [Part of this study was published at the CP-05 workshop].Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Institute for Integrated and Intelligent Systems
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Daniel, James Gray. "Technical director as problem solver West Virginia University Division of Theatre and Dance's production of A flea in her ear /." Morgantown, W. Va. : [West Virginia University Libraries], 2007. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=5531.
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Thesis (M.F.A.)--West Virginia University, 2007.Title from document title page. Document formatted into pages; contains iv, 61 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 23).
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Dirks, Denise. "Mediation and a Problem Solving Approach to Junior Primary Mathematics." University of the Western Cape, 1996. http://hdl.handle.net/11394/8379.
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Magister Educationis - MEdThis study argues that not all children in the Junior Primary phase benefit from the Problem Centred Approach in mathematics that was adapted by the Research, Unit for Mathematics at the University of Stellenbosch (RUMEUS). \One of the reasons could be that not all pupils can construct their own knowledge and methods. There are the highly capable pupils who cope well with this approach. These pupils are able to solve mathematical problems with little or no teacher interaction. Then there are the average and weaker pupils who cannot solve a mathematical problem on their own. These pupils need strategies and skills to solve problems and they need the teacher to mediate these strategies and skills to them, which will help these pupils to become autonomous problem solvers. ,Working in groups can, to some extent, supplement mediation or teacher interaction. Peer group teaching can be effective, whereby pupils are placed in groups so that the more capable pupils can teach concepts or make concepts clearer to the average or weaker pupils). There is, however, the possibility that when pupils of mixed abilities are placed in groups of four there might be one pupil who might refuse to work with the group. This pupil will work on her own and will not share ideas with the other members of the group. If this happens, mediation is necessary for those pupils who cannot solve a mathematical problem on their own. The purpose of this study is to investigate how exposure to mediation can improve pupils' problem solving abilities. As directions for my research I've chosen the first six criteria of Feuerstein's Mediated Learning Experiences (MLE). The first three parameters: intentionality and reciprocity, mediation of transcendence and mediation of meaning _are conditions for an interaction to qualify as MLE. Mediation of competence and regulation of behaviour are functions of specific experiences that combine with the first three to make an adult-child interaction one of mediated learning. Mediation of sharing behaviour . can be added. Here the child and the mediator are engaged in a shared quest for structural change in the child. In addition to this, the five mechanisms of mediational teaching, i.e. process questioning; challenging or asking reasons; bridging; teaching about rules; and emphasising order, predictability, system, sequence and strategy are also used in the implementation of mediation as described by Haywood. Two methods of investigation were chosen. The pupils' problem solving abilities were studied by means of eight word sums, of which the first four word sums were done in the pre-test and the other four word sums in the post-test. After the pre-test and before the post-test there was a period of mediational teaching for the experimental group. During this period and during the post-test the control group was denied mediation. After this research, mediation was also available for the control group. Two pupils from the experimental group were then chosen for further in-depth, think-aloud, person-to-person interviews. The aim of the interviews was to determine why these pupils could not solve the problem in the pre-test, but could successfully solve the post-test question. The results of the word sums in the pre-test and the post-test were compared. The role of strategies and thinking skills is concentrated on in the results. Mediation was not equally successful in all of the four different types of problem sums. Questions one and five contained two or more numbers and here pupils tended to either plus or minus these numbers. Questions two and six also contained numbers, but this is a problem situated in a real life situation. Questions three and seven contained no numbers and questions four and eight compelled pupils to first work out a plan. Mediation was most successful in problem sums situated in a real life situation, followed by problem sums which compelled pupils to first work out a plan, and then by problem sums where there were no numbers. Mediation was least; successful in problem sums that contained two or more numbers. Analysis of these results shows that with mediation there is an improvement in the pupils' problem solving abilities; Mediation can be viewed as S-H-O-H-R, in which the human mediator (H) is interposed between the stimulus (S) and the organism (0), and between the organism and the response (R). We can argue that the Problem Centred Approach without mediation can produce individuals who are little, if at all, affected by their encounter and interaction with new situations. Due to the lack of support in the Problem Centred Approach to Mathematics, it is the aim of this mini-thesis to propose mediation as an essential component in the Problem Centred Approach to Mathematics in the Junior Primary phase.
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Wallace, Ian Patrick. "Improved computational approaches to classical electric energy problems." Thesis, University of Edinburgh, 2017. http://hdl.handle.net/1842/28922.
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This thesis considers three separate but connected problems regarding energy networks: the load flow problem, the optimal power flow problem, and the islanding problem. All three problems are non-convex non linear problems, and so have the potential of returning local solutions. The goal of this thesis is to find solution methods to each of these problems that will minimize the chances of returning a local solution. The thesis first considers the load ow problem and looks into a novel approach to solving load flows, the Holomorphic Embedding Load Flow Method (HELM). The current literature does not provide any HELM models that can accurately handle general power networks containing PV and PQ buses of realistic sizes. This thesis expands upon previous work to present models of HELM capable of solving general networks efficiently, with computational results for the standard IEEE test cases provided for comparison. The thesis next considers the optimal power flow problem, and creates a framework for a load flow-based OPF solver. The OPF solver is designed with incorporating HELM as the load flow solver in mind, and is tested on IEEE test cases to compare it with other available OPF solvers. The OPF solvers are also tested with modified test cases known to have local solutions to show how a LF-OPF solver using HELM is more likely to find the global optimal solution than the other available OPF solvers. The thesis finally investigates solving a full AC-islanding problem, which can be considered as an extension of the transmission switching problem, using a standard MINLP solver and comparing the results to solutions obtained from approximations to the AC problem. Analysing in detail the results of the AC-islanding problem, alterations are made to the standard MINLP solver to allow better results to be obtained, all the while considering the trade-off between results and elapsed time.
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Ding, Jian. "Fast Boundary Element Method Solutions For Three Dimensional Large Scale Problems." Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/6830.
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Efficiency is one of the key issues in numerical simulation of large-scale problems with complex 3-D geometry. Traditional domain based methods, such as finite element methods, may not be suitable for these problems due to, for example, the complexity of mesh generation. The Boundary Element Method (BEM), based on boundary integral formulations (BIE), offers one possible solution to this issue by discretizing only the surface of the domain. However, to date, successful applications of the BEM are mostly limited to linear and continuum problems. The challenges in the extension of the BEM to nonlinear problems or problems with non-continuum boundary conditions (BC) include, but are not limited to, the lack of appropriate BIE and the difficulties in the treatment of the volume integrals that result from the nonlinear terms. In this thesis work, new approaches and techniques based on the BEM have been developed for 3-D nonlinear problems and Stokes problems with slip BC.
For nonlinear problems, a major difficulty in applying the BEM is the treatment of the volume integrals in the BIE. An efficient approach, based on the precorrected-FFT technique, is developed to evaluate the volume integrals. In this approach, the 3-D uniform grid constructed initially to accelerate surface integration is used as the baseline mesh to evaluate volume integrals. The cubes enclosing part of the boundary are partitioned using surface panels. No volume discretization of the interior cubes is necessary. This grid is also used to accelerate volume integration. Based on this approach, accelerated BEM solvers for non-homogeneous and nonlinear problems are developed and tested. Good agreement is achieved between simulation results and analytical results. Qualitative comparison is made with current approaches.
Stokes problems with slip BC are of particular importance in micro gas flows such as those encountered in MEMS devices. An efficient approach based on the BEM combined with the precorrected-FFT technique has been proposed and various techniques have been developed to solve these problems. As the applications of the developed method, drag forces on oscillating objects immersed in an unbounded slip flow are calculated and validated with either analytic solutions or experimental results.
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Nguyen, Thi Phong. "Direct and inverse solvers for scattering problems from locally perturbed infinite periodic layers." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLX004/document.
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Nous sommes intéressés dans cette thèse par l'analyse de la diffraction directe et inverse des ondes par des couches infinies périodiques localement perturbées à une fréquence fixe. Ce problème a des connexions avec le contrôle non destructif des structures périodiques telles que des structures photoniques, des fibres optiques, des réseaux, etc. Nous analysons d'abord le problème direct et établissons certaines conditions sur l'indice de réfraction pour lesquelles il n'existe pas de modes guidés. Ce type de résultat est important car il montre les cas pour lesquels les mesures peuvent être effectuées par exemple sur une couche au dessus de la structure périodique sans perdre des informations importantes dans la partie propagative de l'onde. Nous proposons ensuite une méthode numérique pour résoudre le problème de diffraction basée sur l'utilisation de la transformée de Floquet-Bloch dans les directions de périodicité. Nous discrétisons le problème de manière uniforme dans la variable de Floquet-Bloch et utilisons une méthode spectrale dans la discrétisation spatiale. La discrétisation en espace exploite une reformulation volumétrique du problème dans une cellule (équation intégrale de Lippmann-Schwinger) et une périodisation du noyau dans la direction perpendiculaire à la périodicité. Cette dernière transformation permet d'utiliser des techniques de type FFT pour accélérer le produit matrice-vecteur dans une méthode itérative pour résoudre le système linéaire. On aboutit à un système d'équations intégrales couplées (à cause de la perturbation locale) qui peuvent être résolues en utilisant une décomposition de Jacobi. L'analyse de la convergence est faite seulement dans le cas avec absorption et la validation numérique est réalisées sur des exemples 2D. Pour le problème inverse, nous étendons l'utilisation de trois méthodes d'échantillonnage pour résoudre le problème de la reconstruction de la géométrie du défaut à partir de la connaissance de données mutistatiques associées à des ondes incidentes planes en champ proche (c.à.d incluant certains modes évanescents). Nous analysons ces méthodes pour le problème semi-discrétisée dans la variable Floquet-Bloch. Nous proposons ensuite une nouvelle méthode d'imagerie capable de visualiser directement la géométrie du défaut sans savoir ni les propriétés physiques du milieux périodique, ni les propriétés physiques du défaut. Cette méthode que l'on appelle imagerie-différentielle est basée sur l'analyse des méthodes d'échantillonnage pour un seul mode de Floquet-Bloch et la relation avec les solutions de problèmes de transmission intérieurs d'un type nouveau. Les études théoriques sont corroborées par des expérimentations numériques sur des données synthétiques. Notre analyse est faite d'abord pour l'équation d'onde scalaire où le contraste est sur le terme d'ordre inférieur de l'opérateur de Helmholtz. Nous esquissons ensuite l'extension aux cas où la le contraste est également présent dans l'opérateur principal. Nous complémentons notre travail par deux résultats sur l'analyse du problème de diffraction pour des matériaux périodiques ayant des indices négatifs. Nous établissons en premier le caractère bien posé du problème en 2D dans le cas d'un contraste est égal à -1. Nous montrons également le caractère Fredholm de la formulation Lipmann-Schwinger du problème en utilisant l'approche de T-coercivité dans le cas d'un contraste différent de -1We are interested in this thesis by the analysis of scattering and inverse scattering problems for locally perturbed periodic infinite layers at a fixed frequency. This problem has connexions with non destructive testings of periodic media like photonics structures, optical fibers, gratings, etc. We first analyze the forward scattering problem and establish some conditions under which there exist no guided modes. This type of conditions is important as it shows that measurements can be done on a layer above the structure without loosing substantial informations in the propagative part of the wave. We then propose a numerical method that solves the direct scattering problem based on Floquet-Bloch transform in the periodicity directions of the background media. We discretize the problem uniformly in the Floquet-Bloch variable and use a spectral method in the space variable. The discretization in space exploits a volumetric reformulation of the problem in a cell (Lippmann-Schwinger integral equation) and a periodization of the kernel in the direction orthogonal to the periodicity. The latter allows the use of FFT techniques to speed up Matrix-Vector product in an iterative to solve the linear system. One ends up with a system of coupled integral equations that can be solved using a Jacobi decomposition. The convergence analysis is done for the case with absorption and numerical validating results are conducted in 2D. For the inverse problem we extend the use of three sampling methods to solve the problem of retrieving the defect from the knowledge of mutistatic data associated with incident near field plane waves. We analyze these methods for the semi-discretized problem in the Floquet-Bloch variable. We then propose a new method capable of retrieving directly the defect without knowing either the background material properties nor the defect properties. This so-called differential-imaging functional that we propose is based on the analysis of sampling methods for a single Floquet-Bloch mode and the relation with solutions toso-called interior transmission problems. The theoretical investigations are corroborated with numerical experiments on synthetic data. Our analysis is done first for the scalar wave equation where the contrast is the lower order term of the Helmholtz operator. We then sketch the extension to the cases where the contrast is also present in the main operator. We complement our thesis with two results on the analysis of the scattering problem for periodic materials with negative indices. Weestablish the well posedness of the problem in 2D in the case of a contrast equals -1. We also show the Fredholm properties of the volume potential formulation of the problem using the T-coercivity approach in the case of a contrast different from -1
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Miller, Catherine Marie 1959. "Teachers as problem solvers/problem solvers as teachers: Teachers' practice and teaching of mathematical problem solving." Diss., The University of Arizona, 1996. http://hdl.handle.net/10150/282150.
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This study investigated the relationship among three high school mathematics teachers definitions and beliefs about mathematical problem solving, their problem solving practices and how they teach mathematical problem solving. Each teacher was interviewed three times and observed once during a problem solving lesson. Data comprised of transcriptions of audio tapes, field notes, and completed problem solving checklists were used to prepare the case studies. While the definitions, practices and teaching of the teachers varied, the findings were consistent within each case. The results suggest that how teachers are taught and what they learn as students are related to how they teach mathematical problem solving.
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Ugarte, Crystal. "A numerical investigation of Anderson localization in weakly interacting Bose gases." Thesis, KTH, Numerisk analys, NA, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-269167.
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The ground state of a quantum system is the minimizer of the total energy of that system. The aim of this thesis is to present and numerically solve the Gross-Pitaevskii eigenvalue problem (GPE) as a physical model for the formation of ground states of dilute Bose gases at ultra-low temperatures in a disordered potential. The first part of the report introduces the quantum mechanical phenomenon that arises at ground states of the Bose gases; the Anderson localization, and presents the nonlinear eigenvalue problem and the finite element method (FEM) used to discretize the GPE. The numerical method used to solve the eigenvalue problem for the smallest eigenvalue is called the inverse power iteration method, which is presented and explained. In the second part of the report, the smallest eigenvalue of a linear Schrödinger equation is compared with the numerically computed smallest eigenvalue (ground state) in order to evaluate the accuracy of a linear numerical scheme constructed as first step for numerically solving the non-linear problem. In the next part of the report, the numerical methods are implemented to solve for the eigenvalue and eigenfunction of the (non-linear) GPE at ground state (smallest eigenvalue). The mathematical expression for the quantum energy and smallest eigenvalue of the non-linear system are presented in the report. The methods used to solve the GPE are the FEM and inverse power iteration method and different instances of the Anderson localization are produced. The study shows that the error of the smallest eigenvalue approximation for the linear case without disorder is satisfying when using FEM and Power iteration method. The accuracy of the approximation obtained for the linear case without disorder is satisfying, even for a low numbers of iterations. The methods require many more iterations for solving the GPE with a strong disorder. On the other hand, pronounced instances of Anderson localizations are produced in a certain scaling regime. The study shows that the GPE indeed works well as a physical model for the Anderson localization.Syftet med denna avhandling är att undersöka hur väl Gross-Pitaevskii egenvärdesekvation (GPE) passar som en fysisk modell för bildandet av stationära elektronstater i utspädda Bose-gaser vid extremt låga temperaturer. Fenomenet som skall undersökas heter Anderson lokalisering och uppstår när potentialfältets styrka och störning i systemet är tillräckligt hög. Undersökningen görs i denna avhandling genom att numeriskt lösa GPE samt illustrera olika utfall av Anderson lokaliseringen vid olika numeriska värden. Den första delen av rapporten introducerar det icke-linjära matematiska uttrycket för GPE samt de numeriska metoderna som används för att lösa problemet numerisk: finita elementmetoden (FEM) samt egenvärdesalgoritmen som heter inversiiteration. Finita elementmetoden används för att diskretisera variationsproblemet av GPE och ta fram en enkel algebraisk ekvation. Egenvärdesalgoritmen tillämpas på den algebraiska ekvation för att iterativt beräkna egenfunktionen som motsvarar det minsta egenvärdet. Det minsta egenvärdet av en fullt definierad (linjär) Schrödinger ekvation löses i rapportens andra del. Den linjära ekvationen löses för att ta fram en förenklad numerisk algoritm att utgå ifrån innan den icke-linjära algoritmen tas fram. För att försäkra sig att den linjära algoritmen stämmer bra jämförs det exakta egenvärdet för problemet med ett numeriskt framtaget värde. Undersökningen av den linjära algoritmen visar att vi får en bra uppskattning av egenvärdet - även vid få iterationer. Vidare konstrueras den ickelinjära algoritmen baserat på den linjära. Ekvationen löses och undersökes. Egenfunktionen som motsvarar minsta egenvärdet framtas och beskriver kvantsystemet i lägsta energitillståndet, så kallade grundtillståndet. Undersökningen av GPE visar att de numeriska metoderna kräver många fler iterationer innan en tillräckligt bra uppskattning av egenvärdet fås. Å andra sidan fås markanta Anderson lokaliseringar för ett skalningsområde som beskrivs av styrkan av potentialfältet i relation till dess störning. Slutsatsen är att Gross-Pitaevskii egenvärdesekvation passar bra som en fysisk modell för detta kvantsystem.
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Bousmar, Khadija. "Conception d'un solveur matériel spécifique pour la résolution rapide du problème SAT appliqué à l'évaluation du risque en génie industriel." Electronic Thesis or Diss., Université de Lorraine, 2018. http://www.theses.fr/2018LORR0341.
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Dans cette thèse, nous abordons un sujet dans le domaine du génie industriel se rapportant à la résolution d’un problème de décision, fondamental dans la théorie de la complexité et de la satisfiabilité propositionnelle, nommé SAT. Ce dernier est présenté généralement sous un formalisme mathématique, permettant de modéliser des problèmes complexes, tant académiques qu’issus du monde réel. Ces problèmes sont présentés sous une forme booléenne dans le but de tester leur faisabilité. Ils sont relatifs à plusieurs domaines applicatifs, tels que la vérification de matériels et logiciels, les télécommunications, la médecine, et notamment la planification. L’évolution et les progrès observés ces dernières années dans le domaine de la résolution des problèmes utilisant SAT, a permis de renforcer la conviction que ce domaine peut être encore plus prometteur dans la résolution des problèmes difficiles (complexes ou NP complexes) et qu’il faut lui accorder plus d’intérêt. C’est dans cette optique, que nous nous sommes intéressés à l’appliquer sur des problèmes purement industriels afin de proposer des contributions dans un nouveau domaine d’application. L’objectif de cette thèse est de développer des outils d’aide à la décision pouvant être employés dans le domaine de la gestion du risque industriel. Bien que le formalisme SAT soit très puissant, dans la pratique, quand les problèmes ciblés sont de taille importante, les outils de résolution s’avèrent moins performants. Par conséquent le but de ces travaux de recherche est de développer une architecture matérielle rapide (avec une implémentation ciblée sur FPGA) permettant une accélération massive de la résolution grâce au niveau élevé de traitement parallèle de l’approche matérielle. Dans cette thèse, deux aspects principaux sont étudiés et développés pour résoudre un problème de gestion des ressources de production industriel. Ces aspects sont d’une part, les principes de base de fonctionnement et de résolution d’un solveur générique paramétrable SAT, d’autre part, des méthodes adaptées au principe de fonctionnement retenu pour le solveur matériel. En effet, bien que ciblant des buts comparables à ceux de l’approche logicielle (optimisation du parcours de l’espace de recherche), l’approche matérielle requiert le développement de méthodes de résolutions spécifiques. Ces dernières ont été spécifiquement optimisées pour le domaine applicatif cible qui est celui de l’industrie. L’efficacité de l’approche matérielle développée a montré des résultats satisfaisant, point de vu du nombre de variables utilisés et temps de résolution sur les problèmes testésIn this thesis, we address a topic in the field of industrial engineering related to solving a fundamental decision problem in the theory of complexity and propositional satisfiability called SAT. The latter is usually presented in a mathematical formalism, allowing the modelling of complex problems, both academic and from real world. These problems are presented in boolean form in order to check their feasibility. They relate to several application areas, such as hardware and software verification, telecommunications, medicine, and planning. The evolution and progress observed in recent years in the field of problem-solving using SAT has made it possible to reinforce the conviction that this field can be even more promising in solving difficult (complex or complex NP) problems and that more attention needs to be dedicated to it. It is with this in mind that we have taken an interest in applying it to purely industrial problems in order to propose contributions in a new field of application. The objective of this thesis is to develop decision-support tools that can be used in the field of industrial risk management. Although the SAT formalism is very powerful, in practice, when the targeted problems are large, the resolution tools prove to be less effective. Therefore, the aim of this research is to develop a rapid hardware architecture (with FPGA-targeted implementation) that allows massive acceleration of resolution due to the high level of parallel processing of the hardware approach. In this thesis, two main aspects are studied and developed to solve a problem of management of industrial production resources. These aspects are, on the one hand, the basic principles of operation and resolution of a generic SAT configurable solver and, on the other hand, methods adapted to the operating principle adopted for the hardware solver. Indeed, although targeting goals comparable to those of the software approach (optimization of the search space path), the material approach requires the development of specific resolution methods. These have been specifically optimised for the target application area of industry. The effectiveness of the material approach developed showed satisfactory results, point of view of the number of variables used and resolution time on the problems tested
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Procházka, Lukáš. "Redukce nedeterministických konečných automatů." Master's thesis, Vysoké učení technické v Brně. Fakulta informačních technologií, 2011. http://www.nusl.cz/ntk/nusl-237032.
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Nondeterministic finite automaton is an important tool, which is used to process strings in many different areas of programming. It is important to try to reduce its size for increasing programs' effectiveness. However, this problem is computationally hard, so we need to search for new techniques. Basics of finite automata are described in this work. Some methods for their reduction are then introduced. Usable reduction algorithms are described in greater detail. Then they are implemented and tested. The test results are finally evaluated.
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Bieszczad, Andrzej Carleton University Dissertation Engineering Systems and Computer. "Neuromorphic distributed general problem solvers." Ottawa, 1996.
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Zhang, Huaibao. "HIGH TEMPERATURE FLOW SOLVER FOR AEROTHERMODYNAMICS PROBLEMS." UKnowledge, 2015. https://uknowledge.uky.edu/me_etds/64.
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A weakly ionized hypersonic flow solver for the simulation of reentry flow is firstly developed at the University of Kentucky. This code is the fluid dynamics module of known as Kentucky Aerothermodynamics and Thermal Response System (KATS). The solver uses a second-order finite volume approach to solve the laminar Navier– Stokes equations, species mass conservation and energy balance equations for flow in chemical and thermal non-equilibrium state, and a fully implicit first-order backward Euler method for the time integration. The hypersonic flow solver is then extended to account for very low Mach number flow using the preconditioning and switch of the convective flux scheme to AUSM family. Additionally, a multi-species preconditioner is developed.
The following part of this work involves the coupling of a free flow and a porous medium flow. A new set of equation system for both free flows and porous media flows is constructed, which includes a Darcy–Brinkmann equation for momentum, mass conservation, and energy balance equation. The volume-average technique is used to evaluate the physical properties in the governing equations. Instead of imposing interface boundary conditions, this work aims to couple the free/porous problem through flux balance, therefore, flow behaviors at the interface are satisfied implicitly.
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Price, Christopher John. "Model reuse in diverse problem solvers." Thesis, Aberystwyth University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241799.
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Araujo, Luiz Jonatã Pires de. "A hybrid methodology to solve the container loading problem with weight distribution and cutting problems." Universidade de Fortaleza, 2011. http://dspace.unifor.br/handle/tede/88221.
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Previous issue date: 2011-09-27Transport of goods has represented an important role in economic development throughout the history and ship containerization brought great advantages. Its invention in mid-1950s brought down the cost of transport and reduced time for loading and unloading cargo. Consequently, it increased efficiency of port working and reduced handling cargo to hours instead of weeks, as before. However, the good use of containerization involves new and specialized logistic process, a number of technologies and automated systems to handle a great number of containers and even greater volume of cargo. To answer these requirements, computation appears as important tool. The described scenary has been treated in academic literature as the Container Loading Problem (CLP), with some variants. It is necessary consider practical requirements, for example the stability of cargo or weight distribution. The last one is of vital importance since the position of the centre of gravity of cargo affects the stability during its transport. When desconsidered, it could result in damage to cargo or vehicle. During our research, we were specially interested in this requirement. But, in order compare the found solutions with other ones, we proposed a methodology to measures the weight distribution. So, to the described problem, specifically the Knapsack Loading Problem (3D-KLP), this work presents a methodology that not only maximizes the packed cargo volume but also optimizes the weight distribution, its great contribution. Mainly if we consider that the cargo to be packed is composed by items with different densities, which turns the problem more difficult. The present methodology is composed by two phases with distinct goals. The first phase is concerned with maximize the weight distribution combining a search algorithm, the backtracking, with heuristics that solve integer linear programming models. The second phase executes a Genetic Algorithm to maximize the weight distribution of previously packed cargo. We also present a justification for why genetic algorithm was used in our methodology. An additional application was made to solve cutting problems. This class of problems occurs in various industrial process, when it is necessary to cut different types of material as glass, wood or parper, with a minimum of waste. We use a well-known benchmark test to compare our results with other approaches. This work also presents a case study of our implementation using some real data in a factory of stoves and refrigerators in Brazil. It shown promising results in reduced time. Keywords: Container Loading Problem, Knapsack Loading Problem, Weight Distribution, Integer Programming, Backtracking, Genetic Algorithms.
O transporte de carga tem representado um papel fundamental no desenvolvimento econômico no decorrer da história e a conteinerização trouxe grandes vantagens. Seu advento reduziu os custos de transporte bem como o tempo de carga. Portanto, aumentou a eficiência do trabalho em portos e reduziu o tempo necessário para operações com carga para horas, ao invés de semanas como anteriormente. Contudo, o bom uso dos contêineres involve novos e especializados processos logísticos, uma grande quantidade de tecnologias além de sistemas automatizados para manipular uma elevada quantidade de contêineres e ainda maior volume de carga. Para atender a estes requisitos, computação aparece como uma importante ferramenta. O cenário descrito tem sido tratado na literatura acadêmica como o Problema de Carregamento de Contêiner (CLP, do inglês Container Loading Problem), com algumas variantes. é também necessário considerar requisitos práticos como, por exemplo, a estabilidade da carga ou distribuição do peso. Este último de vital importância uma vez que o centro de gravidade da carga afeta a estabilidade durante seu transporte. Se descosiderado, pode-se danificar tanto a carga como o veículo. Durante nossa pesquisa, nós estivemos especialmente interessados neste requisito. E a fim de comparar a qualidade dos resultados obtidos, propusemos uma maneira de mensurar a distribuição do peso. Portanto, dado o problema descrito, especificamente o 3D Knapsack Loading Problem, este trabalho apresenta um algoritmo que não apenas maximiza o volume total carregado mas também otimiza a distribuição do peso da carga, sua grande contribuição. Principalmente se considerarmos que a carga é composta de itens com diferentes valores de densidade, o que torna o problema ainda mais difícil. A metodologia consiste em duas fases com objetivos diferentes. A primeira fase ocupa-se em maximizar o volume carregado por combinar um algoritmo de busca, o backtracking, com heurísticas que resolvem modelos de programação linear inteira. A segunda fase executa um algoritmo genético para maximizar a distribuição do peso da carga previamente colocada. Apresentamos também uma justificativa do porque algoritmo genéticos foram usados em nossa metodologia. Uma aplicação adicional foi feita para resolver problemas de corte. Esta classe de problemas ocorre em vários processos industriais, quando é necessário cortar diferentes tipos de materiais, como vidro, madeira ou papel, com um mínimo de desperdício. A fim de comparação, usamos bibliotecas de teste bem conhecidas na literatura e um estudo de caso usando informações reais de uma fábrica de fogões e geladeiras no Brasil. São apresentados resultados promissores alcançados em tempo reduzido. Palavras-chave: Problema de Carregamento de Contêiner, Knapsack Loading Problem, Distribuição do Peso, Programação Linear Inteira, Backtracking, Algoritmos Genéticos.
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Dewaal, Nicholas. "The Importance of the Riemann-Hilbert Problem to Solve a Class of Optimal Control Problems." Diss., CLICK HERE for online access, 2007. http://contentdm.lib.byu.edu/ETD/image/etd1759.pdf.
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Venkata, Narasimha Koushik Srinath. "Ant Colony Optimization Technique to Solve Min-Max MultiDepot Vehicle Routing Problem." University of Cincinnati / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1324399082.
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Lu, Zhaosong. "Algorithm Design and Analysis for Large-Scale Semidefinite Programming and Nonlinear Programming." Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7151.
Full textAbstract:
The limiting behavior of weighted paths associated with the semidefinite program (SDP) map $X^{1/2}SX^{1/2}$ was studied and some applications to error bound analysis and superlinear convergence of a class of
primal-dual interior-point methods were provided. A new approach for solving large-scale well-structured sparse SDPs via a saddle point mirror-prox algorithm with ${cal O}(epsilon^{-1})$ efficiency was developed based on exploiting sparsity structure and reformulating SDPs into smooth convex-concave saddle point problems. An iterative solver-based
long-step primal-dual infeasible path-following algorithm for convex quadratic programming (CQP) was developed. The search directions of
this algorithm were computed by means of a preconditioned iterative linear solver. A uniform bound, depending only on the CQP data, on
the number of iterations performed by a preconditioned iterative linear solver was established. A polynomial bound on the number of
iterations of this algorithm was also obtained. One efficient ``nearly exact' type of method for solving large-scale ``low-rank' trust region
subproblems was proposed by completely avoiding the computations of Cholesky or partial Cholesky factorizations. A computational study of this method was also provided by applying it to solve some large-scale nonlinear programming problems.
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Beuchler, Sven. "Fast solvers for degenerated problems." Universitätsbibliothek Chemnitz, 2006. http://nbn-resolving.de/urn:nbn:de:swb:ch1-200600611.
Full textAbstract:
In this paper, finite element discretizations of the
degenerated operator
-ω2(y) uxx-ω2(x)uyy=g
in the unit square are investigated, where the
weight function satisfies ω(ξ)=ξα
with α ≥ 0.
We propose two multi-level methods in order to
solve the resulting system of linear algebraic
equations. The first method is a multi-grid
algorithm with line-smoother.
A proof of the smoothing property is given.
The second method is a BPX-like preconditioner
which we call MTS-BPX preconditioner.
We show that the upper eigenvalue bound of the
MTS-BPX preconditioned system matrix grows
proportionally to the level number.
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Kohengadol, Roni A. "Nonlinear solvers for plasticity problems." Link to electronic thesis, 2004. http://www.wpi.edu/Pubs/ETD/Available/etd-0408104-111231.
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Medina, Juan Pablo. "Bitter beers: a spatial orientation problem solved." Revista de Química, 2014. http://repositorio.pucp.edu.pe/index/handle/123456789/99714.
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La determinación de la estereoquímica en los compuestos orgánicos ha sido un problema que la comunidad científica ha ido dando solución a lo largo de los años. Diferentes métodos han surgido, como la difracción de rayos X o los distintos tipos de Resonancia Magnética (RMN). Sin embargo, se acaba de descubrir que el método utilizado hasta ahora en la determinación de la configuración absoluta de los α-ácidos, que provienen del lúpulo utilizado en la elaboración de las cervezas bitter, parece que no era el correcto.Determination of the stereochemistry of organic compounds has been a problem that the scientific community has been giving solution to over the years. Different methods have emerged, such as X-ray Diffraction or different types of Nuclear Magnetic Resonance (NMR). However, it just has been discovered that the method used in the determination of the absolute configuration of the α-acids derived from hops used in the manufacture of bitter beers, was not the appropriate.
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Lewis, Ryan. "A Problem Well Defined is Nearly Solved." University of Cincinnati / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1277124765.
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Shaw-Hones, Gayle E. Haslam Elizabeth L. "Learning to solve problems within a pharmaceutical organization : designing problem and story-based constructivist e-learning environments /." Philadelphia, Pa. : Drexel University, 2008. http://hdl.handle.net/1860/2827.
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Liestøl, Lars. "Adaption of a two phase solver for axisymmetric problems." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for energi- og prosessteknikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18792.
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This report documents the adaptation of a two dimensional two phaseNavier-Stokes solver to axisymmetric problems. The changes fromCartesian to cylindrical coordinates are thoroughly described with finitedifference methods for the heat equation, Poisson equation, singleand two phase Navier-Stokes equations.The jump conditions at interfacesare modified to accommodate these changes for the two phaseNavier-Stokes equations.The changes to the solver are done step by step, and every changeis verified through intermediate test cases with analytical solutions tolimit the possible sources of errors.Finally all stepwise changes are joined together to form an axisymmetrictwo phase Navier-Stokes solver. Results are presented for aresting bubble, and for both viscous and inviscid oscillating ellipticbubbles.
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McCluskey, T. L. "Experience-driven heuristic acquisition in general problem solvers." Thesis, City University London, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234449.
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Lopez, Lurdes. "HELPING AT-RISK STUDENTS SOLVE MATHEMATICAL WORD PROBLEMS THROUGH THE USE OF DIRECT INSTRUCTION AND PROBLEM SOLVING STRATEGIES." Master's thesis, University of Central Florida, 2008. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3193.
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This action research study examined the influence mathematical strategies had on middle school students' mathematical ability. The purpose of this action research study was to observe students mathematical abilities and to investigate whether teaching students problem-solving strategies in mathematics will enhance student's mathematical thinking and their ability to comprehend and solve word problems. The study took place in an urban school in Orlando, Florida in the fall of 2004. The subjects will be 12 eighth grade students assigned to my intensive math class. Quantitative data was collected. Students' took a pre and post test designed to measure and give students practice on mathematical skills. Students worked individually on practice problems, answered questions daily in their problem solving notebook and mathematics journals. Results showed the effectiveness of the use of direct instruction and problem-solving strategies on at-risk students. M.Ed.
Other
Graduate Studies;
K-8 Math and Science MEd
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Nemani, Ashish Kumar. "Combinational approaches to solve scheduling problems." [Gainesville, Fla.] : University of Florida, 2009. http://purl.fcla.edu/fcla/etd/UFE0041090.
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Drexler, Michael. "Newton's method as a global solver for non-linear problems." Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360197.
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Whitford, Angela Tracy. "Heuristic approaches to solve the frequency assignment problem." Thesis, Goldsmiths College (University of London), 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321956.
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Vazquez, ortiz Karla Esmeralda. "Advanced methods to solve the maximum parsimony problem." Thesis, Angers, 2016. http://www.theses.fr/2016ANGE0015/document.
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La reconstruction phylogénétique est considérée comme un élément central de divers domaines comme l’écologie, la biologie et la physiologie moléculaire pour lesquels les relations généalogiques entre séquences d’espèces ou de gènes, représentées sous forme d’arbres, peuvent apporter des éclairages significatifs à la compréhension de phénomènes biologiques. Le problème de Maximum de Parcimonie est une approche importante pour résoudre la reconstruction phylogénétique en se basant sur un critère d’optimalité pour lequel l’arbre comprenant le moins de mutations est préféré. Dans cette thèse nous proposons différentes méthodes pour s’attaquer à la nature combinatoire de ce problème NP-complet. Premièrement, nous présentons un algorithme de Recuit Simulé compétitif qui nous a permis de trouver des solutions de meilleure qualité pour un ensemble de problèmes. Deuxièmement, nous proposons une nouvelle technique de Path-Relinking qui semble intéressante pour comparer des arbres mais pas pour trouver des solutions de meilleure qualité. Troisièmement, nous donnons le code d’une implantation sur GPU de la fonction objectif dont l’intérêt est de réduire le temps d’exécution de la recherche pour des instances dont la longueur des séquences est importante. Finalement, nous introduisons un prédicteur capable d’estimer le score optimum pour un vaste ensemble d’instances avec une très grande précisionPhylogenetic reconstruction is considered a central underpinning of diverse fields like ecology, molecular biology and physiology where genealogical relationships of species or gene sequences represented as trees can provide the most meaningful insights into biology. Maximum Parsimony (MP) is an important approach to solve the phylogenetic reconstruction based on an optimality criterion under which the tree that minimizes the total number of genetic transformations is preferred. In this thesis we propose different methods to cope with the combinatorial nature of this NP-complete problem. First we present a competitive Simulated Annealing algorithm which helped us find trees of better parsimony score than the ones that were known for a set of instances. Second, we propose a Path-Relinking technique that appears to be suitable for tree comparison but not for finding trees of better quality. Third, we give a GPU implementation of the objective function of the problem that can reduce the runtime for instances that have an important number of residues per taxon. Finally, we introduce a predictor that is able to estimate the best parsimony score of a huge set of instances with a high accuracy