• Journal of the Korean Graphic Arts Communication Society
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• v.26 no.2
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• pp.45-54
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• 2008

We have manufactured a photoresist which has excellent dispersity and good applying property due to 330 cps of viscosity for environment-friendly and economical maskless screen plate making. And the photoresist applied on the screen stretched was exposed with mask by UV-LED light source so we could manufacture the photoresist which proper for the UV light source. And it was developed by air spray with $1.7\;kgf/cm^2$ of injection pressure. Because of the excellence of power and resolution of the UV-LED light sourse, the pencil hardness and solvent resistance of curing photoresist film were excellent as those of conventional photoresist film. Moreover the $100{\mu}m$-width stripe image which has sharp edges was formed. So we confirmed a possibility of dry development process by air spray method.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.54-60
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• 2008

The atomization characteristics of the dual air supplying twin-fluid nozzle were investigated experimentally using PIV and PDA systems. The two-fluid nozzle is composed of three main parts: the feeding injector to supply fluid that is controlled by a PWM (pulse-width modulation) mode, the adaptor as a device with the ports for supplying the carrier and assist air and the main nozzle to produce the spray. The main nozzle has the swirl tip with four equally spaced tangential slots, which give the injecting fluid an angular momentum. The angle of the swirl tip varied with 0$^{\circ}$ 30$^{\circ}$, 60$^{\circ}$ and 90$^{\circ}$, and the ratios of carrier air to assist air and ALR(total air to liquid) were 0.55 and 1.23, respectively. The macroscopic behavior of the spray was investigated using PIV system, and the mean velocity, turbulent intensity and SMD distributions of the sprays were measured using PDA system. As the results, the mean axial velocity at the spray centerline decrease with the increase of the swirl angle. The turbulent intensities of the axial and radial velocity were increased with the increase of the swirl angle. The mean SMD (Sauter mean diameter) of the radial direction along the axial distance shows the lowest value at the swirl angle of 60$^{\circ}$.

• Journal of Welding and Joining
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• v.25 no.5
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• pp.58-63
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• 2007

The relationship between GMA welding conditions and the bead shape of overlay weld was studied by using ${\Phi}1.6mm$ hypo-eutectic metal-cored wire designed for hardfacing against the severe metal-to-metal wear. As the welding voltage increased, the dilution also increased but the sudden drop of dilution was observed at $30{\sim}33V$. It was considered to be due to the decrease of penetration resulting from the change of transfer mode, from short circuit to spray. It was also found that the behavior of penetration with welding current was dependant on the transfer mode. The short circuit mode exerted the penetration to decrease while the spray mode did it to increase with increase of welding current. The former was considered to be responsible for the remarkable decrease in dilution at low welding voltage region. The change of transfer mode also had an effect on the behavior of bead width with welding current but it did not on the bead spreadability defined as W/H ratio. It was considered that the optimal welding conditions for multi-pass overlay welding could be obtained from the bead spreadability suitable for bead lapping and the dilution as low as possible in the spray transfer mode.

• Korean Journal of Metals and Materials
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• v.49 no.3
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• pp.221-230
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• 2011

The cold spray process is an emerging technology that utilizes high velocity metallic particles for surface coating. Metallic powder particles are injected into a converging-diverging de Laval nozzle and accelerated to a high velocity by a supersonic gas flow. The cold spray process normally uses a circular nozzle that has a rather narrow spraying range. To overcome this fault, a slit nozzle was considered in this study. The slit nozzle is anticipated to reduce the coating process time because it has a wider coating width than the circular nozzle. However, the slit nozzle can reduce the coating efficiency because it does not allow as much gas and particle velocity as the circular nozzle. To improve the coating efficiency of a slit nozzle, the shape of the slit nozzle was modified. And the results of gas flow and particle behaviour according to the nozzlers shape were compared by the a numerical analysis. As a results, as Expansion Ratio(ER) of 7.5 was found to be the most optimal condition for enhancing the spraying efficiency when the ER was changed by the variation of nozzle neck and exit size.

• Journal of Bio-Environment Control
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• v.27 no.4
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• pp.407-414
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• 2018

This study was aimed to evaluate the effect of application method and concentration of gibberellin $A_3$ ($GA_3$) on the growth, runner production, and seedling quality of strawberry plants (Fragaria ${\times}$ ananassa Duch. cv. Maehyang) during nursery period. The mother plants of strawberry were transplanted in pot ($64{\times}27{\times}18cm$) filled with commercial growing medium on March 20, 2018. $GA_3$ concentration was applied as 0, 50, 100 or $200mg{\cdot}L^{-1}$ with spray or drench to 45 mL per plant at 4 weeks after transplanting, respectively. Nutrient solution was supplied with the EC $1.5dS{\cdot}m^{-1}$ after the transplanting and supplied 350 mL per pot twice a day (15 min per one time) after rooting. The growth characteristics of mother plants of strawberry were measured at 7 weeks after treatment, and growth characteristics of daughter plants of strawberry were measured at 10 weeks after treatment. Runner length and diameter of mother plant was the longest or thickest in the spray with $200mg{\cdot}L^{-1}$ than the other treatments, respectively. Soil-plant analysis development (SPAD) value of mother plant was the lowest in spray with $200mg{\cdot}L^{-1}$. However, leaf length, leaf width, and crown diameter showed no significant differences in all treatment among application method and concentration of $GA_3$. As the concentration of $GA_3$ increased, physiological disorder like stretchiness of crown occurred more. The physiological disorder was the most occurred in spray treatment with $200mg{\cdot}L^{-1}$, but drench treatment occurred less than spray treatment. The number of runners and daughter plants increased with increasing concentration of $GA_3$ regardless of application methods. In the growth characteristics of the daughter plants, leaf length and leaf width of first daughter plant, plant height, crown diameter, leaf area and SPAD value of second daughter plant, and plant height of third daughter plant were the significantly greatest in drench with $100mg{\cdot}L^{-1}$ treatment. This results indicate that growth and runner production of mother plants and growth of daughter plants of strawberry were the best achieved by drench application in the $100mg{\cdot}L^{-1}$ $GA_3$.

• Journal of Bio-Environment Control
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• v.22 no.4
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• pp.303-308
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• 2013

A remote controlled sprayer has designed, manufactured and experimented to spray well on pear trees with pesticides. This study was executed to automate pest management of pear trees. Types of spray nozzle, which was used on the system, were analyzed experimentally to find an optimal spray equipment configuration with several nozzles. Attributions of ultrasonic sensors were analyzed to adjust spraying distance of an unmanned sprayer system. This paper investigated shapes of pear trees and cultivating environment of pear orchard. In order to select optimal spray environment, liquid distribution was measured while angle of nozzle was changed. Additionally, liquid distribution by distance and sprayed liquid capacity by side distance were measured. According to information of shapes of pear trees and cultivating environment of pear orchard, sprayer frames of an unmanned sprayer system were manufactured and sprayer frames were suitable for interval of pear trees. The sprayer system could adjust width of sprayer frames to 2.5 m and height of sprayer frames to 1.7 m. Optimal angle of nozzle, and optimal distance between objects and nozzle were $15^{\circ}$ and 0.8 m. When side distance was placed from 1.2 m to 1.8 m, sprayed capacity reached to the highest amount.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.3
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• pp.205-209
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• 2017

Unlike spherical drop impact, ellipsoidal drop impact can control the bouncing height on a heated surface by significantly altering impact behavior. To scrutinize the effect of the aspect ratio (AR) of the drop on the bounce suppression, in this study, non-axisymmetric spreading behaviors are observed from two side views and characterized based on the spreading width of the drop for horizontal principal axes. In addition, the maximum spreading width is investigated for various ARs. The results show that as the AR increases, the maximum spreading width of the minor axis increases, whereas that of the major axis shows no significant variation. In the regime of high AR and high impact velocity, liquid fragmentations by three parts are observed during bouncing. These fragmentations are discussed in this work. The hydrodynamic features of ellipsoidal drop impact will help understand bouncing control on non-wetting surfaces for several applications, such as self-cleaning and spray cooling.

• Horticultural Science & Technology
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• v.31 no.5
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• pp.544-551
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• 2013

The effect of different silicon (Si) sources and methods of application on the growth of two chrysanthemum cultivars grown in a soilless substrate was investigated. Rooted terminal cuttings of Dendranthema grandiflorum 'Lemmon Eye' and 'Pink Eye' were transplanted into pots containing a coir-based substrate. A nutrient solution containing 0 or $50mg{\cdot}L^{-1}$ Si from calcium silicate ($CaSiO_3$), potassium silicate ($K_2SiO_3$) or sodium silicate ($Na_2SiO_3$) was supplied once a day through an ebb-and-flood sub irrigation system. A foliar spray of 0 or $50mg{\cdot}L^{-1}$ Si was applied twice a week. Cultivar and application method had a significant effect on plant height. Cultivar, application method, and Si source had a significant effect on plant width. Of the three Si sources studied, $K_2SiO_3$ was found to be the best for the increasing number of flowers, followed by $CaSiO_3$ and $Na_2SiO_3$. In both the cultivars, sub irrigational supply of Si developed necrotic lesions in the older leaves at the beginning of the flowering stage as compared to the control and foliar spray of Si. Cultivar, application method, Si source, and their interactions had significant influence on leaf tissue concentrations of calcium (Ca), potassium (K), phosphorus (P), magnesium (Mg), sulfur (S), sodium (Na), boron (B), iron (Fe), and zinc (Zn). The addition of Si to the nutrient solution decreased leaf tissue concentrations of Ca, Mg, S, Na, B, Cu, Fe, and Mn in both cultivars. The greatest Si concentration in leaf tissue was found in 'Lemmon Eye' ($1420{\mu}g{\cdot}g^{-1}$) and 'Pink Eye' ($1683{\mu}g{\cdot}g^{-1}$) when $K_2SiO_3$ was applied through a sub irrigation system and by foliar spray, respectively.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1723-1726
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• 2003

Clean and well maintained roadway signs are important for preserving driver's safety. The existing signs on the roadway must be periodically re-painted in order to maintain clean state. However, current sign painting operations are manually performed now. These are very slow and workers are exposed to very dangerous and hazard working environment. In this paper, we present the method for automating this job with gantry robot and spray system. In addition, we suggest two design concepts to resolve the problem that it is impractical to make the gantry system so big as to cover whole lane width. In order to show the validity of this system, the painting operation is simulated and experimentally executed.

• Journal of ILASS-Korea
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• v.5 no.3
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• pp.9-16
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• 2000

In a SI engine, three-way catalyst converter has the best efficiency when A/F ratio is near the stoichiometry. The feedback control using oxygen sensors in the commercial engine has limits caused by the system delays. So it is necessary to control fuel quantity in accordance with intake air amount in order to reduce exhaust emission and improve the specific fuel consumption. Precise A/F ratio control requires measurement of air amount with respect to the cylinder and injection fuel according to the air amount In this paper, we applied nonlinear fuel injection model and developed the algorithm of A/F ratio control. This algorithm includes the methods of measurement of transient air mass flowing into each cylinder, of calculation of injection pulse width for measured air mass, and the method of feedback and engine control by using lambda sensor. Also we developed control program for IBM-PC by using C++ Builder, and tested it in the commercial engine.