• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.2
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• pp.220-223
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• 2016

This letter proposes a low noise amplifier which has low noise figure and high linearity simultaneously using a cascode structure with an additional transistor. The proposed structure minimizes the noise source by using optimizing transistor sizes and also improves linearity from the current bleeding technique. The device was fabricated in a $0.5{\mu}m$ GaAs pHEMT process and has noise figure of 1.1 dB, a voltage gain of 15.0 dB, an $OIP_3$ of 30.8 dBm and an input/output return loss of 11.6 dB/10.4 dB from 1.8 to 2.6 GHz.

• 건축구조
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• v.18 no.6
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• pp.53-60
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• 2011

Revit Structure(이하 Revit)는 Autodesk사에서 만든 BIM Tool이다. Revit에 관한 특징은 본 회지 7.8월호에 다루었다. Revit은 현재 국내에 가장 많이 보급되어 있고 관련 서적도 많은 BIM Tool로써 BIM작성, 물량산출, 도면작성 등을 수행할 수 있다. 지금까지 많은 프로젝트가 Revit으로 수행되었고 사용자도 많다. 그럼 7 8월호에 제시한 구조BIM 프로세스에 따른 간단한 설명과 Revit을 통한 BIM작성에 대해 소개하겠다. 자세한 내용은 추후에 BIM교육에서 다룰 예정이다.

• Bulletin of the Korean Mathematical Society
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• v.58 no.6
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• pp.1445-1461
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• 2021

The aim of this paper is to show the local well-posedness of 2 dimensional Dirac equations with power type and Hartree type nonlin-earity derived from honeycomb structure in H^s for s > $\frac{7}{8}$ and s > $\frac{3}{8}$, respectively. We also provide the smoothness failure of flows of Dirac equations.

• Bulletin of the Korean Chemical Society
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• v.16 no.9
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• pp.823-826
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• 1995

The crystal structure of a sulfur sorption complex of the dehydrated partially Co2+ exchanged zeolite A (a=12.058(2) Å) has been determined by single-crystal X-ray techniques. The crystal structure was solved and refined in cubic space group Pm3m at 21(1) ℃. Ion Exchange with aqueous 0.05 M Co(NO3)2 was done by the static method. The crystal of Na4Co4-A was dehydrated at 380 ℃ and 2 × 10-6 Torr for 2 days, followed by exposure to about 100 Torr of sulfur at 330 ℃ for 72 h. Full matrix least-squares refinement converged to R1=0.084 and Rw=0.074 with 102 reflections for which I > 3σ(I). Crystallographic analysis shows that 2.8 Co2+ ions and 4 Na+ ions per unit cell occupy 6-ring sites on the threefold axes. 1.2 Co2+ ions occupy the 8-ring sites on fourfold axes. 2.8 Co2+ ions at Co(1) are recessed 0.66 Å into the large cavity and 4 Na+ ion at Na(1) are recessed 0.77 Å into the sodalite cavity from the (111) plane of O(3)'s. Approximately 16 sulfur atoms were sorbed per unit cell. Two S8 rings, each in a butterfly form, are found in the large cavity. The bond length between S and its adjacent S is 2.27(3) Å. The distance between 6-ring Co2+ ion and its adjacent sulfur is 2.53 (2) Å and that between 8-ring Co2+ ions and its adjacent sulfur is 2.72(9) Å. The angles of S-S'-S and S'-S-S'/ in octasulfur rings are 119.0(2)°and 113.0(2)°, respectively.

• Transactions of the Korean hydrogen and new energy society
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• v.13 no.3
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• pp.181-189
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• 2002

A series of multicomponent $Zr_{0.8}Ti_{0.2}Mn_{0.4}V_{0.6}Ni_{1-x}Fe_{x}$ (x=0.00, 0.08, 0.15, 0.22, and 0.30) alloys are prepared and their oystal structure and P-C-T curves are examined. The electrochemical properties of these allqys such as activation conditions, discharge capacity, cycling performance are also investigated. $Zr_{0.8}Ti_{0.2}Mn_{0.4}V_{0.6}Ni_{1-x}Fe_{x}$ (x=0.00, 0.08, 0.15, 0.22 and 0.30) have the C14 Laves phase hexagonal structure. The electrode was activated by the hot-charging treatment. The best activation conditions were the current density 120 mA/g and the hot-charging time 12h at $80^{\circ}C$ in the case of the alloy with x=0.00. The discharge capacity increased rapidly until the fourth cycle and then decreased. The discharge capacity increased again from the 13th cycle, arriving at 234 mAh/g at the 50th cycle. The discharge capacily just after activation decreases with the increase in the amount of the substituted Fe but the cycling performance is improved. The discharge capacity after activation of the alloy with x=0.00 is 157 mAh/g at the current density 120 mA/g. $Zr_{0.8}Ti_{0.2}Mn_{0.4}V_{0.6}Ni_{0.85}Fe_{0.15}$ is a good composition with a medium quantity of discharge capacities and a good cycling performance. The ICP analysis of the electrolyte for these electrodes after 50 charge-discharge cycles shows that the concentrations of V and Zr are relatively high. Another series of multicomponent $Zr_{0.8}Ti_{0.2}Mn_{0.4}V_{0.6}Ni_{0.85}M_{0.15}$ (M = Fe, Co, Cu, Mo and Al) alloys are prepared. They also have the C14 Laves phase hexagonal structure. The alloys with M = Co and Fe have relatively larger hydrogen storage capacities. The discharge capacities just after activation are relatively large in the case of the alloys with M = Al and Cu. They are 212 and 170 mAh/g, respectivety, at the current density 120mA/g. The $Zr_{0.8}Ti_{0.2}Mn_{0.4}V_{0.6}Ni_{0.85}Co_{0.15}$ alloy is the best one with a relatively large discharge capacity and a good cycling performance.

• Bulletin of the Korean Chemical Society
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• v.15 no.11
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• pp.953-957
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• 1994

Pseudospectral Hartree-Fock(PSHF) gradient calculations with $6-31G^{**}$ basis set have been carried out to determine the structure of D-Asparagine molecule $(C_4N_2O_3H_8)$ with improved grids and with the BFGS method. The modified PSHF method, despite partial optimization of the gradient code, turned out to be still faster than the conventional ab initio method, GAUSSIAN 90 program by more than twice. The optimum geometry of D-Asparagine obtained by the PSHF method is in good agreement with those calculated by the GAUSSIAN 90 program (within 0.0036 ${\AA}$ for bond lengths, 0.8 degrees for bond angles, and 1.6 degrees for torsional angles) except for three torsional angles. Here, rather large discrepancy of these three torsional angles (5-6 degrees) is attributed to the small differences in the optimum bond lengths and angles between the PSHF and GAUSSIAN 90 calculations.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.41 no.6
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• pp.466-470
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• 2008

Microsatellite DNA markers were used to investigate the genetic diversity and population structure of Pacific abalone Haliotis discus hannai collected from six locations (Uljin, Ulsan, Daechon, Taean, Wando, and Yosu) where hatchery-produced abalone have been released intensively. There was no distinguishable difference in the observed and expected heterozygosities between the six populations and a cultured population. However, there was a difference in the number of alleles per locus: 12.8 for the cultured population and 13.8 to 15.8 for the six populations. The proportion of stocked abalone ranged from 41.1 to 92.7% for wild-caught populations with a decreasing tendency of alleles per locus for an increasing proportion of stocked abalone. A departure from Hardy-Weinberg equilibrium (HWE) assessed using the Markov chain procedure (P<0.05) was observed in the six populations and cultured population at loci Hdh145 and Hdh5l2. The pairwise Fst test (P<0.05) showed a significant difference between the Uljin and Ulsan populations and four remaining populations (Wando, Daechon, Yosu, and the cultured population), among which the Wando population differed less than the other three populations (Daechon, Yosu, and the cultured population).

• Journal of Information Display
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• v.8 no.2
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• pp.20-24
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• 2007

Efficient white organic light-emitting diodes are fabricated with the blue and red electroluminescent (EL) units electrically connected in a stacked tandem structure by using a transparent doped organic p/n junction. The blue and red EL units consist of the light-emitting layer of 1,4-bis(2,2-diphenyl vinyl)benzene (DPVBi) and 4-dicyanomethylene-2-methyl-6-[2-(2,3,6,7-tetrahydro-1H,5H-benzo[i,j] quinolizin-8-yl)vinyl]-4H-pyran) (DCM2) doped tris(8-hydroxyquinoline) aluminum $(Alq_3)$, respectively. The organic p-n junction consists of ${\alpha}-NPD$ doped with $FeCl_3$ (15 % by weight ratio) and $Alq_3$ doped with Li (10 %). The EL spectra exhibit two peaks at 448 and 606 nm, resulting in white light-emission with the Commission Internationale d'Eclairage (CIE) chromaticity coordinates of (0.36, 0.24). The tandem device shows the quantum efficiency of about 2.2 % at a luminance of 100 $cd/m^2$, higher than individual blue and red EL devices.

• Electrical & Electronic Materials
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• v.8 no.6
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• pp.780-786
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• 1995

For the execution of RIETAN program adopting Rietveld Analysis Method, the sample superconductor is made according to the solid state synthesis method at 920.deg. C for 24hrs, and was examined for the optimization of parameters needed to analyze Rietveld method with the input of the measured pattern data after measuring the pattern resulted from the X-ray diffraction. It was proven that the lattice constant of the superconductor which was consisted of Pmmm orthorhombic crystal structure in the analyzed space group correspond to the presented theoretical lattice constant a=3.8887(8).angs., b=3.8238(4).angs., c=11.7079.angs.. Therefore, it was examined and confin-ned that the R factor, which was compensated after analyzing the structure of superconductor resulted from this experimented data with the computer simulation, was refined to $R_{wp}$=8.83[%], $R_{P}$=6.47[%], $R_{I}$=10.08[%], $R_{F}$=7.19[%], $R_{E}$=3.76[%]. On the basis of these experimental data, the significant parameter such as the scale factor(S) and the zero point shift(Z) and FWHM value(U,V,W) were optimized as follows; S=2.0827E-3, Z=0.2146, U=4.2761E-2, V=1.7983E-2, and W=2.6768E-2.2.2.2.2.2.

• Composites Research
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• v.34 no.6
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• pp.373-379
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• 2021

A series of novel PBI/SrTiO₃ nanocomposite membranes composed of polybenzimidazole (PBI) and strontium titanate (SrTiO₃) with a perovskite structure were fabricated with various concentrations of SrTiO₃ through a solution casting method. Various characterization techniques such as proton nuclear magnetic resonance, thermogravimetric analysis, atomic force microscopy (AFM) and AC impedance spectroscopy were used to investigate the chemical structure, thermal, phosphate absorption and morphological properties, and proton conductivity of the fabricated nanocomposite membranes. The optimized PBI/SrTiO₃-8 polymer nanocomposite membrane containing 8wt% of SrTiO₃ showed a higher proton conductivity of 7.95 × 10^-2 S/cm at 160℃ compared to other nanocomposite membranes. The PBI/SrTiO₃-8 composite membrane also showed higher thermal stability compared to pristine PBI. In addition, the roughness change of the polymer composite membrane was also investigated by AFM. Based on these results, nanocomposite membranes based on perovskite structures are expected to be considered as potential candidates for high-temperature PEM fuel cell applications.