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정연철,여석준,JUNG Yeon-Cheol,YOA Suk-Jun 한국수산과학회 1992 한국수산과학회지 Vol.25 No.2
The water-quality control for coastal waters is continuously required in view point of the environmental protection. The purpose of this study is to simulate the hydrodynamic process and the dispersion phenomena of several pollutants in Suyeong Bay, Pusan. The present study employs the depth-averaged 2-dimensional model for nemerical simulation of the hydrodynamics and diffusion. The nemerical solution is obtained by ADI(Altenating Direction Implicit) scheme which is frequently used for tidal current and diffusion computations in the coastal zone. To verify the nunlerical results, the field observations of various water quality parameters such as COD, SS and nutrients were performed during the spring tide. In the results of this study, the computed tidal currents show the clockwise flows for ebb tide and counter-clockwise flows for flood tide. In comparison with the water-qualities in ebb tide and flood tide, there seems to be slightly deteriorated in ebb tide and especially near the estuary of Suyeong River. In flood tide, however, the water-quality near Kwangan Beach is deteriorated. The computed distributions of COD and SS are in god agreements with the observed ones, while those of $PO_4\;^{3-}-P\;and\;NO_3\;^--N$ show slight differences due to the complex transformation processes.
이영문(Young-Moon Lee),손재환(Jae-Hwan Son),박건우(Geon-Woo Park),정희철(Hee-Chul Jung),정연철(Yeon-Cheol Jeong) 한국기계가공학회 2007 한국기계가공학회 춘추계학술대회 논문집 Vol.2007 No.-
In grinding processes, the maximum undeformed chip thickness, hmax, is one of the most important parameters as actual depth of cut by a grain. In order to estimate the maximum undeformed chip thickness in grinding operation, it is necessary to obtain the successive cutting point spacing. In the past it was obtained by experiments. In the average grain model, the average successive cutting point spacing has been obtained using the given grinding input conditions and it is possible to estimate the maximum undeformed chip thickness without using any experimentally obtained data. In this paper, as verifying the validity of this model, three kinds of experiments have been performed with CBN grinding wheels different concentration. As increase of the concentration, the number of cutting point per unit area increased but the grinding scratch spacing and the average grain spacing decreased. The average successive cutting point spacing and the maximum undeformed chip thickness decreased too. The estimated maximum undeformed chip thickness by using the average grain model has been found in the range of the experimentally obtained data.
TiO₂ 촉매를 첨가한 자가 가습 연료전지용 MEA의 제조
변정연(Byun, Jung-Yeon),이용진(Lee, Yong-Jin),주민철(Ju, Min-Cheol),김화용(Kim, Hwa-Yong) 한국신재생에너지학회 2008 한국신재생에너지학회 학술대회논문집 Vol.2008 No.05
A novel self-humidifying composite membrane for the proton exchange membrane fuel cell (PEMFC) at low humidity condition was developed. The Pt/TiO₂ catalyst particles were synthesized via supercritical impregnation methods. Pt precursor was dissolved in supercritical carbon dioxide and impregnated onto TiO₂ particles. Pt precursors were platinum(II) acetylacetonate, Dimethyl(1,5-cyclooctadiene) platinum(II) and we controlled the ratio of Pt to TiO₂. The impregnated Pt precursor was converted to TiO₂ supported Pt nanoparticle under various reducing conditions. Pt/TiO₂ catalyst particles were dispersed uniformly into the Nafion solution, and then Pt/TiO₂/Nafion composite membrane was prepared using solution-cast method. The self-humidifying composite membrane could minimize membrane conductivity loss under dry conditions due to the presence of catalyst and hydrophilic Pt/TiO₂ particles. To optimize the performance of MEA, amount of ionomer loading was controlled. And mixed catalysts were used. The cell performance of MEA was obviously improved under dry conditions at 65?C.
연료전지의 자가 가습 Pt/TiO₂/Nafion 전해질막의 제조
변정연(Byun, Jung-Yeon),김효원(Kim, Hyo-Won),주민철(Ju, Min-Cheol),김화용(Kim, Hwang-Yong) 한국신재생에너지학회 2007 한국신재생에너지학회 학술대회논문집 Vol.2007 No.11
A novel self-humidifying composite membrane for the proton exchange membrane fuel cell (PEMFC) at low humidity condition was developed. The Pt/TiO₂ catalyst particles were synthesized via supercritical impregnation methods. Pt precursor was dissolved in supercritical carbon dioxide and impregnated onto TiO₂ particles. Pt precursors were platinum(II) acetylacetonate, Dimethyl(1,5-cyclooctadiene) platinum(II) and we controlled the ratio of Pt to TiO₂ The impregnated Pt precursor was converted to TiO₂ supported Pt nanoparticle under various reducing conditions. TiO₂ catalyst particles were dispersed uniformly into the Nafion solution, and then Pt/TiO₂/Nafioncomposite membrane was prepared using solution-cast method. The size, dispersion and content of the platinum had been characterized with Transmission Electron Micrograph (TEM), X-ray diffract ion (XRD) and Inductively Coupled Plasma - Atomic Emission Spectrometer (ICP-AES). The cell performance with the self-humidifying composite membrane was compared with a recast Nafion membrane under both humidified and dry conditions at 65 ?C.
최영미,안무업,안희철,최정태,유기철,장석준,박인철,송근정,홍은석,정성필,김승환,황정연,조준휘 대한응급의학회 2002 대한응급의학회지 Vol.13 No.4
Purpose: From June 20, 2000, to June 24, 2000, for five days, nationwide hospitals and clinics went on strike in opposition to the government's policy on the separation of dispensaries from medical practice. The present study examined the present state of medical examination and treatment and the management system of the third medical institution to indicate a model for dealing with such strikes ahead in the future. Methods: The present state of the medical examination and management system in eight hospitals of the nationwide emergency medical centers was examined. The term of strike, June 20, 2000, to June 24, 2000, for five days, was the subject term; Five weekdays of the week just prior to the strikes and two consecutive holidays, January 1, 2000, and January 2, 2000, were chosen as a contrast group. Results: During the term of strike, the number of patients was larger than it was on the weekdays, but was less than it was on consecutive-holidays. ^1) In severity triage, the ratio of emergency patients increased but non-emergency and delayed patients decreased than consecutive-holidays, and the number of medical personnel decreased for all types of visits. The attending hospitals in cases of disease increased, and^2) the ratio of internal medicine, general surgery, obstetrics, orthopedics patients increased than consecutive-holidays level, and the ratio of gynecology, phychiatry, opthalmology patients increased than consecutive-holidays and weekdays level. The ratio of cases in CPR decreased, and deliveries was at the same level as it was on the weekdays. Both radiation tests and emergency tests decreased. Conclusion: During a strike, carrying out severity triage and operating emergency outpatient care for non-emergency patients, such as outpatients, may be desirable. Adding emergency-treatment manpower to the areas where the number of patients increased, ^3) putting additional nursing and assistance manpower in emergency and operation rooms, providing for administration manning at the consecutive-holidays level, and resetting radiation and examination manpower at the consecutive-holidays level should be considered in managing effectively and emergency medical center.