• 드라이브 ㆍ 컨트롤
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• 제12권4호
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• pp.54-59
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• 2015

Due to the tendency to use high speed pneumatic cylinders to improve productivity, cushioning devices are adopted to decelerate the piston motion of pneumatic cylinders to reduce noise, vibration, and impact. This paper presents a comparison of the cushion characteristics of a high speed pneumatic cylinder with a relief valve type cushioning device. The system parameters selected are the damping coefficient, Coulomb friction, heat transfer coefficient, and cracking pressure of the relief valve in the air cushioning device. The integral of the time multiplied square error (ITSE) is used to quantitative measure the cushioning performance to assess the effect of varying these. The cushioning performance achieved good results when the ITSE is a minimum value. In a comparison of the piston displacement and velocity with the variations in system parameters, the heat transfer coefficients are not as significantly affected as the other. Also, the cracking pressure of the relief valve is mainly affected by the pressure and temperature in the cushion chamber.

• Journal of Electrical Engineering and Technology
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• 제7권3호
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• pp.389-395
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• 2012

In this paper, we analyzed the frequency spectrum of the electromagnetic waves radiated by an electric discharge as a basic study to develop an on-line diagnostic technique for power equipment installed inside closed-switchboards. In order to simulate local and series arc discharges caused by an electric field concentration and poor connections, three types of electrode systems were fabricated, consisting of needle and plane electrodes and an arc generator meeting the specifications of UL 1699. The experiment was carried out in an electromagnetic anechoic chamber, and the measurement system consisted of a PD free transformer, a loop antenna with a frequency bandwidth of 150 kHz-30 MHz, an ultra log periodic antenna with a frequency bandwidth of 30 MHz-2 GHz, and an EMI test receiver with a frequency bandwidth of 3 Hz-3 GHz. According to the experimental results, the frequency spectra of the electrical discharges were widely distributed across a range of 150 kHz-400 MHz, depending on the defects, while commonly found between 150 kHz and 10 MHz. Therefore, considering the ambient noise and antenna characteristics, the best frequency bandwidth for a measurement system to monitor abnormal conditions by detecting electromagnetic waves in closedswitchboards is 150 kHz-10 MHz.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 동계학술발표대회 논문집
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• pp.175-180
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• 2008

This paper is dedicated to the development of cooling devices such as mLHP with Fan-Fin system limited by noise and vibration. As we know, Heat pipe has the limitation of cooling capability to cool down the electronics. It is bounded by capillary and thermal limitation but heat load that it has to deal with is increasing. Especially Today's electronic technology has a tendency to integrate lots of function into the small piece of a processor like Dual core having 35W heat load for mobile and desktop computer respectively. There is an optimum operating condition of temperature, below $70^{\circ}C$, during the maximum heat load, 35W. There is the motivation needed to develop the new type of cooling devices and we can discuss about the new challenge beyond heat pipe.

• Nuclear Engineering and Technology
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• 제49권4호
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• pp.810-816
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• 2017

A graphite calorimetry system was built and tested under irradiation. The noise level of the temperature measurement system was approximately 0.08 mK (peak to peak). The temperature of the core part rose by approximately 8.6 mK at 800 MU (monitor unit) for 6-MV X-ray beams, and it increased as X-ray energy increased. The temperature rise showed less spread when it was normalized to the accumulated charge, as measured by an external monitoring chamber. The radiation energy absorbed by the core part was determined to have values of $0.798J/{\mu}C$, $0.389J/{\mu}C$, and $0.352J/{\mu}C$ at 6 MV, 10 MV, and 18 MV, respectively. These values were so consistent among repeated runs that their coefficient of variance was less than 0.15%.

• 한국유체기계학회 논문집
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• 제7권5호
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• pp.13-19
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• 2004

Centrifugal blowers are widely used for air handling units in industry applications. The blower has a centrifugal impeller and a scroll casing including a driving component such as an electric motor. The impeller takes forward or backward blades to induce flows into the blower, Comprehensive investigation according to the two kinds of blades is systematically carried out for a guidance of design for this kind research. It is observed that flow rate of the blower with forward blades is larger than that of the system with backward blades. Otherwise, the system noise is more pronounced in the case of the blower with forward blades. The reason is due to larger velocity from the rotating forward blades that pose obtuse angle with the circumferential direction. The distinguished characteristics are validated by a parallel experiments with a wind tunnel and in an anechoic chamber. Numerical analysis for the system shows detail information inside the blades and the casing. A series of figures to show the flow details offer deep understanding of the performance of a centrifugal blower with different blades.

• 한국정밀공학회지
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• 제18권1호
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• pp.89-97
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• 2001

A microgyroscope, which vibrates in two orthogonal axes on the substrate plane, is designed and fabricated. The shuttle mass of the vibrating gyroscope consists of two parts. The one is outer shuttle mass which vibrates in driving mode guided by four folded springs attached to anchors. And the other is inner shuttle mass which vibrates in driving mode as the outer frame does and also can vibrate in sensing mode guided by four folded springs attached to the outer shuttle mass. Due to the directions of vibrating mode, it is possible to fabricate the gyroscope with simplified process by using polysilicon on insulator structure. Fabrication processes of the microgyroscope are composed of anisotropic silicon etching by RIE, gas-phase etching (GPE) of the buried sacrificial oxide layer, metal electrode formation. An eletromechanical model of the vibrating microgyroscope was modeled and bandwidth characteristics of the gyroscope operates at DC 4V and AC 0.1V in a vacuum chamber of 100mtorr. The detection circuit consists of a discrete sense amplifier and a noise canceling circuit. Using the evaluated electromechanical model, an operating condition for high performance of the gyroscope is obtained.

• 한국터널지하공간학회 논문집
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• 제24권1호
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• pp.79-94
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• 2022

도심지 포화 상태로 인한 지하공간 개발의 일환으로 터널 건설의 수요가 증가하고 있다. 쉴드 TBM 공법은 진동과 소음을 최소화하며 굴착과 동시에 지반 변형을 최소화하는 공법으로, 국내 도심지 터널 시공은 대체로 쉴드 TBM이 적용되고 있다. 도심지 지반침하 예측의 중요성은 나날이 증가하고 있으며 쉴드 TBM 시공의 경우 지반 변형을 최소화 하지만 터널굴착에 의한 지반침하는 필연적으로 발생한다. 따라서 본 연구에서는 도심지 적용성이 높은 쉴드 TBM과 지반침하와의 상관성을 분석하여 지반침하에 주요한 영향을 미치는 쉴드 TBM 시공인자를 제시하고자 한다. 실제 현장에서 수집한 쉴드 TBM 시공데이터와 지반침하 계측데이터 간 상관관계 분석을 수행하였으며, 상관성 정도를 상관계수 "r"로 표현하였다. 그 결과 지반침하에 영향을 미치는 쉴드 TBM 주요 시공인자는 추력(Thrust force), 토크(Torque), 챔버압(Chamber pressure), 뒷채움압(Backfill pressure), 배토량(Muck discharge)으로 나타났다. 본 연구 결과를 통해 향후 쉴드 TBM 운용 시 지반침하를 사전에 예측 및 제어 할 수 있도록 주요 시공데이터에 대한 판단 기준 제시에 기여할 것으로 기대된다.

• 한국지반공학회논문집
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• 제23권8호
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• pp.17-33
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• 2007

지반의 전단파 속도 주상도를 도출하는데 있어 다운홀 기법은 하나의 시추공을 이용하고 간단한 지표면 가진원을 사용하므로 매우 경제적이다. 그러나 실험을 통해 획득한 신호에서 전단파 성분의 도달시간 정보를 정확히 도출하지 못할 경우 최종 결과의 신뢰성이 떨어지게 된다. 따라서 다운홀 기법에 있어 최종 결과의 신뢰성을 높이기 위해 도달 시간 정보의 결정 방법에 대한 고찰은 매우 중요하다. 본 논문에서는 총 6가지 방법을 이용하여 다운홀 시험을 통해 획득한 신호에서 도달시간 정보를 획득, 비교하고자 하였으며 각 방법에 대한 효율적인 비교 및 검증을 위하여 유한요소 해석 및 실내 모형 토조 시험을 수행하였다. 유한요소 해석을 이용한 검증에서는 모델의 입력치와, 실내 모형 토조에서는 벤더 엘리먼트 시험 결과와의 비교를 통해 각 방법의 오차정도를 비교해 보았다. 초동 추정 방법의 결과는 다른 방법에 비해 오차정도가 매우 컸다. 다른 방법들 또한 획득 파형의 특성에 따라 오차 정도가 달랐으며 정확한 값을 제공하지 못하는 것을 볼 수 있었다. 그 중에서 상호상관법이 적용성이 가장 뛰어난 것으로 판단되었으며 현장 시험 데이터를 이용한 추가적인 검토를 통해 확인할 수 있었다.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2011년도 한국우주과학회보 제20권1호
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• pp.23.4-23.4
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• 2011

MIRIS is the main payload of the Science and Technology Satellite-3 (STSAT-3). which is being developed by KASI for infrared survey observation of the Galactic plane at Paschen alpha wavelength. Wideband filters in I and H band will also be used to observe cosmic infrared background. The MIRIS will perform astronomical observations in the near-infrared wavelengths of 0.9~2 ${\mu}m$ using a 256 ${\times}$ 256 Teledyne PICNIC FPA sensor providing a 3.67 ${\times}$ 3.67 degree field of view with a pixel scale of 51.6 arcsec. The flight model of the MIRIS has been recently developed, The system performance tests have been made in the laboratory, including opto-mechanics test, vibration test, thermal vacuum test and passive cooling test down to 200K, using a thermally controlled vacuum chamber. Several focus tests showed good agreements compared to initial design parameters. Recent efforts are being concentrated to improve the system performances, particularly to reduce readout noise level in electronics. After assembly and integration into the satellite bus, the MIRIS will be launched in 2012.

• Progress in Superconductivity
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• 제10권2호
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• pp.99-102
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• 2009

We report our development of the fabrication process of sub-micron scale $Al-AlO_x-Al$ tunnel junction by using electron-beam lithography and double-angle shadow evaporation technique. We used double-layer resist to construct a suspended bridge structure, and double-angle electron-beam evaporation to form a sub-micron scale overlapped junction. We adopted an e-beam insensitive resist as a bottom sacrificing layer. Tunnel barrier was formed by oxidation of the bottom aluminum layer between the bottom and top electrode deposition, which was done in a separate load-lock chamber. The junction resistance is designed and controlled to be 50 $\Omega$ to match the impedance of the transmission line. The junctions will be used in the broadband shot noise thermometry experiment, which will serve as a link between the electrical unit and the thermodynamic unit.