• Journal of Korea Water Resources Association
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• v.49 no.10
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• pp.887-901
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• 2016

Cohesive sediments form flocs through the flocculation process. The size and density of floc are variable whereas those of a fine sediment are always assumed to be constant. The settling velocity, one of main factors of sediment transport, is determined by size and density of particle. Therefore, the flocculation process plays an important role in transport of cohesive sediment. It is of great difficulty to directly measure the density of floc in the field due to technical limitation at present. It is a popular approach to estimate the density of floc by applying the fractal theory. The main assumption of fractal theory is the self-similarity. This study aims to examine the applicability of fractal theory to cohesive sediment in small rivers of Korea. Sampling sediment has been conducted in two different basins of Geum river and Yeongsan river. The results of settling experiments using commercial camera show that the sediment in Geum river basin follows the main concept of fractal theory whereas the sediment in Yeongsan river basin does not have a clear relationship between floc size and fractal dimension. It is known from this finding that the fractal theory is not easily applicable under the condition that the cohesive sediment includes the high content of organic matter.

• Tunnel and Underground Space
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• v.20 no.2
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• pp.105-111
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• 2010

This study is to consider applicability of spiral bolt strain gauge as an instrument measuring behavior of soft ground foundation and rock slope. When the instrument was installed on the ground, it can be useful to identify the state of ground behavior because it has the characteristics of flexibility, as well as to apply the ground reinforcement because it has higher pull-out resistance to the ground. From the measurement of behavior to soft ground foundation, the strain shows a stable state in the beginning, then was observed significant change in the upper and the middle of spiral bolt strain gauge after 400 days. This is analyzed that ground loosening, which is due to occurred frequent earthquake of magnitude 1~2 with increased rainfall, lead to the instability of the ground. From the measurement of behavior to rock slope, the strain shows a stable state with very little change in a period of 0~50 days and the biggest strain at 4.2 m (P6) in a period of 50~100 days, then other places except P6 was maintained at a stable state in a period of 100~160 days. The reason is analyzed because that blasting for excavated limestone surrounding was affected to the largest at P6. However, based on the size of strain change by behavior of the soft ground foundation and rock slope, it is considered that the present condition are not effected on stability of retaining structure and rock slope. In conclusion, the proposed spiral bolt strain gauge can be useful to measure behavior of soft ground foundation and rock slope, and also to be measured behavior as well as reinforcement of the target ground.

• Journal of Preventive Medicine and Public Health
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• v.34 no.4
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• pp.427-436
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• 2001

Objective : To estimate the prevalence of congenital heart disease from the 1990 student heart disease screening program. Methods : The heart disease screening program for elementary students was conducted in Kyonggi-do, in 1998. The subjects of the present study comprised the 40,402 students who attended the schools in the catchment area of a collaborative university hospital and who participated in the primary examination. The congenital heart disease (CHD) patients were initially identified through a questionnaire about prior medical history, and further through diagnostic tests & medical examinations in the secondary & the tertiary examinations. Certain assumptions were used in the estimation of the number of CHD cases among non-participants of the secondary & tertiary examinations. The overall prevalence of CHD was estimated by adding the CHD detection rates of the participants and the estimated prevalence of the non-participants. Results : Among the 40,402 primary participants, 1,655 were referred further, of whom 79.1% (1,309) participated in the secondary examination. Of these, 121 were referred to the tertiary examination, with a participation rate at this last stage of 80.2%. The positive predictive value (PPV) of the screening tools was the highest when the results of both EKG and the questionnaire were positive. Because 85.9% of the detected cases had a past history of CHD, PPV was higher when the selection criteria in the questionnaire included past CHD history than when it didnt. The CHD defection rate among the participants was 1.76 cases/1,000 and the presumed number of cases among the non-participants was 31; giving an estimated final CHD prevalence of 2.52 cases/1,000 (95% CI : 2.06-3.06). Among the identified cases of CHD, VSD (52.8%) was the most common, followed by PDA (9.7%), TOF (9.7%) & PS (9.7%). Conclusion : Because the characteristics of the non-participants differed from those of the participants, the estimation of prevalence was influenced by the participation rate. Of the detected cases, 85.9% had a past history of diagnosis or operation for CMD. These findings suggested that the prevalence estimated in this study may be an underestimation of the actual condition. Therefore, a birth cohort study is required in order to more accurately estimate the prevalence and the effects of the program.

• Korean Journal of Acupuncture
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• v.22 no.1
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• pp.7-21
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• 2005

Objectives : In the present study, the effect of electroacupuncture (EA) applied to SI6 and won-rak point on the ankle sprain model was examined. A common source of persistent pain in humans is the lateral ankle sprain. Methods : To model this condition, the rat's right ankle was bent repeatedly, overextending lateral ligaments, for 4 min under enflurane anesthesia. The rat subsequently showed swelling of the ankle and a reduced stepping force of the affected limb for the next several days. The reduced stepping force of the limb was presumably due to a painful ankle. EA was applied to the several acupuncture point on the contralateral forelimb for 30 min under gaseous anesthesia. After the termination of EA, behavioral tests measuring stepping force and Paw volume were Periodically conducted during the next 4 h and 18 h respectively. Results : EA applied to $SI_6$ with won-rak point produced more powerful improvement of stepping force of the sprained foot than to $SI_6$ alone lasting for at least 4 h. However, neigher $KI_4$ point nor $BL_{64}$ point produced any significant increase of weight bearing force. The improvement of stepping pressure was interpreted as an analgesic effect. The analgesic effect was specific to the acupuncture point since the analgesic effort on the ankle sprain pain model could not be mimicked by EA applied to $KI_4$ or $BL_{64}$. In addition, EA applied to $SI_6$ with won-rak combination point showed inhibitory effect on the paw edema induced by ankle sprain. Also, COX-2 protein expression increased by ankle sprain were suppressed by the EA stimulation. Conclusion : These data suggest that EA with won-rak combination point produces a more potent analgesic effect on the ankle sprain pain model in the rat and that EA with won-rak combination point induced anti-inflammatory effect through the suppression of COX-2 protein expression.

• Journal of Life Science
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• v.21 no.2
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• pp.286-291
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• 2011

Hypoxia is a common condition found in a wide range of solid tumors and is often associated with metastasis and poor clinical outcomes. In the present study, we found that HIF-$1{\alpha}$ was induced by cobalt chloride (500 ${\mu}M$) treatment on human lung cancer cells, A549 and H460, for 24 hr. However, cobalt chloride (500 ${\mu}M$) did not affect cell proliferation of A549 and H460 in 48 hr. Cobalt chloride (500 ${\mu}M$) additionally induced epithelial-to-mesenchymal-like transition (EMT) such as reduced E-cadherin expression and increased ${\alpha}$-SMA expression. These results were confirmed by immunofluorecence experiment in H460 cells. E-cadherin was localized on the outer cell membrane. However, when the cells were treated with 500 ${\mu}M$ cobalt chloride for 24 hr, diffuse E-cadherin staining was observed, characteristic of a migratory mesenchymal phenotype. We also found that cobalt chloride induced integrin ${\beta}3$ expression and FAK phosphorylation in human lung cancer cells using western blotting and FACS anlaysis. Our data suggest that integrin ${\beta}3$-induced FAK phosphorylation may be developed into target molecules for blocking tumor metastasis.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.1
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• pp.47-54
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• 2013

This study investigates the crack growth behavior due to primary water stress corrosion cracking (PWSCC) in the dissimilar metal butt weld of a reactor piping using Alloy 82/182. First, detailed finite element stress analyses were performed to predict the stress distribution of the dissimilar metal butt weld in which the hydrostatic and the normal operating loads as well as the weld residual stresses were considered to evaluate the stress redistribution due to mechanical loadings. Based on the stress distributions along the wall thickness of the dissimilar metal butt weld, the crack growth behavior of the postulated axial and circumferential cracks were predicted, from which the crack growth diagram due to PWSCC was proposed. The present results can be applied to predict the crack growth rate in the dissimilar metal butt weld of reactor piping due to PWSCC.

• Korean Journal of Organic Agriculture
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• v.22 no.4
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• pp.801-813
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• 2014

A study was conducted to improve the biological activity of two medicinal plants, Eucommia ulmoides Oliv. and Glycyrrhiza uralensis, by fermentation. The biological activity was assessed by determining antibacterial, antioxidant and antimethanogenic properties. Fermentation was achieved by adding the plant materials in MRS broth at 10% (w/v) and different starter cultures at 1% (v/v). Condition for fermentation were incubation temperature of $30^{\circ}C$ and agitation at 150 rpm for 48 h. Six starter cultures, Weissella confusa NJ28 (Genbank accession number KJ914897), Weissella cibaria NJ33 (Genbank accession number KJ914898), Lactobacillus curvatus NJ40 (Genbank accession number KJ914899), Lactobacillus brevis NJ42 (Genbank accession number KJ914900), Lactobacillus plantarum NJ45 (Genbank accession number KJ914901) and Lactobacillus sakei NJ48 (Genbank accession number KJ914902) were used. Antibacterial activity was observed in L. curvatus NJ40 and L. plantarum NJ45 only as opposed to other treatments, including the non-fermented groups, which showed no antibacterial activity. Both plants showed antioxidant activity, although E. ulmoides Oliv. had lower activity than G. uralensis. However, fermentation by all strains significantly improved (p<0.05), antioxidant activity in both plants compared to non-fermented treatment. Six treatments were based on antibacterial activity results, selected for in vitro rumen fermentation; 1) non-fermented E. ulmoides, 2) fermented E. ulmoides NJ40, 3) fermented E. ulmoides NJ45, 4) non-fermented G. uralensis, 5) fermented G. uralensis NJ40, 6) fermented G. uralensis NJ45. A negative control was also added, making a total of 7 treatments for the in vitro experiment. Medicinal plant-based treatments significantly improved (p<0.05) total volatile fatty acid (VFA) concentration. Significant methane reduction per mol of VFA were observed in G. uralensis (p<0.05). Based on the present study, fermentation improves the biological activity of E. ulmoides Oliv. and G. uralensis. Fermented G. uralensis could also be applied as an enteric methane mitigating agent in ruminant animals.

• Applied Chemistry for Engineering
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• v.23 no.6
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• pp.594-598
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• 2012

In the present study, biogas was produced from the anaerobic digestion of marine macroalgae (Laminaria japonica) biomass. The optimal anaerobic condition for producing the sludge was the freeze treatment at $-70^{\circ}C$ for 20 min. Total amounts of hydrogen and methane gas produced were 667.28 mL/L and 3420.24 mL/L, respectively, which were 2.7 and 3.4 times greater than that in the control group. Freeze treatment of sludge produced the maximum biogas under an initial optimum pH of 7.0 and the maximum biomass at an initial optimum pH of 8.0. We confirmed that biogas production was greatly reduced under acidic conditions compared to that under alkaline conditions. Sludge was freeze treated, and the biomass and sludge production was optimal the total amounts of hydrogen and methane gas produced were 643.73 mL/L and 4291.6 mL/L, respectively, which were 2.6 and 4.3 times greater than in the control group. Also the results showed that under optimal conditions in a 5-L bioreactor, a maximum of 1605.03 mL/L of hydrogen and 4593.71 mL/L of methane gas could be produced by the substrate contained in the marine macroalgae biomass.

• Korean Journal of Ecology and Environment
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• v.36 no.2 s.103
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• pp.161-171
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• 2003

The present study evaluated water quality variation, limiting nutrient, and sediment of a shallow eutrophic lake (Lake Ilgam) in the metropolitan area from 2000 to 2002. According to annual mean chl.a ($77.2{\pm}36.6\;{\mu}g/l) and TP ($66.6{\pm}20.5\;{\mu}g/l) concentration and trophic state index (>60), Lake llgam was in very eutrophic status. Both inorganic nitrogen ($NH_3-N$ and $NH_3-N$) and phosphorus (SRP) concentrations in the water column increased during winter and spring, but decreased during summer followed by the phytoplankton development. Evidence for phosphorus and nitrogen as being the potential limiting nutrients for phytoplankton growth was supported by the ratio of DIN/DIP (by mass) (${\sim}$835.8), TSI derivations analysis, and algal growth potential bioassay. Based on the results of TSI derivations, strong nutrient limitation by both N and P occurred from September to November when P content in sediment (114.6 mg P/kg) was relatively low compared with the summer. Sediment contained a large amount of nitrogen (TKN: 4,452${\pm}$283.0mg N/kg dry sediment). Phosphorus content in sediment (TP: 313${\pm}$155 mg P/kg) was relatively low with temporal change. P release rate (0.29${\pm}$0.02 mg $m^{-2}$ $day^{-1}$) was high under the aerobic condition at pH 9. These results indicate that the sediment could play an important role as a source of a limiting nutrient, and temporal change of P content in the sediment is closely related with water quality, especially algal biomass change in Lake llgam.

• Korean Journal of Ecology and Environment
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• v.41 no.1
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• pp.34-42
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• 2008

Water quality standards (WQS) are mandatory to guarantee the human health and protection of aquatic ecosystems, and maintain the condition of suitable water quality. The present WQS for the protection of human health in Korea contain nine substances (As, Cd, $Cr^{6+}$, CN, Pb, Hg, ABS, organophosphorus compounds and PCBs), but it is insufficient to preserve the human and aquatic ecosystem from a variety of chemicals. Therefore, it is necessary to expand the substance of WQS for the protection of human health. In this study, we chose the 20 chemicals from 43 chemicals of the project entitled 'Development of Integrated Methodology for Evaluation of Water Environment'. The methodology for calculating water quality criteria was amended from the US Environmental Protection Agency (US EPA)'s equation for deriving ambient water quality criteria for the protection of human health. The factors including fish intake, drinking water intake, and human body weight used in the equation reflected Korean situations. The monitoring values were derived from the water quality monitoring data in Korean four main rivers. The orders of priorities of chemicals were evaluated by human health risk assessment, and the proposed WQS was derived by technical and economic analyses. These results were reflected to expand the WQS for the protection of human health.