• JSTS:Journal of Semiconductor Technology and Science
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• v.5 no.2
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• pp.83-88
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• 2005

The interface-states between the top silicon layer and buried oxide layer of nano-SOI substrate were developed. Also, the effects of thermal treatment processes on the interface-state distributions were investigated for the first time by using pseudo-MOSFETs. We found that the interface-state distributions were strongly influenced by the thermal treatment processes. The interface-states were generated by the rapid thermal annealing (RTA) process. Increasing the RTA temperature over $800^{\circ}C$, the interface-state density considerably increased. Especially, a peak of interface-states distribution that contributes a hump phenomenon of subthreshold curve in the inversion mode operation of pseudo-MOSFETs was observed at the conduction band side of the energy gap, hut it was not observed in the accumulation mode operation. On the other hand, the increased interface-state density by the RTA process was effectively reduced by the relatively low temperature annealing process in a conventional thermal annealing (CTA) process.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1997.10a
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• pp.66-75
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• 1997

This study was undertaken to investigate tribology characteristics of the alumina ceramics($Al_2O_3$) of the various purity for the variation of ambient condition such as air and vacuum. The wear test was carried out under different experimental condition using the wear test device, which was designed for this study, and in which the annular surface of wear testing specimens as well as mate specimen made of STB2 steel, were subjected to sliding speed, applied load and the sliding distance. The results obtained were as follows. As the ambient pressure decreases, the friction coefficient increases because the protective layer made of absorption due to decrease of the amount of ambient gas can not be formed. As the friction coefficient paticularly for 85% alumina lower than 95% and 99.7% in the alumina purity increases by an influence of heat accumulation caused by small elastic modulus and thermal conductivity. The friction surface of ceramics can be protected in the air by the influence of the oxides transfered from STB2. However, in the vacuum, the protective layer made of the absorption substance can not be formed due to the decrease of ambient gas.

• Journal of information and communication convergence engineering
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• v.13 no.4
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• pp.257-263
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• 2015

In this study, organic field-effect transistors (OFETs) using a copper phthalocyanine (CuPc) material as an active layer and SiO₂ as a gate insulator were fabricated with varying active layer thicknesses and channel lengths. Further, using a thermal evaporation method in a high-vacuum system, we fabricated a CuPc FET device of the top-contact type and used Au materials for the source and drain electrodes. In order to discuss the channel formation and FET characteristics, we observed the typical current-voltage characteristics and calculated the threshold voltage of the CuPc FET device. We also found that the capacitance reached approximately 97 pF at a negative applied voltage and increased upon the accumulation of carriers at the interface of the metal and the CuPc material. We observed the typical behavior of a FET when used as an n-channel FET. Moreover, we calculated the threshold voltage to be about 15-20 V at V_DS = -80 V.

• KSBB Journal
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• v.15 no.5
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• pp.514-520
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• 2000

Simultaneous nitrification and denitrification of ammonia and organic compounds-containing wastewater were performed in a fluidized bed biofilm reactor with polysulfone(PS) hollow fiber as a double layer biomass carrier. The PS hollow fiber fragment has both aerobic and anoxic environments for the nitrifiaction and denitrification at the shell and lumen-side respectively. The reactor system showed about 80% nitrification efficiency stably throughout the ammonia load conditions applied in the experiment. Denitrification efficiency depended on organic load and C/N ratio. High free ammonia concentration and low dissolved oxygen resulted in nitrite accumulation which leads to enhance organic carbon efficiency in denitrification when compared to nitrate denitrification. The simultaneous nitrification and denitrification reactor system has an economic advantages in reduced chemical cost of organic carbon for denitrification as well as compact reactor configuration.

• Journal of the Korean Vacuum Society
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• v.4 no.S2
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• pp.156-162
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• 1995

For a stimulating neural electrode, the charge density should be as large as possible to provide adequate stimulation of the nervous system while allowing for miniaturization of the electrode. Since iridium oxide is able to produce high charge densities while preventing undesirable reactions due to charge storage, it has become a promising material for neural prostheses. Successful production of stable Ir and Ir oxide films on various substrates now limits the use of this material. Ir was deposited on two differently prepared surface of (mirror finish, passivation) surgical Ti-6AI-4V with several methods. Ion beam mixing of sputter deposited Ir films on passivated Ti-6AI-4V produced stable and good adherent Ir films. It was found that the increase in charge density of pure Ir on continuous cyclingis due to the accumulation of the oxide phase ( associated with a large surface area) in which the valence state of iridium changes and the double-layer capacitance increases. This study also showed that the double layer capacitance is equally or even more responsible for the high charge density of anodically formed Ir oxide.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.9 no.5
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• pp.50-59
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• 2006

This study was initiated to investigate soil chemical properties under different soil systems. Data such as soil acidity(pH), electrical conductivity(EC), organic matter content(OMC), and cation exchange capacity(CEC) were analyzed with samples from multi-layer, USGA, and mono-layer systems. N, P, K and micronutrients were also measured. Multi-layer system was built up to 60-cm depth with rootzone layer, intermediate layer and two drainage layers. USGA system 45 centimeters deep was constructed with rootzone layer, intermediate layer and drainage layer. Mono-layer system, however, was made only with a 30-cm rootzone layer. Differences were observed in soil pH, EC, OMC, CEC and micronutrients. Soil pH was acceptable for turfgrass growth a year after establishment, being 5.5 to 6.5 in the study. Differences were greatly observed for EC among soil systems. Values of EC for multi-layer, USGA, and mono-layer systems were 39.79, 31.26 and 103.54 uS/em, respectively. The increase rate was approximately 4 to 8 times greater with mono-layer system than those with other two systems. Therefore, it was necessary to avoid micronutrient deficiency such as Fe, Mn etc. through an effective management program in mono-layer system because of its faster potential feasibility of salt accumulation. The greatest OMC was associated with USGA system, being 0.97% which was 11% over that of the other systems. Slight differences were observed for CEC among them. Mono-layer system produced 1.45 me/100g, 10.3% and 8.9% lower in CEC than those of multi-layer and USGA system, respectively. Micronutrients such as Fe, Zn, and Mn etc. were below the level required for turf growth, regardless of soil systems. It was considered that one year after turf establishment was not enough to build up micronutrients in sand-based soil systems to the normal level for a turf growth. These results demonstrate that intensive management program including grow-in concept fertilization should be integrated into sand-based soil systems, even after a year in establishment. Regular nutrient monitoring by soil analyses is a strong necessity to decide the kinds and amount of fertilizer. Also, strategic management program must be selectively employed according to sports turf soil systems.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.5
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• pp.838-848
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• 1992

The objective of the study is to provide a theoretical tools for analyzing the fracture of leyered composites with a center crack. It is assumed that the composite is composed of successive accumulation of the fiber layer and resin layer with the fiber layer being perfectly bonded to the resin layer except the region of a center crack. In-plane shear loading (Mode II) and the anti-plane shear loading (Mode III) are considered separately. Boundary value problems are formulated by using a plane theory of elasticity and governing equations are reduced to a Fredholm integral equation of a second kind. The equation is solved numerically and the stress intensity factors are obtained. The normalized Mode II and Mode III stress intensity factors are evaluated for various combinations of material properties and for various geometrical parametes.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.9
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• pp.1158-1165
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• 2021

This paper proposes a CNN accelerator which is optimized Pooling layer operation incorporated in Multiplication And Accumulation(MAC) to reduce the memory size. For optimizing memory and data path circuit, the quantized 8bit integer weights are used instead of 32bit floating-point weights for pre-training of MNIST data set. To reduce chip area, the proposed CNN model is reduced by a convolutional layer, a 4*4 Max Pooling, and two fully connected layers. And all the operations use specific MAC with approximation adders and multipliers. 94% of internal memory size reduction is achieved by simultaneously performing the convolution and the pooling operation in the proposed architecture. The proposed accelerator chip is designed by using TSMC65nmGP CMOS process. That has about half size of our previous paper, 0.8*0.9 = 0.72mm². The presented CNN accelerator chip achieves 94% accuracy and 77us inference time per an MNIST image.

• Microbiology and Biotechnology Letters
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• v.1 no.1
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• pp.13-18
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• 1973

For the production of Nucleic acid derivatives by microorganisms, adenineless mutants were induced from Bacillus subtilis with the mutagens, ultraviolet rays and diethylsulfate. And total strains of 62 adenineless mutants were isolated. These mutants were found to have an ability of accumulating u. v. absorbing substances in the culture broth. They were analyzed to be hypoxanthine, uracil, and other unknown compound by means of two dimensional thin layer chromatography, u. v. absorption spectra, and I. R. absorption spectrum. Mutant BS-137 was screened out to accumulate hypoxanthine, which was isolated from the culture broth through activated carbon column and recrystallize from cold water. The effect of the medium compositions on hypoxanthine accumulation were examined for the mutant BS-137. Glucose appeared to be the best carbon source, but molasses could be substitute for it, NaNO$_3$ and yeast extract were especially good sources of nitrogen.

• Journal of Korean Society of Water and Wastewater
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• v.35 no.3
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• pp.197-204
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• 2021

In MBR, extracellular polymeric substance (EPS) is known as an important factor of fouling; soluble EPS (sEPS) affects internal contamination of membrane, and bound EPS (bEPS) affects the formation of the cake layer. The production of EPS changes according to the composition of influent, which affects fouling characteristics. Therefore, in this study, the effects of the F/M ratio on the sEPS concentration, bEPS content, and fouling were evaluated. The effects of F/M ratio on the amount and composition of EPS were confirmed by setting conditions that were very low or higher than the general F/M ratio of MBR, and the fouling occurrence characteristics were evaluated by filtration resistance distribution. As a result, it was found that the sEPS increased significantly with the increase of the F/M ratio. When the substrate was depleted, bEPS content decreased because bEPS was hydrolyzed into BAP and seemed to be used as a substrate. In contrast, when the substrate is sufficient, UAP (utilization-associated products) was rapidly generated in proportion with the consumption of the substrate. UAP has a relatively higher Protein/Carbohydrate ratio (P/C ratio) than BAP, and this means, it has a higher adhesive force to the membrane surface. As a result, UAP seems like causing fouling rather than BAP (biomass-associated products). Therefore, R_f (Resistance of internal contamination) increased rapidly with the increase of UAP, and R_c (Resistance of cake layer) increased with the accumulation of bEPS in proportion, and as a result, the fouling interval was shortened. According to this study, a high F/M ratio leads to an increment in UAP generation and accumulation of bEPS, and by these UAP and bEPS, membrane fouling is promoted.