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정우태,이웅수 한국균학회 1980 韓國菌學會誌 Vol.8 No.2
The antifungal activity of salicylaldehyde-o-phenylenediimine, a derivative of Schiff base, was studied in vitro against various species of fungi, especially, dermatophytes. The antifungal tests were performed according to the tube-dilution method, and all subcultures were incubated at room temperature for 14 days. Salicylaldehyde-o-phenylenediimine was effective against fungi such as Trichophyton mentagrophytes, Trichophyton rubrum, Microsporum canis and Fonsecaea compacts. Trichophyton mentagropirytts was inhibited at 20㎍ per ㎖, Trichophyton rubrum at 40㎍ per ㎖, Microsporum cams at 6㎍ per ㎖, and Fonsecaea compacts at 2㎍ per ㎖.
소형 레일표면 연마장치의 제어 변수에 따른 연마 영향 분석
정우태,신지선 한국철도학회 2020 한국철도학회논문집 Vol.23 No.7
Long run operation of railway vehicle and accumulated passing tonnage on railway track can cause failure and deformation of track rails. Critical deformations of or damage to rails also reduce rail life and cause safety accidents such as derailments. Therefore, rail grinding work can be conducted as railway maintenance. In general, while railway grinding vehicles are suitable for relatively long range rail grinding, portable grinding machines are used for short range grinding or local rail recovery by manual operators. Thus, rail surface quality after manual grinding can vary depending on operator experience. In this paper, we have analyzed control variables that affect the grinding quality when a recently developed autonomous grinding machine is used. In particular, we have investigated major control variables to achieve optimal grinding conditions such as stiffness of the vertical axis for grinding depth control, rotating speed of grinder, and torque changes. As a result, sufficient rotating speed of the grinding stone can help to reduce position errors of the grinding machine. In addition, higher motor torque of the grinding spindle axis during grinding steps was required as grinding steps increase. The results can help to improve the operational performance when grinding machine is operated with optimal control conditions.
정우태 한국철도학회 2020 한국철도학회논문집 Vol.23 No.5
Continuous particulate matter and water liquid particles in air inflow used in cooling the electronic equipment in railway vehicles can cause malfunctions and reduce the efficiency of the equipment. In order to prevent particle inflow, an inertial filter can be applied at the air inlet section of the railway vehicle, especially for freight railway vehicles. However, there are no guidelines in selecting design factors of inertial filters, although shapes and gaps in designing the baffle of the inertial filter and flow rate of the intake air can affect the efficiency of the pressure drop and particle collection. Therefore, in this paper, we have used CFD analysis to determine the pressure change and particle removal rate with changes of various design factors of inertial filers. That is, we have found that a relatively narrow gap between baffles can improve the particle collection rate; however, it also generates a high pressure gradient, which is not suitable for railway vehicle inertial filters, which require high flow rate at the air inlet. As a result, we have verified that intake flow rate can affect the performance of the inertial filter of railway vehicles and the particle removal rate according to gap changes of baffles.
정우태,김선기 한국철도학회 2024 한국철도학회논문집 Vol.27 No.1
Rails installed on railroad tracks undergo various types of wear, cracking and deformation due to continuous contact and interaction with wheels of rail vehicles. Such rail wear and damage not only cause noise and vibration and affect ride comfort, but also, when continuously accumulated, cause safety accidents such as derailments. Therefore, to prolong the service life of rails and prevent safety accidents, rails should be inspected by continuous monitoring and subjected to maintenance such as rail polishing. In this study, we derived conditions suitable for rail grinding by adjusting the main design variables of grindstones used in rail grinding work. Specifically, abrasive stones were manufactured by changing the abrasive grit size, binder strength, etc., and grinding performance tests were conducted by manufacturing an abrasive simulation test device. In addition, changes of torque acting in direction of grinding depth and length of rail according to changes of grinding speed were observed, and optimum grinding conditions were determined. As a result, it was confirmed that the smaller the particle size of the abrasive and the higher the strength of the binder, the lower the torque value of the grinding wheel. 철도 궤도에 설치된 레일은 철도 차량의 차륜과의 지속적인 접촉과 상호작용 통하여 다양한 마모, 균열, 변형이 발생하게 된다. 이러한 레일의 마모와 손상은 소음과 진동의 유발과 승차감에 영향을 줄 뿐 아니라, 지속적으로 누적될 경우에는 탈선 등의 안전사고의 원인이 된다. 따라서 궤도 레일은 지속적인 모니터링을 통한 검측과 레일 연마와 같은 유지보수 작업을 통하여 수명연장과 안전사고 예방을 수행하고 있다. 본 연구에서는 철도 레일의 연마작업에서 사용되는 연마지석의 주요 설계변수의 조정을 통하여 레일 연마에 적합한 조건을 도출하고자 하였다. 특히 연마제 입도 크기, 결합제 강도 등을 변화하여 연마지석을 제작하였으며, 연마모사 시험장치를 제작하여 연마 성능시험을 수행하였다. 또한 연마 속도 변화에 따른 연마 깊이 방향, 레일 길이 방향에 작용하는 토크 변화를 관찰하고, 최적의 연마조건을 분석하였다. 결과적으로 연마제의 입도가 작고 결합제의 강도가 높을수록 연마지석의 토크 값이 감소함을 확인하였다.