울산공단지역의 대기중 휘발성 유기화합물에 대한 위해도 평가

이진홍,남병현,윤미정 한국산업안전학회 1999 한국안전학회지 Vol.14 No.2

This study focused on risk assessment for inhalation of airborne volatile organic compounds (VOCs) in Ulsan industrial complex area. For non-carcinogenic risk, even the highest hazard index of toluene was estimated to be 4.8 × 10^(-2), which was much lower than 1. The total hazard index of VOCs was estimated to be 5.8 × 10^(-2). However, lifetime average cancer risk from the inhalation of airborne VOCs was estimated to be about 1.1 × 10^(-3), which was much higher than a risk standard of 10^(-5). The risk of 4.4 × 10^(-5) came from benzene, the only human carcinogen among VOCs, while that of 1.05 × 10^(-3) from probable human carcinogens including 1,3-butadiene and 1,2-dichloroethane. About 70% and 20% of total VOC cancer risk was due to the inhalation of 1,3-butadiene and 1,2-dichloroethane, respectively. Therefore, proper risk management of these 3 VOCs was required for the protection of health from cancer burden in Ulsan industrial complex area.

최근의 금형 표면기술 현황

김성완,이구현,남기석,권식철,백운승 한국열처리공학회 2000 熱處理工學會誌 Vol.13 No.2

음향방출법에 의한 고강도 구조용 내화강의 열화특성에 관한 연구

강창룡,김현수,남기우,김부안 한국열처리공학회 2000 熱處理工學會誌 Vol.13 No.5

Demand for new nondestructive evaluations is growing to detect tensile crack growth behavior to predict long term performance of materials and structure in aggressive environments, especially when they are in non-visible area. Acoustic emission technique is well suited to these problems and has drawn a keen interests because of its dynamic detection ability, extreme sensitivity and location of growing defects. In this study, we investigated the strength of fire resistance steel for frame structure by tensile test after degradation treatment and analysed acoustic emission signals obtained from tensile test with time frequency analysis methods. In the T and TN specimens(under 600℃-10min) consisting of ferrite and pearlite structure, most of acoustic emission events were produced near yield point, mainly due to the dislocation activities during the deformation. However, B specimen under 600℃-10min had a two peak which was attribute to the presence of martensite phase. The first peak is before yield point and the second after yield point. The sources of second acoustic emission peak were the debonding of martensite-martensite interface and the micro-cracking of brittle martensite phase. In 600℃-30min to 700℃-60min, many signals were observed before yield point and were decreased after yield point.

강자성체 박막(Co-Ni)의 자기-저항효과에 관한 연구(2)

손대락,장충근,유중렬,남선우 한국센서학회 1994 센서학회지 Vol.3 No.1

Grid type 70Ni-30Co thin films on slide glass at 250℃ has been fabricated to develope. From fabricated sensors using above process, we investigated the relation of temperature, resistivity, line width to magnetoresistance and we obtained the following results after observation of coercive force, saturated magnetization, maxium usable sensitivity, duty time, slew rate, white noise, resolution of the sensors. We confirmed that the 600Å thin film at 250℃ formed crystalized magnetic anisotropy spontanernisly and the sensor using the thin film had capability of detecting magnetic field with sensitivity of 230 nT. In these devices, the magnetoresistance change was increased linearly in ±10 Oe range, and the magnetoresistance effect was increased when the ratio between line width and length was increased. When the devices was soldered using indium, the temperature-resistivity coefficient showed 8 X 10^(-3)/deg and increased during the specific properties as magnetic field sensor were weakened. In this studies, the coercive forces of the films were about 5.1 A/cm and saturated magnetizations were 0.64 T, and the delay time in these devises was 5 ㎲ and slew rate showed 0.39 Oe/us and white noise was -120 dB.

소년체전 육상선수들의 주전 종목과 체력간의 관계 연구

남상남 한국운동과학회 2000 운동과학 Vol.9 No.1

소년체전선수들의 주전종목과 체력과 관계 연구. 운동과학. 제 9권 제 1호. (211)-(220), 2000. 본 연구의 목적은 전국 소년 체전 남자 육상 선발선수들의 세부 종목(단거리, 중거리, 장거리, 투척, 도약)별 기초의학, 기초체력, 최대점증운동부하(근력, 근지구력, 순발력, 유연성, 민첩성, 평형성, 유연성, 심폐지구력검사를 실시하여 체력 지표와 종목간의 관계를 찾는 것이다. 피검자는 소년체전 남자육상 선발 선수 50명으로 하였다. 이들은 질병유무를 확인하기 위해 기초의학검사(신장, 체중, 체지방, 비만도, 폐활량, 문진검사)를 실시하였으며 기초체력측정장비(Helmas)에 의하여 체력 요인중 6가지(근력, 근지구력, 순발력, 유연성, 민첩성, 평형성)를 측정하였고, 심폐기능 측정을 위하여 Quinton사의 호흡가스 분석기와 트레드밀을 이용하여 최대점증운동부하 검사를 실시하였다. 결과에 대한 자료처리 IBM PC 팬티엄III에서 SAS 6.12version 프로그램을 이용하여 각 항목별 측정치의 평균(mean), 표준편차(standard deviation)를 산출하였으며 각 선수군 간의 각 항목별 평균치의 검증은 일원변량분석(One-way analysis of variance)을 하였으며, scheffe's의 사후 검정을 실시했다. 전국 소년 체전 참가 선수들의 전공 종목과 체력 지표들간의 관계를 비교 분석한 결과 다음과 같은 사실을 발견하였다. 첫째, 기초의학 검사에서는 체중, 비만도, 안정시 심박수, 폐활량, %폐활량에서 세부종목간에 유의한 차이를 보였다(사후 검정 : 체중-투>단, 투>도, 투>중장, 비만도-투>단, 투>도, 투>중장, 안정시 심박수-중장>도약, 폐활량-투>중장, %폐활량-투>중장). 둘째, 기초체력검사에서는 악력(사후검정 : 투>중장), 제자리높이뛰기(사후 점점 : 단>중장)에서 세부종목간에 유의한 차이를 보였다. 셋째, 운동부하 검사에서는 최대산소 섭취량(사후검정 : 중장>도, 중장>투), 무산소 역치 시점의 산소섭취량(사후검정 : 중장>투, 중장>단, 중장>도), 최대 운동시간(사후검정 : 중장>도, 중장>투)에서 세부종목간에 유의한 차이를 보였다. 넷째, 체력지표와 세부종목과의 관계분석을 적용하여 세부종목별 특성에 맞고 신축성 있는 훈련을 실시해야 하며 세부 종목별 체력지표의 특성이 다른 경향을 보이는 선수는 세부종목을 바꿔주어야 한다. The study of relation on physical fitness and major events in athletics children. Exercise silence, 9(1): 211-220, 2000. The Purpose of this study was to research a suitable physical strength of athletics children. The subjects were 50 players who divided into four groups by 12 of short runner, 18 of middle-long distance runner, 10 of jumping and 10 of throwers For the purpose, measured 10 items in basic medical test, 9 items in basic physical strength test and 7 items in graded exercise test. The results of the study are summarized as follows : First, Body Weight, resting heartrate(RHR), FVC(Forced vital capacity), FEV1(forced expiratory volume for 1 second) perceived expiratory volume showed significant consequence on the basic medical test in each group(Scheffe's : Body Weight - throwers>short runners, throwers>jumpers, throwers>middle-long distance runners, : RHR - middle-long distance runners>jumper, perceived expiratory volume : throwers>middle-long distance runners). Second, Arm contraction, Sargent Jump showed significant consequence on the Physical fitness test in each group(Scheffe's : Arm contraction - throwers>middle-long distance runners, Sargent Jump - short runners > middle-long distance runners). Third, VO₂max, at-VO₂, Exercise Time showed significant consequence on the graded maximal exercise test in each group(Scheffe's : VO₂max - middle-long distance runners>jumpers, middle-long distance runners>throwers, at-VO₂ - middle-long distance runners>throwers, middle-long distance runners>short runners, middle-long distance runners>jumpers, Exercise Time - middle-long distance runners>jumpers, middle-long distance runners>throwers). Fourth, The selection of major event was fixed by the result of relation between physical factors and events. Therefore a coach have to change unsuitable major event.

오스테나이트계 스테인리스강에 대한 질소 고용화 처리 및 그 효과

남태운,허정 한국열처리공학회 2000 熱處理工學會誌 Vol.13 No.5

As a case hardening process for stainless steels, nitriding is more preferred and widely used than carburizing which deterioates corrosion resistance severely. In order to add the nitrogen into the stainless steels, passive film on the surface must be removed effectively before nitriding. Conventional gas nitriding process is performed in the temperature range of 500 to 600℃ with NH₃ gas, which often leads to sensitization of stainless steels. In this study, we tried to activate passive film of austenitic stainless steels by heating at low pressure.(900℃, 5×10^(-2) Torr.) Nitriding was performed at the solution treatment temperature of 1100℃ with nitrogen molecules instead of NH₃gas. An attainable nitrogen content in a case depends on the nitrogen gas pressure at constant nitriding temperature. A case depth is proportional to the square not of solution time, which suggests that inward diffusion of nitrogen follows the Fick's 2nd law. Surface nitrogen atoms are dissolved as interstitial solutes, or precipitated in the form of MN, M₂N nitrides, which increase the case hardeness. Dissolved nitrogen in the case enhances the cavitation resistance of austenitic stainless steels dramatically.

용융 붕사욕 침지법에 의해 금형용 강에 형성된 VC coating 층의 밀착성과 내마모성에 관한 연구

남태운,이병권 한국열처리공학회 2000 熱處理工學會誌 Vol.13 No.2

A study on adhesion and wear resistance of VC(vanadium carbide) coating on die steels, STD11 and STD61, has been carried out. The VC coating on the die steels was made by immersing them in molten borax bath, a kind of TRD(thermo-reactive deposition and diffusion). Adhesion strength and wear resistance were investigated using scratch test, indentation test and plate-disc test(Ogoshi type) respectively. The influence of sliding distance on the amount of wear has been determined and dominant wear mechanisms has been characterized using optical microscopy, scanning electron microscopy and EDS spectroscopy. The critical adhesion strength(L_c) between VC coating layer and substrate(STD11) was increased to 60N(L_c) in the scratch test. In the case of STD61, the strength increased to 24N. The wear resistance of VC coated die steels was excellent because the diffusion layer formed just below the coating layer. The dominant wear mechanism was identified as adhesive wear for VC coating die steels which were worn by combination of cracking and plucking of VC fragments and disc.

고농도 침탄기술 현황

남기석,이기정 한국열처리공학회 2001 熱處理工學會誌 Vol.14 No.2

유한 요소 모형을 이용한 어린이의 머리 충격 부상에 관한 연구

김영은,남대훈,왕규창 한국산업안전학회 1997 한국안전학회지 Vol.12 No.4

The dynamic response of the human brain to direct impact was studied by three-dimensional finite element modeling. The model includes a layered shell closely representing the cranial bones with the interior contents occupied by an incompressible continuum to simulate the brain. Falx and tentorium modeled with 4 node membrane element were also incorporated. The computed pressure-time histories at 4 locations within the brain element compared quite favorably with previously published experimental data from cadaver experiments. Therefore, the purpose of this study was to determine the effects of the impact direction on the dynamic response of the brain in children. A parametric study was subsequently conducted to identify the model response when the age and impact site were varied.

SM45C 강의 열처리변형 제어를 위한 냉각매질의 특성

류성기,남태현,안민주,박중학 한국열처리공학회 2000 熱處理工學會誌 Vol.13 No.5

This study deals with the characteristic of refrigerant for heat-treatment deformation control of SM45C steel. The control of heat-treatment deformation must need the progress of production parts for a landing gear. Most of the deformation is occurred on unequal cooling. The unequal cooling is occurred by a property of quenching refrigeration. When a heated metal is deposited in the refrigeration, the cooling speed is so slow in early period of cooling because of occurring a steam-curtain. After more cooling, the steam-curtain is destroyed. In this progress, the cooling speed is very fast. The object of this study is to control the deformation of heat-treatment for landing gear by improving the conditions of quenching. The cooling curves and cooling rates of water, oil and polymer solution are obtained and illustrated. From the characteristics of the quenching refrigerant, the effects of heat-treatments on thermal deformation and fatigue strength are also investigated.