• 디지털산업정보학회논문지
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• 제4권4호
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• pp.41-49
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• 2008

Sensor networks are often deployed in unattended environments, thus leaving these networks vulnerable to false data injection attacks in which an adversary injects forged reports into the network through compromised nodes. Such attacks by compromised sensors can cause not only false alarms but also the depletion of the finite amount of energy in a battery powered network. In order to reduce damage from these attacks, several security solutions have been proposed. Researchers have also proposed some techniques to increase the energy-efficiency of such security solutions. In this paper, we propose a CH(Cluster Header) selection algorithm to choose low power delivery method in sensor networks. The CNP(Contract Net Protocol), which is an approach to solve distribution problems, is applied to choose CHs for event sensing. As a result of employing CNP, the proposed method can prevent dropping of sensing reports with an insufficient number of message authentication codes during the forwarding process, and is efficient in terms of energy saving.

• Journal of Power Electronics
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• 제11권2호
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• pp.237-243
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• 2011

Lithium batteries are widely used in mobile electronic devices due to their higher voltage and energy density, lighter weight and longer life cycle when compared to other secondary batteries. In particular, a high demand for lithium batteries is expected for electric cars. In the case of the lithium batteries used in electric cars, driving distance must be calculated accurately and discharging should not be done below a level that makes it impossible to crank. Therefore, accurate information on the state-of-charge (SOC) becomes an essential element for reliable driving. In this paper, a novel method for estimating the SOC of lithium polymer batteries using AC impedance is proposed. In the proposed method, the parameters are extracted by fitting the measured impedance spectrum on an equivalent impedance model and the variation in the parameter values at each SOC is used to estimate the SOC. Also to shorten the long length of time required for the measurement of the impedance spectrum, a novel method is proposed that can extract the equivalent impedance model parameters of lithium polymer batteries with the impedance measured at only two specific frequencies. Experiments are conducted on lithium polymer batteries, with similar capacities, made by different manufacturers to prove the validity of the proposed method.

• Journal of Electrical Engineering and Technology
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• 제9권6호
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• pp.2004-2012
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• 2014

Energy storage devices are necessary to obtain stable utilization of renewable energy sources. When black-out occurs, distributed renewable power sources with energy storage devices can operate under standalone mode as uninterruptable power supply. This paper proposes a dynamic response analysis with small-signal modeling for the standalone operation of a photovoltaic power generation system that includes a bidirectional charger/discharger with a battery. Furthermore, it proposes a DC-link voltage controller design of the entire power conditioning system, using the storage current under standalone operation. The purpose of this controller is to guarantee the stable operation of the renewable source and the storage subsystem, with the power conversion of a very efficient bypass-type PCS. This paper presents the operating principle and design guidelines of the proposed scheme, along with performance analysis and simulation. Finally, a hardware prototype of 1-kW power conditioning system with an energy storage device is implemented, for experimental verification of the proposed converter system.

• 한국신뢰성학회지:신뢰성응용연구
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• 제16권3호
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• pp.238-244
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• 2016

Purpose: Domestic electric railway Regenerative Energy Storage System seriously affects the maintenance cost of the total operating expenses of nearly 60% of the total LCC (Life Cycle Cost) due to high dependence on foreign Leading company. Therefore by developing the system, it is important to lower the maintenance cost in the domestic supply. This study about the capacitor Reliability test and the purpose of this study is development electric railway Regenerative Energy Storage System. Methods: In case of, having a close relation between the temperature and the reaction rate, Accelerated Model was known that according to Arrhenius' law of chemical activity. If you apply this formula in using allowable temperature range of the capacitor can induce the Arrhenius empirical formula used in much Manufacture Fields. We evaluate the capacitors Leading company through the Arrhenius model. in order to providing a base for the localization of Ultra Capacitor. Conclusion: In this paper, we conducted a reliability test. And it was performed by the accelerated life test and Cycle Test with temperature and C-rate. and then MTBF and B10 life are estimated by analyzing the accelerated life test result. This is thought to need detailed study applying complex stress than about whether it matches the actual behavior in electric railway.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권12호
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• pp.5712-5728
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• 2017

Recently, there are many studies, that considering green wireless cellular networks, have taken the energy consumption of the base station (BS) into consideration. In this work, we first introduce an energy consumption model of multi-mode sharing BS powered by multiple energy sources including renewable energy, local storage and power grid. Then communication load requests of the BS are transformed to energy demand queues, and battery energy level and worst-case delay constraints are considered into the virtual queue to ensure the network QoS when our objective is to minimize the long term electricity cost of BSs. Lyapunov optimization method is applied to work out the optimization objective without knowing the future information of the communication load, real-time electricity market price and renewable energy availability. Finally, linear programming is used, and the corresponding energy efficient scheduling policy is obtained. The performance analysis of our proposed online algorithm based on real-world traces demonstrates that it can greatly reduce one day's electricity cost of individual BS.

• 한국실천공학교육학회논문지
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• 제4권2호
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• pp.129-135
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• 2012

전기자동차들을 수학적으로 모델링하고 시뮬레이션 하는 많은 방법들이 있다. 전기 자동차의 각 요소들은 다른 물리적인 배경과 모델들을 갖고 있으나, 하나의 수학적 모델로 구성하기란 어려우므로 다양한 물리적 모델이 요구된다. 시뮬레이션이 목적에 따라 수행할 시뮬레이션에 관한 디양한 레벨들이 있다. 즉, 개념 체계 레벨, 회로 레벨, 더 상세한 요소레벨로 구성된다. 본 연구에서는 전기 자동차에서 여러 가지 요소들에 대한 다양한 물리적 모델들과, 다중레벨 시뮬레이션에 관하여 연구하고자 한다. 또한, 본 시뮬레이션 방법은 공학교육에 학습효과를 향상 시킬 수 있다.

• 전기학회논문지
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• 제65권12호
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• pp.2197-2210
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• 2016

Recently, the trend of zero emissions has increased in automotive engineering because of environmental problems and regulations. Therefore, the development of battery electric vehicles (EVs), hybrid/plug-in hybrid electric vehicles (HEVs/PHEVs), and fuel cell electric vehicles (FCEVs) has been mainstreamed. In particular, for light-duty electric vehicles, improvement in electric motor performance is directly linked to driving range and driving performance. In this paper, using an improved design for the interior permanent magnet synchronous motor (IPMSM), the EV driving range for the light-duty EV was extended. In the electromagnetic design process, a 2D finite element method (FEM) was used. Furthermore, to consider mechanical stress, ANSYS Workbench was adopted. To conduct a vehicle simulation, the vehicle was modeled to include an electric motor model, energy storage model, and regenerative braking. From these results, using the advanced vehicle simulator (ADVISOR) based on MATLAB Simulink, a vehicle simulation was performed, and the effects of the improved design were described.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2017년도 춘계학술대회
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• pp.275-278
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• 2017

차량의 교류발전기는 성능 및 효율에 따라 자동차의 연비와 배기가스에 많은 영향을 준다. 효율을 개선시키고 연비를 향상시키려는 노력은 자동차업체및 업체를 중심으로 계속되고 있다. 본논문은 A교류 발전기의 설계절차를 정리하고 같은 크기의 교류발전기에서 출력을 최적화하는 인자를 발굴하여 실차의 조건에서 충방전 Simulation을 통해 Energy Balance를 검증하였다.

• 기술혁신학회지
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• 제7권1호
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• pp.64-88
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• 2004

This paper aims at investigating which factors play important roles in selecting government's new core IT industries and how competitive they are. We surveyed 6 competitiveness factors and 17 IT industries for the expert group. The logit and probit models were estimated and SWOT analysis was performed. The empirical results show that government put emphasis on marketability, externality and technology, not publicity, when selecting IT new core industry. The skilled human resources turn out to be a threat factor in the government selected IT new core industries such as home-network, third generation semi-conductor. Therefore, training or education system for skilled labors is required to develop and nurture such industries. The contribution to small medium venture industry and publicity are lower in the several industries such as intelligent service robots, post PC, embodied S/W, next generation battery, which are selected by government, not by standardized data based criterion. in such industries, marketabilities, technology, skilled human resources are threats factors to such industries. Therefore every effort for enhancing the marketability and R&D investment and education system for skilled labor are necessary to develop the industries.

• International journal of advanced smart convergence
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• 제10권4호
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• pp.256-262
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• 2021

In order for small electric vehicles to drive on hilly roads in Korea, methods to improve the climbing ability and power performance of vehicles should be taken. In order to improve the power performance of small electric vehicles, the performance of motors mounted on electric vehicles should be improved. However, if the performance of the motor is improved to improve the power performance of the electric vehicle, it is possible to lower the price competitiveness accordingly. In addition, the power consumption of the battery is rapidly increased to drive the high-performance motor, so in order to introduce the small electric vehicle into the domestic market, various problems must be overcome. In order to commercialize small electric vehicles that do not emit harmful exhaust gases to the human body in the hilly domestic terrain, it is effective to introduce a separate continuously variable transmission system that can improve the climbing ability and power transmission ability. In this study, we propose a proprietary model of continuously variable transmissions that can be applied to small electric vehicles. The proposed continuously variable transmission is equipped with a spring in the driving pulley and the driven pulley, and has the advantage of performing a shift that increases torque in a situation where the vehicle needs to increase torque when driving on a hill. In addition, the basic design for commercialization of the proposed continuously variable transmission was carried out, and the prototype manufactured and attached to the body of a small electric vehicle.