• Journal of Korea Foundry Society
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• v.15 no.6
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• pp.574-587
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• 1995

The $SiC_p-reinforced$ preforms fabricated by spray casting process were hot-extruded and subsequently T6-treated, and the morphology of the silicon phase and the grain size for these preforms and extruded samples were examined by Image Analyzer. Experimental observation revealed that with increase in volume percent of SiC particles, the grain size and silicon phase of the $Al-Si/SiC_p$ composites become finer, the shape of Si phase is changed from blocky to granular type, and aspect ratio of Si phase tend to become unity. Wear-tests with various sliding velocities, show that the wear resistance of spray cast specimen is increased remarkably compare to the permanent mold cast specimen at the sliding velocity range of $1.98{\sim}2.38m/sec$.. Microstructural observations for the worn surfaces of specimens revealed that wear resistance of Al-Si alloys at certain sliding velocities could be improved not only by the fine grain size of aluminum matrix but also the fine size and granular shape of silicon phases. The wear resistance of $SiC_p$ reinforced aluminum composites was found to be sensitive to the volume percentage of the reinforcing particles. The worn surfaces with various sliding velocities, show that change in wear mechanism seems to occur at the sliding velocity of near 2m/sec for all samples, and such a change in mechanism is delayed with increase in $SiC_p$ volume fraction.

• Korean Journal of Materials Research
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• v.27 no.6
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• pp.325-330
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• 2017

Photoelectron-hole separation efficiency plays an important role in the enhancement of the photocatalytic activity of photocatalysts towards the degradation of organic molecules. In this study, $TiO_2/TiOF_2$ heterostructured composite powders with suitable band structures, which structures are able to separate photoelectron-hole pairs, have been synthesized using a simple and versatile ultrasonic spray pyrolysis process. In addition, their phase volume fractions have been controlled by varying the pyrolysis temperature from $400^{\circ}C$ to $800^{\circ}C$. The structural and optical properties of the synthesized powders have been characterized by X-ray diffraction, scanning electronic microscopy and UV-vis spectroscopy. The powder with a phase volume ratio close to 1, compared with single $TiOF_2$ and other composite powders with different phase volume fractions, was found to have superior photocatalytic activity for the degradation of rhodamine B. This result shows that the $TiO_2/TiOF_2$ heterostructure promotes the separation of the photoinduced electrons and holes and that this powder can be applicable to environmental cleaning applications.

• Korean Journal of Weed Science
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• v.18 no.4
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• pp.304-313
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• 1998

Foliar retention of pyribenzoxim (1% EC) was measured using the fluorescent dye rhodamine B, and related to efficacy and phytotoxicity to barnyardgarss (Echinochloa crusgalli) and rice (Oryza sativa cv. Chucheong), respectively. Effects of nozzle types (8002E flat-fan and disk-type), addition of adjuvant, variation of herbicide concentration or spray volume were compared. In barnyardgrass, foliar retention of pyribenzoxim at a recommended condition (application rate : 30g ai/ha, spray volume : 1000 L/ha) was 2.3 to 2.7 or 1.4 to $1.5{\mu}g$ ai/g fresh foliage when sprayed using the disk-type nozzle with or without adjuvant, respectively, and 0.6 to 0.7 or 0.3 to $0.5{\mu}g$ ai/g fresh foliage when sprayed using the flat-fan nozzle with or without adjuvant, respectively. The slope of increase in foliar retention was 1.0 to 1.8 when application rates increased from 10 to 60g ai/ha at 1000 L/ha, while that was 1.6 to 2.4 when spray volume increased from 330 to 2000 L/ha at $30{\mu}g$ ai/L concentration. Foliar retention of pyribenzoxim had a close relationship with herbicidal activity; regardless of spray conditions, retention to provide 90% control was about $0.8{\mu}g$ ai/g fresh foliage, and below this retention amount, efficacy decreased almost linearly. In rice, foliar retention at the recommended condition was 1.9 to 2.3 or 1.2 to $1.3{\mu}g$ ai/g fresh foliage when sprayed using the disk-type nozzle with or without adjuvant, respectively, and 0.6 to 0.9 or $0.3{\mu}g$ ai/g fresh foliage when sprayed using the flat-fan nozzle with or without adjuvant, respectively. The slope of increase in foliar retention was 1.0 to 2.8 when application rates increased from 30 to 120g ai/ha at 1000 L/ha, while that was 1.3 to 4.4 when spray volume increased from 1000 to 4000 L/ha at $30{\mu}g$ ai/L concentration. Despite the great difference in retention, rice phytotoxicity was not observed in any of these spray conditions, suggesting retention differences within 4-fold increase of application rate or spray volume do not affect rice safety. When pyribenzoxim 1EC was sprayed in tank-mix with several other commercial pesticide formulations, its retention to rice foliage tended to increase by 30 to 50%.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.3
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• pp.351-358
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• 2006

The capability of high pressure injection with small fuel quantify at all engine operating conditions is one of the main feature in common rail fuel injection system, which is used in small and light-duty Diesel engine. The key parameter for the better atomized fuel sprays and multiple injections of this common rail fuel injection control, that can be freely selected irrespective of the engine speed and load is the mechanism controlling the needle energizing and movement in high pressure Diesel injector. In the electro-hydraulic injector, the injection nozzle is being opened and closed by movement of the injector's needle which is balanced by pressure between the nozzle seat and the needle control chamber. This study describes the macroscopic spray structure characteristics of the common rail Diesel injectors with different electric driving method i.e. the solenoid-driven and piezo-driven type. The macroscopic spray characteristics such as spray tip speed. spray tip penetration and spray cone angle were investigated by the high speed spray, which is measured by the back diffusion light illumination method with optical system for the high speed temporal photography in a constant volume chamber pressurized by nitrogen gas. As the results, the prototype piezo-driven injector system was designed and fabricated for the first time in domestic case and the effect of injector's needle response driven by different drive type was compared between the solenoid and piezo-driven injector It was found therefore. that the piezo-driven injector showed faster needle response and had better needle control capability by altering the electric input value than the solenoid-driven injector.

• Journal of ILASS-Korea
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• v.26 no.3
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• pp.127-134
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• 2021

Fire sprinkler initial spray was analyzed by Large eddy simulation (LES) and Volume of Fluid (VoF) integrated method. The IsoAdvector geometric VoF was used to identify the liquid-gas interface clearly even with the large Courant-Friedrichs-Lewy number. To reduce the computational costs, sector meshes and Adaptive Mesh Refinement up to level 3 were used. Base mesh size was 1 mm, which is roughly equivalent to the initial sprinkler droplet. Top surface radius of boss and deflector size were modified to investigate the effects of sprinkler head design on primary breakup process. When top surface radius of boss was increased, vertical liquid sheet was formed. This phenomenon reduced the sheet breakup radius, sheet thickness and velocity. Due to reduced liquid sheet thickness, a large amount of ligaments was created from the liquid sheet. As a result, there was a dramatic decrease in volume per surface area, indicating an increase in breakup process. Spray pattern viewed in radial direction also changed when top surface radius of boss increased. When top surface radius of boss was increased, a T-shaped pattern was observed while a V-shaped pattern was observed in all other cases. When the deflector size increases, the spray pattern remains V-shaped, even if the top surface radius of boss increased. Further studies on promoting atomization of the water supplied to the lower part of the sprinkler head in the T-shape pattern should be conducted.

• Asian Journal of Turfgrass Science
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• v.25 no.2
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• pp.160-170
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• 2011

Commercial formulation of fungicides was studied in vitro for sensitivity against Typhula species causal agents of Typhula blight. Efficacies of fungicides application, spray volume, nozzle types and fungicides applied time (early fall and late fall) were evaluated for their influence on the chemical control of Typhula blight of turfgrass during the winter season in Wisconsin. All fungicides effectively reduced the mycelial growth of eight isolates of Typhula spp. in vitro on potato dextrose agar (PDA) media. For inhibitory effects on mycelial growth of eight isolates, propiconazole was the most effective at $1.0{\mu}g$ active ingredient (a.i) / ml of PDA. Typhula incarnata two isolates were significantly more sensitive to all fungicides of PDA than six isolates of three varieties of T. ishikariensis. For 2 years in field experiment, unsprayed control has significantly more disease severity than seven fungicides were applied to field plots at two locations. Propiconazole was the most effective for controlling Typhula blight, at two locations in both years. The level of disease control was not dependent on fungicides spray volume or nozzle types at two locations. The disease damage treated with triadimefon applied time (early fall and late fall) was not significantly different at two location for two years.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.214-219
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• 2001

In this study, numerical investigation has been performed on the spreading and solidification of a droplet impacting onto a solid substrate in the thermal spray process. The finite difference method with volume-of-fluid approach is used to analyze the free surface flow and the source-based enthalpy method is employed to model the latent heat release during the solidification. In this work, the numerical model is validated through the comparison of the present numerical result with experimental data available for the flat substrate.

• Journal of ILASS-Korea
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• v.20 no.3
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• pp.175-180
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• 2015

A series of sprinkler discharging tests was conducted to measure the droplet size and its distribution of residential fire sprinkler heads. Droplet sizes in sprinkler spray were measured using a laser diffraction method for the flush, circular and pendent type sprinkler head. In this study, the $D_{v,50}$ of the flush type sprinkler heads were ranged between $530{\sim}1040{\mu}m$ and those of circular and pendent type were $988{\mu}m$ and $916{\mu}m$, respectively. The measured cumulative volume distributions were followed by a combination of the log-normal and Rosin-Rammler distribution which is widely used in the computational fire analysis and the parameters of distribution function were obtained from the best fit line through the measured data.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.2
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• pp.263-268
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• 2004

The characteristics of Diesel spray droplets, such as the velocity and the diameter were simultaneously measured by using an improved Interferometric Laser Imaging for Droplet Sizing method. The experiments were carried out using an accumulator-type unit injector system and a constant-volume vessel. Two dimensional cross-section photographs of sprays were also taken using a double-pulsed Nd- YAG laser sheet and a linear array CCD camera. As a result, interesting relations between the droplets diameter and the velocity were found.

• Journal of the Korean institute of surface engineering
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• v.29 no.6
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• pp.745-752
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• 1996

Wear property of plasma spray coating in $Cr_2O_3$ powder manufatured of spray dry method on the aluminum substrate was inspected for the application of piston-ring of automotive enginel. The plama spray coatings were varied with feed rate and particle size. Used the ball-on disc type tribometer, wear volume, friction, surface rougness were investigated. The delamination of the coating layer were observed with SEM. Also the cross-section of wear track were investigated, using optical microscopy. As a result of experiment, wear mechanism was addressed in the various coating process.