• Journal of the Korea Organic Resources Recycling Association
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• v.6 no.1
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• pp.53-66
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• 1998

This study was carried out to investigate the typical composition of food waste from municipal solid wastes (MSW) and unit food waste generation rates from different sources in the model cities and to study the food waste management system from unit household to composting facilities. The annual average food waste composition of MSW was determined as 49% in Taejon and 52% in Chungnam Province, respectively. No big difference in food waste composition was found among the different sources. Since the paper waste generally occupied the half of food waste, over 75% of MSW was found to be compostable or biodegradable. Per capita food waste generation rate, 200~250g/capita day was determined by the direct measurement from 32 households, while 380g/capita day for Chungnam Province and 400 g/capita day for Taejon were estimated by the load count analysis In the sanitary landfills. This difference means people contribute generating food waste at outside house approximately twice as much as that at inside house. Per capita food waste generation rates from several sources were determined as follows; 166~215g/capita day at municipalities, 400g/visitor day at a first class hotel, 170g/student day at a university restaurant. Food waste generation from restaurant was strongly dependant upon it's level or quality; 670g/capita day at the high level restaurant, 190g/capita day at the middle class and 60 g/capita day at the lower class restaurant. The food waste reduction rate in a In situ fermentor showed 30~40g/kg day.

• International Journal of Highway Engineering
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• v.13 no.4
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• pp.81-91
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• 2011

This study was conducted to evaluate the necessity of the anchor lug system in continuously reinforced concrete pavement(CRCP) by comparing longitudinal displacements of CRCPs with and without anchor lugs, and to investigate the effect of horizontal cracking on CRCP performance by measuring the vertical displacements. The measurements before and after the anchor lug section was separated were conducted for 12 days in June, and for 14 days in August after the abrupt displacements according to cutting disappeared, respectively. This short term measurement results showed that when anchor lugs were installed, a daily displacement variation at any location was less than 0.1mm; therefore, longitudinal movements were negligibly small. When there were no anchor lugs, longitudinal displacements mainly occurred near the free end and the displacement variation was small; therefore, an expansion joint system seems to be employed at a CRCP terminus without installing anchor lugs. However, further studies are needed to verify the terminus behavior due to annual temperature changes. The horizontal crack width variation was ignorable and did not affect the vertical displacement of the slab. Therefore, the horizontal crack did not delaminate the slab and did not seem to reduce the structural capacity and performance of CRCP.

• Journal of Korea Water Resources Association
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• v.36 no.5
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• pp.787-797
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• 2003

The characteristics of concentrations and loads of Total Nitrogen(T-N), Total Phosphorus(T-P), and Chemical Oxygen Demand (COD) in mountain stream water were examined from September 2000 through August 2001. The 92.5-ha study watershed in Chungbuk Province consists of 59% mixed forest and 30% coniferous forest. Streamflow was measured and water samples were collected at about 10 day intervals for dry days and at 2-6 hour intervals for a storm event at the study watershed outlet. The mean concentration of COD in streamflow for rainy days was significantly (p < 0.05) higher than for dry days. The mean concentrations of T-N and T-P in vegetation growing season (May to October) were lower than those in vegetation dormant season (November to April). Low concentrations of pollutants during vegetation growing season are likely due to the heavy demand for nutrients by the vegetation and biological activity associated with a warming of soil. The ratios of pollutants loads during storm periods to annual pollutants loads were 87% for T-N, 83% for T-p, and 87% for COD. The unit loads of pollutants for study area were estimated at 5.9 kg/ha $\cdot$ yr for T-N, 0.15 kg/ha $\cdot$ yr for T-p, and 23.9 kg/ha $\cdot$ yr for COD. The removal efficiency of pollutants in study area were 24% for T-N, 58% for T-P and 66% for COD, indicating that a study area shows water purification function.

• Geophysics and Geophysical Exploration
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• v.21 no.1
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• pp.8-14
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• 2018

For the purpose of maintenance and prevention of earth fill dams against damage from natural hazards, automatic monitoring through various measuring instruments and resistivity survey has been carried out. Reservoirs and embankments have the structural vulnerability on the agricultural usages since most of them were built more than thirty years ago. The main aim to use monitoring method is to verify the safety and integrity of the dam. Resistivity survey can detect potential weaknesses, such as defective zones, anomalous seepages or internal erosion processes. Permanent resistivity monitoring systems were installed at a reservoir, which daily measurements have been taken every 6 hour. Using monitoring data for one year, anomalous seepage and structural defects were clarified for dam safety. Annual water level fluctuations are around 10 m. During their operation, reservoir dams are subject to a never-ending hydraulic load from the reservoir, which over the years may cause changes in the properties of the inner parts of the dam construction. Detailed analysis of the monitoring results was performed and showed that resistivities at most locations have been very stable over the full monitoring period excluding the effects of water fluctuation and seasons. To investigate the detectability of weak zone using the DC resistivity monitoring, numerical modeling with a simplified model for the drainage at a reservoir dam was also performed. The results showed that the seepage zone near drainage in a reservoir dam could be detected by resistivity response change.

• Journal of Korea Water Resources Association
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• v.37 no.11
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• pp.959-967
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• 2004

The concentrations and loads of total nitrogen (TN), total phosphorus (TP), and chemical oxygen demand (COD) in wet deposition were investigated at Chungbuk National University in Cheongju, Chungbuk. Event based precipitation samples were collected during 1998 to 2003. The precipitation-weighted mean concentrations of pollutants were 0.60 mg/L for TN, 0.014 mg/L for TP, and 4.8 mg/L for COD, which were smaller than its arithmetic mean concentrations by 26% for TN, 18% for TP, and 14% for COD. The concentrations of TN, TP, and COD significantly decreased with precipitation. Mean concentrations of pollutants in spring (March-May) were higher than in other seasons likely due to dust caused by wind erosion and sand-dust storms, pollen etc. Significant relationships were determined between TN and TP, and TN and COD. Annual loads of wet deposition averaged 7.9 kg/ha$\cdot$yr for TN, 0.19 kg/ha$\cdot$yr for TP, and 63.9 kg/ha$\cdot$yr for COD, which are almost identical to the values of TN and TP but slightly higher than COD value reported in Japan.

• Journal of Energy Engineering
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• v.24 no.2
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• pp.129-143
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• 2015

Increasing concerns on climate change and energy security accelerated policies to reduce green-house gas emission, especially from the transportation sector. Electric vehicle (EV) has been on the spotlight to deal with such environmental issue and V2G (Vehicle-to-Grid) technology began to draw attentions as an alternative to reduce ownership costs while contributing to an efficient and decentralized power grid. This study conducts a scenario analysis on total cost of ownership of EV under V2G scheme and compare with non-V2G EV and Internal Combustion Engine (ICE) vehicle. As result, V2G service is expected to provide an annual average profit of $210 to EV users willing to reverse flow its residual power in the battery. The profit from V2G service leaves a margin of $4,530 over operational lifetime, compared with $2,420 cost of charge for non-V2G EV. In summary, total cost of ownership of V2G-capable EV was 6.2% less than non-V2G EV and 10.2% higher than ICE vehicle. The results confirm a comparative economic advantage of operating EV under V2G scheme. Increased number of EVs with V2G service has shown to provide positive effects to power industry for valley filling in load distribution, thus, favorably increasing the overall economic feasibility.

• Journal of Korean Society on Water Environment
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• v.31 no.6
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• pp.665-679
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• 2015

Yearly mean temperature in the 29 lakes surveyed ranges from 12.6 (Suncheon) to 13.9℃ (Mokpo), the lowest in −2.7℃ (January) and the highest in 25.9℃ (July). Monthly mean the amount of rainfall recorded the highest of 336.7 mm in August and the lowest with 4.9 mm in January. A total of 424 species of phytoplankton were identified. They were 157 Chlorophyceae, 161 Bacillariophyceae, 39 Cyanophyceae, and 67 other algal taxa. The phytoplankton diversity were low in stream type reservoirs such as Guemho, Youngsan and Youngam. The population density of phytoplankton ranged from 19 to 53,161 cells/ml. Annual mean of total zooplankton abundance in 45 sites was 369±827 ind./L (n=180). Rotifers were the most common taxa and their relative abundance was high (65~77%). The benthic microinvertebrate fauna of 10 reservoirs of Jeonnam province were 71 species of 61 genera of 44 families of 16 orders of 7 classes of 4 phyla. Aquatic insects of Phylum Arthropoda were 50 species of 44 genera of 28 families of 6 orders. The number of individuals was 6,132. Diptera was highiest (41.3%), and Ephemeroptera (31.0%), Trichoptera (17.5%), Anellida (3.8%), Mollusca (3.3%), Crustacea (0.4%). Large hydrophytes were identified 32 taxa, 2 varieties 30 species 26 genera and 20 families. Especially, Jijung and Juam lakes require management such as physical remove of this ecosystem disturbance field plants. Fishes were identified total 44 taxa, such as 25 Cyprinidae (56.8%), 8 Cobitidae (17.0%), 3 Gobiidae (6.4%), 2 Bagridae (4.3%), 2 Osmeridae (4.3%), 2 Odontobutidae (4.3%), 2 Centrachidae (4.3%), 1 Siluridae (2.1%), and 1 Centropomidae (2.1%). A pale chub was dominant species (18.9%).

• Journal of Korean Society on Water Environment
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• v.36 no.4
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• pp.284-299
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• 2020

Dam reservoirs play a particularly crucial role in processing the allochthonous and the autochthonous dissolved (DOC) and the particulate (POC) organic carbon and in the budget of global carbon cycle. However, the complex physical and biogeochemical processes make it difficult to capture the temporal and spatial dynamics of the DOC and the POC in reservoirs. The purpose of this study was to simulate the dynamics of the DOC and the POC in Daecheong Reservoir using the 3-D hydrodynamics and water quality model (AEM3D), and to quantify the mass balance through the source and sink fluxes analysis. The AEM3D model was calibrated using field data collected in 2017 and showed reasonable performance in the water temperature and the water quality simulations. The results showed that the allochthonous and autochthonous proportions of the annual total organic carbon (TOC) loads in the reservoir were 55.5% and 44.5%, respectively. In season, the allochthonous loading was the highest (72.7%) in summer, while in autumn, the autochthonous loading was the majority (77.1%) because of the basal metabolism of the phytoplankton. The amount of the DOC discharged to downstream of the dam was similar to the allochthonous load into the reservoir. However, the POC was removed by approximately 96.6% in the reservoir mainly by the sedimentation. The POC sedimentation flux was 36.21 g-C/㎡/yr. In terms of space, the contribution rate of the autochthonous organic carbon loading was high in order of the riverine zone, the transitional zone, and the lacustrine zone. The results of the study provide important information on the TOC management in the watersheds with extensive stagnant water, such as dam reservoirs and weir pools.

• The Journal of Korean Academy of Prosthodontics
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• v.44 no.4
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• pp.394-404
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• 2006

Statement of problem: A conventional 3-unit fixed partial denture design with a pontic between two retainers is the most commonly used. However in cases where the mental nerve is in close proximity to the second premolar, a cantilever design can be considered. As such, logical and scientific evidence is lacking for the number and position of implants to be placed for partially edentulous patients, and no clear-cut set of treatment principles currently exist. Purpose : The purpose of this study was to evaluate prognosis of implant-supported fixed partial dentures and to compare changes in bone level which may rise due to the different factors. Material and method : The present study examined radiographical marginal bone loss in patients treated with implant-supported fixed partial dentures (87 prostheses supported by 227 implants) and evaluated the influence of the span of the pontic, type of the opposing dentition. Clinical complications were studied using a retrospective method. Within the limitation of this study. the following result were drawn Result, 1. Seven of a total of 227 implants restored with fixed prostheses failed, resulting in a 96.9% success rate. 2. Complications encountered during recall appointments included dissolution of temporary luting agent (17 cases), porcelain fracture (8 cases), loosened screws (5 cases), gingival recession (4 cases), and gingival enlargement (1 case). 3. Marginal bone loss, 1 year after prosthesis placement, was significant(P<0.05) in the group that underwent bone grafting, however no difference in annual resorption rate was observed afterwards. 4. Marginal bono loss, 1 year post-placement, was greater in cantilever-type prostheses than in centric pontic protheses (P<0.05). 5. Marginal bone loss was more pronounced in posterior regions compared to anterior regions (P<0.05). 6. The degree of marginal bone loss was proportional to the length of the pontic (P<0.05). Conclusion: The success rate of implant-supported fixed partial dentures, including marginal bone loss, was satisfactory in the present study. Factors influencing marginal bone loss included whether bone graft was performed, location of the pontic (s), location of the surgical area in the arch pontic span. Long-term evaluation is necessary for implant-supported fixed partial dentures, as are further studies on the relationship between functional load and the number of implants to be placed.

• KSBB Journal
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• v.22 no.2
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• pp.102-108
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• 2007

A sewage was treated using a vertical flow zeolite-filled reed bed. The sewage from the student dormitory of Changwon National University was fed into the reed bed for 10 minutes every 6 hours at the hydraulic load of $314L/m^3{\cdot}$day. The filtering height of the reed bed was 100 em and the zeolite mixture was filled in the reed bed. The mixture consisted of the same volume of two types of zeolite: 0.5$\sim$1 mm and 1$\sim$3 mm in diameter. Annual average removal efficiency was 88 89.9%, $COD_{Cr}$ 86.1 %, $COD_{Mn}$ 81.2%, T-N 34.0%, $NH_4^+$-N 97.3% and T-P 34.6%. T-N of effluent was mostly $NO_3^-$-N and the concentration of $NO_2^-$-N in effluent was lower than 0.1 mg/L. All removal efficiencies did not show a remarkable seasonal change. The ranking of phosphorous fractions fixed to the zeolite in column test was Ca-P > Fe-P > reductant soluble Fe-P > occluded P > saloid P > AI-P at all depths of the filter. All phosphorous fractions except for AI-P reduced at deeper filter layer, while their content ratios increased at deeper filter layer. Organic matter content was the highest at the highest layer (0$\sim$5 cm from the top of the filter) and only small differences were observed at the deeper filter layer than 5 em from the top. Organic matter content increased at all depths of the filter with the operating time.