• Journal of Environmental Science International
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• v.18 no.11
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• pp.1261-1270
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• 2009

Fifty hydrocarbon-metabolizing microorganisms were isolated from soil samples polluted by the petroleum oils in Gamman-dong, Busan. Among them, strain 2-3A, showing strong emulsification activity, was selected by oil film-collapsing method. This bacterium was identified as Acinetobacter sp. and designated as Acinetobacter sp. 2-3A. The optimum temperature and pH on the growth of Acinetobacter sp. 2-3A were $25^{\circ}C$ and pH 7.0, respectively. The carbon and nitrogen sources for the most effective emulsification activity were 3.0% olive oil and 0.5% peptone, respectively. The 0.15% potassium phosphate was the most effective emulsification activity as a phosphate source. The optimum emulsification activity condition was $20^{\circ}C$, pH 7.0, and 2.0% NaCl. The optimum time for the best production of biosurfactant was 27 hrs. The emulsification stability was maintained at the temperature range from $4^{\circ}C$ to $100^{\circ}C$, pH range from 6.0 to 10.0, and NaCl range from 0% to 10%. For the oil resolvability of the biosurfactant, the residual oils were investigated by gas chromatography. As a result, it was verified that the biosurfactant decreased and decomposed crude oils from $_nC_{10}$ to $_nC_{32}$.

• Research in Plant Disease
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• v.8 no.4
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• pp.234-238
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• 2002

In vitro and in vivo activities of a biocontrol agent, Bacillus stearothermophilus strain YC4194 was evaluated for the control of Pythium damping-off of cucumber. B. stearothermophilus YC4194 inhibited germination of cystospores and formation of zoosporangia of Pythium aphanidermatum in vitro. Incorporation of a bentonite and talc based formulation(10$^{9}$ cfu/g) of B. stearothermophilus YC4194 to the nursery soils (10 g/ι soil) resulted In a significant (p=0.01) reduction in the disease severity of cucumber damping-off after inoculation with P. aphanidermatum. The control efficacy of B. stearothermophilus YC4194 formulation was not different from that of the fungicides, dimethomorph, metalaxyl, ethaboxam. When the cucumber plants were transplanted to the soil inoculated with P. aphanidermatum zoospores, the B. stearothermophilus YC4194 maintained the high population density in rhizosphere soil upto 10$^{7}$ cfu/g until 15 days after treatment.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.2
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• pp.177-189
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• 1992

This paper aims at developing a finite element program to predict undrained behavior of granular soil by using elasto-plastic constitutive model. A computer program developed by authors based on Christian's techniques for undrained behaviour of the soil has been employed coupled with Lade's single work-hardening model. Modification of the program for drained behaviour, considering restraint of volumetric strain, makes it possible to analize the underained behaviour. To validate the newly developed program, comparison of results was performed between numerical values and experimental data for Baekma river sand as well as Sacrmento river sand studied by Seed and Lee. The program is evaluated to have high accuracy.

• Journal of Biosystems Engineering
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• v.14 no.4
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• pp.221-228
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• 1989

A data acquisition system was designed to measure the forces on a rolling coulter in three coordinated directions, angular velocity of the coulter and travel speed of a soil bin. The data acquisition system consisted of a dynamometer, speed transducers, a signal conditioner, an inter-face board, an Aim-65 microcomputer and a digital data recorder. Strain gages were attached on the surface of the dynamometer and connected to form three Wheatstone bridges, which measure the draft force, the vertical force and the side force on the coulter. An interaction among three dimensional forces was found during the calibration. A matrix procedure was used to correct the forces for this interaction. Rotary shaft encoders were mounted on the coulter and on the soil bin drive to measure the angular velocity of the coulter and the travel speed of the soil bin. The angular velocity and the travel speed were computed by counting the number of pulse signals from the rotary shaft encoders every 0.2 second. The digital signals from the rotary shaft encoders were connected to counters and the analog signals from the dynamometer, after passing through the signal conditioner, were connected to the A/D converter. The microcomputer programs, written in assembly language, were developed to read signals from the transducers, convert them to actual unit, display them upon request and record them on a sigital tape every 0.2 second.

• Advances in Computational Design
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• v.3 no.2
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• pp.201-212
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• 2018

Decrease in availability of suitable subbase and base course materials for highway construction leads to a search for economic method of converting locally available troublesome soil to suitable one for highway construction. Present study insights on evaluation of benefits of stabilization of subgrade soils in term of extension in service life (TBR) and layer thickness reduction (LTR). Laboratory investigation consisting of Atterberg limit, Compaction, California Bearing Ratio, unconfined compressive strength and triaxial shear strength tests were carried out on two types of soil for varying percentages of stabilizers. Vertical compressive strains at the top of unstabilized and stabilized subgrade soils were found out by elastoplastic finite element analysis using commercial software ANSYS. The values of vertical compressive strains at the top of unstabilized and stabilized subgrade, were further used to estimate layer thickness reduction or extension in service life of the pavement due to stabilization. Finite element modeling of the flexible pavement layered structure provides modern technology and sophisticated characterization of materials that can be accommodated in the analysis and enhances the reliability for the prediction of pavement response for improved design methodology. If the pavement section is kept same for unstabilized and stabilized subgrade soils, pavement resting on lime, fly ash and fiber stabilized subgrade soil B will have service life 2.84, 1.84 and 1.67 times than that of unstabilized pavement respectively. The flexible pavement resting on stabilized subgrade is beneficial in reducing the construction material. Actual savings would depend on the option exercised by the designer for reducing the thickness of an individual layer.

• Journal of the Korean Geosynthetics Society
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• v.16 no.2
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• pp.175-181
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• 2017

This paper presents the results of an investigation into the effect of forced temperature change cycles on physical and mechanical properties of sand and weathered granite soil. The effect of forced temperature change cycles on the particle arrangement and the thermal conductivity was first investigated. A series of triaxial compression tests on the soils were also performed to look into the effect of temperature change cycles on the stress-strain-strength behavior.

• Earthquakes and Structures
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• v.23 no.1
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• pp.101-113
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• 2022

A new type of fabricated subway station construction technology can effectively solve these problems. For a new type of metro structure form, it is necessary to clarify its mechanical properties, especially the seismic performance. A soil-structure elastoplastic finite element model is established to perform three-dimensional nonlinear dynamic time-history analysis based on the first fabricated station structure-Yuanjiadian station of Changchun Metro Line 2, China. Firstly, the nonlinear seismic response characteristics of the fabricated and cast-in-place subway stations under different seismic wave excitations are compared and analyzed. Then, a comprehensive analysis of several important parameters that may affect the seismic response of fabricated subway stations is given. The results show that the maximum plastic strain, the interlayer deformation, and the internal force of fabricated station structures are smaller than that of cast-in-place structure, which indicates that the fabricated station structure has good deformation coordination capability and mechanical properties. The seismic responses of fabricated stations were mainly affected by the soil-structure stiffness ratio, the soil inertia effect, and earthquake load conditions rarely mentioned in cast-in-place stations. The critical parameters have little effect on the interlayer deformation but significantly affect the joints' opening distance and contact stress, which can be used as the evaluation index of the seismic performance of fabricated station structures. The presented results can better understand the seismic responses and guide the seismic design of the fabricated station.

• Geomechanics and Engineering
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• v.32 no.6
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• pp.601-613
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• 2023

Low liquid limit silt, widely distributed in the middle and down reaches of Yellow River, has the disadvantages of poor grading, less clay content and poor colloidal activity. It is very easy to cause vehicle jumping at the bridge-embankment transition section when the low liquid limit silt used as the backfill at the abutment back. In this paper, a series of laboratory tests were carried out to study the physical and mechanical properties of the low liquid limit silt used as back filling. Ground granulated blast furnace slag (GGBFS) was excited by active MgO and hydrated lime to solidify silt as abutment backfill. The optimum ratio of firming agent and the compaction and mechanical properties of reinforced soil were revealed through compaction test and unconfined compressive strength (UCS) test. Scanning electron microscope (SEM) test was used to study the pore characteristics and hydration products of reinforced soil. 6% hydrated lime and alkali activated slag were used to solidify silt and fill the model of subgrade respectively. The pavement settlement regulation and soil internal stress-strain regulation of subgrade with different materials under uniformly distributed load were studied by model experiment. The effect of alkali activated slag curing agent on curing silt was verified. The research results can provide technical support for highway construction in silt area of the Yellow River alluvial plain.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.1
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• pp.106-114
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• 2006

Uses of geosynthetics as a reinforcing material for earth structures have ever increased due to their excellent economy. fine external appearance. and easy construction. In the current practice of geosynthetics. however, the lacks of the standardized method of evaluating the soil/geosynthetics friction properties and the inconsistency of conventional design methods develop confusion to the civil engineers. The purpose of site monitoring of the retaining wall reinforced by geogrids was to evaluate the applicability of existing design methods to, and performance of. CHAMSTONE wall system. Full scale field performance during and after construction was monitored by incorporating instrumentation including strain gauges on the geogrid and soil pressure cells. The difference of the reinforcing effects of geosynthetics embedded in the soil will be also investigated by comparing of the line and curve types of retaining wall reinforced by geogrids with block type facings.

• Journal of Microbiology and Biotechnology
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• v.3 no.1
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• pp.57-60
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• 1993

The herbicidal compound, 3D5 was isolated from the culture broth of strain 3D5, a soil isolate. Based on taxonomic studies, this culture was identified as Streptomyces sp. 3D5.