剩余振幅调制对波长调制光谱信号线型的影响

在基于可调谐二极管激光吸收光谱技术的痕量气体检测中,波长直接调制时剩余振幅调制也会伴随发生,并对检测信号的线型和系统噪声产生严重影响。为了探讨剩余振幅调制对波长调制光谱二次谐波信号线型的影响,采用同时考虑振幅调制和波长调制两种影响因素的计算方法,理论分析出二次谐波信号的计算公式,与仅考虑波长调制的信号计算方式进行同条件线型计算比对,取得了二次谐波信号基线和正负峰值随剩余振幅调制的变化数据。结果表明,剩余振幅调制的大小对检测信号的线型和信号基线有直接影响,采用这种方法计算得出的二次谐波信号线型更贴近实际检测。     

基于波长调制光谱技术的二氧化碳浓度测量

以可调谐激光二极管吸收光谱技术为基础,结合波长调制光谱技术,对不同体积浓度的二氧化碳气体进行检测。分别分析正弦波调制信号的不同调制电压及调制频率对二次谐波信号波形及峰值的影响。结果显示当调制电压为0.25 V、调制频率为10 kHz时,得到的二次谐波信号较好。在此基础上,利用实验室中搭建的单光路测量系统对不同浓度的CO2气体进行检测,得到气体浓度与二次谐波峰值线性相关系数为0.998,系统的检测极限为450 ppm。研究为该类系统调制系数的选择提供了实验依据,为工业应用打下了基础。     

调制相位差对TDLAS信噪比的影响

用可调谐二极管激光吸收光谱技术检测气体时,不同的调制相位差结果不同。为了提高谐波检测灵敏度,采用同时考虑频率调制与振幅调制的方法分析和提取二次谐波信号,推导了相位差与二次谐波信号光电流和残余幅度调制噪声光电流的函数关系表达式,通过模拟实验分别取得了二次谐波信号和残余幅度调制噪声随相位差的变化趋势,并重点分析了相位差对信噪比的影响。结果表明,振幅调整和频率调制之间的相位差对信噪比的影响很大,与典型值/2时相比,最大降幅为59.18%;调制相位差是继残余幅度调制之外,影响信噪比的一个重要因素。     

CBOC信号处理中的二次采样方法

为了降低信号捕获跟踪运算量,针对Galileo信号CBOC调制提出了一种新的CBOC信号处理中的二次采样算法。分析了CBOC信号调制方式及功率谱密度,介绍了CBOC信号二次采样算法,提出了CBOC信号处理二次采样方法的处理模型。仿真结果表明,CBOC信号处理中的二次采样算法可以实现信号的CBOC解调,降低了运算量并简化了Galileo接收机的捕获跟踪设计。     

基于MZ调制器工作点控制的前端电路设计

设计了马赫-曾德尔(MZ)调制器工作点控制的前端电路.利用运放OP27设计文氏桥电路,产生1 kHz余弦波,作为扰动信号加到MZ调制器的RF端.运用运放OP27设计带通滤波器,从探测器分别提取一次谐波和二次谐波.利用乘法器MLT04实现对一次谐波和二次谐波的检波,分别得到一次谐波的幅度调制信号和二次谐波的幅度调制信号.这两个调制信号含有调制器工作点的相位信息,为后续的软件控制提供了两路含有相位信息的信号,使整个控制系统的实现更准确.     

TDLAS技术气体检测二次谐波信号的仿真与分析

可调谐半导体激光吸收光谱(TDLAS)技术结合半导体激光器可调谐的特点及气体分子对特定波长能量光的吸收特性,凭借灵敏度高、响应时间短等优势广泛应用于气体浓度检测。TDLAS技术气体浓度检测包括波长调制、气体吸收、二次谐波解调等环节,吸收信号的二次谐波分量携带气体浓度信息,用于计算气体浓度。利用MATLAB对气体检测过程进行了信号仿真,并利用数字锁相放大算法提取了二次谐波信号,验证了二次谐波与气体浓度的关系。通过仿真分析了二次谐波信号随调制系数的变化关系,以便确定较佳的调制参数,为后续系统搭建与气体检测实验提供参考。     

基于峰宽修正的玻璃药瓶内氧气残留浓度的检测研究

玻璃药瓶中的氧气残留对瓶中药品的无菌特性造成了严重的威胁。采用波长调制光谱（Wavelength Modulated Spectrum, WMS）技术解调得到的二次谐波信号峰高值作为氧浓度反演的基础。然而,在用二次谐波信号测量气体浓度时,由于调制深度的变化会导致二次谐波峰值的变化,这通常会给系统带来误差,进而降低浓度的反演精度。而调制深度受调制电流波动、温度和压强变化等因素的影响不能直接计算获得进而修正。针对这一问题,本文成功地将调制深度与二次谐波峰高的关系转换为二次谐波峰宽和峰高的关系。然后,利用峰宽校正后的谐波峰高对气体浓度进行反演。初步实验表明,利用峰宽校正后的谐波峰高对瓶内气体浓度进行预测的准确性提高了2.1%,且系统的整体鲁棒性也得以提升。本文提出的校正方法不需要系统参数信息与气体成分信息,可以直接从谐波信号本身出发对调制深度进行校正,十分适合于工业现场的在线氧气浓度预测。     

雷达目标反射信号二次调制特征的计算和模拟

提出了一种空中目标雷达回波信号二次调制特征的模拟方法.建立了空中目标发动机旋转部件的反射信号模型,模拟飞机发动机旋转桨叶的雷达截面积、旋转转速、微多普勒频率等特征.通过仿真分析了不同观测角度情况下,空中目标反射信号的时域和频域二次调制特征.     

光谱线宽对可调谐激光调制吸收光谱技术测量CO2浓度的影响

在利用可调谐激光调制吸收光谱技术进行测量时,气体参量改变将导致线宽变化,从而影响二次谐波信号峰值的大小.针对于Lorentz线型,给出了线宽变化对二次谐波峰值影响的理论分析及利用二次谐波信号峰谷比值进行修正的方法.在10 cm的吸收池内利用1578.22 nm处的吸收谱线对CO2进行了测晕,在不同调制幅度下验证了不同工况中线宽对二次谐波信号的影响.结果表明,利用二次谐波峰谷比值确定调制系数进行修正可有效地减小由于工况改变时线宽变化对测量带来的影响,当压力由1.0×105Pa变化至1.5×105Pa时,修正前后的测量相对误差分别为34.3%与1.8%;当气体体积分数在20%～100%变化时,修正前后的平均误差分别为12.8%与1.8%.     

基于二次调制的远程通信信息安全系统设计

为了解决传统远程通信信息安全系统存在的运行效率低、安全性差等问题,提出并设计了基于二次调制的远程通信信息安全系统。设计系统的整体框架结构,在确定整体结构后进行系统的硬件与软件设计,硬件部分的模块为主控模块、采用二次调制的通信模块、安全模块。在此基础上,根据远程通信信息系统的安全需求完成系统软件设计。最后进行实验验证所提系统的整体性能。实验结果表明,所设计的基于二次调制的远程通信信息安全系统具有较高的运行效率,且信号覆盖全面性较高,具有一定的实际应用性。     

一种新的变步长LMS算法在通信对消技术的应用

本文通过分析几种变步长LMS算法,结合VSS-NLMS算发和NLMS算法的优点,采用符号函数降低原有算法的计算复杂度,对变步长参数进行调整,提出了一种改进的变步长LMS算法,通过仿真验证,新提出的算法在收敛速度和稳态误差上也有一定优点,具有工程实际意义。     

Effect of sodium selenite on the activity of antioxidant enzymes (superoxide dismutase, glutathione peroxidase) during hepatocarcinogenesis

Influence of sodium selenite on functioning of the systems of intracellular generation and detoxication of active oxygen compounds in hepatocarcinogenesis induced by diethylnitrosamine has been studied in experiments on rats. It has been shown that the duration of latent period initiated by ions of Fe2+ chemiluminescence of homogenate of the liver rather objectively reflects the state of the functioning of the systems in charge of the formation and utilization of free radicals of oxygen in a cell. It is supposed that one of the mechanisms of anticarcinogenic action of selenium is connected with its antioxidant functions in the organism and consists in the increase of the activity of superoxide dismutation and selenium-dependent glutathione peroxidases, providing a reliable level of enzymatic protection of normal cells from disturbing action of "active oxygen".     

Statistical characteristics of chaoticity and incomplete chaoticity of irregular oscillations generated by a strongly nonlinear autonomous system with two degrees of freedom

The notion of the interval of nonergodicity as one of the statistical characteristics for time realizations of an irregular process is introduced. A method for determination of this factor based from the analysis of autocorrelation functions of truncated realizations is developed. The chaoticity of irregular oscillations in a strongly nonlinear autonomous system with two degrees of freedom is proved using the criterion of decomposition of time correlations. The statistical indication of the existence of incomplete chaoticity of oscillations in the case of incomplete decomposition of correlations is formulated. Conditions of weak distortions of the energy spectrum for truncated realizations are determined. Probability distribution functions for the characteristics of an irregular time process in the studied system are considered.     

Modeling of wideband slow-wave structures of coupled-cavities-chain type by the impedance design of experiments

The results of investigation on the possibility of a substantial extension of the operating-frequency band of a slow-wave structure of coupled-cavities-chain type are presented for the case of a small variation in the slowing factor of the phase velocity of a wave, including, in the case of convergence of the cavity and slot passbands. The investigation is performed with the use of regression models for electrodynamic characteristics of the slowing structure that are constructed on the basis of the results obtained by the impedance design of experiments. Variants of wideband chains of coupled cavities with differences in the phase-velocity slowing factor of ±3% and the operating width of the cavity passband of up to 35%, as well as structures with merging of the cavity and slot passbands and a resulting passband of up to 70% and a coupling impedance of 18–0.4 Ω, are obtained.     

基于物联网的图书馆管理系统

针对物联网的基本概念、起源、发展以及物联网关键技术,针对图书馆借书流程、图书快速定位、图书安全等问题与RFID技术的应用进行设计。通过介绍智能图书馆对于物联网技术的应用,提出智能图书馆的智能化和便捷化,同时也提出了发展物联网的重要意义,通过对只能图书馆的设计,让人们真切感受到物联网对人们生活的提升。     

左手材料的色散和等倾干涉

研究了左手材料棱镜的色散特性和左手材料平行平板的等倾干涉特性。对于左手材料棱镜而言,其色散时出射光偏离原来的传播方向与右手材料棱镜的色散规律恰好相反,且对于同一种单色光而言,当入射角相同时,左手材料棱镜的色散偏向角大于右手材料棱镜的色散偏向角。在研究左手材料平行平板的等倾干涉特性时,推导了反射光和透射光焦平面上的光强分布公式,分析了等倾干涉条纹的级数与亮、暗条纹的关系,讨论了光程差的影响因素及影响规律,推导了存在半波损失情况下的等倾圆环的亮环半径公式和暗环宽度公式。研究发现:对于左手材料平行平板的等倾干涉条纹而言,等倾干涉圆环中心处的干涉级数较小;偏离圆环中心越远,干涉条纹的级数越大。这一规律和右手材料平行平板的等倾干涉条纹规律不同。     

Radiation from a Plasma Layer with a Strong Longitudinal Irregularity

The efficiency of conversion of the energy of a surface wave into radiation at longitudinal irregularities of a planar plasma layer is studied. The analysis is performed by the spectral expansion of the field in a complete set of surface and pseudosurface waves. The system of integro-differential equations for the coefficients of expansion that determine the amplitudes of the transmitted, reflected, and scattered waves as well as the radiation pattern is solved in the case of a rapid change in the plasma density. The coefficients of transformation of energy into the energy of radiation as functions of the gradient of the plasma density for different values of the electrical length of the region of plasma irregularity and the electric thickness of the plasma layer are found. Examples are demonstrated when the fraction of the energy of the surface wave transformed into radiation reaches 60–70%. Radiation patterns that proved to be highly directional and having one lobe with the maximum at an angle of a few degrees to the direction of propagation of the surface wave are calculated.     

Simulation of the absorption of a femtosecond laser pulse in crystalline silicon

The effect of the nonlinearity of the absorptivity and absorption coefficient on the process of the intense photoexcitation of silicon is studied on the basis of a model of the two-photon excitation of a semiconductor with consideration for external emission. Correlation between the results of simulation of the absorption of a femtosecond laser pulse in single-crystal silicon and experimental data under conditions of the femtosecond excitation of surface plasmon polaritons makes it possible to refine the mechanism of changes in the absorptivity and to make an inference regarding the necessity of considering these changes when assessing the conditions of the laser treatment of semiconductors. Avenues for further improvement of the theoretical model are discussed.     

Elimination of cyclic phase slips of single-frequency kinematic GNSS observations

The results of development of a new method for the estimation and elimination of cyclic phase slips of single-frequency kinematic GNSS observations have been presented. The investigations and verification of the proposed method were performed using simulations and real GPS observations. Conditions of the continuity restoration of phase observations were determined; the specified conditions ensure a reliable elimination of cyclic phase slips under conditions of the partial and total loss of observations on intervals of up to 30 s. The possibilities of enhancing the reliability of elimination of phase slips were investigated using a group of increments of observations obtained under the free running and differential modes of coordinate determinations. It was shown that the reliability of solving the problem in question was critically dependent on the use of smoothed code observations. The smoothing of code observations makes it possible to achieve a much larger effect as compared with an attempt of increasing the number of satellites in the current constellation.     

Prospects of a slotline utilization as the excitation element of a quasi-optical hemispherical resonator for the problems of liquids dielectrometry

Inthis article we propose the utilization of a quasi-optical resonator in the form of the resonant cavity of hemispherical shape in the metal as a measurement cell of a dielectrometer for the investigation of electrophysical properties of liquids. We have carried out the investigations of electromagnetic characteristics of the utilized resonator in the case of the air filling and of the partial filling by the analyzed liquids (benzene, butanol, ethanol, methanol). The possibility of effective excitation of whispering gallery modes using the slot line has been demonstrated. We have determined the possibilities of the utilized investigation technique of the electrophysical properties of different liquids and of their identification based on the variations of electromagnetic characteristics of the proposed measurement cell. It has been shown that in the case of a small perturbation of the resonance fields by samples of liquids (with volume up to 3 ml) this technique for the proposed resonator possesses a high sensitivity and resolution capability for the identification of liquids with a relatively small difference of the electrophysical parameters.