• Journal of the Korean Institute of Telematics and Electronics
• /
• v.27 no.11
• /
• pp.77-82
• /
• 1990

The temperature and the composition dependence of the dielectric properties of the solid solution materials in the system $xBa(Zn_{1/3}Nb_{2/3})O_{3}\[BZN]-(1-x)\Sr(Zn_{1/3}Nb{2/3)O_{3}\[SZN]$ at microwave frequency was studied. The dielectric constant and unloaded Q were $40.5{\pm}0.5,5980{\pm}100$ respectively for BZN at 10 GHz and $36.9{\pm}0.5,2700{\pm}100$ for SZN at 10.2GHz. The temperature coefficient of the resonant frequency was $+27.5ppm/{\circ}C$ for BZN and $-39.1ppm/{\circ}C$ for SZN. The results also showed that 0.3 BZN-0.7 SZN is the most temperature-stable composition among xBZN-(1-x) SZN solid solutions. In this case, the dielectric constant, the unloaded Q and $\tau_{f}$ at 9.8GHz were $41.5{\pm}0.2,2920{\pm}100$ and $-3.5ppm/{\circ}C$, respectively.

• Journal of the Korean Vacuum Society
• /
• v.19 no.2
• /
• pp.134-140
• /
• 2010

We have investigated the contactless electroreflectance (CER) properties of $In_{0.5}(Ga_{1-x}Al_x)_{0.5}P$/GaAs double heterostructures grown by metal-organic chemical vapour deposition (MOCVD). The CER measurements on the sample were studied as a function of temperature, modulation voltage ($V_{ac}$), and dc bias voltage ($V_{bias}$). Five signals observed at room temperature are related to the GaAs, $In_{0.5}Ga_{0.5}P$, $In_{0.5}(Ga_{0.73}Al_{0.27})_{0.5}P$, $In_{0.5}(Ga_{0.5}Al_{0.5})_{0.5}P$, and $In_{0.5}(Ga_{0.2}Al_{0.8})_{0.5}P$ transitions, respectively. From the temperature dependence of CER spectrum, the Varshni coefficients and broadening parameters were determined and discussed. In addition, we found that the behavior of the CER amplitude for the reverse bias is larger than that of the forward.

• Journal of the Korean Electrochemical Society
• /
• v.8 no.2
• /
• pp.82-87
• /
• 2005

The cathode material, $LiNi_{0.5}Mn_{1.5}O_4$, for high voltage applications of Li-ion batteries exhibits impurity phases due to oxygen deficiency during the high temperature heat treatment. The impurity phase reduces the electrochemical properties of the electrode since the deficiency spinel structure disturbs the lithium ion intercalation and deintercalation. In this study, Cr-substituted $LiNi_{0.5-x}Mn_{1.5}Cr_xO_4(0{\leq}x{\leq}0.05)$ powders are synthesized by a sol-gel method in order to reduce the amount of the impurity phases in the $LiNi_{0.5-x}Mn_{1.5}Cr_xO_4$. Thermal analysis of the cathode material shows that the $LiNi_{0.5}Mn_{1.5}O_4$ without Cr substitution looses $2\%$ of its weight due to oxygen deficiency but the amount of weight loss is diminished when Cr is substituted. XRD analysis also supports the reduction of the impurity phases in the cathode after chromium substitution, suggesting that the improvement of the electrochemical properties such as the capacity retention and electrochemical stability are attributed to the low content of impurity phases in the Cr-substituted $LiNi_{0.5-x}Mn_{1.5}Cr_xO_4.$

• The Journal of the Korea institute of electronic communication sciences
• /
• v.8 no.4
• /
• pp.535-540
• /
• 2013

We design a slotted waveguide antenna for X-band which a 1.4m length with slot depth variation. A 54 slot array is modeled and simulated by CST, and the side lobe level is suppressed effectively in a certain range of frequency. The experimental results of the antenna show that its gain, maximum sidelobe level and half power beam-width are 21.8dB, -31dB and 2.0deg, respectively.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.13 no.3
• /
• pp.216-220
• /
• 1988

The design and performance of 12GHz low-noise amplifierwith GaAs MESFET and microstrip line are described. It contains DC blocks with symmetric line and chip capacitor, respectively. The low-noise amplifier with chip capacitor and DC block exhibits a 8-11 dB gain over 11.8-12.1 GHz and 16-18dB gain over 12.16-12.19GHz, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1989.06a
• /
• pp.49-51
• /
• 1989

The effect of Mo elenent and annealing condition on the magnetic properties were investigated in Fe$_{80}$B$_{12}$Si$_{8}$ amorphous alloy. With increasing Mo contents, soft magnetic properties were improved by decreasing coercive force and increasing maximum permeability. These improvements were attributed to the decreasing of magnetostriction by Mo addition. The annealing treatment also improved the soft magnetic properties of (Fe$_{1-x}$ Mo$_{x}$)$_{80}$ B$_{12}$ Si$_{8}$ amorphous alloys. It could be thought that these improvements were ascribed to the relaxation of internal stress.nal stress.ess.

• Journal of the Korean Institute of Telematics and Electronics A
• /
• v.31A no.5
• /
• pp.58-67
• /
• 1994

In this paper, It was designed the 2.8GHz local oscillator which convert 14.5 14.8GHz uplink frequency to 11.7 12.0GHz downlink frequency by the receiving mixer on the communication satellite transponder according to the rating of domestic satellite. Mukunghwa 1. To prevent the variation of the communication channel bandwidth, it needs a high stability and low phase noise characteristics. So we designed to get the target frequencey by multipling the output signal from the crystal oscillator. We got the simplicity of the circuit by manufacturing the X4 multiplier with transistor which is ordinarily used as a device of a below X3 multiplier for the efficiency.

• Korean Journal Plant Pathology
• /
• v.12 no.2
• /
• pp.169-175
• /
• 1996

콩 불마름병균 Xanthomonas campestris pv. glycines 8ra는 X. c. pv. vesicatoria에 길항력이 있는 bacteriocin인 glycinecin을 생성 분비한다. Bacteriocin 생성 분비 능력이 있는 콩 불마름병균을 효과적인 생물학적 방제원으로 활용하기 위해서는 좀더 체계적인 연구가 필요하여, bacteriocin 생성에 관계되는 유전자의 분리를 시도하였다. 약 2,000개의 Xanthomonas campestris pv. glycines 8ra cosmid library에서 bacteriocin의 생성 분비 능력을 조사하여 다섯 개의 clone을, pG011, pG0113, pG33과 pG35, 선발하였다. 그중 한 clone pG08을 임의로 선택하여 plasmid DNA를 분리하였다. Plasmid pG08에서 약 6.0 kb의 DNA를 떼어내어 다른 plasmid vector에 넣은 subclone pBL5는 bacteriocin의 생성 분비 능력이 있었다. Plasmid pG08을 제한효소 처리후 다시 접함시켜 만든 몇 개의 subclone과 pBL5의 제한효소 지도를 비교 분석한 결과 약 3.0 kb의 BamHI-HindIII 부분의 DNA가 bacteriocin의 생성에 관계함을 알았다.

• Journal of Microbiology and Biotechnology
• /
• v.27 no.7
• /
• pp.1331-1335
• /
• 2017

In this study, the feasibility of introducing calcite-forming bacteria into concrete pavements to improve their mechanical performance was investigated. Lysinibacillus sphaericus WJ-8, which was isolated in a previous study and is capable of exhibiting high urease activity and calcite production, was used. When analyzed via scanning electron microscopy (SEM) and X-ray diffraction, WJ-8 showed a significant amount of calcite precipitation. The compressive strength of cement mortar mixed with WJ-8 cells and nutrient medium (urea with calcium lactate) increased by 10% compared with that of the controls. Energy dispersive x-ray spectroscopy analyses confirmed that the increase in strength was due to the calcite formed by the WJ-8 cells.

• Bulletin of the Korean Chemical Society
• /
• v.13 no.3
• /
• pp.256-259
• /
• 1992

The 14-membered tetraaza macrocyclic ligand 1,8-diethyl-5,12-dimethyl-1,4,8,11-tetraazacyclote tradeca-4,11-diene(B) can be synthesized as its dihydroperchlorate salt by the one-pot reaction of 2-ethylaminoethylamine, methylvinyl ketone, and perchloric acid in absolute ethanol. The reaction of Ni(II) or Cu(II) ion and the salt yields $[M(B)]^{2+}$ (M = Ni(II) or Cu(II)), which reacts with $NaBH_4$ to produce $[M(D)]^{2+}$ (D = 1,8-diethyl-5,12-dimethyl-1,4,8,11-tetraazacyclote tradecane). The complexes $[M(L)]^{2+}$ (L = B or D) have planar geometry and contain two ethyl groups at the donor nitrogen atoms of the ligands. The red solids $[Cu(B)](X)_2(X)$ = $ClO_4-$ or $PF_6^-$) react with water molecules of atmospheric moisture to produce the purple solids in which water molecules are coordinated to the metal ion. Synthesis, characterization, and the properties of the new N-ethylated macrocyclic ligands and their Ni(II) and Cu(II) complexes are reported.