Response of coastal marine eco-environment to river fluxes into the sea: A case study of the Huanghe (Yellow) River mouth and adjacent waters

The impact of the Huanghe (Yellow) River outflows on its estuary was investigated with river gauging and shipboard hydrographic observations. The river flux has been decreasing dramatically; the discharges of water and sediment in the 1990s dropped to 27.4% and 31.9% of those in the 1950s, respectively, resulting in frequent and lengthy events of downstream channel dry-up since the 1970s. There were accumulatively 897 zero-flow days during the 1990s in the river course below the Lijin Hydrological Station, 100 km upstream from the river mouth, which is 82.4% of that in 1972. As freshwater input decreases, river-borne nutrients to the estuarine increased significantly. Concentration of dissolved inorganic nitrogen (DIN) in the 1990s was four times of that in 1950s. Changes in amount and content of the riverine inputs have greatly affected the estuarine ecosystem. Over the past several decades, sea surface temperature and salinity in the estuary and its adjacent waters increased and their distribution pattern altered in response to the reduction of freshwater inflow. The distribution of and seasonal succession in nutrient concentrations in the surface layer have also changed with a shift of river outlet and the decrease in riverine nutrient loads. Furthermore, deterioration of estuarine ecosystem by less river input has decreased primary productivity in the deltaic region waters, and in turn depressed the fishery. (C) 2008 Published by Elsevier Ltd.

PCBs and its coupling with eco-environments in Southern Yellow Sea surface sediments

In this paper, the spatial distribution and source of the PCBs in surface sediments of the Southern Yellow Sea (SYS) and influencing factors, such as the sediment characteristics (components, relative proportions and total organic carbon contents), and hydrodynamic conditions were analyzed. PCB concentrations in the surface sediments ranged from 518-5848 pg/g, with average values of 1715 pg/g decreasing sharply compared to last year. In the study area, the PCB pollution level in the middle area was the highest, followed by that of the east coast and the west coast, respectively. Although the PCB level in the coastal areas was lower than that in the middle areas, it was proven in our study that the Yellow Sea obtained PCBs by virtue of river inputs. There was a positive and pertinent correlation between the clay proportion and PCB concentrations, and the increase of the PCB concentrations was directly proportional to the increase of TOC contents, with r = 0.61, but it was contrary to the sediment grain size. Consequently, the factors controlling PCB distribution had direct or indirect relationships with sediment grain size; moreover, the hydrodynamic conditions determined the sediment components and grain size. In conclusion, hydrodynamic conditions of the Yellow Sea were the most important influencing factors effecting the distribution of PCBs in the surface sediments of the SYS. (C) 2007 Elsevier Ltd. All rights reserved.

Theoretical and experimental research on time-optimal trajectory planning and control of industrial robots

提出了一种用于工业机器人时间最优轨迹规划及轨迹控制的新方法，它可以确保在关节位移、速度、加速度以及二阶加速度边界值的约束下，机器人手部沿笛卡尔空间中规定路径运动的时间阳短。在这种方法中，所规划的关节轨迹都采用二次多项式加余弦函数的形式，不仅可以保证各关节运动的位移、速度 、加速度连续而且还可以保证各关节运动的二阶加速度连续。采用这种方法，既可以提高机器人的工作效率又可以延长机器人的工作寿命以PUMA560机器人为对象进行了计算机仿真和机器人实验，结果表明这种方法是正确的有效的。它为工业机器人在非线性运动学约束条件下的时间最优轨迹规划及控制问题提供了一种较好的解决方案。

An industrial scale dehydration process for natural gas involving membranes

An industrial scale dehydration process based on hollow fiber membranes for lowering the dew point of natural gas is described in this paper. A pilot test with the feed flux scale of 12x10(4) Nm(3)/d was carried out. Dew points of -8 degreesC-13 degreesC at a gas transport pressure in the pipeline of 4.6M Pa and methane recovery of more than 98% were attained. The water vapor content of the product gas could be maintained around 0.01 vol% during a continuous run of about 700 hours. The effects of feed flux and operation pressure on methane recovery and water vapor content were also investigated. Additionally, some auxiliary technologies, such as a full-time engine using natural gas as fuel and the utilization of vent gas in the process, are also discussed. A small amount of the vent gas from the system was used as a fuel for an engine to drive vacuum pumps, and the heat expelled from the engine was used to warm up the natural gas feed. The whole system can be operated in a self-sustainable manner from an energy point of view, and has a relatively high efficiency in the utilization of natural gas.