• Journal of dental hygiene science
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• v.15 no.4
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• pp.472-479
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• 2015

The purpose of this study is to examine musculoskeletal disorders and grasp the relationship between working environment factors and stress and musculoskeletal disorders in dental hygienists. The self-administered questionnaire survey was conducted with 483 dental hygienists working in Gwangju who were selected by convenience sampling. Frequency analysis, crosstab analysis, t-test, and multiple logistic regression analysis were made. Subjects' musculoskeletal disorders that complain of severe pains were 29.8%. The relationship between working environment factors and stress and musculoskeletal disorders were examined. As a result, work break frequency of working environment factors and stress were found to influence musculoskeletal disorders. For working environment factors, the odds ratio of musculoskeletal disorders of the two breaks group was 0.29 (95% confidence interval [CI], 0.11~0.73), compared with the no break group, indicating less musculoskeletal disorders. However, no significant difference was found in one break and more than three breaks groups. The odds ratio of musculoskeletal disorders of stress was 0.44 (95% CI, 0.27~0.70), indicating negative correlation. As break frequency was moderate (two breaks), musculoskeletal disorders became decreased. Stress showed negative correlation with musculoskeletal disorders.

• Journal of Preventive Medicine and Public Health
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• v.22 no.1 s.25
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• pp.116-124
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• 1989

To assay the cytogenetic toxicity of $NiCl_2,\;K_2Cr_2O_7CdCl_2,\;and\;HgCl_2$, the frequencies of sister chromatid exchanges(SCEs) and chromosomal aberrations were observed in the metaphase chromosomes of the human lymphocytes which were cultured with above materials. The frequencies of SCEs are dose-dependently increased by all materials in this experiment. Chromosomal aberrations, especially gap and break, are increased by the nickel and chromic compounds, while not significantly increased by the cadmium and mercurial compounds. This results indicate the dose dependent relationship between the frequencies of SCEs and the concentrations of the heavy metals, but the increasing rates of the SCEs induced by the heavy metals are less sensitive than other mutagens or carcinogens which were confirmed.

• The Journal of the Korea institute of electronic communication sciences
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• v.3 no.1
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• pp.1-7
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• 2008

Submarine cable is the most important IT infrastructure for international communication across oceans. However, a cable fault rarely happens by ship's anchor, fishing gears, submarine earthquake, and so on, and we need to improve on repair time for the reducing expenses of cable repair ship as well as the stability of high-capacity submarine optical network. There are several kinds of cable faults such as Shunt fault, Cable cut, Open fault and Fiber break. When a fault is occurred, cable landing stations(CLS) have to analysis failure quickly and accurately to find the type and the location of a cable fault. During the repair period, CLS should swiftly perform the tests requested by cable repair ship. In order to make rapid progress on cable repair, CLS test technique is very important. So, in order to reduce the repair time, this paper is studying the CLS test techniques of locating a submarine cable fault and of checking the splicing point performed by cable repair ship.

• Elastomers and Composites
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• v.46 no.2
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• pp.138-143
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• 2011

EPDM compounds and vulcanizates containing inorganic filler such as talc, calcium carbonate, or clay as well as carbon black were prepared, and the influence of inorganic filler on properties of the EPDM compounds and vulcanizates were investigated. The bound rubber contents did not significantly increase even though the inorganic filler was added. There were big aggregates in the EPDM samples with high loading inorganic filler. By adding the inorganic filler, the cure times tended to increase and the delta torque decreased. The modulus were on the whole decreased, whereas the elongation at break, tensile strength, and tear strength were increased by adding the inorganic filler. The decreased modulus and increased elongation at break can be explained with the decreased delta torque, the increases of tensile strength and tear strength can be explained with the increased elongation at break. By adding the inorganic filler, level of reinforcing in the EPDM compounds did not increase and the crosslink density decreased.

• Nuclear Engineering and Technology
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• v.26 no.3
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• pp.355-366
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• 1994

The USNRC issued a revised ECCS rule that allows the use of best estimate computer codes for safety analysis. The rule also requires an estimation of uncertainty in calculated system response when applying the best estimate computer codes. A practical realistic evaluation methodology to evaluate the ECCS performance that satisfies the requirements of the ECCS rule has been developed and this paper describes the application of new realistic evaluation methodology to large break LOCA for, the demonstration of the new methodology. The computer code RELAP5/MOD3/KAERI, which was improved from RELAP5/MOD3.1, was used as the best estimate code in the application. The uncertainty of the code was evaluated by assessing several separate and integral effect tests, and for the application to actual plant Kori 3 & 4 was selected as the reference plant. Response surfaces for blowdown and reflood PCTs were generated from the results of the sensitivity analyses and probability distribution functions were established by random sampling or Monte-Carlo method for each response surface. Final uncertainties were quantified at 95% probability level and safety margins for large break LOCA were discussed.

• Journal of Energy Engineering
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• v.16 no.3
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• pp.103-112
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• 2007

Flood issue for nuclear power plants designed and built in 1970 is extremely severe for main steam header compartment and main feedwater line region of intermediate building and lower floor. A calculation for flood level at the main feedwater line isolation compartment is now performing by hand calculation. But, this methodology is quite conservative assumption. The goal of this study was to develop method to analyze flowrate using the RETRAN-3D computer code, and the developed method was applied to flood level analysis following main feedwater line break. As a result of analysis, flood level was low remarkably.

• Journal of Korea Water Resources Association
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• v.31 no.3
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• pp.337-345
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• 1998

DAMBRK-U model is developed for the evaluation of overtopping risk of dam and levee and for the estimation of uncertainty in floodwave simulation. The original algorithm is revised and expanded to include Monte-Carlo analysis to estimate them. The model is tested by applying to hypothetical channels of widening, uniform and narrowing geometry. Larger variation in discharge and water depth are expected at narrower sections of a river. It is calibrated by applying to the Hantan River, where severe damages from Yunchun dam-break and levee overtopping occurred on July, 1996. Overtopping risk of dam is calculated for various discharge conditions for Yunchun-dam, and that of levee is also calculated by comparing levee height with flood level at Hantan recreation area. Simulation results show that the overflow depth of flood level is 1,266~0.782 m and the overflow risk turns out to be 100%.

• Journal of Wetlands Research
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• v.12 no.1
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• pp.33-40
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• 2010

In this study, it has been intended to present the ways to improve some problems such as the difficulty of using the program which had got from the existing study, the computation and application of a lot of parameter and the complicated processing which need to be more simplified. Also It has been tried to bring up the ways to make a flood inundation map and a detailed inundation analysis which could reduce the risk factors. We selected an Anseong-Cheon basin, and wrote a flood inundation scenario based on extreme flood to exceed the planned frequency to consider only overflow and levee break and executed inundation simulation. Researchers conducted an analysis of overflow and levee break using function of HEC-RAS Storage with a One-Dimensional model. It applied Elevation versus Volume Curve for more correct inundation simulation than a method of Area-Time-Depth which used in popular. This study will suggest a mathematical method of SURFER with a little difference of inundation area more simplified and precise flood inundation than complicated Arcview 3.2a which used Query method of Arcview 3.2a.

• Journal of Korean Society on Water Environment
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• v.22 no.3
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• pp.521-526
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• 2006

We have studied the possibility of removing Anabaena macrospora by injecting copper sulfate ($CuSO_4{\cdot}5H_2O$) into the raw water of a drinking water purification plant. Anabaena macrospora caused the unpleasant geosmin odor of drinking water in August 2001. The cell break-point of A. macrospora was 0.3 mg/L of $CuSO_4$. We were able to reduce the standing crops of A. macrospora effectively because $CuSO_4$ could break A. macrospora selectively. Because 0.3 mg/L of $CuSO_4$ could break both cells and akinetes, it reduced the possibility of a recurrent problem for them to meet a favorable condition. When $CuSO_4$ was injected in the early growth phase of algae and the mixing intensity was high, A. macrospora could be removed most effectively. The odor caused by A. macrospora was sustained for a while without any sudden change of environmental condition. Therefore, we hope that it could shorten the period of obstacle by injecting the optimal amount of 0.3 mg/L of $CuSO_4$. The water quality, alkalinity, conductivity, hardness and pH didn't changed by the injection of $CuSO_4$.

• Journal of Convergence for Information Technology
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• v.9 no.11
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• pp.125-133
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• 2019

In this paper, probabilistic flood risk maps were produced for levee break caused by possible flood scenarios. The results of the previous studies were employed for flood stages corresponding to hydrological extreme event quantified uncertainties and then predicted the location of a levee breach. The breach width was estimated by combining empirical equation considered constant width and numerical modeling considered uncertainties on compound geotechnical component. Accordingly, probabilistic breach outflow was computed and probabilistic inundation map was produced by 100 runs of 2D inundation simulation based on reliability analysis. The final probabilistic flood risk map was produced by combining probabilistic inundation map based on flood hazard mapping methodology. The outcomes of the study would be effective in establishing specified emergency actin plan (EAP) and expect to suggest more economical and stable design index.