• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.3
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• pp.88-93
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• 2021

SAW (Submerged Arc Welding) is often used for ship construction or welding pressure vessels and involves spraying a flux in a powder form to a welding site to a certain thickness and continuously supplying electrode wires therein. This welding method enables high current welding up to 1,500 to 3,000 A. Arc efficiency is higher than 95% and the technique allows clean work as it creates less welding fume, which is composed of fine metal oxide particles, and the arc beam is not exposed. In this study, SM490C-TMC thick plates were heterogeneously welded by SAW. Mechanical properties of welds were measured, and welds were assessed macroscopically and for adhering magnetic particles. The following conclusions were drawn. Bending tests showed no spots exploded on sample surfaces or any other defect, and plastic deformation testing confirmed sufficient weld toughness. These results showed the 1F welding method has no shortcomings in terms of bending performance.

• Resources Recycling
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• v.15 no.5 s.73
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• pp.47-51
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• 2006

The total amount of ash generated from the municipal solid waste incineration(MSWI) in Korea was approximately 420,000 tons in 2005 including 68,000 tons of fly ash. Fly ash from MSWI generally contains high amount of CaO (upto ${\sim}50%$) due to the treatment of flue gas by spraying CaO-base materials. Currently, most of fly ash generated is finally ended up with specially designed landfill sites and only less then 20% of fly ash is recycled. In the present work, preparation of $CaCO_3$ from the MSWI ny ash was studied to promote the fly ash recycling. Fly ash obtained from the dust collector in stoker-type MSWI is used to selectively dissolve CaO by using the sugar solution. Then, $CO_2$ gas was passed through the dissolved solution to pro- duce $CaCO_3$ powder. The optimum conditions for CaO dissolution were solid content 10%, reaction time 15 minutes, sugar concentration $10{\sim}15%\;and\;pH\;10.5{\sim}11.0$. The high grade $CaCO_3$ powder was obtained and the experimental conditions are also discussed.

• Journal of Powder Materials
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• v.24 no.6
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• pp.437-443
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• 2017

SiC-based composite materials with light weight, high durability, and high-temperature stability have been actively studied for use in aerospace and defense applications. Moreover, environmental barrier coating (EBC) technologies using oxide-based ceramic materials have been studied to prevent chemical deterioration at a high temperature of $1300^{\circ}C$ or higher. In this study, an ytterbium silicate material, which has recently been actively studied as an environmental barrier coating because of its high-temperature chemical stability, is fabricated on a sintered SiC substrate. $Yb_2O_3$ and $SiO_2$ are used as the raw starting materials to form ytterbium disilicate ($Yb_2Si_2O_7$). Suspension plasma spraying is applied as the coating method. The effect of the mixing method on the particle size and distribution, which affect the coating formation behavior, is investigated using a scanning electron microscope (SEM), an energy dispersive spectrometer (EDS), and X-ray diffraction (XRD) analysis. It is found that the originally designed compounds are not effectively formed because of the refinement and vaporization of the raw material particles, i.e., $SiO_2$, and the formation of a porous coating structure. By changing the coating parameters such as the deposition distance, it is found that a denser coating structure can be formed at a closer deposition distance.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.33 no.4
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• pp.153-157
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• 2023

In order to manufacture a semiconductor circuit, etching, cleaning, and deposition processes are repeated. During these processes, the inside of the processing chamber is exposed to corrosive plasma. Therefore, the coating of the inner wall of the semiconductor equipment with a plasma-resistant material has been attempted to minimize the etching of the coating and particle contaminant generation. In this study, we mixed AlF₃ powder with the solid-state reacted yttrium oxyfluoride (YOF) in order to increase plasma-etching resistance of the plasma spray coated YOF layer. Effects of the mixing ratio of AlF₃ with YOF powder on crystal structure, microstructure and chemical composition were investigated using XRD and FE-SEM. The plasma-etching ratios of the plasma-spray coated layers were calculated and correlation with AlF₃ mixing ratio was analyzed.

• Korean Journal of Environmental Agriculture
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• v.14 no.3
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• pp.312-318
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• 1995

Residues of benfuresate in rice and oxolinic acid in Chinese cabbage were determined through the field experiments in order to establish the safe use and the maximum residue limit(MRL) of these pesticides in Korea. The herbicide benfuresate powder was sprayed into the paddy field with a level of 0.6kg(active ingredient)/ha and rice (Oryza sativa L.) was grown. At harvest, residues of benfuresate in brown rice and stem were analyzed using gas chromatograph. The residue of oxolinic acid in Chinese cabbage (Brassica campestris subsp. napus var pekinesis MAKINO) was analyzed using HPLC after foliar-spraying this fungicide into the cabbages at a level of 15kg/ha. The recovery efficiencies of benfuresate and oxolinic acid were 87-89% and 90-95%, respectively. The respective residues of benfuresate in rice and oxolinic acid in Chinese cabbage were in the range of 0.27-0.46 mg/kg and 0.23-1.53kg/kg. Residual concentrations of these pesticides in crops increased with the increased application frequencies, followed the first-order kinetics and linearly decreased with time. The highest residue of 1.53 mg/kg of oxolinic acid was observed when this fungicide was sprayed six times until three days prior to harvest, but this level was far lower t㏊n 5 mg/kg, which is the maximum residue limit(MRL) set by FAO/WHO.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.29 no.5
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• pp.681-688
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• 1996

To investigate the effort of drying methods on the physicochemical properties of agar, gel strength, viscosity, melting and setting point, and phase transition by differential scanning calorimetery (DSC) during its heating were determined. In addition the structural differences of agar powder by scanning electron microscope (SEM) was examined. The most shortest onset temperature of gel strength increase was extruding method among any other methods. Viscosity of agar with hot air method, 400.00 cps at $45^{\circ}C$, was markedly increased, but with spraying and extruding ones were little change. The melting and setting point, and the temperature for maximum endothermic and enthalpy for agar with extruding one, $80.01^{\circ}C,\;36.05^{\circ}C\;and\;61.72^{\circ}C,\;0.73\;cal/g$, respectively, were lowest among the drying ones. But in the case of reheating after gelling, there were little change in all methods. Observing the surface structure of agar with SEM, extruding method showed the most unstable with absorptive property.

• Microbiology and Biotechnology Letters
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• v.38 no.3
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• pp.308-314
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• 2010

This study was conducted to investigate the characteristics and concentrations of ammonia produced from the livestock swine nightsoil treated with or without the livestock - environment improving agents. Odor generating device made of acryl was made by volume of 96 L to sample the ammonia odor. When swine night soil was placed in the device, concentration of ammonia averaged out at about 23.4 ppmv and ranged from 16 ppmv to 40 ppmv. Removal efficiencies of them showed 50% to 90% as compared to initial level before spraying, when the spray type agents were used immediately after they purchased. The persistence of the efficiency was retained for first two days. Among the agents, the natural deodorant showed the best efficiency of 87 to 99%. To evaluate the effects of 5 kinds of dietary probiotic powders, the experiments were conducted and based dietary treatments without antibiotics on growing piglets. In experiments, 60 piglets ($6.3{\pm}0.2\;kg$) were subjected to a 35-day feeding trial in which the effects of the dietary probiotic powder on the ammonia emission were compared. The ammonia gas emission was measured for every week. Ammonia emission from the swine nightsoil obtained from piglets supplemented with the probiotics power was lower than that of the nightsoil obtained from pigs in the control treatment (without probiotics). In ammonia removal efficiencies of the experimental groups, some products showed from 71% to 99% removal efficiencies throughout the entire period as compared to the control group. On the other hand, initial reduction of ammonia in some product was effective temporarily. After then, it did not show any reduction efficiency of ammonia.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.4
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• pp.307-312
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• 2017

Laser cladding has some advantages compared to conventional cladding technologies such as arc welding and thermal spraying. Laser cladding produces a metallurgically well-bonded clad layer with a lower dilution ratio and few defects. Based on the characteristics of a 1-pass clad layer with many parameters, which were investigated in a previous report, it was found that it was essential to overlap a 1-pass clad layer when cladding a large area. In this study, the shape differences of multi-pass clad layers with various overlapping ratios were compared. Then, the alloying element distribution of cladding with a certain overlapping ratio was investigated using EDS and EPMA. As the overlapping ratio increased, the length of the clad decreased and its height increased. In addition, the height of the multi-pass cladding was higher than that of the 1-pass cladding under the same condition. The Fe content of the highly diluted first clad was found to be approximately 20 % in an element analysis. However in the area outside of the first clad, the Fe content was decreased to 10 % as a result of minimum dilution, and a uniform distribution of elements was found.

• Korean journal of applied entomology
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• v.59 no.1
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• pp.15-22
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• 2020

Two tephritid fruit flies are infesting pumpkins in Korea. Both are classified into genus of Zeugodacus. The striped fruit fly, Z. scutellata, males are attracted to a lure called Cuelure (CL), which has been used to monitor the occurrence of this fruit fly in the crop field. In contrast, no effective male lure was not developed to monitor the pumpkin fruit fly, Z. depressa. Protein diet lure has been used to attract females of most fruit flies. The addition of terpinyl acetate (TA) was effective to increase the attractiveness of Z. depressa. This study aimed to monitor the occurrence of Z. depressa in pumpkin field with TA-protein diet lure. To validate the efficiency of TA-protein diet lure, Z. scutellata was monitored in a year of 2019 using CL and TA-protein diet lures, and the yearly monitoring data were compared. The occurrence patterns derived from both lures were similar except late season after October. The extended catches of TA-protein diet lure might be explained by the adult diapause induction of Z. scutellata at late September. Monitoring Z. depressa with TA-protein diet lure gave two peaks at mid July and August-September, in which more than 80% catches were females. Based on the attractiveness of TA-protein diet lure, its wettable powder with an addition of spinosad insecticide was formulated and sprayed to pumpkin crops. After 7 days post-spray, the control efficacy recorded more than 70%. However, the control efficacies decreased as the time progressed after the spray. These results demonstrated the application of TA-protein diet lure for monitoring occurrence of Z. depressa in pumpkin-cultivating field conditions. The wettable powder containing spinosad can be applied to develop a new control agent against two pumpkin fruit flies.