• Design & Manufacturing
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• 제12권1호
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• pp.1-6
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• 2018

In this study, we calculated the redistribution of vacancy concentration in metal specimens induced by stress-induced diffusion at a high temperature. To deduce the governing equation, we associated the unit volume change equation of strains with a differential equation of vacancy concentration as a function of stress using the stress-strain relationship. In this governing equation, we considered stress as the only chemical potential parameter to stay in the scope of this study, which provided the vacancy concentration equation as of stress gradient in metals. The equation was then mathematically delineated to derive a analytical solution for a transient, one-dimensional diffusion case. With the help of Korhonen's approximation and the boundary conditions, we successfully deduced a general solution from the governing equation. To visualize the feasibility of our solutions, we applied the solution to two different stress-induced cases - a rod with fixed concentrated stresses at both ends and a rod with varying concentrated stresses at both ends. Although it is necessary to legitimatized the model in the future for improvement, our results showed that the model can be used to interpret the location of structural defects, the formation of vacancy, and furthermore the high temperature behavior of metals.

• 정보관리학회지
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• 제21권2호
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• pp.23-44
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• 2004

본 연구의 목적은 사회심리학 이론을 토대로 지역정보 시스템 이용모형을 개발함으로써, 지역주민을 위한 정보통신 서비스의 이용을 효과적으로 설명하는데 있다. 본 연구를 위해 필자는 Ajzen의 계획적 행위 이론(Theory of Planned Behavior: TPB)을 기본모형으로 선택하였는데, 이 이론은 (1) 지역정보 서비스 이용 결과에 대한 기대, (2) 주변 사람들의 권유, (3) 이용을 가능하게 하는 내외적 요인에 대한 자신의 통제 능력의 지각 등을 기본 골격으로 한다. 계획적 행위 이론은 일반적인 사회행동의 설명에 적용되어온 사회심리 이론이므로 필자는 지역정보 시스템 이용의 행동적 특성을 연구 모형에 반영하기 위하여 두 이론 즉, 인터넷 등 매체 이용을 설명하기 위하여 널리 적용되어온 이용과 충족 이론(Uses and gratifications)과 경영정보시스템 이용을 설명하기 위하여 적용되어 온 기술수용모형(Technology Acceptance Model: TAM)을 추가적으로 검토했다. 417명의 지역정보망 시스템 이용자로 부터 수집된 실증자료를 토대로 구조방정식모형(Structural Equation Model: SEM)을 이용하여 제안된 지역정보 시스템 이용모형을 검증한 후 향상된 수정 모형을 제안했다. 그 결과, 지역정보 시스템 이용에 영향을 미치는 주요 요인들로 지역정보를 이용하고자하는 의도, 태도, 주관적 규범, 정보습득에 대한 기대, 사회적 상호작용에 대한 기대, 지역 연계에 대한 기대, 및 개인관련 규범 신념 등을 밝혀 냈다. 이러한 결과를 중심으로 본 연구의 함의와 후속 연구과제가 결론에서 논의되었다.

• Smart Structures and Systems
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• 제25권2호
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• pp.219-228
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• 2020

This work presents a modified continuum model to explore and investigate static and vibration behaviors of perforated piezoelectric NEMS structure. The perforated nanostructure is modeled as a thin perforated nanobeam element with Euler-Bernoulli kinematic assumptions. A size scale effect is considered by included a nonlocal constitutive equation of Eringen in differential form. Modifications of geometrical parameters of perforated nanobeams are presented in simplified forms. To satisfy the Maxwell's equation, the distribution of electric potential for the piezoelectric nanobeam model is assumed to be varied as a combination of a cosine and linear functions. Hamilton's principle is exploited to develop mathematical governing equations. Modified numerical finite model is adopted to solve the equation of motion and equilibrium equation. The proposed model is validated with previous respectable work. Numerical investigations are presented to illustrate effects of the number of perforated holes, perforation size, nonlocal parameter, boundary conditions, and external electric voltage on the electro-mechanical behaviors of piezoelectric nanobeams.

• 한국농공학회논문집
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• 제55권5호
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• pp.9-16
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• 2013

This study finds the characteristics of long-term settlement of Bottom Ash and to review the application of Singh-Mitchell creep equation and Burgers Model to the creep behavior of Bottom Ash. In the undrained state, it was confirmed that creep behavior appeared in the range to 30-80 % of the maximum deviator stress by applying condition in other three stresses through triaxial compression test after isotropically consolidation. By using sieve analysis, it was compared to each sample that was passed through 9.5 mm, 2 mm, 0.25 mm sieves. Also, using Singh-Mitchell creep equation and Burgers Model, it was compared between the theoretical behavior and the observed behavior for each sample. In the result, it is found that creep behavior of Bottom Ash is similar to the theoretical behavior of Singh-Mitchell creep equation and Burgers Model in early stage and it is possible to predict creep behavior of Bottom Ash by these models.

• Journal of Mechanical Science and Technology
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• 제15권3호
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• pp.392-402
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• 2001

The paper reports a multiple source modeling of low-Reynolds-number dissipation rate equation with aids of DNS data. The key features of the model are to satisfy the wall limiting conditions of the individual source terms in the exact dissipation rate equation using the wall damping functions. The wall damping functions are formulated in term of dimensionless dissipation length scale ι(sup)+(sub)D(≡ι(sub)D($\upsilon$$\xi$)(sup)1/4/$\upsilon$) and the invariants of small and large scale turbulence anisotropy tensors. $\alpha$(sub)ij(=$\mu$(sub)i$\mu$(sub)j/$\kappa$-2$\delta$(sub)ij/3) and e(sub)ij(=$\xi$(sub)ij/$\xi$-2$\delta$(sub)ij/3). The model constants are optimized with aids of DNS data in a plane channel flow. Adopting the dissipation length scale as a parameter of damping function, the applicabilities of $\kappa$-$\xi$ model are extended to the turbulent flow calculation of complex flow passages.

• Journal of Advanced Marine Engineering and Technology
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• 제34권8호
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• pp.1084-1093
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• 2010

화염 전파 특성을 나타내는 G 방정식에 기초한 Sub-grid Scale연소 모델을 이용하여 보염기 주위의 난류 예혼합 연소 해석에 관한 대 와동 모사를 수행하였다. Dynamic SGS 모델이 G방정식에 도입되었으며, 삼각형의 보염기 배면의 예혼합 연소 유동에 의해 검증되었다. 해석결과는 실험결과와의 비교를 통해 속도와 온도분포를 잘 예측하고 있음을 확인하였다.

• Ecology and Resilient Infrastructure
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• 제1권1호
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• pp.1-7
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• 2014

본 연구에서는 파랑과 흐름이 공존하고 있는 해안지역에 이용이 가능한 물에 용해된 물질의 정확한 이동을 예측하기 위한 수심적분형 수치모의 기법을 제시한다. 대상 영역에 일반적으로 발생하는 파랑의 전파와 변형 과정 및 쇄파와 흐름의 발달 과정에 대한 모의가 가능한 boussinesq equation 흐름모형과 동일한 과정을 거쳐 유도된 수심적분형 물질수송모형을 지배방정식으로 이용한다. 지배방정식은 approximate riemann solver를 이용하는 유한체적법을 이용하여 해석한다. 제시된 수치모형을 이용하여 해일발생에 의한 흐름양상을 계측한 실험을 재현하였으며, 해당 수역에 가상의 물질의 이송과 확산에 대한 수치모의를 수행하고 그 결과를 분석하였다.

• 한국치위생학회지
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• 제13권2호
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• pp.221-230
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• 2013

Objectives : This study is to confirm the influencing factors on patients satisfaction and intention to revisit the implant service clinic by structural equation model. Methods : We surveyed 250 implant patients visiting 6 dental clnics(hospitals) in Busan, Changwon, Gimhae city and questionnaire was for four weeks in July 2012, a total 209 patients filled out the questionnaires within July and the complete data were analyzed. we were used structural equation model for analysis to confirm influencing factors on implant patients' satisfaction and intention to revisits. Results : This study finds that factors influencing on implant patients' satisfaction and intention to revisit are reasonable medical fee, medical skill treatment of dentist, dental hygienist and other support staff, administrative procedure, and there existed between influencing factors and the patient's treatment satisfaction as well as intention to revisit. In order to satisfy the implant patients, dentist and hygienists should try to provide high quality of treatment and dental services. Conclusions : The results of this study provide managerially important messages to the managers of dental clinics in order to develope management strategies for new customers.

• 산업경영시스템학회지
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• 제38권2호
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• pp.101-107
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• 2015

Modern football has transformed into a scientific football based on data. With this trend, various methods for tactics studies and outcome prediction have been developed on the perspective of data analysis. In this paper, we propose a structural equation model for football game. We analyze critical factors that affect to the winning of game except psychological parts and the causal relationship between latent variables and observed variables is statistically verified through the proposed structural equation model. The results show that the Passing ability and the Ball possession affect to the Attack ability, and consequently it has a positive impact on the winning of game.

• KIEAE Journal
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• 제9권1호
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• pp.107-113
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• 2009

The energy cost is resulted from the energy use. Its sources are divided into some types and depended on the building use or energy-use type. The energy cost should be affected by the amount of the energy use. The cost could be calculated to consider various factors such as the insulation, heating type, building shape and others. But it can not consider all of the affect factors to the energy cost and need to categorize the factors to the condition for estimating the cost. In this paper, it aimed at providing the estimation model in linear equation and multiple linear regression, utilizing the building exterior condition and management characteristics in apartment housing. Its survey are conducted in two parts of management characteristics and building exterior condition. The correlation analysis is conducted to get rid of the multicolinearity among the inputted factors. The number of linear equation model is 11 and includes the 1st, 2nd and 3rd equation function, power function and others. Among these, it suggested the 2nd and 3rd function and power function in terms of the statistics. In multiple linear regression model, the building volume and management area are inputted to the estimation.