A Method for Rapidly Determining the Optimal Distribution Locations of GNSS Stations for Orbit and ERP Measurement Based on Map Grid Zooming and Genetic Algorithm

Designing the optimal distribution of Global Navigation Satellite System(GNSS)ground stations is crucial for determining the satellite orbit,satellite clock and Earth Rotation Parameters(ERP)at a desired precision using a limited number of stations.In this work,a new criterion for the optimal GNSS station distribution for orbit and ERP determination is proposed,named the minimum Orbit and ERP Dilution of Precision Factor(OEDOP)criterion.To quickly identify the specific station locations for the optimal station distribution on a map,a method for the rapid determination of the selected station locations is developed,which is based on the map grid zooming and heuristic technique.Using the minimum OEDOP criterion and the proposed method for the rapid determination of optimal station locations,an optimal or near-optimal station distribution scheme for 17 newly built BeiDou Navigation Satellite System(BDS)global tracking stations is suggested.To verify the proposed criterion and method,real GNSS data are processed.The results show that the minimum OEDOP criterion is valid,as the smaller the value of OEDOP,the better the precision of the satellite orbit and ERP determination.Relative to the exhaustive method,the proposed method significantly improves the computational efficiency of the optimal station location determination.In the case of 3 newly built stations,the computational efficiency of the proposed method is 35 times greater than that of the exhaustive method.As the number of stations increases,the improvement in the computational efficiency becomes increasingly obvious.

锂离子电池释热机理与模型及安全改性技术研究综述

锂离子电池具有能量功率密度高、寿命长、无记忆效应等优点,被广泛应用于移动电子产品、电动汽车、储能系统、航空航天等领域。然而近年来以电池热失控相关的电动汽车和储能系统安全事故频发,引起高度关注。高能量密度电池的高安全性是推动电池大规模应用的首要保障,以电池产热特性、热失控机理、防护和抑制方法为核心的研究成为近几年电池热安全领域的热点。因此,本文对电池热安全领域的核心问题进行了全面的综述。首先讨论电池在常规工况下的产热特性、热失控链式放热反应以及三种滥用条件下的电池失效机理;其次,阐述电池电化学-热耦合模型以及热失控模型的机理方程、构建、应用及演化;再次,介绍电池正负极材料、隔膜、电解液以及集流体安全改性技术的研究进展;最后本文对该领域的研究趋势做出展望,为提升锂离子电池的本征安全性,防止热失控提供思路和方向。

非水系锂空气电池催化剂

近年来,随着对高性能电池需求的加大,锂空气电池因其超高的理论能量密度成为了研究热点。虽然锂空气电池的发展已取得了一些突破性的进展,但离实际应用差距甚远,仍有很多问题和挑战需要解决。其中,氧电极反应动力学速度缓慢就是一个非常严重的问题。为了促进锂空气电池的发展和应用,国际学术界对改善氧电极动力学速度的催化剂开展了大量的研究工作。本文总结了近年来国内外关于锂空气电池氧电极催化材料的主要研究进展,并对其未来发展作了前景展望。