• Resources Recycling
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• v.19 no.5
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• pp.50-57
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• 2010

Ternary blended concrete(TBC), which contains both fly ash and granulated blast furnace slag, has an initial cost effective and is environment friendly. Furthermore, it has a lot of technical advantages such as the improvement of long term compressive strength, high workability, and the reduction of hydration heat. However, as the use and study on the performance of ternary blended concrete is limited, it is low short term compressive strength. This study was performed to evaluate the characteristics which are a long and short term compressive strengths, permeability and chemical attacks resistance of hardened high early concrete containing slag powder and fly-ash using high early strength cement(HE-TBC). Replacement rate of FA is fixed on 10% and replacement rate of slag powder are 0%, 10%, 20% and 30%. The test results showed that compressive and flexural strength of HE-TBC increased as the slag contents increased from 0% to 30% at the short term of curing. The permeability resistance of HE-TBC(fly ash 10%, blast 30%) was extremely good at the short and long terms. However, high early strength ternary blended concrete had weak on carbonation of chemical attack.

• Journal of the Korean Recycled Construction Resources Institute
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• v.3 no.1
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• pp.64-71
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• 2015

Silica fume is generally adopted as admixture for Ultra High Strength Concrete (UHSC) owing to its remarkable contribution to the strength and durability but increases significantly the fabrication cost of UHSC. Accordingly, this study investigates the replacement of silica fume by blast furnace slag (BS) and fly ash (FA) in order to lower the fabrication cost of 80MPa-UHSC. To that goal, experiment is conducted on the mix proportions of mortar in terms of its binder combination, water-to-binder ratio (W/B) and unit binder content. Based on the experimental data, a mix design of concrete is derived and its properties are verified. The results reveal that a W/B of 21% and unit binder content of $720kg/m^3$ are appropriate to achieve 80MPa-UHSC using a binder composed of 60% of OPC, 30% of BS and 10% of FA. The properties of the corresponding UHSC are seen to be satisfactory with a slump flow of 715mm and compressive strength of 97MPa at 28days. The application of the binder combination derived in this study is analyzed to reduce the cost by 50% of binder compared to the mix using silica fume while realizing equivalent performance.

• Korean Journal of Plant Resources
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• v.18 no.3
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• pp.512-517
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• 2005

To establish the economical cultivation method of Gastrodia elata Blume by controlling the shading rate and the mixing ratio of recycling spawn bed logs, a serial experiment was carried out. When G. elata was grown in the field with no shading, the yield of spawn tuber was higher than that of tuber of G. elata. The yield of G. elata was high in the rainproof green house covered with one layer of $95\%$ shading net, in the rainproof green house covered with two layers of $95\%$ shading net, and in the field with no shading, in that order. In the case of mixing ratio of recycling spawn bed logs, the yield was high in the fresh logs, in the mixing ratio of 2:1, and the ratio of 1:1, in that order. The income of the rainproof green house covered with one layer of $ 95\%$ shading net which brought the best yield was $81\%$ in the mixing ratio of 2:1 over the fresh logs.

• Journal of Internet Computing and Services
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• v.13 no.6
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• pp.41-53
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• 2012

Open educational resources(OER) enable the spread of mutual information exchange and provide advantages to both their users and institutions, such as reducing costs, improving content quality, and establishing relationships. The recent research on OER was about their connection to formal education, copyright trends, and corporate e-learning. There have been very few studies, however, on the utilization of OER and on the problems related to their practical use. Thus, this study was conducted for the purposes of analyzing the status of OER usage in education-related institutions and of providing suggestions for institution operation based on the analysis results, to promote the use of OER. A survey was conducted among more than 200 institutions in Asia, and the survey results showed that 'images and visual materials' are the most commonly used materials in Asia, and that the factors barring OER usage in the said region are 'lack of awareness', 'lack of skills', 'the absence of a reward system', and poor cooperation in participation. To promote OER usage, each institution should provide training courses about awareness, utilization skills, and copyrights. There is also a need to provide support for the establishment of reward systems and environments for OER usage. Finally, more active participation is required for inter-agency cooperation in OER sharing.

• Economic and Environmental Geology
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• v.41 no.6
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• pp.709-717
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• 2008

Rhizofiltration for cesium uptake by sunflowers (Helianthus annuus L.) and beans (Phaseolus vulgaris var.) was investigated for groundwater contamination. The cesium removal by sunflowers was greater than 98% of the total cesium in solution, and the uptake by beans was also greater than 99% within 24 hours of the rhizofiltration, showing that the rhizofiltration has a great capability to remove cesium from the contaminated water system. Experiments at various pH of solution indicated that a solution of pH $5{\sim}9$ yielded very high cesium accumulation in two plants. From the results of the analysis for cesium accumulation in plant parts, about 80% of cesium transferred into the plant from solution was accumulated in the root part and less than 20% of cesium existed in the shoot part (including leaves). Results suggest that only the roots of the fully grown plant used for rhizofiltration should be disposed or post-treated and thus the cost and time to treat massive amounts of grown plants could be dramatically reduced when sunflower and bean are used in the real field. The results of SEM and EDS analyses indicated that the most of cesium were accumulated in the root surface as a ionic phase rather than a soil precipitation phase.

• Journal of the Society of Naval Architects of Korea
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• v.29 no.1
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• pp.173-190
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• 1992

Considerable number of offshore platforms have been built in Korean shipyards ever since 1976. Unlike for the cases of building ships, however, negligible efforts have been made to establish planning methodology for building onshore platforms. Severe congestion has been shown in the processes of assemblying modules of platforms. The module which is the upper part of a platform is a steel structure accommodating various types of outfittings and machinaries. The production planned without proper consideration on allocating work loads by trade used to show severe interferences among trades of workers and resulted in delayed completion. In this paper, a method of planning module assembly in consideration of leveling work loads by trade is discussed. A system of planning has been formulated and tested on a exampled case of producing a mix of 72 modules. The test showed a possibility of saving 31% of manpower and trimming 11% of through put time.

• Clean Technology
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• v.24 no.2
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• pp.87-98
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• 2018

Phosphorus (P) is an essential and irreplaceable element for all living organisms, and it is widely used as a fertilizer. Unfortunately, it is estimated that phosphate reservoir is depleted within about 100 years. Sewage sludge ash (SSA) is an alternative resource for P recovery because of its high P content. However, SSA cannot be directly used as a fertilizer due to heavy metals in it and low P bioavailability. Thermochemical treatment with Cl donor is known to reduce heavy metal contents and increase P bioavailability of SSA. Literature review on thermochemical technologies of SSA for the reduction of heavy metals and bioavailability enhancement has been carried out to estimate the status of current P recovery technology and to develop strategic future research plan for P recovery. The review showed that $CaCl_2$ and $MgCl_2$ were the most effective Cl donors and reaction temperature (< $1000^{\circ}C$) was the critical operation condition for the reduction. The removal efficiency depends on the species of heavy metals. Thermochemical technology of SSA for P recovery showed the possibility of commercial application in the near future to overcome the coming crisis of human sustainability by P depletion, but it needs cost effectiveness and more ecofriendly process to reduce energy consumption.

• Korean Journal of Plant Resources
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• v.24 no.2
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• pp.174-180
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• 2011

This study was conducted to investigate the optimum condition of extraction from fronds of Osmunda japonica to increase antioxidant compounds and antioxidant activity. Powder (1 g) of lyophilized fronds were mixed with three different solvents (MeOH, 80% EtOH and water). Extraction was carried out using not only by immersion (room temp.), heating ($60^{\circ}C$) and stirring (200 rpm) for 6 h, but also by sonication in 42 kHz ultrasonic bath for 15, 30 and 45 min. Extracts were filtered, and adjusted up to 50 mL to determine contents of soluble solids, total polyphenols and total flavonoids. Antioxidant capacity was measured by radical scavenging activity of 0.15 mM DPPH (2,2-diphenyl-1-picrylhydrazyl) and 7.4 mM ABTS [2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)] radical. Among the solvents, MeOH and 80% EtOH appeared to be effective for extraction. Extract obtained from sonication in MeOH for 15 min resulted high polyphenol contents (45.15 $mg{\cdot}g^{-1}$ db) and DPPH radical scavenging activity ($RC_{50}$= 0.35 $mg{\cdot}mL^{-1}$). The highest flavonoid contents was obtained from immersion or heating extraction with MeOH (38.10~38.10 $mg{\cdot}g^{-1}$ db). ABTS radical scavenging was high in same extraction with 80% EtOH ($RC_{50}$= 0.21~0.22 $mg{\cdot}mL^{-1}$). Altogether, our results indicate that the extraction using ultrasonic bath with MeOH as a solvent (for 15~30 minutes) was the most effective way not only for increasing various antioxidant activities but also for saving labor and time in case of fronds of Osmunda japonica.

• Journal of the Korean Recycled Construction Resources Institute
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• v.3 no.3
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• pp.220-227
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• 2015

Ultra high performance concrete (UHPC) uses large quantities of steel fiber, silica fume, filler and superplasticizer for a low water-to-binder ratio (W/B). Despite of exceptional mechanical performances, UHPC exhibits increased viscosity due to the adoption of silica fume and its fabrication cost is costlier than ordinary concrete because of the use of large quantities of expensive materials. Following, this study evaluates the mechanical properties of 180MPa-UHPC using zirconium silica fume (Zr) instead of silica fume with respect to the quantity and type of superplasticizer (SP) and the size of filler. The results reveal that the Zr-UHPC using W/B of 20%, 100% of Zr, amount of SP-L of 2 to 3% and $4{\mu}m$-filler with steel fiber in 1.5 vol.% can develop better fluidity than the traditional mix composition using silica fume and secure a compressive strength higher than 180 MPa. In addition, the proposed mix composition is shown to enable a reduction of the fabrication cost by 33% compared to traditional UHPC.

• Journal of the Korean Recycled Construction Resources Institute
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• v.3 no.3
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• pp.268-276
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• 2015

In this study, $CO_2$ reduction type quaternary component high fluidity concrete was produced with more than 80% reduction in cement quantity to increase the use of industrial byproducts and enhance construction performance, thereby reducing $CO_2$ emissions. Furthermore, the quality properties, and $CO_2$ reduction performance of this concrete were evaluated. As a result of the quality evaluation of quaternary component blended high fluidity concrete with $CO_2$ reduction, the target performance could be achieved with a 80% or more reduction of cement quantity by mixing a large amount of industrial byproducts. The required performance level was obtained even though the flow, dynamic, and durability characteristics decreased a little compared to conventional mix. In addition, to analyze the $CO_2$ reduction performance of quaternary component blended high fluidity concrete with $CO_2$ reduction, the life cycle assessment (LCA) of the concrete was performed and the results showed that compared to the conventional mix, the carbon emissions decreased by 62.2% and the manufacturing cost by 24.5%.