• 한국분무공학회지
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• 제11권2호
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• pp.59-68
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• 2006

Experimental results of the metal powder production with internal mixing, internal impinging and the atomizer coupled with substrate design are presented in this paper. In a test with internal mixing atomizer, mean powder size was decreased from $37{\mu}m\;to\;23{\mu}m$ for Pb65Sn35 alloy as the gas-to-melt mass ratio was increased from 0.04 to 0.17. The particle size further reduces to $16.01{\mu}m$ as the orifice area is increased to $24mm^2$. The micrograph of the metal powder indicates that very fine and spherical metal powder has been produced by this process. In a test program using the internal impinging atomizers, the mean particle size of the metal powder was decreased from $22{\mu}m\;to\;12{\mu}m$ as the gas-to-melt-mass ratio increased from 0.05 to 0.22. The test results of an atomizer coupled with a substrate indicates that the deposition rate of the molten spray on the substrate is controlled by the diameter of the substrate, the height of the substrate ring and the distance of the substrate from the outlet of the atomizer. This in rum determines the powder production rate of the spraying processes. Experimental results indicate that the deposition rate of the spray forming material decreases as the distance between the substrate and the atomizer increases. For example, the deposition rate decreases from 48% to 19% as the substrate is placed at a distance from 20cm to 40cm. On the other hand, the metal powder production rate and its particle size increases as the subsrate is placed far away from the atomizer. The production of metal powder with mean particle size as low as $3.13{\mu}m$ has been achieved, a level which is not achievable by the conventional gas atomization processes.

• 한국결정성장학회지
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• 제32권5호
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• pp.205-211
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• 2022

GSV (Granule Spray in Vacuum)는 상온의 진공하에서 나노 크기의 치밀한 세라믹 코팅층을 형성하는 방법이다. 일반적으로, 단사정의 지르코니아는 1150℃에서 정방정으로 변태하며, 이때 6.5 %의 체적변화를 일으켜 치밀한 단사정의 지르코니아를 만들기 어렵다. 본 연구에서는 코팅 효율에 대한 두 가지 처리 변수의 효과를 조사하는 데 중점을 두었다. 아울러, 특별한 가열과정 없이 형성된 필름의 미세구조에 관찰하였다. 샘플 기판에 증착된 지르코니아 필름에 대한 X-ray diffractometer (XRD) 분석은 단사정 지르코니아 필름이 성공적으로 증착되었음을 보여주었다.

• 생물환경조절학회지
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• 제22권4호
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• pp.303-308
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• 2013

배나무 방제용 무인살포시스템 개발을 위하여 생력화를 위한 작업기기를 설계하였다. 또한, 노즐의 분무유형을 실험적으로 분석하여 적정 살포를 위한 노즐 각도, 노즐과의 거리, 수평방향 살포시 거리를 선정하였다. 본 연구를 수행하기 위하여 배의 과수 형태와 재배 환경을 사전 조사하였다. 살포시스템의 살포진행방향에 적합한 분사 노즐각도를 선정하였다. 배나무와 살포시스템 간의 수직거리에 따라 달라지는 살포 정도를 비교하기 위하여 노즐과의 높이에 따른 분포도를 측정하였다. 배나무와 살포 시스템과의 적정 측면 거리를 선정하기 위하여 측면 살포시 거리에 따라 달라지는 분무량을 측정하였다. 무인살포시스템의 약대는 배의 식재 간격에 적합하도록 좌우가 동일한 형태로 2.5m까지 펼쳐지도록 설계 및 제작 하였다. 또한 일정하지 않은 배나무의 높이에 따라 약대의 높이가 1.7m까지 조절되도록 하였다. 본 시스템에 적합한 노즐 각도는 $15^{\circ}$로 나타났다. 배나무와 살포시스템과의 수직거리는 0.7m에서 0.9m의 간격을 유지하여 약제를 살포해야 된다는 것을 알 수 있었다. 수평방향으로 살포하는 경우 좌우 -0.9m에서 0.9m까지의 분무량이 가장 많았다. 약대와의 거리가 0.9m에서 2.1m일 때 가장 많은 분무량을 나타냈다. 실험을 통하여 배 과수원에서의 무인살포시스템에 맞는 분무 환경을 확인 할 수 있었다. 배 과수와의 거리에 따라 적정 거리를 유지하는 시스템을 개발함으로써 효율적인 약액 살포가 가능하게 하였다. 하지만 본 연구에서 진행된 실험은 제한된 실내 환경에서 진행된 것이기 때문에 제작된 시스템의 실제 과수원 환경에서의 실험이 필요하다.

• Journal of Biosystems Engineering
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• 제25권6호
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• pp.457-462
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• 2000

Boom sprayers have been known by their excellency in field efficiency worker’s safety and pest control efficacy. The boom sprayer in Korea that was developed for paddy field is not suitable for upland field of which shape is irregular and inclination is steep, due to heavy chemical tank long boom width and manual on-off control of spraying. The goal of the study was to develope a boom control system that could control boom angles of left and right boom automatically and independently corresponding to local field slope. The prime mover was selected as a cultivating tractor. Main results of this study were as follows. 1. Ultrasonic sensor whose response time was 0.1s and response angle was within $\pm$20$^{\circ}$was selected to measure distance. Voltage output of the sensor(X, Volt) had a highly significant linear relationship with the vertical distance between the sensor and ground surface(Y, mm) as follows; Y=0.0036X-0.437 2. Left and right section of the boom could be folded up by a position control device(on-off control) which could control the left and right boom independently corresponding to local slope by equalizing distances between the sensor and boom at the center and left/right boom. Most reliable DB(dead band) was experimentally selected to be 75$\Omega$(6cm). 3. At traveling velocity of 0.3~0.5m/s RMS of error between desired and achieved height was less than 4.5cm The developed boom angle controller and boom linkage system were evaluated to be successful in achieving the height control accuracy target of $\pm$10cm.

• 한국항공우주학회지
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• 제44권7호
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• pp.611-619
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• 2016

본 논문에서는 농업용 무인헬기를 위한 LiDAR 기반 충돌방지시스템을 제안하고 개발과정을 소개한다. 충돌방지시스템은 장애물 검출 시스템, 매핑 알고리즘, 충돌회피 알고리즘으로 구성된다. LiDAR 기반의 장애물 검출 시스템은 무인헬기에 탑재되어 실시간으로 장애물 정보를 획득하며, 이를 통해 획득한 정보와 무인헬기 자세/위치 정보를 융합하여 충돌위험성이 있는 장애물에 대해 격자 지도 기법을 적용한 매핑을 수행한다. 무인헬기가 장애물에 접근할 시 확보된 지형정보를 기반으로 충돌방지 경고 생성을 위해 종/횡방향 기동을 고려한 충돌방지 알고리즘을 구현하며, 이를 통해 운용자에게 전달해 회피 기동을 수행한다. 구축된 시스템은 무인헬기를 이용해 항공방제 패턴을 모사한 비행시험을 수행하였으며, 비행시험 결과 충돌방지 성능 및 가능성을 확인하였다.

• 대한기계학회논문집B
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• 제26권6호
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• pp.779-787
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• 2002

The cooling heat transfer by impinging water spray jets on a rotating roll with a relatively large diameter has been investigated under various experimental conditions with 3 different sizes of flat type nozzle. The local heat transfer coefficients were calculated by finite difference method using measured surface temperatures of the circular cylinder as boundary conditions. Results show that a peak value of the heat transfer coefficient is located at the center of sprayed area and there may be a secondary peak at the downstream. The average heat transfer coefficients on the sprayed area were found to be 10 to 22 ㎾/$m^2$$^{\circ}C$, and were not related to spraying pressure, but approximately linearly to flow rate of sprayed water. Also it is found that increasing the distance from roll to nozzle could improve the cooling efficiency by increasing the sprayed area.

• 한국고분자학회:학술대회논문집
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• 한국고분자학회 2006년도 IUPAC International Symposium on Advanced Polymers for Emerging Technologies
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• pp.217-217
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• 2006

The surface energy control capability of electrohydrodynamic force provides electrospraying with various potential advantages such as simple particle size control, mono-dispersity, high recovery, and mild processing conditions. Herein, the one step nano-encapsulation of protein drugs using electrospraying was developed. The major processing parameters such as the conductivity of spraying liquids, flow rate, the distance between electric potentials, etc were examined to obtain the maximum efficiency. The recovery of particles was found relatively high as could be conjectured based on the principle of electrospraying. When organic solvents were employed, the processing windows of electrospraying were relatively narrow than water systems. Efficient nano-encapsulation of BSA with polymers was conveniently achieved using electrospraying at above 12 kV.

• 한국기계가공학회지
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• 제19권8호
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• pp.88-93
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• 2020

The goal of this study is to determine the influence of major factors on the spiral surface microparticle injection machining of cylindrical specimens by the statistical method ANOVA. Before the experiment, rod-shaped test specimens and jigs for helical surface spraying were prepared, and the surface roughness was measured with a surface roughness meter. The injection particle, nozzle diameter, and injection pressure were the primary parameters of the experiment. Other factors that were considered were injection height, injection time, revolutions, and feed distance. The surface roughness after machining was measured, and the effects of the surface roughness data on the primary factors were determined with ANOVA.

• 한국세라믹학회지
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• 제50권5호
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• pp.326-332
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• 2013

In this study, we prepared yttria stabilized zirconia granules for thermal barrier coatings using a spray drying process. First, we characterized the properties of granules such as flow rate and packing density for utilizing the air plasma spray process. The flow rate and packing density data showed 0.732 g/sec and 2.14 $g/cm^3$, respectively, when we used larger and denser particles, which are better than hollow granules or smaller spherical granules. Second, we chose larger, spherical granules fabricated in alcohol solvent as starting powders and sprayed it on the bondcoat/nimonic alloy by an atmospheric plasma spray process varying the process parameters, the feeding rate, gun speed and spray distance. Finally, we evaluated representative thermal and mechanical characteristics. The thermal expansion coefficients of the coatings were $11{\sim}12.7{\times}10^{-6}/^{\circ}C$ and the indentation stress measured was 2.5 GPa at 0.15 of indentation strain.

• Design & Manufacturing
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• 제13권3호
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• pp.41-47
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• 2019

In conventional machining, the use of cutting fluid is essential to reduce cutting heat and to improve machining quality. However, to increase the performance of cutting fluids, various chemical components have been added. However, these chemical components during machining have a negative impact on the health of workers and cutting environment. In current machining, environment-friendly machining is conducted using MQL (minimum quantity lubrication) or cryogenic air spraying to minimize the harmful effects. In this study, the injection nozzle that can combined injecting minimum quantity lubrication(MQL) and cryogenic gas was designed and the shape optimization was performed by using computational fluid dynamics(CFD) and design of experiment(DOE). Performance verification was performed for the designed nozzle. The diameter of the sprayed fluid at a distance of 30 mm from the nozzle was analyzed to be 21 mm. It was also analyzed to lower the aerosol temperature to about 260~270K.