• 한국정밀공학회지
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• 제31권7호
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• pp.605-613
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• 2014

Scanning white-light interferometry is an important measurement option for many surfaces. However, serious profile measurement errors can be present when measuring free-form surfaces being highly curved or tilted. When the object surface slope is not zero, the object and reference rays are no longer common path and optical aberrations impact the measurement. Aberrations mainly occur at the beam splitter in the interference objective and from misalignment in the optical system. Both effects distort the white-light interference signal when the surface slope is not zero. In this paper, we describe a modified version of white-light interferometry for eliminating these measurement errors and improving the accuracy of white-light interferometry. Moreover, we report systematic errors that are caused by optical aberrations when the object is not flat, and compare our proposed method with the conventional processing algorithm using the random ball test.

• 디지털융복합연구
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• 제10권10호
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• pp.313-318
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• 2012

본 논문에서는 X-band 대역용 인체감지센서에 적용될 저 잡음 송수신기 설계 방법을 제안 하였다. 제안된 송수신기에는 기존 송수신기의 출력 신호가 수신 단으로 유입되는 것을 줄이기 위한 회로가 추가되었다. 잡음 제거회로는 분배기와 $90^{\circ}$위상 천이기를 포함하는 Hittite HMC908LC5(I/Q down converter)가 사용되었다. 송수신기 회로와 안테나는 CST MWS를 사용하여 시뮬레이션 하였고 FR-4 기판(h=1.0mm, ${\varepsilon}_r$=4.4)을 사용하여 제작하였다. 설계된 안테나의 특성이 인체감지용 센서에 사용되기에 적합하며 제안된 송수신기와 기존에 사용되고 있는 송수신기의 출력 특성을 비교 한 결과 동등한 특성을 얻었다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 하계종합학술대회 논문집(1)
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• pp.248-251
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• 2000

The ATM-PON is regarded as an effective access network because the system transmits the various user's information through the passive optical splitter in a single platform. The ranging technology is to place all ONUs at the same distance virtually in order to form ATM-PON based on the Time Division Multiplexing (TDM). In This paper, We show the steps about ranging protocol based on ITU-T G.983.1 and ranging procedure modeling. Also, We implement the simulator that considers various environments to verify the time specifications of G.983.1. By using the simulator, We find out the wasted bandwidth which influences active ONUs during the ranging procedure.

• 한국군사과학기술학회지
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• 제20권5호
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• pp.654-664
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• 2017

The temperature profiles upon high speed impact of reactive structural materials were analyzed. A two color pyrometer, which included high-speed camera, spectral splitter, and band pass filters, was utilized to measure transient temperature profiles during and after reactive metal samples impacted into steel plate with velocities of 1600~1700 m/s. The spatial temperature distribution was analyzed from the ratio of spectral radiances at two different wavelength in infrared zone, i.e. 700 and 900 nm. The measured temperatures were calibrated with black body source. Two different types of metal samples, namely aluminum and nickel, were employed to understand reaction behavior upon the impact of samples in ambient condition. According to our experiments, the Ni sample appeared to barely react with ambient air producing an instant small fireball, while Al sample reacts violently with air generating a relatively prolong fireball.

• Advances in aircraft and spacecraft science
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• 제5권4호
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• pp.431-444
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• 2018

Numerical simulations have been conducted to study the unstart/restart characteristics of an over-under turbine-based combined-cycle propulsion system (TBCC) inlet during the inlet transition phase. A dual-solution area exists according to the Kantrowitz theory, in which the inlet states may be different even with the same input parameters. The entire transition process was divided into five stages and the unstart/restart hysteresis loop for each stage was also obtained. These loops construct a hysteresis surface which separates the operating space of the engine into three parts: in which a) inlet can maintain a started state; b) inlet keeps an unstarted state; c) inlet state depends on its initial state. During the transition, the operation of the engine follows a certain order with different backpressures and splitter angles, namely control route, which may result in disparate inlet states. Nine control routes with different backpressures and transition stages were designed to illuminate the route-dependent behavior of the inlet. The control routes operating towards the unstart boundary can make the inlet transit from a started state into an unstarted one. But operating backward the same route cannot make the inlet restart, additional effort should be made.

• 조명전기설비학회논문지
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• 제30권2호
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• pp.11-19
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• 2016

By incorporating a polarization-diversity loop configuration, we have demonstrated the inline switching of transmission and reflection spectra of one of two short-period fiber gratings (SPFGs) with different resonance wavelengths without reconfiguring the filter structure. The proposed filtering apparatus consists of a fiber-pigtailed polarization beam splitter, two SPFGs, and three quarter-wave plates (QWPs). The proposed filter can independently choose the transmission or reflection spectrum of each SPFG through the appropriate adjustment of the orientation angles of the QWPs within the filter without additional optical switches and couplers. The average insertion loss, band rejection ratio, and side-mode suppression ratio of the fabricated filter were measured as ~4.59, ~17.88, and ~19.67dB, respectively.

• 한국자동차공학회논문집
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• 제9권1호
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• pp.45-56
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• 2001

A constant volume combustion chamber is employed to investigate the initial flame kernel development and flame propagation of gasoline-air mixtures with various ignition systems, ignition energy and spark plug electrodes. To do this research, four ignition systems are designed and manufactured, and the ignition energy is controlled by varying the dwell time. Several kinds of spark plugs are also made to analyze the effects of electrodes on flame kernel development. The velocity of flame propagation is measured by the laser deflection method. The output laser beam from He-Ne laser is divided into three parallel beams by a beam splitter. The splitted beams pass through the combustion chamber. They are deflected when contacted with flame front, and the voltage signals from photodiodes change due to deflection. The results show that higher ignition energy raises the flame propagation speed especially under the fuel lean operation. The wider electrode gap, smaller electrode diameter and sharper electrode tip make the speed of the initial flame propagation faster. The speed of the initial flame propagation is affected by electrode material as well. Electrode material with lower melting temperature help the initial flame propagation.

• 한국광학회지
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• 제7권3호
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• pp.191-195
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• 1996

대기오염 연구용 이동형 라이다의 광계통을 설계하였다. 대기오염이나 오종층의 측정을 위해 라이다를 사용하며 군에서는 화생방 오염 측정에도 사용된다. 역 Cassegrain형의 시준기로 평행광을 만들어 평면경에 의해 전송하는 레이저광속과 수신 망원경의 광축이 일치하게 된다. 레이저광속은 대기로 향하여 전송되며 측정하고자 하는 물질에 의해 산란되어 수신 망원경으로 되돌아 온다. 주사반사경은 수직으로 60.deg. 수평으로 180.deg.회전되며 주사한다. 주사반사경은 수신망원경과 분리되어 자동차 지붕위에 설치된다. 수신된 레이저광은 공간주파수 여과기에 의해 여과되고, fabri렌즈에 의해 평행광으로 되어 광속분리기에 의해 2개의 광속으로 나뉘어 검출된다. 각 레이저광은 PM관에 의해 검출되어 증폭되고 분석된다.

• 화약ㆍ발파
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• 제28권1호
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• pp.63-70
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• 2010

본 연구는 유압력을 이용한 할암공법의 진동 및 소음크기에 대한 현장 적용성 판단을 위해 축사와 노후된 주택구조물 근접지역에서 진동과 소음의 크기를 검토하였다. 검토는 할암공법의 작업과정별로 천공, 절개, 집토 및 상차에 따라 발생되는 진동과 소음의 크기를 근접된 위치(10m~80m)에서 측정 분석하여 대상지역에 설정된 진동과 소음의 허용수준과 비교 하였다. 그 결과 국토해양부의 발파공법 분류에 의해 미진동굴착공법으로 할암 공법을 적용하여도 소음도의 영향은 고려되어야 하는 것으로 확인되었다.

• 한국정보통신학회논문지
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• 제9권1호
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• pp.160-164
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• 2005

자동차 번호판 자동인식에서 어두운 조명에서나 날씨가 좋지 않을 경ㅇ 차량의 형상이 왜곡 될 수 있고, 번호판을 식별하는데 어려움이 있다. 이에 본 논문에서는 움직이는 차량의 영상에서 흔들림이 없고, 밝은 햇빛에서 어두운 조명상태까지의 다양한 환경을 수용할 수 있는 자동차 번호판 인식방법을 제안하였다. 제안한 방법은 투시광선을 서로 다른 세기를 갖는 두 개의 빔(beam)으로 분리한 다음 CCD 카메라를 사용하여 두 개의 포착된 이미지를 조합하여 물체가 움직일 때도 동요 없는 이미지를 산출하였다. 실험결과로써 466 개의 움직이는 차량영상을 이용한 결과 98.7%의 인식률을 얻을 수 있었다.