• Structural Engineering and Mechanics
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• 제74권6호
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• pp.809-819
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• 2020

For the first time, the influence of in-plane magnetic field on wave propagation of Graphene Nano-Platelets (GNPs) polymer composite nanoplates is investigated here. The impact of three- parameter Kerr foundation is also considered. There are two different reinforcement distribution patterns (i.e. uniformly and non-uniformly) while the material properties of the nanoplate are estimated through the Halpin-Tsai model and a rule of mixture. To consider the size-dependent behavior of the structure, Eringen Nonlocal Differential Model (ENDM) is utilized. The equations of wave motion derived based on a higher-order shear deformation refined theory through Hamilton's principle and an analytical technique depending on Taylor series utilized to find the wave frequency as well as phase velocity of the GNPs reinforced nanoplates. A parametric investigation is performed to determine the influence of essential phenomena, such as the nonlocality, GNPs conditions, Kerr foundation parameters, and wave number on the both longitudinal and flexural wave characteristics of GNPs reinforced nanoplates.

• International Journal of Automotive Technology
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• 제5권3호
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• pp.155-164
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• 2004

The direct injection gasoline spray-wall interaction was characterized inside a heated pressurized chamber using various visualization techniques, including high-speed laser-sheet macroscopic and microscopic movies up to 25,000 frames per second, shadowgraph, and double-spark particle image velocimetry. Two hollow cone high-pressure swirl injectors having different cone angles were used to inject gasoline onto a heated plate at two different impingement angles. Based on the visualization results, the overall transient spray impingement structure, fuel film formation, and preliminary droplet size and velocity were analyzed. The results show that upward spray vortex inside the spray is more obvious at elevated temperature condition, particularly for the wide-cone-angle injector, due to the vaporization of small droplets and decreased air density. Film build-up on the surface is clearly observed at both ambient and elevated temperature, especially for narrow cone spray. Vapor phase appears at both ambient and elevated temperature conditions, particularly in the toroidal vortex and impingement plume. More rapid impingement and faster horizontal spread after impingement are observed for elevated temperature conditions. Droplet rebounding and film break-up are clearly observed. Post-impingement droplets are significantly smaller than pre-impingement droplets with a more horizontal velocity component regardless of the wall temperature and impingement angle condition.

• 한국안광학회지
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• 제6권2호
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• pp.11-16
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• 2001

렌즈에 가한 응력을 측정하기 위한 편광기는 1/4 파장판-편광판으로 구성하였고, 각 단계별 광파의 $E_1$, $E_2$의 성분을 분석하였다. 주 응력차 ${\sigma}_1-{\sigma}_2$는 무늬 차수(N)가 시료 각 점에서 분석되고, 시료의 광축은 주 응력 방향과 일치하는 것으로부터 2 차원 모델을 결정할 수 있다. 광파에 작용하는 복굴절성과 위상지연은 주 응력차 (${\sigma}_1-{\sigma}_2$)에 비례하고, 최종 광파의 세기는 $sin^2({\Delta}/2)$에 비례하고, ${\Delta}/2=n^{\pi}$ (n=0, 1, 2, ...)일 때 소멸 무늬인 흡광이 일어난다. 실험적 결과로는 렌즈의 외부 응력의 크기에 따라 흡광 band가 이동한다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 하계학술대회 논문집
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• pp.733-736
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• 2001

Instead of a solution technigue producing amorphous LiV$_3$O$_{8}$ form, we prepared Lithium vanadate glass by melting Li$_2$O-P$_2$O$_{5}$-V$_2$O$_{5}$, composition in pt. crucible and by quenching on the copper plate. From the crystallization of Li$_2$O-P$_2$O$_{5}$-V$_2$O$_{5}$, we could abtain crystal phase, LiV$_3$O$_{8}$. The material heat-treated at lower-temperature, 25$0^{\circ}C$ was less crystalline, but had higher capacity. In present paper, we describe eletrochemical properties during crystallization process and find the best crystallization condition of Li$_2$O-P$_2$O$_{5}$-V$_2$O$_{5}$ glass as cathod material.cathod material.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집 Vol.3 No.2
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• pp.797-800
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• 2002

Instead of a solution process producing amorphous $LiV_3O_8$ form, we prepared Lithium vanadate glass by melting $Li_2O-P_2O_5-V_2O_5$ and $Li_2O-P_2O_5-Bi_2O_3-V_2O_5$ composition in pt. crucible and by quenching on the copper plate. From the crystallization of $Li_2O-P_2O_5-V_2O_5$ and $Li_2O-P_2O_5-Bi_2O_3-V_2O_5$, we could abtain glass-ceramics having crystal phase, LiV3O8 from glass matrix. The material heat-treated at lower-temperature, $250^{\circ}C$ had less crystalline and lower capacity, But the material heat-treadted at higher-temperature, $330^{\circ}C$ had higher capacity and $Li_2O-P_2O_5-V_2O_5$ glass-ceramics had higher capacity than $Li_2O-P_2O_5-Bi_2O_3-V_2O_5$ glass-ceramics.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.534-538
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• 2002

Dissimilar friction stir welding of aluminum (AI) alloy 1050 and magnesium (Mg) alloy AZ31 was successfully done in the limited welding parameters. The dissimilar weld showed good quality and facility compared to conventional fusion weld. Transverse cross section perpendicular to the welding direction had no defects. The weld was divided into base material of Al alloy, an irregular shaped stir zone and base material of Mg alloy. The irregular shaped stir zone was roughly located around the initial weld center. The weld interface near plate surface shifted from initial weld centerline to the advancing side. Hardness profile of the weld was heterogeneous, and the hardness value of the stir zone was raised to about 150 Hv to 250 Hv. The mixed phase was identified to intermetallic compound $Mg_{17}$Al$_{12}$ using x-ray diffraction method, energy dispersive x-ray spectroscopy (EDX) and electron probe micro analysis (EPMA). The formation of intermetallic compound $Mg_{17}$Al$_{12}$ during FSW causes the remarkable increase in hardness value in the stir zone.one.

• 한국광학회지
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• 제8권2호
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• pp.99-106
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• 1997

본 논문에서는 변형된 삼각 간섭계를 이용하여 인코히어런트(incoherent) 홀로그래피의 근본적인 문제인 바이어스와 공액영상을 제거할 수 있다는 것을 실험과 수치복원을 통해 입증하였다. 기존의 삼각 간섭계에 간단한 수동소자를 추가하여 구성된 변형된 삼각 간섭계의 출력면쪽에 위치한 wave plates를 이용하여, 변형된 삼각 간섭계내에서 시계방향과 반시계방향으로 진행하는 두 빛의 상대적인 위상차를 조절함으로써 4가지의 빛의 세기를 얻고, 이를 이용하여 바이어스와 공액영상이 제거된 복소홀로그램을 얻었다. 또한 이를 수치적으로 복원한 결과와 기존의 삼각 간섭계를 이용하여 얻은 홀로그램을 수치적으로 복원한 결과를 비교분석함으로써, 변형된 삼각 간섭계를 이용하여 바이어스와 공액영상이 제거되는 것을 실험적으로 증명하였다.

• 대한기계학회논문집A
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• 제26권9호
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• pp.1874-1881
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• 2002

Heat dissipation technology using the flow resonant phenomenon is a kind of a new concept in the heat transfer area. A vibration exciter is needed to enhance air flow mixing which has the natural shedding frequency of thermal system. A mechanical vibrating device for the air flow oscillation is introduced, which is driven by a moving coil actuator with a displacement estimator using strain gage. An analytical dynamic model for this mechanical vibration exciter is presented and its validity is checked by the comparison with experimental data. Values of some unknown system parameters in the analytic model are estimated through the system identification approach. Based on this mathematical model, the vibration exciter using strain displacement estimator is developed. During the experimental verification phase, it turns out the high modal resonant characteristics of a vibrating plate are a major barrier against obtaining a high bandwidth vibration exciter.

• Smart Structures and Systems
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• 제4권4호
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• pp.449-464
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• 2008

An array based, outward monitoring, ultrasonic guided wave based SHM technique using a single transmitter and multiple receivers (STMR), with a small footprint is discussed here. The previous implementation of such SHM arrays used a phase-reconstruction algorithm (that is similar to the beam-steering algorithm) for the imaging of reflectors. These algorithms were found to have a limitation during the imaging of defects/reflectors that are present in the "near-field" of the array. Here, the "near-field" is defined to be approximately 3-4 times the diameter of the compact array. This limitation is caused by approximations in the beam-steering reconstruction algorithm. In this paper, a migration-based reconstruction algorithm, with dispersion correction in the frequency domain, is discussed. Simulation and experimental studies are used to demonstrate that this algorithm improves the reconstruction in the "near-field" without decreasing the ability to reconstruct defects in the "far-field" in both isotropic and anisotropic plates.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1999년도 제14차 학술회의논문집
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• pp.9-12
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• 1999

This paper presents the development of a control architecture for the autonomous underwater vehicle (AUV) with VARIVEC (variable vector) propeller. Moreover this paper also describes the new technique of controlling the servomotors using the Field Programmable Gate Array (FPGA). The AUVs are being currently used fur various work assignments. For the daily measuring task, conventional AUV are too large and too heavy. A small AUV will be necessary for efficient exploration and investigation of a wide range of a sea. AUVs are in the phase of research and development at present and there are still many problems to be solved such as power resources and underwater data transmission. Further, another important task is to make them smaller and lighter for excellent maneuverability and low power. Our goal is to develop a compact and light AUV having the intelligent capabilities. We employed the VARIVEC propeller system utilizing the radio control helicopter elements, which are swash plate and DC servomotors. The VARIVEC propeller can generate six components including thrust, lateral force and moment by changing periodically the blade angle of the propeller during one revolution. It is possible to reduce the number of propellers, mechanism and hence power sources. Our control tests were carried out in an anechoic tank which suppress the reflecting effects of the wall surface. We tested the developed AUV with required performance. Experimental results indicate the effectiveness of our approach. Control of VARIVEC propeller was realized without any difficulty.