轴承变载荷压力实验系统设计

针对现有轴承实验台的加载力不可按照任意载荷谱调节的缺陷,提出了PLC与虚拟仪器共同控制的方案.下位机采用PLC进行简单可靠控制,上位机采用虚拟仪器进行复杂的加载控制.详细阐述了控制方案及与PLC传输协议协调的实现方法.在允许的载荷输入范围内,该方案通过实验台加载力的可调输入,进行设定载荷谱试验,使试验时间有效缩短.试验结果表明,该方案灵活,且成本低,满足了产品测试需求.     

面向分布式网络的信息按需分层分发系统框架

由OMG组织提出的数据分发服务(DDS)采用发布/订购工作机制,它为分布式应用系统提供了实时、高效的按需数据分发模型.首先分析了以数据为中心的按需分发工作机制,结合分布式网络环境的特点,构建了信息按需分层分发系统框架;然后具体给出了框架的组成要素及其功能,并设计了各成员之间按需分发的行为方式以及两层信息分发的交互策略;最后阐述了发布/订购的数据模型及信息过滤方案.该框架为分布式网络构建按需分发系统提供了参考模型,同时也为系统的进一步研究和应用奠定了基础.     

基于SVM和小波分析的脑电信号分类方法

根据癫痫脑电信号与正常脑电信号波形和能量特征的不同,研究了两种的脑电信号分类方法,一种采用支持向量机SVM(Support Vector Machines)分类器对正常脑电和癫痫脑电进行分类;另一种使用小波分析和支持向量机相结合的方法对脑电进行分类,并比较了这两种方法对正常脑电和癫痫脑电分类的正确率。实验结果表明,小波分析和SVM结合的方法对脑电信号分类可以取得更好的效果,能有效区分癫痫脑电和正常脑电。     

High-sensitivity NO2 gas sensors based on flower-like and tube-like ZnO nanomaterials

Hierarchical flower-like and 1D tube-like ZnO architectures were synthesized by a microemulsion-based solvothermal method. Technologies of XRD, SEM and TEM were used to characterize the morphological and structural properties of the products. The influence of the flower-like and tube-like morphologies on their NO₂ sensing properties was investigated. The experimental results showed that high-sensitivity NO₂ gas sensors were fabricated. The sensitivity of the tube-like ZnO gas sensor was much higher than that of the flower-like ZnO gas sensor and the tube-like ZnO gas sensor exhibited shorter response time. The in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) technique was employed to investigate the NO₂ sensing mechanisms. Free nitrate ions, nitrate and nitrite were the main adsorbed species during the adsorption, and NO also existed in the initial period of surface reoxidation. Furthermore, N₂O was formed via NO⁻ and N₂O₂⁻ stemmed from NO and increased upon rising temperature. Moreover, the PL spectra and the XPS spectra further proved that the intensity of donors (oxygen vacancy (V_O) and zinc interstitial (Zn_i)) and surface oxygen species (O₂⁻ and O₂) involved in the gas sensing mechanism leaded to the different sensitivities.     

Event‐Triggered Control for Couple‐Group Multi‐Agent Systems with Logarithmic Quantizers and Communication Delays

This paper mainly investigates the event‐triggered control for couple‐group multi‐agent systems with communication delay. Logarithmic quantization is considered in the communication channels. Event‐triggered control laws are adopted to reduce the frequency of individual actuation updating for discrete‐time agent dynamics. The proposed protocol is efficient as long as the quantization levels are dense enough, i.e. the density of quantization levels goes to infinity is a sufficient condition for the asymptotic consensus of the multi‐agent systems. It turns out that the bounded consensus depends on not only the density of quantization levels, but also the updating strategy of events. Finally, a simulation example is given to demonstrate the effectiveness of the proposed methods.     

Consensus of multiple Euler-Lagrange systems using one Euler-Lagrange System’s velocity measurements

International Journal of Control, Automation and Systems - This brief paper studies the stationary consensus of multiple Euler-Lagrange systems with nonlinear protocols. Two consensus protocols are...     

A Mathematica program for the approximate analytical solution to a nonlinear undamped Duffing equation by a new approximate approach

According to Mickens [R.E. Mickens, Comments on a Generalized Galerkin's method for non-linear oscillators, J. Sound Vib. 118 (1987) 563], the general HB (harmonic balance) method is an approximation to the convergent Fourier series representation of the periodic solution of a nonlinear oscillator and not an approximation to an expansion in terms of a small parameter. Consequently, for a nonlinear undamped Duffing equation with a driving force Bcos(ωx), to find a periodic solution when the fundamental frequency is identical to ω, the corresponding Fourier series can be written as

     

基于数据空间网格划分的PK 树索引结构*

在大规模高维数据挖掘研究中,数据存储与索引方法的有效性是决定算法时空效率的重要因素。将数据空间网格划分策略与高效率的树型索引结构结合起来,可以充分发挥两者在数据组织上的综合优势,将复杂问题转换为结构化的简单重复问题。在统一的框架下给出了各种数据空间网格划分的定义,讨论了两种适用于实现网格化数据索引的R树和PK树索引结构。试验结果表明,PK树在数据存储和索引上具有更高的效率,与网格化数据组织方法结合起来,对于降低大规模高维数据分析问题的时空复杂度具有重要意义。     

模具型腔的切削条件择优与刀具寿命研究

在模腔数控加工过程中,切削条件与刀具寿命和生产效率密切相关.针对模具材料应用田口实验法进行仿真加工和模腔切削实验,择优模腔的切削条件,预测刀具寿命.研究结果表明:主轴转速、径向进刀、轴向进刀和进给率对刀具寿命均有不可忽视的重要影响.将实验得到的最佳匹配切削参数应用于模具加工中,降低了生产成本,提高了生产效率.     

钻井工程设计与工艺软件的发展现状

介绍国内外钻井工程设计与工艺软件特点.经过“十一五”科技攻关,国内已经开发出具有自主知识产权的钻井工程设计与工艺软件,初步解决了我国钻井软件长期依赖于国外软件的局面,基本满足国内油田钻井工程设计与施工分析的需要.