• 산업경영시스템학회지
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• 제21권47호
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• pp.125-138
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• 1998

In this paper, we investigate the effect of re-entrance to the same work station in a job shop with multiple identical machines. System A is defined as the system in which re-entrance is not permitted, and system B is defined as the system in which re-entrance is permitted. By the analytical result of the queueing network, we find that the two systems have the same queue length distributions and utilizations under FIFO dispatching rule when all parameters are same. Simulation models are developed for various comparisons between the two systems, and simulation experiments are conducted for the combinations of five dispatching rules, two average workloads and two due date allowances. Five performance measures are selected for the comparison. The simulation results show that permitting re-entrance affects for some combinations of system environments.

• 한국간호교육학회지
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• 제20권4호
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• pp.596-605
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• 2014

Purpose: This study aims to understand the influence of college entrance system-related factors and scores of college scholastic ability test on a first year nursing student's academic achievement. Method: Data collected include both a descriptive survey designed to assess college entrance system-related factors with respect to 182 nursing students attending a 4-year nursing college program and their test scores in the first year. The data were analyzed via descriptive statistics, Mann-Whitney U test, Kruskal-Wallis test with Bonferroni's correction, and Spearman's rank correlation coefficient through an SPSS 18.0 program. Results: Student academic achievement with regard to college entrance system-related factors exhibited significant divergence from first year grade point averages (hereafter GPA) and natural science grades. Conclusion: This study confirmed the existence of significant differences, depending on the factors regarding the college entrance system. As a result, conducting assessment to evaluate the level of basic knowledge before college entrance is highly recommended. Also recommended is the development of a support program for students projected to have difficulties with respect to their academic achievement.

• 한국자동차공학회논문집
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• 제5권2호
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• pp.50-59
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• 1997

When a front head of train enters a tunnel at a high speed, compression wave is generated at tunnel entrance due to the confinement effect and propagated along the tunnel with sound of speed. The propagated compression wave is reflected at tunnel exit due to abrupt pressure change at passage. The reflected wave is expansion pressure wave. And when the rear head of train goes through the tunnel entrance, another expansion pressure wave is generated and propagated along the tunnel. The pressure drop occurs seriously around train when the two expansion pressure waves come cross on train in the tunnel. In order to reduce the pressure drop, the compression wave front must be controlled because the intensity and magnitude of pressure drop is nearly proportional to that of compression wave at tunnel entrance. This study relates to reduction of the pressure wave gradient with respect to tunnel entrance shape change with various kind of angle and rounding. The results show characteristics of wave propagation in tunnel, usefulness of characteristic curve to estimate proper time domain size in numerical study and measuring time in actual experiment. Also rounding is contributed to improve pressure wave front even if its radius is very small at tunnel entrance. In order to improve of pressure wave front at tunnel entrance, proper angle is prefered to rounding with big radius and an angle of around 14$^{\circ}$ is recommended according to this simulations, And it is expected to reduce additional pressure drop in tunnel when the location and the size of the internal space for attendant equipment are considered in advance.

• 한국과학교육학회지
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• 제36권4호
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• pp.693-704
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• 2016

본 연구는 과학영재학교 조기입학 학생들이 어떤 조건과 상호작용전략을 사용하여 학교적응을 하는지 알아보았다. 이를 위하여 조기입학생 6명과 조기입학 준비학생 2명을 대상으로 심층면담을 하였다. 반구조화 질문을 이용하여 개별심층면담을 실시하여, 과학영재학교에 진학하였을 때 어떠한 걱정과 우려를 가지고 진학하였는지 그리고 학교생활을 하면서 어떻게 적응해 가는지 그 과정을 분석하였다. 본 연구에서는 근거이론 방법을 이용하여, 개방 코딩, 축 코딩, 선택 코딩 과정을 통해 패러다임 모형을 구성하고 핵심범주를 추출하였다. 개방 코딩을 통해 75개의 개념과 21개의 하위범주, 10개의 범주를 추출하였고, 축 코딩 과정에서는 개방 코딩을 통해 추출한 10개의 범주간의 관계를 규명하여 패러다임 모형을 구성하였으며, 선택 코딩과정에서는 '학업적 사회적 정서적 적응 전략을 이용한 학교적응'이라는 핵심범주를 찾아냈다. 이를 통해 과학영재학교에 조기입학하는 학생들의 적응과정에 대해 보다 심층적으로 이해하였다.

• 대한기계학회논문집
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• 제12권5호
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• pp.1189-1196
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• 1988

본 연구에서는 내경이 각각 8.5mm와 10.3mm이며 무차원길이가 각각 710과 1158인 두 개의 시험관을 사용하는 유동장치를 제작하여 시험관 입구에서부터 유체역 학적 경계층(hydrodynamic boundary layer)과 열적 경계층(thermal boundary layer)이 동시에 발달하기 시작하는 경계조건을 형성하고 관벽에서 일정한 열 플럭스(constant heat flux)를 발생하는 조건을 부여하였다. 퇴화현상(degradation)에 대하여 비교적 안정성을 가진 폴리아크라마이드(polyacrylamide) Separan Ap273을 수도물에 용해하여 제조한 폴리머용액으로 유동특성과 열전달특성을 실험하여 열적입구길이와 열전달특성 을 규명하고자 한다.

• 한국해양공학회지
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• 제27권6호
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• pp.32-42
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• 2013

In this paper, a wave-induced swirl water chamber (SWC) for breakwater and wave power generation is introduced and its applicability to wave power generation in the coastal waters of Korea is investigated. The SWC type of wave power generation is a way to drive a turbine using the unidirectional swirl flow that is induced in the back of a curtain wall of a breakwater due to incident waves. The typical wave characteristics are obtained by analyzing the annual statistical wave data from KHOA (Korea Hydrographic and Oceanographic Administration). A numerical analysis is carried out on the variations in the SWC entrance height, wave height, and different installation conditions. For the numerical analysis, a commercial code, Fluent based on FVM, is used. As the entrance height decreases, the mass flow rate through the entrance is rarely changed, whereas the magnitude of the flow velocity of the smaller entrance height is greater than the other ones, which is better for the formation of an SWC swirl flow inside and the flow kinetic energy at the entrance. In cases of installation conditions where a wall is place behind and under SWC, it has been shown that the mass flow rate through the entrance is greater than that in the open condition, and sufficient flow kinetic energy is generated in the entrance for wave power generation. However, the swirl flow kinetic energy is relatively small. Thus, in the future, it is necessary to study the swirl flow generation, which is affected by the SWC shape.

• 한국산업보건학회지
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• 제24권4호
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• pp.471-477
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• 2014

Objectives: This study was conducted to evaluate area exposure of airborne dust and organic gas during entrance and shipment of chicken in poultry farms Methods: Total dust was measured with NIOSH method 0500. The volume of distributed dust and organic gas(Ammonia, TVOC, Hydrogen Sulfide) were measured using direct reading instrument. Results: The range of concentrations of total dust in area sample was $0.07{\sim}4.91mg/m^3$ during the entrance of chicks and $4.37{\sim}9.4mg/m^3$ during shipment respectively. Concentration of ammonia reached approximately 9 ppm during shipment. There was a difference of concentration of total dust in the area sample between shipment and entrance tasks. Conclusions: It was found that the development of a special intervention program by type of task should be considered for reducing respiratory health effects among poultry farmers.

• Journal of Biosystems Engineering
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• 제18권3호
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• pp.275-287
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• 1993

The flow characteristics of the transitional oscillatory flows are investigated analytically and experimentally in the entrance region of a square duct. The systems of conservation equations are analytically solved by linearizing the non-linear convective terms for the developing transitional oscillatory flows in a square duct. The analytical solutions are obtained in the form of infinite series for the velocity profiles. The experimental study for the air flow in a square duct is carried out to measure the velocity profiles and waveforms by using a hot-wire anemometer with the data acquisition and processing systems. The theoretical and experimental results provide the major characteristics of the developing transitional oscillatory flows, such as velocity profiles, velocity waveforms, and entrance length. The velocity profiles in the decelerating phase are larger than those in the accelerating phase for the developing transitional oscillatory flows. The correlations of the entrance length of the transitional oscillatory flows in a square duct are found to be $Le/Dh=K{\cdot}Re_{os}/2({\omega}^+)^2$, where K is 1.23 of an experimental constant.

• 한국터널지하공간학회 논문집
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• 제9권4호
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• pp.377-385
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• 2007

터널을 통과하는 운전자는 터널 외부환경과 내부환경의 차이에서 오는 변화에 많은 어려움을 가지게 된다. 특히 주간에 터널 입구부를 지나는 운전자는 터널 외부의 높은 야외휘도로 인하여 블랙홀 현상을 겪게 되며, 이는 심각한 운전자의 시인도의 감소를 가져오게 된다. 본 논문에서는 운전자가 겪는 블랙홀 현상에 대처하기 위한 방법의 하나인 카운터빔조명의 효과를 검정하기 위하여 실제와 유사한 상황을 컴퓨터에 구현하여 시뮬레이션 하였다. 터널의 조명을 설계함에 있어 특정 터널이 가지고 있는 제반 요소들을 고려한 다양한 상황에서의 운전자 시인도를 분석하고 보다 좋은 운전환경을 위한 터널조명을 만들기 위한 노력이 필요하다. 본 연구에서의 시뮬레이션에 의한 분석은 터널조명 초기 설계단계에서 비교적 단기간에 다양한 조명대안들에 대한 비교, 분석을 가능하게 하는 하나의 접근법이 될 것이다.

• 경영과학
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• 제7권2호
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• pp.22-42
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• 1990

This paper deals with enhancement of the high school equalization assignment system to be executed by the allied entrance examination after the applicants graduated from their middle schools. In prevailing opinion, because educational demander's will has not been considered under the current system, it whose merits have been covered is required to be improved. If the application system of the entrance examination for the high schools will be returned, a situation that it will result in irregularity of the middle school education and in overheating entrance examination seems to appear explicitly. Since the averages of the allied entrance examination score of all the high schools, achieved by the equalization-application nearest assignment system which is named by writers of this paper, are equal, our system is good for maintaining the merits of the current system. More than 50% educational demander's will has been reflected by our system, so that we come to the conclusion that our system is excellent in all the systems verified up to now. Assigning students to the high school to make an average difference between three and five score, we expect that relection rate of the educational demander's will be increased more than 60%.