改进PSO-BP网络在故障诊断中的应用

针对油田抽油机井故障诊断方法较落后的问题,提出一种基于改进PSO-BP网络的故障诊断系统.神经网络权值的训练采用改进的PSO算法,克服了BP学习算法收敛速度慢、易陷入局部极值的缺点.将该网络用于抽油机井的故障诊断,并与传统BP模型的故障诊断结果进行比较.结果表明:基于改进PSO-BP的故障诊断方法正确率达96%以上,可以在更短的时间内、用更少的迭代次数达到精度要求,为设备检修提供了可靠的依据.     

数控机床热误差动态灰色优化建模研究

为降低热误差对加工精度的影响,以减少补偿成本、简化数据采集、提高补偿精度为目标,提出采用灰色GM(0,N)模型进行数控机床热误差建模预测;以优化数据配置、改善补偿系统动态品质、提高鲁棒性为目的,建立了GM(0,N)优化模型。采用智能温度传感器和位移传感器采集了MCH63精密卧式加工中心温度数据和主轴3个方向热位移量,并根据采集数据构建热误差模型。试验结果表明:GM(0,N)建模方法简单,数据量少,运算时间短,预测精度较高;优化模型可根据在线输入的新数据不断修正模型本身,其精度高、鲁棒性强、通用性好,适合于在线建模。     

一种新的小波阈值去噪方法研究

本文研究用组合小波对含噪信号的去噪问题,对均方根误差、信噪比、平滑度等信号指标进行多指标融合作为去噪效果的评价参数,根据评价参数确定最佳小波分解尺度、小波去噪最佳小波基和最佳阈值。新的去噪方法与传统的去噪方法相比,克服了硬阈值不连续的缺点,还克服了软阈值中估计小波系数与分解小波系数之间的恒定偏差的缺点。MATLAB仿真结果表明,新的阈值函数的去噪效果在各指标上都优于传统的阈值去噪方法。     

Flexible top-emitting warm-white organic light-emitting diodes with highly luminous performances and extremely stable chromaticity

The flexible top-emitting white organic light-emitting diode (FTEWOLED) with a very high efficiency but a significant color alteration is achieved with a blue/red/blue sandwiched tri-emission-layer. The voltage-dependent recombination region alternation and the emission mechanism are systematically investigated through a delta-doping method and the time-resolved transient photoluminescence lifetime measurement. By locating the main exciton recombination region at the 4,4′,4″-Tris(carbazol-9-yl)-triphenylamine (TCTA) and 9,9-spirobifluoren-2-yl-diphenyl-phosphine oxide (SPPO1) interface, replacing the carrier-trapping red dopant guest with an orange guest that utilizes energy transfer mechanism, and using a P–I–N structure together with the FIrpic blue guest dopant to balance the electron and hole carriers, an extremely color stable and a very high efficient FTEWOLED is fabricated, with the resulting high current and power efficiencies of 22.7 cd/A and 14.27 lm/W, and a warm white illumination with a small chromaticity variation of (−0.0087, +0.0015) over a broad luminance range of more than four orders of magnitude. In addition, the performances can be further improved to 23,340 cd/m², 24.49 cd/A and 15.39 lm/W with a slight concentration alteration of the orange emitter.     

Deterministic Sensing Matrices Based on Multidimensional Pseudo-Random Sequences

An approach is proposed for producing compressed sensing (CS) matrices via multidimensional pseudo-random sequences. The columns of these matrices are binary Gold code vectors where zeros are replaced by ?1. This technique is mainly applied to restore sub-Nyquist-sampled sparse signals, especially image reconstruction using block CS. First, for the specific requirements of message length and compression ratio, a set Λ which includes all preferred pairs of m-sequences is obtained by a searching algorithm. Then a sensing matrix A _M×N is produced by using structured hardware circuits. In order to better characterize the correlation between any two columns of A, the average coherence is defined and the restricted isometry property (RIP) condition is described accordingly. This RIP condition has strong adaptability to different sparse signals. The experimental results show that with constant values of N and M, the sparsity bound of A is higher than that of a random matrix. Also, the recovery probability may have a maximum increase of 20 % in a noisy environment.     

压缩感知中基于变尺度法的贪婪重构算法的研究

首先将最优化方法中的梯度法与贪婪算法相结合,在已有梯度追踪算法的基础上提出了基于变尺度法的梯度追踪（VMMGP）算法,分析比较这些算法的计算复杂度和存储需求;其次用这些算法分别重构一维、二维信号,分析比较了算法重构效果及其性能好坏。实验结果表明,对于一维信号和二维信号的重构,所提出的VMMGP算法,重构效果是所有梯度追踪算法中最好的。     

Security analysis of two lightweight RFID authentication protocols

One of the key problems in radio frequency identification (RFID) is security and privacy. Many RFID authentication protocols have been proposed to preserve security and privacy of the system. Nevertheless, most of these protocols are analyzed and it is shown that they cannot provide security against some RFID attacks. Strong authentication and strong integrity (SASI) is the first ultra-lightweight authentication protocol introduced rotation shift operation and RFID authentication protocol with permutation (RAPP) is a new ultra-lightweight authentication protocol with permutation. In this paper, we give the security analysis on these two protocols. An active attack is presented on RAPP, and using the property of the left rotation and permutation operations, we can deduce the relationship of bits of random number or secret keys at different positions, thus obtain all the secrets shared by the reader and the tag. A passive full-disclosure attack is proposed on SASI. Using SASI’s construction weakness, our attack can reveal all the secrets shared by the reader and tag by eavesdropping about 48 rounds of the authentication messages.     

基于PCA和PNN的模拟电路故障诊断

为了解决模拟电路故障识别困难的问题,提出一种基于主成分分析和概率神经网络的模拟电路故障诊断方法。该方法对采集到的模拟电路故障信息进行特征提取,将提取的故障特征归一化处理后输入概率神经网络,进行训练和故障模式的分类识别。实验结果表明,该方法是有效的,具有较高的故障诊断率。     

Credibility protection for resource sharing and collaborating in non-center network computing environments

Non-center network computing environments have some unique characteristics, such as instability, heterogeneity, autonomy, distribution and openness, which bring serious issues of security and reliability. This article proposes a brand-new credibility protection mechanism for resource sharing and collaboration in non-center network computing environments. First, the three-dimensional hierarchical classified topology （3DHCT） is proposed, which provides a basic framework for realizations of the identity credibility, the behavior credibility and the capability credibility. Next, the agent technology is utilized to construct the credibility protection model. This article also proposes a new comprehensive credibility evaluation algorithm with simple, efficient, quantitative and able to meet the requirements of evaluating behavior credibility and the capability credibility evaluation as well. The Dempster-Shafer theory of evidence and the combination rule are used to achieve the evaluation of the capability credibility. The behavior credibility is evaluated with the current and historical performance of nodes for providers and consumers to realize more accurate prediction. Based on the non-center network computing simulation test platform, simulation is been conducted to test the performance and validity of the proposed algorithms. Experiment and analysis show that the proposed algorithms are suitable for large-scale, dynamic network computing environments, and able to maintain the credibility for networks without relying on central node, make a non-center network gradually evolve into an orderly, stable and reliable computing environment efficiently.     

包装生产线用工控机PS/2接口的网络化实现

为了可靠地远程操作食品包装生产线上的工控机,设计了一种网络化PS/2接口终端,把键盘鼠标和工控主机分离,把外设和主机间的PS/2双向传输数据网络化,使得键盘和鼠标可以远程操控主机,并且在不同操作系统的主机间快速切换。此设计方便用户对工控主机的操控,增强了使用的灵活性。