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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.
11

Krovinių srautų modeliavimas uždaroje logistikos sistemoje / Modeling of load flows in clique logistic system

Jusevičienė, Kristina 06 June 2006 (has links)
We present an optimization procedure for solving the vehicle routing problem with a fixed heterogeneous fleet of vehicle. We want to minimize the passage price. We look and probe these methods: minimal element, Vogel’s Approximation and heuristic. The modeling vehicle routing problem is based on mathematical formulation. This paper present very well known problems – TSP Traveling Salesperson Problem and M-TSP. Vehicle routing problem is liked M-TSP with some specification, vehicle with a fixed carrying capacity must deliver order of goods to n customers from a single depot. Knowing the distance between customers, the problem is to find tours for the vehicles in such a way that: the total distance traveled by the vehicles is minimized, only one vehicle handles the deliveries for a given customer, the total quantity of goods that a single vehicle delivers cannot be larger than cars capacity.
12

OPTIMAL DISTRIBUTED GENERATION SIZING AND PLACEMENT VIA SINGLE- AND MULTI-OBJECTIVE OPTIMIZATION APPROACHES

Darfoun, Mohamed 09 July 2013 (has links)
Numerous advantages attained by integrating Distributed Generation (DG) in distribution systems. These advantages include decreasing power losses and improving voltage profiles. Such benefits can be achieved and enhanced if DGs are optimally sized and located in the systems. In this thesis, the optimal DG placement and sizing problem is investigated using two approaches. First, the optimization problem is treated as single-objective optimization problem, where the system’s active power losses are considered as the objective to be minimized. Secondly, the problem is tackled as a multi-objective one, focusing on DG installation costs. These problems are formulated as constrained nonlinear optimization problems using the Sequential Quadratic Programming method. A weighted sum method and a fuzzy decision-making method are presented to generate the Pareto optimal front and also to obtain the best compromise solution. Single and multiple DG installation cases are studied and compared to a case without DG, and a 15-bus radial distribution system and 33-bus meshed distribution system are used to demonstrate the effectiveness of the proposed methods.
13

Analysis and Development of Error-Job Mapping and Scheduling for Network-on-Chips with Homogeneous Processors

Karlsson, Erik January 2010 (has links)
Due to increased complexity of today’s computer systems, which are manufactured in recent semiconductor technologies, and the fact that recent semiconductor technologies are more liable to soft errors (non-permanent errors) it is inherently difficult to ensure that the systems are and will remain error-free. Depending on the application, a soft error can have serious consequences for the system. It is therefore important to detect the presence of soft errors as early as possible and recover from the erroneous state and maintain correct operation. There is an entire research area devoted on proposing, implementing and analyzing techniques that can detect and recover from these errors, known as fault tolerance. The drawback of using faulttolerance is that it usually introduces some overhead. This overhead may be for instance redundant hardware, which increases the cost of the system, or it may be a time overhead that negatively impacts on system performance. Thus a main concern when applying fault tolerance is to minimize the imposed overhead while the system is still able to deliver the correct error-free operation. In this thesis we have analyzed one well known fault tolerant technique, Rollback-Recovery with Checkpointing (RRC). This technique is able to detect and recover from errors by taking and storing checkpoints during the execution of a job.Therefore we can think as if a job is divided into a number of execution segments and a checkpoint is taken after executing each execution segment. This technique requires the job to be concurrently executed on two processors. At each checkpoint, both processors exchange data, which contains enough information for the job’s state. The exchanged data are then compared. If the data differ, it means that an error is detected in the previous execution segment and it is therefore re-executed. If the exchanged data are the same, it means that no errors are detected and the data are stored as a safe point from which the job can be restarted later. A time overhead due to exchanging data between processors is therefore introduced, and it increases the average execution time of a job, i.e. the average time required for a given job to complete. The overhead depends on the number of links that has to be traversed (due to data exchange) after each execution segment and the number of execution segments that are needed for the given job. The number of links that has to be traversed after each execution segment is twice the distance between the processors that are executing the same job concurrently. However, this is only true if all the links are fully functional. A link failure can result in a longer route for communication between the processors. Even though all links arefully functional, the number of execution segments still depends on error-free probabilities of the processors, and these error-free probabilities can vary between processors. This implies that the choice of processors affects the total number of links the communication has to traverse. Choosing two processors with higher error-free probability further away from eachother increases the distance, but decreases the number of execution segments, which can result in a lower overhead. By carefully determining the mapping for a given job, one can decrease the overhead, hence decreasing the average execution time. Since it is very common to have a larger number of jobs than available resources, it is not only important to find a good mapping to decrease the average execution time for a whole system, but also a good order of execution for a given set jobs (scheduling of the jobs). We propose in this thesis several mapping and scheduling algorithms that aim to reduce the average execution time in a fault-tolerant multiprocessor System-on-Chip, which uses Network-on-Chip as an underlying interconnect architecture, so that the fault-tolerant technique (RRC) can perform efficiently.
14

Strategies to Minimize Perishable Food Loss in the Retail Grocery Business

Aleruchi, Thankgod Chukwumeka 01 January 2019 (has links)
Supply chain managers in the retail grocery industry face significant challenges in reducing the wastage of perishable food. Perishable food spoilage and deterioration in the retail grocery industry result in a significant loss of profitability and consumer satisfaction. The purpose of this multiple case study was to explore the strategies that supply chain managers in the retail grocery business used to minimize perishable food loss. The perishable inventory theory was used as the conceptual framework. Data were collected from semistructured interviews with 6 Pennsylvania retail grocery supply chain managers who implemented strategies to minimize perishable food loss and from organizational documents. Data analysis was carried out using Yin's 5-step process of compiling, disassembling, reassembling, interpreting, and concluding data. The 3 emergent themes resulting from data analysis were inventory strategy, logistics and deliveries strategy, and information technology strategy. Member checking occurred after transcription and summarization of the interview data. The findings indicated that supply chain managers use first-in-first-out approaches to inventory management, rotation, replenishment, information sharing, and on-time purchasing to minimize perishable food loss. The findings and recommendations of this study might be valuable to supply chain management and retail grocery leaders to create strategic solutions to mitigate the loss of perishable food. The findings of this study might contribute to positive social change through the reduction of perishable food loss, an increased supply of food, lower retail prices to the consumer, and improved customer satisfaction.
15

A web portal with usersubmitted content : Creating a web portal and minimizing its need for administrative work

Winge, Daniel, Winge, Christer January 2017 (has links)
A web portal that publicly displays user-submitted content requires administration in order to ensure undesired content, that is potentially malicious, is excluded. Other administrative aspects that come with a web portal with user-submitted content include user-support and service maintenance. This project was formed in part to develop a new version of an existing web portal for advertising degree projects. The goal of the project is to develop an improved version of the old web portal and ensure that the new version requires as little manual administration work as possible. As how to minimize administration for this type of service was deemed unknown, this thesis takes an inductive approach to exploring how to minimize administration for a web portal with user-submitted content. This thesis results in the presentation of a web portal with new functionality and modified in aspects that the product owner wanted improved. The visual layout is presented along with information on what parts were reused from the old version of the web portal. Design choices that were made with a focus on minimizing administration and design choices in general that were deemed important are presented and motivated. Finally, the thesis concludes that possible areas where administrative work could be reduced depends heavily on the requirements set on the web portal and that the methods used in this thesis were successful in identifying administrative work aspects that can be reduced or eliminated on the web portal developed in this project. It is also concluded that sufficiently advanced automated systems could be useful in reducing the administrative work needed by any type of web portal with user-submitted content. / En webbportal som publikt visar användarskapat innehåll kräver administration för att försäkra att oönskat innehåll, som potentiellt är illvillig, exkluderas. Andra administrativa aspekter som medföljer en webbportal med användarskapat innehåll, inkluderar användarsupport och underhåll av tjänsten. Detta projekt skapades delvis för att utveckla en ny version av en redan existerande webbportal som används för annonsering av examensarbeten.Målet med projektet är att utveckla en förbättrad version av den gamla webbportalen och försäkra att den nya versionen kräver så lite manuellt administrativt arbete som möjligt. Hur minimering av administrativt arbete åstadkoms för denna typ av tjänst ansågs vara okänt, därav valdes ett induktivt tillvägagångssätt till detta projekt för att undersöka hur mängden administrativt arbete minimeras för en webbportal vars innehåll skapas av dess användare. Projektet resulterar i presentationen av en webbportal med ny funktionalitet med modifieringar inom olika aspekter beroende på det som efterfrågats av projektbeställaren. Visuella uppbyggnaden presenteras tillsammans med information angående vilka delar som återanvändes från den gamla version av webbportalen. Designval med fokus på minimering av administrativt arbete samt även generella designval som ansågs viktiga, presenteras och motiveras. Slutligen drar studien slutsatsen att möjliga områden där det administrativa arbetet kan reduceras till stor del beror på kraven satta för webbportalen och att metoderna som användes i denna studie var framgångsrika i att identifiera de aspekter av administrativt arbete som kan reduceras eller elimineras från webbportalen som utvecklades i detta projekt. Slutsatsen dras även att tillräckligt sofistikerade automatiska system kan vara användbara för att reducera administrativt arbete för webbportaler med användarskapat innehåll.
16

Causes of and solutions to reduce excess material in production processes : A study of electrical motors and generators at ABB Machines / Orsaker och lösningar för att minska överblivet material i produktonsprocessen av elektriska motorer och generatorer

Fager, Wilma, Engberg, Hanna January 2023 (has links)
This thesis focus on the investigation of material usage in the production processes of electrical motors and generators at ABB Machines, a company based in Västerås, Sweden. The study aims to understand the reasons for the occurrence of excess material after the assembly of a motor or generator and explore possible solutions to minimize its occurrence. In this study, excess material is defined as the components which was intended to be used in the final assembly of a machine but that has for some reason not been used. The components which qualifies as being defined as excess materials are components which are in the same functioning state as when they were delivered from the supplier, in other words components which has not been processed nor damaged. Further, the components defined as excess materials are only the components, after a machine has been fully assembled, which has been gathered by the production personnel working at the final assembly in pallets. For example, this can be components like screws, tube fittings and cap nuts.  The research method employed in this study was a mix of different methodologies. Five methods, a literature review, registration of materials, interviews, observations and focus groups were used to collect information and data. Thereafter, the observations, interviews and focus groups results were processed through a thematic analysis. The collected quantitative data was analysed through a quantitative analysis. With the collected and summarized information, discussions were held and conclusions were drawn regarding the research questions.  The study reveals several reasons for the occurrence of excess material in manufacturing and these include:  Substitution of material in production: Material substitutions during the production process contribute to the generation of excess material. Errors in drawing material and deficiencies in concept generation: Mistakes in the design phase and concept generation lead to the generation of excess material. Least possible order quantity exceeds the actual need: Ordering minimum quantities that exceed the actual requirements result in excess material. Problems with steering in the ERP system: Issues with the Enterprise Resource Planning system affect material management and contribute to excess material. Excess material is not a prioritized area: The management’s lack of focus on minimizing excess material leads to its occurrence. Uncertainties in stock level: Lack of accurate stock level information causes overstocking and results in excess material.  The potential solutions to address excess material in the manufacturing of electrical motors and generators can be grouped into the following categories: storage, order quantity, goods arrival structure, preparations, and general routines.  Storage: Include stocking frequently used materials, reducing the variety of items in stock to minimize substitutions, introducing specific storage locations for large projects, and implementing flexible warehousing. Order quantity: Involve trimming order quantities, improving the handling of "Dummy purchases", and splitting materials upon arrival for multiple machines in a project. Goods arrival structure: Focus on reviewing pick order sizes, establishing clearer loading systems, controlling material allocation, and synchronizing the release of pick orders. Preparations: This solution include facilitating engineering changes in production groups, streamlining part number reduction, and limiting construction items within categories. General routines: Involves checking the usability of remaining materials, collaborating with fitters and production staff to optimize processes and material choices, reporting material substitutions, and systematically tracing excess material in a database. Uncertainties in stock level: Lack of accurate stock level information causes overstocking and results in excess material.
17

A Simulation and Optimization Study of Spherical Perfectly Matched Layers

Bao, Wentao 18 October 2017 (has links)
No description available.
18

Programação Linear: uma proposta de abordagem no ensino médio / Linear programming: a proposal of approach in high school

Pinheiro, Leandro da Silva 16 June 2016 (has links)
Made available in DSpace on 2016-08-17T13:45:25Z (GMT). No. of bitstreams: 1 Leandro da Silva Pinheiro.pdf: 12011503 bytes, checksum: cfb85a56c46d3b7b25de578ead063b72 (MD5) Previous issue date: 2016-06-16 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Linear Programming problems will be broach in this work together with some ways to find their solutions. Graphically, using geometric figures such as Geogebra, algebraic solutions and, at least, it will be described the use of the tool "Solver"of the Cal spreedsheet of the LibreOffice, that it is easy tool and application in larger problems, relating to the matter worked in high school content, making analogies with situations of applications of this theory in eveyday life of the student without live of highlight the presentation of the great tool that this theory can display and be of geat importance in other areas of knowledge, providing the student with a greater and more "tangible" view of mathmatics as a tool for implementing. / Os problemas de Programação Linear serão abordados neste trabalho juntamente com algumas maneiras de encontrar suas soluções. Graficamente utilizando recursos geométricos como o Geogebra, soluções algébricas e por último será descrita a utilização da ferramenta "Solver" da planilha Calc do LibreOffice, que se trata de uma ferramenta de fácil utilização e aplicação em problemas de dimensões maiores, relacionando com assuntos trabalhados nos conteúdos do Ensino Médio, fazendo analogias com situações de aplicações dessa teoria na vida cotidiana do aluno sem deixar de destacar a apresentação da grandiosa ferramenta que essa teoria pode exibir e ser de grande importância em outras áreas de conhecimento, proporcionando ao aluno uma visão maior e mais "palpável" da Matemática como instrumento de aplicação.
19

A Mathematical Model of Graphene Nanostructures

Rhoads, Daniel Joseph 15 September 2015 (has links)
No description available.
20

Optimal Portfolio Re-Balancing on Fixed Periods using a Cost/Risk Adaptation Model and Stochastic Optimization.

Ehn, Max, Jämte, Marcus January 2023 (has links)
In this thesis we investigate the problem of portfolio re-balancing for fixed periods using a cost/risk adaptation model and stochastic optimization. The cost/risk adaptation model takes theory of optimal liquidity costs and risk preference to build a universe in which we try to find better strategies than conventional ones. The results are focused on the comparison between the conventional execution strategies versus our developed model. We have found that our model outperforms the conventional methods for all assets that has been evaluated, and especially for investors whom value exposure to the markets higher.

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