Subspace analysis of spatial time-frequency distribution matrices

Spatial time-frequency distributions (STFDs) have been previously introduced as the natural means to deal with source signals that are localizable in the time-frequency domain. Previous work in the area has not provided the eigenanalysis of STFD matrices, which is key to understanding their role in solving direction finding and blind source separation problems in multisensor array receivers. The aim of this paper is to examine the eigenstructure of the STFD matrices. We develop the analysis and statistical properties of the subspace estimates based on STFDs for frequency modulated (FM) sources. It is shown that improved estimates are achieved by constructing the subspaces from the time-frequency signatures of the signal arrivals rather than from the data covariance matrices, which are commonly used in conventional subspace estimation methods. This improvement is evident in a low signal-to-noise ratio (SNR) environment and in the cases of closely spaced sources. The paper considers the MUSIC technique to demonstrate the advantages of STFDs and uses it as grounds for comparison between time-frequency and conventional subspace estimates     

Untraceable Analysis of Scalable RFID Security Protocols

Wireless Personal Communications - In order to support robust implementation of IoT, many schemes have been done to provide privacy, anonymity, scalability and customizability. Ray et al.’s...     

俄罗斯红外技术见闻

本文报导了作者在1992年10月参观访问了俄罗斯联邦共和国几个从事红外技术研究开发生产的主要单位,并与有关专家、教授、工程师和企业领导人进行了学术交流,原苏联很重视对红外技术的发展,特別在基础研究方面尤为注重,取得了较好的成就。在产品结构设计方面十分重视实用性和可靠性,某些技术有其独到之处。     

Multistimuli‐Responsive Display Materials to Encrypt Differentiated Information in Bright and Dark Fields

Visually readable codes play a crucial role in anticounterfeiting measures. However, current coding approaches do not enable time‐dependent codes to be visually read, adjusted, and differentiated in bright and dark fields. Here, using a combined strategy of piezoelectric lattice selection, oxygen vacancy engineering, and activator doping, a lanthanide ion‐doped titanate is developed that integrates mechano‐, thermo‐, and photo‐responsive color change (>18 h for bright field), persistent luminescence (>6 h for dark field), and stimulus‐triggered multimodal luminescence. The feasibility of optical encoding, visual displaying, and stimulus‐responsive encrypting of time‐dependent, dual‐field information by using the developed material is demonstrated. In particular, the differentiated display of dual‐field modes is achieved by combining mechanostimulated abolition of only the persistent luminescence and thermo‐ and photostimulated reversal of both the color change and persistent luminescence. The results provide new insights for designing advanced materials and encryption technologies for photonic displays, information security, and intelligent anticounterfeiting.     

房间采暖技术与变频调速综述

本文对房间采暖技术的发展状况、技术原理、构造特点进行了归纳总结,重点分析了地板供暖的优缺点,指出了地板供暖技术在房间采暖设计中的应用前景。针对低温地板热水辐射供暖系统存在的一些工程问题,通过对水泵的控制算法的研究和探讨,提出了地板水供暖系统采用以uPD78F1213为核心的无传感器永磁同步电机矢量控制系统的方案。     

BDN染料的锁模特性和基态恢复时间

本文报道了国产BDN染料的碘乙烷溶液、吡啶溶液和二甲亚砜溶液的锁模特性和基态恢复时间。     

基于数据预测的手机总全向灵敏度(TIS)的快速测试

手机总全向灵敏度（TIS）是OTA测试的重要指标之一。而基于CTIA的步进测试法,测试非常耗时。本文在深入研究基站发射功率和误码率关系的基础上,得出具有一定通用性的拟合函数,进而提出了一种基于数据预测的TIS测试方法。通过编写相应自动测试软件,实现快速测试。该法将大大提高测试效率,有很高的应用和推广价值。     

特柔软型钢丝铠装复合电缆设计探讨

本文主要探讨特柔软型钢丝铠装复合电缆的设计,根据特殊用户实际应用情况,设计出大拉力、超柔软钢丝铠装电缆,设计过程中不仅考虑电缆所应有的电性能,同时还要考虑电缆高强度抗张情况和应用中处于反复收放状态,而且所设计的电缆还要满足恶劣环境.     

组合式熔凝石英微透镜阵列-线列Yba_2Cu_3O_(7-δ)高温超导薄膜红外探测器的研究

采用准分子激光扫描消融法淀积YB32C23O7-δ高温超导薄膜,利用常规光刻工艺制备线列高温超导薄膜器件,采用离子束刻蚀制备与高温超导薄膜器件匹配的熔凝石英微透镜阵列,测试了微透镜／高温超导薄膜器件所构成的混合结构在1～5μm红外波段的几项重要的光响应特性．