• 한국물환경학회지
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• 제37권2호
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• pp.114-127
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• 2021

Water pollution in the lower reaches of the Namhan River is getting worse due to drought and a decrease in water quantity due to climatic changes and hence is affecting the water quality of Paldang Lake. Accordingly, we have used a water quality index (WQI) and statistical analysis in this study to identify the characteristics of the water quality in the lower reaches of the Namhan River, the main causes of water pollution, and tributaries that need priority management. Typically, 10 items (WT, pH, EC, DO, BOD, COD, SS, T-N, T-P, and TOC) were used as the water quality factors for the statistical analysis, and the matrix of data was set as 324 × 10·1. The correlation analysis demonstrated a strong correlation between Chemical Oxygen Demand (COD) and T-P with a high statistical significance (r=0.700, p<0.01). Furthermore, the result of principal component analysis (PCA) revealed that the main factors affecting the change in water quality were T-P and organic substances introduced into the water by rainfall. Based on the Mann-Kendall test, a statistically significant increase in pH was observed in SH-1, DL, SH-2, CM, and BH, along with an increase in WQI in SH-2 and SM. BH was identified as a tributary that needs priority management in the lower reaches of the Namhan River, with a "Somewhat poor" (IV) grade in T-P, "Fair" grade in WQI, and "Marginal" grade in summer.

• 한국물환경학회지
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• 제27권5호
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• pp.699-709
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• 2011

The uses of multi-dimensional hydrodynamic and water quality models are increasing to support a sustainable management of large dam reservoirs in Korea. Any modeling study requires selection of a proper spatial dimension of the model based on the characteristics of spatial variability of concerned simulation variables. For example, a laterally averaged two-dimensional (2D) model, which has been widely used in many large dam reservoirs in Korea, assumes that the lateral variations of hydrodynamic and water quality variables are negligible. However, there has been limited studies to give a justification of the assumption. The objectives of this study were to present the characteristics of spatial variations of water quality variables through intensive field monitoring in Daechung Reservoir, and provide information on a proper spatial dimension for different water quality parameters. The monitoring results showed that the lateral variations of water temperature are marginal, but those of DO, pH, and conductivity could be significant depending on the hydrological conditions and local algal biomass. In particular, the phytoplankton (Chl-a) and nutrient concentrations showed a significant lateral variation at R2 (Daejeongri) during low flow periods in 2008 possibly because of slow lateral mixing of tributary inflow from So-oak Stream and wind driven patchiness.

• 상하수도학회지
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• 제23권6호
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• pp.743-752
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• 2009

One of the major problems associated with operation of domestic sewer lines involves hydraulic problems such as insufficient conveyance capacity, exceeding maximum velocity, and deficiency of minimum velocity. It has also been pointed out that influent concentration lower than design concentration of pollutants, which is mainly caused by unidentified inflow and infiltration, degrades the operational efficiency of many sewage treatment plants (STPs). A computer-added analysis method supporting a coupled simulation of sewage quality and quantity is essentially required to evaluate the status of existing STPs and to improve their efficiency by a proper sewer rehabilitation work. In this study, dynamic water quality simulations were conducted using MOUSE TRAP to investigate the principal parameters that governs the changes of BOD, ${NH_4}^+$, and ${PO_4}^{3-}$3- concentrations within the sewer networks based on data acquired through on-site and laboratory measurements. The BOD, ${NH_4}^+$ and ${PO_4}^{3-}$3- concentrations estimated by MOUSE TRAP was lower than theoretical pollution loads because of sedimentation and decomposition in the sewer. The results revealed that sedimentation is a most important factor than other biological reactions in decreasing pollutant load in the sewers of C-city. The sensitivity analysis of parameters pertaining to water quality changes indicated that the effect of the BOD decay rate, the initial DO concentration, the half-saturation coefficient of dissolved BOD, and the initial sediment depth is marginal. However, the influence of settling rate and temperature is relatively high because sedimentation and precipitation, rather than biological degradation, are dominant processes that affect water quality in the study sewer systems.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제34권3호
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• pp.186-199
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• 2012

Purpose: Single implants, of which screw loosening has been observed frequently, presents problems such as fixtures fractures, marginal bone loss, and inflammation of the soft tissue around the implant. However, the single implant is more conservative, cost effective, and predictable compared to the 3 unit bridge with respect to the long-term outcome. This study evaluated the survival rate as well as future methods aimed at increasing the survival rate in single implants in posterior teeth. Methods: Among the implants placed in the Dankook University Dental Hospital department of Oral & Maxillofacial surgery from January 2001 to June 2008, 599 implants placed in the maxillar and mandibular posterior were evaluated retrospectively. Survival rates were investigated according to implant location, cause of tooth loss, gender, age, general disease, fixture diameter and length, surface texture, implant type and shape, presence of bone graft, surgery stage, surgeons, bone quality and opposite teeth. Results: Out of 599 single implants in posterior teeth, 580 implants survived and the survival rate was 96.8%. The difference in survival rate was statistically significant according to the implant location. The survival rate was low (84.2%) in implants exhibiting a wide diameter (${\geq}5.1mm$) and the surface treated by the acid etching group demonstrated a significantly lower survival rate (91.1%). One stage surgical procedure, which implemented a relatively better bone quality survival rate (100%), was higher than the two stage surgical procedure (96.1%). The survival rate of type IV bone quality (75%) was significantly lower than the other bone quality. Conclusion: Single posterior teeth implant treatments should use an improved surface finishing fixture as well as careful and safe procedures when performing implant surgery in the maxilla premolar and molar regions since bone quality is poor.

• 한국물환경학회지
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• 제29권1호
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• pp.97-106
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• 2013

The temporal and spatial variations of water quality in a stratified reservoir are fully dependent on the characteristics of inflow loading from its watershed and the transport regimes of pollutants after entering the reservoir. Because of the meteorological and hydrological conditions in Korea, the pollutants loading to reservoirs are mostly occur during rainfall events. Therefore it is important to understand the characteristics of pollutants loading from upstream rivers and their spatial propagation through the stratified reservoir during the rainfall events. The objectives of this study were to characterize the water quality variations in upstream rivers of Imha Reservoir during a rainfall event, and the transport and spatial variations of pollutants in the reservoir through extensive field monitoring and laboratory analysis. The results showed that the event mean concentration (EMC) of SS, BOD, $COD_{Mn}$, T-N, T-P, $PO_4-P$ are 8.6 ~ 362.1, 2.5 ~ 5.1, 1.5 ~ 5.1, 1.1 ~ 1.9, 8.3 ~ 57.1, 5.6 ~ 25.7 times greater than the mean concentrations of these parameters during non-rainfall period. The turbidity and SS data showed good linear correlations, but the relationships between flow and SS showed large variations because of hysteresis effect during rising and falling periods of the flood. The ratio of POC to TOC were 12.6 ~ 14.7% during the non-rainfall periods, but increased up to 28.2 ~ 41.7% during the flood event. The turbid flood flow formed underflow and interflow after entering the reservoir, and delivered a great amount of non-point pollutants such as labile and refractory organic matters and nutrients to the metalimnion layer of reservoir, which is just above the thermocline. Spatially, the lateral variations of most water quality parameters were marginal but the vertical variations were significant.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제38권
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• pp.30.1-30.6
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• 2016

Background: The prognosis of wide implants tends to be controversial. While wider implants were initially expected to result in a larger osseointegration area and have higher levels of primary stability, they were reported to have a relatively high rate of failure. The clinical outcome of ultrawide implants of more than 6 mm in diameter was evaluated through a retrospective study. Methods: The investigation was conducted on patients who had received ultrawide implant (${\geq}6mm$ diameter) placements in Seoul National University Bundang Hospital from January 2008 to December 2013. Complications were investigated during the maintenance period, and marginal bone loss was measured using periapical radiography. Primary stability immediately after the implant placement and second stability after second surgery or during impression were measured using $Osstell^{(R)}$ Mentor (Osstell, Sweden) as an implant stability quotient (ISQ). Results: Fifty-eight implants were placed in 53 patients (30 male, 23 female), and they were observed for an average of $50.06{\pm}23.49$ months. The average ISQ value increased from $71.22{\pm}10.26$ to $77.48{\pm}8.98$ (P < 0.005). The primary and secondary stability shows significantly higher at the mandible than at the maxilla (P < 0.001). However, mean survival rate shows 98.28 %. Average marginal bone loss of 0.018 and 0.045 mm were measured at 12 and 24 months after the loading and 0.14 mm at final follow-up date (mean 46.25 months), respectively. Also in this study, the bone loss amount was noticeably small compared to regular implants reported in previous studies. Conclusions: The excellent clinical outcome of ultrawide implants was confirmed. It was determined that an ultrawide implant can be used as an alternative when the bone quality in the posterior teeth is relatively low or when a previous implant has failed.

• 한국지구과학회지
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• 제36권4호
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• pp.367-389
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• 2015

본 연구에서는 Ocean Data View (ODV)를 이용하여 한반도 주변 해역의 수온 염분 분포도를 작성하는 실험 프로그램을 개발하였다. 정선 해양 관측 자료는 본 연구를 위해 새롭게 개발된 별도의 프로그램을 이용하여 ODV 호환형식으로 변환된 후 분석되었다. 새로운 실험 프로그램을 65명의 예비 교사들에게 적용하였을 때, 기존 프로그램을 사용한 같은 집단에 비해 과제 수행 완성도가 매우 향상되었다. 새로운 프로그램에 대한 실험 참가자들의 만족도를 살펴보기 위해 설문지 분석을 실시하였다. 분석 결과 정확하고 빠른 등치선 작성 분야에서 가장 높은 만족도를 나타내었으며, 새로운 실험 프로그램의 이해 및 적용에 관한 긍정적인 반응을 확인하였다.

• 한국식품저장유통학회지
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• 제16권1호
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• pp.17-22
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• 2009

본 연구에서는 소비자의 포도주 속성별 선호분석 및 가격 민감성 분석을 실시하였다. 자료는 대구지역 200명의 소비자들을 대상으로 포도주 시음회 및 설문조사를 통해 수집하였다. 세 종류의 국내산 포도주에 대한 만족도, 재구매 의사 및 타인 추천 의사는 모두 아이스와인(Vin Coree)이 가장 높은 것으로 나타났다. 속성별 만족도는 적포도주 (Royal Campbell)와 백포도주(Vin Coree)의 경우 색깔에 대한 만족도가, 아이스와인(Vin Coree)의 경우 병 디자인에 대한 만족도가 가장 높게 나타났다. 적포도주(Royal Campbell)의 가격은 저가한계점보다 낮기 때문에 가격을 인상하고, 품질을 개선할 필요가 있다. 백포도주(Vin Coree)의 가격은 수용가격대의 범위에 포함되나, 최적가격점보다 상회하므로 가격을 인하하는 것이 유리하다. 아이스와인 (Vin Coree)의 출시가격은 고가한계점의 가격이며, 최적가격점을 훨씬 상회하므로 가격 인하가 필요하다.

• 펄프종이기술
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• 제45권4호
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• pp.21-26
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• 2013

The effect of esterified starch as surface sizing agent for inkjet printing paper has been evaluated and compared with oxidized starch. Also the influence of various additives including cationic poly-DADMAC, stearic acrylic copolymer, calcium chloride, and GCC was examined. Results showed that starch ester gave higher ink density than oxidized starch. Addition of poly-DADMAC improved water fastness. In general, low molecular weight poly-DADMAC performed better than high molecular weight one, and it was attributed to the fact that it gave more uniform film forming characteristics in surface sizing. Use of styrene acrylic acid copolymer increased hydrophobicity of the paper surface, but it did not increase the ink density. Use of GCC and calcium chloride had only marginal effect on printing quality.

• 한국초지조사료학회지
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• 제35권3호
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• pp.207-211
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• 2015

The objective of the study was to measure the beneficial effects of lactic acid bacteria (LAB) inoculation on the nutritive value of oat silage collected from thirteen regions in the Republic of Korea. The contents of crude protein, acid detergent fiber (ADF), neutral detergent fiber (NDF) and crude ash (CA) were slightly lower in LAB inoculated silage when compared with the control silage, whereas inoculation of LAB resulted in increased total digestible nutrient (TDN). Higher number of LAB, but lower count of yeast and fungi indicated the effectiveness of the LAB inoculation on oat silage fermentation. LAB inoculation resulted in low pH silage, which may prevent undesirable microbial growth. The LAB inoculation promoted lactic acid dominant fermentation with marginal levels of acetic acid and butyric acid in oat silage. These data suggest that the LAB inoculation may preserve oat silage at better quality for ruminant animal production.