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61.
Anja Engel Lynn Abramson Jennifer Szlosek Zhanfei Liu Gillian Stewart David Hirschberg Cindy Lee 《Deep Sea Research Part II: Topical Studies in Oceanography》2009,56(18):1408-1419
The quantitative relationship between organic carbon and mineral contents of particles sinking below 1800 m in the ocean indicates that organisms with mineral shells such as coccolithophores are of special importance for transporting carbon into the deep sea. Several hypotheses about the mechanism behind this relationship between minerals and organic matter have been raised, such as mineral protection of organic matter or enhanced sinking rates through ballast addition. We examined organic matter decomposition of calcifying and non-calcifying Emiliania huxleyi cultures in an experiment that allowed aggregation and settling in rotating tanks. Biogenic components such as particulate carbon, particulate nitrogen, particulate volume, pigments, transparent exopolymer particles (TEP), and particulate amino acids in suspended particles and aggregates were followed over a period of 30 d. The overall pattern of decrease in organic matter, the amount of recalcitrant organic matter left after 30 d, and the compositional changes within particulate organic matter indicated that cells without a shell are more subject to loss than calcified cells. It is suggested that biogenic calcite helps in the preservation of particulate organic matter (POM) by offering structural support for organic molecules. Over the course of the experiment, half the particulate organic carbon in both calcifying and non-calcifying cultures was partitioned into aggregates and remained so until the end of the experiment. The partial protection of particulate organic matter from solubilization by biominerals and by aggregation that was observed in our experiment may help explain the robustness of the relationship between organic and mineral matter fluxes in the deep ocean. 相似文献
62.
Cindy Lee Robert A. Armstrong J. Kirk Cochran Anja Engel Scott W. Fowler Madeleine Goutx Pere Masqu Juan Carlos Miquel Michael Peterson Christian Tamburini Stuart Wakeham 《Deep Sea Research Part II: Topical Studies in Oceanography》2009,56(18):1363-1368
The MedFlux project was devised to determine and model relationships between organic matter and mineral ballasts of sinking particulate matter in the ocean. Specifically we investigated the ballast ratio hypothesis, tested various commonly used sampling and modeling techniques, and developed new technologies that would allow better characterization of particle biogeochemistry. Here we describe the rationale for the project, the biogeochemical provenance of the DYFAMED site, the international support structure, and highlights from the papers published here. Additional MedFlux papers can be accessed at the MedFlux web site (http://msrc.sunysb.edu/MedFlux/). 相似文献
63.
Effects of cold eddy on phytoplankton production and assemblages in Luzon strait bordering the South China Sea 总被引:6,自引:0,他引:6
Yuh-Ling Lee Chen Houng-Yung Chen I. -I. Lin Ming-An Lee Jeng Chang 《Journal of Oceanography》2007,63(4):671-683
The biochemical effects of a cold-core eddy that was shed from the Kuroshio Current at the Luzon Strait bordering the South
China Sea (SCS) were studied in late spring, a relatively unproductive season in the SCS. The extent of the eddy was determined
by time-series images of SeaWiFS ocean color, AVHRR sea surface temperature, and TOPEX/Jason-1 sea surface height anomaly.
Nutrient budgets, nitrate-based new production, primary production, and phytoplankton assemblages were compared between the
eddy and its surrounding Kuroshio and SCS waters. The enhanced productivity in the eddy was comparable to wintertime productivity
in the SCS basin, which is supported by upwelled subsurface nitrate under the prevailing Northeastern Monsoon. There were
more Synechococcus, pico-eucaryotes, and diatoms, but less Trichodesmium in the surface water inside the eddy than outside. Prochlorococcus and Richelia intracellularis showed no spatial differences. Water column-integrated primary production (IPP) inside the eddy was 2–3 times that outside
the eddy in the SCS (1.09 vs. 0.59 g C m−2d−1), as was nitrate-based new production (INP) (0.67 vs. 0.25 g C m−2d−1). INP in the eddy was 6 times that in the Kuroshio (0.12 g C m−2d−1). IPP and INP in the eddy were higher than the maximum production values ever measured in the SCS basin. Surface chlorophyll
a concentration (0.40 mg m−3) in the eddy equaled the maximum concentration registered for the SCS basin and was higher than the wintertime average (0.29
± 0.04 mg m−3). INP was 3.5 times as great and IPP was doubled in the eddy compared to the wintertime SCS basin. As cold core eddies form
intermittently all year round as the Kuroshio invades the SCS, their effects on phytoplankton productivity and assemblages
are likely to have important influences on the biogeochemical cycle of the region. 相似文献
64.
65.
We study, by means of a spherical collapse model, the effect of shear, rotation, and baryons on a generalized Chaplygin gas (gCg) dominated universes. We show that shear, rotation, and the baryon presence slow down the collapse with respect to the simple spherical collapse model. The slowing down in the growth of density perturbation is able to solve the instability of the unified dark matter (UDM) models described in previous papers (e.g., Sandvik et al. 2004) at the linear perturbation level, as also shown by a direct comparison of our model with previous results. 相似文献
66.
In this paper, the problem of incident waves propagating over a submerged poro-elastic structure is studied theoretically. A linear wave theory is used to describe the wave motion. The submerged poro-elastic structure is modeled based on Biot's theory, in which the fluid motion is described using the potential wave theory of Sollitt and Cross (1972). In the present approach, the problem domain is divided into four subregions. Using general solutions for each region and matching dynamic and kinematic conditions for neighboring regions, analytic solutions are derived for the wave fields and poro-elastic structure. The present analytic solutions compare very well with simplified cases of impermeable, rigid structures, and with those of porous structures. Using the present analytic solution, the effects of a poro-elastic submerged structure on waves are studied. The results show that softer poro-elastic structures can induce higher reflection and lower transmission from incident waves. For low permeability conditions, the elasticity of the structure can induce resonance, while higher permeability can depress the resonant effects. 相似文献
67.
Hyungwon Shim Bong-Huan Jun Pan-Mook Lee Hyuk Baek Jihong Lee 《Ocean Engineering》2010,37(11-12):1036-1047
This paper presents a control technique for structured undersea tasks that require a high degree of precision. The overall efficiency of tele-operated underwater manipulation is improved by reducing the burden on the human operator. A new workspace-control system composed of a computer and input devices in workspace was developed to support the operator. The computer transforms the desired velocity of end-effector in workspaces to desired joint angles by solving the inverse kinematics of the slave manipulators. The desired joint angles are transferred to the slave controller through RS-485 serial communication, and be followed by the slave manipulator. The developed master system provides advantages in conducting structured tasks(coring, drilling, underwater connector mating, etc.) that require precise control of the end-effector’s motion and attitude. The existing master system, however, is more useful for unstructured tasks than newly developed master system. By combining the two master systems, the work efficiency of the underwater tele-operated manipulator system was improved. This paper presents the development of the workspace-control system and a working strategy to alleviate operator’s burden in underwater works. Experimental results are presented to evaluate the effectiveness of the proposed method using underwater manipulators mounted on the KORDI deep-sea ROV Hemire. 相似文献
68.
The shape optimization of the 2-dimensional wing in ground effect (WIG) has been performed by the integration of CFD (computational fluid dynamics) and MOGA (multi-objective genetic algorithm). Because of the trade-off between the aerodynamic forces and the height stability, it is difficult to satisfy the design requirements of efficiency and stability at the same time. In this study, the lift coefficient, the lift-drag ratio and the static height stability are chosen as the objective functions to obtain the optimal wing profiles of a WIG craft. An NACA0015 airfoil is used for the baseline model; the aerodynamic characteristics of the base model are compared with that of the optimal solutions. The profile of the airfoil is constructed by four Bezier curves with fourteen control points resulting in the eighteen coordinates, which are adopted as the design variables. The optimal solutions of the multi-objective optimization are not unique but a set of the non-dominated optima: the Pareto frontiers or a Pareto set. As the results of the multi-objective optimization, the forty Pareto optima, which include high-lift, high-efficiency, and more stable airfoils on the edge of the 3-dimensional objective space, are obtained at thirty evolutions of the generation. 相似文献
69.
A large mid-channel sand bar in the macrotidal seaway of outer Asan Bay, Korea: 30 years of morphologic response to anthropogenic impacts 总被引:1,自引:1,他引:0
Tae Soo Chang Seong-Pil Kim Dong Geun Yoo Seungjong Lee Eunil Lee 《Geo-Marine Letters》2010,30(1):15-22
Over the past three decades, dike constructions along the shores and dredging activities for navigation purposes have caused
significant sedimentologic/morphologic modifications of a mid-channel bar situated in the tidal seaway of outer Asan Bay,
Korea, as shown by a comparison of two sediment datasets collected in the channel and over the bar in 1977 and 2008. In addition,
three hydrographic charts published in 1976, 1989, and 2006 were analyzed using GIS to estimate sand volume budgets and any
bar migration. The bar is currently about 15 km long and 2–5 km wide, with a relief of 15 m. It is elongated in the tidal
flow direction, but asymmetric in cross section. Chart analyses reveal a dramatic reduction in size and volume over the study
period. An approximate 19% net loss in total sediment volume was calculated between 1976 and 1989. Since then, a net gain
of about 7% has been estimated. The surface areas between selected depth contours reveal a similar pattern, i.e., substantial
shrinking until 1989, followed by slight expansion up to 2006. Comparing selected textural parameters (mean grain size, sorting)
of a 2008 sediment sampling campaign with those of a 1977 survey, it was found that mean grain sizes have decreased by as
much as 1-phi interval, and that the sediments have become more poorly sorted in the vicinity of the bar over the 30-year
study period, probably due to a sudden decrease in tidal energy flux after completion of the adjacent dikes. A particular
feature is the temporary response of the bar to man-made impacts, characterized by substantial shrinking along its southwestern
flank, and slight expansion along its northeastern flank. The observed changes in bar morphology can plausibly be explained
by a sudden decrease in sediment supply resulting from a reduction in tidal prism in the wake of diking. The bar initially
shrunk, but since 1989 has begun to gradually recover. To compensate the deficit, the bar has lowered its base level by scouring
troughs along both flanks. 相似文献
70.
结合T-Matrix方法和雨滴谱仪数据反演双偏振参量,设计了一种雨滴谱反演评估方法(雨滴谱法),利用其反演结果可对双偏振天气雷达数据进行评估。将此方法应用于不同类型降水过程的雷达偏振参量数据质量评估,结果表明:满足微雨条件时,雨滴谱法与传统的微雨滴法均能有效监测由雷达系统误差导致的观测偏差,且评估结果十分接近;不满足微雨条件时,雨滴谱法评估的不同类型降水过程的雷达数据质量与满足微雨条件下的评估结果十分接近,客观证明了系统调整后雷达运行良好、数据质量稳定;不同雨强(R)情况下,雨滴谱法的评估结果具有一致性。10 mm·h-1≤R<20 mm·h-1时,雷达观测的数据质量最为稳定。该雨滴谱法适用范围广,可动态评估双偏振雷达偏振参量质量,有助于雷达调整和数据校正。 相似文献