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이동하,송재원,윤태석,Lee, D.H.,Song, J.W.,Yoon, T.S. 한국천문학회 2013 天文學論叢 Vol.28 No.3
An optical grism for education is fabricated and tested. It is composed of a transmission grating as dispersion element and a prism as diffraction angle compensation device. The transmission grating is Edmundoptics #49-584(spatial frequency 600 lines/mm, dimension $50mm{\times}50mm$). The prism is the fused silica type with angles ($41.3^{\circ}$, $-48.7^{\circ}$, $-90^{\circ}$). The grism device is fabricated by bonding the transmission grating and the prism with an optical adhesive. The zig for assembling the grism, telescope and camera is composed of an aluminum tube, an aluminum disk ring and a T-ring camera adaptor. The fabricated optical grism spectrograph is tested in laboratory using Halogen lamp and Neon lamp with DSLR camera. And the grism assembled with reflector telescope is tested in a field using stellar light. The results show good agreements with design parameters. The wavelength coverage range of the grism is 250 nm at the un-deviated wavelength of 506 nm. The wavelength resolution is 0.11 nm/pixel.
반 보존형 운동량 방정식을 이용한 SPACE 코드의 다차원 열수력 모듈 개선
이동하(D.H. Lee),이승욱(S.W. Lee),정재준(J.J. Jeong) 한국전산유체공학회 2018 한국전산유체공학회지 Vol.23 No.1
Most of nuclear thermal-hydraulic system codes, which adopt a two-fluid model for two-phase flow, use a non-conservative form of momentum equations for numerical convenience. However, it was known that the non-conservative form can cause unphysical momentum convection in some two-phase flow conditions, especially when the two-phase flow was strongly heterogeneous. In order to compensate this defect, a semi-conservative form of momentum equation is suggested, which is non-conservative in time but conservative in space. In this paper, the semi-conservative form of the two-fluid momentum equation was implemented into the multi-dimensional module of the SPACE code. Thereafter, the code was assessed by simulating two multi-dimensional two-phase flow experiments. The results showed that the semi-conservative form has better predicting capability than the non-conservative form.
이애영(A Y. Lee),이동하(D H. Lee),이전영(J. Y Lee) 한국정보과학회 1992 한국정보과학회 학술발표논문집 Vol.19 No.2
오랫동안 객체 지향 데이타 베이스 시스템에 대한 연구가 지속되어 왔으나, 멤버함수의 수정이나 스키망의 변동을 실시간에 수행하려는 노력이 거의 없었다. 본 논문에서는 이러한 동적인 기능을 고려한 데이타 모델을 설계하고 이를 기반으로 구현중인 객체관리 시스템을 소개한다. 구현중인 객체 관리기는 컴파일언어인 C++를 이용하면서도 재컴파일없이 스키마 변동이 가능하며 멤버함수나 트리거등을 수정할 수 있다.
Specific Energy and Specific Power Relationship among Energy Devices
Sang C. Lee(이상철),Osung Kwon(권오성),A. K. Sahu,Sam Park,D. H. Lee(이동하) 한국태양에너지학회 2013 한국태양에너지학회 학술대회논문집 Vol.2013 No.4
The main function of energy devices is to generate power and store energy. The typical storage devices are battery and capacitor; generation devices are internal combution engine(ICE), gas turbine, and fuel cell. Every kinds of energy devices can be compared together in the Ragone plot with respect to specific energy and specific power. Moreover, some difficulties to make position of solar cell in the Ragone plot are proposed. In this paper some analogical explanation is given to understand the underlined meaning. The barrel model is introduced to make analogy; the specific volume and area to the specific energy and specific power. The relationship between the curves depicted in the axises of cell voltage with current and specific energy with specific power is tried to be shown in the viewpoint of device operation conditions. Also, the limitation of the Ragone plot is discussed to encompass the existing energy devices to be utilized as the standard benchmarking chart.
황순욱,최경호,박용헌,이상철,권오성,이동하,Hwang, S.W.,Choi, G.H.,Park, Sam.,Ench, R. Michael,Bates, Alex M.,Lee, S.C.,Kwon, O.S.,Lee, D.H. 한국태양에너지학회 2012 한국태양에너지학회 논문집 Vol.32 No.suppl3
Proton Exchange Membrane Fuel Cells (PEMFC) are the most appropriate for energy source of small robot applications. PEMFC has superior in power density and thermodynamic efficiency as compared with the Direct Methaol Fuel Cell (DMFC). Furthermore, PEMFC has lighter weight and smaller size than DMFC which are very important factors as small robot power system. The most significant factor of mobile robots is weight which relates closely with energy consumption and robot operation. This research tried to find optimum specifications in terms of type, number of cell, active area, cooling method, weight, and size. In order to find optimum 500W PEMFC, six options are designed in this paper and studied to reduce total stack weight by applying new materials and design innovations. However, still remaining problems are thermal management, robot space for energy sources, and soon. For a thermal management, design options need to analysis of Computational Fluid Dynamics (CFD) for determining which option has the improved performance and durability.