• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.3
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• pp.417-426
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• 2016

SWAT model usually underestimates daily peak discharges. To resolve this problem, in this study, the algorithm related with the surface flow simulation was modified by partitioning excessive infiltration based on the relative length between overland flow time of concentration and percolation travel time in soil water zone and by computing time of concentration varying with the amount of surface flow. The modified SWAT was applied to the Chungju dam watershed to assess the increasing effects of daily peak discharges. The daily peaks simulated by the modified SWAT were on average 10% higher than those by original SWAT for the peaks above $5,000m^3/s$. The modified SWAT was found to be able to more accurately reproduce daily peaks, particularly showing increase rates of 9.9%, 18.6% and 12.6%, respectively, for top three peaks that occurred in the years of 1990, 2002, and 2006.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.2
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• pp.299-306
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• 2015

The quality for the domestic pavement is evaluated based on flexural strength at the age of 28 days in accordance with KS regulation. Most specimens of the flexural tensile strength used currently are relatively large ones with a dimension of $150{\times}150{\times}550mm$. Accordingly, it is difficult to treat the specimens, and the utilization of a curing tank is low. In this paper, the study tried to resolve the problem by specimen size specified in the code. For this purpose, a flexural strength test was conducted according to the log scale within the specimen size specified by the KS. And, based on the results of this experiment, a comparative analysis was conducted using the prediction formula of Size Effect Law (SEL) proposed by Bazant to examine the correlation between specimen sizes, so as to use the result as basic data for the reduction of the specimen size in the quality evaluation of concrete pavement.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.3
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• pp.889-900
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• 2013

In a large scale of excavation for the foundation of large-sized structures and underground structures, a considerable amount of earth pressure can occur. Steel beams that have been used to form a temporary structure to support earth pressure may be less economical and less efficient in resisting the high earth pressure. To cope with this problem, PCT(Precast Concrete Truss) system has been devised and investigated both experimentally and analytically. A proper connection method between the concrete truss members was proposed to accommodate fast assembly and disassembly. Full-scale test of PCT system was performed to verify the load-carrying capacity of the PCT system including the connections. The test results were compared with those of structural analysis. The test specimen which corresponds to PCT strut attained the ultimate load without buckling, but the detail of connector members needs to be improved. It is expected that precast concrete truss members can be efficiently incorporated into a temporary structure for deep and large excavation by replacing conventional steel beams.

• Korean Journal of Community Nutrition
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• v.7 no.6
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• pp.741-748
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• 2002

The purpose of this study was to investigate the nutritional intake and dietary habits of women divers in Tongyoung area and to support the guideline for the improvement of their dietary life style by a validation of a Computerized Semi-quantitative Food Frequency Questionaire. Compared to the women at Jeju Island, the Tongyoung divers showed similar heights (154.6 $\pm$ 0.8 cm), weights (53.5 $\pm$ 1.0 kg) and BMIs (23.3 $\pm$0.4) , but they showed especially high levels of body fat (33.8 $\pm$ 0.8) . Their dietary habits showed they usually skipped lunch, but ate too much food at once, which may represent the dietary habits shown by obese people. Over 40% of the divers were taking some nutritious food or complementary food for health, without realizing the efficacy of these foods. The analysis of nutritional intake showed that all of average daily nutrients intakes of those below 50 years were higher than those of the Korean RDA. In the case of those above 50 years, it was shown that the average daily nutrients intakes were also higher than those of the Korean RDA except for energy (94.5%) and calcium (82.1%) . However, some individual divers showed lower nutrients intakes than 75% of RDA for calcium, iron, Vitamin A and Vitamin B$_2$. Also, excessive intakes of phosphorous and sodium could be a dietary problem. There was no correlation between BMI or percentage of body fat and energy, CHO, protein or fat. These results can provide the nutritional information for this special community, women divers, to improve their health.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.2
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• pp.137-148
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• 2012

In pressurized water nuclear reactors, dissimilar metal welds are susceptible to primary water stress corrosion cracking. To access this problem, accurate estimation of welding residual stresses is important. This paper provides general welding residual stress profiles in dissimilar metal nozzle butt welds using finite element analysis. By introducing a simplified shape for dissimilar metal nozzle butt welds, changes in the welding residual stress distribution can be seen using a geometry variable. Based on the results, a welding residual stress profile for dissimilar metal nozzle butt welds is proposed that modifies the existing welding residual stress profile for austenitic pipe butt welds.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.4
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• pp.439-445
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• 2011

Forensic Engineering is the art and science of professionals qualified to serve as engineering experts in courts of law or in arbitration proceedings. Buses using compressed natural gas (CNG) trend to be extended in use internationally as optimal counterplan for reducing discharge gas of light oil due to high concern about environment. However, CNG buses have to be equipped with composite pressure vessels (CPVs); since the CPVs contain compressed natural gas, the risks in the case of accident is very high. Hence, the investigation of such accidents is usually associated with engineering analysis. Among the possible reasons for such CNG explosion accidents is vehicle fire and vessel fracture. By conducting formal inspection and engineering tests, in this study, the cause of vessel explosion is investigated by analyzing the failure mechanism by fractography and by comparing the material properties of a reference part with those of a problem part by adopting instrumented indentation technique.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.8
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• pp.905-910
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• 2014

The steel grating discussed in this study is a drain cover that enhances the rigidity of the steel frame using an inclined inflow tract for wastewater, facilitates smooth drainage, and prevents the escape of bad smell from the drain. Recently, the urban problem of bad smell in sewerage lines has been hindering the improvement of living standards. Moreover, the frequent failure of existing products deters bad smell prevention measures and results in administrative power and budget wastage. The pressure to reduce budgets propels the increased demand for functional steel grating. Thus, this study focused on optimizing the design parameters of a steel grating by simultaneously considering its rigidity and drainage efficiency.

• Journal of Korean Tunnelling and Underground Space Association
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• v.5 no.1
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• pp.3-11
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• 2003

Face stability of a tunnel is a main concern during tunnel excavation. However, there has been only a few studies on this problem while a lot of researches on the support systems have been carried out. In addition, when tunneling is performed below the groundwater level, the groundwater flows into the tunnel so that the seepage forces generated on the tunnel face might give rise to a serious potential for the face instability. In this study, the face stability was evaluated by simultaneously considering two factors: one is the effective stress calculated by upper bound theorem; the other is the seepage forces acting on the tunnel face obtained by numerical analysis under the condition of steady-state groundwater flow. Tunneling in difficult geological conditions often requires auxiliary techniques to guarantee safe tunnel excavations and/or to prevent damage to structures and services around the tunnel. The steel pipe-reinforced multistep grouting has been recently applied to tunnel sites in Korea. Face stability of a tunnel with the steel pipe-reinforced multistep grouting was also analyzed in this study.

• Structural Engineering and Mechanics
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• v.65 no.2
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• pp.173-181
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• 2018

In this paper, finite element (FE) model updating based on multi-objective optimization with the surrogate model for a steel plate girder bridge is investigated. Conventionally, FE model updating for bridge structures uses single-objective optimization with finite element analysis (FEA). In the case of the conventional method, computational burden occurs considerably because a lot of iteration are performed during the updating process. This issue can be addressed by replacing FEA with the surrogate model. The other problem is that the updating result from single-objective optimization depends on the condition of the weighting factors. Previous studies have used the trial-and-error strategy, genetic algorithm, or user's preference to obtain the most preferred model; but it needs considerable computation cost. In this study, the FE model updating method consisting of the surrogate model and multi-objective optimization, which can construct the Pareto-optimal front through a single run without considering the weighting factors, is proposed to overcome the limitations of the single-objective optimization. To verify the proposed method, the results of the proposed method are compared with those of the single-objective optimization. The comparison shows that the updated model from the multi-objective optimization is superior to the result of single-objective optimization in calculation time as well as the relative errors between the updated model and measurement.

• Asian-Australasian Journal of Animal Sciences
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• v.19 no.6
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• pp.865-871
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• 2006

Signs of dental discolouration, difficulty in mastication, bony exostosis and debility were observed in cattle from Qingtongxia Ningxia, China where fluoride concentration in drinking water, soil, fodder, serum, bone, teeth, haircoat and urine were significantly higher than the corresponding health site. The problem of fluorosis in beef cattle is attributable to water containing toxic levels of fluoride. The objective of this paper was therefore to evaluate the influence of fluoride on erythrocyte parameters in cattle under high fluoride and low selenium conditions, as well as the protective efficacy of selenium exposure in feedstuff for bovine endemic fluorosis. Sixteen 6 to 7 year-old high fluoride beef cattle were randomly allotted into two groups each with eight cows: high fluoride control group, and supplemented with 0.25 mg/kg selenium per day for 83 days respectively. In addition, eight 6 to 7 year-old normal control beef cattle were selected from a non-high fluoride site. Blood samples were collected on day 0, 30 and 83 for erythrocyte parameters analysis and scanning electronic microscopy. The results indicated that erythrocytes, hemoglobin, packed cell volume values and $Na^+-K^+$ ATPase activity from affected cattle on the high fluoride site were significantly reduced during the period as compared with the corresponding samples of normal control cattle, a great number of echinocytes were present in peripheral blood, and subsequent anaemia. However, affected cattle exposed to selenium revealed increasable erythrocyte parameters, the extent of elevation in these values being dependent on the duration of supplementation with selenium. These findings suggest that fluoride exposure can cause erythrocyte damage, whereas selenium supplementation can antagonize fluoride-induced generation of free radicals and cumulative effects of lipid peroxidation in erythrocytes. Selenium supplementation may help to alleviate the possible hazards associated with bovine endemic fluorosis.