Systematic and random errors in the determination of respiratory impedance by means of the forced oscillation technique: a theoretical study

The measurement of the impedance of the respiratory system by means of the forced oscillation technique is disturbed by the breathing signal of the subject. The latter introduces systematic and random errors on the obtained impedance values. The size of these errors depends on the relative power of the breathing signal with respect to the forced oscillatory signal x2.     

Limitations on reflector antenna gain by random surface errors,pointing errors, and the angle-of-arrival jitter

The effects of random surface, pointing, and angle-of-arrival errors on the antenna gain are discussed. It is shown that for manufacturing tolerance ratios greater than 10⁵, the random surface errors decrease the antenna gain only when D/λ>3000. The pointing/angle-of-arrival error causes nonnegligible loss in gain when it exceeds approximately a few tenths of the antenna beamwidth. The gain (and the size) of very large reflector antennas is generally limited by the combined effects of the above errors     

基于WPM实现参数固化管理

本文分析了如何高效的实现集中化参数管理,提高参数核查效率,提出了一种利用无线参数管理系统WPM的参数管理和核查方法,能满足对参数的精细化、归一化管理。     

A rapidly converging algorithm for estimating respiratory mechanical parameters in a five-element model

A rapidly converging algorithm for computing values for respiratory mechanical parameters from forced random noise independance data was developed and verified. The algorithm, which was based on a five-element Mead-type model, minimized the sum of squared differences between the model's response and experimental data, while imposing a nonnegativity constraint on the parameter values. It yielded parameter values that showed excellent agreement with values obtained previously using standard nonlinear regression analysis, but required much less computer time, 10 s versus 1 h. When this algorithm is coupled with the forced random impedance data collection techniques, it provides a rapid noninvasive method for estimating respiratory inertance, central resistance, peripheral resistance, and airway compliance. The problem of estimating peripheral compliance was not solved by this algorithm.     

Fe-doped SnO2 obtained by mechanical alloying

In this work, iron-doped SnO₂ powders were prepared by two methods: mechanical alloying and mechanochemical alloying with successive thermal treatment. The influence of different milling conditions such as ball to powder weight ratio, milling time, rotation velocity of supporting disc and the type of iron starting reactive and their Fe concentration on the structural and magnetic properties of the products were investigated. A greater incorporation of Fe in the SnO₂ structure was observed when the samples were prepared by using mechanochemical alloying and successive thermal treatment.     

随机误差对环形阵的旁瓣之影响

分析了随机误差（非统计独立的）对环形阵旁瓣之影响。分别考虑了振幅误差和相位误差两种情形。证明了随机误差可引起旁瓣电平的升高。对于独立的随机误差之情形，还可得到简单的公式。     

Measurement of fractional order model parameters of respiratory mechanical impedance in total liquid ventilation

This study presents a methodology for applying the forced-oscillation technique in total liquid ventilation. It mainly consists of applying sinusoidal volumetric excitation to the respiratory system, and determining the transfer function between the delivered flow rate and resulting airway pressure. The investigated frequency range was f ∈ [0.05, 4] Hz at a constant flow amplitude of 7.5 mL/s. The five parameters of a fractional order lung model, the existing "5-parameter constant-phase model," were identified based on measured impedance spectra. The identification method was validated in silico on computer-generated datasets and the overall process was validated in vitro on a simplified single-compartment mechanical lung model. In vivo data on ten newborn lambs suggested the appropriateness of a fractional-order compliance term to the mechanical impedance to describe the low-frequency behavior of the lung, but did not demonstrate the relevance of a fractional-order inertance term. Typical respiratory system frequency response is presented together with statistical data of the measured in vivo impedance model parameters. This information will be useful for both the design of a robust pressure controller for total liquid ventilators and the monitoring of the patient's respiratory parameters during total liquid ventilation treatment.     

Influence of random phase errors on polarization characteristics of antenna array

Polarization properties of the field of linear antenna arrays with random phase errors in the excitation currents of orthogonal vibrators and a system of biorthogonal radiators are studied. The influence of errors’ correlation on the degree of polarization and ellipticity of antenna with broadside radiation of waves with circular polarization is analyzed.     

EFFECTS OF RANDOM ERRORS ON THE SIDELOBE FOR THE LINEAR ARRAY

The effects of statistically dependent random errors on the sidelobe are analyzed for the linear array.It is shown that the random errors cause a rise in the sidelobe level.The simple formulas can also be obtained for the case of independent random errors.     

随机相位误差对相控阵天线的性能影响

为了对随机相位误差对于相控阵天线波束指向精度和副瓣电平的影响进行分析,以一维均匀直线阵为模型,采用概率统计的手段对波束指向误差的数学期望、方差和峰值副瓣电平进行了推导,并对此结果进行了计算机仿真验证和比较.仿真结果表明,理论公式推导得到的结论与仿真实验的各项结果吻合良好.     

Effect of leaky SAW parameters on V(z) curves obtained by acoustic microscopy

V(z) curves are measured by a reflection-acoustic-microscope system in the nonscanning version. As for V(z) curves, leaky SAWs at the interface of water/solid are known to play an important role. In the letter, the effect of leaky SAW parameters, i.e. phase velocity and attenuation factor, has been numerically analysed on V(z) curves. The numerical calculation is performed for an acoustic line-focus-beam lens by introducing an idealised reflectance function where only a solution of leaky SAW is taken into consideration. It is clarified that the interval of dips and the shape of V(z) curves are strongly affected by the phase velocity and the attenuation factor, respectively.     

随机误差对超低副瓣天线平面近场测量的影响

导出了平面近场测量中近场幅相随机误差所引起的误差谱的解析表达式。利用计算机模拟和统计平均的方法研究了近场幅相随机误差对超低副瓣天线平面近场测量结果的影响 ,并给出不同口径尺寸的超低副瓣天线的平面近场测量 ,为保证- 5 5 d B副瓣± 5 d B的测试精度 ,所能允许的近场幅相随机误差的最大起伏度     

随机误差对模块化阵列天线副瓣的影响

推导了相位误差、单元位置误差和子阵位置误差的取值范围与模块化阵列天线副瓣累积概率的关系,以及单元位置误差、子阵位置误差与整体位置误差的关系.通过实例说明,激励幅相误差、单元位置误差和子阵位置误差,对实现超低副瓣都是至关重要的.     

力学参数测量时由残余电荷导致的误差分析

分析了用静电牵引法测量悬臂梁结构力学参数时 ,由于绝缘层中残余电荷的存在 ,对测试结果带来的影响 ;并提出了利用C V特性曲线确定残余电荷数量的方法 ,将求出的残余电荷数量从静电力的角度进行等效 ,从而求出考虑残余电荷后带来的阈值电压测试误差。该分析方法既适于提高悬臂梁、桥等用来测量力学参数的精度 ,也适于对静电执行器等的精确分析     

随机相位误差影响条带模式合成孔径激光雷达成像的数学模拟

利用基于准单色光衍射光学理论获得的条带模式合成孔径激光雷达(SAL)数据方程,具体分析了系统各参数误差对方位向相位误差的影响,指出载频和目标距离的变化是影响方位向成像的重要因素,目标距离变化微米量级大小即能导致图像完全散焦.对于一个条带式SAL实验室演示成像系统,给出了点目标和扩展面目标在存在不同程度随机相位误差下的仿...     

力学参数测量时由残余电荷导致的误差分析

分析了用静电牵引法测量悬臂梁结构力学参数时，由于绝缘层中残余电荷的存在，对测试结果带来的影响；并提出了利用C-V特性曲线确定残余电荷数量的方法，将求出的残余电荷数量从静电力的角度进行等效，从而求出考虑残余电荷后带来的阈值电压测试误差。该分析方法既适于提高悬臂梁、桥等用来测量力学参数的精度，也适于对静电执行器等的精确分析。     

Partitioning of respiratory mechanical impedance by absolute and differential body plethysmography

We have recently demonstrated the feasibility of partitioning total respiratory impedance (Zrs) into its airway (Zaw) and tissular (Zti) components by measuring alveolar gas compression (Vpl) plethysmographically during pressure oscillations at the airway opening (Peslin et al.). The aim of this study was to comparatively evaluate an alternative approach: the measurement of Zrs and of the transfer function (FTF) between airway flow and body surface flow obtained by absolute body plethysmography. The two approaches are theoretically equivalent, provided thermal and other artifacts are properly eliminated. Zrs and Vpl (method 1) and Zrs and FTF (method 2) were measured in 11 healthy subjects from 4 to 29 Hz, using a pressure-type and a flow-type plethysmograph, respectively. Inspired gas was conditioned to body temperature and pressure, saturated with water vapor in both instances to minimize thermal factors. Zaw and Zti spectra computed from both sets of data were quite similar in shape. Neither airway resistance nor tissue compliance differed significantly; tissue resistance, however, was about 14% lower with method 1, which may be due to imperfect gas conditioning. The reproducibility of the data was similar with the two approaches. We conclude that absolute body plethysmography is as reliable as differential body plethysmography to partition Zrs.     

基于特征参数的随机噪声雷达相关输出研究

随机信号的数字特征参数是信号分析的重要因素,是随机信号波形设计的依据。相关系数和方差是随机信号的两项具有决定作用的特征参数。以随机噪声雷达的一般性相关输出模型为基础,建立了基于相关系数和方差表达的相关输出数学模型。依据该模型深入分析了噪声源信号的相关系数和方差对相关输出和带宽的影响。相关系数决定了相关输出的整体形式;方差影响相关输出的主瓣和旁瓣水平,方差的增大能够有效地抑制旁瓣,使主瓣变窄,主峰变尖锐,分辨率显著提高。仿真实验验证了结论的有效性。此外,建立了在不同形式相关系数情况下噪声源信号方差与调制信号带宽的关系,方差的增大使调制信号的输出带宽增大。     

棱镜—薄膜耦合器的耦合间隙对薄膜参数测量误差的影响

利用等厚干涉法测量了棱镜—薄膜耦合器的耦合间隙,在不同耦合间隙下测量了薄膜波导模式的传播常数、薄膜折射率和薄膜厚度。用 Tien 和 Urich 有关棱镜—薄膜耦合器的理论分析了耦合间隙对薄膜参数测量误差的影响。