23 research outputs found

    SPICA:revealing the hearts of galaxies and forming planetary systems : approach and US contributions

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    How did the diversity of galaxies we see in the modern Universe come to be? When and where did stars within them forge the heavy elements that give rise to the complex chemistry of life? How do planetary systems, the Universe's home for life, emerge from interstellar material? Answering these questions requires techniques that penetrate dust to reveal the detailed contents and processes in obscured regions. The ESA-JAXA Space Infrared Telescope for Cosmology and Astrophysics (SPICA) mission is designed for this, with a focus on sensitive spectroscopy in the 12 to 230 micron range. SPICA offers massive sensitivity improvements with its 2.5-meter primary mirror actively cooled to below 8 K. SPICA one of 3 candidates for the ESA's Cosmic Visions M5 mission, and JAXA has is committed to their portion of the collaboration. ESA will provide the silicon-carbide telescope, science instrument assembly, satellite integration and testing, and the spacecraft bus. JAXA will provide the passive and active cooling system (supporting the

    The Apertif Surveys:The First Six Months

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    Apertif is a new phased-array feed for the Westerbork Synthesis Radio Telescope (WSRT), greatly increasing its field of view and turning it into a natural survey instrument. In July 2019, the Apertif legacy surveys commenced; these are a time-domain survey and a two-tiered imaging survey, with a shallow and medium-deep component. The time-domain survey searches for new (millisecond) pulsars and fast radio bursts (FRBs). The imaging surveys provide neutral hydrogen (HI), radio continuum and polarization data products. With a bandwidth of 300 MHz, Apertif can detect HI out to a redshift of 0.26. The key science goals to be accomplished by Apertif include localization of FRBs (including real-time public alerts), the role of environment and interaction on galaxy properties and gas removal, finding the smallest galaxies, connecting cold gas to AGN, understanding the faint radio population, and studying magnetic fields in galaxies. After a proprietary period, survey data products will be publicly available through the Apertif Long Term Archive (ALTA, https://alta.astron.nl). I will review the progress of the surveys and present the first results from the Apertif surveys, including highlighting the currently available public data

    Online Advertising Assignment Problems Considering Realistic Constraints

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    학위논문 (박사) -- 서울대학교 대학원 : 공과대학 산업공학과, 2020. 8. 문일경.With a drastic increase in online communities, many companies have been paying attention to online advertising. The main advantages of online advertising are traceability, cost-effectiveness, reachability, and interactivity. The benefits facilitate the continuous popularity of online advertising. For Internet-based companies, a well-constructed online advertisement assignment increases their revenue. Hence, the managers need to develop their decision-making processes for assigning online advertisements on their website so that their revenue is maximized. In this dissertation, we consider online advertising assignment problems considering realistic constraints. There are three types of online advertising assignment problems: (i) Display ads problem in adversarial order, (ii) Display ads problem in probabilistic order, and (iii) Online banner advertisement scheduling for advertising effectiveness. Unlike previous assignment problems, the problems are pragmatic approaches that reflect realistic constraints and advertising effectiveness. Moreover, the algorithms the dissertation designs offer important insights into the online advertisement assignment problem. We give a brief explanation of the fundamental methodologies to solve the online advertising assignment problems in Chapter 1. At the end of this chapter, the contributions and outline of the dissertation are also presented. In Chapter 2, we propose the display ads problem in adversarial order. Deterministic algorithms with worst-case guarantees are designed, and the competitive ratios of them are presented. Upper bounds for the problem are also proved. We investigate the display ads problem in probabilistic order in Chapter 3. This chapter presents stochastic online algorithms with scenario-based stochastic programming and Benders decomposition for two probabilistic order models. In Chapter 4, an online banner advertisement scheduling model for advertising effectiveness is designed. We also present the solution methodologies used to obtain valid lower and upper bounds of the model efficiently. Chapter 5 offers conclusions and suggestion for future studies. The approaches to solving the problems are meaningful in both academic and industrial areas. We validate these approaches can solve the problems efficiently and effectively by conducting computational experiments. The models and solution methodologies are expected to be convenient and beneficial when managers at Internet-based companies place online advertisements on their websites.온라인 커뮤니티의 급격한 성장에 따라, 많은 회사들이 온라인 광고에 관심을 기울이고 있다. 온라인 광고의 장점으로는 추적 가능성, 비용 효과성, 도달 가능성, 상호작용성 등이 있다. 온라인에 기반을 두는 회사들은 잘 짜여진 온라인 광고 할당결정에 관심을 두고 있고, 이는 광고 수익과 연관될 수 있다. 따라서 온라인 광고 관리자는 수익을 극대화 할 수 있는 온라인 광고 할당 의사 결정 프로세스를 개발하여야 한다. 본 논문에서는 현실적인 제약을 고려한 온라인 광고 할당 문제들을 제안한다. 본 논문에서 다루는 문제는 (1) adversarial 순서로 진행하는 디스플레이 애드문제, (2) probabilistic 순서로 진행하는 디스플레이 애드문제 그리고 (3) 광고효과를 위한 온라인 배너 광고 일정계획이다. 이전에 제안되었던 광고 할당 문제들과 달리, 본 논문에서 제안한 문제들은 현실적인 제약과 광고효과를 반영하는 실용적인 접근 방식이다. 또한 제안하는 알고리즘은 온라인 광고 할당 문제의 운영관리에 대한 통찰력을 제공한다. 1장에서는 온라인 광고 할당 문제에 대한 문제해결 방법론에 대해 간단히 소개한다. 더불어 연구의 기여와 개요도 제공된다. 2장에서는 adversarial 순서로 진행하는 디스플레이 애드문제를 제안한다. worst-case를 보장하는 결정론적 알고리즘을 설계하고, 이들의 competitive ratio를 증명한다. 더불어 문제의 상한도 입증된다. 3장에서는 probabilistic 순서로 진행하는 디스플레이 애드문제를 제안한다. 시나리오 기반의 확률론적 온라인 알고리즘과 Benders 분해방법을 혼합한 추계 온라인 알고리즘을 제시한다. 4장에서는 광고효과를 위한 온라인 배너 광고 일정계획을 설계한다. 또한, 모델의 유효한 상한과 하한을 효율적으로 얻는 데 사용되는 문제해결 방법론을 제안한다. 5장에서는 본 논문의 결론과 향후 연구를 위한 방향을 제공한다. 본 논문에서 제안하는 문제해결 방법론은 학술 및 산업 분야 모두 의미가 있다. 수치 실험을 통해 문제해결 접근 방식이 문제를 효율적이고 효과적으로 해결할 수 있음을 보인다. 이는 온라인 광고 관리자가 본 논문에서 제안하는 문제와 문제해결 방법론을 통해 온라인 광고 할당관련 의사결정을 진행하는 데 있어 도움이 될 것으로 기대한다.Chapter 1 Introduction 1 1.1 Display Ads Problem 3 1.1.1 Online Algorithm 4 1.2 Online Banner Advertisement Scheduling Problem 5 1.3 Research Motivations and Contributions 6 1.4 Outline of the Dissertation 9 Chapter 2 Online Advertising Assignment Problem in Adversarial Order 12 2.1 Problem Description and Literature Review 12 2.2 Display Ads Problem in Adversarial Order 15 2.3 Deterministic Algorithms for Adversarial Order 17 2.4 Upper Bounds of Deterministic Algorithms for Adversarial Order 22 2.5 Summary 28 Chapter 3 Online Advertising Assignment Problem in Probabilistic Order 30 3.1 Problem Description and Literature Review 30 3.2 Display Ads Problem in Probabilistic Order 33 3.3 Stochastic Online Algorithms for Probabilistic Order 34 3.3.1 Two-Stage Stochastic Programming 35 3.3.2 Known IID model 37 3.3.3 Random permutation model 41 3.3.4 Stochastic approach using primal-dual algorithm 45 3.4 Computational Experiments 48 3.4.1 Results for known IID model 55 3.4.2 Results for random permutation model 57 3.4.3 Managerial insights for Algorithm 3.1 59 3.5 Summary 60 Chapter 4 Online Banner Advertisement Scheduling for Advertising Effectiveness 61 4.1 Problem Description and Literature Review 61 4.2 Mathematical Model 68 4.2.1 Objective function 68 4.2.2 Notations and formulation 72 4.3 Solution Methodologies 74 4.3.1 Heuristic approach to finding valid lower and upper bounds 75 4.3.2 Hybrid tabu search 79 4.4 Computational Experiments 80 4.4.1 Results for problems with small data sets 82 4.4.2 Results for problems with large data sets 84 4.4.3 Results for problems with standard data 86 4.4.4 Managerial insights for the results 90 4.5 Summary 92 Chapter 5 Conclusions and Future Research 93 Appendices 97 A Initial Sequence of the Hybrid Tabu Search 98 B Procedure of the Hybrid Tabu Search 99 C Small Example of the Hybrid Tabu Search 101 D Linearization Technique of Bilinear Form in R2 104 Bibliography 106Docto

    Análise de meta-modelos de escalonamento da produção para problemas em ambientes orientados ao produto

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    Dissertação de mestrado em Engenharia de SistemasNum mercado orientado a satisfazer as necessidades do consumidor, os padrões de qualidade aumentam. Assim sendo a eficiência é um dos fatores que permite ter bons resultados face à concorrência. O aumento da necessidade de produção em altas quantidades e a flexibilidade personalização dos produtos para satisfazer as preferências do consumidor eleva a importância do planeamento da produção. Para auxiliar a implementação da gestão da produção são constantemente desenvolvidas novas tecnologias, dando origem a híbridos de metodologias analíticas e simulação. Estes métodos que combinam as duas abordagens conseguem minimizar as desvantagens dos métodos por separado originando mais rapidamente ou eficientemente soluções. Nesta dissertação são estudadas e analisadas várias configurações de linha de um sistema de produção através de um metamodelo. Esta metodologia foi aplicada a uma família de produtos com vários níveis de dissimilitude da sequência de produção de cada produto. O principal foco na abordagem é o modelo de simulação, do qual considerando os parâmetros e restrições dos cenários analisados é pretendido verificar se existem relações entre as várias variáveis do sistema. São estudadas quatro configurações distintas sendo a linha simples, paralela, reentry e skip. A implementação do metamodelo é realizada em Símio e tem como auxílio o uso do UQLab para facilitar a análise dos resultados.In a market oriented to meeting consumer needs, quality standards are raised. Therefore, efficiency is one of the factors that allows us to have good results in relation to the competition. The increased need for high-volume production and the flexibility to customize products to meet consumer needs increases the importance of production scheduling. To assist the implementation of production management, new technologies are developed, giving rise to hybrids of analytical and simulation methodologies. These combined minimize the disadvantages of the separate methods, originating solutions more quickly or efficiently solutions. In this dissertation, several line configurations of a production system are studied and analyzed using a metamodel. The methodology is applied to a product family with different levels of dissimilarity in the production sequence of the product of each product. The main focus in the approach is the simulation model, which parameter of parameters and restrictions of the scenarios is intended to verify if there are relations between the various variables of the system. For the family of products, four different configurations are studied, being the simple, parallel, reentry and skip flow shop. The implementation of the metamodel is carried out in Simio and is aided by the use of UQLab to facilitate the analysis of the results

    Melhoria do Sistema de Planeamento de Produção

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    No contexto industrial atual, a capacidade de adaptação a uma realidade em mudança constante é vital para a diferenciação de uma organização. Este atributo torna-se ainda mais fulcral num ambiente Make to Order, na medida em que a exigência dos clientes, que procuram produtos entregues rapidamente, com qualidade, diversidade e baixo custo, é cada vez maior. As empresas devem, portanto, ser versáteis e eficientes simultaneamente. A presente dissertação descreve o projeto realizado numa linha de transformação de blocos de cortiça, com o propósito de melhorar o sistema de planeamento existente. Esta linha, onde o tipo de implantação é job-shop, era caracterizada pela falta de critério no balanceamento das laminadoras, assim como na programação da produção do bottleneck. Além disso, a existência de diversas gamas operatórias e tempos de processamento desatualizados em sistema, contribuía para uma maior desorganização no processo de planeamento. Neste sentido, o foco do projeto incidiu no desenvolvimento de uma ferramenta de apoio à decisão que permitisse aos utilizadores, seja o planeador ou o supervisor da área em questão, não só automatizar o processo de programação da produção, como também ter como output um sequenciamento otimizado face àquele que estava inicialmente implementado. Como tal, foi feito um mapeamento do processo produtivo, desde a análise dos equipamentos ao estudo das gamas operatórias existentes. De seguida foi desenvolvida uma ferramenta, em VBA-Excel, que possibilitasse a adaptação ao contexto real da linha, através da definição de determinados parâmetros por parte do utilizador, e a simplicidade de utilização, de forma a que pudesse, de facto, ajudar no processo de decisão. Por fim, o desenvolvimento de heurísticas com o objetivo de reduzir tempos de paragem dos equipamentos. No final, foi concluído que o processo de programação da produção nesta linha através da ferramenta desenvolvida pode contribuir para a redução dos tempos até então despendidos pelo supervisor para a realização da mesma de forma manual. Por outro lado, o estudo realizado contribuiu para corrigir estruturas de produto e definir novos critérios de balanceamento na linha de produção.In the current industrial context, the ability to adapt to a constantly changing reality is vital to the differentiation of an organization. This attribute becomes even more critical in a Make to Order environment, in that customers’ requirements in delivery times, product quality and diversity and low cost are increasing. Therefore, companies must be versatile and efficient at the same time. This dissertation describes the project that was carried out in a cork block transformation production line, where the goal was to improve the existing production planning system. This production line, which follows a job-shop model, was characterized by the lack of discretion in balancing production, as well as in the bottleneck production scheduling. In addition, the existence of different operative ranges and outdated system processing times contributed to a greater disorganization in the production planning process. In this sense, the focus of the project was on the development of a decision support tool that allows users, either the planner or the supervisor, not only to automate the production scheduling process, but also to have as an output an optimized scheduling against the one that was initially implemented. As such, a production process mapping was done, from the analysis of the equipment to the study of the existing operative ranges. Next, a VBA-Excel tool was developed that would allow the adaptation to the actual context of the line, through the definition of certain parameters by the user, and the simplicity of use, so that it could actually help in the decision-making process. Finally, the development of heuristics in order to reduce equipment downtime In the end, it was concluded that the production scheduling process in this line through the developed tool can contribute to the reduction of the times previously spent by the supervisor to carry out the same manually. On the other hand, the study contributed to correct product structures and to define new balancing criteria in the production line
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