• Title/Summary/Keyword: 고유행렬

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Modal Analysis of Automotive Body Model using Mode Synthesis Method (모드합성법을 사용한 차체모델의 모달해석)

  • 장경진;지태한;박영필
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 1995.04a
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    • pp.34-39
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    • 1995
  • 최근 승용차의 급격한 수요증가와 더불어 차량의 승차감 개선에 많은 관심이 집중되면서, 저진동 저소음 차량에 대한 연구가 활발히 이루어지고 있다. 이러한 연구의 일부로서, 수치해석법 및 진동실험에 의하여 복잡한 전체 구조물을 해석할 경우, 계산기의 기억용량, 계산시간, 비용이 많이 들게 되고, 한번 해석을 행한 구조물을 부분적으로 변경할지라도 전체의 계산을 다시 수행해야만 한다. 그래서, 복잡한 전체 구조물을 몇 개의 부분구조물로 나누어, 분계의 특성에 맞게 각기 수치해석법이나 모달실험을 적용한 후, 다시 합성하는 방법이 제시되었는데, 이것이 부분구조합성법이다. 이 방법을 사용하면, 유한요소 모델링이 쉬운 분계와 실험이 쉬운 분계를 서로 구분하여 각기 해석한 후 합성함으로써, 각 분계의 특성에 맞는 효율적인 해석을 수행할 수가 있다. 지금까지의 연구를 살펴보면, 유한요소해석에 의한 모드합성법에서는 Hurty가 구속모드법을 제안한 이래, 불구속모드법, 주종계법 등 많은 연구가 있었으나, 실험모달해석을 병행할 경우에는 결합부에서의 회전자유도의 처리문제, 특성 행렬의 동정문제, 많은 절점으로부터 데이타를 얻어야 하는 등의 어려움이 있었다. 이러한 문제를 개선시켜서 Hermanski등은 회전자유도가 보간된 모드합성법(interpolated mode synthesis, IMS)을 연구하여, 적은 실험데이타만을 사용하면서 단순지지 보에 적용함으로써 타당성을 입증하였다. 한편, 차체는 복잡한 부분구조물들로 이루어져 있으므로, 본 연구에서는 유한요소모델링의 용이함, 실험의 간편성, 계산의 효율성등을 추구하며, 실험과 유한요소해석을 병행한 부분구조합성법을 차량의 BIW(body in white)에 적용하는 방법을 연구하게 되었다. 그 기본연구로서 실험과 유한요소해석을 병행하여 회전자유도를 보간하는 방법을 먼저 단순한 판구조물에 적용을 하고, 나아가 실제 BIW를 축소하여 자체 제작한 모형차에 적용시켜 보았다.물은 분계 A(16개의 사각요소)와 분계 B(8개의 사각요소)로 이루어져 있으며 두개의 스프링으로 결합되어 있다. 설계변수는 강성에 국한하였으며 결합부의 결합형태는 탄성결합과 강결합으로 하였다. 감도해석과 축소임피던스 합성법에 의해 구해진 고유진동수와 FRF를 상용 유한 요소 해석 패키지인 MSC/NASTRAN을 통하여 검증하여 이 연구의 타당성을 검토하였다.인풋기어에서의 회전수 변동을 측정하고, 이 실험 데이타를 기초로 하여 엔진 토크 및 변속기에서의 드래그 토크를 계산하여 엔진-변속기 인풋기어의 반한정계 2자유도 진동모델과 비틀림 특성을 가진 클러치 디스크의 프리댐퍼 영역에 대해 시뮬레이션을 수행하여 클러치 비틀림 기구의 설계인자인 비틀림 강성, 히스테리시스 토크에 따른 비틀림 진동 저감 효과를 연구하고자 한다.성을 확인하였다. 여기서는 실험실 수준의 평 판모델을 제작하고 실제 현장에서 이루어질 수 있는 진동제어 구조물에 대 한 동적실험 및 FRS를 수행하는 과정과 동일하게 따름으로써 실제 발생할 수 있는 오차나 error를 실험실내의 차원에서 파악하여 진동원을 있는 구조 물에 대한 진동제어기술을 보유하고자 한다. 이용한 해마의 부피측정은 해마경화증 환자의 진단에 있어 육안적인 MR 진단이 어려운 제한된 경우에만 실제적 도움을 줄 수 있는 보조적인 방법으로 생각된다.ofile whereas relaxivity at high field is not affected by τS. On the other hand, the change in τV does not affect low field profile but strongly in fluences on both inflection fie이 and the maximum relaxivity value. The results shows a fluences on both inflection field and the maximum relaxivity value. Th

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On the Use of Modal Derivatives for Reduced Order Modeling of a Geometrically Nonlinear Beam (모드 미분을 이용한 기하비선형 보의 축소 모델)

  • Jeong, Yong-Min;Kim, Jun-Sik
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.30 no.4
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    • pp.329-334
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    • 2017
  • The structures, which are made up with the huge number of degrees-of-freedom and the assembly of substructures, have a great complexity. In order to increase the computational efficiency, the analysis models have to be simplified. Many substructuring techniques have been developed to simplify large-scale engineering problems. The techniques are very powerful for solving nonlinear problems which require many iterative calculations. In this paper, a modal derivatives-based model order reduction method, which is able to capture the stretching-bending coupling behavior in geometrically nonlinear systems, is adopted and investigated for its performance evaluation. The quadratic terms in nonlinear beam theory, such as Green-Lagrange strains, can be explained by the modal derivatives. They can be obtained by taking the modal directional derivatives of eigenmodes and form the second order terms of modal reduction basis. The method proposed is then applied to a co-rotational finite element formulation that is well-suited for geometrically nonlinear problems. Numerical results reveal that the end-shortening effect is very important, in which a conventional modal reduction method does not work unless the full model is used. It is demonstrated that the modal derivative approach yields the best compromised result and is very promising for substructuring large-scale geometrically nonlinear problems.

The Suggestion of LINF Algorithm for a Real-time Face Recognition System (실시간 얼굴인식 시스템을 위한 새로운 LINF 알고리즘의 제안)

  • Jang Hye-Kyoung;Kang Dae-Seong
    • Journal of the Institute of Electronics Engineers of Korea SP
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    • v.42 no.4 s.304
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    • pp.79-86
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    • 2005
  • In this paper, we propose a new LINF(Linear Independent Non-negative Factorization) algorithm for real-time face recognition systea This system greatly consists of the two parts: 1) face extraction part; 2) face recognition part. In the face extraction Part we applied subtraction image, the detection of eye and mouth region , and normalization method, and then in the face recognition Part we used LINF in extracted face candidate region images. The existing recognition system using only PCA(Principal Component Analysis) showed low recognition rates, and it was hard in the recognition system using only LDA(Linear Discriminants Analysis) to apply LDA directly when the training set is small. To overcome these shortcomings, we reduced dimension as the matrix that had non-negative value to be different from former eigenfaces and then applied LDA to the matrix in the proposed system We have experimented using self-organized DAIJFace database and ORL database offered by AT(')T laboratory in Cambridge, U.K. to evaluate the performance of the proposed system. The experimental results showed that the proposed method outperformed PCA, LDA, ICA(Independent Component Analysis) and PLMA(PCA-based LDA mixture algorithm) method within the framework of recognition accuracy.

Design of an Optimal Adaptive Filter for the Cancellation of M-wave in the EMG Controlled Functional Electrical Stimulation for Paralyzed Individuals (마비환자의 근전도제에기능적전기자극을 위한 M-wave 제거용 최적적응필터 설계)

  • Yeom Hojoon;Park Youngcheol;Lee Younghee;Yoon Youngro;Shin Taemin;Yoon Hyoungro
    • Journal of Biomedical Engineering Research
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    • v.25 no.6
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    • pp.479-487
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    • 2004
  • Biopotential signals have been used as command in systems using electrical stimulation of motor nerves to restore movement after an injury to the central nervous system (CNS). In order to use the voluntary EMG (electromyography) among the biopotentials as a control signal for the electrical stimulation of the same muscle for CNS injury patients, it is necessary to remove M-wave of having high magnitude from raw data. We designed an optimal filter for removing the M-wave and preserving the voluntary EMG and showed that the optimal filter is eigen filter. We also proved that the previous method using the prediction error filter(PEF) is a suboptimal filtering in the sense of preserving the voluntary EMG. On basis of the data obtained from a model for M-wave and voluntary EMG and from actual CNS injury patients, with false-positive rate analysis, the proposed adaptive filter showed a very promising performance in comparison with previous method.

Validity and Reliability of Daily Life Stress Scale for College Students (대학생 일상생활 스트레스 측정 도구의 타당도와 신뢰도)

  • Park, Jeong-Hye;Kang, Se-Won
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.22 no.5
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    • pp.423-432
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    • 2021
  • This study developed a scale to measure college students' perceived stress levels for adverse life events that may occur in their daily lives and confirmed its validity and reliability. The scale was developed in accordance with DeVellis' scale development guidelines. Data were collected from 1,242 students of a local university in 2020. The collected samples were randomly separated into two groups (A, B). Group A (N=620) was tested for an initial examination of the performance, exploratory factor analysis, multitrait-multimethod matrix, criterion-related validity, and reliability of each item; and verified with group B (N=622) for confirmatory factor analysis and reliability re-test. As a result, the final scale of 33 items and eight factors were developed. The KMO values were 0.92, and Bartlett's spherical test was significant (χ2=12532.42, p<.001); the number of factors with initial eigenvalues of 1.0 or higher was eight; the cumulative factor loadings of 71.5% and the commonality of each item was 0.56 or higher. The reliability of the scale was Cronbach's alpha 0.94; sub-factors' Cronbach's alpha was 0.78 to 0.90. Therefore, these findings suggest that the scale developed in this study would be useful for measuring the stress levels of daily life for college students.

A Study on Teaching the Method of Lagrange Multipliers in the Era of Digital Transformation (라그랑주 승수법의 교수·학습에 대한 소고: 라그랑주 승수법을 활용한 주성분 분석 사례)

  • Lee, Sang-Gu;Nam, Yun;Lee, Jae Hwa
    • Communications of Mathematical Education
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    • v.37 no.1
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    • pp.65-84
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    • 2023
  • The method of Lagrange multipliers, one of the most fundamental algorithms for solving equality constrained optimization problems, has been widely used in basic mathematics for artificial intelligence (AI), linear algebra, optimization theory, and control theory. This method is an important tool that connects calculus and linear algebra. It is actively used in artificial intelligence algorithms including principal component analysis (PCA). Therefore, it is desired that instructors motivate students who first encounter this method in college calculus. In this paper, we provide an integrated perspective for instructors to teach the method of Lagrange multipliers effectively. First, we provide visualization materials and Python-based code, helping to understand the principle of this method. Second, we give a full explanation on the relation between Lagrange multiplier and eigenvalues of a matrix. Third, we give the proof of the first-order optimality condition, which is a fundamental of the method of Lagrange multipliers, and briefly introduce the generalized version of it in optimization. Finally, we give an example of PCA analysis on a real data. These materials can be utilized in class for teaching of the method of Lagrange multipliers.

A METHOD OF CAPABILITY EVALUATION FOR KOREAN PADDY SOILS -Part I. Fertility evaluation and fertility classification (한국답토양의 생산력평가방법에 관한 연구 -1 보(報). 비옥도평가(肥沃度評價) 및 비옥도분류(肥沃度分類))

  • Hong, Ki-Chang;Maeng, Do-Won;Kazutake, Kyuma;Hisao, Furukawa;Suh, Yoon-Soo
    • Korean Journal of Soil Science and Fertilizer
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    • v.12 no.1
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    • pp.1-14
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    • 1979
  • The fertility which is the combined factor is one of the important capability determiants of paddy soils. In this study, we aimed at attaining a quantitative evaluation of soil fertility and further establishing an objective fertility classification on the basis of the fertility evaluation. The samples used in this series studies were collected from Korean paddy field. They include deltas, flood plains, coastal plains, valley plains, fans and low terraces. On the basis of correlation analysis, factor analysis was applied to a set of 15 variables. As a result of factor analysis, five mutually independent and clearly definable fertility component factors were extracted from the 15 variables for the whole 90 surface soil samples. The fertility status of each sample soil could be objectively designated by the score of the five factors. As a means of summarizing the information obtained, taxonomic distances between all pairs of the samples were computed from these five factor scores further to be subjected to numerical taxonomy. Seven fertility groups were formulated, each of which was characterized by one or more of the fertility components. As this fertility classification was based on the present state of soil properties, it would be useful in pointing to the proper direction of further fertility amelioration and improvement for each group to enhance potential productivity of Korean paddy fields.

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An Analytical Study on Stem Growth of Chamaecyparis obtusa (편백(扁栢)의 수간성장(樹幹成長)에 관(關)한 해석적(解析的) 연구(硏究))

  • An, Jong Man;Lee, Kwang Nam
    • Journal of Korean Society of Forest Science
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    • v.77 no.4
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    • pp.429-444
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    • 1988
  • Considering the recent trent toward the development of multiple-use of forest trees, investigations for comprehensive information on these young stands of Hinoki cypress are necessary for rational forest management. From this point of view, 83 sample trees were selected and cut down from 23-ear old stands of Hinoki cypress at Changsung-gun, Chonnam-do. Various stem growth factors of felled trees were measured and canonical correlaton analysis, principal component analysis and factor analysis were applied to investigate the stem growth characteristics, relationships among stem growth factors, and to get potential information and comprehensive information. The results are as follows ; Canonical correlation coefficient between stem volume and quality growth factor was 0.9877. Coefficient of canonical variates showed that DBH among diameter growth factors and height among height growth factors had important effects on stem volume. From the analysis of relationship between stem-volume and canonical variates, which were linearly combined DBH with height as one set, DBH had greater influence on volume growth than height. The 1st-2nd principal components here adopted to fit the effective value of 85% from the pincipal component analysis for 12 stem growth factors. The result showed that the 1st-2nd principal component had cumulative contribution rate of 88.10%. The 1st and the 2nd principal components were interpreted as "size factor" and "shape factor", respectively. From summed proportion of the efficient principal component fur each variate, information of variates except crown diameter, clear length and form height explained more than 87%. Two common factors were set by the eigen value obtained from SMC (squared multiple correlation) of diagonal elements of canonical matrix. There were 2 latent factors, $f_1$ and $f_2$. The former way interpreted as nature of diameter growth system. In inherent phenomenon of 12 growth factor, communalities except clear length and crown diameter had great explanatory poorer of 78.62-98.30%. Eighty three sample trees could he classified into 5 stem types as follows ; medium type within a radius of ${\pm}1$ standard deviation of factor scores, uniformity type in diameter and height growth in the 1st quadrant, slim type in the 2nd quadrant, dwarfish type in the 3rd quadrant, and fall-holed type in the 4 th quadrant.

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