• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.734-737
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• 2004

The synthetic fibers such as polypropylene(PP) and polyvilyl-alcohol(PVA) fiber are poised as a low cost alternative for reinforcement in structural applications. It has been reported that synthetic fiber in cement composites can control restrained tensile stresses and cracks and increase toughness, resistance to impact, corrosion, fatigue and durability. High performance fiber reinforced cementitious composite(HPFRCCs) shows ultra high ductile behavior in the hardened state, because of the fiber bridging properties. Therefore, a variety of experiments have being performed to access the performance of HPFRCCs recently. The research emphasis is on the flexural behavior of HPFRCCs made in synthetic fibers, and how this affects the composite property, and ultimately its strain-hardening performance. Three-point bending tests on HPFECCs are carried out. As the result of the bending tests, HPFRCCs showed high flexural strength and ductility. HPFRCCs made in PVA or Hybrid fiber were, also, superior to PP of singleness. On the other hand, effect of sand volume fraction on HPFRCCs made in PP was insignificant.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.10
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• pp.1137-1143
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• 2012

Creep characteristic is an important failure mechanism when evaluating engineering materials that are soft material as polymers or used as mechanical elements at high temperatures. One of the popular thermo-plastic polymers, Acrylonitrile Butadiene Styrene (ABS) which is used broadly for machine elements material, as it has excellent mechanical properties such as impact resistance, toughness and stiffness compared to other polymers, was studied for creep characteristic at different levels of stress and temperatures. From the experimental results, the creep limit of ABS at room temperature is 80 % of tensile strength which is higher than PE and lower than PC or PMMA. Also the creep limits decreased to linearly as the temperatures increased, up to $80^{\circ}C$ which is the softening temperature of Butadiene ($82^{\circ}C$). Also the secondary stage of creep among the three creep stages for different levels of stress and temperature was non-existent which occurred for many metals by strain hardening effect.

• Structural Engineering and Mechanics
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• v.68 no.2
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• pp.237-245
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• 2018

This study proposes an empirical formulation to predict the maximum deformation of offshore blast wall structure that is subjected to impact loading caused by hydrocarbon explosion. The blast wall model is assumed to be supported by a simply-supported boundary condition and corrugated panel is modelled. In total, 1,620 cases of LS-DYNA simulations were conducted to predict the maximum deformation of blast wall, and they were then used as input data for the development of the empirical formulation by regression analysis. Stainless steel was employed as materials and the strain rate effect was also taken into account. For the development of empirical formulation, a wide range of parametric studies were conducted by considering the main design parameters for corrugated panel, such as geometric properties (corrugation angle, breadth, height and thickness) and load profiles (peak pressure and time). In the case of the blast profile, idealised triangular shape is assumed. It is expected that the obtained empirical formulation will be useful for structural designers to predict maximum deformation of blast wall installed in offshore topside structures in the early design stage.

• Magazine of the Korean Society of Agricultural Engineers
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• v.36 no.4
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• pp.39-47
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• 1994

This research focuses on producing a cheap polymer, and also experiments for marking with the high strength polymer concrete structures. At present only a few tests on shear behavior in polymer reinforced concrete beams(PRC) have been reported. In the current experiments, the reinforced concrete beams with polymer fraction are investigated. The beams in this study are supported by conventional stirrups at appropriate intervals and they are designed to take static loads. The strength of beams are measured and the behavior of beams under each loading are oh served in order to determine some advantages of adding polymer to reinforced concrete beams. The static testing data consist of load, displacement, and strain at specified reinforcement locations, and the support displacement In the static tests, it has been observed that the beams fail in the same way as RC. However, it is observed to he rather weak in impact, hut it can he said that its increase of strength and excellency of repairing are verified. Consequently this work strongly suggests that the steam-curing or the air-curing or the air-curing must be performed to increase the strength.

• Asian-Australasian Journal of Animal Sciences
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• v.12 no.8
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• pp.1316-1323
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• 1999

Extensive emphasis on milk and milk fat yields with no diversion for beef performance increased the yield efficiency of North American dairy cattle. Heavy demand for North American genetics followed national strain comparison trials in Poland, and US and Canadian dairy cattle and germplasm still are an important source of genetics for many countries. Genetic improvement has accelerated in many countries because of the implementation of sampling programs for young bulls and improved evaluation procedures. Rapid access to information and more frequent calculation of genetic information also are having a positive impact on genetic improvement. Traits other than yield should be considered in a breeding program, but those traits mist have a reasonable opportunity for improvement and sufficient economic worth. Because of ever increasing efficiency, the world's milk supply comes from fewer cows each year. However, no decline in the rate of genetic improvement is apparent under current genetic practices; estimates of heritability are increasing, and a decline in yield efficiency is unlikely in the near future. As management improves, especially for subtropical conditions, many of the selection principles used in temperate climates will be adopted for more adverse environmental conditions.

• Journal of Microbiology and Biotechnology
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• v.30 no.7
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• pp.1082-1091
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• 2020

Microbial transglutaminases (MTGs) are widely used in the food industry. In this study, the MTG gene of Streptomyces sp. TYQ1024 was cloned and expressed in a food-grade bacterial strain, Bacillus subtilis SCK6. Extracellular activity of the MTG after codon and signal peptide (SP Ync M) optimization was 20 times that of the pre-optimized enzyme. After purification, the molecular weight of the MTG was 38 kDa and the specific activity was 63.75 U/mg. The optimal temperature and pH for the recombinant MTG activity were 50℃ and 8.0, respectively. MTG activity increased 1.42-fold in the presence of β-ME and 1.6-fold in the presence of DTT. Moreover, 18% sodium chloride still resulted in 83% enzyme activity, which showed good salt tolerance. Cross-linking gelatin with the MTG increased the strength of gelatin 1.67 times and increased the thermal denaturation temperature from 61.8 to 75.8℃. The MTG also significantly increased the strength and thermal stability of gelatin. These characteristics demonstrated the huge commercial potential of MTG, such as for applications in salted protein foods.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.3
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• pp.481-488
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• 1988

In the analysis of impulsive response of plate, Lagrange's theory, Reissner's theory and Mindlin's theory are generally used. But, in applying these theories the impulsive stresses directly underneath the concentrated impact point cannot be analyzed because the solution fails to converge. In this paper, therefore, an attempt for a supported square plate is made by using three-dimensional dynamic theory of elasticity on the supposition that the uniform distributed load acts on the central part of it. In order to clarify the validity of theoretical analysis, the strain variations are measured experimentally for a square glass plate. Finally it is shown that these theoretical results are in close agreement with the experimental results.

• Journal of Korea Foundry Society
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• v.30 no.1
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• pp.22-28
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• 2010

Metal foam is a porous or cellular structure material and representative property is a very high porosity. Foamed materials have very special properties such as sound, vibration, energy and impact absorption capacity. Especially this properties are widely used for safety demands of architecture, auto and aircraft industry. But metal foam need to increased its compression strength and hardness. This study were researched about Al-Si alloy foams with variation amount of Si contents for their fabrication and properties such as porosity, cell structure, microstructure and mechanical properties. The result are that the range of pore size is 2~4 $mm{\phi}$, the high porosity are 88%, high yield strength is 1.8MPa, the strain ratio is 60~70% and vickers hardness is 33.1~50.6.

• Clinical and Experimental Pediatrics
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• v.55 no.3
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• pp.77-82
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• 2012

Human astrovirus (HAstV) is a major cause of acute diarrhea among children, resulting in outbreaks of diarrhea and occasionally hospitalization. Improved surveillance and application of sensitive molecular diagnostics have further defined the impact of HAstV infections in children. These studies have shown that HAstV infections are clinically milder (diarrhea, vomiting, fever) than infections with other enteric agents. Among the 8 serotypes of HAstV identified, serotype 1 is the predominant strain worldwide. In addition to serotype 1, the detection rate of HAstV types 2 to 8 has increased by using newly developed assays. HAstV is less common compared with other major gastroenteritis viruses, including norovirus and rotavirus; however, it is a potentially important viral etiological agent with a significant role in acute gastroenteritis. A better understanding of the molecular epidemiology and characteristics of HAstV strains may be valuable to develop specific prevention strategies.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.12
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• pp.2972-2979
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• 2000

Dynamic characteristics of powder metal is very important to mechanical structures requiring high strength or endurance for impact loading. But owing to distinctive property of powder metal, that is relative, it has been investigated restrictively compared to static characteristics. The objectives of this study is to investigate dynamic characteristics of powder metal and compare it to a fully density material. To find the characteristics, an explicit finite element method is used for simulation of Split Hopkinson Pressure Bar experiment based on the stress wave propagation theory. We obtained a dynamic stress-strain relationship and dynamic behavior of powder metal, as well as the variation of material properties during dynamic deformation.