• KEPCO Journal on Electric Power and Energy
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• v.1 no.1
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• pp.39-46
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• 2015

A outdoor termination installed at the outdoor substation is required to connect undergroud cables and overhead transmission lines. The joint box for AC transmission system is already developed and widely used to interconnect overhead and undergroud systems. But the development of the joint box for DC transmission system was only introduced from China and Japan, but theire developemnt staus and core technologies were not fully reported. In order to implement HVDC systems connecting ovehead transmission lines and undergroud cables, a outdoor termination should be developed, but the detailed specifications and information of this device were not reported. It is estimated that the development of the joint box for DC environment has some technical obstacles including insulating materials, electric field mitigation, thermal temperature rise, and space charge accumuations. Among this, the most important one is the DC elctrical insualtion design. Therefore, in order to investigate the DC elctrical insualton design of outdoor termination, the design of AC slip-on type outdoor termination is reffered, and DC electric field analysis performed to verify the possiblity of application of AC joint box into DC joint box. Especially for DC electric field analysis, temperature rise of insualting materials of a joint box was considered, because the conductivity of materials could be changed due to temperature rise. Furthermore, DC electric field analysis considering transinet state, and polarity reversal state were also investigated to verify which state is the most severe condition for the DC joint box. From the simualtion resulsts, it was shown that the value and the position of maximum electric field was obtained comparing AC state, DC state without temperaure rise, and DC state with temperaure rise. And it was confimred that severe DC electric field was observed considing temperaure rise. Finally, in order to reduce DC eletric field intensifation, different configuration of the joint box was applied and it was not possible to obtain satisfactory results. It means that the slight change of configuration of AC joint box was not the suitable soluton for DC joint box. It is essential to establish novel DC insulaton design skills and method for DC joint box to commercialze this product in the near future.

• Journal of the Korean Institute of Landscape Architecture
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• v.48 no.4
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• pp.41-54
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• 2020

This study was conducted to provide basic data for a transparent and fair bidding system by identifying problems and suggesting improvement measures through an analysis of the bidding status for construction projects and service-related landscaping of multi-family housing. To this end, we used the data from the "Multi-Family Housing Management Information System (K-apt)" that provides the history of apartment maintenance, bidding information, and the electronic bidding system to examine the winning bid status and amount, along with the size and trends of the winning bids by year, and the results of the selection of operators by construction type. As a result, it was found that out of the total number of successful bids (36,831), 4.4% (16,631) were in the landscaping business, and the average winning bid value was found to be about 24 million won. According to the data, 73% of the landscaping cases were valued between 3 million won and 30 million won, and 58.6% of the cases were in the field of "pest prevention and maintenance". 36% of the total number of bids were awarded from February to April, with "general competitive bidding" accounting for 59.8% of the bidding methods. As for the method of selecting the winning bidder, 55% adopted the "lowest bid" and "electronic bidding method," and 45% adopted the "qualification screening system" and "direct bidding method." As an improvement to the problems derived from the bidding status data, the following are recommended: First, the exception clause to the current 'electronic bidding method' application regulations must be minimized to activate the electronic bidding method so that a fair bidding system can be operated. Second, landscaping management standards for green area environmental quality of multi-family housing must be prepared. Third, the provisions for preparing design books, such as detailed statements and drawings before the bidding announcement, and calculating the basic amount shall be prepared so that fair bidding can be made by specifying the details of the project concretely and objectively must be made. Fourth, for various bidding conditions in the 'business operator selection guidelines', detailed guidelines for each condition, not the selection, need to be prepared to maintain fairness and consistency. These measures are believed to beuseful in the fair selection of landscaping operators for multi-family housing projects and to prepare objective and reasonable standards for the maintenance of landscaping facilities and a green environment.

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.34 no.3
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• pp.98-114
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• 2016

The this study aimed to expand urban heritage using Public Goods and to suggest the assemblage of urban heritage and urban spaces in order to improve landscape conservation and management scheme of urban heritage exposed to a rapidly changing urban environment. The results obtained in this study were summarized as follows: First, in order to improve understanding of the heritage in urban spaces, urban heritage were illustrated on a 1:1000 map with all the public facilities surrounding it using a cultural heritage conservation map listed on the Cultural Heritage Administration's web site, standards for changing present condition, and a topographic map. Second, the status and changes of urban heritage and surroundings were analyzed using the minutes of Historical Cultural Heritage Division Committee for 10 years from 2005 to 2014 to create a status map of urban heritage. Land uses surrounding the urban heritage were investigated the areas of conservation potential and the places that can enhance the to find out values of urban heritage. Also, a profile was created to examine the site characteristics surrounding urban heritage, and photos were taken at important heritage areas and public facilities in order to record the field. Third, analyzed were the relationship of the distance, location, function, and distribution between urban heritage and public facilities surrounding the heritage. using visual features and moving routes in order to identify their impacts on urban heritage and their functions as potential resources. In addition, the role of Public Goods in urban spaces and the plan for revitalizing surrounding areas asset were examined. Fourth, selections were made on Public Goods that have direct or indirect effects on urban heritage. The role of public asset was investigated through visual, areal, and linear elements. The results were summarized to suggest improvement landscape and management mauser on of urban heritage.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.11
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• pp.783-789
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• 2011

Recently, auto-thermal thermophilic aerobic digestion (ATAD) has a great attention for destruction of wasted sludge biomass in wastewater treatment plant. Reduction of sludge concentration has been successfully achieved with pilot scale ATAD and ceramic filtration process in field condition. However, high concentration of COD, total nitrogen (TN) and total phosphorus (TP) was observed in filtrate, which should be treated before recirculation of filtrate to biological wastewater treatment plant. This study was focused on removal of nitrogen and phosphorus contained in the filtrate of ATAD, using struvite crystallization method. The effect of operational and environmental parameters (such as, N, P and Mg ion concentration and molar ratio, pH, reaction time, agitation strength, seed dosage, and reaction temperature) on the treatment of TN and TP with struvite crystallization were evaluated. Magnesium (as $MgCl_26H_2O$) and phosphorus (as $K_2HPO_4$) ions were, if necessary, added to increase nitrogen removal efficiency by the crystal formation. Average concentration of $NH_4^+-N$ and $PO_4^{3-}-P$ of the filtrate were 1716.5 mg/L and 325.5 mg/L, respectively. Relationship between removal efficiencies of nitrogen and phosphorus and molar ratios of $Mg^{2+}$ and $PO_4^{3-}-P$ to $NH_4^+-N$ was examined. Crystal formation and nitrogen removal efficiencies were significantly increased as increasing molar ratios of magnesium and phosphorus to nitrogen. As molar ratio of $Mg^{2+}:PO_4^{3-}-P:NH_4^+-N$ were maintained to 2 : 1 : 1 and 2 : 2 : 1, removal efficiencies of nitrogen and phosphorus were 71.6% and 99.9%, and 93.8% and 98.6%, respectively. However, the effect of reaction time, mixing intensity, seed dose and temperature on the struvite crystallization reaction was not significant, comparing to those of molar ratios. Settled sludge volume after struvite crystallization was observed to be reduced with increase of seed dose and to be increased at high temperature.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.2
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• pp.115-123
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• 2013

Stoker type incinerator is one of the most popular one used as municipal solid waste (MSW) incineration because, in general, it is quite suitable for large capacity and need no preprocessing facility. Nowadays, however, since the combustible portion of incoming MSW increases together with the decrease of the moisture content due to prohibition of directly burying food waste in landfill, the heating value of waste is remarkably increasing in comparison with the early stage of incinerator installation. Consequently, the increased heating value in incinerator operation causes a number of serious problems such as reduction of waste amount to be burned due to the boiler heat capacity together with the significant NO generation in high temperature environment. Therefore, in this study, a series of numerical simulation have been made as parameters of waste amount and the fraction of moisture in air stream in order to investigate optimal operating condition for the resolution of the problems associated with the high heating value of waste mentioned above. In specific, a detailed turbulent reaction flow field calculation with NO model was made for the full scale incinerator of D city. To this end, the injection method of moisturized air as oxidizer was intensively reviewed by the addition of moisture water amount from 10% and 20%. The calculation result, in general, showed that the reduction of maximum flame temperature appears consistently due to the combined effects of the increased specific heat of combustion air and vaporization heat by the addition of water moisture. As a consequence, the generation of NOx concentration was substantially reduced. Further, for the case of 20% moisture amount stream, the afterburner region is quite appropriate in temperature range for the operation of SNCR. This suggests the SNCR facility can be considered for reoperation. which is not in service at all due to the increased heating value of MSW.

• Archives of design research
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• v.18 no.3 s.61
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• pp.85-94
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• 2005

Most of product designers use 3D CAD system as a inevitable design tool nowadays and many new products are developed through a concurrent engineering process. However, it is very difficult for novice designers to get the sense of reality from modeling objects shown in the computer screens. Such a intangibility problem comes from the lack of haptic interactions and contextual information about the real space because designers tend to do 3D modeling works only in a virtual space of 3D CAD system. To address this problem, this research investigate the possibility of a interactive quantified structure simulation for product design using AR(augmented reality) which can register a 3D CAD modeling object on the real space. We built a quantified structure simulation system based on AR and conducted a series of experiments to measure how accurately human perceive and adjust the size of virtual objects under varied experimental conditions in the AR environment. The experiment participants adjusted a virtual cube to a reference real cube within 1.3% relative error(5.3% relative StDev). The results gave the strong evidence that the participants can perceive the size of a virtual object very accurately. Furthermore, we found that it is easier to perceive the size of a virtual object in the condition of presenting plenty of real reference objects than few reference objects, and using LCD panel than HMD. We tried to apply the simulation system to identify preference characteristics for the appearance design of a home-service robot as a case study which explores the potential application of the system. There were significant variances in participants' preferred characteristics about robot appearance and that was supposed to come from the lack of typicality of robot image. Then, several characteristic groups were segmented by duster analysis. On the other hand, it was interesting finding that participants have significantly different preference characteristics between robot with arm and armless robot and there was a very strong correlation between the height of robot and arm length as a human body.

• Korean Journal of Environmental Agriculture
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• v.27 no.1
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• pp.27-34
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• 2008

To effectively treat the domestic sewage that was produced on a small-scale in farming and fishing village in order to encourage an ecologically friendly environment, a small-scale sewage treatment apparatus using natural purification methods that consisted of an aerobic and an anaerobic plots were constructed. The efficiency of sewage treatment according to the sewage loading was investigated to obtain the optimum sewage loading in small-scale sewage treatment apparatus. Removal rate of pollutants according to the sewage loading were in the order of $150\;Lm^{-2}day^{-1}{\fallingdotseq}300\;Lm^{-2}day^{-1}>600\;Lm^{-2}day^{-1}$. Therefore, the optimum sewage loading was 300 L m-2 day-1. Under the optimum sewage loading, removal rate of BOD, $COD_{Mn}$, turbidity, T-N and T-P were 99, 94, 99, 49 and 89%, respectively. However, to satisfy the water quality standard in effluent in small-sclae sewage treatment apparatus for domestic sewage treatment, the low removal efficiency of T-N and T-P must be improved. So to improve the removal rate of T-N and T-P, the efficiency of sewage treatment according to the improved sewage treatment process such as, re-treatment at aerobic plot, anaerobic condition of aerobic plot, changing the filter media sizes and the depths in anaerobic plot, and also addition of oyster shells to filter media at anaerobic plot were investigated. In case of 150 cm depth in anaerobic plot with filter medium A (effectivity particle size 1.50 mm) and addition of oyster shells to filter media at anaerobic plot, removal rate of T-N and T-P in both plots were increased by 10 and 3%, and 14 and 7% in comparison with 100 cm depth in anaerobic plot with filter medium B(effectivity particle size 0.95 mm), respectively. The optimum improved sewage treatment process in small-scale sewage treatment apparatus were 150 cm depth in anaerobic plot with filter medium A and addition of oyster shells to filter media at anaerobic plot.

• Korean Journal of Environmental Biology
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• v.31 no.4
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• pp.393-401
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• 2013

The objectives of this study were to analyze structures of fish community and the ecological health using a multi-metric fish model, the Index of Biological Integrity (IBI) in the Backje Weir of Geum River during two periods namely before-the-fishkill ($B_f$) and after-the-fishkill ($A_f$). The total number of fish species observed were 32 and among them 10 species (35%) were Korean endemic species. The exotic species observed were 3 which decreased by 0.4% after-the-fishkill ($A_f$). The dominant species were Opsariichthys uncirostris amurensis (13%) at the Bf period and Squalidus japonicus coreanus (17%) at the Af period in the Backje Weir. At after the fishkill ($A_{f-I}$) total biomass was about 10 times lower than the biomass before-the-fishkill ($B_f$). The biomass of Carassius auratus decreased 98% after-the-fishkill and as time passed by the biomass recovered to nearly 100%. Similar decrease in the biomass occurred in the population of Opsariichthys uncirostris amurensis, while Rhinogobius brunneus population increased. According to the structure analysis of fish community, species richness index, evenness index and species diversity index were high but after-the fishkill, the values of indices decreased. Tolerant species (64%) dominated the fish community, and the sensitive species (2%) were rare, indicating the degradation of the ecosystem. According to analysis of the multi-metric model (IBI), the mean model value of the fish community in Backje Weir was estimated as 17.5 indicating a "fair condition".

• Korean Journal of Agricultural and Forest Meteorology
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• v.11 no.4
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• pp.162-173
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• 2009

Information on the expected geographical shift of suitable zones for growing crops under future climate is a starting point of adaptation planning in agriculture and is attracting much concern from policy makers as well as researchers. Few practical schemes have been developed, however, because of the difficulty in implementing the site-selection concept at an analytical level. In this study, we suggest site-selection criteria for quality Fuji apple production and integrate geospatial data and information available in public domains (e.g., digital elevation model, digital soil maps, digital climate maps, and predictive models for agroclimate and fruit quality) to implement this concept on a GIS platform. Primary criterion for selecting sites suitable for Fuji apple production includes land cover, topography, and soil texture. When the primary criterion is satisfied, climatic conditions such as the length of frost free season, freezing risk during the overwintering period, and the late frost risk in spring are tested as the secondary criterion. Finally, the third criterion checks for fruit quality such as color and shape. Land attributes related to these factors in each criterion were implemented in ArcGIS environment as relevant raster layers for spatial analysis, and retrieval procedures were automated by writing programs compatible with ArcGIS. This scheme was applied to the A1B projected climates for South Korea in the future normal years (2011-2040, 2041-2070, and 2071-2100) as well as the current climate condition observed in 1971-2000 for selecting the sites suitable for quality Fuji apple production in each period. Results showed that this scheme can figure out the geographical shift of suitable zones at landscape scales as well as the latitudinal shift of northern limit for cultivation at national or regional scales.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.35 no.6
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• pp.639-643
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• 2002

Water quality, bacterial phase and fish growth rate were analyzed in the process of artificial seed production of flounder (Paralichtys oliraceus) larvae to investigate the water quality in rearing tank using Ultra Filtration System (UES). Sand Filtration System (SFS) and Ultra Filtration System (Ins) were set up in the experimental group. For the analysis of water quality, pH, salinity, DO, SS, COD, $NH_{4}^{+},\;NO_{2}^{-},\;NO^-,\;DIN$ (dissolved inorganic nitrogen) and DU (dissolved inorganic phosphate) were measured. There was no data difference between SFS group and UES group in most analysis items, but the UEs group showed low salinity and low 55 values, such that salinity was $33.5\%_{\circ}$ in SES group and $30.2\%_{\circ}$ in WS group and 55 was 15.5 mL/L in SES group and 7.0 mL/L for UPS group. For changes in bacterial phase and TBC (Total Bacterial Counts), in SES group, 6$\times$10^{5}CFU/mL in seawater decreased to the ratio of about 116, and TBC, Genus Vibrio and bacteria in the Genus Acinetobacter and Genus Micrococcus sharply increased after nine days, while stable bacterial phase was maintained low in UES group during the experiment except for Genus Ajteromonas. In the growth of the larvae, fish length was 17.0 mm (SGR 14.0) in the SES group and 18.8 mm (SGR 14.3) in the UFS group. It is concluded that when water is supplied for artificial seed production with WS, stabilization of water quality condition and inhibition of bacterial multiplication are possible. When production environment becomes stable, stable growth of fish becomes possible by reduction of environmental stress.