• 대한전기학회논문지:전력기술부문A
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• 제51권6호
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• pp.255-261
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• 2002

Recently, traction motors in trains are supplied with single phase a.c. power. After this power is converted to d.c. power, it is inverted to three phase power to operate traction motors. As going through the process of the conversion, harmonic current is generated in train. The method of conventional analysis on harmonics, studied by RTRI, is modeled with equivalent circuit of ac AT-fed electric railroad system using by the distributed constant circuit. However, this circuit as two-port network model has some difference in comparison with real system. The reason why the conventional method is different from the real system is that the conventional method dose not include three conductor groups, that is catenary, rail, and feeder, and admittance between the conductors for line capacitance. Therefore, this method has a little error. This paper proposes new method to more effectively estimate Harmonic current. In this method, numerous components in electric railway are categorized and each component is defined as a four- port network model. The equivalent circuit for the entire power supply system is also described into a four-port network model with connections of these components. In order to evaluate the efficiency and the accuracy of a proposed method, it is compared with values measured in Kyung-Bu high speed line and ones calculated by the conventional method.

• 대한전기학회논문지:전력기술부문A
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• 제50권5호
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• pp.248-254
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• 2001

The traction power demand highly varies with time and train positions and the traction load is a large-capacity current at single phase converted from 3-phase power system. Subsequently, each phase current converted from 3-phase power system cannot be maintained in balance any longer and thus the traction load can bring about imbalance in three-phase voltage. Therefore, the exact assessment of voltage unbalance must be carried out preferentially as well as load forecast at stages of designing and planning for electric railway system. The evaluation of unbalance voltage in areas, such as electric railway depots should be a prerequisite with more accuracy. The conventional researches on voltage unbalance have dealt with connection schemes of the transformers used in ac AT-fed electric railroads system and induced formulas to briefly evaluate voltage unbalance in the system(3). These formulas are still being used widely due to their easy applicabilities on voltage unbalance evaluation. Meanwhile, they don't take into account detailed characteristics of ac AT-fed electric railroads system, being founded on some assumptions. Accordingly. accuracy still remains in question. This paper proposes a new method to more effectively estimate voltage unbalance index. In this method, numerous diverted circuits in electric railway depots are categorized in three components and each component is defined as a two-port network model. The equivalent circuit for the entire power supply system is also described into a two-port network model by making parallel and/or series connections of these components. Efficiency and accuracy in voltage unbalance calculation as well can be promoted by simplifying the circuits into two-port network models.

• 한국항해항만학회지
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• 제30권9호
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• pp.729-734
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• 2006

The authors aim to establish the theory necessary for developing the free gyroscopic compass and focus on mainly two points. One is to suggest north-finding principle by the angular velocity of the earth's rotation, and the other is to suggest orthogonal coordinate transformations of the motion rate of the spin axis, which transforms the components of motion rate in the free gyro frame into those in the platform frame and that this transformed rate is, in turn, transformed into the NED(north-east-down) navigation frame. Subsequently, ship's heading is obtained by using the fore-aft and athwartship components of the motion rate of the spin axis in the NED frame. In addition it was found how to solve the transformation matrix necessary for transforming each frame.

• 한국항만경제학회지
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• 제20권1호
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• pp.141-151
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• 2004

Although the small and medium ports are actually competing with various strategies, the definition and structural understanding of small and medium ports are not known very much. Therefore this study has launched from this fact, and has the objective of obtaining the structural model for increasing shippers' attraction of small and medium ports. The process began by abstracting the components that composed the success factors through recent research, and grouping it by FA(Factor Analysis) method. Also, by using the FSM(Fuzzy Structural Modeling) method to understand the structure of the grouped components, and the structural model for increasing shippers' attraction of small and medium ports was able to obtain as the result. When analyzing the obtained structural model, easiness of shipment, connection to hubport and efficiency of hinterland network came out to be the most important component groups.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2004년도 춘계학술대회 논문집
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• pp.321-332
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• 2004

The purpose of this research is to introduce the concept of "relationship formation factors" in inter-firm relations and to empirically demonstrate that they are effective in improving the relationship results by means of anmediating variable. Therefore, the basic model of this study consists of the independent, mediating, and dependent variables. First, the independent variable, that is, the relationship formation factors, is further classified into three components： transactional, relational, environmental characteristics. Then, the study empirically examines how each of the three components influences the dependent variable, that is, the business performance(Load Factor), by way of the mediating variables, that is, trust and relationship commitment.

• 한국항해항만학회지
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• 제28권5호
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• pp.373-384
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• 2004

The purpose of this research is to introduce the concept of "relationship formation factors" in inter-firm relations and to empirically demonstrate that they are effective in improving the relationship results by means of an mediating variable. Therefore, the basic model of this study consists of the independent, mediating, and dependent variables. First, the independent variables, that is, the relationship formation factors, are further classified into three components. transactional, relational, and environmental characteristics. Then, the study empirically examines how each of the three components influences the dependent variable. that is, the business performance(Load Factor), by way of the mediating variables, that is, trust and relationship commitment.

• 한국항만경제학회지
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• 제22권1호
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• pp.87-103
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• 2006

The aim of this paper is to establish the evaluation system of improving urban logistics using the QFD(Quality function Deployment) model which can facilitate to grasp the improving degree of realizing the system conforming to the relationship of all process and the process improvement. At the first stage, the established system through the QFD method will be used to evaluate and diagnosis the level of urban logistics in Cheonbuk District. The second stage is to investigate the important components that can make prompt improvement of urban logistics. Then, the sensitivity analysis is to be performed and the degree of improving urban logistics will be presented according to the rising degree of the relevant components.

• 한국항만학회지
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• 제13권1호
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• pp.27-40
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• 1999

This study aims to apply and examine the stochastic approach for empty container repositioning and leasing problem. For this a case study has been carried out on actual data such as various cost components and traffic flow. The results reveal that the proposed methodology produces more realistic results than the conventional deterministic approaches. It is also found that the results are significantly affected by the accuracy of demand and supply forecast.

• 한국환경과학회지
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• 제26권1호
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• pp.109-118
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• 2017

This study was conducted to investigate the effects of intermittent plasma and electrolysis treatments on lettuce (Lactuca sativa var. oak-leaf.), nutrient solution components ($NO_3{^-}-N$, $NH_4{^+}-N$, $PO{_4}^{3-}-P$, $K^+$, $Ca^{2+}$ and $Mg^{2+}$) and environmental parameters (electrical conductivity, total dissolved solids and pH). The recirculating hydroponic cultivation system consisted of planting port, LED lamp, water reservoir and circulating pump. Nutrient solution was circulated in the following order: reservoir ${\rightarrow}$ filtration-plasma or filtration-electrolysis ${\rightarrow}$ planting port ${\rightarrow}$ reservoir. The results showed that nutrient solution components and environmental parameters were changed by plasma or electrolysis treatment. Lettuce growth was not affected by the intermittent plasma or electrolysis treatment with 30 minutes or 90 minutes, respectively. The roots of the lettuce was damaged by excessive plasma and electrolysis treatment. Electrolysis treatment had greater effect on than plasma treatment because of the accumulation of high levels of TRO (Total Residual Oxidants).

• 한국항해항만학회지
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• 제27권5호
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• pp.569-576
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• 2003

우리나라가 속해 있는 동북아지역은 동남아시아와 더불어 세계 물류의 중심지 및 생산공장의 역할을 수행하고 있다. 특히 동북아시아를 선도하고 있는 한국, 중국, 일본의 경우 동아시아의 물류 거점역활 선점과 글로벌기업 유치를 위하여 다양한 Free Zone제도를 제정 도입하여 활성화에 노력을 기울이고 있다. 이러한 상황에서 동 제도의 시행초기 단계에 있는 우리나라의 경우, 주변국을 벤치마킹하여 성공요인을 찾는 것이 시행착오를 줄이고 경쟁의 우위를 확보하는 지름길이 될 것이다. 한편, 주변국의 Free Zone들은 다양한 전략을 가지고 경쟁을 하고 있으나, 우리나라의 경우 자유무역지대 활성화 전략에 포함되는 구성요소간의 종속관계, 계층파악 등의 시스템 적인 차원에서의 접근은 전무한 실정이다. 따라서 본 논문은 이러한 점에 착안하여, 군산 자유무역지대(Free Trade Zone) 성공요인을 파악하고, 이를 바탕으로 하여 군산자유무역지대 활성화를 위한 구조모델을 FSM법을 사용하여 구축하는 것을 연구의 목적으로 하였다.