• KOREAN JOURNAL OF CROP SCIENCE
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• v.52 no.2
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• pp.140-145
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• 2007

This study was carried out to develop effective test method by soybean stink bug and to screen resistant genetic resources against soybean stink bug. The damage pod rate by stink bug showed 40% of most soybean varieties and was selected about 10% low of 10 varieties by 298 variety and degree in soybean at first year Stink bug damage rate research for 102 varieties that stink bug damage rate lowed at first year showed 10% low of 12 varieties and from 20% to 30% of the other varieties. So testing material is "Ilpumgeumjeongkong" to develop for effective test method soybean stink bug and result for stink bug damage rate research of according to growth stage showed rapidly high more full seed than full pod. Full seed stage (R6) was highest to 35.5% for stink bug damage rate. Result of resistant genetic resources selection according to stink bug damage pod rate was lowed of best to 10.3% for "Peking, Sorogkong, Hwangsaegjunjeari and Sobaeknamulkong" in the order. Also, stink bug damage seed rate was similar too. So "Peking, Sorogkong, Hwangsaegjunjeari and Sobaeknamulkong" were thought resistant variety against stink bug. Additional study carried out with "Peking and Sorogkong" so that concretely investigate about stink bug's refuse reaction. This result showed 10.0% for Peking and 14.2% for Sorogkong at R6 stage. But, damage pod rate was rapidly lowed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.11
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• pp.3424-3432
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• 1996

For mechanical system operating at high temperature, damage due to the interaction effect of creep and fatigue plays an important role. The objective of this paper is to develop a modified creep-fatigue damage model which separately analyzes the pure creep damage for hold time and the creep-fatigue interaction damage during startup and shutdown period. The creep damage was calculated by the general creep damage equation and the creep-fatigue interaction damage was calculated by the modified equation which is based on the frequency modified strain range method with strain rate term. In order to verify the proposed model, a service of high temperature low cycle fatigue tests were performed. The test specimens were made from inconel-718 superalloy and the test parameters were wave shape and hold time. A good agreement between the predicted lives based on the proposed model and experimentally obtained ones was observed.

• Tribology and Lubricants
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• v.30 no.6
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• pp.356-363
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• 2014

Marine diesel engines operate in environments in which damage easily occurs from corrosion. Recently, damage to cylinder liners has increased from corrosion wear caused by increased engine power. This damage can cause serious problems in the economy. Thus, many researchers have treated and studied damaged cylinder liners. However, a method is necessary for real-time monitoring of damage to cylinder liners during operation of the engine, before serious damage can occur. This study carries out reciprocating friction and wear tests on a cast iron specimen under various corrosion atmospheres and verifies the variations of friction coefficient and friction surface. Additionally, the friction coefficient and friction status are predicted by using a neural network that learns the vibration and frequency spectrum data from an acceleration sensor. According to our conclusions, amplitude is distributed highly at high frequencies, and values of standard deviation and kurtosis are high when damage to the friction surface is serious. The accuracy rate of the friction coefficient predicted by the neural network is over 80% of the real measured value without NaCl, and application of the neural network is very effective for diagnosing the friction condition and damage to the cylinder liner.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.05a
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• pp.1057-1058
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• 2012

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.10a
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• pp.703-704
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• 2012

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.6
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• pp.93-101
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• 2022

RC Slab bridges in Korea account for more than 70% of the total bridges for more than 20 years of service. As the number of aging structures increases, the importance of safety diagnosis and maintenance of structures increases. For highway bridges, cracks are a main cause of deck deterioration, which is very closely related to the decrease in bridge durability and service life. In addition, the damage rate of expansion joints and bearings accounts for approximately 73% higher than that of major members. Therefore, this study defined damage scenarios combined with devices damages and deck deterioration. The stress distribution and maximum stress on the deck were then evaluated using design vehicle load and daily temperature gradient for single and combined damage scenarios. Furthermore, this study performed damage-spread analysis and predicted condition ratings according to a deck deterioration model generated from the inspection and diagnosis history data of cracks. The heterogeneous damages combined with the member damages of expansion joints and bearings increased the rate of crack area and damage spread, which accelerated the time to reach the condition rating of C. Therefore, damage to bridge members requires proper and prompt repair and replacement, and otherwise it can cause the damage to bridge deck and the spread of the damage.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.4
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• pp.769-777
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• 2015

In this study, the rheological models were introduced and developed to reflect rate dependent tensile behaviour of concrete. In general, mechanical properties(e.g. strength, elasticity, and fracture energy) of concrete are increased under high loading rates. The strength of concrete shows high rate dependency among its mechanical properties, and the tensile strength has higher rate dependency than the compressional strength. To simulate the rate dependency of concrete, original spring set of RBSN(Rigid-Body- Spring-Network) model was adjusted with viscous and friction units(e.g. dashpot and Coulomb friction component). Three types of models( 1) visco-elastic, 2) visco-plastic, and 3) visco-elasto- plastic damage models) are considered, and the constitutive relationships for the models are derived. For validation purpose, direct tensile test were simulated, and characteristics of the three different rheological models were compared with experimental stress-strain responses. Simulation result of the developed visco-elasto-plastic damage(VEPD) model demonstrated well describing and fitting with experimental results.

• Journal of Welding and Joining
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• v.9 no.1
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• pp.40-47
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• 1991

The most fatigue tests carried out under the either stress or strain control, but machines and structures had taken variable stress. This variable stress was treated as statistics based on p-type distributions. In this paper, the cumulative fatigue damage of SM45C round bar specimens having a center hole resulting from block loading with p-distributions in rotating bending conditions, is presented. The value of p was changed in the range from 0.25 to 1; 0.25, 0.5, 0.75, 1. The following conclusions were obtained through the constant stress amplitude experiments and the block loading experiments. (1) In constant loading test, fatigue life was affected by cyclic rate. From experimental data, N$_{f}$ (100cpm)/N$_{f}$(3000cpm)equal to 0.56. (2) In case of the cyclic rate 100cpm and 3000cpm, at the high stress amplitude level the crack propagation life N$_{*}$f is longer than the low stress amplitude level. (3) Miner's hypothesis may be valid for p=0.75 and prediction of fatigue life by Haibach's method agree with experimental data well for the case p=0.5, while the modified Miner's method agree with experimental data well for the case p=0.25.5.

• Journal of Environmental Health Sciences
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• v.19 no.2
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• pp.69-77
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• 1993

In the present study, the comparison of liver damage in carbon tetrachloride (CCl$_4$)-treated rats with that those pretreated with ethanol and an effect of liver injury on the serum and liver xanthine oxidase (XOD) activity were evaluated. The increasing rate of liver weight per body wt., the levels of serum alanine aminotransferase, and the decreasing rate of hepatic glucose-6-phosphatase activity and the protein contents in the liver cell were higher in carbon tetrachloride-treated animals pretreated with ethanol than the carbon tetrachloride-treated group. Especially, the histopathological findings also showed more severe liver damage in the ethanol-pretreated rats than the rats treated with carbon tetrachloride only. In such a experimental condition the xanthine oxidase activity of serum and liver both of carbon tetrachloride-treated rats and those pretreated with ethanol were higher than that of each control group. And the increasing rate of xanthine oxidase enzyme activity to the control group was higher in carbon tetrachloride-treated group pretreated with ethanol than those treated with CCl$_4$. In addition, the heptic uricase activity and the serum levels of uric acid were more increased in carbon tetrachloride-treated group pretreated with ethanol than those in the CCl$_4$-treated rats. On the other hand, there were no statistical differences in hepatic catalase and glutathione S-transferase activities between the CCl$_4$-treated rats and those pretreated with ethanol. In conclusion, it is assumed that the more severe liver damage in ethanol pretreated rats would be due to oxygen free radical produced by the xanthine oxidase system.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.128-128
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• 2010

In this study, we investigated the evolution and reduction of the surface roughness during the high-speed chemical dry thinning process of Si wafers. The direct injection of NO gas into the reactor during the supply of F radicals from NF3 remote plasmas was very effective in increasing the Si thinning rate, due to the NO-induced enhancement of the surface reaction, but resulted in the significant roughening of the thinned Si surface. However, the direct addition of Ar and N2 gas, together with NO gas, decreased the root mean square (RMS) surface roughness of the thinned Si wafer significantly. The process regime for the increasing of the thinning rate and concomitant reduction of the surface roughness was extended at higher Ar gas flow rates. In this way, Si wafer thinning rate as high as $20\;{\mu}m/min$ and very smooth surface roughness was obtained and the mechanical damage of silicon wafer was effectively removed. We also measured die fracture strength of thinned Si wafer in order to understand the effect of chemical dry thinning on removal of mechanical damage generated during mechanical grinding. The die fracture strength of the thinned Si wafers was measured using 3-point bending test and compared. The results indicated that chemical dry thinning with reduced surface roughness and removal of mechanical damage increased the die fracture strength of the thinned Si wafer.