• Journal of Microbiology and Biotechnology
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• v.27 no.8
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• pp.1441-1448
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• 2017

Antibacterial compounds are widely used in the treatment of human and animal diseases. The overuse of antibiotics has led to a rapid rise in the prevalence of drug-resistant bacteria, making the development of new antibacterial compounds essential. This study focused on developing a fast and easy method for identifying marine bacteria that produce antibiotic compounds. Eight randomly selected marine target bacterial species (Agrococcus terreus, Bacillus algicola, Mesoflavibacter zeaxanthinifaciens, Pseudoalteromonas flavipulchra, P. peptidolytica, P. piscicida, P. rubra, and Zunongwangia atlantica) were tested for production of antibacterial compounds against four strains of test bacteria (B. cereus, B. subtilis, Halomonas smyrnensis, and Vibrio alginolyticus). Colony picking was used as the primary screening method. Clear zones were observed around colonies of P. flavipulchra, P. peptidolytica, P. piscicida, and P. rubra tested against B. cereus, B. subtilis, and H. smyrnensis. The efficiency of colony scraping and broth culture methods for antimicrobial compound extraction was also compared using a disk diffusion assay. P. peptidolytica, P. piscicida, and P. rubra showed antagonistic activity against H. smyrnensis, B. cereus, and B. subtilis, respectively, only in the colony scraping method. Our results show that colony picking and colony scraping are effective, quick, and easy methods of screening for antibacterial compound-producing bacteria.

• Journal of Microbiology and Biotechnology
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• v.31 no.2
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• pp.290-297
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• 2021

Leptolyngbya sp. KIOST-1 (LK1) is a newly isolated cyanobacterium that shows no obvious cytotoxicity and contains high protein content for both human and animal diets. However, only limited information is available on its toxic effects. The purpose of this study was to validate the safety of LK1 powder. Following Organisation for Economic Co-operation and Development (OECD) guidelines, a single-dose oral toxicity test in Sprague Dawley rats was performed. Genotoxicity was assessed using a bacterial reverse mutation test with Salmonella typhimurium (strains TA98, TA100, TA1535, and TA1537) and Escherichia coli WP2 uvrA, an in vitro mammalian chromosome aberration test using Chinese hamster lung cells, and an in vivo mammalian erythrocyte micronucleus test using Hsd:ICR (CD-1) SPF mouse bone marrow. After LK1 administration (2,500 mg/kg), there were no LK1-related body weight changes or necropsy findings. The reverse mutation test showed no increased reverse mutation upon exposure to 5,000 ㎍/plate of the LK1 powder, the maximum tested amount. The chromosome aberration test and micronucleus assay demonstrated no chromosomal abnormalities and genotoxicity, respectively, in the presence of the LK1 powder. The absence of physiological findings and genetic abnormalities suggests that LK1 powder is appropriate as a candidate biomass to be used as a safe food ingredient.

• Ocean and Polar Research
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• v.43 no.4
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• pp.229-243
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• 2021

Quality control (QC) to process observed time series has become more critical as the types and amount of observed data have increased along with the development of ocean observing sensors and communication technology. International ocean observing institutions have developed and operated automatic QC procedures for these observed time series. In this study, the performance of automated QC procedures proposed by U.S. IOOS (Integrated Ocean Observing System), NDBC (National Data Buy Center), and OOI (Ocean Observatory Initiative) were evaluated for observed time-series particularly from the Yellow and East China Seas by taking advantage of a confusion matrix. We focused on detecting additive outliers (AO) and temporary change outliers (TCO) based on ocean temperature observation from the Ieodo Ocean Research Station (I-ORS) in 2013. Our results present that the IOOS variability check procedure tends to classify normal data as AO or TCO. The NDBC variability check tracks outliers well but also tends to classify a lot of normal data as abnormal, particularly in the case of rapidly fluctuating time-series. The OOI procedure seems to detect the AO and TCO most effectively and the rate of classifying normal data as abnormal is also the lowest among the international checks. However, all three checks need additional scrutiny because they often fail to classify outliers when intermittent observations are performed or as a result of systematic errors, as well as tending to classify normal data as outliers in the case where there is abrupt change in the observed data due to a sensor being located within a sharp boundary between two water masses, which is a common feature in shallow water observations. Therefore, this study underlines the necessity of developing a new QC algorithm for time-series occurring in a shallow sea.

• Proceedings of KOSOMES biannual meeting
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• 2017.04a
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• pp.234-234
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• 2017

• Journal of Ocean Engineering and Technology
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• v.34 no.3
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• pp.202-207
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• 2020

A track-type underwater construction robot (URI-R) was developed by the Korea Institute of Ocean Science & Technology. Because URI-R uses tracks to move on the seabed, insufficient ground strength may hinder its movement. For smooth operation of URI-R on the seabed, it is important to determine the geotechnical properties of the seabed. To determine these properties, standard penetration test (SPT), cone penetration test (CPT), and sampling are used on land. However, these tests cannot be applied on the seabed due to a high cost owing to the vessel, crane, sampler, and analysis time. To overcome these problems, a free fall cone penetration tester (FFCPT) is being developed. The FFCPT is a device that acquires the geotechnical properties during impact/penetration/finish phases by free fall in water. Depth information is crucial during soil data acquisition. As the FFCPT cannot measure the penetration depth directly, it is estimated indirectly using acceleration. The estimated penetration depth was verified by results of real tests conducted on land.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.1
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• pp.1-6
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• 2017

Tungsten carbide (WC) has been suggested as a new buffer layer for the GaN-on-Si technology. We have investigated and optimized the sputtering condition of WC layer on the Si-substrate. We confirmed the suppression of the Si melt-back phenomenon. In addition, surface energy of WC/Si layer was measured to confirm the possibility as a buffer layer for GaN growth. We found that the surface energy(${\gamma}=82.46mJ/cm^2$) of WC layer is very similar to that of sapphire substrate(${\gamma}=82.71mJ/cm^2$). We grow GaN layer on the WC buffer by using gas-source MBE, and confirm that it is available to grow a single crystalline GaN layer.

• Journal of Astronomy and Space Sciences
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• v.30 no.4
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• pp.321-326
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• 2013

The modulation transfer function (MTF) is a widely used indicator in assessments of remote-sensing image quality. This MTF method is also used to restore information to a standard value to compensate for image degradation caused by atmospheric or satellite jitter effects. In this study, we evaluated MTF values as an image quality indicator for the Geostationary Ocean Color Imager (GOCI). GOCI was launched in 2010 to monitor the ocean and coastal areas of the Korean peninsula. We evaluated in-orbit MTF value based on the GOCI image having a 500-m spatial resolution in the first time. The pulse method was selected to estimate a point spread function (PSF) with an optimal natural target such as a Seamangeum Seawall. Finally, image restoration was performed with a Wiener filter (WF) to calculate the PSF value required for the optimal regularization parameter. After application of the WF to the target image, MTF value is improved 35.06%, and the compensated image shows more sharpness comparing with the original image.

• Journal of information and communication convergence engineering
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• v.11 no.3
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• pp.153-166
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• 2013

A hierarchical time division multiple access (HTDMA) medium access control (MAC) protocol is proposed for clustered mobile underwater acoustic networks. HTDMA consists of two TDMA scheduling protocols (i.e., TDMA1 and TDMA2) in order to accommodate mobile underwater nodes (UNs). TDMA1 is executed among surface stations (e.g., buoys) using terrestrial wireless communication in order to share mobility information obtained from UNs which move cluster to cluster. TDMA2 is executed among UNs, which send data to their surface station as a cluster head in one cluster. By sharing mobility information, a surface station can instantaneously determine the number of time slots in a TDMA2 frame up to as many as the number of UNs which is currently residing in its cluster. This can enhance delay and channel utilization performance by avoiding the occurrence of idle time slots. We analytically investigate the delay of HTDMA, and compare it with that of wellknown contention-free and contention-based MAC protocols, which are TDMA and Slotted-ALOHA, respectively. It is shown that HTDMA remarkably decreases delay, compared with TDMA and Slotted-ALOHA.

• Journal of Microbiology and Biotechnology
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• v.28 no.5
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• pp.776-783
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• 2018

The agarase gene gaa16a was identified from a draft genome sequence of Gilvimarinus agarilyticus JEA5, an agar-utilizing marine bacterium. Recently, three agarase-producing bacteria, G. chinensis, G. polysaccharolyticus, and G. agarilyticus, in the genus Gilvimarinus were reported. However, there have been no reports of the molecular characteristics and biochemical properties of these agarases. In this study, we analyzed the molecular characteristics and biochemical properties of agarases in Gilvimarinus. Gaa16A comprised a 1,323-bp open reading frame encoding 441 amino acids. The predicted molecular mass and isoelectric point were 49 kDa and 4.9, respectively. The amino acid sequence of Gaa16A showed features typical of glycosyl hydrolase family 16 (GH16) ${\beta}$-agarases, including a GH16 domain, carbohydrate-binding region (RICIN domain), and signal peptide. Recombinant Gaa16A (excluding the signal peptide and carbohydrate-binding region, rGaa16A) was expressed as a fused protein with maltose-binding protein at its N-terminus in Escherichia coli. rGaa16A had maximum activity at $55^{\circ}C$ and pH 7.0 and 103 U/mg of specific activity in the presence of 2.5 mM $CaCl_2$. The enzyme hydrolyzed agarose to yield neoagarotetraose as the main product. This enzyme may be useful for industrial production of functional neoagaro-oligosaccharides.

• Ocean and Polar Research
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• v.43 no.3
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• pp.193-203
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• 2021

In-situ experiment using ocean buoys is a direct ocean observation and has been playing an important role from the past to the present based on high reliability. The ocean buoy is operated more stable than before due to the technological development of communication (GPS, satellite, …) and equipment, but still moored buoys are not free from various accidents occurring in the ocean. Nevertheless, there is currently a lack of countermeasures or manuals about mooring accidents. Therefore, in this study, based on the experience of operating buoys conducted for many years, the advantages and disadvantages of ocean buoys according to size were analyzed. and legal procedures before and after buoy mooring were presented to enhance the use of buoys. And it is suggested to realize successful experiment by proposing considerations before mooring the buoy in preparation for an accident.