Widespread and thick loess deposit in the northeastern Tibetan Plateau records paleoclimatic changes over the Quaternary period. In this study, we investigate a loess section located in a high terrace of the Huangshui...Widespread and thick loess deposit in the northeastern Tibetan Plateau records paleoclimatic changes over the Quaternary period. In this study, we investigate a loess section located in a high terrace of the Huangshui River in the Xining Basin, and collect samples at 20-cm intervals by digging a well of 16-m depth (including paleosol S1 and SO and several loess interlayers over the last glacial-interglacial cycle and the Holocene). Concentration of some active elements (Sr and Ca) and inert elements (Rb, Zr, Ti) in these loess samples are measured. The results show that ratios of those elements (oxide), such as Rb/Sr, Ti/Sr, and Zr/CaO ratios, would indicate sensitively paleoclimatic changes, especially the history of precipitation over the last glacial-interglacial and the Holocene. Moreover, the curves of Rb/Sr, Ti/Sr, and Zr/CaO ratios had almost the same variable trends from the bottom to the top and also closely correlated with values of magnetic susceptibility and the global marine δ^18O record. But compared with the curves of magnetic susceptibility, the changes of ratios of these elements (oxide) are clearer and easy to understand. Therefore, the ratios of these typical chemical elements in the loess deposit may be used as an excellent index to investigate the history of paleoclimate, particularly precipitation changes in the northeastern Tibetan Plateau.展开更多
快速傅里叶变换(fast Fourier transform,FFT)在数字信号处理中占据核心地位.随着高性能超长点数FFT需求的增长,数字信号处理器(digital signal processor,DSP)的计算能力越来越难以满足需求,集成FFT加速器成为重要的发展趋势.为了支持...快速傅里叶变换(fast Fourier transform,FFT)在数字信号处理中占据核心地位.随着高性能超长点数FFT需求的增长,数字信号处理器(digital signal processor,DSP)的计算能力越来越难以满足需求,集成FFT加速器成为重要的发展趋势.为了支持超长点数FFT,将2维分解算法推广到多维,提出一种可集成于DSP的高性能超长点数FFT加速器结构.该结构通过基于素数个存储体的无冲突体编址方法实现了3维转置运算;通过递推算法实现了高效铰链因子生成;使用单精度浮点二项融合点积运算和融合加-减运算,对FFT运算电路进行了精细化设计.实现了对4G点数单精度浮点FFT计算的支持.综合结果表明:FFT加速器运行频率能够达到1GHz以上,性能达到640Gflop/s.在支持的点数和性能方面都较已有研究成果取得大幅提升.展开更多
Due to the extremely arid climate in the western Qaidam Basin,the groundwater almost becomes the single water source for local residents and industrial production.It is necessary to know the reliable information on th...Due to the extremely arid climate in the western Qaidam Basin,the groundwater almost becomes the single water source for local residents and industrial production.It is necessary to know the reliable information on the groundwater cycle in this region for reasonable and sustainable exploitation of the groundwater resources with the further execution of recycling economy policies.This study focused on the recharge,the flow rate and the discharge of groundwater in the western Qaidam Basin through investigations on water chemistry and isotopes.Hydrological,chemical and isotopic characteristics show that the groundwater in the western Qaidam Basin was recharged by meltwater from new surface snow and old bottom glaciers on the northern slope of the Kunlun Mountains.In addition,the results also prove that the source water is enough and stable,and the rates of the circulation and renewal of the groundwater are relatively quick.Therefore,it can be concluded that the groundwater resources would guarantee the regional requirement if the meltwater volume of the mountains has not a great changes in future,moreover,water exploitation should be limited to the renewable amount of the groundwater reservoir in the western Qaidam Basin.展开更多
Chemistry of major and minor elements,87Sr/86Sr,δD,δ18O and δ34S of brines were measured from Tertiary strata and Quaternary salt lakes in the western Qaidam Basin.The water chemistry data show that all oilfield br...Chemistry of major and minor elements,87Sr/86Sr,δD,δ18O and δ34S of brines were measured from Tertiary strata and Quaternary salt lakes in the western Qaidam Basin.The water chemistry data show that all oilfield brines are CaCl2 type.They were enriched in Ca2+,B3+,Li+,Sr2+,Br-,and were depleted in Mg2+,SO42-,which indicated that these brines had the characteristics of deeply circulated water.The relationship between δD and δ18O shows that all data of these brines decline towards the Global Meteoric Water Line(GWL) and Qaidam Meteoric Water Line(QWL),and that the intersection between oilfield brines and Meteoric Water Lines was close to the local spring and fresh water in the piedmont in the western Qaidam Basin.The results suggest that oilfield brines has initially originated from meteoric water,and then might be affected by water-rock metamorphose,because most oilfield brines distribute in the range of metamorphosing water.The 87Sr/86Sr values of most oilfield brines range from 0.71121 to 0.71194,and was less than that in salt lake water(>0.712),but close to that of halite in the study area.These imply that salt dissolution occurred in the process of migration.In addition,all oilfield brines have obviously much positive δ34S values(ranging from 26.46‰ to 54.57‰) than that of salt lake brines,which was caused by bacterial sulfate reduction resulting in positive shift of δ34S value and depleteed SO42-in oilfield brines.Combined with water chemical data and δD,δ18O,87Sr/86Sr,δ34S values,we concluded that oilfield brines mainly originate from the deeply circulated meteoric waters,and then are affected by salt dissolution,water-rock metamorphose,sulfate reduction and dolomitization during the process of migration.These processes alter the chemical compositions of oilfield brines and accumulate rich elements(such as B,Li,Sr,Br,K and so on) for sustainable utilization of salt lake resources in the Qaidam Basin.展开更多
In this study, with the method of vacuum extraction, two evaporative processes of soil water and free water under equilibrium condition were simulated. For each sample,water vapor was condensed by liquid nitrogen and ...In this study, with the method of vacuum extraction, two evaporative processes of soil water and free water under equilibrium condition were simulated. For each sample,water vapor was condensed by liquid nitrogen and was collected in four time intervals. From the analysis of hydrogen and oxygen isotopic compositions of the water collected at different times, it was discovered that the isotope fractionation of soil water also follows the mode, which is just the same as the evaporative process of free water. The relationship between the stable hydrogen and oxygen isotopes in residual water showed that the simulative evaporation line was close to the global meteoric water line (GMWL) under the equilibrium condition at about 20℃. Comparison of the two types of evaporative processes indicated that the isotope fractionation and evaporation velocity of soil water were only slightly modified by the Van der Waals force.展开更多
Since 2006,we have conducted a geological exploration of the Khammuane area in southeastern Laos.Several thick sequences of potash deposits containing sylvite and carnallite were discovered from drilling Paleocene str...Since 2006,we have conducted a geological exploration of the Khammuane area in southeastern Laos.Several thick sequences of potash deposits containing sylvite and carnallite were discovered from drilling Paleocene strata of the Thangon Formation(E1tg).To constrain the origin of the brine that formed thick sequences of salt mineral deposits,we measured the strontium and boron isotope composition of some salt minerals in the potash deposit.Boron isotope composition of halite-and potash-associated minerals in the Khammuane potash deposit varied from 19.91%to 31.01‰,which differs significantly from continental evaporates(-6.83‰--5.79‰)but is very close to that of salts precipitated from evapo-concentrated seawater(10‰-36‰).The 87Sr/86Sr ratios(0.707542 to 0.709461)of salts were also close to the values of Paleocene seawater(0.70772 to 0.707830).The content of Br-(0.01%-0.25%)and Br×103/Cl ratios(0.10-0.52)of halite were>10 times higher than that of common continental salts.These characteristics indicate clearly that the Laos potash deposits were deposited from seawater.The small variation in boron and strontium isotopes in all salt sedimentary sequences(gypsum-halite-potash-halite)also suggests that the recharge source should be stable and the effects of other continental water mixing are negligible.Large-scale potash deposits are commonly precipitated from seawater.Hence,the results of recent regional drilling work and geochemical research suggest extensive potash resources could occur in the Thangon Formation of southeastern Laos.展开更多
文摘Widespread and thick loess deposit in the northeastern Tibetan Plateau records paleoclimatic changes over the Quaternary period. In this study, we investigate a loess section located in a high terrace of the Huangshui River in the Xining Basin, and collect samples at 20-cm intervals by digging a well of 16-m depth (including paleosol S1 and SO and several loess interlayers over the last glacial-interglacial cycle and the Holocene). Concentration of some active elements (Sr and Ca) and inert elements (Rb, Zr, Ti) in these loess samples are measured. The results show that ratios of those elements (oxide), such as Rb/Sr, Ti/Sr, and Zr/CaO ratios, would indicate sensitively paleoclimatic changes, especially the history of precipitation over the last glacial-interglacial and the Holocene. Moreover, the curves of Rb/Sr, Ti/Sr, and Zr/CaO ratios had almost the same variable trends from the bottom to the top and also closely correlated with values of magnetic susceptibility and the global marine δ^18O record. But compared with the curves of magnetic susceptibility, the changes of ratios of these elements (oxide) are clearer and easy to understand. Therefore, the ratios of these typical chemical elements in the loess deposit may be used as an excellent index to investigate the history of paleoclimate, particularly precipitation changes in the northeastern Tibetan Plateau.
文摘快速傅里叶变换(fast Fourier transform,FFT)在数字信号处理中占据核心地位.随着高性能超长点数FFT需求的增长,数字信号处理器(digital signal processor,DSP)的计算能力越来越难以满足需求,集成FFT加速器成为重要的发展趋势.为了支持超长点数FFT,将2维分解算法推广到多维,提出一种可集成于DSP的高性能超长点数FFT加速器结构.该结构通过基于素数个存储体的无冲突体编址方法实现了3维转置运算;通过递推算法实现了高效铰链因子生成;使用单精度浮点二项融合点积运算和融合加-减运算,对FFT运算电路进行了精细化设计.实现了对4G点数单精度浮点FFT计算的支持.综合结果表明:FFT加速器运行频率能够达到1GHz以上,性能达到640Gflop/s.在支持的点数和性能方面都较已有研究成果取得大幅提升.
基金Under the auspices of National Natural Science Foundation of China (No 40603007)
文摘Due to the extremely arid climate in the western Qaidam Basin,the groundwater almost becomes the single water source for local residents and industrial production.It is necessary to know the reliable information on the groundwater cycle in this region for reasonable and sustainable exploitation of the groundwater resources with the further execution of recycling economy policies.This study focused on the recharge,the flow rate and the discharge of groundwater in the western Qaidam Basin through investigations on water chemistry and isotopes.Hydrological,chemical and isotopic characteristics show that the groundwater in the western Qaidam Basin was recharged by meltwater from new surface snow and old bottom glaciers on the northern slope of the Kunlun Mountains.In addition,the results also prove that the source water is enough and stable,and the rates of the circulation and renewal of the groundwater are relatively quick.Therefore,it can be concluded that the groundwater resources would guarantee the regional requirement if the meltwater volume of the mountains has not a great changes in future,moreover,water exploitation should be limited to the renewable amount of the groundwater reservoir in the western Qaidam Basin.
基金supported by CAS Major Basic Preliminary Program (2004CCA03500)the National Natural Science Foundation of China (No. 40603007)
文摘Chemistry of major and minor elements,87Sr/86Sr,δD,δ18O and δ34S of brines were measured from Tertiary strata and Quaternary salt lakes in the western Qaidam Basin.The water chemistry data show that all oilfield brines are CaCl2 type.They were enriched in Ca2+,B3+,Li+,Sr2+,Br-,and were depleted in Mg2+,SO42-,which indicated that these brines had the characteristics of deeply circulated water.The relationship between δD and δ18O shows that all data of these brines decline towards the Global Meteoric Water Line(GWL) and Qaidam Meteoric Water Line(QWL),and that the intersection between oilfield brines and Meteoric Water Lines was close to the local spring and fresh water in the piedmont in the western Qaidam Basin.The results suggest that oilfield brines has initially originated from meteoric water,and then might be affected by water-rock metamorphose,because most oilfield brines distribute in the range of metamorphosing water.The 87Sr/86Sr values of most oilfield brines range from 0.71121 to 0.71194,and was less than that in salt lake water(>0.712),but close to that of halite in the study area.These imply that salt dissolution occurred in the process of migration.In addition,all oilfield brines have obviously much positive δ34S values(ranging from 26.46‰ to 54.57‰) than that of salt lake brines,which was caused by bacterial sulfate reduction resulting in positive shift of δ34S value and depleteed SO42-in oilfield brines.Combined with water chemical data and δD,δ18O,87Sr/86Sr,δ34S values,we concluded that oilfield brines mainly originate from the deeply circulated meteoric waters,and then are affected by salt dissolution,water-rock metamorphose,sulfate reduction and dolomitization during the process of migration.These processes alter the chemical compositions of oilfield brines and accumulate rich elements(such as B,Li,Sr,Br,K and so on) for sustainable utilization of salt lake resources in the Qaidam Basin.
基金supports provided by International Atomic Energy TC Project (No. PRC\08\015)the National Natural Science Founda-tion of China (No. 50579017)
文摘In this study, with the method of vacuum extraction, two evaporative processes of soil water and free water under equilibrium condition were simulated. For each sample,water vapor was condensed by liquid nitrogen and was collected in four time intervals. From the analysis of hydrogen and oxygen isotopic compositions of the water collected at different times, it was discovered that the isotope fractionation of soil water also follows the mode, which is just the same as the evaporative process of free water. The relationship between the stable hydrogen and oxygen isotopes in residual water showed that the simulative evaporation line was close to the global meteoric water line (GMWL) under the equilibrium condition at about 20℃. Comparison of the two types of evaporative processes indicated that the isotope fractionation and evaporation velocity of soil water were only slightly modified by the Van der Waals force.
基金supported by the National Natural Science Foundation of China(40603007 and 40903024)
文摘Since 2006,we have conducted a geological exploration of the Khammuane area in southeastern Laos.Several thick sequences of potash deposits containing sylvite and carnallite were discovered from drilling Paleocene strata of the Thangon Formation(E1tg).To constrain the origin of the brine that formed thick sequences of salt mineral deposits,we measured the strontium and boron isotope composition of some salt minerals in the potash deposit.Boron isotope composition of halite-and potash-associated minerals in the Khammuane potash deposit varied from 19.91%to 31.01‰,which differs significantly from continental evaporates(-6.83‰--5.79‰)but is very close to that of salts precipitated from evapo-concentrated seawater(10‰-36‰).The 87Sr/86Sr ratios(0.707542 to 0.709461)of salts were also close to the values of Paleocene seawater(0.70772 to 0.707830).The content of Br-(0.01%-0.25%)and Br×103/Cl ratios(0.10-0.52)of halite were>10 times higher than that of common continental salts.These characteristics indicate clearly that the Laos potash deposits were deposited from seawater.The small variation in boron and strontium isotopes in all salt sedimentary sequences(gypsum-halite-potash-halite)also suggests that the recharge source should be stable and the effects of other continental water mixing are negligible.Large-scale potash deposits are commonly precipitated from seawater.Hence,the results of recent regional drilling work and geochemical research suggest extensive potash resources could occur in the Thangon Formation of southeastern Laos.