• Smart Structures and Systems
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• 제17권4호
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• pp.611-629
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• 2016

This study presents a new approach of surrogate modeling for time-consuming finite element analysis. A surrogate model is widely used to reduce the computational cost under an iterative computational analysis. Although a variety of the methods have been widely investigated, there are still difficulties in surrogate modeling from a practical point of view: (1) How to derive optimal design of experiments (i.e., the number of training samples and their locations); and (2) diagnostics of the surrogate model. To overcome these difficulties, we propose a sequential surrogate modeling based on Gaussian process model (GPM) with self-adaptive sampling. The proposed approach not only enables further sampling to make GPM more accurate, but also evaluates the model adequacy within a sequential framework. The applicability of the proposed approach is first demonstrated by using mathematical test functions. Then, it is applied as a substitute of the iterative finite element analysis to Monte Carlo simulation for a response uncertainty analysis under correlated input uncertainties. In all numerical studies, it is successful to build GPM automatically with the minimal user intervention. The proposed approach can be customized for the various response surfaces and help a less experienced user save his/her efforts.

• 인터넷정보학회논문지
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• 제22권1호
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• pp.1-11
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• 2021

Estimation of distribution algorithm (EDA) is a popular stochastic metaheuristic algorithm. EDA has been widely utilized in various optimization problems. However, it has been shown that the diversity of the population gradually decreases during the iterations, which makes EDA easily lead to premature convergence. This article introduces a hybrid estimation of distribution algorithm (EDA) with differential evolution (DE) based on self-adaptive strategy, namely HEDADE-SA. Firstly, an alternative probability model is used in sampling to improve population diversity. Secondly, the proposed algorithm is combined with DE, and a self-adaptive strategy is adopted to improve the convergence speed of the algorithm. Finally, twenty-five benchmark problems are conducted to verify the performance of HEDADE-SA. Experimental results indicate that HEDADE-SA is a feasible and effective algorithm.

• 대한기계학회논문집
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• 제18권8호
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• pp.1939-1951
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• 1994

This study introduces a new tool breakage detecting technology comprised of an unsupervised neural network combined with adaptive time series autoregressive(AR) model where parameters are estimated recursively at each sampling instant using a parameter adaptation algorithm based on an RLS(Recursive Least Square). Experiment indicates that AR parameters are good features for tool breakage, therefore it can be detected by tracking the evolution of the AR parameters during milling process. an ART 2(Adaptive Resonance Theory 2) neural network is used for clustering of tool states using these parameters and the network is capable of self organizing without supervised learning. This system operates successfully under the wide range of cutting conditions without a priori knowledge of the process, with fast monitoring time.

• 대한기계학회논문집A
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• 제27권9호
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• pp.1463-1468
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• 2003

This paper presented the real-time self-tuning learning control based on evolutionary computation, which proves its superiority in finding of the optimal solution at the off-line learning method. The individuals of the populations are reduced in order to learn the evolutionary strategy in real-time, and new method that guarantee the convergence of evolutionary mutations is proposed. It is possible to control the control object slightly varied as time changes. As the state value of the control object is generated, evolutionary strategy is applied each sampling time because the learning process of an estimation, selection, mutation is done in real-time. These algorithms can be applied; the people who do not have knowledge about the technical tuning of dynamic systems could design the controller or problems in which the characteristics of the system dynamics are slightly varied as time changes.

• 한국정보시스템학회지:정보시스템연구
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• 제18권1호
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• pp.25-46
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• 2009

According to adaptive structuration theory, faithfulness of appropriation(FOA), and consensus on appropriation(COA) are variables for measuring appropriation in use of IT. FOA is the level of interpreting and using the intentions of the IT designers objectively and COA is the level of agreement on ways of using IT among or with user group independently of designers' intention. In traditional theories of IT adoption, computer self-efficacy(CSE), self evaluation on abilities of using computer, has been considered as one of the important individual differences. which would influence on beliefs of using IT. Therefore, considering the relationship among CSE, FOA, COA and attitude, we can hypothesize that CSE would play a moderation varaible among appropriation related variables relationships, FOA-attitude and COA-attitude. The objective of this study is an analysis of CSE's moderation effects in causality relationship among appropriation measuring variables. For this purpose, we propose a research model where there are four hypotheses for moderation effects of CSE on the relationships between appropriation variables. We test these hypotheses by sampling ERP and groupware users. In result, our proposed hypotheses except moderation effect of COA-usefulness are accepted. Main contribution of this study is to identify the relationship between CSE and AST. This study implies that very careful consideration of users' CSE is necessary in order to perform managerial activities based on FOA and COA in IT management department.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집B
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• pp.105-109
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• 2001

This paper discuss the real-time self-tuning learning control based on evolutionary computation, which proves its the superiority in the finding of the optimal solution at the off-line learning method. The individuals are reduced in order to learn the evolutionary strategy in real-time, and new method that guarantee the convergence of evolutionary mutations are proposed. It possible to control the control object varied as time changes. As the state value of the control object is generated, applied evolutionary strategy each sampling time because the learning process of an estimation, selection, mutation in real-time. These algorithms can be applied, the people who do not have knowledge about the technical tuning of dynamic systems could design the controller or problems in which the characteristics of the system dynamics are slightly varied as time changes.

• 한국심리학회지 : 문화 및 사회문제
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• 제15권4호
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• pp.565-589
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• 2009

본 연구에서는 게임 사용의 부정적 결과에 초점을 둔 선행 연구와 달리, 게임활용의 긍정적 결과로서의 적응적 게임활용도를 측정하는 도구를 개발하고 타당화하였다. 예비조사를 통해 적응적 게임활용 측정 도구를 개발하고, 유층표집을 통해 선정된 전국 중고등학생 600명을 대상으로 본조사를 실시하였다. 연구결과 활력 경험, 생활경험 확장, 여가 선용, 몰입 경험, 자긍심 경험, 통제력 경험, 사회적 지지망 유지 및 확장 등 7개의 요인으로 구성되는 척도의 신뢰도와 시간에 걸친 안정성이 확인되었다. 또한, 척도의 구성타당도, 변별타당도, 및 공인타당도를 확인하였다. 게임 연구의 외연 확장과 관련한 본 연구의 시사점과 장래 연구 방향을 논의하였다.

• Asian Pacific Journal of Cancer Prevention
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• 제14권12호
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• pp.7451-7457
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• 2013

Background: Understanding and enhancing change capabilities, including Practice Adaptive Reserve (PAR), of Community Health Centers (CHCs) may mitigate cancer-related health disparities. Materials and Methods: Using stratified random sampling, we recruited 232 staff from seven CHCs serving Asian Pacific Islander communities to complete a self-administered survey. We performed multilevel regression analyses to examine PAR composite scores by CHC, position type, and number of years worked at their clinic. Results: The mean PAR score was 0.7 (s.d. 0.14). Higher scores were associated with a greater perceived likelihood that clinic staff would participate in an evidence-based intervention (EBI). Constructs such as communication, clinic flow, sensemaking, change valence, and resource availability were positively associated with EBI implementation or trended toward significance. Conclusions: PAR scores are positively associated with perceived likelihood of clinic staff participation in cancer screening EBI. Future research is needed to determine PAR levels most conducive to implementing change and to developing interventions that enhance Adaptive Reserve.

• Journal of Power Electronics
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• 제16권4호
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• pp.1513-1525
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• 2016

Rapid and accurate phase synchronization is critical for the reliable control of grid-tied inverters. However, the commonly used software phase-locked loop methods do not always satisfy the need for high-speed and accurate phase synchronization under severe grid imbalance conditions. To address this problem, this study develops a novel open-loop phase locking scheme based on a synchronous reference frame. The proposed scheme is characterized by remarkable response speed, high accuracy, and easy implementation. It comprises three functional cascaded blocks: fast orthogonal signal generation block, fast fundamental-frequency positive sequence component construction block, and fast phase calculation block. The developed virtual orthogonal signal generation method in the first block, which is characterized by noise immunity and high accuracy, can effectively avoid approximation errors and noise amplification in a wide range of sampling frequencies. In the second block, which is the foundation for achieving fast phase synchronization within 3 ms, the fundamental-frequency positive sequence components of unsymmetrical grid voltages can be achieved with the developed orthogonal signal construction strategy and the symmetrical component method. The real-time grid phase can be consequently obtained in the third block, which is free from self-tuning closed-loop control and thus improves the dynamic performance of the proposed scheme. The proposed scheme is adaptive to severe unsymmetrical grid voltages with sudden changes in magnitude, phase, and/or frequency. Moreover, this scheme is able to eliminate phase errors induced by harmonics and random noise. The validity and utility of the proposed scheme are verified by the experimental results.

• 한국주거학회논문집
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• 제20권6호
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• pp.1-10
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• 2009

Rapid social change affects residential environments and this in turn creates new stimuli to which people have to adapt. These stimuli have been seen to increase stress levels. Therefore, dwellers in these environments try to reduce stress through various methods. The purpose of this paper is to: 1) identify the general trends of coping styles about residential environmental stress, 2) analyze the differences in socio-demographic characteristics and how the physical characteristics of buildings affect stress, find out how personal backgrounds affect stress levels and the ability to get rid of environmental-related stress. The subjects in this study consisted of people living in multi-family housing in Gwangju. The city is divided into 5 districts and used quota sampling. 324 housewives were surveyed from the households by self-administered questionnaires. The survey was conducted in December, 2006, after the questionnaire was revised based on the results of preliminary survey. After all the questionnaires were collected, the data was coded and analyzed using the SPSS 12.0 program. This study confirmed that the manner in which those in multi-family housing coped with stress. Especially, we need a policy which seriously considers residents who are of low social-economic standing. As well as being exposed to residential environmental stress, they also have no means to deal with it. The age of a building had a strong impact on coping styles about residential environmental stress. We have to make special studies about the adaptive reuse of buildings for the reduction of residential environmental stress and to greatly improve coping styles. In conclusion, it emphasized the importance of education, information, and economic aid. Reasonable housing management would surely lead to a rise in residential satisfaction and the promotion of residential welfare.