• Proceedings of the Korean Vacuum Society Conference
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• 1998.02a
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• pp.109-109
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• 1998

최근 들어 MOCVD 법으로 성장시킨 GaN, InGaN, AIGaN를 이용한 광소자 ( (LED, LD)와 전자소자(FET, MODFET)에 대한 관심이 고조되면서, MOCVD 법 을 이용한 GaN 중심의 질화물 반도체 성장에 관심이 집중되고 있다. 금번 실험에 사용된 MOCVD 장비는 수직형 MOCVD 장비이다. 특히, wafer c carner를 1$\alpha$)() rpm이상의 고속으로 회전시킬 수 있는 장치로서 원료 가스의 반웅 기 내에서의 흐름을 균일하게 하여 uniformity가 높은 질화물 반도체를 성장시킬 수 있다 .. GaN 에피충은 c-plane 사파이어를 기판으로 하여 11 00 "C 이상의 고온 에서 수소를 이용하여 기판을 cleaning하고, 500 "C 부근에서 핵생성충올 성장시 킨 후 1050 "C에서 trimethylgallium(TMGa)과 NI-h를 이용하여 성장시켰다. n n -GaN를 성장시키기 위해서는 SiH4을 사용하였으며, InGaN의 경우는 t trimethylindium(TMIn)을 In원 료 가스로 하여 635 - 725 "C 범 위 에 서 성 장시 켰 다. 성 장된 undoped GaN, n-GaN, InGaN는 X -ray di잔raction(XRD), H떠l m measurement, Photoluminescence(PU동올 이용하여 결정성과 전기적 및 광학적 특성올 고찰하였다 .. 2ttm 두께로 성장된 undoped G값V박막의 경우 Hall 측정결과 6 6 X lOI6/e며 정도의 낮은 도핑 농도를 보였으며, V!lII ratio(2500 - 5000)증가에 따라 결정성이 향상됨을 GaN (102)면의 X -ray e -rocking분석올 통하여 확인하 였다 .. n-GaN의 경우 SiH4양올 3 - 13 sccm으로 증가시킴에 따라 n -type 도명농 도가 선형적으로 증가하였고, 1017/c며 범위 내로 도평이 된 경우 상온에서 300 e마 N Ns 이상의 high mobility를 얻올 수 있었다 .. PL 관측 결과로부터 Si 도핑으로 인 하여 GaN bandedge emission이 강화됨을 알 수 있었다 .. InGaN 박막의 경우 성 장온도를 낮춤에 따라서 m의 양을 증가시킬 수 있었다. 또한 유량비(TMIn I T TMGa)가 1에 가까운 경 우에서도 온도를 635 "C 정도로 낮훈 경우 410 nm정도에 서 PL bandedge peak올 얻을 수 있었으며, 이 때의 반치폭은 50 meV정도의 낮 은 값을 보였다. 반치폭은 50 meV정도의 낮 은 값을 보였다.

• Proceedings of the KIEE Conference
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• 1995.07c
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• pp.1391-1393
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• 1995

An electron gun system for the Pohang Light Source has been installed and operated successfully. The basic design parameters are acceleration voltage of 80 kV, maximum peak emission current of 5 A, minimum pulse width of 1 ns, and maximum repetition rate of 100 Hz. The gun has a triode structure and is composed of a cathode, a focusing electrode(Wehnelt), and an anode. To sustain a $5{\times}10^{-9}$Torr vacuum, a $230{\ell}/s$ Ion pump has been adopted. We adopted a control and monitoring system based on the fiber-optic technology. In this article, we present the structure and operation principle of the system with special interest on the nanosecond pulser, remote control and monitoring system.

• Microbiology and Biotechnology Letters
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• v.20 no.6
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• pp.699-703
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• 1992

An oriental drug, named NP-S, traditionally used as a therapeutic agent for hepatitis B was characterized by separating into volatile and non-volatile fractions. The volatile fraction contained ammonia as determined by ammonia kit and eight peaks when it was analyzed by gas chromatography that are not identified yet. The elemental analysis showed that the non-volatile fraction contained 15.5% carbon, 4.8% hydrogen, 11% nitrogen, and 10% sulfur along with a few trace elements such as Cl, Si, Mg and Zn. NP-S contained 6.7% peptide, 0.3% free amino acids such as Lys, Pro, Arg, lie, Tyr, Phe, His, Thr and Ser and 0.1% inorganic phosphate. The drug showed antimicrobial activity against Salmonella typhimurium, StaPhylococcus aureus and Candida albieans and also had antioxidant activity when thiobarbituric acid reacting substances(TBARS) method was applied.

• Journal of The Korean Society of Grassland and Forage Science
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• v.16 no.3
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• pp.245-252
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• 1996

This experiment was carried out to investigate the effect of feeding order bay-concentrate-silage, concentratehay- silage, silage-concentrate-hay, silage-concentrate-hay, concentrate-silage-hay) on ruminal characteristics change with 3 fistulated dry Holstein cows in a Latin square design. The main results obtained were as follows : DM intake in forage hayconcentrate-silage feeding order was 1.65% of body weight, which is the highest of all treatments, but that in concentrate-hay-silage 1.4%, which is the lowest. The difference between max and min rumen pH in hayconcentrate-silage feeding order was lowest as 0.55, but there is no significant. The mean rumen $NH_3N$ content in silage-concentrate-hay feeding order was highest as 6.12mg/100ml, but that in silageconcentrate-hay feeding order lowest as 4.82mg/100ml. Acetic acid and propionic acid content was highest in forage hay-concentrate-silage feeding order. but there is no significant. The ratio of acetic acid to propionic acid averaged 3.47~3.69(NS). In conclusion, the best feeding order fitted in ruminal physiology was forage hay-concentrate-silage.

• The Korean Journal of Physiology and Pharmacology
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• v.17 no.5
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• pp.441-446
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• 2013

In the present study, the anti-depressant like effect of methyl gallate (MG) isolated from the stem bark of Acer barbinerve was examined in ICR mice. Body weight (BDW) and blood glucose (BDG) levels significantly decreased in the repeated restraint stress (RRS) group (2 h/day for 14 days) compared to the no stress (NS) group. To examine the effect of MG on RS-induced BDW loss and hypoglycemia, MG (10 mg/kg) and the anti-depressant fluoxetine (10 mg/kg) were administered daily for 14 days. Orally administered MG and fluoxetine significantly attenuated the RS-induced BDW loss and hypoglycemia. Interestingly, MG administered mice showed increased BDG levels in the normal and glucose feeding condition. Chronic RS-subjected mice showed immobilized and depressed behaviors. The effect of MG on the depressed behaviors was evaluated using the tail-suspension test (TST) and the forced swimming test (FST). In both tests, RS-induced immobilized behaviors were significantly reversed in MG and fluoxetine administered groups. Taken together, MG significantly attenuated the RS-induced BDW loss, hypoglycemia, and depressed behaviors. Considering that decreased BDG levels (hypoglycemia) can cause depression, MG may exert its anti-depressant like effect by preventing hypoglycemia. Our results suggest that MG isolated from A. barbinerve can exert anti-depressant like effect, and could be used as a new and natural anti-depressant therapy.

• Wind and Structures
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• v.5 no.2_3_4
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• pp.301-316
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• 2002

An important goal of computational wind engineering is to impact the design process with simulations of flow around buildings and bridges. One challenging aspect of this goal is to solve the Navier-Stokes (NS) equations accurately. For the unsteady computations, an adaptive finite element technique may reduce the computer time and storage. The preliminary application of a p-version as well as an h-version adaptive technique to computational wind engineering has been reported in previous paper. The details on the implementation of p-adaptive technique will be discussed in this paper. In this technique, two posteriori error estimations, which are based on the velocity and vorticity, are first presented. Then, the polynomial order of the interpolation function is increased continuously element by element until the estimated error is less than the accepted. The second through sixth orders of hierarchical functions are used as the interpolation polynomials. Unequal order interpolations are used for velocity and pressure. Using the flow around a circular cylinder with Reynolds number of 1000 the two error estimators are compared. The result show that the estimated error based on the velocity is lower than that based on the vorticity.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2002.09a
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• pp.379-381
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• 2002

A single CdZnTe detector is tested for suitability in a prototype CT/ SPECT system designed to acquire both emission and transmission data. The detector has the size of 1${\times}$l-cm$^2$ with 4${\times}$4 1.5${\times}$l.5mm$^2$ pixellated anodes. Since the detector is smaller than imaged object, we translated it in an arc centered at the x-ray tube to image larger objects. Pulse counting electronics with very short shaping time (50 ns) are used to satisfy high photon rates in x-ray imaging, and response linearity up to 3${\times}$10$\^$5/ counts per second per detector element is achieved. The energy resolution of 122-keV gamma-ray is measured to be 14%. We have characterized the system performance by scanning a radiographic resolution phantom .and the Hoffman brain phantom. The spatial resolution of CT and SPECT are about 1 mm and 7 mm, respectively.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.28A no.10
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• pp.821-829
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• 1991

In this paper, a BICMOS technology that has CMOS devices for digital application and bipolar devices for high voltage (80V) analog applications is presented. Basic concept to design BICMOS device is simple process technology without making too many performance trade-offs. The base line process is poly gate p-well CMOS process and three additional masking steps are added to improve bipolar characteristics. The key ingredients of bipolar integration are n+ buried layer process, up/down isolation process and p-well base process. The bipolar base region is formed simultaneously with the region of CMOS p-well area to reduce mask and heat cycle steps. As a result, hFE value of NPN bipolar transistor is 100-150(Ic=1mA). Collector resistance value is 138 ohm in case of bent type collector structure. Breakdown voltage of BVebo, BVcbo and BVceo are 21V, 115V and78V respectively. Threshold voltage is ${\pm}$1.0V for NMOS and PMOS transistor. Breakdown voltage of NMOS and PMOS transistor is obtained 22V and 19V respectively. 41 stage CMOS ring oscillator has 0.8ns delay time.

• Proceedings of the KIEE Conference
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• 2005.11a
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• pp.96-99
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• 2005

In this study, we build system and techniques of evaluating the interruption performance of the GCB with experimental method. We constructed a simplified synthetic test circuit of which ability is up to 245kV, 50kA BTF test. And We composed a model test circuit breaker with puffer assisted self blasting type GCB. With this circuit breaker, we carried out the experiment of no load and SLF90. During the tests, we measured the several factors such as stroke, pressure, arc temperature, the voltage and current near the current zero and dI/dt, dV/dt. Arc conductivity before 200ns before current zero which is one of the indexes of the thermal recovery of a GCB was measured. With these kinds of measurement, we could estimate the performance of a GCB fundamentally. Futhermore these results were used to adjust the arc modeling with CFD(computational fluid dynamics) and we could increase the plausibility of the analytical method.

• Current Optics and Photonics
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• v.1 no.4
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• pp.402-411
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• 2017

Combined LIBS-Raman spectroscopy has been widely studied, due to its complementary capabilities as an elemental analyzer that can acquire signals of atoms, ions, and molecules. In this study, the classification of polymorphs was performed by laser-induced breakdown spectroscopy (LIBS) to overcome the limitation in molecular analysis; the results were verified by Raman spectroscopy. LIBS signals of the $CaCO_3$ polymorphs calcite and aragonite, and $CaSO_4{\cdot}2H_2O$ (gypsum) and $CaSO_4$ (anhydrite), were acquired using a Nd:YAG laser (532 nm, 6 ns). While the molecular study was performed using Raman spectroscopy, LIBS could also provide sufficient key data for classifying samples containing different molecular densities and structures, using the peculiar signal ratio of $5s{\rightarrow}4p$ for the orbital transition of two polymorphs that contain Ca. The basic principle was analyzed by electronic motion in plasma and electronic transition in atoms or ions. The key factors for the classification of polymorphs were the different electron quantities in the unit-cell volume of each sample, and the selection rule in electric-dipole transitions. The present work has extended the capabilities of LIBS in molecular analysis, as well as in atomic and ionic analysis.