分类： 物理学 >> 核物理学 提交时间： 2023-06-07
摘要：An ZrV2 alloy is typically susceptible to poisoning by impurity gases, which causes a considerable reduction in the hydrogen-storage properties of the alloy. In this study, the adsorption characteristics of oxygen on ZrV2 surfaces doped with Hf, Ti, and Pd are investigated, and the influence of oxygen on the hydrogen storage performance of the alloy was discussed. Subsequently, the adsorption energy, bond-length change, density of states, and differential charge density of the alloy before and after doping are analyzed using the first-principles method. The theoretical results show that Ti doping has a limited effect on the adsorption of oxygen atoms on the ZrV2 surface, whereas Hf doping decreases the adsorption energy of oxygen on the ZrV2 surface. Oxygen atoms are more difficult to adsorb at most adsorption sites on Pd-containing surfaces, which indicates that Pd has the best anti-poisoning properties, followed by Hf. The analysis of the differential charge density and partial density of states shows that the electron interaction between the oxygen atom and surface atom of the alloys is weakened, and the total energy is reduced after Hf and Pd doping. Based on theoretical calculations, the hydrogen-absorption kinetics of ZrV2, Zr0.9Hf0.1V2, and Zr(V0.9Pd0.1)2 alloys are studied in a hydrogen–oxygen mixture of 0.5 vol% O2 at 25℃. The experimental results show that the hydrogen-storage capacities of ZrV2, Zr0.9Hf0.1V2, and Zr(V0.9Pd0.1)2 decrease to 19%, 69%, and 80% of their original values, respectively. The order of alloy resistance to 0.5 vol% O2 poisoning is Zr(V0.9Pd0.1)2>Zr0.9Hf0.1V2>ZrV2. Pd retains its original hydrogen absorption performance to a greater extent than undoped surfaces, and it has the strongest resistance to poisoning, which is consistent with previous theoretical calculations.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Yi Zhao
Wangchen Xue
Shaolin Xiong
Qi Luo
Yuanhao Wang
Jiacong Liu
Heng Yu
Xiaoyun Zhao
Yue Huang
Jinyuan Liao
Jianchao Sun
Xiaobo Li
Qibin Yi
Ce Cai
Shuo Xiao
Shenglun Xie
Chao Zheng
Yanqiu Zhang
Chenwei Wang
Wenjun Tan
摘要：Fast and reliable localization of high-energy transients is crucial for characterizing the burst properties and guiding the follow-up observations. Localization based on the relative counts of different detectors has been widely used for all-sky gamma-ray monitors. There are two major methods for this counts distribution localization: $\chi^{2}$ minimization method and the Bayesian method. Here we propose a modified Bayesian method that could take advantage of both the accuracy of the Bayesian method and the simplicity of the $\chi^{2}$ method. With comprehensive simulations, we find that our Bayesian method with Poisson likelihood is generally more applicable for various bursts than $\chi^{2}$ method, especially for weak bursts. We further proposed a location-spectrum iteration approach based on the Bayesian inference, which could alleviate the problems caused by the spectral difference between the burst and location templates. Our method is very suitable for scenarios with limited computation resources or time-sensitive applications, such as in-flight localization software, and low-latency localization for rapid follow-up observations.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Yi Zhao
Wangchen Xue
Shaolin Xiong
Qi Luo
Yuanhao Wang
Jiacong Liu
Heng Yu
Xiaoyun Zhao
Yue Huang
Jinyuan Liao
Jianchao Sun
Xiaobo Li
Qibin Yi
Ce Cai
Shuo Xiao
Shenglun Xie
Chao Zheng
Yanqiu Zhang
Chenwei Wang
Wenjun Tan
摘要：Fast and reliable localization of high-energy transients is crucial for characterizing the burst properties and guiding the follow-up observations. Localization based on the relative counts of different detectors has been widely used for all-sky gamma-ray monitors. There are two major methods for this counts distribution localization: $\chi^{2}$ minimization method and the Bayesian method. Here we propose a modified Bayesian method that could take advantage of both the accuracy of the Bayesian method and the simplicity of the $\chi^{2}$ method. With comprehensive simulations, we find that our Bayesian method with Poisson likelihood is generally more applicable for various bursts than $\chi^{2}$ method, especially for weak bursts. We further proposed a location-spectrum iteration approach based on the Bayesian inference, which could alleviate the problems caused by the spectral difference between the burst and location templates. Our method is very suitable for scenarios with limited computation resources or time-sensitive applications, such as in-flight localization software, and low-latency localization for rapid follow-up observations.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Jian Ge
Hui Zhang
Weicheng Zang
Hongping Deng
Shude Mao
Ji-Wei Xie
Hui-Gen Liu
Ji-Lin Zhou
Kevin Willis
Chelsea Huang
Steve B. Howell
Fabo Feng
Jiapeng Zhu
Xinyu Yao
Beibei Liu
Masataka Aizawa
Wei Zhu
Ya-Ping Li
Bo Ma
Quanzhi Ye
摘要：We propose to develop a wide-field and ultra-high-precision photometric survey mission, temporarily named "Earth 2.0 (ET)". This mission is designed to measure, for the first time, the occurrence rate and the orbital distributions of Earth-sized planets. ET consists of seven 30cm telescopes, to be launched to the Earth-Sun's L2 point. Six of these are transit telescopes with a field of view of 500 square degrees. Staring in the direction that encompasses the original Kepler field for four continuous years, this monitoring will return tens of thousands of transiting planets, including the elusive Earth twins orbiting solar-type stars. The seventh telescope is a 30cm microlensing telescope that will monitor an area of 4 square degrees toward the galactic bulge. This, combined with simultaneous ground-based KMTNet observations, will measure masses for hundreds of long-period and free-floating planets. Together, the transit and the microlensing telescopes will revolutionize our understandings of terrestrial planets across a large swath of orbital distances and free space. In addition, the survey data will also facilitate studies in the fields of asteroseismology, Galactic archeology, time-domain sciences, and black holes in binaries.
点击量
通过
点击量
下载量
评论
待评议
