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이동훈,목연수,장성록,권혁무,윤원영,옥영석,최용석,배동철 한국산업안전학회 1999 한국안전학회지 Vol.14 No.3
The purpose of this study is to analyze death injuries and operation troubles of urban transit. No difference was shown in death rates between Line 1 of Pusan urban transit and Line 5, 7, and 8 of Seoul metropolitan transit. And relief time by another train did not depend upon the number of crews. We concluded that thorough inspection and preventive maintenance of trains and facilities are necessary for safe and timely service of urban transit.
박경규,박형근,김연수,이문성,김진오,조영덕,이영홍,봉형근,조주영,이준성,심찬섭,황성규,함정식,장재영,권귀향 대한내과학회 1997 대한내과학회지 Vol.53 No.2
Duodenal obstruction is the third leading cause of intrinsic obstruction of the alimentary tract in the newborn, the other causes are imperforate anus and esophageal atresia. If the obstruction is incomplete, as with a fenestrated duodenal membrane, the presentation of the symptoms may be delayed and the diagnosis overlooked. And so they are rarely diagnosed in the adult. Diagnosis can be made by contrast duodenography but is more definitive with endoscopy. This is the first case report of a 21-year-old female with duodenal membrane, associated with incomplete rotation of intestine and uterus bicornis, diagnosed by hypotonic duodenography and endoscopy, preoperatively, and successfully treated with duodenoduodenostomy.
문인기,고흥석,장준연,최성규 대한금속재료학회(대한금속학회) 1999 대한금속·재료학회지 Vol.37 No.12
The study is an attempt to understand the basic characteristics of ECAP(Equal Channel Angular Pressing) which gives large shear deformation without any change in the dimension of material. Microstructure comparison was performed between pure Al and Al-7 wt% Si alloys after the ECAP. Emphasis was put on the microstructural change of Al-Si alloys consisting of two phase (primary Al + eutectic Si) where eutectic Si appears different shape and size depending on the modification. The pressing leads to the development of subgrain bands of Al and the fracture of unmodified eutectic Si. The eutectic Si may form dislocation tangles by acting as an obstacle to movement of dislocation, which can be proved with the location of eutectic Si on recrystallized grain boundary. It is obvious that ECAP results in a fine grain structure in Al-Si alloy without decohesion between Al matrix and eutectic Si.
문인기,고흥석,장준연,최성규 대한금속재료학회(대한금속학회) 1999 대한금속·재료학회지 Vol.37 No.4
The study focuses on the basic deformation mechanism of ECAP (Equal Channel Angular Pressing) which gives a large shear deformation without change in the reduction of area. A model deformation in which a plasticine is pressed through a transparent die shows a typical shear deformation in detail. ECAP was performed on a commercial pure aluminum and an Al-7%Si alloy in order to investigate the change in the microstructure after ECAP. Friction force between specimen and die acts to prevent uniform shear deformation of a specimen. ECAP significantly reduces grain size of both aluminum alloys below the order of micronmeter by giving a large shear deformation, which provides a new method for grain refinement. A drastic increase in the yield strength combined with a small increase in the strain hardening is observed in both ECA pressed aluminum alloys. The ECAP is believed to be very effective in the grain refinement.
Zn-0.3wt.% Al 합금의 초소성 변형에 따른 미세조직의 변화
이원절,박찬경,하태권,손중락,장영원 대한금속재료학회(대한금속학회) 1998 대한금속·재료학회지 Vol.36 No.9
The superplastic deformation of Zn-0.3wt.%Al alloys were investigated at room temperature under various strain rate. These alloys were highly elongated up to 1400% at the initial strain rate of 2×10^(-4)/s, revealing the rate sensitivity parameter of about 0.4. In order to investigate the microstructural change during superplastic deformation, the transmission electron microscopy(TEM) studies were performed on the specimen elongated up to the 100% tensile strain at various strain rate. The microstructure was composed of zinc rich matrix phase, with 1㎛ in grain size, and Al rich second phases precipitated generally at grain boundaries and/or triple point. In region III(5×10^(-2)/s), the high density of dislocations were observed within the grains and deformation twins were also formed within the grains. In region II(2^*10^(-4)/s), however, the dislocations were highly localized along the grain boundaries and deformation twins were not observed. Observation of severe deformation along the grain boundaries and grain boundary migration(GBM) suggest that grain boundary sliding(GBS) is a dominant mechanism of superplastic deformation in this alloy.
이동훈,목연수,장성록,고성석 한국산업안전학회 1999 한국안전학회지 Vol.14 No.1
Due to the work characteristics of shipyard industry, subcontractors are essential and employees of them consist of 25% of the total employee. Problems of their safety management are as follows; - obscurity of safety management responsibility - flimsiness of subcontractor's safety awareness - absence of ability to develop safety techniques and to provide safety equipments - lack of opportunity of safety education The purpose of this study is modelling safety management system of shipyard industry subcontractors to reduce industrial accidents by employees of subcontractors. A phased model contained organization and work responsibility of related departments, safety management planning and evaluation system, safe work supporting system, safety education supporting system.
Fe3Al 금속간화합물의 항복강도 이상거동과 변형기구 고찰
박찬경,장영원,전현조 대한금속재료학회(대한금속학회) 2000 대한금속·재료학회지 Vol.38 No.8
It is well known that Fe₃Al intermetallic compound shows an anomalous peak of the yield strength at about 500℃. That is, the yield strengths increase with increasing deformation temperature in the range of 300℃-500$quot;℃, and then decrease at higher temperatures. The dislocation structure was examined by transmission electron microscopy, and high temperature mechanical properties were examined by tensile and load relaxation tests. The flow stress curves obtained from lead relaxation bests were then analyzed in terms of internal variable deformation theory. It was found that the flow curves consisted of three micro-deformation mechanisms i.e inelastic deformation mode, plastic deformation mode and dislocation creep deformation mode, depending on both dislocation structure and deformation temperature. The flow curves could be well described by the constitutive equations of these three micro-deformation mechanisms based on the internal variable deformation theory.
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.