Nickel coated on beech wood by electroless nickel coating: effects of complexing agent concentrations on nickel film properties

In order to obtain beech wood substrates with new functions as conductive materials and to develop their utilities in industrial fields, the technique of electroless nickel coating on the beech wood substrate was employed. The influence of complexing agent concentration [Na₂EDTA·2H₂O] on the nickel surface resistivity was studied. The process conditions were Ni(CH₃COO)₂·4H₂O 0.103?mol/L, CH₃CHOCOOH 18.18?mL/L, N₂H₅OH 54.54?mL/L, NaOH 0.193?mol/L, pH value of 9.5, temperature of 75?°C, and the complexing agent concentration varied between 0.012 and 0.061?mol/L. By means of XRD, EDXRF, and SEM, the chemical composition and morphology of the prepared films were investigated. The results showed that when the complexing agent concentration increased from 0.012 to 0.061?mol/L in the electroless nickel coating baths, the gained nickel mass on the beech wood substrate decreased from 17.04 to 9.03?mg/cm², the nickel crystallite sizes reduced from 16.1 to 1.41?nm and the electric measurements demonstrated that the nickel surface resistivity rose from 0.004 to 192.16?kΩ/cm².     

Polymerization-induced Phase Separation: Phase Behavior Developments and Hydrodynamic Interaction

The process of polymer synthesis based on polymerization-induced phase separation (PIPS) is revisited from the theoretical point of view. Cahn–Hilliard–Cook theories for spinodal decomposition are adapted to describe the kinetics of phase separation and deduce the time-resolved scattering function, while the double reaction model is used to describe the kinetics of polymerization. Coupling of these two kinetics is provided by the Carother's equation relating the fraction of reacted monomers to the degree of polymerization at time t, denoted N(t). It is argued that the approach to criticality is governed by a critical parameter, χ_c, that is different from the usual parameter for spinodal decomposition, χ_s, deduced from the second derivative of the free energy. While the latter parameter depends on the reciprocal degree of polymerization N^?1(t), the former one depends on its time integral. This leads to significant consequences on the phase behavior developments during the PIPS process. Hydrodynamic interactions are found to speed up the emergence of instability modes. Although the qualitative trends remain similar to those of the Rouse dynamics, important quantitative changes are found due to the long-range viscous flow effects.     

The critical behavior of Kac-type models for semi-infinite systems

The critical behavior of the layer magnetizations and local susceptibilities of theD-vector lattice models with Kac-type ferromagnetic interactions for a semi-infinite system is studied. These local quantities behave less singularly than the bulk ones, showing that this is not peculiar to the two-dimensional Ising model. Moreover, the limiting form (at the critical point) of the magnetization profile can be obtained, which, when properly scaled, satisfies the minimum condition in the Landau theory for a semi-infinite continuous system. Landau-type critical behavior is thus recovered.     

各向异性材料中共线刚性线夹杂的纵向剪切问题

本文研究各向异性材料中共线刚性线夹杂，（有时称作“硬裂纹”或“反裂纹”问题）的纵向剪切问题。利用复变函数方法，提出了一般问题的公式和某些实际重要问题的封闭形式解，考察了刚性线端点附近的应力分布．从本文解答的特殊情形，可以直接导出各向同性材料相应问题的公式和结果，包括某些已有的结果￣［７］．     

基于连续量子级联激光器的1103.4cm–1处NH3混叠吸收光谱特性研究

由于NH3在大气气溶胶化学中具有重要作用,所以快速和精确反演NH3浓度对环境问题非常重要.本文以9.05μm的室温连续量子级联激光器(quantum cascade laser,QCL)作为光源,采用波长扫描直接吸收可调谐二极管激光吸收光谱(tunable diode laser absorption spectroscopy,TDLAS)技术,研究了QCL在1103.4 cm–1的光谱特性,获得了激光器控制的温度电流与波长的关系.设计了QCL二级温控的低压实验平台,测量氨气在1103.4 cm–1处的6条混叠吸收线,在降低压强的情况下谱线展宽变小,使混叠光谱分离,由此计算各条吸收线的线强,进一步对测量不确定度进行分析.针对混叠严重的光谱提出了低压分离单光谱精确反演气体浓度的方法,并进行了实验验证.通过与HITRAN数据库进行结果对比,得出氨气在1103.4 cm–1的实验测量线强值与数据库偏差为2.71%-4.71%,实验测量线强值的不确定度在2.42%-8.92%,极低压条件下反演浓度与实际值的偏差在1%-3%.     

Difference equations in statistical mechanics. I. Cluster statistics models

A review and some new results are presented for several cluster statistics models, solutions of which can be reduced to difference equations. Mathematical techniques suitable for solving these equations are surveyed.     

A thermochemical instability. II. Inhomogeneous fluctuations

The behavior of coupled stochastic fields near a cusp bifurcation is studied. The results are applied to a thermochemical model and the possibility of observing nonclassical critidal behavior is discussed.     

Exact partition functions and correlation functions of multiple Hamiltonian walks on the Manhattan lattice

This is a general and exact study of multiple Hamiltonian walks (HAW) filling the two-dimensional (2D) Manhattan lattice. We generalize the original exact solution for a single HAW by Kasteleyn to a system ofmultiple closed walks, aimed at modeling a polymer melt. In 2D, two basic nonequivalent topological situations are distinguished. (1) the Hamiltonian loops are allrooted andcontractible to a point:adjacent one to another, and, on a torus,homotopic to zero. (2) the loops can encircle one another and, on a torus, canwind around it. Forcase 1, the grand canonical partition function and multiple correlation functions are calculated exactly as those of multiple rooted spanningtrees or of a massive 2Dfree field, critical at zero mass (zero fugacity). The conformally invariant continuum limit on a Manhattantorus is studied in detail. The melt entropy is calculated exactly. We also consider the relevant effect of free boundary conditions. The number of single HAWs on Manhattan lattices with other perimeter shapes (rectangular, Kagomé, triangular, and arbitrary) is studied and related to the spectral theory of the Dirichlet Laplacian. This allows the calculation of exact shape-dependent configuration exponents y. An exact surface critical exponent is obtained. Forcase 2, nested and winding Hamiltonian circuits are allowed. An exact equivalence to thecritical Q-state Potts model exists, whereQ ^1/2 is the walk fugacity. The Hamiltonian system is then always critical (forQ<-4). The exact critical exponents, in infinite numbers, are universal and identical to those of theO(n=Q ^1/2) model in its low-temperature phase, i.e. are those of dense polymers. The exact critical partition functions on the torus are given from conformai invariance theory. These models 1 and 2 yield the two first exactly solved models of polymer melts.     

Fourier acceleration of iterative processes in disordered systems

Technical details are given on how to use Fourier acceleration with iterative processes such as relaxation and conjugate gradient methods. These methods are often used to solve large linear systems of equations, but become hopelessly slow very rapidly as the size of the set of equations to be solved increases. Fourier acceleration is a method designed to alleviate these problems and result in a very fast algorithm. The method is explained for the Jacobi relaxation and conjugate gradient methods and is applied to two models: the random resistor network and the random central-force network. In the first model, acceleration works very well; in the second, little is gained. We discuss reasons for this. We also include a discussion of stopping criteria.