As shown in comparisons of the characteristics of inter-annual and inter-decadal variability and periodical changes in the number of tropical cyclones forming over the western North Pacific by three major forecast cen...As shown in comparisons of the characteristics of inter-annual and inter-decadal variability and periodical changes in the number of tropical cyclones forming over the western North Pacific by three major forecast centers, i.e. China Meteorological Administration (CMA), Regional Specialized Meteorological Center of Tokyo (JMA) and Joint Typhoon Warning Center (JTWC) of Guam, there are the following important points. (1) Climatology of tropical cyclone (TC) or typhoon (TC on the intensity of TS or stronger) shows some difference in tropical cyclone frequency among the centers, which is more notable with TC than with typhoon. Both of them are more at the database of CMA than at those of the other two centers. (2) The difference is too significant to ignore in the inter-annual variability of tropical cyclone frequency between CMA and JTWC, which mainly results from the obvious difference in the inter-annual variability of the number of generated tropical depression (TD) between the two databases. The difference is small in the inter-annual variability of TS formations among all the three databases, and consistence is good between JMA and CMA or JTWC. (3) Though differences are not significant in the periodical variation of TC formations between CMA and JTWC, they are markedly apart in the inter-decadal variability, which is mainly shown by an anti-phase during the 1990s. (4) Non-homogeneity may exist around the late stage of the 1960s in the data of tropical cyclone frequency.展开更多
This study combines the three-dimensional model of the high-temperature proton exchange membrane fuel cell(HT-PEMFC)with theoretical analysis,by optimizing the structure of the fuel cell,adding a semicircular baffle i...This study combines the three-dimensional model of the high-temperature proton exchange membrane fuel cell(HT-PEMFC)with theoretical analysis,by optimizing the structure of the fuel cell,adding a semicircular baffle in the gas channel and implementing novelly arranged obstacles to improve the PEMFC performance. The effects of velocity distribution,interface reactant concentration and pressure drop on performance are studied. The results show that adding obstacles in the gas channel will produce vertical velocity and can improve output performance,especially in the case of high current density and higher baffle radius. The superiority of the optimized structure in mass transfer capacity is proved,and a mechanism explanation is given for the improvement of performance.展开更多
An analytical method, using sector field inductively coupled plasma mass spectrometry （SF-ICP-MS） for rapid simultaneous determination of Be, Na, Mg, Si, Ca, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, As, Sn, Sb, Pb and Bi in e...An analytical method, using sector field inductively coupled plasma mass spectrometry （SF-ICP-MS） for rapid simultaneous determination of Be, Na, Mg, Si, Ca, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, As, Sn, Sb, Pb and Bi in electrolytic manganese metal, was described. At the beginning, the samples were decomposed by HNO3 and H2504, and then analyzed by SF-ICP-MS. Most of the spectral interferences could be avoided by measuring in different mass resolution modes. The matrix effects due to the excess of sulfuric acid and Mn were evaluated. Correction of matrix effects was conducted by using the internal standard elements. The optimum condition for the determination was investigated and discussed. The detection limit is in the range of 0.001-0.169 gg/L. The current method is applied to the determination of trace impurities in electrolytic manganese metal. And experiments show that good results can be obtained much faster, more accurately and conveniently by current method.展开更多
Increased sedimentation rates have been attributed to increased anthropogenic activity in watersheds throughout Florida and many parts of the world. The Manatee River, located on the west coast of Florida （USA）, lik...Increased sedimentation rates have been attributed to increased anthropogenic activity in watersheds throughout Florida and many parts of the world. The Manatee River, located on the west coast of Florida （USA）, like many other coastal watersheds, has experienced depletion in natural resources, increased nutrient loading, and increased pollution. LARs （linear accumulation rates） from watersheds throughout Florida suggest that anthropogenic activity increased bulk sedimentation by as much as 4-fold. The objective of this study was to construct a record of sedimentation and improve upon previous studies by determining individual sedimentary constituent MARs （mass accumulation rates） based on short lived radioisotopes （2~~pb and 234Th） to characterize changes in sedimentation attributed to increased anthropogenic development. This study constructed records of sedimentary accumulation rates to compare pre-development records to the past 100 years of anthropogenic development and identified specific changes in sedimentation attributed to anthropogenic activity. Anthropogenic development increased deposition of terrigenous material into the river from 2-fold to I 0-fold （0.3-2.0 g/cm2/yr） over three periods： （1） predevelopment period （1900-1941）; （2） agricultural development period （1941-1970）; （3） urban development period （1970-2010）. The mobilization of this amount of terrigenous material has implications for effects on water quality and biological communities within the river.展开更多
基金Natural science foundation of Hainan Province (409005)
文摘As shown in comparisons of the characteristics of inter-annual and inter-decadal variability and periodical changes in the number of tropical cyclones forming over the western North Pacific by three major forecast centers, i.e. China Meteorological Administration (CMA), Regional Specialized Meteorological Center of Tokyo (JMA) and Joint Typhoon Warning Center (JTWC) of Guam, there are the following important points. (1) Climatology of tropical cyclone (TC) or typhoon (TC on the intensity of TS or stronger) shows some difference in tropical cyclone frequency among the centers, which is more notable with TC than with typhoon. Both of them are more at the database of CMA than at those of the other two centers. (2) The difference is too significant to ignore in the inter-annual variability of tropical cyclone frequency between CMA and JTWC, which mainly results from the obvious difference in the inter-annual variability of the number of generated tropical depression (TD) between the two databases. The difference is small in the inter-annual variability of TS formations among all the three databases, and consistence is good between JMA and CMA or JTWC. (3) Though differences are not significant in the periodical variation of TC formations between CMA and JTWC, they are markedly apart in the inter-decadal variability, which is mainly shown by an anti-phase during the 1990s. (4) Non-homogeneity may exist around the late stage of the 1960s in the data of tropical cyclone frequency.
基金supported by the De-fense Industrial Technology Development Program (No. JCKY2018605B006)the Aviation Science Fund (No. 201928052002)
文摘This study combines the three-dimensional model of the high-temperature proton exchange membrane fuel cell(HT-PEMFC)with theoretical analysis,by optimizing the structure of the fuel cell,adding a semicircular baffle in the gas channel and implementing novelly arranged obstacles to improve the PEMFC performance. The effects of velocity distribution,interface reactant concentration and pressure drop on performance are studied. The results show that adding obstacles in the gas channel will produce vertical velocity and can improve output performance,especially in the case of high current density and higher baffle radius. The superiority of the optimized structure in mass transfer capacity is proved,and a mechanism explanation is given for the improvement of performance.
基金Project(21075138)supported by the National Natural Science Foundation of ChinaProject(cstc2013jcyjA10088)supported by Chongqing Natural Science Foundation,ChinaProject(KJ121311)supported by Scientific and Technological Research Program of Chongqing Municipal Education Commission,China
文摘An analytical method, using sector field inductively coupled plasma mass spectrometry （SF-ICP-MS） for rapid simultaneous determination of Be, Na, Mg, Si, Ca, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, As, Sn, Sb, Pb and Bi in electrolytic manganese metal, was described. At the beginning, the samples were decomposed by HNO3 and H2504, and then analyzed by SF-ICP-MS. Most of the spectral interferences could be avoided by measuring in different mass resolution modes. The matrix effects due to the excess of sulfuric acid and Mn were evaluated. Correction of matrix effects was conducted by using the internal standard elements. The optimum condition for the determination was investigated and discussed. The detection limit is in the range of 0.001-0.169 gg/L. The current method is applied to the determination of trace impurities in electrolytic manganese metal. And experiments show that good results can be obtained much faster, more accurately and conveniently by current method.
文摘Increased sedimentation rates have been attributed to increased anthropogenic activity in watersheds throughout Florida and many parts of the world. The Manatee River, located on the west coast of Florida （USA）, like many other coastal watersheds, has experienced depletion in natural resources, increased nutrient loading, and increased pollution. LARs （linear accumulation rates） from watersheds throughout Florida suggest that anthropogenic activity increased bulk sedimentation by as much as 4-fold. The objective of this study was to construct a record of sedimentation and improve upon previous studies by determining individual sedimentary constituent MARs （mass accumulation rates） based on short lived radioisotopes （2~~pb and 234Th） to characterize changes in sedimentation attributed to increased anthropogenic development. This study constructed records of sedimentary accumulation rates to compare pre-development records to the past 100 years of anthropogenic development and identified specific changes in sedimentation attributed to anthropogenic activity. Anthropogenic development increased deposition of terrigenous material into the river from 2-fold to I 0-fold （0.3-2.0 g/cm2/yr） over three periods： （1） predevelopment period （1900-1941）; （2） agricultural development period （1941-1970）; （3） urban development period （1970-2010）. The mobilization of this amount of terrigenous material has implications for effects on water quality and biological communities within the river.
