• 한국대기환경학회지
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• 제8권4호
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• pp.247-256
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• 1992

Airborne suspended particulates were collected at Shinchon by a high volume cascade impactor from Sep. 1990 to Aug. 1991. Organic matter was extracted from particulates and fractionated by liquid-liquid extraction and thin layer chromatography. Substances in the PAHs and nitroarenes'subfraction of neutral fraction were determined by capillary gas chromatography. Based on unit risk estimates by multi-stage model of benzo[a]pyrene and the results of exposure estimates, cancer risk was assessed. The annual average concentration of total suspended particulates was 201.77g/$m^3$. The percentage of fine particulates was 57.40. The concentration of total suspended particulates showed seasonal variations and was high in winter and spring. The average concentration of extractable organic matter was 8.12g/$m^3$. In all, 21 PAHs were identified and quantified. The annual concentration of fluoranthene was 2.38ng/$m^3$, and that was the highest value of all PAHs. A carcinogenic compound, benzo[a]pyrene, was at a concentration of 1.84ng/$m^3$. All the 10 nitroarenes were also identified and quantified. The major nitroarene in the Shinchon area was 2,7-dinitrofluorene. The annual concentration of 1-nitropyrene was 1.56ng/$m^3$. Concentrations of PAHs and nitroarenes were high in winter and low in summer. The life time excess risk estimates of benzo[a]pyrene was calculated as 0.96 persons/a million population in this experiment. In the rank of relative potenties, carcinogenic effects of the other PAHs were calculated as 0.004-0.108 persons/a million population.

• Asian-Australasian Journal of Animal Sciences
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• 제22권1호
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• pp.42-48
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• 2009

An in vitro incubation study was conducted to investigate effects of 2-bromoethanesulfonic acid (BES) on ruminal fermentation characteristics and methanogen population. BES at the final concentration of 0, 1 and 5 mM with two different substrates having a different ratio of timothy and concentrate (100% timothy vs. 40% timothy-60% concentrate) was incubated for 0, 24, 48 and 72 h in a $39^{\circ}C$ incubator. Total DNA extracted from culture fluid was used as a template for real-time PCR to measure the population of methanogens. Four different primer sets were used for amplification of total bacteria, total methanogens, the order Methanobacteriales and the order Methanomicrobiales. BES reduced (p<0.01) total gas and methane production in a dose-dependent manner. BES at 5 mM inhibited methane production by more than 95% compared to the control. An interaction between substrate and level of BES in total gas and methane was detected (p<0.01). The decrease of methane production with increasing BES level was more pronounced on mixed substrate than on timothy alone. However, hydrogen production was increased by BES treatment (p<0.01). Total VFA concentration was not affected, but molar percentage of propionate and butyrate was increased and acetate to propionate ratio was reduced by BES treatment (p<0.01). BES did not affect the population density of total bacteria but reduced (p<0.01) the population of total methanogens, the order Methanobacteriales and the order Methanomicrobiales in a dose-dependent manner. The type of substrate did not influence the trend, although the magnitude of response was different between all-roughage and 40% roughage substrate.

• 한국항만학회지
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• 제11권2호
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• pp.305-320
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• 1997

The objective of this paper is to analysis & forecast on the change in spatial structures of southeast region by development of the Seoul-Pusan high-speed Rail. To measure the spatial structures, it was used the method of mean center and standard distance among of centrographic measures as analytical tools. The changes of spatial structures patten over time and space in the southeast region were surveyed using population and employment data of 57 zones. And also, to forecast the spatial structures of the southeast region after opening of the Seoul-Pusan high-speed rail, it was supposed three(3) scenarios which designed using influential area with centering around of the proposed high-speed rail stations. Therefore, the results of this research indicate as follows; 1) The spatial structures of population is showed a trend of continual concentration toward Ulsan city area, and also the spatial structures of employment is showed a trend of continual dispersion over time. 2) The forecast of three93) scenarios supposed after opening of the Seoul-Pusan high-speed rail in 2006 show a change of the spatial structures with both population concentration and employment dispersion. In the meantime, the rapid increase of population and wide dispersion of employment is reform with centering around HSR stations which builted in the southeast region after opening of high-speed rail. 3) It shall furnish valuable data to establish the development strategy of urban and local region, and also forecast the change of spatial structures about population and employment in influential area which passed on high-speed rail line & stations by method of mean center and standard distance among of centrographic measures as analytical tools.

• 한국항공운항학회지
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• 제32권1호
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• pp.79-90
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• 2024

UAM is emerging due to the deepening population concentration in the metropolitan area and the problem of congested ground transportation in urban areas. Accordingly, along with research on eVTOL aircraft for UAM services, interest in vertiport, the interest in vertiports, the infrastructure that allows eVTOLs to take off and land, is also increasing. However, behind the concentration of population in the metropolitan area, aphenomenon of local extinction is occurring in conjunction with the aging population. AAM, which moves quickly through 3D space, can be an effective SOC facility in times of local extinction crisis. In this paper, we introduce a design plan from the perspective of a complex transper center for a regional hub-level vertiport that can connect with local high-speed rail and utilize local airports in compliance with the vertiport design guidelines issued by FAA(Federal Aviation Administration) and EASA(European union Aviation Safety Agency). We would like to present Vertiport's future operation plan.

• Journal of Ecology and Environment
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• 제37권2호
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• pp.99-104
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• 2014

We estimated the influence of environmental factors on zooplankton communities at 25 reservoirs during winter (December 2010 to January 2011). Among zooplankton groups, Cyclops vicinus is more dominant during winter, and this is positively related to withered vegetation area and dissolved oxygen level. Therefore, the presence of withered vegetation might be considered as an important factor to determine C. vicinus distribution during winter. We considered that withered vegetation might be utilized as a habitat for C. vicinus, as well as provide an attachment substrate for periphytic algae. Abundance of periphytic algae can lead to high concentration of dissolved oxygen. Although copepods prefer high water temperatures for increasing their population growth, if Cyclops can overcome low temperature stress that leads to disruption of population, their population growth initiation in the next growing season (i.e. next spring) is possibly propelled by the winter population.

• Environmental Engineering Research
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• 제19권2호
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• pp.165-174
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• 2014

A model combining multi-dimensional discretized population balance equations with a computational fluid dynamics simulation (CFD-DPBE model) was developed and applied to simulate turbulent flocculation and sedimentation processes in sediment retention basins. Computation fluid dynamics and the discretized population balance equations were solved to generate steady state flow field data and simulate flocculation and sedimentation processes in a sequential manner. Up-to-date numerical algorithms, such as operator splitting and LeVeque flux-corrected upwind schemes, were applied to cope with the computational demands caused by complexity and nonlinearity of the population balance equations and the instability caused by advection-dominated transport. In a modeling and simulation study with a two-dimensional simplified pond system, applicability of the CFD-DPBE model was demonstrated by tracking mass balances and floc size evolutions and by examining particle/floc size and solid concentration distributions. Thus, the CFD-DPBE model may be used as a valuable simulation tool for natural and engineered flocculation and sedimentation systems as well as for flocculant-aided sediment retention ponds.

• 한국환경생태학회지
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• 제25권1호
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• pp.10-16
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• 2011

본 연구는 제주도 용수저수지 주변 호랑가시나무개체군을 식물사회학적 방법으로 분류하고, 식생과 토양과의 상관관계를 밝히고자 분포서열법에 의한 분석을 실시하였다. 호랑가시나무개체군은 꾸지뽕나무우점개체군, 상동나무우점개체군, 예덕나무우점개체군으로 분류되었다. 토양분석 결과 유기물함량 14.62~17.35%, 전질소함량 0.39~0.51%, 유효인산함량 8.83~20.15mg/kg, 치환성 K 0.44~0.64cmol+/kg, Ca 5.79~6.87cmol+/kg, Mg 3.43~4.19cmol+/kg이며, 토양 pH는 5.41~5.80인 것으로 조사되었다. 예덕나무우점개체군은 유효인산과 유기물함량이 많고 치환성 K, Mg의 양료가 적은 입지에 분포하는 것으로 분석되었다. 상동나무우점개체군과 꾸지뽕나무우점개체군은 유효인산과 유기물함량이 적고 치환성 K, Mg의 양료가 많은 입지에 분포하는 것으로 조사되었다. 호랑가시나무 자생지 보호를 위해 수관층을 피압하고 있는 덩굴식물 제거작업이 이루어져야 하며, 지속적인 생태모니터링과 자생지 보존을 위한 관리방안이 수립되어야 한다.

• Asian Pacific Journal of Cancer Prevention
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• 제15권13호
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• pp.5187-5194
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• 2014

Background: Numerous studies have suggested that selenium deficiency may be associated with an increased risk for several types of cancer, but few have focused on thyroid cancer. Materials and Methods: We examined the association between post-diagnostic fingernail selenium levels and differentiated thyroid cancer risk in a French Polynesian matched case-control study. Conditional logistic regression models were used to estimate odds ratios and 95% confidence intervals. Results: The median selenium concentration among controls was $0.76{\mu}g/g$. Significantly, we found no association between fingernail selenium levels and thyroid cancer risk after conditioning on year of birth and sex and additionally adjusting for date of birth (highest versus lowest quartile: odds-ratio=1.12, 95% confidence interval: 0.66-1.90; p-trend=0.30). After additional adjustment for other covariates, this association remained non-significant (p-trend=0.60). When restricting the analysis to thyroid cancer of 10 mm or more, selenium in nails was non-significantly positively linked to thyroid cancer risk (p-trend=0.09). Although no significant interaction was evidenced between iodine in nails and selenium in nails effect (p=0.70), a non-significant (p-trend =0.10) positive association between selenium and thyroid cancer risk was seen in patients with less than 3 ppm of iodine in nails. The highest fingernail selenium concentration in French Polynesia was in the Marquises Islands ($M=0.87{\mu}g/g$) and in the Tuamotu-Gambier Archipelago ($M=0.86{\mu}g/g$). Conclusions: Our results do not support, among individuals with sufficient levels of selenium, that greater long-term exposure to selenium may reduce thyroid cancer risk. Because these findings are based on post-diagnostic measures, studies with prediagnostic selenium are needed for corroboration.

• 한국환경보건학회지
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• 제41권2호
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• pp.71-81
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• 2015

Objectives: Photochemical ozone pollution is associated with increased mortality risk. This study aims to assess the population exposure to ozone according to population characteristics for high ozone days in the Busan metropolitan region (BMR). Methods: The ozone exposure assessment in this study was performed using the WRF-CMAQ simulated ozone concentrations and the population data in the BMR. The settled and daytime population and their activity were considered to conduct the static and dynamic ozone exposure assessment. Results: Applying a static exposure assessment, in case that high ozone occurred throughout Busan area, the highest exposure levels were evaluated in urban neighborhoods. In case of ozone pollution in outer Busan, because sensitive groups have been relatively higher exposure, this case was also evaluated as part of that should not be overlooked. The dynamic exposure was higher than static exposure because the number of population exposed to ozone of high concentration is increased. This approach is important in a regard consider that daytime population distribution when high ozone occur. Conclusion: This study shows the different population exposure according to various ozone distributions for each episode day. Considering demographic characteristic such as population density and activity should be important to understanding the population exposure assessment when ozone pollution occurs.

• 한국지하수토양환경학회지:지하수토양환경
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• 제20권7호
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• pp.121-134
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• 2015

Spatial and temporal changes in algal population in Yongdam reservoir and ecological factors that induced the changes in the size and composition of algal population were investigated by monthly sampling at ten locations in the reservoir. Nutritional state of the reservoir was identified to be phosphorus-limited with nitrogen to phosphorus (N : P) ratio much greater than 17 in most samples. Algal population was dominated by three taxonomic groups, diatoms, chlorophytes and cyanobacteria. Although explosive algal growth was not observed in the summer, algal population showed transition with time of the dominant algal type from diatoms in the winter to cyanobacteria in the summer. Chlorophyta was not the dominant group in the reservoir although they maintained relatively stable number of cells in the reservoir and showed increase in population from March to May. The application of statistical methods revealed that the factors inducing changes in cell number of each group were water temperature for diatoms and cyanobacteria and phosphorus concentration for chlorophyte. Fluctuation of cyanobacterial population was mainly observed near the inlet of tributaries while diatoms showed higher variation inside the reservoir.