• Journal of the Earthquake Engineering Society of Korea
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• v.12 no.1
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• pp.29-42
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• 2008

The objective of this study is to investigate the effects of rigid end platens on effective stresses in soil mass during consolidation. The friction between the teeth of top cap/base pedestal and the specimen during consolidation decreases the radial and tangential effective stresses in RC specimens. However, it is unpractical to measure the effective stresses in the soil specimen. Two approaches were used to evaluate the state of stress in RC specimens during consolidation. First, careful measurements were made of small strain shear modulus, $G_{max}$ in specimens with carefully controlled void ratios and stress histories, to infer the state of stress. And second, a finite element analysis was performed to analytically evaluate the effect of various soil parameters on the state of stress in RC specimens during consolidation. By combining these experimental and analytical results, an example was performed to predict the average state of stress in RC specimens during consolidation.

• Coupled systems mechanics
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• v.8 no.4
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• pp.299-313
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• 2019

The paper represents computer modeling of the deformed state of physically nonlinear transversally isotropic bodies with hole. In order to describe the anisotropy of the mechanical properties of transversally-isotropic materials a structurally phenomenological model has been used. This model allows representing the initial material in the form of the coupled isotropic materials: the basic material (binder) considered from the positions of continuum mechanics and the fiber material oriented along the anisotropy direction of the original material. It is assumed that the fibers perceive only the axial tensile-compression forces and are deformed together with the base material. To solve the problems of the theory of plasticity, simplified theories of small elastoplastic deformation have been used for a transversely-isotropic body, developed by B.E. Pobedrya. A simplified theory allows applying the theory of small elastoplastic deformations to solve specific applied problems, since in this case the fibrous medium is replaced by an equivalent transversely isotropic medium with effective mechanical parameters. The essence of simplification is that with simple stretching of composite in direction of the transversal isotropy axis and in direction perpendicular to it, plastic deformations do not arise. As a result, the intensity of stresses and deformations both along the principal axis of the transversal isotropy and along the perpendicular plane of isotropy is determined separately. The representation of the fibrous composite in the form of a homogeneous anisotropic material with effective mechanical parameters allows for a sufficiently accurate calculation of stresses and strains. The calculation is carried out under different loading conditions, keeping in mind that both sizes characterizing the fibrous material fiber thickness and the gap between the fibers-are several orders smaller than the radius of the hole. Based on the simplified theory and the finite element method, a computer model of nonlinear deformation of fibrous composites is constructed. For carrying out computational experiments, a specialized software package was developed. The effect of hole configuration on the distribution of deformation and stress fields in the vicinity of concentrators was investigated.

• Journal of Sensor Science and Technology
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• v.32 no.4
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• pp.238-245
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• 2023

0.75(Bi_1/2Na_1/2)TiO₃-0.25SrTiO₃ (BNT-25ST) ceramics with high densities were successfully prepared at a sintering temperature of 1,000℃ by adding a mixture of 1 mol% CuO and 0.5 mol% Na₂CO₃ or 0.5 mol% CuO and 0.25 mol% Na₂CO₃. Double polarization-electric field (P-E) hysteresis curves and sprout-shaped bipolar strain-electric field (S-E) hysteresis curves with small negative strains were observed in the pristine and CuO-added BNT-25ST ceramics whereas the Na₂CO₃-added sample showed similar P-E and S-E curves to a typical ferroelectric. The pristine BNT-25ST ceramics showed an extremely large strain and a large-signal piezoelectric strain constant (d₃₃^*): 0.287 % at 80 kV/cm and 850 pm/V at 20 kV/cm. Similar values, 0.248 % at 80 kV/cm and 655 pm/V at 20 kV/cm, were obtained in the CuO-added sample. However, the pristine and CuO-added samples showed large hysteresis in unipolar S-E curves at an electric field of less than 20 kV/cm. The Na₂CO₃-added sample showed smaller values of the strain and d₃₃^* but displayed a linear change and small hysteresis in the unipolar S-E curve. The co-added sample with CuO and Na₂CO₃ displayed intermediate P-E and S-E hysteresis curves.

• Journal of Sensor Science and Technology
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• v.22 no.1
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• pp.71-75
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• 2013

Nuclear containment building is used as second blockage to protect us from a radiation leakage caused by the natural disaster or any accidents, so it's safety is important and must be kept with continuous surveillance. In this study, we measured the strain of a nuclear containment building's wall by using FBG sensor and investigated the structural safety of a nuclear containment building. 50 FBG strain sensors and 18 FBG strain sensors were attached on the side wall and upper dome of a nuclear containment building, respectively. We measured the strains of the outside concrete wall during the Structural Integrity Test (SIT) of a nuclear containment building. The strain of an upper dome was larger than that of a side wall, about $200{\mu}{\varepsilon}$. And the very small strain was measured at vertical direction of a side wall. These experimental results were used to evaluate the structural health of nuclear containment building.

• Korean Journal of Veterinary Research
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• v.27 no.2
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• pp.259-267
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• 1987

Enterotoxigenic E. coli (ETEC) cause an acute diarrhea (white scour) in both animals and humans. The disease process initially involves the adherence and colonization of the mucosal surface of the small intestine, followed by the elaboration of a heat-labile enterotoxin (LT) and/or heat-stable enterotoxin (ST). Intestinal adherence or colonization by ETEC is generally mediated by a specific surface-associated pilus (fimbrial) antigen that endows the bacteria with the capacity to adhere to epitherial cell surface. Fourteen monoclonal antibodies (MAbs) directed against pili antigens of ETEC were obtained by cell fusion/hybridoma technique. They were characterized by indirect immunofluorescence assay (IFA), and divided into four groups: specific to K99 antigen (group 1), cross-reactive with K99 and F41 antigens (group 2), specific to K88 antigen (group 3) and specific to 987P and K88 antigens (group 4), respectively. These MAbs demonstrated the distinct pili (K) antigens on the surface of ETEC by IFA, and could be utilized as diagnostic reagent for the identification of ETEC. When eighty-seven field isolates of E. coli from piglet with diarrhea were tested by group 3 MAb, fourty-two strains (48.3%) has K88 pilus antigen suggesting that this is one of the major pilus antigen of ETEC present in fifeld.

• Explosives and Blasting
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• v.35 no.2
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• pp.9-17
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• 2017

The Wheatstone bridge is an important electrical circuit that is widely used to measure extremely small resistance changes in strain gages. The strain gages are attached to the structure or specimen whose deformation is to be detected. The Wheatstone bridge finds one of its major applications in the areas of static and dynamic strength tests for various engineering materials. In the split Hopkinson pressure bar (SHPB) system, for example, the bridge circuit is required to measure the dynamic strains of the incident and transmitted bars along which the stress wave propagates. In this article, the principles of the Wheatstone bridge circuit are in detail explained for easy reference during laboratory experiments associated with rock dynamics. Especially, the circuit arrangements of the quater, half, and full bridges are presented with their basic uses.

• Advances in nano research
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• v.6 no.1
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• pp.57-80
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• 2018

In this study, the thermal loading effect on free vibration characteristics of carbon nanotubes (CNTs) with multiple cracks is studied. Various boundary conditions for nanotube are taken in to account. In order to take the small scale effect, the nonlocal elasticity of Eringen is employed in the framework of Euler-Bernoulli beam theory. This theory states that the stress at a reference point is a function of strains at all points in the continuum. A cracked nanotube is assumed to be consisted of two segments that are connected by a rotational spring which is located in the position of the cracked section. Hamilton's principle is used to achieve the governing equations. Influences of the nonlocal parameter, crack severity, temperature change and the number of cracks on the system frequencies are investigated. Also, it is found that at room or lower temperature the natural frequency for CNT decreases as the value of temperature change increases, while at temperature higher than room temperature the natural frequency of CNT increases as the value of temperature change increases. Various boundary conditions have been applied to the nanotube.

• KSBB Journal
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• v.14 no.1
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• pp.66-70
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• 1999

Comparison of lead removal characteristics between two strains, Aureobasidium pullulans and Saccharomyces cerevisiae, and effects of extracellular polymeric substances(EPS) excreted by microorganisms on the removal of lead were investigated. The capacity of lead biosorption to A. pullulans which had EPS was increased as the storage time of the cells increased, due to the increased amounts of excreted EPS. When the EPS were removed from A. pullulans cells, the amounts of adsorbed lead were very small(10% of the cell with EPS). In the case of s. cerevisiae which had no EPS, the lead removal capacity was nearly constant with storage time except early stage, but the spending time to reach an equilibrium state decreased with increasing storage time because of lowering the function of cell membrane. Therefore, it seems that the phenomena of lead biosorption were remarkably affected by the presence of extracellular polymeric substances.

• The Korean Journal of Food And Nutrition
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• v.1 no.1
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• pp.33-40
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• 1988

A Study was conducted to investigate the effect of feeding Lactobacillus casei YS on the growing performance and gastrointestinal flora of the suckling piglets, which were delivered from 2 heads of three-way crossbred(Landrace$\times$Large White$\times$Duroc) pigs, for 4 weeks. The results from the present study was summarized as follows. Average body weight gains of feeding group was slightly better than that of control group and diarrhea was prevented by successive 7 days feeding. Population levels of lactic acid bacteria were maintained about 107 colony forming unit(cfu) per gram of the contents in both feeding and control group at upper parts of small intestine. In this part, coliform count was greatly reduced in (ceding group but not in control group. pH values of the intestinal contents were gradually decreased especially at the upper part of alimentary track of feeding group. Among lactic acid bacteria, L. salivarius, L. cases and L. fermentum were found most predominant strains in feeding group, Wheareas L. salivarius, L. acidophilus and L. cunts in control group. In the other hand, Escherichia coli recovered from scouring pigs were resistant to the drug such as streptomycin, ampicillin and sensitive to gentamycin and neomycin in vitro test.

• Journal of Microbiology
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• v.33 no.2
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• pp.95-102
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• 1995

A probability identification matrix of acidophilic Streptomyces was constructed. The phenetic data of the strains were derived from numerical classification described by Seong et al. The minimum number of diagnostic characters was determined using computer programs for calculation of different separation indices. The resulting matrix consisted of 25 clusters versus 53 characters. Theoretical evaluation of this matrix was achieved by estimating the chuster overlap and the identification scores for the Hypothetical Median Organisms (HMO) and for the representatives of each cluster. Cluster overlap was found to be relatively small. Identification scores for the HMO and the randomly selected representatives of each cluster were satisfactory. The matrix was assessed practically by applying the matrix to the identification of unknown isolates. Of the unknown isolates, 71.9% were clearly identified to one of eight clusters. The numerical classification data was also used to design a selective isolation medium for antibiotic-producing organisms. Four chemical substances including 2 antibiotics were determined by the DLACHAR program as diagnostic for the isolation of target organisms which have antimicrobial activity against Micrococcus luteus. It was possible to detect the increased rate of selective isolation on the synthesized medium. Theresults show that the numerical phenetic data can be applied to a variety of purposes, such as construction of identification matrix and selective isolation medium for acidophilic antinomycetes.