• Journal of the Korean Ceramic Society
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• v.53 no.4
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• pp.450-455
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• 2016

Color change in single-crystal, yellow, red, purple, and colorless cubic zirconias (CZs) was investigated as a function of annealing in vacuum and air atmosphere at $800-1400^{\circ}C$ for 30 min, for development of a damascene process of plugging a precious metal paste at the elevated temperature. Coloring-element contents of the CZs were evaluated using WD-XRF, and the color change determined visually by naked eye, and using a digital camera and UV-Vis-NIR color analyzer. WD-XRF showed that all of the CZs had cubic-phase stabilizer elements and coloring elements. All CZs that underwent vacuum annealing exhibited a slight color change at $<900^{\circ}C$, while their colors began to change to black at $1100^{\circ}C$, and became opaque black at $1400^{\circ}C$. After air annealing, there was almost no color change up to $1400^{\circ}C$. Since red and purple CZs showed greater color difference (CD) values than the others, the degree of CD is likely to depend on the original color of the CZ due to the different stabilities of their coloring elements during annealing. Based on our results, it is suggested that annealing in air at $<900^{\circ}C$ is advantageous, and assorted colored CZs can be used for precious metal damascene.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.864-870
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• 2001

Flame propagation along vortex tube was experimentally investigated. The vortex tube was generated by the ejection of propane from a nozzle through a single stroke motion of a speaker and the ignition was induced from a single pulse laser. Non-reactive flow fields were visualized using shadow technique. From these images, vortex ring size and translational velocity were measured in order to determine the ignition time and position. Flame structure and flame speed were measured using high speed CCD camera. Flame speed was accelerated during the initial stage of flame kernel growth, and reached near constant value during steady propagation period. Near the completion of propagation, flame speed was decelerated and then extinguished. Flame speed along the non-premixed vortex tube was found to be linearly proportional to circulation, which was similar to that of the flame propagation along premixed vortex ring. Ignition position minimally affects the propagation characteristics. These imply that flame is propagating along the maximum speed locus expected to be along stoichiometric contour and also support the existence of tribrachial flames.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.35 no.5
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• pp.339-348
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• 2017

Due to recent improvements in computer processing speed and image processing technology, researches are being actively carried out to combine information from a camera with existing GNSS (Global Navigation Satellite System) and dead reckoning. In this study, the mathematical model based on SPR (Single Photo Resection) is derived for image-based assistant algorithm for vehicle positioning. Simulation test is performed to analyze factors affecting SPR. In addition, GNSS/on-board vehicle sensor/image based positioning algorithm is developed by combining image-based positioning algorithm with existing positioning algorithm. The performance of the integrated algorithm is evaluated by the actual driving test and landmark's position data, which is required to perform SPR, based on simulation. The precision of the horizontal position error is 1.79m in the case of the existing positioning algorithm, and that of the integrated positioning algorithm is 0.12m at the points where SPR is performed. In future research, it is necessary to develop an optimized algorithm based on the actual landmark's position data.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.488-491
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• 2006

In this paper, a slim type actuator is proposed rising a bimorph PZT and a circular rotor link. The bimorph contacts the circular rotor, and its displacement generates the rotational motion of the rotor. The rotor causes the linear motion of AF and zoom lens through gear and a motion guide. The proposed model enables the actuations of many lens groups for zoom module by extending the single lens model. The important design parameter is the contact force determined by the frictional coefficient and preload between the rotor and PZT bimorph. A prototype of the single actuator model is manufactured and experiments results using LDV and tachometer are compared to the theoretical and numerical predictions. Experiments show the linear bimorph actuator model meets the performance criteria of the lens actuation, and it can be applicable to various slim type actuators for AF and zoom motions in mobile cameras.

• Proceedings of the KIEE Conference
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• 2008.10b
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• pp.379-381
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• 2008

본 논문에서는 가정용 비디오 게임에 사용 가능한 고속의 저가형 모션캡쳐, 시스템에 사용되는 전 방향 특성을 갖는 IR 능동 마커의 개발을 목표로 하고 있다. 현재 영화나 게임에서 모션캡쳐를 응용한 시스템 및 컨텐츠들이 많이 선보기고 있으며, 인기를 모으고 있는 추세이다. 이러한 흐름에 맞추어 우리는 이미 저가이면서 속도가 빠른 PSD(Position Sensitive Detector) 센서를 이용만 스테레오 비젼 기반의 PSD 모션캡쳐 시스템(Stereo vision based PSD motion capture system)과 광량 보정 기반의 단일 PSD 모션캡쳐 시스템(Intensity Calibration based single PSD motion capture system) 그리고 일정간격의 두 능동마커 기반의 단안 PSD 모션캡쳐 시스템(Two active markers at fixed distance based single PSD motion capture system)등을 소개한 바 있다. 본 논문에서 제안하는 전방향 특성을 갖는 IR 능동 마커는 일정간격의 두 능동마커 기반의 단안 PSD 모션캡쳐 시스템에 적용하여 보다 정밀한 3차원 좌표 측정을 할 수 있도록 한다. 이를 위해 본 논문에서는 동일 특성을 갖는 마커를 제작하고 평가하여 일정간격의 두 능동마커 기반의 단안 PSD 모션캡쳐 시스템에 적합한 마커의 제작 방법을 제안하였다.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.796-801
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• 2007

The optical performance of the mirror for satellite camera is highly dependent on the adhesive properties between the mirror and its support. In order to design a mirror with high optical performance, the mechanical properties of adhesives should be well defined. In this research, the mechanical properties of three kinds of space adhesives are studied. In case of the materials which show nearly incompressible behavior such as space adhesives, it is important to measure shear modulus which governs deviatoric stress components. Shear moduli of the adhesives are determined by using single lap adhesively bonded joint. For the shear tests, several points have been selected from $-20^{\circ}C$ to $50^{\circ}C$ which is operating temperature range of the adhesive. The shear modulus of each adhesive is expressed as a function of temperature. Characteristics of the adhesives are discussed regarding their temperature sensitivity. The analysis results of RMS wavefront error w.r.t shear modulus are presented.

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.6
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• pp.51-59
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• 2000

In-cylinder spray flow motion plays an important in the adjustment of mixture preparation with a fundamental spray characteristics and in-cylinder flow field well in direct-injection gasoline engine. In this study, the fundamental spray characteristics such as mean drop size, velocity distribution, spray angle were measured and in-cylinder spray flow motion was visualized in order to optimize intake port, piston top land and combustion chamber shapes in the development stage of mass-produced G야 engine. For these experiments, the PDPA measurements and Mie scattering technique were used for detailed spray characteristics and in-cylinder spray motions were obtained by use of ICCD camera through the single-cylinder optical engine. From the experimental results, the test injector shows a good low-end linearity between the dynamic flow and fuel injection pulse width and the fuel spray of 20mm or less in SMD with good spray symmetry. In addition, the in-cylinder tumble flow has more effect on the homogeneous mixture formation than that of in-cylinder swirl flow at early injection mode and the in-cylinder swirl flow plays a better role of stratified mixture preparation than tumble flow at late injection mode.

• Journal of the Korean Society of Safety
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• v.29 no.5
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• pp.15-21
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• 2014

The aim of this work is conduct the study on light weight and structural performance improvement of the composite wind power blade. GFRP (Glass Fiber Reinforced Plastic) pre-empted by CFRP(Carbon Fiber Reinforced Plastic), the major material of wind power blade, was identified the superiority of mechanical performance through the tensile and fatigue test. SENT(Single Edge Notched Tension) specimen fracture test was conducted on the specimen that laminated together 2 ply CFRP with 4 ply GFRP through DIC(Digital Image Correlation) analysis. The SENT specimen thickness and $a_0/W$ ratio is 1.45 mm and 0.2, respectively. The fracture test accomplished with displacement control with 0.1 mm/min at the room temperature. The experimental apparatus used for the fracture test consisted of a 50kN universal dynamic tester and CCD camera connected to a personal computer (PC), which was used to record images of the specimen surface. Following data acquisition, the images and load-displacements were transferred to the PC, on which the DIC software was implement. The experiment and DIC analysis results show that CFRP/GFRP laminated composite exhibits improvement of the strength, compared with that of the existing blade material. This study shows the result that the strength of CFRP rotor blade of wind turbine satisfies through the experimental and DIC method.

• 한국연소학회:학술대회논문집
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• 2005.10a
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• pp.120-131
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• 2005

The evaporation characteristics of single and multicomponent droplets hanging at the tip of a quartz fiber are studied experimentally at the different environmental conditions under normal gravity. Heptane and Hexadecane are selected as two fuels with different evaporation rates and boiling temperatures. At the first step, the evaporation of single component droplet of both fuels has been examined separately. At the next step the evaporation of several blends of these two fuels, as a binary component droplet, has been studied. The temperature and pressure range is selected between 400 and 700 $^{\circ}C$, and 0.1 and 2.5 MPa, respectively. High temperature environment has been provided by a falling electrical furnace. The initial diameter of droplet was in range of 1.1 and 1.3 mm. The evaporation process was recorded by a high speed CCD camera. The results of binary droplet evaporation show the three staged evaporation. In the the first stage the more volatile component evaporates. The droplet temperature rises after an almost non evaporating period and in the third stage a quasi linear evaporation takes place. The evaporation of the binary droplet at low pressure is accompanied with bubble formation and droplet fragmentation and leads to incomplete microexplosion. The component concentration affects the evaporation behavior of the first two stages. The bubble formation and droplet distortion does not appear at high environment pressure. Nomenclature

• Journal of the Korean Society of Combustion
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• v.20 no.3
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• pp.13-20
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• 2015

The performance of a direct-injection diesel engine often depends on the strength of swirl or squish, the shape of combustion chamber, the number of nozzle holes, etc. This is natural because the combustion in the cylinder was affected by the mixture formation process. Since the available duration to make the mixture formation of air-fuel is very short, it is difficult to make complete mixture. Therefore, an early stage of combustion is violent, which leads to the weakness of noise and vibration. In this paper, the combustion process of a common-rail diesel engine was studied by employing two kinds of pistons. One has several cavities on the piston crown to intensify the squish during the compression stroke in order to improve the atomization of fuel, we call this multi cavity piston in this paper. The other is a toroidal single cavity piston, generally used in high speed diesel engines. To take photographs of flame and flaming duration, a four-stroke diesel engine was remodeled into a two-stroke visible single cylinder engine and a high speed video camera was used.