The matric algorithm of Lyapunov exponent for the experimental data obtained in dynamic analysis

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布尔矩阵的幂敛指数集

给出了不含非零对角元的ｎ阶布尔矩阵的幂敛指数集的明显表达式,从而完全解决了布尔矩阵依赖于非零对角元个数的幂敛指数集的刻画问题。     

Stability of Riccati's Equation with Random Stationary Coefficients

The purpose of this paper is to study under weak conditions of stabilizability and detectability, the asymptotic behavior of the matrix Riccati equation which arises in stochastic control and filtering with random stationary coefficients. We prove the existence of a stationary solution of this Riccati equation. This solution is attracting, in the sense that if P _t is another solution, then onverges to 0 exponentially fast as t tends to +∞ , at a rate given by the smallest positive Lyapunov exponent of the associated Hamiltonian matrices. Accepted 13 January 1998     

耦合映象格子系统的相互同步化

研究了两个耦合格子动力系统的非线性相互作用。当两个耦合格子系统一样时,则导致完全同步化。而当两个耦合格子系统的参数不一样或者这两个系统不相同时,则导致广义同步化。计算了Lyapunov指数谱。     

Application of high-frequency ultrasound standing waves for the recovery of lipids from high-fat dairy effluent

Effect of high-frequency ultrasonication was examined on wastewater of a cheese manufacturing plant. Tests were carried out at two frequencies (500 kHz and 1 MHz) and two temperatures (22 and 40 °C). Samples were subjected to different energy densities; 7.5, 30.2, 60.5 and 121.0 J/mL at 500 kHz and 7.9, 31.7, 63.4 and 126.8 J/mL at 1 MHz to observe the creaming and recovery of lipid. These energy densities correspond to 30, 120, 240 and 480 s of sonication. Sonication was performed using a single plate transducer and reflector system at 40 W to create standing wave to coalesce and flocculate lipid globules. Recovery was higher at 40 °C after 480 s of sonication at both frequencies (77% at 500 kHz and 75% at 1 MHz). The lowest recovery of 47% was observed at 500 kHz and 22 °C at all applied energy densities. Changes in particle size and turbidity in the bottom aliquot indicated that high-frequency ultrasound caused coagulation and aggregation and settling of colloidal particles. Increase in particle size was observed to be highest at 1 MHz, 40 °C and 480 s of sonication. These results confirm that high-frequency ultrasound standing wave technology can be used to recover lipid from high-lipid dairy wastewater including that from cheese manufacturing.     

AlN晶体物理气相传输法生长坩埚的热场分析

采用物理气相传输法在钨制坩埚上制备AlN单晶.通过采用COMSOL软件中的固体传热和磁场模块,对AlN晶体生长的坩埚的热场进行仿真,同时针对不同的线圈直径以及不同的线圈位置对坩埚热场的影响进行模拟,提出了相应的处理方式.结果表明:当线圈直径增大,坩埚结晶区和升华区的温度在相同的加热时间下会增加,并且增加的温度存在峰值.当线圈的垂直位置发生变化的时候,结晶区和升华区的温度场也会发生变化,从上向下移动的过程中仍然存在温度的峰值,并且结晶区和升华区的温度关系会发生翻转,导致温度梯度阻碍晶体生长.在晶体生长过程中升华区和结晶区的温度关系依旧会发生翻转.但是通过线圈跟随籽晶表面生长层的变厚而同步移动,可以保持相对稳定的温度关系,维持晶体正常持续生长.     

纯钨红外光谱发射率特性研究

光谱发射率是一个重要的热物性参数,在辐射测温、热传输计算等领域有着广泛的应用。钨作为一种重要的金属,关于其光谱发射率的研究报道较少。利用黑体炉、傅里叶红外光谱仪、加热装置和光学系统搭建了一套能量对比法光谱发射率测量装置,该装置能够测量3~20μm的光谱发射率,测量装置的整体不确定度优于5%。利用该装置测量了纯钨在4个温度点(573, 673, 773和873 K)的法向光谱发射率,重点探讨了氧化、温度、波长和加热时间对纯钨光谱发射率的影响。研究结果表明:纯钨在表面未氧化的情况下,光谱发射率在几个温度点的变化规律基本一致,且数值相差较小,而当其表面发生氧化后光谱发射率迅速增加,在某些波长处出现了强烈的振荡。表面未氧化时纯钨的光谱发射率受温度的影响较小,随着温度的增加仅出现微小的增加,但是当表面发生氧化后,随温度的升高而迅速增大。纯钨的光谱发射率整体上随着波长的增加而减小,但是当表面发生氧化后,由于表面氧化膜与钨金属基底发生干涉效应,在4, 9, 12.5和16.5μm处均出现了峰值。在573和673 K,纯钨的光谱发射率随着加热时间的增加无明显变化。然而,随着温度的升高,在773和873 K时,光谱发射率随着加热时间增加而增大,在773 K时光谱发射率随加热时间的增加增幅较大,因为在该温度点,纯钨表面刚开始发生氧化,氧化速率较大,在873 K时光谱发射率随加热时间的增加增幅较为平缓,并且随着加热时间的增长呈现稳定的趋势。综上,纯钨的光谱发射率在温度较低和表面未氧化时较为稳定。随着温度的升高,当表面发生氧化后,光谱发射率迅速增大,并且在多个波长位置出现了强烈的振荡。由此可见,纯钨光谱发射率受温度、波长、加热时间的影响较大,在实际应用过程中,特别是在辐射测温过程中,如果把纯钨的光谱发射率看做常数将会带来较大的测量误差。该研究将进一步丰富钨的光谱发射率数据,并为其在科学研究和应用中提供数据支持。     

AMS-02超导磁体300K-80K受控冷却系统的工艺流程设计

300K-80K受控冷却系统是AMS-02探测器的低温地面支持设备(CGSE)系统中的重要子系统,其主要作用是实现AMS-02磁体从常温(约300K)到接近液氮温度(约80K)的冷却。对该系统进行了工艺流程设计,在恒温器内设置多个调节阀和温度、压力、流量检测元件,通过自动调节手段控制经该系统冷却后前往磁体的氦气的温度和流量。同时介绍了该系统的组成及低温恒温器、HX1、HX2和HX3的结构和特点。