Broad-band phase retrieval method for transient radial shearing interference using chirp Z transform technique

The transient radial shearing interferometry technique based on fast Fourier transform(FFT)provides a means for the measurement of the wavefront phase of transient light field.However,which factors affect the spatial bandwidth of the wavefront phase measurement of this technology and how to achieve high-precision measurement of the broad-band transient wavefront phase are problems that need to be studied further.To this end,a theoretical model of phase-retrieved bandwidth of radial shearing interferometry is established in this paper.The influence of the spatial carrier frequency and the calculation window on phase-retrieved bandwidth is analyzed,and the optimal carrier frequency and calculation window are obtained.On this basis,a broad-band transient radial shearing interference phase-retrieval method based on chirp Z transform(CZT)is proposed,and the corresponding algorithm is given.Through theoretical simulation,a known phase is used to generate the interferogram and it is retrieved by the traditional method and the proposed method respectively.The residual wavefront RMS of the traditional method is 0.146λ,and it is 0.037λfor the proposed method,which manifests an improvement of accuracy by an order of magnitude.At the same time,different levels of signal-to-noise ratios(SNRs)from 50 dB to 10 dB of the interferogram are simulated,and the RMS of the residual wavefront is from 0.040λto 0.066λ.In terms of experiments,an experimental verification device based on a phase-only spatial light modulator is built,and the known phase on the modulator is retrieved from the actual interferogram.The RMS of the residual wavefront retrieved through FFT is 0.112λ,and it decreases to 0.035λthrough CZT.The experimental results verify the effectiveness of the method proposed in this paper.Furthermore,the method can be used in other types of spatial carrier frequency interference,such as lateral shearing interference,rotational shearing interference,flipping shearing interference,and four-wave shearing interference.

Research of range measure precision for LFMCW system based on Chirp-Z transform

A new method of increasing the range measure preci- sion by Chirp- Z transform in the level Radar has been put up in this paper. The main assignment of this research is to accom- plish the FFT and Chirp- Z transform. At the same time, the af- fection of the two range measure methods has been analyzed in this paper. This method can increase both the calculation effi- ciency and range measure precision remarkably by theory calcu- lating and digital emulation.

基于Z变换和改进FRI的LFM信号参数估计方法研究

为了完成线性调频(linear frequency modulation,LFM)信号的稀疏采样,并利用稀疏数据对原始信号参数进行估计,本文提出了一种基于Z变换和改进有限新息率(finite rate of innovation,FRI)的LFM信号参数估计方法。以Z变换理论为基础,设计了一种数学模型,一旦信号能够表达成该数学模型的结构形式,就能通过Z变换和零化滤波器的方法估计信号参数。然后,利用了自相关延迟的FRI结构对LFM信号采样,该结构不仅完成了LFM信号的稀疏采样,而且稀疏采样结果能够与数学模型结构相符。在理论上通过数学论证的方式证明了所提方法能够用于获取LFM信号参数信息,并通过仿真和实测数据验证了所提方法的有效性,理论和实验结果表明该方法只需要4个采样点就能实现对LFM信号的参数估计,并且实验中的参数估计误差均在3%以内,极大的提高有限新息率采样的参数估计效率。

基于反射系数谱Z变换的电缆缺陷定位方法

针对传统缺陷定位函数分辨率较低且数据冗余度较高的问题,本文提出了一种基于反射系数谱Z变换的电缆缺陷定位方法。首先利用传输线理论建立了电缆的反射系数谱模型,分析反射系数谱定位电缆缺陷的可行性。然后介绍Z变换的原理,根据反射系数谱的特征确定Z变换算法中各参数的值,构建了新的电缆缺陷定位函数。缺陷定位实验的仿真与实测结果显示,相比于传统的方法,本文所提方法中电缆缺陷定位函数的分辨率更高,并且数据的冗余度更低,能更精准地定位电缆缺陷,同时可以减少干扰峰的影响,为电缆缺陷的定位提供了新的思路。

Z-Transform Based Instantaneous Unit Hydrograph for Hilly Watersheds

Present study emphasizes the applicability of linear theory concept onto hilly watersheds. For this purpose, Z-transform technique was used to derive the instantaneous unit hydrograph (IUH) from the transfer function of autoregressive and moving average (ARMA) type linear difference equation. Parameters of the ARMA type rainfall-runoff process were estimated by least-squares method. The derived IUH from Z-transform (i.e. ARMA-IUH) has been used to compute the hydrologic response i.e. direct runoff hydrograph (DRH). Fur-ther, the superiority of the proposed approach has been tested by comparing the results through the results obtained from the Nash-IUH. Analyzing the results obtained from ARMA-IUH and Nash-IUH for the two hilly watersheds of North Western Himalayas shows the applicability of the linear theory concept even in turbulent flow conditions which are frequently encountered in hilly terrains under similar conditions of flow.

TIME DOMAIN ANALYSIS OF TRANSIENT PROPAGATION IN INHOMOGENEOUS MAGNETIZED PLASMA USING Z-TRANSFORMS

The electromagnetic propagation through an inhomogeneous magnetized plasma slab is studied using the Z-transform formulation of the Finite-Difference Time-Domain(FDTD) method. The direction of electromagnetic propagation is parallel to the biasing magnetic filed. To validate the Z-transform algorithm, the reflection and transmission coefficients for the right-hand circularly polarized wave of the homogeneous magnetized plasma slab are computed by means of discrete Fourier transform. The comparison between the reflection and transmission coefficients of the homogeneous plasma slab and analytical values indicates that Z-transform algorithm is very accurate. When the plasma frequency varies according to the square root and parabolic relations, the reflection and transmission coefficients of the inhomogeneous magnetized plasma slab are computed.

9-脱氧-9-同型红霉素A(Z)肟合成工艺研究

以9-脱氧-9-同型红霉素A(E)肟为原料、氢氧化锂为催化剂,合成了9-脱氧-9-同型红霉素A(Z)肟,利用核磁共振、红外光谱和质谱对其结构进行表征,并考察了溶剂、温度、投料比对其构型转化的影响。最终确定n[9-脱氧-9-同型红霉素A(E)肟]∶n(氢氧化锂)=1∶5,在无水乙醇中反应,温度为20~30℃时,构型转化理想,产品物质的量收率达到81%,9-脱氧-9-同型红霉素A(Z)肟质量分数达到96.2%。

Log-Time Sampling of Signals: Zeta Transform

We introduce a general framework for the log-time sampling of continuous-time signals. We define the zeta transform based on the log-time sampling scheme, where the signal x(t)is sampled at time instants tn=Tlogn,n=1,2,....The zeta transform of the log-time sampled signals can be described by a linear combination of Riemann zeta function, which firmly joins the log-time sampling process to the number theory. The instantaneous sampling frequency of the log-sampled signal equals fn=n/T,n=1,2,..., i.e. it increases linearly with the sampling number. We describe the properties of the log-sampled signals and discuss several applications in nonuniform sampling schemes.

Refinement and Transformation from Z Specification to C+ +

As a kind of formal specification language, Z has gained a position in the field of software development, but there is still no standard way of transforming Z specification into executable code that is promising in increasing the quality, reusability and maintainability of software.With the automatic programming model of software engineering, through the analysis for Z specification language, a feasible semi-automatic way of refinement and transformation is proposed, and the correctness of the procedure is also discussed.

Criterion of Magnetic Saturation and Simulation of Nonlinear Magnetization for a Linear Multi-core Pulse Transformer

The linear multi-core pulse transformer is an important primary driving source used in pulsed power apparatus for the production of dense plasma owing to its compact, relatively low-cost and easy-to-handle characteristics. The evaluation of the magnetic saturation of the transformer cores is essential to the transformer design, because the energy transfer efficiency of the transformer will degrade significantly after magnetic saturation. This work proposes analytical formulas of the criterion of magnetic saturation for the cores when the transformer drives practical loads. Furthermore, an electric circuit model based on a dependent source treatment for simulating the electric behavior of the cores related to their nonlinear magnetization is developed using the initial magnetization curve of the cores. The numerical simulation with the model is used to evaluate the validity of the criterion. Both the criterion and the model are found to be in agreement with the experimental data.

连续三态模式开关前置型准Z源高增益Boost变换器的特性

为了全面了解开关前置型准Z源Boost变换器的性能,对其在连续三态模式(continuous triple-state mode, CTSM)下的工作原理和稳态特性进行了深入分析。相比于传统的电流连续导通模式(continuous conduction mode, CCM)和连续双向导通模式(continuous bidirectional conduction mode, CBCM),CTSM下该变换器保留了功率管电压应力相等且约为输出电压一半的优点,但是具有更高的电压增益;此外,电感L2的体积大幅度减小,开关管实现了零电流开通,且所有二极管能自然关断。通过一台280 W/100 kHz实验样机验证了理论分析的正确性。实验表明,输出电压400 V条件下,在全负载范围内CTSM都具有显著的效率优势,其最大效率为97.1%。

基于Chirp-z变换的低复杂度双基前视SAR扩展NLCS成像算法

双基合成孔径雷达(SAR)由于收发分置的特殊几何构型,具备对前视区域高分辨成像的优势,在精确制导、自主着陆、对敌打击等领域有着重要应用价值。但是双基前视SAR具有强回波二维耦合特性,成像算法需要的处理流程更为复杂。扩展非线性变标(ENLCS)算法虽然能够有效解决这种构型下空变的距离徙动(RCM)和多普勒参数问题,但在将雷达数据从回波域映射至图像域的过程中,会带来一定的数据量冗余,而且ENLCS的方位向处理流程过长,导致算法的数据量和存储成本大大增加,很难满足相关领域实时性的要求。为了降低ENLCS算法的运算复杂度与数据冗余度,提高算法实时成像处理的效率,文中通过在距离徙动校正(RCMC)过程中采用Chirp-z变换(CZT)结构实现无插值的Keystone变换(KT)降低运算复杂度,并在ENLCS均衡过程中加入线性因子显著降低数据映射过程中的冗余量,进一步对算法方位向处理过程加速。与原算法相比,总体运算量及耗时更低。仿真和实测数据的处理结果验证了算法的有效性和高时效性。

Z世代消费理念下企业营销管理的品牌年轻化及转型路径研究--以好利来、贵州茅台为例

随着新消费环境和消费需求的改变,很多老字号品牌在快速发展的市场环境中遇到了较大困境,品牌正逐渐朝着年轻化、品牌化、风格化的方向转型发展,从而更加适应未来消费市场的发展趋势。本文基于Z世代为代表的年轻消费群体的消费行为和消费特征,以好利来和贵州茅台企业为研究案例,为老字号品牌探索出更加适应未来市场的营销策略。最后,本文提出利用超级符号、场景化营销、赋予新的产品属性等营销手段,帮助老字号重振品牌,吸引年轻人的消费关注,打造个性化的品牌形象,从而获得更长远的发展。

Z公司财务共享服务实施问题及对策探讨

在信息全球化、经济蓬勃发展的时代下,实施财务共享服务是对企业管理和控制活动的一种创新,对于财务管理模式的改变和财务人员职能转型都具有重要的意义。Z公司通过实施财务共享服务,将日常的财务活动中一些基础、繁琐、重复性高的工作转移到财务共享中心进行集中处理,降低管理成本,提高效率。文章主要介绍了Z公司在实施财务共享服务之后的成效,并对仍需改进的地方提出了相应的对策。

Z型调容变压器及其绕组设计

现有的调容变压器存在小容量时零序阻抗大,三相电压易出现不平衡的问题。本文笔者介绍了Z型调容变压器的原理及特点,着重说明了其绕组的设计方法,仿真了错误设计时变压器大、小容量下磁场强度分布情况,并给出了实物验证结果。

对准系统的Z向串扰解决方案

在对准系统中,相机可以在焦深范围内采集到清晰的标记图像。当相机安装存在微小倾斜角度时,照明光束不能垂直照射在标记平面上,导致相机拍摄的标记中心相对于视场中心的偏移量会随着焦面高度的微小变化会发生细微的变化。尽管使用相同的图像处理算法,标记在焦深范围内的不同焦面高度下的水平向对准位置有所差异,这严重影响了设备的水平向对准性能。为保证设备的对准精度,提出一种校正光束倾斜的方法至关重要。因此,提出了一种基于坐标系转换的Z向串扰解决方案,以实现对系统的光束倾斜校正,从而使水平对准位置不受Z向高度影响。

一种基于Chirp-Z变换的闪变测量方法

对IEC推荐的闪变测量方法进行分析后发现,如果波动分量的频率和幅值已知,则瞬时闪变视感度S可以直接由其得出,本文在此基础上提出了一种新的闪变测量方法。首先使用平方检波法提取出产生闪变的波动信号,对其进行线性调频Z变换(Chirp-Z Transform,CZT)得出波动分量的幅值和频率,然后根据波动分量的幅值和频率求出瞬时闪变视感度。使用CZT进行波动分量的提取,可以在不延长采样时间的前提下获得比快速傅里叶变换(FFT)更高的频率分辨率,有效降低了频谱泄漏造成的误差。通过仿真和试验对IEC方法和本文提出的方法进行了比较,结果证明了本文所提方法的正确性和有效性。

基于插值线性调频Z变换的间谐波分析方法

为获得准确的间谐波信号的频率分布估计值,文章提出了基于插值线性调频Z变换(chirp Z transform,CZT)的间谐波分析方法。该方法通过CZT变换获得精确的等价于离散傅里叶变换结果的间谐波信号的频率分布估计值,利用基于Rife-Vincent Ⅲ窗的双谱线插值修正公式修正上述估计结果,得到了较精确的各次谐波和间谐波参数。仿真结果验证了该方法的正确性和有效性,与现有方法的比较结果表明,相同采样频率下该方法的检测精度更高。

基于级数反演的弹载SAR下降段CZT成像算法

导弹下降段飞行速度快、飞行轨迹复杂,并且弹上成像实时性要求较高,给弹载SAR成像算法提出了新的要求。针对上述问题,该文提出了基于级数反演的CZT成像算法。文中首先给出了下降段点目标斜距表达式,并用泰勒级数对斜距进行高阶展开,接着用级数反演法得到了信号2维频谱高阶近似表达式,然后详细分析了频谱中各项的空变性对成像的影响,并在此基础上推导了改进的CZT成像算法并分析了其运算量。该算法能够精确校正空变的距离徙动,所有操作都由快速傅里叶变换和相位点乘完成,具有较高的效率。仿真结果证明,该文算法能够在下降段实现全孔径高精度成像。