• Electrical & Electronic Materials
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• v.8 no.1
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• pp.95-101
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• 1995

Crystallizable glasses with precipitation of celsian, anorthite, wollastonite and gahnite were prepared for the purpose of insulating dielectric layers in devices such as integrated circuit substrates. The starting glasses were prepared by melting the batches for 1 hour at 1450.deg. C and then Quenching to a distilled water. And crystallization behavior of these glasses were studied by DTA, TMA, XRD analysis and by the measurement of dielectric properties. The overall composition of the glass-ceramic consists in weight percent of 30-35% A1$_{2}$O$_{3}$, 13-26% BaO, 5-21% CaO, 10-24% ZnO, 4.5-9.0% TiO$_{2}$ and 4-8% B$_{2}$O$_{3}$. As a result, in barium-rich glasses only celsian phase was developed in the range of 850-900.deg. C. Also, the thermal expansion coefficient, dielectric constant and quality factor of these glass-ceramics were 68*10$^{-7}$ /.deg. C, about 9 and more than 1000, respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.11
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• pp.1005-1009
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• 2006

High quality three-dimensional (3D) heterostructures were constructed by selective area (SA) molecular beam epitaxy (MBE) using a specially patterned GaAs (001) substrate to improve the efficiency of tarrier transport. MBE growth parameters such as substrate temperature, V/III ratio, growth ratio, group V sources (As2, As4) were varied to calibrate the selective area growth conditions and the 3D GaAs-AlGaAs heterostructures were fabricated into the ridge type and the V-groove type. Scanning micro-photoluminescence $({\mu}-PL)$ measurements and the following analysis revealed that the gradually (adiabatically) coupled 1D-2DEG (electron gas) field effect transistor (FET) system was successfully realized. These 3D-heterostructures are expected to be useful for the realization of high-performance mesoscopic electronic devices and circuits since it makes it possible to form direct ohmic contact onto the (quasi) 1D electron channel.

• Journal of The Korean Society of Grassland and Forage Science
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• v.35 no.3
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• pp.264-268
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• 2015

The present research investigated copper and cadmium stress-induced differentially expressed genes (DEGs) using annealing control primers (ACP) with the differential display reverse transcription polymerase chain reaction technique in alfalfa (Medicago sativa L. cv. Vernal) leaves. Alfalfa leaves were subjected to $250{\mu}M$ of copper and cadmium treatment for a period of 6 h. A total of 120 ACPs was used. During copper and cadmium treatment, 6 DEGs were found to be up or down regulated. During copper stress treatment, 1 DEG was up-regulated, and 3 novel genes were discovered. Similarly, during cadmium stress treatment, 1 DEG was up-regulated and 5 novel genes were identified. Among all 6 DEGs, DEG-4 was identified as the gene for trans-2,3-enoyl-CoA reductase, DEG-5 was identified as the gene for senescence-associated protein DIN1 and DEG-6 was identified for caffeic acid O-methyltransferase. All the up-regulated genes may play a role in copper and cadmium stress tolerance in alfalfa.

• Korean Journal of Food Science and Technology
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• v.12 no.3
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• pp.176-181
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• 1980

Yeast invertase was immobilized on the 2 kinds of matrices : one is an indirectly coupled enzyme to the cyanogen bromide activated Sepharose by using ${\omega}-aminohexyl$ group as an extension arm, and the other is a tightly adsorbed enzyme on the modified hydrophobic cellulose derivative which has a phenoxyacetyl group as a linkage. The enzyme preparation coupled on Sepharose retained 26.0% of the original activity against sucrose as a substrate, while the preparation immobilized on phenoxyacetyl cellulose retained 72.9% . The immobilized invertase preparation on ${\omega}-aminohexyl$ Sepharose showed the optimal pH 4.5, optimal temperature $60^{\circ}C$, activation energy $5,941\;cal/mole{\cdot}deg$ and Km' 22.2 mM against sucrose, while the preparation adsorbed on phenoxyacetyl cellulose showed the optimal pH 4.0, optimal temperature $60^{\circ}C$, activation energy $7,769\;cal/mole{\cdot}deg$ and Km' 69.9 mM.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.2
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• pp.139-152
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• 1998

In the present study, the flow characteristics of developing laminar oscillatory flows in a square -sectional 180 deg. curved duct are investigated experimentally. The experimental study using air in a square-sectional 180 deg. curved duct is carried out to measure velocity distributions with a data acquisition and LDV (Laser Doppler Velocimetry) processing system. In this system, Rotating Machinery Resolver (RMR) and PHASE program are used to obtain the results of unsteady flows. The major flow characteristics of developing oscillatory flows are found by analyzing velocity curves, mean velocity profiles, time-averaged velocity distribution of secondary flow, wall shear stress distributions, and entrance lengths. In a lower dimensionless angular frequency, the axial velocity distribution of laminar oscillatory flow in a curved duct shows a convex shape in a central part and axial symmetry. The maximum value of wall shear stress in a lower dimensionless angular frequency is located in an outside wall, but according to increasing the dimensionless angular frequency, the maximum of wall shear stress is moved to inner wall. The entrance lengths of laminar oscillatory flows in a square-sectional 180 deg. curved duct is obtained to 90 deg. of bended angle of duct in this experimental conditions.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.44 no.7
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• pp.914-918
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• 1995

In this study, Pb(Zr$_{x}$ Ti$_{1-x}$ )O$_{3}$ (x=0.65, 0.52, 0.35) thin films were fabricated by Sol-Gel method. A stock solution with excess Pb 10[mol%] of Pb(Zr$_{x}$ Ti$_{1-x}$ )O$_{3}$ was made and spin-coated on the Pt/SiO$_{2}$/Si substrate at 4000[rpm] for 30[sec.]. Coated specimens were dried on the hot-plate at 400[.deg. C] for 10[min.]. Sintering temperature and time were 500~800[.deg. C] and 1~60[min.]. The coating process was repeated 6 times and the final thickness of the thin films were about 4800[A]. To investigate crystallization condition, PZT thin films were analyzed with sintering temperature, time and composition by the XRD. The microstructure of thin fulms were investigated by SEM. The ferroelectric perovskite phases precipitated under the sintering of 700[.deg. C] for 1 hours. In the PZT(52/48) composition, dielectric constant and dielectric loss were 2133, 2.2[%] at room temperature, respectively.ively.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.4
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• pp.9-17
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• 1998

BiNbO$_{4}$ ceramics with 0.07wt% V$_{2}$O$_{5}$ and 0.03wt% CuO (BNC3V7) sintered at 900 .deg. C where it is possible for these to be co-fired with ag electronde. Dielectric constant of 44.3 TCF (Thermal Coefficient of resonance Frequency) of 2 ppm/.deg. C and Qxf value 22,000 GHz can be obtained from BNC3V7. the laminatedchip LC filter is indispensible to the minimaturization of PCS (Personal Communication System) terminals. Therefore, multilayer type BPF has been fabricated by screen-printing with silver electrode after tape casting. The simulated characteristics of the fabricated filters sintered at 900.deg. C werecomparedwith the designed ones. for Band Pass Filter widths was similar that ofdesigned ones. For Low Pass Filter (LPF), insertion loss value of band pass widths (2.4 dB) which is a few higher than that of designed (1dB), but characteristization of band pass widths was similar that of designed ones.s.of designed ones.s.

• 전기의세계
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• v.22 no.2
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• pp.45-50
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• 1973

Amorphous semiconducting diodes from As Te Ge systm of which resitivity are 10$^{6}$ -10$^{8}$ .ohm.-cm order, are made and they exhibited several conducting states. A high conductivity, low conductivity and memory state are reported. Temperature dependency of the specimens are widerange. According to the procedure and cooling method, specimens are made easily or not. Threshold voltage of switching and memory diodes is in proportional to compositonal quantity of Arsenic. Threshold voltage is changed widely according to ambient temperature. Threshold voltage of #132 is 620V at 25.deg. C, 70V at 100.deg. C.

• Electrical & Electronic Materials
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• v.5 no.3
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• pp.295-301
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• 1992

본 연구는 고분자 압전 재료인 PVDF 필름을 시료로 사용하고 분극 조건을 변화시켜 가며 분극화 시킨후 압전계수를 측정하였다. 또한 X-선 회절 장치와 DSC 장치를 이용하여 결정구조 변화를 조사하였으며 또한 분극에 의해 생성된 결정의 용융특성도 관찰하였다. 분극되지 않은 시료의 용융 온도는 약 175.deg.C 부근에서 나타났으나 분극된 시료는 분극 전압이 증가함에 따라 184.deg.C부근에서 새로운 용융점이 나타나기 시작하였으며 분극 전압이 증가할수록 새로운 용융점이 점차 뚜렷해졌다.

• Electrical & Electronic Materials
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• v.10 no.2
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• pp.166-171
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• 1997

The photomachinable glass-ceramics of Ag and CeO$_{2}$ added to Li$_{2}$O-Al$_{2}$O$_{3}$-SiO$_{2}$-K$_{2}$O glass system was investigated as a function of UV irradiation time. The temperature of optimum nucleation and crystal growth temperature were confirmed at 525.deg. C, 630.deg. C respectively using DTA and TMA. The phases of Li$_{2}$O.SiO$_{2}$ habit were lath-like and/or dendrite type and [002] direction of Li$_{2}$O.SiO$_{2}$ / Li$_{2}$O.2SiO$_{2}$ phases were changed according to the UV irradiation time by 400 W, 362 nm UV light source. Under that condition, the optimum UV irradiation time was 5 min.