• 열처리공학회지
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• 제14권3호
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• pp.155-159
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• 2001

The thermal shock resistance has been investigated and compared in three hot-work tool steels. The resistance to thermal shock is first of all a matter of good toughness and ductility. Therefore, a proper hot-work tool steel should be characterized by high fracture strength and high temperature toughness. In this study, new test method is proposed to measure the thermal shock resistance. New method is basically based on Uddeholm' thermal shock test but some modification has been properly applied. Based on these results, some critical temperature($T_{fractures}$) at which fracture occur can be measured to characterize the thermal resistance of the materials. The specific values of ${\Delta}T$, the temperature difference between holding temperature and $T_{fractures}$, has been successfully used as a measure of the thermal shock resistance in this study, the results showed that the thermal shock method used in this study was properly modified.

• 한국식품영양학회지
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• 제30권4호
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• pp.830-840
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• 2017

Excessive body weight gain during the growth period of early life may predispose individuals towards obesity and metabolic disorder in later life. We investigated the possibility of using the food efficiency ratio as an early indicator for predicting susceptibility to diet-induced obesity and insulin resistance. Four-week-old, prepubertal, male Sprague Dawley rats were divided into obesity-prone and obesity-resistant groups based on food efficiency ratio values after five days on a high-fat diet. Metabolic parameters measured after 2, 6, and 10 weeks, and specific phenotypes were compared with each group. Obesity-prone rats had higher increases in body weight and fat mass compared to obesity-resistant rats over the study period. Obesity-prone rats became glucose intolerant early in this study and remained so throughout the experimental period, with increases in fat weight and leptin levels occurring first, followed by increases in insulin level. Gluconeogenesis and insulin resistance significantly increased in obesity-prone groups in which activities of glucose-6-phosphatase and phosphoenolpyruvate carboxykinase were increased and glucokinase activity decreased. Higher food efficiency ratio at an early age was closely correlated with body fat accumulation, hyperleptinemia, and hyperinsulinemia of middle and elderly age. We suggest a high food efficiency ratio in prepubertal subjects may be a useful predictor of future obesity and insulin resistance.

• 수산해양기술연구
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• 제57권1호
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• pp.1-9
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• 2021

Trawl fishing is a fishing method in which a large, motorized trawler tows a bag-shaped net to catch fish living at the bottom or middle layers. For a trawl gear, it is of utmost importance to select the gear size and towing speed suitable for the effective horsepower (EHP) of the trawler in the design stage. In general, the power required to move an object is proportional to the product of the object speed and resistance; therefore, there are various choices for the gear resistance and towing speed given the effective horsepower of the trawler. However, there have been few studies on the gear design of an appropriate scale for the towing speed given the effective horsepower of the trawler. In this study, the resistance and shape of three types of midwater trawl gears were analyzed using SimuTrawl, a computer simulation tool. In addition, the relationship between the propulsion force and speed of the ship was clarified when the size and effective horsepower of the trawler were determined. Finally, we suggested the relationship between the towing speed and the resistance of the gear when the trawler towed the net was investigated, and a specific method of selecting the gear size according to the towing speed.

• 전자공학회논문지A
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• 제31A권10호
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• pp.87-93
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• 1994

Ohmic contacts between Au and p-HgHg_{0.7}Cd_{0.3}Te$ with low specific contact resistance have been obtained. The contact region of the wafer is first pre-heated for 5 seconds in a rapid thermal processing equipment. The temperature reaches a maximum value of about 200$^{\circ}C$ at the end of the 5 seconds. Next, a thin Au film is formed on the contact region by immersing the sample in AuCl$_{3}$ solution. the sample is then post-annealed in the same condition as the pre-heating after Pb/In pad metals are deposited on the electroless Au contacts. The specific contact resistance measured by transmission line model is 5${\times}10^{-3}{\Omega}cm^{2}$ at 80K. RBS and differential Hall measurement data suggest that the above low resistance ohmic contact is ascribed to surface traps and increased gold diffusion rate.

• 대한기계학회논문집
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• 제18권9호
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• pp.2374-2385
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• 1994

SiCw/Al composite material is especially attractive because of their superior specific strength, specific stiffness, corrosion fatigue resistance, creep resistance, and wear resistance compared with the corresponding wrought Al alloy. In this study, Fatigue crack growth behavior and fatigue crack path morphology(FCPM) of SiC whisker reinforced Al 6061 alloy with 25% SiC volume fraction and Al 6061 allay were performed. Result of the fatigue crack growth test sgiwed that fatigue crack growth rate of SiCw/Al 6061 composite was slower than that of Al 6061 matrix therefore it was confirmed that Sic whisker have a excellent fatigue resistance. And Al 6061 matrix had only FCPM perpendicular to loading direction. On the other hand SiCw/Al 6061 composite had three types in fatigue crack path morphology. First type is that both sides FCPM of artificial notch are perpendicular to loading direction. Second type is that a FCPM in artifical notch has slant angle to loading direction and the other side FCPM is perpendicular to loading direction. Third type is that both sides FCPM of notch have slant angle to loading direction. It was considered that this kinds of phenomena were due to non-uniform distribution of SiC whisker and confirmed by SEM observation for fracture mechanism study.

• 한국주조공학회지
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• 제25권2호
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• pp.73-79
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• 2005

Effects of Cr and Ni addition on damping capacity, mechanical property, and corrosion resistance of Fe-17%Mn martensitic alloy have been studied. Martensite start temperature($M_{S}$) of the alloy decreases linearly with increasing Cr and Ni contents up to 15%. The damping capacity decreases gradually from 27 to 22% in specific damping capacity(SDC) with increasing Cr and Ni contents from zero to 10%, and decreases rapidly with further Cr and Ni content in Fe-17%Mn alloy. The tensile strength of the alloy maintains a level of 60 $kgf/mm^{2}$ regardless of Cr content with an elongation of 20 to 25%. But, in case of Fe-17%Mn-x%Ni alloy, the tensile strength decreased rapidly with the Ni content of above 10% because of austenite morphology. Immersion test in 5% NaCl solution leads to the result that the corrosion resistance of the alloy becomes excellent above 10% Cr. From the above results, it is concluded that the optimum Cr content to improve the mechanical property and corrosion resistance of the alloy in 5%NaCl solution with a lesser decrease in damping capacity is about 10%. In the case of 5% $H_{2}SO_{4}$ condition, the Fe-17%Mn-10%Ni is an optimum alloy.

• 한국수산과학회지
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• 제54권4호
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• pp.388-396
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• 2021

Antimicrobial resistance patterns of Escherichia coli were investigated. Strains were isolated from 310 shellfish, 36 crustaceans, and 12 fish collected off the West Coast of Korea from April 2019 to October 2020. Two hundred and ninety-five E. coli strains were isolated from shellfish, 100 from crustaceans, and 54 from fish. Strains isolated from shellfish showed the highest resistance to ampicillin (27.5%), whereas those from crustaceans were resistant to sulfisoxazole (30.0%) and those from fish were resistant to ampicillin (59.3%) and sulfisoxazole (59.3%). Ceftazidime resistance was observed in strains isolated from short neck and hard clams, whereas gentamicin resistance was observed in strains from fish. Multi-drug resistance was observed in 56 strains (48.7%) isolated from shellfish, 11 (28.2%) from crustaceans and 27 (73.0%) from fish. Depending on the source of isolation, the strains showed specific antimicrobial resistance tendency. Strains isolated from shellfish showed 12 different multi-drug resistance patterns, whereas those from crustaceans showed high resistance (59%) to a single antimicrobial agent and those from fish showed a broad trend of multi-drug resistance to more than eight antimicrobials.

• 한국물환경학회지
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• 제20권4호
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• pp.370-375
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• 2004

Synthetic organic polyelectrolytes can be used to condition sludges to enhance their dewaterability. When conditioning biological sludges, the charge on the polymer has a significant impact on the effectiveness of the polymer as a conditioner. The objectives of this investigation were to determine the most effective type and dosage of polymer for conditioning digested sludge prior to dewatering, and to investigate the relationship between dewaterability and particle size. 3 types of digested sludge were used under the different digestion processes like anaerobic digestion, aerobic digestion and intermittent aerobic digestion. CST(capillary suction time), TTF(time-to-filter) and SRF(specific resistance to filtration) were tested as a dewaterability index and the number of particle distribution was analyzed using particle size analyzer. The results indicate that cationic polymer appears to be required for effective conditioning of these 3 types digested sludge and the optimal polymer dosage is about 0.6% of SS. CST and TTF are well correlated with mean particle diameter of which the dimension order is 1.7.

• 신재생에너지
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• 제6권1호
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• pp.38-45
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• 2010

Abstract Under the physical stress on photovoltaic (PV) module, it will be warped according to elongation of the front glass and then micro-crack will be occurred in the thermally sealed solar cell. This micro-crack leads to drop of short circuit current of the PV module. This is because of increase of resistance component by micro-crack. Micro-crack at specific solar cell in the module lessens the durability of PV module with reduced output, hot-spot caused by solar cell output mismatch and increased resistance component. This study shows the relation between electrical characteristics and micro- cracks due to mechanical stress on PV module.

• 국제초고층학회논문집
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• 제12권3호
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• pp.235-239
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• 2023

In this study, the fire resistance performance of the concrete-filled steel tube (CFT) columns and thin steel-plate composite (TSC) beams installed at a 20-story office building were designed using a performance-based structural fire design. Because of the lack of any specific provisions in the building code and guidelines for structural engineers about the performance-based approach, the only prescriptive approach has been selected for designing fire-resistant structures in Korea. To evaluate the fire resistance performance of the CFT columns and TSC beams, finite element analysis verified by the experimental results studied by several researchers was conducted with ABAQUS. From the fire scenario, the temperature distributions of the CFT columns and TSC beams were found via finite element analysis and the behaviors of the CFT columns and TSC beams were investigated in the structural field based on the temperature distribution.