Air–sea exchange of mercury vapour over the Gulf of Gda sk and southern Baltic Sea

The total gaseous mercury (TGM) in air over the coastal station at Hel and over the southern Baltic Sea was measured during the summer and winter conditions. Recorded 30-min resolution TGM data showed both higher concentrations and variability during the summer compared to the winter conditions. The summer TGM data ranged from 1.1 to 7.5 ng m⁻³, while the winter data ranged from 0.8 to 4.4 ng m⁻³. The TGM content in air over the southern Baltic Sea indicated that, in general, during the summer conditions, the sea-to-air transport of gaseous mercury dominated, while during the winter season, a tendency of gaseous mercury to sink into the water has been found. The evidences of enhanced water-to-air transfer of mercury vapour were noted, in particular, over the shallow waters of the Gulf of Gda sk under the strong water-to-air temperature gradients. Obtained results indicate that under such conditions, the coastal waters could act as a significant source of mercury vapour that may contribute to the overall budget of atmospheric mercury over the Baltic proper.     

矿物绝缘电缆船用分析

文献所述矿物绝缘电缆指氧化镁绝缘铜管护套电缆,执行GB/T 13033-2007/IEC 60702:2002《额定电压750V及以下矿物绝缘电缆及终端》,耐火性能同时通过BS 6387 C.W.Z考核。符合《钢质海船入级规范》相关电缆的规定,产品经弯曲试验、压扁试验,表明用作耐火电缆,较之等同耐火等级及等同载流量的其它电缆,适合实船敷设。     

On the key role of nutrient data to constrain a coupled physical–biogeochemical assimilative model of the North Atlantic Ocean

A sequential assimilative system has been implemented into a coupled physical–biogeochemical model (CPBM) of the North Atlantic basin at eddy-permitting resolution (1/4°), with the long-term goal of estimating the basin scale patterns of the oceanic primary production and their seasonal variability. The assimilation system, which is based on the SEEK filter [Brasseur, P., Verron, J., 2006. The SEEK filter method for data assimilation in oceanography: a synthesis. Ocean Dynamics. doi: 10.1007/s10236-006-0080-3], has been adapted to this CPBM in order to control the physical and biogeochemical components of the coupled model separately or in combination. The assimilated data are the satellite Topex/Poseidon and ERS altimetric data, the AVHRR Sea Surface Temperature observations, and the Levitus climatology for salinity, temperature and nitrate.In the present study, different assimilation experiments are conducted to assess the relative usefulness of the assimilated data to improve the representation of the primary production by the CPBM. Consistently with the results obtained by Berline et al. [Berline, L., Brankart, J-M., Brasseur, P., Ourmières, Y., Verron, J., 2007. Improving the physics of a coupled physical–biogeochemical model of the North Atlantic through data assimilation: impact on the ecosystem. J. Mar. Syst. 64 (1–4), 153–172] with a comparable assimilative model, it is shown that the assimilation of physical data alone can improve the representation of the mixed layer depth, but the impact on the ecosystem is rather weak. In some situations, the physical data assimilation can even worsen the ecosystem response for areas where the prior nutrient distribution is significantly incorrect. However, these experiments also show that the combined assimilation of physical and nutrient data has a positive impact on the phytoplankton patterns by comparison with SeaWiFS ocean colour data, demonstrating the good complementarity between SST, altimetry and in situ nutrient data. These results suggest that more intensive in situ measurements of biogeochemical nutrients are urgently needed at basin scale to initiate a permanent monitoring of oceanic ecosystems.     

基于参数化有限元的深潜器主框架优化设计

深潜器主框架是一个大型空间刚架结构,如何对这类复杂的工程结构进行优化,使其既满足自身的强度和刚度要求,同时又满足总体设计对主框架重量和布置的要求,这些仅仅根据经验是不够的,如何充分利用现有的大型通用有限元软件的优化设计功能显得尤为重要.本文利用现有通用大型有限元软件MSC Patran/Nastran,基于参数化设计的思想,对深潜器主框架进行了两个方面的优化设计:首先在初步设计方案的基础上,应用有限元静力分析功能,对方案进行渐进结构拓扑优化;其次,对选定的方案,分别采用可行方向法、序列线性规划法和序列二次规划法这3种优化算法对主框架进行优化,并比较各优化方法的适用性,说明了对于复杂结构存在的目标函数多峰值现象.结果表明,通过参数驱动有限元优化能够显著减轻主框架的整体重量,使材料达到最大的利用效率,具有实用意义.