一种混沌扩频序列的产生方法及其优选算法

提出一种基于组合映射模型产生混沌扩频序列的方法. 根据扩频序列的特性要求和多址干扰性能指标,给出了一种混沌扩频序列的优选算法;将得到的优选序列应用于直扩码分多址系统,在不同信道条件下进行仿真,并与优选的Logistic混沌扩频序列进行性能比较,结果表明本方法产生的混沌扩频序列具有和Logistic混沌扩频序列相近的良好性能,而且保密性更好. 关键词： 码分多址 优选算法 多径信道 误码率     

Dynamic response of a half-space to radial shear surface loadings

Summary The axisymmetric response of an elastic half-space to the sudden application of radial shear surface loadings is investigated in this paper. Exact expressions for the surface displacement components are developed by means of integral transforms and complex functions. Numerical results are presented in diagrams to show the wave propagation on the surface due to the dynamic loadings, and the wave front singularities in the displacement components are particularly discussed. It is found that, for a given point on the half-space surface, Rayleigh surface waves issued from the nearest and farthest disturbances give rise to a jump or a two-sided logarithmic singularity in the displacement components.     

Physical layer security performance of NOMA-assisted vehicular communication systems over double-Rayleigh fading channels

In this paper, we investigate the secrecy performance of a downlink non-orthogonal multiple access enabled V2V communication system wherein a source vehicle communicates with two authenticated user vehicles, i.e., far user and near user, in the presence of a passive eavesdropper vehicle. Moreover, we formulate two scenarios based on the eavesdropper’s decoding capabilities; (1) Scenario I: when the eavesdropper vehicle has comparable decoding capabilities as with the authorized user vehicles, and (2) Scenario II: when the eavesdropper is entirely capable of perfectly decoding the signals from both authorized user vehicles. For such a system configuration with Scenarios I & II, we deduce the analytical expressions for the secrecy outage probability (SOP) and ergodic secrecy capacity over independent but not necessarily identically distributed double-Rayleigh fading channels. Further, to obtain insights into the secrecy diversity order for the legitimate user vehicles under Scenarios I & II, we present the asymptotic SOP analysis by taking three cases into account; (1) Case 1: when the average transmit signal-to-noise ratio approaches infinity, (2) Case 2: when the average channel gains of the user vehicles tend to infinity with fixed average channel gains corresponding to the eavesdropper, and (3) Case 3: when the average channel gains pertaining to the user vehicles and the eavesdropper tend to infinity. From which, we can infer that the secrecy diversity order of the far user vehicle is zero for Cases 1, 2, & 3, whereas the secrecy diversity order of the near user vehicle is zero for Cases 1 & 3 and one for Case 2, under Scenarios I & II. The numerical and simulation results corroborate our theoretical investigations. Our results demonstrate the impact of transmit power, power allocation factor, channel conditions of legitimate users and eavesdropper on the system’s secrecy performance.     

Union bounds on the symbol error probability of LoRa modulation for flat Rician block fading channels

In this paper the symbol error performance of LoRa modulation is addressed for flat Rician block fading channels. First the exact symbol error probability of the LoRa modulation on Rician fading is derived. Then the upper and lower union bounds are employed on the derived symbol error probability. The proposed bounds are compared against the exact symbol error probability, the numerical evaluation of the symbol error probability and the state-of-art approximation of the LoRa symbol error probability. Numerical results show that while the proposed upper bound is very tight to the exact symbol error probability, there is approximately a 2.5 dB gap for the lower bound.     

靛蓝胭脂红共振瑞利散射法测定蛋白质

在pH 2.34的B-R缓冲溶液中,靛蓝胭脂红及蛋白质的共振瑞利散射(RRS)均十分微弱。但两者结合时,形成的复合物能使RRS信号急剧增强,最大散射波长为393 nm。测定人血清白蛋白、牛血清白蛋白、γ-人球蛋白、卵白蛋白的线性范围分别为0.1~3.7、0.08~3.0、0.05~2.0、0.1~2.4 mg/L;相应的检出限分别为24.6、20.7、20.4、25.7μg/L。本法用于人血清、牛奶、豆浆、尿液中总蛋白质的测定,结果与经典的考马斯亮蓝法一致。     

锂离子电池正极材料LiNi0.4Co0.2Mn0.4O2的合成、表征及电化学性能

以过渡金属乙酸盐和氢氧化锂为原料, 应用共沉淀或流变相预处理高温烧结法优化并制备出LiNi0.4Co0.2Mn0.4O2正极材料. X射线衍射技术(XRD)及Rietveld结构精修、扫描电子显微技术(SEM)、综合热分析(TG-DSC)表征结果和电化学测试结果表明, 该材料具有单一层状结构, 颗粒大小均匀, 热稳定性好, 首次放电比容量高达208.7 mA·h/g(2.0-4.6V, 0.1 C), 电化学性能优异. 非原位(ex situ)XRD测定结果表明, 材料充至高电位下发生的不可逆相变造成了材料的循环容量衰减.     

钠离子电池正极材料NaNi1/3Co1/3Mn1/3O2高压衰减机理

首次通过简单的固相反应合成了NaNi_1/3Co_1/3Mn_1/3O₂材料,并对其合适的电化学工作条件进行了探索。在此基础上对其在高充电电压下的衰减机理进行了研究。通过非原位XRD分析结构的变化,同时结合电化学阻抗谱等电化学手段综合分析材料在高压下的充放机理。     

一致最终有界性与无限时滞泛函微分方程周期解

本文证明了在具有衰减记忆的允许相空间中,无限时滞泛函微分方程的解的一致最终有界性蕴含了周期解的存在性．     

Analysis of Multi-Path Fading and the Doppler Effect for Reconfigurable-Intelligent-Surface-Assisted Wireless Networks

The randomness property of wireless channels restricts the improvement of their performance in wireless networks. As a novel solution for overcoming this, a reconfigurable intelligent surface (RIS) was introduced to reshape wireless physical environments. Initially, the multi-path and Doppler effects are discussed in a case in which a reflector was considered to reflect the incident signal for wireless communication. Subsequently, the results for the transmission signal were analyzed when a reflector was coated with an RIS. Specifically, the multi-path fading stemming from the movement of the mobile transmitter was eliminated or mitigated by utilizing an RIS. Meanwhile, the Doppler effect was also reduced to restrain the rapid fluctuations in the transmission signal by using a tunable RIS in real time. The simulation results demonstrate that the magnitude and spectrum of the received signal can be regulated by an RIS. The multi-path fading and Doppler effect can be effectively mitigated when the reflector is coated with an RIS in wireless networks.     

硫酸耐而蓝-肝素体系的共振瑞利散射光谱及其分析应用

提出了共振瑞利散射法(RRS)测定肝素的新方法.在pH为5.7～7.5的B-R缓冲溶液中,硫酸耐而蓝与肝素结合生成离子缔合物,使溶液共振瑞利散射(RRS)增强,其最大散射峰位于738 nm,另在536、 395、 305 nm有3个较弱的散射峰.肝素的质量浓度在0.01～0.5 mg/L范围内,与RRS强度有良好的线性关系,对肝素的检出限(3σ)达0.42 μg/L.研究了适宜的反应条件和影响因素,该方法用于肝素钠注射液的测定,回收率为98.6%～102.5%.