• Nuclear Engineering and Technology
• /
• v.38 no.2
• /
• pp.139-146
• /
• 2006

An experimental study was performed to evaluate the effects of surface coating and an enhanced insulation structure on the downward facing boiling process and the critical heat flux on the outer surface of a hemispherical vessel. Steady-state boiling tests were conducted in the Subscale Boundary Layer Boiling (SBLB) facility using an enhanced vessel/insulation design for the cases with and without vessel coatings. Based on the boiling data, CHF correlations were obtained for both plain and coated vessels. It was found that the nucleate boiling rates and the local CHF limits for the case with micro-porous layer coating were consistently higher than those values for a plain vessel at the same angular location. The enhancement in the local CHF limits and nucleate boiling rates was mainly due to the micro-porous layer coating that increased the local liquid supply rate toward the vaporization sites on the vessel surface. For the case with thermal insulation, the local CHF limit tended to increase from the bottom center at first, then decrease toward the minimum gap location, and finally increase toward the equator. This non-monotonic behavior, which differed significantly from the case without thermal insulation, was evidently due to the local variation of the two-phase motions in the annular channel between the test vessel and the insulation structure.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.6 no.3
• /
• pp.111-117
• /
• 1997

The sudden-stop apparatus is made to measure the residual stress of the infinitesimal area at the turning work surface by using the X-ray stress apparatus. This study is trued to make the cutting work the instantaneous stopping state in the normal working state. The behaviour of work material near the tool is estimated. The estimation method is that the distribution of residual stress can be also measured. The object is to clarify and control the mechanism to leave the adequate stress of the finishing surface. It's beginning is due to observe the occurrence state of the residual stress at the cutting work. The result obtained by this study is as follows. The chips are not separated from the work materials at all the cutting experiments of built-up edges or the shearing areas etc. which can be precisely observed by using the sudden-stop apparatus. The strain of movable system which can be seen at the part of working layer means the size of strain. This experiment proves that the working strain should be lessened to make the size of strain control the residual stress happened at the cutting surface.

• Journal of the Korean Ceramic Society
• /
• v.36 no.11
• /
• pp.1211-1216
• /
• 1999

TiO2 thin films were prepared by reactive magnetron sputtering on glass substrate and subjected into investigation about their hydrophilic properties. Varing Ar/O2 ration and post annealing at 50$0^{\circ}C$ for 12h anatase and rutile phases of TiO2 films were obtained. Hydrophilic properties were evaluated by determination of contact angle of water droplet on TiO2 surface. On as-annealed TiO2 films water droplet spreaded widely with ~0$^{\circ}$contact angle. Sonication(60 Hz, 28kHz 40kHz) and following dark room treatments turned these hydrophilic TiO2 films into hydrophobic state. All of hydrophobic films were converted recersibly into their original state after UV illumination. Hydrophobic states of anatase films were saturated after sonication and remain same during dark room treatment. But it was found that the conversion into hydrophobic state of rutile films progressed. further after sonication. Therefore it was concluded that Ti3+/Ti+4 ratio is the key to determine hydrophilicity of TiO2 surface so that different surface structure of polymorphs could lead to unique characteristics.

• Ocean Systems Engineering
• /
• v.1 no.1
• /
• pp.17-28
• /
• 2011

The purpose of this paper is to demonstrate the efficacy of modeling a surface effect ship's air-cushion flexible seal utilizing a two-dimensional beam under steady state conditions. This effort is the initial phase of developing a more complex three-dimensional model of the air-seal-water fluid-structure interaction. The beam model incorporates the seal flexural rigidity and mass with large deformations while assuming linear elastic material response. The hydrodynamic pressure is derived utilizing the OpenFOAM computational fluid dynamic (CFD) solver for a given set of steady-state flow condition. The pressure distribution derived by the CFD solver is compared with the pressure required to deform the seal beam model. The air pressure, flow conditions and seal geometry are obtained from experimental analysis. The experimental data was derived from large-scale experimental tests utilizing a test apparatus of a canonical surface effect ship's flexible seal in a towing tank over a variety of test conditions.

• Nuclear Engineering and Technology
• /
• v.52 no.10
• /
• pp.2290-2298
• /
• 2020

The damage of first wall material in fusion reactor due to the bubbles caused by plasma has been studied by introducing a relation between the von Mises equivalent stress and the temperature field. The locations and shapes of the bubbles and the synergetic effect between the different bubbles under steady operational conditions have been studied using the finite elements method. Under transient heat loads, plastic deformations have been found to occur, and are significantly enhanced by the presence of the bubbles. The calculated concentration locations of von Mises equivalent stress are well consistent with the observed crack positions of the tungsten surface in many test experiments. Our simulations show that the damage of the bubbles is not severe enough to lead to catastrophic failure of the tungsten armor; however, it can cause local and gradual detachment of tungsten surface, which provides a reasonable explanation for the observed pits and rough or hairy surface morphology etc. Considering the transient heat loads, the lower bound of the security thickness of the tungsten tile is estimated to be greater than 2 mm.

• Journal of Microbiology and Biotechnology
• /
• v.20 no.11
• /
• pp.1471-1480
• /
• 2010

An extremely thermostable xylanase gene, xynB, from the hyperthermophilic bacterium Thermotoga maritima MSB8 was successful expressed in Kluyveromyces lactis. The response surface methodology (RSM) was also applied to optimize the medium components for the production of XynB secreted by the recombinant K. lactis. The secretion level (102 mg/l) and enzyme activity (49 U/ml) of XynB in the optimized medium (yeast extract, lactose, and urea; YLU) were much higher than those (56 mg/l, 16 U/ml) in the original medium (yeast extract, lactose, and peptone; YLP). The secretory efficiency of mature XynB was also improved when using the YLU medium. When the mRNA levels of 13 characterized secretion-related genes in the K. lactis cultured in YLP and YLU were detected using a semiquantitative RT-PCR method, the unfolded protein response (UPR)-related genes, including ero1, hac1, and kar2, were found to be up-regulated in the K. lactis cultured in YLU. Therefore, the nutrient ingredients, especially the nitrogen source, were shown to have a significant influence on the XynB secretory efficiency of the host K. lactis.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.38 no.5
• /
• pp.116-124
• /
• 1996

The purpose of The work described in this paper is to clear up the initial moisture content, specific surface, air drying and freezing-thawing process on liquid limit of clayey soils distributed widely at estuary of three main rivers in the west coast. To this end, a series of tests were conducted on clayey soils samples with natural state and treated state. From the test results, the liquid limit was decreased with decrement of initial moisture content, air drying process, and freezing-thawing cycles and increased with increment of specific surface. The specific surface which influenced on the liquid limit is over $25 m^2$m$^2$/g, and their relationships are well formulated. Air drying process is expected to improve the engineering properties of the soils such the pro-water properties were changed to anti-water proper-ties through lowering of water holding as resulted to incline from A-7-5 to A-5 on the soil classificaction plastic chart. The freezing-thawing process decreased 20% of liquid limit, especially under the first cycle of the behavious, as a result of above mentioned reasons, phase change of soil-water system brought the decrement of specific surface and affected to the liquid limit.

• Journal of Korea Technical Association of The Pulp and Paper Industry
• /
• v.34 no.2
• /
• pp.73-83
• /
• 2002

Gloss is very important optical property influencing the perceived quality of the paper surface as well as the surface after printing. Although the average gloss level of paper products or printed images is important to meet end use specifications, the occurrence of gloss mottle, or non-uniformity of gloss, is often of greater concern for meeting quality requirements, especially for the high gloss paper. Gloss variation originates from the irregularities of paper surface, especially surface roughness of paper. Roughness of paper can be divided into micro-roughness (under $1\mu m$ scale in variation) and macro-roughness (over $1\mu m$ scale in variation) depending on the scale of the irregularities. A clearer understanding of the gloss variation of paper can be achieved by separating the contributions of these two scales of roughness, and characterizing them independently. In order to do this, a novel gloss measuring method was introduced. This can detect local gloss with very high resolution. The effect of macro-roughness on gloss variation, which was identified by the measurable surface topography, was separated from the total gloss variation by using this method. The effect of micro-roughness was then estimated indirectly. The local gloss variations of various paper samples were then evaluated to demonstrate the utility of this approach.

• International Journal of Concrete Structures and Materials
• /
• v.9 no.1
• /
• pp.119-132
• /
• 2015

Electrical resistivity is an important physical property of portland cement concrete which is directly related to chloride induced corrosion process. This study examined the electrical surface resistivity (SR) and bulk electrical resistivity (BR) of concrete cylinders for various binary and ternary based high-performance concrete (HPC) mixtures from 7 to 161 days. Two different types of instruments were utilized for this investigation and they were 4 point Wenner probe meter for SR and Merlin conductivity tester for bulk resistivity measurements. Chronological development of electrical resistivity as well as correlation between two types of resistivity on several days was established for all concrete mixtures. The ratio of experimental surface resistance to bulk resistance and corresponding resistivity was computed and compared with theoretical values. Results depicted that bulk and SR are well correlated for different groups of HPC mixtures and these mixtures have attained higher range of electrical resistivity for both types of measurements. In addition, this study presents distribution of surface and bulk resistivity in different permeability classes as proposed by Florida Department of Transportation (FDOT) specification from 7 to 161 days. Furthermore, electrical resistivity data for several HPC mixtures and testing procedure provide multiple promising options for long lasting bridge decks against chloride induced corrosion due to its ease of implementation, repeatability, non-destructive nature, and low cost.

• Journal of Korean Physical Therapy Science
• /
• v.29 no.1
• /
• pp.55-63
• /
• 2022

Background: This study investigated the effect of erector spinae and quadratus lumbar kinesio taping and support surface conditions on abdominal muscle activity during plank exercise. Design: Within-Group design. Methods: A total of twenty-three healthy men and women participated in this study. Abdominal muscle (both external obliques and internal oblique muscle) contraction was analyzed through EMG measurement with the presence or absence of kinesio taping applied to the erector spinae muscle and quadratus lumborum muscle during plank exercise and the difference between the support surfaces (stable surface and unstable surface) as variables. Abdominal EMG was attached to the right external oblique, left external oblique, right internal oblique, and left internal oblique. Results: The results showed that Abdominal left and right external obliques and internal obliques showed significant increases in activity when kinesio taping was applied to the erector spinae and quadratus lumborum muscles and unstable ground (p<0.05). Conclusion: In this study, we confirmed that the activity of the abdominal muscles was significantly increased during the plank operation in the state where the kinesio tape was attached. In addition, it was confirmed that the activity of the abdominal muscles was significantly increased during the plank operation on the unstable surface. These results suggest that in the state of kinesio tape attached and instability, plank motion has a positive effect on abdominal muscle activity.