The problem of H∞ stability analysis and control synthesis of switched systems with delayed states under arb/trary switchirg laws is considered. By means of Lyapunov function and linear matrix inequality tools, suffi...The problem of H∞ stability analysis and control synthesis of switched systems with delayed states under arb/trary switchirg laws is considered. By means of Lyapunov function and linear matrix inequality tools, sufficient ctmdition of H∞ stability is presented in terms of linear matrix inequalities. Furthermore, the robust H∞ control synthesis via state feedback and output feedack is studied. Finally, a numerical example is given to demonstrate the effectiveness of the proposed method.展开更多
The objective of this study was to provide reliable basis for decision making for national food security and layout and structure adjustment of grain production in the northeastern China. The data of mean daily air te...The objective of this study was to provide reliable basis for decision making for national food security and layout and structure adjustment of grain production in the northeastern China. The data of mean daily air temperature of 1961-2009 from 106 meteorological stations in the northeastern China were chosen in this study. Using statistical methods and isoline method, the spatio-temporal changes of various decadal ≥10℃accumulated temperature and the climatic means of ≥10℃ accumulated temperature were studied in this paper. The results showed that 1) The geo- graphical distribution of ≥10℃ accumulated temperature in the northeastern China could be influenced directly by the latitude, longitude and altitude. If latitude moved one degree northward, the average decrease amplitude of the climatic means was 101.9℃ in the study area. 2) The means of decadal ≥10℃ accumulated temperature rose since the 1980s, and their increase amplitudes became larger in the 1990s and the 2010s obviously. Compared with those of the 1980s, ≥10℃ accumulated temperature increased by about 100℃ in the mountainous and plain areas in the 1990s; compared with those of the 1990s, ≥10℃ accumulated temperature increased by about 200℃ in the Hulun Buir High Plain and the Songnen Plain, and 100℃ in the Sanjiang Plain and the Liaohe Plain in the 2010s. 3) The means of the decada ≥10℃accumulated temperature for 106 meteorological stations in the northeastern China increased with the rate of 145.57℃/10yr in 1961-2009.4) The climatic means of ≥10℃ accumulated temperature increased from 1961-1990 to 1971-2000 and 1981-2009. Compared with the climatic mean of 1971-2000, that of 1981-2009 had increased by above 50℃ in most of the study area, even up to 156℃. Compared with the climatic mean of 1961-1990, that of 1981-2009 increased by above 100℃ in most parts of the study area, even up to 200℃. 5) The maximum northward shift, eastward and westward extension amplitudes of3100℃, 3300℃ and 3500℃ isolines were larger among all isolines for the climatic means of the three phases. Compared with the positions of the isolines of 1961-1990, those amplitudes of 31000C isoline of 1981-2009 were 145 km, 109 km and 64 km, respectively; those of 3300℃ isoline were 154 km, 54 km and 64 km, respectively; and the maximum northward shift of 3500℃ isoline was about 100 km.展开更多
The Chaoyanggou oil field is a fractured low-permeability reservoir, where the distribution of oil and gas is controlled by the distribution and development of fractures.Based on outcrop, drilling core, thin section a...The Chaoyanggou oil field is a fractured low-permeability reservoir, where the distribution of oil and gas is controlled by the distribution and development of fractures.Based on outcrop, drilling core, thin section and log data, the development characteristics of fractures in this area are described.On this basis, the degree of fracture development was predicted by quantitative analysis of fracture strength and numerical simulation.The result shows that four groups of structural fractures, i.e., in near NS, and EW directions and in due NW and NE directions, were developed in the reservoir, with the nearly NS and EW fractures dominant, which are the along bedding decollement fractures formed by compressive folding action, while low angle shear fractures are related to thrusts.These fractures are mainly formed in the reversed tectonic stage at the end of the Mingshui formation during the Cretaceous period.The degree of fracture development is controlled by such factors as lithology, stratum thickness, faults, folds and depth.The fractures are developed with a clear zonation and are best developed in the northern zone, moderately developed towards the south and poorly developed in the middle zone.These prediction results are in good agreement with interpretation results from logs.展开更多
Scientific development is an invaluable asset to a country.Policies and development modes should be carried out based on scientific findings not only in industry,but also in transportation infrastructure construction....Scientific development is an invaluable asset to a country.Policies and development modes should be carried out based on scientific findings not only in industry,but also in transportation infrastructure construction.Building an integrated transportation system,which is in line with the national requirements of China and supports sustainable socio-economic development,is a key strategic issue related to building a moderately prosperous society and achieving realistic goals of a medium-level developed country.Based on a systematic review of the advances in China's transportation infrastructure over the last 60 years,this paper explores the main drivers of transportation development,including national policy,transportation structure,investment efficiency,and technological innovation.Analysis shows that China's comprehensive transportation infrastructure construction since 1949 can be divided into five stages initiated by these drivers,which correspond to four transition modes:policy transition,structural transition,efficiency transition,and technology transition.The transition path of China's transportation development shows that the dominant factors have changed,and the interval for each transition has shortened.With the implementation of the '12th Five-Year Plan',China's transportation infrastructure construction is showing some new characteristics and facing a new development transition.Finally,this paper analyzes the trends in transportation development in China and concludes that technological innovation will be the main driving force to increase the transportation supply and service area in the future.展开更多
This paper introduces a proposal for reservoir volume calculation in rainwater harvesting systems. The proposed method can be used for reservoir volume design in rainwater harvesting systems and is based on three impo...This paper introduces a proposal for reservoir volume calculation in rainwater harvesting systems. The proposed method can be used for reservoir volume design in rainwater harvesting systems and is based on three important variables. These variables are water demand, system efficiency and repayment time. Several simulations were carried out in different scenarios considering typical values of both catchment area (for low-income and medium-income households) and water demand, with fixed water and tank costs. Results showed that the integrated analysis of demand, efficiency and repayment time may assist designers to determine a more adequate reservoir volume.展开更多
My principal objective in this paper is to examine what position liberal egalitarians should take regarding the issue of immigration. Given that liberal egalitarians grant central importance to individual autonomy and...My principal objective in this paper is to examine what position liberal egalitarians should take regarding the issue of immigration. Given that liberal egalitarians grant central importance to individual autonomy and the moral equality of all persons, their rejection of restrictive immigration policies appears to follow from these central normative commitments. Liberal egalitarians such as Joseph Carens and Phillip Cole have argued that those who are committed to individual autonomy and moral equality should advocate for an open borders position in immigration. I argue that it is a serious mistake for liberal egalitarians to advocate open national borders and that borders should instead be strategically regulated to reduce global economic inequalities through immigration policies systematically integrated into development programs for the poorest and most vulnerable countries. Open borders would create an open market for immigration slots to choice countries of destination, which out of practical necessity would have to delimit the number of new immigrants. It is well known in migration studies that those who are more educated, young, and have more resources are more likely to migrate than the very young, the elderly, the infirm, and the poorest individuals. Those left behind in developing countries suffer serious negative consequences from the emigration of the most highly educated, capable, and talented individuals in their society. I then argue that liberal egalitarians should grant particular moral consideration to the world's poorest and most vulnerable and that immigration policies strategically designed to prioritize their needs are actually more consistent with the dual commitments of individual autonomy and moral equality than an open borders position. I propose three principles of global justice that are consistent with liberal egalitarianism that should guide transnational moral obligations. I end the paper by arguing that two of these principles can be used to justify restricted immigration policies that would enable developed countries to partially discharge some of their moral obligations to developing countries while enhancing the autonomy of the world's most vulnerable people.展开更多
In its effort towards becoming a developed nation in the next decade, Malaysia has incorporated its education system with National Higher Education Action Plan initiatives to produce a next generation of populace who ...In its effort towards becoming a developed nation in the next decade, Malaysia has incorporated its education system with National Higher Education Action Plan initiatives to produce a next generation of populace who are no more dependent on the government for various aids. For the past decade, creation of entrepreneurs through a formal education has become the mainstay of the local Higher Education Institutions (HEI). Pursuing of an entrepreneurship education by means of a degree programme has emerged as one of the popular choice among undergraduates as an option for rewarding and full time career. Because of this. there has been an increased demand for entrepreneurship education and training in Malaysia to nurture entrepreneurial characteristics. The national agenda is to encourage the younger generations to be nurtured into becoming job-creators rather than job-seekers once they leave the educational system. Given this trend, HEIs need to undertake some policy changes, including faculty or school overall legislation and the development of alternative specialized programs, to be more accommodating to future entrepreneurs. This paper provides an insight into entrepreneurship education, as one of the programs that can generate interest among undergraduates to enhance entrepreneurial characteristics in order to create good entrepreneurs.展开更多
Chinese traditional family-based society is the legal basis for political, patriarchal hierarchy and national politics Consistent hierarchy, as represented by the family law civil law is to adjust the traditional soci...Chinese traditional family-based society is the legal basis for political, patriarchal hierarchy and national politics Consistent hierarchy, as represented by the family law civil law is to adjust the traditional social relations, maintaining the main legal norms of social order, Family law as one of the most important traditional Chinese society, the legal system, and the state law regulating social order constitute the dual legal structure. And its fundamental purpose is to maintain social harmony and stability of the feudal rule of order.展开更多
Developing countries establishing international branch campuses (IBCs) is an emerging trend, and currently compromises 17% percent of the market in terms of the number of IBCs. While researchers have applied differe...Developing countries establishing international branch campuses (IBCs) is an emerging trend, and currently compromises 17% percent of the market in terms of the number of IBCs. While researchers have applied different social science perspectives to analyze cross-border higher education and IBCs, they usually emphasize developed countries as exporters and developing countries as importers of higher education. The phenomenon of developing countries as exporters of higher education has seldom been looked at so far in the research. This paper first describes the current development of IBCs, then illustrates what social science perspectives have been used on this topic, followed by how push-pull theory relates to developing countries being exporters of IBCs. The paper aims to combine E.S. Lee's push-pull theory and Gu's push-pull framework to analyze the push and pull factors in their advertisement and marketing claims when higher education institutions (HEIs) from developing countries plan to establish branch campuses in foreign countries. Soochow University in Laos is used as a case study. Furthermore, intermediate barriers and solutions are also identified in this case study. However, this case study has its own uniqueness and only serves heuristic for future research.展开更多
Over the past decade higher education reforms in most European countries have been oriented towards creating a European Higher Education Area which is envisaged in the Bologna Declaration.Based on an illustration of a...Over the past decade higher education reforms in most European countries have been oriented towards creating a European Higher Education Area which is envisaged in the Bologna Declaration.Based on an illustration of a variety of difficulties encountered higher education institutions in a wide range of participating countries,this article indicates a less optimistic view on the achievements to date in the Bologna Process.It argues that the tension of interests between the designers of the Process and its national and institutional practitioners undermines the actual progress towards the supranational objectives.It is suggested that most difficulties in relation to harmonizing national structures of higher education lie in the varying degrees of cultural dependency on traditions and academic autonomy across the engaged European countries.展开更多
To achieve the overall goals and purposes of education is closely related to the living environments of students.Different family backgrounds will put children into a situation where they face unfair competition.Accor...To achieve the overall goals and purposes of education is closely related to the living environments of students.Different family backgrounds will put children into a situation where they face unfair competition.According to a survey conducted in China’s Urumqi and Changchun about parents’awareness of educating their children,this paper will suggest that families with different backgrounds have different expectations for their children’s education.Moreover,it suggests that parents’social status is related to their children’s education expectations.Therefore,we can find that parents’social status influences their children’s education,and their positions in social class are related to education.展开更多
The authors define the equi-nuclearity of uniform Roe algebras of a family of metric spaces. For a discrete metric space X with bounded geometry which is covered by a family of subspaces {Xi}i=1^∞, if {C^*(Xi)}i=1...The authors define the equi-nuclearity of uniform Roe algebras of a family of metric spaces. For a discrete metric space X with bounded geometry which is covered by a family of subspaces {Xi}i=1^∞, if {C^*(Xi)}i=1^∞ are equi-nuclear and under some proper gluing conditions, it is proved that C*(X) is nuclear. Furthermore, it is claimed that in general, the coarse Roe algebra C^* (X) is not nuclear.展开更多
In this study, the Pb/U fractionation between zircon and uraninite during femtosecond Laser Ablation Inductively Coupled Plasma Mass Spectrometry (fs-LA-ICP-MS) analysis was studied in detail. The results show signi...In this study, the Pb/U fractionation between zircon and uraninite during femtosecond Laser Ablation Inductively Coupled Plasma Mass Spectrometry (fs-LA-ICP-MS) analysis was studied in detail. The results show significant Pb/U fractionation between zircon and uraninite during fs-LA-ICP-MS analysis that when calibrated against the zircon standard M257, the obtained U-Pb age of the Chinese national uraninite standard GBW04420 is 17% older than the recommended value. Thus, the accurate in-situ U-Pb dating of uraninite by LA-ICP-MS requires matrix-matched external standards for calibration. Uraninite in thin sections of two U-mineralized leucogranite from the Gaudeanmus in Namibia was analyzed by a fs-LA-ICP-MS equipped with a Signal Smooth Device (SSD), using laser spot and frequency of 10 μm and 1 Hz, respectively. When calibrated using GBW04420 as the external standard, two samples give weighted mean 2066pb/238U ages of 504±3 Ma (2σ, n=21) and 503±3 Ma (2σ, n=22), and only one of two samples yields a concordia U-Pb age of 507±1 Ma (2or, n=21). These results are consistent with ID-TIMS U-Pb ages of 509±1 and 508±12 Ma and are also indistinguishable from zircon U-Pb upper intercept ages of 506±33 Ma (2σ, n=29) and 501±51 Ma (2σ, n=29). The present study shows that in-situ U-Pb dating of uraninite can deliver more reliable formation ages of the deposit than dating coeval high-U zircon because the latter commonly suffer significant Pb loss after formation. Our results confirm that GBW04420 is an ideal matrix matching standard for in-situ U-Pb dating of uraninite.展开更多
基金supported by the National“863”Foundation of China under Grant 2007AA04Z193
文摘The problem of H∞ stability analysis and control synthesis of switched systems with delayed states under arb/trary switchirg laws is considered. By means of Lyapunov function and linear matrix inequality tools, sufficient ctmdition of H∞ stability is presented in terms of linear matrix inequalities. Furthermore, the robust H∞ control synthesis via state feedback and output feedack is studied. Finally, a numerical example is given to demonstrate the effectiveness of the proposed method.
基金Under the auspices of National Natural Science Foundation of China (No. 40771190)Special Fund for Meteorological Scientific Research in the Public Interest (No. GYHY200706030)
文摘The objective of this study was to provide reliable basis for decision making for national food security and layout and structure adjustment of grain production in the northeastern China. The data of mean daily air temperature of 1961-2009 from 106 meteorological stations in the northeastern China were chosen in this study. Using statistical methods and isoline method, the spatio-temporal changes of various decadal ≥10℃accumulated temperature and the climatic means of ≥10℃ accumulated temperature were studied in this paper. The results showed that 1) The geo- graphical distribution of ≥10℃ accumulated temperature in the northeastern China could be influenced directly by the latitude, longitude and altitude. If latitude moved one degree northward, the average decrease amplitude of the climatic means was 101.9℃ in the study area. 2) The means of decadal ≥10℃ accumulated temperature rose since the 1980s, and their increase amplitudes became larger in the 1990s and the 2010s obviously. Compared with those of the 1980s, ≥10℃ accumulated temperature increased by about 100℃ in the mountainous and plain areas in the 1990s; compared with those of the 1990s, ≥10℃ accumulated temperature increased by about 200℃ in the Hulun Buir High Plain and the Songnen Plain, and 100℃ in the Sanjiang Plain and the Liaohe Plain in the 2010s. 3) The means of the decada ≥10℃accumulated temperature for 106 meteorological stations in the northeastern China increased with the rate of 145.57℃/10yr in 1961-2009.4) The climatic means of ≥10℃ accumulated temperature increased from 1961-1990 to 1971-2000 and 1981-2009. Compared with the climatic mean of 1971-2000, that of 1981-2009 had increased by above 50℃ in most of the study area, even up to 156℃. Compared with the climatic mean of 1961-1990, that of 1981-2009 increased by above 100℃ in most parts of the study area, even up to 200℃. 5) The maximum northward shift, eastward and westward extension amplitudes of3100℃, 3300℃ and 3500℃ isolines were larger among all isolines for the climatic means of the three phases. Compared with the positions of the isolines of 1961-1990, those amplitudes of 31000C isoline of 1981-2009 were 145 km, 109 km and 64 km, respectively; those of 3300℃ isoline were 154 km, 54 km and 64 km, respectively; and the maximum northward shift of 3500℃ isoline was about 100 km.
基金Project 40772086 supported by the National Natural Science Foundation of China
文摘The Chaoyanggou oil field is a fractured low-permeability reservoir, where the distribution of oil and gas is controlled by the distribution and development of fractures.Based on outcrop, drilling core, thin section and log data, the development characteristics of fractures in this area are described.On this basis, the degree of fracture development was predicted by quantitative analysis of fracture strength and numerical simulation.The result shows that four groups of structural fractures, i.e., in near NS, and EW directions and in due NW and NE directions, were developed in the reservoir, with the nearly NS and EW fractures dominant, which are the along bedding decollement fractures formed by compressive folding action, while low angle shear fractures are related to thrusts.These fractures are mainly formed in the reversed tectonic stage at the end of the Mingshui formation during the Cretaceous period.The degree of fracture development is controlled by such factors as lithology, stratum thickness, faults, folds and depth.The fractures are developed with a clear zonation and are best developed in the northern zone, moderately developed towards the south and poorly developed in the middle zone.These prediction results are in good agreement with interpretation results from logs.
基金Under the auspices of National Natural Science Foundation of China(No.41171107,41001082)Programme of Bingwei Excellent Young Scientists of Institute of Geographic Sciences and Natural Resources Research,Chinese Academy of Sciences
文摘Scientific development is an invaluable asset to a country.Policies and development modes should be carried out based on scientific findings not only in industry,but also in transportation infrastructure construction.Building an integrated transportation system,which is in line with the national requirements of China and supports sustainable socio-economic development,is a key strategic issue related to building a moderately prosperous society and achieving realistic goals of a medium-level developed country.Based on a systematic review of the advances in China's transportation infrastructure over the last 60 years,this paper explores the main drivers of transportation development,including national policy,transportation structure,investment efficiency,and technological innovation.Analysis shows that China's comprehensive transportation infrastructure construction since 1949 can be divided into five stages initiated by these drivers,which correspond to four transition modes:policy transition,structural transition,efficiency transition,and technology transition.The transition path of China's transportation development shows that the dominant factors have changed,and the interval for each transition has shortened.With the implementation of the '12th Five-Year Plan',China's transportation infrastructure construction is showing some new characteristics and facing a new development transition.Finally,this paper analyzes the trends in transportation development in China and concludes that technological innovation will be the main driving force to increase the transportation supply and service area in the future.
文摘This paper introduces a proposal for reservoir volume calculation in rainwater harvesting systems. The proposed method can be used for reservoir volume design in rainwater harvesting systems and is based on three important variables. These variables are water demand, system efficiency and repayment time. Several simulations were carried out in different scenarios considering typical values of both catchment area (for low-income and medium-income households) and water demand, with fixed water and tank costs. Results showed that the integrated analysis of demand, efficiency and repayment time may assist designers to determine a more adequate reservoir volume.
文摘My principal objective in this paper is to examine what position liberal egalitarians should take regarding the issue of immigration. Given that liberal egalitarians grant central importance to individual autonomy and the moral equality of all persons, their rejection of restrictive immigration policies appears to follow from these central normative commitments. Liberal egalitarians such as Joseph Carens and Phillip Cole have argued that those who are committed to individual autonomy and moral equality should advocate for an open borders position in immigration. I argue that it is a serious mistake for liberal egalitarians to advocate open national borders and that borders should instead be strategically regulated to reduce global economic inequalities through immigration policies systematically integrated into development programs for the poorest and most vulnerable countries. Open borders would create an open market for immigration slots to choice countries of destination, which out of practical necessity would have to delimit the number of new immigrants. It is well known in migration studies that those who are more educated, young, and have more resources are more likely to migrate than the very young, the elderly, the infirm, and the poorest individuals. Those left behind in developing countries suffer serious negative consequences from the emigration of the most highly educated, capable, and talented individuals in their society. I then argue that liberal egalitarians should grant particular moral consideration to the world's poorest and most vulnerable and that immigration policies strategically designed to prioritize their needs are actually more consistent with the dual commitments of individual autonomy and moral equality than an open borders position. I propose three principles of global justice that are consistent with liberal egalitarianism that should guide transnational moral obligations. I end the paper by arguing that two of these principles can be used to justify restricted immigration policies that would enable developed countries to partially discharge some of their moral obligations to developing countries while enhancing the autonomy of the world's most vulnerable people.
文摘In its effort towards becoming a developed nation in the next decade, Malaysia has incorporated its education system with National Higher Education Action Plan initiatives to produce a next generation of populace who are no more dependent on the government for various aids. For the past decade, creation of entrepreneurs through a formal education has become the mainstay of the local Higher Education Institutions (HEI). Pursuing of an entrepreneurship education by means of a degree programme has emerged as one of the popular choice among undergraduates as an option for rewarding and full time career. Because of this. there has been an increased demand for entrepreneurship education and training in Malaysia to nurture entrepreneurial characteristics. The national agenda is to encourage the younger generations to be nurtured into becoming job-creators rather than job-seekers once they leave the educational system. Given this trend, HEIs need to undertake some policy changes, including faculty or school overall legislation and the development of alternative specialized programs, to be more accommodating to future entrepreneurs. This paper provides an insight into entrepreneurship education, as one of the programs that can generate interest among undergraduates to enhance entrepreneurial characteristics in order to create good entrepreneurs.
文摘Chinese traditional family-based society is the legal basis for political, patriarchal hierarchy and national politics Consistent hierarchy, as represented by the family law civil law is to adjust the traditional social relations, maintaining the main legal norms of social order, Family law as one of the most important traditional Chinese society, the legal system, and the state law regulating social order constitute the dual legal structure. And its fundamental purpose is to maintain social harmony and stability of the feudal rule of order.
文摘Developing countries establishing international branch campuses (IBCs) is an emerging trend, and currently compromises 17% percent of the market in terms of the number of IBCs. While researchers have applied different social science perspectives to analyze cross-border higher education and IBCs, they usually emphasize developed countries as exporters and developing countries as importers of higher education. The phenomenon of developing countries as exporters of higher education has seldom been looked at so far in the research. This paper first describes the current development of IBCs, then illustrates what social science perspectives have been used on this topic, followed by how push-pull theory relates to developing countries being exporters of IBCs. The paper aims to combine E.S. Lee's push-pull theory and Gu's push-pull framework to analyze the push and pull factors in their advertisement and marketing claims when higher education institutions (HEIs) from developing countries plan to establish branch campuses in foreign countries. Soochow University in Laos is used as a case study. Furthermore, intermediate barriers and solutions are also identified in this case study. However, this case study has its own uniqueness and only serves heuristic for future research.
文摘Over the past decade higher education reforms in most European countries have been oriented towards creating a European Higher Education Area which is envisaged in the Bologna Declaration.Based on an illustration of a variety of difficulties encountered higher education institutions in a wide range of participating countries,this article indicates a less optimistic view on the achievements to date in the Bologna Process.It argues that the tension of interests between the designers of the Process and its national and institutional practitioners undermines the actual progress towards the supranational objectives.It is suggested that most difficulties in relation to harmonizing national structures of higher education lie in the varying degrees of cultural dependency on traditions and academic autonomy across the engaged European countries.
文摘To achieve the overall goals and purposes of education is closely related to the living environments of students.Different family backgrounds will put children into a situation where they face unfair competition.According to a survey conducted in China’s Urumqi and Changchun about parents’awareness of educating their children,this paper will suggest that families with different backgrounds have different expectations for their children’s education.Moreover,it suggests that parents’social status is related to their children’s education expectations.Therefore,we can find that parents’social status influences their children’s education,and their positions in social class are related to education.
基金supported by the National Natural Science Foundation of China(Nos.10731020,10971023)the Shu Guang Project of Shanghai Municipal Education Commission and Shanghai Education DepartmentFoundation(No.07SG38)the Foundation of the Ministry of Education of China
文摘The authors define the equi-nuclearity of uniform Roe algebras of a family of metric spaces. For a discrete metric space X with bounded geometry which is covered by a family of subspaces {Xi}i=1^∞, if {C^*(Xi)}i=1^∞ are equi-nuclear and under some proper gluing conditions, it is proved that C*(X) is nuclear. Furthermore, it is claimed that in general, the coarse Roe algebra C^* (X) is not nuclear.
基金supported by the National Natural Science Foundation of China(Grant Nos.41203027 and 41473031)the State Administration of Foreign Expert Affairs of China(Grant No.B07039)the Special Fund for Basic Scientific Research of Central Colleges,China University of Geosciences(Wuhan)(Grant No.CUGL140403)
文摘In this study, the Pb/U fractionation between zircon and uraninite during femtosecond Laser Ablation Inductively Coupled Plasma Mass Spectrometry (fs-LA-ICP-MS) analysis was studied in detail. The results show significant Pb/U fractionation between zircon and uraninite during fs-LA-ICP-MS analysis that when calibrated against the zircon standard M257, the obtained U-Pb age of the Chinese national uraninite standard GBW04420 is 17% older than the recommended value. Thus, the accurate in-situ U-Pb dating of uraninite by LA-ICP-MS requires matrix-matched external standards for calibration. Uraninite in thin sections of two U-mineralized leucogranite from the Gaudeanmus in Namibia was analyzed by a fs-LA-ICP-MS equipped with a Signal Smooth Device (SSD), using laser spot and frequency of 10 μm and 1 Hz, respectively. When calibrated using GBW04420 as the external standard, two samples give weighted mean 2066pb/238U ages of 504±3 Ma (2σ, n=21) and 503±3 Ma (2σ, n=22), and only one of two samples yields a concordia U-Pb age of 507±1 Ma (2or, n=21). These results are consistent with ID-TIMS U-Pb ages of 509±1 and 508±12 Ma and are also indistinguishable from zircon U-Pb upper intercept ages of 506±33 Ma (2σ, n=29) and 501±51 Ma (2σ, n=29). The present study shows that in-situ U-Pb dating of uraninite can deliver more reliable formation ages of the deposit than dating coeval high-U zircon because the latter commonly suffer significant Pb loss after formation. Our results confirm that GBW04420 is an ideal matrix matching standard for in-situ U-Pb dating of uraninite.