• 한국소음진동공학회논문집
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• 제22권11호
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• pp.1144-1151
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• 2012

A damage in structure alters its dynamic characteristics. The change is characterized by changes in the modal parameter, i.e., modal frequencies, modal damping value and mode shape associated with each modal frequency. Changes also occur in some of the structural parameters; namely, the mass, damping, stiffness matrices of the structure. In this paper, evaluation of changes in stiffness matrix of a structure is presented as a method not only for identifying the presence of the damage but also locating the damage. It is shown that changed stiffness matrix can be accurately estimated a sensitivity coefficient matrix derived from modifying mode shapes, First, with 4 story shear structure models, the effect of presence of damage in a structure on its stiffness matrix is studied. By using these analytical model, the effectiveness of using change of stiffness matrix in detecting and locating damages is demonstrated. To validate the predicted changing stiffness and its location, the obtained results are compared to the reanalysis result which shows good agreement.

• Macromolecular Research
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• 제11권4호
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• pp.283-290
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• 2003

Organic drugs including aspirin, omeprazole, and naproxen with three different levels of octanol/water partition coefficient were examined for their release behavior from the amphiphilic PCL-b-PEO-b-PCL (PCEC) matrix. Scanning electron micrograph (SEM) of PCEC illustrated a well defined two-phase morphology consisted of dispersed poly(ethylene oxide) (PEO) domain and continuous polycaprolactone (PCL) phase. Differential scanning calorimetry (DSC) and X-ray diffractometry (XRD) experiments veri tied that three model drugs are dissolved as a molecular dispersion in PCEC matrix. The release of hydrophilic aspirin closely followed the water absorption profile of the matrix indicating that its major fraction is present in PEO domain. However, substantial amount of aspirin present in less hydrophilic region displayed discontinuous biphasic release pattern. In the case of omeprazole with intermediate hydrophobicity consistent release behavior was observed for a period of 24 hrs after the rapid liberation of ca. 10% of the drug presumably partitioned in PEO phase. It was ascribed to the fact that the progressive hydration of PCEC matrix gradually increased the chance of drug/water exposure to compensate the exhaustion of device. Naproxen with the highest octanol/water distribution coefficient among three model drugs exhibited a limited release of 35% for 24 hrs. Finally, hydroxypropyl methylcellulose phthalate (HPMCP)/PCEC blend matrix demonstrated an accelerated and quantitative release of hydrophobic naproxen by generating high porosity and thereby expanding polymer/water interface.

• 동력기계공학회지
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• 제3권1호
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• pp.74-79
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• 1999

This paper describes formulation for algorithm of time historical response analysis of vibration for straight-line structure. This method is derived from a combination of the transfer stiffness coefficient method and the Newmark method. And this present method improves the computational accuracy of the transient vibration response analysis remarkably owing to several advantages of the transfer stiffness coefficient method. We regarded the structure as a lumped mass system here. The analysis algorithm for the time historical response was formulated for the straight-line structure containing crooked, tree type system. The validity of the present method compared with the transfer matrix method and the Finite Element Method for transient vibration analysis is demonstrated through the numerical computations.

• Journal of electromagnetic engineering and science
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• 제6권3호
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• pp.155-159
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• 2006

An efficient method is presented to design filters without the similarity transform of their coupling coefficient matrix as circuit parameters, which is very tedious due to pivoting and deciding rotation angles needed during the iterations. The transfer function of a filter is directly used for the design and its desired form is derived by the optimized rational-function fitting technique. A 3rd order coaxial lowpass filter is taken as an example to validate the proposed method.

• 한국정밀공학회지
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• 제14권12호
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• pp.166-173
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• 1997

Influence coefficients on two-plane flexible rotor balancing model are derived by using the transfer matrix method. The model has a rigid uniform cylinder at mid-span of flexible shafts. Both faces of the rigid cylinder are used as the balancing planes. Calculated influence coefficients show that there exist the rotating speed ranges which are useless or insensitive for the balancing. Gyroscopic effect and damping are considered in the study and their effects are discussed.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.898-902
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• 2003

For linear descriptor systems, we consider the $H_{INFTY}$ controller design problem via output feedback. Both static output feedback and dynamic one are discussed. First, in the case of static output feedback, we reduce our control problem to solving a bilinear matrix inequality (BMI) with respect to the controller coefficient matrix, a Lyapunov matrix and a matrix related to the descriptor matrix. Under a matching condition between the descriptor matrix and the measured output matrix (or the control input matrix), we propose setting the Lyapunov matrix in the BMI as being block diagonal appropriately so that the BMI is reduced to LMIs. For fixed-order dynamic $H_{INFTY}$ output feedback, we formulate the control problem equivalently as the one of static output feedback design, and thus the same approach can be applied.

• 한국전산구조공학회논문집
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• 제16권1호
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• pp.9-18
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• 2003

파양한 구조물의 정적해석에서 매트릭스구조해석법은 가상 폭넓게 사용되고 있는 강력한 해석기법이다. 그러나 이 방법으로 많은 수의 자유도를 갖는 구조물을 정확히 해석하기 위해서는 많은 계산 메모리와 빠른 처리 능력을 갖춘 고성능 컴퓨터를 필요로하는 취약점이 있다. 따라서 매트릭스구조해석법으로 많은 수의 자유노를 갖는 구조물을 퍼스널 컴퓨터 상에서 정확히 해석하기에는 곤란한 경우가 많다. 매트릭스구조해석법치 이러한 취약점을 극복하기 위하여, 저자들은 전달강성계수법을 제안한다. 전달강성계수법은 해석대상 구조물에 대한 강성계수의 전달에 기본 개념을 두고 있으am로 퍼스널 컴퓨터에 매우 적합한 해석기법이다. 본 논문에서는 골조추조물에 대한 정적해석 알고리듬을 전달강성계수법으로 정식화한다. 그리고 전달강성계수법, NASTRAN, 매트릭스구조해석법 그리고 해석해에 의한 계산 결과들의 비교를 통해 전달강성계수법의 유효성을 확인한다.

• 정보처리학회논문지:컴퓨터 및 통신 시스템
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• 제2권11호
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• pp.483-488
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• 2013

사용자들은 외부 스토리지를 사용함으로써 언제, 어디서나 자신의 데이터에 접근할 수 있다. 하지만 자신의 데이터가 어떻게 관리되고 있는지는 알 수 없다. 심지어 자신의 데이터에 손상이 발생하여도 인지할 수 없다. 이와 같은 불편을 해결하기 위해 외부 스토리지 검증기법들이 제안되었다. 대부분의 기법들이 준동형 검증 태그(homomorphic verifiable tags)를 사용하고 있지만, 이는 데이터를 지수로 하여 계산하기 때문에 효율성에 한계가 있다. 본 논문에서는 외부 스토리지 무결성 검증의 새로운 접근 방법으로써 계수행렬을 이용한 기법을 제안한다. 제안하는 기법은 데이터를 계수행렬의 형태로 변환하여 검증에 사용한다. 검증과정은 선형연립방정식의 해를 구하는 형태로 진행되며, 검증자는 수식에 해벡터를 대입함으로써 쉽게 검증을 수행할 수 있다. 제안하는 기법을 사용하면 검증자는 sqrt(n) 크기의 데이터로 크기가 n인 데이터를 검증할 수 있다.

• 호남수학학술지
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• 제32권3호
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• pp.399-412
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• 2010

In this paper, we consider a preconditioned accelerated overrelaxation (PAOR) method to solve systems of linear equations. We show the convergence of the PAOR method. We also give com-parison results when the coefficient matrix is an L- or H-matrix. Finally, we provide some numerical experiments to show efficiency of PAOR method.

• 대한수학회보
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• 제49권5호
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• pp.997-1006
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• 2012

In this paper, we study convergence of multisplitting methods with preweighting for solving a linear system whose coefficient matrix is an H-matrix corresponding to both the AOR multisplitting and the SSOR multisplitting. Numerical results are also provided to confirm theoretical results for the convergence of multisplitting methods with preweighting.