• Journal of Species Research
• /
• v.6 no.2
• /
• pp.119-128
• /
• 2017

Within a comprehensive, widescale investigation of indigenous prokaryotic species in Korea, 29 bacterial strains in the phylum Bacteroidetes were isolated from diverse environmental habitats that included soil, plant roots, natural caves, tidal flats, freshwater from lakes, and seawater. Based on their high 16S rRNA gene sequence similarities (>99.1%) and the formation of robust phylogenetic clades with the closest type species, each strain likely belonged to an independent and predefined bacterial species. There are no publications or official reports of the isolation of these 29 species in Korea. Our study provides strong evidence that seven species in three genera in the order Cytophagales, 15 species in 13 genera in the order Flavobacteriales and seven species in five genera in the order Sphingobacteriales, all within the phylum Bacteriodetes, are new reports of bacterial species in Korea. Gram reaction, colony and cell morphology, basic biochemical characteristics, isolation source, and strain IDs are described in the species description section.

• Journal of Species Research
• /
• v.6 no.2
• /
• pp.129-140
• /
• 2017

During a comprehensive investigation of indigenous prokaryotic species in Korea, a total 31 bacterial strains assigned to the class Alphaproteobacteria were isolated from diverse environmental habitats including freshwater, seawater, brackish water, ginseng soil, plant roots, natural caves, and tidal flats. Based on their high 16S rRNA gene sequence similarities(>99.1%) and formation of robust phylogenetic clades with the closest type species, each strain was assigned to an independent and predefined bacterial species. Because there were no published or official reports regarding the isolation of these 31 species in Korea, this study identified three species in two genera in the order Caulobacterales, 12 species in 10 genera in the order Rhodobacterales, three species in two genera in the order Rhizobiales, two species in two genera in the order Rhodospirillales and 11 species in seven genera, all in the order Sphingomonadaceae within the Alphaproteobacteria are reported as new alphaproteobacterial species in Korea. Gram reaction, colony and cell morphology, basic biochemical characteristics, isolation source, and strain IDs are described in the species description section.

• Korean Journal of Microbiology
• /
• v.42 no.1
• /
• pp.7-11
• /
• 2006

To see effect of marine rock powder and fungal culture supernatant, we analyzed the biodegradation rates of harmful marine dinoflagellate, Heterosigma akashiwo and Prorocentrum minimum for developing the effective control methodology of algal bloom. Relatively low removal rates were observed in the treatment of marine rock powder or buffer solution alone. However, the lysis of H. akashiwo and P. minimum was enhanced in the combined treatments of marine rock powder with fungal supernatant. The effective concentration and exposure time of fungal supernatant for the lysis of H. akashiwo and P. minimum were 5 ml/l and 30 minutes, respectively. These results suggest that the fungal supernatant may be a biocontrol agent for the control of algal blooms in seawater.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.11a
• /
• pp.773-776
• /
• 2008

The corrosion of steel in concrete is significant in marine environment. Marine bridges are readily deteriorated due to the exposure to marine environment. Salt damage is one of the most detrimental causes to concrete bridges and port structures. Especially, the splash and tidal zones around water line are comparatively important in terms of safety and life-time point of view. During the last several decades, cathodic protection (cp) has been commonly accepted as an effective technique for corrosion control in concrete structures. Zn-mesh sacrificial anode has been recently developed and started to apply to the bridge column cp in marine condition. The detailed parameters regarding Zn-mesh cp technique, however, have not well understood. This study is to investigate how much Zn-mesh cp influences along the concrete column at elevated temperature. About 100cm column specimens with eight of 10cm segment rebars have been used to measure the variation of cp potential with the distance from Zn-mesh anode at both 10$^{\circ}$C and 40$^{\circ}$C in natural seawater. The cp potential change and current diminishment along the column specimens have been discussed for the optimum design of cp by Zn-mesh sacrificial anode

• Journal of Advanced Marine Engineering and Technology
• /
• v.38 no.6
• /
• pp.698-703
• /
• 2014

Currently, demand of liquefied natural gas as an alternatice energy inceases because of depletion of fossil fuels. it is accompanied by inceasing demand of LNG ship. Consequentially, it is expected that demand of bellows for LNG ship increase. The material used for LNG vessels's bellows is an alloy of INCOLOY 825 and STS316L, which are strong against low-temperature brittleness and seawater corrosion. This study establishes the welding condition of LNG vessel's bellows material in extremely low temperature, and analyzes the formability of weld through Erichsen Test. When welding was conducted at optimal condition, tensile strength of weld presneted strength value up to 90% compared with base metal. As results of formalbility through Erichsen test, very good weld that failure occrued in base metal was gotten.

• Ocean Science Journal
• /
• v.40 no.2
• /
• pp.91-100
• /
• 2005

Bioassay using the marine bacteria, Vibrio fischeri and rotifer, Brachionus plicatilis, and chemical analyses were conducted to assess the toxicity of the various sewage sludges, one of the major ocean dumped materials in the Yellow Sea of Korea. Sludge elutriates extracted by filtered seawater were used to estimate the ecotoxicity of the sludge. Chemical characterization included the analyses of organic contents, heavy metals, and persistent organic pollutants in sludge. Bacterial bioluminescent inhibition (15 min), rotifer mortality (24 hr) and rotifer population growth inhibition (48 hr) assay were conducted to estimate the sludge toxicity. EC50 15 min (inhibition concentration of bioluminescence after 15 minutes exposed) values by Microtox(R) bioassay clearly revealed different toxicity levels depending on the sludge sources. Highest toxicity for the bacteria was found with the sludge extract from dyeing waste and followed by industrial waste, livestock waste, and leather processing waste. Clear toxic effects on the bacteria were not found in the sludge extract from filtration bed sludge and rural sewage sludge. Consistent with Microtox(R) results, rotifer neonate mortality and population growth inhibition test also showed highest toxicity in dyeing waste and low in filtration bed and rural sewage sludge. High concentrations of persistent organic pollutants (POPs) and heavy metals were measured in the samples from the industrial wastes, leather processing plant waste sludge, and urban sewage sludge. However, there was no significant correlation between pollutant concentration levels and the toxicity values of the sludge. This suggests that the ecotoxicity in addition to the chemical analyses of various sludge samples must be estimated before release of potential harmful waste in the natural environment as part of an ecological risk assessment.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.24 no.2
• /
• pp.175-182
• /
• 2006

The efficient management for minimum losses and demage precautions of fragile region against coastal disasters such as seismic waves and seawater overflows is proceeding continually. This study is to analyze inundation trace and extract expected damage areas with historic records of tsunami using Geographic Information System. Creating a digital elevation model of the Mangsang and the Nobong region in the east coast, we marked inundation record of tsunami and forecasted the flood area with a seismic wave height between 3 m and 5 m. The inundation trace layers and the expected damage areas on the cadastral map layer were superimposed individually. Consequently, the range and lot numbers of inundation expected area were calculated and inundation areas of 5 m tsunami were increased by 2.8 times than 3 m tsunami in case of subject regions. Analyzed results are expected to use evacuation work in case of seismic waves and to predict the compensation of the damaged area. And this study is expected to use suitable countermeasure for prevention from natural disasters.

• Journal of the Korean institute of surface engineering
• /
• v.49 no.5
• /
• pp.431-438
• /
• 2016

This research investigated the relationship between the corrosion damage characteristics of offshore wind steel substructure and the time of current density application by electrochemical accelerated short-term corrosion test. The galvanostatic corrosion was conducted on the steel specimens in natural seawater with a constant current density ranging from $1mA/cm^2$ to $200mA/cm^2$ for 1 ~ 180 min. Macro and micro observation was carried out on the surface of the corrosion damaged area using SEM and 3-dimensional analysis microscope. The weight loss of the specimens before and after was calculated as the difference between the initial weight prior to corrosion and weight after removal of the corrosion product. It was shown that during galvanostaic corrosion process, the corrosion behavior could be characterized by the onset of pitting corrosion in the early stage and the uniform corrosion in the late stage, showing damage development in the depth direction with the time of current application. The result of the 3D analysis revealed that both damage depth and surface roughness increased with increasing time of current application. The weight loss curves with time showed that a coefficient of determination ($R^2$) was relatively high for the relationship between the time of current application and weight loss. As a result, the degree of corrosion can be controlled by simply varying the time of current application.

• Journal of the Korean GEO-environmental Society
• /
• v.14 no.7
• /
• pp.57-66
• /
• 2013

Coastal structures are functioning in complex natural phenomena such as wave, tide, seawater penetration and abrasion. So the behavior of the coastal structures material is important, because coastal structure material is directly linked to stability of the coastal structures. For this reason, to determine the behaviour characteristics, material design standard is required on the coastal structure under sea wave load. Especially, identification on the behavior of the coastal structure has not been investigated yet properly considering interaction structure and sea wave load. In this study, to identify the behaviour characteristics of the coastal structure caused by waves, the behavior of the coastal structure depending on the magnitude of the wave loads was intensively analyzed.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.14 no.2
• /
• pp.127-133
• /
• 2008

We assessed the coastal landscape of Jeju and Busan cities, respectively. In the study, we tried to estimate the coastal landscape based on the micro-scale and visualization landscape concepts. According to the estimation, the seawater pumping line causes the serious problem of coastal landscape. It means that water management treatment system of coastal region has been an important problem in Jeju city and Busan city since the slight problem was not corrected such as the distributions of pipeline of the pumping system making a bad view in coastal region. To solve the problem, we observed the pipeline distributions that were on the surface around the coastal region. we proposed two methods, that is, one is a short time treatment, the other is a long time one. The short is based on the colour treatment, which is pipeline colour changing into surround natural one. The long time is the construction design method which needs construction management method. Although the later method was very useful in Jeju island and Busan city. However, it takes a lot of time and money. Therefore, in the situation, the short time plan is more useful method than the long time one.