Delta-sigma Modulation for Digital DC-DC Controllers

Wanki Hong,Kitae Kim,Youngkil Choi,Seongyoung Ryu,Insuck Kim,Hyungdong Rho,Sanho Byun,Jeongjin Roh 대한전자공학회 2005 ITC-CSCC :International Technical Conference on Ci Vol.2005 No.3

고집적 반도체를 위한 테스트 순서 조정 방법

김완기(Wanki Kim),장재필(Jaepill Jang),홍종기(Jonggi Hong),홍기진(Gijin Hong),안진호(Jin-Ho Ahn) 대한전기학회 2015 대한전기학회 학술대회 논문집 Vol.2015 No.2

Inhibitory Effects of Flavonoids from Spatholobus suberectus on Sortase A and Sortase A-Mediated Aggregation of Streptococcus mutans

( Wanki Park ),( Chan-hong Ahn ),( Hyunjoo Cho ),( Chang-kwon Kim ),( Jongheon Shin ),( Ki-bong Oh ) 한국미생물생명공학회(구 한국산업미생물학회) 2017 Journal of microbiology and biotechnology Vol.27 No.8

Seven flavonoids were isolated from Spatholobus suberectus via repetitive column chromatography and high-performance liquid chromatography. The chemical structures of these compounds were identified by spectroscopic analysis and comparison with values reported in the literature. Among the flavonoids tested, 7-hydroxy-6-methoxyflavanone (1) and formononetin (4) exhibited strong inhibitory activity against Streptococcus mutans SrtA, with IC₅₀ values of 46.1 and 41.8 μM, respectively, but did not affect cell viability. The onset and magnitude of inhibition of saliva-induced aggregation in S. mutans treated with compounds 1 and 4 were comparable to the behavior of a srtA-deletion mutant without treatment.

외부 위험신호 자동 감지형 헤드셋

김완기(Wanki Kim),홍기진(Gijin Hong),장원석(Wonseok Jang),안진호(Jin-Ho Ahn) 대한전기학회 2015 정보 및 제어 심포지엄 논문집 Vol.2015 No.10

Analysis of Changes in Stride Length, Time, and Electromyography Finding Depending on Athletic Crouch Start Method

( Kyungill Lee ),( Wanki Hong ),( Eung Gyu Kim ) 한국운동역학회 2017 한국운동역학회지 Vol.27 No.1

Objective: The purpose of this study was to compare and analyze the kinematic variables and electromyography (EMG) findings that change with varying characteristics of crouch start and feedback provision, and to provide the fundamental data for record improvement in 400 mH. Method: Four short-distance runners participated in the experiment. The analyzed variables were elapsed time per interval, stride length, and muscle activities in three lower limb muscles. These variables were analyzed by using Kwon3d XP and Noraxon Myoresearch. The participants were subjected to three conditions, including two conditions that relate to the thrusting foot on the rear block and another condition pertinent to feedback provision. Results: In terms of a one-step interval, the elapsed time in condition A was longer than that in condition B, and the one after the feedback was the longest. The stride length of a one-step interval was the longest in condition A. The stride length of a two-step interval was the shortest in condition A. The muscle activity during a one-step interval showed differences in vastus medialis and medial gastrocnemius, with condition A being the highest. Conclusion: When the non-dominant left foot was located at the back, negative results were observed in terms of elapsed time and stride length. Moreover, an imbalance in muscle activity was observed between the left and right feet when the left foot was placed at the back. As a result, significant differences in elapsed time, stride length, and muscle activity were observed depending on the foot placed on the rear block. In conclusion, we identified the characteristics of crouch start in 400 mH, and a specialized program must be suggested.

Analysis on Biomechanical Differences Depending on Changes in Postures during Farm Work

Chulgab Lee,Wanki Hong 대한인간공학회 2016 大韓人間工學會誌 Vol.35 No.5

Objective: This study looks into biomechanical variables occurring when one moves in a sitting posture, and presents objective references to make improvements in work environments of farm workers. Background: The farmers have more common musculoskeletal disorders compared to other professions, because they are much more exposed to biomechanical risk factors. The sitting posture that is the representative form of the squatted, can cause typical knee joint diseases, such as osteoarthritis or patellofemoral pain syndrome of the knee joint. Therefore, a quantitative study of knee load upon the movement in a squatting posture is required. Method: In order to proceed with its investigation, the study examined movements in a sitting posture with and without a lower body supporter through a threedimensional image analysis and by using Surface EMG. The study compared and analyzed the average muscle activity and the maximum muscle activity as well. Results: Every movement in a sitting posture is related to loads onto the knee joints and, when the farm workers move to sides, the study observed a high level of bowlegged moment. The study also noticed differences in muscle activity of medial gastrocnemius with and without the lower body supporter. Conclusion and Application: The study argues that what has been discussed so far is evidence to prove how the farm working environments should be improved in consideration of these movements observed when the farm workers move in a sitting posture.

Analysis of Changes in Stride Length, Time, and Electromyography Finding Depending on Athletic Crouch Start Method

Lee, Kyungill,Hong, Wanki,Kim, Eung Gyu Korean Society of Sport Biomechanics 2017 한국운동역학회지 Vol.27 No.1

Objective: The purpose of this study was to compare and analyze the kinematic variables and electromyography (EMG) findings that change with varying characteristics of crouch start and feedback provision, and to provide the fundamental data for record improvement in 400 mH. Method: Four short-distance runners participated in the experiment. The analyzed variables were elapsed time per interval, stride length, and muscle activities in three lower limb muscles. These variables were analyzed by using Kwon3d XP and Noraxon Myoresearch. The participants were subjected to three conditions, including two conditions that relate to the thrusting foot on the rear block and another condition pertinent to feedback provision. Results: In terms of a one-step interval, the elapsed time in condition A was longer than that in condition B, and the one after the feedback was the longest. The stride length of a one-step interval was the longest in condition A. The stride length of a two-step interval was the shortest in condition A. The muscle activity during a one-step interval showed differences in vastus medialis and medial gastrocnemius, with condition A being the highest. Conclusion: When the non-dominant left foot was located at the back, negative results were observed in terms of elapsed time and stride length. Moreover, an imbalance in muscle activity was observed between the left and right feet when the left foot was placed at the back. As a result, significant differences in elapsed time, stride length, and muscle activity were observed depending on the foot placed on the rear block. In conclusion, we identified the characteristics of crouch start in 400 mH, and a specialized program must be suggested.

DC-DC 컨버터를 위한 디지털 방식의 컨트롤러 회로

홍완기,김기태,김인석,노정진,Hong, Wanki,Kim, Kitae,Kim, Insuck,Roh, Jeongjin 대한전자공학회 2005 電子工學會論文誌-SD (Semiconductor and devices) Vol.42 No.10

휴대용 전자제품의 증가에 따라 배터리의 사용 시간을 증가시키기 위한 파워메니지먼트 회로의 설계는 매우 중요해 지고 있다. 이에 따라 switching power supply, 특히 DC-DC 변환기의 필요성은 더욱 커지고 있다. 기존 DC-DC 변환기용 컨트롤로 칩들은 순수한 아날로그 방식으로 설계되어 왔었다. 본 논문에서는 아날로그 방식의 단점을 극복하기 위한 디지털방식 컨트롤러 칩의 제작 및 측정된 연구 결과를 소개한다. 디지털 컨트롤러의 장점으로는 설계시간이 빠르고, 설계 변경을 쉽게 할수 있다는 점이다. 그러나 DC-DC 컨버터의 최종 출력 전압은 아날로그 전압이기 때문에, 아날로그를 디지털로 변환해 주는 장치가 디지털 컨트롤러에는 필수적이다. 본 논문에서는 기존의 flash 방식의 데이터 변환기 대신에 회로설계가 단순화된 델타시그마 모듈레이션을 사용하여 아날로그 신호를 디지털 신호로 변환하였다. 개발된 CMOS 컨트롤로 칩은 테스트 보드 측정을 통하여 성공적인 동작이 검증되었다. A DC-DC converter with digital controller is realized. the digital controller has several advantages such as robustness, fast design time, and high flexibility. however, since the DC-DC output voltage is analog, an analog-to-digital conversion scheme is always essential in all digital controllers. A simple and efficient delta-sigma modulator is used as a conversion scheme in out implementation. The measurement results show good voltage regulation

폐경 후 중년여성의 하지 근력 수준이 골밀도에 미치는 영향: 연령의 조절 효과

이철갑 ( Chulgab Lee ),김응규 ( Eunggyu Kim ),홍완기 ( Wanki Hong ) 사단법인 아시아문화학술원 2021 인문사회 21 Vol.12 No.1

본 연구 목적은 폐경기 중년여성들의 하지 근력이 대퇴부 골밀도에 미치는 영향력과 불변성인 연령이 조절 변인으로 작용하는지 알아보기 위함이다. 이를 위해 폐경기인 중년여성 151명을 대상으로 하지 근력을 측정하였고, X-ray 골밀도 측정기를 통해 대퇴부 골밀도를 측정하였다. 자료처리는 SPSS Ver. 23.0 통계패키지 프로그램을 이용하여 상관분석과 위계적 회귀분석을 실시하였다. 연구 결과는 다음과 같다. 첫째, 골밀도와 하지 근력은 정적상관이 나타났다. 둘째, 골밀도와 연령은 부적상관이 나타났다. 셋째, 하지 근력이 골밀도에 영향을 미치지만 연령이 조절 변인으로 나타나지 않았다. 이러한 연구를 중심으로 연령에 영향 없이 하지 근력 강화를 통해 골밀도 수준을 유지 또는 증진 시킬 수 있는 이론적 근거를 확인하였고, 골다공증 예방을 위해서는 체중 부하 근력 강화 운동이 설계되어야 함이 확인되었다. The purpose of this study is to find out the influence of lower extremity muscle strength on thigh bone density in middle-aged women in menopause and whether the invariant age acts as a moderating variable. To this end, muscle strength was measured for 151 middle-aged women in menopause, and femoral bone density was measured through an X-ray bone density meter. Data processing was performed using the SPSS Ver.23.0 statistical package program to perform correlation and hierarchical regression analysis. The results of the study are as follows. First, the bone density and lower extremity muscle showed static correlation. Second, bone density and age were not correlated. Third, lower extremity muscle affects bone density, but age did not appear to be a moderating variable. These studies have identified theoretical grounds for maintaining or enhancing bone density levels by strengthening lower extremity muscle strength regardless of age, and confirmed that weight load strength exercises should be designed to prevent osteoporosis.