• Journal of the Korea Institute of Building Construction
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• v.17 no.3
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• pp.227-234
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• 2017

This research analyzes the properties of mortar following the rise in water-cement ratio and applicability as an eco-friendly construction supply by using the mudflats of a dredged arena as a substitute for aggregate. The results of a experiment of the flow showed that the flow value decreases as the amount of mudflats increases. A test for chloride content showed that the chloride content increases with the amount of mudflats. In the compression of specimen mixed with mudflat and the testing of tensile strength, the strength weakened as the addition ratio of mudflats rose. However, with 14-day strength as the standard, most specimen showed more strength than the plain, and 14-day strength was higher than 28-day strength. It appears to be experimental error in the mixing process from the viscosity and cohesion of mudflats, and it is considered that there will be a need for an experiment on mixing methods of mudflats in the future. The compressive strength of this research was the strongest with 70% in water-cement ratio, and the tensile strength was strongest with 80% in water-cement ratio. In the evaluation of surface analysis, 70% water-cement ratio, which is finest in strength, mixing, and compactness, was selected to analyze the roughness of the surface, and the results showed that the surface became smoother as the addition ratio of mudflats increases. In conclusion, it appears that 70% water-cement ratio is the optimal mixing ratio for mortar and 10 to 30% addition ratio of mudflats the optimal ratio. It also appears that the application of interior finishing material like bricks and tiles and interior plastering material using the mudflats are possible.

• Journal of Korean Society of Forest Science
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• v.106 no.1
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• pp.70-76
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• 2017

Among the forest road pavement methods, the majority of current constructions utilize concrete pavements but it has disadvantages as follows: many cracked concrete pavements generated by the erosion of underlying soil layers, could not be used as forest roads in steep slope during winter, and cement contains hazardous chemicals (hexavalent chromium, etc.). In order to supplement the limitations of the use of concrete pavement, this study was conducted to investigate the operation process and cost, the strength and compaction of the experimental forest road pavement(85 m) utilizing eco-friendly solidification material at Goryeong-gun, Gyeongsangbuk-do. The work elements of experimental forest road paving were classified into: preparation, Roadbed excavation, Roadbed grading, subgrade compaction, form work, collection and selection of site soil, mixing site soil and eco-friendly solidification material, paving by eco-friendly solidification material, compaction by vibrating roller and curing. The result of economic analysis using construction cost shows that for concrete costs total to $38,681won/m^3$ while for the eco-friendly paving material it is $38,245won/m^3$. Thus the construction costs for concrete and the eco-friendly paving material are similar. And the results of the Schmidt Hammer test for strength analysis by curing period are 10.5-13.5 MPa for 7 days, 18.1-22.7 MPa for 14 days, and 20.8-23.0 MPa for 28 days.

• The Journal of Engineering Geology
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• v.13 no.4
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• pp.419-428
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• 2003

In order to evaluate groundwater movement and the infiltration of contaminants, such as petroleum products, the determination of porosity and effective porosity is very important. Porosity and effective porosity are important physical parameters that determine the transfer and movement of water and solutes in porous media. Various methods of determining these parameters have been developed, with varying degrees of accuracy and applicability. Most of the existing methods produce static results. They do not produce instantaneous and real time of porosity and effective porosity in a porous media. In this study, we used a new permittivity method called Frequency Domain Reflectometry with Vector analyzer (FDR-V) to determine the porosity and effective porosity of some sand samples in the laboratory. The advantage of the FDR-V method is that it instantaneously determines the temporal variation of dielectric constants of porous media. Then, the porosity and the effective porosity of porous media are computed using well established empirical equations. Results obtained from the FDR-V method compared favorably with results from other permittivity methods such as gravimetric, injection and replacement tests. The ratio of effective porosity to porosity was 85 - 92 %, when FDR-V was used. This value compared favourably with 90 %, which has been usually quoted in previous studies. Considering the convenience and its applicability, the EDR-V permittivity holds a great potential in porous media and contaminant transport studies.

• KIPS Transactions on Computer and Communication Systems
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• v.2 no.12
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• pp.533-540
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• 2013

Anonymity is the one of main reasons for substantial improvement of Internet. It encourages various users to express their opinion freely and helps Internet based distributed systems vitalize. But, anonymity can cause unexpected threats because personal information of an online user is hidden. Especially, distributed systems are threatened by Sybil attack, where one malicious user creates and manages multiple fake online identities. To prevent Sybil attack, the traditional solutions include increasing the complexity of identity generation and mapping online identities to real-world identities. But, even though the high complexity of identity generation increases the generation cost of Sybil identities, eventually they are generated and there is no further way to suppress their activity. Also, the mapping between online identities and real identities may cause high possibility of losing anonymity. Recently, some methods using online social network to prevent Sybil attack are researched. In this paper, a new method is proposed for extracting a user's system-wide Sybil-resistant trust value by using the properties embedded in online social network graphs. The proposed method can be categorized into 3 types based on sampling and decision strategies. By using graphs sampled from Facebook, the performance of the 3 types of the proposed method is evaluated. Moreover, the impact of Sybil attack on nodes with different characteristics is evaluated in order to understand the behavior of Sybil attack.

• Composites Research
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• v.34 no.5
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• pp.290-295
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• 2021

The application of lightweight structural composites to automobiles as a solution in line with global fuel economy regulations to curb global warming is recognized as a megatrend. This study was conducted to provide a technical approach that can respond to the issue of replacing parts that require conductive properties to maximize the application of thermoplastic carbon fiber reinforced plastics (CFRPs), which are advantageous in terms of repair, disposal and recycling. By utilizing the properties of the low-viscosity polymerizable oligomer matrix, it was possible to prepare a thermoplastic CFRP exhibiting excellent impregnation properties while uniformly mixing the conductive filler. Various carbon-based conductive fillers such as carbon black, carbon nanotubes, graphene nanoplatelets, graphite, and pitch-based carbon fibers were filled up to the maximum content, and electrical and thermal conductive properties of the fabricated composites were compared and studied. It was confirmed that the maximum incorporation of filler was the most important factor to control the conductive properties of the composites rather than the type or shape of the conductive carbon filler. Experimental results were observed in which it might be advantageous to apply a one-dimensional conductive carbon filler to improve electrical conductivity, whereas it might be advantageous to apply a two-dimensional conductive carbon filler to improve thermal conductivity. The results of this study can provide potential insight into the optimization of structural design for controlling the conductive properties of thermoplastic CFRPs.

• Tunnel and Underground Space
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• v.31 no.6
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• pp.469-479
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• 2021

As a material for preventing spalling of concrete, the effectiveness of PP fiber has already been confirmed. However, it is necessary to consider the maximum temperature that occurs during a fire, and to solve the mixing problem and the strength reduction problem that occur depending on the mixing amount. In this study, the fire resistance performance of tunnel segment linings according to the PP fiber content and air volume under the RABT fire scenario was investigated. As a result, no spalling or cross-sectional loss occurred in all test specimens, and when the PP fiber content was small, the maximum temperature was relatively high and the maximum temperature arrival time was also fast. On the other hand, no trend was found for the maximum temperature and arrival time according to the difference in air volume. In the internal temperature distribution results for the PP fiber mixing amount of 0.75, 1.0, 1.5, and 2.0 kg/m³, the results of 0.75 and 1.0 kg/m³ showed similar temperature distribution, and the results of 1.5 and 2.0 kg/m³ were similar. It was confirmed that the internal temperature distribution tends to decrease at the same depth when the amount of PP fiber mixed is large, and it was confirmed that a remarkable difference occurred from the results of 1.0 kg/m³ and 1.5 kg/m³ of PP fiber mixed amounts.

• Journal of the Korean Society of Radiology
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• v.11 no.5
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• pp.297-302
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• 2017

Recently, building materials and air purification filters with eco-friendly charcoal are actively studying to reduce the concentration of radon gas in indoor air. In this study, radon reduction performance was assessed by designing and producing new panel-type activated carbon filter that can be handled more efficiently than conventional charcoal filters, which can reduce radon gas. For the fabrication of our panel-type activated carbon filter, first the pressed molding product after mixing activated carbon powder and polyurethane. Then, through diamond cutting, the activated carbon filter of 2 mm, 4 mm and 6 mm thickness were fabricated. To investigate the physical characteristics of the fabricated activated carbon filter, a surface area and flexural strength measurement was performed. In addition, to evaluate the reduction performance of radon gas in indoor, the radon concentration of before and after the filter passes from a constant amount of air flow using three acrylic chambers was measured, respectively. As a result, the surface area of the fabricated activated carbon was approximately $1,008m^2/g$ showing similar value to conventional products. Also, the flexural load was found to have three times higher value than the gypsum board with 435 N. Finally, the radon reduction efficiency from indoor gas improved as the thickness of the activated carbon increases, resulting in an excellent radon removal rate of more than 90 % in the 6 mm thick filter. From the experimental results, the panel-type activated carbon is considered to be available as an eco-friendly building material to reduce radon gas in an enclosed indoor environment.

• Culinary science and hospitality research
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• v.21 no.4
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• pp.16-28
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• 2015

The purpose of this study, as a part of developing a new french dressing, was to present the best conditions to make improved kiwi dressing, suitable for the tastes of modern people, the processing and cooking methods of different ratios of green kiwi and gold kiwi have been sought to develop a new type of dressing, then its antioxidant have been defined, and used for producing kiwi dressing. Each 150g of different Kiwi purees, made based on the most preferable combinations from the pre-test were used for kiwi dressing, and thereafter its quality characteristics, and physical properties were investigated, as well as a sensory test was conducted. The highest viscosity of kiwi dressing was test sample GD2, and in general that of combining both types of kiwis were higher than that of either single kiwi. The sugar content was decreased by changing the Gold kiwi portion(p<0.05). The chromaticity in general increased with increases in the Gold kiwi portion, and a-value(brightness) and b-value(redness) of sample GD1 were the highest by -2.75 and 17.50(p<0.05). From the acceptability test, the highest overall acceptability was the dressing sample combining Gold kiwi and Green kiwi at a ratio of 1:1. Based on the study results, it is expected that the dressing, made of kiwi puree, mixing Green kiwi and Gold kiwi by 1:1 ratio, and adding 130g of edible oil, 50g of onion, 40g of sugar, and 5g of salt, would improve the quality and overall acceptability of the dressing.

• Korean Journal of Ecology and Environment
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• v.57 no.1
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• pp.39-50
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• 2024

In ecosystems within limited resources, interspecific competition is inevitable, often leading to the competitive exclusion of inferior species. This study aims to provide foundational information for the conservation and restoration management of Microphysogobio rapidus by evaluating species' ecological response to biological factors within its habitat. To understand this relationship, we collected food web organisms from site where M. rapidus coexist with Microphysogobio yaluensis, a specie ecologically similar to M. rapidus, and evaluated the trophic levels (TL), isotopic niche space (INS), and the overlap of INS among fishes within the habitat using stable isotope analysis. Our analysis revealed that the M. rapidus exhibited a higher TL than M. yaluensis, with TL of 2.6 and 2.4, respectively. M. yaluensis exhibited a broad INS, significantly influencing the feeding characteristics of most fish. Conversely, M. rapidus showed a narrow INS and asymmetric feeding relationships with other species, in habitats with high competition levels. This feeding characteristics of M. rapidus indicate that the increase in competitors sharing the similar resources lead to a decrease in available resources and, consequently, is expected to result in a decrease in their density.