• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1999년도 제29회 춘계학술대회
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• pp.197-202
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• 1999

A mechanical face seal is a tribe-element intended to control the leakage of working fluid at the interface of a rotating shaft and its housing. The leakage of working fluid decreases as the seal surfaces get closer each other. But a very small seal clearance results in a drastic reduction of seal life because of high wear and heat generation. Therefore, in the design of mechanical face seals the compromise between low leakage and acceptable life is important and presents a difficult design problem. And the gap geometry of seal clearance affects seal performance very much and becomes an important design variable. In this study the Reynolds equation for the sealing dam of mechanical face seals is numerically analyzed using the Galerkin Finite Element Method, which can be readily applied to various seal geometries. The film pressures of the sealing dam are analyzed, including the effects of the seal face coning and tilt. Then, opening forces, restoring moments, leakages, and dynamic coefficients are calculated.

• Tribology and Lubricants
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• 제12권4호
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• pp.35-42
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• 1996

The labyrinth seal is one of the widely used non-contact type mechanical seal. Current work was emphasized on the investigation of the air jet effect on the labyrinth seal. To improve the sealing capability of conventional labyrinth seal, air jet was injected against through the leakage flow. In this study, both of the numerical analysis by CFD (Computational Fluid Dynamics) and the experimental measurement were carried out. Both of the turbulence aad the compressible flow model were introduced in CFD analysis. The sealing effect of the leakage clearance and the air jet magnitude were studied in the experiment. The reason of the enhanced sealing was explained as a reduction of effective clearance by jetting air. As a result, the air jet could reduce the effective clearance with a wide range of leakage clearance.

• 한국산업정보학회논문지
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• 제8권3호
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• pp.105-110
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• 2003

본 연구에서는 마이크로미립 이송시스템의 에어 누수가 과다함으로 인해 압축에어를 사용하는 큰 문제점을 발생되어 로터리피더의 에어누수를 기존대비 50% 감소시켰으며 생산제조원가 면에서도 기존가격의 60%수준으로 개발함으로써 원료의 원활한 이송이 될 수 있는 장치의 개발에 대해 입증하였다.

• Journal of Electrical Engineering and Technology
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• 제11권2호
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• pp.393-404
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• 2016

In this paper, a carrier-based pulse with modulation (PWM) strategy for three-phase three-level inverter is dealt with, which can keep the common mode voltage constant with minimized switching frequency. The voltage gain and the switching frequency in overall operating ranges including overmodulation are investigated and the analytic equations are presented. Finally, the leakage current reduction effect is confirmed by carrying out simulation and experiment. It will be pointed out that the leakage current cannot be perfectly eliminated because of the dead time.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문집
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• pp.799-804
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• 2002

In this paper the leakage prediction and rotordynamic analysis of an annular seal with a smooth rotor and spiral-grooved stator are performed. For developing 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 pressure flow through the spiral groove. Results by the present analysis are compared with available experimental data. For leakage the analysis results generally show a reasonable agreement to the experimental results. For rotordynamic coefficients the analysis results show the same trend as the experimental results for rotor speed with spiral angles, but their magnitudes show somewhat large deviations.

• 전자공학회논문지A
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• 제32A권5호
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• pp.54-59
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• 1995

We have proposed a novel self-aligned offset gated polysilicon TFTs device without an offset mask in order to reduce a leakage current and suppress a kink effect. The photolithographic process steps of the new TFTs device are identical to those of conventional non-offset structure TFTs and an additional mask to fabricate an offset structure is not required in our device due to the self-aligned process. The new device has demonstrated a lower leakage current and a better ON/OFF current ratio compared with the conventional non-offset device. The new TFT device also exhibits a considerable reduction of the kink effect because a very thin film TFT devices may be easily fabricated due to the elimination of contact over-etch problem.

• 산업기술연구
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• 제35권
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• pp.41-45
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• 2015

This paper presents a development of the ELB (Electronic Leakage Breaker) based on a reduction of standby power dissipation as with maintaining conventional performance. In order to minimize the standby power consumption of the conventional circuit, we analyze the cause of 0.3W dissipation of the circuit. By employing the TR-triggered circuit to secure the standby power of 0.10W after testing and evaluation while CRD inserted circuit showed the performance of 0.17W levels. Implementing SMPS IC and TNR device circuit was designed and showed of its power to less than 0.06W. Developed ELB is expected much standby power savings in large power distributor or heavy users.

• 대한전기학회논문지
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• 제43권2호
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• pp.312-317
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• 1994

We studied the fabrication and electrical characteristics of high voltage hydrogenerated amorphous silicon thin film transistor using plasma enchanced chemical vapor deposition(PECVD). The device shows 2500${\AA}$ SiOS12T, 400-1500${\AA}$ a-Si tickness, 350V output voltage and 9.55${\times}$10S04T average on/off current ratio. We found that the leakage current of high voltage TFT occurred 0-70V drain voltage. As the leakage current depend on the a-Si thickness, the leakage current of high voltage TFT decreased by reduction of the a-Si thickness.

• Wind and Structures
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• 제28권2호
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• pp.89-97
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• 2019

The non-linear equations governing wind-induced internal pressures for a two-compartment building with background leakage are linearized based on some reasonable assumptions. The explicit admittance functions for both building compartments are derived, and the equivalent damping coefficients of the coupling internal pressure system are iteratively obtained. The RMS values of the internal pressure coefficients calculated from the non-linear equations and linearized equations are compared. Results indicate that the linearized equations generally have good calculation precision when the porosity ratio is less than 20%. Parameters are analyzed on the explicit admittance functions. Results show that the peaks of the internal pressure in the compartment without an external opening (Compartment 2) are higher than that in the compartment with an external opening (Compartment 1) at lower Helmholtz frequency. By contrast, the resonance peak of the internal pressure in compartment 2 is lower than that in compartment 1 at higher Helmholtz frequencies.

• 한국통신학회논문지
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• 제32권12C호
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• pp.1175-1187
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• 2007

이동통신 기지국 시스템에서 송신 신호의 PAR 성능을 (peak-to-average power ratio) 개선함으로써 범용 전력 증폭기의 사용이 가능하게 되며, 이로 인해 전체적인 기지국 비용의 절감을 기대할 수 있다. 일반적으로 PAR 값을 줄임으로 인해 기지국 송신신호의 인근 대역 간섭 제한 성능을 나타내는 ACLR이나 (adjacent channel leakage ratio) 품질을 나타내는 EVM이나 (error vector magnitude) PCDE 성능의 (peak code domain error) 열화를 발생시킨다. 본 논문에서 이러한 문제점을 해결하기 위하여 필터링 기반의 CFR 방식인 (crest factor reduction) FDCFR 알고리즘을 (filter-dependent CFR) 소개하며, 히스토그램 기반 코드 영역 보상(HBWCDC; histogram based waterfilling code domain compensation)기법을 제안한다. 본 논문에서 제안한 CFR 알고리즘은 PAR 감소뿐만 아니라 앞서 언급한 ACLR, EVM 및 PCDE등의 성능 열화를 방지한다.