• The Plant Pathology Journal
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• v.24 no.3
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• pp.309-316
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• 2008

Mycelium of Ophiostoma quercus albino strain cultured in liquid culture media was harvested, lyophilized, and stored for examining biocontrol efficacy against wood discoloration by staining fungi in the laboratory and field conditions. Dry weight of mycelium grown in brown sugar yeast extract broth(BYB) showed 3.8 times higher than that grown in potato dextrose broth(PDB). The optimum culture period in BYB was 4 weeks. In vitality test of the albino strain, the lyophilized mycelium stored in liquid nitrogen($-196^{\circ}C$) or in a refrigerator($4^{\circ}C$) kept the vitality until 13 months after storage; however, the mycelium stored at room temperature lost the vitality completely after 13 months. The mycelium stored in liquid nitrogen or in a refrigerator protected wood chips from the discoloration by pretreating mycelial suspension on pine wood chips. The mycelium stored at room temperature for 7 months also showed complete protection. These results suggest that the lyophilized mycelium have a biocontrol efficacy only if it keeps the least vitality. In the field conditions, both albino strain and $Woodguard^{(R)}$(commercial chemical protectant) showed significant differences(p=0.05) in discoloration rate as compared to the non-treated control when these were treated on the wood logs of Pinus rigida. The albino strain showed better protection than $Woodguard^{(R)}$. Isolation frequency of blue stain fungi from the chips of wood logs treated with the albino strain was 0% at three months after treatment, while that treated with $Woodguard^{(R)}$ was 76.7%. In another experiment, pre-treatment of mycelial suspension on the cut surface of wood logs also showed significant protection from wood discoloration. Spraying of both albino strain on the cut surface and insecticides on the bark also showed relatively good control effects as compared to insecticide alone on the bark or nontreated control.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.15 no.6
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• pp.32-37
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• 2006

Micron size Co-alloy(T800) powder was coated on Inconel 718 by HVOF thermal spraying for the studies of the improvement of durability of high speed spindle by using Taguchi program for the parameters of spray distance, flow rates of hydrogen and oxygen and powder feed rate. The optimal coating process was determined by the studies of coating properties such as micro-structure, porosity, surface roughness and micro hardness. Friction and wear behaviors of coatings were investigated by sliding wear test at room temperature and $1000^{\circ}F(538^{\circ}C)$. At both room temperature and $538^{\circ}C$ the sliding wear debris and friction coefficients of the coating were drastically reduced compared with the surface of non-coated parent material. This shows that Co-alloy powder coating is highly recommendable for the durability improvement surface coating of high speed air-bearing spindle. At high temperature wear traces and friction coefficients of both coating and non-coating were drastically reduced compared with those of room temperature since the brittle oxides were formed easily on the surface, and the brittle oxide phases were attrited by the reciprocating sliding wear according to the complicated mixed wear mechanisms These oxide particles, partially melts and the melts play role as lubricant and reduce the wear and friction coefficient. This also shows that Co-alloy powder coating is highly recommendable far the durability improvement surface coating on the surface vulnerable to frictional heat such as high speed spindles.

• Korean Journal of Medicinal Crop Science
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• v.22 no.6
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• pp.483-488
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• 2014

Lime-bordeaux mixture (LBM) has been used instead of pesticides in ginseng field and orchard since the 1960's in Korea. In this experiment, LBM was made with different concentrations and sprayed in the field of ginseng for eco-friendly cultivation. Growth characteristics and disease such as alternaria blight, anthracnose, and gray mold were investigated in 4-5 year old ginseng after spraying LBM. LBM caused a little damage on leaf when it was sprayed at the time of leafing stage, late April and early May. Root weights of five-year-old ginseng were 43.1~51.5 g and 41.2~46.6 g in the plot of mid-April and mid-May treatments, respectively. These growth levels were further reduced as compared with that of the chemicals treatment plot. The rate of diseases in the plot of 6-6 and 8-8 ratio were 0.0~4.8% and 0.0~4.4%, respectively, which was similar with that in the plot of chemical control for alternaria blight and anthracnose. However, LBM had little effect on controling gray mold. It showed lower control effect in the plot of 4-4 ratio than that of chemical control. This result will be expected to be a useful guide that can be used in the field to the farmers of the ginseng.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.3
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• pp.1229-1235
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• 2014

At the LPG vehicle air intake system, most of dust particles in the air cleaner are removed. However very small particles are not removed and accumulated. The accumulation of carbon in air intake system is going to affect the idle speed control and sensor signal. It also causes engine chattering and transmission troubles of automatic transmission. This is study about cleaning up intake system using cleaning chemical. We can clean up the intake system by spraying cleaning liquid onto intake device when the engine is idling after intake hose is removed from warmed up vehicle. We can obtain the following experimental results by cleaning up ISC, surge tank, intake manifold, intake valves and combustion chamber. According to this results, the stroll valve works correctly and power rate of engine is up to the standard, it is smoothy to control the idling speed when a vehicle pulls up. After cleaning up CO grow down about 0.15%, HC does about 20~100 ppm.

• Design & Manufacturing
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• v.12 no.2
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• pp.34-39
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• 2018

The biggest topics in the automobile industry are light weightening and fuel efficiency improvement. There's a lot of research going on. It is focused on light weight materials. Light weight material is seen as the best way to reduce fuel consumption and to solve the problem of environmental pollution and resource depletion. For the light weight materials, new materials such as aluminum, magnesium, and carbon-hardening materials can be found. Research on the joining techniques of dual materials, improvement of material properties by improving the method of manufacture of existing materials, and studies on ultra-high strength steel sheets are expected to take up the most weight in lightweight materials. As the strength of the ultra-high strength steel sheets increases during forming, it is difficult to obtain dimensional precision due to the increase in elastic restoring force compared to mild or high strength steel sheets. Spring back is known to be affected by a number of factors due to poor plastic molding, and can be divided into the effects of the material spraying and the process. The study on the plasticitic variables were studied as plasticitic factors that can be controlled by a part company. Tensile testing of ultra-high strength materials was conducted to derive properties for plasticitic analysis and to analyze spring back with two factors controlling the height of the bead and blank holding force by adding tensile force and controlling the flow rate.

• Korean Journal of Environmental Agriculture
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• v.2 no.1
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• pp.1-5
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• 1983

A study was undertaken to investigate the persistence of diazinon in two different soils under field conditions. Half-life of diazinon granule(5%) incorporated into soils at a rate of 0.15 ㎏ a.i./l0a was 11 and $9{\sim}12$ days in Suweon and Iri soil under field conditions, respectively. Diazinon residues in brown rice and rice straw harvested from Suweon field were also evaluated by scheduled application intervals. On the basis of maximum residue limit of diazinon in brown rice, it is recommended that the insecticide could be applied upto 15 days before harvest at the limit of 4 spraying times.

• Korean Journal Plant Pathology
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• v.11 no.1
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• pp.9-16
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• 1995

Undiluted neoasozin solution (6.5% a.i.), an arsenic fungicide, was sprayed on 169 cankers of apple trees from early March to September in 1987 twice at intervals of one week without scraping off the affected barks. Among the treated cankers, 79.9% ceased to grow within 1∼7 weeks, 13.0% showed partial development, and 7.1% grew continuously to girdle the branches. The partially developed cankers, however, could also be cured by an additional spray after slightly piercing at the edge of cankers to facilitate the penetration of the chemical. When the canker growth was blocked, cankers were encircled by cracks developed at the marginal area of the cankers. If the cracks developed once, very few cankers grew beyond them. The above results suggest that the crack development may be the consequence of the host defense activity to wall off the pathogen. In addition to the curative efficacy, the neoasozin solution inhibited sporulation of the pathogenic fungus almost completely. However, the pathogen survived for more than three months in some cankers that externally appeared to be cured, suggesting that an indirect mode of action of the chemical against apple Valsa canker seems to be still more persuasive than the direct fungicidal effect. In the final examination conducted in the mid April of the next year, 72.7% of the cankers were completely cured by the two successive neoasozin treatments. Moreover the cure rate became 83.1% if that of partially developed cankers which were also completely cured by an additional treatment was also taken into account. Since 1989 when this method was widely applied in apple orchards in Korea, apple Valsa canker has been effectively controlled to reach a tolerable level.

• Korean Journal of Materials Research
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• v.30 no.1
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• pp.38-43
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• 2020

Sand casting 3D printing uses a binder jetting method to produce a mold having complicated shape by spraying a binder on sand coated with activator. Appropriate heat treatment process in sand mold fabrication can increase the degree of polymerization to improve flexural strength. However, long heat treatment of over 24 hours decreases flexural strength and reliability due to chemical bond decomposition through thermal degradation. The main role of the activator is to control the reaction rate between the polymer chains. As a result, when the activator composition is increased from 0.15 wt% to 0.25 wt%, the flexural strength is increased by 218 N/㎠. However, excess activator (0.40 wt%) has been shown to decrease reliability without increasing flexural strength. The main role of the binder is to control the flexural strength of the specimen. As the binder composition is increased from 2.00 wt% to 4.00 wt%, the flexural strength increases to about 255 N/㎠, indicating the maximum flexural strength increase. Finally, the reliability of the flexural strength of the fabricated specimens is evaluated by a Weibull plot. Weibull modulus calculations are used to evaluate the flexural strength reliability of the specimens, and maximum reliability value of 11.7 is obtained at 0.20 wt% activator composition. Therefore, it is confirmed that this composition has maximum flexural strength reliability.

• Corrosion Science and Technology
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• v.11 no.6
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• pp.263-269
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• 2012

Copper alloys are commonly applied to ship's propellers, pumps and valves which are serviced in seawater due to their good castability and corrosion resistance. In the environment of high flow velocity, however, erosion damage predominates over corrosion damage. In particular, the cavitation in seawater environment accelerates surface damage to copper alloys, resulting in degradation of products and economic losses and also threatening safety. The surface was coated with WC-27NiCr by high velocity oxygen fuel(HVOF) spraying technique to attain durability and cavitation resistance of copper alloys under high velocity/pressure flow. The cavitation test was performed for the WC-27NiCr coating deposited by HVOF in seawater at the amplitude of $30{\mu}m$ with seawater temperature. The cavitation at $15^{\circ}C$ caused exfoliation of the coating layer in 17.5 hours while that of $25^{\circ}C$ caused the exfoliation in 12.5 hours. When the temperature of seawater was elevated to $25^{\circ}C$ from $15^{\circ}C$, more damage was induced by over 160%. Although WC-27NiCr has good durability, corrosion resistance and eletrochemical stability, the cavitation damage rate of the coating layer could remarkably increase at the elevated temperatures under cavitation environments.

• Korean Journal of Materials Research
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• v.24 no.2
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• pp.98-104
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• 2014

Vacuum kinetic spray(VKS) is a relatively advanced process for fabricating thin/thick and dense ceramic coatings via submicron-sized particle impact at room temperature. However, unfortunately, the particle velocity, which is an important value for investigating the deposition mechanism, has not been clarified yet. Thus, in this research, VKS average particle velocities were derived by numerical analysis method(CFD: computational fluid dynamics) connected with an experimental approach(SCM: slit cell method). When the process gas or powder particles are accelerated by a compressive force generated by gas pressure in kinetic spraying, a tensile force generated by the vacuum in the VKS system accelerates the process gas. As a result, the gas is able to reach supersonic speed even though only 0.6MPa gas pressure is used in VKS. In addition, small size powders can be accelerated up to supersonic velocity by means of the drag-force of the low pressure process gas flow. Furthermore, in this process, the increase of gas flow makes the drag-force stronger and gas distribution more homogenized in the pipe, by which the total particle average velocity becomes higher and the difference between max. and min. particle velocity decreases. Consequently, the control of particle size and gas flow rate are important factors in making the velocity of particles high enough for successful deposition in the VKS system.