• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.1326-1331
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• 2009

Drying process in the cylindrical thin film layer of sludge with the thickness less than a few millimeters has been investigated. Thin film drying is specially designed and used to dry the viscous materials like sewage sludge. The thin film layer of sludge is dried on the metallic cylindrical surface through which thermal energy is supplied to the layer during drying. The wall temperature is assumed to be constant during drying in the present study for the simplification. In order to solve the equations, the mass transfer rate on the drying surface should be determined. The mass flux of evaporated water vapor on the surface is estimated with the formulation given in the literature. The effect of some physical parameters on drying has been examined to figure out the drying characteristics of the sludge layer.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2014년도 추계학술대회 논문집
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• pp.215-215
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• 2014

Composites layer of Al-Cr-Ni-O system was prepared on a steel plate by hydro-thermal process at $700^{\circ}C$ for 12 hours, which phase identification and thermal conductivity were determined. The composites layer consisted of aluminum nitride, alumina, chromium carbide and aluminium, which density was $3.7kg/m^3$. The thermal conductivity of the coating layer determined by thermal data acquisition system was about 98.0 W/m/ which depended on the AlN content. Numerical modelling of the heat transfer behavior of the coating layer was well agreement with the empirical data.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 하계학술발표대회 논문집
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• pp.1128-1133
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• 2008

Drying process in the thin film layer of sludge with the thickness less than a few millimeters has been investigated using the simple one-dimensional model. Thin film drying is usually used to dry the viscous materials like sewage sludge. The thin film layer of sludge is dried on the metallic surface through which thermal energy is supplied to the layer during drying. In order to solve the equations, the mass transfer rate on the drying surface should be determined. The mass flux of evaporated water vapor on the surface is estimated with the formulation given in the literature. The effect of heating temperature, film thickness, and air velocity on drying has been examined to figure out the drying characteristics of the sludge layer.

• 설비공학논문집
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• 제13권12호
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• pp.1282-1287
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• 2001

This study presents the numerical analysis of natural convection of a micro- environments with air permeability in the clothing air-layer. As a numerical model the clothing air layer of shoulder and arm were adopted. Finite volume method for two-dimensional laminar flow was used for the analysis of flow and thermal characteristics of velocity, temperature and concentration in the air layer between body and clothing. As temperature boundary conditions, a body skin has a high temperature with $34^{\circ}C$ and the environmental temperatures are 5, 15 and $25^{\circ}C$ for various permeability coefficients. The distributions of concentration, temperature and velocity are shown that two large cells form at horizontal and vertical air layer, respectively. As the temperature difference between body skin and environment decreases, the heat transfer is decreased rapidly.

• 한국산학기술학회논문지
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• 제16권3호
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• pp.1605-1610
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• 2015

본 논문은 냉장고의 열손실의 약 30%를 차지하고 있는 가스켓 주위의 열전달 해석시 복사열전달을 고려하지 않은 경우와 고려한 경우가 많은 차이가 있어서 가스켓 주위의 열전달 해석시 복사열전달 고려 여부에 따른 열손실 효과를 살펴보는 연구이다. 이를 위해 가스켓 주위를 단순화한 형상으로 모델링하여 열전달 전산해석을 수행하였다. 본 연구를 통해서 가스켓 내부의 공기층을 단순히 전도열전달만 고려한 경우 열손실이 $25.6W/m^2$이고 복사열전달을 함께 고려한 경우 $55.0W/m^2$로 약 2.2배 크게 나타남을 알 수 있었다. 가스켓 내부에 복사열전달 차단판을 0에서 7개로 변화하면서 복사열전달 저감 효과를 살펴본 결과 차단판 개수가 증가하여 7개 인 경우는 설치하지 않은 경우에 비하여 열손실이 $55.0W/m^2$에서 $36.7W/m^2$로 33% 감소함을 알 수 있었다. 또한 같은 개수의 복사 차단판일 경우는 냉장고 내부와 외부에 치우치는 쪽으로 설치하는 것이 가스켓의 가운데에 설치하는 것 보다 효과적임을 알 수 있었다.

• 한국재료학회지
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• 제30권3호
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• pp.142-148
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• 2020

Graphene has attracted the interest of many researchers due to various its advantages such as high mobility, high transparency, and strong mechanical strength. However, large-area graphene is grown at high temperatures of about 1,000 ℃ and must be transferred to various substrates for various applications. As a result, transferred graphene shows many defects such as wrinkles/ripples and cracks that happen during the transfer process. In this study, we address transfer-free, large-scale, and high-quality monolayer graphene. Monolayer graphene was grown at low temperatures on Ti (10nm)-buffered Si (001) and PET substrates via plasma-assisted thermal chemical vapor deposition (PATCVD). The graphene area is small at low mTorr range of operating pressure, while 4 × 4 ㎠ scale graphene is grown at high working pressures from 1.5 to 1.8 Torr. Four-inch wafer scale graphene growth is achieved at growth conditions of 1.8 Torr working pressure and 150 ℃ growth temperature. The monolayer graphene that is grown directly on the Ti-buffer layer reveals a transparency of 97.4 % at a wavelength of 550 nm, a carrier mobility of about 7,000 ㎠/V×s, and a sheet resistance of 98 W/□. Transfer-free, large-scale, high-quality monolayer graphene can be applied to flexible and stretchable electronic devices.

• 에너지공학
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• 제24권1호
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• pp.78-87
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• 2015

중대사고시 금속용융물층의 열속 집중 현상(Focusig effect)에 대해 상부와 측면벽의 냉각 조건과 높이를 변화시키면서 실험과 수치해석을 수행하였다. 상사성(Analogy) 원리를 이용해 열전달 실험 대신 물질전달 실험을 수행하였으며 황산-황산구리 수용액의 전기도금계를 물질전달계로 채택하였다. $Ra_H$ 수 $8.49{\times}10^7{\sim}5.43{\times}10^9$ 범위에서 상부와 측면벽의 냉각 조건을 세 가지로, 높이를 네 가지로 변화시키면서 열전달을 측정하였다. 상부만 냉각인 경우의 실험결과를 동일한 조건인 Rayleigh-Benard 자연대류 상관식과 비교한 바 Dropkin과 Somerscales, Globe와 Dropkin의 상관식과 매우 일치하였다. 측면벽만 냉각인 경우, 상부와 측면벽 모두 냉각인 경우, 상부만 냉각인 경우 순으로 열전달이 감소하였고, 냉각 조건을 고정한 상태에서 높이를 감소시킬수록 측면 열전달이 향상되었다.

• 대한전자공학회논문지SD
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• 제41권2호
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• pp.39-45
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• 2004

본 논문에서는 직렬 ATA 물리층에 대한 설계 및 칩 제작 후 테스트 결과와 성능 평가를 서술하였다. 직렬 ATA 의 물리층은 +/-250㎷ 의 전압 레벨과 1.5㎓ 속도를 지니는 차등 NRZ 직렬 데이터 스트림을 송신 및 수신하는 회로와 1.5㎓ 송신 PLL 회로, 수신된 1.5Gbps 직렬 데이터 스트림에서 데이터 및 송신 클럭을 복원하는 회로와 SERDES 회로 및 OOB 신호 발생 및 검파 회로 등으로 구성하였다. 설계된 직렬 ATA 물리층은 UMC 사의 0.18㎛ 표준 CMOS 공정을 이용하여 칩으로 제작 후 성능을 검증하였다. 특성 검토 결과 대부분 사양을 만족하였고, 데이터 전송 속도 1.5Gbps 사양은 실지 측정치가 1.38Gbps 로 목표 사양에 8％ 미달되었다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제14권1호
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• pp.1-19
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• 2020

In an underlay cognitive simultaneous wireless information and power transfer (SWIPT) network, communication from secondary user (SU) to secondary destination (SD) is accomplished with decode-and-forward (DF) relays. Multiple energy-constrained relays are assumed to harvest energy from SU via power splitting (PS) protocol and complete SU secure information transmission with beamforming. Hence, physical layer security (PLS) is investigated in cognitive SWIPT network. In order to interfere with eavesdropper and improve relay's energy efficiency, a destination-assisted jamming scheme is proposed. Namely, SD transmits artificial noise (AN) to interfere with eavesdropping, while jamming signal can also provide harvested energy to relays. Beamforming vector and power splitting ratio are jointly optimized with the objective of SU secrecy capacity maximization. We solve this non-convex optimization problem via a general two-stage procedure. Firstly, we obtain the optimal beamforming vector through semi-definite relaxation (SDR) method with a fixed power splitting ratio. Secondly, the best power splitting ratio can be obtained by one-dimensional search. We provide simulation results to verify the proposed solution. Simulation results show that the scheme achieves the maximum SD secrecy rate with appropriate selection of power splitting ratio, and the proposed scheme guarantees security in cognitive SWIPT networks.

• 한국수정란이식학회지
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• 제14권1호
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• pp.59-67
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• 1999

To make up the medium for quantitative selection of capacitated-sperm through sucrose layer, the effects of BSA, caffeine, heparin and progesterone on sperm swim-up migration and movement were examined. And the results obtained were as follows; 1. BSA of 4mg/ml in bMSS stimulated sperm migration and movement, and attracted capacitated-sperm. 2. Caffeine of 5mM in bMSS containing 4mg/ml BSA stimulated sperm movement and attracted capacitated-sperm. 3. Heparin of 20$\mu\textrm{g}$/ml in bMAA containing both 4mg/ml BSA and 5mM caffeine stimulated movement and capacitation of sperm. 4. Progesterone of 50$\mu\textrm{g}$/ml in bMSS containing all 4mg/ml BSA, 5mM caffeine and 20$\mu\textrm{g}$/ml heparin (BCHP-MSS) attracted capacitated-sperm. 5. Effect of BCHP-MSS on sperm on sperm attraction was not different from effect of 10% follicular fluid solution (FF-MSS) on sperm swim-up separation. In conclusion, bMSS with 4mg/ml BSA, 5mM caffeine, 20$\mu\textrm{g}$/ml heparin and 50$\mu\textrm{g}$/ml progesterone(BCHP-MSS) was a optimal condition for selection of capacitated-sperm through sucrose layer.