• 한국정보통신학회논문지
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• 제23권4호
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• pp.394-400
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• 2019

잡음 제거는 디지털 영상처리 과정에서 필수적으로 이루어지며, 다양한 분야에서 그 목적과 환경에 맞는 알고리즘을 개발하기 위해 많은 연구가 진행되고 있다. 그러나 기존 임펄스 잡음 제거 방법들은 영상의 에지 성분 및 고주파 성분의 잡음 제거에 다소 미흡한 성능을 보이고 있다. 따라서 본 논문에서는 고주파 성분을 보존하기 위해 잡음 판단에 따른 잡음 밀도에 따라 마스크의 범위를 확장하였다. 선택된 마스크는 임펄스 잡음을 제외한 내부 화소의 메디안 값과 표준편차를 기준으로 화소 범위가 설정된다. 그리고 화소 범위에 존재하는 화소는 거리에 따른 가중치를 적용하여 최종 출력 계산에 사용하였다. 제안한 알고리즘은 기존 방법에 비해 영상의 에지 부분 및 고주파 성분이 많은 영역에서 잡음 제거성능이 우수하였으며, 시뮬레이션을 통해 성능을 비교하였다.

• 전자공학회논문지S
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• 제34S권5호
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• pp.1-14
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• 1997

We consider transmission beamforming techniques for frequency-division-duplex (FDD) wireless communication systems using adaptive arrays to improve the signal quality of the array transmission link. We develop a simple effective transmission beamforming technique based on an approximated frequency tranlsation (AFT) to derive the tranmsiion beamforming weights from the uplink channel vector. This technique exploits the invariance of the short-time averaged fast fading statistics to small frequency translations. A simple approximate relationship that relates the transmission channel vector to the reception channel vector is derived. We have developed its practical alternative in which the frequency translation of the channel vector is performed at the principal angle of arrival (AOA) of the u;link synthestic angular spectrum instead of the mean AOA. To analyze the performance of the proposed methods, we consider the power loss incurred by applying the estimated channel vector instead of the true downlink channel vector. The performance is analyzed as a function of the mean AOA, the angular spread, the number of elements, frequncy difference between the uplink and the downlink, and the angle distribution. Their performance is also compared with that of the direct weight reuse method and the AOA based methods.

• 한국수자원학회논문집
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• 제31권5호
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• pp.599-612
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• 1998

수송방정식의 양면적은 특성으로 인하여 이송항이 지배적인 흐름에 있어서 수송방정식의 수채해석은 매우 난해하다. 특히 유한요소법을 사용하여 수치해석할 때, 상류방향으로 더 많은 가중치를 두기 위하여 변화된 시행함수를 사용한다. 이러한 방법을 Petrov-Galerkin 방법이라고 한다. 본 논문에서는 N+1 과 N+2 Petrov-Galerkin 방법을 격자 Peclet 수가 큰 수송문제에 적용하였다. 주파수맞춤 기법을 사용하여 N+2 Petrov- Galerkin 방법을 격자 Peclet 수가 큰 소송문제에 적용하였다. 주파수맞춤 기법을 사용하여 N+2 Petrov-Galerkin 방법의 적정 풍상정도를 찾아내었고, 그 결과를 토의하였다. 이 기법의 시행함수는 이송항과 확산항의 상대적 크기에 따라 그 모양이 변화된다. 수치실험을 통하여 제시된 새로운 수치해석기법의 우수성을 설명하였다.

• 대한인간공학회지
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• 제18권1호
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• pp.1-12
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• 1999

The objective of this study was to investigate the metabolic energy consumption rate of the psychophysical Maximum Acceptable Weight of Loads (MAWLs) for different manual materials handling tasks. Lifting activities with four different lifting frequencies (2, 5, 8, 11 lifts/min) for a lifting range (from floor to 76cm height) were studied. The oxygen consumption rate and heart rate were measured or recorded while subjects were lifting their MAWLs. It was found that the relationship between MAWL and frequency can be described best by the exponential function with the R-sq value 0.9865 for this study. Psychophysical MAWL decreased from 22.38 to 7.48 kg, while the oxygen consumption rate with the MAWL increased from 717.8 to $1114.7m{\ell}-O_2/min$ as the frequency increased from 2 to 11 lifts/min. Heart rate also increased from 104.5 to 120.7 bpm. The ratio of oxygen consumption for the MAWL to the Physical Work Capacity (PWC) ranged from 28 to 43%. The MAWLs were greater than or equal to the Maximum Permissible Limits (MPLs) when the frequencies were higher than 8 lifts/min. It seems that the MAWLs by psychophysical approach when the frequencies were higher than 8 lifts/min tend to be overestimated from the viewpoint of the physiological criterion of the oxygen consumption rates. From these findings it is suggested that the NIOSH Guideline should not be directly applied to Korean without reasonable modifications.

• 보건의료산업학회지
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• 제14권1호
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• pp.137-146
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• 2020

Objectives: The aim of this study was to investigate cognitive function decline by socio-demographic and health-related characteristics (health behaviors and health status) using 5th Korean Longitudinal Study of Aging panel data. Methods: The subjects were 4,440 community-dwelling people aged over 57 years. The data were analyzed with descriptive statistics, frequency analysis, χ²-test, and binary logistic regression analysis using SPSS ver. 25.0. Results: The findings revealed that socio-demographic characteristics (gender, age, area of residence, educational level, marital status, number of children, number of grand-children) and health-related characteristics (smoking, drinking, regular exercise, weight category by body mass index, hypertension and diabetes mellitus) were factors that influenced cognitive function decline (p<.05). Conclusions: Cognitive function decline was closely related to health behaviors and disease types. Future studies must examine related constructs to accurately determine these relationships among various populations. The present study could be used as a tool for the development and implementation of health promotion and prevention strategies.

• 한국수산과학회지
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• 제36권2호
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• pp.144-150
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• 2003

Reproductive biology and population dynamics of Latreutes planirostris were investigated on the south western waters of Korea from June 2001 to May 2002. This paper describes sex ratio, population growth, and reproductive aspects of Latreutes planirostris. Brood size was an isometric function of female carapace length. Based on dry weight, reproduction effort (mass of eggs/mass of female) averaged 0.23. Ovarian examination showed that there was significantly higher gonadosomatic index from May to September, with a peak in June. Statistical analysis revealed that the ovarian dry weight of females with eyed eggs was significantly higher than that of those with non-eyed eggs. This suggests that females were potentially consecutive breeders. Sex ratio showed that female is more numerous than male. Growth parameters mortality and recruitment were estimated by monthly length-frequency data. Growth parameters were estimated, using the seasonalized von Bertalanffy growth function model $(L\infty\;=\;12.70\;mm\;CL,\;K\;=\;0.87yr^{-1},\;C\;=\;0.96,\;WP\;=\;0.59)$. The recruitment pattern was twice a year.

• Journal of Power Electronics
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• 제11권5호
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• pp.621-631
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• 2011

In space qualified DC-DC converters, optimization of the following electrical characteristics is of greater interest in comparison with other specifications; power loss/efficiency, output voltage ripple and volume/weight. The main goal of this paper is to present an appropriate solution for optimizing the above mentioned characteristics. For this purpose, a comprehensive power loss model of a DC-DC converter is fully developed. Proper models are also demonstrated for assessment of the output voltage ripple and the utilized transformer volume as the bulkiest component in a DC-DC converter. In order to provide a test bed for evaluation of the proposed models, a 50W push-pull DC-DC converter is designed and implemented. Finally, a novel cost function with three assigned weight functions is proposed in order to have a trade-off among the power loss, the output voltage ripple and the utilized transformer volume of the converter. The cost function is optimized for applications in which volume has the highest priority in comparison with power loss and ripple. The optimization results show that the transformer volume can be decreased by up to 51% and this result is verified by experimental results. The developed models and algorithms in this paper can be used for other DC-DC converter topologies with some minor modifications.

• 근관절건강학회지
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• 제12권2호
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• pp.109-118
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• 2005

Purpose: The purpose of this study was to identify the effects of aquatic exercise program on pain, body weight, fatigue, flexibility in elderly women with osteoarthritis. Methods: The subjects of the study were sixty nine elderly women(age over 65years)who have an osteoarthritis. Aquatic exercise program consist of approximately one hour of exercise in water, two days per week, for six weeks. Data were gathered from September 2002 to August 2004 using a questionnaire and measuring body weight, flexibility of shoulder.. Data were analyzed with the SPSS Win 10.0 using frequency and paired t-test for differences between pre-exercise and post-exercise. Results: The results of this study are as follows: pain score, fatigue, body weight of post test were lower than those of pre test(t=5.587, p=0.000 ; t=3.394, p=0.001 ; t=4.664, p=0.000). Right and left flexibility scores of post test were better than those of pretest(Left: t=4.736, p=0.000 ; righrt: t=4.733, p=0.000). Conclusion: From these results, it is concluded that the aquatic exercise program can be effective in increasing physical and psychological function in elderly women.

• 대한한의학원전학회지
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• 제27권4호
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• pp.73-84
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• 2014

Objectives : I'd like to mimic JunChenZuoShe Theory as Herb weight ratio grade. And than analyze the characteristics of the prescription based on the Herb weight ratio grade from Taepyeonghyeminhwajegukbang, Somunsunmyungronbang and Nansilbijang. Methods : At first, we have changed herb informations to Herb weight ratio. The second we have decided the ranking of herb weight ratio. The third we have entered herb weight ratio grade. Finally we have counted frequency of first grade herb from the Taepyeonghyeminhwajegukbang, Somunsunmyungronbang and Nansilbijang. Results : We could use a new search function to find prescription by herb weight ratio grade. And than we could find out prescription efficacy rate of the ancient documents. Conclusions : We have entered herb weight ratio grade values by herb weight ratio ranking of top 10%, 30%, 60%. So we could find out that buqi(補氣) efficacy is used most often in the Taepyeonghyeminhwajegukbang, Somunsunmyungronbang and Nansilbijang. In the rate of qingrezaoshi(淸熱燥濕) efficacy, fasanfengre(發散風熱) efficacy, fasanfenghan(發散風寒) efficacy, Nansilbijang is higher than Taepyeonghyeminhwajegukbang. In the rate of qingrezaoshi(淸熱燥濕) efficacy, gongxia(攻下) efficacy, Somunsunmyungronbang is higher than Taepyeonghyeminhwajegukbang.

• 한국통신학회논문지
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• 제32권8C호
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• pp.758-766
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• 2007

높은 주파수 효율 때문에 무선 통신에 널리 쓰이고 있는 직교 주파수 분할 다중화 방식의(orthogonal frequency division multiplexing: OFDM) 문제점 중 하나는 높은 첨두대평균 전력비(peak to average power ratio: PAPR) 이다. 본 논문에서는 제한된 되먹임 정보를 가지는 송신 다중 안테나(multiple input single output: MISO) 빔성형 OFDM(beamforming OFDM) 시스템을 위한 PAPR 감소 기법을 제안한다. 제안된 방식은 채널의 영공간(null space)에서 생성된 부가신호를 원 신호에 더하여 PAPR을 줄이는 방법에 기반한다. 먼저 전체 채널 되먹임을 가정한 기존의 시스템을 부분 채널 정보 되먹임 시스템에 적용할 때의 문제점을 파악하고, 이를 바탕으로 수신 성능 열화를 줄이면서 PAPR을 감소시키는 부가 신호에 대한 가중 함수를 제안한다. 가중 함수는 수치적으로 구하며 컴퓨터 모의 실험을 통해 제안된 방식이 비트오류율(bit error rate: BER) 성능 손실은 거의 없으면서 2.5dB 정도의 PAPR감소 효과를 얻을 수 있음을 보인다.