• Proceedings of the IEEK Conference
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• 1998.10a
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• pp.577-580
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• 1998

This paper presents the characteristics of each MOS device and Bipolar device, then investigates about how these devices take effect on BiCMOS inverter from 300K to 470K. The turn-off and Logic swing characteristics of BiCMOS inverter are degraded by the electrical characteristics of the MOS to around 400K, but over that temperature enhanced by the characteristics of the Bipolar transistor.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.14 no.5
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• pp.211-214
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• 2004

Carbon nanofiber bundles were formed on silicon substrate using microwave plasma-enhanced chemical vapor deposition system. These bundles were vertically well-grown under the high negative bias voltage condition. The bundles were composed of the individual carbon nanofiber having less than 100 nm diameters. Turn-on voltage of the field emission was measured around 0.8 V/$\mu\textrm{m}$. Fowler-Nordheim plot of the measured values confirmed the field emission characteristic of the measured current.

• Publications of The Korean Astronomical Society
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• v.7 no.1
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• pp.71-77
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• 1992

An axisymmetric, stationary electrodynamic model of the central engine of an active galactic nucleus has been well formulated by Macdonald and Thorne. In this model the relativistic region around the central black hole must be filled by highly conducting plasma and the equations of magnetohydrodynamics are then satisfied. In this paper we analyze magnetohydrodynamic wave propagation in this region. We find that there are three distinct types of waves - the Alfven wave and two magnetosonic waves. The wave equations turn out to be not very different from those in nonrelativistic case except they are redshifted.

• Korean System Dynamics Review
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• v.3 no.1
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• pp.131-163
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• 2002

This study examines the effect that the prepaid trust has in saving the troubled business. Developing a formal system dynamics model, building on case studies of corporate turnaround, we developed a mathematical model on the relationship between the prepaid trust and corporate turnaround. The Model shows how the prepaid trust can shift an organizational system from fragile condition to resilient condition of a firm. This study elaborartes a new set of conditions under which organizations may turn around via prepaid trust of stakeholders.

• International Journal of Precision Engineering and Manufacturing
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• v.4 no.3
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• pp.5-11
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• 2003

A simulation model for radial magnetic bearings is presented. The model incorporates hysteresis, saturation and eddy current effects. A simple magnetization model that describes hysteresis and saturation is proposed. Eddy currents are taken into consideration by assuming that they are generated by single-turn fictitious coils wrapped around each magnetic flux path. The dynamic equations describing the simulation model can easily incorporate the operation of switching power amplifier. A simulation of a typical 8-pole radial magnetic bearing produces switching waveforms very similar to the experimental observation.

• Proceedings of the Optical Society of Korea Conference
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• 2008.02a
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• pp.93-94
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• 2008

In order to suppress the current crowding in light emitting diodes (LEDs) grown on sapphire substrate, the effect of nonuniform contact resistivity between TME layer and p-GaN layer on the LED surface was theoretically investigated. The analysis results showed that current crowding occurring around p-electrode could be considerably improved, which in turn would be helpful to improve the electrostatic discharge (ESD) characteristic.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 2002.05a
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• pp.375-380
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• 2002

국내 정유공장의 역사는 1964년에 울산에서 가동하기 시작하여 1970년에 여천, 1973년에 인천, 1976년에 부산, 1990년에 온산, 그리고, 1989년에 서산에서 정유공장을 설치하여 가동하였다. 이들의 정유공장에서 1964년부터 1995년까지 발생한 사고사례 285건을 수집하여 정리하였다./sup 1)/ 285건의 사고를 분석하여 연도별 사고발생건수의 추이 및 운전형태별 사고발생건수의 분포를 작성하였다.(중략)

• International Journal of Aeronautical and Space Sciences
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• v.14 no.1
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• pp.67-74
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• 2013

Nonlinear guidance law combined with a pseudo pursuit guidance is proposed, to perform stationary target observation mission. Multiple UAVs are considered, with waypoint constraint. The whole guidance is divided into two steps: firstly, waypoint approach, with specified incidence angle; and secondly, loitering around the stationary target. Geometric approach is used to consider the constraint on the waypoint, and a specified phase angle between the loitering UAV and the approaching UAV. In the waypoint approach step, UAVs fly to the waypoint using the pseudo pursuit guidance law. After passing the waypoint, UAVs turn around the target, using a distance error dynamics-based guidance law. Numerical simulations are performed, to verify the performance of the proposed guidance law.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2000.10a
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• pp.365-370
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• 2000

Sea dike construction for the tidal flat reclamation works in estuary and coast may change the characteristics of tidal motion and wave conditions in the region. In turn, a new hydraulic condition provides the impacts on sediment transport pattern and forms a new morphological environment. Also, morphological changes during the closure works of sea dike are closely related with a safy of sea dike. Therefore, the prediction of morphological changes is required secure the safe closure work and the economic design of sea dikes. To investigate morphological changes due to sea dike construction, hydrodynamic changes of tides and waves have to be evaluated, then sediment transport and sea bottom changes are computed. Mathematical modelling is required for representation of interrelation of tidal motion, wave and sediment transport. In this study, numerical model MORSYS is applied to compute the hydrodynamics and morphological changes around the closure gap for Saemankuem dike. This model allows a flexible integration of the module for waves, currents, sediment transport and bottom changes.

• Tribology and Lubricants
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• v.22 no.3
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• pp.155-163
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• 2006

Ring, groove and cylinder bore wear may not be a problem in most current automotive engines. However, a small change in ring face, groove geometry and cylinder bore diameter can significantly affect the lubrication characteristics and ring axial motion. This in turn can cause to change inter-ring pressure, blowby and oil consumption in an engine. Therefore, by predicting the wear of piston ring face, ring groove and cylinder bore altogether, the changed ring end gap and the changed volume of gas reservoir can be calculated. Then the excessive oil consumption can be predicted. Being based on the calculation of gas flow amount by the theory of piston ring dynamics and gas flow, and the calculation of oil film thickness and friction force by the analysis of piston ring lubrication, the calculation theory of oil amount through top ring gap into combustion chamber will be set. This is estimated as engine oil consumption. Furthermore, the wear theories of ring, groove and cylinder bore are included. Then the each amount of wear is to be obtained. The changed oil consumption caused by the new end gap and the new volume of oil reservoir around second land, can be calculated at some engine running interval. Meanwhile, the wear amount and oil consumption occurred during engine durability cycle are compared with the calculated values. Next, the calculated amount of oil consumption and wear are compared with the guideline of each part's wear and oil consumption. So, the timing of part repair and engine life cycle can be predicted in advance without performing engine durability test. The wear data of rings, grooves and cylinder bore are obtained from three engines before and after engine durability test. The calculated wear data of each part are turn out to be around the band of averaged test values or a little below.