• 한국정밀공학회지
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• 제17권9호
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• pp.145-150
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• 2000

Out-of-sphericity is degree of deformation of an air bearing sphere deviated from a perfect sphere. This paper investigates numerically the effect of out-of-sphericity error on the radial stiffness of an air bearing Three types of out-of-sphericity modes are considered. in this study the stiffness is calculated from pressure distribution at the bearing surface which is obtained by solving th Reynolds equation. in some cases large out-of-sphericity errors are found to improve the stiffnesses of air bearings. This implies that an air bearing of perfect hemispheres is not necessarily of the best performance. Thus much labor and cost in manufacturing air bearings can be saved, In addition the radial stiffness of an air bearing depends greatly on the application direction.

• 전기학회논문지
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• 제58권1호
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• pp.119-125
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• 2009

This paper deals with the characteristics of soil ionization affecting the dynamic performance of grounding systems under lightning impulse voltage. A concentric hemispherical electrode system was employed in order to facilitate the field calculation and analysis of the experimental results. The parameters such as the ionization threshold and breakdown field intensity, the pre-ionization and the post ionization resistances, the time-lag to ionization, the transient impedance, the equivalent ionized radius for various soil media were measured and analyzed. The dynamic characteristics of ionization processes under lightning impulse voltage are strongly dependent on the types of soil and water content. As a result, a soil ionization reduces the ground resistance and there is a little effect of applied impulse polarity on the soil ionization threshold field intensity. Although the ionization threshold field intensity of wet clay with 30% water content is the highest, its ionized zone was found to be the smallest amongst the test samples.

• 한국표면공학회지
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• 제49권5호
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• pp.447-453
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• 2016

In this study, we intended to extend the life of electropolishing solution through the reduction of electric resistance by improving the electrolysis efficiency. The optimum conditions were obtained by half round bus bar and Taguchi method. As the main control factors in the electropolishing process, current density, polishing time, electrolyte temperature and flow rate were selected. The electrolyte temperature was the most significant to the electrolysis efficiency. The optimum conditions for the life extension of electropolishing solution were as follows: current density, $45A/dm^2$; polishing time, 6 min; electrolyte temperature, $70^{\circ}C$; flow rate, 11 L/min. As a results of ANOVA of SN ratios, it was found that the electrolyte temperature was significant factor at the 90% confidence level.

• 분석과학
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• 제13권6호
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• pp.705-711
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• 2000

리튬 이차전지용 부극 재료로 페놀 수지로 부터 유도된 boron을 doping한 polyacene에 구조적 특성, 표면 특성 및 전기적 특성을 연구하였다. Polyacene탄소질에 boron의 함유량을 각각 5%, 10%, 15%, 20% 첨가하여 특성화하였다. X-선 회절 결과에 따르면, 이들 시료들은 대표적인 무정형 탄소의 회절형태를 나타내었다. 표면 상태는 반구형의 표면상태를 가지고 있음을 SEM 결과로부터 알 수 있었다. 전지의 이온과 전자전달효과를 알아보기 위한 전기 화학적 충전/방전 특성과 임피던스 측정의 결과에 의하면, 10%와 15% boron이 첨가된 시료는 다소 우수한 특성을 나타내고 있다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 춘계학술대회 논문집
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• pp.164-169
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• 2005

A.T.S.의 스위칭 구조와 접점 환경은 주로 아크 전류, 접촉 저항, 아크 시간 등의 불리적 요인이 주로 마모와 특성에 영향을 미치게 된다. 사용되는 접점 재료는 W 또는 WC-Cu 계로 형상과 크기는 전형적인 반구형 구조의 접촉으로 구동이 이루어진다. 따라서 A.T.S.용 접점의 아크 마모 특성 시험을 위한 고려 요인은 이러한 점을 고려하여 시험과 분석이 이루어 졌다. 접점의 마모 특성 실험식으로부터 실제적인 관점에서 보면 제한된 수명을 나타내는 $n_L$을 보장하기 때문에 b<1의 경우가 가장 바람직한 결과로 ATS 접점 시편의 경우 $b{\fallingdotseq}0.99$로 안정된 접점 아크 마모 특성을 갖는 것으로 판단된다. 아크 전압에 대한 모델링과 실험에서 접점 간극 거리 1<0.1mm, 아크전류 i<100A의 시험 조건에 대해 검토한 결과 ATS 접점 시편의 아크전압은 $u_a=10.2V$로 계산되었다. 이 값은 설험적인 값과 상당히 접근하는 특성을 갖는 것으로 나타났으며, 아크에 의한 마모를 억제하기 위해 첨가하는 WC 또는 W의 복합 소결로 인해 아크 에너지가 감소되는 것을 보여준다. 한편 접점의 아크 동작이 분리되는 순간의 동작 시험에서 기존 W(50%wt)-Cu(50%wt) 접점의 값과 비교하면 분리시 아크 전압은 상대적으로 낮아지는 현상은 W강화 첨가량의 증가로 인한 아크 에너지 감소의 제한성을 나타내는 것으로 사료된다.

• 제어로봇시스템학회논문지
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• 제19권10호
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• pp.947-954
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• 2013

This article focuses on a hemispherical resonator gyro driven by the Coriolis effect. The operational principle of resonator gyros and mathematical models are introduced. These models are useful to explain the behavior of a resonator and to design controllers. Several control tests of a resonator have been done. A resonator has been excited by electromagnets controlled by a computer. Its amplitude has been adjusted by a PI control. The transient response is matched with a simulation result based on a mathematical model. A vibrating pattern may drift due to non-uniform factors of a resonator. The drift of the vibrating pattern is controlled and aligned to a reference direction by a PI control. These results are very useful to understand the behavior of resonator gyros and to design advanced control algorithm for better performance.

• 센서학회지
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• 제22권6호
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• pp.433-438
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• 2013

In this paper, we found surface shapes are affected by several parameters of RIE, such as RF power, pressure, temp, and process times. The reflectance of pyramid and half sphere structures show differences among shapes, size, height, and depth of those structures. We made about $1{\mu}m$ pyramid and half sphere shapes of silicon surface with RIE. For comparing the reflectance, pyramid and half sphere structures are fabricated with same height. Pyramid structure cell shows higher cell efficiency of 12.5% by 1.1% than one of half sphere structure of 11.4%. The light absorption is more increased through the pyramid structure than half sphere structure.

• 수산해양기술연구
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• 제46권2호
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• pp.115-125
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• 2010

In order to design the optimal escape vent for the coon strip shrimp pot, the tank experiments were conducted with the model pot of five different slit height and slit width, respectively. The optimal height and width of escape vent were determined to 20mm and 40mm by tank experiments, respectively. These were determined by the 50% selection carapace length which was denoted to 25mm in selectivity curve. The escape experiments were conducted to determine a number of escape vent with the original shrimp pot to be set the designed escape vent from 2 vents to 10 vents increasing at intervals of 2 vents in tank. The optimal number of escape vents denoted 8 vents. Therefore, to apply the escape vent in commercial shrimp pot will be efficient to reduce small size shrimps to catch.

• 수산해양기술연구
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• 제50권3호
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• pp.284-291
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• 2014

Finely-striate buccinum Buccinum striatissimum, a species of whelks, is caught mainly by pot in the eastern coastal waters of Korea. In order to determine the size selectivity of pot for the species, comparative fishing experiments were conducted near Yeongil Bay from June to September in 2003 using the dome-shaped pots with different five mesh sizes (17.1, 24.8, 35.3, 39.8, and 48.3 mm). The parameters of logistic equation were estimated by the SELECT (Share Each Length's Catch Total) method based on a multinomial distribution. The model with the estimated split parameter was found to fit the catch data best. The master selection curve was estimated to be s (R)=exp (13.044R-16.438)/[1 + exp (13.044R-16.438)], where R is the ratio of shell height to mesh size. The relative shell height of 50% retention was 1.260, and the selection range was 0.168. Enlargement in mesh size of the pot allows more small-sized whelks to escape.

• 미생물학회지
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• 제55권2호
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• pp.117-122
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• 2019

점액세균 Myxococcus stipitatus는 순수분리를 위한 농화배양 과정에서는 자연기질 표면에서 자루가 달린 구형 자실체를 형성한다. 하지만 순수 분리된 균주가 이러한 형태의 자실체를 형성하도록 하는 한천배지는 알려져 있지 않다. M. stipitatus DSM 14675 균주는 CYS 평판배지에서 반구형 자실체 유사 구조물을 형성하므로 CYS 배지 성분이 자실체 형성에 미치는 영향을 조사하였다. 그리고 이를 기초로 M. stipitatus 세포들이 구에 자루가 달린 자실체를 형성하는 한천배지 조성을 개발하였다. 본 연구에서는 또 이와 함께 M. stipitatus DSM 14675 균주가 분산하여 성장하는 액체배지도 개발하였다.