磁存储读写通道伺服Burst信号采样模型的优化与仿真分析

在伺服系统中,为了计算出伺服位置误差信号（PES）,需对伺服burst信号进行高精度采样并通过FFT计算。但目前大多数公司为了降低成本,使用带硬盘控制器芯片88i6310作为伺服读写通道控制芯片,其读写通道伺服系统都采用6位ADC转换器,并且伺服系统和数据信号共用采样电路。由于采样时会产生量化噪声干扰,因此对伺服burst信号来说6位分辨率的ADC转换器显然是不够的,经过FFr计算后burst信号会产生较大的误差。首先依据采样量化误差模型分析了现有的伺服系统过采样模型,并提出了改进型的伺服系统过采样模型。通过仿真得知,改进型采样方案将平均量化误差由原来的0．38LSB降到了0．14LSB,A1X2转换器的分辨率由原来的7．5bit提高到8．8bit。     

On the effectiveness of preprocessing methods when dealing with different levels of class imbalance

The present paper investigates the influence of both the imbalance ratio and the classifier on the performance of several resampling strategies to deal with imbalanced data sets. The study focuses on evaluating how learning is affected when different resampling algorithms transform the originally imbalanced data into artificially balanced class distributions. Experiments over 17 real data sets using eight different classifiers, four resampling algorithms and four performance evaluation measures show that over-sampling the minority class consistently outperforms under-sampling the majority class when data sets are strongly imbalanced, whereas there are not significant differences for databases with a low imbalance. Results also indicate that the classifier has a very poor influence on the effectiveness of the resampling strategies.     

视频处理中的重采样

针对数字视频领域信号重建的问题,分析了各种常见的算法,对算法的性能和复杂度进行了分析,根据硬件实现的要求,选取了一种较合适的算法,并给出了硬件实现的结果。     

Nonparametric estimation of pair-copula constructions with the empirical pair-copula

A pair-copula construction is a decomposition of a multivariate copula into a structured system, called regular vine, of bivariate copulae or pair-copulae. The standard practice is to model these pair-copulae parametrically, inducing a model risk, with errors potentially propagating throughout the vine structure. The empirical pair-copula provides a nonparametric alternative, which is conjectured to still achieve the parametric convergence rate. Its main advantage for the user is that it does not require the choice of parametric models for each of the pair-copulae constituting the construction. It can be used as a basis for inference on dependence measures, for selecting an appropriate vine structure, and for testing for conditional independence.     

法国高分辨率双子星PLEIADES简介及相关技术分析

法国在国际卫星影像市场上占据举足轻重的地位,其0.5米分辨率PLEIADES卫星的发射,在国防、测绘、农林等领域应用前景广阔,军事、社会意义重大。本文将该卫星的主要技术参数与其他卫星进行了对比,并对其重构图像技术进行了深入分析,为读者更好地了解该卫星提供帮助。     

Reducing Variance of Committee Prediction with Resampling Techniques

Algorithms for reducing variance in neural network prediction using committee and resampling techniques bootstrap and cross-validation are presented. Their effectiveness is tested on data sets with different levels of noise and on medical diagnosis data sets. The methods are most effective when the noise level in the data is high or the size of the learning set is small, which consequently produces high variance. The algorithms will not be of much help in cases where the error of prediction is mainly due to bias. An increase in bias is observed due to smaller effective learning size in the bootstrap and crossvalidation committee. The impact of increased bias on the performance ranges from negligible to completely undermining the benefit of reducing the variance.     

Bootstrapping Sequential Change-Point Tests

Abstract

In this article we propose some bootstrapping methods to obtain critical values for sequential change-point tests. We consider a change in the mean with i.i.d. errors. Theoretical results show the asymptotic validity of the proposed bootstrap procedures. A simulation study compares the bootstrap and the asymptotic tests and shows that the studentized bootstrap test behave generally better than asymptotic tests if measured by α- resp. β-errors and its run length.     

Speech Resampling Detection Based on Inconsistency of Band Energy

Speech resampling is a typical tempering behavior, which is often integrated into various speech forgeries, such as splicing, electronic disguising, quality faking and so on. By analyzing the principle of resampling, we found that, compared with natural speech, the inconsistency between the bandwidth of the resampled speech and its sampling ratio will be caused because the interpolation process in resampling is imperfect. Based on our observation, a new resampling detection algorithm based on the inconsistency of band energy is proposed. First, according to the sampling ratio of the suspected speech, a band-pass Butterworth filter is designed to filter out the residual signal. Then, the logarithmic ratio of band energy is calculated by the suspected speech and the filtered speech. Finally, with the logarithmic ratio, the resampled and original speech can be discriminated. The experimental results show that the proposed algorithm can effectively detect the resampling behavior under various conditions and is robust to MP3 compression.     

基于重采样理论和均值滤波的三相电路谐波检测方法

该文提出了基于重采样理论和均值滤波的数字化谐波检测方法，该方法降低了数字低通滤波器的阶数和计算量。文中设计了一个数字谐波检测系统，该系统根据三相三线制电网的有功电流ip和无功电流iq只含3n(n为整数)次谐波这一特征设计数字均值低通滤波器；根据重采样理论在确保ip和iq的直流分量Ip和Iq的频谱不混叠的情况下可对lp和iq分别进行4倍重采样。通过该数字系统可实现电网谐波电流实时精确地提取。仿真试验表明，它既保留了数字滤波器的准确性，又克服了长期以来数字滤波器跟随性和实时性差的问题，具有较高的实用价值。