• International Journal of Highway Engineering
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• v.14 no.5
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• pp.93-99
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• 2012

PURPOSES: The purpose of this study is to compare the alkali-silica reactivity for mortar bar and concrete prism specimens using crushed aggregates of 5 types in Korea. And the alkali-silica reactivity for those aggregates are measured by chemical test method. METHODS: The alkali-silica reactivity for those aggregates was measured by chemical test method of KS F 2545, mortar-bar test of KS F 2546, accelerated mortar-bar test method of ASTM C 1260 and concrete prism test method of ASTM C 1293, relatively. RESULTS: The alkali-silica reactivity for those aggregates was verified by chemical test of KS F 2546 and accelerated mortar-bar test of ASTM C 1260. However, it was not by mortar-bar test of KS F 2546 and concrete prism test of ASTM C 1293. CONCLUSIONS: The above results showed that relationship among the four test methods were very low. The results from 3 types of test methods using cement-aggregate combinations appeared to be different. Because the environmental conditions of test methods for measuring the alkali-silica reactivity such as equivalent alkali content(external source), humidity, temperature, and times were different though the aggregates were same. Moreover, alkali-silica reactivity showed the biggest impact when alkalis were supplied form outside and exposed to environmental conditions. The accelerated mortar-bar test method seems to be most appropriate test method for concrete structures exposed to alkali environment.

• Journal of the Korea Concrete Institute
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• v.12 no.2
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• pp.3-11
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• 2000

There is a possibility of poor-state concrete filling condition due to segregation and interlocking of aggregate and paste when a high performance concrete is used at reinforced concrete structure without compaction. This study was conducted to evaluate the flexural behavior of high performance concrete beams with design parameters such as c, t and different concrete filling conditions. Different concrete filling conditions were intentionally made such that the first type specimen was soundly cast to obtain the perfect concrete filling condition. Second type was cast in such a way that up to the longitudinal tensile reinforcement from the top, good concrete was filled while poor concrete was poured for the bottom part to simulate the poor strength, workability and unsatisfactory compaction. Third type was cast in such a was that up to the neutral axis of the beam section from the top, good concrete was filled while so did for the bottom part as the second type. The test results were analyzed in terms of load-displacement response, failure pattern, crack width and crack spacing. The test results indicate that have no effect of concrete filling conditions on the yielding strength of structures. But, have a grate influence on the stiffness and ductility of structures.

• Journal of the Society of Naval Architects of Korea
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• v.50 no.2
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• pp.88-94
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• 2013

The primary objective of the current work is to obviously analyze regarding effects of trim conditions of a ship on resistance performance using model test and CFD. Model tests at a towing tank are conducted to investigate resistance for trim conditions at the given same displacement. Measured resistance shows small but distinct differences according to trim conditions. However, these differences are difficult to be clarified by measured physical quantities and wave pattern analysis from model tests. CFD is employed for the assessment of resistance performance according to trim conditions. The flow computation is conducted considering free surface and dynamic trim using a commercial CFD code (STAR-CCM+). The initiative of the present work is to systematically demonstrate pressure resistance acting on each region of divided finite zones of ship surface along the length and draught direction of surface when pressure distribution on the ship is interpreted. Also, a standard to assess the pressure resistance applied on the divided regions of a ship is established.

• Korean Membrane Journal
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• v.8 no.1
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• pp.21-30
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• 2006

A faujasite NaY zeolite membrane was prepared on a tubular ${\alpha}-Al_2O_3$ support by the secondary growth process, and effects of permeation test conditions on the $CO_2/N_2$ separation were investigated. A NaY zeolite membrane with good $CO_2/N_2$ separation was successfully synthesized by using the hydrothermal solution ($Al_2O_3:SiO_2:Na_2O:H_2O$ = 1:6:14:840 in a molar base): at a permeation temperature of $30^{\circ}C$, its $CO_2$ permeance and $CO_2/N_2$ separation factor were $2.5{\times}10^{-7}mol/m^2secPa$ and 34, respectively. The $CO_2$ and $N_2$ permeations were highly dependent on permeation test conditions (feed composition, feeding rate, feed pressure, He sweeping rate and permeation temperature). The results indicated that (i) $CO_2$ and $N_2$ permeations through NaY zeolite membrane are governed by surface and micropore diffusions, respectively, (ii) the preparation of NaY zeolite membrane with a large permeating area is one of the most difficult hurdles for its real applications, and (iii) the retardation of $N_2$ permeation is an effective key to improve $CO_2/N_2$ separation factor in NaY zeolite membrane.

• Journal of Welding and Joining
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• v.29 no.2
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• pp.72-79
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• 2011

The scope of this investigation is to evaluate the effect of joining parameters on the microstructural features and mechanical properties of dissimilar aluminum alloys, 1mm-thickness fixing AA6K31 at the top position and fixing AA5J32 at the bottom position. The friction stir lap welds were studied under various welding conditions, rotation speed of 1000, 1250, 1500rpm and welding speed of 100, 300, 500, 700mm/min, respectively. Mechanical test has been investigated in terms of tensile shear test and hardness test. The results showed that three type nugget shapes such as onion ring, zigzag type, hooking with the void, have been observed with revolutionary pitch. All welding conditions fractured at the HAZ of top plate, A6K31 and also the strength compare with base metal of lap joints were low efficiency, 52~63%. The thickness of fractured position was decreased with the lower heat input conditions. The relationships were excellent due to linear between the effective thickness of fractured position and peak load. The fractured position was the interface between joint area and not joint area. Also the strength efficiency compared with base metal was lower than decreasing rate of thickness because the hardness was decreased at fractured position due to softened material.

• Journal of the Korean Home Economics Association
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• v.42 no.3
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• pp.145-158
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• 2004

Experimental conditions for evaluating chitosan antibacterial activities were established. The chitosan antibacterial activities were measured against the Staphylococcus aureus and evaluated for their application to antibacterial textile finishing. The strain of Staphylococcus aureus used in this experiments was KCTC 1916. The chitosan antibacterial activities were estimated from the bacterial densities or ％reduction of bacteria in chitosan solutions and bacterial culture mixtures after incubation under specific conditions. Six parameters as follows were evaluated to optimize the experimental conditions for measuring antibacterial activities. The different combinations of mixtures according to the different ratios of chitosan solutions to the bacterial cultures showed different antibacterial activities. However, the chitosan antibacterial activities could be evaluated by comparing the data obtained from the same combinations of mixtures. The solvent influence on the chitosan solution antibacterial activities could be eliminated using control solution containing the same concentration of acetic acid. The initial pH of the chitosan -bacterial mixtures also affected the chitosan antibacterial activity; at a higher pH, higher activity in terms of ％reduction of bacteria was observed. In case of the bacterial solution without either the acetic acid or chitosan, the initial pH of the solution did not significantly affect bacterial growth. The ％ reduction of bacteria increased when contact times of bacteria with chitosan in the chitosan -bacterial mixture were expended upto 24 hours. However, the chitosan antibacterial activities could be successfully evaluated at contact time 0 where the chitosan-bacterial mixture was plated immediately after mixing and incubated to measure the bacterial number to 24 hours. Evaluating ％reduction of bacteria in the test mixtures after incubation were not changed when the inoculated bacterial concentrations were 2.3${\times}$10$\^$0/ml to 2.3${\times}$10$\^$6/ml. The optimal range of incubation time of the petri-Dish after plating the chitosan-bacterial mixture was 24 to 72 hours depending on the antibacterial activities of the test solutions.

• Journal of the Society of Naval Architects of Korea
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• v.58 no.3
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• pp.158-166
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• 2021

In this paper, a numerical analysis technique using a body force model is investigated to estimate the available net thrust of multi-pod-driven ice-breaking vessels under bollard pull and overload conditions. To employ the body force model in present flow simulations, drag and thrust components acting on the pod unit are calculated by using Propeller Open Water (POW) test data. The available net thrusts according to the direction of operation are evaluated in both bollard pull and overload conditions under deep water. The simulation results are compared with the model test data. The available net thrusts, calculated by the present analysis for ahead operating modes at 3~6 knots which are typical speeds of the target vessel in arctic field, are agreed well with the model test results. It is also found that the present result for astern operating mode appears approximately 6 % larger than the model test result. In addition, the available net thrusts are calculated under the both operating conditions accompanied by shallow water effects, and the main cause of the difference is studied. Based on the result of the present study, it is confirmed that the body force model can be applied to the performance evaluation of multi-pod propulsion system and the main engine selection in early design stage of the vessel.

• Interdisciplinary Bio Central
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• v.2 no.2
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• pp.4.1-4.6
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• 2010

The most common type of microarray experiment has a simple design using microarray data obtained from two different groups or conditions. A typical method to identify differentially expressed genes (DEGs) between two conditions is the conventional Student's t-test. The t-test is based on the simple estimation of the population variance for a gene using the sample variance of its expression levels. Although empirical Bayes approach improves on the t-statistic by not giving a high rank to genes only because they have a small sample variance, the basic assumption for this is same as the ordinary t-test which is the equality of variances across experimental groups. The t-test and empirical Bayes approach suffer from low statistical power because of the assumption of normal and unimodal distributions for the microarray data analysis. We propose a method to address these problems that is robust to outliers or skewed data, while maintaining the advantages of the classical t-test or modified t-statistics. The resulting data transformation to fit the normality assumption increases the statistical power for identifying DEGs using these statistics.

• Transactions of Materials Processing
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• v.22 no.2
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• pp.86-92
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• 2013

When stamping ultra-high-strength steel (UHSS), the phenomenon of galling, which corresponds to a transfer of material from the sheet to the tool surface, occurs because of the high contact pressure between tool and workpiece. Galling leads to increased friction, unstable interface conditions, scratches on the sheet and the tool surfaces and, eventually, premature tool surface failures. Therefore, a simple and accurate evaluation method for tool scratching is necessary for the selection of tool material and coating, as well as for a better optimization of process conditions such as blank holder force and die radius. In this study, the pin-on-disc (PODT) and pin-on-flat surface (POFST) tests are conducted to quantitatively evaluate scratch-related tool life for stamping of UHSS. The variation of the friction coefficient is used as an indicator of scratch resulted from galling. The U-channel ironing test (UCIT) is performed in order to validate the results of the friction tests. This study shows that the POFST test provides a good quantitative estimation of tool life based on the occurrence of scratch.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.9
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• pp.2924-2932
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• 1996

As the environmental pollution can be greatly reduced and the waste heat can be also recovered through a combustion of municipal solid waste, the incineration begins to be highlighted recently in our country. But it is very difficult to be operated with constant combustion conditions for a long time as the domestic waste is composed of various components, contains a large percentage of water, and has a low heating value. Therefore, the cold flow test and partial hot flow test were conducted in the incinerator by use of injection angles of a secondary air affecting fluid flow as the first action to maintain the optimum combustion conditions. A model to a scale of 1:10 was designed and manufactured through the similarity of model and prototype flows. Velocities and temperatures were measured through the experiment. From the results, fluid flows of secondary air obtained from partial hot flow test correspond almost well with those of main flow obtained from cold flow test. Consequently, injection angles of secondary air are proved to affect main flow decisively.