The abundances of long-lived radioactive elements Th and U observed in metal-poor halo stars can be used as chronometers to determine the age of individual stars, and hence set a lower limit on the age of the Galaxy a...The abundances of long-lived radioactive elements Th and U observed in metal-poor halo stars can be used as chronometers to determine the age of individual stars, and hence set a lower limit on the age of the Galaxy and hence of the universe. This radioactive dating requires the zero-decay productions of Th and U, which involves complicated r-process nucleosynthesis calculations. Several parametric r-process models have been used to calculate the initial abundance ratios of Th/Eu and U/Th, but, due to the sharp sensitivity of these models to nuclear physics inputs, the calculations have relatively large uncertainties which lead to large uncertainties in the age determinations. In order to reduce these uncertainties, we present a simple method to estimate the initial productions of Th and U, which only depends on the solar system abundances and the stellar abundances of stable r-process elements. From our calculations of the initial abundance ratios of Th/Eu and U/Th, we re-estimate the ages of those very metal-poor halo stars with published abundances of Th and U. Our age estimates are consistent, within the errors, with the other age determinations derived from r-process models, and offer useful constrains for r-process theoretical calculations. The advantages and limitations of our simple method of radioactive dating are discussed.展开更多
近日,英国皇家建筑师学会(The Royal Institute of British Architects,简称R旧A),颁布了2021年获奖名单:其中,总统研究奖(WBA President’s Award for Research)的得主是来自香港大学的林君翰(John Lin)和索尼·德巴克托尼(Sony De...近日,英国皇家建筑师学会(The Royal Institute of British Architects,简称R旧A),颁布了2021年获奖名单:其中,总统研究奖(WBA President’s Award for Research)的得主是来自香港大学的林君翰(John Lin)和索尼·德巴克托尼(Sony Devabhaktuni),他们的项目是As found house:来自中国农村的自建者的实验。展开更多
Since ancient times, the mining and excavation of minerals have been highly valued by all countries, which have played an important role in national development and social production and life. As early as 1970s and 19...Since ancient times, the mining and excavation of minerals have been highly valued by all countries, which have played an important role in national development and social production and life. As early as 1970s and 1980s, China began to vigorously develop the mining industry, among which the excavation of Daqing Oilfield is more famous, and it can still provide a steady stream of petroleum minerals today. In the past, some safety accidents often occurred in the process of mineral exploitation projects, resulting in casualties and economic losses, which were a kind of loss to the society and the industry. The emergence of geological exploration technology for mineral exploitation made people hope to reduce the risk coefficient of mineral exploitation and improve the efficiency of mineral exploitation, and had an optimized direction. In this paper, the concept and application of geological exploration technology, as well as a series of problems and obstacles will be discussed, combined with examples of remote sensing exploration technology, hoping to provide some reference for future mineral exploration.展开更多
With the development of geological research in China, more and more workers will effectively integrate the science and technology of geological prospecting and exploration, so as to promote the development of geologic...With the development of geological research in China, more and more workers will effectively integrate the science and technology of geological prospecting and exploration, so as to promote the development of geological management to the maximum extent. In the specific implementation process, technicians should understand the distribution of mineral resources, integrate the technical structure and basic rules of prospecting with science and technology, follow the principles of prospecting and exploration technology, and seek innovative application means. At the same time, the rapid development of modern science and technology brings good news to the geological exploration industry, and comprehensively uses various modern technical means to promote the continuous improvement of geological exploration technology level. This is an important work that exploration units and practitioners are committed to.展开更多
基金Supported by the National Natural Science Foundation of China.
文摘The abundances of long-lived radioactive elements Th and U observed in metal-poor halo stars can be used as chronometers to determine the age of individual stars, and hence set a lower limit on the age of the Galaxy and hence of the universe. This radioactive dating requires the zero-decay productions of Th and U, which involves complicated r-process nucleosynthesis calculations. Several parametric r-process models have been used to calculate the initial abundance ratios of Th/Eu and U/Th, but, due to the sharp sensitivity of these models to nuclear physics inputs, the calculations have relatively large uncertainties which lead to large uncertainties in the age determinations. In order to reduce these uncertainties, we present a simple method to estimate the initial productions of Th and U, which only depends on the solar system abundances and the stellar abundances of stable r-process elements. From our calculations of the initial abundance ratios of Th/Eu and U/Th, we re-estimate the ages of those very metal-poor halo stars with published abundances of Th and U. Our age estimates are consistent, within the errors, with the other age determinations derived from r-process models, and offer useful constrains for r-process theoretical calculations. The advantages and limitations of our simple method of radioactive dating are discussed.
文摘近日,英国皇家建筑师学会(The Royal Institute of British Architects,简称R旧A),颁布了2021年获奖名单:其中,总统研究奖(WBA President’s Award for Research)的得主是来自香港大学的林君翰(John Lin)和索尼·德巴克托尼(Sony Devabhaktuni),他们的项目是As found house:来自中国农村的自建者的实验。
文摘Since ancient times, the mining and excavation of minerals have been highly valued by all countries, which have played an important role in national development and social production and life. As early as 1970s and 1980s, China began to vigorously develop the mining industry, among which the excavation of Daqing Oilfield is more famous, and it can still provide a steady stream of petroleum minerals today. In the past, some safety accidents often occurred in the process of mineral exploitation projects, resulting in casualties and economic losses, which were a kind of loss to the society and the industry. The emergence of geological exploration technology for mineral exploitation made people hope to reduce the risk coefficient of mineral exploitation and improve the efficiency of mineral exploitation, and had an optimized direction. In this paper, the concept and application of geological exploration technology, as well as a series of problems and obstacles will be discussed, combined with examples of remote sensing exploration technology, hoping to provide some reference for future mineral exploration.
文摘With the development of geological research in China, more and more workers will effectively integrate the science and technology of geological prospecting and exploration, so as to promote the development of geological management to the maximum extent. In the specific implementation process, technicians should understand the distribution of mineral resources, integrate the technical structure and basic rules of prospecting with science and technology, follow the principles of prospecting and exploration technology, and seek innovative application means. At the same time, the rapid development of modern science and technology brings good news to the geological exploration industry, and comprehensively uses various modern technical means to promote the continuous improvement of geological exploration technology level. This is an important work that exploration units and practitioners are committed to.
