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  • Publication . Report . 1989
    Closed Access English
    Country: Netherlands
  • Closed Access English
    Country: Netherlands
  • Open Access English
    Authors: 
    Congying Han; Lijun Xu; Guoping He;
    Publisher: COMPUTING AND INFORMATICS

    This paper considers the problem of mining recent frequent itemsets over data streams. As the data grows without limit at a rapid rate, it is hard to track the new changes of frequent itemsets over data streams. We propose an efficient one-pass algorithm in sliding windows over data streams with an error bound guarantee. This algorithm does not need to refer to obsolete transactions when they are removed from the sliding window. It exploits a compact data structure to maintain potentially frequent itemsets so that it can output recent frequent itemsets at any time. Flexible queries for continuous transactions in the sliding window can be answered with an error bound guarantee.

  • English
    Authors: 
    SATO, KAIJI;
  • Publication . Master thesis . 2017
    Open Access English
    Authors: 
    Al Dalwi, Kameran Kamal Salman;
    Publisher: Fen Bilimleri Enstitüsü

    Bu tezin amacı Bazyan Doğal Gaz Güç Santralinin (BGPP) modellemesini ve benzetim çalışmasını yapmaktır. Dünyanın gelişen bölgelerindeki enerji talebi son yıllarda belirgin bir artış göstermiştir. Bundan dolayı, yüksek verim, belirgin güç çıkışı, düşük çevre kirlilik emisyonu ve mevcut yakıtların muhtemel kullanımları için düşük işletme ve bakım maliyetlerine sahip güç üretim santrallerini kullanmak önemlidir. Endüstriyel gaz tribünleri güç üretimi için kurulu teknolojilerden bir tanesidir. Güç tedarik sistemleri enerji system elemanlarının kesin modellerine ihtiyaç duyar. Uyarıcı, hız control ve gaz tribünü üretim ünitelerinin önemli bileşenleridir. İlk olarak tribünün her bir parçası bir transfer fonksiyonu ile tanımlanmış ve daha sonra ise blok model oluşturulmuştur. Tribüne ek olarak, güç sistemi dengeleyicisi (PSS2B)'ne sahip IEEE AC7B tipi uyartım sistemi, senkron jeneratör ve bir transformatör benzetim çalışmalarında dikkate alınmıştır. Bu model daha sonra BGPP üreticilerinin veri listelerinden alınmış gerçek veriler kullanılarak Irakta yeni inşa edilmiş BGPP'ye uyarlanmıştır. Benzetim için istasyon bir yüke bağlanmıştır. Benzetim çalışmaları küçük sinyal bozucuları altında uygulanmıştır. Örneğin, birim-adım denetleyici değişikliği ve bununla birlikte toprak arızası ve üç-faz arıza gibi büyük bozucu şartlar. Her adımda rotor açısı, ivmelenen güç, bağlantı gerilimi ve rotor hızı gibi farklı sistem değişkenleri kaydedilmiş ve çizilmiştir. The aim of this thesis is to investigate the modeling and simulation of the Bazyan gas power plant (BGPP). The demand for energy in the developing regions of the world has shown a clear increase in the recent past. Therefore, it is important to use power generations that have high efficiency and specific power output, low pollutant emissions and low operating and maintenance costs for possible use of available fuels. Industrial gas turbines are one of the established technologies for power generation. Power supply systems require the exact models of energy system elements. Exciter, speed control and gas turbine are important components of the production units. First, each part of the turbine is described by its transfer function, and then the block model is thoroughly built. In addition to the turbine, the IEEE AC7B excitation system with an Power system stabilizer (PSS2B), a synchronous generator and a transformer are considered in simulation studies. This model is then adapted to the newly installed gas power plant in the north of Iraq, called Bazyan Gas Power Plant (BGPP), using real data from the data sheets of the BGPP manufacturers. For the simulation, the station is connected to a load. Simulation studies are carried out under small signal disturbances, For example, a unit-step controller change, as well as large disturbing conditions such as ground fault and three phase faults. In each step, various system variables such as rotor angle, acceleration power, connection voltage and rotor speed are recorded and plotted. 113

  • Publication . Article . 2008
    Open Access English
    Authors: 
    Ararat, Melsa; Yurtoglu, B.Burcin;
    Publisher: Baskent University
    Country: Turkey

    This survey gives an overview of the current state of knowledge on the question whether corporate governance structures worldwide are determinants of differences in economic performance. We look at the identities of owners, monitoring boards, and legal systems and argue that some though not all corporate governance structures give rise to differences in performance. In doing that we also look at the impact of the degree of competition in product markets on governance structures. The paper ends with a tentative outlook as to the prospects of corporate governance structures converging worldwide.

  • Open Access English
    Authors: 
    Troupin, Charles; Beltran, Joan Pau; Frontera, Biel; Gómara, Sonia; Gomila, Miquel; Krietemeyer, Andreas; Muñoz, Cristian; Rújula, Miquel Àngel; Serra, Inma; Tintoré, Joaquín;
    Publisher: Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (IT)
    Country: Belgium
  • Publication . Other literature type . 2006
    Open Access English
    Authors: 
    Terzi, Evimaria;
    Publisher: Helsingin yliopisto
    Country: Finland

    The analysis of sequential data is required in many diverse areas such as telecommunications, stock market analysis, and bioinformatics. A basic problem related to the analysis of sequential data is the sequence segmentation problem. A sequence segmentation is a partition of the sequence into a number of non-overlapping segments that cover all data points, such that each segment is as homogeneous as possible. This problem can be solved optimally using a standard dynamic programming algorithm. In the first part of the thesis, we present a new approximation algorithm for the sequence segmentation problem. This algorithm has smaller running time than the optimal dynamic programming algorithm, while it has bounded approximation ratio. The basic idea is to divide the input sequence into subsequences, solve the problem optimally in each subsequence, and then appropriately combine the solutions to the subproblems into one final solution. In the second part of the thesis, we study alternative segmentation models that are devised to better fit the data. More specifically, we focus on clustered segmentations and segmentations with rearrangements. While in the standard segmentation of a multidimensional sequence all dimensions share the same segment boundaries, in a clustered segmentation the multidimensional sequence is segmented in such a way that dimensions are allowed to form clusters. Each cluster of dimensions is then segmented separately. We formally define the problem of clustered segmentations and we experimentally show that segmenting sequences using this segmentation model, leads to solutions with smaller error for the same model cost. Segmentation with rearrangements is a novel variation to the segmentation problem: in addition to partitioning the sequence we also seek to apply a limited amount of reordering, so that the overall representation error is minimized. We formulate the problem of segmentation with rearrangements and we show that it is an NP-hard problem to solve or even to approximate. We devise effective algorithms for the proposed problem, combining ideas from dynamic programming and outlier detection algorithms in sequences. In the final part of the thesis, we discuss the problem of aggregating results of segmentation algorithms on the same set of data points. In this case, we are interested in producing a partitioning of the data that agrees as much as possible with the input partitions. We show that this problem can be solved optimally in polynomial time using dynamic programming. Furthermore, we show that not all data points are candidates for segment boundaries in the optimal solution.

  • Open Access English
    Authors: 
    Montes Luján, Héctor Guillermo;
    Publisher: Uniandes

    The wind power penetration into the system, as other intermittent energy sources, have impacts in grid frequency performance that lead to increase system reserve and to reduce the power extraction in the wind turbines. In this document, an integration analysis of the Battery Energy Storage System (BESS) is presented with its dynamics characteristics, This in order to identify the optimal size of an aggregated system in order to support frequency regulation. Once the large potential for the provision of frequency control services is identified, in this document the batteries are used to increase the frequency performance of the grid. The primary frequency control presented takes into account the dynamic response of the integrated system with wind turbines and BESS, while the LFC have a robust performance due to system inertia uncertainties. La integración de la energía eólica en la red, como otras fuentes de energía intermitentes, tiene un impacto en el desempeño del control de frecuencia del sistema que conduce al aumento en la reserva del sistema y la reducción de la extracción de energía en las turbinas eólicas. En este documento se analiza el gran potencial de los Sistemas de Almacenamiento Energético con Baterías (BESS) para la provisión de servicios de control de frecuencia, y se presenta un desarrollo metodológico para el dimensionamiento óptimo. El análisis presentado toma en cuenta la respuesta dinámica del sistema integrado con aerogeneradores y BESS, y los beneficios sociales que se pueden obtener en los mercados de electricidad mediante la implementación de estos sistemas. Magíster en Ingeniería Eléctrica Maestría

  • Publication . Book . 2014
    Restricted English
    Publisher: Kölner Wissenschaftsverlag
    Country: Denmark
Include:
28,601,548 Research products, page 1 of 2,860,155
  • Publication . Report . 1989
    Closed Access English
    Country: Netherlands
  • Closed Access English
    Country: Netherlands
  • Open Access English
    Authors: 
    Congying Han; Lijun Xu; Guoping He;
    Publisher: COMPUTING AND INFORMATICS

    This paper considers the problem of mining recent frequent itemsets over data streams. As the data grows without limit at a rapid rate, it is hard to track the new changes of frequent itemsets over data streams. We propose an efficient one-pass algorithm in sliding windows over data streams with an error bound guarantee. This algorithm does not need to refer to obsolete transactions when they are removed from the sliding window. It exploits a compact data structure to maintain potentially frequent itemsets so that it can output recent frequent itemsets at any time. Flexible queries for continuous transactions in the sliding window can be answered with an error bound guarantee.

  • English
    Authors: 
    SATO, KAIJI;
  • Publication . Master thesis . 2017
    Open Access English
    Authors: 
    Al Dalwi, Kameran Kamal Salman;
    Publisher: Fen Bilimleri Enstitüsü

    Bu tezin amacı Bazyan Doğal Gaz Güç Santralinin (BGPP) modellemesini ve benzetim çalışmasını yapmaktır. Dünyanın gelişen bölgelerindeki enerji talebi son yıllarda belirgin bir artış göstermiştir. Bundan dolayı, yüksek verim, belirgin güç çıkışı, düşük çevre kirlilik emisyonu ve mevcut yakıtların muhtemel kullanımları için düşük işletme ve bakım maliyetlerine sahip güç üretim santrallerini kullanmak önemlidir. Endüstriyel gaz tribünleri güç üretimi için kurulu teknolojilerden bir tanesidir. Güç tedarik sistemleri enerji system elemanlarının kesin modellerine ihtiyaç duyar. Uyarıcı, hız control ve gaz tribünü üretim ünitelerinin önemli bileşenleridir. İlk olarak tribünün her bir parçası bir transfer fonksiyonu ile tanımlanmış ve daha sonra ise blok model oluşturulmuştur. Tribüne ek olarak, güç sistemi dengeleyicisi (PSS2B)'ne sahip IEEE AC7B tipi uyartım sistemi, senkron jeneratör ve bir transformatör benzetim çalışmalarında dikkate alınmıştır. Bu model daha sonra BGPP üreticilerinin veri listelerinden alınmış gerçek veriler kullanılarak Irakta yeni inşa edilmiş BGPP'ye uyarlanmıştır. Benzetim için istasyon bir yüke bağlanmıştır. Benzetim çalışmaları küçük sinyal bozucuları altında uygulanmıştır. Örneğin, birim-adım denetleyici değişikliği ve bununla birlikte toprak arızası ve üç-faz arıza gibi büyük bozucu şartlar. Her adımda rotor açısı, ivmelenen güç, bağlantı gerilimi ve rotor hızı gibi farklı sistem değişkenleri kaydedilmiş ve çizilmiştir. The aim of this thesis is to investigate the modeling and simulation of the Bazyan gas power plant (BGPP). The demand for energy in the developing regions of the world has shown a clear increase in the recent past. Therefore, it is important to use power generations that have high efficiency and specific power output, low pollutant emissions and low operating and maintenance costs for possible use of available fuels. Industrial gas turbines are one of the established technologies for power generation. Power supply systems require the exact models of energy system elements. Exciter, speed control and gas turbine are important components of the production units. First, each part of the turbine is described by its transfer function, and then the block model is thoroughly built. In addition to the turbine, the IEEE AC7B excitation system with an Power system stabilizer (PSS2B), a synchronous generator and a transformer are considered in simulation studies. This model is then adapted to the newly installed gas power plant in the north of Iraq, called Bazyan Gas Power Plant (BGPP), using real data from the data sheets of the BGPP manufacturers. For the simulation, the station is connected to a load. Simulation studies are carried out under small signal disturbances, For example, a unit-step controller change, as well as large disturbing conditions such as ground fault and three phase faults. In each step, various system variables such as rotor angle, acceleration power, connection voltage and rotor speed are recorded and plotted. 113

  • Publication . Article . 2008
    Open Access English
    Authors: 
    Ararat, Melsa; Yurtoglu, B.Burcin;
    Publisher: Baskent University
    Country: Turkey

    This survey gives an overview of the current state of knowledge on the question whether corporate governance structures worldwide are determinants of differences in economic performance. We look at the identities of owners, monitoring boards, and legal systems and argue that some though not all corporate governance structures give rise to differences in performance. In doing that we also look at the impact of the degree of competition in product markets on governance structures. The paper ends with a tentative outlook as to the prospects of corporate governance structures converging worldwide.

  • Open Access English
    Authors: 
    Troupin, Charles; Beltran, Joan Pau; Frontera, Biel; Gómara, Sonia; Gomila, Miquel; Krietemeyer, Andreas; Muñoz, Cristian; Rújula, Miquel Àngel; Serra, Inma; Tintoré, Joaquín;
    Publisher: Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (IT)
    Country: Belgium
  • Publication . Other literature type . 2006
    Open Access English
    Authors: 
    Terzi, Evimaria;
    Publisher: Helsingin yliopisto
    Country: Finland

    The analysis of sequential data is required in many diverse areas such as telecommunications, stock market analysis, and bioinformatics. A basic problem related to the analysis of sequential data is the sequence segmentation problem. A sequence segmentation is a partition of the sequence into a number of non-overlapping segments that cover all data points, such that each segment is as homogeneous as possible. This problem can be solved optimally using a standard dynamic programming algorithm. In the first part of the thesis, we present a new approximation algorithm for the sequence segmentation problem. This algorithm has smaller running time than the optimal dynamic programming algorithm, while it has bounded approximation ratio. The basic idea is to divide the input sequence into subsequences, solve the problem optimally in each subsequence, and then appropriately combine the solutions to the subproblems into one final solution. In the second part of the thesis, we study alternative segmentation models that are devised to better fit the data. More specifically, we focus on clustered segmentations and segmentations with rearrangements. While in the standard segmentation of a multidimensional sequence all dimensions share the same segment boundaries, in a clustered segmentation the multidimensional sequence is segmented in such a way that dimensions are allowed to form clusters. Each cluster of dimensions is then segmented separately. We formally define the problem of clustered segmentations and we experimentally show that segmenting sequences using this segmentation model, leads to solutions with smaller error for the same model cost. Segmentation with rearrangements is a novel variation to the segmentation problem: in addition to partitioning the sequence we also seek to apply a limited amount of reordering, so that the overall representation error is minimized. We formulate the problem of segmentation with rearrangements and we show that it is an NP-hard problem to solve or even to approximate. We devise effective algorithms for the proposed problem, combining ideas from dynamic programming and outlier detection algorithms in sequences. In the final part of the thesis, we discuss the problem of aggregating results of segmentation algorithms on the same set of data points. In this case, we are interested in producing a partitioning of the data that agrees as much as possible with the input partitions. We show that this problem can be solved optimally in polynomial time using dynamic programming. Furthermore, we show that not all data points are candidates for segment boundaries in the optimal solution.

  • Open Access English
    Authors: 
    Montes Luján, Héctor Guillermo;
    Publisher: Uniandes

    The wind power penetration into the system, as other intermittent energy sources, have impacts in grid frequency performance that lead to increase system reserve and to reduce the power extraction in the wind turbines. In this document, an integration analysis of the Battery Energy Storage System (BESS) is presented with its dynamics characteristics, This in order to identify the optimal size of an aggregated system in order to support frequency regulation. Once the large potential for the provision of frequency control services is identified, in this document the batteries are used to increase the frequency performance of the grid. The primary frequency control presented takes into account the dynamic response of the integrated system with wind turbines and BESS, while the LFC have a robust performance due to system inertia uncertainties. La integración de la energía eólica en la red, como otras fuentes de energía intermitentes, tiene un impacto en el desempeño del control de frecuencia del sistema que conduce al aumento en la reserva del sistema y la reducción de la extracción de energía en las turbinas eólicas. En este documento se analiza el gran potencial de los Sistemas de Almacenamiento Energético con Baterías (BESS) para la provisión de servicios de control de frecuencia, y se presenta un desarrollo metodológico para el dimensionamiento óptimo. El análisis presentado toma en cuenta la respuesta dinámica del sistema integrado con aerogeneradores y BESS, y los beneficios sociales que se pueden obtener en los mercados de electricidad mediante la implementación de estos sistemas. Magíster en Ingeniería Eléctrica Maestría

  • Publication . Book . 2014
    Restricted English
    Publisher: Kölner Wissenschaftsverlag
    Country: Denmark
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