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    Wyświetlanie 1-8 z 8
    Tytuł:
    A study of parallel techniques for dimensionality reduction and its impact on the quality of text processing algorithms
    Autorzy:
    Pietroń, M.
    Wielgosz, M.
    Karwatowski, M.
    Wiatr, K.
    Powiązania:
    https://bibliotekanauki.pl/articles/114190.pdf
    Data publikacji:
    2015
    Wydawca:
    Stowarzyszenie Inżynierów i Techników Mechaników Polskich
    Tematy:
    singular value decomposition
    vector space model
    TFIDF
    Opis:
    The presented algorithms employ the Vector Space Model (VSM) and its enhancements such as TFIDF (Term Frequency Inverse Document Frequency) with Singular Value Decomposition (SVD). TFIDF were applied to emphasize the important features of documents and SVD was used to reduce the analysis space. Consequently, a series of experiments were conducted. They revealed important properties of the algorithms and their accuracy. The accuracy of the algorithms was estimated in terms of their ability to match the human classification of the subject. For unsupervised algorithms the entropy was used as a quality evaluation measure. The combination of VSM, TFIDF, and SVD came out to be the best performing unsupervised algorithm with entropy of 0.16.
    Źródło:
    Measurement Automation Monitoring; 2015, 61, 7; 352-353
    2450-2855
    Pojawia się w:
    Measurement Automation Monitoring
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Document Clustering : Concepts, Metrics and Algorithms
    Autorzy:
    Tarczynski, T.
    Powiązania:
    https://bibliotekanauki.pl/articles/226231.pdf
    Data publikacji:
    2011
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    document clustering
    text mining
    k-means
    hierarchical clustersting
    vector space model
    Opis:
    Document clustering, which is also refered to as text clustering, is a technique of unsupervised document organisation. Text clustering is used to group documents into subsets that consist of texts that are similar to each orher. These subsets are called clusters. Document clustering algorithms are widely used in web searching engines to produce results relevant to a query. An example of practical use of those techniques are Yahoo! hierarchies of documents [1]. Another application of document clustering is browsing which is defined as searching session without well specific goal. The browsing techniques heavily relies on document clustering. In this article we examine the most important concepts related to document clustering. Besides the algorithms we present comprehensive discussion about representation of documents, calculation of similarity between documents and evaluation of clusters quality.
    Źródło:
    International Journal of Electronics and Telecommunications; 2011, 57, 3; 271-277
    2300-1933
    Pojawia się w:
    International Journal of Electronics and Telecommunications
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Latent semantic indexing for patent documents
    Autorzy:
    Moldovan, A.
    Boţ, R. I.
    Wanka, G.
    Powiązania:
    https://bibliotekanauki.pl/articles/908440.pdf
    Data publikacji:
    2005
    Wydawca:
    Uniwersytet Zielonogórski. Oficyna Wydawnicza
    Tematy:
    indeksowanie semantyczne
    rozkład wartości szczególnych
    model przestrzeni wektorowej
    klasyfikacja patentowa
    Latent Semantic Indexing (LSI)
    singular value decomposition (SVD)
    vector space model (VSM)
    patent classification
    Opis:
    Since the huge database of patent documents is continuously increasing, the issue of classifying, updating and retrieving patent documents turned into an acute necessity. Therefore, we investigate the efficiency of applying Latent Semantic Indexing, an automatic indexing method of information retrieval, to some classes of patent documents from the United States Patent Classification System. We present some experiments that provide the optimal number of dimensions for the Latent Semantic Space and we compare the performance of Latent Semantic Indexing (LSI) to the Vector Space Model (VSM) technique applied to real life text documents, namely, patent documents. However, we do not strongly recommend the LSI as an improved alternative method to the VSM, since the results are not significantly better.
    Źródło:
    International Journal of Applied Mathematics and Computer Science; 2005, 15, 4; 551-560
    1641-876X
    2083-8492
    Pojawia się w:
    International Journal of Applied Mathematics and Computer Science
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    A new closed loop speed control strategy for a vector controlled three-phase induction motor drive
    Autorzy:
    Tripathi, A.
    Dey, A.
    Dwivedi, B.
    Singh, B.
    Chandra, D.
    Powiązania:
    https://bibliotekanauki.pl/articles/262777.pdf
    Data publikacji:
    2008
    Wydawca:
    Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie
    Tematy:
    space vector modulation
    VSI
    induction motor model
    transients
    steady state value
    Opis:
    This paper presents a completely mathematical equations based model on control of torque and speed of a three-phase indirect vector controlled VSI fed cage induction motor drive that is controlled through the space vector modulated method. This enables a wide range of acceptability of the model for various values of load and for various types and ratings of induction motors. The uniqueness of the model lies in the fact that the deviations in the torque and speed on sudden application of reference step change in speed values are minimum i.e. when any sudden change in the speed reference is desired, the speed and torque waveforms reveal that the time taken in coming back to their final steady state values is very less and the motor overcomes the perturbation with negligible transients. The same is verified through the simulated results.
    Źródło:
    Electrical Power Quality and Utilisation. Journal; 2008, 14, 1; 67-72
    1896-4672
    Pojawia się w:
    Electrical Power Quality and Utilisation. Journal
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Model predictive direct power control of energy storage quasi-Z-source grid-connected inverter
    Autorzy:
    Tang, Min'an
    Yang, Shangmei
    Zhang, Kaiyue
    Wang, Qianqian
    Liu, Chenggang
    Dong, Xuewang
    Powiązania:
    https://bibliotekanauki.pl/articles/2042769.pdf
    Data publikacji:
    2022
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    quasi Z-Source
    inverter
    energy storage
    power control
    model predictive
    space vector
    Opis:
    In order to overcome the shortcoming of large switching losses caused by variable switching frequency appears in the conventional finite control set model predictive control (FCS-MPC) algorithm, a model predictive direct power control (MP-DPC) for an energy storage quasi-Z-source inverter (ES-qZSI) is proposed. Firstly, the power prediction model of the ES-qZSI is established based on the instantaneous power theory. Then the average voltage vector in the coordinate system is optimized by the power cost function. Finally, the average voltage vector is used as the modulation signal, and the corresponding switching signal with fixed frequency is generated by the shoot-through segment space vector pulse width modulation (SVPWM) technology. The simulation results show that the ES-qZSI realizes six shoot-through actions per control cycle and achieves the constant frequency control of the system, which verifies the correctness of the proposed control strategy.
    Źródło:
    Archives of Electrical Engineering; 2022, 71, 1; 21-35
    1427-4221
    2300-2506
    Pojawia się w:
    Archives of Electrical Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Predictive-SVM control method dedicated to an AC/DC converter with an LCL grid filter
    Autorzy:
    Dmitruk, K.
    Powiązania:
    https://bibliotekanauki.pl/articles/200760.pdf
    Data publikacji:
    2020
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    three-phase voltage converter
    model predictive control
    space vector modulation
    infinite control set
    Opis:
    This paper presents simulation and laboratory test results of an implementation of an infinite control set model predictive control into a three-phase AC/DC converter. The connection between the converter and electric grid is made through an LCL filter, which is characterized by a better reduction of grid current distortions and smaller (cheaper) components in comparison to an L-type filter. On the other hand, this type of filter can cause strong resonance at specific current harmonics, which is efficiently suppressed by the control strategy focusing on the strict control input filter capacitors voltage vector. The presented method links the benefits of using linear control methods based on a space vector modulator and the nonlinear ones, which result in excellent control performance in a steady state as well as in a transient state.
    Źródło:
    Bulletin of the Polish Academy of Sciences. Technical Sciences; 2020, 68, 5; 1049-1056
    0239-7528
    Pojawia się w:
    Bulletin of the Polish Academy of Sciences. Technical Sciences
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Network analyses with the use of spatial databases
    Autorzy:
    Budkowski, Szczepan
    Powiązania:
    https://bibliotekanauki.pl/articles/2175190.pdf
    Data publikacji:
    2022
    Wydawca:
    Uniwersytet Rolniczy im. Hugona Kołłątaja w Krakowie
    Tematy:
    geographic information system
    database
    network analysis
    space management
    raster data model
    vector data model
    system informacji geograficznej
    baza danych
    gospodarka przestrzenna
    analiza sieci
    model wektorowy
    model rastowy
    Opis:
    An analysis is the process of browsing and searching for specific information from an entire dataset. The simplest analysis that can be performed on the data is visual analysis. However, it does not provide absolute certainty as to correctness and quality. A more advanced way of selecting required data is computer-based analysis. Analytical operations are performed on the data entered into the computer. The user defines the query, and the program performs calculations and displays the answer on the monitor screen. The aim of this publication is to conduct network analyses with the use of spatial databases. Besides focusing on the analysis as the leading research method, the paper also adopts this method to analyze the literature on the subject. In addition, the paper points to the complementary roles of the raster model and the vector model, emphasizing their coexistence. The paper shows a variety of applications of GIS analyses, from simple buffers around selected areas, through selection, and the intersection of layers, to network analyses. The high degree of advancement of GIS tools allows to build advanced models in which analyses that go beyond the original application of the collected databases can be run.
    Źródło:
    Geomatics, Landmanagement and Landscape; 2022, 3; 93--102
    2300-1496
    Pojawia się w:
    Geomatics, Landmanagement and Landscape
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Model matematyczny napędu z silnikiem indukcyjnym - metoda DTC-SVM
    Mathematical model of induction motor - DTC-SVM method
    Autorzy:
    Sieklucki, G.
    Orzechowski, T.
    Sykulski, R.
    Powiązania:
    https://bibliotekanauki.pl/articles/320332.pdf
    Data publikacji:
    2010
    Wydawca:
    Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
    Tematy:
    silnik indukcyjny klatkowy
    model matematyczny
    bezpośrednie sterowanie momentem (DTC)
    metoda wektora przestrzennego w modulacji szerokości impulsu (SVM lub SVPWM)
    squirrel cage induction motor
    mathematical model
    direct torque control (DTC)
    space vector pulse with modulation method (SVM or SVPWM)
    Opis:
    W artykule omówiono strukturę i zasadę pracy układu DTC-SYM. W pracy przedstawiono nieliniowy model matematyczny silnika indukcyjnego w wirującym układzie współrzędnych. Wektor strumienia stojana przyjęto jako oś odniesienia (d). W rozważaniach pominięto dynamikę przemiennika częstotliwości. Celem analizy było uproszczenie (linearyzacja) modelu obwodu strumienia stojan oraz wytwarzania momentu elektrycznego. Zostały przedstawione wyniki badań symulacyjnych, które pozwalają określić błędy linearyzacji modeli. Zamieszczono transmitancje, które mogą zostać wykorzystane w procesie optymalizacji parametrycznej regulatorów.
    Structure and the principle of the work of the DTC-SYM system are talked over in the article. The nonlinear mathematical model of the induction motor in a revolving reference frame is introduced in the work. The stator flux vector is taken as the axis of the reference frame (d). The dynamics of the power electronics frequency converter are neglected in considerations. The simplification (linearization) of the stator flux circuit model and the production of the motor torque is the aim of the analysis. There are presented the results of the simulating researches which let qualify the models linearization errors. The transfer-functions which can be used in the parametric optimization process of regulators was inserted.
    Źródło:
    Elektrotechnika i Elektronika; 2010, 29, 1--2; 33-40
    1640-7202
    Pojawia się w:
    Elektrotechnika i Elektronika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-8 z 8

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