To investigate the impacts of nutrient concentrations and N：P：Si ratios on the ecosystem of the Huanghai Sea （Yellow Sea）, the current status and long-term variation of nutrients concentrations and ratios as well ...To investigate the impacts of nutrient concentrations and N：P：Si ratios on the ecosystem of the Huanghai Sea （Yellow Sea）, the current status and long-term variation of nutrients concentrations and ratios as well as phytoplankton community structure in the Huanghai Sea were collected and analyzed. The results reveal great annual and seasonal fluctuations in the nutrient concentrations and N：P：Si ratios during 1998-2008 with no clear pattern observed in the whole region. Yet on a seasonal scale of spring and in the coastal regions such as the Jiaozhou Bay and Sanggou Bay, the increase of DIN concentration and N：P ratio as well as the decrease of phosphate and sili- cate concentrations and Si：N ratios were relatively significant. Many pelagic ecosystem changes have occurred concurrent with these changes of the nutrient regime, such as the recent increase of primary production, changes of phytoplankton chlorophyll a biomass and abundance, an increase of eutrophication, and occurrence of HABs. In addition, new trends in the variation of nutrients seem to be developing in some particular transect such as 36N, which suggests that long-term and systematic ecosystem monitoring in the Huanghai Sea is necessary.展开更多
Three mesocosm experiments were conducted in the East China Sea during blooms of Prorocentrum donghaiense Lu in May of 1998,2002 and 2003 to examine the role of nutrients in the formation of these harmful algae blooms...Three mesocosm experiments were conducted in the East China Sea during blooms of Prorocentrum donghaiense Lu in May of 1998,2002 and 2003 to examine the role of nutrients in the formation of these harmful algae blooms（HABs）.The results showed that there was interspecies competition between P.donghaiense and Skeletonema costatum（Grev.） Cleve.The cell number of P.donghaiense and S.costatum accounted for about 85% and 11% of the total cell number of phytoplankton respectively at the beginning of the experiment in May 1998.In May 2002,at the beginning of the experiment,the cell number of P.donghaiense accounted for 55%-66% of the total and S.costatum accounted for 32%-42%.The density of P.donghaiense and S.costatum was over 95% and 1%-5% respectively in May 2003.The results of these three mesocosm experiments showed that the dominant species in this specific community varied with different nutrient availability.Under low-phosphate conditions,the dominant species was P.donghaiense,while S.costatum became dominant in phosphate-replete cases.The average growth rate（1.08 d-1） of S.costatum in exponential growth phase was higher than that（0.39 d-1） of P.donghaiense.In the mesocosm,S.costatum predominated in the mesocosm by its rapid growth.When phosphorus was depleted,the cell number of S.costatum dropped rapidly,while P.donghaiense Lu decreased more slowly.The results from mesocosm experiment may explain why：（1） P.donghaiense bloom usually occurs in May,when phosphate concentration is low;（2） the bloom of S.costatum appears in early spring and summer time,when nutrients increase with increasing Changjiang River（Yangtze River） runoff;（3） the bloom of S.costatum is short and that of P.donghaiense Lu can last more than a month in the East China Sea.展开更多
Cryogenic machining is a new technology which makes use of the special mechanicalprcperties of niaterials in a cryogenic or a 'super cold' state for machining. The control of acryogenic machining system(CMS)i...Cryogenic machining is a new technology which makes use of the special mechanicalprcperties of niaterials in a cryogenic or a 'super cold' state for machining. The control of acryogenic machining system(CMS)is one of the key problems which need to be solved for practi-cal cryogenic machining A temperature field control principle is presented which calculates theheat source temperature in the light of the tool temperature field information, and a control mod-el of three-dimensional dynamic temperature field for CMS is established, and the boundary con-ditions and the heat source of temperature field in orthogonal cutting are discussed. Based on theinvestigation of the control feature and technique. a prototype system for controlling CMS is crea-ted.展开更多
基金The China-Korea Cooperative Research on the Yellow Sea Cold Water Massthe National Key Basic Research Project of China under contract No. 2010CB428703
文摘To investigate the impacts of nutrient concentrations and N：P：Si ratios on the ecosystem of the Huanghai Sea （Yellow Sea）, the current status and long-term variation of nutrients concentrations and ratios as well as phytoplankton community structure in the Huanghai Sea were collected and analyzed. The results reveal great annual and seasonal fluctuations in the nutrient concentrations and N：P：Si ratios during 1998-2008 with no clear pattern observed in the whole region. Yet on a seasonal scale of spring and in the coastal regions such as the Jiaozhou Bay and Sanggou Bay, the increase of DIN concentration and N：P ratio as well as the decrease of phosphate and sili- cate concentrations and Si：N ratios were relatively significant. Many pelagic ecosystem changes have occurred concurrent with these changes of the nutrient regime, such as the recent increase of primary production, changes of phytoplankton chlorophyll a biomass and abundance, an increase of eutrophication, and occurrence of HABs. In addition, new trends in the variation of nutrients seem to be developing in some particular transect such as 36N, which suggests that long-term and systematic ecosystem monitoring in the Huanghai Sea is necessary.
基金The National Natural Science Foundation of China under contract Nos 40490262 and 3730114the CEOHAB Research Project of Na-tional Key Basic Research Development Program("973") of China under contract No. 2001CB409700
文摘Three mesocosm experiments were conducted in the East China Sea during blooms of Prorocentrum donghaiense Lu in May of 1998,2002 and 2003 to examine the role of nutrients in the formation of these harmful algae blooms（HABs）.The results showed that there was interspecies competition between P.donghaiense and Skeletonema costatum（Grev.） Cleve.The cell number of P.donghaiense and S.costatum accounted for about 85% and 11% of the total cell number of phytoplankton respectively at the beginning of the experiment in May 1998.In May 2002,at the beginning of the experiment,the cell number of P.donghaiense accounted for 55%-66% of the total and S.costatum accounted for 32%-42%.The density of P.donghaiense and S.costatum was over 95% and 1%-5% respectively in May 2003.The results of these three mesocosm experiments showed that the dominant species in this specific community varied with different nutrient availability.Under low-phosphate conditions,the dominant species was P.donghaiense,while S.costatum became dominant in phosphate-replete cases.The average growth rate（1.08 d-1） of S.costatum in exponential growth phase was higher than that（0.39 d-1） of P.donghaiense.In the mesocosm,S.costatum predominated in the mesocosm by its rapid growth.When phosphorus was depleted,the cell number of S.costatum dropped rapidly,while P.donghaiense Lu decreased more slowly.The results from mesocosm experiment may explain why：（1） P.donghaiense bloom usually occurs in May,when phosphate concentration is low;（2） the bloom of S.costatum appears in early spring and summer time,when nutrients increase with increasing Changjiang River（Yangtze River） runoff;（3） the bloom of S.costatum is short and that of P.donghaiense Lu can last more than a month in the East China Sea.
文摘Cryogenic machining is a new technology which makes use of the special mechanicalprcperties of niaterials in a cryogenic or a 'super cold' state for machining. The control of acryogenic machining system(CMS)is one of the key problems which need to be solved for practi-cal cryogenic machining A temperature field control principle is presented which calculates theheat source temperature in the light of the tool temperature field information, and a control mod-el of three-dimensional dynamic temperature field for CMS is established, and the boundary con-ditions and the heat source of temperature field in orthogonal cutting are discussed. Based on theinvestigation of the control feature and technique. a prototype system for controlling CMS is crea-ted.
