• Polymer(Korea)
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• v.30 no.5
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• pp.407-411
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• 2006

The SiC-based ceramic nanopatterns were prepared by placing polydimethylsiloxane (PDMS) mold from DVD master on the spincoated polyvinylsilaeane (PVS) or allylhydridopolycaybosilane (AHPCS) as ceramic precursors to fabricate line pattern via UV-nanoimprint lithography (UV-NIL), and subsequent pyrolysis at $800^{\circ}C$ in nitrogen atmosphere. As the dimensional change of polymeric and ceramic patterns was comparatively investigated by AFM and SEM, the shrinkage in height was 38.5% for PVS derived pattern and 24.1% for AHPCS derived pattern while the shrinkage in width was 18.8% for PVS and 16.7% for AHPCS. It indicates that higher ceramic yield of the ceramic precursor resulted in less shrinkage, and the strong adhesion between the substrate and the pattern caused anisotropic shrinkage. This preliminary work suggests that NIL is a promissing route for fabricating ceramic MEMS devices, with the development on the shrinkage control.

• Korean Journal of Optics and Photonics
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• v.13 no.6
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• pp.559-563
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• 2002

We measure the 3-dimensional temporal behavior of the light emitted from the discharge cell of a plasma display panel (PDP) by using a scanned point detecting system. The light signal detected by a PM tube is sent to the oscilloscope, and the oscilloscope is connected to a PC with GPIB. From the resultant temporal behaviors, we could analyze the discharge characteristics of the panel with a Ne-Xe (4%) mixing gas at a 400 torr pressure. The top view of the panel shows that discharge moves from the inner edge of the cathode electrode to the outer cathode electrode, forming an arc shape. The side view of the panel shows that the light is detected up to 150 $\mu\textrm{m}$ up the barrier rib. After a trigger pulse is applied, peak intensity is detected at 730 ns and peak intensity position is located at the center of the ITO electrodes.

• The Journal of the Petrological Society of Korea
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• v.26 no.1
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• pp.83-91
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• 2017

In order to determine the runout range of pyroclastic density currents on Jeju island, lava dome collapse on 8 locations of outer rim of Baekrokdam crater were simulated by TITAN2D numerical simulation program. We set parameters as internal friction angle as $30^{\circ}$ and bed friction angle as $20^{\circ}$ to control velocity of currents occurred by lava dome collapse. Then we set the height and radius of lava dome, initial speed of collapse and simulation times. And we carried out numerical simulations for a total of 96 scenarios. The result shows that the maximum runout distance was 13.4 km in case of lava dome collapse. This study can be used database for manufacturing of hazard map to minimize damages caused by pyroclastic density currents occurred on Jeju island.

• Journal of the Korean Society of Hazard Mitigation
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• v.7 no.3
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• pp.69-78
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• 2007

In this study, a time-dependent aspect of an embankment failure is considered to simulate a flood inundation map and calculate overtopping discharge induced by an embankment failure. A numerical model has been developed by solving the two dimensional nonlinear shallow water equations with a finite volume method on unstructured grids. To analyze a Riemann problem, the HLLC approximate Riemann solver and the Weighted Averaged Flux method are employed by using a TVD limiter and the source term treatment is also employed by using the operator splitting method. Firstly, the numerical model is applied to a dam break problem and a sloping seawall. Obtained numerical results show good agreements with experimental data. Secondly, the model is applied to a flow induced by an embankment failure by assuming that the width and elevation of embankment are varied with time-dependent functions. As a result of the comparison with each numerical overtopping discharge, established flood inundation discharges in the previous studies are overestimated than the result of the present numerical model.

• KDI Journal of Economic Policy
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• v.21 no.2
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• pp.3-54
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• 1999

1997년의 경제위기는 근본적으로 많은 차입금에도 불구하고 장기간에 걸쳐 낮은 수익성을 보인 기업들이 불황에 직면하여 도산위험이 급증함으로써 발생한 것으로 판단된다. 그러면, 기업들의 수익성은 왜 이렇게 낮은 것일까? 본 연구는 지배대주주와 소액주주간의 갈등이 기업의 수익성을 저하시킨 한 원인으로 작용했다는 가설을 실증적으로 규명하고자 한다. 우리나라 기업들, 특히 기업집단의 경우 지배대주주의 개인소유지분은 높지 않지만 기업경영에 대한 통제력은 매우 강하다. 기업경영에 대한 감시와 책임경영이 확립되지 않는 경제에서 지배대주주가 기업자산을 개인적 이익에 따라 운영하는 경우 편익은 독점하지만 이에 따른 수익성 하락 등의 비용은 다른 주주와 소유 지분율에 따라 공유하게 되므로 사적이익을 추구할 유인이 크다. 본 연구는 1992년부터 1997년까지의 공기업 및 금융기관을 제외한 외부감사대상기업의 재무자료를 기초로 영업이익률, 경상이익률, 그리고 순이익률이 주주간의 이해상충에 의해 어떻게 영향을 받았는가를 분석하였다. 수익성 분석에 있어 상장여부, 자산운영(관계회사 및 비관계회사에 대한 투자), 재벌소속 여부, 기업규모, 재무구조 그리고 산업적 특성 및 기업의 경영 및 사업 전략적 특성을 제어하였다. 다른 조건이 동일하다고 가정하면 상장된 기업의 수익성은 비상장기업보다 낮다. 상장기업의 경우는 대주주의 소유지분이 낮은 반면에 외부주주의 비중이 높기 때문에 대주주가 개인의 이익을 추구하고자 하는 유인이 강하게 작용한 결과로 판단된다. 또한 재벌에 소독된 기업의 수익성은 독립기업들의 수익성보다 낮을 뿐만 아니라 계열회사의 유가증권 및 대여금 등에 대한 투자가 증가할수록 기업의 경상이익률 및 순이익률이 낮아진다. 반면에 비관계회사에 대한 투자자산은 경상이익률 및 순이익률을 높이는 것으로 나타났다. 재벌에 소속된 상장회사가 관계회사에 투자하는 경우는 투자기업의 수익성이 더욱 낮아지는 것으로 나타났다. 관계회사에 대한 투자는 수익성에 기초한 투자가 아니며 대주주의 지분이 낮은 상장기업에서 소액주주의 이익에 반하여 계열사에 대한 투자형태로 자원이 이전되고 있음을 시사한다. 본 논문의 분석 결과는 외부주주와 내부주주간의 이해상충이 기업의 수익성을 저하시킨다는 가설과 일관된다. 따라서 대주주가 개인적 이익을 추구하고자 하는 유인을 견제하고 소액주주의 권리를 강화하도록 지배구조를 확립해야 할 것이다.

• The Transactions of the Korean Institute of Power Electronics
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• v.10 no.4
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• pp.380-387
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• 2005

We report the performance of an open-frame type low-voltage high-current DC-DC converter module developed using an active clamp forward converter circuit and single ended rectifier. The converter module is designed with the specifications of an 3.3V output voltage, 30A output current, 100W output power and 36-75V input voltage. The synchronous rectifier is used to reduce the conduction loss at high current level and constant current control using precision PCB resistance is adapted to enhance the over current protection function in the system configuration. A prototype converter module is successfully implemented within 8mm height and quarter brick size (58x37mm) and recorded an $95W/in^3$ power density, 90.6$\%$ efficiency and 0.07$\%$ voltage regulation for the entire Input voltage range, thereby demonstrating its application potentials to future telecommunication electronics.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.11
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• pp.7949-7956
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• 2015

This paper introduced the RAR(Reinforced Abutment for Railroads) to reduce settlement of transitional zone and horizontal displacement of abutment by constructing backfill before abutment. We expect that it has more economical and better performance which was validated by numerical analyses. First, transitional zone settlements and horizontal displacements of existing abutment were evaluated for various heights and ground conditions by using finite element analysis program. Then, numerical analyses of it under the same conditions were performed and its results were compared with existing abutment's ones. From the numerical analysis, we found that the responses(settlement and horizontal displacement) of transitional zone of the RAR is about 20% and 34% of one of existing abutment due to the effect of backfill stabilizing. We expected that the RAR having small foundations could be economic way to construct abutment with the control of responses such as, settlement, horizontal displacement, and earth pressure.

• The KIPS Transactions:PartA
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• v.12A no.2 s.92
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• pp.171-180
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• 2005

In distributed systems data are replicated and stored at several nodes to increase the availability and overall performance. Here Quorum protocol doffing a certain set of replicas required for read/write operation exists for global concurrency control. One of the representative replication Protocols - the Tree Quorum protocol - has a drawback of rapidly growing number of replicas as the level increases, while the Grid protocol requires the same operation cost even without any failure. In this paper, thus, we propose a new replication protocol called hybrid protocol which capitalizes the merits of the existing protocols and solves the problems of them at the same time. The proposed hybrid protocol has very low operation cost in the absence of failure like the tree quorum protocol, and has relatively lower operation cost and higher availability than existing protocols when failure occurs by employing tree architecture as the overall organization while each level of the tree is organized as a row of a grid architecture. It is thus effective to be applied to survival storage system. We conduct cost and availability analysis of the proposed protocol through mathematical modeling, and response time and throughput are compared with those of the Tree Quorum protocol through computer simulation.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.2 no.2
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• pp.69-77
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• 2009

Small size and low profile antenna for mobile vehicular-top-mounted is needed in satellite communication services such as DBS, Satellite Internet and VSAT. In middle latitudes, the development of an array antenna which has the conformal, low profile and 45 degree beam tilted configuration, and has the high gain with sharp beamwidth, low sidelobe and low loss is required for Ka band satellite communication. In this paper, in order to meet with these performances, an array antenna consisting of the vertical polarized waveguide longitudinal slots based on the leaky-wave mode of traveling wave antenna is proposed. Especially, for the lower sidelobe level the radiation power control using a design method of the different slot width is proposed. An array antenna consisting of 32 leakywave elements is showing 34.4 dBi of gain, 3.6 degree of beamwidth, below than -25 dB of sidelobe level, 43 degree of beam tilt angle in center frequency 20.0 GHz. Feed network designed by waveguide cooperated feed shows good performance of wideband and low loss.

• Journal of Korea Water Resources Association
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• v.31 no.3
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• pp.279-290
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• 1998

The height and speed of the shock wave are critical data in flood-control operations or in the design of channel walls and bridges along rivers with high flow velocities. Therefore, a numerical model is needed for simulating flow discontinuity over a wide range of conditions. In this study, a governing equation. As a Riemann solver Roe(1981)'s one is used. The model employs the modified MUSCL for handling the unstructured grids in this research. this model that adopts the explicit tradditional twl dimmensional dam break problems, two hydraulic dam break model is simulations, and a steady state simulation in a curved channel. Conclusions of this research are as follows : 1) the finite volume method can be combined with the Godonov-type method that is useful for modeling shocks. Hence, the finite volume method is suitable for modeling shocks. 2) The finite volume model combined with the modified MUSCL is successful in modeling shock. Therefore, modified MUSCL is proved to be valid.