Analysis of acoustic performance of glass fiber felts after water absorption and their estimation results by artificial neural network

Abstract

The acoustic performance of glass fiber felts after water absorption was researched in the paper. The effects of sound frequency and moisture content on the sound transmission loss (STL) and sound absorption coefficient (SAC) were analyzed. In addition, two types of artificial neural networks (ANN) were established to estimate the acoustic performance. In the first ANN model, the sound frequency and moisture content were chosen as input parameters to predict the STL and SAC values. In another model, the output parameters were replaced by the ratios of STL and SAC to areal density. In order to evaluate the accuracy of the two models, the mean relative error and correlation coefficient were calculated respectively. It has been proved that the predicted values resulted from ANN models fit well with the measured values.     

抗野值自适应Kalman滤波在无人机测风数据处理中的应用

针对无人机风场测量值含连续野值较多,且其噪声统计先验知识不足的问题,运用一种抗野值自适应Kalman滤波算法来提高其测风精度。在对模糊自适应Kalman滤波算法分析的基础上,该算法将一个压缩影响函数加权于滤波方程的新息上,根据新息的方差和均值变化自适应调整修正权值,使修正后的新息序列能够保持原有性质。相关分析结果表明,该算法能有效地克服较大野值和成片野值对滤波的不利影响,保证滤波精度,适用于无人机风场测量。     

脉冲横流对末修弹气动特性的影响分析

为了分析脉冲末修弹的气动特性,建立了末修弹横向喷流工作前后的非定常数值计算模型,计算了脉冲横流在不同作用位置时末修弹的阻力系数、升力系数和俯仰力矩系数,揭示了脉冲横流对末修弹气动特性影响随其作用位置和弹体马赫数的变化规律。结果表明:脉冲横流对弹体阻力的影响不大,对升力和俯仰力矩影响明显。末修弹产生的附加升力系数随脉冲发动机喷口位置后移而增大,且当马赫数在0.6～1.1范围时,该系数随着马赫数增加而影响减小;气动焦点位置随着喷口位置后移亦向后移动,且随着马赫数增加而移动速度减慢。     

Light scattering in monodisperse systems – from suspensions to transparent ceramics

Predicting the in-line transmittance of transparent ceramics via model calculations is a useful guide for materials design and optimization of preparation process. However, the absence of reliable input information (volume fractions and size) usually precludes the direct verification of these calculations. On the other hand, suspensions, which can be prepared with well controlled volume fractions of the solids selected, may serve as model systems that are amenable to verification. This paper describes the procedure to perform these calculations, and compares calculated data for suspensions of monodisperse spheres of amorphous silica with spectrophotometric measurements of silica monosphere suspensions with four different concentrations. Moreover, completely analogous model calculations are performed for bubbles in silica glass and pores in spinel ceramics. The results are discussed on the basis on 3D graphs, the use of which is highly recommended. The results may be considered as a benchmark for future model calculations for polydisperse systems.     

LabVIEW在特种电机教学实验平台中的应用

本文介绍了“电机学”教学实验平台组成和工作原理,分析了基于LabVIEW的测试平台的设计方法。我们利用该平台对波形分析、空载特性测试模块分别进行对比测试实验,结果表明测试平台软件具有较高的测试精度和实用性。将其应用于实验课程教学中,可以比对并验证手动测试实验结果,同时还大大提高实验的效率。     

Identifying user preferences with Wrapper-based Decision Trees

Wrapper feature selection approaches are widely used to choose a small subset of relevant features from a dataset. However, Wrappers suffer from the fact that they only use a single classifier. The downside to this is that each classifier will have its own biases and will therefore select very different features. To overcome the biases of individual classifiers, we propose a new data mining method called Wrapper-based Decision Trees (WDT). The WDT method uses multiple classifiers for selecting relevant features and decision trees to visualize relationships among the selected features. We use the WDT to investigate the influences of the levels of computer experience on users’ preferences for the design of search engines. The benefit of using WDT lies within the fact that it can uncover the most accurate set of relevant features to help differentiate the preferences of users with diverse levels of computer experience. The results indicate that the users with varied levels of computer experiences have different preferences regarding the following features: the number of icons, the arrangement of search results, and the presentation of error messages. Such findings can be used to develop personalized search engines to accommodate users’ different levels of computer experience.     

光纤陀螺实时小波去噪中的阈值选取

在使用小波域阈值滤波方法消除光纤陀螺输出噪声时,阈值的确定和阈值函数的选取是两个关键问题,它们直接关系到小波滤波的滤波效果,目前关于此方面的讨论较多基于离线分析。在综合考虑了实时性与滤波效果后提出了一种改进的阈值确定方法,并针对强制去噪动态性能差的问题提出了一种新的小波系数处理策略,最后利用LabVIEW软件对该算法进行了工程实现。通过试验验证,此方法在不影响滤波效果的前提下具有实时性能好的优点,具有较好的工程应用价值。     

基于光盘库管理系统的虚拟化技术研究

目前,存储虚拟化技术取得了很大的发展,很多产品化的解决方案已经出来,虚拟光盘库技术就是虚拟存储的发展方向之一。采用虚拟光盘库技术,具有良好的实用性能,与现有光盘库存储应用方式一样,可以不改变现有存储应用管理软件,保护用户投资。同时数据的存取速度将大幅提升,数据安全性高,通过VDL模块将数据存储在光盘或光盘库中,光盘或光盘库就可以保持离线,避免数据由于系统被破坏而丢失。此外,设备投入成本低,采用光盘存储的成本要远远低于磁带库和磁盘阵列。