• Tribology and Lubricants
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• 제13권3호
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• pp.56-62
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• 1997

Sealing an oil-air mixture plays important roles to have an enhanced lubrication for high speed spindle. High speed spindles require non-contact type sealing mechanism. In this study, an optimum seal design to minimize leakage is concerned in the aspect of flow control. This paper categorizes geometries of mostly used non-contact type seals and analyzes each leakage characteristics to minimize a leakage on sealing area. Effect of minimum clearance and its position are considered according to variation of detail geometry. The estimation of non-leaking property is determined by amount of pressure drop in the leakage path assuming constant leakage flow. To simulate an oil jet or oil mist type high speed spindle lubrication, the working fluid is regarded as two phases that are mixed flow of oil phase and air phase. Both of the turbulence and the compressible flow model were introduced in CFD(Computational Fluid Dynamics) analysis. Design parameters has been induced to minimize leakage in limited space, and a methodological study on geometrical optimization has been conducted.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집
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• pp.379-382
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• 2002

GaAs has wide band gap, Therefore that malarial can used high Temperature application. in this paper explain to current-voltage characteristics of thermal effect. we experiment on thermal test of current-voltage characteristics and gate leakage current with real device. As a result, we propose a current-volatage characteristics model. that model base on gate leakage current, and gate leakage current influence gate source voltage.

• 대한기계학회논문집B
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• 제31권4호
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• pp.357-366
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• 2007

The present study investigated local heat/mass transfer characteristics on the surface of the rotating turbine blade with various incidence angles. The experiments are conducted in a low speed annular cascade with a single stage turbine. The blade has a flat tip with the mean tip clearance of 2.5% of the blade chord. A naphthalene sublimation method is used to measure detailed mass transfer coefficient on the blade. At design condition, the inlet Reynolds number is $Re_c=1.5{\times}10^5$ which results in the blade rotation speed of 255.8 rpm. Also, the effect of off-design condition is examined with various incidence angles between $-15^{\circ}$ and $+7{\circ}$. The results indicated that the incidence angle has significant effects on the blade surface heat transfer. In mid-span region, the laminar separation region on the pressure side is reduced and the laminar flow region on the suction side shrinks with increasing incidence angle. Near the tip, the effect of tip leakage flow increases in span wise and axial directions as the incidence angle decreases because the tip leakage flow is formed near the suction side surface. However, the effect of tip leakage flow is reduced with positive incidence angle.

• 전기학회논문지
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• 제62권7호
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• pp.891-897
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• 2013

The power system frequency plays an important role in monitoring and controlling the power system. The frequency can be measured through discrete Fourier transform (DFT) coefficients of its positive fundamental frequency. The accuracy of the frequency estimate is severely affected by noise in the power system signal and the leakage effect of the negative fundamental frequency in DFT. This paper proposes a DFT-based frequency estimation algorithm to cope with the noise as well as the leakage effect. In this algorithm, two suitable digital filters are introduced to reduce efficiently frequency estimate error due to the noise. These filters are designed to use a digital bandpass filter and a second-degree integrator. The effectiveness of the proposed algorithm in reduction of frequency estimate error is verified through simulations on noise, harmonics and frequency deviation.

• 한국화재소방학회논문지
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• 제33권4호
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• pp.112-120
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• 2019

본 연구에서는 위험물안전관리법상 제4류 위험물에 해당하는 벤젠을 대상 물질로 선정하여 항만시설의 하역 과정에서 화재 및 누출사고가 발생하는 경우 가상의 시나리오를 통해 "독성(Toxic)"과 "액면화재(Pool fire)"에 대한 피해 규모를 정량적으로 평가하고자 하였다. 평가방법은 국내 화학물질안전원에서 범용프로그램으로 지원하는 KORA 프로그램을 활용하였으며, 벤젠의 화재 및 누출사고에 대한 피해영향 범위를 예측한 결과 독성으로 인한 피해 범위의 경우 누출공의 크기가 감소함에 따라 "최악의 사고시나리오" 대비 사고 피해영향 범위가 최대 5.11%까지 감소하는 것을 확인할 수 있었으며, 누출시간에 대한 피해영향 범위의 경우 누출시간 5 min 대비 10 min에서 145.12% 증가하였으며 20 min에서는 212.29%로 증가하였다. 또한, 액면화재로 인한 피해의 경우 "최악의 사고시나리오"에서 복사열에 의한 피해영향 범위는 취급시설을 중심으로 반경 228.8 m로 나타났으며, "대안의 사고시나리오"의 경우 복사열에 의한 피해영향 범위는 누출공의 크기가 배관 단면적이 감소함에 따라 "최악의 사고시나리오" 대비 사고 피해영향 범위가 최대 8.26%까지 감소하는 것을 확인할 수 있었다.

• 전기전자학회논문지
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• 제27권4호
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• pp.644-649
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• 2023

DRAM(Dynamic Random Access Memory) 스케일링 과정에서 발생하는 셀간 거리의 감소에 따라 STI(Shallow Trench Isolation)두께 감소는 문턱이하 누설이 증가되는 패싱워드라인 효과를 유발한다. 인접한 패싱워드라인에 인가된 전압으로 인한 문턱이하누설 전류의 증가는 데이터 보존시간에 영향을 주며, 리프레시의 동작 횟수가 증가되어 DRAM의 소비 전력을 증가시키는 요인이 된다. 본 논문에서는 TCAD Simulation을 통해 패싱워드라인 효과에 대한 원인을 확인한다. 결과적으로, 패싱워드라인 효과가 발생하는 DRAM 동작상황을 확인하고, 이때 패싱워드라인 효과로 인해 전체 누설전류의 원인에 따른 비중이 달라지는 것을 확인하였다. 이를 통해, GIDL(Gate Induced Drain Leakage)에 의한 누설전류뿐만 아니라 문턱이하 누설전류를 고려의 필요성을 확인하며 이에 따른 DRAM 구조의 개선 방향의 지침이 될 수 있다.

• 한국유체기계학회 논문집
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• 제6권1호
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• pp.14-22
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• 2003

In this paper the leakage prediction md rotordynamic analysis of an annular seal with a smooth rotor and spiral-grooved stator is performed. For the development of a theoretical model, the three-control-volume analysis of the circumferentially-grooved seal is expanded by considering pressure reduction due to the pumping effect of spiral groove and pressurized flow through the spiral groove. Validation on the present analysis is achieved by comparisons with available experimental data. For the leakage prediction the present analysis generally shows a reasonable agreement with experimental results. Rotordynamic coefficients for rotor speed with spiral angles show same trend, but the magnitudes of rotordynamic coefficients yield differences between analysis and experimental results.

• 대한전기학회논문지
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• 제41권2호
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• pp.170-177
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• 1992

Contact resistance and contact leakage current of the Al/TiSiS12T/Si system are investigated for NS0+T and PS0+T junctions. SALICIDE (Self Aligned Silicide) process was used to make the Al/TiSiS12T/Si system. Titanium disilicide is one of the most common silicides because of its thermal stability, ability to form selective formation and low resistivity. In this paper, RTA temperature effect and Junction implant dose effect were evaluated to characterize contact resistance and contact leakage current. The TiSiS12T contact resistance to NS0+T silicon is lower than that to PS0+T silicon, and TiSiS12T of contact leakage current to NS0+T silicon is lower than that to PS0+T silicon. Contact resistance and contact leakage current of the Al/TiSiS12T/Si system by this method were possible for VLSI application.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.1189-1194
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• 2002

Acoustic intensity is usually estimated by the cross-spectrum of acoustic pressure at two adjacent micrphones. The cross-spectrum calculated by digital Fourier transform technique will unavoidally have leakage error since the period of signal will not be usually coincident with record length. Therefore, the acoustic intensity estimated by the conventional r]n analyzer will show distorted value. In this paper the expression of the Fourier transformed data of a harmonic signal is formulated when there is leakage error. The method to elimate the effect of leakage error from the contaminated data is also proposed. Some numerical examples show the validation of the proposed method.

• Restorative Dentistry and Endodontics
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• 제27권4호
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• pp.389-393
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• 2002

The marginal integrity of the crown can be broken during endodontic access cavity preparation due to the vibration of burs. Therefore, the purpose of this study was to evaluate the effect of endodontic access cavity preparation on the marginal leakage of full veneer gold crowns. 24 intact molars were mounted in acrylic resin blocks and prepared for crowns by a restorative dentist and crowns were cast with gold alloy. 20 Crowns were cemented with glass ionomer cement and 2 crowns were not cemented for positive control. 200 thermo-cycles from 5$^{\circ}C$ to 5$0^{\circ}C$ with a travel time of 20s were completed. Then samples were randomly divided into 2 experimental groups of 9 each. Endodontic access preparation and zinc-oxide eugenol temporary fillings were done in Group 1. Teeth in Group 2 were not treated. Samples were coated with 2 layers of nail varnish and were immersed in 1% methylene blue dye for 20 hrs. Endodontic access was prepared in 2 samples, which were coated with nail varnish on all surfaces for negative control. After washing in running water gold crowns were cut with a #330 bur. Four buccolingual sections, 2 mm apart, were cut from the central section of each tooth and were examined and scored under the microscope for dye leakage. Score 1: leakage to the cervical 1/3 of the axial wall, Score 2: leakage to the middle 1/3 of the axial wall, Score 3: leakage to the coronal 1/3 of the axial wall, Score 4: leakage to the occlusal surface. The median value for Group 1 is 4 and for Group 2 is 2. The result of this study showed that samples in Group 1 leaked more than those in Group 2. This finding was significant(P<0.001).