• 교육녹색환경연구
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• 제4권4호
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• pp.1-18
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• 2004

Research has been carried out to study thermal environment in a classroom under three kinds of air diffusion temperature and six kinds of air diffusion direction for ceiling type air conditioner. The velocity and temperature distributions of air in the room calculated by 3-dimensional numerical method(PHOENICS), This present study was also conducted to calculate the Air Diffusion Performance Index(ADPI) for cooling conditions and Predicted Percentage of Dissatisfied(PPD) for heating conditions. This analysis shows that the optimum angle of ceiling type air conditioner's diffusion is $15{\sim}30^{\circ}$ for cooling mode and about $15{\sim}45^{\circ}$ for heating mode in these calculating conditions. And also analysis has been carried out to evaluate thermal comfort of vertical and horizontal cross section of classroom.

• Journal of Korean Vacuum Science & Technology
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• 제1권1호
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• pp.30-37
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• 1997

Interactions of Cu films with Si substrates separated by thin layers of molybdenum and molybdenum nitride were investigated in the viewpoint of diffusion barrier to copper. the diffusion barrier behavior of the layers was studied as functions of deposition and annealing conditions by cross-sectional transmission electron microscopy and Nomarski microscopy. the layers deposited at $N_2$ gas ratios of 0.4 and 0.5 exhibited good diffusion barrier behaviors up to $700^{\circ}C$, mainly due to the phase transformation of molybdenum to $\gamma$-Mo$_2$N phase. The increase in the N gas ratio in deposition elevates the lower limit of barrier failure temperature. Futhermore, amorphous molybdenum nitride films deposited at 20$0^{\circ}C$ and 30$0^{\circ}C$ did not fail, while the crystalline $\gamma$-Mo$_2$N films deposited at 40$0^{\circ}C$ and 50$0^{\circ}C$ showed signs of interlayer interactions between Cu and Si after annealing at 75$0^{\circ}C$ for 30 minutes. Therefore, the amorphous nature of the molybdenum nitride layer enhanced its ability to reduce Cu diffusion and its stability as a diffusion barrier at elevated temperatures.

• 소성∙가공
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• 제28권1호
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• pp.15-20
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• 2019

The superplastic forming/diffusion bonding process has been developed to fabricate a core frame structure with joint nodes out of tubes, for the development of a titanium high performance bicycle. The hydroforming process has been applied for bulging of a tube in the superplastic condition before, and during the diffusion bonding process. In this experiment, a commercial Ti-3Al-2.5V tube was selected as raw material for the study. The forming experiment has been performed using a servo-hydraulic press with a capacity of 200 ton. Next, nitrogen gas was used to acquire necessary pressure for the bulging and bonding of the tubes to fabricate the joint nodes. The pertinent processing temperature was $870^{\circ}C$ for the superplastic hydroforming/diffusion bonding (SHF/DB) process, using the Ti-3Al-2.5V tube. The bonding quality and the progress of bulging and diffusion bonding have been observed by the investigation of the joining interfaces at the cross section of the joint structure. The control of the nitrogen pressure throughout the SHF/DB process, was an important factor to avoid any significant defects in the joint structure. The whole progress stage of the diffusion bonding could be observed at a joint interface. A core structure with 5 joint nodes to manufacture a titanium bicycle could be obtained in a SHF/DB process.

• 신재생에너지
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• 제3권3호
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• pp.14-19
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• 2007

A flow channel model of a bipolar plate with varying cross-sectional area was newly designed for improving performance and efficiency of a PEM fuel cell stack. As a result, the varying cross-sectional area model showed poor uniformity in velocity distribution, however, maximum velocity in the flow path is about 30% faster than that of the uniform cross-sectional area model. The proposed varying cross-sectional area model is expected to diffuse operating fluids more easily into diffusion layer because it has relatively higher values in pressure distribution compared with other flow channel models. It is expected that the implementation of the varying cross-sectional area model can reduce not only the mass transport loss but also the activation loss in a PEM fuel cell, and open circuit voltage of a fuel cell can thus be increased slightly.

• E2M - 전기 전자와 첨단 소재
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• 제10권4호
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• pp.342-348
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• 1997

In this paper, the behavior of electron swarm parameters and energy distribution function of the discharge under high E/N condition in e$^{-10}$ -CF$_{4}$ gas have been analysed over the E/N range from 1-300(Td) by the MCS and BEq methods using set of electron collision cross section determined by the authors. The swarm parameters and energy distribution function have been calculated for the pulsed Townsend, steady-state Townsend and Time of Flight methods. The results gained that the value of electron swarm parameters such as the electron drift velocity, the electron ionization and attachment coefficients and longitudinal diffusion coefficients in agreement with the experimental and theoretical data for a range of E/N. The electron energy distribution function has been explained and analysed in e$^{-10}$ -CF$_{4}$ at E/N : 5, 10, 100, 200, 300(Td) for a case of the equilibrium region in the mean electron energy and respective set of electron collision cross sections. The validity of the results has been confirmed by TOF and SST methods.

• 전기학회논문지P
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• 제63권4호
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• pp.317-321
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• 2014

This paper describes the information for quantitative simulation of weakly ionized plasma. We must grasp the meaning of the plasma state condition to utilize engineering application and to understand materials of plasma state. Using quantitative simulations of weakly ionized plasma, we can analyze gas characteristic. In this paper, the electron Ionization and diffusion Coefficients in $CH_4$ has been analysed over the E/N range 0.1~300[Td], at the 300[$^{\circ}K$] by the two term approximation Boltzmann equation method and Monte Carlo Simulation. Boltzmann equation method has also been used to predict swarm parameter using the same cross sections as input. The behavior of electron has been calculated to give swarm parameter for the electron energy distribution function has been analysed in $CH_4$ at E/N=10, 100 for a case of the equilibrium region in the mean energy. A set of electron collision cross section has been assembled and used in Monte Carlo simulation to predict values of swarm parameters. The result of Boltzmann equation and Monte Carlo Simulation has been compared with experimental data by Ohmori, Lucas and Carter. The swarm parameter from the swarm study are expected to sever as a critical test of current theories of low energy scattering by atoms and molecules.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 1998년도 추계학술대회논문집:21세기에 대비한 지능형 통합항만관리
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• pp.211-221
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• 1998

A digital image processing technique which is able to get the velocity vector distribution of a surface of the spilled oil in the ocean without contacting the flow itself. This technique is based upon the PIV(Particle Imaging Velocimetry) technique and its system mainly consists of a high sensitive camera, a CCD camera, an image grabber, and a host computer in which an image processing algorithm is adopted for velocity vector acquisition. For the acquisition of the advective velocity vector of floating matters on the ocean, a new multi-frame tracking algorithm is proposed, and for the acquisition of the diffusion velocity vector distribution of the spilt oil onto the water surface, a high sensitive gray-level cross-correlation algorithm is proposed.

• 한국항만학회지
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• 제12권2호
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• pp.291-302
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• 1998

A digital image processing technique which is able to be used for getting the velocity vector distribution of a surface of the spilt oil in the ocean without contacting the flow itself. This technique is based upon the PIV(Particle Imaging Velocimetry) technique and its system mainly consists of a high sensitive camera, a CCD camera, an image grabber, and a host computer in which an image processing algorithm is adopted for velocity vector acquisition. For the acquisition of the advective velocity vector of floating matters on the ocean, a new multi-frame tracking algorithm is proposed, and for the acquisition of the diffusion velocity vector distribution of the spilt oil onto the water surface, a high sensitive gray-level cross-correlation algorithm is proposed.

• 한국통신학회논문지
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• 제32권5C호
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• pp.542-549
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• 2007

편미분 방정식을 도입하여 새로운 영상처리 기술을 개발하려는 연구가 활발히 진행 중이며, 특히 확산 방정식을 풀어 잡음 제거, 영상 복원, 에지 검출 및 영상 분할 등에 응용할 수 있는 이미지 확산 알고리즘에 관심이 높다. 본 논문에서는 기존의 비등방성 확산 방식이 결국은 커널 크기가 작은 적응 필터링 방식과 동일한 효과를 낸다는 것을 보이고, 확산 과정에서 선형 필터의 단점을 보완할 수 있도록 가중 미디언(WM, Weighted Median) 필터를 적용한 새로운 확산 기법을 제안하였다. 제안된 WM 필터가 비등방성 커널을 갖도록 필터계수에 대응하는 가중치들을 이미지의 국부적인 변화량에 따라 적응적으로 가변할 수 있는 기법을 제안하였다. 뿐만 아니라 반복 과정에서의 확산 속도를 증가할 수 있도록 커널의 크기를 증가시키기 위한 방안도 제시하였다. 실제 영상을 사용한 실험을 통하여 제안된 방식이 기존의 방식에 비해 잡음 제거 (특히 임펄스성 잡음) 특성이나 에지 보존 특성이 더 우수하다는 것을 보였다. 또한 기존의 방식에 비해 확장된 크기를 갖는 커널을 이용함으로써 확산 속도를 높일 수 있다는 것을 보였다.

• 한국세라믹학회지
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• 제31권12호
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• pp.1459-1466
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• 1994

A novel technique for determining the oxygen tracer diffusion coefficients in oxides was developed. After the 16O-18O solid-gas exchange reactions between 16O in the oxides and 18O in the ambient gas, Raman spectra of the cross sections of oxide samples were measured in a spatial resolution of 5 ${\mu}{\textrm}{m}$. From thus obtained Raman spectra, depth profiles of 18O concentration in the oxide samples were calculated. The oxygen tracer diffusion coefficients and the surface exchange coefficients were determined under the assumptions that samples are semi-infinite slab and that the surface exchange reactionsare not negligible. The oxygen tracer diffusion coefficient of 2.8 mol% Y2O3-containing tetragonal ZrO2 polycrystals, 8 mol% Y2O3-containing ZrO2 polycrystals, and 10 mol% Y2O3-containing cubic ZrO2 single crystals (along the a axis) are as follows.