Pulsed Wavemeter Timing Reference for Sampling Oscilloscope Calibration

A pulsed wavemeter technique is described that is useful as a source of microwave frequency sine waves for the time base calibration of sampling oscilloscopes.     

基于自适应采样的自由曲面偏置算法

应用基于形状的自适应采样算法，给出了一种自由曲面的偏置.算法。首先从微分几何的观点出发，建立了原曲面与偏置曲面之间曲率上的对应关系。然后在原曲面上根据偏置曲面的曲率分布进行数据点的采样计算，并将采样结果进行偏置处理，最后得到给定精度下的偏置曲面。算例表明，给定相同的允许误差，本方法能明显减少所需偏置点的个数，降低了偏置曲面插值及进一步处理的难度。     

提高零件轮廓测量机偏心调整精度的方法

为了满足研制的零件轮廓测量机实现回转体零件的非接触自动测量,利用激光测头等部件设计了偏心自动调整机构．由于系统中有交流伺服电机驱动器干扰信号,激光测头容易受到环境电磁干扰,造成偏心调整的定心误差较大．为此,在介绍偏心调整控制原理的基础上,针对干扰信号的特点,设计了一种滤除干扰信号的电路,给出了电路框图和关键电路．实验结果表明：偏心调整的定心误差由原来的0．6mm降至0．1mm,能够提高偏心调整的精度．对交流伺服电机驱动器干扰信号的处理具有实际的指导意义．     

Estimation of the Fraction Defective in Curtailed Sampling Plans by Attributes

In this paper we have obtained the maximum likelihood estimate of the fraction defective (p) under three different sampling plans. Plan 1 considers complete inspection of the sample, Plan 2 considers curtailing of the inspection at the rejection stage and Plan 3 considers curtailing of the inspection at both the acceptance and rejection stages.     

High Accuracy Network Cardinalities Estimation by Step Sampling Revision on GPU

Host cardinality estimation is an important research field in network management and network security. The host cardinality estimation algorithm based on the linear estimator array is a common method. Existing algorithms do not take memory footprint into account when selecting the number of estimators used by each host. This paper analyzes the relationship between memory occupancy and estimation accuracy and compares the effects of different parameters on algorithm accuracy. The cardinality estimating algorithm is a kind of random algorithm, and there is a deviation between the estimated results and the actual cardinalities. The deviation is affected by some systematical factors, such as the random parameters inherent in linear estimator and the random functions used to map a host to different linear estimators. These random factors cannot be reduced by merging multiple estimators, and existing algorithms cannot remove the deviation caused by such factors. In this paper, we regard the estimation deviation as a random variable and proposed a sampling method, recorded as the linear estimator array step sampling algorithm (L2S), to reduce the influence of the random deviation. L2S improves the accuracy of the estimated cardinalities by evaluating and remove the expected value of random deviation. The cardinality estimation algorithm based on the estimator array is a computationally intensive algorithm, which takes a lot of time when processing high-speed network data in a serial environment. To solve this problem, a method is proposed to port the cardinality estimating algorithm based on the estimator array to the Graphics Processing Unit (GPU). Experiments on real-world highspeed network traffic show that L2S can reduce the absolute bias by more than 22% on average, and the extra time is less than 61 milliseconds on average.     

Standard Histogram Test Precision of ADC Gain and Offset Error Estimation

The quality of measurements made in any system is quantified by supplying the expanded uncertainty of the result, as recommended in the Guide to Uncertainty in Measurement. In a system that involves analog-to-digital converters (ADCs), one of the sources of uncertainty is the converters gain and offset error. The uncertainty of these two parameters should be known in order to compute the uncertainty of the measurements made with the system. In this paper, we study the uncertainty of terminal-based defined gain and offset error that are estimated using a standard histogram test in the presence of an additive noise.     

高速采样示波器中的时基失真及其估计

介绍了时基失真的概念及产生原理。改进了美国NIST提出的时基失真的数学模型，据此模型仿真出时基失真的数据，进而仿真出测量数据。给出了为估计采样示波器的时基失真所采取的方法——最小二乘法。这种方法需要在多相位、多频率上测量信号，可以精确地估计谐波模型的阶数。最后介绍了如何根据已经得到的估计值来修正时基失真。     

提高同步采样精度的一种改进算法

由于同步采样在实际情况中很难实现严格同步，当采样信号与待测信号不严格同步时，必将产生频谱泄漏误差和截断误差。为了克服同步采样法的这一缺点，本文给出一种改进算法，其基本思想是修改采样序列使之接近理想采样序列。仿真研究表明，改进算法提高了测量精度，计算量较少，实时性也有所提高。     

Censored Sampling in Curtailed Sampling Plans by Attributes

In this paper we have considered four different ways of reporting the results of sampling inspection associated with the curtailed sampling plans of [2]. These cases take into consideration that some information of the inspection results is suppressed and hence these cases turn to be particular cases of censored sampling. Maximum likelihood estimate of the fraction defective and its asymptotic variance are obtained and comparison is made between the cases considered here and cases in [2].     

非正态过程能力指数估计及抽样方案设计

在实际生产中许多稳定的加工过程不一定满足正态性假设，使得传统的过程能力指数度量失准。为此介绍总结了若干种数据转换方式，将质量特性的分布映射为正态形式，在此基础上再计算过程能力指数。讨论了过程能力指数置信下限与抽样容量、批量产品不合格率之间的对应关系，并给出了非正态分布条件下加工过程抽样方案的设计流程。以某曲轴加工过程为例给出案例分析。     

基于β面截断重要抽样法可靠性灵敏度估计及其方差分析

基于β面的截断重要抽样法可以用来求解单失效模式可靠性灵敏度.该方法在设计点处作失效面的虚拟切面β面,而β面将变量空间分割成重要抽样区域R和非重要抽样区域S.在R和S区域分别建立相应的截断重要抽样密度函数hR(x)和hs(x),从hR(x)和hs(x)中抽取的样本量按照R和S区域对可靠性灵敏度的贡献来分配,并通过迭代模拟...     

Zubair Lomax Distribution: Properties and Estimation Based on Ranked Set Sampling

In this article, we offer a new adapted model with three parameters, called Zubair Lomax distribution. The new model can be very useful in analyzing and modeling real data and provides better fits than some others new models. Primary properties of the Zubair Lomax model are determined by moments, probability weighted moments, Renyi entropy, quantile function and stochastic ordering, among others. Maximum likelihood method is used to estimate the population parameters, owing to simple random sample and ranked set sampling schemes. The behavior of the maximum likelihood estimates for the model parameters is studied using Monte Carlo simulation. Criteria measures including biases, mean square errors and relative efficiencies are used to compare estimates. Regarding the simulation study, we observe that the estimates based on ranked set sampling are more efficient compared to the estimates based on simple random sample. The importance and flexibility of Zubair Lomax are validated empirically in modeling two types of lifetime data.     

Biased Reduced Sampling: Detectability of an Attribute and Estimation of Prevalence

In surveilling a population, detection of systems with an attribute of interest and estimation of the prevalence of the attribute in the population are two main goals. Due to cost constraints, only a subset of all components of sampled systems may be fully tested. Biasing the sampling to increase the probability of choosing a component with an attribute of interest ameliorates the impact of reduced sampling. In this paper, we consider the impact of biased reduced sampling on detection and propose an approach for estimating the prevalence of the attribute in the population which properly accounts for the biasing. The proposed method is illustrated with a simulated example. Copyright © 2005 John Wiley & Sons, Ltd.     

变时基采样锤击法高精度传递函数的估计

传统锤击法试验模态分析时面临着高采样率带来噪声干扰、频率分辨率不足的问题，应怀樵等人发明了对力锤信号使用高采样频率、对响应信号采用较低采样频率的变时基采样技术（VTB），一定程度上改善了测试结果，但仍然存在变时基采样设置不灵活，传递函数在固有频率半功率带宽里分辨率不足、精度不高的问题。基于连续傅里叶谱变换、Chirp-z变换方法，提出一种新的锤击法变时基传递函数高精度估计方法，可很好地解决传统变时基技术存在的问题。并采用数值模型、悬臂梁现场测试进行验证，结果表明所提出的算法优于传统等时间间隔采样技术，比传统变时基技术更为灵活，得到的传递函数质量较好，使得变时基采样技术具有较高的识别精度，可解决高采样率与频率分辨率不足的问题。     

Efficient Sampling by Artificial Attributes

Hypotheses about the fraction of items in a lot possessing a “specification attribute” X < L can be tested by generally sampling the variable X or directly sampling the attribute of interest. When the process variance is known, it is often more efficient to test against “compressed limits” for one or more “artificial” attributes X < L_a , X < L_b etc.

This study discusses the efficient choice of one or two compressed limits. General guidelines for this choice are suggested, and then evaluated under many hypothetical test specifications. One compressed limit offered ~40% – 97% savings over direct attribute sampling; two limits allowed about 20% further savings.     

Adaptive Input Estimation Methods for Improving the Bandwidth of Microgyroscopes

Unlike an accelerometer, the input to a vibratory microgyroscope is a product of the periodic excitation and the angular velocity to be detected. Consequently, the detection of the angular velocity requires a demodulation process involving a signal whose frequency is close to the resonance. Due to this special circumstance the dynamic performance characteristics such as the bandwidth of the microgyroscope sensors is severely limited. In this paper, we present adaptive input estimation methods to achieve wide bandwidth dynamic characteristics. Specifically, we present an adaptive estimator-based technique to estimate the angular motion by providing the Coriolis force as the input to the adaptive estimator. We present two methods, namely, the open-loop method and the closed-loop method. Both methods provide identical dynamic characteristics. But for the open-loop method, we require complete knowledge of all the parameters of the microgyroscopes whereas the closed-loop method can also be used where precise knowledge of the dynamic characteristics of the microgyroscopes is not available     

残余应力对RF MEMS开关谐振频率偏移的影响

由沉积工艺产生的残余应力对RF MEMS开关的动态特性有重要影响。利用变量分离法推导出桥模式RF MEMS开关的频率方程组。给出二分法求解频率方程的流程图,并进行实例计算。计算结果表明,残余应力引起的频率偏移随着t/L的减小而增加;残余应力与频率偏移之间呈现出明显的非线性特性。     

基于一元对称幂基的等距曲面有理逼近算法

给出了基于一元对称幂基的等距曲面蒙面逼近新算法。利用一元对称幂基逼近张量积Bézier曲面u向曲线的等距曲线,得到一组等距逼近曲线,取固定的v值,得到一组数据点,用反算控制顶点的方法得到过这组数据点的v向曲线。对这两组曲线用蒙面算法得到逼近的有理等距曲面。该算法计算简单,将二元等距曲面有理逼近转化为一元曲线有理逼近,同时方便地解决了整体误差问题,随着对称幂基阶数的升高,可以得到较理想的逼近效果。     

平面度误差的不确定度估计方法及取样点数量的确定

主要阐述在工程测量方案设计阶段,如何采用最小二乘法估算被测要素平面度误差的不确定度和如何确定合理的采样点数,即测量设备的单点坐标不确定度已知时,采用理想点坐标估算法,计算不定乘数系数,继而获得被测要素的采样点数量及其最小二乘法平面度误差的测量不确定度.     

Offset scatter reduction of spinning rotor gauges by vibration isolation

The spinning rotor gauge is an accurate vacuum gauge of good long-term stability. Many efforts have been aimed at the reduction of the uncertainties of this device. Here we examine the possibility of reducing the uncertainty in the low-pressure range caused by the scatter of the pressure-independent residual drag (offset). Random vibrations exposed to the system produce random eddy currents and lead to an additional scatter of the offset value. We tested different configurations, where the suspension head only was isolated from vibration or where both suspension head and stainless steel thimble were isolated. Data sets containing time, frequency of the rotor, relative deceleration rate and temperature were taken at residual pressure conditions. It was found that vibration isolation of the suspension head alone does not cause a significant reduction of the offset scatter, while vibration isolation of suspension head and thimble reduces the scatter by a factor of down to . Surprisingly, it was found that the size of the reduction depends on the controller suspension head unit used for the measurement.