• 한국항공우주학회지
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• 제47권9호
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• pp.658-664
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• 2019

핀틀 인젝터를 사용하는 액체로켓개발에 있어서 분무특성인 분무각도, 액적크기, 액적의 분포정도는 중요한 요소이다. 세 종류의 다중 홀형 핀틀 팁과 연속형 핀틀 팁을 설계하여 분무실험을 수행하였다. 다중 홀형 인젝터에서 홀 개수에 따른 액적크기는 크게 차이가 없었으며, 홀 개수가 많을수록 액적이 균일하게 분포하였다. 연속형 핀틀은 다중 홀형 핀틀보다 액적의 미립화가 잘 이루어 지고 공간내로 더 고르게 분산되는 것을 확인하였다. 핀틀의 액체분사면적조절을 통한 추력제어는 다중 홀형보다는 면 접촉 닫힘(face-shutoff)이 용이한 연속형 핀틀이 적합하다. 각 핀틀 팁의 TMR에 따른 분무각을 측정하여 특정한 경향성과 그에 해당하는 경험식을 도출하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 추계학술대회 논문집 학회본부 C
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• pp.1160-1163
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• 1999

In this study, we developed FE-tip lithography system that could apply to multi-tip system and did lithography using FE-tip. The software that control FE-tip lithography system, was proposed for acquiring more adaptive data to compensate the effect of fluctuation. We found that the fluctuation effect was reduced. The minimum line width was related to applied voltage and we observed a movement of Z-axis piezo stage to correct the error of this system. When FE current was 5nA, scanning speed was $3{\mu}m/sec$ and applied voltage was 200V, we made a line pattern which had minimum line width of 614 nm. If we reduce applied voltage to several decades and increase scanning speed to $20{\mu}m/sec$, it is possible to set the minimum line width of 100 nm. The proposed system can be easily applied to multi FE-tip lithography system.

• 동력기계공학회지
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• 제19권3호
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• pp.11-15
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• 2015

In this paper, the multi-point hydrogen detection system based on the combination of the hetero-core optical fiber SPR hydrogen tip sensor and interrogator by pseudorandom noise (PN) code correlation reflectometry has been developed. In a light intensity-based experiment with an LED operating at 850 nm, it has been presented that a transmitted loss change of 0.32dB was induced with a response time of 25 s for 4% $H_2$ in $N_2$ in the case of the 25-nm Au, 60-nm $Ta_2O_5$, and 5-nm Pd multi-layers film. The proposed sensor characteristic shows excellent reproducibility in terms of loss level and time response for the in- and out- $H_2$ action. In addition, in the experiment for multi-point hydrogen detection, all sensors show the real-time response for 4% hydrogen adding with reproducible working. As a result, the real-time multi-point hydrogen detection could be realized by means of the combination of interrogating system and hetero-core optical fiber SPR hydrogen tip sensors.

• 대한토목학회논문집
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• 제32권6A호
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• pp.379-387
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• 2012

본 연구에서는 새로운 에너지 수확용 Multi-layer 블록 구조를 제시하고 고체 및 Shell 유한 요소를 사용하여 다양한 기하학적 형상 변화에 대한 자유진동 특성을 분석하고 압전 성능을 실험적으로 평가한다. 본 연구에서 제시하는 블록 구조에 대한 2차원 및 3차원 유한요소 모델은 해석의 정확성 뿐 만 아니라 전체 진동 모드를 정확히 보여준다는 점에서 장점을 갖는다. ABAQUS가 적용된 유한요소 모델은 다양한 Tip mass 및 PZT 변화에 따른 Multi-layer 블록 구조의 자유진동을 분석하기 위하여 사용되었다. 특히, 본 연구에서 제시한 결과는 블록구조 전체의 기하학적 형상, Tip mass 및 Hole의 유무, Tip mass 및 PZT의 위치변화 등에 대하여 국부 및 전체 진동 모드에 미치는 중요한 영향들에 대하여 초점을 둔다. 또한, 실험실 규모의 실제 모형 실험을 수행하여 개발한 에너지 블록구조의 발전성능을 평가하였다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2011년도 춘계학술대회 논문집
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• pp.593-594
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• 2011

• International Journal of Precision Engineering and Manufacturing
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• 제6권2호
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• pp.50-54
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• 2005

We report a simple, low cost, and reliable method for assembling a multi-walled nanotube (MWNT) to the end of a metal coated scanning probe microscopy (SPM) tip. By dropping the MWNT solution and applying an electric field between an SPM tip and an electrode, MWNTs which were dispersed into a dielectric solution were directly assembled onto the apex of the SPM tip due to the attraction by the dielectrophoretic force. The effective measurement of a MWNT -attached SPM tip was demonstrated by direct comparison with AFM images of a standard sample with a bare AFM tip.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2004년도 유체기계 연구개발 발표회 논문집
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• pp.390-395
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• 2004

The characteristics of the circular arc shaped multi-blade windmil are investigatedl. The prototypical windmill was tested in the laboratory at wind tunnel speeds of 5.5, 9.4m/s. and the model windmill was also tested in the laboratory, The power and torque coefficients were studied as functions of the blade section, the aspect ratio for blade diameter and windmill radius(M = 0.3, 0.5, 0.7), the number of blades and finally the tip-speed ratio. The analysis of the experimental results for the model windmill showed that there is the highest revolutions per minute(R.P.M) at the circular arc shaped multi-blade windmill having the blade number 10, aspect ratio(M = 0.7). and the results for the prototypical windmill showed that the power coefficient increased to a maximum value and then decreased again with an increase in the tip speed ratio, while the torque coefficient decreased directly with an increase in the tip speed ratio Finally, the experimental results were compared with the Savonius blade. the maximum power coefficient for the arc shaped blade was greater than for the Savonius blade and occured at a lower tip speed ratio.

• 대한기계학회논문집B
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• 제33권5호
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• pp.373-380
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• 2009

The evaporation process of multi-component fuel is different from one of a single component, because the properties of each component affects among the components. In actual engine, the spatial distribution of fuel vapor concentration dominates auto-ignition and initial combustion, and depends on the volatility and diffusivity of each component fuel contained in the multi-component fuel. Then, this study proposes a simplified numerical scheme for analysis of evaporation process of multi-component fuel sprays. Evaporation process is calculated by KIVA-II code based on the simple two-phases region that is approximated by modified saturated liquid-vapor line, which was obtained by connecting the 50% distillation temperature for each component under several pressure fields. Consequently, it can be quantitatively simulated that vapor of low boiling fuel component mostly exists around nozzle and spray tip region, the high boiling duel component, on the other hand, mostly appears near the spray tip.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.923-928
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• 2004

AFM tip has been used for surface profiling with a fine resolution, but there is a barrier to improve its performance because of the low aspect ratio. Many researchers have solved this problem with attaching carbon nanotube (CNT) to Si-tip. In this paper, we proposed the aligner system that composed of dual type stage system, and these stages could attach a carbon nanotube to tungsten-tip in vacuum condition. We used tungsten tip instead of Si-tip because of its conductivity. The aligner system proposed in this paper has 10 degree-of-freedom that 3 in the first stage and 7 in the second stage. With picomotors and piezotube, the first stage has the resolution about several tens of nm and the second stage has a resolution about a nm. We experimented on characterization of Nano Aligner System and operated picomotors in SEM environment.

• Restorative Dentistry and Endodontics
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• 제46권4호
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• pp.51.1-51.13
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• 2021

Objectives: This study aimed to evaluate the effect of improper positioning single-peak and multi-peak lights on color change, microhardness of bottom and top, and surface topography of bulk fill and incremental composites after artificial aging for 1 year. Materials and Methods: Bulk fill and incremental composites were cured using multi-peak and single-peak light-emitting diode (LED) following 4 clinical conditions: (1) optimal condition (no angulation or tip displacement), (2) tip-displacement (2 mm), (3) slight tip angulation (α = 20°) and (4) moderate tip angulation (α = 35°). After 1-year of water aging, the specimens were analyzed for color changes (ΔE), Vickers hardness, surface topography (Ra, Rt, and Rv), and scanning electron microscopy. Results: For samples cured by single-peak LED, the improper positioning significantly increases the color change compared to the optimal position regardless of the type of composite (p < 0.001). For multi-peak LED, the type of resin composite and the curing condition displayed a significant effect on ΔE (p < 0.001). For both LEDs, the Vickers hardness and bottom/top ratio of Vickers hardness were affected by the type of composite and the curing condition (p < 0.01). Conclusions: The bulk fill composite presented greater resistance to wear, higher color stability, and better microhardness than the incremental composite when subjected to improper curing. The multi-peak LED improves curing under improper conditions compared to single-peak LED. Prevention of errors when curing composites requires the attention of all personnel involved in the patient's care once the clinical relevance of the appropriate polymerization reflects on reliable long-term outcomes.