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주기적 물림강성 변화와 백래쉬에 의한 기어구동계의 비선형 동특성
조윤수(Cho, Yun-Su),최연선(Choi, Yeon-Sun) 한국소음진동공학회 2002 한국소음진동공학회 논문집 Vol.12 No.12
Main sources of the nitration of a gear-pair system are backlash and transmission error, the difference between required and actual rotation during gear meshing. This paper presents the nonlinear dynamic characteristics of gear motions due to the existence of backlash and periodic variation of meshing stiffness, which is assumed as a one-term harmonic component. Gear motions are classified as three types with the consideration of backlash. Each response is calculated using the harmonic balance method and confirmed by numerical integration. The responses with the increase of the rotating speed show abrupt changes in its magnitude for the variation of the preload, exciting force, and damping coefficient. The result also shows that there is a chaotic motion with some specific design parameters and operating conditions In gear diving system. Consequently the design of gear driving system with low nitration and noise requires the study on the effects of nonlinear dynamic characteristics due to stiffness variation and backlash.
피부 병원성균에 대한 오배자 천연 복합물의 시너지 항균 효과
김주희 ( Ju Hee Kim ),최연선 ( Yun Sun Choi ),김왕배 ( Wang Bae Kim ),박진오 ( Jin Oh Park ),임동중 ( Dong Joong Im ) 대한화장품학회 2021 대한화장품학회지 Vol.47 No.2
본 연구는 항균 활성을 갖는 천연 소재를 검색하고 화장품의 보존제로써 적용을 위해 진행되었다. 디스크 확산법(disc diffusion method)을 통해 피부 병원성균 3 종(Staphylococcus aureus, Escherichia coli (E. coli), Pseudomonas aeruginosa)과 효모균(Candida albicans (C. albicans))에서의 천연 항균 소재 9 종을 검색하였다. Inhibition zone 크기를 측정한 결과, 오배자 추출물(Rhus Semialata gall (Gallnut) extract), 참나무 목초액(Oak vinegar) 그리고 폴리리신(ε-polylysine)은 10 mm 이상으로 다른 추출물에 비해 우수한 항균활성을 나타내었다. 병원성균 3종과 효모균, 곰팡이균(Aspergillus brasiliensis (A. brasiliensis))에서 최소살균농도(minimum bactericidal concentration, MBC)를 측정한 결과, 오배자 추출물과 참나무 목초액은 5 종의 병원성균에서 10∼ 20 mg/mL와 20 ∼ 40 mg/mL, 폴리리신의 경우 진균류에서 0.5 ∼ 2 mg/mL으로 살균 작용에 의한 항균효과를 각각 확인하였다. Checkerboard 방법에 따라 오배자 추출물과 참나무 목초액, 오배자 추출물과 폴리리신의 혼합 비율에 따른 시너지 효과(synergistic effect), 부가 효과(additive effect), 무관함(indifferent) 그리고 상쇄 효과(antagonistic effect)를 평가하였다. 그 결과, 단독으로 사용할 때보다 오배자 추출물과 참나무 목초액 복합물은 E. coli, C. albicans, A. brasiliensis를, 오배자 추출물과 폴리리신 복합물은 C. albicans, A. brasiliensis를 4 배 낮은 농도에서 99.9% 억제하며 항균 시너지 효과를 확인하였다. 오배자 추출물과 참나무 목초액 복합물은 S. aureus와 P. aeruginosa를 2 배 낮은 농도에서 억제하며 부가 효과가 확인되었다. 이로써, 오배자 천연 복합물은 항균 시너지 효과를 발휘할 수 있음을 입증했을 뿐만 아니라 넓은 항균 스펙트럼을 갖춘 천연 방부 시스템으로 써 화장품에서 응용할 수 있을 것으로 기대된다. This study was attempted to investigate natural materials with antimicrobial activity and to apply as natural preservatives in cosmetics. The disc diffusion method was used to search for nine species of natural antibacterial material for three species of skin pathogenic bacteria (Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa) and Candida albicans. As a result of measuring the size of inhibition zone, Rhus Semialata gall (Gallnut) extract, Oak vinegar, and ε-polylysine were showed strongest antibacterial activities (> 10 mm). The Minimum Bactericidal Concentration (MBC) of gallnut and oak vinegar ranged from 10 to 20 mg/mL and from 20 to 40 mg/mL against five human skin pathogens. The MBC of ε-polylysine ranged from 0.5 to 2 mg/mL in fungus. The synergic effect of gallnut extract/oak vinegar mixture and gallnut extract/ε-polylysine mixture were evaluated by checkerboard test. Compared to when used alone, the MBC of gallnut extract/oak vinegar mixture were at 4 times lower concentration against E. coli, C. albicans, and A. brasiliensis. Also Furthermore, the MBC of gallnut extract/ε-polylysine mixture were at 4 times lower concentration against C. albicans and A. brasiliensis. It was confirmed that the combination of gallnut extract with oak vinegar or ε-polylysine resulted in synergistic antibacterial effect against three human skin pathogens. Thus, it is expected that gallnut extract and natural product mixture can not only demonstrate antibacterial synergies, but also be applied in cosmetics as a natural preservative system with a wide antibacterial spectrum.
이승일(Lee Seung-Il),윤차중(Yun Cha-Jung),최연선(Choi Yeon-Sun),신범식(Shin bum-Sik) 한국철도학회 2006 한국철도학회 학술발표대회논문집 Vol.- No.-
The study is to analyze dynamo test results for various commercial pads in order to verify the performance of brake disk with CV-NCM cast iron. The developed brake disk will apply to 200 km/h tilting trains that is being developed as one part of project for speed-up on Korean existing railroad. The test program is made out suitably for braking condition and performance of test equipment by referring UIC 541-3. Two kinds of resin pad and one kind of foreign sintered pad suitable for 200 km/h trains are used as various commercial pad for the dynamo test. The data aquisition for the maximum and smallest temperature, hot spot, etc. on disk and pad is performed by using the thermocouples and thermal imaging cameras. From this research, we obtained braking characteristics between CV-NCM cast iron disk and pad of various material and will be utilized usefully as basis data of performance optimization of developing sintered pad. Subway line becomes an important way of transportation as road traffic goes to limit. Recently the large number of passengers of the subway lines near metropolitan area, In-Cheon, Su-Won, Pyung-Teak and Chon-An, is rapidly increasing. The electric cars of the No. 1 subway line in the suburbs are now running fast compared to the downtown area. However, the fast electric car can be uncomfortable to ride in, because there are so much noise and vibration. In this research, the running characteristics of the electric car of the No. 1 subway line in the suburbs is investigated through the measurements of the noise and vibration at running condition.
복합항균제제를 첨가한 생면의 미생물학적 및 이화학적 품질 특성
현정은(Jeong-Eun Hyun),황진하(Jin-Ha Hwang),최연선(Yun-Sun Choi),한아름(Areum Han),윤재현(Jae-Hyun Yoon),배영민(Young-Min Bae),이호(Ho Lee),김철(Chul Kim),이명구(Myunggu Lee),심명국(Myeungkuk Shim),임경현(Kyung-Hyun Im),이선영(Sun-You 동아시아식생활학회 2016 동아시아식생활학회지 Vol.26 No.5
This study was conducted to investigate the effects of natural preservatives (G3, G3-1, F3, and F3-1) using Cordyceps militaris on improvement of food quality and safety of noodle during storage. Wheat flour noodle were prepared using three different concentrations of natural preservatives (0.100, 0.200, and 0.400%). Changes in microbial populations, pH value, titratable acidity, and sensory evaluation were measured during storage at 12±2℃ for 3 days. Overall, use of natural preservatives resulted in lower levels of total mesophilic bacteria, coliform, yeast and mold in noodle compared to the control. In particular, natural preservatives using 2× MIC concentrations (0.400%) of F3 and F3-1 were effective at maintaining levels of total mesophilic bacteria for noodle during storage. The pH values of noodle made with F3 and F3-1 were higher than the others. The titratable acidity of noodle with natural preservatives did not significantly change during storage. In sensory evaluation, appearance, color, and overall acceptability of noodle with F3 and F3-1 were preferred than the control. These results could provide useful information for developing an alternative preservation method to improve food quality and shelf-life of noodle using natural preservatives.
조윤수,최연선 成均館大學校 科學技術硏究所 2001 論文集 Vol.52 No.2
Gears are made of two or more wheels with teeth around their edges that fit into the teeth of another wheel. They have been designed to transfer power or movement by means of shafts. The faults of a gear in its shape and teeth causes the vibration and noise of the machine having gears. A qualitied gear can guarantee the quality and life of the machine. However, it is vary difficult to inspect the qulity of gear due to its complexity in its shape and teeth. In this research, an automatic inspection system for gear fault detection is tried to develop using a machine vision. A CCD camera and a frame grabber are used for the image processing of the gear images and edge comparison methods are implemented to examine the gear fault. Despite the roughness, the results shows the possibility and convenience for gear fault detection using image processing technique.