Earticle

To study the species composition of fish and distribution of ichthyoplanktons the coastal waters of Dodu-dong, Jeju was investigated for a total of four times underwater at spring (May) and autumn (November) 2008. Fish specimens were collected with a small net by SCUBA diving and fish specimens difficult to collect were photographed underwater using a underwater camera and a camcorder. A total of 43 species, 19 families, 3 orders were collected, and the dominant fish species were Chromis notata and Halichoeres tenuispinnis. The collected fish eggs and larvae were identified as belonging 4 species. The most dominant species Engraulis japonicus and Parabelnnius yatabei. The number of fish species was higher in autumn (November) than in spring (May), whereas the numbers of fish eggs were higher in spring (May). During the survey period, there were observed subtropical fish such as Chaetodontoplus septentrionalis, Microcanthus strigatus, Pomacentrus coelestis, Choerodon azurio, Labroides dimidiatus, Pseudolabrus eoethinus, Stethojulis interrupta terina, Siganus fuscescens and Ostracion immaculatus. The impacts of climate change, such as increasing water temperature have the potential to change geographical fish distribution. Further studies are need to consistently monitoring on the appearance of new subtropical fish correlated with climate change.

In teleosts fish, a number of species perform spectacular migrations between seawater and freshwater environmental conditions. Japanese eel, Anguilla japonica is a commercially important species and catadromous fish that grows in fresh water, and moves to the sea to spawn. This study investigated the histological changes of organs of A. japonica based on acclimated to the aquatic environment of the seawater. To understand histological changes of organs tissue of A. japonica based on fresh water condition and seawater condition, 6 specimens (mean TL 62±2 cm, mean BW 578±43 g) were used for comparative observation using gills and skin. A large amount of mucous cells were found and chloride cells were rarely observed in the gills in fresh water condition. However, mucous cells were not observed and chloride cells were increased in seawater condition. In the skin, mucous cells were observed in each layer of epidermis from fresh water condition. On the other hand, mucous cells of seawater condition were decreased in each layer of epidermis. In the future, additional comparative studies on environmental characteristics related to the aspect of artificial sex maturation by hormone treatment, another organ tissue changes and osmotic pressure will be necessary.

The fish fauna of Hyodon-cheon and Soesokkak in Jeju-do, Korea, was investigated for a total of 15 days underwater from 20 Oct. to 5 Nov. 2008. Fish specimens were collected with a small net by SCUBA diving and fish specimens difficult to collect were photographed underwater using a underwater camera and camcorder. The fish specimens collected from the Hyodon-cheon were identified as 6 species, belonging to 3 families and 3 orders. and the fish specimens of Soesokkak were identified as 30 species, belonging to 22 families and 7 orders. The most dominant species were observed 3 species of Gobiidae in Hyodon-cheon and 7 species of Gobiidae in Seosokkak. Further studies are need to consistently monitoring on a varieties of environmental conditions in Hyodon-cheon and Soesokkak area.

Until recent, primordial germ cells(PGCs) are recognized only by morphological observation, such as their large size and low nucleocytoplasmic ratio. For the molecular analysis of the reproduction, it is important to identify a specific marker of germ cell development and differentiation. The VASA, which was first identified in Drosophila, is reported as a germ-line cell specific marker gene in animals. Many other researches verified its germ cell specific expression during embryogenesis and gametogenesis. VASA is a member of the DEAD(Asp-Glu-Ala-Asp) protein family of ATP-dependent RNA helicase, and plays a critical role in germ-line cell linage. Vasa is expected to be an useful molecular marker for identification of PGCs in reproduction researches of aquaculture species. In this study, we isolated the vasa cDNA, and surveyed its gonad-specific expression in Paralichthys olivaceus. The full-length cDNA of P. olivaceus vasa cDNA was isolated and deduced amino acid sequence was compared to those of the other teleosts. It was 2,461bp long, consisted in 646 amino acids in its ORF region, 175bp of 5’-UTR, and 345bp 3’-UTR. Flounder VASA contained conserved DEAD box, arginine-glycine rich region, and other domains were found. Flounder vasa expressed strongly in the testis and ovary, confirming its property as an gonad-specific marker. These result is expected to be an useful marker for flounder reproduction research and related aquaculture industry.

This experimental study was performed to investigate the mechanical properties of concrete with different replacement rate of recycled fine aggregate. Variables were replacement rate of 0%, 50% and 100% and whether or not inclusion of microfine aggregate. As the replacement rate increased, the compressive strength and the slump of recycled aggregate concrete decreased and the air content in the concrete increased. When the coarse and fine aggregates were completely replaced with the recycled aggregates, the compressive strength was decreased by 20%. And when the microfine aggregates were not included in the fine aggregates, the performance of the recycled aggregate concrete was improved.

Materials such as concrete, rocks, and masonry are often used for structures and their quality is usually verified by compression strength tests on core specimen. However, their quality is not uniform for the entire structure and local defects such as cracks, delamination, voids, honeycombing cannot easily be detected in compression tests on core specimen. In this case, impact-echo method can be used to determine the location and size of defects of materials of structures on site. It is simple enough for on-site tests and yet has relatively good accuracy. It can also be used to measure the thickness of concrete or rocks. This study provides a brief description of the method, test equipment, and two case studies describing its applicability. One of its applicability is to estimate the integrity of large rocks on site and the other applicability is to determine the location of the defect of a sheath grouting of a prestressed-concrete girder bridge.

Experiments were carried out for the turbulent swirling flow and heat transfer characteristics of an eccentric expansion in a circular tube with a constant heat flux. The uniform heat flux condition was imposed to the downstream of an eccentric expansion by using an electrically heated tube and the flow upstream of the expansion was unheated and fully developed. experimental data are presented for local axial velocities and local heat transfer rates in the tube downstream of an abrupt 3:1 expansion. Air was used as the working fluid. In the upstream tube, the Reynolds number was varied from 4*104 to 10*104 and swirl number range(based on the swirl geometry, I.e., L/d ratio) in which the experiments were conducted was L/d = 0, 10. The results obtained are summarized as flows. 1) Fully development region showed from x/d=22 to downstream in case of non swirl flow but x/d=30 on the swirl flow 2) The wall temperature and the bulk temperature showed high when Reynolds numbers was small and swirl intensity was increased. 3) The location of the maximum NU/NUDB showed at the point of 4 step hights, for Re=6*104. 4) Reattachments

In this paper, the authors propose a approach to control problem of the marine vessels which are controlled by actuators. The vessel control problem in the specified area is called a Dynamic Positioning System(DPS). The main objective of this paper is to obtain more useful control design method for DPS. In this problem, a complicate fact is control allocation which is a numerical method for distributing the control signal to the controlled system. For this, many results have been given and verified by other researchers using two individual processes. It means that the controller design and control allocation design process are carried out individually. In this paper, the authors give more sophisticated design solution on this issue. In which the controller design and control allocation problem are unified by a robust controller design problem and Fuzzy methods. The usefulness of proposed approach is verified by simulation with a supply vessel model and found works well.