• Proceedings of the Korean Institute of Building Construction Conference
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• 2008.11a
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• pp.89-92
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• 2008

This research analyzed the basic characteristics of unhardened concrete and the compression strength characteristics of hardened concrete according to liquidity retention agent mix rate change to improve the liquidity fluidity retention performance of high performance concrete, and produced the following results. The moment fluidity retention agent is added according to fluidity retention agent mix rate change, which increased fluidity retention agent mix rate, slump flow decreased, and in the case of slump flow according to the progress time change by the fluidity retention agent mix rates, the more fluidity retention agent mix rate increased, the lower slump flow change rate became. The moment fluidity retention agent is added according to fluidity retention agent mix rate change, fluidity retention agent mix rate increased compared to non-mixture of fluidity retention agent, and the air amount by progress time change by the fluidity retention agent mix rates slightly increased, however target range is still met and unit volume mass is inversely proportional to air amount. Compression strength according to age progress by the fluidity retention agent mix rates was shown to increase slightly with increase in fluidity retention agent mix rate, and yet the difference was not significant.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 1998.11a
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• pp.206-215
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• 1998

Using of geosynthetics with linear materials(sand, gravel, clay soil) is rapidly increased in landfill. With geosynthetics, geotextiles often expose to solar radiation(Ultraviolet) on long terms during the installation. In this paper, the results will represent the strength retention rate and tensile retention rate of geotextiles between outdoor exposed and protected by 15cm thickness of soil. As a result of cumulating solar radiation in geotextiles was increased, the strength retentions rate of P.P(500g/$m^2$), P.P(700g/$m^2$) and P.P(1000g/$m^2$) were decreased and the lower weight of unit area of geotextiles, the faster decrease of strength retention rate. P.E.T(600g/$m^2$) was showed a distinctive trend that the strength retention rate increased. The tensile retention rate of tested geotextiles was decreased during the simulation. However, the strength and tensile retention rate of geotextiles covered by soil had changed insignificantly. Therefore, it can surmise that the soil covering will help geotextiles to be protected from UV effecting

• Journal of the Korean Society of Tobacco Science
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• v.8 no.1
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• pp.3-12
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• 1986

Extensive studies have been made of the effects of freeness and the calcium carbonate on the physical properties of hand-sheets from commercial flax, kenaf and NBKP. As freeness increased, the hand-sheets from the pulps above showed higher retention rate of calcium carbonate, brightness, opacity and tensile strength but lower value of porosity. Among these, the retention rate(46%) showed the highest value In kenaf, the porosity(205 c.u.) in flax, and the opacity(67%) and the tensile strength(2.8kg) in NBKP respectively. Under the constant freeness, retention rate of calcium carbonate in hand-sheets increased until 1.4 times pulp weight was added in flax and kenaf but, in NBKP, decreased from the beginning of 0.8 times with the highest retention rate. Results above led to higher porosity, opacity, brightness but lowered tensile strength. Mixed pulp(Kenaf+ NBKP) showed higher retention rate than each pulp. Pictures of X-ray diffraction and scanning electron microscope demonstrated that both of domestic and foreign calcium carbonates were calcite of spindle form. The brightness of foreign calcium carbonate was higher by 295 than that of domestic one. The average particle size of calcium carbonate was 2.1 U m(domestic), 3.6 U m(foreign).

• Journal of Korean Society on Water Environment
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• v.33 no.5
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• pp.563-571
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• 2017

Because of the rapid progress of urbanization in recent decades, the proportion of impervious areas in cities has increased. As a result, hydrological properties of urban streams have changed and non-point pollution sources have increased, that have had considerable influence on human life and ecosystems. To manage these situations, application of non-point pollution reduction facilities and LID facilities are expanding recently. In this study, it is investigated if rainfall interception rate used in design of non-point pollution reduction facilities can be applied to design of LID facilities. For this purpose, EPA SWMM is constructed for part of Noksan National Industrial Complex area wherein long-term observed storm water data can be obtained and storm water interception rates for various design capacities of a bio-retention LID facility reservoirs are estimated. While sensitivity of storm water interception rate according to design specifications of bio-retention facility is not large, sensitivity of storm water interception rate according to regional rainfall characteristics is relatively large. As a result of comparing present rainfall interception rate estimation method with the one proposed in this study, the present method is highly likely to overestimate performance of the bio-retention facility. Finally, a new storm water interception rate formula for bio-retention LID facility is proposed.

• Journal of Environmental Science International
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• v.31 no.12
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• pp.1013-1025
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• 2022

This study was carried out to analyze water cycle characteristics and evaluate water retention function in Jeju Gotjawal forest from 2013 to 2017. The average ratio of throughfall, stemflow, interception loss in Seonhul Gotjawal (SH) and Cheongsu Gotjawal (CS) was 43.1%, 15.8%, and 41.1%, respectively. Rainfall-throughfall, rainfall-stemflow, and rainfall-interception loss were expressed as linear regression equation (p<0.001). The comparison results showed that SH was higher than CS (p<0.05), indicating that the canopy area had an important effect on the difference in stand structure. The average water resources retention rate of the Gotjawal region was 41.9%, which is similar to the total water resources retention rate (40.6%) of Jeju Special Self-Governing Province (JSSGP). Currently, the development of Gotjawal is in progress in JSSGP. The development of Gotjawal will lead to a decrease in the water resources retention rate due to changes in the surface environment such as an increase in impervious areas, which will affect the total groundwater content of JSSGP. Therefore, the conservation of the Gotjawal area is judged to be very important from the point of view of water conservation.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.32 no.1
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• pp.33-40
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• 2000

The effectiveness of silica-based microgels prepared through the reaction of sulfuric acid and sodium silicate as a component of Compozil system has been evaluated . Silica based microgels with better performance in retention and drainage than a commercial colloidal silica sol have been successfully prepared. Silica gels with the highest charge density were obtained when product pH was controlled to 9. And highly charged silica-based microgels showed greater retention and freeness performance than a commerical product. In particular the difference in retention, turbidity , and freeness between these microgels and a commercial product was eminent at low addition rate. The effects of reaction conditions including reaction temperature, process water quality and feeing rate on product efficiency in improving retention and drainage were also investigated and discussed.

• Nuclear Engineering and Technology
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• v.56 no.10
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• pp.4068-4076
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• 2024

In the event of severe accidents in pressurized water reactor (PWR) nuclear power plants, the potential leakage of radioactive aerosols through containment cracks poses a considerable radioactive hazard to the public. Understanding aerosol transport and retention in cracks helps reduce the conservatism and uncertainty of radioactive hazard assessment. Concrete cracks are recognized as a pivotal pathway for the leakage of radioactive aerosols, and several researchers have undertaken experimental investigations concerning the aerosol transport and retention in concrete cracks. However, the majority of these studies have rather low gas flow Reynolds numbers. In this work, an experimental setup is built to study aerosol transport and retention in concrete cracks under high Reynolds number flow. The TiO₂ aerosol with a mass median diameter of 1 ㎛ and two concrete crack specimens are used in experiments. The results of gas flow experiments indicate that the Reynolds number is capable of reaching 10547. Combining the flow experimental data and Suzuki's formula, the equivalent heights of these two crack specimens are approximated as 303.67 ㎛ and 231.48 ㎛. The experimental results indicate a notably high retention rate of aerosols, exceeding 0.8. Furthermore, under high Reynolds number flow, the retention rate varies over a relatively narrow range, with the larger the equivalent height of the crack resulting in a lower retention rate. The experimental results match well with the mechanistic analysis based on inertial deposition theory, demonstrating the rationality of the inertial deposition theory.

• Research in Community and Public Health Nursing
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• v.15 no.1
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• pp.76-83
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• 2004

Purpose: This study was aimed at investigating the relationship between retention of the maternal child health handbook, awareness of DPT additional immunization and DPT additional immunization, and to provide basic information to enhance the DPT additional immunization rate. Method: The study subjects were 312 women whose children were between four and six years old, and residing in six provinces of Gyungsangnam do. Data was collected with a 10 item questionnaire by interviews from July 1st to 30th, 2003, and analyzed with descriptive statistics and X2 test at a significance level of 0.05, by two tailed test. Results: The awareness of DPT additional immunization was significantly higher in the women who retained the maternal child health handbook, than their counterparts. The rate of DPT additional immunization was significantly higher in the women who were aware of the DPT additional immunization or who retained the maternal child health handbook, than their counterpart. Conclusion: The DPT additional immunization rate was related to retention of the maternal child health handbook and awareness of DPT additional immunization. Therefore it is recommended that measures be developed and taken to increase the retention rate of the maternal child health handbook and awareness of DPT additional immunization, to enhance the rate of DPT additional immunization.

• Journal of the Korean Society of Food Science and Nutrition
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• v.19 no.6
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• pp.555-564
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• 1990

The headspace gas chromatographic(analytical) technique was used to evaluate the retention of volatiles in fruit juices during freeze drying as a function of freezing rate, the content of initial solid and chamber pressure. The effects of freezing rate and drying time on the volatile retention under the experimental conditions were marked, particulary at long freezing time. The retention of volatiles in the freeze dried was largely affected by the freezing rate. The highest volatile loss under the freeze drying conditions was observed during the first stage of drying. The behavior during freeze drying of the volatile substances was affected by high content of initial solid. The volatile retention was higher in quick freeze drying than slow freeze drying and low pressure than high.

• Korean Journal of Environmental Agriculture
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• v.22 no.4
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• pp.251-254
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• 2003

Phosphorous removal rate and emergent plant growth were examined of a surface-flow constructed treatment wetland system, whose dimensions were 31 meter in length and 12 meter in width. The system was established on floodplain in the down reach of the Kwangju Stream in Korea in one and half months from May to June 2001. Cattails(Typha angustiflora) were transplanted in the system. They were dug out of natural wetlands and stems were cut at about 40 cm height from their bottom ends. Water of the Kwangju Stream were funneled into it via a pipe by gravity flow and its effluent were discharged back into it. The stems of cattails grew from 45.2 cm in July 2001 up to 186 cm in September 2001 and the number of cattail stems per square meter increased from 22 in July 2001 to 53 in September 2001. The early establishment of cattails was good. Volume and water quality of inflow and outflow were analyzed from July 2001 through December 2001. Inflow averaged $40\;m^3/day$ and hydraulic retention time was about 1.5 days. The concentration of total phosphorous in influent and effluent was 0.85 mg/L, 0.41 mg/L, respectively. The average removal rate of total phosphorous in the system was about 52%. The retention efficiency was slightly lower, compared with that in surface-flow wetlands operating in North America, whose retention efficiency was reported to be about 57%. The lower abatement rate could result from the initial stage of the system and inclusion of two cold months into the six-month monitoring period. Root rhizosphere in wetland soils and litter-soil layers on bottoms were not properly developed. Increase of standing density of cattails within a few years will establish both root zones and substrates beneficial to the removal of phosphorous, which may lead to increase of the phosphorous retention rate. The system was submerged one time by heavy storm during the monitoring period. The inundation, however, scarcely disturb its environment.