• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.2
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• pp.124-134
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• 2013

This study investigated the effect of surface water on concrete substrate on adhesive strength in tension of very high flowable SBR-modified cement mortar. The specimens were prepared with proportionally mixing SBR latex, ordinary portland cement, silica sand, superplasticizer and viscosity enhancing agent. Polymer cement ratio (P/C) were 10, 20, 30, 50 and 75% and the weight ratio of fine aggregate to cement were 1:1 and 1:3. The specimens obtained with different P/C and C:F were characterized by unit weight, flow test, crack resistance and adhesion test. After basic tests, two mixtures of P/C=20% and 30% in case of C:F=1:1, and one mixture of P/C=50% in case of C:F=1:3 were selected, respectively. These three selected specimens were studied about the effect of surface water evenly sprayed on concrete substrate by a amount of 0, 0.006, 0.012, 0.017, 0.024g per unit area ($cm^2$) of concrete substrate surface The results show that surface water on concrete substrate increases the adhesive strength in tension of high flowable SBR-modified cement mortar and improve the flowability compared to the non-sprayed case.

• Korean Journal of Agricultural Science
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• v.24 no.2
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• pp.170-181
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• 1997

The number of modernized green houses have been increased to produce high quality and high-payoff farm products. The unit investment costs per pyeong($3.3058m^2$) for building a glass house was estimated at 449 thousand won. On the other hand, the unit prices for the PC house with iron frame and the vynil house with automatic control system were revealed 365 thousand won and 93 thousand won respectively. The main objective of the study was to identify the financial feasibility of the green house investment prevailed in rural area. At present, some farmers have selected the green house without any consideration of profitability of crops and accessiblity of their fanning practices and technology. For the soundness of green house cultivation and management, the indices of finacial efficiency for the modernized green houses were necessary. The decesion making criteria such as NPV(Net Present Value), IRR(Internal Rate of Return), B/C Ratio and Payback Period were analyzed for the individual high investment facilities considering the present farmer's technology and on-farm benefits and costs. The results of the feasibility analysis of green houses were as follows: 1. In case of 100% private burden of the investment costs, NPV revealed only positive value for the vinyl house with automatic system and IRR for the house was also estimated at more than 10% and B/C Ratio was amounted to more than 1.0. On the other hand, the other glass and PC houses showed negative NPV and unacceptable B/C ratio and IRR. 2. In case of the following terms and conditions as 50% Government subsidy, 20% loans and 30% farmers burden of the total investment cost, all the green houses showed acceptable IRR, B/C Ratio and NPV. 3. The financial feasibility of the glass house was acceptable in tomato cultivation rather than in cucumber cultivation. The payback periods of cucumber were represented as 8.9 years for glass house, 8.5 years for PC house and 4.1 years for vinyl house with automatic system respectively. In conclution, the glass and PC house cultivation of high value vegetables were only acceptable under the Goverment subsidy and loan systems from the view point of farmer's financial situations. On account of the unacceptable economic rate of return, the government subsidy and loan policy for glass house cultivation should be transfered to the vinyl and pc houses in the future.

• Journal of the Korean Society of Mechanical Technology
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• v.20 no.6
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• pp.763-769
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• 2018

In this research, in order to improve the heat retention of greenhouse, comparative analysis of the heat flux of the marketed multi-later insulating curtain was carried out. Experiments is conducted by fabricating a test apparatus for investigating the heat flux characteristics. The multi-later insulating curtain used for the experiment was compared using the P, N, S, U and T company, which are commercially available, and the heat flux due to temperature difference between the experimental apparatus and the outside was compared and analyzed. When the internal temperature of the experimental result is the maximum temperature $60^{\circ}C$, the heat flux of multi-later insulating curtain is T Co.($73.1W/m^2$) > S Co.($119.5W/m^2$) > U Co.($155W/m^2$) > N Co.($163.1W/m^2$) > P Co.($177.7W/m^2$). The heat flux means the quantity of heat passing through the unit time per unit area, and the higher the numerical value, the higher the quantity of heat passing through the multi-layer insulating curtain. This can be determined that high heat fluxes produce low heat resistance. Further, it has been found that the weight of the insulating curtain is largely unrelated to the heat insulating property, and the heat insulating curtain having a thickness containing a high internal air layer is excellent in the heat insulating property. In the future when manufacturing a heat insulating curtain, It is judged that it is desirable to manufacture a combination of heat insulating materials that contain a high internal air layer content and that can maintain the air layer even for long-term use while minimizing the volume.

• Journal of Korean Home Economics Education Association
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• v.34 no.2
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• pp.129-152
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• 2022

The purpose of this study was to develop a sustainable dietary education program for middle school home economics subject using a teaching strategy to improve the empowerment of adolescents and to verify and evaluate the effectiveness of the program. To achieve the purpose of this study, the program was developed and evaluated according to the ADDIE teaching design model. The contents related to the dietary area were extracted from the technical & home economics curriculum of the 2015 revised middle school and SDGs, and their relevance was analyzed to select the contents of dietary education. The program developed based on the analysis results is 'dietary life together' and consists of five learning topics: 'living together in the global village', 'maintaining healthy diet', 'creating a dietary culture together', 'living with nature and people', and 'maintaining a safe diet'. As a strategy for improving empowerment, we presented four situations, each of which represents value judgment, prediction of results, responsible behavior choice, and decision making. The developed program was reviewed by experts and applied to 17 unit classes for 17 weeks (1 unit hour per week) to the third graders of middle schools in Gyeonggi-do. Significant differences were found between before and after the class measurements of the personal empowerment and the political and social empowerment, which shows the classes were effective in improving empowerment. However, since there was no significant difference in interpersonal empowerment before and after the program, suggestions were made to utilize strategies to facilitate discussion and cooperative learning when implementing the program. The students who participated in the class evaluated the program positively as a whole. The program was evaluated to have helped the students believe they could change society through solving dietary problems.

• Journal of Bio-Environment Control
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• v.27 no.2
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• pp.117-124
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• 2018

Recently, the interest and consumption of mini watermelon (Citrullus lunatus Thunb.) are increasing due to nuclear family and one person household. However, there's no research for mini watermelon. Therefore, the purpose of the study is to develop standard cultivation method of mini watermelon. The test cultivar is 'Minimi', which is a small-sized fruit, the rootstock is 'Bullojangsaeng', which is a cucurbit line. Grafted plants were transplanted on April 5, 2017, and harvested in early July. Cultivated types were 3 methods, which are ${\cap}-form$, arched, and runner type, and plant spacing were 40, 60, and 80 cm, respectively. The rowth and yield in ${\cap}-form$ was higher than that of the arched and runner types, and the sugar content was higher a bit. The yield per unit area was about 50% higher than ${\cap}-form$, which can be plant density cultivation than that of the runner type. The number of seeds per fruit of 'Minimi' was similar to that of 'Sambokggul', but seed weight was one third lower than that of 'Sambokggul'. The content of lycopene was 30% higher than that of 'Sambokggul' watermelon, and the main sugar content is similar to or slightly less. In conclusion, the ${\cap}-form$ staking cultivation was superior to the runner type or arched cultivation in terms of fruit setting ratio, yield and quality.

• Journal of the Korea Institute of Building Construction
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• v.19 no.6
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• pp.539-547
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• 2019

Recently, the international community signed a climate change agreement to prevent global warming. Yet currently, the fossil fuels have been widely used in to supply building energy for cooling and heating. The Green Building certification (G-SEED), an energy efficiency rating for new or existing buildings requires that buildings meet certain conditions. Insulation is used as a building material to reduce the energy supply to buildings and to improve the thermal insulation, and it accounts for more than 90% of the total heat resistance provided by the building surface components that meet the energy-saving design standards of new buildings. In this investigation, a performance evaluation study was conducted through an experimental study by directly extracting the foam polystyrene insulation on-site during the remodeling of a building that was in the range of 22~38 years old. Through tests, it was found that the thermal conductivity of the extrusion method insulation (XPS) was reduced by 48% and the compressive strength of XPS decreased by 36% compared to KS M 3808, which is the initial quality standard. For bead method insulation (EPS) with a thickness of 50mm, the thermal conductivity, the compressive strength, and flexural failure load were similar to the initial quality standard. Therefore, in the calculation of the primary energy requirement per unit area per year, the performance of bead method insulation can be estimated simply by considering the thickness of the insulation, while a correction factor that considers its performance deterioration should be applied when extrusion method insulation is used.

• Journal of Bio-Environment Control
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• v.24 no.3
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• pp.258-263
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• 2015

This study was conducted to evaluate the effects of the fog-cooling system on the growth and yield characteristics of two large-fruited paprika cultivars during summer cultivation season. The temperature inside the greenhouse equipped with fog-cooling system was $2-3^{\circ}C$ lower than that in the control. The results of study show the possibilities of maintaining indoor temperatures below $35^{\circ}C$ and relative humidity at the level of 80% using fogcooling system during hot seasons of the year. Plant height, fruit weight and number of fruits per plant were higher for both cultivars in the fog-cooling treatment compared to those in control. Mean fruit weight and yield per unit area were higher in the fog-cooling treatment than those in the control. However there were no significant differences in sugar content, flesh thickness and locule number of fruits due to fog-cooling system. Number of fruits with epidermal cracking was decreased in the fog-cooling system for both paprika cultivars. Mineral contents of plants such as nitrogen (N), potassium (K), calcium (Ca), magnesium (Mg), were not affected due to fog-cooling treatment.

• Journal of Environmental Science International
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• v.23 no.6
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• pp.1075-1083
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• 2014

The objective of this study was to evaluate the effect of cutting types on microclimate and growth characteristics of afforested tree in Quercus acutissima stand after different types of cutting. The difference in temperature reaching $5.2^{\circ}C$ was shown in between clear cutting and selective cutting treatments. On July and August days with temperatures more than $35^{\circ}C$ often appeared in clear cutting stand. The values of VPD in July and August were higher than those in other months. Maximum VPD of 3.99 kPa was shown in clear cutting stand on May 23 as a prolonged rainless days appeared. However, VPD in selective cutting stand always stayed under 3.0 kPa throughout growing season. A higher intensity was shown in clear cutting and strip clear cutting stands, reaching to more than $1,600{\mu}mol\;m^{-2}s^{-1}$ at midday on early August, while that in selective cutting stand stayed about 1,500. In relative growth rate selective cutting stand showed a significantly higher relative growth rate in plant height than those in other cutting stands (p<0.05). The number of leaf in current-year branches significantly increased in selective cutting stand, whereas no increase was shown in clear cutting and strip clear cutting stands (p<0.05). In addition, relative elongation rate of current year branch also showed higher values in selective cutting stand compared with that in strip clear cutting stand (p<0.05). However, leaf mass per unit area (LMA) was higher in order of strip clear cutting, clear cutting, and selective cutting stands. From these results it is concluded that environmental conditions in clear cutting and strip clear cutting stands during growing season are more stressful to afforested tree species, resulting in lower relative growth in plant height, elongation of current-year branches, and leaf number per branch compared with those in selective cutting stand. Consequently, more data must be accumulated in the field to find out best cutting type in plantation considering the adaptational characteristic of each tree species varies with species and life span of tree is long.

• Journal of Korea Foresty Energy
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• v.24 no.2
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• pp.10-15
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• 2005

This study was achieved by purpose to measure carbon emissions by conversion of forest land in Korea to correspond to UNFCCC. The conversion of forest land data extracted in forest basis statistical data during the latest 5 years from 2000 to 2004, and biomass carbon emissions used biomass extension factor by forest types and carbon conversion factor. During the latest 5 years, the forest land of the annual means about 7,200ha was conversed as other expenditure and tree volume of the annual mean about $212,000m^3$ was felled. It was calculated that total biomass carbon emissions by conversion of the forest land emits annual mean 105,000tC during the latest 5 years. Biomass carbon emissions by forest types was calculated that coniferous forest emits 54,000tC and deciduous forest emits 51,000tC. It was calculated that carbon emissions per ha by conversion of the forest land emits annual mean 14.4tC/ha during the latest 5 years. Seeing by forest types, coniferous forest emits 13.3tC/ha and deciduous forest emits 18.5tC/ha. Therefore, it was shown that deciduous forest emits more carbon per unit area than coniferous forest.

• Polymer(Korea)
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• v.30 no.1
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• pp.75-79
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• 2006

Silica nanoparticles for polymeric dental restorative composites were prepared by Stober method, and then the effects of surface treatment of silica particles with Lmethacrylofpropyltrimethofsilane $(\gamma-MPS)$ on the dispersity of the silica particles in the organic matrix was investigated. Particles having various average size were prepared by using controlled amounts of tetraethylorthosilicate(TEOS), water, and catalyst and by changing solvent used for reaction. The site of particles prepared by using methanol as solvent was smaller than that prepared by using ethanol as solvent. In addition, the size of particles was increased by decreasing amounts of water and by increasing amounts of TEOS and catalyst. Hydrophobic silica nanoparticles was prepared by reacting hydrophilic nanoparticles with $\gamma-MPS$ to improve interfacial properties with organic matrix. Amounts of $\gamma-MPS$ per unit mass of the particles was increased by decreasing particle size. even though the amount of $\gamma-MPS$ per specific surface area were nearly the same regardless of the particle size. The dispersity of the silica particles in the organic matrix was improved when the surface treated silica particles were used for preparing the polymeric dental restorative composites.