• 한국항공우주학회지
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• 제35권5호
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• pp.438-445
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• 2007

액체로켓엔진에서 발생하는 고주파 연소 불안정 제어를 위한 수동 안정화 제어 기구로 음향공을 적용하여, 선형 음향 해석 및 상온 음향 실험을 통해 감쇠 효과의 적합성을 검증하였다. 단일 음향공의 기하학적 형상에 따른 음향 감쇠 효과를 비교하기 위하여 오리피스 직경, 길이를 변화시킨 몇 가지 음향공 모델에 대해 유해 공진주파수 감쇠 효과를 정량적으로 비교, 분석하였다. 다음으로 음향공의 개수에 따른 음향 감쇠 효과를 비교하였다. 주파수 응답함수를 통한 유해주파수 감쇠 성능은 개수 증가에 따라서 우수해졌지만 흡음계수를 통한 최적의 효율 관점에서 볼 때 오히려 과도한 댐핑으로 인한 해당 주파수의 감쇠 효율이 낮아지는 경향이 발생한다. 결론적으로 음향공을 이용한 제어를 위해서는 유해주파수를 감쇠시킬 수 있는 기하학적 형상을 통한 정확한 동조가 필요하다. 또한, 부피의 제약을 고려한 최적의 효율을 발휘할 수 있는 음향공의 형상 설계와 개수의 선택이 절대적으로 필요함을 입증한다.

• 한국재료학회지
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• 제19권12호
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• pp.637-643
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• 2009

In this study, we analyzed the effect of silicon oxynitride matrix on the optical properties of Au nanoparticles dispersed on composite film and explored the effectiveness of the silicon in fine tuning the refractive index of the composite film for applications in optical waveguide devices. The atomic fraction of nitrogen in $SiO_xN_y$ films was controlled by varying the relative flow ratio of nitrogen gas in reactive sputtering and was evaluated optically using an effective medium theory with Bruggeman geometry consisting of a random mixture between $SiO_2$ and $Si_3N_4$. The Au nanoparticles were embedded in the $SiO_xN_y$ matrix by employing the alternating deposition technique and clearly showed an absorption peak due to the excitation of surface plasmon. With increasing nitrogen atomic fraction in the matrix, the surface plasmon resonance wavelength shifted to a longer wavelength (a red-shift) with an enhanced resonance absorption. These characteristics were interpreted using the Maxwell-Garnett effective medium theory. The formation of a guided mode in a slab waveguide consisting of 3 $\mu$m thick Au:$SiO_xN_y$ nanocomposite film was confirmed at the telecommunication wavelength of 1550 nm by prism coupler method and compared with the case of using $SiO_2$ matrix. The use of $SiO_xN_y$ matrix provides an effective way of controlling the mode confinement while maintaining or even enhancing the surface plasmon resonance properties.

• 한국약용작물학회지
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• 제23권2호
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• pp.138-143
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• 2015

This study was carried out to evaluate the preventive effect of three forms of Korean ginseng roots (fresh, white and red) against bisphenol A (BPA) toxicity in mouse male germ cells (GC-2spd, TM3, TM4). ROS (reactive oxygen species) generation were measured by DCF-DA (2',7'-dichlorohydrofluorescein diacetate) assay. Also, semi-quantitative reverse transcriptase polymerase chain reaction (RT-PCR) was performed to quantify the mRNA expression levels of apoptosis-related genes, Bax (pro-apoptotic gene) and Bcl2 (anti-apoptotic gene). ROS generation was increased by $50{\mu}M$ BPA, but definitely decreased by treatment with Korean ginseng extracts (fresh, white and red) in mouse male germ cells. In especial, Korean fresh ginseng extract reduced significantly ROS production to normal control. In addition, Korean fresh and white ginseng extracts suppressed the apoptosis of mouse male germ cells by fine-tuning mRNA levels of apoptotic genes changed by BPA. In general, Korean fresh ginseng extract was more effective than white ginseng extract for reducing BPA-induced oxidative stress and apoptosis in mouse male germ cells. Therefore, Korean fresh and white ginseng may help to alleviate biphenol A toxicity in mouse male germ cells.

• Geomechanics and Engineering
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• 제14권2호
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• pp.161-174
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• 2018

The present study investigates the soil-structure interaction (SSI) effects on the seismic performance of smart base-isolated structures. The adopted control algorithm for tuning the control force plays a key role in successful implementation of such structures; however, in most studied carried out in the literature, these algorithms are designed without considering the SSI effect. Considering the SSI effects, a linear quadratic regulator (LQR) controller is employed to seismic control of a smart base-isolated structure. A particle swarm optimization (PSO) algorithm is used to tune the gain matrix of the controller in both cases without and with SSI effects. In order to conduct a parametric study, three types of soil, three well-known earthquakes and a vast range of period of the superstructure are considered for assessment the SSI effects on seismic control process of the smart-base isolated structure. The adopted controller is able to make a significant reduction in base displacement. However, any attempt to decrease the maximum base displacement results in slight increasing in superstructure accelerations. The maximum and RMS base displacements of the smart base-isolated structures in the case of considering SSI effects are more than the corresponding responses in the case of ignoring SSI effects. Overall, it is also observed that the maximum and RMS base displacements of the structure are increased by increasing the natural period of the superstructure. Furthermore, it can be concluded that the maximum and RMS superstructure accelerations are significant influenced by the frequency content of earthquake excitations and the natural frequency of the superstructure. The results show that the design of the controller is very influenced by the SSI effects. In addition, the simulation results demonstrate that the ignoring the SSI effect provides an unfavorable control system, which may lead to decline in the seismic performance of the smart-base isolated structure including the SSI effects.

• 접착 및 계면
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• 제23권2호
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• pp.53-58
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• 2022

본 연구는 AlO_x유전체 표면에 유기 자립조립 단분자막 (self-assembled monolayer, SAM) 중간층을 도입함으로써 유전체의 표면특성을 제어하고, 최종적으로 유기전하변조트랜지스터 (Organic charge modulated field-effect transistor, OCMFET)의 전기적 특성을 향상시킨 결과를 제시하였다. 유기 중간층을 적용함으로써, OCMFET의 컨트롤 게이트(CG, Control gate)와 플로팅 게이트 (FG, Floating gate) 사이 커패시터 플레이트로 작용하는 산화알루미늄 게이트 유전체의 표면 에너지를 제어하였으며, FET의 가장 중요한 성능변수인 전계효과 이동도(field-effect transistor, μ_FET)를 향상시켰다. 사용된 SAMs은 네가지의 PA (Octadecylphosphonic acid, Butylphosphonic acid, (3-Bromopropyl)phosphonic acid, (3-Aminopropyl) phosphonic acid)를 사용하여 형성하였으며, 각각 0.73, 0.41, 0.34, 0.15 cm2V^-1s^-1의 μ_OCMFET를 나타내었다. 이 연구를 통해 유기 SAM 중간층의 알킬 체인(Alkyl chain)의 길이 및 말단기의 특성이 소자의 전기적 성능을 제어하는데 중요한 요인임을 확인하였으며, 이 결과를 통해 향후 최적의 센서 플랫폼으로서의 OCMFET 소자성능 최적화에 기여할 수 있을 것으로 기대한다.

• ETRI Journal
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• 제38권4호
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• pp.665-674
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• 2016

We designed and fabricated a semiconductor optical amplifier-integrated dual-mode laser (SOA-DML) as a compact and widely tunable continuous-wave terahertz (CW THz) beat source, and a pin-photodiode (pin-PD) integrated with a log-periodic planar antenna as a CW THz emitter. The SOA-DML chip consists of two distributed feedback lasers, a phase section for a tunable beat source, an amplifier, and a tapered spot-size converter for high output power and fiber-coupling efficiency. The SOA-DML module exhibits an output power of more than 15 dBm and clear four-wave mixing throughout the entire tuning range. Using integrated micro-heaters, we were able to tune the optical beat frequency from 380 GHz to 1,120 GHz. In addition, the effect of benzocyclobutene polymer in the antenna design of a pin-PD was considered. Furthermore, a dual active photodiode (PD) for high output power was designed, resulting in a 1.7-fold increase in efficiency compared with a single active PD at 220 GHz. Finally, herein we successfully show the feasibility of the CW THz system by demonstrating THz frequency-domain spectroscopy of an ${\alpha}$-lactose pellet using the modularized SOA-DML and a PD emitter.

• 대한전자공학회논문지TC
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• 제48권2호
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• pp.85-89
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• 2011

본 논문에서는 메타구조를 이용하여 하나의 RF LDMOS로 새로운 Class-E 전력증폭기를 구현하였다. CRLH 구조는 Class-E 전력증폭기 특성을 갖는 메타물질 전송 선로를 만들 수 있다. CRLH 전송 선로는 전력증폭기의 정합 회로를 구현을 위하여 주파수 오프셋과 CRLH 전송 선로의 비선형 위상 기울기에 의해 얻을 수 있다. 또한, 제안된 전력증폭기의 효율을 향상 시키기 위하여 출력 정합 회로에 CRLH 구조를 이용하여 구현하였다. 동작 주파수는 13.56MHz로 정하였다. Class-E 전력 증폭기의 측정된 출력 전력은 39.83dBm, 이득은 11.83 dB이다. 이 지점에서 얻은 전력효율(PAE)은 73%이다.

• 한국광학회지
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• 제17권4호
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• pp.371-380
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• 2006

금으로 된 금속선 광 도파로를 따라 속박되는 장거리 표면 플라즈몬을 이용하여 파장 가변 필터를 설계하고 제작하였다. 실리콘 기판 위에 제작된 금속선 도파로는 두 층의 열광학 폴리머 사이에 샌드위치 구조로 끼어 있도록 설계되었다. 도파로의 바로 윗면에는 유전체로 된 Bragg 회절격자가 적합한 주기로 제작되어, 중심 파장이 광통신 파장대 (1520$\sim$1570 nm)에 있으면서 높은 소광률($\sim$25 dB)을 갖는 파의 반사가 가능했고, 전체손실은 25 dB/cm 이하로 나타났다. 또한, 제작된 파장 가변 필터가 폴리머의 열-광학적 특성에 의해 파장가변 필터 소자로서의 응용이 가능함을 확인했으며, 금속선 광 도파로에 직접 연결된 전극 구조에 동시에 가해준 전류에 의해 파장이 가변 될 수 있음을 실험적으로 확인하였다.

• Journal of Electrical Engineering and Technology
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• 제10권4호
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• pp.1726-1733
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• 2015

In order to study the effect of the high-altitude and dusty weather in northwest of China on the corona characteristics of transmission lines, a corona caged based experimental system with sandy and dusty flow condition is numerically investigated and designed. This system overcomes the difficulties caused by harsh environment and offers easy usage for off-site tests. The design parameters are mainly determined by the characteristics of strong sandstorm in northwest region and test requirements. By the comparison of numerical simulation of the particle diffusion in four programs with rectangular or circular air-duct, a practical technology, which introduces swirl to control the particle diffusion length, is obtained. Accordingly, the structure of round air-duct with swirl elbow in inlet and outlet of high level segment is selected as final program. Systems of control and measurement are designed at the same time. Field tuning results show that the test system could ensure the range of sandy and dusty coverage. The wind speed, sandy and dusty concentration could be controlled and meet the requirements of accuracy. The experimental system has many features, such as simple structure, easy to be assembled, disassembled, transported and operated, small space occupied.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.537-537
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• 2013

Cyclotron-accelerated ion beams are used for various researches, such as nuclear physics, nuclear chemistry, biotechnology, and material sciences including radio-isotope production. Recently considerable applications are asked to the cyclotron development undertaken to meet user requirements of various ions'energies, intensities, and their pulsed beams. For instance, a cocktail beam acceleration technique rapidly changing the ion species and energies was developed to irradiating integrated circuit chips. Also a chopping system in a cyclotron injection line is considered for producing a pulsed ion beam with a relatively long period compared with that generated by the resonance frequency. For the research in neutron time-of-flight measurement, a single-pulsed beam with a repetition interval of the order of mili-seconds or longer is necessary to have a good resolution and to remove background events. In this paper a feasibility of pulsed beam with an external ion source is simulated by adopting a combination system of a chopper accompanying with a bunching stage in the injection line and an additional chopper after the exit of the cyclotron in order to produce beam pulses with a range of $1{\mu}s{\sim}1ms$ periods from a resonance RF cycle. The pulseperiod will be adjusted by chopping the number of beam bunches from the injected pulses in the injection line. However, the longer pulses will have reduced number of beam pulses and sacrificed beam currents. Because the beam users need an intense single pulsed beam, a careful tuning of the acceleration phase and a high-intense external ion source are necessary to achieve an intense single-pulsed beam from the cyclotron. It is essential to strictly match the acceleration phase of injected beams in the central region of the cyclotron to improve its efficiency. An effect of space charge at each pulse from the ion source will be also considered.