Effects of temperature and salinity on the asexual reproduction of <Emphasis Type="Italic">Nemopilema nomurai</Emphasis> (Scyphozoa: Rhizostomeae)     

Hye Eun Lee  Chang Hoon Han  ByeongHo Kim  Won Duk Yoon 《Ocean Science Journal》2017,52(4):573-579

Asexual reproduction of polyps of Nemopilema nomurai, of which massive blooms have occurred in Korean waters every summer since 2003, were tested under 20 combinations of temperature (10, 15, 20, and 25°C) and salinity (12, 17, 22, 27, and 32 psu). Production of podocysts increased with increasing temperature (20 and 25°C), while strobilaton and ephyral liberation occurred at low temperatures (10 and 15°C). Temperature also affected the initiation of ephyral liberation (approximately 25 days at 15°C, and 50 days at 10 and 20°C, respectively). The number of podocysts was only significantly different between 27 and 32 psu, and salinity had no significant effect on the excystment of podocysts, ephyral liberlation, showing N. nomurai is euryhaline. These results demonstrated that temperature is an important factor on both the podocysts production and ephyrae liberation, possibly explaining early spring liberation of ephyrae and continuous introduction of medusae into Korean coastal waters through summer to fall.  相似文献   

Response of Pile Groups Driven in Sand Subjected to Combined Loads     

Yoon Seok Choi  Jintae Lee  Monica Prezzi  Rodrigo Salgado 《Geotechnical and Geological Engineering》2017,35(4):1587-1604

Although the loads applied on piles are usually a combination of both vertical and lateral loads, very limited experimental research has been done on the response of pile groups subjected to combined loads. Due to pile–soil–pile interaction in pile groups, the response of a pile group may differ substantially from that of a single pile. This difference depends on soil state and pile spacing. This paper presents results of experiments designed to investigate pile interaction effects on the response of pile groups subjected to both axial and lateral loads. The experiments were load tests performed on model pile groups (2 × 2 pile groups) in calibration chamber sand samples. The model piles were driven into the sand samples prepared with different relative densities using a sand pluviator. The combined load tests were performed on the model pile groups subjected to different axial load levels, i.e., 0 (pure lateral loading), 25, 50, and 75% of the ultimate axial load capacity of the pile groups, defined as the load corresponding to a settlement of 10% of the model pile diameter. The combined load test results showed that the bending moment and lateral deflection at the head of the piles increased substantially for tests performed in the presence of axial loads, suggesting that the presence of axial loads on groups of piles driven in sand is detrimental to their lateral capacity.  相似文献   

Wintertime suspended sediment simulation in the Huanghai and East China Seas   总被引：1，自引：0，他引：1  

CHOI Byung Ho  MUN Jong Yoon  KO Jin Seok 《海洋学报(英文版)》2005,24(1):46-59

A simulation of suspended sediment movement relating to tidal and wave forcing during a winter monsoon in November 1983 in the Huanghai and East China Seas continental shelf is attempted by using the model describing the cohesive/non-cohesive sediment resuspension generated by interactions between currents and waves.model simulation showed that sediment concentration was increased by resuspension at shallow depths during the strong storm conditions due to high bottom stress interacted between currents and waves. This result is in general agreement with observations in horizontal distribution of suspended sediment distribution.At three current meter mooring positions off the southern Shandong Peninsula resuspension occurred only at a depth of 22m,nearest coastal position and at deeper parts at depths of 51 and 80m wave-current interaction effects were not significant. It has shown that the present model simulation demonstrated the capability of reproduction of suspended sediment movement under wintertime extreme event reasonably well.  相似文献   

Hydraulic and Thermal Conductivities of Kaolin–Silica Mixtures under Different Consolidation Stresses     

Keunbo Park  Junhwan Lee  Hyung-Koo Yoon 《Marine Georesources & Geotechnology》2016,34(6):532-541

Stable backfill materials for the heat sensitive structures of buried power cables, hot water pipes, and gas pipelines are suggested to have low permeability and high heat transfer characteristics. The hydraulic and thermal conductivities of backfill materials or clay liners are important parameters in proper design and construction of geotechnical structures involved with heat transfers. In this study, to investigate the optimal natural backfill or liner materials, thermal and hydraulic conductivities of kaolin–silica mixtures examined based on the results from laboratory tests under different consolidation conditions. From the experiment results, the thermal conductivity increases while hydraulic conductivity decreases with increasing density during consolidation process. As a result, back-fill materials with high kaolin content under low consolidation stress were desirable materials for burial of heat sensitive structures.  相似文献   

Stress-Strain Behavior of Light-Weighted Soils     

Gil-Lim Yoon  Byung-Tak Kim 《Marine Georesources & Geotechnology》2013,31(3):248-266

Unconfined and triaxial compression tests were carried out to examine the behavior of light-weighted soils (LWS) consisting of expanded polystyrene (EPS), dredged soils, and cement with respect to initial water content. The stress-strain behavior of LWS are analyzed with varying initial water content and silt contents of dredged soils, cement ratio, and confined stress. As initial water contents increase, the compressibility index increases and the preconsolidation pressure was vice versa. As initial water contents increase, the slope of stress-strain curve in elastic zone increases and strain rate at failure decreases and the strain rate at failure was not changed by the being of foams. As initial water contents increase, a compressive strength of LWS decreases. The decrement ratio of compressive strength of LWS with foams increases as cement content increases and initial water contents decreases. The compressive strength increases as silt contents increases.  相似文献   

Dissolved trace metals in the Western Mediterranean Sea: total concentration and fraction isolated by C18 Sep-Pak technique     

Yi-Yong Yoon  Jean-Marie Martin  Marie Helen Cott 《Marine Chemistry》1999,66(3-4)

An investigation of trace metal distributions in the Western Mediterranean Sea was carried out during the RRS Discovery cruise (July 1993) in which a transect from the Strait of Gibraltar to the Strait of Sicily was conducted. Organically complexed dissolved trace metals and their total concentrations were measured to investigate the end-members and to predict the environmental capacity of the Mediterranean for potential toxic metals. The distribution of trace metals can be accounted for by the mixing of several end-members and by some atmospheric inputs to the surface water. For Pb and Fe, the effects of the atmospheric inputs are more pronounced than for the other metals. Due to the rapid exchange of water masses, the Western Mediterranean may have the ability to assimilate the increased external inputs for some trace metals such as Cu, Cd, Ni and Zn. But the external inputs for Pb and Fe exceed the removal capacity of the Western Mediterranean and these elements may accumulate in the water column of the western basin. The C18 Sep-Pak technique and direct determination by DPASV were used to determine the amount of trace metal–organic complexes. The C18 Sep-Pak column isolates only a small fraction of trace metals except for Cu. The maximum hydrophobic fractions for the studied trace metals, except for Cd and Pb, which are not detectable, were found in the subsurface layer at all stations. This maximum may well be linked to picoplankton activity and the picoplankton, prochlorophytes may have an important role in the speciation of dissolved Cu as well as Synechococcus. These organic ligands for Cu were produced at the maximum of biological activity in the Western Mediterranean basin and seem to be accumulated at halocline level by Mediterranean hydrodynamic characteristics. However, direct determination by DPASV showed that the major part of Cu, Cd and Pb, complexed by organic materials, was not isolated by C18 Sep-Pak technique.  相似文献