二维直方图θ-划分最大平均离差阈值分割算法

鉴于常用二维直方图区域直分法存在错分, 最近提出的斜分法不具普遍性, 而基于L1范数的最小一乘准则比最小二乘准则更为合理且简捷, 提出了适用面更广的基于二维直方图θ-划分和最大类间平均离差的图像阈值分割算法. 首先给出了二维直方图θ-划分方法, 采用4条平行斜线及1条其法线与灰度级轴成 θ 角的直线划分二维直方图区域, 按灰度级和邻域平均灰度级的加权和进行阈值分割, 斜分法可视为该方法中θ=45° 的特例; 然后导出了二维直方图θ-划分最大类间平均离差阈值选取公式及其快速递推算法; 最后给出了θ 取不同值时的分割结果及运行时间. θ 取较小值时, 边界形状准确性较高, θ 取较大值时, 抗噪性较强, 应用时可根据实际图像特点及需求合理选取 θ 的值. 与常规二维直方图直分最大类间方差法及最大类间平均离差法相比, 所需运行时间相近, 但本文提出的方法所得分割结果更为准确, 抵抗噪声更为稳健, 且存储空间也大为减少.     

物位计测量技术分析及应用研究

雷达物位技术是物位测量技术中发展较快的技术之一,但我国雷达物位仪表的研发还比较落后。分析了雷达物位计市场所占比重最大的两种测量方式——雷达脉冲测量和连续波线性调频测量的信号处理方式,比较了它们各自的优缺点,并指出了在应用中应注意的问题;同时,探讨了物位计开发过程中的技术难点,并根据我国现有的技术条件提出了相应的解决方案。     

一种带渐消因子的偏差配准和目标跟踪算法

在多平台多传感器跟踪系统中,提出一种带渐消因子的偏差配准和目标跟踪算法,结合配准偏差和目标状态形成扩维状态变量以构造新的偏差配准模型,在跟踪过程中引入渐消因子对突变的目标状态变量进行快速响应。仿真结果表明,该算法能使系统偏差估计迅速收敛到真实值附近,在偏差发生突变时,具有较好的自适应性,并且可以提高系统的整体跟踪精度。     

基于代理随机数的低成本RFID安全协议

针对低成本电子标签安全隐私保护能力和防跟踪能力较弱的问题,采用读写器代理生成随机数的方法,提出一种面向大容量被动型标签的新型无线射频识别(RFID)安全认证协议。理论分析证明,该协议具有前向安全性,能够防止位置隐私攻击、窃听攻击,保障数据的保密性、可靠性和一致性,且硬件复杂度较低,适用于低成本电子标签。     

Approximate periodic solutions for the Helmholtz-Duffing equation

Approximate periodic solutions for the Helmholtz-Duffing oscillator are obtained in this paper. He’s Energy Balance Method (HEBM) and He’s Frequency Amplitude Formulation (HFAF) are adopted as the solution methods. Oscillation natural frequencies are analytically analyzed. Error analysis is carried out and accuracy of the solution methods is evaluated.     

A resonating rheometer using two polymer membranes for measuring liquid viscosity and mass density

A resonating sensor for mechanical liquid properties facilitating measurements at two different modes of operation is presented. One mode is more sensitive to liquid viscosity the other to mass density. A sample liquid is subjected to time-harmonic shear stress induced by two opposed vibrating polymer membranes. These membranes, placed in an external static magnetic field, carry two conductive paths each. The first path is used to actuate the membranes by means of Lorentz forces while the second acts as a pick-up coil providing an induced voltage representing the movement of the membrane. From the resulting frequency response the liquid's viscosity and mass density can be deduced. This double membrane based setup allows examining the test liquid at adjustable frequencies in the low kilohertz range from 500 Hz to 20 kHz by varying the gap between both membranes. The sensor is suitable, e.g., for low cost handheld devices with inline capabilities and disposable sensor elements for measuring Newtonian liquids such as, e.g., oils and aqueous solutions.     

Estimating the fundamental matrix based on least absolute deviation

The epipolar geometry is the intrinsic projective geometry between two views, and the algebraic representation of it is the fundamental matrix. Estimating the fundamental matrix requires solving an over-determined equation. Many classical approaches assume that the error values of the over-determined equation obey a Gaussian distribution. However, the performances of these approaches may decrease significantly when the noise is large and heterogeneous. This paper proposes a novel technique for estimating the fundamental matrix based on least absolute deviation (LAD), which is also known as the L₁ method. Then a linear iterative algorithm is presented. The experimental results on some indoor and outdoor scenes show that the proposed algorithm yields the accurate and robust estimates of the fundamental matrix when the noise is non-Gaussian.     

Liquid-state motion sensing

This paper demonstrates a liquid droplet-based motion sensing system which has the advantages of simple fabrication, low power consumption and digital signal processing. The sensor consists of a dielectric substrate patterned with an array of microelectrodes, and a saline droplet as the proof mass. Once an external linear acceleration is applied, the inertial force moves the droplet on the micropatterned substrate. The acceleration is determined from the movement profile detected by the microelectrodes. In order to enhance the threshold and the sensitivity of motion sensing, two surface treatment approaches are utilized to create superhydrophobic surfaces. The result shows that the minimal sliding angle that can move a 20 μl droplet on the superhydrophobic surface is lower than 1°, corresponding to a threshold of lower than 0.017 g. A lumped-parameter model is developed to estimate the dynamic behavior of the proposed system. The result shows that the frequency response of the droplet-based sensor is more significant at low frequencies than at high frequencies, which is distinct from solid-state accelerometers. Measurement under a constant acceleration shows that the predicted value derived from the measurement has a good match with the actual applied acceleration, validating the proposed system as a viable alternative for motion sensing.     

Structure damage diagnosis using neural network and feature fusion

A structure damage diagnosis method combining the wavelet packet decomposition, multi-sensor feature fusion theory and neural network pattern classification was presented. Firstly, vibration signals gathered from sensors were decomposed using orthogonal wavelet. Secondly, the relative energy of decomposed frequency band was calculated. Thirdly, the input feature vectors of neural network classifier were built by fusing wavelet packet relative energy distribution of these sensors. Finally, with the trained classifier, damage diagnosis and assessment was realized. The result indicates that, a much more precise and reliable diagnosis information is obtained and the diagnosis accuracy is improved as well.     

现场总线在冷矫直机辅机控制系统中的应用

本文结合冷矫辅机的电气控制系统,介绍了特殊管厂热处理线冷矫直机辅机的生产工艺,分析了控制系统的工艺流程和需求,着重描述了基于Profibus—DP现场总线的该区域控制系统的结构和调速系统的构成,以及S7—300PLC、ET200M远程I／O站和ATV71系列变频器的通信功能、网络组态和参数设置。通过Profibus—DP数据通信以实现对施耐德ATV71变频器和ET200M的网络化控制,使冷矫辅机的电气控制系统高效地运行。