NB-IoT(Narrow Band Internet of Things)是基于蜂窝窄带物联网的一种新兴技术,是物联网的一个重要分支。随着NB-IoT终端设备的规模不断增大,物联网安全面临数据泄露、中间人攻击等安全威胁。本论文针对NB-IoT技术的数据安全传输研究,...NB-IoT(Narrow Band Internet of Things)是基于蜂窝窄带物联网的一种新兴技术,是物联网的一个重要分支。随着NB-IoT终端设备的规模不断增大,物联网安全面临数据泄露、中间人攻击等安全威胁。本论文针对NB-IoT技术的数据安全传输研究,从物联网终端安全和应用服务安全两方面进行分析,结合密码技术给出了NB-IoT系统安全模型,提出了基于物联网应用层数据信源加密传输机制,给出了轻量级身份认证协议和数据加密传输协议,论证了该方案的安全性,通过实验验证了所提方案的可行性和适用性。展开更多
In this work, we choose Nb3Al/Nb3Sn as a new test case for flat/steep band model of superconductivity. Based on the density functional theory in the generalized gradient approximation, the electronic structure of Nb3A...In this work, we choose Nb3Al/Nb3Sn as a new test case for flat/steep band model of superconductivity. Based on the density functional theory in the generalized gradient approximation, the electronic structure of Nb3Al/ Nb3Sn has been studied. The obtained results agree well with those of the earlier studies and show clearly fiat bands around the Fermi level. The steep bands as characterized in this work locate around the M point in the first Brillouin zone. The obtained results reveal that Nb3Al/Nb3Sn fits more to the ＂Flat/steep＂ band model than to the van-Hove singularity scenario. The fiat/steep band condition for superconductivity implies a different thermodynamic behavior of superconductors other than that predicted from the conventional BCS theory. This observation sets up an indicator for selecting a suitable superconductor when its large-scale industrial use is needed, for example, in superconducting maglev system or ITER project.展开更多
以热力学和动力学理论为基础,研究了 Nb 微合金钢热变形过程中铁素体相的形核及长大过程,在形核速率计算中引入变形储能、晶界凸阶及微合金元素的作用,建立了低温变形诱导铁素体相变的动力学模型,分析了热变形参数和化学成分对相变分数...以热力学和动力学理论为基础,研究了 Nb 微合金钢热变形过程中铁素体相的形核及长大过程,在形核速率计算中引入变形储能、晶界凸阶及微合金元素的作用,建立了低温变形诱导铁素体相变的动力学模型,分析了热变形参数和化学成分对相变分数和晶粒尺寸的影响．变形温度的降低和变形程度的增加,促进了α相变过程,相变体积分数增加,晶粒得到细化．C 与 Mn 含量增加的效果则相反．模型应用于热轧带钢生产过程的模拟,计算结果和实测结果吻合良好．展开更多
文摘NB-IoT(Narrow Band Internet of Things)是基于蜂窝窄带物联网的一种新兴技术,是物联网的一个重要分支。随着NB-IoT终端设备的规模不断增大,物联网安全面临数据泄露、中间人攻击等安全威胁。本论文针对NB-IoT技术的数据安全传输研究,从物联网终端安全和应用服务安全两方面进行分析,结合密码技术给出了NB-IoT系统安全模型,提出了基于物联网应用层数据信源加密传输机制,给出了轻量级身份认证协议和数据加密传输协议,论证了该方案的安全性,通过实验验证了所提方案的可行性和适用性。
基金supported by the National Natural Science Foundation of China(No.52071002)the National Natural Science Foundation of Anhui Province,China(No.2008085QE200)the Major Science and Technology Project of Precious Metal Materials Genetic Engineering in Yunnan Province,China(Nos.2019ZE001-1,202002AB080001)。
基金financially supported by the Science Foundation for International Cooperation of Sichuan Province (2014HH0016)the Fundamental Research Funds for the Central Universities (SWJTU2014: A0920502051113-10000)National Magnetic Confinement Fusion Science Program (2011GB112001)
文摘In this work, we choose Nb3Al/Nb3Sn as a new test case for flat/steep band model of superconductivity. Based on the density functional theory in the generalized gradient approximation, the electronic structure of Nb3Al/ Nb3Sn has been studied. The obtained results agree well with those of the earlier studies and show clearly fiat bands around the Fermi level. The steep bands as characterized in this work locate around the M point in the first Brillouin zone. The obtained results reveal that Nb3Al/Nb3Sn fits more to the ＂Flat/steep＂ band model than to the van-Hove singularity scenario. The fiat/steep band condition for superconductivity implies a different thermodynamic behavior of superconductors other than that predicted from the conventional BCS theory. This observation sets up an indicator for selecting a suitable superconductor when its large-scale industrial use is needed, for example, in superconducting maglev system or ITER project.
