Song [Song D 2004 Phys. Rev. A69034301] first proposed two key distribution schemes with the symmetry feature.We find that, in the schemes, the private channels which Alice and Bob publicly announce the initial Bell s...Song [Song D 2004 Phys. Rev. A69034301] first proposed two key distribution schemes with the symmetry feature.We find that, in the schemes, the private channels which Alice and Bob publicly announce the initial Bell state or the measurement result through are not needed in discovering keys, and Song’s encoding methods do not arrive at the optimization.Here, an optimized encoding method is given so that the efficiencies of Song’s schemes are improved by 7/3 times. Interestingly, this optimized encoding method can be extended to the key distribution scheme composed of generalized Bell states.展开更多
近年来,极端高温干旱等灾害事件频发,给经济和社会带来巨大影响,尤其是2022年夏季,我国中东部地区遭遇了持续性高温和严重干旱,造成了严重经济损失。标准化加权平均降水(Standardized Weighted Average Precipitation,SWAP)指数基于简...近年来,极端高温干旱等灾害事件频发,给经济和社会带来巨大影响,尤其是2022年夏季,我国中东部地区遭遇了持续性高温和严重干旱,造成了严重经济损失。标准化加权平均降水(Standardized Weighted Average Precipitation,SWAP)指数基于简单物理模型,考虑前期降水的累积效应与衰减效应,能够准确地反映当前旱涝状况,并展现对应的演变过程。为了探究此次干旱事件的变化特征,本文将该方法与传统的标准化降水指数(Standardized Precipitation Index,SPI)进行对比,采用该方法对2022年夏季的干旱进行逐日监测,并结合游程理论,对干旱的极端程度进行了量化分析。结果表明:SWAP指数在逐日尺度上的监测效果更优,能够提供更为精确的干旱信息。本次事件中干旱首先出现在华北和东北地区,随后蔓延至西北和华南地区,最终在8月中旬大部分地区都呈现严重干旱的状态。此次干旱是近62 a以来最为极端的干旱事件,在不同阈值下,干旱日数、干旱日SWAP累积量和干旱强度均达到了历史最高水平。本研究为评估干旱事件的极端程度提供了新的方法,为未来干旱的监测、预警及气候灾害的管理与应对提供了科学依据与技术支持。展开更多
基金supported by the National Natural Science Foundation of China(Grant No.11205115)the Program for Academic Leader Reserve Candidates in Tongling University(Grant No.2014tlxyxs30)the 2014-year Program for Excellent Youth Talents in University of Anhui Province,China
文摘Song [Song D 2004 Phys. Rev. A69034301] first proposed two key distribution schemes with the symmetry feature.We find that, in the schemes, the private channels which Alice and Bob publicly announce the initial Bell state or the measurement result through are not needed in discovering keys, and Song’s encoding methods do not arrive at the optimization.Here, an optimized encoding method is given so that the efficiencies of Song’s schemes are improved by 7/3 times. Interestingly, this optimized encoding method can be extended to the key distribution scheme composed of generalized Bell states.
