• Journal of the Korean GEO-environmental Society
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• v.13 no.6
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• pp.91-100
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• 2012

Wireless monitoring system for the structural health evaluation has a limit to the reliability of measured response. The objective of this study is to evaluate an effective measurement range of the wireless monitoring system on the analyzed data. For the wireless monitoring system, Bluetooth and Wi-Fi are applied to datalogger-receiver and receiver-personal computer, respectively. For the model of the monopile structure response, a laboratory-scale monopile is manufactured with Mono Cast Nylon and a lateral loading is applied by hammer impacting. Strain gauges attached on the model monopile are connected with the datalogger. The distances of datalogger-receiver and receiver-personal computer are changed for the evaluation of the measurement range. Experimental results show that the receiving rates of the response remain almost constant within limited distance, while the receiving rates dramatically decrease out of effective range. In addition, the receiving rates affect on the measured natural frequencies of the model monopile. This study suggests that the effective range evaluation of the wireless monitoring system may be used for the determination of a monitoring distance to the monopile installed in the offshore wind farm.

• Journal of the Korean GEO-environmental Society
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• v.9 no.6
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• pp.31-41
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• 2008

Consolidation characteristics of reclamated ground with dredged soil and methods of evaluating them are investigated in this paper. For a dredged and reclamated ground with a very high water content, self-weight consolidation being progressed, its consolidation characteristics are difficult to find since it is almost impossible to have a undisturbed sample. In order to overcome such a problem, methods of laboratory tests with disturbed sample were studied to obtain consolidation parameters required to analyze consolidation settlement in practices, using the conventional infinitesimal consolidation theory, were evaluated by carrying out various laboratory tests with disturbed soils such as oedometer test, constant rate of deformation test, Rowe-cell tests with ring diameters of 60 mm, 100 mm and 150 mm and the centrifuge model tests with 40 g-levels. Constitutive relations of void ratio - effective vertical stress - permeability were evaluated by using the inverse technique implemented with the finite strain consolidation theory and results of centrifuge model tests. Design soil parameters related to consolidation such as compression index, swelling index, coefficient of volume change and vertical and horizontal consolidation coefficients were proposed properly by analyzing the various test results comprehensively.

• 대한공업교육학회지
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• v.31 no.1
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• pp.200-210
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• 2006

This C-ring test, normally employed for evaluating susceptibility to stress-corrosion cracking, was determined to be a suitable small scale test to evaluate PWHT(Post-Weld Heat Treatment) cracking susceptibility. This test is possible to incorporate an actual weld, to introduce a notch into the coarse grained HAZ(Heat Affected Zone), to load the coarse grained HAZ any level of stress ad, most importantly, since the C-ring is an approximately constant strain type test, the stress decreases with time at temperature in a manner similar to that of an actual steel weldment. The procedure employed in making the C-ring was presented in the experimental procedure section, however, several points deserve further discussion. The walls of the weld groove are made along radial lines form the center of th var in order to obtain an HAZ which is oriented perpendicular to the walls of the machined C-ring. Therefore, the plane of maximum stress will be aligned through the HAZ and, therefore, crack propagation will not be forced to deviate form the plane of maximum stress in order to remain in the coarse grained HAZ as is the case with the Y groove test.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.1
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• pp.119-127
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• 2014

The application of sulfur polymer emulsion (SPE) as an acrylate substitute for semi-rigid pavement grout was evaluated, and the performance improvement by employing PVA fibers were also evaluated. The result indicated that the filling ratio of semi-rigid pavement material decreased as the fiber content increased, but it was measured to be 92~94% in every mixing condition, which satisfies the target performance, 90%. The maximum Marshall stability value of semi-rigid pavement material was measured to be 25.4 kN, which is about 4.7 times higher than the Korean Standard required for semi-rigid pavement material, 5.0 kN. The dynamic stability evaluation of semi-rigid pavement material indicated that the resistance to deformation from the wheel tracking test was improved by an SPE substitution, and in every mixing condition, the deformation converged to a constant value after 45 minutes with the same dynamic stability of 31,500 times/mm. The strain at the flexural failure was about 0.53%, which shows superior rigidity to asphalt pavements. The examination of abrasion resistance and impact resistance showed that the loss ratio was 9.8~6.0% in every mixing condition, which indicates a good abrasion resistance. Also, when fiber content ratio was 0.3%, the impact resistance was 2.82 times higher compared to plain (i.e., when fibers were not added). In the limited range of this study, an SPE substitution ratio of 30% was found to be an optimal level considering the mechanical and durability performance. In addition, it is thought that semi-rigid pavement material with superior performance could be manufactured if fiber content ratio up to 0.3% is applied depending on the purpose of use.

• Journal of the Korean GEO-environmental Society
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• v.13 no.12
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• pp.5-16
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• 2012

The second scientific antarctic station of South Korea is under construction at Terra Nova Bay located in eastern Antarctica. Ground condition in the Antarctica is frozen in general, but there are seasonal frozen grounds with active layers sporadically. When the active layer is frozen, frost heaving occurs that might cause the differential movement of frozen ground and the failure of structures. Therefore, it is necessary to determine the frost heaving susceptibility of soils at Terra Nova Bay before starting antarctic station construction. This study presents experimental investigation of the frost heaving susceptibility of soil samples with variation of particle sizes and unfrozen water contents. The soil samples were taken from five different locations at Terra Nova Bay and physical properties, unfrozen water content, and frost heaving tests were performed. For the frost heaving tests, soil specimens were frozen with constant freezing temperatures at the top and with drainage at the bottom in order to stimulate the frost heaving. The frost heaving tests provide volume expansion, volumetric strain, and heaving rate which can be used to analyze the relationship between the frost heaving vs. particle size and the frost heaving vs. unfrozen water content. Experimental results show that the more the fine contents exist in soils, the more frost heaving occurs. In addition, the frost heaving depends on unfrozen water content. Experimental data can be used to evaluate the frost heaving susceptibility of soils at the future construction site in the Antarctica.

• The Korean Journal of Zoology
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• v.13 no.2
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• pp.44-50
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• 1970

This experiment was made in order to observe the change in contents of the total cholesterol, free cholesterol and ester cholesterol in the liver and serum by the feeding of glucose and sucrose. The animals used for the experiment were adult male albino rat from a pure strain, weighing 285-332g. The animals were divided into standard, glucose and sucrose diet groups. The glucose and sucrose diet groups were redivided into 10%, 25% and 40% diet groups. Their liver and serum were used as sample after they were fed with the corresponding diets, respectively, for two months. 1. In the liver, the total cholesterol and ester cholesterol contents in the 40% glucose diet group were significantly increased and the free cholesterol contents in all diets were respectively increased, compared with the standard diet group. 2. In the serum, the total cholesterol contents in both diet groups, the 10% glucose and 10% sucrose, were decreased but the content in the 40% sucrose diet group was increased, compared with the standard diet group. The free cholesterol contents in the 10 and 40% glucose diet and 10% sucrose diet group were decreased, compared with the standard diet group. The ester cholesterol contents in the 10% glucose and 10% sucrose diet groups were decreased but the content in the 40% sucrose diet group was increased, compared with the standard diet group. Being taken into consideration of the above facts it was acquired that the cholesterol contents are affected by the amounts and kinds of dietary carbohydrate when the protein contents in each diet were constant.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.1
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• pp.81-94
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• 2010

This paper deals with the fracture simulation of UHPFRC girder with the interface type model. Based on the existing numerical simulation of quasi-brittle fracture in normal strength concrete, constitutive modeling for UHPFRC I-girder has been improved by including a tensile hardening at the failure surface. The finite element formulation is based on a triangular unit, constructed from constant strain triangles, with nodes along its sides and neither at the vertex nor the center of the unit. Fracture is simulated through a hardening/softening fracture constitutive law in tension, a softening fracture constitutive law in shear as well as in compression at the boundary nodes, with the material within the triangular unit remaining linear elastic. LCP is used to formulate the path-dependent hardening-softening behavior in non-holonomic rate form and a mathematical programming algorithm is employed to solve the LCP. The piece-wise linear inelastic yielding-failure/failure surface is modeled with two compressive caps, two Mohr-Coulomb failure surfaces, a tensile yielding surface and a tensile failure surface. The comparison between test results and numerical results indicates this method effectively simulates the deformation and failure of specimen.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.3C
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• pp.201-207
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• 2006

Soil tests are generally conducted using a membrane to measure a pore water pressure. However, it has also been recognized that the membrane penetrates into the specimen by the change of the confining pressure, and it results in the erroneous measurement in the pore water pressure and the volumetric strain. This study examined the effectiveness of the correction equation of the membrane penetration on the basis of the experimental data acquired during the isotropic unloading and the cyclic shear process using the hollow cylindrical shear test equipment. The results showed that the membrane penetration by the correction equation could be overestimated when the mean effective stress was lower than 20kPa in this study. The limitations originated from the sudden increase near the zero effective stress, and in order to prevent the overestimation in low effective stress condition, the use of the constant a was proposed in this study. Furthermore, the correction equation for the membrane penetration had to be applied carefully when the initial relative density was high and the density changes were occurred by the relocation of the soil particle by the liquefaction.

• Microbiology and Biotechnology Letters
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• v.30 no.2
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• pp.142-150
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• 2002

Streptomyces polychromogenes IFO 13072 was used as a strain producing cholesterol oxidase(EC 1.1.3.6). The conditions of cholesterol oxidase production were investigated. The optimum composition of medium for production of the enzyme was 1% dextrin, 0.5% casamino acid, 0.1% $KH_2$PO$_4$, 0.5% $NaNO_3$ and 0.05% $MgSO_4$(pH 7.3). The enzyme was purified specifically by cholesterol affinity column chromatography with a yield of 23.2%. The purified enzyme showed a single polypeptide on SDS-PAGE and the molecular weight was estimated about 52,000 daltons. The optimum pH and temperature of the cholesterol oxidase were pH 7.0 and $37^{\circ}C$, respectively. The enzyme was stable in the range of pH 6.0~7.0 and $25^{\circ}C$. The cholesterol oxidase activity was strongly inhibited by metal ions such as $Hg^{2＋}$ and $Fe^{2＋}$ and inhibitors such as dithiothreitol, mercaptoethanol and isonicotinic acid. The Michaelis constant(Km) for the cholesterol was found to be 25 mM by Lineweaver-Burk plot analysis.

• Applied Biological Chemistry
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• v.12
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• pp.69-74
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• 1969

This glucose isomerizing enzyme, which Actinomyces sp. (strain, K-17) produced, was inhibited by citrate, oxalate, ethylene diamine tetraacetic acid and cysteine on the enzyme reaction. This enzyme isomerized xylose to ketose as well as glucose. The Michaelis constant of this enzyme was $7.2X\;10^{-1}M.$. on D-glucose. The enzyme activity of intact cells which were harvested in the none xylose containing medium was very weak. If these intact cells of low activity were treated in the buffered xylose solution, its activity was considerably increased. After fifteen hours at $32^{\circ}C$. on xylose treatment, the enzyme activity was increased to equilibrium and the treating condition was proper at neutral pH and in aerobic state. The adequate concentration of xylose on the treatment was about 0.5 percent.