• Journal of the Korean Society of Safety
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• v.13 no.4
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• pp.113-120
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• 1998

Fatigue crack growth rates(i.e. crack initiation and crack growth of short and long crack) are investigated using commercial plates of high strength Al alloy 7075-T651 for the transverse-longitudinal(T-L) direction in air, water and sea water. Also, the evaluation direct current potential drop(D.C.P.D) method and the fractographical analysis by SEM are carried out. Near threshold region, short crack growth rates were much faster than those of comparable long cracks, and these short crack growth rates actually decrease with increasing crack growth and eventually merge with long crack data. Fatigue crack propagation rates in aggressive media(i.e. sea water) increase noticeably over three times those in air. One of the most significant characters in this phenomenon as a corrosion-fatigue causes an acceleration in crack growth rates. Sea water environment, particularly Cl$^{[-10]}$ solution brings the most detrimental effects to aluminum alloy. The result of fractographical morphology in air, water and sea water by SEM shows obvious dimpled rupture and typical striation in air, but transgranular fracture surface in water and sea water.

• Korean Management Science Review
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• v.16 no.1
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• pp.51-61
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• 1999

Pipeline is an important transportation mode for ail products. The popeline transportation and storage rates affect the popeline usage, and the popeline usage also affects the transportation revenue and operating costs of the popeline. The purpose of our study is to develop a decision support system simulating popeline transportation and storage rates for maximizing the utilization and profitability of the oil pipeline and apply it to the real situation. To do this, a simulation model to help the decision maker decide the rates of the oil pipeline is first proposed. Second, a simulation program is developed, which enables the user to evaluate the various scenarios of oil transportation and storage rates. Finally, this program is applied to the case study of oil industry in korea.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.15 no.4
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• pp.32-38
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• 2019

In this study, the effect of hot water supply flow rates on energy consumption for radiant floor heating system in apartment were researched by computer simulation. The parametric study of different hot water supply flow rates was done with regard to energy performance and control characteristics, respectively. Also the effect of different hot water supply flow rates on the hot water supply temperatures is studied. As a result, energy consumption were reduced but the response time is increased by reducing the supply flow rate. And energy consumption can be saved by adjusting the hot water supply temperatures with different supply flow rates.

• Journal of the korean society of oceanography
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• v.37 no.2
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• pp.76-81
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• 2002

I investigated whether US naval pulp wastes (pulverized paper products), which is planned to be dumped into offshore waters, may affect the ecology of major components of marine zooplankton. The presence of slurry (0.6% concentration - wet weight ; wet weight) did not significantly affect the population growth rates of the heterotrophic dinoflagellate Polykrikos kofoidii fed on Lingulodinium polyedrum, but significantly reduced the ingestion rates of the calanoid copepods Acartia spp. on L. polyedrum and those of the copepod Calanus pacificus on Akashiwo sanguinea (previously Gymnodinium sanguineum). However, C. pacificus, originally exposed to 0.6% slurry for 24 hour, can recover its feeding rates when slurry disappears. Therefore, if slurry is diluted quickly due to trubulence after being dumped at 0.6% concentration, its presence may not affect Calanus. Chemicals leached from slurry did not affect the feeding rate of Calanus. Therefore, mechanical interference by slurry on the feeding and/or swimming of copepods may be mainly responsible for the reduction of the ingestion rates.

• Journal of Korean Society on Water Environment
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• v.22 no.6
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• pp.1075-1081
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• 2006

In this research, mortality rates of pathogen indicator microorganisms discharged from various point sources and diffuse sources in urban area were measured. Water samples were taken at domestic sewer, combined sewer overflow, effluent from a wastewater treatment plant, urban river, and sediment of an urban river. Mortality rates of indicator microorganisms in domestic sewer estimated by assuming the first order kinetics at $20^{\circ}C$ were as follows: total coliform = 0.092/day, fecal coliform = 0.185/day, E. coli = 0.252/day, and fecal streptococci = 0.281/day. Sensitivity of mortality rates of total coliform on temperature was estimated as $K_{temp}=K_{20}{\times}1.162^{(temp-20)}$ for the range of $10-20^{\circ}C$. Mortality rates due to sunlight were measured as 1.22-1.59/day while mortality rate due to settling for 40 min were estimated as $9.21{\times}10^3-20.0{\times}10^3/day$.

• Asian Journal for Public Opinion Research
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• v.1 no.2
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• pp.128-146
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• 2014

Incentives are often included in survey design because they are known to improve response rates, at least moderately. This paper describes the changes in the response rates when incentives were introduced into a longitudinal survey. The National Survey of Student Engagement was conducted annually at Indiana University Bloomington from 2000 through 2012. In 2010, incentives were introduced in an attempt to reverse the declining response rates. The incentives performed as expected, raising the AAPOR Response Rate 3 from 24% in 2009 to 36% in 2010. From 2010 through 2012, different types of incentives were tried but the response rates did not change substantially. The results from the changes in incentives can help survey practitioners decide the number and types of incentives that might be used effectively to increase response rates.

• The Journal of Asian Finance, Economics and Business
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• v.1 no.1
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• pp.5-14
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• 2014

This paper empirically examines the short-run and long-run causal relationship between stock market prices and exchange rates in Chinese stock markets using monthly data from January 2002 to December 2012 retrieved from the National Bureau of Statistics of the People's Republic of China. Unit root, cointegration tests, vector error correction estimates, block exogeneity Wald tests, impulse responses, variance decomposition techniques and structural break tests are employed. This study found 1) long-run causality from exchange rates to stock prices in Chinese stock markets and 2) short-run causality from Japanese yen and Korean won exchange rates to stock prices in the Shanghai Stock Exchange strongly prevails while in the Shenzhen Stock Exchange weakly prevails. The impact of the global financial crisis from 2007 to 2009 on Chinese stock markets was insignificant.

• Journal of Labour Economics
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• v.31 no.3
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• pp.21-46
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• 2008

This paper estimates of the effect of Clean Workplace Program on industrial accident rates among firms with fewer than 50 workers. The program subsidizes selected firms for work environment improvement. After controling for selectivity and fixed effects in difference-in-difference model, we find that the program reduces the accident rates by 0.34%p, which amount to a decline of 15.8% in total accident rates.

• Journal of the korean society of oceanography
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• v.38 no.4
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• pp.157-165
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• 2003

In order to understand the characteristics of sedimentary environments in Ulleung Basin of the East Sea (Sea of Japan), three sediment cores were taken with a box corer during R/V Tamyang cruise in October 1999. Activities of $^{7}Be,{\;}^{210}Pb,{\;}^{226}Ra,{\;}^{234}Th,{\;}^{238}{\;}and{\;}^{137}Cs$ in sediment samples were determined by non-destructive gamma-ray spectrometry. Rates of sedimentation and particle mixing were estimated by best fitting an advection­diffusion particle mixing model to the data of $^{7}Be,{\;}^{234}Th,{\;}and{\;}^{210}Pb$. Estimated sedimentation rates were 0.06-0.08 cm/yr and particle mixing rates were $0.13-0.65{\;}\textrm{cm}^2/yr$. The use of multiple tracers in our study prevented us from probable up to 38% overestimation of sedimentation rates.

• Magazine of the Korean Society of Agricultural Engineers
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• v.30 no.1
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• pp.50-62
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• 1988

This study refers to the development of a hydrologic model simulating daily inflow and release rates for irrigation reservoirs. A daily - based model is needed for adequate operation of an irrigation reservoir sufficing the water demand for paddy fields which is closely related to meteorological conditions. Inflow rates to a reservoir need to be accurately described, which may be simulated using a hydrologic model from daily rainfall data. And the objective of this paper is to develop, test, and apply a hydrologic model for daily runoff simmulation. A well - known tank model was selected and modified to simulate daily inflow rates. The model parameters were calibrated using observed runoff data from twelve watersheds, Relationships between the parameters and the watershed characteristics were derived by a multiple regression analysis. The simulation results were in agreement with the data. The inflow model was found to simulate low flow conditions more accurately than high flow conditions, which may be adequate for water resources utilization.