• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.30-30
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• 2011

The wave-cutoff tool is a new diagnostic method to measure electron density and electron temperature. Most of the plasma diagnostic tools have the disadvantage that their application to processing plasma where toxic and reactive gases are used gives rise to many problems such as contamination, perturbation, precision of measurement, and so on. We can minimize these problems by using the wave-cutoff method. Here, we will present the results obtained through the development of the wave-cutoff diagnostic method. The frequency spectrum characteristics of the wave-cutoff probe will be obtained experimentally and analyzed through the microwave field simulation by using the CST-MW studio simulator. The plasma parameters are measured with the wave-cutoff method in various discharge conditions and its results will be compared with the results of Langmuir probe. Another disadvantage is that other diagnostic methods spend a long time (~ a few seconds) to measure plasma parameters. In this presentation, a fast measurement method will be also introduced. The wave-cutoff probe system consists of two antennas and a network analyzer. The network analyzer provides the transmission spectrum and the reflection spectrum by frequency sweeping. The plasma parameters such as electron density and electron temperature are obtained through these spectra. The frequency sweeping time, the time resolution of the wave-cutoff method, is about 1 second. A short pulse with a broad band spectrum of a few GHz is used with an oscilloscope to acquire the spectra data in a short time. The data acquisition time can be reduced with this method. Here, the plasma parameter measurement methods, Langmuir probe, pulsed wave-cutoff method and frequency sweeping wave-cutoff method, are compared. The measurement results are well matched. The real time resolution is less than 1 ?sec. The pulsed wave-cutoff technique is found to be very useful in the transient plasmas such as pulsed plasma and tokamak edge plasma.

• 대한물리의학회지
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• 제9권1호
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• pp.101-106
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• 2014

PURPOSE: This study was to provide reference data and examine stroke and healty older differences in sit-to-stand test. This study were to determine utility of the 5 repetition sit to stand for discriminating between fallers and non-fallers, identifying an appropriate cutoff score to delineate between the groups. METHODS: Ninety-five participants were recruited. Seventy-two individuals with stroke and twenty-three healthy older agreed to participate in the study. Falls were recorded using a self-administered questionnaire. The 5 repetition sit to stand test measured the time taken to complete t repetitions of the sit to stand maneuver. The time from the initial seated position to the final seated position after completing five stands was the test measure. A cutoff score regarding 5 repetition sit to stand performance in fallers vs. non-fallers, stroke patients vs. healthy older and <60 vs. $$\geq_-$$ age groups was determined using and ROC curve. RESULTS: Cutoff score of 9.9 seconds were found to be discriminatory between healthy older and subjects with stroke. Cutoff score of 15.5 seconds were found to be discriminatory between fallers and non-fallers. Cutoff score of 18.3 seconds were found to be discriminatory between <60 and $$\geq_-$$ age groups. CONCLUSION: The 5-repetition sit-to stand test is quick, easily administered measure useful for gross determination of fall risk in people with stroke.

• 한국기계가공학회지
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• 제10권5호
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• pp.91-96
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• 2011

This study aims to analyze the flow characteristics of turbo-fan which is applied to the industrial field. Numerical analysis has been carried out to investigate the pulsation behavior of exhaust air flown out turbo fan by rotating impeller with constant speed. Moving mesh technique is proved as time-accurate solution for the flow inside impeller. As numerical results come within the error range of 1% by comparing with theoretical results, the numerical analysis can be verified. Cutoff angle has large influence on the amplitude of pulsation and the least pulsation of flow can be generated by the cutoff angle of $20^{\circ}$.

• 전기학회논문지
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• 제57권8호
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• pp.1464-1469
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• 2008

A CMOS Gm-C filter with variable cutoff frequency applicable for using in the direct conversion receiver is designed. The designed filter comprises the CMOS differential transconductors, and the gm of the transconductor is controlled by the bias voltage. This configuration can compensate variant of the cutoff frequency which could be generated by external noises, and also be used in multiband receiver. As a results of HSPICE simulation, the control range of the cutoff frequency is $1.5MHz{\sim}3.5MHz$ and the gain control range is $-2.8dB{\sim}2.6dB$. The layout of the designed 5th-order Elliptic low-pass filter is performed to fabricate a chip using $2.5V-0.25{\mu}m$ CMOS processing parameter.

• 대한의용생체공학회:의공학회지
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• 제25권2호
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• pp.137-144
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• 2004

심전도 신호에는 근 잡음과 전원잡음 둥의 잡음이 섞이는 경우가 많다. 이러한 잡음들은 심전도 신호의 주요 주파수 성분에 비하여 상대적으로 고주파 성분이지만 전체적으로 보면 주파수 스펙트럼이 중첩된다. 본 논문에서는 연속적으로 변하는 차단주파수를 가지는 시변 저역통과 디지털필터를 이용하여 원신호의 왜곡을 최소화하면서 잡음을 제거하는 신호처리 방법에 대하여 기술한다 이 필터는 차단주파수 제어기와 가변차단주파수 저역통과필터로 구성된다. 차단주파수 제어기는 잡음이 포함된 심전도 신호로부터 신호의 기울기를 이용하여 차단주파수 제어 신호를 생성한다. 가변차단주파수 저역통과필터의 구현을 위해서 본 논문에서는 컨벡스 조합 필터와 계수보간 필터로 불리는 새로운 두 가지 필터 설계방법을 제안하였으며, 이 두 가지 방법을 이용함으로써 저역통과필터의 차단주파수를 임의의 제한된 구간에서 연속적으로 변화시키는 것이 가능하였다. 고주파 잡음이 첨가된 심전도 신호에서 가변차단주파수 저역통과필터의 잡음 제거 능력이 우수함을 보였으며, 본 논문에서 제안된 가변차단주파수 저역퉁과필터는 심전도 신호의 전처리에 유용하게 사용되어질 것으로 판단된다. 특히, 제어된 환경이 아닌 일상생활 환경에서 심전도를 측정하는 재택건강관리 시스템에서 신호의 품질을 개선하는 데에 효과가 있을 것으로 기대한다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 하계종합학술대회 논문집 II
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• pp.763-766
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• 2003

A direct parameter extraction method using several two-port parameter equations derived in cutoff and active bias modes has been studied to obtain an accurate Gummel-Poon BJT model. First, dc model parameters were extracted from slopes and y-axis intercepts of I-V curve and Gummel plot. The pad capacitances and junction capacitance parameters were determined by using measured S-parameter sets in the cutoff bias. The resistance and transit time parameters were extracted by using measured S-parameter sets in the active bias.

• 농업과학연구
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• 제30권1호
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• pp.89-101
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• 2003

For the pre-feasibility study and project evaluation, the discount rate or cutoff rate should be given by the government authority. To get the Benefit/Cost Ratio, NPV(Net Present Value) and IRR(Internal Rate of Return) of the public investment projects, the pertinent and realistic discount rate should be determined to be suitable to the present time period. The cut-off rates in Korea were equivalent to 15% in 1970's, 10% in 1980's and 8% in 1990's. The prevailing rate of discount as 8% is considered not to be suitable for the 2000's public project appraisal considering the present interest rates on deposit and national bonds. To determine the socio-economic feasibility of the public projects, the IRR should be bigger than the present cutoff rate. When we still use the high old rate of discount, the analytical results of project appraisal will show always economically unfeasible. Therefore the new rate of discount suitable for present time should be determined by the government. The public projects to be implemented in 2000 year onward are recommended to be adapted 5% of cutoff rate for the project appraisal and evaluation according to the results of reviewing the tendency of discount rates and market rates of interest in Korea.

• 대한전자공학회논문지SD
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• 제42권12호
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• pp.1-8
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• 2005

본 연구에서는 측정된 S-파라미터로부터 추출된 Nano-scale MOSFET 등가회로 파라미터의 scaling 방정식을 사용하여 차단주파수의 게이트 길이 종속성을 모델화하였다. 모델된 차단주파수는 게이트 길이가 줄어듬에 따라서 크게 증가하다가, 점점 증가율이 크게 감소하는 경향을 보였다. 이는 게이트 길이가 감소함에 따라 내부전달시간은 크게 줄어들지만, 외부 기생 충전시간은 상대적으로 조금씩 감소하기 때문이다. 이와 같은 새로운 게이트길이 종속 모델은 Nano-scale MOSFET의 RF성능을 최적화시키는 데 큰 도움이 될 것이다.

• Clinical and Experimental Pediatrics
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• 제62권7호
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• pp.261-268
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• 2019

Purpose: This study aimed to evaluate the time trends of waist circumference (WC) and waist-height ratio (WHR), and to present WC and WHR distributions with optimal WHR cutoff for abdominal obesity in Korean children and adolescents. Methods: We performed a retrospective cross-sectional analysis of data from 13,257 children and adolescents (6,987 boys and 6,270 girls) aged 6-18 years who were included in the third to sixth Korea National Health and Nutrition Examination Survey (KNHANES, 2005-2015). Linear regression analyses were used to identify secular changes in WC and WHR by age, sex, and KNHANES waves. A receiver operating characteristic curve analysis was used to determine the optimal WHR cutoff values for abdominal obesity and cardiometabolic risk factors. Results: The mean WC and WHR distributions from 2005 to 2015 showed no significant secular changes between the KNHANES 4 waves (P for trend ${\geq}0.05$ in all ages and both sexes). The mean WCs in the present study were lower than those in the 2007 Korean National Growth Charts. The mean WHR at ages <13 years was statistically higher in the boys than in the girls, but did not significantly differ between the sexes among those aged 13 to 18 years. The optimal WHR cutoff for abdominal obesity was 0.48 (area under the curve, 0.985; 95% confidence interval, 0.985-0.985) in the 13- to 18-year-old adolescents. Conclusion: WC and WHR showed no secular changes over 10 years. The optimal WHR cutoff for abdominal obesity of 0.48 is useful for diagnosing and managing obesity and thus preventing obesity-related cardiometabolic complications in 13- to 18-year-old Korean adolescents.

• 대한의용생체공학회:의공학회지
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• 제16권2호
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• pp.231-238
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• 1995

Tc-99m-MIBI 심근 SPECT에서 심근조직에 비하여 간섭취가 상대적으로 높고 이들이 서로 가까이에 위치해 있는 경우 단축단면상의 하위부 또는 하위중격부에서 발생하는 인위적 관류결손의 정도와 여과기의 차단주파수의 관계를 분석하였다. 이러한 영향은 단축단면상 뿐만 아니라 심근 극성지도에서도 관찰되는데, 심근단층상에서 계수분포가 균일하지 못하고 간과 같이 특정부위에 방사능의 집적도가 높은 경우 단층상 재구성시 차단 파수의 적절한 설정에 따라 이 효과를 줄일 수 있는 방법을 제안하였다. 본 연구에서 분석에 사용된 여과기는 저역통과여과기로 이를 사용하는 경우에는 차단주파수를 0.4Nyquist 이상으로 하면 인위적 관류결손의 정도를 충분히 줄일 수 있었다. 그러나 높은 차단주파수에서는 심근영상의 균일도가 떨어지고 배후방사능 및 기타 잡음요인이 효과적으로 제거되지 않기 때문에 적절한 차단주파수의 설정이 중요하며, 본 연구에 사용된 영상에서 여과방법에 따른 원주프로필의 변화가 미세하여 후처리방법을 사용하여 분석하였다. 또한 역투사방법이 비선형적이므로 특정 영상보다는 다양한 간-심근 방사능비에 따른 영상을 분석하여 비선형성을 배제한 연구가 향후 진행되어야 한다.