In this paper, we study the appearance of limit cycles from the equator and isochronicity of infinity in polynomial vector fields with no singular points at infinity. We give a recursive formula to compute the singula...In this paper, we study the appearance of limit cycles from the equator and isochronicity of infinity in polynomial vector fields with no singular points at infinity. We give a recursive formula to compute the singular point quantities of a class of cubic polynomial systems, which is used to calculate the first seven singular point quantities. Further, we prove that such a cubic vector field can have maximal seven limit cycles in the neighborhood of infinity. We actually and construct a system that has seven limit cycles. The positions of these limit cycles can be given exactly without constructing the Poincare cycle fields. The technique employed in this work is essentially different from the previously widely used ones. Finally, the isochronous center conditions at infinity are given.展开更多
In this paper, we discuss the complex isochronicity of a sixth degree polynomial system. We first adopt a new algorithm to find necessary conditions for complex isochronicity, then prove the sufficient conditions usin...In this paper, we discuss the complex isochronicity of a sixth degree polynomial system. We first adopt a new algorithm to find necessary conditions for complex isochronicity, then prove the sufficient conditions using effective methods.展开更多
Due to its ubiquitous occurrence in igneous,metamorphic,and sedimentary rocks and its wide application in geochronology and geochemistry,zircon has become the most widely used accessory mineral in the geological commu...Due to its ubiquitous occurrence in igneous,metamorphic,and sedimentary rocks and its wide application in geochronology and geochemistry,zircon has become the most widely used accessory mineral in the geological community.Nevertheless,the decay of U and Th causes radiation damage to the zircon structure,resulting in various degrees of metamictization,which can affect the accuracy of U–Pb dates and Hf and O isotope results.If the degree of zircon radiation damage can be quantified,the influence on geochemical analyses can be evaluated,and the results can be corrected more precisely.In this paper,synthetic and natural zircon crystals with different crystallization ages were selected for Raman spectroscopy analysis,cathodoluminescence imaging,and determination of the U and Th concentrations.The results show that Raman FWHM(full width at half bandmaximum)and Raman shift correlate with alpha dose(Da)ofzirconsfollowingtheseequations,FWHM=44.36(±2.32)×[1-exp(-2.74×Da)]-+1.7(±0.19),Raman Shift=-6.53×Da+1007.69.Analysis of synthetic zircon crystals shows that doped REEs(rare earth elements and P)can also lead to an increase in the FWHM.However,this effect can be ignored for natural zircon samples with REE contents at a normal level of hundreds to a few thousand ppm.The FWHM and Raman shift can be used as proxies to measure the degree of zircon radiation damage.Using the updated equations to calculate the latest age when zircon began to accumulate radiation damage,a more accurate and more meaningful“radiation damage age”can be obtained.展开更多
The Rb-Sr whole-rock isochron,age 1636±66 Ma of Mirgarani granite,is the one of the oldest granite dated in the northwestern part of the Chhotanagpur Granite Gneiss Complex(CGGC).The initial Sr ratio is 0.715...The Rb-Sr whole-rock isochron,age 1636±66 Ma of Mirgarani granite,is the one of the oldest granite dated in the northwestern part of the Chhotanagpur Granite Gneiss Complex(CGGC).The initial Sr ratio is 0.715±0.012(MSWD=0.11),showing an S-type affinity.The Mirgarani granite has intruded the migmatite complex of the Dudhi Group and forms the Mirgarani formation comparable to the granites of the Bihar Mica Belt around Hazaribagh(1590±30 Ma).The present studies have established the chronostratigraphy of the Dudhi Group and adjoining areas in CGGC.Petro-graphic and geochemical studies revealed that the granite is enriched in Rb(271 ppm),Pb(77 ppm),Th(25 ppm),and U(33 ppm)and depleted in Sr(95 ppm),Nb(16 ppm),Ba(399 ppm)and Zr(143 ppm)contents as compared to the normal granite.The Mirgarani granite is a peraluminous(A/CNK=1.23),high potassic(K_(2)O 6.42%),Calc-Alkalic to Alkali-Calcic{(Na_(2)O+K_(2)O)-CaO=6.29}S-Type granite,a feature supported by the presence of modal garnet and normative corundum(2.68%).The Mirgarani granite is considered to have been formed by the anatexis of a crustal sedimentary protolith at a depth of approximately 30 km with temperatures ranging from 685-700℃ during the Co-lumbian-Nuna Supercontinent.展开更多
The mafic dykes are composed of a series of northwest-trending diabase in Kuokesu of the Kuruktag region, Xinjiang. Four whole-rock samples of the mafic dykes in the region give an 40Ar/36Ar–40K/36Ar isochron age of ...The mafic dykes are composed of a series of northwest-trending diabase in Kuokesu of the Kuruktag region, Xinjiang. Four whole-rock samples of the mafic dykes in the region give an 40Ar/36Ar–40K/36Ar isochron age of 282 Ma with the initial 40Ar/36Ar = 507. The characteristics of the major, trace and rare earth elements of the dyke rocks indicate that they belong to the calc-alkaline series and were emplaced in extensional structures at an intermediate depth of the crust. This shows that there was a large-scale extension in the Permian Period, which might be associated with the post-collisional extension of the ancient Tianshan Mountains.展开更多
Lead isotopic analytic data of 30 ores gathered from the Zhuanmiao boron deposit, Wengquangou boron (iron) deposit and its Dongtaizi Ore Member constitute three isochrons, the corresponding ages of which are 1902 ...Lead isotopic analytic data of 30 ores gathered from the Zhuanmiao boron deposit, Wengquangou boron (iron) deposit and its Dongtaizi Ore Member constitute three isochrons, the corresponding ages of which are 1902 ± 12 Ma, 1852 ± 9 Ma and 1917 ± 48 Ma. Lead isotopic analyses of marble from the Xiquegou Member of the Qingchenzi orefield yield a Pb-Pb isochron age of 1844 ± 27 Ma. 40Ar-39Ar quick neutron activation dating of phlogopites and microclines coexisting with ore minerals in the Wengquangou boron (iron) and Zhuanmiao boron deposits shows that: (1) the phlogopite from the Wengquangou has a plateau age of 1923 ± 1.5 Ma and an isochron age of 1924 ± 2.5 Ma; (2) the microcline from the Wengquangou has the plateau age of 1407 ± 5.4 Ma and 220 ± 12 Ma and an isochron age of 1403 ± 19 Ma; (3) the phlogopites from the Zhuanmiao yield a plateau age 1918 ± 1.3 Ma and an isochron age of 1918 ± 2.9 Ma; (4) the microclines from the Zhuanmiao yield the plateau age of 1420 ± 16 Ma and 250 ± 8 Ma and an isochron age of 1425 ± 19 Ma and 269 ± 16 Ma. These ages indicate that the eastern Liaoning area happened around 1900 Ma, an important tectonomagmatic event, which is consistent with the worldwide Mid-Proterozoic tectonomagmatic event. During this period, the Proterozoic Liaohe Group was folded and underwent strong normal metamorphism, and the (hydrothermal) sedimentary boron deposits (or source beds) formed earlier were strongly superimposed by mineralization, resulting in enrichment of boron; later regional geological processes made little contribution to the formation of the boron deposits. Lead isotopic components show that the U-Pb and Th-Pb isotopic system reached homogenization in the ores whereas only the U-Pb isotopic system reached homogenization in the marble from the Xiquegou district, which indicates that the boron deposits superimposed in the studied area endured a relatively strong process of hydrothermal migmatization during the end phase of early Proterozoic metamorphism.展开更多
The black shale series that formed in the Edi- acaran-Cambrian transition are important stratigraphic records of the co-evolution of the paleo-ocean, -climate, and -biology. In this study, we measured Re-Os isotopic c...The black shale series that formed in the Edi- acaran-Cambrian transition are important stratigraphic records of the co-evolution of the paleo-ocean, -climate, and -biology. In this study, we measured Re-Os isotopic compositions of the black shale in the Niutitang Formation from the Gezhongwu section in Zhijin, Guizhou Province. The samples had high Re and Os contents, with Re ranging from 21.27 to 312.78 ng/g and Os ranging from 0.455 to 7.789 ng/g. The Re-Os isotope isochron age of 522.9 ± 8.6 Ma implies deposition of the Niutitang black shale predated the Chengjiang Fauna, providing an age constraint for the expansion of oceanic anoxia in the study area. The initial ^187Os/^188Os ratio of 0.826 ± 0.026 indi- cates that enhanced continental weathering might have triggered the expansion of the oceanic anoxia.展开更多
Located on the northeast margin of the Qiangtang terrane between the Jinshajiang suture zone and Bangonghu-Nujiang suture zone,the Dongmozhazhua and Mohailaheng Pb-Zn deposits in the Yushu area of Qinghai Province are...Located on the northeast margin of the Qiangtang terrane between the Jinshajiang suture zone and Bangonghu-Nujiang suture zone,the Dongmozhazhua and Mohailaheng Pb-Zn deposits in the Yushu area of Qinghai Province are representative Pb-Zn deposits of the Pb-Zn-Cu polymetallic mineralization belt in the northern part of the Nujiang-Lancangjiang-Jinshajiang area,which are in the front belt of the Yushu thrust nappe system.The formed environments of these two deposits are different from those of sediment-hosted base metal deposits elsewhere in the world.The authors hold that they were formed during the Indian-Asian continental collision and developed within the fold-thrust belt combined with thrust and strike-slip-related Cenozoic basins in the interior of the collisional zone.Studying on the metallogenic epochs of these two deposits is helpful to the understanding of ore-forming regularity of the regional Pb-Zn-Cu mineralization belt and also to the search for new deposits in this region.The age of the Dongmozhazhua deposit has been determined by the Rb-Sr isochron method for sphalerite residues,whereas the age of the Mohailaheng deposit has been determined by the Rb-Sr isochron method for sphalerite residues and the Sm-Nd isochron method for fluorite.The age of the Dongmozhazhua deposit is 35.0-±0.0 Ma ((87Sr/86Sr)0=0.708807) for sphalerite residues.The age of the Mohailaheng deposit is 32.2±0.4 Ma ((87Sr/86Sr)o=0.708514) for sphalerite residues and 31.8±0.3 Ma ((143Nd/144Nd)o=0.512362) for fluorite with an average of 32.0 Ma.Together with the regional geological setting during mineralization,a possible tectonic model for metallogeny of the Dongmozhazhua and Mohailaheng Pb-Zn deposits has been established.These two ages are close to the ages of the Pb-Zn deposits in the Lanping and Tuotuohe basins,indicating that it is possible that the narrow 1000-kilometer-long belt controlled by a thrust nappe system on the eastern and northern margins of the Tibetan plateau could be a giant Pb-Zn mineralized belt.展开更多
In this work, a parametric approach is presented and utilized to determine the creep properties of weldments; then the model of creep strain for cross weld specimen is given. On the basis of the experimental results, ...In this work, a parametric approach is presented and utilized to determine the creep properties of weldments; then the model of creep strain for cross weld specimen is given. On the basis of the experimental results, attempt has been made to establish equations of the isochronous stress-strain for weld joint that can predict the function of loading and service time in use of the creep data of base metal and weld metal.展开更多
IEEE 1394b is a high-speed data bus that is widely used in local area networks and consumer electronics. To best utilize this data bus, we need to fully understand its per- formance. To evaluate its performance for bo...IEEE 1394b is a high-speed data bus that is widely used in local area networks and consumer electronics. To best utilize this data bus, we need to fully understand its per- formance. To evaluate its performance for both isochronous and asynchronous data transfers, we model the IEEE 1394b bus using Deterministic and Stochastic Pelri Nets (DSPNs), and conduct simulations using TimeNET 4.0. Using the DSPNs model, we simulate both the average waiting times of isochronous and asynchronous packets. From the simulation results, we determine the factors that influence performance, such as throughput, size of packets, arrival rate of packets, number of isochronous channels, and bus configuration.展开更多
The Wujiatai Formation, which is well exposed in Huangjiatai-Xichahe region of the northern Kongling area of central Yangtze Craton, is a suite of epimetamorphic conglomerates to pebbly sandstones to fine sandstone-do...The Wujiatai Formation, which is well exposed in Huangjiatai-Xichahe region of the northern Kongling area of central Yangtze Craton, is a suite of epimetamorphic conglomerates to pebbly sandstones to fine sandstone-dolostones deposited in littoral-carbonate platform facies. The formation has angular unconformity contacts with both the overlying Neoproterozoic Nantuo Formation and the underlying Paleoproterozoic Huanglianghe Formation complex. Detrital zircons from metafine sandstones of the lower Wujiatai Formation have ages ranging from 3377 –1828 Ma, with the youngest zircons dating to about 1828 Ma. In addition, whole-rock Pb-Pb isochron ages from dolostones in the upper Wujiatai Formation yield an age of 1718±230 Ma. These dates constrain the depositional age of the Wujiatai Formation between 1800 Ma and 1600 Ma. These are the earliest Mesoproterozoic sedimentary records reported in the Kongling region, and fill the gaps in Early Mesoproterozoic stratigraphy in Yangtze Craton. Histograms of detrital zircon ages for the Wujiatai Formation reveal four major peaks at 2039 Ma, 2691 Ma, 2966 Ma and 3377 Ma, which is consistent with the ages of the basement rocks that underlie the center of Yangtze Craton, indicating that sediment provenance is mainly from the Kongling complex. The lower Wujiatai Formation mainly consists of clastic rocks, whereas the upper Wujiatai Formation consists of dolostones. This stratigraphic change implies a deepening sequence in an expanding basin with an initial cratonic rifting tectonic setting, corresponding to the initial breakup of the Columbia supercontinent in Yangtze Craton.展开更多
Isochronous mass spectrometry(IMS)of heavyion storage rings is a powerful tool for the mass measurements of short-lived nuclei.In IMS experiments,masses are determined through precision measurements of the revolution ...Isochronous mass spectrometry(IMS)of heavyion storage rings is a powerful tool for the mass measurements of short-lived nuclei.In IMS experiments,masses are determined through precision measurements of the revolution times of the ions stored in the ring.However,the revolution times cannot be resolved for particles with nearly the same mass-to-charge(m/q)ratios.To overcome this limitation and to extract the accurate revolution times for such pairs of ion species with very close m/q ratios,in our early work on particle identification,we analyzed the amplitudes of the timing signals from the detector based on the emission of secondary electrons.Here,the previous data analysis method is further improved by considering the signal amplitudes,detection efficiencies,and number of stored ions in the ring.A sensitive Z-dependent parameter is introduced in the data analysis,leading to a better resolution of ^(34)Ar^(18+) and ^(51)Co^(27+) with A/Z=17/9.The mean revolution times of ^(34)Ar^(18+) and ^(51)Co^(27+) are deduced,although their time difference is merely 1.8 ps.The uncorrected,overlapped peak of these ions has a full width at half maximum of 7.7 ps.The mass excess of ^(51)Co was determined to be-27;332e41T keV,which is in agreement with the previous value of-27;342e48T keV.展开更多
By using the magnetic field map, equilibrium orbit, operating point of v r and v z and beam trajectories after stripper for Cyclone 10/5 have been calculated. The positions of two strippers and two targets have been d...By using the magnetic field map, equilibrium orbit, operating point of v r and v z and beam trajectories after stripper for Cyclone 10/5 have been calculated. The positions of two strippers and two targets have been determined. The numerical simulation is consistent with experimental tests.展开更多
The number of the limit cycles bifurcating in small quadratic perturbations of quadratic systems with an ischronous center is studied, it turns out that the cyclicity of the period annulus around one kind of quadratic...The number of the limit cycles bifurcating in small quadratic perturbations of quadratic systems with an ischronous center is studied, it turns out that the cyclicity of the period annulus around one kind of quadratic isochronous center is two.展开更多
Based on the Rb-Sr isotopic study of the granitoids in the Hengduan Mountains, the classification andgeologic significance of whole-rock Rb-Sr isochrons as well as the factors influencing homogenization of theisotopic...Based on the Rb-Sr isotopic study of the granitoids in the Hengduan Mountains, the classification andgeologic significance of whole-rock Rb-Sr isochrons as well as the factors influencing homogenization of theisotopic systems are discussed. Usually. there is no good linear correlation of isochrons for diorites andalkali-rich intrusive rocks (including alkaline rock and alkalic granite). But by means of the external isochron ofmonominerals from the rocks. isochrons with good linear correlation as well as ages and Sr initial ratios with ahigh confidence can be obtained. In order to obtain a satisfactory isochron, the discriminant parameters shouldbe calculated from the Rb/Sr ratios and estimated ages of samples. Only those that meet the requirements canbe used as the Rb-Sr isochrons. The quality of an isochron should be judged from three factors, i.e. correlationcoefficient. MSWD and homogenization degree.展开更多
This paper discusses the Rb-Sr geochemical behaviour of illites in the sedimentary process, and points out that illites of the lmd and lm types could reach Sr-isotopic equilibrium with its environmental medium during ...This paper discusses the Rb-Sr geochemical behaviour of illites in the sedimentary process, and points out that illites of the lmd and lm types could reach Sr-isotopic equilibrium with its environmental medium during the sedimentary process and initial stage of diagenesis, and illite grains of different sizes have various Rb contents. A new dating method for sedimentary rocks----a dating model of illite grain Rb-Sr isochron----is established, in consideration of the geochemical process of Sr-isotopic homogenization and differentiation in the course of their formation and evolution. In addition, the paper concerns the application of the dating model to the Precambrian unmetamorphosed sedimentary rocks in western Henan Province, which gives satisfactory results coincident with the geological facts.展开更多
In this paper,the northern mountainous area of Fuzhou City which is an ungauged basin has been taken for example to discuss the method of design flood calculation by means of combining the DEM(digital elevation model)...In this paper,the northern mountainous area of Fuzhou City which is an ungauged basin has been taken for example to discuss the method of design flood calculation by means of combining the DEM(digital elevation model) and the Xin'anjiang Model(three components).The problem of estimating the parameters of the runoff model has been solved by using the parameters of the reference station.In the conflux calculation,the isochrones are obtained by DEM which helps to avoid the cumbersome work of drawing them on the map.With the establishment of the digital elevation model throughout the country,it is practically significant to use it in the hydrological estimation.展开更多
Sm Nd isotopic compositions of eight lamprophyre samples, which come from the Gezhen gold bearing shear zone on western Hainan Island, are measured. The Sm Nd isochron age is 495.98±13.14 Ma, (143Nd/144Nd)0=0.512...Sm Nd isotopic compositions of eight lamprophyre samples, which come from the Gezhen gold bearing shear zone on western Hainan Island, are measured. The Sm Nd isochron age is 495.98±13.14 Ma, (143Nd/144Nd)0=0.512094, εNd(t) ranges from +1.80 to +2.00 and TDM from 982 Ma to 1196 Ma (average: 1060 Ma). The authors point out that the whole rock Sm Nd isochron age (495.98±13.14 Ma) really represents the petrogenetic age of lamprophyre and the time of magmatism during subsequent subduction.展开更多
SiCw/Al and SiCw/6061Al composites, which contained 15 vol pct of whiskers, were fabricated through a squeeze cast route followed by cold rolling and isochronal annealing. Effects of whicker, solution atoms and precip...SiCw/Al and SiCw/6061Al composites, which contained 15 vol pct of whiskers, were fabricated through a squeeze cast route followed by cold rolling and isochronal annealing. Effects of whicker, solution atoms and precipitates on isochronal annealing behavior of cold rolled composites were investigated by comparing the isochronal annealing behavior between pure Al, SiCw/Al, solution-treated SiCw/6061Al and aged SiCw/6061Al. It was found that the recrystallization of SiCw/Al composite occurs earlier than that of pure Al, indicating SiCw has a role of particle stimulated nucleation. Solution atoms have no significant influence on the isochronal annealing behavior of SiCw/6061Al composite, while precipitates have such a strong retarding effect on the recrystallization of SiCw/6061Al composite that the isochronal annealing curve of aged SiCw/6061 composite loses the definable recrystallization step.展开更多
This paper studies the problem of isochronal synchronization of chaotic systems with time-delayed mutual coupling. Based on the invariance principle of differential equations, an adaptive feedback scheme is proposed f...This paper studies the problem of isochronal synchronization of chaotic systems with time-delayed mutual coupling. Based on the invariance principle of differential equations, an adaptive feedback scheme is proposed for the stability of isochronal synchronization between two identical chaotic systems. Unlike the usual linear feedback, the variable feedback strength is automatically adapted to isochronally synchronize two identical chaotic systems with delay-coupled, so this scheme is analytical, and simple to implement in practice. Simulation results show that the isochronal synchronization behavior is determined by time delay.展开更多
文摘In this paper, we study the appearance of limit cycles from the equator and isochronicity of infinity in polynomial vector fields with no singular points at infinity. We give a recursive formula to compute the singular point quantities of a class of cubic polynomial systems, which is used to calculate the first seven singular point quantities. Further, we prove that such a cubic vector field can have maximal seven limit cycles in the neighborhood of infinity. We actually and construct a system that has seven limit cycles. The positions of these limit cycles can be given exactly without constructing the Poincare cycle fields. The technique employed in this work is essentially different from the previously widely used ones. Finally, the isochronous center conditions at infinity are given.
基金the Fundation of Hubei Education Bureau(2003A008).
文摘In this paper, we discuss the complex isochronicity of a sixth degree polynomial system. We first adopt a new algorithm to find necessary conditions for complex isochronicity, then prove the sufficient conditions using effective methods.
基金supported by funds from the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(XDB 41000000)the National Natural Science Foundation of China(41973002,41772187)+1 种基金the Fundamental Research Funds for the Central UniversitiesNatural Sciences and Engineering Research Council of Canada(NSERC)Discovery Grant to J.M Hanchar(RGPIN/004649-2015)。
文摘Due to its ubiquitous occurrence in igneous,metamorphic,and sedimentary rocks and its wide application in geochronology and geochemistry,zircon has become the most widely used accessory mineral in the geological community.Nevertheless,the decay of U and Th causes radiation damage to the zircon structure,resulting in various degrees of metamictization,which can affect the accuracy of U–Pb dates and Hf and O isotope results.If the degree of zircon radiation damage can be quantified,the influence on geochemical analyses can be evaluated,and the results can be corrected more precisely.In this paper,synthetic and natural zircon crystals with different crystallization ages were selected for Raman spectroscopy analysis,cathodoluminescence imaging,and determination of the U and Th concentrations.The results show that Raman FWHM(full width at half bandmaximum)and Raman shift correlate with alpha dose(Da)ofzirconsfollowingtheseequations,FWHM=44.36(±2.32)×[1-exp(-2.74×Da)]-+1.7(±0.19),Raman Shift=-6.53×Da+1007.69.Analysis of synthetic zircon crystals shows that doped REEs(rare earth elements and P)can also lead to an increase in the FWHM.However,this effect can be ignored for natural zircon samples with REE contents at a normal level of hundreds to a few thousand ppm.The FWHM and Raman shift can be used as proxies to measure the degree of zircon radiation damage.Using the updated equations to calculate the latest age when zircon began to accumulate radiation damage,a more accurate and more meaningful“radiation damage age”can be obtained.
文摘The Rb-Sr whole-rock isochron,age 1636±66 Ma of Mirgarani granite,is the one of the oldest granite dated in the northwestern part of the Chhotanagpur Granite Gneiss Complex(CGGC).The initial Sr ratio is 0.715±0.012(MSWD=0.11),showing an S-type affinity.The Mirgarani granite has intruded the migmatite complex of the Dudhi Group and forms the Mirgarani formation comparable to the granites of the Bihar Mica Belt around Hazaribagh(1590±30 Ma).The present studies have established the chronostratigraphy of the Dudhi Group and adjoining areas in CGGC.Petro-graphic and geochemical studies revealed that the granite is enriched in Rb(271 ppm),Pb(77 ppm),Th(25 ppm),and U(33 ppm)and depleted in Sr(95 ppm),Nb(16 ppm),Ba(399 ppm)and Zr(143 ppm)contents as compared to the normal granite.The Mirgarani granite is a peraluminous(A/CNK=1.23),high potassic(K_(2)O 6.42%),Calc-Alkalic to Alkali-Calcic{(Na_(2)O+K_(2)O)-CaO=6.29}S-Type granite,a feature supported by the presence of modal garnet and normative corundum(2.68%).The Mirgarani granite is considered to have been formed by the anatexis of a crustal sedimentary protolith at a depth of approximately 30 km with temperatures ranging from 685-700℃ during the Co-lumbian-Nuna Supercontinent.
基金This study was supported by the State"Ninth Five-Year Plan"Key Project No.96-915-05-02.
文摘The mafic dykes are composed of a series of northwest-trending diabase in Kuokesu of the Kuruktag region, Xinjiang. Four whole-rock samples of the mafic dykes in the region give an 40Ar/36Ar–40K/36Ar isochron age of 282 Ma with the initial 40Ar/36Ar = 507. The characteristics of the major, trace and rare earth elements of the dyke rocks indicate that they belong to the calc-alkaline series and were emplaced in extensional structures at an intermediate depth of the crust. This shows that there was a large-scale extension in the Permian Period, which might be associated with the post-collisional extension of the ancient Tianshan Mountains.
基金supported by the National 973 Project of China(G1999043201)
文摘Lead isotopic analytic data of 30 ores gathered from the Zhuanmiao boron deposit, Wengquangou boron (iron) deposit and its Dongtaizi Ore Member constitute three isochrons, the corresponding ages of which are 1902 ± 12 Ma, 1852 ± 9 Ma and 1917 ± 48 Ma. Lead isotopic analyses of marble from the Xiquegou Member of the Qingchenzi orefield yield a Pb-Pb isochron age of 1844 ± 27 Ma. 40Ar-39Ar quick neutron activation dating of phlogopites and microclines coexisting with ore minerals in the Wengquangou boron (iron) and Zhuanmiao boron deposits shows that: (1) the phlogopite from the Wengquangou has a plateau age of 1923 ± 1.5 Ma and an isochron age of 1924 ± 2.5 Ma; (2) the microcline from the Wengquangou has the plateau age of 1407 ± 5.4 Ma and 220 ± 12 Ma and an isochron age of 1403 ± 19 Ma; (3) the phlogopites from the Zhuanmiao yield a plateau age 1918 ± 1.3 Ma and an isochron age of 1918 ± 2.9 Ma; (4) the microclines from the Zhuanmiao yield the plateau age of 1420 ± 16 Ma and 250 ± 8 Ma and an isochron age of 1425 ± 19 Ma and 269 ± 16 Ma. These ages indicate that the eastern Liaoning area happened around 1900 Ma, an important tectonomagmatic event, which is consistent with the worldwide Mid-Proterozoic tectonomagmatic event. During this period, the Proterozoic Liaohe Group was folded and underwent strong normal metamorphism, and the (hydrothermal) sedimentary boron deposits (or source beds) formed earlier were strongly superimposed by mineralization, resulting in enrichment of boron; later regional geological processes made little contribution to the formation of the boron deposits. Lead isotopic components show that the U-Pb and Th-Pb isotopic system reached homogenization in the ores whereas only the U-Pb isotopic system reached homogenization in the marble from the Xiquegou district, which indicates that the boron deposits superimposed in the studied area endured a relatively strong process of hydrothermal migmatization during the end phase of early Proterozoic metamorphism.
基金supported by the China Geological Survey (DD20160346)the National Natural Science Foundation of China (41472089)the Guizhou Geological Prospecting Fund (2016091)
文摘The black shale series that formed in the Edi- acaran-Cambrian transition are important stratigraphic records of the co-evolution of the paleo-ocean, -climate, and -biology. In this study, we measured Re-Os isotopic compositions of the black shale in the Niutitang Formation from the Gezhongwu section in Zhijin, Guizhou Province. The samples had high Re and Os contents, with Re ranging from 21.27 to 312.78 ng/g and Os ranging from 0.455 to 7.789 ng/g. The Re-Os isotope isochron age of 522.9 ± 8.6 Ma implies deposition of the Niutitang black shale predated the Chengjiang Fauna, providing an age constraint for the expansion of oceanic anoxia in the study area. The initial ^187Os/^188Os ratio of 0.826 ± 0.026 indi- cates that enhanced continental weathering might have triggered the expansion of the oceanic anoxia.
文摘Located on the northeast margin of the Qiangtang terrane between the Jinshajiang suture zone and Bangonghu-Nujiang suture zone,the Dongmozhazhua and Mohailaheng Pb-Zn deposits in the Yushu area of Qinghai Province are representative Pb-Zn deposits of the Pb-Zn-Cu polymetallic mineralization belt in the northern part of the Nujiang-Lancangjiang-Jinshajiang area,which are in the front belt of the Yushu thrust nappe system.The formed environments of these two deposits are different from those of sediment-hosted base metal deposits elsewhere in the world.The authors hold that they were formed during the Indian-Asian continental collision and developed within the fold-thrust belt combined with thrust and strike-slip-related Cenozoic basins in the interior of the collisional zone.Studying on the metallogenic epochs of these two deposits is helpful to the understanding of ore-forming regularity of the regional Pb-Zn-Cu mineralization belt and also to the search for new deposits in this region.The age of the Dongmozhazhua deposit has been determined by the Rb-Sr isochron method for sphalerite residues,whereas the age of the Mohailaheng deposit has been determined by the Rb-Sr isochron method for sphalerite residues and the Sm-Nd isochron method for fluorite.The age of the Dongmozhazhua deposit is 35.0-±0.0 Ma ((87Sr/86Sr)0=0.708807) for sphalerite residues.The age of the Mohailaheng deposit is 32.2±0.4 Ma ((87Sr/86Sr)o=0.708514) for sphalerite residues and 31.8±0.3 Ma ((143Nd/144Nd)o=0.512362) for fluorite with an average of 32.0 Ma.Together with the regional geological setting during mineralization,a possible tectonic model for metallogeny of the Dongmozhazhua and Mohailaheng Pb-Zn deposits has been established.These two ages are close to the ages of the Pb-Zn deposits in the Lanping and Tuotuohe basins,indicating that it is possible that the narrow 1000-kilometer-long belt controlled by a thrust nappe system on the eastern and northern margins of the Tibetan plateau could be a giant Pb-Zn mineralized belt.
基金supports provided by Natural Science Foundation of Shanghai(contract No.03ZR14022)the“Tenth Five”National Key Technological Research and Development Program(contract No.2001BA803B03)National Natural Science Foundation of China(contract No.50225517)are gratefully acknowledged.
文摘In this work, a parametric approach is presented and utilized to determine the creep properties of weldments; then the model of creep strain for cross weld specimen is given. On the basis of the experimental results, attempt has been made to establish equations of the isochronous stress-strain for weld joint that can predict the function of loading and service time in use of the creep data of base metal and weld metal.
基金supported by the Aeronautics Science Foundation of China under Grant No. 2008ZC51
文摘IEEE 1394b is a high-speed data bus that is widely used in local area networks and consumer electronics. To best utilize this data bus, we need to fully understand its per- formance. To evaluate its performance for both isochronous and asynchronous data transfers, we model the IEEE 1394b bus using Deterministic and Stochastic Pelri Nets (DSPNs), and conduct simulations using TimeNET 4.0. Using the DSPNs model, we simulate both the average waiting times of isochronous and asynchronous packets. From the simulation results, we determine the factors that influence performance, such as throughput, size of packets, arrival rate of packets, number of isochronous channels, and bus configuration.
基金supported by the National Science Foundation of China (41530104, 41303026)the projects of China Geological Survey (121201009000161427, DD20160029, DD20160030).
文摘The Wujiatai Formation, which is well exposed in Huangjiatai-Xichahe region of the northern Kongling area of central Yangtze Craton, is a suite of epimetamorphic conglomerates to pebbly sandstones to fine sandstone-dolostones deposited in littoral-carbonate platform facies. The formation has angular unconformity contacts with both the overlying Neoproterozoic Nantuo Formation and the underlying Paleoproterozoic Huanglianghe Formation complex. Detrital zircons from metafine sandstones of the lower Wujiatai Formation have ages ranging from 3377 –1828 Ma, with the youngest zircons dating to about 1828 Ma. In addition, whole-rock Pb-Pb isochron ages from dolostones in the upper Wujiatai Formation yield an age of 1718±230 Ma. These dates constrain the depositional age of the Wujiatai Formation between 1800 Ma and 1600 Ma. These are the earliest Mesoproterozoic sedimentary records reported in the Kongling region, and fill the gaps in Early Mesoproterozoic stratigraphy in Yangtze Craton. Histograms of detrital zircon ages for the Wujiatai Formation reveal four major peaks at 2039 Ma, 2691 Ma, 2966 Ma and 3377 Ma, which is consistent with the ages of the basement rocks that underlie the center of Yangtze Craton, indicating that sediment provenance is mainly from the Kongling complex. The lower Wujiatai Formation mainly consists of clastic rocks, whereas the upper Wujiatai Formation consists of dolostones. This stratigraphic change implies a deepening sequence in an expanding basin with an initial cratonic rifting tectonic setting, corresponding to the initial breakup of the Columbia supercontinent in Yangtze Craton.
基金This work was supported by the National Key R&D Program of China(Nos.2016YFA0400504 and 2018YFA0404401)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB34000000)+4 种基金the National Natural Science Foundation of China(Nos.11905261,11805032,11975280,and 11605248)the CAS "Light of West China" Program,the China Postdoctoral Science Foundation(No.2019M660250)the FRIB-CSC Fellowship,China(No.201704910964)the International Postdoctoral Exchange Fellowship Program 2017 by the Office of China Postdoctoral Council(No.60 Document of OCPC,2017)the European Research Council(ERC)under the European Union’s Horizon 2020 Research and Innovation Programme(No.682841 "ASTRUm").
文摘Isochronous mass spectrometry(IMS)of heavyion storage rings is a powerful tool for the mass measurements of short-lived nuclei.In IMS experiments,masses are determined through precision measurements of the revolution times of the ions stored in the ring.However,the revolution times cannot be resolved for particles with nearly the same mass-to-charge(m/q)ratios.To overcome this limitation and to extract the accurate revolution times for such pairs of ion species with very close m/q ratios,in our early work on particle identification,we analyzed the amplitudes of the timing signals from the detector based on the emission of secondary electrons.Here,the previous data analysis method is further improved by considering the signal amplitudes,detection efficiencies,and number of stored ions in the ring.A sensitive Z-dependent parameter is introduced in the data analysis,leading to a better resolution of ^(34)Ar^(18+) and ^(51)Co^(27+) with A/Z=17/9.The mean revolution times of ^(34)Ar^(18+) and ^(51)Co^(27+) are deduced,although their time difference is merely 1.8 ps.The uncorrected,overlapped peak of these ions has a full width at half maximum of 7.7 ps.The mass excess of ^(51)Co was determined to be-27;332e41T keV,which is in agreement with the previous value of-27;342e48T keV.
文摘By using the magnetic field map, equilibrium orbit, operating point of v r and v z and beam trajectories after stripper for Cyclone 10/5 have been calculated. The positions of two strippers and two targets have been determined. The numerical simulation is consistent with experimental tests.
基金Supported by the National Natural Science Foundation of China( No.195 310 70 ) and Natural Science Fundation ofHubei Province( No.98J12 1)
文摘The number of the limit cycles bifurcating in small quadratic perturbations of quadratic systems with an ischronous center is studied, it turns out that the cyclicity of the period annulus around one kind of quadratic isochronous center is two.
文摘Based on the Rb-Sr isotopic study of the granitoids in the Hengduan Mountains, the classification andgeologic significance of whole-rock Rb-Sr isochrons as well as the factors influencing homogenization of theisotopic systems are discussed. Usually. there is no good linear correlation of isochrons for diorites andalkali-rich intrusive rocks (including alkaline rock and alkalic granite). But by means of the external isochron ofmonominerals from the rocks. isochrons with good linear correlation as well as ages and Sr initial ratios with ahigh confidence can be obtained. In order to obtain a satisfactory isochron, the discriminant parameters shouldbe calculated from the Rb/Sr ratios and estimated ages of samples. Only those that meet the requirements canbe used as the Rb-Sr isochrons. The quality of an isochron should be judged from three factors, i.e. correlationcoefficient. MSWD and homogenization degree.
基金This research was financially supported by the Academia Sinica Foundation
文摘This paper discusses the Rb-Sr geochemical behaviour of illites in the sedimentary process, and points out that illites of the lmd and lm types could reach Sr-isotopic equilibrium with its environmental medium during the sedimentary process and initial stage of diagenesis, and illite grains of different sizes have various Rb contents. A new dating method for sedimentary rocks----a dating model of illite grain Rb-Sr isochron----is established, in consideration of the geochemical process of Sr-isotopic homogenization and differentiation in the course of their formation and evolution. In addition, the paper concerns the application of the dating model to the Precambrian unmetamorphosed sedimentary rocks in western Henan Province, which gives satisfactory results coincident with the geological facts.
基金National Science Foundation of China (No. 50879051)
文摘In this paper,the northern mountainous area of Fuzhou City which is an ungauged basin has been taken for example to discuss the method of design flood calculation by means of combining the DEM(digital elevation model) and the Xin'anjiang Model(three components).The problem of estimating the parameters of the runoff model has been solved by using the parameters of the reference station.In the conflux calculation,the isochrones are obtained by DEM which helps to avoid the cumbersome work of drawing them on the map.With the establishment of the digital elevation model throughout the country,it is practically significant to use it in the hydrological estimation.
文摘Sm Nd isotopic compositions of eight lamprophyre samples, which come from the Gezhen gold bearing shear zone on western Hainan Island, are measured. The Sm Nd isochron age is 495.98±13.14 Ma, (143Nd/144Nd)0=0.512094, εNd(t) ranges from +1.80 to +2.00 and TDM from 982 Ma to 1196 Ma (average: 1060 Ma). The authors point out that the whole rock Sm Nd isochron age (495.98±13.14 Ma) really represents the petrogenetic age of lamprophyre and the time of magmatism during subsequent subduction.
文摘SiCw/Al and SiCw/6061Al composites, which contained 15 vol pct of whiskers, were fabricated through a squeeze cast route followed by cold rolling and isochronal annealing. Effects of whicker, solution atoms and precipitates on isochronal annealing behavior of cold rolled composites were investigated by comparing the isochronal annealing behavior between pure Al, SiCw/Al, solution-treated SiCw/6061Al and aged SiCw/6061Al. It was found that the recrystallization of SiCw/Al composite occurs earlier than that of pure Al, indicating SiCw has a role of particle stimulated nucleation. Solution atoms have no significant influence on the isochronal annealing behavior of SiCw/6061Al composite, while precipitates have such a strong retarding effect on the recrystallization of SiCw/6061Al composite that the isochronal annealing curve of aged SiCw/6061 composite loses the definable recrystallization step.
文摘This paper studies the problem of isochronal synchronization of chaotic systems with time-delayed mutual coupling. Based on the invariance principle of differential equations, an adaptive feedback scheme is proposed for the stability of isochronal synchronization between two identical chaotic systems. Unlike the usual linear feedback, the variable feedback strength is automatically adapted to isochronally synchronize two identical chaotic systems with delay-coupled, so this scheme is analytical, and simple to implement in practice. Simulation results show that the isochronal synchronization behavior is determined by time delay.