• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.1
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• pp.76-79
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• 2016

This paper describes the successful development and the performance of X-band 50 W pulsed power amplifier using a 50 W GaN-on-SiC high electron mobility transistor. The GaN HEMT with a gate length of $0.25{\mu}m$ and a total gate width of 12 mm were fabricated. The X-band pulsed power amplifier exhibited an output power of 50 W with a power gain of 6 dB in a frequency range of 9.2~9.5 GHz. It also shows a maximum output power density of 4.16 W/mm. This 50 W GaN HEMT and X-band 50 W pulsed power amplifier are suitable for the radar systems and related applications in X-band.

• Journal of the Korean Chemical Society
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• v.32 no.6
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• pp.593-602
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• 1988

Polymer-supported crown ethers (Ps-CE) which can be used for phase-transfer catalyst (PTC) were synthesized for the purpose of allowing reusable function to ordinary crown ethers, and the kinetics of the liquid-solid-liquid triphase-catalyzed nucleophilic displacement reaction of iodide (aqueous phase) on 1-bromooctane (organic phase) using synthesized Ps-CE (solid) were studied. Ps-CE were obtained by grafting of hydroxymethyl crown ethers to 1~2% cross-linked chloromethylated polystyrene. All reactions followed a pseudo-first order dependency on the 1-bromooctane concentration and the observed rate constants $(k_{obsd})$ were linearly related to the molar equivalents of Ps-CE, and were subjected to the influence of cross-linking density of polymer backbone, solvent and the reaction temperature. The catalytic activity of Ps-CE was also compared with that of structurally similar soluble crown ethers, and used Ps-CE were easily recovered after the reaction by simple filtration and could be reused without loss of catalytic activity in the same anionic displacement reaction. Enthalpies and entropies of activation associated with the displacement were 10~20kcal $mol^{-1}, 20~55eu. respectively, and the free energy of activation was ~30kcal mol^{-1}$.

• Journal of Pharmaceutical Investigation
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• v.38 no.6
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• pp.373-380
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• 2008

In order to develop optimal formulation and iontophoresis condition for the transdermal delivery of levodopa, we have evaluated the effect of two permeation enhancers, ethanol and oleic acid in microemulsion, on transdermal delivery of levodopa. In vitro flux studies were performed at $33^{\circ}C$, using side-by-side diffusion cell and full thickness hairless mouse skin. Current density applied was $0.4\;mA/cm^2$ and current was off after 6 hours application. Levodopa was analysed by HPLC at 280 nm. The o/w microemulsions of oleic acid in buffer solution (pH 2.5 & 4.5) were prepared using oleic acid, Tween 80 and ethanol. The existence of microemulsion regions were investigated in pseudo-ternary phase diagrams. Contrary to our expectation, cumulative amount of levodopa transported from microemulsion (pH 2.5) for 10 hours was similar to that from aqueous solution in all delivery methods (passive, anodal and cathodal). When pH of the micro-emulsion was pH 4.5, cumulative amount of levodopa transported for 10 hours increased about 40% (anodal) to 50% (cathodal), when compared to that from aqueous solution. Flux from pH 4.5 microemulsion showed higher value than that from pH 2.5 in all delivery methods. These results seem to indicate that electroosmosis plays more dominant role than electrorepulsion in the flux of levodopa at pH 2.5. The effect of ethanol on iontophoretic flux was studied using pH 2.5 phosphate buffer solution containing 3% or 5% (v/v) ethanol. Flux enhancement was observed in passive and anodal delivery as the concentration of the ethanol increased. Without ethanol, cathodal delivery showed higher flux than anodal delivery. Anodal delivery increased the cumulative amount of levodopa transported 1.6 fold by 5% ethanol after 10 hours. However, in cathodal delivery, no flux enhancement of levodopa was observed during current application and only marginal increase in cumulative amount transported after 10 hours was observed by 5% ethanol. These results seem to be related to the decrease in dielectric constant of the medium and the lipid extraction of the ethanol, which decrease the electroosmotic flow, and thus decrease the flux. Overall, the results provide important insights into the role of electroosmosis and electrorepulsion in the transport of levodopa through skin, and provide some useful informations for optimal formulation for levodopa.

• Journal of Korean Society of Forest Science
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• v.98 no.3
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• pp.339-350
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• 2009

This study was carried out to investigate distributional condition of rare plants and useful plant resources, and to verify distributional patterns of understory vegetation associated with the upper layer's vegetation structure. Total 59 families, 160 genera, 218 kinds of vascular plants were identified at the study site including 6 rare plants designated by Korea Forest Service (Lloydia triflora Bak., Trillium kamtschaticum Pall., Lilium distichum Nakai, Anemone koraiensis Nakai, Iris odaesanensis Y.N. Lee, Viola diamantica Nakai). Twenty three species of useful plant resources were also identified at the site; 8 of them showed clustered distributions and the others were prone to scatter. Actual vegetation of this study area consisted of one natural community dominated by Quercus mongolica Fisch. and three disturbed communities of Larix kaempferi (Lamb.) Carriere, Abies holophylla Max. and/or a herbaceous vegetation resulting from forest removal and strong wind of mountain top. This classification was strongly supported by cluster analysis based on the surveyed plot data. Distributional patterns of understory vegetation within forest stand were somewhat related to overstory vegetation structure, but showed a different tendency according to site condition, species composition, and competitive pressure among understory vegetation. Therefore, in order to protect the important understory components as forest genetic resources, forest treatments such as density control of overstory should be implanted based on understanding of impact on understory's dynamics and growing condition.

• Journal of the Microelectronics and Packaging Society
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• v.8 no.3
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• pp.49-53
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• 2001

Vortical etching experiments of ($SrBi_2Ta_2O_9$)/Si thin films have been performed by using the inductively coupled plasma reactive ion etching (ICP-ME) apparatus. The purposes of these experiments are to get the effective area of vertical surface. Because this technology is very important to get good qualities of ferroelectric gate structure, capacitor and the minimum parasitic effects related to the excellent performances of the FRAM (Ferroelectric Random Access Memory) device. The reacting gases were Ar and $Cl_2$gases, and various $Ar/C1_2$flow ratios were used. The etching experiments were carried out at various RF powers such as 700, 700, 500W and at various DC powers such as 200, 150, 100, 50W, respectively. The maximum etch rate of $SrBi_2Ta_2O_9$/Si thin films was 1050 A/min at the $Ar/C1_2$ gas ratio of 20/16, RF power of 700 W and DC power of 200 W. From the SEM (scanning electron microscopy) image of the SBT thin films, the wall angle was as good as about $82^{\circ}$.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.19 no.5
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• pp.97-105
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• 2020

Recently, for a smart city, there is a demand for a technology for acquiring traffic information using an intelligent road infrastructure and managing it. In the meantime, various technologies such as loop detectors, ultrasonic detectors, and image detectors have been used to analyze road traffic information but these have difficulty in collecting various informations, such as traffic density and length of a queue required for building a traffic information DB for moving vehicles. Therefore, in this paper, assuming a smart city built on the basis of a camera infrastructure such as intelligent CCTV on the road, a solution for calculating the traffic DB of moving vehicles using Vision Tracking of road CCTV cameras is presented. Simulation and verification of basic performance were conducted and solution can be usefully utilized in related fields as a new intelligent traffic DB calculation solution that reflects the environment of road-mounted CCTV cameras and moving vehicles in a variable smart city road environment. It is expected to be there.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.20 no.4
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• pp.195-200
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• 2020

With the growing interest in fossil fuel depletion and environmental pollution, railroad cars operating in Korea are in progress as the conversion from diesel to electric vehicles expands. The photovoltaic system, which is applied as an example of the conversion of electric vehicles, is infinite and pollution-free, and can produce energy without generating hazards such as air pollution, noise, heat, and vibration, and maintain fuel transportation and power generation facilities. There is an advantage that is rarely needed. However, the amount of electricity produced depends on the amount of solar radiation by region, and the energy density is low due to the power generation of about 25㎡/ kWp, so a large installation area is required and the installation place has limited problems. In view of these problems, many studies have been applied to fuel cells in the railway field. In particular, the plan to link the fuel cell power generation system railroad power supply system must be linked to the power supply system that supplies power to the railroad, unlike solar and wind power. Therefore, it has a close relationship with railroad cars and the linkage method can vary greatly depending on the system topology. Therefore, in this paper, we study the validity through simulation modeling related to linkage analysis according to system topology.

• International Journal of Oral Biology
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• v.32 no.4
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• pp.119-125
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• 2007

Dlx3 is a homeodomain protein and is known to play a role in development and differentiation of many tissues. Deletion of four base pairs in DLX3 (NT3198) is causally related to tricho-dento-osseous (TDO) syndrome (OMIM #190320), a genetic disorder manifested by taurodontism, hair abnormalities, and increased bone density in the cranium. The molecular mechanisms that explain the phenotypic characteristics of TDO syndrome have not been clearly determined. In this study, we examined phenotypic characteristics of wild type DLX3(wtDlx3) and 4-BP DEL DLX3 (TDO mtDlx3) in C2C12 cells. To investigate how wtDlx3 and TDO mtDlx3 differentially regulate osteoblastic differentiation, reporter assays were performed by using luciferase reporters containing the promoters of alkaline phosphatase, bone sialoprotein or osteocalcin. Both wtDlx3 and TDO mtDlx3 enhanced significantly all the reporter activities but the effect of mtDlx3 was much weaker than that of wtDlx3. In spite of these differences in reporter activity, electrophoretic mobility shift assay showed that both wtDlx3 and TDO mtDlx3 formed similar amounts of DNA binding complexes with Dlx3 binding consensus sequence or with ALP promoter oligonucleotide bearing the Dlx3 binding core sequence. TDO mtDlx3 exhibits a longer half-life than wtDlx3 and it corresponds to PESTfind analysis result showing that potential PEST sequence was missed in carboxy terminal of TDO mtDlx3. In addition, co-immunoprecipitation demonstrated that TDO mtDlx3 binds to Msx2 more strongly than wtDlx3. Taken together, though TDO mtDlx3 acted as a weaker transcriptional activator than wtDlx3 in osteoblastic cells, there is possibility that during in vivo osteoblast differentiation TDO mtDlx3 may antagonize transcriptional repressor activity of Msx2 more effectively and for longer period than wtDlx3, resulting in enhancement of osteoblast differentiation.

• Journal of Korean Society of Forest Science
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• v.95 no.6
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• pp.711-715
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• 2006

This study was conducted to clarify the characteristics of habitats and small rodent populations between remnant removed and left areas caused by different remnant treatment on forest floor in fired coniferous forest, Mt Gumbong, Samcheok, Korea, There were higher value of variables of understory coverage, snags, downed coarse woody debris (CWD) in natural restored area. Mean number of captured individuals and body weights of Apodemus peninsulae and Eothenomys regulus were more higher in remnant left area than in removed area, The differences in density and body weight of small rodents would be related with habitats between both study areas. The remove of remnant trees on the forest floor would not be good for small rodents. The more detailed and long-term researches would be needed for proper restoration in fired forest area.

• Journal of The Korean Astronomical Society
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• v.47 no.2
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• pp.77-86
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• 2014

Using a cosmological ${\Lambda}CDM$ simulation, we analyze the differences between the widely-used spin parameters suggested by Peebles and Bullock. The dimensionless spin parameter ${\lambda}$ proposed by Peebles is theoretically well-justified but includes an annoying term, the potential energy, which cannot be directly obtained from observations and is computationally expensive to calculate in numerical simulations. The Bullock's spin parameter ${\lambda}^{\prime}$ avoids this problem assuming the isothermal density profile of a virialized halo in the Newtonian potential model. However, we find that there exists a substantial discrepancy between ${\lambda}$ and ${\lambda}^{\prime}$ depending on the adopted potential model (Newtonian or Plummer) to calculate the halo total energy and that their redshift evolutions differ to each other significantly. Therefore, we introduce a new spin parameter, ${\lambda}^{\prime\prime}$, which is simply designed to roughly recover the value of ${\lambda}$ but to use the same halo quantities as used in ${\lambda}^{\prime}$. If the Plummer potential is adopted, the ${\lambda}^{\prime\prime}$ is related to the Bullock's definition as ${\lambda}^{\prime\prime}=0.80{\times}(1+z)^{-1/12}{\lambda}^{\prime}$. Hence, the new spin parameter ${\lambda}^{\prime\prime}$ distribution becomes consistent with a log-normal distribution frequently seen for the ${\lambda}^{\prime}$ while its mean value is much closer to that of ${\lambda}$. On the other hand, in case of the Newtonian potential model, we obtain the relation of ${\lambda}^{\prime\prime}=(1+z)^{-1/8}{\lambda}^{\prime}$; there is no significant difference at z = 0 as found by others but ${\lambda}^{\prime}$ becomes more overestimated than ${\lambda}$ or ${\lambda}^{\prime\prime}$ at higher redshifts. We also investigate the dependence of halo spin parameters on halo mass and redshift. We clearly show that although the ${\lambda}^{\prime}$ for small-mass halos with $M_h$ < $2{\times}10^{12}M_{\odot}$ seems redshift independent after z = 1, all the spin parameters explored, on the whole, show a stronger correlation with the increasing halo mass at higher redshifts.