Synchronization and chaos control by quorum sensing mechanism

Diverse rhythms are generated by thousands of oscillators that somehow manage to operate synchronously. By using mathematical and computational modeling, we consider the synchronization and chaos control among chaotic oscillators coupled indirectly but through a quorum sensing mechanism. Some sufficient criteria for synchronization under quorum sensing are given based on traditional Lyapunov function method. The Melnikov function method is used to theoretically explain how to suppress chaotic Lorenz systems to different types of periodic oscillators in quorum sensing mechanics. Numerical studies for classical Lorenz and Rössler systems illustrate the theoretical results.     

Compressive sensing using chaotic sequence based on Chebyshev map

Compressive sensing is a new sampling theory which allows for signal sampling at a sub-Nyquist rate. In order to ensure exact reconstruction from very few measurements, one should design a stable sensing matrix, which satisfies restricted isometry property (RIP), such that it preserves the significant information of original signal in sensing procedure. In this paper, a novel sensing matrix is proposed based on the Chebyshev chaotic system, and the Chebyshev chaotic sensing matrix (CsCSM) is proved to satisfy RIP with overwhelming probability. Numerical simulations show that the CsCSM is sufficient to guarantee exact recovery, which is similar to random sensing matrices such as Gaussian sensing matrix. However, the CsCSM can be easily implemented in hardware circuit and will be more beneficial in some applications which require security and privacy, as opposed to random sensing matrices.     

静电悬浮转子微陀螺微位移数字化电容检测通道设计

微位移检测是实现静电悬浮转子微陀螺闭环起支和稳定悬浮控制的重要前提。针对微陀螺轴向起支和悬浮的检测要求、特点及主要技术指标,设计了完整的电容式微位移检测通道。该通道主要由前置C/V转换、差动放大、四阶压控电压源有源带通滤波、相敏解调、四阶Butterworth低通滤波和16位A/D转换等环节组成,具有激励带宽大、检测精度高及数字化输出等特点。试验表明,检测通道的灵敏度为1.4V/pF,线性度为2.11%,微位移检测分辨力优于10nm,能够满足微陀螺轴向起支和稳定悬浮的检测要求。     

Distributed strain sensing using frequency-modulated continuous-wave reflectometric optical technique

This paper presents an analysis describing the feasibility of a distributed optical fiber strain sensor whose principle of operation is based on the frequency-modulated continuous-wave (FMCW) reflectometry technique. The system consists of a frequency-swept laser diode and an unbalanced two-beam interferometer. In this system, the test arm comprises a number of single-mode fibers, which act as the sensing fibers, with a mirror at the far end and mechanical splices as the connectors, as well as the reflectors. Theoretical analysis shows that the measuring resolution of the strain is inversely proportional to the length of the sensing fiber. The strain variation of the sensing fiber is measured by demodulating the phase shift of the beat signal using a heterodyne signal processing system, and therefore the requirement of a high precision temperature control of the light source can be eliminated in this way. The comparison between the theoretical and experimental values of the strain resolution showed excellent agreement.     

基于电容检测接口ASIC的闭环微机械加速度计

对于采用微传感器和接口ASIC两芯片方案来实现的电容式微机械加速度计来说,寄生电容是影响其性能的重要因素之一。采用采样电荷结构,设计实现了电容检测接口ASIC电路,该电路具有对寄生电容不敏感的特点,并在0.35-μm CMOS标准工艺下流片实现。基于流片得到的电容检测ASIC样片,以梳齿式硅微传感器为敏感元件,采用滞后比例积分调节器,通过力平衡反馈方案设计实现了一种闭环微机械加速度计。实验结果表明:该闭环微加速度计的灵敏度为650 mV/g,噪声基底为23.17μg Hz。     

一种薄膜式的光纤压力传感技术

提出了一种薄膜式的光纤压力传感技术,用于测量冲击波的反射超压峰值。该技术通过建立待测压力与薄膜加速度之间的正比例关系来获取压力。结合Fabry-Perot腔光学干涉测量技术,设计并加工实现了一种光纤压力传感器。开展数值模拟和激波管实验,结果证明,该压力获取技术可行,且该技术具有无须标定、制作简单、成本低廉、测量精度高、响应时间快的优点。     

A physically based model for stress sensing using magnetostrictive composites

Magnetostrictive composites are of considerable interest for real-time remote force sensing and structural health monitoring. In this paper, we introduce a new procedure for modeling the magnetic field induced by an external load applied on an epoxy-based composite material filled with Terfenol-D particles. This model is based on an assumed sequence of physical processes that occur at the microscopic scale, and it includes both domain switching and magnetization rotation. The modeling procedure is demonstrated on a problem relevant for load sensing applications in which the magnetostrictive composite is subjected to a uniaxial compression. Comparison of the calculated and experimental results strengthens the validity of the assumed sequence of physical processes and provides valuable insights important for application developments.     

Nonlinear dynamics of micromechanical resonator arrays for mass sensing

Nonlinear Dynamics - This paper investigates the mass sensing capability of an array of a few identical electrostatically actuated microbeams, as a first step toward the implementation of arrays of...     

Joint image compression–encryption scheme using entropy coding and compressive sensing

Nonlinear Dynamics - Recently, compressive sensing (CS)-based joint compression–encryption schemes have been widely investigated due to their high efficiency and good security for images....     

Laser-Raman remote temperature sensing in liquids

A feasibility study has been conducted on the use of laser-Raman spectroscopy as a remote temperature sensing technique for liquids. Empirical relations between the temperature and parameters describing Raman band intensities were determined over a temperature range of 15 to 65 °C in carbon tetrachloride, benzene, ethylene glycol, aqueous sodium nitrate (5 M), and water. Using a 2-W argon ion laser and two 0.25-m monochromators in tandem, it was possible to measure temperatures in water to within 2 °C and, in ethylene glycol, to within 4 °C.     

基于MSCMG大型遥感卫星高精度姿态控制方法

针对大力矩飞轮前馈和闭环反馈补偿复杂、对精度影响敏感性大的问题,提出了基于磁浮控制力矩陀螺闭环补偿的大型遥感卫星高精度姿态控制方法。该方法采用磁悬浮力矩陀螺为控制执行机构,通过变结构反馈补偿控制律设计,建立新的运动补偿控制系统,减小相机和卫星本体耦合效应。基于磁浮力矩陀螺力矩大、反向激励扰动小、精度高的特性,将其应用于对地遥感成像相机运动补偿控制系统中,仿真结果表明,与飞轮前馈补偿相比,姿态稳定度提高了一个数量级,有效提高空间大惯量卫星姿态控制的稳定度,提升相机对地成像质量;研究结果可为甚高精度卫星姿态控制与载荷运动补偿提供参考。     

A novel spectrogram visual security encryption algorithm based on block compressed sensing and five-dimensional chaotic system

Based on block compressed sensing theory, combined with a five-dimensional chaotic system, we propose and analyze a novel spectrogram visual security encryption algorithm. This research is devoted to solving the compression, encryption and steganography problems of spectrograms involving large data volumes and high complexity. First, the discrete wavelet transform is applied to the spectrogram to generate the coefficient matrix. Then, block compressed sensing is applied to compress and preencrypt the spectrogram. Second, we design a new five-dimensional chaotic system. Then, several typical evaluation methods, such as the phase diagram, Lyapunov exponent, bifurcation diagram and sample entropy, are applied to deeply analyze the chaotic behavior and dynamic performance of the system. Moreover, the corresponding Simulink model has been built, which proves the realizability of the chaotic system. Importantly, the measurement matrix required for compressed sensing is constructed by the chaotic sequence. Third, dynamic Josephus scrambling and annular diffusion are performed on the secret image to obtain the cipher image. Finally, an improved least significant bit embedding method and alpha channel synchronous embedding are designed to obtain a steganographic image with visual security properties. To make the initial keys of each image completely different from other images, the required keys are produced using the SHA-256 algorithm. The experimental results confirm that the visual security cryptosystem designed in this study has better compression performance, visual security and reconstruction quality. Furthermore, it is able to effectively defend against a variety of conventional attack methods, such as statistical attacks and entropy attacks.

     

A micromechanical mass sensing method based on amplitude tracking within an ultra-wide broadband resonance

We propose a mass sensing scheme in which amplitude shifts within a nonlinear ultra-wide broadband resonance serve as indicators for mass detection. To achieve the broad resonance bandwidth, we considered a nonlinear design of the resonator comprised of a doubly clamped beam with a concentrated mass at its center. A reduced-order model of the beam system was constructed in the form of a discrete spring-mass system that contains cubic stiffness due to axial stretching of the beam in addition to linear stiffness (Duffing equation). The cubic nonlinearity has a stiffening effect on the frequency response causing nonlinear bending of the frequency response toward higher frequencies. Interestingly, we found that the presence of the concentrated mass broadens the resonant bandwidth significantly, allowing for an ultra-wide operational range of frequencies and response amplitudes in the proposed mass sensing scheme. A secondary effect of the cubic nonlinearity is strong amplification of the third harmonic in the beam’s response. We computationally study the sensitivity of the first and third harmonic amplitudes to mass addition and find that both metrics are more sensitive than the linearized natural frequency and that in particular, the third harmonic amplitude is most sensitive. This type of open-loop mass sensing avoids complex feedback control and time-consuming frequency sweeping. Moreover, the mass resolution is within a functional range, and the design parameters of the resonator are reasonable from a manufacturing perspective.     

航空遥感用三轴惯性稳定平台动力学建模与仿真

航空遥感用三轴惯性稳定平台由于其机械结构特点,飞机姿态的扰动会耦合到安装在平台的相机上,影响相机的成像质量。为了对复杂耦合关系进行分析,从分析力学的角度出发,采用拉格朗日第二类方程,考虑轴承摩擦,建立了航空遥感用三轴惯性稳定平台动力学模型。在此基础上,对基座振动对相机相对于惯性系的扰动进行了数值仿真。仿真结果表明:基座振动同框架间的耦合力矩相比,基座振动对相机相对于惯性系的扰动占主导作用。当轴承间为动摩擦时,基座振动频率越高,对相机相对惯性系的扰动越小,并从理论上证明了此结论的正确性。研究结果为深入研究航空遥感用三轴惯性稳定平台的振动主动控制提供了理论依据。     

Modeling a synthetic biological chaotic system: relaxation oscillators coupled by quorum sensing

Chaos exists in biological systems. Through investigating synthetic genetic relaxation oscillators coupled by quorum sensing, this paper reports a chaotic system. The detailed dynamical behaviors of this chaotic biological system are investigated, including Lyapunov exponents spectrum, bifurcation, and Poincaré mapping.     

基于超导的全张量重力梯度敏感头设计

基于超导的迈斯纳效应与超导量子干涉技术,结合柔性并联机构理论,设计一种基于超导的全张量重力梯度敏感头。敏感头采用6个完全相同的同时具有移动与转动自由度的敏感结构,对称的布置在正六面体外,对称面的两个敏感结构相对旋转90°成垂直状态。轴向间距使两个敏感结构直接测量重力梯度轴向分量,相互垂直使两个敏感结构既可以测量重力梯度交叉分量,也可以测量共模角加速度。利用超导线圈的电感变化响应质量块位移,进一步通过超导回路将其转变为磁场变化,并由超导量子干涉器进行检测。敏感结构采用8分支的柔性并联机构支承,构成空间对称的形式,可以实现对称的力学特性,保证各处的柔性铰链产生均匀变形,减少非对称的偏移,避免单一铰链的应力集中,具有沿轴移动刚度与绕轴转动刚度小、非设计的寄生误差方向刚度大的优势。在惯性系下的全张量重力梯度值可由坐标变换得到,可以预期得到1E的测量精度。     

Influence of Vickers tip imperfection on depth sensing indentation tests

In the last decade, the development of depth sensing indentation equipment has permitted two of the most conventional mechanical properties of materials to be easily determined: hardness and Young’s modulus. Some care is needed to accurate results from the experimental determination of the aforementioned mechanical properties. In this study, numerical simulations were performed on two well-known materials (Bk7 glass, AISI M2 steel) and on fictitious materials with a wide range of mechanical properties, using Vickers indenters with different sizes of tip imperfections. The purpose is to estimate the influence of the size of the defect on the hardness and Young’s modulus results obtained by ultramicro and nanoindentation tests.     

Rolling deformation of truck tires: Measurement and analysis using a tire sensing approach

Measurements on rolling tire deformation provide deep insights into the mechanism of generating tire forces and moments. For free rolling tires, substantial attention has been given to the rolling resistance because of its significant impact on the fuel consumption and CO₂ emissions. This paper attempts to investigate the rolling resistance force through measurements of the rolling deformation of truck tires using a tire sensing approach. An optical tire sensor system is used to measure rolling tire deformation, which includes the deformed inner profile, sidewall deformation, and tread deformation. Measurements were conducted on a test truck for both new and used tires. In addition, the influences from operational factors such as wheel load and inflation pressure on tread deformation were examined and analyzed.     

航空遥感用惯性稳定平台动力学耦合分析

航空遥感用惯性稳定平台承载重量较大的成像载荷,系统相对复杂,耦合明显。根据航空遥感用三轴惯性稳定平台的结构特点,应用矢量叠加原理推导了平台环架运动学方程,建立了欧拉动力学模型,并分析了基座运动情况下各环架间的动力学耦合误差。仿真结果表明,基座对平台环架耦合较大,环架交叉耦合相对较小,且在外界干扰下基座及环架间的耦合加强。研究结果为稳定平台控制系统设计提供了依据。     

Wavefront sensing for single view three-component three-dimensional flow velocimetry

We present the application of wavefront sensing to particle image velocimetry for three-component (3C), three-dimensional (3D) flow measurement from a single view. The technique is based upon measuring the wavefront scattered by a tracer particle and from that wavefront the 3D tracer location can be determined. Hence, from a temporally resolved sequence of 3D particle locations the velocity vector field is obtained. Two approaches to capture the data required to measure the wavefronts are described: multi-planar imaging using a distorted diffraction grating and an anamorphic technique. Both techniques are optically efficient, robust and compatible with coherent and incoherent scattering from flow tracers. The depth (range) resolution and repeatability have been quantified experimentally using a single mode fiber source representing a tracer particle. The anamorphic approach is shown to have the greatest measurement range and hence was selected for the first proof of principle experiments using this technique for 3D particle imaging velocimetry (PIV) on a sparsely seeded gas phase flow.