• Journal of the Korea Institute of Information Security & Cryptology
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• v.26 no.4
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• pp.941-951
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• 2016

Limitation of fossil energy from one side and the efficiency of the electrical engine from another side motivate the industrials to encourage people for utilizing electric vehicles (EVs). To decrease the cost of EVs, the size of battery should be reduced which causes an inconvenient frequent recharging. Wireless charging is a solution for charging of electric vehicles on the move, but frequent charging causes to disclose users' location information. In this paper, we first propose an infrastructure for wireless charging of electric vehicles, and then we explain security issues that can be stated in this condition.

• Journal of Biosystems Engineering
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• v.21 no.4
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• pp.422-428
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• 1996

This study was conducted to developed to develop a simple battery-powered autonomous vehicle for greenhouse works. A steering method using speed difference of two independent driving motors was adopted. DC motor driving circuit, speed control circuit and controller using one-chip microcomputer were constructed. The inputs of controller are rolling of the vehicle and current speed of driving motors. Using these signals, automatic guidance system along furrow was developed. A computer simulation program by the kenematic analysis was developed to find out optimal control algorithm. The results of this study are as follows. 1. Automatic guidance system along the furrow that adopted two independent driving motors and rolling of vehicle was developed. 2. The results of simulation showed that PID control was adequate to automatic guidance system along furrow. 3. Two commercial 12V battery serially connected were able to drive the vehicle on the soil ground for five hours in continuous operation and for four hours in intermittent operation without recharging the battery. 4. The speed range was 0-0.7m/s and the rolling of vehicle could be controlled within $pm5^{\circ}$ range. 5. From a series of tests, developed vehicle was found to be a useful tool for greenhouse works.

• Journal of Korean Society on Water Environment
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• v.26 no.6
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• pp.1040-1048
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• 2010

An infiltration storage can be installed as a method of reducing runoff from catchment and increasing stream flow during the dry period by recharging groundwater. However, there is no proper model and method that can be used to design storage capacity of an infiltration storage in Korea. The purpose of the study is to evaluate capacities of infiltration storages planned on Jeju-do in Korea by modifying Storm Water Management Model (SWMM). The basic equations for the infiltration storage are same as those of the infiltration trench used in MIDUSS. Infiltration rates of the infiltration storages were first measured by double ring infiltrometers, and then the modified model was applied to evaluate adequacy for the capacities of three infiltration storages planned on Jeju-do in Korea. The application results show that the two infiltration storages with higher infiltration rates have adequate capacities to infiltrate the total water inflow to the storages. However, the other infiltration storage with lower infiltration rates has not sufficient capacity to infiltrate the total water inflow to the storage and release occurs to the downstream region. The simulation model and method applied can be used for capacity evaluation of future infiltration storages on highly pervious areas in Jeju-do.

• IE interfaces
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• v.23 no.2
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• pp.108-117
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• 2010

Wireless sensor network may be installed where it is hard to access or where one has to constantly gather data without any human's monitoring. Sensors which compose a sensor network are usually small with poor battery capacities and thus energy-efficient usage is very important because of difficulties in replacing or recharging the batteries to make the lifetime of the whole sensor network longer. LEACH protocol, a well-known hierarchical routing protocol, may resolve this problem by distributing the role of cluster header evenly to the sensor nodes in the whole area of network at each round. In this thesis, we introduce a variant of LEACH protocol which considers the distance between base station and sensors in the way that if a node is far from the base station then the probability that this node becomes a cluster header is low. Experiments to evaluate the energy efficiency and the ability to collect the information show that the proposed method in this paper has maintained much wider sensing area while keeping the energy efficiency same as LEACH.

• Journal of The Korean Society of Agricultural Engineers
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• v.53 no.6
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• pp.145-152
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• 2011

In order to heat greenhouse nearby river channel, riverbank filtration water source heat pump was developed for getting plenty of heat flux from geothermal energy. Recharging well, thermal storage tank with separating insulation plate and filtering tank for eliminating iron, manganese were mainly developed for making the coefficient of performance (COP) of heat pump higher. Heating system using riverbank filtration water source heat pump was installed at a paprika greenhouse in the Jinju region where a single fold of vinyl cover and 2 layers of horizontal thermal curtain were installed as a part of temperature keeping and heat insulation with a greenhouse area of 3,185 $m^2$. 320,000 kcal/h was supplied for performing a site application tests. A greenhouse heating test was performed from Feb. 1, 2011 to Apr. 30, 2011. As the result of that, COPh of the heat pump was measured in the range of 4.0~4.5, while COPS of the system was represented as 2.9~3.3. COP measured of the heat pump was very good and well responded to indoor heating temperature of the environment control system of a greenhouse.

• Proceedings of the Korean Society of Environment and Ecology Conference
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• 2009.10a
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• pp.1-16
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• 2009

Japan is one of the major forest-rich countries in the world with two thirds of its national territory covered with forests. The various functions of forests, including the prevention of global warming, conservation of national land, recharging of water resources, and maintenance of biotic diversity, play an important role in our safe, secure, and comfortable living. With the increasing national expectations on the role of forests to contribute to the prevention of global warming and "Accelerating forest carbon-sink measures to achieve Kyoto Protocol Commitment", it is necessary to make efforts toward a large-scale forest regeneration in order to secure an absorption of 13 million carbon tons through forest carbon sink for the achievement of the target of six percent reduction under the Kyoto Protocol. Most importantly, however, is to accelerate the measures for forests as absorption sources, including thinning and other forestry management activities. However, there is a situation, among others, where thinning is not implemented properly due to the decreased willingness of forest owners to manage forests, because of the long-term low demand for domestic lumber and lumber prices. In addition, forestry workers are aging and decreasing in number. Thus, the circumstances surrounding forestry are severe. It is necessary for the protection of our precious forests to make efforts to create and maintain forests with activities that involve citizens such as the "National Movement for Utsukushii Mori Zukuri(Fostering Beautiful Forests)".

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.51 no.12
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• pp.584-590
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• 2002

Crowbar system is usually applied to a pulsed power system in which a capacitor bank is discharged into a load. This provides a free wheeling path for the load current and prevents the capacitor from recharging due to a reverse voltage. Usually diodes have been used as a crowbar switch, but it is not a practical system because the cost of the diodes goes up enormously with increasing the system voltage and current. This paper presents a novel protection scheme of a charging and discharging system of a 300 kJ capacitor bank using a low-cost crowbar system which consists of a crowbar switch and resistors. Triggered vacuum switch(TVS) was used for a crowbar switch, and Rogowski coil was used to determine a trigger time of TVS. When this crowbar system is applied to our pulsed power system which consists of capacitor bank($123muF$), inductor() for forming a pulse, load resistor$(100 m\Omega)$, and a closing switch, instantaneous reversal voltage of capacitor bank could be limited less than 1.8 ㎸ until capacitor bank was charred to 17 ㎸.

• Journal of Power System Engineering
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• v.11 no.3
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• pp.29-34
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• 2007

Existent researches about indoor thermal environment have been focused on to seek human's comfort in daytime. Also researches about thermal comfort during the sleeping time that is important for resting and recharging to modern people have been seldom existed. At present, as global warming phenomenon is being continued, most people are going through inconvenience by sultriness during the sleeping hours in sweltering summer night. Therefore we need another control method of an air conditioner to keep human's thermal comfort. Ambient temperature is a common factor of the environment, but analysis of its effect on human body physiology is still unknown. The effect of ambient temperature on human sleep has been increasingly studied in the last decade. This research investigated about optimal indoor temperature to maintain proper skin temperature and comfortable sleep when indoor air is cooled by an air conditioner in sweltering summer night.

• Journal of Power Electronics
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• v.16 no.6
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• pp.2359-2367
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• 2016

Inductive power transfer (IPT) systems have become increasingly popular in recharging electric vehicle (EV) batteries. This paper presents an investigation of a series parallel/series (SP/S) resonant compensation network based IPT system for EVs with further optimized circular pads (CPs). After the further optimization, the magnetic coupling coefficient and power transfer capacity of the CPs are significantly improved. In this system, based on a series compensation network on the secondary side, the constant output voltage, utilizing a simple yet effective control method (fixed-frequency control), is realized for the receiving terminal at a settled relative position under different load conditions. In addition, with a SP compensation network on the primary side, zero voltage switching (ZVS) of the inverter is universally achieved. Simulations and experiments have been implemented to validate the favorable applicability of the modified optimization of CPs and the proposed SP/S IPT system.

• Journal of Institute of Control, Robotics and Systems
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• v.11 no.8
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• pp.696-703
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• 2005

Since most autonomous mobile robots are powered by a battery, it is important to increase the continuous operating time without recharging. This can be achieved by improving the energy efficiency of a mobile robot, but little research on energy efficiency has been performed. This paper proposes two methods for improving the energy efficiency of an omnidirectional mobile robot.. One method is to realize a continuously variable transmission (CVT) by adopting the mechanism of steerable omnidirectional wheels. The other is the proposed steering algorithm in which wheel arrangement of the mobile robot is continuously adjusted so as to obtain the maximum energy efficiency of the motors during navigation. In addition, new omnidirectional wheels which can be transformed to the conventional wheels depending on the driving conditions are proposed to compensate for less efficient omnidirectional drive mode. Various tests show that motion control of the OMR-SOW works satisfactorily and the proposed steering algorithm for CVT can provide higher energy efficiency than the algorithm using a fixed steering angle. In addition, it is shown that the differential drive mode can give better energy efficiency than the omnidirectional drive mode.