• 한국자동차공학회논문집
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• 제20권1호
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• pp.53-60
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• 2012

As enforced by the regulation on the improving fuel efficiency and increased the demand on green technology, many interests are focused on electric vehicles and hybrid vehicles. Thus the technology development in electrification of vehicle operation system, including steering and braking field, is actively progressive. Especially electric power steering substitutes for hydraulic power steering rapidly in the market, which is more complex and bigger in packaging volume compared with electric power steering system. The core component in electric power steering system is a motor, which is required to be silent and powerful to guarantee required system performance. Brushless synchronous motors are widely used and many variations of the motors are introduced in the market, while the performance of each type is not well defined or studied for electric power steering system. In this paper, recent developments in brushless synchronous motor are reviewed and compared applying finite element analysis in electromagnetic field. As results, each characteristic of different types of brushless synchronous motors is compared and summarized for optimized selection in electric power steering system.

• 한국철도학회논문집
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• 제8권4호
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• pp.361-366
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• 2005

The high investment is necessary for the new high speed lines. So the KRRI has been interested in the possibility of upgrading the existing line in order to speed up the train in the conventional lines. The pantograph in train is indispensable in order to supply the electrification equipments with power in safe. The pantograph and the overhead wire form a dynamic coupled system and they affect each other through the contact force. Unfortunately, as the operational speed of a train increases, the vibration of the pantograph and the overhead wire also increases. This may lead to a zero contact force between the pantograph head and the overhead wire, which can results in the loss of contact, arching and abrasion. If the arching and spark happen between the pantograph and the overhead catenary system, the EMI(electro magnetic interface) and noises may occur. After all, the quality of current collection is deteriorated. This paper describes the dynamic response between the pantograph and catenary system by the numerical simulations and presents the LQ-servo controller to reduce the contact force variation

• 전기학회논문지
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• 제66권9호
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• pp.1431-1436
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• 2017

The high-speed railway of catenary system, supplies a stable electric power supply to the train by satisfying the special conditions between pantograph and trolley wire, which operates more than 250km/h mutually sliding and feeding electric lines. According to Korean Railway Standard KRS PW 0026-13 (R), the standard for the grip strength of the dropper clamp in conventional line is established, but the high-speed railway line is not yet. When the grip strength of the dropper clamp is detached from the catenary line of the high-speed railway line, various problems may occur, such as damage to the pantograph due to the collision and arcing. In this paper, it is expected to be used as a basic data for establishing the durability criteria of the high-speed railway dropper clamp by verifying the dropper clamp on the Gyeong-bu and Honam high-speed line.

• Journal of Electrical Engineering and Technology
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• 제13권6호
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• pp.2553-2560
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• 2018

In Korea, there are no instances where a hydrogen fuel cell power generation system has been used in a railway vehicle. Only the basic topology has been studied. In the previous study, conventional converters using a single switch were applied to the fuel cell power generation system. Therefore, current stress on the switch at converter on-off transitions would be large when controlling a large-capacity railway vehicle. In addition, since the input side ripple is also large, there is a problem with a shortening of the lifetime of both the fuel cell power generation system and the inductor. In this paper, a soft-switching transformer inductor boost converter for fuel cell powered railway vehicles was proposed. A technique to reduce both the switching current stress generated during on-off transitions, and the input ripple current flowing in the inductor were studied. The soft-switching TIB converter uses a transformer-type inductor to configure the entire circuit in an interleaved method, and reduces both input current ripple and the current ripple of the inductor and switch.

• 한국생산제조학회지
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• 제22권6호
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• pp.908-912
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• 2013

Because of their longer operating times and larger size relative to conventional fans, the cooling fans mounted in buses consume larger amounts of energy. Most of the cooling fans mounted in a bus are connected to the engine by a viscous clutch. A viscous cooling fan's speed is determined by its fluid temperature, which is affected by the air flow through the radiator. The fan does not react immediately to the coolant temperature and in doing so causes unnecessary energy consumption. Therefore, the fuel economy of buses using viscous fans can be improved by changing to an electric cooling fan design, which can be actively controlled. In addition, electric power consumption is increased by using electric cooling fans. Thus, when electric fans are applied in conjunction with the alternator management system (AMS), the fuel economy is further enhanced. In this study, simulations were performed to predict coolant temperature and cooling fan speeds. Simulations were performed for both viscous and electric cooling fans, and power consumption was calculated. Additionally, fuel economy was calculated applying both the alternator management system and the electric cooling fan.

• Journal of Electrical Engineering and Technology
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• 제12권5호
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• pp.1916-1924
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• 2017

Fossil oil, as the main energy of transportation, is destined to be exhausted. The electrification of transportation is a sustainable solution to the energy crisis, since electric power could be acquired from the inexhaustible sun, wind and water. Among all the problems that hinder the development of Electric Vehicle (EV) industry, charging issue might be the most prominent one. In this paper, the service process of a charging station with Battery Energy Storage System (BESS) is analyzed by means of $Cram{\acute{e}}r$ - Lundberg model which has been intensively utilized in ruin theory. The service quality is proposed in two dimensions: the service efficiency and the service reliability. The arrival rate and State of Charge (SOC) upon arrival are derived from 2009 National Household Travel Survey (NHTS). The simulations are performed to show how the service quality is determined by the system parameters such as the number of servers, the service rate, the initial capacity, the charge rate and the maximum waiting time. At last, the economic analysis of the system is conducted and the best combination of the system parameters are given.

• 한국태양광발전학회지
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• 제6권1호
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• pp.8-20
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• 2020

Nepal has huge potential of hydro and other renewable energy resources including solar energy. However, only 70% of the total population have access to electricity despite the long history of hydropower development in the country. Still more than 37% population in rural areas and around 73% population in Karnali Province, one of the least developed provinces, are living without access to electricity despite taking several initiatives and implementing various policies by government supporting electrification in off-grid rural areas. Government together with donors and private sector has extensively been promoting the off-grid solar photovoltaic (PV) echnology in un-electrified areas to increase electricity access. So far, more than 900,000 households in rural areas of Nepal are getting electricity from stand-alone solar PV systems. However, there are many challenges including financial, technical, institutional, and governance barriers in Nepal. This study based on extensive review of literatures and author's own long working experiences in renewable energy sector in Nepal, shares the best practices and lessons of off-grid solar PV for increasing access to electricity in rural areas of Nepal. This study suggests that flexible financial instruments, financial innovations, bundling of PV systems for concentrating energy loads, adopting standards process, local capacity building, and combination of technology, financing and institutional aspects are a key for enhancing effectiveness of solar PV technology in rural areas of Nepal.

• 핵의학기술
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• 제16권2호
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• pp.135-138
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• 2012

Purpose : This research the isotope of handling was to an actual act of the radiological defense which it follows in career of the clinical pathological companies in order to inquire the interrelation for a radiological defense. Materials and Methods : The tool of this research with question from 2010 October until November did electrification Chwung Cheng and the Seoul isotope thread clinical pathological company with the object person and it investigated in direct question or mail method, the data which is collected used SPSS19.0 programs and frequency and percentage and t-test, ANOVA, it used it analyzed a multiple regression analysis method. Results : The interrelationship of the radiological defense which it follows in career was visible the interrelation which considers statistically (p<0.01). But the correlation coefficient appeared lowly with 0.196. With the variable who affects in radiological defense act it appeared with worker providing by law educations and RI license acquisitions. Conclusion : There is to business progress and the radiological defense act respects a worker safety stands the unit only is the fact which is important. Consequently a possibility of saying that the radiation worker education is necessary, it executes the education which is continuous, RI license acquisitions, there is.

• 태양에너지
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• 제18권3호
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• pp.147-151
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• 1998

Several PV-diesel hybrid systems were built in isolated islands in Korea, where they are far from the inland to be supplied the electric power to a utility level from it. A lot of efforts has been concentrated to find a cost-effective electric supply system with higher reliability and minimum maintenance when compared with a diesel generator. For this purpose, an autonomous PV-diesel hybrid system with multi-channel remote monitoring system was investigated to supply electric power under minimum operating cost and maintenance in a small isolated island. In this report, the economic analysis was performed for comparison with photovoltaic system and diesel generator by computer simulation. And it was proven that a PV system is more cost-effective than an internal combustion engine for the remote island with less than 150 households. Especially, in the case of islands with less than 50 households, the initial construction cost of the PV system is comparable to and its operating cost is about 70% less than the diesel generator.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2009년도 춘계학술대회 논문집
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• pp.331-340
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• 2009

This study is objected by suggesting rationalization method of management and maintenance cost for railway investment assessment. The estimate of rational benefit and cost are a work of vital importance to decide railway investment as preliminary feasibility investigation is institutionally reinforced since January 2007. In particular, railway management and maintenance cost have to be applied to realistic and detail cost as railway investment assessment guide. For example, types of railway, construction of new line, improvement of conventional line, double tracking, railway electrification. However, railway investment assessment is inconsistency because of estimating the railway management and maintenance cost using existing unrealistic management and maintenance cost. Therefore, this study is performed parametric analysis effecting on the railway management and maintenance cost considered new technique, enhanced facilities and improved standard. Also, it suggests the itemized standard management and maintenance cost. Finally, it will be helped to establish the base of railway investment through the rationalization method of management and maintenance cost.