• Journal of Microbiology and Biotechnology
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• 제16권10호
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• pp.1597-1604
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• 2006

To screen for an anti-yeast substance (AYS), many bacteria were isolated from soil and a strain AY2000 was selected. The strain AY2000 was identified as Rahnella aquatilis by morphology, biochemical properties, and 16S r-RNA nucleotide sequence analyses. The strain AY2000 showed anti-yeast activity against Candida albicans and Saccharomyces cerevisiae, whereas R. aquatilis ATCC33071 as a type strain did not show the activity against the yeasts under the same condition. The growth of yeast cell was significantly inhibited by AYS produced by the strain AY2000, as shown by optical density and MTT assay. The minimum inhibitory concentration (MIC) of the AYS against S. cerevisiae and C. albicans at $28^{\circ}C\;was\;20{\mu}g/ml\;and\;60{\mu}g/ml$, respectively. The MIC of AYS against hyphae of C. albicans at $37^{\circ}C\;was\;600{\mu}g/ml$. Scanning electron microscopic analysis revealed that yeast cells treated with AYS had an irregular form with a wrinkled and rough surface.

• Geomechanics and Engineering
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• 제2권4호
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• pp.281-302
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• 2010

An extended model for the response of a rigid footing on a reinforced foundation bed on super soft soil is proposed by incorporating the rough membrane element into the granular bed. The super soft soil, the granular bed and the reinforcement are modeled as non-linear Winkler springs, non-linear Pasternak layer and rough membrane respectively. The hyperbolic stress-displacement response of the super soft soil and the hyperbolic shear stress-shear strain response of the granular fill are considered. The finite deformation theory is used since large settlements are expected to develop due to deformation of the super-soft soil. Parametric studies quantify the effect of each parameter on the stress-settlement response of the reinforced foundation bed, the settlement and tension profiles.

• Geomechanics and Engineering
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• 제18권4호
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• pp.391-406
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• 2019

The aim of this paper was to study the influence of the footing shape and the effect of the roughness of the foundation base on the bearing capacity of shallow foundations on rock masses. For this purpose the finite difference method was used to analyze the bearing capacity of various types and states of rock masses under the assumption of Hoek-Brown failure criterion, for both plane strain and axisymmetric model, and considering smooth and rough interface. The results were analyzed based on a sensitivity study of four varying parameters: foundation width, rock material constant (mo), uniaxial compressive strength and geological strength index. Knowing how each parameter influences the bearing capacity depending on the footing shape (circular vs strip footing) and the footing base interface roughness (smooth vs rough), two correlation factors were developed to estimate the percentage increase of the ultimate bearing capacity as a function of the footing shape and the roughness of the footing base interface.

• 지질공학
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• 제8권3호
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• pp.215-224
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• 1998

LVDT에 의해 전체변형율이 측정되었고, 국부적 변형율은 변형율게이지에 의해 측정되었다. 또한 공시체에서의 응력 분포를 알기 위하여 유한요소법에 의한 축대칭 탄소성 해석을 하였다. 단면구속영향을 고려하면 H/D=1인 경우에 특히 구속영향을 크게 받는다. 또한 공시체 직경에 대한 공시체 길이가 길어질수록 영향을 적게 받는다는 것을 알 수 있다. 공시체와 재하판과의 접촉면에서 응력 및 변위 분포는 접촉하고 있는 두 재료의 탄성계수비와 접촉면의 마찰저항에 크게 좌우된다. 즉 암석공시체에 대한 재하판의 영향은 경암에서보다 연암에서 더 현저하다 또한 단면구속이 변형율 분포에 미치는 영향 및 치수효과는 강성이 큰 암석에서 현저하게 나타난다.

• Tribology and Lubricants
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• 제34권1호
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• pp.1-8
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• 2018

This paper presents the analysis of friction master curves for a sliding elastomer on rough granite. The hysteresis friction is calculated using an analytical model that considers the energy spent during the local deformation of the rubber due to surface asperities. The adhesion friction is also considered for dry friction prediction. The viscoelastic modulus of the rubber compound and the large-strain effective modulus are obtained from dynamic mechanical analysis (DMA). We accurately demonstrate the large strain of rubber that contacts with road substrate using the GW theory. We found that the rubber block deforms approximately to 40% strain. In addition, the viscoelastic master curve considering nonlinearity (at 40% strain) is derived based on the above finding. As viscoelasticity strongly depends on temperature, it can be assumed that the influence of velocity on friction is connected to the viscoelastic shift factors gained from DMA using the time-temperature superposition. In this study, we apply these shift factors to measure friction on dry granite over a velocity range for various temperatures. The measurements are compared to simulated hysteresis and adhesion friction using the Kluppel friction theory. Although friction results in the low-speed band match well with the simulation results, there are differences in the predicted and experimental results as the velocity increases. Thus, additional research is required for a more precise explanation of the viscoelastic material properties for better prediction of rubber friction characteristics.

• 한국지반공학회논문집
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• 제15권4호
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• pp.3-17
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• 1999

대응력반전시 모래의 거동을 연구하기 위하여 여러 가지 응력경로에 따른 비틀림전단시험이 수행되었다. 응력경로는 토르크의 작용방향에 따라 시계방향과 반시계방향으로 구분할 수 있으며 대응력반전을 포함하는 응력경로에 대한 소성변형률증분의 방향이 응력상태 및 응력증분의 방향과 비교된다. 이들 시험 결과로부터, St, Venant의 원리를 이용한 등방경화이론은 최초재하와 파괴점 부근에서 소성변형률증분의 방향이 응력의 방향과 일치하는 좋은 결과를 나타내었으나 응력반전에 의한 감하과 재재하 부분에서는 차이가 있는 것으로 나타났다.

• Geomechanics and Engineering
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• 제7권4호
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• pp.355-374
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• 2014

An analytical solution of the fully coupled system of equations governing the plane strain deformation of a poroelastic medium with anisotropic permeability and compressible fluid and solid constituents is obtained. This solution is used to study the consolidation of a poroelastic clay layer with free permeable surface resting on a rough-rigid permeable or impermeable base. The stresses and the pore pressure are taken as the basic state variables. Displacements are obtained by integrating the coupled constitutive relations. The case of normal surface loading is discussed in detail. The solution is obtained in the Laplace-Fourier domain. Two integrations are required to obtain the solution in the space-time domain which are evaluated numerically for normal strip loading. Consolidation of the clay layer and diffusion of pore pressure is studied for both the bases. It is found that the time settlement is accelerated by the permeability of the base. Initially, the pore pressure is not affected by the permeability of the base, but has a significant effect, as we move towards the bottom of the layer. Also, anisotropy in permeability and compressibilities of constituents of the poroelastic medium have a significant effect on the consolidation of the clay layer.

• 한국균학회지
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• 제48권2호
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• pp.87-93
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• 2020

A fungal strain designated KNU-WDM2A2 was isolated from mosquitoes in Gimcheon, Korea. The pure culture was transferred to potato dextrose agar (PDA) and synthetic nutrient agar (SNA) media and attained a diameter of 90 mm after 10 days of incubation at 25℃. The colonies were whitish to light pink and cottony to wooly, with an abundant production of aerial mycelia. The strain produced hyaline to slightly yellowish conidiophores that were rough-walled and branched, with conidiogenous cells arising terminally or laterally. Conidia were unicellular, hyaline to light brown, smooth, and oval or ovoid to clavate, with a size of 4.1-6.9×2.5-3.3 ㎛ (n=65). A phylogenetic analysis was conducted using the internal transcribed spacer (ITS) regions and 28S rDNA of large subunit (LSU) sequences, to support the cultural and morphological characteristics. The KNU-WDM2A2 strain was identified here as Biscogniauxia petrensis, new to Korea.

• 한국균학회지
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• 제49권3호
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• pp.315-324
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• 2021

In this study, the fungal strains KNU-Gunwi 2B and KNU-SOT5 were isolated from root-soil in a hillside and the cherry tree bark (Prunus serrulata), respectively from Gyeongbuk province in Korea. The strain KNU-SOT5 produced dark brown chlamydospores that were smooth to lightly rough-walled, globose to ellipsoidal, and the conidia were aseptate, guttulate, mostly fusiform with a diameter of 5.3-17.6×4.2-7.0 ㎛. Strain KNU-Gunwi 2B produced phialides that were smooth-walled, cylindrical with semi-papillate apices and the conidia were pale-green, broadly ellipsoid, and sometimes cylindrical with a diameter of 4.4-8.0×2.3-4.0 ㎛. The strain KNU-SOT5 and KNU-Gunwi 2B were resolved based on cultural and morphological characteristics, along with the phylogenetic analysis using the small subunit (SSU), large subunit (LSU), and internal transcribed spacers (ITS) regions. The fungal strains KNU-SOT5 and KNU-Gunwi 2B were identified as Dothidea insculpta and Metarhizium rileyi, which have not been reported in Korea.

• Geomechanics and Engineering
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• 제11권2호
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• pp.235-252
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• 2016

This paper presents a new numerical solution of the ultimate lateral capacity of rectangular piles in clay. The two-dimensional plane strain finite element was employed to determine the limit load of this problem. A rectangular pile is subjected to purely lateral loading along either its major or minor axes. Complete parametric studies were performed for two dimensionless variables including: (1) the aspect ratios of rectangular piles were studied in the full range from plates to square piles loaded along either their major or minor axes; and (2) the adhesion factors between the soil-pile interface were studied in the complete range from smooth surfaces to rough surfaces. It was found that the dimensionless load factor of rectangular piles showed a highly non-linear function with the aspect ratio of piles and a slightly non-linear function with the adhesion factor at the soil-pile interface. In addition, the dimensionless load factor of rectangular piles loaded along the major axis was significantly higher than that loaded along the minor axis until it converged to the same value at square piles. The solutions of finite element analyses were verified with the finite element limit analysis for selected cases. The empirical equation of the dimensionless load factor of rectangular piles was also proposed based on the data of finite element analysis. Because of the plane strain condition of the top view section, results can be only applied to the full-flow failure mechanism around the pile for the prediction of limiting pressure at the deeper length of a very long pile with full tension interface that does not allow any separation at soil-pile interfaces.