• The Journal of Korean Physical Therapy
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• 제21권4호
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• pp.97-102
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• 2009

Purpose: The purpose of this study was to investigate the effects of low intensity pulsed ultrasound on TGF-$\beta$1 expression and healing of rat femur penetrating fractures. Methods: Rats were anesthetized with ketamine and xylazine. Using aseptic technique, we exposed the lateral right femoral diaphysis with removal of the periosteum. We made one hole along its long axis with an electrically-driven 1.8 mm diameter drill bit. Postoperatively, rats were divided into two groups (a control group, n=15; an experimental group, n=15). The experimental group was treated with low intensity pulsed ultrasound (pulse rate: 1:4, 0.5 W/$cm^2$, 10 minutes, 1 time per day) for 3 weeks. The control group was treated with sham ultrasound (with the US unit turned off). Results: The experimental group achieved more callus formation and TGF-$\beta$1 expression than the control group at the $7^{th}$, $14^{th}$ and $21^{st}$ days after low intensity pulsed ultrasound treatment. Conclusion: This study suggests that low intensity pulsed ultrasound facilitates bone fracture repair, possibly via increased TGF-$\beta$1 expression.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2005년도 전력전자학술대회 논문집
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• pp.207-210
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• 2005

This paper describes a design of several ship's emergency lighting system(SELS) that power factor is improved and power is controlled extensively, and techniques to control and monitor this system in remote distance by PC serial communication. The remote monitoring control system is composed of emergency power supply system (EPSS), half bridge(HB)inverter, fluorescent lamp(FL), microprocessor, multi communication interface. EPSS checks the voltage of the emergency backup battery in real time. In case that the voltage of 13[V] or less has been detected for 5[msec] or longer for 3 times in a row, charger circuit is connected for battery charging. Experimental works using proposed system confirm that speedy and stable power to be supplied when main power source cut-off, compared with conventional analog type, and input power up to 35.0[%] by adjusting of pulse frequency of the HB inverter.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 춘계합동학술대회 논문집
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• pp.149-152
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• 2002

If the ambient temperature rises for AC PDP, some of the discharge cells are turned off because of the misfiring during address period. Particularly, the misfiring of the 'last scan line is more serious than that of the first. In order to compensate the misfiring in such that case, different addressing voltage is applied at each cell such as progressively increasing pulse voltage instead of constant one. As a result, the addressing time and discharge charge of the last scan line have become similar to those of the first scan line and the phenomenon of misfiring has disappeared.

• Journal of Astronomy and Space Sciences
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• 제37권4호
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• pp.219-228
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• 2020

A CubeSat platform has become a popular choice due to inexpensive commercial off-the-shelf (COTS) components and low launch cost. However, it requires more power-efficient and higher-data rate downlink capability for space applications related to remote sensing. In addition, the platform is limited by the size, weight and power (SWaP) constraints as well as the regulatory issue of licensing the radio frequency (RF) spectrum. The requirements and limitations have put optical communications on promising alternatives to RF communications for a CubeSat platform, owing to the power efficiency and high data rate as well as the license free spectrum. In this study, we analyzed the performance of optical downlink communications compatible with CubeSat platforms in terms of data rate, bit error rate (BER) and outage probability. Mathematical models of BER and outage probability were derived based on not only the log-normal model of atmospheric turbulence but also a transmitter with a finite extinction ratio. Given the fixed slot width, the optimal guard time and modulation orders were chosen to achieve the target data rate. And the two performance metrics, BER and outage data rate, were analyzed and discussed with respect to beam divergence angle, scintillation index and zenith angle.

• 대한산업공학회지
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• 제38권3호
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• pp.220-226
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• 2012

The Electric discharge machining (EDM) process is used to minimize the difference between designed feature and machined feature while the most workpiece is removed through the cutting processes. The tiny-deep hole machining and perpendicular wall machining in mold and die are good applications of EDM. Among EDM equipment, the super drill uses the hollowed electrode to eliminate the debris which causes the second discharge with the electrode and degrades the machining quality. Through the hollow, the high pressured discharge oil is supplied to remove the debris together with the spindle rotation. The thin-hollow electrode tends to easily wear out compared to the sold die-sinking electrode and its wear rate is might not allowed to monitor in real time during discharging. Up to now, the wear amount is measured by off line method, which leads machining time to increase because the hole pass-through moment can be check by visual (manually) with the extra tool path. Therefore, this study suggests the attractive method to evaluate the hole pass-through moment in which the gap voltage and z-axis encoder pulse are monitored to predict the moment. The commercial super drill is used to validate the proposed method and the experiment is carried out.

• Structural Engineering and Mechanics
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• 제61권3호
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• pp.347-357
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• 2017

The applications of active control is being more popular nowadays. Several control algorithms have been developed to determine optimum control force. In this paper, a Chaotic Particle Swarm Optimization (CPSO) technique, based on Logistic map, is used to compute the optimum control force of active tendon system. A chaotic exploration is used to search the solution space for optimum control force. The response control of Multi-Degree of Freedom (MDOF) shear buildings, equipped with active tendons, is introduced as an optimization problem, based on Instantaneous Optimal Active Control algorithm. Three MDOFs are simulated in this paper. Two examples out of three, which have been previously controlled using Lattice type Probabilistic Neural Network (LPNN) and Block Pulse Functions (BPFs), are taken from prior works in order to compare the efficiency of the current method. In the present study, a maximum allowable value of control force is added to the original problem. Later, a twenty-story shear building, as the third and more realistic example, is considered and controlled. Besides, the required Central Processing Unit (CPU) time of CPSO control algorithm is investigated. Although the CPU time of LPNN and BPFs methods of prior works is not available, the results show that a full state measurement is necessary, especially when there are more than three control devices. The results show that CPSO algorithm has a good performance, especially in the presence of the cut-off limit of tendon force; therefore, can widely be used in the field of optimum active control of actual buildings.

• Journal of Power Electronics
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• 제13권4호
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• pp.516-527
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• 2013

This paper presents a new overall system for state-of-available-power (SoAP) prediction for a lithium-ion battery pack. The essential part of this method is based on an adaptive network architecture which utilizes both fuzzy model (FIS) and artificial neural network (ANN) into the framework of adaptive neuro-fuzzy inference system (ANFIS). While battery aging proceeds, the system is capable of delivering accurate power prediction not only for room temperature, but also at lower temperatures at which power prediction is most challenging. Due to design property of ANN, the network parameters are adapted on-line to the current battery states (state-of-charge (SoC), state-of-health (SoH), temperature). SoC is required as an input parameter to SoAP module and high accuracy is crucial for a reliable on-line adaptation. Therefore, a reasonable way to determine the battery state variables is proposed applying a combination of several partly different algorithms. Among other SoC boundary estimation methods, robust extended Kalman filter (REKF) for recalibration of amp hour counters was implemented. ANFIS then achieves the SoAP estimation by means of time forward voltage prognosis (TFVP) before a power pulse occurs. The trade-off between computational cost of batch-learning and accuracy during on-line adaptation was optimized resulting in a real-time system with TFVP absolute error less than 1%. The verification was performed on a software-in-the-loop test bench setup using a 53 Ah lithium-ion cell.

• 한국인터넷방송통신학회논문지
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• 제18권6호
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• pp.169-180
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• 2018

백색 발광다이오드(LEDs)는 형광등보다 경제적이며 높은 밝기, 수명, 내구성을 제공한다. 이러한 LED는 사람들의 일상생활과 밀접하게 연결되어 있기 때문에 LED의 조광제어는 에너지 절약과 삶의 질 향상에 중요한 요소이다. 이 LED를 사용하는 가시광통신시스템에서는 안테나 수에 비례해 채널 용량을 확보할 수 있다는 점에서 복수의 MIMO(입력 다중 출력) 기술이 많은 관심을 끌었다. 본 논문은 가시광통신(VLC) 시스템에서 적용된 공간-시간 블록 코드(STBC) 기법의 세 가지 변조의 전력 성능을 분석한다. 변조 방식은 RZ-OOK(Return-to-On-Ok), 가변 펄스 위치 변조(VPPM), 중첩 펄스 위치 변조(OPPM) 및 조광 제어를 적용하였다. 전력 요구사항과 전력 소비는 세 가지 종류의 변조 하에서 $2{\times}2$ STBC-VLC 환경에서 전력 효율을 비교하는 지표로 사용되었다. 조광 제어가 각 변조 체계의 통신 성능에 영향을 미치는지 확인하였다. 확인 결과 VPPM은 세 가지 변조 중 소비량이 더 많았으며 OPPM은 VPPM에 비해 에너지 절감 효과를 보였다.

• 한국통신학회논문지
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• 제30권11A호
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• pp.1027-1034
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• 2005

수십 센터미터 이내의 오차를 만족시키는 거리/위치인식 기능 및 저속 데이터 송수신 기능 구현을 주목적으로 발족된 저속 WPAN(LR-WPAN: Low Rate Wireless Personal Area Network)의 표준화 그룹인 IEEE802.15.4a에서는 간단하고 경제적이며 전력 소모가 적은 송수신기 구조를 요구한다. 이에 본 논문에서는 PEWB(Parallel Energy Window Banks)를 이용한 독창적인 비동기 OOK(On-Off Keying) 방식 UWB(Ultra-Wide Band) 송수신기 구조를 제안한다. 또한 무선 다중경로 페이딩 채널 상황을 다소 극복할 수 있게 유연성 있는 운영이 가능한 송수신기 구조를 위해 펄스 및 비트 반복 기법을 사용한다. 제안된 송수신기 구조의 잡음 특성 분석을 위해 chi-square 분포가 적용되며, 반복적 계산을 통해 얻어진 최적임계값을 적용하며 비트오율 성능을 분석한다. 모의실험 결과, 10-5의 비트오율을 얻기 위한 신호대잡음비 및 수신에너지 적분시간은, LOS(Line-Of-Sight) 주거 환경의 경우 15.3dB, 32ns이고, NLOS(Non-Line-Of-Sight) 실외 환경의 경우 16.2dB, 72ns이다. 최소의 비트오율을 얻기 위한 적분에너지 대 전체 수신에너지 비는 약 $86\%$이다.

• 한국자동차공학회논문집
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• 제16권4호
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• pp.56-62
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• 2008

A synthetic gas reformed from hydrocarbon-based fuels consists of $H_2$, CO and $N_2$. Hydrogen contained in the synthetic gas is a very useful species in chemical processes, due to its wide flammability range and fast burning speed. The ESGI (Exhaust Synthetic Gas Injection) technology is developed to shorten the light-off time of three way catalysts through combustion of the synthetic gas in the exhaust manifold during the cold start period of SI engines. Before the ESGI technology is applied to the test engine, the authors set a test rig that consists of gas temperature and composition controllers, an exhaust pulse generator and an exhaust manifold with a visualization window, in order to optimize the point and conditions of injection of the synthetic gas. Through measuring burned gas temperatures and taking photographs of synthetic gas combustion at the outlet of the exhaust manifold, the authors tried to find the optimal injection point and conditions. Analysis of burned gas composition has been performed for various $O_2$ concentrations. As a result, when the synthetic gas is injected at the port outlet of the cylinder No. 4 and $O_2$ concentration exceeds 4%, combustion of the synthetic gas is strong and effective in the exhaust manifold.