• 한국농공학회지
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• 제39권6호
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• pp.99-110
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• 1997

The study was conducted in order to investigate the basic geotechnical properties of sand-bentonite mixtures with the various bentonite contents. The results obtained are as follows : 1. Optimum moisture content of sand-bentonite mixtures was approximately 17.10~18.52% corresponding to the maximum dry density of 1.58~1 .64gf/$cm^3$. As the bentonite contents and curing peroid increased, both the maximum dry density and optimum moisture content of sand-bentonite mixtures increased. 2. The unconfined compressive strength of sand-bentonite mixtures increased as the increase of bentonite content, but it did not change along the curing period. 3. The sand-bentonite mixtures ruptured at 8~15% of the axial strain and the maxi-mum shearing stress was about O.7Okgf/$cm^2$. 4. According to the increase of bentonite content, the cohesion intercept and internal friction of the sand-bentonite mixtures increased slightly in the shear test, while the cohesion intercept increased largely, and the internal friction angle decreased largely in the triaxial test. 5. Both the initial void ratio and swelling of the sand-bentonite mixtures were very low with respect to the consolidation pressure increase. 6. The swelling and shrinkage of sand-bentonite mixtures increased slightly according to the increment of bentonite content.

• Geomechanics and Engineering
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• 제31권3호
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• pp.305-318
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• 2022

Permeable reactive barriers used for groundwater treatment require proper estimation of the reactive material behavior regarding the emplacement method. This study evaluates the dry emplacement of zeolite (clinoptilolite) to be used as a reactive material in the barrier by carrying out several geotechnical laboratory tests. Dry zeolite samples, exhibited higher wetting-induced compression strains at the higher vertical stresses, up to 12% at 400 kN/m². The swelling potential was observed to be limited with a 3.5 swell index and less than 1% free swelling strain. Direct shear tests revealed that inundation reduces the shear strength of a dry zeolite column by a maximum of 10%. Falling head permeability tests indicate decreasing permeability values with increasing the vertical effective stress. Regarding self-loading and inundation, the porosity along the zeolite column was calculated using a proposed 1D numerical model to predict the permeability with depth considering the laboratory tests. The calculated discharge efficiency was significantly decreased with depth and less than 2% relative to the top for barrier depths deeper than 20 m. Finally, the importance of directional dependence in the permeability of the zeolite medium for calibrating 2D finite element flow analysis was highlighted by bench-scale tests performed under 2D flow conditions.

• 한국산학기술학회논문지
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• 제19권4호
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• pp.123-131
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• 2018

본 연구는 ${\bigcirc}{\bigcirc}$ 고속국도 공사 중 발생된 이암 절토 사면의 붕괴 요인 분석 및 대책방안을 제시하였다. 기반암인 이암에 대해 실내시험을 수행하고, 국제 기준에 의거해 공학적인 특성을 규명하였다. 그리고 설계 시 수행되었던 사면안정해석을 재검토 하였다. 또한, Swelling-Slaking 현상으로 인해 기반암인 이암의 강도열화특성을 고려한 안정해석을 추가적으로 수행하였다. 기반암인 이암에 대해 Swelling-Slaking Test 결과, 풍화내구성은 낮음-보통으로 나타났으며, 팽창변형률은 매우 낮음으로 나타났다. 설계 안정해석 검토 결과, 이암의 공학적 특성을 고려하지 않고, 한계평형해석을 이용해 실제와 상이한 결과가 나타났다. 강도열화특성을 고려한 추가안정해석 결과, 사면의 붕괴지점과 안정해석의 최대전단변형률 발생지점이 동일하게 나타났으며, 건기시 우기시 모두 기준 안전율을 만족하지 못하였다. 붕괴 사면의 대책방안으로는 사면경사완화공법이 가장 적절하였다. 유한요소해석을 통해 완화 경사를 산정하였다. 완화 경사의 현장 적용성을 위해 시추공영상촬영과 비교한 결과, 미고결된 이암의 대부분이 제거되는 것으로 나타나 미고결된 이암으로 인한 추가적인 붕괴 위험성은 현격히 저하되는 것으로 나타났다.

• 한국지반공학회논문집
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• 제37권11호
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• pp.83-92
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• 2021

본 연구에서는 공극률이 큰 포항지역 이암의 특성을 평가하고자 유효공극률 측정, 전자 현미경(SEM) 관찰 및 X-선 회절분석(XRD), 슬레이킹, 팽창, 수침기간에 따른 일축압축강도 특성을 분석하였다. 16개의 시험편(정육면체, 5cm)에 대한 시험결과, 유효공극률(porosity)은 평균 14.67%로 일반적인 이암 공극률보다 높은 공극률을 보였으며, 전자 현미경(SEM) 관찰을 통해 실제로 공극률이 큼을 확인하였다. X-선 회절분석결과 팽윤성 점토광물 함유량은 2.3~4.1%(녹니석, 카올린)로 선행연구 된 포항지역 이암보다 낮은 점토 함유량을 보였다. 슬레이크 내구성 지수는 37.73~87.73%로 저~중정도 내구성을 보여 선행연구 결과 대비 다소 낮은 내구성을 보였으며, 팽윤성은 30분간 장축방향 최대 흡수팽창 변화률 1.79~1.82%로 급격하게 팽창함을 확인하였다. 수침에 따른 일축압축강도 감소 특성은 수침 10분 경과 후 만에 시험편이 급격히 풍화되어 강도가 감소하여 기존 포항지역 이암과 관련된 선행연구의 결과와도 상이함을 확인하였다. 이것은 연구대상 이암의 큰 공극률 때문으로 판단된다.

• The Plant Pathology Journal
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• 제31권3호
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• pp.278-289
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• 2015

Indigenous strains of Trichoderma species isolated from rhizosphere soils of Tea gardens of Assam, north eastern state of India were assessed for in vitro antagonism against two important tea fungal pathogens namely Pestalotia theae and Fusarium solani. A potent antagonist against both tea pathogenic fungi, designated as SDRLIN1, was selected and identified as Trichoderma viride. The strain also showed substantial antifungal activity against five standard phytopathogenic fungi. Culture filtrate collected from stationary growth phase of the antagonist demonstrated a significantly higher degree of inhibitory activity against all the test fungi, demonstrating the presence of an optimal blend of extracellular antifungal metabolites. Moreover, quantitative enzyme assay of exponential and stationary culture filtrates revealed that the activity of cellulase, ${\beta}$-1,3-glucanase, pectinase, and amylase was highest in the exponential phase, whereas the activity of proteases and chitinase was noted highest in the stationary phase. Morphological changes such as hyphal swelling and distortion were also observed in the fungal pathogen grown on potato dextrose agar containing stationary phase culture filtrate. Moreover, the antifungal activity of the filtrate was significantly reduced but not entirely after heat or proteinase K treatment, demonstrating substantial role of certain unknown thermostable antifungal compound(s) in the inhibitory activity.

• 공업화학
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• 제5권6호
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• pp.943-948
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• 1994

본 실험에서는 카본블랙 함량에 따른 미가황고무 혼합물의 물리적 특성과 가황고무 혼합물의 팽윤거동에 대해 고찰하였다. 카본블랙 함량 증가에 따라 미가황고무 혼합물 중의 bound rubber 함량은 증가하였으며 ${\alpha}_f$는 1.46이었다. 또한 고무 혼합물 중의 카본블랙은 구형입자의 거동을 보여주었다. Mooney-Rivlin의 응력-변형 방법에 의해 구한 가황고무의 $C_1$값은 카본블랙 함량 증가에 따라 증가하는 경향을 보였다.

• 한국농공학회지
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• 제34권4호
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• pp.69-79
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• 1992

To estimate soil behavior and structural characteristics under the conditions of cyclic loading, freezing & thawing and initial state, several testing was performed and obtained following results. 1.After repeated freezing and thawing processes, original soil structure was destroyed and changed to globular structure from honeycomb or tube in its structure types. Also above processes resulted increasing the soil compression strain while decreasing the failure stress in stress-strain relationship and reached the soil structure into the mode of brittle fracture. Under cyclic loading conditions, soil cluster which was originally dispersed structure colloided with each other, seperated, and finally the soil failed due to the effect of overcompaction. 2.Through the stabilization processes seperated by four steps, the structure of soil skeleton was changed to quite different globular type. The degree of compressibility of soil was decreased in the normally consolidated zone, while the strength against external load increased due to soil particle stabilization. 3.Soil stress-strain chracteristics were largely influenced by repeated up and down processes of temperature. The maximum deformation was obtained in the case of temperature between 0 10˚C by the reseon of particle cluster reformation. 4.Soil compressibility was largely influenced by the optimum moisture content. Under freezing process, swelling could be found and its magnitude was proportional to the density of soil. 5.Density of soil was decreased as increasing the number or repeated freezing and thawing processes and the largest decreasing rate was found at the first turning point from freezing to thawing cycle.

• 한국자동차공학회논문집
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• 제13권5호
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• pp.152-162
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• 2005

Coolant rubber hoses for automobile radiators can be degraded and thus failed due to the influence of contacting stresses of air and coolant liquid under the thermal and mechanical loadings. In this study, test analysis was carried out for evaluating the degradation and failure mechanisms of coolant hose materials. Two kinds of EPDM rubber materials applicable to the hoses were adopted: commonly-used ethylene-propylene diene monomer(EPDM) rubbers and EPDM rubbers with high resistance against electro-chemical degradation (ECD). An increase of surface hardness and a large reduction of failure strain were shown due to the formation of oxidation layer for the specimens which had been kept in a high temperature air chamber. Coolant ageing effects took place only by an amount of pure thermal degradation. The specimens degraded by ECD test showed a swelling behavior and a considerable increase in weight on account of the penetration of coolant liquid into the skin and interior of the rubber specimens. The ECD induced material softening as well as drastic reduction in strength and failure strain. However EPDM rubbers designed for high resistance against ECD revealed a large improvement in reduction of failure strain and weight. This study finally established a procedure for reliability analysis and evaluation of the degradation and failure mechanisms of EPDM rubbers used in coolant hoses for automobile radiators.

• 한국방재학회:학술대회논문집
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• 한국방재학회 2007년도 정기총회 및 학술발표대회
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• pp.37-40
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• 2007

Although masonry buildings fell into disfavour in the 1990's because of factors such ac bricklayers' high labor costs, bad reputation of poorly constructed masonry, masonry face wall is still preferred in korea as well as in other countries for its decorative value. Recently may problems with masonry face wall with opening have been reported, including cracks, deflection, swelling and even wall collapse in old masonry buildings, that mainly induced from the corrosion of connecting materials. So, it is necessary to develop the effective and uncorrosion connector. Therefore, this study aims to investigate the structural performance of masonry face walls with opening constructed by new connectors, spiral stainless anchors and to provide basic data for the field application of this method. The specimen reinforced bed joint has maximum load and displacement any other specimens.

• Journal of Microbiology and Biotechnology
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• 제4권4호
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• pp.349-353
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• 1994

An isolate 90-GT-302, identified as Kitasatosporia kimorexae, was found to produce antibiotics that induce mycelial swelling in Magnaporthe grisea, and Fusarium solani. The strain produced at least 5 antibiotics. Among them, the main active compound designated as kimorexin A was isolated and its physico-chemical properties and biological activities were examined, and as a result was found to be of the thiopeptide antibiotic. A comparison between the properties of kimorexin A and those of the known thiopeptide antibiotics led us to conclude that kimorexin A was a new thiopeptide polythiazolyl antibiotic. Kimorexin A showed a narrow antimicrobial spectrum against very limited genus of phytopathogenic fungi. It prevented host plants from infections of Rhizoctonia solani and absolute parasitic fungi, such as Sphaerotheca fuliginea and Puccinia recondita, almost completely at the treatment concentration of approximately 20 ppm.