• 한국분무공학회지
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• 제13권3호
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• pp.134-142
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• 2008

In the case of heavy duty diesel engines, the Urea-SCR system is currently considered to reduce the NOx emission as a proved technology, and it is widely studied to get the high performance and durability. However, the nozzles to inject the urea-water solution into the exhaust pipe occur some problems, including the nozzle clogging, deposition of urea-water solution on the inner wall of the exhaust pipe, resulting in the production of urea salt. In this study, a swirl-type twin-fluid nozzle to produce more fine droplets was used as a method to solve the problems. The effect of the nozzle cap geometry, including the length to diameter ratio ($l_o/d_o$) and chamfer, on the spray characteristics were investigated experimentally. The length to diameter ratio of nozzle cap were varied from 0.25 to 1.125. The chamfer angle of the nozzle cap was constant at 90o. The mean velocity and droplet size distributions of the spray were measured using a 2-D PDA (phase Doppler analyzer) system, and the spray half-width, AMD (arithmetic mean diameter) and SMD (Sauter mean diameter) were analyzed. At result, The larger length to diameter ratio of nozzle cap were more small SMD and AMD. The effect of the chamfer did increase the radial velocity, while it did not affect the atomization effect.

• 방사성폐기물학회지
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• 제5권4호
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• pp.297-308
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• 2007

폐액증발기 농축폐액의 폴리머고화를 위하여 붕산 함유 건조분말에 액상규산나트륨을 과립화제로 활용하여 점적 형태로 분사하고 평균 $2{\sim}4mm$ 크기의 과립을 제조하는 농축폐액 과립화 설비를 제작하였다. 또한 폐수지 폴리머 고형화에 대해 미국 원자력규제위원회(NRC)의 인증을 받은 신규 고화기술을 과립화된 농축폐액에 성공적으로 적용하였다. 상기 고화설비는 기계적인 혼합 대신 중력을 이용한 in-situ 고화처리 방식으로 폐기물의 추가적인 부피증가가 없고 폐기물 적재량을 최대화할 수 있다. 생산된 폴리머 고화체의 성능평가를 위해 화재시험, 압축강도시험, 침출 및 침수시험, 방사선조사시험, 열순환시험을 표준시험법에 따라 수행하였다.

• 한국세라믹학회지
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• 제44권2호
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• pp.124-131
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• 2007

In this study, first the ADU gel particle, an intermediate for final $UO_2$ kernel of a HTGR nuclear fuel, was prepared from sol-gel method using the broth solution which was made by mixing of the uranyl nitrate, poly vinyl alcohol and tetra-hydrofurfuryl alcohol. The prepared dried-ADU gel particles were converted to the $UO_2\;via\;UO_3$ from thermal treatment with the 4% $H_2$ atmosphere. The sizes of the spherical liquid droplets appeared $1900{\sim}2100{\mu}m$, and the harmony between the flow rate of the broth solution and the frequency and the amplitude of a vibrating system are important factors for the spherical ADU gel particles via the mono size spherical droplets. From the XRD and FT-IR analyses, the prepared ADU gel particles were judged to be a $UO_3{\cdot}xNH_3{\cdot}yH_2O$ form, and the most important factor during the thermal treatment of the dried-ADU gel particle must be avoided a rapidly heating rate in the range of $180{\sim}400^{\circ}C$, and the heating rate should be kept below $5^{\circ}C/min$.

• 대한기계학회논문집B
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• 제22권8호
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• pp.1111-1120
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• 1998

Spray Drying Absorber(SDA) system, where the combustion product gas is mixed with atomized limestone-slurry droplets and then the chemical reaction of $SO_2$ with alkaline components of the liquid droplets forms sulfates, has been widely used to eliminate $SO_2$ gas from coal fired power plants and waste incinerators. Liquid atomization is necessary because it can maximize the reaction efficiency by increasing the total surface area and dispersion angle of the alkaline components. First, numerical calculations using FLUENT are carried out to investigate $SO_2$ concentration distribution and thus to calculate $SO_2$ removal efficiency. So to attain the optimized spray conditions, then an electrostatic spraying system is set up and spray visualization is performed to show the effect of an electric field on overall droplet size. Next, the effect of an electric field on the concentrations of $SO_2$ is experimentally examined. Field strength is varied from -10 kV to 10 kV and configurations of conduction charging and induction charging are utilized. Consequently, the electrostatic removal efficiency of 501 increases about 30% with the applied voltage of ${\pm}10kV$ but is independent of polarity of the applied voltage. It Is also found that the conduction charging configuration results in higher efficiency of $SO_2$ removal that the induction charging configuration. Finally, the effect of slurry temperature on $SO_2$ removal is studied. The temperature influences on the electrostatic removal efficiency of $SO_2$.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 2000년도 THE THIRD INTERNATIONAL CONFERENCE ON AGRICULTURAL MACHINERY ENGINEERING. V.III
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• pp.613-622
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• 2000

Watering operation for oyster mushroom growing houses is regarded as drudgery and time consuming farm operation for growers. Most of mushroom growing beds in oyster mushroom growing houses are designed as two-row with four floor beds, therefore the watering and ventilation between the bed floors are much difficult for farmers because of its structural design. The study aimed to reduce the watering operation and improve the mushroom growing environment through the humidification and air supply on mushroom growing beds. Results showed that appropriate size of nozzle is between 0.8~0.5ml/s for the humidification and higher than the 2.0ml/s for the watering. The optimum water supply pressure was regarded as between 1.0~2.0MPa and the uniform distribution of droplet on the bed showed on air flow speed of 14m/s. The prototype was equipped with twin nozzle with. the humidification nozzle of 0.85ml/s and watering nozzle of 5.0ml/s, and the air blast fan with the air speed of 10m/sec in each air spout. In the field test in a practical scale mushroom growing house, it was well operated dependant on the set desire by a electric control unit. The machine can be practically used as air blast watering and air blast humidification for oyster mushroom growing farms without manual.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2003년도 추계학술발표강연 및 논문개요집
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• pp.132-132
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• 2003

Second-order nonlinear optical(NLO) materials have been extensively studied for applications in photonic devices, such as frequency doubling and electro-optical(EO) modulation, because of their large optical nonlinearity, excellent processibility, low dielectric constant, and high laser damage thresholds. The poling behaviour of NLO chromophore in organic/inorganic matrixes showed the randomization of poled NLO chromophore in the absence of poling Held. The liquid crystal molecules in a droplet showed a long-range orientational order along a director. Therefore, liquid crystal effects on poling behaviour of NLO chromophore dispersed in organically modified inorganic sol-gel materials were investigated. Using sol-gel process for the development of NLO material has received increasing attention, Organically modifked inorganic NLO sol-Eel materials are obtained via incorporation of the organic NLO active chromophore into an alkoxysilane based inorganic network. One of the most important thing in this works was that tetraethoxysilane(TEOS) and methyltrimathoxysilane(HTMS) were used as precursor followed by hydrolysis and condensation without using any acidic catalyst during the process. The NLO chromophores in the liquid crystal nanodomains were well mixed with I/O hybrid matrix, deposited on transparent ITO-coated glasses. The poling behaviour of liquid crystal effects of NLO chromophore dispersed in I/O hybrid matrix were investigated by UV-vis spectroscopy. Size distribution and morphology of the NLO chromophores doped in the liquid crystal nanodomains dispersed in I/O hybrid matrix were investigated by SEM.

• 한국식품과학회지
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• 제36권1호
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• pp.19-24
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• 2004

5% corn oil과 17 mM Brij 700으로 제조한 corn oil-in-water emulsion(O/W)의 droplet의 크기는 첨가되는 phenol의 양이 많아질수록 지방구가 다소 커지는 경향을 보였으며, continuous phase의 surfactant 양은 대조구에 비해 다소 낮아졌다. O/W에 녹차로부터 분리한 phenol류를 100-200 ppm의 농도로 첨가하고 30일간 저장하며 hydroperoxide의 생성량을 측정한 결과 대조구에 비해 낮은 hydroperoxide 함량을 보여 유도기간이 길어지는 것으로 나타났으며, phenol 종류별 hydroperoxide 생성억제 효과는 BHT > procyanidin B3-3-O-gallate>(+)-gallocatechin>(+)-catechin의 순서로 나타났다. 지방 산화의 결과 발생하는 aldehyde의 함량을 측정함으로서 산화정도를 측정하기 위하여 headspace hexanal 양을 측정한 결과, 대조구는 15일까지 hexanal이 검출되지 않았으나 phenol 첨가구는 20-30일로 headspace aldehyde의 불검출기간이 길어졌으며, 농도가 증가할수록 낮은 함량을 나타내었다. Phenol 종류별 headspacealdehyde 생성 억제 효과는 BHT > procyanidin B3-3-O-gallate > (+)-gallocatechin >(+)-catechin의 순서로 나타났다.

• Macromolecular Research
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• 제15권4호
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• pp.308-314
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• 2007

The effects of a compatibilizer on polypropylene (PP)/poly(acrylonitrile-butadiene-styrene) (ABS) blends were studied. Blends of the PP/ABS, with PP-g-SAN copolymer as a compatibilizer, were prepared using a twin screw extruder. The flexural and impact strength of the PP/ABS blends with the PP-g-SAN copolymer increased significantly with PP-rich compositions on the addition of the PP-g-SAN copolymer at 3 phr. The increase in the mechanical properties of the PP/ABS/PP-g-SAN blend may have been due to the toughening effects of the ABS in the PP-rich compositions. In the morphology study of the PP/ABS/PP-g-SAN (80/20) blend with the PP-g-SAN copolymer, the minimum droplet size, $5.1{\mu}m$, was observed with the addition on phr of the PP-g-SAN copolymer. The complex viscosity of the PP/ABS/PP-g-SAN (80/20) blends increased with the addition of3 phr of the PP-g-SAN copolymer. From the above mechanical properties, morphology and complex viscosity results for the PP/ABS blends, it is suggested that the compatibility is more increased with the PP-rich composition (PP:ABS=80/20 wt%) of the PP/ABS blend on the addition of 3 phr of the PP-g-SAN copolymer.

• 치과방사선
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• 제18권1호
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• pp.31-45
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• 1988

The author studied the histopathologic changes according to a single or a split dose and the time after irradiation on the acinar cells of rat parotid gland. 99 Sprague Dawley rats, weighing about l20gm, were divided into control and 3 experimental groups. In experimental groups, GroupⅠ and Ⅱ were delivered a single dose of l5Gy, 18Gy and Group Ⅲ and Ⅳ were delivered two equal split doses of 9Gy, 10.5Gy for a 4 hours interval, respectively. The experimental groups were delivered by a cobalt-60 teletherapy unit with a dose rate of 222cGy/min, source-skin distance of 50㎝, depth of l㎝ and a field size of l2×5㎝. The animals were sacrificed at 1, 2, 3, 6, 12 hours, 1, 3, 7 days after irradiation and examined by light and electron microscopy. The results were as follows: 1. As the radiation dose increased and the acinar cells delivered a single dose exposure were more damaged, and the change of acinar cells appeared faster than those of a split dose exposure. 2. The histopathologic change of acinar cells appeared at 1 hour after irradiation. The recovery from damaged acinar cells appeared at 1 day after irradiation and there was a tendency that the recovery from damage of a split dose exposure was somewhat later than that of a single dose exposure. 3. Light microscope showed atrophic change of acinar cells and nucleus, degeneration and vesicle formation of cytoplasm, widening of intercellular space and interlobular space. 4. Electron microscope showed loss of nuclear membrane, degeneration of nucleus and nucleoli, clumping of cytoplasm, widening and degeneration of rough endoplasmic reticulum, loss of cristae of mitochondria, lysosome, autophagosome and lipid droplet. 5. Electron microscopically, the change of rough endoplasmic reticulum was the most prominent and this appeared at 1 hour after irradiation as early changes of acinar cells. The nuclear change appeared at 2 hours after irradiation and the loss of cristae of mitochondria was observed at 2 hours after irradiation in all experimental groups.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.385-388
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• 2002

The researches of a two-phase atomizers have been carried out in the field of automotive and aerospace industries in order to improve the atomization performance of the liquid droplets ejecting from these nozzles. The smaller droplets have the advantages of the reduction of environmental pollution matter and effective use of energy through the improvement of heat and mass transfer efficiency. Thus, to propose the basic information of two-phase flow, an internal mixing atomizer was designed, its shape factor was 0.6 and the liquid feeding hole was positioned at the center of the mixing tube which was used to mix the air and liquid. The experimental work was performed in the field after the nozzle exit orifice. The measurement of the liquid droplets was made by PDPA system. This system can measure the velocity and size of the droplets simultaneously. The number of the droplets used in this calculation was set to 10,000. The flow patterns were regulated by ALR (Air to Liquid mass Ratio). ALR was varied from 0.1024 to 0.3238 depending on the mass flow rate of the air. The analysis of sampling data was mainly focused on the spray characteristics such as flow characteristics distributions, half-width of spray, RMS, and turbulent kinetic energy with ALR.