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261.
Free vibration analysis of symmetrically laminated composite plates resting on Pasternak elastic support and coupled with an ideal, incompressible and inviscid fluid is the objective of the present work. The fluid domain is considered to be infinite in the length direction but bounded in the depth and width directions. In order to derive the eigenvalue equation, Rayleigh-Ritz method is applied for the fluid-plate-foundation system. The efficiency of the method is proved by comparison studies with those reported in the open literature. At the end, parametric studies are carried out to examine the impact of different parameters on the natural frequencies. 相似文献
262.
In order to solve unsteady incompressible Navier–Stokes(N–S) equations, a new stabilized finite element method,called the viscous-splitting least square FEM, is proposed. In the model, the N–S equations are split into diffusive and convective parts in each time step. The diffusive part is discretized by the backward difference method in time and discretized by the standard Galerkin method in space. The convective part is a first-order nonlinear equation.After the linearization of the nonlinear part by Newton's method, the convective part is also discretized by the backward difference method in time and discretized by least square scheme in space. C~0-type element can be used for interpolation of the velocity and pressure in the present model. Driven cavity flow and flow past a circular cylinder are conducted to validate the present model. Numerical results agree with previous numerical results, and the model has high accuracy and can be used to simulate problems with complex geometry. 相似文献
263.
The penetration depth of torpedo anchor in two-layered soil bed was experimentally investigated. A total of 177 experimental data were obtained in laboratory by varying the undrained shear strength of the two-layered soil and the thickness of the top soil layer. The geometric parameters of the anchor and the soil properties (the liquid limit, plastic limit, specific gravity, undrained shear strength, density, and water content) were measured. Based on the energy analysis and present test data, an empirical formula to predict the penetration depth of torpedo anchor in two-layered soil bed was proposed. The proposed formula was extensively validated by laboratory and field data of previous researchers. The results were in good agreement with those obtained for two-layered and single-layered soil bed. Finally, a sensitivity analysis on the parameters in the formula was performed. 相似文献
264.
Eung-Oh Kim Seong-Jong Yoon Kyoung-Hyun Park Dae-Hyun Kim Jeung-Wan Do Eun-Seob Cho 《Ocean Science Journal》2009,44(4):215-220
Fish have developed color vision that is closely adapted to their photic environments, where both spectral sensitivity and the number of visual opsins are influenced. The mackerel used in this study is one of the most important fishery stocks in Korea. The opsin gene of the mackerel juveniles after 20 days in hatching was isolated and characterized based on the molecular study of visual photoreceptor. The full-length mackerel opsin gene was obtained by PCR amplification of genomic DNA, as well as cDNA synthesis. Sequence analysis of the opsin gene showed that it contained a 1,080 bp open reading frame encoding 360 amino acids. Based on Schiff’s base formation (S114, K119), glycosylation (E3, F37) and palmitoylation (S281, 282), the deduced amino acid sequence had a typical rod opsin. The mackerel and Gempylus serpens showed 73.7% DNA homology on opsin gene, which was higher than any other of investigated species. In the analysis of phylogenetic relationship, the genetic placement of the mackerel is closer to that of Scombroidei than Labroidei, with supporting somewhat strong bootstrap value. In the analysis of Northern and RT-PCR, the probed products were observed only in rapidly growing juveniles. These findings indicate that in mackerel opsin mRNA expression can be detected in day-20 hatching larvae. It may play an important role in stimulating growth hormone. 相似文献
265.
Shiho Kobayashi Eisuke Hashimoto Masayuki Nagao Yoshio Takasugi 《Journal of Oceanography》2009,65(5):657-664
We observed tidal currents, turbulent energy dissipation and water column stratification at the entrance of a narrow strait
(Neko Seto) in the Seto Inland Sea, Japan, using a free-falling turbulent microstructure profiler (TurboMAP) and acoustic
Doppler current profiler (ADCP). The variation in turbulent energy dissipation at the entrance of the strait was not at quarter-diurnal
frequency but at semi-diurnal frequency; turbulent energy dissipation was enhanced during the ebb tide, although it was moderate
during the flood tide. This result is consistent with the results of Takasugi (1993), which showed the asymmetry of tidal
energy loss during a semidiurnal tidal cycle using control volume analysis. It is suggested that significant turbulent energy
dissipation is generated in the strait, which influences the properties of water outside the strait when tidal currents flow
out from the strait. 相似文献
266.
The R/V Mirai conducted hydrographic surveys in the western Arctic Ocean during summer 2004 (Mirai04) over wide east-west
ranges from Alaska to eastern Siberia, where sea-ice cover has been greatly reduced in recent summers. The obtained data reveal
differences in silicate profiles between shelf slope areas east and west of the Chukchi Plateau, the ridge that divides the
Canada Basin into the Alaskan and east Siberian sides. East of the plateau, a single silicate maximum was found in a layer
of Pacific-origin winter water, as examined in many previous studies. In contrast, west of the plateau, we found vertical
double silicate maxima, which are reported for the first time in this study. The shallower silicate maximum corresponded to
an N** minimum, signaling denitrification at the shelf bottom. This suggests that the shallower silicate maximum was caused
by the spreading of shelf water. In contrast, the deeper silicate maximum corresponded to an oxygen minimum and a maximum
silicate/phosphate ratio (Si/P), suggesting that this deeper maximum resulted from the decomposition of opal-shelled organisms.
We also compared a silicate profile from Mirai04 to aprofile from the Arctic Ocean Section 94 (AOS94) expedition of 1994,
a heavy ice year. The results suggest that sea-ice loss has enhanced biological activities, likely resulting in the appearance
of the deeper silicate maximum. 相似文献
267.
268.
269.
The purpose of this study was to examine the structural changes that macrozoobenthic communities underwent as a result of the annual summer hypoxia at the northern part of Gamak Bay, Korea. During this study period, summer hypoxia occurred at the northern part of Gamak Bay in July. Under hypoxic conditions, both the number of species and population density decreased rapidly. Species diversity also manifested lower values during this hypoxic period. Faunal composition changed seasonally with Capitella capitata dominant at the hypoxic sites in spring but disappearing in summer. The health condition of the benthic faunal community assessed by the composition of functional groups within community also changed due to the summer hypoxia from a slightly polluted condition to a highly polluted condition. From these results it has been shown that the recent macrozoobenthic community structure in Gamak Bay has returned to a state similar to what it was before dredging works commenced. 相似文献
270.
Takashi Doi Michiaki Takano Kei Okamura Tamaki Ura Toshitaka Gamo 《Journal of Oceanography》2008,64(3):471-477
We present the results of a chemical survey at a submarine volcano, Teishi Knoll, obtained using a submersible in-situ Mn
analyzer (GAMOS) mounted on an autonomous underwater vehicle (AUV) platform. During this survey, high-resolution data of dissolved
Mn were obtained in three dimensions in nearly real time. The AUV enabled continuous detailed observations along a preprogrammed
pathway, which could not have been performed with conventional CTD hydrocasts. During this observation, anomalously high dissolved
Mn concentrations were obtained within the crater, corresponding to high water temperatures. The anomalies might be a hydrothermal
signature due to volcanic activity from the crater. 相似文献