• International Journal of Naval Architecture and Ocean Engineering
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• 제10권2호
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• pp.170-179
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• 2018

This paper introduces a new method to study the hydroelastic behavior of hinged Very Large Floating Structures (VLFSs). A hinged two-module structure is used to confirm the present approach. For each module, the hydroelasticity theory proposed by Lu et al. (2016) is adopted to consider the coupled effects of wave dynamics and structural deformation. The continuous condition at the connection position between two adjacent modules is also satisfied. Then the hydroelastic motion equation can be established and numerically solved to obtain the vertical displacement, force and bending moment of the hinged structure. The results calculated by the present new method are compared with those obtained using three-dimensional hydroelasticity theory (Fu et al., 2007), which shows rather good agreement.

• Structural Engineering and Mechanics
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• 제55권3호
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• pp.655-674
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• 2015

In this paper, a new and simplified method is presented in which the natural frequencies of the uniform and non-uniform beams are calculated through simple mathematical relationships. The various vibration problems such as: Rayleigh beam under variable axial force, axial vibration of a bar with and without end discrete spring, torsional vibration of a bar with an attached mass moment of inertia, flexural vibration of the beam with laterally distributed elastic springs and also flexural vibration of the beam with effects of viscose damping are investigated. The governing differential equations are first obtained and then; according to a harmonic vibration, are converted into single variable equations in terms of location. Through repetitive integrations, the governing equations are converted into weak form integral equations. The mode shape functions of the vibration are approximated using a power series. Substitution of the power series into the integral equations results in a system of linear algebraic equations. The natural frequencies are determined by calculation of a non-trivial solution for system of equations. The efficiency and convergence rate of the current approach are investigated through comparison of the numerical results obtained with those obtained from other published references and results of available finite element software.

• 대한조선학회논문집
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• 제52권3호
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• pp.187-197
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• 2015

This study aims the development of a semi-analytic method for the parametric roll of large containerships advancing in longitudinal waves. A 1.5 Degree-of-Freedom(DOF) model is proposed to account the change of transverse stability induced by wave elevations and vertical motions (heave and pitch). By approximating the nonlinearity of restoring moment at large heel angles, the magnitude of roll amplitude is predicted as well as susceptibility check for parametric roll occurrence. In order to increase the accuracy of the prediction, the relationship between righting arm(GZ) and metacentric height(GM) is examined in the presence of incident waves, and then a new formula is proposed. Based on the linear approximation of the mean and first harmonic component of GM, the equation of parametric roll in irregular wave excitations is introduced, and the computational results of the proposed model are validated by comparing those of weakly nonlinear simulation based on an impulse-response-function method combined with strip theory. The present semi-analytic doesn’ t require heavy computational effort, so that it is very efficient particularly when numerous sea conditions for the analysis of parametric roll should be considered.

• 한국소음진동공학회논문집
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• 제17권5호
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• pp.415-426
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• 2007

링크모션 펀치프레스는 많은 링크들이 서로 연결되어 있으며 각각의 링크는 고속에서 구속 운동을 수행한다. 그 결과 동적 불평형 힘과 모멘트가 프레스의 메인프레임으로 전달되며 원하지 않는 진동을 수반한다. 이로 인하여 생산성과 정확한 스탬핑 작업의 저하를 초래한다. 이 논문은 기구학 및 동역학 분석에 기초하여 링크모션 펀치프레스의 다이나믹 언발란스를 저감하는 효과적인 방법을 제시한다. 그리고 디자인 변화가 필요할 때마다 메커니즘의 모델 구성을 자동화하기 위한 디자인 변수 방식을 소개한다. 질량, 질량관성모멘트, 질량중심 등의 링크들의 관성 성질을 얻기 위하여 3차원 캐드 소프트웨어를 활용하였다. 메커니즘의 기구학적, 동역학적 거동에 주요한 영향을 미치는 일부 링크들의 디자인을 변화시킬 때 얻을 수 있는 다양한 조합에 대하여 동역학 시뮬레이션을 수행하였다.

• 한국정보통신학회논문지
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• 제11권7호
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• pp.1341-1347
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• 2007

기존의 광류 (Optical flow)는 국소적 처리를 시작점으로 하는 bottom-up수법에 의해서 구하였다. 이에 반해, 본 논문은 영상유체보존식과 함수 전개법에 의해 영상 전체의 움직임을 차수가 낮은 모드로 부터 순차적으로 전개하는 bottom-down수법을 새로운 수법으로 제안한다. 의료 영상에 있어서 명도는 움직임이 있어도 불변으로 유지하려는 경우가 많다. 그러나 이 같은 영상계열에서의 움직임은 좌표 변환에 의해서 대응된다. 본 수법의 경우 광류는 선형모멘트방정식의 함수에 관한 도함수를 이용하는 투영법에 의해서 반복계산으로 구하여 진다. 본 논문에서는 심장의 영상계열을 이용하여 기존의 Horn and Schunck기법, Standard multigrid기법과 본 수법의 알고리즘을 비교 평가하여 유효성을 나타낸다.

• The Journal of Asian Finance, Economics and Business
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• 제7권12호
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• pp.919-926
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• 2020

The purpose of this study is to analyze and test the effect of financial ratios and macroeconomics on Islamic stock returns listed in Jakarta Islamic Index (JII) other than to assess whether investment risk can be an intervening variable in this study. The type of research is explanatory in nature with a quantitative descriptive approach. The data used is based on secondary sources with a sample group of 29 companies listed on JII for a 5-year period ending 31 December 2018. The data obtained were analyzed by using SEM (Structural Equation Model) with AMOS (Analysis Moment of Structural) 21 program. The results of the study show that only financial ratios affect sharia stock returns and investment risk, while the mediation test found that investment risk does not act as a mediating variable between financial ratios and macroeconomics and Islamic stock return. These findings indicate that the role of the company's financial health is very important. Besides affecting the rate of return obtained, the company's financial health can also reflect the level of risk that investors will accept in the future. By improving financial performance properly, a company will have a positive impact on various interested parties and minimize the level of investor losses.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 춘계학술대회논문집
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• pp.892-896
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• 2001

백색잡음 불규칙 과정으로 모델링된 난류형태의 유체운동에 의하여 가진되는 비선형 시스템의 특성과 제어기법에 대해 연구하였다. 고려된 물리적인 모델은 주질량과 끝단 집중질량을 갖는 보형태의 구조물이다. 그 지배방정식은 확률론적 관점에서 F-P-K 접근법으로 유도되었고, 비선형 해석법으로 Gaussian Closure방법을 이용하였다. 비선형 시스템의 제어기법으로는 슬라이딩 모드 제어기를 최초로 확률영역에서 설계하고 그 효과를 확률영역 및 시간영역에서 고찰하였다.

• Structural Engineering and Mechanics
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• 제24권2호
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• pp.137-154
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• 2006

The reliable pushover analysis of RC structures requires a realistic prediction of moment-curvature relations, which can be obtained by utilizing proper constitutive models for the stress-strain relationships of laterally confined concrete members. Theoretical approach of Mander is still a single stress-strain model, which employs a multiaxial failure surface for the determination of the ultimate strength of confined concrete. Alternatively, this paper introduces a simple and practical failure criterion for confined concrete with emphasis on introduction of significant modifications into the two-parameter Drucker-Prager model. The new criterion is only applicable to triaxial compression stress state which is exactly the case in the RC columns. Unlike many existing multi-parameter criteria proposed for the concrete fracture, the model needs only the compressive strength of concrete as an independent parameter and also implies for the influence of the Lode angle on the material strength. Adopting Saenz equation for stress-strain plots, satisfactory agreement between the measured and predicted results for the available experimental test data of confined normal and high strength concrete specimens is obtained. Moreover, it is found that further work involving the confinement pressure is still encouraging since the confinement model of Mander overestimates the ultimate strength of some RC columns.

• The Journal of Asian Finance, Economics and Business
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• 제8권5호
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• pp.1119-1128
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• 2021

This study aims to investigate a model for reducing workplace deviance from employees' perspectives. Specifically, it examines the relationship between workplace spirituality and workplace deviance through the improvement of organizational commitment. Through the quantitative approach, questionnaires were distributed to 400 civil servants in the various government agencies in Indonesia. Structural Equation Model with Analysis of Moment Structures (SEM-AMOS) was used to analyze the data and test the hypotheses. The results reveal that workplace spirituality has no significant negative effect directly on workplace deviance, but it has a significantly positive effect on organizational commitment. Organizational commitment also has a significant negative effect on workplace deviance. The non-significance of workplace spirituality's direct effect on workplace deviance proves that there is a full mediation effect of organizational commitment. It implies that, to reduce workplace deviance, merely workplace spirituality is not adequate, but it should enhance organizational commitment. The findings can add an understanding of the empirical evidence related to the relationship between workplace spirituality, organizational commitment, and workplace deviance. Practically, the top decision-makers in civil servant institutions need to consider the right strategies, policies, and real efforts to carry out workplace spirituality practices and organizational commitment by designing a control system.

• Structural Engineering and Mechanics
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• 제27권6호
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• pp.713-739
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• 2007

Nowadays computers can perform symbolic computations in addition to mere number crunching operations for which they were originally designed. Symbolic computation opens up exciting possibilities in Structural Mechanics and engineering. Classical areas have been increasingly neglected due to the advent of computers as well as general purpose finite element software. But now, classical analysis has reemerged as an attractive computer option due to the capabilities of symbolic computation. The repetitive cycles of simultaneous - equation sets required by the finite element technique can be eliminated by solving a single set in symbolic form, thus generating a truly closed-form solution. This consequently saves in data preparation, storage and execution time. The power of Symbolic computation is demonstrated by six examples by applying symbolic computation 1) to solve coupled shear wall 2) to generate beam element matrices 3) to find the natural frequency of a shear frame using transfer matrix method 4) to find the stresses of a plate subjected to in-plane loading using Levy's approach 5) to draw the influence surface for deflection of an isotropic plate simply supported on all sides 6) to get dynamic equilibrium equations from Lagrange equation. This paper also presents yet another computationally efficient and accurate numerical method which is based on the concept of derivative of a function expressed as a weighted linear sum of the function values at all the mesh points. Again this method is applied to solve the problems of 1) coupled shear wall 2) lateral buckling of thin-walled beams due to moment gradient 3) buckling of a column and 4) static and buckling analysis of circular plates of uniform or non-uniform thickness. The numerical results obtained are compared with those available in existing literature in order to verify their accuracy.