超幂零群的性质研究

幂零群的研究一直是有限群理论研究的重要组成部分。我们知道幂零群G存在正规群列:G=G1Gr=1,因子群GiGi+1￡Z(G Gi+1)。本文研究幂零群的推广。假设群的因子群是超中心的及GiGi+1是循环群,在此基础上,引出超幂零群的概念。利用有限群理论对有限超幂零群的性质进行研究,得到一些有意义的结果。     

从索书号看国家图书馆基藏本文献的变化

详细介绍了国家图书馆基藏本各种文献类型的索书号形式及其在不同时期的变化情况,以进一步完善索书号的文献功能,规范馆藏文献的分类排架工作。     

模n高斯整数环的零因子图的中心集和半径

研究模n高斯整数环的零因子图的中心集和半径,得到模n高斯整数环的零因子图半径为0、1、2时的充要条件,同时对每一个正整数n,给出模n高斯整数环的零因子图的中心集。     

SH-1型组装式大型浮标的设计

针对整体式大型海洋资料浮标海上生存能力不强，加工制造、布放运输不便等问题，设计了一种直径为6 m的组装式的大型浮标。利用船舶静力学的计算方法，确定了浮标的型深为2.2 m、重心高为0.9 m以及其他基本参数，并对浮标的稳性衡准数进行校核，结果满足使用要求。该设计为浮标加工质量的可控性提供了合理化依据。     

新乡市平原体育(会展)中心的SWOT分析——平原体育(会展)中心系列研究之一

运用SWOT分析法,分析了平原体育(会展)中心建设及经营管理的优势、劣势及环境中的机会和威胁,并提出了应对策略.     

基于mIBE的密钥托管和身份撤销方案

针对现有方案中存在不能防止KGC(密钥产生中心)冒充合法用户身份的问题,提出一种基于mIBE的密钥托管和身份撤销方案.该方案通过由KGC和PRA(私钥撤销机构)共同为用户颁发的身份密钥来确认其身份.基于盲技术使得KGC和PRA之间的保密信息可在公共通道上传输,解决了现有方案需额外增加安全通道的负担.     

Integrative taxonomic analysis reveals a new species of Leptobrachium (Anura: Megophryidae) from north-eastern Cambodia and central Vietnam

ABSTRACT

Species boundaries within the red-eyed Leptobrachium of southern Indochina have been uncertain. Leptobrachium pullum and L. mouhoti from upper and lower elevations, respectively, of the Langbian Plateau of southern Vietnam and eastern Cambodia differ in body size but have relatively low interspecific mitochondrial DNA divergence, leading to speculation that these might represent a single species with an elevational cline in body size. The recent discovery of an allopatric high-elevation population of red-eyed Leptobrachium on the Kon Tum Plateau (= Central Highlands) of north-eastern Cambodia and central Vietnam has been referred to both species, and to a putatively undescribed species. We examine variation in morphology of adults and tadpoles, mitochondrial DNA, 11 nuclear genes and advertisement calls, and show corroborating lines of evidence for the existence of three species of red-eyed Leptobrachium in southern Indochina. Although the three species are reciprocally monophyletic in mitochondrial DNA, their shallow mitochondrial DNA divergences are not mirrored by morphology, advertisement calls, or – in part – nuclear DNA, and probably reflect past mitochondrial introgression rather than recent speciation. The Central Highlands taxon is described herein as a new species.

http://www.zoobank.org/urn:lsid:zoobank.org:pub:CE6650AF-D9FB-40F4-8A2E-9B4E23AAC205     

Hybrid micromotion-scattering center model for synthetic aperture radar micromotion target imaging

Micromotion is an important target feature, although the target micromotion has an unfavorable influence on the synthetic aperture radar （SAR） image interpretation due to defocusing. This paper introduces micromotion parameters into the scattering center model to obtain a hybrid micromotion-scattering center model, and then proposes an optimization algorithm based on the maximal likelihood estimation to solve the model for jointly obtaining target motion and scattering parameters. Initial value estimation methods using targets＇ ghost images are then presented to guarantee the global and fast convergence. Simulation results show the effectiveness of the proposed algorithm especially in high precision estimation and multiple targets processing.     

2003～2018年昆明市呈贡区土地利用动态变化时空特征分析

为应对昆明市呈贡区城镇化快速发展带来的土地利用矛盾突出的问题,本文采用土地利用转移矩阵、标准差椭圆分析、平均中心分析、热点分析的方法,研究该区域15年间建设用地扩张情况与区域发展特征。实验结果表明：2003年-2018年呈贡区建设用地共增加了101.91,绿地共增加了57.01,耕地共减少了175.97 。同时呈贡区扩张展现出明显的方向性,以东北-西南方向为主轴进行倾斜,建设用地的平均中心向南缓慢移动,其热点已发展到全区西部、中部大部分区域。     

双峰截尾变量的矩界

对具有给定的EXi=mi(i=1,2,3)和双峰的随机变量X∈[0,M],得到截尾变量max(0,X-K)的均值的矩界,以及小值概率的上界.这些问题来源于双峰分布下小值概率及欧氏期权等的研究,所用方法基于控制待估函数和测度变换.