• Transactions of Materials Processing
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• v.20 no.5
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• pp.362-368
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• 2011

For the purpose of improving crashworthiness qualities and maximizing weight saving efficiency, TWB's(tailor welded blanks) of quench-hardenable boron steel sheet formed by hot stamping processes has been used for automotive BIW (body in white) applications. In this work, the flow behaviors of TWB of quench-hardenable boron steel sheet were investigated in uniaxial tension tests at elevated temperature. TWB's having a uniform thickness of 1.4mm were fabricated by laser welding. Specimens with two weld line directions were used to test the mechanical property and reliability of the weld zone. After heating at $950^{\circ}C$ for 5min, the specimens were subjected to tension test at 650, 700 and $800^{\circ}C$ with a strain rate of 0.01 /s and at $700^{\circ}C$ with strain rates of 0.01, 0.1 and 1/s. The ultimate strength of the weld zones was higher than that of the base materials at 650 and $700^{\circ}C$, but was similar to the base metal at $800^{\circ}C$. Fracture occurred at the base material at 650 and $700^{\circ}C$, but at the weld zone at $800^{\circ}C$.

• Journal of the Korean Wood Science and Technology
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• v.24 no.1
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• pp.17-26
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• 1996

This research was accomplished to evaluate possibility of using paper sludge for the raw materials of wood based panel products. The experimental panels were manufactured by four mixed ratios, the proportion of paper sludge to wood particle: 20:80, 30:70, 40:60, 50:50% (oven dry weight basis) and by three composition types, sludge-particle mixed board, three layered sludge-particle board and three layered particle board. They were tested mechanical (bending strength and internal bond) and physical properties (water absorption, thickness swelling and linear expansion). From the results they were shown that bending strength of mixed and three layered sludge-particle board were decreased with increasing of composition ratios of sludge. And the mechanical and physical properties of the boards of three layered composition types have superior to those of mixed composition type. Although composition ratios of sludge increased, the internal bond strength and dimensional stability of sludge-particle board not decreased quantitatively. We concluded that the mechanical and physical properties of three layered sludge-particle board were similar w those of three layered particle-board (control) made by our laboratory design. Therefore, it was recognized that paper sludge can be used as potential raw material in particle-board manufacturing industry.

• Journal of Life Science
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• v.6 no.1
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• pp.14-26
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• 1996

In order to effectively utilize fish(Cod, Gadus macrocephalus) bone obtained as fish waste in fish manufactory, the preparation of the fish bone gelatin were attempted by heat extracting method from collagen protein contained in the fish bone. The methods of two kinds pretreatments (the B-type by alkali pretreatment and the E-type by enzyme pretreatment) for fish bone and the optimal extraction conditions to prepare gelatin from pretreated fish bone were investigated. Physical properties and functionalities of the two type fish bone gelatins obtained were compared with the commercial gelatin and the fish skin gelatin. The optimal extraction conditions of the B-type and the E-type gelatins were 5 folds of added water with material(w/w), pH 5.0, 3 hrs of extraction time and 60$\circ$C of extraction temperature. The yield of the B-type and the E-type gelatins were 32.6% and 28.1 %, respectively. The B-type gelatin was superior to the E-type un all physical properties. Molecular weight of the B-type was larger than that of the E-type due to its pretreatment method. Among the composition of amino acids, the amino acids such as glycine, alanine, glutamic acid and imino acids(proline and hydroxyproline) were responsible for 68$\sim$70% of the total amino acids. Functionalities of the fish bone gelatin were almost similar to commercial gelatin.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.1
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• pp.34-41
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• 2003

Finite element analysis of end-to-end artery/PTFE anastomosis recently have been researched. But, these studies were carried out without the compensation for the error of finite element analysis and assumed the artery and PTFE as the simple cylindrical shape in spite of being the fatty tissue which covers the heart. Therefore, we performed the convergency study with respect to increasing the element numbers and considered the fatty tissue as the elastic foundation in the finite element analysis. The results are as fallow ： 1. An anastomosis with the thinner thickness and larger diameter PTFE than artery could reduce the compliance disagreement. 2. A fatty tissue was affected to reduce the compliance mismatch in the vicinity of anastomosis of different material. Therefore a hypercompliant zone become narrorw and a compliance discrepancy decrease between the artery and the PTFE about 70%. And radial displacement with respect to longitudinal direction of an artery and the PTFE anastomosis was similar to a sectional compliance.

• Food Science and Biotechnology
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• v.15 no.1
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• pp.39-43
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• 2006

Levels of quercetin in different parts of onion were investigated using high performance liquid chromatography (HPLC) and liquid chromatography mass spectrometry (LC/MS) suitable for use with functional food material. Two main peaks were observed on HPLC chromatograms from the extracts of the skin, and the outer, middle, and core parts of onion. Using LC/MS, peak 1 was tentatively identified as quercetin monoglucoside at m/z 466.4, and peak 2 as quercetin with [M]+ at m/z 303.3. The levels of quercetin in the skin, and the outer, middle and core parts of the plant were 16.83,2.67,0.95, and 0.35 mg/g, respectively. In the study of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, skin, the nonedible part, contained the highest amount of quercetin, compared to the other edible parts, and showed the highest DPPH radical scavenging activity. Levels of quercetin and DPPH radical scavenging activity increased from core to skin. All parts of onion exhibited the strongest antibacterial activity only against Staphylococcus aureus and Vibro parahaemolyticus. Antibacterial activities of onion exhibited that S. aureus was more sensitive than V. parahaemolyticus. Among the four onion extracts, the middle part showed the strongest inhibitory activity against S. aureus but all onion extracts showed similar antibacterial activities against V. parahaemolyticus.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.675-675
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• 2013

CIGS thin films have received a great attention as a promising material for solar cells due to their high absorption coefficient, appropriate bandgap, long-term stability, and low cost production. CIGS thin films have been deposited by various methods such as co-evaporation, sputtering, spray pyrolysis and electro-deposition. In this study, Cu(In,Ga)Se2(CIGS) thin films were prepared using a single quaternary target by rf magnetron sputtering. The effect of sulfurization on the structural, compositional and electrical properties of the films was examined in order to develop the deposition process. An optimal sulfurization process will be selected for the preparation of CIGS thin films with good structural, optical and electrical properties by applying various sulfurization processes. In addition, the electrical properties of CIGS thin films were investigated by post-deposition annealing process. The carrier concentration of CIG(SSe) thin films after sulfurization was increased from $10^{14}cm^{-3}$ to $10^{16}cm^{-3}$ and the resistivity was increased from 10 ${\Omega}cm$ to $10^3$ ${\Omega}cm$. It is confirmed that CIG(SSe) thin films prepared at optimal deposition condition have similar atomic ratio to the target value after sulfurization.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1247-1248
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• 2006

We fabricated YBCO film using a TFA-MOD method. In order to enhance the reaction kinetics and to control the formation of the second phases, $Y_2Ba_1Cu_1O_x$ and $Ba_3Cu_5O_8$ powders were used as precursors (the so called "211 process"). The films were calcined at $460^{\circ}C$ and then fired at $750^{\circ}C-800^{\circ}C$ in a 12.1% humidified $Ar-O_2$ atmosphere. We found that the microstructure varied significantly with the firing temperature. The textures of all of the films were similar and mainly biaxial. For the film fired at $775^{\circ}C$, the critical current was obtained to be 39 A/cm-width (corresponding critical current density is 2.0 MA/$cm^2$).

• Current Photovoltaic Research
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• v.1 no.1
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• pp.11-16
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• 2013

The current solar cell industry is experiencing a temporary plateau due to a sluggish economy and oversupply. It is expected that the solar industry can see similar growth to that of the recent past by overcoming the current situation, as there is growing demand globally for solar energy. The current situation led to restructuring of the world's solar industry, and domestic firms will need to have competitiveness through strategic approaches and proprietary technology to survive in the global solar market. Crystalline and amorphous silicon based solar cells have led the solar industry and occupied half or more of the market thus far. They will do so in the future PV market as well by playing a pivotal role in the solar industry. In this paper, the current status and prospects of silicon based solar cells, from materials to comprehensive and high efficiency technology that can emerge in the future, are discussed.

• Restorative Dentistry and Endodontics
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• v.15 no.1
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• pp.20-32
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• 1990

The plane strain fracture toughness of a material characterize the resistance to fracture in the presence of a sharp crack under severe tensile condition. Fracture toughness can be determined by indentation method. The purpose of this study was to investigate the fracture toughness of dental amalgams by measuring the plane strain fracture toughness and the fracture toughness from indentation method. Two conventional and four high copper amalgam alloys were employed for this study. The amalgams were prepared according to the A.D.A. spec. No. 1 and inserted into the specially designed mould with the single edge notch specimen to use in 3-point bending method. The specimens (20mm long, 4mm wide, 2mm thick) were stored at $37^{\circ}C$ for 1 week, and tested in 3-point bending by means of Instron at a cross-head speed of 1mm/min. In indentation method, the specimens were made in same manner as single edge notch specimens. The test was conducted with Vickers hardness tester at 10kg load. The following results were obtained. 1. The plane strain fracture toughness and the fracture toughness from indentation method were higher in the low copper amalgams than the high copper amalgams. 2. In high copper amalgams, the fracture toughness of amalgams decreases according as the copper contents increase. 3. In similar copper contents, the single composition amalgams have a higher fracture toughness than the admixed amalgams.

• Composites Research
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• v.14 no.6
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• pp.1-8
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• 2001

In this paper, the sandwich panel composites consisting of core material and face sheet were studied to evaluate the mechanical properties, noise level and fire resistance including flammability, smoke, and toxicity. Four types of sandwich panel were prepared using various kinds of panel and honeycomb materials. It was observed that Al honeycomb/Al skin composite materials had the excellent flatwise tensile strength and edgewise compressive strength compared with other types of composites. The flatwise compressive strength and flexural strength of Nomex honeycomb/Al skin composite were higher than those of other composites. PMI form/Al skin composite showed the higher core shear strength and facing bending strength. From the experimental results of flame resistance tests, it can be said that the phenol based skin composite has the excellent flame retardation properties, which are similar to those of the commercial skin composites.