• Journal of Korea Foundry Society
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• v.26 no.1
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• pp.17-26
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• 2006

The substitution of cooling method from water quenching to air cooling after solution heat treatment was aimed for the development of a convenient and economical heat treatment process of duplex stainless steels without deterioration of mechanical and corrosion resistant properties for the industry. In order to achieve this goal, the mechanical properties and corrosion properties of a ASTM A890-4A duplex stainless steel were systematically investigated as functions of casting condition and cooling method after solution heat treatment. A 3-stepped sand mold and a permanent Y-block mold were used to check the effects of solidification structure and cooling rate after solution heat treatment. The microstructural characteristics such as the ferrite/austenite phase ratio and the precipitation behavior of ${\sigma}$ phase and carbides were investigated by combined analysis of OM and SEM-EDX with an aid of TTT diagram. Hardness and tension test were performed to evaluate the mechanical properties. Impact property at $-40^{\circ}C$ and corrosion resistance were also examined to check the possibility of the industrial application of this basic study. Throughout this investigation, air-cooling method was proved to effectively substitute for water-quenching process after the solution heat treatment, when the duplex stainless steel was sand mold cast with a thickness below 15 mm or permanent mold cast with a thickness below 20 mm.

• Journal of Ginseng Research
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• v.44 no.1
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• pp.154-160
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• 2020

Background: Korean ginseng (Panax ginseng Meyer) powder is in rising demand because powder forms of foods are convenient to handle and are highly preservable. However, ginseng powder (GP) manufactured using the conventional process of air drying and dry milling suffers nutrient destruction and a lack of microbiological safety. The objective of this study was to prepare GP using a novel process comprised of UV-TiO₂ photocatalysis (UVTP) as a prewashing step, wet grinding, high hydrostatic pressure (HHP), and freeze-drying treatments. Methods: The effects of UVTP and HHP treatments on the microbial population, ginsenoside concentration, and physiological characteristics of GP were evaluated. Results: When UVTP for 10 min and HHP at 600 MPa for 5 min were combined, initial 4.95 log CFU/g-fw counts of total aerobes in fresh ginseng were reduced to lower than the detection limit. The levels of 7 major ginsenosides in UVTP-HHP-treated GP were significantly higher than in untreated control samples. Stronger inhibitory effects against inflammatory mediator production and antioxidant activity were observed in UVTP-HHP-treated GP than in untreated samples. There were also no significant differences in CIELAB color values of UVTP-HHP-treated GP compared with untreated control samples. Conclusion: Combined processing of UVTP and HHP increased ginsenoside levels and enhanced the microbiological safety and physiological activity of GP.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.11
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• pp.1014-1021
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• 1998

We evaluated the effect of processing variables on microstructural evolution interface irregularity between Ag sheath and superconductor core and resultant critical current density(J$_{c}$) of (Bi,Pb)$_2$Sr$_2$Ca$_2$Cu$_3$O$_{x}$(2223) superconductor tape. The value of J$_{c}$ was significantly influenced by the interface irregularity, degree of texturing and relative 2223 content. The interface became more irregular(sausage effect), while the degree of texturing gradually improved as the dimension of tape decreased during forming process. As the dimension of wire/tape were changed from diameter of 3.25 mm to thickness of 0.20 mm, J$_{c}$ value was observed to be increased by 10 times. In addition, optimum sintering temperature for improved J$_{c}$ was observed to be 835$^{\circ}C$ in a ambient atmosphere probably due to combined effect of both improved texturing and high 2223 content. Microstructural investigation showed the degree of texturing was degraded by the existence of both second phases and interface irregularity. It was observed that larger grain size and better texturing was developed near relatively flat interface compared to those inside superconducting core.ting core.

• Journal of Hydrogen and New Energy
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• v.34 no.1
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• pp.1-7
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• 2023

A fuel handling process combined with a pressure swing adsorption system (PSA) was simulated to produce pure hydrogen with a purity greater than 99.97%. The simulation consists of two parts. The fuel processing part consisting of reformer and water-gas shift reaction was simulated with Aspen plus^®, and the hydrogen purification part consisting of PSA was simulated with Aspen Adsorption^®. In this study, the effect of reformer temperature and pressure on the total hydrogen production yield was investigated. Simulations were performed over a temperature range of 700 to 1,000℃ and a pressure range of 1 to 10 bar. The total hydrogen production yield increased with increasing temperature and decreasing pressure. The maximum hydrogen yield was less than 50% in the simulation and will be lower in the real process.

• The Journal of the Convergence on Culture Technology
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• v.3 no.4
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• pp.165-169
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• 2017

CNN(Convolutional Nerual Network) is one of the algorithms that show superior performance in image recognition and classification among machine learning algorithms. CNN is simple, but it has a large amount of computation and it takes a lot of time. Consequently, in this paper we performed an parallel processing unit for the convolution layer, pooling layer and the fully connected layer, which consumes a lot of handling time in the process of CNN, through the SIMT(Single Instruction Multiple Thread)'s structure of GPGPU(General-Purpose computing on Graphics Processing Units).And we also expect to improve performance by reducing the number of memory accesses and directly using the output of convolution layer not storing it in pooling layer. In this paper, we use MNIST dataset to verify this experiment and confirm that the proposed CNN structure is 12.38% better than existing structure.

• Journal of Biosystems Engineering
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• v.19 no.2
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• pp.124-137
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• 1994

Visual features of a mushroom(Lentinus Edodes, L.) are critical in grading and sorting as most agricultural products are. Because of its complex and various visual features, grading and sorting of mushrooms have been done manually by the human expert. To realize the automatic handling and grading of mushrooms in real time, the computer vision system should be utilized and the efficient and robust processing of the camera captured visual information be provided. Since visual features of a mushroom are distributed over the front and back sides, recognizing sides and states of the stalk including the stalk orientation from the captured image is a prime process in the automatic task processing. In this paper, the efficient and robust recognition process identifying the front and back side and the state of the stalk was developed and its performance was compared with other recognition trials. First, recognition was tried based on the rule set up with some experimental heuristics using the quantitative features such as geometry and texture extracted from the segmented mushroom image. And the neural net based learning recognition was done without extracting quantitative features. For network inputs the segmented binary image obtained from the combined type automatic thresholding was tested first. And then the gray valued raw camera image was directly utilized. The state of the stalk seriously affects the measured size of the mushroom cap. When its effect is serious, the stalk should be excluded in mushroom cap sizing. In this paper, the stalk removal process followed by the boundary regeneration of the cap image was also presented. The neural net based gray valued raw image processing showed the successful results for our recognition task. The developed technology through this research may open the new way of the quality inspection and sorting especially for the agricultural products whose visual features are fuzzy and not uniquely defined.

• Journal of Korean Society for Atmospheric Environment
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• v.18 no.2
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• pp.139-148
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• 2002

Both UV Photolysis and Phtocatalytic Oxidation Processing are an emerging technology for the abatemant of Volatile Organic Compounds (VOCs) in atmospheric -pressure air streams. However, each process has some drawbacks of their own. The former is little known as an application for air pollution treatment, so it has been a rare choice in the field. Therefore we have to do more experiment and study for its application for treatment of VOCs. Although the latter has been used in the industrial fields, it still has a difficulty in decomposing high concentrations of VOCs. To solute these problems, we have been studying simultaneous application of those two technologies. We have studied the effects of background gas composition and gas temperature on the decomposition chemistry. It has shown that concentration of TCE and B.T.X., diameter of reactor, and wavelength of lamp have effects on decomposition efficiency. When using Photolysis Process only, the rates of fractional conversion of each material are found at TCE 79%, Benzene 65%, Toluene 68%, Xylene 76%. In case of Photocatalytic Oxidation Process only, the rates of fractional conversion decreased drastically above 30 ppm. When there two methods were combined, the rates of fractional conversion of each material are enhanced such as TCE 93%, Benzene 75%, Toluene 81%, Xylene 90%. Therefore, we conclude that the combination of Photolysis-Photocatalytic Oxidation process is more efficient than each individual process.

• Transactions of Materials Processing
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• v.23 no.4
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• pp.211-220
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• 2014

The outer race of a constant velocity (CV) joint having six inner ball grooves has traditionally been manufactured by multi-stage warm forging, which includes forward extrusion, upsetting, backward extrusions, necking, ironing and sizing, and machining. In the current study, a multi-stage cold forging process is examined and an assessment for replacing and modifying the conventional multi-stage warm forging is made. The proposed procedure is simplified to the backward extrusion of the conventional process, and the sizing and necking are combined into a single sizing-necking step. Thus, the forging surface of the six ball grooves can be obtained without additional machining. To verify the suitability of the proposed process, a 3-dimensional numerical simulation on each operation was performed. The forging loads were also predicted. In addition, a structural integrity evaluation for the tools was carried out. Based on the results, it is shown that the dimensional requirements of the outer race can be well met.

• Laser Solutions
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• v.8 no.2
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• pp.21-32
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• 2005

The excimer laser ablation of a polymer occurs by the excitation of chemical bonds to energy levels that are above the dissociation energy. In this process, however, fragmented debris is finally ejected explosively by the scission of bonds and accumulates on the material surface. In the present work, a process for eliminating surface debris contamination generated by the laser ablation of a polymer is developed. The proposed approach for removing surface debris utilizes an erasable ink pasted on a polymide. The ink pasted polyimide is ablated by KrF excimer laser. The surface debris ejected from the polyimide is then combined with the ink layer on the polymer. Finally, both the surface debris and the ink layer are removed using adhesive tape or alcohol solvent. The results suggest that the erasable ink method is a simple, low cost, and extremely effective debris eliminating process.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.04a
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• pp.603-607
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• 2002

Recently, the need leer transporting and manipulating minute amount of fluids in microscale channels (so-called micro-fluidics) has been increasing, especially in biotechnology and biochemical processing. This work demonstrates that the mechano-chemical process which consists of mechanical abrasive action combined with chemical process can be used to fabricate micro-fluidic channels more rapidly and cost effectively than other methods. In this work, capillary filling of fluids in micro-channels was investigated by theoretical approaches and experiments. From the experimental results, it is expected that a complex micro-fluidic system can be fabricated using the micro- fabrication technique and microsystem packaging method described in this work.