• Korean Journal of Computational Design and Engineering
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• v.12 no.3
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• pp.220-232
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• 2007

Current geometric modeling and analysis are commonly based on B-Rep modeling and a finite elements method respectively. Furthermore, it is difficult to represent an object whose material property is heterogeneous using the B-Rep method because the B-Rep is basically used for homogeneous models. In addition, meshes are required to analyze a property of a model when the finite elements method is applied. However, the process of generating meshes from B-Rep is cumbersome and sometimes difficult especially when the model is deformed as time goes by because the topology of deforming meshes are changed. To overcome those problems in modeling and analysis including homogeneous and heterogeneous materials, we suggest a unified modeling and analysis method based on implicit representation of the model using R-function which is suggested by Rvachev. For implicit modeling of an object a distance field is approximated and blended for a complex object. Using the implicit function mesh-free analysis is possible where meshes are not necessary. Generally mesh-free analysis requires heavy computational cost compared to a finite elements method. To improve the computing time of function evaluation, we utilize GPU programming. Finally, we give an example of a simple pipe design problem and show modeling and analysis process using our unified modeling and analysis method.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.50 no.8
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• pp.388-394
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• 2001

This paper presents how to determine the optimal operating points of Unified Power Flow controllers (UPFC) the line flow control of which can enhance system security level. In order to analyze the effect of these devices on the power system, the decoupled model has been employed as a mathematical model of UPFC for power flow analysis. The security index that indicates the level of congestion of transmission line has been proposed and minimized by iterative method. The sensitivity of objective function for control variables of and UPFC has been derived, and it represents the change in the security index for a given set of changes in real power outputs of UPFC. The proposed algorithm with sensitivity analysis gives the optimal set of operating points of multiple UPECs that reduces the index or increases the security margin and Marquart method has been adopted as an optimization method because of stable convergence. The algorithm is verified by the 10-unit 39-bus New England system that includes multiple FACTS devices. The simulation results show that the power flow congestion can be relieved in normal state and the security margin can be guaranteed even in a fault condition by the cooperative operation of multiple UPECs.

• Steel and Composite Structures
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• v.34 no.2
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• pp.241-260
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• 2020

This article presented a comprehensive model to study static buckling stability and associated mode-shapes of higher shear deformation theories of sandwich laminated composite beam under the compression of varying axial load function. Four higher order shear deformation beam theories are considered in formulation and analysis. So, the model can consider the influence of both thick and thin beams without needing to shear correction factor. The compression force can be described through axial direction by uniform constant, linear and parabolic distribution functions. The Hamilton's principle is exploited to derive equilibrium governing equations of unified sandwich laminated beams. The governing equilibrium differential equations are transformed to algebraic system of equations by using numerical differential quadrature method (DQM). The system of equations is solved as an eigenvalue problem to get critical buckling loads and their corresponding mode-shapes. The stability of DQM in determining of buckling loads of sandwich structure is performed. The validation studies are achieved and the obtained results are matched with those. Parametric studies are presented to figure out effects of in-plane load type, sandwich thickness, fiber orientation and boundary conditions on buckling loads and mode-shapes. The present model is important in designing process of aircraft, naval structural components, and naval structural when non-uniform in-plane compressive loading is dominated.

• The Journal of Asian Finance, Economics and Business
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• v.8 no.11
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• pp.253-264
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• 2021

The COVID-19 pandemic has imposed a number of restrictions on the lives of people and services, forcing them to adopt a "New Normal" way of living. Contactless technologies provide a mechanism to reduce the risk of infection, encouraging people to use touchless payment methods. The aim of this study is to develop an integrated framework based on the Health Belief Model and the Unified Theory of Acceptance and Use of Technology to justify the use of mobile payment during the COVID-19 pandemic in Vietnam. Based on a survey of 434 samples, the proposed conceptual model was empirically justified using structural equation modeling (SEM). This study found that performance expectancy, effort expectancy, enjoyment, perceived severity, and perceived susceptibility significantly and positively influenced behavioral intention of using contactless payment technologies. In addition, this study discovered that effort expectancy, perceived severity, and perceived susceptibility all have a positive impact on performance expectancy, while enjoyment triggered users' effort expectancy. By adding novel insights into the literature on the acceptance of technology during the pandemic, this study makes a major contribution to justifying how contactless payment technologies can reduce the risk of getting infected by COVID-19.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.26 no.4
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• pp.54-63
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• 2018

Airlines are promoting self-service based technology by introducing mobile check-in, Kiosk and self-back drop systems, which will help customer satisfaction and efficiency. This study is about the usage intension to use Technology-based Airline Self-Service, the purpose of this study is to examine the key variables affecting Unified Theory of Acceptance (UTAUT2) in using Technology-based Airline Self-Service. According to the results of the ANOVA, there was a significant difference among the groups according to the experience of the self-service device. And analysis results using Structural Equation Model(SEM) was suggested that the performance expectation and hedonic motive of UTAUT2 model were found to have significant influence on initial trust. Also, initial trust affects the intention to use. There are some moderating effects on the structural equation by groups according to the experience of the self-service device. This research has significance in that it can help establish a marketing strategy of airlines to expand the self-service based on the airline technology.

• Advances in aircraft and spacecraft science
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• v.9 no.4
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• pp.301-318
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• 2022

This paper presents the free vibration analysis of 3D printed sandwich beams by using high-order theories based on the Carrera Unified Formulation (CUF). In particular, the component-wise (CW) approach is adopted to achieve a high fidelity model of the printed part. The present model has been used to build an accurate database for collecting first natural frequency of the beams, then predicting Young's modulus based on an inverse problem formulation. The database is built from a set of randomly generated material properties of various values of modulus of elasticity. The inverse problem then allows finding the elastic modulus of the input parameters starting from the information on the required set of the output achieved experimentally. The natural frequencies evaluated during the experimental test acquired using a Digital Image Correlation method have been compared with the results obtained by the means of CUF-CW model. The results obtained from the free-vibration analysis of the FDM beams, performed by higher-order one-dimensional models contained in CUF, are compared with ABAQUS results both first five natural frequency and degree of freedoms. The results have shown that the proposed 1D approach can provide 3D accuracy, in terms of free vibration analysis of FDM printed sandwich beams with a significant reduction in the computational costs.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.29 no.1
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• pp.19-28
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• 2016

In the case of structural analysis for building structures, the super-structure and the sub-structure are analyzed by using separate structural models in the field because of time saving, facile result interpretation and easy analysis of dynamic behavior. However this separate structural model violated the compatibility condition of structural analysis and it can not consider the interaction of superand sub- structures. In the present study, the analysis results of this separate model were compared to those of the unified model of super- and sub- structures which can consider the interaction of super- and sub- structures and reflect the realistic boundary conditions. According to the comparison results, the the analysis model using separate models can underestimate the member force and deflection of structural members in the super-structures and overestimate the deflection and member force of sub-structures. Therefore, in the case of high-rise buildings, irregular shaped buildings, buildings which are expected to be affected by large differential settlement and remodeling buildings, the unified structural model for super- and sub- structures was recommended for structural analysis instead of the separate structural model.

• The Journal of the Korea Contents Association
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• v.6 no.8
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• pp.114-123
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• 2006

The practical value of the third place using ubiquitous digital technology has been increasing rapidly, therefore it is inevitable to educate students of spatial design in the interdisciplinary education system based on the unified technology of digital in order to cultivate leading designers to adapt new era of spatial design. After a research for the unified form of spatial planning and case studies of foreign educations, this study addresses the issues to classify the interdisciplinary teaching form into three educational categories digital interactive education, digital unified education and digital creative education. Finally, the study proposes the basic form of the ideal and futuristic education of spatial design with the distinguished results after conducting the model curriculum by the above categories.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.8
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• pp.34-43
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• 2007

This paper presents a methodology on the AHP(Analytic Hierarchy Process) to calculate unified power quality index which provide an overall assessment of the distribution system performance. To obtain the unified power quality index. we propose the use of the AHP model and consider contingency using Monte Carlo simulation. The proposed method is especially useful and effective for planning. We have applied the proposed method to an actual relatively large system.

• Proceedings of the Korea Information Processing Society Conference
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• 2005.05a
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• pp.1049-1052
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• 2005

웹 기술 기반의 컨텐츠 개발 및 운영으로 다른 환경에서의 컨텐츠 활용을 토대로 교육자원의 정보들을 통합 운영할 수 있는 관리 중심체인 e-learning 시스템의 중요성과 필요성이 대두되고 교육용 어플리케이션은 현재 표준화되지 않은 개발 프로세스를 기반하여 개발하고 있는 실정이다. 따라서, 국제적 표준인 SCORM(Sharable Content Object Reference Model)을 기반으로 높은 재사용성과 유지보수성을 극대화하기 위해 컴포넌트 개발 방법론(Component Based Development)을 적용해서 체계적으로 교육자원을 개발하고 지원하기 위한 교수-학습지원 시스템에 초점둔 연구가 요구된다. 따라서, 본 논문에서는 컴포넌트 개발 방법론중에서 Unified Process를 이용하여 교수-학습지원 시스템을 정의하고 SCORM기반의 메타데이터를 이용한 컨텐츠저장소에 관한 분석 및 설계를 한다. 이를 통해 실제 교수자가 필요로하는 컨텐츠 제공을 함으로써 재사용성 향상으로 교수-학습지원 시스템의 효율성을 극대화하고자 한다.