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趙熙燦 忠州大學校 1982 한국교통대학교 논문집 Vol.15 No.1
As tensile loading (Mode I Defermation) acts on the notched or cracked thin plate (2-Demension), there occurs a local plastic zone in the notch tip or crack tip due to the stress concentration. In this paper, I considered the stress distribution of the tip plane in the plastic zone and the elastic zone. Particularly, I considered the stress distribution how to be effective by the local plasticity in the elastic zone.
Production of Submicron Particles by Centrifugal Mill
조희찬,이훈 한국자원공학회 2007 Geosystem engineering Vol.10 No.4
A centrifugal mill can be advanced by changing the gyration diameter ratio (G/D). The submicron grinding characteristics of four different minerals (limestone, talc, illite and silica) were investigated at various operating conditions by using a centrifugal mill. The result was that the optimum G/D ratio to produce submicron particles was different for each mineral. The size distribution was modified by interpolation and the final median size of the product was 110 nm.
조희찬 忠州大學校 2010 한국교통대학교 논문집 Vol.45 No.-
Recently, studies of intimate environmental energy harvesting have drawn attention with developments of sensor, MEMS, small electric devices and so on. There are a lot of energy harvesting equipments using solar, wind, piezoelectric energy and so on as power generator. In this paper, unimorph piezoelectric cantilever beams due to width variation have been studied in static state. The smaller the ratio of widths get, the larger deflections of free ends, bending stresses in each section and stiffness of each beam grow. The analyzed results show that the triangular cantilever beam as mechanical structure of piezoelectric energy harvester using low frequency vibrations to occur in circumference is effective shape
조희찬 忠州大學校 2011 한국교통대학교 논문집 Vol.46 No.-
Recently, studies of intimate environmental energy harvesting have drawn attention with developments of sensor, MEMS, small electric devices and so on. There are lots of energy harvesting equipments using solar, wind, piezoelectric energy and so on as power generator. In this paper, a bimorph piezoelectric cantilever beam with a proof mass added on the free end has been studied in dynamic characteristics due to base excitation to occur from a circumference vibration with low frequency. The frequency equation of the beam be closely related to the ratio of beam and proof mass. Therefore, it is possible to estimate a proof mass due to the frequency of base excitation and a beam mass. The output voltages can be induced from theoretical calculation and it is dependent upon the beam length and thickness. The shorter beam length, the larger thickness, the output voltages increase
자원활용분야 게재논문을 통해 살펴본 시대적 연구경향 고찰
조희찬 한국자원공학회 2012 한국자원공학회지 Vol.49 No.5
This paper presents an analysis of historical patterns and R&D trends in mineral processing in Korea for the last 50 years. The analysis is based on the papers published in the Journal of the Korean Society for Geosystem Engineering for the time period 1960 through 2012. It shows that the number of papers related to mineral processing has steadily increased at an annual rate of 46% for the last 40 years. Separation/concentration was the most frequent topics in 1960’s, but in recent years, the topics has since diversified into other area and are fairly evenly divided between five different areas: separation/concentration, metallurgical processing, material processing, and recycling. 본고에서는 학회지에 수록된 자원 활용 분야의 논문에 대하여 시대별로 주요 관심 분야를 분석함으로써 학회의 시대적 변천사를 간접적으로 살펴보았다. 자원활용분야 논문 수는 1960년 이후 연 평균 46%의 증가율을 보였다. 1960년대는 분리/선별에 관한 논문이 가장 많았으나 후 점차 다양화 하여 최근에는 분리/선별, 제련, 소재, 리싸이클링 분야에 골고루 분포하고 있다.
조희찬,김희송 대한기계학회 1992 대한기계학회논문집 Vol.16 No.4
본 연구에서는 Kelvin의 기본해와 초기응력 증분에 의해 정식화된 경계적분방 정식을 이용하여 점차적으로 외력을 증가시켰을 때, 선형등방경화재에 국부적으로 생 기는 항복영역과 항복하중, 탄소성 응력해석등을 재료비선형문제로 해석하였다. 이 때 초기응력 증분을 결정함에 있어서 종래에는 등가 소성변형률을 수렴판정으로 해석 하였지만, 이는 구분적인 선형 경화재와 온도 의존성 문제에는 적당하지 않으므로 암 기용일등은 등가응력과 응력-변형률 선도를 이용하여 수렴판정을 하였다. 그러나 이 방법은 소성역에서의 기울기가 변화하는 곳에서는 피할 수 없는 오차가 존재한다. 따라서 여기에서는 계산된 초기응력 증분에 의한 초기 탄성변형률에너지 증분과 응력 -변형률선도로 부터 구해지는 초기 탄성변형률에너지 증분을 이용한 수렴판정으로 초 기응력증분을 결정하였다. 또한, 내부영역적분을 일부 해석적인 적분과 수치적분을 병행한 경우와 전부 수치적분방법으로 내압을 받는 실린더와 단순 인장하중이 작용하 는 양편 Ⅴ형 노치를 갖는 박판의 경우에 적용하여 해석하였으며, 그 결과를 유한요소 법 프로그램인 NISA(numerically integrated elements for system analysis)로 구한 결과치와 비교, 고찰하였다. This study is concerned with an application of the Boundary Element Method to 2-dimensional elastoplastic stress analysis on the material nonlinearities. The boundary integral formulation adopted an initial stress equation in the inelastic term. In order to determine the initial stress increment, the increment of initial elastic strain energy due to elastic increment in stressstrain curve was used as the convergence criterion during iterative process. For the validity of this procedure, the results of B.E.M. with constant elements and NISA with linear elements where compared on the thin plate with 2 edge v-notches under static tension and the thick cylinder under internal pressure. And this paper compared the results of using unmedical integral with the results of using semi-analytical integral on the plastic domain integral.
경계요소법을 이용한 방음벽의 형상에 따른 음향방사특성해석
趙熙燦 忠州大學校 1997 한국교통대학교 논문집 Vol.32 No.1
The boundary element method is widely used for acoustic problems. This paper also is concerned with an application of the B.E.M. for the analysis of sound radiation characteristics of different shapes of soundproofing wall. The relations between various shapes of soundproofing wall and sound fields have been studied. And soundproof effect at geometrical viewpoint on the assumption of no diffraction have been considered. Generally, this study presents that the soundproof area of end-slanted walls becomes wide in the case of near field and that soundproof area of end-straight walls becomes wide in the case of far field. Based on these results, I suggest a more decisive design data of shape of soundproofing wall for effective soundproofing due to various sound fields.
정전용량형 압력센서에서 센터 보스를 갖는 원형 다이어프램의 특성해석
조희찬 忠州大學校 2012 한국교통대학교 논문집 Vol.47 No.-
It is an effective to improve a structure and shape of a diaphragm as a sensing part for enhancing sensitivity and performance of a capacitive pressure sensor. Therefore, the characteristics of the circular diaphragm with a center boss in a capacitive pressure sensor have been studied for getting high performance in a low pressure in this paper. When the boss has a large radius in circular diaphragm, the capacitive pressure sensor has the higher sensitivity than that of the circular diaphragm which doesn’t have a boss structure in this research. But It is thought that the endurance of the diaphragm reduce for the reason of an excess shearing force to act on the diaphragm in the case of that the center boss radius is a more than about 36% of diaphragm radius.
경계요소법을 이용한 균열 성장 방향의 예측에 관한 연구
趙熙燦 忠州大學校 1998 한국교통대학교 논문집 Vol.33 No.1
Realistic engineering problem in fracture mechanics requires the study of crack behavior under a variety of loading condition. The problems are sufficiently complex that, even for 2 dimensinal cases, numerical techniques must be used. B.E.M. is particularly successful in the case of crack problems because they involve very simple boundary modelling and provide fast computation of solution. The stress in tensity factors and J-integral values have been widly used in numerical studies of crack growth. Therefore, in this paper, I analyze the stress intensity factor, J-integral value and prediction of crack growth direction of single edge cracked plates using BEASY as a program of boundary element method. And I will assist in effecting machinery and structures of design and safty estimate from these results.
趙熙燦 충주대학교 1994 한국교통대학교 논문집 Vol.29 No.1
Two-dimensional impulsive stresses are analyzed by the boundary element method with time-stepping numerical scheme(scheme 2) using the time-dependent fundamental solution. In order to calculate internal stresses, this is accomplished numerically using triangular cells in domain. The dynamic stress concentration factors of the circle hole and the ellipic notches in a strip are obtained from the ratio of normal stress that calculated from numerical integration to maximum stress at the same time. The validity of the procedure is confirmed by the numerical results, and it is shown that the dynamic stress concentrations are approximately ten percent larger than the static ones.