• Journal of IKEEE
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• v.20 no.3
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• pp.220-225
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• 2016

In this paer, low on-resistance and high-power trench gate MOSFET (Metal-Oxide-Silicon Field Effect Transistor) incorporating current sensing FET (Field Effect Transistor) is proposed and evaluated. The trench gate power MOSFET was fabricated with $0.6{\mu}m$ trench width and $3.0{\mu}m$ cell pitch. Compared with the main switching MOSFET, the on-chip current sensing FET has the same device structure and geometry. In order to improve cell density and device reliability, self-aligned trench etching and hydrogen annealing techniques were performed. Moreover, maintaining low threshold voltage and simultaneously improving gate oxide relialility, the stacked gate oxide structure combining thermal and CVD (chemical vapor deposition) oxides was adopted. The on-resistance and breakdown voltage of the high density trench gate device were evaluated $24m{\Omega}$ and 100 V, respectively. The measured current sensing ratio and it's variation depending on the gate voltage were approximately 70:1 and less than 5.6 %.

• Nuclear Engineering and Technology
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• v.13 no.2
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• pp.85-96
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• 1981

A preliminary study of the isotope hydrology of the Han River Valley is presented. This investigation is part of a project whose overall aim is to relate the levels of heavy metal ions to the dynamics of the groundwater movement in order to establish (i) whether there is any evidence for the deterioration in groundwater quality associated with the release of industrial effluents and (ii) if so, to determine the migration path-ways. Evidence is adduced that the recharge mechanism is principally determined by the degree of urbanisation. In the metropolitan area of Seoul, river recharge dominates probably due to the combined effects of reduced infiltration and increased pumpage. In the inter-urban region, the major source of recharge is local precipitation. During the spring sampling period when the river levels were low. evidence was obtained for appreciable groundwater infiltration in the vicinity of the upstream transect. No significant correlations were observed between the levels of heavy metals in the groundwater, and the recharge mechanism, the distance from the river or the electrical conductivity of the samples.

• Journal of Adhesion and Interface
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• v.2 no.4
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• pp.10-23
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• 2001

In order to increase the lower values of % grafting and monomer conversion in the emulsion graft polymerization of methylmethacrylate(MMA) onto sodium alginate (SA; a polymer electrolyte) with alginic acid-g-PMMA, the graft polymerization with water soluble (methanol and acetone) and insoluble solvents was carried out using a varity of solvent amounts and agitating rates. And some physical properties of the graft polymer were also investigated. In the polymerizations with water insoluble solvent, there were pronounced improvements in both % grafting and MMA conversion by the promotion of MMA diffusion from the core to the SA adsorpted on the outer layer of particle and that of MMA complex formation with SA. And the effect was larger for the solvents (cyclohexane, decalin) which do not dissolve PMMA. On the other hand, in the polymerization with water soluble solvent, there was an significant increase in MMA conversion and a considerable increase in the % grafting by the destruction of electrical double layer around the SA chains, abstracting the hydrated water in the layer and the effect was more potential in the case of methanol which is a precipitant of PMMA.

• 한국지구물리탐사학회:학술대회논문집
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• 1999.08a
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• pp.92-116
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• 1999

Tomographic approaches to image underground structure using electrical properties, can be divided into DC resistivity, electromagnetic, and radar tomography, based on the operating frequency. DC resistivity and radar tomography methods have been recently applied to site investigation for engineering purpose in Korea. This paper review these two tomography methods, through the case histories acquired in Korea. As another method of borehole radar survey, borehole radar reflection method is included, and its inherent problem and solution are discussed, how to find the azimuth angle of reflector using direction-finding-antenna. Since the velocity anisotropy of radar wave has been commonly encountered in field data, anisotropic radar tomography is discussed in this paper. In DC resistivity tomography, two subjects are focussed, electrode arrays, and borehole effect owing to the conductive fluid in borehole. Using the numerical modeling data, various kinds of electrode ways are compared, and borehole effect is illustrated. Most of the case histories presented in this paper are compared with known geology, core logging data, and/or Televiewer images.

• Journal of the Korea Society for Simulation
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• v.26 no.2
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• pp.1-8
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• 2017

High Level Architecture(HLA) is a specification for interoperation among heterogeneous simulators which are executed in a distributed environment. HLA originally allows many federates to join in a federation using a single RTI(Run-Time Infrastructure). As the target systems become more complex, the need for the interoperation of federations, performed in a RTI-RTI interoperation environment, has been growing. It can be performed by the confederation interface with the agents, which subrogate the API calls and callbacks of each federation. The existing studies have assumed that the object models of each federation are based on same HLA standard and their object descriptions are equal. Because the existing federations are usually not under this assumption, this paper proposes the integration process of object models for the federation interoperation environment. To integrate the object models for the interoperation of federations, this process resolves the differences of HLA standards, provides conversion process between objects with different descriptions and excludes the security objects. We expect that this process enhances the reusability and effectiveness of interoperation of federations in various domains.

• Molecules and Cells
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• v.39 no.4
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• pp.352-357
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• 2016

Vertebrate neurogenesis requires inhibition of endogenous bone morphogenetic protein (BMP) signals in the ectoderm. Blocking of BMPs in animal cap explants causes the formation of anterior neural tissues as a default fate. To identify genes involved in the anterior neural specification, we analyzed gene expression profiles using a Xenopus Affymetrix Gene Chip after BMP-4 inhibition in animal cap explants. We found that the xCyp26c gene, encoding a retinoic acid (RA) degradation enzyme, was upregulated following inhibition of BMP signaling in early neuroectodermal cells. Whole-mount in situ hybridization analysis showed that xCyp26c expression started in the anterior region during the early neurula stage. Overexpression of xCyp26c weakly induced neural genes in animal cap explants. xCyp26c abolished the expression of all trans-/cis-RA-induced posterior genes, but not basic FGF-induced posterior genes. Depletion of xCyp26c by morpholino-oligonucleotides suppressed the normal formation of the axis and head, indicating that xCyp26c plays a critical role in the specification of anterior neural tissue in whole embryos. In animal cap explants, however, xCyp26c morpholinos did not alter anterior-to-posterior neural tissue formation. Together, these results suggest that xCyp26c plays a specific role in anterior-posterior (A-P) neural patterning of Xenopus embryos.

• Korean Journal of Materials Research
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• v.8 no.10
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• pp.925-930
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• 1998

EPMA and XPS on $Bi_2Sr_2-\chi_LCa_1+\chi_LCu_2O_{8+d}$($\chi_L$ = 0.01, 0.2, 0.3, 0.4, 0.5, 0.6) films by LPE method were performed in order to investigate Sr and Ca distributions in SrO- and Ca-layers. It is found that $T_C^{zero}$ carrier concentration and lattice parameter c monotonically decreases with increasing $\chi_L$. Sr and Ca contents in Ca-layer change in proportion to that in melt. On the other hand, in SrO-layer, Ca content strongly depends on Sr content in that layer and not on Ca content in melt. Since deficiency in SrO-layer increases and $T_C^{zero}$ creases with $\chi_L$,t is found that the deficiencies of Sr and Ca atoms in the SrO-layer has a influence on reducing $T_C^{zero}$.

• Korean Chemical Engineering Research
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• v.45 no.3
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• pp.242-248
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• 2007

For an optimal design of automotive electric system, it is important to have a reliable modeling tool to predict the charge-discharge behaviors of the automotive battery. In this work, a two-dimensional modeling was carried out to predict the charge-discharge behaviors of a 12-V automotive lead-acid battery. The model accounted for electrochemical kinetics and ionic mass transfer in a battery cell. In order to validate the modeling, modeling results were compared with the experimental data of the charge-discharge behaviors of a lead-acid battery. The discharge behaviors were measured with three different discharge rates of C/5, C/10, and C/20 at operating temperature of $25^{\circ}C$. The batteries were charged with constant current of 30A until the charging voltage reached to a predetermined value of 14.24 V and then the charging voltage was kept constant. The discharge and charge curves from the measurements and modeling were in good agreement. Based on the modeling, the distributions of the electrical potentials of the solid and solution phases, the porosity of the electrodes, and the current density within the electrodes as well as the acid concentration can be predicted as a function of charge and discharge time.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.4
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• pp.360-370
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• 2013

When best-effort traffic users are supported in a downlink small-cell network, conventional schemes assign the channels experiencing low co-channel interference at each base station and provide a better downlink performance to the user near its serving base station, so that conventional schemes are not suitable to fairly support all users. In this paper, we propose a decentralized frequency reuse scheme for a small-cell network, where each basestation chooses a set of channels to fairly support the best-effort traffic users regardless of the distances to their serving basestation. After performing the conventional scheme that each basestation selects the channels which are not used in its adjacent basestations, it updates assigned channels improving the performance of low throughput users in a fully distributed manner with mitigating the overall throughput performance loss. The computer simulation demonstrates that the average throughput performance of the 10th percentile throughput users is improved up to 15% in some case compared to that of the conventional scheme, while allowing the overall throughput loss around 3%.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.8
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• pp.511-519
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• 2017

In this study, we have performed tests to improve the productivity of hybrid solar stills, which can be operated by solar thermal energy and/or waste heat of exhaust gas from electrical generators. The experimental apparatus is a hybrid solar still with a $1m{\times}2m$ collecting area, which consists of a conventional simple solar still and a vertical multi-effect diffusion(MED) section. The experiments were conducted under various operating conditions, with two identical hybrid solar stills, using solar radiation as the energy source. The results of the tests showed that the yield of the hybrid solar still depends on the various operating conditions. Insulation at the side glasses and a lower basin seawater level increased the productivity of the hybrid solar still. Reflecting fins with less than 47% reflectivity unexpectedly decreased the total productivity. However, the various feeding flow rate of the seawater into MED part did not show clear effects on productivity in the tested range.