Dynamical analysis,circuit realization,and application in pseudorandom number generators of a fractional-order laser chaotic system

A new five-dimensional fractional-order laser chaotic system (FOLCS) is constructed by incorporating complex variables and fractional calculus into a Lorentz-Haken-type laser system. Dynamical behavior of the system, circuit realization and application in pseudorandom number generators are studied. Many types of multi-stable states are discovered in the system. Interestingly, there are two types of state transition phenomena in the system, one is the chaotic state degenerates to a periodical state, and the other is the intermittent chaotic oscillation. In addition, the complexity of the system when two parameters change simultaneously is measured by the spectral entropy algorithm. Moreover, a digital circuit is design and the chaotic oscillation behaviors of the system are verified on this circuit. Finally, a pseudo-random sequence generator is designed using the FOLCS, and the statistical characteristics of the generated pseudo-random sequence are tested with the NIST-800-22. This study enriches the research on the dynamics and applications of FOLCS.     

用于SCA ASIC测试的数字读出模块设计

高速开关电容阵列(SCA)具有高速采样、低功耗的特点,基于SCA的高速波形数字化是目前高精度时间测量的一个重要研究方向。为此,我们开展SCA芯片的研究,目前已设计完成原型ASIC设计,并正在进行后续版本的改进设计。为便于未来多版本ASIC的测试和评估,需设计具有一定通用性的数字读出模块,本论文工作主要介绍此模块的设计工作以及相应的数据读出软件。数字读出模块基于FPGA实现对待测ASIC的控制、配置及数据读出,采用DDR3片外存储芯片,使用USB3.0等接口进行数据传输;上位机软件基于Python3.7设计,实现了数据采集与波形绘制等功能。目前已使用设计完成的数字读出模块对第2版SCA ASIC进行了初步的测试,测试结果表明,此读出模块工作正常,且SCA芯片输出结果符合预期。     

Dynamical Analysis of a New Chaotic Fractional Discrete-Time System and Its Control

This article proposes a new fractional-order discrete-time chaotic system, without equilibria, included two quadratic nonlinearities terms. The dynamics of this system were experimentally investigated via bifurcation diagrams and largest Lyapunov exponent. Besides, some chaotic tests such as the 0–1 test and approximate entropy (ApEn) were included to detect the performance of our numerical results. Furthermore, a valid control method of stabilization is introduced to regulate the proposed system in such a way as to force all its states to adaptively tend toward the equilibrium point at zero. All theoretical findings in this work have been verified numerically using MATLAB software package.     

受限亚音速气流中倒置悬臂壁板静气弹稳定性的理论及实验研究

板壳结构在航空航天、高速列车、能量采集等诸多工程领域已经得到了广泛应用. 将悬臂壁板倒置于轴向气流中并在壁板周围流场中设置刚性壁面可有效地调控壁板的失稳速度, 是俘能器优化设计的重要措施之一. 但针对刚性壁面作用下亚音速气流中倒置悬臂壁板的失稳机制仍需要开展深入研究. 本文以受限亚音速气流中倒置的二维悬臂壁板为对象, 以理论分析及风洞实验为手段, 研究了单侧刚性壁面效应对倒置悬臂壁板静态失稳特性的影响规律. 在理论分析中, 首先应用镜像函数法来处理壁面约束条件, 基于算子理论研究获得了以Possio积分方程为表征的壁板气动力, 壁面效应实际表征为一包含移位Tricomi算子的复合算子; 然后将壁板失稳方程的求解问题转化为定区间上的函数逼近问题; 最后, 依据Wererstrass定理并利用最小二乘法求解该最优函数, 以获得系统的失稳临界参数. 在试验研究中依据压杆稳定原理设计了壁板静态失稳的测试方法并完成了风洞实验. 理论分析结果表明, 壁板会发生发散(静气动弹性)失稳, 临界动压随壁板与壁面间距的增加而增大并最终趋于稳定(无壁面情况); 通过理论与风洞实验结果的对比分析, 验证了本文气动力及理论分析的适用性及准确性. 针对倒置悬臂壁板结构的气动弹性失稳问题, 本文提出的方法不涉及系统方程的离散及特征值求解问题, 而是将其转化为了定区间上的函数逼近问题进行求解, 这为弹性结构静气动弹性失稳问题的研究提供了一个可行的新思路.      

Using a Novel and Easy-to-Use Sandwich Structure Device to Evaluate the Cooling Properties of Cool Materials

A number of cool materials have been designed and used in hot weather to minimize the heat coming from sunlight. Traditionally, solar reflectance and infrared emittance were measured to characterize the cooling properties of cool materials. However, these methods could represent the cooling property only indirectly. In this work, a sandwich structure device that can straightforwardly measure the cooling properties of cool materials was designed. Two cool materials, including high-density polyethylene (HDPE) and polyvinyl chloride (PVC), were selected to verify the device. For the purpose of comparison, UV-vis-NIR spectral characterization was also used to evaluate the cooling properties of the selected materials. The results, especially for the HDPE/Green 260 composite sample, which presents much lower solar reflectance but better cooling property, indicated that the cooling properties cannot be entirely represented by only the reflectance or transmittance, and the sandwich structure device was able to make up for this deficiency.     

大豆脲酶诱导碳酸钙沉淀的多因素影响分析

本文探究了多个影响因素对大豆脲酶诱导碳酸钙沉淀(SICP)的影响,以优选出主要影响因素并提供其最佳范围。首先分析了脲酶浓度和温度对脲酶活性的影响;之后通过正交实验设计,进行25种工况的SICP水溶液实验,研究不同因素组合下Ca²⁺利用率的变化规律;最后借助扫描电子显微镜观测不同工况下生成碳酸钙的形态。结果表明:低温有利于脲酶的保存及活性发挥,5 ℃时脲酶活性能保持21 d以上;同一温度下,脲酶浓度越大,脲酶初始活性越高,脲酶完全失活所需时间越短。pH值、脲酶与胶结液体积比是影响Ca²⁺利用率的主要因素。为达到较高的Ca²⁺利用率,脲酶和胶结液最佳体积比为1,氯化钙与尿素最佳浓度比为1.5,Ca²⁺最佳浓度为1 mol/L。当脲酶浓度较低时生成的六面体状碳酸钙较多;随着脲酶浓度的增大,所沉淀的碳酸钙向球形转变。大豆中富含的天冬氨酸是控制碳酸钙形态的重要因素。     

Synthesis of Heat-resistant Polymers by Thiol–Ene Reaction of N-Allylmaleimide Copolymers Using Glycoluril Crosslinkers with Rigid Molecular Structures

We carried out the thermal curing of the copolymers of N-allylmaleimide (AMI) and 2-ethylhexyl acrylate (2EHA) using 1,3,4,6-tetra(2-mercaproethyl)glycoluril ( G1 ), 1,3,4,6-tetra(3-mercaptopropyl)glycoluril ( G2 ), 1,3,4,6-tetraallylglycoluril ( G3 ), triallylisocyanurate (TAIC), and pentaerythritol tetrakis(3-mercaptobutyrate) (PEMB) as the crosslinkers. Based on the results for the analysis of thiol–ene reactions monitored by IR spectroscopy, it was confirmed that the curing rate significantly depended on the combination of the used crosslinkers. The insoluble fraction after curing was more than 90% for the systems using the glycoluril crosslinkers, while the conversion of the allyl groups was suppressed due to the rigid structure of these crosslinkers. The heat resistance and the mechanical properties of the crosslinked polymers were investigated by thermogravimetric analysis, differential scanning calorimetry, dynamic mechanical analysis, and mechanical tensile tests. For the products cured using the glycoluril crosslinkers, the glass transition temperature (T_g) and the maximum temperature of thermal decomposition (T_max) were 54–59 °C and 395–409 °C, respectively, being higher than those for the cured product prepared with PEMB and TAIC as the conventional crosslinkers. The elasticity (75–139 MPa), the maximum strength (3.0–4.1 MPa), and the adhesion strength (6.7–10.7 MPa) for the polymers cured with the glycoluril crosslinkers, determined by the mechanical tensile and single lap-shear adhesion tests, were higher than those for cured materials produced with PEMB. Thus, the thermal and mechanical properties of the maleimide copolymers were efficiently enhanced by crosslinking using the rigid glycoluril compounds. © 2020 Wiley Periodicals, Inc. J. Polym. Sci. 2020 , 58, 923–931     

石英砂粒径对水合物沉积物力学性质的影响

利用自主研发的水合物沉积物原位合成与力学性质测试的高压低温三轴仪,通过多级加荷的试验方法,以不同粒径的砂粒作为沉积物骨架进行三轴压缩试验,得到了剪切过程的应力-应变关系曲线,以及不同粒径尺寸沉积物的强度,还有剪切过程中的体积变化关系。结果表明:含水合物沉积物强度随着沉积物粒径尺寸的增大而增强;在降压剪切过程中,所有粒径的水合物沉积物式样均有明显的剪缩现象。     

Periodic,breather and rogue wave solutions for a generalized (3+1)-dimensional variable-coefficient B-type Kadomtsev–Petviashvili equation in fluid dynamics

Under investigation in this paper is a generalized (3+1)-dimensional variable-coefficient B-type Kadomtsev–Petviashvili equation, which describes the propagation of nonlinear waves in fluid dynamics. Periodic wave solutions are constructed by virtue of the Hirota–Riemann method. Based on the extended homoclinic test approach, breather and rogue wave solutions are obtained. Moreover, through the symbolic computation, the relationship between the one-periodic wave solutions and one-soliton solutions has been analytically discussed, and it is shown that the one-periodic wave solutions approach the one-soliton solutions when the amplitude $\eta \to 0$.