• 한국정밀공학회지
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• 제29권3호
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• pp.307-312
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• 2012

This study aims to investigate the effect of the post weld treatments on the fatigue life of T-type welded structure made by a SM50A steel material, generally used for excavators, because changes in the geometry, material and surface properties of welded regions affect the fatigue life of welded structures. T-type test specimens were prepared by the CO2 welding of rolled steel plates (SM50A steel) with a thickness of 10 mm at a welding speed of 30 cm/min and these Ttype welded specimens were further treated by UIT (Ultrasonic Impact Treatment) and/or toegrinding post welding treatment methods. In order to investigate improvements on the fatigue life of the samples. 3-point bending fatigue tests were conducted with a stress ratio of R=0.1 under a cyclic loading environment at a frequency of 5 Hz, via a hydraulic fatigue testing machine (${\pm}100\;kN$, MTS 809). The tests were performed at room temperature. The fatigue life of UIT specimens was approximately 25 times longer than that of as-welded specimens at a stress amplitude of 281 MPa, while toe-grinding specimens exhibited 4.15 times longer fatigue life. The current results could provide important guidelines to determine the proper post weld treatment methodologies of T-type welded parts for excavators with a satisfactory fatigue life although under severe operating conditions.

• Journal of Radiation Protection and Research
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• 제27권2호
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• pp.95-100
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• 2002

원자력발전소에서 주로 발생되는 금속폐기물인 탄소강을 중성염전해질인 1.7M의 황산나트륨($Na_2SO_4$)과 질산나트륨($NaNO_3$)을 이용하여 기존전해제염과 개선된 전해제염공정의 비교실험을 수행하였다. 양극은 인코넬, 음극은 티타늄으로 하여 상온에서 1시간동안 반응시켜 금속폐기물 모재의 weight loss, 두께변화. 전해질 내 침전물농도, SEM을 이용하여 제염전후의 금속폐기물 표면의 형상을 분석하였다. 실험결과 개선된 전해제염 적용시 전해질 종류별 전류밀도 변화에 따른 실험에서는 전류밀도가 $0.1{\sim}0.6A/cm^2$으로 증가함에 따라 1.7M의 황산나트륨 적용시 금속폐기물 모재의 두께변화는 $0.48{\pm}0.005{\sim}67.7{\pm}0.02{\mu}m$, 1.7M의 질산나트륨 적용시에는 $0.06{\pm}0.005{\sim}17.7{\pm}0.05{\mu}m$로 나타나 같은 전류밀도에서 황산나트륨 적용시 금속폐기물 모재의 표면 제염효율이 더욱 높은 양상을 보였다. 또한 전류밀도 $0.3A/cm^2$ 및 1.7M의 황산나트륨의 조건에서 개선된 전해제염 적용 시 $9.8{\pm}0.01{\mu}m$의 금속폐기물 두께변화를 보여 기존전해제염 적용시인 $3.7{\pm}0.03{\mu}m$의 금속폐기물 두께변화보다 2배 이상의 표면 제염효과를 보였다.

• 대한기계학회논문집
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• 제18권3호
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• pp.600-611
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• 1994

The purpose of this research is to propose a model for the prediction of residual strength. For this purpose, two-paremeter model based on Caprino's is developed and formulated by the ratio of indentation due to impact and normalized residual strength. The damage zone is considered only as an indentation. Impact tests are carried out on laminated composites by steel balls. Test material is carbon/epoxy laminate. The specimens are composed of $[{\pm}45^{\circ}/0^{\circ}/90^{\circ}]_2$ and $[\pm}45^{\circ}]_4$ stacking sequence and have $0.75^T{\times}0.26^W{\times}100^L(mm) dimension. A proposed model shows a good correlation with the experimental results And failure mechanism due to high impact velocity is discussed on CFRP laminates to examine the initiation and development of damage by fractography and ultrasonic image ststem. The effect of the unidirectional ply position on the residual strength is considered here.

• Journal of Chest Surgery
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• 제34권2호
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• pp.167-172
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• 2001

배경: 누두흉은 앞가슴 기형 중 가장 흔하며 Meyer 등이 1911년 수술적 교정을 시행한 이래로 많은 술식들이 개발되어 왔다. 이들의 대부분은 전흉벽에 상처를 내고 늑연골을 자르는 과정이 필요하였다. 그러나 Nuss 등에 의해서 상기 과정없이 작은 옆가슴의 상처와 stainless steel bar로 흉골의 기형을 교정하는 국소침습적 방법이 개발되었다. 대상 및 방법: 1999년 11월부터 2000년 7월까지 누두흉의 교정을 원하는 환자 14예를 대상으로 하였다. 수술은 15세미만에서는 pectus bar를 1개를 사용하였고 그 이상에서는 2개를 사용하여 교정하였다. 결과: 남자는 11예, 여자는 3예 였으며 나이는 2세에서 52세 사이였다. 누두흉 지표는 5.3$\pm$1.84였고 비대칭지표는 1.06$\pm$0.03이였다. 수술 후 2일째 모두 일반병실로 올라갔다. 평균 재원기간은 4.2일이였다. 술후 합병증으로 성인에서 기흉 1예, 혈흉 1예, 그리고 나중에 발생한 흉막액 1예가 있었다. 결론: 누두흉에서 Nuss 술식으로 좋은 결과를 얻었다. 성인에서도 bar 2개를 이용하여 교정이 가능하였으나 소아에 비하여 합병증이 많이 발생하였는데 이는 성인에서 근육이 발달되어 있고, 뼈의 골화가 다 진행되었기 때문이다.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 1994년도 춘계학술대회강연 및 발표대회 강연및 발표논문 초록집
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• pp.7-7
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• 1994

For more than a decade components of low alloy iron powder with nickel and/or molybdenum for general engineering applications have been manufactured from powder metal. In the time to come such PM steel components will gain increasing significance. Because of various manufacturing difficulties they are mostly produced in two separate steps - sintering and hardening - which means high energy and labour requirements. The paper describes how such PM components are produced in just one run through a conveyor belt furnace with automatic atmosphere control and gas quenching zone. Energy and labour costs are low and reproducible quality is exceilent. The mechanical properties obtained with some powder alloys are presented as well.

• 설비공학논문집
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• 제13권6호
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• pp.462-473
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• 2001

Due to the coupling between momentum and energy transport theoretical analysis of the loop performance is very complicate, therefore it is necessary that these problems be solved by experimental investigation before applying th loop thermosyphon to heat exchanger design. The evaporator and condenser of the loop thermosyphon were made of carbon-steel, and distilled water was used as working fluid in the experiments. From the experimental data correlations of heat transfer coefficient for evaporator and condenser sections were obtained. For heat fluxes in th range of 13~78kW/$m^2$, the correlation equations of heat transfer coefficients in evaporator and condenser predict the experimental behavior to within $\p$\pm$5% and\;\pm20$% respectively.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2003년도 추계학술대회 논문집
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• pp.237-239
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• 2003

A high-temperature superconductor (HTS) journal bearing was studied for loss. Two HTS bearings support the rotor at top and bottom. The rotor weight is 4 kg and the length is about 300 mm. Both the top and bottom bearings have two permanent magnet (PM) rings with an iron pole piece separating them. Each HTS journal bearing is composed of six pieces of superconductor blocks of size 35$\times$25$\times$10 mm. The HTS blocks are encased in a cryochamber through which liquid nitrogen flows. The inner spool of the cryochamber is made from G-10 to reduce eddy current loss, and the rest of the cryochamber is stainless steel. The magnetic field from the PM rings ＜ 10 mT on the stainless part. The rotational drag was measured over the same speed range. Results indicate that the 10 mT design criteria for magnetic field on the stainless part of the cryochamber is too high.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.570-571
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• 2006

The mixed atomized iron powders with 0.3% graphite and 1% Ni powders were cold pressed and sintered at $1200^{\circ}C$ for 30 min under pure Ar gas atmosphere. Some of the sintered specimens were intercritically annealed at $760^{\circ}C$ and quenched in water (single quenching). The other sintered specimens were first fully austenized at $890^{\circ}C$ and water quenched. These specimens were then intercritically annealed at $760^{\circ}C$ and re-quenched in water. The experimental results showed that the wear coefficient effectively decreased in the double quenched specimen.

• 한국환경보건학회지
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• 제25권3호
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• pp.108-112
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• 1999

A study was conducted for the effects of input energy on fume formation ratios based on electrode(FFR$_{electrode}(g/kg_{electrode})),\;deposited\;metal(FFR_{weld}(g/kg_{weld}))\;and\;slag(FFR_{slag}(g/kg_{slag}))\;at\;CO_2$ flux cored arc welding on stainless steel. Experiments were run in well designed welding fume box. Six types of flux cored wires were used and three levels of current and voltages were given. The measured values of $FFR_{electrode},\;FFR_{weld},\;FFR_{slag}\;are\;7.90{\pm}1.47\;g/kg_{electrode},\;9.18{\pm}1.65\;g/kg_{\electrode},\;71.8{\pm}24.2\;g/kg_{slag}$ respectively. Fume formation ratios are not increased dramatically by input energy because of simultaneous increasing of melted electrodes, deposited metal and slag. The results indicate that the test of fume formation ratios in the research on production of low fume welding wire can be run at the fixed condition of input energy rather than various condition.

• Asian-Australasian Journal of Animal Sciences
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• 제17권6호
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• pp.836-842
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• 2004

An experiment was conducted to study the performance of broilers chicks (2 to 42 d of age) fed diets containing pearl millet (PM, Pennisetum typhoides), foxtail millet (FOM, Setaria italica) or finger millet (FIM, Elusine coracana) totally replacing (w/w) yellow maize (YM) with and with out supplementing non-starch polysaccharide (NSP) hydrolysing enzymes at the rate of 0.5 g/kg diet. Enzyme preparation contained amylase 2,400 units, hemi-cellulase 5,400 units, cellulase 12,000 units, protease 2,400 units and beta-glucanase 106 units/g. Each diet was fed to eight replicates (five female Vencob broilers/replicate) housed in stainless steel battery brooders. The estimated metabolizable energy (ME) contents of YM, PM, FOM and FIM were FM (PM) were about 3,389, 2,736, 3,303 and 2,846 kcal/kg, respectively. Total replacement of YM with FOM did not influence the body weight gain, ready to cook yield, relative weights of giblet, liver, intestine, lymphoid organs (bursa and spleen) and length of intestine, antibody titers and livability at 42 d of age. But the food efficiency decreased significantly in FOM fed broilers compared those fed YM. Further, the fat content in thigh muscle reduced with FOM fed groups compared to those fed YM. The performance of broilers decreased significantly in PM and FIM fed broilers compared to those fed YM. The relative weights of giblet, gizzard and liver increased in FIM fed groups compared to those fed YM as the principal source of energy in broilers. Incorporation of NSP hydrolysing enzymes in commercial broiler diets improved the efficiency of feed utilization during starter phase but not at 42 d of age. The results thus indicate that yellow maize can be replaced in toto on weight basis in commercial broiler diets without affecting the performance. Supplementation of NSP hydrolysing enzymes was beneficial in enhancing feed utilization during the starter phase.