• Korean Chemical Engineering Research
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• v.58 no.3
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• pp.369-380
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• 2020

Most mono-crystalline silicon ingots are manufactured by the Czochralski (Cz) process. But If there are oxygen impurities, These Si-ingot tends to show low-efficiency when it is processed to be solar cell substrate. For making single-crystal Si- ingot, We need Czochralski (Cz) process which melts molten Si and then crystallizing it with seed of single-crystal Si. For melts poly Si-chunk and forming of single-crystalline Si-ingot, the heat transfer plays a main role in the structure of Cz-process. In this study to obtain high-quality Si ingot, the Cz-process was modified with the process design. The crystal growth simulation was employed with pulling rate and rotation speed optimization. Studies for modified Cz-process and the corresponding results have been discussed. The results revealed that using crystal growth simulation, we optimized the oxygen concentration of single crystal silicon by the optimal design of the pulling rate, rotation speed and melt charge level of Cz-process.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.12 no.4
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• pp.202-209
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• 2002

The stochiometric mix of evaporating materials for the $CuInSe_2$single crystal thin films was prepared from horizontal furnace. To obtain the single crystal thin films, $CuInSe_2$compound crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by the Hot Wall Epitaxy (HWE) system. The source and substrate temperature were $620^{\circ}C$ and $410^{\circ}C$, respectively. The crystalline structure of single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). The carrier density and mobility of $CuInSe_2$single crystal thin films measured from Hall effect by van der Pauw method. From the photocurrent spectrum by illumination of perpendicular light on the c-axis of the $CuInSe_2$single crystal thin film, we have found that the values of spin orbit splitting $\Delta$So and the crystal field splitting $\Delta$Cr. From the photoluminescence measurement on $CuInSe_2$single crystal thin film, we observed free exciton ($E_x$) existing only high quality crystal and neutral bound exciton ($A^{\circ}$, X) having very strong peak intensity. Then, the full-width-at-half-maximum (FWHM) and binding energy of neutral donor bound exciton were 7 meV and 5.9 meV, respectivity. By haynes rule, an activation energy of impurity was 59 meV.

• YAKHAK HOEJI
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• v.3 no.1
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• pp.4-9
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• 1957

Effects of antibioties on micro-organism have been reported by many scientists, such as Krampitz and Werkman, Fisher, Gale and Rodwell, Klimick Cavalito and Bailey, Umbreit, etc. On the mechanism by which penicillin act, Fisher(1947), Platt(1947), and Cavallito, considered that penicillin might act on bacteria by inhibiting with the normal function of SH-group of glutathione in the metabolism of the cell. Resenbrance of penicillin to gultathione in structure and the inactivation of penicillin by cysteine make us approve of the above inhibiting theory of SH-group. Galland (1947) and Schmidt (1947) reported that penicillin inhibited the activity of ribonuclease, Phosphatase, and mononucleotidase. Gale (1948) discovered that the gram positive bacteria had lost the power to uptake glutamic acid by ribonucleic acid in the medium contained penicillin: growth of gram positive organism was inhibited by the results that penicillin inhibited the uptake of amino acid byribonucleic acid, acting on ribonucleic acid of gram positive bacteria. Hotchkiss (1950) cultured S. aureus in the medium contained glucose and amino acids, and studied the effect of penicillin on protein synthesis. Peptide formation in living cells was inhibited by penicillin, while amono acid was utilized as before the addition of penicillin. On the otherhand, Binkley (1951) found penicillin interfered hydrolase of glutath one, and Hans (1950) reported penicillin inhibited the transpeptidation. On the machanism by which streptomycin acts. Cohen (1947) reported steptomycin made a irreversible complex with desoxyribonucleic acid, by the fact that desoxyribonucleic acid formed the precipitates with diguanide group of steptomycin. Zeller (1951) reported, on the other hand, streptomycin inhibited diamine oxidease. Geiger (1947) and Umbreit (1949) reported that steptomycin inhibited condensation of oxaloacetate and pyruvate in E. Coli and Oginsky et al (1949) reported steptomycin inhibited oxaloacetate-pyruvate reaction in Kreb's cycle. On the mechanism by which terramycin acts, Hahn & Wisseman (1951) reported that the formation of adaptive enzyme was inhibited by terramycin in E. Coli cultivated in the medium contained loctose, and that the protein synthesis was inhibited by terramycin. However, effects of antibiotics on amino acid metabolism have not been discussed much in spite of its important role in living cells. Especislly, effects of anitibiotics on higher plants have scarcely been reported. Here, to prove the effect of antibiotics on higher plants, and the mechanism by which, through amino acid metabolism, they promote or inhibit growth of plants, amino acids in bean plants treated with penicillin, streptomycin, and terramycin were analyzed by paper chromatography. And to clarify the antagonis of cysteine (as SH-group) against penicillin, through amino acid metabolism, amino acids in bean plants treated with cystene and penicillin, at the same time, were also analyzed.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.6 no.3
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• pp.341-350
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• 1996

The CdS thin films are grown on quartz plate by hot wall epitaxy. The source and substrate temperature is $590^{\circ}C$ and $400^{\circ}C$ respectively, and thickness of the film is $2.5\;\mu\textrm{m}$. Using extrapolation method of X-ray diffraction patterns for the CdS thin film, it was found hexagonal structure whose lattice constant a and c were $4.137\;{\AA}$ and $6.713\;{\AA}$, respectively. Hall effect on this sample was measured by the method of van der Pauw and studied on cattirer density and mobility depending on temperature. From hall data, the mobility was likely to be decreased by piezoelectric scattering in the temperature range 30 K to 200 K and by polar optical scattering in the temperature range 200 K to 293 K. In order to explore the applicability as a photoconductive cell we measured the sensitivity ($\gamma$), the ratio of photocurrent to darkcurrent (pc/dc), maximum allowable power dissipation (MAPD), spectral response and response time. The results indicated that for the samples annealed in Cu vapor the photoconductive characteristics are the best. Then we obtained the sensitivity of 0.99, the value of pc/dc of $9.42{\times}10^{6}$, the MAPD of 318 mW, and the rise and decay time of 10 ms and 9 ms, respectively.

• Korean Chemical Engineering Research
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• v.49 no.2
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• pp.250-255
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• 2011

In this study, by using the polymeric membrane separation process, the $CO_{2}/CH_{4}$ separation and $H_{2}S$ removal from biogas were performed in order to $CH_{4}$ purification and enrichment for the fuel cell energy source application. Fibers were spun by dry/wet phase inversion method. The module was manufactured by fabricating fibers after surface coating with silicone elastomer. The scanning electron microscopy(SEM) studies showed that the produced fibers typically had an asymmetric structure; a dense top layer supported by a porous, sponge substructure. The permeance of $CO_{2}$ and $CO_{2}/CH_{4}$ selectivity increased with pressure and temperature. Mixture gas with increasing pressure and temperature, removal efficiency of the $CO_{2}$ and $H_{2}S$ were decreased while concentration of $CH_{4}$ was increased up to 100%. When retentate flow rate was increased with the decreasing of pressure and temperature the $CH_{4}$ recovery ratio in retentate side was increased while the $CH_{4}$ purity in retentate side was decreased.

• JSTS:Journal of Semiconductor Technology and Science
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• v.16 no.1
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• pp.91-105
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• 2016

Carbon Nanotube Field-Effect Transistors (CNTFETs) have been studied as candidates for post Si CMOS owing to the better electrostatic control and high mobility. To enhance the immunity against short - channel effects (SCEs), the novel channel and gate engineered architectures have been proposed to improve CNTFETs performance. This work presents a comprehensive study of the influence of channel and gate engineering on the CNTFET switching, high frequency and circuit level performance of carbon nanotube field-effect transistors (CNTFETs). At device level, the effects of channel and gate engineering on the switching and high frequency characteristics for CNTFET have been theoretically investigated by using a quantum kinetic model. This model is based on two-dimensional non-equilibrium Green's functions (NEGF) solved self - consistently with Poisson's equations. It is revealed that hetero - material - gate and lightly doped drain and source CNTFET (HMG - LDDS - CNTFET) structure can significantly reduce leakage current, enhance control ability of the gate on channel, improve the switching speed, and is more suitable for use in low power, high frequency circuits. At circuit level, using the HSPICE with look - up table(LUT) based Verilog - A models, the impact of the channel and gate engineering on basic digital circuits (inverter, static random access memory cell) have been investigated systematically. The performance parameters of circuits have been calculated and the optimum metal gate workfunction combinations of ${\Phi}_{M1}/{\Phi}_{M2}$ have been concluded in terms of power consumption, average delay, stability, energy consumption and power - delay product (PDP). In addition, we discuss and compare the CNTFET-based circuit designs of various logic gates, including ternary and binary logic. Simulation results indicate that LDDS - HMG - CNTFET circuits with ternary logic gate design have significantly better performance in comparison with other structures.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.6
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• pp.80-88
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• 2008

In this paper, the block cipher algorithms, 3-DES(Triple Data Encryption Standard), AES(Advanced Encryption Standard), SEED, HASH(SHA-1), which are domestic and international standards, have been implemented as an integrated cryptographic engine for smart card applications. For small area and low power design which are essential requirements for portable devices, arithmetic resources are shared for iteration steps in each algorithm, and a two-level clock gating technique was used to reduce the dynamic power consumption. The integrated cryptographic engine was verified with ALTERA Excalbur EPXA10F1020C device, requiring 7,729 LEs(Logic Elements) and 512 Bytes ROM, and its maximum clock speed was 24.83 MHz. When designed by using Samsung 0.18 um STD130 standard cell library, the engine consisted of 44,452 gates and had up to 50 MHz operation clock speed. It was estimated to consume 2.96 mW, 3.03 mW, 2.63 mW, 7.06 mW power at 3-DES, AES, SEED, SHA-1 modes respectively when operating at 25 MHz clock. We found that it has better area-power optimized structure than other existing designs for smart cards and various embedded security systems.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.3
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• pp.59-67
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• 2013

Reed-Solomon (RS) codes are powerful error-correcting codes used in diverse applications. Recently, algebraic soft-decision decoding algorithm for RS codes that can correct the errors beyond the error correcting bound has been proposed. The algorithm requires very intensive computations for interpolation, therefore an efficient VLSI architecture, which is realizable in hardware with a moderate hardware complexity, is mandatory for various applications. In this paper, we propose an efficient architecture with low hardware complexity for interpolation in soft-decision list decoding of Reed-Solomon codes. The proposed architecture processes the candidate polynomial in such a way that the terms of X degrees are processed in serial and the terms of Y degrees are processed in parallel. The processing order of candidate polynomials adaptively changes to increase the efficiency of memory access for coefficients; this minimizes the internal registers and the number of memory accesses and simplifies the memory structure by combining and storing data in memory. Also, the proposed architecture shows high hardware efficiency, since each module is balanced in terms of latency and the modules are maximally overlapped in schedule. The proposed interpolation architecture for the (255, 239) RS list decoder is designed and synthesized using the DongbuHitek $0.18{\mu}m$ standard cell library, the number of gate counts is 25.1K and the maximum operating frequency is 200 MHz.

• Journal of the korean academy of Pediatric Dentistry
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• v.47 no.4
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• pp.406-415
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• 2020

Silver diamine fluoride (SDF) is an effective and efficient agent for arresting dental caries. It can be useful in treating children with behavioral or medical limitations. The purpose of this study was to evaluate the antimicrobial effect of SDF by using salivary biofilm. Pellicle-like saliva coated structure was prepared by using unstimulated saliva. For developing cariogenic biofilm, Streptococcus mutans was added to the mixture of pooled saliva and inoculated into a saliva coated glass or chamber. SDF was applied to cariogenic biofilm to evaluate the antimicrobial effect of SDF. As time passed, total bacteria and S. mutans were reduced after application of SDF (p < 0.000). Confocal laser scanning microscope also showed the increment of the ratio of dead cell. As a result of experiment using enamel and dentin of primary teeth, it was confirmed that the growth of cariogenic biofilm was inhibited when the SDF was treated (p = 0.029 each). This study showed excellent anti-microbial effect of SDF. And anti-caries effect in clinical practice can be expected.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.9
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• pp.931-935
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• 2012

In this study, we fabricate and investigate low-temperature solid oxide fuel cells with a ceramic substrate/porous metal/ceramic/porous metal structure. To realize low-temperature operation in solid oxide fuel cells, the membrane should be fabricated to have a thickness of the order of a few hundreds nanometers to minimize IR loss. Yttrium-doped barium zirconate (BYZ), a proton conductor, was used as the electrolyte. We deposited a 350-nm-thick Pt (anode) layer on a porous substrate by sputter deposition. We also deposited a 1-${\mu}m$-thick BYZ layer on the Pt anode using pulsed laser deposition (PLD). Finally, we deposited a 200-nm-thick Pt (cathode) layer on the BYZ electrolyte by sputter deposition. The open circuit voltage (OCV) is 0.806 V, and the maximum power density is 11.9 mW/$cm^2$ at $350^{\circ}C$. Even though a fully dense electrolyte is deposited via PLD, a cross-sectional transmission electron microscopy (TEM) image reveals many voids and defects.