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박재용,유진식,황승민,임민규,오영규,김용대,한석영,맹주성 한국공작기계학회 2008 한국공작기계학회 추계학술대회논문집 Vol.2008 No.-
An active micro-mixer, which is composed of an oscillating micro-stirrer in the micro-channel to provide effective mixing was optimized. The effects of molecular diffusion and disturbance by the stirrer were considered with regard to two types of mixer models: the simple straight micro-channel and micro-channel with an oscillating stirrer. Two types of mixer models were studied by analyzing mixing behaviors such as their interaction after the stirrer. The mixing was calculated by Lattice Boltzmann methods using the D2Q9 model. In this study, the time-averaged mixing index formula was used to estimate the mixing performance of time-dependent flow. The mixing indices of the two models were compared. From the results, it was found that the mixer with an oscillating stirrer was much more enhanced' and stabilized. Therefore, an approximate optimization of an active micro-mixer with an oscillating stirrer was performed using Kriging method with OLHD (Optimal Latin Hypercube Design) in order to determine the optimal design variables. The design parameters were established as the frequency, the length and the angle of the stirrer. The optimal values were obtained as 1.5754, 0.803D and ±45°, respectively. It was found that the mixing index of the optimal design increased by 83.36% compared with that of the original design.
목재펠릿과 주택용 목재펠릿보일러의 품질기준에 관한 국내외 비교연구
이승록, 한규성 충북대학교 농업과학기술연구소 2022 農業科學硏究 Vol.38 No.2
Wood pellets, a representative bioenergy source, are actively used world widely. Wood pellets made in the domestic volume were around 0.65 million tons in 2021 and the scale was generally grow- ing up, which implies that South Korea’s wood pellet processing technology has reached a significant level. To guarantee a reasonable supply of wood pellet fuels as carbon-neutral sources, quality standards for related products and combustion equipment standards must be clearly established. In line with this, the authors compared major changes in domestic wood pellet quality standards with ISO standards. South Korea's wood pellet quality standards policy has undergone various changes over a period of a decade and has been improved to an equivalent level to the internationally. In addition, it was confirmed that the ‘Clean Air Conversion Act’ to be discharged for biomass-using facilities such as wood pellets have been gradually strengthened as the times change. Also comparing domestic and foreign quality standards based on small-scale combustion equipment which is using wood pellets as fuel, the authors found that domestic standards need to make improvements to meet the EU's combustor emission gas quality stan- dard level.
임민규,박재용,황승민,오영규,박재용,한석영 한국공작기계학회 2009 한국공작기계학회 춘계학술대회논문집 Vol.2009 No.-
The objective of this work is to integrate reliability analysis into topology optimization problems. The reliability index determines design domain and uncertainty value. The elemental sensitivity numbers are calculated from finite element analysis and then converted to the nodal sensitivity numbers in the design domain. A mesh-independency filter using nodal variables is introduced to determine the addition of elements and eliminate unnecessary structural details below a certain length scale in the design. To further enhance the convergence of the optimization process, the accuracy of elemental sensitivity numbers is improved by its historical information. Application of the RBTO model gives a different topology relative to DTO. It is found that the RBTO model yields more reliable optimal topologies than those produced by DTO.
레이저가공기를 이용한 SAPH400의 절단특성에 관한 연구
조규재,박종남,이승철 朝鮮大學校 機械技術硏究所 2004 機械技術硏究 Vol.7 No.1
본 연구의 목적은 자동차 구조용 열간 압연강(SAPH400)의 몇 가지에 대한 최적의 절단 가공 조건을 구하기 위한 실험이다. 현재 대부분의 절단가공은 기계적인 방법이 활용되고 있으며,절단속도와 정밀도,금형제작,공구수명 등의 문제점이 많아 CO₂레이저 가공기를 이용하여 이를 해결하고자 하였다. 실험은 유입가스의 압력,절단속도 및 출력의 변화를 주었을 경우 절단면의 조도와 폭에 어떤 영향을 주는가를 연구 · 분석하였다. 실험결과 출력,절단속도 및 절단가스압력을 변화시켰을 때 출력은 1500W,절단속도는 1100mm/min. 절단 가스압력은 0.5kgf/㎠마 일 때 가장 양호한 표면 거칠기 값 18.06㎛을 나타냈다. This study aims at making experiments to fine the optimum cutting processing conditions of some sheets in common use of Steel Automobile Press Hot 400(SAPH400). Current mechanical methods for cutting processing of most have several problems in relation to cutting speed, precision, manufacture of metal mold and life of tools, which we tried to solve by using the CO₂ Laser Machining. We studied and analyzed what effects on the roughness and width of a section changes in the pressure of blowing gas, cutting speed and power according to the quality and thickness of the material might exert. The results from this experimental study are summarized as follows, when power, cutting speed and gas pressure were changed, the finest value of surface roughness, 18.06㎛ was attained at power of 1500W, cutting speed of 1100mm/min and gas pressure of 0.5kgf/㎠.
매개변수적으로 엮어진 Logistic 사상의 Basin 구조
신규승 경희대학교 자연과학종합연구원 1997 자연과학논문집 Vol.3 No.-
매개변수적으로 결합된 유기계에 대한 연구의 일환으로 단순히 logistic 사상을 중첩시킨 이차원 사상 방정식에서 끌개(attractor)들과 그 basin에 대하여 살펴보았다. 그 결과 이들의 끌개의 구조가 자기유사구조를 보인다는 점과 아울러 그들의 basin의 구조가 원이나 logistic함수와 관련된 곡선형태를 보이는 등 흥미로운 도형적인 양상이 나타남을 볼 수 있었다.
閔勝圭,玄在慶 慶熙大學校 1991 論文集 Vol.20 No.-
The achromatic 90˚ and 180˚ phase retarder devices are designed that are made of three right-angle prisms cemented together. These devices exploit the upon total internal reflections at the reflecting surfaces of prisms. The light beam is totally internally reflected four times, and input and output beams maintain collinearity. It is seen that neither the usual FK-3 prisms nor the BK-7 prisms yield 90˚ and 180˚ phase retardation. However, if the reflecting surfaces are coated with suitable dielectric thin films, achromatic phase shifts of the magnitude desired can be obtained. MgF_2 and ZnS are used as low and high refractive-index film materials in the computations. The optimum MgF_2 and ZnS layer thicknesses are obtained by minimizing the standard donation. In the case of BK-7 device, if only one surface is coated with an optimal thickness of 15.63 nm ZnS 67.53 nm MgF_2, a standard deviation of 1.66˚ is obtained over the wavelength range 405-707 nm. In the case of FK-3 device, if all four surfaces are coated, it is necessary to use a MgF_2 layer of 54.4 nm for each surface to obtain a minimum in the standard deviation of 0.61˚ over the wavelength range 405-707 nm.