• 소성∙가공
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• 제1권1호
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• pp.42-51
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• 1992

The ring compression test has been widely employed as an experimental means to determine the friction factor. The calibration curves are obtained by the rigid-plastic finite element analysis for various work-hardening exponent and strain-rate hardening exponent. The effects of work-hardening exponent and strain-rate hardening exponent are thoroughly studied and discussed from the finite element computation. The change of friction factor during height reduction in ring compression is also discussed. Then, the method to estimate the change of friction factor during ring compression is proposed.

• 분석과학
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• 제8권4호
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• pp.411-418
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• 1995

A method for the direct determination of elemental content in each of aerosol particles by inductively coupled plasma atomic emission (ICP-AES) or mass spectrometry (ICP-MS) is described. This method is based upon the introduction of diluted aerosol into an ICP and the measurement of either the flash emission intensities of an atomic spectral line or ion intensities. A pulse-height analyzer is used for the measurement of the distribution of the elemental content. In order to calibrate the measuring system, monodisperse aerosols are used. The potentials of the method are shown by demonstrating the copper emission signals from the aerosols generated at a small electric switch, a study of the relation between the decreasing rate of particle number density and particle size, and measurements of calcium contents in the individual biological cells.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1996년도 추계학술대회 논문집
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• pp.349-352
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• 1996

When the ideality factor of collector current of AIGaAs/GaAs Heterojunction Bipolar Transistors (HBTs) is larger than unity, conventional $I_{CO}$ / $T^2$ versus 1000/T plot used in the determination of the barrier height of base-emitter junction of HBT was deviated from the straight line. We introduced the effective temperature $T_{eff}$ as nT in the Thermionic-emission equation. The modified $I_{CO}$ /TB versus 1000/ $T_{eff}$ plot was on the straight line in the temperature range considered. The activation energy obtained from the modified plot is 1.61 eV. The conduction band discontinuity calculated using this value was 0.305 eV and this value is coincident with the generally accepted value of 0.3 eV. eV.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1994년도 추계학술대회 논문집
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• pp.141-148
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• 1994

In order to improve the productivity of cold forging at low production cost, an integrated system's approach is necessary in handling the material preparation and the optimum process design, considering the forming machines, tooling, and operation including quality control. As the first step toward this approach, an expert system for multi-stage cold forging process design for fasteners with various head geometries is developed using Prolog language on IBM 486 PC. For effective representation of the complex part geometries, the system uses the multiple element input, and the forward inference scheme in determination of the initial billet size and intermediate forging steps. In order to determine intermediate steps, the basic empirical rules for extrusion, heading, and trimming were applied. The required forming loads and global strain distributions at each forging step were calculated and displayed on the PC monitor. The designed process sequence drawing can be obtained by AutoCAD. The developed system will be useful in reducing trial and error of design engineers in determining the diameter and height of the initial cylindrical billet from the final product geometry and the intermediate necessary sequences.

• Journal of Welding and Joining
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• 제18권5호
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• pp.63-69
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• 2000

A genetic algorithm was applied to an arc welding process to determine near optimal settings of welding process parameters which produce good weld quality. This method searches for optimal settings of welding parameters through systematic experiments without a model between input and output variables. It has an advantage of being able to find optimal conditions with a fewer number of experiments than conventional full factorial design. A genetic algorithm was applied to optimization of weld bead geometry. In the optimization problem, the input variables was wire feed rate, welding voltage, and welding speed and the output variables were bead height, bead width, and penetration. The number of level for each input variable is 16, 16, and 8, respectively. Therefore, according to the conventional full factorial design, in order to find the optimal welding conditions, 2048 experiments must be performed. The genetic algorithm, however, found the near optimal welding conditions from less than 40 experiments.

• 대한화학회지
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• 제9권2호
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• pp.96-100
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• 1965

우리나라 硏究用 原子爐 TRIGA Mark Ⅱ에 依한 無擔體의 Fe-59를 製造할 目的으로 分離法과 放射化學的 純度 및 核反應斷面積을 檢討하였다. 分離된 Fe-59를 ${\gamma}$-ray spectrometry와 半減期測定에 依하여 純度를 定한 結果 99.9%以上이었다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2001년도 사면안정 설계 및 시공 특별강연회
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• pp.19-30
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• 2001

This paper represents a case study to determine optimal rock properties and to analyse the safety of slopes excavated in faulted and severly weathered ground. The study site consists of two slopes with a length of 240m and a height of 30m in contact with a tunnel. Significant efforts have been exerted for determining the proper strength parameters such as cohesion and internal friction of rockmass by back analyses as well as laboratory and in-situ tests. Limit equilibrium analyses have also been conducted using these properties.

• 한국정보처리학회논문지
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• 제1권3호
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• pp.409-417
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• 1994

고도행렬로부터 등고선을 추출하는데 있어, 가장 중요한 문제는 하나의 격자에 네개의 통과점이 발생하는 이상 상황(degenerate case)의 해결이다. 본 논문은 이상 상황 검사와 다음점 결정을 동시에 수행하는 방법을 기술한다. 이 방법은 최소 횟수 의 배열 인덱싱을 필요로 한다. 또한 통과점을 모서리점의 높이차에 따라 LOWER/ HIGHER로 표시하고, 이 정보를 이용하여 보다 적은 횟수의 배열 인덱싱을 필요로하는 방법을 제안한다. 그리고 통과점을 표시하고 이들을 추적하기에 적합한 자료구조를 구체적으로 기술한다.

• 약학회지
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• 제22권3호
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• pp.157-162
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• 1978

Total organic carbon(TOC) can be determined by means of combustion and flame ionization detector. The principle of string method is that a sample acidified to pH2 and transferred into combustion tube by string is oxidized with air. Another combustion tube method is that organic compounds are oxidized in the combustion tube charged with CuO and cobalt asbestos after the acidified sample is injected directly by microsyringe. Carbon dioxide evolved was reduced under specially treated nickel catalyst and hydrogen, the methane produced was detected by flame ionization detector. Linear relationship was found between concentration and the peak height by the string method. The peak area in the case of combustion tube method is in the range of 1-200ppm. The coefficient of variation by string method was 2.3% and that by combustion tube method was 1.8%. The lower detectable limit was about 10mol. Advantages of the latter are simplicity, sensitivity and reproducibility. TOC in contineous stream can also be determined automatically by means of the string method.

• Korean Journal of Geomatics
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• 제2권1호
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• pp.31-35
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• 2002

This paper describes an experiment for three-dimensional positioning for a pair of KOMPSAT stereostrips using the ancillary data and a single ground control point. The photogrammetric model for three-dimensional positioning was performed as follows: first, initialization of orbital and attitude parameters derived from ancillary data; second, adjustment of orbital and attitude parameters for the satellite to minimize the ground position error with respect to a GCP using the collinearity condition; third, determination of actual satellite position; and lastly, space intersection. This model was tested for a pair of stereo strips with 0.6 base-to-height ratio and GCPs identified from a 1:5,000 scale digital map. As the result, the satellite position of offset was corrected by only one GCP and the accuracy for the geometric modeling showed 38.89m RMSE.