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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
61

Kombinace evolučních algoritmů a programování s omezujícími podmínkami pro rozvrhování / Combination of Evolutionary Algorithms and Constraint Programming for Scheduling

Štola, Miroslav January 2016 (has links)
Scheduling problems and constraint satisfaction problems are generally known to be extremely hard. This thesis proposes a new evolutionary al- gorithm approach to solve a constrained-based scheduling problem. In this approach, variable orderings are evolved. The variable ordering serves as a parameter for the constraint solver. Its purpose is to determine the order in which variables are labelled by the solver. Hence the evolving individuals may be encoded as permutations. Therefore, our approach can be applied to a wider range of constraint satisfaction problems. Methods for generating the initial population of individuals based on the analysis of the precedence constraints graph are proposed. New genetic operators are presented and successfully applied. Our approach succeeded in finding a range of diverse schedules with the optimal makespan. Furthermore, multi-objective opti- mization was successfully attempted with the NSGA-II. 1
62

Ordenamento e propriedades dielétricas em microondas dos sistemas (Ba1-xSrx)3CaNb2O9 e (Ba1-yLay)3Ca1+yNb2-yO9 / Structural ordering and microwave dielectric properties of (Ba1-xSrx)3CaNb2O9 and (Ba1-yLay)3Ca1+yNb2-yO9 systems

Rodrigues, João Elias Figueiredo Soares 13 July 2017 (has links)
Materiais dielétricos para operação em microondas constituem um ponto importante para usos em sistemas de comunicação móvel/via satélite, incluindo sistemas de monitoramento terrestres, internet/telefonia para celulares, internet das coisas, além do interesse militar para elaboração de radares. Avanços importantes nesse setor tecnológico só foram outorgados, graças ao emprego ostensivo de ressoadores dielétricos (RDs). Esses dispositivos constituem cerâmicas óxidas com baixa perda dielétrica em microondas, com demanda para sua miniaturização. O sistema deverá possuir alta constante dielétrica nesse intervalo e o dispositivo deve ser termicamente estável, ou seja, suas propriedades dielétricas não se alterarão com a temperatura. A busca por materiais de alto desempenho resultou na descoberta das perovskitas ordenadas 1:1 e 1:2, com estequiometria A2BBO6 e A3BB2O9, respectivamente. Tais sistemas ordenam o sítio B, da perovskita ABO3, gerando o empilhamento dos planos cristalinos com B e B, intercalados e na direção [1 1 1]c. Os resultados da literatura mostram que o ordenamento possui papel fundamental na obtenção de ressoadores de baixa perda dielétrica. Ademais, poucos estudos reportam as propriedades dos sistemas contendo os cátions Ca e Nb, no sítio B. Portanto, essa tese dedicou-se à investigação das propriedades dielétricas do sistema Ba3CaNb2O9 e, posteriormente, a modificação desse com a substituição dos cátions Ba2+ por Sr2+ e La3+. As amostras foram preparadas pelo método de reação do estado sólido e, posteriormente, caracterizadas pela difração de raios X, espalhamento Raman, espectroscopia de impedância e desempenho em microondas, além de técnicas complementares como análise térmica, densidade por imersão e microscopia eletrônica de varredura. Os resultados demonstraram a coexistência dos domínios 1:1 e 1:2 no sistema Ba3CaNb2O9, sendo possível manipulá-los mediante condições da sinterização. Microestruturalmente, esses domínios são regiões no cristalito com diferentes ordens catiônicas e, assim, com propriedades cristalográficas e vibracionais diferentes. Pela impedância, notou-se que o ressoador Ba3CaNb2O9 tende a conduzir mais quando possui uma tendência para o domínio 1:1. Tal resultado foi confirmado em microondas, onde a redução da perda dielétrica foi correlacionada à diminuição do domínio 1:1 na estrutura cristalina dos ressoadores. Na solução sólida com Sr2+, uma transição da fase trigonal D3d3 para monoclínica C2h3 foi detectada nos pós-calcinados, sendo oriunda das inclinações octaédricas do sistema de Glazer a0b-b-. As cerâmicas desse sistema foram sinterizadas a 1500 °C por 26 h, cujo resultado ilustrou uma tendência à ordem 1:1 para x ≥ 0,30. No sistema com La3+, observou-se, além da coexistência, os monodomínios 1:1 e 1:2. O sistema com monodomínios 1:1, BaLaCaNbO6 (y = 0,50), evidenciou uma distorção monoclínica intrínseca. Esta distorção foi associada às inclinações octaédricas do sistema de Glazer a0b-b-, reduzindo a simetria da fase cúbica Oh5 para monoclínica C2h3. Por fim, o desempenho como ressoador dielétrico dos sistemas BaLaCaNbO6 e Ba3CaNb2O9 foi avaliado. O primeiro sistema mostrou os seguintes valores: permissividade relativa εg ∼ 26, Qu × fR ∼ 10.506 GHz e coeficiente τf ∼ -55 ppm.K-1. O segundo sistema revelou os dados: permissividade εg ∼ 43, Qu × fR ∼ 15.752 GHz e o coeficiente τf ∼ 278 ppm.K-1. / Dielectric materials for microwave applications play an important role in mobile and satellite communication systems, including terrestrial monitoring, internet/mobile devices, internet of things, as well as the military uses as the radar developments. Advances in this technological field were only possible due to the ostensive use of dielectric resonators (DRs). These devices constitute oxide ceramics with a low dielectric loss in microwave frequency. The system must have high dielectric constant and such a device must be thermally stable. The search for highperformance materials granted the discovery of 1:1 and 1:2 ordered perovskites, with general formula A2BBO6 and A3BB2O9, respectively. These systems depict the B-site ordering of ABO3 perovskite, inducing the crystalline planes stacking in the [1 1 1]c direction. The literature results showed that the ordering plays an essential role in the low loss ceramics. Moreover, few studies reported the features of the systems containing the Ca and Nb cations at the B-site. Therefore, our work drives the dielectric properties of the Ba3CaNb2O9 system and, then, the modification induced by Ba2+ substitution by Sr2+ and La3+. The samples were prepared by the conventional solid-state reaction method and probed by X-ray diffraction, Raman scattering, impedance spectroscopy and microwave performance, as well as other techniques such as thermal analysis, density measurement, and electron microscopy. Our findings elucidated the coexistence of 1:1 and 1:2 domains in Ba3CaNb2O9 ceramics, being possible to manipulate them by sintering conditions. Such an ordered domain denotes regions in the crystallites with different cationic order and with different crystallographic and vibrational behavior. By the impedance spectroscopy, it was observed that Ba3CaNb2O9 ceramics tend to conduct more when they present a tendency towards the 1:1 domains. The earlier result was also confirmed in microwave frequency, in which the dielectric loss decreasing was correlated to the decrease of the 1:1 domain in the crystal structure. In the strontium solid solution, a transition from the D3d3 trigonal phase to the C2h3 monoclinic one was noted in powder samples, being derived from octahedral tilting (a0b-b- Glazer system). In the lanthanum system, besides the coexistence, the monodomains 1:1 and 1:2 were observed. Otherwise, the 1:1 monodomain system, BaLaCaNbO6 (y = 0.50), exhibited an intrinsic monoclinic distortion. This distortion was ascribed to the octahedral tilting (a0b-b- Glazer system), lowering the crystal symmetry from Oh5 cubic phase to the C2h3 monoclinic phase. The dielectric resonator performances of the BaLaCaNbO6 and Ba3CaNb2O9 systems were evaluated. The first system showed the following values: permittivity εg ∼ 26, Qu × fR ∼ 10.506 GHz and coefficient τf ∼ -55 ppm.K-1. The second system exhibited the data: permittivity εg ∼ 43, Qu × fR ∼ 15.752 GHz and coefficient τf ∼ 278 ppm.K-1.
63

Performance Measurement in the eCommerce Industry.

Donkor, Simon 29 April 2003 (has links)
The eCommerce industry introduced new business principles, as well as new strategies for achieving these principles, and as a result some traditional measures of success are no longer valid. We classified and ranked the performance of twenty business-to-consumer eCommerce companies by developing critical benchmarks using the Balanced scorecard methodology. We applied a Latent class model, a statistical model along the Bayesian framework, to facilitate the determination of the best and worst performing companies. An eCommerce site's greatest asset is its customers, which is why some of the most valued and sophisticated metrics used today evolve around customer behavior. The results from our classification and ranking procedure showed that companies that ranked high overall also ranked comparatively well in the customer analysis ranking, For example, Amazon.com, one of the highest rated eCommerce companies with a large customer base ranked second in the critical benchmark developed towards measuring customer analysis. The results from our simulation also showed that the Latent class model is a good fit for the classification procedure, and it has a high classification rate for the worst and best performing companies. The resulting work offers a practical tool with the ability to identify profitable investment opportunities for financial managers and analysts.
64

Efficient Factor Graph Fusion for Multi-robot Mapping

Natarajan, Ramkumar 12 June 2017 (has links)
"This work presents a novel method to efficiently factorize the combination of multiple factor graphs having common variables of estimation. The fast-paced innovation in the algebraic graph theory has enabled new tools of state estimation like factor graphs. Recent factor graph formulation for Simultaneous Localization and Mapping (SLAM) like Incremental Smoothing and Mapping using the Bayes tree (ISAM2) has been very successful and garnered much attention. Variable ordering, a well-known technique in linear algebra is employed for solving the factor graph. Our primary contribution in this work is to reuse the variable ordering of the graphs being combined to find the ordering of the fused graph. In the case of mapping, multiple robots provide a great advantage over single robot by providing a faster map coverage and better estimation quality. This coupled with an inevitable increase in the number of robots around us produce a demand for faster algorithms. For example, a city full of self-driving cars could pool their observation measurements rapidly to plan a traffic free navigation. By reusing the variable ordering of the parent graphs we were able to produce an order-of-magnitude difference in the time required for solving the fused graph. We also provide a formal verification to show that the proposed strategy does not violate any of the relevant standards. A common problem in multi-robot SLAM is relative pose graph initialization to produce a globally consistent map. The other contribution addresses this by minimizing a specially formulated error function as a part of solving the factor graph. The performance is illustrated on a publicly available SuiteSparse dataset and the multi-robot AP Hill dataset."
65

GestÃo integrada: o municÃpio de Icapuà e os programas de administraÃÃo da orla marÃtima. / Integrated management: the municipality of Icapuà and the programs of administration of the maritime shore.

Cristina Maria Aleme Romcy 20 December 2005 (has links)
CoordenaÃÃo de AperfeiÃoamento de NÃvel Superior / A ocupaÃÃo desordenada da orla marÃtima tem provocado conflitos de uso e de degradaÃÃo ambiental tendo como causas o desconhecimento dos bens pÃblicos e dos seus recursos ambientais, como tambÃm a falta de integraÃÃo entre os setores governamentais e a sociedade. Este trabalho contribuiu para o ordenamento costeiro, considerando a complexidade nos processos de integraÃÃo das polÃticas de planejamento e de uso e ocupaÃÃo da orla, tendo como fundamentos bÃsicos metodolÃgicos os princÃpios do desenvolvimento sustentÃvel. Foram realizados estudos relacionados com uma ampla revisÃo bibliogrÃfica sobre planejamento e gestÃo da zona costeira, aliados a pesquisa de campo, aplicaÃÃo de questionÃrios, registros iconogrÃficos e da organizaÃÃo e leitura cartogrÃfica oficial do estado e municÃpio. Com base nestes elementos, apresentou-se uma proposiÃÃo crÃtica do Projeto Orla, contribuindo para promover e efetivar a gestÃo integrada da orla marÃtima nas Ãreas do patrimÃnio da uniÃo. Evidenciou-se, como recomendaÃÃes finais, a necessidade de ampla participaÃÃo social nas propostas e programas de conservaÃÃo da paisagem costeira, da ocupaÃÃo ordenada dos seus espaÃos e do uso dos recursos ambientais mediante a parceria com os trÃs nÃveis de governo. / The disordered occupation of the seashore has been causing usage and environmental degradation conflicts, having as causes the unawareness of the public properties and their environmental resources, as well as the lack of integration between the government sectors and the society. This work aims to contribute to the coastal ordering considering the integration process of the usage and occupation planning policies of the shore, and the sustainable development principles studied through field research, questionnaires, bibliographical surveys, iconographical registrations, and organization and reading of the official cartography of the state and municipality. Based on these elements, the Shore Project promotes the integrated management of the seashore within the union real-estate areas, through its conservation, ordered occupation of their spaces, and usage of the environmental resources through the partnership of the three government levels and the civil society.
66

Shellability of the Bruhat Order on Borel Orbit Closures

January 2013 (has links)
Involutions and fixed-point-free involutions arise naturally as representatives for certain Borel orbits in invertible matrices. Similarly, partial involutions and partial fixed-point-free involutions represent certain Borel orbits in matrices which are not necessarily invertible. Inclusion relations among Borel orbit closures induce a partial order on these discrete parameterizing sets. In this dissertation we investigate the associated order complex of these posets. In particular, we prove that the order complex of the Bruhat poset of Borel orbit closures is shellable in symmetric as well as skew-symmetric matrices. / acase@tulane.edu
67

An Inventory Model With Two Truckload Transportation and Quantity Discounts

Santhanam, Ramesh T 28 October 2005 (has links)
Transportation plays a vital role in the movement of raw materials and finished goods from one place to another. Trucks play a vital role in the movement of materials and are indispensable part of almost every shipment, both domestic and international. On the average, thirty-nine percent of the total logistics cost is spent on transportation. Therefore reducing the transportation cost may significantly reduce the total logistics cost. The total annual logistics cost considered in this research includes ordering cost, material cost, transportation cost and inventory holding cost. The main objective of this research is to develop algorithms for finding the optimal ordering quantity that minimizes total annual logistics cost, when the suppliers offer No quantity discounts All-unit quantity discounts Incremental quantity discounts This research considers truckload transportation where two truck sizes are available. The algorithm developed in this research will identify the optimum ordering quantity and the optimum number of trucks required to ship the ordering quantity. MATLAB programming of the algorithm will analyze the factors that affect that the total annual logistics cost.
68

The organisational and communication implications of electronic ordering systems for hospital pathology services

Georgiou, Andrew January 2009 (has links)
Doctor of Philosophy / Computerised Provider Order Entry (CPOE) systems provide clinicians with the ability to electronically enter hospital orders for laboratory tests and services. CPOE is able to integrate with hospital information systems and provide point of care decision support to users thereby making a potentially significant contribution to the efficiency and effectiveness of care delivery. The evidence of the impact of CPOE systems on pathology services is not extensive and insufficient attention has been paid to their effect on organisational and communication processes. This thesis aimed to investigate the implications of CPOE systems for pathology laboratories, their work processes and relationships with other hospital departments, using comparative examinations to identify the tasks they are involved in and the particular needs the laboratories expect to be filled by the new system. This longitudinal study of a CPOE system was carried out over three years using multiple cases from a hospital pathology service based at a large Sydney teaching hospital. Multi-methods using quantitative and qualitative data were employed to achieve triangulation of data, theory and methods. The findings provide evidence of a significant 14.3% reduction of laboratory turnaround times from 42 to 36 minutes when laboratory data for two months were compared before and after CPOE implementation. The findings also reveal changes in the pattern and organisation of information communication, highlighting transformations in the way that work is planned, negotiated and synchronised. These findings are drawn together in a comprehensive organisational communication framework that is highly relevant for developing a contingent and situational understanding of the impact of CPOE on pathology services.
69

Agent Ordering and Nogood Repairs in Distributed Constraint Solving

Zhou, Lingzhong, n/a January 2006 (has links)
The distributed constraint satisfaction problem is a general formalization used to represent problems in distributed multi-agent systems. A large body of problems in artificial intelligence and computer science can be easily formulated as distributed constraint satisfaction problems. In this thesis we study agent ordering, effects of no-goods, search efficiency and threshold repairing in distributed constraint satisfaction problems and its variants. A summary of contributions is as follows: 1. We present a new algorithm, Dynamic Agent Ordering. A distinctive feature of this algorithm is that it uses the degree of unsatisfiability as a guiding parameter to dynamically determine agent ordering during the search. We show through an empirical study that our algorithm performs better than the existing approaches. In our approach, the independence of agents is guaranteed and agents without neighbouring relationships can run concurrently and asynchronously. (Part of this work was published in the Australian Al Conference (80)). 2. We extend the Dynamic Agent Ordering algorithm by incorporating a novel technique called nogood repairing. This results in a dramatic reduction in the nogoods being stored, and communication costs. In an empirical study, we11 show that this approach outperforms an equivalent static ordering algorithm and a current state-of-the-art technique in terms of execution time, memory usage and communication cost. (Part of this work was published at FLAIRS Conference (81)). Further, we introduce a new algorithm, Over-constrained Dynamic Agent Ordering, that breaks new ground in handling multiple variables per agent in distributed over-constrained satisfaction problems. The algorithm also uses the degree of unsatisfiability as a measure for relaxing constraints, and hence as a way to guide the search toward the best optimal solution(s). By applying our Threshold Repair method, we can solve a distributed constraint satisfaction problem without knowing whether the problem is under- or over-constrained. In an experimental study, we show that the new algorithm compares favourably to an implementation of asynchronous weak commitment search adapted to handle over-constrained problems. (Part of this work was published at the Canadian AI conference (79)).
70

Mössbauer spectroscopy on selectred magnetic compounds

Kalska-Szostko, Beata January 2000 (has links)
<p>The applications of magnetic materials are related to their magnetic and crystal structure as well as electronic properties. In this thesis, mainly experimental methods have been focussed on novel materials and bulk materials. A selection of materials were studied by several techniques like Mössbauer spectroscopy, X-ray and neutron diffraction and magnetisation measurements.</p><p>New technology allow us to prepare artificial materials with unic magnetic properties. Magnetic multilayers are very interesting not only from phenomenological point of view but also as good applications materials. In this work will be shown some results from Fe/V and Fe/Co multilayer system</p><p>The (Fe<sub>1-x</sub>Mn<sub>x</sub>)<sub>3</sub>P system has been studied at both ends of the composition range. At the Fe-rich end, compounds exhibiting ferromagnetic ordering are formed, while at the Mn-rich end, an antiferromagnetic coupling was discovered. The experimental results are supported by theoretical calculations.</p><p>Rare-earth compounds with focus on Fe<sub>0.65</sub>Er<sub>0.2</sub>B<sub>0.15</sub> were studied by means of traditional Mössbauer spectroscopy, Monochromatic Circular Polarized Mössbauer Spectroscopy, X-ray diffraction and magnetic mesurements. This compound shows interesting behaviour of Fe magnetic moment at low and room temperature.</p><p>The first magnetic studies on rhombohedral Li<sub>3</sub>Fe<sub>2</sub>(PO<sub>4</sub>)<sub>3</sub> at low temperature has also been made and an antiferromagnetic structure was revealed.</p>

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