Parameter Determination for Reductive Dechlorination of Chlorinated Solvents

The contamination of subsurface due to the chlorinated solvents such as tetrachlorethylene (PCE) and trichlorethylene (TCE) is one of the most difficult environmental problems to treat. Bioremediation has been shown by many researchers to be a remedial alternative for this type of contamination. Chlorinated solvents are not directly mineralized but rather are transformed by microorganisms into one or more intermediate compounds before converting into a final compound. These sequential reactions, termed “reductive dehalogenation”, consist of replacing a chlorine atom by a hydrogen atom. The pathway of degradation of PCE can be expressed by the following scheme PCE → TCE → DCE → VC → ETH, where dichloroethene (DCE), vinyl chloride (VC) and finally ETH is ethylene. Since the biotransformation rate coefficients of each intermediate compound are different, they have to be determined very precisely to establish an effective treatment operation. The sequential decay can be described by Michaelis–Menten’s kinetics, which constitutes a highly nonlinear system of ordinary differential equations (ODEs). This is very sensitive to the changes of biotransformation rate coefficients. In this study we introduce a methodology how to numerically estimate the rate coefficients for Michaelis–Menten’s equations from the knowledge of the concentrations of PCE, TCE, DCE, VC and ETH. The efficiency of the proposed method is demonstrated on some examples. Estimated biotransformation coefficients are employed to predict the concentrations of chlorinated solvents. Computations and measurements show a very good agreement.     

Logistic模型的预测应用两例

利用灰色建模法对Logistic模型中的参数进行估计,并将其应用于温州人口以及温州民用汽车拥有量的预测上取得了良好的预测效果.     

Aging, rejuvenation and memory phenomena in spin glasses

In this paper, we review several important features of the out-of-equilibrium dynamics of spin glasses. Starting with the simplest experiments, we discuss the scaling laws used to describe the isothermal aging observed in spin glasses after a quench down to the low-temperature phase. We report in particular new results on the sub-aging behaviour of spin glasses. We then discuss the rejuvenation and memory effects observed when a spin glass is submitted to temperature variations during aging, from the point of view of both energy landscape pictures and real-space pictures. We highlight the fact that both approaches point out the necessity of hierarchical processes involved in aging. Finally, we report an investigation of the effect of small temperature variations on aging in spin glass samples with various anisotropies which indicates that this hierarchy depends on the spin anisotropy.     

变参数非等间距GM(1,1)模型及应用

在对非等间距序列建模时,考虑到序列本身的特点,结合GM(1,1)模型的建模过程,提出了一种对非等间距序列建立变参数GM(1,1)模型的方法,并将其应用于具体实例进行分析,计算结果表明本文提出的方法具有较高的精度,从而为解决非等间距序列的拟合及预测问题提供了一种比较好的思路.     

基于公共因子扩展的因子分析的EM算法

在一般因子分析模型的基础上,假设连续的潜在向量(公共因子)与另一观察随机向量有关,并假定是一个多元线性回归模型,对由此扩展的因子分析模型进行分析.主要通过EM算法给出模型中参数的估计.文中给出了它的详细推导过程.     

Changes in electrical resistance of carbon‐black‐filled silicone rubber composite during compression

We studied the changes in the electrical resistance of carbon black filled silicone rubber composite, which is the sensitive element of the flexible force sensor, as a function of time during compression. The experimental results show that there is a sudden increase of the electrical resistance along with the sudden increase of the stress immediately after the compression. When the sample strain is kept constant, the electrical resistance and the stress both decay with time. The data of the stress relaxation and the resistance relaxation both can be fitted by the linear combination of two exponential functions. Based on the shell structure theory, the experimental phenomena are explained from the view that the uniaxial pressure induces the changes in the effective conductive paths. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2700–2706, 2007     

Solubility parameters of poly(sulfonyldiphenylene phenylphosphonate) and its miscibility with poly(ethylene terephthalate)

The solubility behaviors of poly(sulfonyldiphenylene phenylphosphonate) (PSPPP), a very efficient flame retardant for poly(ethylene terephthalate) (PET), in more than 50 solvents were examined. Its solubility parameters (δ) were determined by the intrinsic viscosity and turbidic titration methods. The two methods obtained consistent results, δ = 21.0–21.6 J^1/2/cm^3/2 and δ = 21.0 J^1/2/cm^3/2, and the three‐dimensional solubility parameters were δ_d = 18.9 J^1/2/cm^3/2, δ_p = 8.8 J^1/2/cm^3/2, and δ_h = 5.9 J^1/2/cm^3/2. The miscibility of PSPPP with PET was estimated by the calculation of the heats of mixing, which were related to the difference between the solubility parameters of PSPPP and PET. Fourier transform infrared was used to examine the interactions between PSPPP and PET macromolecules, which were the internal factors of polymer–polymer miscibility. The results showed that PSPPP and PET were miscible within a very wide composition range, especially with less than 15 wt % PSPPP, a composition of interest for the preparation of flame‐retardant PET. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2296–2301, 2003     

利用光子统计概率测量单分子光子源的信号背景比

理论上研究了基于Hanbury Brown Twiss 探测方式，利用单光子和双光子统计概率P RS(1),PRS(2),直接测量单分子光子源的信号背景比.在研究过程中同时考 虑到单分子布居于暂稳态和探测器量子效率对测量结果的影响.在满足PRS(1)2 PRS(2)-3PRS(2)的条件时，研究给出了一种有效测量信号背景比的方 法SBR=P2RS(1)/2PRS(2).另外，分析讨论了Mandel参数Q 与信号背景比之间的关系. 关键词： 单分子光子源 信号背景比 光子统计 暂稳态 Mandel参数     

射频场照射下同核体系的弛豫

根据WBR理论和同核体系的特点,构造出了一个相应的三维转动,利用Wigner旋转矩阵的特性并借助于计算机代数语言,计算出了射频场照射下同核体系完整的弛豫方程组.在此基础上,给出了射频场照射下纵向与横向弛豫时间的计算公式,并从理论上研究了射频场的照射对同核体系弛豫的影响.研究结果表明:1)射频场的照射对同核体系的弛豫有一定程度的影响.2)在射频场的照射下,同核体系的纵向弛豫时间T1小于无射频场时的T1,而横向弛豫时间T2大于无射频场时的T2.3)纵向弛豫时间T1随射频场的增强而逐渐减小,横向弛豫时间T2随射频场的增强而逐渐增大. 关键词： 核磁共振 弛豫 射频场 三维转动