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지표면상을 전파하는 소음의 초과감쇠 산정방법에 관한 연구
오재응,김동규,임동규,Oh, J.E.,Kim, D.G.,Yim, T.K. 한국음향학회 1988 韓國音響學會誌 Vol.7 No.2
본 연구는 소음전파에 대한 옥외실험과 축적 음향모형실험에 의해서 지표면에 의한 초과감쇠 특징을 밝힌 것으로써, 옥외실험에 의한 소음전파감쇠는 음향출력이 큰 소형엔진을 사용하여, 거리감쇠로부터 산출한 실측의 초과감쇠와 Log(D/(Hs+Hr))의 관계를 확인했다. 그 결과 소음전파감쇠는 풍향, 주파수에 따라 다르며 직선회귀 된다는 것을 알 수 있었다. 그리고, 지표면상의 초과감쇠치는 통기저항을 이용해서 Log(D/Hs+Hr))을 파라미터로써 구할 수 있었고, 가장 적당한 통기저항$\sigma$는 실측의 초과감쇠치와 임의의 $\sigma$에 대한 $L=-20Log\mid1+(r_1/r_2)Qexp(ik, \bigtriangleup r)\mid$ 식의 평균자승 오차가 가장 적어질 때 결정된다. 모형의 지표로써 축척 1/40의 모형실험으로, 큰 무향실내에서 거리감쇠의 측정을 한 결과, 실측치와의 대응이 충분하다는 것을 확인했다. This study is to explain the characteristic of excess attenuation on the ground through the outdoors experiment about noise propagation and the reduced model experiment of acoustic. The outdoors experiment on the attenuation of noise propagation was tried with the small engine that had large acoustic output, and then it was conformed that there was relationship between the excess attenuation calculated by measurement from distance attenuation and Log(D/(Hs+Hr)). As a result, it was found that the attenuation of noise propogation depended upon the direction of the wind and frequency and was regressed in a straight line. And the numerical values of excess attenuation on the ground could be calculated by regarding Log(D/(Hs+Hr)) as a parameter with an airing resistance $\sigma$. It was found that when the mean square error between the excess attenuation calculated by measurement and the value calculated by a fomula $L=-20Log\mid1+(r_1/r_2)Qexp(ik, \bigtriangleup r)\mid$ about optional $\sigma$ was least, the optimal decision of u was made. As the characteristic of model is the model experiment on a reduced scale of 1 to 40, It was conformed that it corresponds enough with the measurement value with measuring the distance attenuation in the large anecoic chamber.
고알루미늄 (高) 내열주철에서의 (耐熱鑄鐵) 흑연구상화와 (黑鉛球狀化) 내산화성에 (耐酸化性) 관한 연구
김동규,나형용 ( D . K . Kim,H . Y . La ) 한국주조공학회 1981 한국주조공학회지 Vol.1 No.2
N/A Graphite spheroidization and scaling resistance of cast iron containing 5-10% Al were investigated. It is impossible to obtain spheroidal graphite in cast iron containing Al with 8 % and over, but possible to obtain spheroidal graphite even in cast iron with an Al content of about 10 % by increasing Si contant. In the scaling test carried out under the heating condition of 950℃ in air for total of 50 hours, the scaling resistance of cast iron containing Al with 8 % and over was remarkably superior, and also spheroidal graphite cast iron was superior to flake graphite cast iron. The scale became thinner more compacts and more protective with increasing Al content.
김동규,Kim, D.K. 한국전자통신연구원 2015 전자통신동향분석 Vol.30 No.5
도로함몰 사고 증가를 계기로 지하 구조물의 안전 관리 방법, 특히 비파괴 검사 장비에 대한 관심이 고조되고 있다. 지중투과 레이더 기술은 전자파의 투과, 반사 특성을 이용한 비파괴 검사 기술로써 투과 깊이, 투과 해상도 등 비파괴 검사 성능 측면에서 가장 주목받고 있는 기술이다. 본고에서는 지중투과 레이더 기술의 특징, 국외 제품 동향을 살펴본다.
결정소성 유한요소해석을 통한 IF 강의 미세조직 및 집합조직 예측
김동규(D. K. Kim),김재민(J. M. Kim),박원웅(W. W. Park),임용택(Y. T. Im),이용신(Y. S. Lee) 한국소성가공학회 2013 한국소성가공학회 학술대회 논문집 Vol.2013 No.10
In the present investigation, a three dimensional crystal plasticity finite element method (CPFEM) was used to simulate microstructure and texture evolution of body-centered cubic (BCC) crystalline material during plastic deformation at room temperature. To account for crystallographic slip and rotation, a rate-dependent crystal constitutive law with hardening model was incorporated into an in-house program, CAMPform3D. Microstructural heterogeneity and anisotropy were taken into account by assigning a crystal orientation to each integration point of the element and determining the stiffness matrix of the individual crystal. Based on the experimental observation by electron backscatter diffraction (EBSD) measurement of the as-received IF steel sheet, a representative volume element (RVE) of the initial microstructure was generated by using the Voronoi tessellation scheme. The microstructure and texture evolution during plane strain deformation of IF steel was investigated by comparing numerical results with the experimentally measured microstructure by EBSD in terms of grain morphology and texture.
자율 주행 반송차의 궤적 오차와 마찰력에 대한 매개 변수의 민감도 해석
김동규(D.K.Kim),박기환(K.H.Park),김수현(S.H.Kim),곽윤근(Y.K.Kwak) 한국자동차공학회 1996 한국 자동차공학회논문집 Vol.4 No.2
In order to obtain the principal design data for developing the Autonomous Robot Vehicle (ARV). Sensitivity analysis on the trajectory error and friction force with respect to the dynamic parameters is performed. In the straight motion, the trajectory error has been proved to be much affected by the mass variance of the ARV while the lateral friction force is much affected by the location of the mass center. In the curved motion, the effect of mass and moment of inertia is Considered importantly. In addition, the lateral offset gives more effect than the geometric dimension of the ARV on the trajectory errors and friction force.
김동규(D.K KIM),김영수(Y.S KIM),이규현(K.H LEE),이문용(M.Y LEE) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.4
The roll-forming process is often used to manufacture long, thin-walled products such as a pipe. The final cross-section is a comparatively simple open-channel, a closed tube section or a complex profile with several bends. In recent years, that process is often applied to the bumper rail in the automotive industries. In this study, a optimal roll flower model and proper roll-pass sequences can be suggested by analyzing total effective strain, thickness and longitudinal strain according to the roll-pass with FEM simulation. And also effects of the process parameters on the final shape formed by roll forming defects a evaluated.
다차원 스펙트럼 해석법을 이용한 엔진 소음의 전달특성 규명에 관한 연구
김동규(D. K. Kim),송재은(J. E. Song),백문열(M. Y. Beck),오재응(J. E. Oh) 한국자동차공학회 1996 한국 자동차공학회논문집 Vol.4 No.3
With the advance of the standard of living, the demand on automobile goes beyond the simple transportion equipment, therefore the interior noise reduction has been the important factor forim-procement of the ride quality. Idling noise is a major vehicle characteristic determining occupant comfort. In the present research two approaches for noise source identification based on theory for multi-input system have been investigated. The concept of the frequency response function and the multi-dimensional spectral analysis were used to estimated the spectra of the noise source<br/>
AA1050의 정적 재결정에 대한 셀룰라 오토마타 모델링
김동규(D. K. Kim),이호원(H. W. Lee),정경환(K. H. Jung),임용택(Y. T. Im) 한국소성가공학회 2010 한국소성가공학회 학술대회 논문집 Vol.2010 No.10
In the present investigation, a two dimensional probabilistic cellular automata (CA) model is used to simulate primary recrystallization of cold rolled AA1050. Electron backscatter diffraction measurement data is used as an input for the simulation to consider highly heterogeneous distribution of the stored energy and orientations over the initial microstructure. Nucleation process is assumed to be site-saturated. To contemplate anisotropic property of grain boundary migration, the grain boundary mobilitywas represented as a function of misorientation and the pressure was expressed as a function of dislocation density difference, curvature, and misorientation. The results of CA simulations were then compared with the Johnson-Mehl-Avrami-Kolmogorov (JMAK) theory in order to investigate the effects of nucleation criteria and curvature-driven pressure on the microstructure and the kinetics of primary recrystallization.