• Communications for Statistical Applications and Methods
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• 제8권3호
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• pp.719-729
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• 2001

Overlap Maximization is a sampling technique to reduce survey costs and costs associated with the survey. It was first studied by Keyfitz(1951). Ernst(1998) presented a remarkable procedure for maximizing the overlap when the sampling units can be selected for two identical stratified designs simultaneously, But the approach involves mimicking the behaviour of nonlinear function by linear function and so it is less direct, even though the stratification problem for the overlap corresponds directly to the linear programming problem. furthermore, it uses the controlled selection algorithm that repeatedly needs zero-restricted controlled roundings, which are solutions of capacitated transportation problems. In this paper we suggest a comparatively simple procedure to use linear programming in order to maximize the overlap. We show how this procedure can be implemented practically.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.401-402
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• 2002

The flow characteristics of ice slurry which was made from $6.5{\%}$ ethylene glycol-water solution flowing in the special pipings including the enlargement, the contraction and the orifice were experimentally investigated. The flow patterns and the pressure drops were measured in acrylic pipes when the fraction of ice were varied from $0\;to\;30{\%}$. The pressure drop behavior of the contraction and the orifice appears to be similar to that of the elbow pipe, since these piping may provide similar frictional resistance to the elbow. In the mean while, the pressure drop increased unexpectedly high with the Ice fraction in the enlargement pipe. It seems that the onset of sharp increase in the pressure drop depends on the flowing time as well as the ice fraction and the flow rate.

• 설비공학논문집
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• 제14권5호
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• pp.385-390
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• 2002

To clarify the hydraulic characteristics of ice slurry which made from 6.5% ethylene glycol-water solution flowing through circular pipes of small diameter, experimental studies were performed. The flow pattern was observed and the pressure drop was measured in acrylic pipes with inner diameter of 24 mm. The results of flow visualization revealed that ice particles flowed along the top of pipes in the ranges of small ice fraction and low flow rate, while Ice particles diffused into the whole region of pipes flowed like a homogeneous flow for high flow rate and high ice fraction. An increase in frictional pressure drop was measured as the ice fraction increased in all pipes and unstable flow was observed for up-ward vertical pipe.

• 한국응급구조학회지
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• 제11권1호
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• pp.65-72
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• 2007

The purpose of this study was teacher's perception on young children's safety life, safety accident, and safety education and provided basic data of administrating teacher's education for young children's safety. Subjects of this study were teachers of young children attending for their education. 230 questionnaires were provided and 181 were collected and 170 were used for data analysis. Data collected were analyzed with SPSS WIN 2.0 program. The results of the study were as follows : 1. Regarding teacher's perception on types of young children's safety accident, play accident was high(70.0%). 2. With regard to teacher's perception on causes of accident, lacks of perception was high(64.1%). 3. Of transportation means in accident, 119 ambulance use was high(60.5%) 4. Regarding teacher' perception on accident prevention, direct attention of education by paramedics was high(48.2%).

• 전기화학회지
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• 제12권2호
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• pp.167-172
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• 2009

Direct methanol fuel cells(DMFCs) are receiving significant attention in the portable power source and electric vehicular transportation because of its high energy efficiency as liquid fuel, low cost, and no requirement of fuel reforming process. In this study, we synthesized the Sulfonated poly(ether ether ketone) (SPEEK) to evaluate the possibility of use as a proton exchange membrane for DMFC. And poly(vinylidienedifluoride) (PVDF) was used to increase proton conductivity in SPEEK and simultaneously to prevent methanol transport through the cross linked membrane. Furthermore, in order to improve the electrical composite properties for DMFC applications.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 하계학술대회 논문집 A
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• pp.49-51
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• 1994

LIM has been developed for use in the industry, transportation, OA, FA because of the merits of direct drive and simple structure. The thrust control of LIM usually has been the average thrust control. However, vector control is required to control the instantaneous thrust force for an accurate positioning and speed control. To obtain dynamic vector control characteristics, it is important to make equivalent circuits which represent exactly LIM In this paper, asymmetrical d-q equivalent circuits is built [1] and vector control characteristics is calculated by simulation using these circuits.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 하계학술발표대회 논문집
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• pp.1007-1012
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• 2008

Demand for the highly efficient and high performance urban energy supply system having been continuously increased according to the rise of quality of life and continuously increased energy cost all over the world. The district heating and cooling system is very effective way for energy saving, cost reduction, and demand side management of energy. There are several district cooling supply technologies such as chilled water direct transportation, installation of absorption type chiller in the user side, and desiccant cooling. This study investigates the advantage and technical problems of each district cooling technology. Also, it is necessary political and financial support system for the extension of district cooling system.

• Computational Structural Engineering : An International Journal
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• 제2권1호
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• pp.11-17
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• 2002

Cost-effectiveness in design is considered for determining the target reliability of concrete bridges under seismic actions. This objective can be achieved based on the economic optimization of the expected life-cycle cost of a bridge, which includes initial cost, direct losses, and indirect losses of a bridge due to strong earthquakes over its lifetime. A separating factor is defined to consider the redundancy of a transportation network. The Park-Ang damage model is employed to define the damage of a bridge under seismic action, and a Monte Carlo method based on the DRAIN-2DX program is developed to assess the failure probability of a bridge. The results for an example bridge analyzed in this paper show that the optimal target failure probability depends on the traffic volume carried by the bridge and is between 1.0×10/sup -3/ to 3.0×10/sup -3/ over a life of 50 years.

• 한국항해항만학회지
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• 제42권2호
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• pp.137-142
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• 2018

Vietnam is entering an important phase of urbanization that corresponds to the current economic development. Developing logistics of Vietnam in general, and Haiphong particularly, is urgent in order to meet the need for the economic development of Viet Nam in this period of international integration. Hai Phong's development record over the past 20 years is remarkable. In conjunction with the local government's efforts, external factors, such as increasing direct foreign investment, is turning Hai Phong into Vietnam's logistics hub. However, even though Hai Phong accounted for 98% of North Vietnam's throughput, its logistics services are low level, the ports are fragmented, and the port management scale is backward, with the legal system overlapping. This paper has systematically evaluated the development of Haiphong city during recent years, then offers some solutions to develop logistics for Hai Phong ports.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2016년도 춘계학술대회
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• pp.577-578
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• 2016

본 논문에서는 차량운행 시 일어날 수 있는 졸음운전 사고를 예방하기 위해 맥박 센서를 이용하여 차량 안전시스템 구성을 제안하였다. 제안한 차량 안전시스템은 운전자의 졸음운전 상태를 판단하여 경보를 알리고, 이를 이용하여 운전자는 돌발적인 상황이나 위험상황을 미리 인지하여 직접적인 사고 및 2차 사고를 예방 할 수 있다.