• Journal of Soil and Groundwater Environment
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• v.18 no.7
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• pp.81-89
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• 2013

Concerns have been raised over the impact of nano materials on soil and groundwater environment with the increasing attention to the potential applications of carbon nano materials in various fields. Particularly, carbon nano materials introduced into water environment readily make complexes with humic acid (HA) due to their hydrophobic nature, so there have been increasing numbers of studies on the interaction between HA and carbon nano materials. In this study, we investigated the solubility of HA and multiwalled carbon nanotubes (MWCNT) in three different surfactant solutions of sodium dodecyl sulfate (SDS), Brij 30 and Triton X-100, and evaluated whether the HA can be effectively desorbed from the surface of MWCNT by surfactant. The objective of this study was to determine the optimal adsorption condition for HA to MWCNT. Futhermore, sodium dodecyl sulfate (SDS), Brij 30, Triton X-100 were used to elucidate the effect of desorption and separation on adsorbed HA on MWCNT. As a result, HA solution with 12.7 mg of total organic carbon (TOC) and 5 mg of MWCNT showed the highest adsorption capacity at pH 3 reacted for 72 hrs. Weight solubilizing ratio (WSR) of surfactants on HA and MWCNT was calculated. HA had approximately 2 times lower adsorption capacity for the applied three surfactants compared to those of MWCNT, implying that the desorption of HA may occur from the HA/MWCNT complex. According to the results of adsorption isotherm and weight solubilizing ratio (WSR), the most effective surfactants was the SDS 1% soluiton, showing 53.63% desorption of HA at pH 3.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.6
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• pp.928-935
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• 2012

World Agriculture faces daunting challenges in feeding the growing population today. Reduction in arable land extent due to numerous reasons threatens achievement of food and nutritional security. Under this back ground, agricultural use of acidic soils, which account for approximately 40 % of the world arable lands is of utmost important. However, due to aluminum (Al) toxicity and low available phosphorous (P) content, crop production in acidic soils is restricted. Citrus, in this context, gains worldwide recognition as a crop adapted to harsh environments. The present paper reviewed Al toxicity and possible toxicity alleviation tactics in citrus. As reported for many other crops, inhibition of root elongation, photosynthesis and growth is experienced in citrus also due to Al toxicity. Focusing at toxicity alleviation, interaction between boron (B) and Al as well as phosphorus and Al has been discussed intensively. Al toxicity in citrus could be alleviated by P through increasing immobilization of Al in roots and P level in shoots rather than through increasing organic acid secretion, which has been widely reported in other crops. Boron-induced changes in Al speciation and/or sub-cellular compartmentation has also been suggested in amelioration of root inhibition in citrus. Despite the species-dependent manner of response to Al toxicity, many commercially important citrus species can be grown successfully in acidic soils, provided toxicity alleviation Agro-biological tactics such as addition of phosphorous fertilizers are used properly.

• Structural Engineering and Mechanics
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• v.52 no.6
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• pp.1069-1084
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• 2014

The long-term performance of plates resting on viscoelastic foundations is a major concern in the analysis of soil-structure interaction. As a powerful mathematical tool, fractional calculus may address these plate-on-foundation problems. In this paper, a fractionalized Zener model is proposed to study the time-dependent behavior of a uniformly loaded rectangular thin foundation plate. By use of the viscoelastic-elastic correspondence principle and the Laplace transforms, the analytical solutions were obtained in terms of the Mittag-Leffler function. Through the analysis of a numerical example, the calculated plate deflection, bending moment and foundation reaction were compared to those from ideal elastic and standard viscoelastic models. It is found that the upper and lower bound solutions of the plate response estimated by the proposed model can be determined using the elastic model. Based on a parametric study, the impacts of model parameters on the long-term performance of a foundation plate were systematically investigated. The results show that the two spring stiffnesses govern the upper and lower bound solutions of the plate response. By varying the values of the fractional differential order and the coefficient of viscosity, the time-dependent behavior of a foundation plate can be accurately captured. The fractional differential order seems to be dependent on the mechanical properties of the ground soil. A sandy foundation will have a small fractional differential order while in order to simulate the creeping of clay foundation, a larger fractional differential order value is needed. The fractionalized Zener model is capable of accounting for the primary and secondary consolidation processes of the foundation soil and can be used to predict the plate performance over many decades of time.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.3
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• pp.241-248
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• 1987

The theoretical backgrounds of the several methods were surveyed and reviewed to fin out the adequate one to determine equivalent modal damping values in solving the dynamic problem of soil-structure interaction by mode superposition method. Furthermore the rigorous damping matrix of equation of motion was obtained through component mode synthesis technique and used in direct integration of the equation. The analytical results by direct integration method were compared with those of mode superposition approach using the various sets of equivalent modal damping values calculated by the methods to be reviewed. Two types of superstructures and four kinds of subsurface conditions were considered and combined to make soil-structure coupled models. It was realized that dissipating energy method gives the equivalent modal damping values which lead the most similar results to direct integration ones. In case of fixed base, the responses of all methods except stiffness weighted approach are almost equal to those of direct integration method.

• Journal of the Korean Society of Clothing and Textiles
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• v.18 no.4
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• pp.524-535
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• 1994

The interaction and detergency between oily soil and surfactant solution were studied Samples used were tristearin, tripalmitin and their mixture as a triglyceride, myristic acid as a fatty acid and sodium dodecyl sulfate (SDS) as surfactant. The results were as follows: 1. The mixtures of model oily soils were formed of eutectic point and their melting point were lower than them of individual oily soils. 2. The formation of liquid crystalline (LC) phase was recognized in the triangle phase diagram for SDS~ water~model oily soil system. The areas of LC phase region were in the order of SHS~ water~myristir acid> SDS~ water~mixture of tristearin, tripalmitin and myristic acid (TS/TP/M)>SDS~water~mixture of tristearin and tripalmitin (TS/TP) 3. The LC phase region expanded to wide concentration range of SDS solution and high concentration range of model oily soil with increasing temperature. Particularity, the LC phase region expanded highly at $30~40^{\circ}C$ but when the temperature was elevated above $40^{\circ}C$, expanding tendency decreased. 4. In the system of myristic acid and TS/TP/M contacted with SDS solution, the LC phase was already formed at $28^{\circ}C$ and the region of the LC phase were expanded with increasing temperature. But in the system of TS/TP contacted with SDS solution, the LC phase was not formed in whole experiment temperature. 5. The detergency of myristic acid was very high ann it was recognized that the formation of the LC phase played an important role in the detergency. The detergency of TS/TP was very for low, but when TS/TF was mixed with myristic acid, the detergency of TS/TP increased. It is supposed that the LC phase was formed butween SDS solution and myristic acid promoted to penetration of SDS solution into the inner parts of TS/TP.

• Journal of the Korean Geotechnical Society
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• v.28 no.10
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• pp.27-40
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• 2012

In the design of a piled raft, the axial resistance is offered by the raft and group piles acting on the same supporting ground soils. As a consequence, pile - soil - raft and pile - soil interactions, occurring by stress and displacement duplication with pile and raft loading conditions, act as a key element changing resistances of the raft and group piles. In this study, a series of centrifuge model tests have been performed to compare the axial behavior of group pile and raft with that of a piled raft (having 16 component piles with an array of $4{\times}4$) in sands with different relative densities. The test results revealed that the increase of settlement resistance occurs separately with settlement by group pile - soil interactions. The axial resistance of group piles (at piled raft) increases by group pile - raft (pile cap) interactions and that of raft (at piled raft) decreases by group pile - raft (pile cap) interactions.

• Journal of the Korean Geotechnical Society
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• v.29 no.3
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• pp.29-40
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• 2013

Seismic response of single degree of freedom system supported by shallow foundation was analyzed by using nonlinear explicit finite difference element code. Numerical analysis results were verified with dynamic centrifuge test results of the same soil profile and structural dimensions with the numerical analysis model at a centrifugal acceleration of 20 g. Differences between the analysis and the test results induced by the boundary conditions of control points can be reduced by adding additional local damping to the natural born cyclic hysteretic damping of the soil strata. The analysis results show good agreement with the test results in terms of both time histories and response spectra. Thus, it can be concluded that the nonlinear explicit finite difference element code will be a useful technique for estimating seismic residual displacement, earthpressure etc. which are difficult to measure during laboratory tests and real earthquake.

• Journal of the Korean Geotechnical Society
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• v.34 no.7
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• pp.51-58
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• 2018

In this study a series of centrifuge tests were carried out in dry sand to analyze the comparison of lateral pile behavior for static loading and dynamic loading condition. In case of static loading condition, the lateral displacement was applied up to 50% of pile diameter by deflection control method. And the input sine wave of 0.1 g~0.4 g amplitude and 1 Hz frequency was applied at the base of the soil box using shaking table for dynamic loading condition. From comparison of experimental static p-y curve obtained from static loading tests with API p-y curves, API p-y curves can predict well within 20% error the ultimate subgrade reaction force of static loading condition. The ultimate subgrade reaction force of experimental dynamic p-y curve is 5 times larger than that of API p-y curves and experimental static p-y curves. Therefore, pseudo-static analysis applied to existing p-y curve for seismic design could greatly underestimate the soil resistance at non-linear domain and cause overly conservative design.

• Journal of Korean Society of Forest Science
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• v.59 no.1
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• pp.121-142
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• 1983

Recently mycorrhizal research has been one of the most fast-growing research areas in modern plant science and microbiology. The application potential of mycorrhizal techniques to agriculture and forestry is enormous in view of the ubiquitous nature of mycorrhizae and known benefits of mycorrhizae to host plants. Unfortunately, very few scientists in Korea are currently involved in mycorrhizal research. When a team of American plant pathologists visited Korea in September 1982 to participate in the Korea-U.S.A. Joint Seminar on Forest Diseases and Insect Pests, they were surprised by the principal author's statement that there was no single research project on mycorrhizae sponsored by Korean government or any scientific institutions. The author initiated a few years ago a research project on the ecology of tree mycorrhizae with a foreign financial support. Major areas of interest were survey of ectomycorrhizae in relation to soil fertility, taxonomic distribution of mycorrhizae among woody plants, identification of ectomycorrhizal fungi, and growth response of woody plants to artificial inoculation. In spite of the enormous application potential of mycorrhizae to agronomic plants, the subject of mycorrhizae has not been recognized by Korean agronomists, foresters or pathologists. The purpose of this review rather written in Korean is to introduce the techniques of mycorrhizal research to Korean scientists and to urge them to participate in challenging new scientific field which might bring us a remarkable increase in crop productivity and tree growth through manipulation of this unique symbiosis. In this review, following topics were discussed in the same order: introduction; brief history of mycorrhizal research; morphology and classification of mycorrhizae; distribution of mycorrhizae in plant kingdom and in soil profile; physiology of mycorrhizae (functions, mineral nutrition, mycorrhizal formation); interaction of mycorrhizae with soil-born plant pathogens. mycorrhizae in nitrogen-fixing plants; application of mycorrhizal techniques to nursery practices (isolation, culture, inoculation, and response); prospect in the future.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.3
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• pp.1053-1058
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• 2010

Infinite element approach has been widely used to analysis soil-structure interaction, in which the soil domain is treated as infinite domain. However, most of the developed infinite element has been formulated in the frequency domain rather than the time domain to include the frequency contents of the earthquake or vibration wave. Due to that, those approaches have a critical limitation which is restricted to the linear elastic analysis. To main objective of this research is to develop the infinite element in the time domain to cooperate the inelastic soil and structure behavior. Developed infinite element is verified with the results of finite element analysis modeled in large domain. The nonlinear analysis also conducted to demonstrate the application of developed infinite element. Hence, based on above-mentioned statements, it can be concluded that the propose approach would assist for structure-seismic design.