基于相似变换的CEFQPSK交叉调制模型设计与分析

针对传统FQPSK调制方式存在包络起伏及中心点不连续问题,在对FQPSK进行改进的基础上,提出一种波形集完全对称的恒定包络FQPSK调制方案。通过类比I/Q调制与连续相位调制过程,确定相似变换参量;通过等效替换,导出恒定包络FQPSK信号表示成连续相位调制的形式。对改进后恒包络FQPSK模型进行了仿真分析,仿真结果表明新方法继承了FQPSK调制信号良好的性能,实现简单,为非线性信道下数据传输处理提供了有价值的技术参考。     

变频调技术在铁路范围内的应用

介绍了变频调速在铁路范围内的应用，重点叙述了变频技术在铁路锅炉房鼓引风、行车、恒压供水、空压机和冲洗泵方面应用。     

PCB的低介电性能要求与发展

文章概述了PcB中介质性能对信号传输性能的影响。低介质性能的主体方向是降低增强材料和“复合”增强材料。     

一种新型高精度高温度稳定性恒流源研究

研究一种应用混合集成电路技术实现的新型高精度和高温度稳定性的恒流源,以适应当前系统对恒流源高精度、高温度稳定性和较大电流的需求。在详细分析电路结构和工作原理的基础上,讨论如何提高电路的精度和温度稳定性,并给出具体的解决方案,对关键部分给出了设计电路图,最后对采样电阻的设计和布线艺术给出了合理的方案。投片测试分析表明:该设计安全可靠,达到高温度稳定性和高精度设计目标。该电路具有较小的体积和较好的性能,满足型号系统的要求。灵活的设计方式使其具有较好的使用价值和应用前景。     

一个恒定Lyapunov指数谱鲁棒混沌系统及其微控制器实现

在基本Sprott-B混沌系统数学模型的基础上,引入一个控制参数进行系统改造,构建出一个恒定Lyapunov指数谱鲁棒混沌系统。通过相轨图、Lyapunov指数谱和分岔图等动力学工具对系统进行了仿真分析。研究结果表明,系统对唯一的控制参数保持恒定的Lyapunov指数谱,从而工作于鲁棒混沌状态,理论分析则揭示出控制参数对于系统的混沌振荡具有线性或非线性调幅作用。此外,在以改进的Euler算法进行离散化后,采用微控制器MSP430F249进行了实验验证,证明了系统的可实现性。     

大学物理实验RC电路时间常数的Multisim仿真测试

基于探索大学物理电学实验仿真技术的目的。采用Multisiml0仿真软件对RC电路时间常数参数进行了仿真实验测试。从RC电路电容充、放电时电容电压uc的表达式出发,分析了Mc与时间常数之间的关系,给出了几种Muhisim仿真测试时间常数的实验方案。仿真实验可直观形象地描述RC电路的工作过程及有关参数测试。将电路的硬件实验方式向多元化方式转移,利于培养知识综合、知识应用、知识迁移的能力,使电路分析更加灵活和直观。     

Euryhaline Hydrogel with Constant Swelling and Salinity-Enhanced Mechanical Strength in a Wide Salinity Range

In nature, many biological organisms possess a unique osmoregulation feature that enables them to survive in environments of different salinity, which is called euryhaline characteristics (e.g., salmon that can survive in freshwater and seawater). Drawing inspiration from these salinity-tolerant organisms, here a strategy that integrates two polymer chain segments with different salinity tolerances is reported to produce a euryhaline hydrogel with stable water retention, constant swelling properties, superoleophobicity, and low-adhesion to oil in aqueous environments over a wide range of salinity. The formation of internal dynamic complementary crosslinks is a key structural factor of the euryhaline attributes. The euryhaline hydrogel-coated meshes can be successfully utilized in various oil/aqueous phase separation in a wide range of salinity. Furthermore, by creating a double network with dynamic bonds, superior euryhaline hydrogel with unique salinity-enhanced mechanical strength can be obtained. It is anticipated that the euryhaline hydrogel will have broad application prospects in complex and variable ionic environments.     

Photoelectrochemical properties of sol–gel synthesized titanium dioxide nano-particles using different acids: X-ray photoelectron spectroscopy reveals the induced effect of hydrolysis precursor

Properties such as crystalline structure (X-ray diffraction – XRD), surface chemistry–electronic states (X-ray photoelectron spectroscopy – XPS), morphology and particle size-distribution (Transmission Electron Microscopy – TEM), electronic structure-band-gap (UV–vis spectroscopy) and surface area (BET-nitrogen physisorption) were analyzed for titanium dioxide (TiO₂)-semiconductor-surfaces synthesized by sol–gel route using nitric, acetic and phosphoric acids as hydrolysis precursors. According to XRD analysis, it was established that anatase phase has been obtained with a particle size linked to the acid of hydrolysis employed (i.e. dissociation constant), as also demonstrated by TEM and area BET. On the other hand, using XPS, a shift toward lower binding energies was observed from TiO₂ obtained using HNO₃ promoting some structural modification and the reduction in the band-gap, inducing a better faradic current-performance by decreasing charge-transfer resistance during polarization and at induced-generated photocurrent using UV-light.     

Impedance and dielectric analysis of polycrystalline undoped and Fe doped SnS2

Polycrystalline Sn_1−xFe_xS₂ samples with (x=0, 0.125, 0.250 and 0.375) have been prepared by the molten salt solid state reaction method. The X-ray diffraction (XRD) shows that all the samples crystallize in the hexagonal structure, with P-3m1 space group in preferred orientation of (011). The electrical properties have been studied by complex impedance spectroscopy over the frequency range (20 Hz up to 1 MHz) at room temperature. The Nyquist plot for all samples have been fitted using ZMAN software. The impedance analysis showed that all samples exhibit both bulk and grain boundary contributions and it was found that by increasing the iron content, the resistance increases, but, the dielectric constant and dielectric loss tangent decrease which leads to decrease in conduction. The absorption coefficient (α) has been calculated from the complex dielectric constant. Interestingly, there was a significant correlation between the electromagnetic wave absorption and the reduction in the peak intensity of the XRD patterns indicating that when the iron content increases the sample seems to be a good absorber of electromagnetic waves.     

全光纤VISAR系统中条纹常数的分析

全光纤VISAR系统具有大的测速范围,其测速的动态范围和条纹常数有关。从干涉光路的实现原理出发,推导出速度与条纹常数的关系式,并分析了FVISAR系统不同速度分档下的条纹常数确定。在保证1．5％精度及假设光源相干长度为1 mm的前提下,给出了具体的速度分档情况。