• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2001년도 제33회 춘계학술대회 개최
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• pp.334-339
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• 2001

The nonlinear vibration characteristics of hydrodynamic journal bearings with a circumferentially groove are analyzed numerically when the external sinusoidal disturbances are given to the rotor-bearing system continuously. Also, the cavitation algorithm implementing the Jakobsson-Floberg-Olsson boundary condition is adopted to predict cavitation regions in the fluid film more accurately than conventional analysis which uses the Reynolds condition. It is found that the difference between linear and nonlinear analysis is much more remarkable as the amplitude of external disturbance increases, and it depends upon the excitation frequency of external disturbance. It is also shown that the cavity region in the fluid film is increased as the amplitude or excitation frequency of external disturbance increases. The whirling center of the steady state orbit moves closer to the bearing center as the amplitude or the excitation frequency of the external disturbance increases because of smaller range of full film region.

• Tribology and Lubricants
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• 제5권2호
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• pp.48-54
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• 1989

The effects of angular misalignment, coning and the temperature difference between the primary seal ring and the seal seat on the pressure distribution in mechanical face seals are analyzed. The modified Reynolds equation for the temperature dependent viscosity was solved by a finite difference approximation and Gauss-Seidel method. It is shown that the amplitude of pressure is significantly affected by the misalignment of the seals and a large temperature difference between the rotor and the stator.

• 감성과학
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• 제13권3호
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• pp.541-550
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• 2010

본 연구에서는 P300-기반 숨긴정보검사(P300 CIT)에서 검사자극들 간의 물리적 유사성이 P300 진폭과 검사의 효율성에 미치는 영향을 검증하였다. 사고를 당하여 자신의 이름을 기억하지 못한다고 허위로 주장하는 허위기억상실을 가정한 상황에서, 실험참여자의 이름을 숨긴정보(관련자극)로 사용하여 P300 CIT를 실시하였다. 이 검사에서 실험참여자의 과제는 목표자극과 나머지 자극을 변별하는 것이었다. 한 집단의 실험참여자들은 목표자극과 관련자극, 무관련자극들 간의 물리적 유사성이 낮은 조건(저난도 조건)에서 검사를 받았으며, 다른 한 집단의 실험참여자들은 검사자극들 간의 물리적 유사성이 높은 조건(고난도 조건)에서 검사를 받았다. 기저선-정점 P300 진폭을 측정치로 사용한 경우, 난이도 조건과 자극유형의 상호작용효과가 $\alpha$=.10 수준에서 유의하였다(p=.052). 저난도 조건에서는 관련자극과 무관련자극 간의 P300 진폭차이가 유의하였으며, 고난도 조건에서는 관련자극과 무관련자극 간의 P300 진폭차이가 유의하지 않았다. 정점-정점 P300 진폭을 측정치로 사용한 경우, 난이도 조건과 자극유형의 상호작용효과가 유의하지 않았으며, 저난도 조건과 고난도 조건 모두에서 관련자극과 무관련자극간의 P300 진폭차이가 유의하였다. 기저선-정점 P300 진폭을 이용한 개인별 판단결과, 저난도 조건과 고난도 조건 간의 정확판단율 차이가 유의하지 않았으며, 정점-정점 P300 진폭을 이용한 개인별 판단결과도 저난도 조건과 고난도 조건 간의 정확판단율 차이가 유의하지 않았다. 그러나, 난이도 조건 간의 정확판단율 차이가 기저선-정점 P300 진폭을 이용한 경우보다 정점-정점 P300 진폭을 이용한 경우에 더 작은 경향이 있었다. 이러한 결과는 검사자극들 간의 물리적 유사성이 높을 때에도 P300 CIT의 효율성이 크게 감소하지 않는다는 것을 의미한다.

• Annals of Clinical Neurophysiology
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• 제4권2호
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• pp.108-113
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• 2002

Background and Objective : Carpal tunnel syndrome (CTS) is the most common mononeuropathy encountered in clinical practice. No single procedure or group of procedures has demonstrated adequate sensitivity. F-wave study in CTS is very rarely reported. To determine the diagnostic usefulness of new parameters of F-wave and comparative study of F-wave parameters of median and ulnar nerves in patients with CTS. Methods : F-wave responses of median and ulnar nerves were analyzed from 27 patients with clinically diagnosed CTS and 22 age and gender-matched normal control. Conventional F-wave parameters were studied. Also, the usefulness of new parameters such as mean and maximal ulnar-median F-wave latency differences, ulnar-median F-wave persistence and chronodispersion differences, median/ulnar F-wave amplitude ratio, and F-wave conduction velocity (FCV) using mean and maximal latency were assessed. Results : Compared with controls, median F-wave minimal, maximal and mean latencies, mean F-wave amplitude/M-wave amplitude, minimal, mean and maximal ulnar-median F-wave latency differences, and FCVs using minimal, maximal and mean latency were significant (P<0.05~0.001). Median F-wave minimal, maximal and mean latencies, mean ulnar-median F-wave latency difference, and FCVs using minimal, maximal and mean latency showed high sensitivity and specificity. Mean ulnar-median F-wave latency difference and FCVs using maximal and mean latency were new parameters. Conclusion : New F-wave parameter including mean ulnar- median F-wave latency difference and FCVs using maximal and mean latency may be a useful to assess the CTS. Also, median F-wave minimal, maximal and mean latencies, and FCV using minimal latency may be included in routine diagnostic tests in CTS.

• 한국전자파학회논문지
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• 제22권2호
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• pp.182-190
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• 2011

진폭 변조를 이용한 거리 측정 시스템은 반송파를 진폭 변조하여 송수신한 신호의 진폭 변조 신호의 위상차를 사용하여 거리를 측정하게 된다. 진폭 변조 거리 측정 시스템에서 문제가 되는 안테나 간의 누설 신호 및 불요 신호에 의한 측정 오차를 최소화하기 위해 능동반사기를 사용하여 주파수 대역을 바꾸어 송신하는 방식이 제안되었다. 본 논문에서는 모호성이 없는 측정 거리를 확장하면서도 정밀한 측정을 가능하게 하는 새로운 위상측정부의 구현에 대해 설명하고 있다. 즉, 8 MHz 및 1 MHz의 두 개의 변조 주파수를 교차적으로 선택하여 변조함으로써, 150 m까지의 거리를 2 cm 이하의 오차로서 측정할 수 있게 하였다. 위상측정부는 정밀한 위상 측정을 위하여 높은 변조 주파수는 JK 플립플롭 위상차 측정기를 사용하고, 낮은 변조 주파수일 경우는 XOR 위상차 측정기를 사용하였다.

• Journal of Astronomy and Space Sciences
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• 제27권1호
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• pp.21-30
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• 2010

In processing space geodetic data, mapping functions are used to convert the tropospheric signal delay along the zenith direction to the line of sight direction. In this study, we compared three mapping functions by evaluating their effects on the tropospheric signal delay and position estimates in GPS data processing. The three mapping functions tested are Niell Mapping Function (NMF), Vienna Mapping Function 1 (VMF1), and Global Mapping Function (GMF). The tropospheric delay and height estimates from VMF1 and GMF are compared with the ones obtained with NMF. The differences among mapping functions show annual signals with the maximum occurring in February or August. To quantitatively estimate the discrepancies among mapping functions, we calculated the maximum difference and the amplitude using a curve fitting technique. Both the maximum difference and amplitude have high correlations with the latitude of the site. Also, the smallest difference was found around $30^{\circ}N$ and the amplitudes increase toward higher latitudes. In the height estimates, the choice of mapping function did not significantly affect the vertical velocity estimate, and the precision of height estimates was improved at most of the sites when VMF1 or GMF was used instead of NMF.

• The Journal of Korean Physical Therapy
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• 제17권4호
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• pp.621-631
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• 2005

The purpose of this study was to measure magnitude of lower leg muscle activity during dynamic stability tests performed on an unstable board by subjects with sprained lateral ankles. Fifteen lateral ankle sprain subjects(8 male, 7 female) participated in this study. The muscle activity was measured at gastrocnemious, tibialis anterior, peroneus longus during dynamic stability tests performed on Biodex stability system as surface EMG. The EMG amplitude of each muscle was normalized to the amplitude in the maximal voluntary isometric contraction(MVIC) of each muscle. As results, peroneus longus evidenced significant difference at stable and unstable grade comparing injured with uninjured sides. Gastrocnemious and tibialis anterior evidenced no significant difference. Change of muscle activity with stable and unstable grade evidenced no significant difference on injured and uninjured sides. The data provided information on peroneus longus contributes to dynamic stability after lateral ankle sprains. Peroneus longus training program may have to be emphasized after an ankle sprain.

• Journal of Photoscience
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• 제7권4호
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• pp.161-167
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• 2000

Temperature-dependent electroretinogram responses were investigated in the dark adapted bullfrog eyes within the physiological temperature range 0-40$\^{C}$. In hypothermic process(25→0→25$\^{C}$), the amplitude of b-and c-wave decreased with lowering the temperature again. Both b-wave amplitude and threshold responses were maximal around 15$\^{C}$ during the temperature increment. Upon warming to room temperature again (25$\^{C}$), the b-wave amplitude was approximately doubled as compared to that of control without temperature changes. During the hyperthermic process (25→40→25$\^{C}$), however, the responses decreased with warming, and the wave amplitude failed to recover by cooling to 25$\^{C}$ again. As describe above, the recoveries of ERG in both processes show the striking difference. The hypothermia induces the amplification of the b-wave, that is, enhances the retinal function with the temperature recovery toward room temperature. While the hypertherima produces the decrease of the b-wave even though recovered to room temperature, which indicates an irreversible retina. The morphological alteration is shown both hypothermic and hyperthermic process, such as an appearance of large vacuoles and degenerating outer segments, more intense in hyperthermia, similar to light induced damage.

• Journal of Acupuncture Research
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• 제29권6호
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• pp.57-71
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• 2012

Objectives : The purpose of this study is to find the effects of Sa-Am stomach tonifying acupuncture on radial pulse through the parameters difference. Methods : Forty healthy subjects participated in this study, acupuncture group and control group were divided. Radial pulse were measured using 3 dimensional pulse imaging system(DMP-3000). 19 parameters that significantly changed were selected after comparing between acupuncture group and control group. Then, 19 parameters were analyzed before, immediately after, 30 minutes after and 60 minutes after acupuncture in acupucture group. Results : 1. Heart rate, pulse period, T/T1, T2/T, T4/T, T5/T, T-T4, (T-T4)/T and T4/(T-T4) significantly changed after acupuncture. 2. H1 Amplitude, H2 Amplitude, H4 Amplitude and H5 Amplitude significantly changed after acupuncture. 3. Area of Pulse Wave, Systolic Pulse Area, Diastolic Pulse Area and Area of W significantly changed after acupuncture. 4. AIx/HR significantly changed after acupuncture. Conclusion : Stomach Tonifying Acupuncture exerts an influence on radial pulse parameters. Further radial pulse change study on various acupuncture treatment is required.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2005년도 후기학술대회논문집
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• pp.220-221
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• 2005

Sub-bottom profiler(SBP) has been used extensively for the mapping of basement in the foundation design of offshore structure, for pre- and post-dredging operations within harbors and channels, for selection of pipeline routes, sitting of drilling platforms, and in the exploration for an aggregates such as sands and gravels. During the construction of Siwha embankment for irrigation water and the expansion of arable land, the breaking of an embankment unfortunately occurred so that a lot of riprap was swept away and widely dispersed by the tide and strong current. The feasibility study for the construction of the tidal-powered electric plant in Siwha embankment was performed quite recently. Therefore we made use of SBP survey to investigate the distribution of the lost riprap. We could successfully map out the distribution of the lost riprap from the reflection amplitude characteristics of the sediments in SBP data set. We demonstrated the variation of reflection amplitude versus the sediments with and/or without riprap by means of the numerical modeling of acoustic wave equation using finite difference method. Also we examined an amplitude anomaly of the ripraped area through the physical modeling using ultrasonic.