• Advances in concrete construction
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• v.9 no.4
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• pp.387-395
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• 2020

This study has been carried out in two-phases to develop Fiber Reinforced Self-Compacting Concrete (FRSCC) performance. In the first phase, the composition of the quaternary composite binder compromised CEM I 42.5N (58-70%), Rice Husk Ash (25-37%), quartz sand (2.5-7.5%) and limestone crushing waste (2.5-7.5%) were optimized. And in the second phase, the effect of two fiber types (steel brass-plated and basalt) was investigated on the SCC optimized with the optimum CB as disperse reinforcement at 6 different ratios of 1, 1.2, 1.4, 1.6, 1.8, and 2.0% by weight of mix for each type. In this study, the theoretical principles of the synthesis of self-compacting dispersion-reinforced concrete have been developed which consists of optimizing structure-formation processes through the use of a mineral modifier, together with ground crushed cement in a vario-planetary mill to a specific surface area of 550 m2 / kg. The amorphous silica in the modifier composition intensifies the binding of calcium hydroxide formed during the hydration of C3S, helps reduce the basicity of the cement-composite, while reducing the growth of portlandite crystals. Limestone particles contribute to the formation of calcium hydrocarbonate and, together with fine ground quartz sand; act as microfiller, clogging the pores of the cement. Furthermore, the results revealed that the effect of fiber addition improves the mechanical properties of FRSCC. It was found that the steel fiber performed better than basalt fiber on tensile strength and modulus of elasticity; however, both fibers have the same performance on the first crack strength and sample destruction of FRSCC. It also illustrates that there will be an optimum percentage of fiber addition.

• Atmosphere
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• v.29 no.5
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• pp.659-669
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• 2019

This study assesses the quality of the total column ozone (TCO) data from five reanalysis datasets against nine independent observation in East Asia. The assessed datasets are the ECMWF Interim reanalysis (ERAI), Monitoring Atmosphere Composition and Climate reanalysis (MACC), Copernicus Atmosphere Monitoring Service reanalysis (CAMS), the NASA Modern-Era Retrospective analysis for Research and Applications, Version2 (MERRA2), and NCEP Climate Forecast System Reanalysis (CFSR). All datasets reasonably well capture the spatial distribution, annual cycle and interannual variability of TCO in East Asia. In particular, characteristics of TCO according to the latitude difference were similar at all points with a maximum bias of less than about 4%. Among them, CAMS and CFSR show the smallest mean bias and root-mean square error across all nine ground-based observations. This result indicates that while TCO data in modern reanalyses are reasonably good, CAMS and CFSR TCO data are the best for analysing the spatio-temporal variability and change of TCO in East Asia.

• Bulletin of the Korean Space Science Society
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• 2011.04a
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• pp.26.3-27
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• 2011

Formation of a steep plasma density gradient in the middle-latitude ionosphere during geomagnetic storms and the latitudinal migration of its location depending on the storm phase are suggested to be associated with the ionospheric signature of the plasmapause. We test this idea by using the satellite and ground observation data during the 11 April 2001 storm. The locations of the steep plasma density gradient identified by TOPEX/Poseidon (2001 LT) and DMSP (1800 and 2130 LT) satellites coincide with the ionospheric footprints of the plasmapause identified by the IMAGE satellite. This observation may support the dependence of the middle-latitude plasma density gradient location on the plasmapause motion, but does not explain why the steep density gradient whose morphology is largely different from the morphology of the middle-latitude ionization trough during quiet period is formed in association with the plasmapause. The ionospheric disturbances in the total electron content (TEC) maps shows that the steep TEC gradient is formed at the boundary of the positive ionospheric storm in low-middle latitudes and the negative ionospheric storm in middle-high latitudes. We interpret that the thermospheric neutral composition disturbance in the dayside is confined within the middle-high latitude ionospheric convection zone. The neutral composition latitudes and, therefore, the locations of the steep plasma density gradient coincide with the footprints of the plasmapause. The TEC maps show that the appearance of the steep plasma density gradient in the pre-midnight sector during the recovery phase is related to the co-rotation of the gradient that is created during the main phase.

• Journal of Ecology and Environment
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• v.34 no.4
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• pp.347-355
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• 2011

Effects of forest thinning on community level properties have not been understood yet in Korea. We investigated regeneration patterns and trajectories after a disturbance by applying a chronosequence approach. Light availability, litter and woody debris cover, and species composition were determined for twenty 50 m line-transect samples representing a disturbance duration gradient (within 11 years). Environmental factors such as light availability and coverage of woody debris and litter changed abruptly after thinning and then returned to the pre-disturbance state. Although species richness was gained at shrub and ground layer in a limited way in both forests, cover of various functional types revealed diversity in their responses. Notably, Alnus firma stands exhibited a larger increment of cover in woody plants. Ordination analysis revealed different regeneration trajectories between natural and planted stands. Based on ordination analysis, rehabilitated stands showed movement to alternative states compared with natural ones, reflecting lower resilience to perturbation (i.e., lower stability). Our results suggest that community resilience to artificial thinning depends on properties of the dominant species. But to get more explanatory ecological information, longer-term static observations are required.

• Journal of Animal Science and Technology
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• v.46 no.3
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• pp.443-450
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• 2004

To examine the potentiality of grassland dominated with turf-type grasses, which are mainly used for the establishment of green spaces, forage production and its utilization as forage resources, dry matter yield and forage quality of three different turf-type mixtures were estimated throughout three consecutive experimental years. According to the experiment, the mean of dry matter(DM) yield, chemical composition, DM digestibility, crude protein dry matter(CPDM) and digestible dry matter(DDM) yield was not significantly different among species(p > 0.05) over three experimental years. Botanical composition of three dominant species(tall fescue, Kentucky bluegrass and perennial ryegrass) was 42, 35 and 28%, respectively, in three mixtures at the last cutting(6th) in 2001. The botanical composition of three dominated species such as tall fescue, Kentucky bluegrass and perennial ryegrass was maintained 84% of the total plants in all types of mixtures. Therefore, It is observed that the mixture types did not closely affect the botanical composition. But botanical composition of the other species such as redtop(8%) and creeping bentgrass(6${\sim}$7%) was low. Especially, that of red fescue was the least(1${\sim}$2%) of all mixed species. As mentioned above, any difference was not observed in DM yields, forage quality and botanical composition among mixture types. Therefore, any types of mixtures can be used as public green spaces like school ground areas or river-sides, and as forage resources additionally.

• Journal of the Korean Institute of Educational Facilities
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• v.18 no.4
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• pp.57-67
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• 2011

In this study, it did comparative analysis on the arrangement, construction and size of rooms applied in the early design stage at the time of prize-winning with the changed ground plans in the final design of those prize-winning works in design contests and BTL hold since 2007 for middle and high schools in Gyeonggi, Daejeon, Chungcheong regions. Through the analysis, this study intends to present those matters to be changed in the facilities standards of each local education office so that it can be referred to the assessment of spatial construction and proper size being planned in the future for middle and high schools and reflected flexibly in consideration of various educational conditions and characteristics of schools by regions. Furthermore, it has the objective to play a part for the establishment of much better environment of educational facilities by provision of reference materials to those matters being changed into proper ones not into the minimum ones of the school facilities standards as the national level. For case analysis, it analyzed various rooms classified by necessary spaces. Since names of rooms and spatial constructions to constitute facilities are different from each local education office and also the analysis by each room has some limitation in the changes and improvement of rooms for a wide range, it proceeded with detailed classifications of school building facilities by each necessary space.

• Journal of Korean Society of Forest Science
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• v.100 no.1
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• pp.34-41
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• 2011

Vegetation structure, composition and diversity were quantified for 10 samples ($10m{\times}10m$) representing woody vegetation and for 30 samples ($1m {\times}3m$) representing understory vegetation in Pinus parviflora and Tsuga sieboldii forest of Taeharyeong, Ulleung-gun (Gyeongsangbuk-do). P. parviflora was limitedly advanced to sapling layer from seedling stage, and based on Mantel tests, composition of canopy layer was not established in ground woody vegetation. Non-metric multidimensional scaling revealed influence of biotic and abiotic factors in species composition of woody and understory vegetation. In the result of multiple regression model, abundance of P. parviflora (density and breast height area) and percent cover of woody debris were significant predict variables for understory diversity. These results suggest that relatively large disturbance is required for regeneration of P. parviflora and T. sieboldii forest, and control of expansion of monocultural understory species that monopolize resources such as Carex blepharicarpa and Maianthemum dilatatum, is necessary for maintenance of diversity.

• Korean Journal of Agricultural Science
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• v.42 no.3
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• pp.191-199
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• 2015

We conducted this research to observe the changes of surface morphology and composition of clay minerals influenced by various concentrations of fluoric acid. Hydrofluoric acid (HA), a solution of hydrogen fluoride (HF) in water, is a colourless solution that is highly corrosive, capable of dissolving many materials, especially oxides. To do this, we treated several concentrations of HA on the ground soil samples collected from the agricultural experimental station located at Chungnam National University to observe the influence of fluoric acid on the changes of surface structures and elemental composition of clay particles. Generally, microscopic examination showed that the HA can not only attack an edge of clay particles but also start at any point where structural defects and weaknesses predisposed sites to acid. The orderly flake arrangement of clay minerals may reflect certain crystal symmetry elements. The ESEM-EDS results of element composition of clay particles influenced by HA indicated the changes of structures of clay minerals. It is also clear from the formation of etch figures and element composition of clay particles that the product layer at least partially dissolved or disintegrated in the presence of acid. Conclusively, the clay structures can be strongly influenced by concentrations of HA, resulting in changes of physical and chemical properties that can determine the behavior of solute transport as well as mobility of ions in soils.

• Journal of The Korea Institute of Healthcare Architecture
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• v.20 no.4
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• pp.67-80
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• 2014

Purpose : Long-term Care Insurance sets up facility standard and installation standard of aged care facilities and decides the presence of minimum number of rooms and its size in care facilities by using systematic instruments. Therefore, most aged care facilities had renovation in expansion and reconstruction following the revised regulations and even facility space structure and space composition are continuously improving. The study is to determine the purpose and trend by comparing before and after space composition of facilities which followed the implementation of Long-term Care Insurance and also to suggest hierarchical space composition suitable for aged care facilities through derived problems and to provide basic materials to plan the most appropriate facility for the aged. Methods : J-graph based on Space Syntax Theory will be schematized through in-site facility survey and before and after facility floor plan. Space composition trend will be analyzed by comparing indexes through S3 program. Results : As a result of 5 cases analysis, the following results were found; the average of whole space depth is increasing due to the Extension, the number of volunteers is decreasing and rooms for geriatric care helpers are being created due to the geriatric care helper introduction duty. Also, there are solariums being created to improve the health of the aged and dispensaries are being placed on every floor with the increase of documentary work for geriatric care helpers. With the policy implementation, care facility space composition and structure are changing with facility standard and it was analyzed that facilities were mostly put under the control of limited number of people in care room and total ground area per person. It was also found that there is increase in care space integration through before and after comparison of whole integration value. This is considered as the important result not only in facility standard satisfaction, but also in care support of geriatric care helpers and the aged, its main users. Implication : In order for elderly care facilities to have quality improvement and to develop as suitable facilities for characteristics of the aged, independent environmental facility standard preparation of elderly care facilities is needed through mutual cooperation of construction fields with regulation and policy related researches.

• Journal of Korean Society on Water Environment
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• v.34 no.5
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• pp.447-461
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• 2018

To realize river restoration that ecological characteristics of the river are reflected, we classified the river into four reaches of valley stream, upstream, midstream, and downstream based on substrate as well as riverbed gradient obtained from the relationship between distance from the river mouth, and above sea level. Considering that the rivers of Korea have been dominated by various and intense artificial interferences over a lengthy period, we determined cross sectional range of the river based on the geological map and clarified transformation degree by reach. Vegetation profile diagram was prepared by depicting horizontal range and vertical stratification of major vegetation appearing in a belt transect of 10 m breadth installed between weirs constructed in both sides of the river. Restoration models by river reach were prepared based on breadth of waterway, bare ground, herb, shrub, and tree dominated vegetation zones on vegetation profiles wherein a flooding regime was reflected. Species composition information collected from vegetation established in each zone was systematized to use for restoring each reach ecologically. Further, background that longitudinal reaches and horizontal zones were divided, was discussed by comparing with case studies in foreign countries. In addition, necessity of ecological restoration of the river was discussed based on degree of integrity of Korean rivers, ecological significance of riparian vegetation, and importance of reference information for ecological restoration of the river.