• Journal of the Korea Convergence Society
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• v.9 no.9
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• pp.47-52
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• 2018

Wi-Fi enabled Internet of Things (IoTs) had a substantial impact on society, economy and industry. However wireless connectivity technologies in unlicensed band such as Wi-Fi are vulnerable to interferences. They also face difficulty providing wireless connectivity over long range in dense networks due to the dynamically changed interference effect and asymmetric interference conditions. In this paper, robust acknowledgement transmission scheme is proposed for long range IoTs. According to the proposed scheme, it is possible to control the transmission rate of the transmission success rate of the response frame by adjusting the transmission rate of the response frame when the interference is present asymmetrically. It is also possible to use higher data rate when high quality link is guaranteed. The evaluation results demonstrated the proposed scheme improves the aggregate throughput by at most 9 Mbps when 20 MHz bandwidth transmission mode was adopted.

• Journal of Korea Water Resources Association
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• v.30 no.4
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• pp.367-377
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• 1997

In order to set public policy to overcome 'water crises' on both quantity and quality of water, we looked into the national-economic role of Korea water utility by two approaches. First, we examined the relationship between water consumption and economic growth during 1978-94, a period of rapid increase in water consumption caused by prompt industrialization and urbanization. The price and income elasticities of aggregate and sectoral demand for water were estimated. Second, we developed a static input-output(I-O) framework for analysing water issues in the short run. In addition, we discussed two topics in its application: i) sectoral failure(shortage) costs by supply-driven I-O model, ii) Leontief price model's sectoral pervasive effects of price due to rise in water rate. In conclusion, we found that investments to water sector and water shortage has a big influence on the standard of living and industrial production. Also we found that raising water rate to encourage conservation or to create investment funds decreases demand for water significantly but has a small influence on overall price levels.

• Journal of the Korea Institute of Building Construction
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• v.13 no.3
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• pp.282-290
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• 2013

In this study, the adjustment range of mixture factor with replacement mineral admixture was reviewed to secure the mixture change data of high volume concrete compared to general concrete. When changing the concrete mix to high volume concrete within the universal concrete mixing, the adjustment range of mixture to ensure optimum quality is as follows. Unit-water content is $20{\sim}30kg/m^3$ downward. Fine aggregate ratio dropped by approximately 1% when W/B was reduced by 5%, and it is reduced by approximately 0.12% when there is a 5% increase in the total replacement rate. When the FA replacement rate was increased by 5%, the AE agent was approximately 20% to 30% higher compared with the conventional one. When the FA and BS replacement rate rose by 5%, W/B was reduced by about 1 to 4%.

• Journal of Korea Spatial Information System Society
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• v.8 no.3
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• pp.27-37
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• 2006

It defined the standard list of the urban foundation facility which from the local self-government it is managing with commonness and standard items and standard option and a construction plan it drew up "Urban Foundation Facility Electronic Library" it researched. "Urban Foundation Facility Electronic Library" defines with the aggregate of the component DB which lets to collect the organization, quality and form of the urban Foundation facility back attribute item system from the Geographic Information System(GIS). Consequently after the "Urban Foundation Facility Electronic Library" is constructed, it presented the application plan from on-the-spot inspection. Also it applied in the ubiquitous environment which is actualized quickly the plan which it does in the RFID and sensor network and electronic library grafting it presented. The connection use of the RFID and was possible from the Facility civil official test which applies the RFID.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.445-448
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• 2008

It is essential that concrete component is made up with aggregate, cement and water. But today, Public concern is increasing of a variety structure and ocean environmental, resource recycle. Also, According to heat of hydration rising, Concrete is make a causative of concrete-crack. Concrete-crack cause a falling-off in quality of concrete. consequently, High-performance concrete is evaluated by concrete material properties and carbonation resistance with different admixture(fixing fly-ash 20%), granulated blast furnace slag replacement ratio (30%, 45%) different W/B (26%, 30%, 34%) and XRD(X-ray Diffraction) analysis.

• The Korean Journal of Quaternary Research
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• v.21 no.1
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• pp.1-14
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• 2007

In this study we experiment on sand deposits (tine aggregates) taken from the old river-bed of the Bonghwang-cheon of Geum River Basin, and evaluate physical properties of fine aggregates in comparison to the KS quality regulation. As a result of experimentation, particle size of fine aggregates is generally smaller in the downstream area than in the upstream area. In addition, physical properties of the fine aggregates tend to depend on the bedrock type. Physical properties of fine aggregates show a strong positive correlation with particle size of old river-bed sediments. Finally, the general physical properties of fine aggregates are conformable to the KS quality regulation, except density and proportion of materials finer than $75{\mu}m$.

• Journal of the Korean Geotechnical Society
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• v.31 no.10
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• pp.37-47
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• 2015

Recently, the quality of drilled shafts concrete has been improved significantly due to the improved concrete performance, upgraded concrete materials, and better management of on-site constructions. Despite the development, current conventional quality management on concrete constructions is still used without any criticism. In this study, compressive strength test results of more than 200 concrete specimens after 7 and 28 days of curing were collected from one site at Songdo area of Incheon. The concrete specimens were prepared from the concrete with aggregate maximum dimensions of 25 mm, target compressive strength of 40 MPa, and slump of 180 mm. Influential factors including concrete temperature, air temperature, amount of slump, amount of air, amount of salinity on concrete specimen were also examined. The database was established from collected information and statistical analyses were performed. Analyzed results confirm that "the difference between concrete temperature and air temperature" has the largest impact on the compressive strengths of specimens at the durations of 7 and 28 days.

• Journal of Korea Water Resources Association
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• v.40 no.2 s.175
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• pp.183-190
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• 2007

Soil layer in vegetation filter strip is one of the very important factor for reduction of non-point pollutants by physical, chemical and biological reactions of it through infiltration process. This study was carried out to prepare more effective vegetation filter strip through modification of soil layer for river water quality improvement. Therefore, the main aims of this study are to compare and evaluate normal (straighten type) and modified (step type) vegetation filter strip, which make artificially change the soil layer to improve infiltration ability, through bench scale experiments. In the results of this study, vegetation filter strip of step type is much more highly reduction effectiveness of pollutants in surface flow compared with normal vegetation filter strip. In case of below effluent, however, it appeared that the vegetation filter strip modified soil layer showed lower reduction effectiveness of pollutants than the general vegetation filter strip. This result was judged because effluent through the vegetation filter strip of step type passed bigger size of aggregate or sand than the vegetation filter strip of straighten type. If we compare it as a definition of pollutant load to estimate total amount of reduced pollutants by vegetation filter strip, reduced pollutants load by step type showed higher than those by straighten type because below effluent amount relied on total effluent amount was higher at step type (4%) than at straighten type (2%). In conclusion, the vegetation filter strip of step type to improve infiltration effect is much more reduction effectiveness of pollutants than vegetation filter strip of straighten type.

• Archives of design research
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• v.13 no.1
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• pp.121-130
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• 2000

This study can be expressed by gathered and formed into the exhibition space's structure practical progress/ application. For the one model of fascinating exhibition's space thru inter-space's pertinent adjustment, production between spactator and exhibition constituent on an exhibition story-line, I adjusted the focus to follow mentioned methods systematically for the example; An exhibition space is completed to be very impressive and attractive space by proper adjustment and production of M-M/C interface in exhibition storyline. Quantity space is transfered into quality space through the transmission of an exhibition which can be define as the point of an exhibition structure. And also could de transferd into a bodily sensation space that inherent full of interactive constituent. Changeable exhibition constituents (exhibition item and text) that sporadically expatiated (not trimed, the original form) in the process of an exhibition structure draw much higer quality of the optimal solution in optimize process which is given when aggregate again to contextual flow of synthetic exhibition scenario. Reconstruction of individual exhibition constituents to the new story, that is, transference of exhibition text to exhibition context is inspirit to an exhibition by maximize the exhibition effect in connection can be systematized through carrying out an outcentripetalpart. However, since pattern of an exhibition structure that consequtively meet variety spacetime of an exhibittion environmental can't be exist, this study presents centralizing the exhibition plan of Korea communication pavilion of the annual Expo Comm Wireress Korea, sustained process from design proposal, research and analysis to synthesis, development, transmission and management to an example of an applying crystallization.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.38 no.4
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• pp.611-619
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• 2018

Basalt powder sludge (abbreviated BPS) is an inevitable industry by product resulted from the stone processing. Recently, demands for natural materials have been increasing in the construction and landscaping fields, therefore, amounts of BPS have been also increasing. Since most of BPS are used as landfill and earth soil, it is necessary to figure out to expedite their utilization. In this study, by considering the characteristics of precipitation of Jeju, effectiveness of BPS as a filler for asphalt compounds mixed with cement were analyzed. As a result, BPS satisfies quality criterion required in KS F 3501. Marshall mixing designs were performed to determine the optimal asphalt content for the Modified recycling asphalt mixture (27% recycling aggregate) and the Normal asphalt mixture. Effectiveness of BPS were identified by the Marshall Stability Test with the mixing ratio (level 3) of two asphalt compounds and composition ration (level 3) of BPS and cement. Performance of asphalt compounds shown appropriate effect of mixing and composition ratios of the filler were assessed. Test results show that two types of asphalt compounds satisfy the quality standards of the MLIT (2015). Therefore, BPS could be used as filler for asphalt compounds.