• 한국분무공학회지
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• 제28권3호
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• pp.113-118
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• 2023

This study investigates the evaporation characteristics of paired sessile droplets on a heated substrate. In particular, the evaporation time and contact line behaviors were analyzed based on the droplet-to-droplet distance and substrate temperature. The contact line behavior and volume variations were visualized using the shadowgraph method. It was observed that the contact diameter and contact angle exhibited similar behavior for both single and paired droplets regardless of the droplet-to-droplet distance and substrate temperature. The paired droplets demonstrated a longer evaporation time than the single droplet due to the vapor accumulation between the droplets. Furthermore, the scaled lifetime, defined as the ratio of evaporation time between paired and single droplets, increased as the droplet-to-droplet distance decreased and decreased as the substrate temperature increased, attributed natural convection.

• 한국건설순환자원학회논문집
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• 제5권2호
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• pp.83-90
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• 2010

As a reinforced fabric, asbestos has been utilized as a fire-resistant material as it has a superior flexural stiffness and heat resistance up to $1500^{\circ}C$. However, due to its harmfulness, its use has been prohibited recently and the even the installed asbestos materials are being repaired or supplemented if there is a concern about flying. Asbestos is mainly used for construction panels as a reinforced fabric and coating materials to ensure the fire-resistance of steel frames. Asbestos was used as fire-resistant materials for steel frames until 1991 and then prohibited as Act on Industrial Safety and Health limits the concentration of asbestos in the air. Classified as a designated waste according to Act on Waste Control, asbestos must be buried if there is no possibility of flying (panel-type materials) or cement-solidified and then buried if there is a possibility of flying (spray coating material) In general, it is required that a new waste landfill include a certain landfill facility for designated waste, but in reality there is an absolute storage of landfill facilities for designated waste as they only install facilities of the size required by the regulations. This could result in the 2nd environmental pollution as they cannot process asbestos wastes which will be generated in large volume in the future. This study explores a method that melts asbestos wastes at $700^{\circ}C$ rather than cement-solidifying the waste asbestos from construction sites, especially asbestos-containing spray coating. The study results showed that there was no change in the composition and shape even though asbestos wastes was melted at $1300^{\circ}C$, but there was a change for the specimen which was process in advance for low temperature melting and then melt at $900^{\circ}C$.

• 한국환경복원기술학회지
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• 제9권6호
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• pp.143-151
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• 2006

Currently, there are researches about environment-friendly road construction plans led by the Ministry of Construction and Transportation in progress. Therefore, in order to create the revegetation techniques of thin layer-soil combination media hydroseeding measures by actively using native herbs and native woody plants instead of using imported foreign grasses as a concept of sustainable environment-friendly land development, this thesis is going to identify problems that can appear when applying the thin- layer-soil-media hydroseeding measures by the suggested in the "Slope revegetation design and guidelines" proposed by the Ministry of Construction and Transportation, and to propose improvement plans for the problems.To this aim, a seeding mixture selection test was conducted by the goal of slope restoration, and a test group for artificial slope was created. As for a test for June sowing, it was intended to identify appropriate combination quantity by conducting a test that differentiates the combination quantity, and as for a test for September sowing, an artificial slope test was conducted by creating an artificial bank for earth and soil and applying 1~2cm and 3~4cm thickness after differentiating the seed combination volume and slope aspects.

• Journal of Biosystems Engineering
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• 제17권3호
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• pp.229-236
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• 1992

In an effort to localize the spray-dryer which is markedly used for drying food materials, a experiment was carried out with a wheel type atomizer locally designed and manufactured to evaluate the effect of rotational speed, feed rate and physical properties of liquid food material on the droplet size, and to develop a model to predict the droplet size sprayed at various operational conditions. The result are summarized as follows. 1. The frequency of droplet size sprayed from the atomizer at every treatment were similar to normal distributions. 2. Under the test conditions adopted in this study, that is, rotational speed of the atomizer ranging from 15,000 to 20,000 rpm (55.0 m/sec - 73.3 m/sec), feed rate from 14 to 37 kg/hr and viscosity of the material from 1.14 to 350 cP, the mean volume-surface dia. of droplets was decreased as increase in rotational speed and was not affected significantly by the feed rate and viscosity. 3. Through the dimensional analysis, a prediction model was developed as follows : $$\frac{Dvs}{r}=K[\frac{Q}{{\mu}r}]^a[\frac{rN^2}{g}]^b[\frac{{\rho}^2r^3g}{{\mu}^2}]^c[\frac{L}{r}]^d$$ and it was proved that the above model was better in degree of fitness than other models reported. 4. A prediction equation for the droplet size sprayed from the atomizer under the test was expressed as follows : $$\frac{Dvs}{r}=0.0215[\frac{Q}{{\mu}r}]^{0.06}[\frac{rN^2}{g}]^{0.3314}[\frac{{\mu}^2}{{\rho}^2r^3g}]^{0.0158}$$.

• 대한기계학회논문집
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• 제14권6호
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• pp.1613-1620
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• 1990

본 연구에서는 일반적인 레이저 유속계를 사용하여 광전 증폭관내에 핀흘 대 신에 슬릿(slit)을 장치하고 광전증폭관을 측정영역에 90˚가 되도록 설치하여 in-situ calibration을 수행함으로써 분무의 입경과 속도를 동시에 계측할수 있다는 Yoon의 결과를 이용하고 모든 입자들의 궤적은 동일한 확률을 갖는다는 Yule와 Holve, Self의 가정을 기초로한 수학적인 Deconvolution에 의하여 계측방법에 발생되는 모순 점을 해결하였다. 일반적으로 분무특성해석을 위해서는 분무를 지배하는 기하학적인 변수, 입경분포, 액적의 속도분포, 밀도분포, 입경과 속도의 상관계수, 입자의 증발율 등이 규명 되어야하는데 본 연구에서는 이상류 동축노즐을 제작하고 이의 분무특성을 해석하기위하여 액적의 속도분포, 입경분포, 입경과 속도의 상관계수, 수밀도분포 등 을 계측하였다.

• Composites Research
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• 제24권6호
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• pp.7-11
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• 2011

우레탄 수지 첨가에 의한 다이니마/비닐에스터 복합재료의 방탄효과 향상을 고찰하였다. 첫째로 우레탄 수지와 비닐에스터 수지를 스프레이 코팅하여 프리프레그를 제조하였으며, 수지함량을 21%로 조절하였다. 또한 혼합수지를 스프레이 코팅과 필름코팅으로 비교를 위한 프리프레그를 제조하였다. 그 다음 이들을 상온에서 1-2시간, 그리고 필요시 $100^{\circ}C$ 30분 정도 건조시켰다. 이들 프리프레그를 24층 적층한 다음 $120^{\circ}C$에서 5분 동안 정치 시킨 후 25분 동안 150 $kg/cm^2$ 압력하에서 경화 시켰다. 모의 파편탄(17 gr)을 이용하여 이들 복합재료의 방탄성능($V_{50}$)를 측정하였으며, UP127 및 EB8200으로 제조된 시편은 XSR10으로 제조된 시편에 비하여 각각 6.5 및 9.0 % 향상된 값을 보였다.

• 한국재료학회지
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• 제30권7호
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• pp.350-358
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• 2020

A variety of composite powders having different aluminum and carbon contents are prepared using various organic solvents having different amounts of carbon atoms in unit volume as ball milling agents for titanium and aluminum ball milling. The effects of substrate temperature and post-heat treatment on the texture and hardness of the coating are investigated by spraying with this reduced pressure plasma spray. The aluminum part of the composite powder evaporates during spraying, so that the film aluminum content is 30.9 mass%~37.4 mass% and the carbon content is 0.64 mass%~1.69 mass%. The main constituent phase of the coating formed on the water-cooled substrate is a non-planar α₂ phase, obtained by supersaturated carbon regardless of the alloy composition. When these films are heat-treated at 1123 K, the main constituent phase becomes γ phase, and fine Ti₂AlC precipitates to increase the film hardness. However, when heat treatment is performed at a higher temperature, the hardness is lowered. The main constitutional phase of the coating formed on the preheated substrate is an equilibrium gamma phase, and fine Ti₂AlC precipitates. The hardness of this coating is much higher than the hardness of the coating in the sprayed state formed on the water-cooled substrate. When hot pressing is applied to the coating, the porosity decreases but hardness also decreases because Ti₂AlC grows. The amount of Ti₂AlC in the hot-pressed film is 4.9 vol% to 15.3 vol%, depending on the carbon content of the film.

• 한국화재소방학회논문지
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• 제31권4호
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• pp.59-64
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• 2017

본 연구에서는 2유체노즐의 액체풀 (Liquid pool) 화재 소화 성능에 대하여 선행적인 검토를 수행하였다. 액체풀 화재의 경우, 에탄올 (Ethanol) 1200 ml를 이용하였으며, 물 공급 유량은 632 ml/min, 공기의 공급 유량은 40 l/min과 70 l/min으로 설정하였다. 본 실험조건에서 2유체노즐을 이용하여 화재 소화 실험을 수행하였고, 2유체노즐의 분사 특성 (액적 크기 및 유량 분포)을 측정하였다. 실험 결과, 공기의 유량이 많은 조건에서 빠른 시간 안에 성공적으로 화재를 소화할 수 있었고, 이러한 결과에 대하여 가시화 및 2유체노즐 분사 특성 데이터를 토대로 분석하였다. 또한, 기존 연구의 일부 결과와 비교를 통하여, 2유체노즐이 단일유체노즐에 비해 더욱 작은 물의 유량 조건에서도 화재 소화를 할 수 있을 가능성이 있음을 확인하였다.

• 한국산업보건학회지
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• 제24권1호
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• pp.59-64
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• 2014

Objectives: The principal aim of this study is to investigate and analyze domestic usage amounts of insecticide in rice cultivation in order to provide fundamental data for establishing a job-exposure matrix(JEM) related to farmers working with agricultural insecticides. Materials and Methods: An investigation of domestic usage amounts of insecticides rice cultivation was performed through two methods. The first method utilized information on agricultural pesticides published annually by the Korea Crop Protection Association(KCPA). The second method made use of area of cultivation of rice as officially determined by Statistics Korea(SK). An estimation of domestic usage of insecticides in rice cultivation through the second method was determined by multiplying the total cultivation area of rice($m^2$) by the optimal spray volume of insecticides for rice cultivation per unit of cultivation area($kg/m^2$). Results: As a result of the analysis of public data regarding insecticides in rice cultivation, it was found that the domestic usage amount has decreased sharply from the first year of market sales(1969) to the final data year(2012). There is little difference in the annual usage trend of insecticides in rice cultivation between shipment and estimation. Also, the annual usage trends of insecticides in rice cultivation based on regional classification were nearly similar to those based on the overall aspect. Conclusions: The region which used the largest volume of insecticide in rice cultivation in Korea was the Jeolla Provinces, followed by the Gyeonsang Provinces, the Chungcheong Provinces, Seoul/Gyeonggi Province, Gangwon Province and Jeju Province. Substantially, the mean ratio of usage amounts of insecticide based on shipments and those based on estimation by cultivation area was $96{\pm}29%$, which indicates that the domestic usage amount of insecticide for rice cultivation corresponded to the optimal spray standard per unit area.

• 청정기술
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• 제29권3호
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• pp.178-184
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• 2023

전이금속 칼코젠화물은 소듐 이차전지의 음극재로서 높은 이론 용량을 가지나 충·방전 과정에서 큰 부피 팽창으로 인해 짧은 수명 특성을 보이며, 낮은 전기전도도로 인해 출력 특성을 저하시킨다는 문제가 있다. 이를 해결하기 위해, 본 연구에서는 분무열분해와 후 열처리 공정을 통해 다공성의 CNT ball과 (Ni,Co)Se₂ 나노결정이 복합된 구조체를 합성하였으며, 이를 소듐 이차전지의 음극에 적용시켜 전기화학적 특성을 평가하였다. 합성된 소재는 분무열분해 동안 Polystyrene(PS) 나노비드의 분해로 인해 다공성 구조를 형성하여 충방전 과정에서 발생하는 부피팽창을 효과적으로 수용하였으며, CNT 소재와의 복합화를 통해 전기화학적 성능을 향상시킬 수 있었다. 이로 인해 다공성 구조의 (Ni,Co)Se₂-CNT 복합소재는 0.2 A g^-1의 전류밀도에서 698 mA h g^-1의 높은 초기 방전용량을 보였으며, 100 사이클 후 400 mA h g^-1의 방전용량을 유지함을 보였다.