• Journal of Korean Tunnelling and Underground Space Association
• /
• v.20 no.4
• /
• pp.743-755
• /
• 2018

Tunnel is a semi-closed structure similar to underground space where the smoke generated from fire fills the space fast while escaping from the space slow. Because of such characteristics, when the fire breaks out by traffic accident, the vehicles are jammed making it difficult for the people to evacuate from the scene as well as for the fire engine to gain access to the scene. For such reasons, tunnels are globally categorized into some disaster classes for differentiated facilities and operation approaches. In Korea, less than a 1 km-long tunnel accounts for 80.0% and such a short tunnel which is categorized into Class III is not required to have smoke control system. In this study, a full-scale fire test was conducted in a bid to apply air curtain system using heat-resistant sirocco fan to a less than 1 km-long tunnel. To that end, heat resistance test to verify the normal operation at $250^{\circ}C$ for 60 minutes was conducted. Consequently, despite of rapid rising-temperature and increasing-carbon dioxide inside the air curtain (direction of fire in tunnel), initial condition was found to have been sustained outside the air curtain (opposite direction of fire in tunnel).

• Nuclear Engineering and Technology
• /
• v.47 no.6
• /
• pp.678-699
• /
• 2015

Although the harsh space environment imposes many severe challenges to space pioneers, space exploration is a realistic and profitable goal for long-term humanity survival. One of the viable and promising options to overcome the harsh environment of space is nuclear propulsion. Particularly, the Nuclear Thermal Rocket (NTR) is a leading candidate for nearterm human missions to Mars and beyond due to its relatively high thrust and efficiency. Traditional NTR designs use typically high power reactors with fast or epithermal neutron spectrums to simplify core design and to maximize thrust. In parallel there are a series of new NTR designs with lower thrust and higher efficiency, designed to enhance mission versatility and safety through the use of redundant engines (when used in a clustered engine arrangement) for future commercialization. This paper proposes a new NTR design of the second design philosophy, Korea Advanced NUclear Thermal Engine Rocket (KANUTER), for future space applications. The KANUTER consists of an Extremely High Temperature Gas cooled Reactor (EHTGR) utilizing hydrogen propellant, a propulsion system, and an optional electricity generation system to provide propulsion as well as electricity generation. The innovatively small engine has the characteristics of high efficiency, being compact and lightweight, and bimodal capability. The notable characteristics result from the moderated EHTGR design, uniquely utilizing the integrated fuel element with an ultra heat-resistant carbide fuel, an efficient metal hydride moderator, protectively cooling channels and an individual pressure tube in an all-in-one package. The EHTGR can be bimodally operated in a propulsion mode of $100MW_{th}$ and an electricity generation mode of $100MW_{th}$, equipped with a dynamic energy conversion system. To investigate the design features of the new reactor and to estimate referential engine performance, a preliminary design study in terms of neutronics and thermohydraulics was carried out. The result indicates that the innovative design has great potential for high propellant efficiency and thrust-to-weight of engine ratio, compared with the existing NTR designs. However, the build-up of fission products in fuel has a significant impact on the bimodal operation of the moderated reactor such as xenon-induced dead time. This issue can be overcome by building in excess reactivity and control margin for the reactor design.

• Korean Journal of Microbiology
• /
• v.47 no.4
• /
• pp.308-315
• /
• 2011

The purpose of this work was to examine the antimicrobial activity derived from the lactic acid bacterium, UK-3 isolated from the vaginas of women of childbearing age. Various physiological and biochemical properties of this strain were characterized. Both the BIOLOG system and phylogenetic analysis using 16S rRNA sequencing were utilized for identification, and the strain was designated as Lactobacillus plantarum UK-3, and registered in GenBank as [JK266589]. Growth rate, production of organic acids (e.g., lactic acid and acetic acid), and pH during growth were monitored. The maximum concentrations of lactic acid and acetic acid were approximately 684.11 mM and 174.26 mM, respectively, and pH changed from 7.0 to 3.7 after 72 h of incubation. High performance liquid chromatography was used to confirm lactic acid and acetic acid production. Significant antimicrobial activity of the concentrated supernatant was demonstrated against various Gram-positive (e.g., Staphylococcus aureus, Staphylococcus epidermidis, Methicillin-resistant Staphylococcus aureus, Enterococcus faecalis, Neisseria species., Listeria monocytogenes), Gram-negative bacteria (e.g., Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis), and yeast (e.g., Candida albicans) by the plate diffusion method. As a result, the concentrated L. plantarum UK-3 cultures had lower acidity and inhibited the growth of all microorganisms tested, whereas the growth of L. acidophilus was not affected.

• Korean Journal of Materials Research
• /
• v.10 no.10
• /
• pp.703-708
• /
• 2000

As the engine design changes to get high efficiency and performance of commercial diesel engine, surface w wear of the earn follower becomes an important issue as applied load increasing at the contact face between cam follower and cam. We developed the ceramic cam follower made of sili$\infty$n nitride ceramic which was more wear resistant than the cast iron or sintered metal cam follower. Ceramic cam follower was made by direct brazing of thin ceramic disk to steel body using an active brazing alloy without the interlayer. In-situ crowning(R), resulted from the difference of thermal expansion coefficient between ceramic and carbon steel after direct brazing without any stress-relieving inter]ayer, could be controlled. When a earbon steel was heated above $A_{c1}$ point and then c$\infty$led, the expansion curve represented a hysteresis. Appropriate crowning was achieved below the $A_{c1}$ point(about $723^{\circ}C$) and crowning increased with brazing temperature exponentially above the $A_{c1}$ point. Optimum brazing temperature range was from 700 to $720^{\circ}C$. We developed successfully the ceramic cam follower having appropriate crowning and being inexpensive. Also we could successfully control the crowning of ceramic earn follower by hysteresis behavior of thermal expansion of earbon steel during direct brazing process.

• Food Science of Animal Resources
• /
• v.30 no.2
• /
• pp.179-184
• /
• 2010

Escherichia coli O157:H7 is a food-borne pathogen that causes bloody diarrhea, hemorrhagic colitis, and hemolytic uremic syndrome (HUS). We compared three selective media and evaluated the performance of immunomagnetic separation (IMS) for the detection of low levels of E. coli O157:H7 in ground beef and radish sprouts with different levels of background flora. Bulk food samples (500 g for each trial) were artificially inoculated with nalidixic acid-resistant E. coli O157:H7 at the lowest dose that would generate 20 partial-positive samples of 25 g each. All samples were homogenized in mTSB (225 mL) and incubated overnight at $37^{\circ}C$. IMS was performed using the enriched mTSB samples (1 mL) along with conventional spreads plated onto three different selective media: Sorbitol MacConkey agar (SMAC), Sorbitol MacConkey agar with cefixime and tellulite (CT-SMAC), and Sorbitol MacConkey agar with nalidixic acid (NAL-SMAC) as the gold standard. Two suspicious colonies from each medium were selected and confirmed usinga serological test after transfer to tryptic soy broth with yeast extract (TSAYE). CT-SMAC was better than SMAC for detecting E. coli O157:H7 in all food types. Although there was no statistical difference in the number of positive samples when using IMS vs. non-IMS techniques, more positive samples were detected when IMS was used in both ground beef and radish sprouts. It appears that the improvement was more significant in radish sprouts, which had a higher level of background flora than ground beef. The results also suggest that the combination of CT-SMAC and IMS is sufficient to recover low levels of E. coli O157:H7 in high background flora food samples.

• Korean Journal of Breeding Science
• /
• v.43 no.6
• /
• pp.538-542
• /
• 2011

A new malting barley variety, 'Baegho', was developed from a cross between Azuma Golden and Nishinochikara in 1998. An elite line, YMB2139-2B-1-10-2, was selected in 2005 and designated as Milyang137. It showed good agronomic performance in the regional adaptation yield trials (RYT) from 2006 to 2008 and was released with the name of 'Baegho' having high yielding and BaYMV and powdery mildew resistance. The average heading and maturing dates of 'Baegho' were April 21 and May 28, which were 3 and 2 day later than those of Hopum, check variety, at the RYT, respectively. 'Baegho' has shoter culm length (78 cm), more spikes ($1,062per\;m^2$) and heavier 1,000 grain weight (40.7 g) than those of Hopum, respectively. 'Baegho' is resistant to domestic BaYMV strains I, III and IV and powdery mildew at Iksan. In growth habit, 'Baegho' is close to type (IV) that is distinguished from other Korean malting barley cultivars, which could tolerant to premature heading damage that is major concern for the practice of the malting barley cropping. The yield potential of 'Baegho' in the RYT was about 5.57 MT/ha, which is about 13% higher than those of Hopum. This variety has good malting quality in grain and malting analysis showed better 1,000 grain weight, husk rate, diastatic power than those of Hopum. 'Baegho' applied for protection of new varieties of plant in 2009.

• Korean Journal of Breeding Science
• /
• v.41 no.4
• /
• pp.568-573
• /
• 2009

A new soybean variety, "Singang", was released by NICS, RDA in 2008. It is resistant to soybean mosic virus (SMV), which is one of the most serious diseases in soybean production. "Singang" had been developed for seven years by molecular marker-assisted selection (MAS) breeding method using recurrent parent, "Sowon", and donor parent, "L29" which has the SMV-resistance gene, Rsv3. Selected promising breeding line, Suwon 242, was evaluated in yield trials for 2 years from 2005 to 2006 at NICS. Regional yield trials were performed for 3 years from 2006 to 2008 in five locations including Jeju. Agronomic characteristics of "Singang" is a determinate growth habit, purple flower color, grey pubescence, yellow testa, light brown hilum and lanceolate leaflet shape. "Singang" showed the similar performance to "Sowon" cultivar. This variety showed 3 days shorter in days to maturity than the check variety (Pungsannamul). The average yield under regional yield trials in five location was 2.78t/ha. It is adaptable to the whole country except for Gangwon province.

• Microbiology and Biotechnology Letters
• /
• v.49 no.3
• /
• pp.413-424
• /
• 2021

In order to enhance rhizoremediation performance, which remediates contaminated soils using the interactions between plants and microorganisms in rhizosphere, it is required to develop effective microbial resources that simultaneously degrade contaminants and promote plant growth. In this study, heavy metal-resistant rhizobacteria, which had been cultivated in soils contaminated with heavy metals (copper, cadmium, and lead) and diesel were isolated from rhizospheres of maize and tall fescue. After that, the isolates were qualitatively evaluated for plant growth promoting (PGP) activities, heavy metal tolerance, and diesel degradability. As a result, six strains with heavy metal tolerance, PGP activities, and diesel degradability were isolated. Strains CuM5 and CdM2 were isolated from the rhizosphere soils of maize, and were identified as belonging to the genus Cupriavidus. From the rhizosphere soils of tall fescue, strains CuT6, CdT2, CdT5, and PbT3 were isolated and were identified as Fulvimonas soli, Cupriavidus sp., Novosphingobium sp., and Bacillus sp., respectively. Cupriavidus sp. CuM5 and CdM2 showed a low heavy metal tolerance and diesel degradability, but exhibited an excellent PGP ability. Among the six isolates, Cupriavidus sp. CdT2 and Bacillus sp. PbT3 showed the best diesel degradability. Additionally, Bacillus sp. PbT3 also exhibited excellent heavy metal tolerance and PGP abilities. These results indicate that the isolates can be used as promising microbial resources to promote plant growth and restore soils with contaminated heavy metals and diesel.

• Journal of Navigation and Port Research
• /
• v.43 no.3
• /
• pp.172-178
• /
• 2019

Although the needs for providing resilient PNT information are increasing, threats due to the intentional RFI or space weather change are challenging to resolve. eLoran, which is a terrestrial navigation system that use a high-power signal is considered as a best back-up navigation system. Depending on the user's environment in the eLoran system, the user may use one of E-field or H-field antennas. H-field antenna, which has no restriction on setting stable ground and is relatively resistant to noise of general electronic equipment, is composed of two loops, and shows anisotropic gain pattern due to the different measurement at the two loops. Therefore, the H-field antenna's phase estimation value of signal varies depending on its direction even at the static environment. The error due to the direction of the signal should be eliminated if the user want to estimate the own position more precisely. In this paper, a method to compensate the error according to the geometric distribution between the H-field antenna and the transmitting station is proposed. A model was developed to compensate the directional error of H-field antenna based on the signal generated from the eLoran signal simulator. The model is then used to the survey measurement performed in the land area and verify its performance.

• Korean Journal of Clinical Laboratory Science
• /
• v.51 no.2
• /
• pp.214-220
• /
• 2019

Hwangryunhaedok-tang (HT) is prescribed in oriental medicine to treat inflammation-related diseases. This study examined the anti-bacterial effect to select the index components of Traditional Chinese Medicine (TCM) HT. The disc diffusion method and minimum inhibition concentrations (MIC) tests were conducted to measure the antibacterial activity of HT. The strains were Staphylococcus aureus ATCC 25923 and Escherichia coli 23724. Berberine and geniposide were selected as the index components of HT and were analyzed quantitatively by high-performance liquid chromatography (HPLC). As a result, the inhibition ring was formed at $11.7{\pm}1.3mm$ and $8.7{\pm}0.7mm$ at HT 20 mg and 10 mg on S.aureus ATCC 25923, respectively; and $8.0{\pm}0.0mm$ at HT 20 mg on E.coli ATCC 23724. The MIC were 31.25 mg/mL in S.aureus ATCC 25923 and 125.0 mg/mL in E.coli ATCC 23724. In quantitative analysis for standardization, HT contained 16.55 mg/g of berberine and 81.85 mg/g of geniposide. Overall, when antibiotics are developed using natural products, they may reduce the side effects and inhibit resistant bacteria. If research on HT continuously proceeds, positive developments are expected to be made in oriental medicine as well as in various other industries.