• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.242-242
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• 2011

현재 반도체 및 디스플레이 장비들이 공정 매개변수 및 플라즈마 변수를 독립적으로 제어하기 위하여 전원 주파수를 다양하게 사용된다. 플라즈마의 상태나 에너지 전달 효율은 반도체 및 디스플레이 공정에 중요한 요소이다. 따라서 플라즈마 발생장치의 전원 주파수를 바꾸었을 때의 플라즈마 밀도와 에너지 전달 효율에 관하여 연구하였다. 공정용 유도 결합 플라즈마(ICP)를 발생시키기 위하여 신호 발생기에서 전력 증폭기와 임피던스 정합회로(Matcher)를 거쳐 반응 용기에서 플라즈마를 발생시켰다. 6 mTorr의 압력에서 주파수는 13.56 MHz에서부터 80 MHz까지, 15~60 W의 전력을 인가하였다. 플라즈마의 에너지 효율을 측정은 제작한 로고스키코일(Rogowski Coil)을 이용하여 시스템 전반을 등가회로로 계산하였으며, 플라즈마 밀도는 반응용기 중앙에서 부유 탐침법을 적용하여 도출하였다. 같은 전력 조건에서 주파수가 증가함에 따라 플라즈마 밀도가 증가함을 볼 수 있었다. 그러나 플라즈마 에너지 효율은 주파수가 높아짐에 따라 점점 커지다 작아지는 경향을 볼 수 있었다. 에너지 전달 효율의 변화는 정합회로의 표피효과(Skin effect)에 기인하며 플라즈마 밀도의 변화는 이온의 에너지 손실에 기인한다.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.7 no.1
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• pp.39-43
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• 2013

In this paper, we present a effective method of gait rehabilitation training using critical point of median frequency in muscle fatigue analysis using EMG. To target the five healthy volunteers, EMG signal were measured in the quadriceps femoris muscle and the tibialis anterior muscle in order to determine muscle fatigue. We performed a test targeting three adult male for 30 minutes on a treadmill at a speed of 6km/h same. EMG signal analysis in frequency and median frequency is calculated to quantification of muscle fatigue, and calculated the critical point which is saturated by muscle fatigue during 30 minutes. We set saturated point the threshold which muscle can withstand. The results of this paper, we are able to quantify the threshold of the muscle.

• Journal of Biomedical Engineering Research
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• v.24 no.1
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• pp.31-36
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• 2003

Impact characteristics of six DM(Diabetes Mellitus) shoe insole materials (Podian, Plastazote black, Plastazote white, Flexible PU foam, Podialene 200 blue and Podia flex) and three multi-density insoles (AP, OS and PW insoles) were determined in the present study, using a self-designed impact measurement system. The coefficient of restitution, the median frequency and the attenuation index were calculated for each material, based on impact forces and linear accelerations. Podian revealed the superiority in the coefficient of restitution and the attenuation index. The median frequency of the Flexible PU foam was the smallest. Results also showed that the heel region was the most impact-attenuated among other areas in the insole. OS insole showed the better characteristics in the coefficient of restitution and the median frequency. but there was no significant difference in the attenuation index. Similar impact characteristics were found in all areas in PW insole. since it was basically of the same dual-density polyurethane.

• Journal of Korea Society of Industrial Information Systems
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• v.16 no.4
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• pp.99-105
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• 2011

This paper presents a method to design a centralized repetitive controller that is robust to variations in the multiple system parameters. The uncertain parameters are specified probabilistically by their probability distribution functions. Instead of working with the distribution functions directly, the centralized repetitive controller is designed from a set of models that are generated from the specified probability functions. With this multiple-model design approach, any number of uncertain parameters that follow any type of distribution functions can be treated. Furthermore, the controller is derived by minimizing a frequency-domain based cost function that produces monotonic convergence of the tracking error as a function of repetition number. Numerical illustrations show how the proposed multiple-model design method produces a repetitive controller that is significantly more robust than an optimal repetitive controller designed from a single nominal model of the multiple system.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.9
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• pp.124-129
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• 1997

The purpose of this study is to predict the stability and frequency response of multipurpose vehicle. The vehicle model has seven degrees of freedom. The motion equations are derived by using Lagrangian equation and linearized. The positions of eigenvalues of model which are dominated by lateral velocity, yaw rate, roll rate of sprung mass are used to predict the stability of motion. The resonse of sprung mass to steering wheel is simulated in time domain. It is predicted that the roll response of sprung mass would rather be improved by modifying the position of eigenvalues. The responses of sprung mass to steering wheel are also simulated in frequency domain. The magnitude and phase plots of gains are evaluated in driver's steering input frequency range.

• The Journal of the Korea institute of electronic communication sciences
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• v.8 no.8
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• pp.1271-1276
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• 2013

This study selected 22 male subjects to examine the maintenance period of static and ballistic stretching applied to rectus femoris, divided them into 11 static stretching group and 11 ballistic stretching group and analyzed changes in median frequency and in maximal voluntary isometric contraction before stretching and at 30 sec, 1 min, 3 min, 5 min, and 10 min after stretching. Median frequency showed significant differences in changes according to time and groups after the test of main effects. It was reduced after 3 min. in both static stretching and ballistic stretching groups and then increased again. Maximal voluntary isometric contraction showed significant differences in changes according to time and groups from the results of the main effect test. Static stretching group was reduced at 3 min after the experiment and then increased after that and ballistic stretching group was reduced at 5 min after the experiment and then increased again. In conclusion, changes were shown according to time after stretching and the effects of ballistic stretching were maintained a little longer than those of static stretching.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.4A
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• pp.316-323
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• 2009

Power allocation of soft frequency reuse(SFR) to increase cell edge user throughput by reducing inter-cell interference is proposed for coordinated cellular systems. SFR is the effective technique to increase cell edge user throughput, however, it costs the degradation of total system throughput. The cost increases when SFR operated in distributed resource controlled systems fails to be fast adaptive in the change of user distribution. The proposed scheme enables coordinated cells to control transmit power adaptively depending on user distribution so that it minimizes the loss of system throughput introduced from SFR while it guarantees enhancement of cell edge user throughput. Through system level simulation considering neighboring two cells, evaluation result for adaptive power allocation is shown compared with static power allocation.

• Journal of IKEEE
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• v.28 no.1
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• pp.72-77
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• 2024

In this paper, a triple-mode frequency-tunable filter is proposed to meet the recent demands of various frequency bands of mobile communication services. This filter has a tunable structure that can adjust the resonance frequency using a variable capacitor. To improve the quality factor, a SIW(Substrate Integrated Waveguide) structure was introduced and a structure that induces three resonance modes was implemented through a circular hole located in the center. The change in electric field distribution and resonance frequency by the variable capacitor was simulated using HFSS, and the change in electric field distribution and resonance frequency of Triple Mode mode was confirmed.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.2 no.1
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• pp.17-22
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• 2009

In this paper, we extract well-known parameters such as zero crossing rate(ZCR), low band energy(Band) and median frequency(MDF) from surface electromyogram (EMG), and compare to evaluate themselves as measures for fatigue. In experiments, 3 males and 3 females volunteered to participate in surface EMG recordings placed on the biceps brachii and each recording experiment continued until exhaustion.

• Proceedings of the KIEE Conference
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• 2004.11d
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• pp.122-126
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• 2004

직격뇌가 높은 건축물에 치거나 인접 건물로부터 뇌전류가 유입되었을 때 잘못된 피뢰설비로 인한 피해는 매우 심각한 실정이다. 낙뢰가 치는 순간에 반도체와 같은 민감한 전자부품을 사용하는 전자 및 통신기기는 뇌전류로 인한 전자기장의 영향으로 오동작이 발생하거나 부품의 손상을 입기가 쉽다. 본 논문에서는 건축물 구조체에 직격뇌가 유입되었을 때 건축물 구조체 및 건물 주위에 나타나는 전위분포특성을 연구하였다. 본 논문에서 30m 높이 건축물의 상부 모서리와 중앙부 그리고 건축물 하부 모서리와 중앙부로 뇌전류가 유입된다고 가정하여 건축물의 전계분포특성을 시뮬레이션하였으며, 뇌전류는 2중 지수함수형태로 모의된 20kA 임펄스 서지 전류를 주입하였다. 뇌서지 전류의 주파수 특성은 Fast Fourier Transform(FFT)을 이용하여 얻었으며, 얻어진 주파수 값을 이용하여 건축물 구조체와 인접지역의 Scalar Potentials과 Electric Fields의 특성을 시뮬레이션하였다. 또한 철골 빔 건축물의 철골 빔에 직접 뇌전류가 유입되는 경우와 건물 하부의 접지전극에 뇌전류가 유입되는 경우로 분리 하여 연구하였다. 그 결과 뇌전류의 유입경로가 건축물의 모서리부분 보다는 중심부에 위치될 때 전위 및 전계 크기가 작았으며 건축 철골구조물보다 건축물 하부에 접지전극이 설치될 때 더 낮은 전계 값을 갖는 것을 확인하였다.