• Geomechanics and Engineering
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• 제12권2호
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• pp.313-326
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• 2017

Based on the reliability theory and limit analysis method, the roof stability of a shallow tunnel is investigated under the condition of surface settlement. Nonlinear Hoek-Brown failure criterion is adopted in the present analysis. With the consideration of surface settlement, the internal energy and external work are calculated. Equating the rate of energy dissipation to the external rate of work, the expression of support pressure is derived. With the help of variational approach, a performance function is proposed to reliability analysis. Improved response surface method is used to calculate the Hasofer-Lind reliability index and the failure probability. In order to assess the validity of the present results, Monte-Carlo simulation is performed to examine the correctness. Sensitivity analysis is used to estimate the influence of different variables on reliability index. Among random variables, the unit weight significantly affects the reliability index. It is found that the greater coefficient of variation of variables lead to the higher failure probability. On the basis of the discussions, the reliability-based design is achieved to calculate the required tunnel support pressure under different situations when the target reliability index is obtained.

• 한국광학회지
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• 제11권4호
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• pp.239-245
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• 2000

본 논문에서는 회절광학소자를 이용하여 컴팩트형 디지털 스틸 카메라용 광학계를 설계 및 평가하였다. 기존의 디지털 스틸 카메라용 광학계가 retrofocus 형태인 것에 비해 컴팩트한 광학계를 얻기 위해서 telephoto 형태로 구성하였다. 또한, 본 광학계를 회절광학소자와 굴절광학소자가 결합된 hybrid 플라스틱 렌즈 1매와 순수한 굴절광학소자 1매로 구성하여 무게, 부피등을 줄이고자 하였다. Gauss 괄호를 이용한 근축 광선추적을 통해 초기 설계치를 수치 해석적인 방법으로 구하였다. 제1면을 비구면화하고, 색수차를 보정하기 위해 제2면을 회절광학소자를 이용하여 설계된 광학계는 1/4" CCD, F/4에 대응되도록 최적화하였다. 최종적으로 설계된 광학계의 초점거리는 3.89mm, 전장(overall length)은 5.19mm로서 컴팩트하며, 현재의 디지털스틸 카메라용 광학계에서 요구하는 성능을 충분히 만족하며, 차세대 화상통신용 광학계에 응용될 수 있을것으로 기대된다.

• 수산해양기술연구
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• 제23권3호
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• pp.1-1
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• 1987

이상으로부터 다음의 결론을 얻는다. 조파저항 이론의 전개에서 Michell 적분보다 더욱 정밀한 Neumann-Kelvin 문제가 복잡한 kernel 함수 때문에 많은 시간과 노력이 필요하지만, 원점 부근에서 Kelvin 소오스의 점근거동을 조사하여 세장체 근사를 행함으로 N-K 문제의 kernel 함수에 대한 근사와 동등하게 처리될 수 있었다. 조파저항의 계산 결과가 Michell 적분과 비슷한 경향을 보이나, 실험치와의 정확한 비교를 할 수 없었다. 그러나 세장선 이론을 적용함으로써 훨씬 복잡하고 지루한 작업을 들 수 있었다. 전진 속도를 갖는 경우에는 수정된 Green정리를 이용하면 될 것으로 기대된다.

• Advances in concrete construction
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• 제9권3호
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• pp.327-335
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• 2020

Concrete pipes are considered important structures playing integral role in spread of cities besides transportation of gas as well as oil for far distances. Further, concrete structures under seismic load, show behaviors which require to be investigated and improved. Therefore, present research concerns dynamic stress and strain alongside deflection assessment of a concrete pipe carrying water-based nanofluid subjected to seismic loads. This pipe placed in soil is modeled through spring as well as damper. Navier-Stokes equation is utilized in order to gain force created via fluid and, moreover, mixture rule is applied to regard the influences related to nanoparticles. So as to model the structure mathematically, higher order refined shear deformation theory is exercised and with respect to energy method, the motion equations are obtained eventually. The obtained motion equations will be solved with Galerkin and Newmark procedures and consequently, the concrete pipe's dynamic stress, strain as well as deflection can be evaluated. Further, various parameters containing volume percent of nanoparticles, internal fluid, soil foundation, damping and length to diameter proportion of the pipe and their influences upon dynamic stress and strain besides displacement will be analyzed. According to conclusions, increase in volume percent of nanoparticles leads to decrease in dynamic stress, strain as well as displacement of structure.

• Archives of Plastic Surgery
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• 제40권4호
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• pp.312-319
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• 2013

Over the past decade, driven by advances in educational theory and pressures for efficiency in the clinical environment, there has been a shift in surgical education and training towards enhanced simulation training. Microsurgery is a technical skill with a steep competency learning curve on which the clinical outcome greatly depends. This paper investigates the evidence for educational and training interventions of traditional microsurgical skills courses in order to establish the best evidence practice in education and training and curriculum design. A systematic review of MEDLINE, EMBASE, and PubMed databases was performed to identify randomized control trials looking at educational and training interventions that objectively improved microsurgical skill acquisition, and these were critically appraised using the BestBETs group methodology. The databases search yielded 1,148, 1,460, and 2,277 citations respectively. These were then further limited to randomized controlled trials from which abstract reviews reduced the number to 5 relevant randomised controlled clinical trials. The best evidence supported a laboratory based low fidelity model microsurgical skills curriculum. There was strong evidence that technical skills acquired on low fidelity models transfers to improved performance on higher fidelity human cadaver models and that self directed practice leads to improved technical performance. Although there is significant paucity in the literature to support current microsurgical education and training practices, simulated training on low fidelity models in microsurgery is an effective intervention that leads to acquisition of transferable skills and improved technical performance. Further research to identify educational interventions associated with accelerated skill acquisition is required.

• 한국건설관리학회:학술대회논문집
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• 한국건설관리학회 2008년도 정기학술발표대회 논문집
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• pp.551-556
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• 2008

식스시그마는 처음소개 된 이래로 20련 동안 전략적인 측면과 방법론적인 측면 모두에서 식스시그마는 끊임없는 변화를 거듭하고 있다. 식스시그마와 다른 비즈니스 전략과의 접목을 통해 보다 높은 시너지효과를 창출할 수 있는 경영혁신전략의 개발에 대한 관심은 대단히 높다. 린 생산방식 등과의 접목에 대해 많은 연구와 실행이 추진되고 있으며 특히, 린과 식스시그마가 접목된 린 식스시그마는 식스시그마를 통해 성과를 올린 여러 기업들이 보다 발전된 형태의 혁신전략으로서 도입을 추진하고 있다. 하지만 현재 린과 식스시그마를 접목한 린식스시그마에 대한 연구나 여러 기업들의 적용이 이루어지고 있지만 건설분야에서는 연구나 실제 적용사례들이 부족한 상태이다. 이러한 문제점을 해결하고자 6시그마를 이용하여 시행된 프로젝트를 통하여 건설분야에서의 식스시그마의 방법론인 DMAIC의 프로세스를 구체화시키고 선행연구된 린식스시그마 연구를 통하여 DMAIC 프로세스를 발전시키고 건설분야에 식스시그마 DMAIC 프로세스를 재구성하여 제시하고자 한다.

• 치위생과학회지
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• 제18권1호
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• pp.50-59
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• 2018

The purpose of this study was to develop a motivational interviewing (MI) training program to improve competency in communication and to effect the evaluated changes that would occur in dental students' counseling techniques as result of the training in the program. The study proceeded through the program via role-play practice, which was explained effectively during the MI program training process. A convenience sample of 43 fourth-year dental hygiene students was recruited. Twenty-two students were randomly assigned to the intervention group and 21 to the control group in the order of recruitment. The theoretical lecture was delivered over 3 hours and the practice was done in parallel by applying cases occurring in clinic settings. The practice was technical training, partner practice, and small group practice. The intervention group received three hour MI lecture while the control group received no lecture. Evaluation through role-play practice was separated according to "researcher's viewpoint," "counselor's role viewpoint," and "patient's role viewpoint." The results of the analysis showed that the intervention group had higher MI skills and ability than the control group. Furthermore, program participants showed positive impressions to the MI training program. The use of coaching sessions improved the MI techniques and counseling skills of dental hygiene students learning MI. The effect of the application of the MI training program was that the MI training improved counseling skills and interviewing abilities. Moreover, continuous training and feedback enhanced MI techniques and core skills. Training using lectures in parallel with practice rather than education through theory alone improved students' techniques. Application of role play through the combined method of the MI program was confirmed by an effective training method.

• 한국가구학회지
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• 제26권3호
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• pp.267-273
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• 2015

This study is a review on the relationship between furniture purchasers and producers in the Joseon period. Understanding the relationships in our traditional spirit and the Joseon furniture that reflects a aesthetic sense is a meaningful work. Joseon was to build an ideal country which put emphasis on the order and harmony through Theory of 'Yeak' as the confucianism nation. Human aesthetics, which emphasis on the spiritual value by confirmity to nature and forcus on the relaxed, deficient personality rather than completeness was established as the central formative consciousness of the Joseon Dynasty. The nature of things in the confucian scholar prior to the representations of things is expressed in the form of master craftsman's skill and soul. Formative consciousness of the confucian scholar is to realize ideals by communciation and interchange with master craftsman's soul in the form of the Joseon furniture. The beauty of restraint and brevity in the Joseon Dynasty furniture includes meanings and procedures of art work. It implies an orderer's purpose of production and a producer's products. Understanding the spirit of times in the production becomes the cornerstone capable of getting closer to the furniture ultimate proper function. These problems have a very close relationship with the problems of modern people's commnuication. We expect an even higher growth of the furniture by achieving more improved communication based on the consumer's great insight and the producer's passion.

• Steel and Composite Structures
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• 제44권4호
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• pp.531-543
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• 2022

An exact dynamic analytical method for free vibrations of continuous partial-interaction composite beams is proposed based on the Timoshenko beam theory. The main advantage of this method is that the independent shear deformations and rotary inertia of sub-beams are considered, which is more in line with the reality. Therefore, the accuracy of eigenfrequencies obtained by this method is significantly improved, especially for higher order modes, compared to the existing methods where the rotary angles of both sub-beams are assumed to be equal irrespective of the differences in the shear stiffness of each sub-beam. Furthermore, the solutions obtained by the proposed method are exact owing to no introduction of approximated displacement and force fields in the derivation. In addition, an exact analytical solution for the case of simply supported is obtained. Based on this, an approximate expression for the fundamental frequency of continuous partial-interaction composite beams is also proposed, which is useful for practical engineering applications. Finally, the practicability and effectiveness of the proposed method and the approximate expression are explored using numerical and experimental examples; The influence factors including the interfacial interaction, shear modulus ratio, span-to-depth ratio, and side-to-main span length ratio on the eigenfrequencies are presented and discussed in detail.

• 한국강구조학회 논문집
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• 제11권4호통권41호
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• pp.373-384
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• 1999

복합재료를 사용한 비등방성 원통형 쉘 구조형식은 단일소재의 재료역학적인 단점을 극복할 수 있다. 본 연구의 목적은 1차전단변형효과가 고려된 비등방성 원통형 쉘을 해석하는 것이다. 전단변형효과가 고려된 원통형 쉘의 거동은 기존의 고전적인 해와 길이-두께비에 따라 상당한 거동의 차이를 보이므로 이러한 전단변형효과의 고찰은 매우 중요하다고 사료된다. 또한 본 연구는 유한요소법에 근간한 상용 공학프로그램인 ANSYS와 본 연구의 프로그램결과를 비교, 검증하였으며, 비등방성 원통형 쉘의 중심각의 변화, 화이버의 보강각도 변화, 탄성계수비의 변화 등에 따른 쉘의 처짐 및 단면력을 분석하였다. 본 논문에서 사용한 유한차분법에 의한 해는 기존의 해석적인 방법으로는 해석하기 어려운 보다 다양하고 복잡한 조건을 갖는 문제에 대하여 보다 정확한 해를 얻을 수 있다. 따라서 본 논문에서 제시한 유한차분법을 이용한 다양한 비등방성 원통형 쉘의 해석결과는 복합 신소재를 사용하는 쉘 구조체의 실용화에 앞서 다양한 기준을 제시할 수 있을 것으로 판단된다.