• Title, Summary, Keyword: parametric search

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Algorithms of the Parametric Adaptation of Models of Complex Systems by Discrete Observations

  • Radjabov, Bakhtiyor;Khidirova, Charos
    • Journal of Multimedia Information System
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    • v.4 no.4
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    • pp.317-320
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    • 2017
  • This paper examines approaches to the development of algorithms of parametric identification of models of complex systems from discrete observations. A modification of a known algorithm Kaczmarz which is designed for closed systems with perturbations, based on the methods of random search and investigates their statistical properties.

Tests for Causality from Internet Search to Return and Volatility of Cryptocurrency: Evidence from Causality in Moments (인터넷 검색을 통한 암호화폐 수익률 및 변동성에 대한 인과검정: 적률인과 접근)

  • Jeong, Ki-Ho;Ha, Sung Ho
    • The Journal of Information Systems
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    • v.29 no.1
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    • pp.289-301
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    • 2020
  • Purpose This study analyzes whether Internet search of cryptocurrency has a causal relationship to return and volatility of cryptocurrency. Design/methodology/approach Google Trend was used as a measure of the level of Internet search, and the parametric tests of Granger causality in the 1st moment and the 2nd moment were adopted as the analysis method. We used Bitcoin's dollar-based price, which is the No. 1 market value among cryptocurrency. Findings The results showed that the Internet search measured by Google Trends has a causal relationship to cryptocurrency in both average and volatility, while there is a difference in causality and its degree according to the search area and category that Google Trend user should set. Because the Granger causality is based on the improvement of prediction, the analysis results of this study indicate that Internet search can be used as a leading indicator in predicting return and volatility of cryptocurrency.

Dual-Halbach Array Permanent Magnet Tubular Generator for Free-Piston Generator

  • Beigi, Hassan Moradi Cheshmeh;Akbari, Sohrab
    • Journal of Magnetics
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    • v.20 no.4
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    • pp.405-412
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    • 2015
  • In this study, we describe the effects of changing the magnet shape of permanent magnets (PMs) in a rotor Halbach-array PM generator for reciprocating free piston generator applications. More specifically, the rectangular-shaped magnets were replaced by the trapezoidal-shaped magnets. The initial design, an analytical magnetic field solution of rectangular shaped magnets, is presented and air-gap magnetic flux density and thrust force were estimated. The results were compared to the finite element analysis (FEA) showing excellent agreement. Using FEA, the effect of the shape of the magnets on the flux density and thrust force waveforms is analyzed. Moreover, the proportion of the Halbach array in the machine was optimized by the means of a parametric search. The results obtained from the analytical calculations and FEA were validated by comparing to those of Radial-array PM generator.

Methodological Problems in Information Retrieval Research (정보검색 연구의 방법론에 관한 고찰)

  • 이명희
    • Journal of the Korean BIBLIA Society for library and Information Science
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    • v.7 no.1
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    • pp.231-246
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    • 1994
  • A major problem for information retrieval research in the past three decades has been methodology, even though some progress has been made in obtaining useful results from methodologically sound experiments. Within a methodology, potential problems include artificial data generated by the researcher, small sample size interpretation of findings. Critics have pointed out that some room exists for improving methodology of information retrieval research; using existing data, having big enough sample size, including large numbers of search queries, introducing more control in relation to variables, utilizing more appropriate performance measures, conducting rests carefully and evaluating findings properly. Relevance judgments depend entirely on the perception of the user and on the situation of the moment. In an experiment, the best judge of relevance is a user with a well defined information need. Normally more than two categories for relevance judgments are desirable becase there are degrees of relevance. In experimental design, careful control of variables is meeded for internal validity. When no single database exists for comparison, existing operational databases should be used cautiously, Careful control for the variations of search queries, inter-searcher sonsistency, intra-searcher consistency and search strategies is necessary. Parametric statistics requiring rigid assumptions are not appropriate in information retrieval research and non-parametric statistics requiring few assumptions are necessary. Particularly, the sign test and the Wilcoxon test are good alternatives.

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Finite Element Analysis of Axisymmetric Multi-Stage Deep Drawing Processes (축대칭 다단계 디프드로잉 공정의 유한요소해석)

  • 윤정환;유동진;양동열;김석관
    • Transactions of Materials Processing
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    • v.3 no.4
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    • pp.468-481
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    • 1994
  • Mathematical description of arbitrarily-shaped tool surface are introduced by parametric patch approaches along with the related contact search algorithm. In order to maintain the advantages of membrane elements and to incoporate the bending effect, a BEAM(Bending Energy Augmented Membrane) element is proposed. Computation are carried out for some complex axisymmetric multi-stage deep drawing to verify the validity and the effectiveness of the proposed method.

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Search of Optimal Contexts for Context-adaptive Coding of Stereo Parameters in Parametric Stereo of Enhanced aacPlus (Enhanced aacPlus의 Parametric Stereo에서 스테레오 파라미터의 컨텍스트 적응 코딩을 위한 최적 컨텍스트 탐색)

  • Pang, Hee-Suk
    • The Journal of the Acoustical Society of Korea
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    • v.31 no.7
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    • pp.435-440
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    • 2012
  • We propose optimal contexts for context-adaptive coding of stereo parameters in parametric stereo (PS) of enhanced aacPlus. For the quantized indexes of stereo parameters, 8 context candidates were proposed based on the index values and their combinations adjacent to a source index in the time-stereo band domain, where the time-stereo band region was further divided into 4 regions based on refresh/non-refresh frames and stereo bands. The optimal contexts for each region were proposed by experiments, which are expected to be used for context-adaptive coding of PS for improved performance.

A Parametric Study of Displacement Measurements Using Digital Image Correlation Method

  • Ha, Kuen-Dong
    • Journal of Mechanical Science and Technology
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    • v.14 no.5
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    • pp.518-529
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    • 2000
  • A detailed and thorough parametric study of digital image correlation method is presented. A theoretical background and development of the method were introduced and the effects of various parameters on the determination of displacement outputs from the raw original and deformed image information were examined. Use of the normalized correlation coefficient, the use of 20 to 40 pixels for a searching window side, 6 variables searching, bi-cubic spline sub pixel interpolations and the use of coarse-fine search are some of the key choices among the results of parametric studies. The displacement outputs can be further processed with two dimensional curve fitting for the data noise reduction as well as displacement gradient calculation.

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Controller Design for Affine T-S Fuzzy System with Parametric Uncertainties (파라미터 불확실성을 갖는 어핀 T-S 퍼지 시스템의 제어기 설계)

  • Lee, Sang-In;Park, Jin-Bae;Joo, Young-Hoon
    • Proceedings of the Korean Institute of Intelligent Systems Conference
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    • pp.133-136
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    • 2004
  • This paper proposes a stability condition in affine Takagi-Sugeno (T-S) fuzzy systems with parametric uncertainties and then, introduces the design method of a fuzzy-model-based controller which guarantees the stability. The analysis is based on Lyapunov functions that are continuous and piecewise quadratic. The search for a piecewise quadratic Lyapunov function can be represented in terms of linear matrix inequalities (LMIs).

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Controller Design for Discrete-Time Affine T-S Fuzzy System with Parametric Uncertainties (파라미터 불확실성을 갖는 이산시간 어핀 T-S 퍼지 시스템의 제어기 설계)

  • Lee, Sang-In;Park, Jin-Bae;Joo, Young-Hoon
    • Proceedings of the KIEE Conference
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    • pp.2516-2518
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    • 2004
  • This paper proposes a stability condition in discrete-time affine Takagi-Sugeno (T-S) fuzzy systems with parametric uncertainties and then, introduces the design method of a fuzzy-model-based controller which guarantees the stability. The analysis is based on Lyapunov functions that are continuous and piecewise quadratic. The search for a piecewise quadratic Lyapunov function can be represented in terms of linear matrix inequalities (LMIs).

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Design of Controller for Affine Takagi-Sugeno Fuzzy System with Parametric Uncertainties via BMI

  • Lee, Sang-In;Joo, Young-Hoon;Park, Jin-Bae
    • 제어로봇시스템학회:학술대회논문집
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    • pp.658-662
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    • 2004
  • This paper develops a stability analysis and controller synthesis methodology for a continuous-time affine Takagi-Sugeno (T-S) fuzzy systems with parametric uncertainties. Affine T-S fuzzy system can be an advantage because it may be able to approximate nonlinear functions to high accuracy with fewer rules than the homogeneous T-S fuzzy systems with linear consequents only. The analysis is based on Lyapunov functions that are continuous and piecewise quadratic. The search for a piecewise quadratic Lyapunov function can be represented in terms of bilinear matrix inequalities (BMIs). A simulation example is given to illustrate the application of the proposed method.

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