• 한국결정학회지
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• 제8권2호
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• pp.81-88
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• 1997

GaN와 $NH_3$를 source gas로 사용하여 (0001) sapphire 기판에 CVPE(Chloride Vapor Epitaxy)방법으로 GaN 박막을 성장시킨후 그 특성을 조사하였다. 성장온도 $970^{\circ}C$ 부터 $1040^{\circ}C$ 영역에서 source gas의 유량비를 변화하면서 최적증착조건을 구현하였고, GaN증착이전에 $NH_3$ 가스로써 질화전처리를 하였다. 수행된 실험조건범위내에서 최적증착조건은 증착온도 $1040^{\circ}C$에서 질화전 처리 3분으로 III/V source gas의 유량비율이 2일 때 였으며, 이때의 XRD분석에서의 FWHM값은(0001) peak에서 약 0.32deg를 나타내었다. GaN박막성장속도는 이때 약 $1040^{\circ}C$였다.

• 소성∙가공
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• 제3권2호
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• pp.215-228
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• 1994

The purpose of this paper is to pursue a general method to determine both the flow stress of a material and the friction factor by ring compression test. The materials are assumed to obey the expanded n-power hardening rule including the strain-rate effect. Ring compression is simulated by the rigid-plastic finite element method to obtain the database used in determining the flow stress and friction factor. The Simulation is conducted for various strain hardening exponent, strain-rate sensitivity, friction factor, and compressing speed, as variables. It is assumed that the friction factor is constant during the compression process. To evaluate the compatibility of the database, experiments are carried out at room and evaluated temperature using specimens of aluminum 6061-T6 under dry and grease lubrication condition. It is shown that the proposed test method is useful and easy to use in determining the flow stress and the friction factor.

• 약학회지
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• 제39권5호
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• pp.480-486
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• 1995

The change in discharge current of a glow discharge has been shown the potential sensitive detector for gas chromatography. To investigate the effect of carrier gas on the electrical characteristics of the discharge and the peak response, the discharge pressure, gas flow rate, and discharge gap have been studied. The discharge gas included the Ar, He, and N$_{2}$. The gas flow rate has been found one of the important parameters to affect both the electrical characteristics and the peak response.

• 한국환경보건학회지
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• 제35권1호
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• pp.64-70
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• 2009

The aims of this study is to examine the effects of the changes in HRT(Hydraulic Retention Time) and media charge in a water-mill, among other operation factors, on the nitrogen and phosphorus removal in order to use up-flow anaerobic reactors, anoxic reactors and water-mill aerobic reactors for sewage treatment. The extension of HRT improved the nitrogen removal efficiency, however the removal pattern was constant regardless of HRT. The removal of phosphorus was constant (80%-90%) regardless of the change in HRT. The removal rate with change in influx load varied such that at the OLR (Organic Load Rate) of 1-3 kg/d, the T-N removal efficiency was 80.7%-88.9% and the T-P removal efficiency was 82.9%-89.3% while at the NLR (Nitrogen Loading Rate) of 0.108-0.156 kg/d the removal efficiencies were 80.7-88.9% (T-N) and 82.9-89.3% (T-P). The analyses of the nitrogen and phosphorous removal characteristics with the C/N and C/P ratio showed that the mean T-N removal rate was 88% at the C/N ratio of 1.2-2.6, and that the mean T-P removal rate was 86% at the C/P ratio of 7.2-14.1. Also, the analysis of nitrogen and phosphorous removal characteristics were analyzed in relation to media charge. The comparison between with and without media charge in the water-mill showed that while the nitrogen removal efficiencies were 86-94% and 85-89% respectively, the difference of phosphorous removal efficiencies were between the two conditions was not significant, thus it suggested that the media charge has less effect on the removal efficiency of phosphorous compared to that of nitrogen.

• KSBB Journal
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• 제6권2호
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• pp.147-156
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• 1991

Diazotized chitin (CHITN) was synthesized reacting with NaN3 and HCl to alkaline hydrolyzed chitin for the support of immobilized enzyme. Immobilized $\beta$-glucosidase on diazotized chitin(CHITN-Gase) was produced reacting with glutaraldehyds as bifunctional reagent. CHITN-Gase activities were determined reacting with p-nitrophenol-$\beta$-D-glucopyranoside in plug flow reactor as a reference. Optimum temperature, optimum pH, reaction constant and deactivation rate were determined with variation of flow rate and H/D. The particle size of immobilized enzyme in the best was, 35 mesh (CHITN35-Gase). The optimum conditions of immobilized enzyme were $70^{\circ}C$ in temperature and 5.0 in pH. Diameter and flow rate of plug flow reactor in the best was 8.5mm in diameter and 0.8ml/min in flow rate. Reaction constant was mainly influenced by electrostatic force. The best glucose hydrolizing activities of CHITN3 5-Gase was 3.34$\times$10-5 M/1. while that of native-$\beta$-glucosidase was 2.44$\times$10-5 M/1.

• 한국진공학회지
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• 제20권4호
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• pp.266-270
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• 2011

본 연구에서는 W (Tungsten)를 주 구성 물질로 불순물 C (Carbon)과 N (Nitrogen)을 첨가한 W-C-N 확산방지막 시편을 제조하였고, $N_2$가스의 유량을 변화시키면서 확산방지막을 제조하여 각각의 시료에 대하여 $600^{\circ}C$열처리를 하였다. 실험 결과 질소유량의 변화에 따라 시편의 탄소성 구간층의 물성 변화율이 시편의 탄성구간보다 큰 것을 알아냈다. 이는 질소 가스의 유량 변화가 시편의 탄소성 구간에 더욱 직접적으로 연관이 되었다는 것을 알 수 있었다. 각 시료는 16회 연속 압입 실험을 실시하여 Stress-strain curve를 통하여 질소 가스의 유량이 2 sccm인 박막의 분산이 적음을 알아냈고, 연속압입을 통하여 얻어진 상항복점의 표준 편차 역시 질소 가스의 유량이 2 sccm인 박막이 가장 적다는 것을 알 수 있었다. Stress-strain curve 분산과 상항복점의 Stress 값의 표준 편차의 크기로 부터 박막의 안정도를 예상할 수 있었으며, 이 결과로부터 W-C-N 박막은 질소 유량에 따라 박막의 안정도가 변화하는 것을 알았다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 하계학술대회 논문집 Vol.7
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• pp.521-522
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• 2006

In this paper, hybrid air-water discharges were used to develop an optimal condition for providing a high level of water decomposition for hydrogen yield. Electrical and optical phenomena accompanying the discharges were investigated along with feeding gases, flow rates, and point-to-plane electrode gap distance. The primary focus of this experiment was put on the optical emission of the near UV range, with the energy threshold sufficient for water dissociation and excitation. The $OH(A^{2+},'=0\;X^2,"=0$) band's optical emission intensity indicated the presence of plasma chemical reactions involving hydrogen formation. In the gaseous atmosphere saturated with water vapor the OH(A-X) band intensity was relatively high compared to the liquid and transient phases although the optical emission strongly depended on the flow rate and type of feeding gas. In the gaseous phase discharge phenomenon for Ar carrier gas transformed into a gliding arc via the flow rate growth. OH(A-X) band's intensity increased according to the flow rate or residence time of He feeding gas. Reciprocal tendency was acquired for $N_2$ and Ar carrier gases. The peak value of OH(A-X) intensity was observed in the proximity of the water surface, however in the cases of Ar and $N_2$ with 0.5 SLM flow rate peaks shifted to the region below the water surface. Rotational temperature ($T_{rot}$) was estimated to be in the range of 900-3600 K, according to the carrier gas and flow rate, which corresponds to the arc-like-streamer discharge.

• 센서학회지
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• 제14권1호
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• pp.22-27
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• 2005

A thermoelectric flow sensor for small quantity of gas flow rate was fabricated using silicon wafer semiconductor process and bulk micromachining technology. Evanohm R alloy heater and chromel-constantan thermocouples were used as a generation heat unit and sensing parts, respectively. The heater and thermocouples are thermally isolated on the $Si_{3}N_{4}/SiO_{2}/Si_{3}N_{4}$ laminated membrane. The characteristics of this sensor were observed in the flow rate range from 0.2 slm to 1.0 slm and the heater power from 0.72 mW to 5.63 mW. The results showed that the sensitivities $(({\partial}({\Delta}V)/{\partial}(\dot{q}));{\;}{\Delta}V$ : voltage difference, $\dot{q}$ : flow rate) were increased in accordance with heater power rise and decreasing of flow rate.

• 대한화학회지
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• 제41권5호
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• pp.256-265
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• 1997

토양과 수질시료 중에서 nitrite, nitrate 그리고 ammonia성 질소를 빠르고 연속적으로 정량할 수 있는 방법에 관하여 연구하였다. 실제시료를 측정하기전에 각 성분의 표준시료를 사용하여 FIA의 구조적 인자(주입 양, 반응코일 길이 그리고 흐름속도)를 결정하였다. Nitrite는 Griess reaction에 의해 sulfanilamide와 반응 후 N-(1-naphthylenediamine dihydrochloride)과 결합하여 azo 색소를 형성시킨 후 540 nm에서 측정하였고, nitrate는 hydrazine을 사용하여 nitride로 환원시킨 후 측정하였다. Ammonia는 Nessler법을 사용하여 440 nm에서 측정하였다. 최적 조건에서 $N(NO_2^-),\;N(NO_3^-)와\;N(NH_4^+)$의 검출한계(S/N=3)는 0.1 ㎍/ML, 0.4 ㎍/mL 그리고 0.3 ㎍/ML이었다. 실제시료를 비색법, ion chromatography 및 FIA로 측정하여 비교한 결과 상호 일치성이 80~125%로 나타내어 만족스러웠다. 시료의 주입횟수는 30회/시간 이상으로 조절할 수 있었다.

• 대한기계학회논문집
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• 제19권10호
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• pp.2647-2656
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• 1995

The present work was performed to axially and radially investigate the local cold storage performance in the cylindrical tank with the spherical capsules inserted n-Tetradecane as a new cold storage material. The local cold storage performance of the capsules in the tank was experimentally investigated for the inlet temperature of -7, -5, -3, 0.deg. C, for the flow rate of 0.95, 1.89, 2.84, 6.00 l/min, and for the diameter ratio of 4.9, 9.0, 13.1. The local cold storage performance in the case of using water applied for the commercial ice-ball system was axially investigated by changing the flow rate only with the inlet temperature of -7.deg. C and the diameter ratio of 9.0 in order to compare with the performance in the case of using n-Tetradecane. For the case of using n-Tetradecane, the difference of cold storage period between the first and the seventh story was increased as the inlet temperature was increased and the flow rate was decreased. The capsules at the center of the tank showed the supercooling and the increased cold storage period compared with the capsules at the wall of the tank due to the small porosity and insufficient cold storage performance at the center of the tank as the diameter ratio is increased. The case using water showed worse cold storage performance due to comparatively large supercooling than the case using n-Tetradecane.