• Journal of Advanced Research in Ocean Engineering
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• v.1 no.1
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• pp.1-13
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• 2015

Post-Katrina investigations revealed that most earthen levee damage occurred on the levee crest and landward-side slope as a result of either wave overtopping, storm surge overflow, or a combination of both. In this paper, combined wave overtopping and storm surge overflow of a levee embankment strengthened with high performance turf reinforcement mat (HPTRM) system was studied in a purely Lagrangian and meshless approach, two-dimensional smoothed particle hydrodynamics (SPH) model. After the SPH model is calibrated with full-scale overtopping test results, the overtopping discharge, flow thickness, flow velocity, average overtopping velocity, shear stress, and soil erosion rate are calculated. New equations are developed for average overtopping discharge. The shear stresses on landward-side slope are calculated and the characteristics of soil loss are given. Equations are also provided to estimate soil loss rate. The range of the application of these equations is discussed.

• Journal of Korean Association for Spatial Structures
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• v.16 no.4
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• pp.59-66
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• 2016

Recently damage of structures and loss of life by terrorism are internationally increasing. Among these terror that have a possibility to can happen in korea and that can caused lot of human life loss is the vehicle terror. To prevent the vehicle terror, the anti-ram barriers are needed. But domestic standard about anti-ram barriers are not clear. So, in this study, we will utilize and analyze the vehicle impact to evaluate the efficiency of the domestic bollard and suggest the installation standard of those. In Korea, granite, elastic, steel and stainless bollard are used. The performance of those bollard is not available. Elastic bollard couldn't stop the vehicle, and the others just could stop the vehicle only at the speed under 10kph. Therefore, set the variable to reinforce, and evaluate the defence efficiency of bollard. As a result, granite and elastic bollard was not suitable for the anti-ram barriers. Performance of steel bollard increased as thickness grew. So steel bollard should must be thicker than 10T. And the concrete compressive strength effected insignificantly on the defence efficiency, so more than 24MPa compressive concrete be used. Performance of stainless bollard increased as thickness grew. So stainless bollard should must be thicker than 13T.

• Fire Science and Engineering
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• v.16 no.4
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• pp.49-58
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• 2002

A large number of accidents at an underground place have been happening, including the gas explosion under construction of subway; the fires of underground utility and underground shopping malls, and other explosion, at home and abroad recently. These accidents make the function of a city ineffective due to the paralyses of electricity and communications net as well as the loss of property and cause people to feel unsecured with accompaniment of a heavy of toll of lives. This research will show evaluation methods of a numerical value of expected average loss space of combustion with the use of probability in order to present potential risk of combustion growth that underground space might cause, and how designer decides a system that enables us to compare and evaluate relatively the effectiveness of measures for preventing burning by calculating the expansion route and the damage size of burning in case of fire.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.35 no.4
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• pp.370-374
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• 1990

A field experiment was conducted to investigate the influence of water weevil damage on growth and grain guality in rice. Plant height was shortened, number of tillers per hill decreased and maximum tillering stage delayed in damaged field by rice water weevil. Heading date was delayed by 1-2days, culm lenght shortened, panicle lengthened, number of panicles decreaced, number of panicles per spikelet increased, ripened grain ratio decreased in damaged field by rice water weevil. Yield per 10a was decreased 4-22% in damaged field compared with that in undamaged field by rice water weevil, yield loss in late transplanting (June 23) was larger than that in early transplanting (May 20). Imperfect kerml rice, especially green kernel rice, was increased in damaged field by rice water weevil.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.365-366
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• 2002

The sliding wear behavior of ultra high molecular weight polyethylene (UHMWPE) was examined on a novel low temperature degradation-free zirconia/alumina composite material and conventional alumina and zirconia ceramics used for femoral head in total hip joint replacement. The wear of UHMWPE pins against these ceramic disks was evaluated by performing linear reciprocal sliding and repeat pass rotational sliding tests for one million cycles in bovine serum. The weight loss of polyethylene against the novel low temperature degradation-free zirconia/alumina composite disks was much less than those against conventional ceramics for all tests. The mean weight loss of the polyethylene pins was more io the linear reciprocal sliding test than in the repeal pass rotational sliding lest for all kinds of disk materials. Neither the coherent transfer film nor the surface damage was observed on the surface of the novel zirconia/alumina composite disks during the test. The observed r,'stilts indicated that the wear of the polyethylene was closely related to contacting materials and kinematic motions. In conclusion, the novel zirconia/alumina composite leads the least wear of polyethylene among the tested ceramics and demonstrates the potential as lhe alternative materials for femoral head in total hip joint replacement.

• Journal of the Korean Society of Combustion
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• v.13 no.4
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• pp.1-7
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• 2008

Strict pollutant regulations of NOx emission and increasing awareness of the environmental damage stimulated interest in research to obtain useful information regarding CO and NOx reductions at the same time. In this study, $CH_4$/air premixed flame was examined numerically to reduce CO and NOx emission level simultaneously in the post-flame region by the heat loss models in which radiative and combined conductive and convective heat losses were included. To reduce the NOx emission, first heat exchanger location was decided near the flame. After first heat exchanger was decided for the optimal NOx emission(about 30 ppm), in order to decide the optimal CO emission(about 30ppm), seocond heat exchanger location was tested and decided for several cases. Finally, the optimal location of heat exchanger for minimal CO and NOx emission simultaneously were determined and suggested.

• Food Science of Animal Resources
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• v.36 no.5
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• pp.650-655
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• 2016

This study investigated the effects of artificial supercooling followed by still air freezing (SSF) on the qualities of pork loin. The qualities of pork frozen by SSF were compared with the fresh control (CT, stored at 4℃ for 24 h), slow freezing (SAF, still air freezing) and rapid freezing (EIF, ethanol immersion freezing) treatments. Compared with no supercooling phenomena of SAF and EIF, the extent of supercooling obtained by SSF treatment was 1.4℃. Despite that SSF was conducted with the same method with SAF, application of artificial supercooling accelerated the phase transition (traverse from -0.6℃ to -5℃) from 3.07 h (SAF) to 2.23 h (SSF). The observation of a microstructure indicated that the SSF prevented tissue damage caused by ice crystallization and maintained the structural integrity. The estimated quality parameters reflected that SSF exhibited superior meat quality compared with slow freezing (SAF). SSF showed better water-holding capacity (lower thawing loss, cooking loss and expressible moisture) and tenderness than SAF, and these quality parameters of SSF were not significantly different with ultra-fast freezing treatment (EIF). Consequently, the results demonstrated that the generation of supercooling followed by conventional freezing potentially had the advantage of minimizing the quality deterioration caused by the slow freezing of meat.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.11
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• pp.991-994
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• 2007

In this paper, we have designed the anti-reflection(AR) coating for $1400{\sim}1600$ nm wavelength range on the ferrule facet of optical connector. The low-temperature ion-assisted deposition was applied to AR coating on the ferrule facet in order to avoid damage of optical connector. We have measured the refractive index of coating film($Ta_2O_5\;and\;SiO_2$) using the ellipsometer and optimized the film thickness using the SEM and thickness measurement equipment. UV-VIS-NIR spectrophotometer is used to measure transmissivity of the AR coated ferrule facet. The refractive index of $Ta_2O_5\;and\;SiO_2$ is $2.123{\sim}2.125$ and $1.44{\sim}1.442$, respectively, for $1400{\sim}1600$ nm wavelength range. The transmissivity of the AR coated ferule facet is more than 99.8 % for $1425{\sim}1575$ nm wavelength range and more than 99.5 % for $1400{\sim}1600$ nm wavelength range. The return loss of the AR coated ferrule facet is 30.1 dB.

• Progress in Superconductivity and Cryogenics
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• v.23 no.4
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• pp.44-48
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• 2021

In order to obtain ultra-high resolution MRI images, research and development of 11 T or higher superconducting magnets have been actively conducted in the world, recently. The high-temperature superconductor (HTS), first discovered in 1986, was very limited in industrial application until mid-2010, despite its high critical current characteristics in the high magnetic field compared to the low-temperature superconductor. This is because HTS magnets were unable to operate stably due to the thermal damage when a quench occurred. With the introduction of no-insulation (NI) HTS magnet winding technology that does not burn electrically, it could be expected that the HTS magnets are dramatically reduced in weight, volume, and cost. In this paper, a 6 T-class NI HTS magnet for basic characteristic analysis was designed, and a distributed equivalent circuit model of the NI coils was configured to analyze the charging current characteristics caused by excitation current, and the charge delay phenomenon and loss were predicted through the development of a simulation model. Additionally, the critical current of the NI HTS magnets was estimated, considering the magnetic field, its angle and temperature with a given current. The loss due to charging delay characteristics was analyzed and the result was shown. It is meaningful to obtain detailed operation technology to secure a stable operation protocol for a 6T NI HTS magnet which is actually manufactured.

• Biomedical Science Letters
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• v.27 no.4
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• pp.248-254
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• 2021

Ulcerative colitis (UC), chronic inflammatory bowel disease, is characterized by severe inflammation in the colon. Tea is one of the most popular beverages consumed worldwide. Pu-erh tea, a unique Chinese tea produced by microbial activities, possesses a broad range of health-promoting effects, including anti-aging, anti-Alzheimer's disease, antioxidation and anti-obesity. However, the inhibitory effect of Pu-erh tea on intestinal inflammation and the underlying mechanism remain unclear. The present study was designed to evaluate the regulatory effect of Pu-erh tea extract (PTE) on dextran sulfate sodium (DSS)-induced colitis clinical signs by analyzing the weight loss and colon length in mice. The inhibitory effects of PTE on inflammatory mediators, such as interleukin (IL)-6 and tumor necrosis factor (TNF)-α, and the activation of nuclear factor-κB (NF-κB) were also determined in DSS-treated colitis tissue. We observed that PTE treatment significantly inhibited the DSS-induced clinical symptoms of weight loss, decrease,in colon length, and colon tissue damage in mice. Moreover, PTE attenuated the DSS-induced levels of IL-6 and TNF-α in colon tissue. We also demonstrated the anti-inflammatory mechanism of PTE by suppressing the activation of NF-κB in DSS-treated colon tissues. Collectively, the findings provide experimental evidence that PTE may be effective in preventing and treatment of intestinal inflammatory disorders, including UC.