Topological Phase Transition of Non-Hermitian Crosslinked Chain

The contents of topological classification of matter are enriched by non-Hermiticity, such as exceptional points, bulk-edge correspondence, and skin effects. Physically, gain and loss can be introduced by imaginary on-site potentials of lattice Hamiltonians, and the topological phase transition for a cross-linked chain in the presence of such non-Hermiticity is investigated. The topological phase diagram in terms of a winding number is obtained analytically with phase boundaries coinciding with the surfaces of exceptional points. The topologically original edge states with distribution mainly at the joints between domains of different phases are protected even for long chains. The non-Hermitian topological feature can also be reflected by vortex structures in the vector fields of complex eigenenergies, expected values of Pauli matrices, and trajectories of these quantities. This model may be implemented in coupled photonic crystals, fermions trapped in optical lattice, or non-Hermitian electrical-circuit lattices, and the edge states are immune to various kinds of disorders until topological phase transition occurs. This work gives insight into the influence of non-Hermiticity on topological phase of matter.     

Light Diffraction of Aligned Polymer Fibers Periodically Dispersed by Phase Separation of Liquid Crystal and Polymer

We have confirmed light diffraction of aligned polymer fibers obtained by a phase separation of an anisotropic-phase solution of liquid crystal and polymer. He—Ne laser light passing through the polymer fibers was scattered in the axis vertical to the fibers, and had two peaks of light intensity symmetrical to the center of the transmitting laser spot. The two peaks were found to be caused by light diffraction due to the periodic polymer-fiber dispersion because the peaks corresponded to values calculated by intervals between the fibers. The periodical fiber networks are considered to be formed by anisotropic spinodal decomposition. This effect can be used to measure the dispersion order of the polymer fibers. © 2004 The Optical Society of Japan     

Stress-Strain Behaviors and Crosslinked Networks Studies of Natural Rubber-Zinc Dimethacrylate Composites

The stress-strain behaviors of natural rubber (NR)-zinc methacrylate (ZDMA) composite have been studied by uniaxial tension. The results indicated that there was a large reinforcement by ZDMA and the NR/ZDMA composites exhibited a high stress-softening effect. Meanwhile, the recovery stretch curve was close to the second stretch curve; thus a weak stress recovery of the composites was shown. The analysis of crosslink density indicated that the damage to the crosslink network was mainly due to the breakage of ionic crosslinks at low strain (100%). A more developed ionic crosslink network was formed at a higher content of ZDMA. When the vulcanizate is subjected to loading in tension, the ionic crosslink network will suffer the force first. Next, the slippage of ionic bonds will take place under the stress. A new ionic crosslink network might be formed rapidly after the ionic bonds were broken during the stretching. Therefore, it could not return to the initial state. The analysis of crosslink density and stress recovery indicated that the rubber chains could be adsorbed to the ZDMA aggregates due to the formation of poly-zinc methacrylate (PZDMA). A molecular analysis of NR/ZDMA composites is proposed in the last part of this article.     

Gelation,Network Structure and Properties of Physically Crosslinked Gelatin Gels: Effect of Salt Cation Valence

A series of physically cross-linked gelatin networks with and without salts (NaCl, CaCl₂ and CrCl₃) were prepared. The effect of the valence of the cations at the same concentration on the gelation of the gelatin was investigated by a rheometer. It was found that both the gelation temperature and the distance between crosslinks of the networks increased with an increase in valence of the cations. However, the opposite trend was observed for the storage modulus of the gels. Moreover, the influences of the valence and concentration of cations on the swelling and thermal behaviors of the gelatin composite films were studied in detail. It was generally observed that the equilibrium swelling ratio (ESR) decreased with salt concentration for all three cations following the trend ESR for Cr³⁺ <Ca²⁺ <Na⁺. However, the glass transition temperature (T_g) showed an opposite dependence on the valence and concentration of the cations. The relationships between the network structure and the properties of the gelatin composite films are discussed based on two effects (shielding and crosslinking effect), caused by the introduction of the salts.     

Phase separation and domain structure of iron-based ordering alloys

The process of ordering with phase separation and domain structure of Fe-Al and Fe-Ga alloys in the regions of mixed phases A2 + B2 and A2 + DO₃ have been investigated by transmission electron microscopy. Observation by dark field micrographs with superlattice reflections revealed a complicated process of phase separation strongly depending on alloy composition and temperature, which was in good agreement with thermodynamics based on Landau's phenomenological theory.     

Gelation Rheology and Water Absorption Behavior of Semi-Interpenetrating Polymer Networks of Polyacrylamide and Carboxymethyl Cellulose

Gelation rheology and swelling behavior of novel semi-interpenetrating polymer network (semi-IPN) hydrogels based on polyacrylamide are described. These hydrogels were prepared by solution cross-linking of partially hydrolyzed polyacrylamide and carboxymethyl cellulose (CMC), using chromium triacetate. Effects of CMC content on the gelation process and swelling behavior in tap water and different electrolyte solutions were investigated. Study of the gelation behavior using dynamic rheometery showed that the limiting storage modulus of the semi-IPN gels increased with increasing CMC content. Enhancement of storage modulus was more than two times for the semi-IPN gels containing 50 wt% CMC. It was also found that increasing the CMC content decreased the loss factor, indicating that the elastic properties of this gelling system increase more strongly than the viscous properties. The swelling ratio of the semi-IPN gels in tap water, NaCl and CaCl₂ solutions, and synthetic oil reservoir water slightly decreased as the concentration of the CMC increased. The improved storage modulus and slightly decreased swelling capacity in oil reservoir water make these semi-IPN hydrogels potentially good candidates for excess water treatment in oil recovery applications.     

偶氮苯液晶薄膜相位共轭的光学记录研究

利用间并四波混频研究了一种偶氮苯液昌聚合物的相位共轭和光学记录特性，在近共振条件下，用低功率Ｎｄ：ＹＡＧ倍频激光得到高效率的相位共轭光和高阶衍射光，当光强达到１０Ｗ／ｃｍ＾２量级时，薄膜显示出光记录效应，即在撒掉写入光之后，相位共轭波并不消失，进一步大光强到１０＾３Ｗ／ｃｍ＾２量级时，出现三组分别只与前向泵浦光，后向泵浦光和信号有关的高阶衍射光。其中观察到第三阶衍射光，且在撒掉任两束光后，所剩一束     

Dynamic Scaling and Fractal Behavior of Phase Dispersion in Multicomponent Polymer Blends

Dynamic scaling and fractal behavior of phase dispersion in a binary polymer mixture of polypropylene with poly(cis-butadiene) rubber during processing in a batch mixer was studied by means of a back small-angle laser scattering (BSALS) online system. In the late stage of phase dispersion, a special fractal behavior was found; different overlapped line groups existed simultaneously and the temporal distribution was stochastic. We defined the special behavior as quasi-self-similarity and calculated the fractal dimension, D _p, by using the power spectrum method. The results show that the evolution of different fractal dimensions with time is consistent with average chord length of the dispersed phase.     

Critical Behavior of Nonlinear Properties in Percolating Superconductor/Nonlinear-Normal Conductor Networks

The critical behavior of nonlinear response in random networks of superconductor/nonlinear-normal conductors below the percolation threshold is investigated. Two cases are examined: (i) The nonlinear normal conductor has weakly nonlinear current (i)-voltage (ν) response of the form ν = ri + bi^α (bi^α-1《t and α > 1). Both the crossover current density and the crossover electric field are introduced to mark the transition between the linear and nonlinear responses of the network and are found to have power-law dependencies ～(f_c - f)^H and ～(f_c - f)^M as the percolation threshold f_c of the superconductor is approached from below, where H = ν_d - s_d > 0, M = ν_d > 0, ν_d and s_d are the correlation length exponent and the critical exponent of linear conductivity in percolating S/N system respectively; (ii) The nonlinear-normal conductor has strongly nonlinear ν-i response, i.e., i = X^να The effective nonlinear response X_e, behaves as X_e ～(f_c - f)^-W(α), where W ( α ) is the critical exponent of the nonlinear response x_e(α) and is α-dependent in general. The results are compared with recently published data, reasonable agreement is found.     

Influence of Quantal and Statistical Fluctuations on Phase Transitions in Finite Nuclei

Investigations on thermal evolution of pairing-phase transition and shape-phase transition in light nuclei are made as a function of pair gap, deformation, temperature and angular momentum using a finite temperature statistical approach with main emphasis to fluctuations. The occurrence of a peak structure in the specific heat predicted as signals of the pairing-phase and shape-phase transitions are reviewed and it is found that they are not actually true phase
transitions and it is only an artifact of the mean field models. Since quantal number and spin fluctuations and statistical fluctuations in pair gap, deformation degrees of freedom and energy when incorporated, it wash out the pairing-phase transition and smooth out the shape-phase transition. Phase transitions due to collapse of pair gap and deformation is discussed and a clear picture of pairing-phase transition in light nuclei is presented in which pairing transition is reconciled.     

Structure Development via Reaction-Induced Phase Separation in Polymer Mixtures: Analysis of Early- and Late-Stage Demixing and Computer Simulations at Non-Isoquench Depths

The effects of phase separation during polymerization of a monomer/polymer mixture were studied. The kinetics of the spinodal decomposition of glycidyl phenyl ether/polystyrene (95/5) during polymerization was investigated using a light-scattering technique. This phase separation during polymerization was comparatively different from the one observed at the isoquench depth such that (i) there was significantly more time before any observable fluctuation, and (ii) the periodic distance of the resulting two-phase structure in the later stages decreased with time. To further investigate the influence of a continually increasing quench depth on phase separation, a diglycidyl aminophenol/diglycidyl ether of bisphenol A (50/50) system with a simple phase diagram was investigated using ultra-small-angle X-ray scattering analysis, and a similar phase separation behavior was observed. Furthermore, computer simulations using the dynamic self-consistent field method were performed to interpret polymer morphology during the demixing driven by chemical reactions. The simulation results suggested that the periodic distance of the resulting two-phase structure formed in the later stages decreases with time. The time dependence of the concentration fluctuations observed in these simulations provided a satisfying explanation for the morphologies formed as a result of a continuously increasing quench depth.     

Swelling Behavior of Physically Cross-Linked Gelatin Gels in Varied Salt Solutions

A series of physically cross-linked gelatin networks were prepared and the effects of salt concentration and chemical valence of the salt ions on the swelling properties of the gelatin gels were studied in detail. It was found that the swelling behaviors as polyelectrolytic or polyampholytic gels depended on the charge distribution on the gelatin chains. The swelling capacity of polyelectrolytic gels with excess positive charges decreased with an increase in salt concentrations. However, the swelling capacity of polyelectrolytic gels with excess negative charges showed a nonmonotonic change with salt concentration. For polyampholytic gels, the equilibrium swelling ratio increased monotonously with the concentration of NaCl and CaCl₂ solutions_. On the other hand, the swelling capacities of the polymer networks increased first and were then followed by a decrease with an increase in the concentration of AlCl₃ solution. Moreover, the swelling kinetics of the gelatin gels in varied salt solutions with different concentrations was also investigated.     

Phase and number fluctuation of the orthonormalization eigenstates of α~k

In this paper,the phase fluctuations of the orthonormalization eigenstates ofa~k(k>3)were calculated in coherent state representation.The results show that the fluctuat-ing properties of cosine and sine operators are the same,the phase fluctuations of│ψ_j〉_k(j ≠0)are always equal to 1/2,and the phase fluctuations of │ψ_0〉_k are the increasing function of│a│~2.When │a│~2→0 and │a│~2→∞,the limit values of phase fluctuations are 1/4 and 1/2respectively.The uncertainty relation between the particle number and the phase was dis-cussed.     

Temporal Behavior of Phase Conjugate Wave in Self-Pumped Phase Conjugator with Internal Total Reflection

Several temporal behaviors of the phase-conjugate output of a self-pumped phase conjugator with internal total reflection in BaTiO₃ crystal have been investigated as a function of the beam entrance position and incident angle on the crystal. Different sets of these conditions cause different behavior of phase conjugate wave which are unstable or pulsed output as well as temporally stable output. Classification of these temporal behaviors in phase conjugate wave by incident condition are shown.     

Structural,Elastic, and Electronic Properties of a New Phase of Carbon

Based on density function theory with the ultrasoft pseudopotential scheme in the frame of the local density approximation and the generalized gradient approximation, the structural, elastic, and electronic properties of carbon with P222₁ phase have been systematically studied in this paper. The calculated results show that the P222₁ phase of carbon is mechanically stable and dynamically stable at ambient pressure. The anisotropy studies of Young's modulus, Poisson's ratio, shear anisotropic factor, the percentage of elastic anisotropy for bulk modulus, the percentage of elastic anisotropy for shear modulus and the universal anisotropic index show that P222₁ phase of carbon exhibits anisotropy. In addition, P222₁ phase is an indirect semiconductor with bandgap of 3.423 eV. But, the band gap of P222₁ phase for carbon increase with increasing pressure.     

Numerical Simulation of Phase Separation Kinetic of Polymer Solutions Using the Spectral Discrete Cosine Transform Method

A spectral discrete cosine transform (DCT) method was used to solve numerically the spatio-temporal nonlinear Cahn-Hilliard equation for a temperature-induced phase separation process of a polymer solution. The properties of a high molecular weight polystyrene solution were used in the model to reflect the behavior of a real world polymer system. Based on the value of the initial concentration, three different final morphologies of the phase separated system, granular, interconnected, and microcellular, were identified. It was shown that the initial concentration is the main factor to determine the high rate of the phase separation when the phase separation time is the primary desired parameter. The degree of phase separation, as a quantitative measure of the phase separation process, indicates the rate and amount of separated polymer material for practical applications. The model is capable of providing quantitative information of morphology evolution during phase separation processes for microstructure control purposes. The structure factor profile was extracted as a theoretical output that enables comparison with scattering experiments observations as the finger-print of phase separation morphological evolution. It is shown that the DCT method is a very suitable and feasible method for solution of the nonlinear partial differential equation of phase separation kinetics.     

Preparation and Swelling Behavior of Partially Hydrolyzed Polyacrylamide Nanocomposite Hydrogels in Electrolyte Solutions

In this research, nanocomposite hydrogels were prepared by cross‐linking of partially hydrolyzed polyacrylamide/sodium montmorillonite aqueous solutions with chromium triacetate. The gelation process and influence of nanoclay content and salt concentration on swelling behavior were investigated. Study of gelation behavior using dynamic rheometry method showed that increasing the nanoclay content decreases the storage modulus, due to the partial adsorption of polymer chains onto the clay surface and ionic interaction between negative layers of sodium montmorillonite and Cr.³⁺ By increasing the cross‐linker concentration of the gelation system, the viscous energy dissipation properties of the nanocomposite gel decreases. Swelling ratio of the nanocomposite gels in distilled water decreased as the concentration of the nanoclay increased. However, nanocomposite gels showed lower salt sensitivity in electrolyte media compared with unfilled gels.     

锗R8相结构的压力效应及电子性质

 使用第一性原理方法研究了锗R8相在压力下的电子结构。计算基于平面波基组,使用模守恒赝势和局域密度近似。对锗R8相结构参数的压力依赖性也进行了研究,包括晶格常数、伞状角、原子位置参数随压力的变化情况。计算得到的R8相的能带结构表明,锗R8相属于半金属相。对总的态密度和分波态密度进行了分析,并考虑了轨道分布情况,态密度呈现出带边的锐化。同时得到锗R8相的两种不同键的键长随压力的变化情况,并分析了这种变化的起因。