The structure of dissipation in the western Irish Sea front

We report on an intensive campaign in the summer of 2006 to observe turbulent energy dissipation in the vicinity of a tidal mixing front which separates well mixed and seasonally stratified regimes in the western Irish Sea. The rate of turbulent dissipation ε was observed on a section across the front by a combination of vertical profiles with the FLY dissipation profiler and horizontal profiles by shear sensors mounted on an AUV (Autosub). Mean flow conditions and stratification were obtained from a bed mounted ADCP and a vertical chain of thermistors on a mooring. During an Autosub mission of 60 h, the vehicle, moving at a speed of ~ 1.2 m s^− 1, completed 10 useable frontal crossings between end points which were allowed to move with the mean flow. The results were combined with parallel measurements of the vertical profile of ε which were made using FLY for periods of up to 13 h at positions along the Autosub track. The two data sets, which show a satisfactory degree of consistency, were combined to elucidate the space–time variation of dissipation in the frontal zone. Using harmonic analysis, the spatial structure of dissipation was separated from the strong time dependent signal at the M₄ tidal frequency to yield a picture of the cross-frontal distribution of energy dissipation. A complementary picture of the frontal velocity field was obtained from a moored ADCP and estimates of the mean velocity derived from the thermal wind using the observed density distribution. which indicated the presence of a strong (0.2 m s^− 1) jet-like flow in the high gradient region of the front. Under neap tidal conditions, mean dissipation varied across the section by 3 orders of magnitude exceeding 10^− 2 W m^− 3 near the seabed in the mixed regime and decreasing to 10^− 5 W m^− 3. in the strongly stratified interior regime. The spatial pattern of dissipation is consistent in general form with the predictions of models of tidal mixing and does not reflect any strong influence by the frontal jet.     

A dense water outflow from the Ross Sea, Antarctica: Mixing and the contribution of tides

We use hydrographic, current, and microstructure measurements, and tide-forced ocean models, to estimate benthic and interfacial mixing impacting the evolution of a bottom-trapped outflow of dense shelf water from the Drygalski Trough in the northwestern Ross Sea. During summer 2003 an energetic outflow was observed from the outer shelf ( 500 m isobath) to the  1600 m isobath on the continental slope. Outflow thickness was as great as  200 m, and mean speeds were  0.6 m s^− 1 relative to background currents exceeding  1 m s^− 1 that were primarily tidal in origin. No outflow was detected on the slope in winter 2004, although a thin layer of dense shelf water was present on the outer shelf. When the outflow was well-developed, the estimated benthic stress was of order one Pascal and the bulk Froude number over the upper slope exceeded one. Diapycnal scalar diffusivity (K_z) values in the transition region at the top of the outflow, estimated from Thorpe-scale analysis of potential density and measurements of microscale temperature gradient from sensors attached to the CTD rosette, were of order 10^− 3−10^− 2 m² s^− 1. For two cases where the upper outflow boundary was particularly sharply defined, entrainment rate w_e was estimated from K_z and bulk outflow parameters to be  10^− 3 m s^− 1 ( 100 m day^− 1). A tide-forced, three-dimensional primitive equation ocean model with Mellor-Yamada level 2.5 turbulence closure scheme for diapycnal mixing yields results consistent with a significant tidal role in mixing associated with benthic stress and shear within the stratified ocean interior.     

中子倍增公式在连续提棒事故瞬态特性模拟中的应用

通过中子倍增公式建立模型,分别计算船用核动力反应堆在低功率和高功率运行时发生连续提棒事故后的各主要参数的变化,并将计算结果与三维实时仿真软件计算结果进行比较。结果表明,计算结果与三维实时仿真软件计算结果比较符合,可为事故的处置提供依据。     

水泥土湿喷桩在高速公路海相软土处理中的应用评价

针对海相软土含水量大、粘粒含量高的特点,采用水泥土湿喷桩复合地基处理方式。通过对湿喷桩处理段的大量检测结果进行统计分析,得出的一些结论对于高速公路的软基处理具有实际意义。     

生物柴油应用现状和船用前景

介绍生物柴油的性能特点和国内外发展现状,探讨生物柴油应用于船舶动力装置上所应解决的主要问题,包括制备适合于船舶动力装置使用且能大规模生产的船用生物柴油,船舶柴油机燃烧生物柴油的可靠性、经济性和排放性研究以及对燃油系统的功能要求,指出生物柴油代替现有矿物柴油的前景和研究的迫切性.     

国外海上浮动核电站政策和标准规范

在对国外海上浮动核电站相关的国际法律法规和标准规范研究现状的基础上,重点分析俄罗斯船级社和俄罗斯监察局海上浮动核电站相关标准规范,以为我国开展海上浮动核电站建设所需的标准规范研究提供参考与借鉴。     

Simple Identification of Some Coastal Marine Habitats by Modeling with Sea-Chart Data

A simple numerical model was applied to distinguish permanently oxygenated marine sill basins from periodically anoxic basins in Nordland County, northern Norway. Input data are sill depth, width of the tidal channel, sea surface area, and tidal range. The model produces a Topography Tidal Factor (TTF) that seems to be an adequate index correlating with empirical field data when sills have saddle depths <30 m. The depth of the pycnocline, and the oxygen concentration of the basin water increases logarithmically with the calculated TTF value toward an asymptotic level. At TTF ≥0.02 basins are mostly well-oxygenated and have a permanent fauna of epibenthic and hyperbenthic animals. Basins with TTF <0.02 may become anoxic each autumn, which permanently prevents establishment of communities with multi-annual sessile benthos. Low oxygen concentration may also cause seasonal variation in the occurrence of motile species. In tidal channels, the abundance of bivalves and fish, as well as the biodiversity in general, probably increases with TTF. The applied method may be universally valid in regions shaped by glacial erosion but needs to be further developed by more detailed studies.     

搅拌桩处理公路软弱地基施工工艺的探讨

以搅拌桩工艺处理软土地基,使其承压性能达到道路施工的必要条件。基于工程实践对其使用工艺进行技术优化,对于提高作业效率和降低工程成本是十分必要的。     

Turning Off the Heat: Impacts of Power Plant Decommissioning on Green Turtle Research in San Diego Bay

Green turtles (Chelonia mydas) are among the most high profile species in San Diego Bay, California, and understanding impacts of coastal development and industry is essential to the management and conservation of this local population. Here we describe power plant changing energy production and its impact on turtle habitat use and our ability to research and manage this population. For over 20 years, green sea turtles have been captured, assessed, and tagged near the South Bay Power Plant (SBPP) in the San Diego Bay; from 2002–2011, 104 turtles were captured on 212 occasions. As the 50-year-old SBPP generates less energy, effluent patterns change and water temperatures decrease, presumably to more natural conditions. There has been a concurrent decrease in turtle-capture success, perhaps due to lesser visitation to the effluent site where nets are tended. Seasonal catch-per-unit-effort declined from a high of 4.14 turtles per monitoring day, to a nine-year low of 1.33 during the 2010–2011 season. It is already apparent that management decisions related to energy policy are affecting the habitat and behavior of this stock of endangered turtles. Green turtles are expected to remain in the San Diego Bay after the SBPP becomes inoperative and continuing research will monitor future impacts and distribution shifts resulting from the expected changes in thermal pattern within south San Diego Bay. Research efforts to study this population (i.e., capture methods and locations) will require modification in response to these changes. Lessons learned here are applicable to the immediate coastal development of San Diego, as well as at similar interactions between marine turtles and industrial thermal effluent discharge throughout Southern California, the United States, and beyond.     

沥青搅拌设备燃烧系统的使用维护及故障排查研究

随着我国公路建设的快速发展，越来越多的施工技术应用于公路的建设中，因此施工设备面临着很大的挑战。针对施工中沥青搅拌设备燃烧系统发生的开启风门较大、设备内部阀芯被杂质或者油品堵塞以及无法点火等问题进行了细致的探讨，分析故障排查方法，以保障路面施工不受影响。