• Proceedings of the KIPE Conference
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• 1999.07a
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• pp.595-598
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• 1999

A new of the automotive High Intensity Discharge(HID) lamp ballast systems is proposed. Proposed scheme is consisted of the high frequency DC-DC converter and low frequency DC-AC inverter as same as conventional HID ballast system. But this system separates ignition voltage from dc link voltage, which results to used the lower voltage rating power devices for HID lamp ballast system compared with conventional system. As a result, proposed system has a lower cost and higher efficiency.

• 제어로봇시스템학회:학술대회논문집
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• 1990.10a
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• pp.681-686
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• 1990

The existing Swash Plate Type Axial Piston Motor rapidly drops efficiency at high speed in comparison with low speed. This is the reason why the motor was designed only in a viewpoint of minimum of power supply. But, in this paper, the motor which was optimally designed in a veiwpoint not only power supply but also load capacitancy, flow loss volume, axial stiffness and tilting stiffness keeps up high efficiency at high speed.

• Proceedings of the KIEE Conference
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• 2002.11d
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• pp.36-38
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• 2002

Low voltage circuit breakers which interrupt rapidly and raise the reliability of power supply are widly used in power distribution systems. In the paper, it was investigated how much Interrupting capability was improved by correcting the shape of the contact system in molded case circuit breaker(below MCCB), Prior to the interrupting testing, it was necessary for the optimum design to analyze magnetic forces on the contact system, generated by current and flux density. This paper presents both our compuational analysis and test results contact system in MCCB.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.10A
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• pp.776-783
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• 2009

Current-cut circuit is an effective method to obtain low power consumption in wireless communication systems as high speed OFDM. For the operation of current-mode FFT LSI with analog signal processing essentially requires current-mode serial-to-parallel/parallel-to-serial converter with multi input and output structure. However, the Hold-mode operation of current-mode serial-to-parallel/parallel-to-serial converter has unnecessary power consumption. We propose a novel current-mode serial-to-parallel/parallel-to-serial converter with current-cut circuit and full chip simulation results agree with experimental data of low power consumption. The proposed current-mode serial-to-parallel/parallel-to-serial converter promise the wide application of the current-mode analog signal processing in the field of low power wireless communication LSI.

• Journal of Power Electronics
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• v.15 no.3
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• pp.621-633
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• 2015

This paper proposes the analysis and design of a DC-side symmetrical zero-current-switching (ZCS) Class-D current-source driven resonant rectifier to improve the low power-factor and high line current harmonic distortion of lighting applications. An analysis of the junction capacitance effect of Class-D ZCS rectifier diodes, which has a significant impact on line current harmonic distortion, is discussed in this paper. The design procedure is based on the principle of the symmetrical Class-D ZCS rectifier, which ensures more accurate results and provides a more systematic and feasible analysis methodology. Improvement in the power quality is achieved by using the output characteristics of the DC-side Class-D ZCS rectifier, which is inserted between the front-end bridge-rectifier and the bulk-filter capacitor. By using this symmetrical topology, the conduction angle of the bridge-rectifier diode current is increased and the low line harmonic distortion and power-factor near unity were naturally achieved. The peak and ripple values of the line current are also reduced, which allows for a reduced filter-inductor volume of the electromagnetic interference (EMI) filter. In addition, low-cost standard-recovery diodes can be employed as a bridge-rectifier. The validity of the theoretical analysis is confirmed by simulation and experimental results.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.12
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• pp.5998-6016
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• 2017

In thin-film transistor liquid-crystal displays (TFT-LCDs), which are most commonly used in mobile devices, the backlight accounts for about 70% of the power consumption. Therefore, most low-power-related studies focus on realizing power savings through backlight dimming. Image compensation is performed to mitigate the visual distortion caused by the backlight dimming. Therefore, popular techniques include pixel compensation for brightness recovery and contrast enhancement, such as histogram equalization. However, existing pixel compensation techniques often have limitations with respect to blur owing to the pixel saturation phenomenon, or because contrast enhancement cannot adequately satisfy the human visual system (HVS). To overcome these, in this study, we propose a novel dimming technique to achieve both power saving and HVS-awareness by combining the pixel compensation and histogram specifications, which convert the original cumulative density function (CDF) by designing and using the desired CDF of an image. Because the process of obtaining the desired CDF is customized to consider image characteristics, histogram specification is found to achieve better HVS-awareness than histogram equalization. For the experiments, we employ the LIVE image database, and we use the structural similarity (SSIM) index to measure the degree of visual satisfaction. The experimental results show that the proposed technique achieves up to 15.9% increase in the SSIM index compared with existing dimming techniques that use pixel compensation and histogram equalization in the case of the same low-power ratio. Further, the results indicate that it achieves improved HVS-awareness and increased power saving concurrently compared with previous techniques.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.2
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• pp.466-474
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• 2014

According to wireless network technology and mobile processors performance were improved, the small wireless mobile device such as smart phones has been widely utilized. The mobile devices can be used GPS information, thereby the services based on location information was increased. GPS was impossible to provide location information in indoor and signal shading environment, and the tracking systems based on short distance wireless communication are required infrastructure. The IEEE 802.11 based tracking system is possible estimation using APs, however the tracking device is exhausted battery power seriously. In this paper, we propose IEEE 802.11 based low-power tracking system. We reduced power consumption from channel scanning and network connection. For performance evaluation, we designed and implemented the tracking tag device, and measured power consumption of the device. As the simulation result, we confirmed that the power consumption was reduced 46% compare to the standard execution.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.7
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• pp.372-379
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• 2014

When a hand-held device with limited battery transmits and receives data using short-range wireless communication systems, such as WLAN(Wireless Local Area Network) or high speed WPAN(Wireless Personal Area Network), instead of mobile communication systems, the device is able to reduce the power consumption due to the reduced transmission distance. However, if there are many WLAN or high speed WPAN systems around the device, non-negligible power may be consumed by receiving and decoding the packets which have nothing to do with the device. In this paper, we propose a scheme reducing the power consumption by including physical-layer ID in WLAN or WPAN packets and avoiding unnecessary packet receptions. Also, we describe a method to determine the optimum number of physical-layer IDs.

• Korean System Dynamics Review
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• v.15 no.1
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• pp.51-74
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• 2014

Despite the high efficiency of nuclear power plant, people in Korea do not give approvals and supports the facilities because the risk of the accidents and incidents. In particular, the low level of safety culture is a crucial mechanism that damages the robustness of the NPP. By considering the various definitions of safety culture and analyzing the major reasons of incidents, the conceptual safety culture model is made by using Causal Loop Diagramming. For sustaining development of nuclear power, social supports, incentives and organizational learning are needed. It also requires the coordination of work schedules and the expansion of human resource for protecting the rules and procedures in NPP. Decommissioning aging nuclear power plants will prevent a serious accident. In order to promote the safety culture, Korea Hydro & Nuclear Power Corporation should disclose more information to the public and promote the internal and external communications.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.353-356
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• 1997

Vehicle steering system determines the direction of a vehicle. A manual steering system consists of mechanical connections between the steering wheel and tires. Recent power steering system adds an actuator to help a driver to steer easily at low speed. However, at front collision, the driver can be injured by steering shaft and the power steering pump decreases the engine power. To solve these problems, electronic power steering system which connects the steering wheel and tires with electronic connection is proposed, that has advantages such as decrease of engine load and increase of driver safety reactive. Since the ratio between driver's steering torque and steering torque of tires can be controlled freely, the torque which is delivered from the road to the driver through tires and steering wheel can be reshaped to make the driver feel comfortable. In this paper, the ratio of delivering steering torque and the magnitude of force to be delivered from road to driver has been controlled using fuzzy controller, and it's effectiveness has been shown through simulation results.