• 대한인간공학회지
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• 제9권2호
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• pp.65-72
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• 1990

The historical development process and the current research trends of ergonmics in Korea are reviewed and organized in this paper. The recommended research directions in the near future are also discussed based upon the analyses of the potential major key industries of Korea in 1990's. Keynords: Human Engineering Society of Korea; Research activities in Ergonomics; Ergonomics educations

• 한국지반공학회지:지반
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• 제12권3호
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• pp.149-164
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• 1996

탄성지반에서 지반스프링을 이용하여 굴착단계별로 토류벽의 거동을 검토하였다. 토막선형함수를 이용하여 지반계수에 따른 p-y 특성곡선을 산정한 수 있는 수학적 모델을 사용하였고, 토류벽의 굴착단계는 beam-column 방법에 의해 분석하였다. 개발된 프로그램의 신뢰도는 예측치와 실제변위의 비교를 통해 검증하였다. 건설단계를 잘 반영하므로, 앵커로 지지된 토류벽의 변위예측이 향상되었다. 분석결과에 따르면 제안된 방법은 민감도해석에 적용되는 계수들의 상대적 중요성의 평가에 효과적으로 이용될 수 있다.

• 실천공학교육논문지
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• 제8권2호
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• pp.137-146
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• 2016

연구는 교육전문가로서 초 중 고 일반교사 및 대학교수가 담당해야 할 상담자 역할의 중요성에 주목하여 최근 10년간 이루어진 국내 연구 동향을 분석하고, 향후 연구의 방향을 제시하기 위해 수행되었다. 이를 위해 분석대상 80편의 논문에 대해 연도, 연구주제, 연구방법에 따라 분석하였다. 그 결과, 첫째, 2006년부터 2015년까지 꾸준히 연구가 진행되어 왔으나 초등학교(60.9%)에 편중되어 있었고, 중학교(15.8%), 고등학교(15.8%), 대학에서의 일반교수 상담(7.5%)은 매우 부족하였다. 둘째, 7개 연구주제별로 보았을 때, 상담에 대한 요구와 실태를 살펴보는 조사연구(73.8%)가 대부분이었고, 주로 석사학위논문(76.3%)으로 진행된 연구였다. 셋째, 대부분의 연구가 양적연구(91.3%)이고, 질적연구는 매우 미흡함을 알 수 있었다. 끝으로, 이러한 결과에 대한 논의, 연구의 제한점, 향후 연구에 대해 제언하였다.

• 한국정보통신학회논문지
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• 제26권2호
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• pp.288-293
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• 2022

비대면 코딩 교육에서 시공간 제약에 의한 불편함을 줄이고 교육의 효과를 높이기 위해 메타버스(metaverse)라는 새로운 도구에 대한 기대치가 높아지고 있다. 메타버스의 핵심요소 중 하나는 3차원 가상공간에서의 상호작용이다. 하지만 대부분의 기존 메타버스 기반 교육에서는 상호작용이 이루어지지 않고 단방향 교육에 메타버스가 활용되는 경우가 많아 양방향 코딩 교육에는 적합하지 않다. 본 논문에서는 교수자-학생 간 상호작용이 가능한 양방향 코딩 교육을 위해 새로운 메타버스 활용 방법을 제안한다. 제안 방법에서는 교수자 및 학생들의 코딩 화면을 3차원 가상공간에 공유하고 확인할 수 있으며, 학생의 요청이 있을 때마다 교수자가 원격제어를 통해 직접 학생의 소스코드를 교정해주는 등의 피드백을 제공할 수 있다. 이러한 메타버스 가상공간에서는 교수자가 2명 이상인 다대다 교육이 가능하다는 장점이 있다. 제안하는 메타버스 활용 방안에 대해 메타버스 환경 구성과 교육 안을 도출하고, 장점 및 전제조건에 대해 요약하였다.

• Journal of Mechanical Science and Technology
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• 제16권8호
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• pp.1072-1078
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• 2002

The constrained motion requires the determination of constraint force acting on unconstrained systems for satisfying given constraints. Most of the methods to decide the force depend on numerical approaches such that the Lagrange multiplier method, and the other methods need vector analysis or complicated intermediate process. In 1992, Udwadia and Kalaba presented the generalized inverse method to describe the constrained motion as well as to calculate the constraint force. The generalized inverse method has the advantages which do not require any linearization process for the control of nonlinear systems and can explicitly describe the motion of holonomically and/or nongolonomically constrained systems. In this paper, an explicit equation to describe the constrained motion is derived by minimizing the performance index, which is a function of constraint force vector, with respect to the constraint force. At this time, it is shown that the positive-definite weighting matrix in the performance index must be the inverse of mass matrix on the basis of the Gauss's principle and the derived differential equation coincides with the generalized inverse method. The effectiveness of this method is illustrated by means of two numerical applications.

• 한국지반공학회지:지반
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• 제13권3호
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• pp.21-32
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• 1997

본 연구에서는 암반의 국부파괴 현상을 현실적으로 모형 화하기 위하여 혼합체기법을 적용한 새로운 유한요소를 제안하였다. 이를 위하여 각 유한요소의 적분점에서 재료의 안정성을 검토하고 필요시 국부파괴 요소와 인접한 암반 물성을 이용한 혼합체 물성을 도출하였으며 국부파괴 후의 재료 거동을 추적하였다. 제시한 모형을 사용하면 변형율 연화 모형을 사용하더라도 유한요소망의 객관성을 유지할 수 있으며 국부파괴 이후 재료의 거동을 현실적으로 모형화 할 수 있다. 또한 유한요소 갯수가 비교적 작더라도 수치해석 결과와 실험 결과가 잘 일치하고 있음을 알 수 있다.

• Journal of Biosystems Engineering
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• 제26권6호
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• pp.509-516
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• 2001

This paper introduced some advantages of the time-frequency analysis of vibration and investigated, using the time-frequency transform, the characteristics of the transient motion of a tractor seat, which occurred during the tractor traversed over a rectangular obstacle on the flat surface. The characteristics of the short-time courier and wavelet transforms as time-frequency analysis methods were introduced and discussed to figure out which is more suitable to the analysis of the transient motions of agricultural tractors. Using each transform, transient vibration of a tractor seat was analyzed. Results of the analysis showed that the transient vibration of the seat was influenced by the natural frequencies of vertical mode of chassis, pitching mode of engine and pitching mode of cab of the tractor. The time sequence of the natural mode of tractor vibration was also revealed by the time-frequency analysis. The vibration path analysis by the time-frequency transform showed that the vibration energies transmitted from the front mounts to the seat were less than those from the rear mounts. The energy reduction ratios between the cab mounts and seat were also estimated to be about 72∼78%. The front mounts showed larger reduction than the rear mounts. However, the reduction difference between the right and left sides mounts was negligibly small. The short time Fourier transform was found to be a proper method for investigating the transient motions of farm machines and their effects on the ride vibration.

• Journal of Mechanical Science and Technology
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• 제15권7호
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• pp.941-950
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• 2001

A study of counter-current two-phase flow in narrow rectangular channels has been performed. Two-phase flow regimes were experimentally investigated in a 760mm long and 100mm wide test section with 2.0 and 5.0mm gap widths. The resulting flow regime maps were compared with the existing transition criteria. The experimental data and the transition criteria of the models showed relatively good agreement. However, the discrepancies between the experimental data and the model predictions of the flow regime transition become pronounced as the gap width increased. As the gap width increased the transition gas superficial velocities increased. The critical void fraction for the bubbly-to-slug transition was observed to be about 0.25. The two-phase distribution parameter for the slug flow was larger for the narrower channel. The uncertainties in the distribution parameter could lead to a disagreement in slug-to-churn transition between the experimental findings and the transition criteria. For the transition from churn to annular flow the effect of liquid superficial velocity was found to be insignificant.

• Journal of Mechanical Science and Technology
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• 제16권3호
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• pp.354-362
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• 2002

In this paper, the heat transfer characteristics of a self-oscillating heat pipe are experimentally investigated for the effect of various working fluid fill charge ratios and heat loads. The characteristics of temperature oscillations of the working fluid are also analysed based on chaotic dynamics. The heat pipe is composed of a heating section, a cooling section and an adiabatic section, and has a 0.002m internal diameter, a 0.34m length in each turn and consists of 19 turns. The heating and the cooling portion of each turn has a length of 70mm. A series of experiments was carried out to measure the temperature distributions and the pressure variations of the heat pipe. Furthermore, heat transfer performance, effective thermal conductivity, boiling heat transfer and condensation heat transfer coefficients are calculated for various operating conditions. Experimental results show the efficacy of this type of heat pipe.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 1996년도 International Conference on Agricultural Machinery Engineering Proceedings
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• pp.802-811
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• 1996

Farmers need alternatives for weed control due to the desire to reduce chemicals used in farming. However, conventional mechanical cultivation cannot selectively remove weeds located in the seedline between crop plants and there are no selective heribicides for some crop/weed situations. Since hand labor is costly , an automated weed control system could be feasible. A robotic weed control system can also reduce or eliminate the need for chemicals. Currently no such system exists for removing weeds located in the seedline between crop plants. The goal of this project is to build a real-time , machine vision weed control system that can detect crop and weed locations. remove weeds and thin crop plants. In order to accomplish this objective , a real-time robotic system was developed to identify and locate outdoor plants using machine vision technology, pattern recognition techniques, knowledge-based decision theory, and robotics. The prototype weed control system is composed f a real-time computer vision system, a uniform illumination device, and a precision chemical application system. The prototype system is mounted on the UC Davis Robotic Cultivator , which finds the center of the seedline of crop plants. Field tests showed that the robotic spraying system correctly targeted simulated weeds (metal coins of 2.54 cm diameter) with an average error of 0.78 cm and the standard deviation of 0.62cm.