• Journal of the Korean Geosynthetics Society
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• v.4 no.2
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• pp.11-18
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• 2005

A pilot scale filed model test and 2-D numerical analysis was conducted to evaluate the effectiveness of constructing a geogrid-reinforced and pile-supported embankment system over soft ground to reduce differential settlement, and the results are presented hearin. Three-by-three pile groups with varying the space between pile were driven into a layer of soft marine clay and a layer of geogrid was used as reinforcement over each pile group. 2-D numerical analysis has been conducted by using the FLAC-2D(Fast Lagrangian Analysis of Continua) program for same condition of field model test. The settlement, vertical stress, and strain of geogrid due to the construction of embankment were measured at various locations. Based on the field model test and numerical analysis results, pile reinforcement generated the soil arching at the midspan of pile cap and the geogrid reinforcement helps reduce the differential settlement of the soft ground by tensile strength of geogrid. Also for $D/b{\geq}6.0$, the effectiveness of geogrid reinforcement in reducing settlement is negligible.

• Journal of the Korean Geotechnical Society
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• v.20 no.5
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• pp.99-107
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• 2004

Anisotropic characteristics of deformation are important to understand the particular behavior in the pre-failure state of soils. Recent experiments show that cross-anisotropic moduli of granular soils can be expressed by functions of normal stresses in the corresponding directions, which is closely linked to micromechanical characteristics of particles. Granular soils are composed of a number of particles so that the force-displacement relationship at each contact point governs the macroscopic stress-strain relationship. Therefore, the micromechanical approach in which the deformation of granular soils is regarded as a mutual interaction between particle contacts is one of the best ways to investigate the anisotropic elastic deformation of soils. In this study, a numerical program based on the theory of micromechanics is developed. Generalized contact model for the irregular contact surface of soil particles is adopted to represent the force-displacement relationship in each contact point far the realistic prediction of anisotropic moduli. To evaluate the model parameters, a set of analytical solutions of anisotropic elastic moduli is derived in the isotropic stress condition. A detailed procedure to determine the model parameters is proposed with emphasis on the practical applicability of micromechanical program to analyze the elastic behavior of the granular soils.

• KSBB Journal
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• v.14 no.1
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• pp.103-108
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• 1999

A bacterium having strong fibrinolytic activity, S7-16 strain, was isolated from soil. The isolated bacterium was identified and named as Bacillus sp. S7-16. The optimal composition of the medium for the production of fibrinolytic enzyme by Bacillus sp. S7-16 was 0.5%(w/v) polypeptone, 0.5%(w/v) yeast extract, 0.3%(w/v) NaCl, 0.1% (w/v) $KH_2PO_4,\;0.3%(w/v)\;K_2PHO_4,\;and\;0.01%(w/v)\;MgSO_4{\cdot}7H_2O$. The optimal temperature and initial pH of the medium for the production of the enzyme were $35^{\circ}C$ and 7.0, respectively. The maximum production of the fibrinolytic enzyme was obtained after 24 hours of the incubation. Under the above conditions, the culture supernatant had strong fibrinolytic activity. Within pH4~11, the crude fibrinolytic enzyme was stable. The enzyme was stable up to $50^{\circ}C$. The optimum pH and temperature for the enzyme activity were around 7.5 and $40^{\circ}C$, respectively.

• Journal of Biosystems Engineering
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• v.36 no.2
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• pp.79-88
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• 2011

The purpose of this study was to analyze power requirement of an agricultural tractor by major field operations. First a survey was conducted to obtain annual usage ratio of agricultural tractor by field operation. Plowing, rotary tillage, and loader operations were selected as major field operations of agricultural tractor. Second, a power measurement system was constructed with strain-gauge sensors to measure torque of four driving axles and a PTO axle, speed sensors to measure rotational speed of the driving axles and an engine shaft, pressure sensors to measure pressure of hydraulic pumps, an I/O interface to acquire the sensor signals, and an embedded system to calculate power requirement. Third, the major field operations were experimented under fields with different soil conditions following planned operation paths. Power requirement was analyzed during the total operation period consisted of actual operation period (plowing, rotary tillage, and loader operations) and period before and after the actual operation (3-point hitch operating, forward and reverse driving, braking, and steering). Power requirement of tractor major components such as driving axle part, PTO part, main hydraulic part, and auxiliary hydraulic part were measured and calculated to determine usage ratio of agricultural tractor power. Results of averaged power requirement for actual field operation and total operation were 23.1 and 17.5 kW, 24.6 and 19.1 kW, and 14.9 and 8.9 kW, respectively, for plowing, rotary tillage, and loader operations. The results showed that rotary tillage required the greatest power among the operations. Averaged power requirement of driving axles, PTO axle, main hydraulic part, and auxiliary part during the actual field operation were 8.1, 7.8, 3.4, and 1.5 kW, respectively, and the total requirement power was about 70 % (20.8 kW) of the rated power. Averaged power requirement of driving axles, PTO axle, main hydraulic, and auxiliary hydraulic for the total operation period were 6.5, 6.0, 2.1, 0.9 kW, respectively, and total requirement power was about 52 % (15.5 kW) of the rated power. Driving axles required the greatest amount of power among the components.

• BMB Reports
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• v.37 no.3
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• pp.282-291
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• 2004

Phytases catalyze the release of phosphate from phytic acid. Phytase-producing microorganisms were selected by culturing the soil extracts on agar plates containing phytic acid. Two hundred colonies that exhibited potential phytase activity were selected for further study. The colony showing the highest phytase activity was identified as Aspergillus niger and designated strain 113. The phytase gene from A. niger 113 (phyI1) was isolated, cloned, and characterized. The nucleotide and deduced amino acid sequence identity between phyI1 and phyA from NRRL3135 were 90% and 98%, respectively. The identity between phyI1 and phyA from SK-57 was 89% and 96%. A synthetic phytase gene, phyI1s, was synthesized by successive PCR and transformed into the yeast expression vector carrying a signal peptide that was designed and synthesized using P. pastoris biased codon. For the phytase expression and secretion, the construct was integrated into the genome of P. pastoris by homologous recombination. Over-expressing strains were selected and fermented. It was discovered that ~4.2 g phytase could be purified from one liter of culture fluid. The activity of the resulting phytase was 9.5 U/mg. Due to the heavy glycosylation, the expressed phytase varied in size (120, 95, 85, and 64 kDa), but could be deglycosylated to a homogeneous 64 kDa species. An enzymatic kinetics analysis showed that the phytase had two pH optima (pH 2.0 and pH 5.0) and an optimum temperature of $60^{\circ}C$.

• Parasites, Hosts and Diseases
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• v.30 no.4
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• pp.289-298
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• 1992

Acanthamoeba sap., free-living amoebae inhabited in moist soil, pond, freshwater, sewage, atmosphere and swimming pool, may be causative protozoa of the fatal primary amoebic meningoence-phalitis in experimental animals and humans. In this study, Acar,thamoeba spry. , including Acan. thamoeba sp. YM-4 (isolated strain from Korea) had been compared by the two-dimensional electrophoresis and hybridoma technique as well as the difference of morphological characteristics. Trophozoite of Acenthamoeba sp. YM-4 is usually uninucleate and show the hyaline filamentous projections (acanthopoda) . No aagellate stage observed. Cysts have two walls, the outer wall is nearly circular, but inner wall is oval or some irregular. As results of SDS-PAGE for Iysate of Acanthamoeba sp. VM-4, 16 major protein fractions are similiar to those of A. cuzbertsoni, but different to A. royreba and A. polyphaga. Findings of two-dimensional electrophoretic patterns of Acanthamceba sp. YM-4 are almost same to those of A. culberssoni, The isotope of monoclonal antibodies produced from McAY 6, McAY 7, McAY 8, McAY 13 and McAY 16 clones were IgGl, and McAY 10 and McAY 11 clones were IsM. As results of the cross-reactivity among various amoebae using ELISA with monoclonal antibodies, McAY 7 monoclonal antibody (molecular weight 43 kDa by EITB) was only reacted with Acanthamoeba sp. YM-4, but McAY 6 and McAY 10 monoclonal antibodies were reacted to A. cuzbertsoni as well as Acanthamoeba sp. YM-4.

• Microbiology and Biotechnology Letters
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• v.7 no.3
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• pp.135-140
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• 1979

A Streptomyces sp. strain AS-727 which was capable of producing penicillinase, was isolated from soil. The enzyme production was affected by the carbon and nitrogen sources added. Among them so far tested, glucose (or maltose) and sodium nitrate increased the enzyme production. And the amount of enzyme prodced reached maximum in 4 days cultivation. The optimla pH and temperature of the penicillinase was between pH 6.0 to 8.0 and 4$0^{\circ}C$ respectively. The stabel pH range of the enzyme was stable at 4$0^{\circ}C$, but it lost about 30％ and 40％ of the the activity respectively when it was treated at 6$0^{\circ}C$ and 8$0^{\circ}C$ for 60 minutes. The activity of the enzyme was inhibited by Z $n^{++}$, but A $g^{+}$, $Co^{++}$, $_Mn^{++}$, $Ca^{++}$, P $b^{++}$ did not affected enzyme activity. Peculiarly, the enzyme protein precipitated by freezing or addition of ammonium sulfate, urea, sodium chloride and some organic solvents as etanol, methanol, acetone was not dissolved in deionized water or any buffer solution.n.n.ion.n.n.

• Microbiology and Biotechnology Letters
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• v.29 no.3
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• pp.142-148
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• 2001

An indigenous antagonistic bacterium Bacillus sp. 7079 was isolated from a local soil sampled at Kyongju area in Korea . The strain has strong antagonistic ability which was originated from multifunctional mechanisms of chitinase and antibiotic and is a powerful antagonistic biocontrol agent against red-pepper rotting fungus Phytophthora capsici and Wilt fungus Fusarium oxysporum. The chitinase might degrade the cell wasll for Fusarium species. The selected Bacilus sp. 7079 was identified as a Bacillus amyloliquefaciens 7079. The maximal production of the chitinase from B, amyloliquefaciens 7079 were obtained in chitin-yeast extract medium containing 0.7%, $K_2$$HPO_4$, $0.2KH_2$$PO_4$, 0.1% ($NH_4$)$_2$$SO_4$, 0.05% sodium cirate, 0.01% $MgSO_4$$7H_2$O, 0.1% yeast extract and 0.1% colloidal chitin after cultivation of 3 days at pH 7.0 and $30^{\circ}C$. The best carbon and nitrogen sources for the production of the chitinase from B amyloliquefaciens 7079 were determined to be 0.1% colloi- dal chitin and 0.15% proteose peptone NO 3 respectively, The antagonistic activity of B amyloliquefaciens 7079 was confirmed using P. capsici by in vivo pot test with red-pepper plant.

• Journal of Microbiology and Biotechnology
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• v.15 no.6
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• pp.1286-1298
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• 2005

The genus Paenibacillus is a new group of bacilli separated from the genus Bacillus, and most of species have been isolated from soil. In the present study, we collected 450 spore-forming bacilli from the roots of winter crops, such as barley, wheat, onion, green onion, and Chinese cabbage, which were cultivated in the southern part of Korea. Among these 450 isolates, 104 Paenibacillus-like isolates were selected, based on their colony shape, odor, color, and endospore morphology, and 41 isolates were then finally identified as Paenibacillus spp. by 16S rDNA sequencing. Among the 41 Paenibacillus isolates, 23 were classified as P. polymyxa, a type species of the genus Paenibacillus, based on comparison of the 16S rDNA sequences with those of 32 type strains of the genus Paenibacillus from the GenBank database. Thirty-five isolates among the 41 Paenibacillus isolates exhibited antagonistic activity towards plant fungal and bacterial pathogens, whereas 24 isolates had a significant growth-enhancing effect on cucumber seedlings, when applied to the seeds. An assessment of the root-colonization capacity under gnotobiotic conditions revealed that all 41 isolates were able to colonize cucumber roots without any significant difference. Twenty-one of the Paenibacillus isolates were shown to contain the nifH gene, which is an indicator of $N_{2}$ fixation. However, the other 20 isolates, including the reference strain E681, did not incorporate the nifH gene. To investigate the diversity of the isolates, a BOX-PCR was performed, and the resulting electrophoresis patterns allowed the 41 Paenibacillus isolates to be divided into three groups (Groups A, B, and C). One group included Paenibacillus strains isolated mainly from barley or wheat, whereas the other two groups contained strains isolated from diverse plant samples. Accordingly, the present results showed that the Paenibacillus isolates collected from the rhizosphere of winter crops were diverse in their biological and genetic characteristics, and they are good candidates for further application studies.

• Microbiology and Biotechnology Letters
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• v.44 no.3
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• pp.333-340
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• 2016

An alkaline protease was purified and characterized from an alkalophilic microorganism, Bacillus sp. DK1122, isolated from soil in central Korea. The optimum temperature and pH for the growth of the producer strain were 40℃ and pH 9.0, respectively. The protease was produced aerobically at 40℃ after 24 h incubation in modified Horikoshi I medium (pH 9.0) containing 0.5% (w/v) glucose, 0.8% (w/v) yeast extract, 0.5% (w/v) polypeptone, 0.1% (w/v) K₂HPO₄, 0.02% (w/v) MgSO₄·7H₂O, 1% (w/v) Na₂CO₃, and 3% (w/v) NaCl. The alkaline protease was purified by 70% ammonium sulfate precipitation of the culture supernatant of Bacillus sp. DK1122, followed by CM-Sepharose chromatography. The molecular weight of the enzyme was estimated to be 27 kDa on the basis of SDS-PAGE. The optimum temperature and pH for the protease activity were 60℃ and pH 9.0, respectively. Addition of CaCl₂ increased the thermal stability of the purified protease, where 90% of protease activity was retained at 60℃ for up to 3 h. Consequently, it is expected that the alkaline protease from this study, exhibiting stability at pH 7–9 and 60℃, may be promising for application in the food and detergent industries.