• Journal of Microbiology and Biotechnology
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• v.30 no.9
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• pp.1310-1320
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• 2020

Low-quality soil for land reuse is a crucial problem in vegetation quality and especially to waste disposal sites in mining areas. It is necessary to find suitable materials to improve the soil quality and especially to increase soil microbial diversity and activity. In this study, pot experiments were conducted to investigate the effect of a mixed material of humic acid, super absorbent polymer and biochar on low-quality soil indexes and the microbial community response. The indexes included soil physicochemical properties and the corresponding plant growth. The results showed that the mixed material could improve chemical properties and physical structure of soil by increasing the bulk density, porosity, macro aggregate, and promote the mineralization of nutrient elements in soil. The best performance was achieved by adding 3 g·kg^-1 super absorbent polymer, 3 g·kg^-1 humic acid, and 10 g·kg^-1 biochar to soil with plant total nitrogen, dry weight and height increased by 85.18%, 266.41% and 74.06%, respectively. Physicochemical properties caused changes in soil microbial diversity. Acidobacteria, Bacteroidetes, Chloroflexi, Cyanobacteria, Firmicutes, Nitrospirae, Planctomycetes, and Proteobacteria were significantly positively correlated with most of the physical, chemical and plant indicators. Actinobacteria and Armatimonadetes were significantly negatively correlated with most measurement factors. Therefore, this study can contribute to improving the understanding of low-quality soil and how it affects soil microbial functions and sustainability.

• International Journal of Concrete Structures and Materials
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• v.2 no.1
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• pp.35-39
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• 2008

This experimental study examines the applicability of polymer mortar permanent forms using a methyl methacrylate (MMA) solution of waste expanded polystyrene (EPS) to develop effective recycling processes for the EPS, referring to the flexural behavior of a polymer-impregnated mortar permanent form with almost the same performance as commercial products. An MMA solution of EPS is prepared by dissolving EPS in MMA, and unreinforced and steel fiber-reinforced polymer mortars are mixed using the EPS-MMA-based solution as a liquid resin or binder. Polymer mortar permanent forms (PMPFs) using the EPS-MMA-based polymer mortars without and with steel fiber and crimped wire cloth reinforcements and steel fiber-reinforced polymer-impregnated mortar permanent form (PIMPF) are prepared on trial, and tested for flexural behavior under four-point (third-point) loading. The EPS-MMAbased PMPFs are more ductile than the PIMPF, and have a high load-bearing capacity. Consequently, they can replace PIMPF in practical applications.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.791-794
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• 1999

Exact estimation of cement content in a hardened concrete can provide useful data to evaluate the quality and strength of the concrete and might be used to inspect the quality of precast concrete secondary products. Observation obtained in this research included : (1) the volume of coarse aggregate in the hardened concrete measured by the area comparison method has a high accuracy ; (2) the cement content in the mortar and the X-ray intensity of Ca-K$\alpha$ have a correlation factor of 0.96 ; (3) the cement content in the ready mixed concrete was estimated with high accuracy such as correlation factor of 0.99 and standard deviation of 0.64.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.1083-1088
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• 2001

To do performance evaluations about inorganic permanent form mixed in admixture(fly ash, silica fume) and after placed concrete, it is examined reinforcement materials in the permanent form from shear strength, bond strength and flexural strength tests. In this study, permanent form was inserted with reinforcement metal fitting is strength-tested in several method. The result of this study is belows. ⑴ In bond strength test, Most specimens are satisfied with criterion-6 kgf/$cm^{2}$ ⑵ Irrelative with the inserted metal fitting's shape, unevenness and aggregate, Permanent form and after placed concrete have good condition in the shear strength test. ⑶ In flexural test, there is no drop out of permanent form. Most cracks are located in nearby the strain point

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.317-322
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• 2001

This paper investigates the influence of fine aggregates on bleeding of concrete. According to test results, as water content decreases, crushed sand content increases, fluidity shows decline tendency. As for aggregates kinds, concrete using sea sand shows most fluidity loss among the tested results. Compressive strength gains highly when crushed sand is used. As for bleeding of concrete, bleeding shows decline tendency because of increasing in powder content and filling effect of voids. Bleeding amount is in a decreasing order of magnitude for concretes made with the following aggregates: sea sand, river sand, and crushed sand. Accordingly, crushed sand mixed with river sand and sea sand with certain proportion enable to reduce bleeding and enhance strength.

• Journal of the Korean Applied Science and Technology
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• v.13 no.3
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• pp.43-49
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• 1996

Metachromatic properties of admixture of thionine and methylene blue(MB) in aqueous solution and phospholipid bilayer membrane have been studied by absorption spectroscopy. When thionine and MB were mixed, new coaggregate has been formed because of MB was redistributed to thionine aggregate. In phosphlipid bilayer membrane system, the highly concentrated thionine was easily formed the coaggregation with MB moiety independent of MB concentration, and absorption band of admixture were more transferred to short wavelength than aqueous system. In monomeric thionine concentration, the coaggregation band was observed at the middle wavelength between the site of monomeric thionine and the site of dimeric MB in the presence of lipid bilayer membrane.

• Journal of the Korean Operations Research and Management Science Society
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• v.26 no.1
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• pp.33-44
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• 2001

In this paper, we address a problem of traffic grooming and wavelength routing in all optical WDM ring networks. Given a traffic demand for each node pair, we should aggregate the traffic onto lightpaths between pairs of nodes to transport the demand, and set up the routing path for each lightpath with minimum number of wavelengths to be assigned to lightpaths. In this paper, we formulate our problem as a mixed Integer Programming model. Owing to the problem complexity, it is hard to find an optimal solution for our problem. hence, we develop a heuristic algorithm to solve our problem efficiently. From the computational experiments, we can find the proposed heuristic is very satisfactory in both the computation time and the solution quality generated.

• Journal of Environmental Science International
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• v.18 no.9
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• pp.993-1000
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• 2009

The development of a new type of soil-cement concrete pavement using volcaniclastic is the main purpose of this study. Various mixture ratios, specimens' penetration resistance, time of setting, slump flow of fleshly mixed concrete, compressive strength and color characteristics of hardened concrete were studied. It was concluded that the optimum weight ratio of cement:volcaniclastic to produce good properties of soil-cement concrete is 1:3 and the use of volcaniclastic as main aggregate can improve the concrete surface color that is warm earth-tone road color. Therefore, commercial development for soil-cement concrete pavement using volcaniclastic is highly promising.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.52-57
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• 1999

The aimed of this study is to analyze the qualities of foundry waste sand and the basic physic of the concrete mixed with the foundry waste sand, as a way of study for reusing the foundry waste sand disused in the foundry as the fine aggregate for concrete. According to the experimental results, the foundry waste sand is composed of silica ore whose main ingredient is SiO2 and doesn't produce harmful objects of hydration reaction, and the fluidity of concrete shows a decline with the increase of replacement ratio of foundry waste sand, and the compress strength, the tensile strength, the elastic modulus of concrete containing foundry waste sand are improved at the replacement rate of 25%.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.29-32
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• 2006

The techniques related to ultra-high strength concrete(UHSC) became the key issue in recent days since requirements of the high-rise building which story is over than 100 gradually increases. Therefore, for the development of 150MPa UHSC this research is generally categorized by 4 parts: development of pre-mixed binders, evaluation for the fire performance of coarse aggregate, optimization of the mixture proportion, and mock-up test. Finally, based on the optimized mixture and its laboratory tests, mock-up test for wall and column specimens were carried out to simulate and evaluate the UHSC in real situation. The mechanical properties of core specimens were compared with the cylinder specimens made in laboratory. For instance, it showed the reasonable the results that the strength at the age of 91 days is 183MPa.