• Journal of environmental and Sanitary engineering
• /
• v.15 no.3
• /
• pp.88-93
• /
• 2000

The objective of this study was to depict the kinetic behavior of the platinum catalyst for the deep oxidation of VOCs and their mixture. The oxidation characteristics of VOCs, which were benzene, toluene, and styrene, was studies on a 0.5% $Pt/{\gamma}-Al_2O_3$ catalyst. The reactivity increases in order benzene>toluene>styrene. In mixtures, remarkable effects on reaction rate and selectivity have been evident ; the strongest inhibiting effect was shown by styrene and increases in a reverse order with respect to that of reactivity. The reaction model reveals that there is a competition between the two reactants for the oxidized catalyst. Thus, the nontoxic catalytic oxidation process was suggested as the new VOCs control technology.

• Korean Journal of Optics and Photonics
• /
• v.24 no.5
• /
• pp.251-255
• /
• 2013

In this paper, the characteristics of a humidity sensor implemented by Mach Zehnder Interferometer (MZI) in a Planar Lightwave Circuit (PLC) have been designed and demonstrated. The humidity outside is detected with polyvinylpyrrolidone (PVP) coated on the etched arm of the MZI. The length of the etched arm is 10 mm and the PVP was coated by dip-coating into the etched region. As the refractive index of the PVP changes with the surrounding humidity, the PVP-coated humidity sensor presented changes in the interferogram depending on RH (Relative Humidity) around the PLC. The measured results show that the proposed humidity sensor works successfully in the range of 30% to 80% of RH.

• Korean Journal of Optics and Photonics
• /
• v.8 no.3
• /
• pp.189-193
• /
• 1997

Aspheric pick-up lenses are increasingly used in consumer products such as computer and multimedia, as their mass production has become possible owing to the injection molding process. However still much work needs to be done for more effective manufacture of aspheric lenses, one area of which is the in-line inspection of produced lenses. In this paper, we present a lateral-shearing interferometer that has specially been designed to have a high immunity to external vibration and atmospheric disturbance. The interferometer comprises four prisms. They are directly attached to each other using an immersion oil so that relative sliding motions between the prisms are allowed. Their relative displacement can readily generate necessary lateral-shearing and phase-shifting to determine the wavefront of the beam collimated by the lens under inspection. A special phase-measuring algorithm of arbitrary-bucket is adopted to compensate the phase-shifting error caused by the thickness reduction in the immersion oil. Zernike polynomial fitting has done for determinating quantitative aberration of aspheric pick-up lenses. The interferometer built in this work is robust to external mechanical vibration and atmospheric disturbance so that experimental results show that it has a repeatability of less than λ/100.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.30 no.2A
• /
• pp.34-42
• /
• 2005

In orthogonal frequency-division multiple access (OFDMA) uplink environments, asynchronously received signals can cause multiple access interference (MAI). This paper focuses on the performance degradation due to the MAI over frequency-selective fading channels. We first introduce the timing misalignment, which is defined as the relative timing difference between asynchronous timing error of uplink user and reference time of the base station, and analytically derive the MAI using the power delay profile of wide-sense stationary uncorrelated scattering (WSSUS) channel model. Then, the effective signal-to-noise ratio (SNR) and the average symbol error probability (SEP) are derived. The proposed analytical results are verified through simulations with respect to the region of the timing misalignment and the number of asynchronous users.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.34 no.5
• /
• pp.56-64
• /
• 2006

Station collocation of closely placed multiple GEO spacecraft is required to avoid the problem of collision risk, attitude sensor interference and/or occultation. This paper presents the method of obtaining the orbit correction scheme for collocating two GEO spacecraft within a small station-keeping box. The relative motion of each spacecraft with respect to the virtual geostationary satellite is precisely expressed in terms of power and trigonometry functions. This closed-form orbit propagator is used to define the constraint conditions which meet the requirements for the station collocation. Finally, the technique of constrained optimization is used to find the orbit maneuver sequence. Nonlinear simulations are performed and their results are compared with those of the classical method.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.39A no.1
• /
• pp.28-35
• /
• 2014

In this paper, we propose a SSD(simultaneous single band duplex) system with turbo equalizer for full-duplex over harsh ISI(inter symbol interference) channel. The proposed system uses RF(radio frequency) cancellation and digital cancellation to cancel self-interference caused by simultaneous single band duplex communication. Also, using turbo equalizer, the proposed system equalizes signal after digital cancellation. In this paper, we design SSD system with turbo equalizer. And then we evaluate BER(bit error rate) performance of the proposed system comparison with SSD system with adaptive equalizer. We use simulink program to confirm BER performance of the proposed system. The simulation results shows that the proposed system equalizes received signal effectively over harsh ISI channel and BER performance of the proposed system is better than BER performance of SSD system with adaptive equalizer.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.15 no.5
• /
• pp.1462-1471
• /
• 1991

본 연구에서는 미소 결함주위에서 발생, 전파하는 균열들에 미치는 초기 결함 깊이와 상호 간섭 영향을 검토하기 위하여 기존 재료가 갖고 있는 결함이나 비금속 개 재물로 대신할 수 있다고 생각되는 미소 원공의 크기를 변화시킨 모델에 대해 유한 요 소법을 이용하여 3차원적으로 응력을 해석하였다. 실제 사용하고 있는 부재에 결함 들이 존재할 경우 응력장의 간섭으로 피로 균열 진전이 가속화됨으로 미소 원공 주위 의 응력 분포 및 미소 원공사이의 응력장의 간섭과 미소 원공에서 발생, 전파하는 표 면 균열의 응력 확대 계수에 미치는 영향에 대하여 비교검토 하였다.

• 한국지구과학회:학술대회논문집
• /
• 2010.04a
• /
• pp.116-116
• /
• 2010

마이크로퀘이사들은 고중력 천체와 보통의 별이 공전하며 서로의 물질도 이동하는 근접 쌍성계로서, 불규칙하고 간헐적으로 플레어와 그에 수반하는 상대론적인 속도로 분출되는 물질을 분출하는 현상, 즉 마이크로퀘이사 현상을 보인다. 두 천체사이의 거리는 수백만 킬로미터이고, 특히 물질을 분출하는 것으로 믿어지는 고중력 천체 주변의 크기는 수천 킬로미터 정도인데 반하여, 우리로 부터의 거리는 보통 10 킬로 kpc 이상이다. 따라서 마이크로퀘이사 현상의 영상을 얻으려면 초장기선 전파간섭계를 이용해야 한다. 우리는 일본의 초장기선 전파간섭계 VERA를 이용하여 VERA J2032+4057의 플레어 상태에서의 물질 분출 현상을 영상화 하였다. VERA J2032+4057의 플레어와 불질분출은 매우 복잡하여 여러 가지 모델들을 써서 영상을 해석해 보았다.

• The Science & Technology
• /
• no.9 s.412
• /
• pp.44-47
• /
• 2003

아인슈타인이 지난 1916년 발표한 일바상대론을 통해 처음으로 제시한 중력장의 실체를 찾는 작업이 프랑스와 이탈리아의 실험물리학자들에 의해 본격화됐다. 7월 23일 피사의 사탑으로 유명한 이탈리아 피사에서 수 킬로미터 떨어진 카시나 평원에서 두 나라의 물리학자들은 지난 1996년 착공해 최근 완성한 중력장 간섭계 VIGRO를 공개했다. 지금까지 누구도 시도하지 못했던 간섭계제작의 아이디어를 낸 지 10년만의 일이다. 프랑스와 이탈리아 정부가 공동으로 1억 5천만 유로를 들여 완성한 VIGRO는 앞으로 1년간의 시험가동 기간을 거친 뒤 본격적으로 우주에서 발생하는 중력장의 실체를 밝혀내게 된다.

• Proceedings of the Optical Society of Korea Conference
• /
• 2001.02a
• /
• pp.92-93
• /
• 2001

주파수 안정화 레이저 광원은 10-6 이상의 상대 불확도가 필요한 간섭계에서 널리 쓰이고 있으며 특히 변위 측정 시스템에서는 반드시 쓰이고 있다. 상용화된 많은 변위 측정 시스템은 신호 대 잡음비가 우수하고 광학계의 정렬이 더 쉬운 헤테로다인 방식을 채택하고 있으며 이를 위해서 서로 수직 선형 편광인 다른 주파수의 광을 내보내는 광원이 필요하다. 현재 헤테로다인 변위 측정 시스템에 쓰이고 있는 광원은 이중 주파수 광원을 만드는 방식에 따라 지만 효과(Zeeman effect)를 이용한 지만 레이저(HP사)와 음향-광 변조기(Acousto-optic modulator)를 이용한 이중 주파수 레이저(Zy해사)가 있다. (중략)