Significance of Non-isothermal Kinetic Data. A statistical study

Arrhenius parameters values, in non-isothermal kinetic vaporisation processes for a series of compounds with related structures, have been calculated. This was made using a method of calculation that allows to find the most probable vaporisation mechanisms. According to this method DTG curves were compared with some theoretical ones reported in literature, whose shape results to be only a function of the mechanisms. In this way the choice of the mathematical functions which can be inserted in the kinetic equations, was influenced by the shape of the DTG plots and other thermal analysis signals thus allowing to choose the most probable mechanisms. The kinetic parameters derived from these mechanisms were compared, using statistical analysis, with those obtained from another method of calculation based on ‘a priori’ vaporisation mechanism chosen for the investigated liquid–gas transition. The standard deviations of the slope and of the intercept, together with the standard deviation and the square correlation coefficient (r ²) of the linear regression equations related to the mechanisms of the two methods were calculated. Student t-test, Fisher F-test, confidence intervals (c.i.) and residuals valueswere also given. Statistical analysis shows that the mechanisms obtained with the former method (diffusive and geometrical models) and the related Arrhenius parameters result to be more significant (in terms of probability) than the corresponding quantities of the latter for which a first-order model was chosen. This revised version was published online in August 2006 with corrections to the Cover Date.     

Ab initio studies of the protonation of CO,N2 and NO+: Calculation of the minimum energy reaction paths

Ab initio molecular orbital calculations employing a 4-31G basis set have been used to study the minimum energy paths for the formation of HCO⁺, COH⁺, and HCOH²⁺ from CO by protonation. The protonation of N₂ to give NNH⁺ and HNNH²⁺ and of NO⁺ to form HNO²⁺ and NOH²⁺ have also been investigated. All species formed have linear equilibrium geometries and the minimum energy path for approach of the proton is along the line-of-centers of the heavy atoms. Energy barriers to the formation of the various species are given, where appropriate, and changes in geometry, ordering of molecular orbitals and orbital occupancy are discussed.     

Synthesis of mono meso-pyridyl 21,23-dithiaporphyrins and unsymmetrical non-covalent porphyrin dimers

A new method has been developed to synthesize 21,23-dithiaporphyrins having one pyridyl group at the meso position. The method required easily available unknown precursors and the condensation resulted in mono meso-pyridyl 21,23-dithiaporphyrins as single products in 8-11% yield. Two of the three mono meso-pyridyl N₂S₂ porphyrins were used to synthesize non-covalent unsymmetrical porphyrin dimers containing one N₂S₂ and one N₄ porphyrin cores.     

环形腔高掺Er3 窄线宽光纤激光器实验研究

报道了采用光纤光栅（FBG）短直腔选频结构的环形腔窄线宽光纤激光器。采用约3m长高掺Er^3光纤，LD抽运阈值功率约为11mW，在25mW976nm有效抽运功率时输出信号功率为2．65mW，斜效率约为15％；输出激光3dB线宽小于0．01nm，20dB线宽小于0．04nm，边模抑制比（SMSR）为48dB；观察到输出信号光波长漂移范围为0．06nm。     

准数字示样DRFM对线性调频脉压雷达的干扰和仿真

传统的干扰信号通过线性调频雷达脉冲压缩处理后,能量损失严重,不能很好的完成干扰的任务.本文简述了DRFM的原理、分类和优缺点,提出准数字示样DRFM的干扰方式,分析这种方式对线性调频脉压雷达干扰的有效性并对此进行仿真.     

基于DDS的有源相控阵天线

有源相控阵天线不仅能提高通信系统的性能,而且还能扩充其功能,所以在通信领域的应用越来越广泛.本文介绍一种没有高频移相器的8单元有源相控阵天线系统,它由平面天线阵、数字T/R组件、接收DBF和系统控制分析软件等组成.其基本原理是在发射模式下,利用直接数字合成(DDS)代替传统的高频移相器和衰减器.由于DDS的工作频率比较低,需要通过上变频到系统所需要的工作频率(2.0GHz).在发射模式下,通过控制DDS完成发射波束形成所必需的幅度、相位加权和上变频所必需的本振信号;在接收模式下,则利用DDS技术产生接收信号下变频所必需的本振信号,然后采用DBF技术形成接收波束.文中详细介绍了基于DDS的有源相控阵天线的实现方法和实验结果.通过8单元基于DDS的有源相控阵天线系统的研究,证实了DDS技术在相控阵天线中应用的显著优点和相控阵天线在通信领域具有潜在应用市场.     

基于循环平稳的复调频信号检测性能研究

针对加性色噪声和乘性色噪声联合干扰下的雷达运动目标检测问题进行了研究.首先利用循环平稳信号处理原理,分析了加性噪声和乘性噪声联合干扰下的复调频信号的循环统计特性,在此基础上构造了基于二阶循环矩的检测统计量,推导了检测统计量的输出信噪比与观测噪声统计特性的关系.最后利用Monte-Carlo仿真试验得到检测性能的曲线,并与基于时频分布的Wigner-Hough检测器做了比较,仿真试验进一步验证了本文提出的二阶循环矩检测器性能要优于Wigner-Hough检测器.     

一些结构线性系统的SBE与P-SBE的比较

很多重要的结构矩阵都属于Rn或Cn上纯量积定义的Jordan代数J或者是Lie代数L.本文比较线性系统AX=B关于近似解的范数型结构向后误差(SBE)与偏结构向后误差(P-SBE).这里系数矩阵A∈J或A∈L.在给出若干预备性结果后,先对单右端项情形比较SBE与P-SBE,然后对多右端项情形比较.部分结果是Sun近期的一些结果的推广.     

Scalable Network Coding for Heterogeneous Devices over Embedded Fields

In complex network environments, there always exist heterogeneous devices with different computational powers. In this work, we propose a novel scalable random linear network coding (RLNC) framework based on embedded fields, so as to endow heterogeneous receivers with different decoding capabilities. In this framework, the source linearly combines the original packets over embedded fields based on a precoding matrix and then encodes the precoded packets over GF(2) before transmission to the network. After justifying the arithmetic compatibility over different finite fields in the encoding process, we derive a sufficient and necessary condition for decodability over different fields. Moreover, we theoretically study the construction of an optimal precoding matrix in terms of decodability. The numerical analysis in classical wireless broadcast networks illustrates that the proposed scalable RLNC not only guarantees a better decoding compatibility over different fields compared with classical RLNC over a single field, but also outperforms Fulcrum RLNC in terms of a better decoding performance over GF(2). Moreover, we take the sparsity of the received binary coding vector into consideration, and demonstrate that for a large enough batch size, this sparsity does not affect the completion delay performance much in a wireless broadcast network.     

Security Analysis of DBTRU Cryptosystem

DBTRU was proposed by Thang and Binh in 2015. As a variant of NTRU, the integer polynomial ring is replaced by two binary truncated polynomial rings GF(2)[x]/(xn+1). DBTRU has some advantages over NTRU in terms of security and performance. In this paper, we propose a polynomial-time linear algebra attack against the DBTRU cryptosystem, which can break DBTRU for all recommended parameter choices. The paper shows that the plaintext can be achieved in less than 1 s via the linear algebra attack on a single PC.