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.     

Experimental study of the cavitation noise and vibration induced by the choked flow in a Venturi reactor

In this paper, the cavitation performance and corresponding pressure pulsation, noise and vibration induced by the choked cavitating flow in a Venturi reactor are investigated experimentally under different cavitation conditions by using high-speed camera and high frequency sensors. Based on the instantaneous continuous cavitation images, the Proper Orthogonal Decomposition (POD), a tool to analyze the large-scale cavitation flow structure, is applied to investigate the choked cavitating flow dynamics. The POD results show that two mechanisms, re-entrant jet flow mechanism and shock wave mechanism, govern the shedding and collapse of cavitation cloud at different pressure ratios. These mechanisms contribute to the variation of pressure pulsation, noise and vibration at different pressure ratios. The pressure pulsation spectrum behaves differently in various cavitation regions induced by the choked cavitating flow. Due to the existence of low pressure in re-entrant region, the influence of high frequency fluctuation on pressure pulsation caused by re-entrant flow is small. Moreover, with the increase of pressure ratio, the induced noise and vibration intensity decreases gradually, then increases and reaches a maximum value. Finally, it drops to a low and stable level. Despite different inlet pressures, the intensity of cavitation noise and vibration reaches the maximum value at the same pressure ratio. Specifically, the FFT analysis of noise and vibration signals indicates that low frequency component prevails at small pressure ratio owing to the re-entrant jet mechanism, while high frequency component prevails at large pressure ratio owing to the shock wave mechanism. The relationship between the choked cavitation dynamics and the induced pressure pulsation, noise and vibration in the Venturi reactor is highlighted. The results can provide guidance for the optimal operation condition of the Venturi reactor for cavitation applications such as water treatment.     

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.     

Wave-based vibration control of large cable net structures

Large cable net structures have been widely applied in aerospace engineering due to the feature of light-weight, high packaging efficiency, and high thermal stability. Structural vibrations induced by a variety of disturbances are inevitable in the space environment, resulting in the requirement of effective vibration control strategies for large cable net structures. Since the large cable net structures have many closely spaced vibrational modes in the range of low frequencies, traditional modal based control may cause modal truncation and spillover problems. In this paper, a wave-based boundary control strategy is adopted and its effectiveness to control the vibration of cable net structures is investigated, by transfer function analysis and numerical methods. It is found that the structural vibration can be absolutely resisted by applying the wave-based boundary controllers onto all the exterior nodes, when disturbances come from the external boundaries of the cable net. Our results in this paper can provide a theoretical basis for the vibration control of large cable net structures.     

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     

Influence of moisture and CO2 on the material behavior of thermoplastic elastomers for beer bottle closures

Metal closures with a polymer-based sealing for beer bottles have been known since the late nineteen-sixties. However, to what extent which parameter of the polymer sealing gasket plays a role in closure performance to keep the beer quality to a highest level possible is not fully understood. For this purpose three thermoplastic elastomer (TPE) liners were investigated by differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectrometry, dynamical mechanical analysis (DMA), scanning electron microscopy (SEM) and surface roughness in order to understand the effect of relative humidity (RH) and carbon dioxide (CO₂) on their physical and chemical properties as well as their macromolecular structures. The TPEs’ viscoelasticity in the frequency domain under different isothermal conditions was evaluated. RH and CO₂ were effective for changes in thermomechanical and surface properties. Liner C was found to have lower seal performance attributed to its relatively higher crystallinity, stiffness, weaker bond structure and rougher surface. Vibrations can lead to seal leakage in Liner B due to its higher damping behavior during production and transportation. Liner A outperforms others due to stabile behavior within the operational temperature range.     

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。