• Computers and Concrete
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• v.13 no.1
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• pp.71-82
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• 2014

Chloride ion ingress is one of the major problems that affect the durability of concrete structures such as bridge decks, concrete pavements, and other structures exposed to harsh saline environments. Therefore, durability based design of concrete structures in severe condition has gained great significance in recent decades and various mathematical models for estimating the service life of rein-forced concrete have been proposed. In spite of comprehensive researches on the corrosion of rein-forced concrete, there are still various controversial concepts in quantitation of durability parameters such as chloride diffusion coefficient and surface chloride content. Effect of environment conditions on the durability of concrete structures is one of the most important issues. Hence, regional investigations are necessary for durability based design and evaluation of the models. Persian Gulf is one of the most aggressive regions of the world because of elevated temperature and humidity as well as high content of chloride ions in seawater. The aim of this study is evaluation of some parameters of durability of RC structures in marine environment from viewpoint of corrosion initiation. For this purpose, some experiments were carried out on the real RC structures and in laboratory. The result showed that various uncertainties in parameters of durability were existed.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.43 no.1
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• pp.63-68
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• 2010

Ecological characteristics of Undariopsis peterseniana, an endangered brown alga, were investigated from January to December 2007 at Jeju Island, Korea. The U. peterseniana population formed dense patches at depths of 12~17 m depth. Growth in length of the alga reached a maximum of $168{\pm}36cm$ at June. Sorus were observed from May to August, and a maturation peak was detected in June, when bottom seawater temperatures were around $18^{\circ}C$. After zoospore release, the alga bleached and disappeared after August. Developmental initiation of sporophytes occurred at temperature above $15^{\circ}C$, and sorus formation required approximately 236 degree-days. This is the first study to examine a U. peterseniana population throughout the entire year in a natural habitat.

• Fisheries and Aquatic Sciences
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• v.14 no.3
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• pp.186-191
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• 2011

An agar-degrading enzyme-producing strain was isolated from seawater. The isolate was identified as Microbulbifer sp. SD-1 by 16S rRNA sequencing analysis. The optimal pH and temperature for growth were 6.0 and $30^{\circ}C$, respectively, and growth was possible at pH 9.0 and $60^{\circ}C$. The isolate required 5% NaCl for optimal growth and showed 45% growth activity without NaCl. Agar concentrations of 0-0.4% in the medium did not affect growth. Thin-layer chromatography analysis revealed that this strain could degrade agar into a monosaccharide and oligosaccharide, which may have industrial applications.

• Animal cells and systems
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• v.11 no.2
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• pp.227-234
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• 2007

Spermatogenesis, the reproductive cycle, and the size at first sexual maturity in male Mactra chinensis were investigated by cytological and histological observations. The spermatozoon exhibits a primitive type morphology and is similar to those of other bivalves in that it contains a short midpiece with four mitochondria surrounding the centrioles. The morphologies of the sperm nucleus type and the acrosome shape of this species are cylindrical and modified cap-like, respectively. The spermatozoon is approximately $40-45\;{\mu}m$ in length including the sperm nucleus (about $1.46\;{\mu}m$), acrosome (about $1.20\;{\mu}m$) and tail flagellum. The axoneme of the sperm tail flagellum consists of nine pairs of microtubules at the periphery and a pair at the center. The axoneme of the sperm tail shows a 9+2 structure. The spawning period of this species lasts from June to September, and the main spawning occurs in July and August, when the seawater temperature is greater than $20^{\circ}C$. The percentage of individual male clams at first sexual maturity was 56.5% for those whose shell lengths were 35.1-40.0 mm, and 100% for over 45.1 mm. Accordingly, harvesting clams <35.1 mm in shell length could potentially cause a drastic reduction in recruitment, and a measure indicating a prohibitory fishing size should be taken for adequate fisheries management.

• 한국전산유체공학회:학술대회논문집
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• 2011.05a
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• pp.275-277
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• 2011

KOGAS(Korea Gas Corporation) uses two-type vaporizers to send customers natural gas with imported LNG. In winter season, SMVs(SubMerged combustion Vaporizers) are mainly operated due to low seawater temperature. SMVs consume the natural gas of 1,520 $Nm^3/hr$ and emit a lot of $CO_2$ in winter time. If carbon taxes are activated on climate change, the tax burden will be severely heavy. Accordingly this work carried out numerical simulation with a commercail CFX code to investigate its possibility on the practical use of pure oxygen combustion of SMVs to reduce $CO_2$ and to improve its efficiency. First, a nozzle of a SMV's combustor is modelled. The combustion characteristics of Air/Fuel and Oxygen/Fuel are analyzed under folly insulated condition. Although we couldn't find the carbon reduction and the efficient elevation when the pure oxygen/fuel type was compared to the existing air/fuel one, we need a further study to investigate the effect of $CO_2$ recirculation.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.6 no.3
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• pp.65-72
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• 1997

The horizontal corrosion fatigue tester has been developed for investigating environmental strength. Using this tester, we investigated about corrosion fatigue caracteristics for A106-Gr B steel weldments in 3.5% synthetic seawater and room temperature. Considered parameter is only frequency of 1, 3 and 5Hz.. and Corrosion fatigue crack length was measured by DC potential difference method. From the results, we could find that the horizontal corrosion fatigue tester could be well applied to estimation of fatigue strength. and, In case of 5Hz., corrosion fatigue crack growth pate of A106-Gr B steel weldment was transgranular, and of 1 and 3Hz. showed that transgranular and interfranular was mixed. Also, Material constants of corrosion fatigue crack growth estimated in each frequency were C=9.33$\times$$10^{-9}$ and m=2.93 in 1Hz., C=9.77$\times$$10^{-10}$ and m=3.47 in 3Hz., C=1.02$\times$$10^{-10}$ and m=4.05 in 5Hz

• Proceedings of the Korean Society of Developmental Biology Conference
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• 2001.02a
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• pp.46-49
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• 2001

R. Philippinarum is dioecious and oviparous. In the early vitellogenic oocyte, the Golgi apparatus and mitochondria present in the perinuclear region are involved in the formation of lipid droplets and in lipid granule formation. In the late vitellogenic oocyte, the endoplasmic reticulum, mitochondria in the cytoplasm are involved in the formation of proteid yolk granules. At this time, exogenous lipid granular substance and glycogen particles in the germinal epithelium are passed into the ooplasm of oocyte through the microvilli of the vitelline envelope. Ripe oocytes are about 55-60 $\mu$ m in diameter. The spawning period was once a year between early June and early October, and the main spawning occurred between July and August when seawater temperature was approximately 20 C. The reproductive cycle of this species can be categorized into five successive stages: early active stage (February to March), late active stage (April to May), ripe stage (April to August), partially spawned stage (June to October), and spent/inactive stage (August to March). Gonad developmental phases by histological qualitative analysis showed similar results with those of quantitative image analysis.

• Journal of the Korean Society of Marine Environment & Safety
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• v.1 no.2
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• pp.53-60
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• 1995

We measured lagrangian currents in the coastal regions off east coast of Korea. The experiment sites are the Ulijin region where Polar Front of the East Sea is formed and the Ulgi region where coastal upwelling occurs frequently in summer. Each drifters are equipped with GPS receiver, and their trajectories are montiored by receiving the data transmitted from drifters through radio signal. The experiment with 'transmitting' GPS is very useful in monitering flows in coastal regions. Trajectories of drifters in the Uljin Polar Front region in October 1994 showed counterclockwise flow pattern. The flow pattern agrees with the SST distributions obtained from NOAA-11 AVHRR image for the same period. The lagrangian trajectories of drifters at 5m and 15m depths in the Ulgi region for normal period of April 1995 showed that the currents at the top 15m layer are almost uniform and their magnitude is 29cm/s. However, the currents, measured by KORDI, during the upwelling period of June 1994 showed that the currents at 5m depth were 1.2 times stronger than those at 15m depth. The current pattern in the Ulgi upwelling region agrees with the horizontal and vertical distributions of seawater temperature measured by NFRDA at the same period.

• Journal of Marine Bioscience and Biotechnology
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• v.2 no.4
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• pp.263-266
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• 2007

Vibrio vulnificusis a causative agent of serious diseases in humans resulting from the contact of wound with seawater or consumption of raw seafood. Several studies aimed at detecting V. vulnificus have targeted vvh as a representative virulence toxin gene belonging to the bacterium. In this study, we targeted the rpoS gene, a general stress regulator, to detect V. vulnificus. PCR specificity was identified by amplification of 8 V. vulnificus templates and by the loss of a PCR product with 36 non-V. vulnificus strains. The PCR assay had the 273-bp fragment and the sensitivity of 10 pg DNA from V. vulnificus. SYBR Green I-based real-time PCR assay targeting the rpoS gene showed a melting temperature of approximately $84^{\circ}C$ for V. vulnificus strains. The minimum level of detection by real-time PCR was 2 pg of purified genomic DNA, or $10^3$ V. vulnificus cells from pure cultured broth and $10^3$ cells in 1g of oyster tissue homogenates. These data indicate that real-time PCR is a sensitive, species-specific, and rapid method for detecting this bacterium using the rpoS gene in pure cultures and in infected oyster tissues.

• Fisheries and Aquatic Sciences
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• v.13 no.1
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• pp.49-55
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• 2010

A bacterial strain with phytase and glucose-1-phosphatase activity was isolated from seawater. The colony was identified as an Enterobacter cloacae strain and named E. cloacae B11. A gene, agpEnB11, coding for an intracellular acid glucose phosphatase was cloned from the strain and sequenced. It comprised 1,242 nucleotides and encoded a polypeptide of 413 amino acids. Recombinant glucose-1-phosphatase (AgpEn) was overexpressed in Escherichia coli and purified using Ni-NTA column under native conditions. Purified protein displayed a single band of 47 kDa on SDS-PAGE. AgpEn hydrolyzed a wide variety of phosphorylated compounds, with high activity for glucose-1-phosphate and glucose-6-phosphate. Optimum pH and temperature for enzyme activity were pH 5.0 and $50^{\circ}C$, respectively. Enzyme activity was stimulated by $Ca^{2+}$ and $Co^{2+}$, and inhibited by $Cu^{2+}$.