一种基于流水线ADC的余量增益误差校准技术

由于传统流水线ADC的精度难以满足实际应用,在电压域与时间域混合的流水线ADC结构基础上,针对余量放大器的增益误差,提出了双通道环路校准算法,引入辅助放大器,构造一条新的估算增益路径,使MDAC的输出在放大器的增益误差被消除之后再被流水线后级采样。在采样频率为100 MHz、输入频率为40 MHz时进行仿真实验,实验结果表明流水线ADC的性能参数得到了优化,达到了提升精度的目的,证明了该方法的有效性。

一种嵌入式小波四叉树帧间编码算法

提出了一种新的嵌入式小波四叉树帧间编码算法。算法对于运动补偿余量误差帧首先进行小波变换 ,并选取适当的阈值 ,用重要图表示大于该阈值的重要系数。根据残差帧小波系数的统计特性 ,用四叉树方法编码重要图 ,并对重要系数作位面编码 ,生成嵌入式码流。实验表明 ,与EZW ,ZTE等算法相比较 ,该算法编码效率高 ,复现图像质量好。

基于交易网络特征向量中心度量的可疑洗钱识别系统

针对可疑洗钱识别问题,提出了基于交易网络特征向量中心度量的可疑洗钱行为检测系统。检测系统包含交易数据预处理、特征向量中心度量、时序检测分析三个关键子算法。同时还给出了三种用于检测异常交易行为的度量指标。通过对银行交易数据进行的实验仿真,验证了系统的有效性。

平面毛坯尺寸标注的新方法及应用

为有效减小毛坯尺寸误差对粗加工余量的影响,以保证毛坯各面粗加工余量误差最小为目标,对平面毛坯尺寸基准选择方法进行了研究。研究了毛坯在机械加工中粗基准的特征,结果表明,若毛坯各个面的尺寸设计基准都采用组合定位基准,则毛坯各面的粗加工余量误差最小。通过对某箱体零件新旧两种毛坯尺寸标注方法进行综合分析对比,证明了平面毛坯尺寸标注法对减小工件粗加工余量和提高工件精度具有积极意义。

基于最短路径的杠杆毛坯尺寸设计

传统毛坯尺寸设计方法中,毛坯尺寸基准与零件图上的基准一致,忽略了工艺过程的差异,使得加工余量误差增大。基于最短尺寸路径原理,以减小毛坯尺寸的累积误差为目标,对平面毛坯尺寸基准的选择原则进行归纳总结。以车床杠杆零件为例,根据工件的组合定位的情况,将多个基准抽象成一个基准向量,进而确定毛坯尺寸基准,最终完成杠杆毛坯尺寸标注。通过对比传统方法和新方法下各加工面的粗加工余量以及加工面与非加工面之间的尺寸误差,得出新方法可以减小加工余量误差,提高了工件加工效率及精度。

Residual life estimation based on bivariate Wiener degradation process with measurement errors

An adaptive method of residual life estimation for deteriorated products with two performance characteristics (PCs) was proposed, which was sharply different from existing work that only utilized one-dimensional degradation data. Once new degradation information was available, the residual life of the product being monitored could be estimated in an adaptive manner. Here, it was assumed that the degradation of each PC over time was governed by a Wiener degradation process and the dependency between them was characterized by the Frank copula function. A bivariate Wiener process model with measurement errors was used to model the degradation measurements. A two-stage method and the Markov chain Monte Carlo (MCMC) method were combined to estimate the unknown parameters in sequence. Results from a numerical example about fatigue cracks show that the proposed method is valid as the relative error is small.

Real time remaining useful life prediction based on nonlinear Wiener based degradation processes with measurement errors

Real time remaining useful life(RUL) prediction based on condition monitoring is an essential part in condition based maintenance(CBM). In the current methods about the real time RUL prediction of the nonlinear degradation process, the measurement error is not considered and forecasting uncertainty is large. Therefore, an approximate analytical RUL distribution in a closed-form of a nonlinear Wiener based degradation process with measurement errors was proposed. The maximum likelihood estimation approach was used to estimate the unknown fixed parameters in the proposed model. When the newly observed data are available, the random parameter is updated by the Bayesian method to make the estimation adapt to the item's individual characteristic and reduce the uncertainty of the estimation. The simulation results show that considering measurement errors in the degradation process can significantly improve the accuracy of real time RUL prediction.

船舶电缆长度设计确定的一般方法及合理性分析

据统计，我公司与日本多家船厂建造的同类型散货船上，电缆敷设总用量要比日本同行多百分之二十左右。造成造船成本的增加。本文从几个方面分析了影响电缆设计用量和电缆敷设总用量的原因，给出了具体的解决方法。