• Proceedings of the KIEE Conference
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• 1998.07b
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• pp.560-562
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• 1998

A new approach to developing battery SOC indicator for electric vehicle is discussed in this paper. One of the most difficult problems associated with the development of electric vehicle is the battery indicator which reliably informs the state of charge(SOC) of the battery to the driver. And the condition to be satisfied with SOC indicator installed on the electric vehicle is that it should be used under frequently variable load. A new method to determining SOC using neural networks(NN) is proposed to satify the condition. The training data of NN are obtained by using mathematical model of lead-acid battery, and calculating discharge currents and terminal voltages while battery discharges with constant current. The 3-layered NN with back propagation algorithm is used Simulation results show that the proposed method is appropriate as SOC indicator of the battery.

• Journal of Electrical Engineering and Technology
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• v.13 no.2
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• pp.631-636
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• 2018

This paper proposed an optimal operation strategy for a hybrid energy storage system (HESS) with a lithium-ion battery and lead-acid battery for mild hybrid electric vehicles (mild HEVs). The proposed mild HEV system is targeted to mount the electric motor and the battery to a conventional internal combustion engine vehicle. Because the proposed mild HEV includes the motor and energy storage device of small capacity, the system focuses on low system cost and small size. To overcome these limitations, it is necessary to use a lead acid battery which is used for a vehicle. Thus, it is possible to use more energy using HESS with a lithium battery and a lead storage battery. The HESS, which combines the lithium-ion battery and the secondary battery in parallel, can achieve better performance by using the two types of energy storage systems with different characteristics. However, the system requires an operation strategy because accurate and selective control of the batteries for each situation is necessary. In this paper, an optimal operation strategy is proposed considering characteristics of each energy storage system, state-of-charge (SOC), bidirectional converters, the desired output power, and driving conditions in the mild HEV system. The performance of the proposed system is evaluated through several case studies with respect to energy capacity, SOC, battery characteristic, and system efficiency.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.882-883
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• 2013

With the development of the society, pure electric vehicles will be surely important of the future. Electric vehicle requires various technology like motor driving, battery management, operational efficiencies and so on. Battery management is indeed the most important to enhance battery's performance and life. This paper has deeply discussed and studied on the lithium-polymer battery management system of pure electric vehicle. First of all we have analyzed the characteristic of the lithium-polymer batteries and the factors influenced on the state of charge. Then a logical SOC measuring method has been raised, which is the combination of open circuit voltage and Ah integration. The next we will introduce the design of battery management system, the battery management system performs many functions, such as inspecting the whole process, when it's running cell equalization protecting and diagnosing the battery, estimating the state of charge. The module design style including microcontroller, data aquisition module, charging control module and serial communication module. To arrive at conclusions, the battery management system which this paper has introduced is reliable and economical.

• Proceedings of the KIPE Conference
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• 2001.07a
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• pp.114-117
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• 2001

In the Electric Vehicle(EV) driving system, the Battery Management System(BMS) is very important and an essential equipment. Particularly, BMS monitors the State of Charge(SOC), voltage, current, and temperature of the battery modules when Electric Vehicle is in the state of motoring or charging. Major roles of BMS are like these the first, estimation of State of Charge(SOC), the second, detection of the unbalance of the voltage between battery modules, the third, control of the available limit of the voltage and temperature of batteries by monitoring the batteries status during motoring or charging. In this research, We have focused on estimating SOC of battery according to the status of Electric Vehicle and the BMS operation algorithm. The result for algorithm of SOC estimation is presented. It have been modified, compensated, and verified by means of the experiment.

• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.4
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• pp.1-11
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• 2021

To develop technologies for the stable operation of electric propulsion systems, the exhaust plume behavior of electric thrusters was studied using PIC-DSMC(particle-in-cell and direct simulation Monte Carlo). For the numerical analysis, the Simple Electron Fluid Model using Boltzmann relation was employed, and the charge and momentum exchanges due to atom-ion collisions were considered. The results of this study agreed with the plasma potentials measured experimentally. Near the thruster exit, active collisions among particles and charge exchanges created slow ions and fast atoms, which were expected to significantly affect the trajectory and velocity of the thruster exhaust plume.

• Journal of Environmental Science International
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• v.33 no.7
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• pp.523-532
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• 2024

In popular tourist destinations such as Jeju and Gangwon, electric rental cars are increasingly adopted. However, sudden battery drain due to weather conditions can pose safety issues. To address this, we developed a battery consumption analysis model that considers resistive energy factors such as acceleration, rolling resistance, and aerodynamic drag. Focusing on the effects of ambient temperature and wind speed, the model's performance was evaluated during an empirical validation period from November to December 2023. Comparing predicted and actual state of charge (SoC) across different routes identified ambient temperature, wind speed, and driving time as major sources of error. The mean absolute error (MAE) increased with lower temperatures due to reduced battery efficiency. Higher wind speeds on routes 1 and 6 resulted in larger errors, indicating the model's limitation in considering only tailwinds for aerodynamic drag calculations. Additionally, longer driving times led to higher actual SoC than predicted, suggesting the need to account for varying driver habits influenced by road conditions. Our model, providing more accurate SoC predictions to prevent battery depletion incidents, shows high potential for application in navigation apps for electric vehicle users in tourist areas. Future research should endeavor to the model by including wind direction, HVAC system usage, and braking frequency to improve prediction accuracy further.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.666-669
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• 2008

Droplet in miniaturized microfluidic systems have received much focused attention recently. In this work, electrical charging phenomenon of a conducting water droplet on the electrode under the dc electric field is studied and using this phenomenon droplet actuation method for microreactor applications is experimentally demonstrated. To find effects of key factors, the effects of electric field, medium viscosity, and droplet size are investigated. A scaling law of charging for the conducting droplet is derived from the experimental results. Unlike the case of a perfect conductor, the estimated amount of electrical charge ($Q_{est}$) of a water droplet is proportional to the 1.59 power of the droplet radius (R) and the 1.33 power of the electric field strength (E). (For a spherical perfect conductor, Q is proportional to R2 and E.) It is thought that the differences are mainly due to incomplete charging of a water droplet resulted from the combined effect of electrochemical reaction at electrode and the relatively low conductivity of water. Using this phenomenon, we demonstrate the transport of the charged droplet and fusion of two oppositely-charged droplets. When electric field is subjected sequentially on the electrode, the charged droplet is transported on the electrode. For the visualization of fusion of charged droplets, the precipitation reaction is used. When subjected to a DC voltage, two droplets charged are moving and merging toward each other due to the Coulombic force and chemical reaction is simultaneously occurred by coalescence of droplets. It may be due to the interchange effect of charge. It is shown that the droplet can be used for microreactor where transporting, merging etc. of reagents constitute unit operation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.11
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• pp.5156-5163
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• 2011

Electric Motorcycle is one of the most promising candidates for future transportation because of its outstanding fuel economy and environmental pollution. Before prototyping a realistic electric motorcycle, a reliable simulation program is required to test the capacities of the power sources and optimize the parameters of an electric motorcycle. This process can reduce the expenses during the designing of an electric motorcycle system. In this paper, we present an electric motorcycle system simulation program implemented on Matlab, which can model drivetrain and powertrain systems in an easy, natural way within Simulink and PSAT. And the analysis of design parameters such as max power, capacity, state of charge, slope angle is carried out by the simulation and experimental method. The predicted results by the development model were a good agreement with experimentally obtained results.

• The Transactions of the Korean Institute of Power Electronics
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• v.22 no.5
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• pp.373-381
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• 2017

The electric vehicle market has increased rapidly in recent years. Established global automakers have announced that electric cars will be developed and distributed. Furthermore, current electric cars are not merely breezes, instead, they are the mainstream of automobiles. However, high prices, short mileage, and long charge times are the main obstacles to the spread of electric vehicles. To solve these problems, the competition for technology development for the expansion of electric vehicles worldwide intensifies because of the improvements in mileage, price reduction, and expansion of charging infrastructure. In this paper, the trends in the development of key technologies for electric vehicles in overseas markets and the present strategic goals for the development of key technologies for electric vehicles in Korea will be identified.

• Bulletin of the Korean Chemical Society
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• v.33 no.3
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• pp.795-802
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• 2012

Geminate electron-hole recombination in organic solids in the presence of a donor-acceptor heterojunction is studied by computer simulations. We analyze how the charge-pair separation probability in such systems is affected by energetic disorder of the media, anisotropy of charge-carrier mobilities, and other factors. We show that in energetically disordered systems the effect of heterojunction on the charge-pair separation probability is stronger than that in idealized systems without disorder. We also show that a mismatch between electron and hole mobilities reduces the separation probability, although in energetically disordered systems this effect is weaker compared to the case of no energetic disorder. We demonstrate that the most important factor that determines the charge-pair separation probability is the ratio of the sum of electron and hole mobilities to the rate constant of recombination reaction. We also consider systems with mobility anisotropy and calculate the electric field dependence of the charge-pair separation probability for all possible orientations of high-mobility axes in the donor and acceptor phases. We theoretically show that it is possible to increase the charge-pair separation probability by controlling the mobility anisotropy in heterojunction systems and in consequence to achieve higher efficiencies of organic photovoltaic devices.