Small angle x—ray scattering study on the conformation of polystyrene in toluene during adding anti—solvent CO2

The conformatiopn of polystyrene in the anti-solvent process of supercritical fluids(compressed CO2 polystyrene toluene)has been studied by small angle x-ray scattering with synchrotron radiation as an x-ray source.Coilto-globule transformation of the polystyrene chain was observed with the increase of the anti-solvent CO2 pressure;i.e.polystrene coiled at a prssure lower than the cloud point pressure(Pc)and turned into a globle with a uniform density at pressures higher than Pc.Fractal behaviour was also found in the chain contraction.and the mass fractal dimension increased with increasing CO2 pressure.     

INFINITE PERIODIC SOLUTIONS TO A CLASS OF SECOND-ORDER NEUTRAL DIFFERENTIAL EQUATIONS

By means of variational structure and Z2 group index theory, we obtain infinite periodic solutions to a class of second-order neutral differential equations.     

Improvement of wettability and detergency of polymeric materials by excimer UV treatment

The 172 nm ultraviolet (UV) excimer light was exposed to polyethylene (PE), polypropylene, poly(ethylene terephthalate) and nylon 6 surfaces in ambient air. Changes in the contact angle and particle deposition in liquid due to UV treatment were investigated from the viewpoints of wettability and detergency. For all polymers, the wettability and the acid-base component of the surface free energy evaluated by the contact angle measurements increased remarkably by UV treatment of 1 min. From surface analyses of the polymer surfaces by X-ray photoelectron spectroscopy and atomic force microscopy, oxygen concentration was found to increase after UV treatment, whereas little topographical change was observed. The deposition of PE and nylon 12 particles onto the polymer surface was examined, in situ, in water, water/ethanol mixture, ethanol and n-heptane. Although the number of deposited particles was largely dependent on the kinds of the particle, the substrate and the liquid, a significant decrease in the deposition due to UV treatment was confirmed in any system.     

Influence of the β‐crystalline phase on the mechanical properties of unfilled and calcium carbonate‐filled polypropylene: Ductile cracking and impact behavior

The β‐crystalline form of isotactic poly(propylene) (PP) has been long recognized to have a greater mechanical absorption capacity than the α‐crystalline form. This is of major importance for improving impact properties and crack resistance of injection‐molding parts. Unfilled PP samples together with calcium carbonate‐filled PP samples having various β/α‐phase ratios, with nearly constant morphological parameters, have been investigated from the standpoint of ductile crack propagation and impact behavior. The presence of the β‐crystalline phase turned out to improve both properties. The β spherulites are notably more prone to craze initiation than α spherulites that display a propensity for cracking. Subsequent crack propagation appears to be faster in the latter ones. The plastic zone ahead from the crack tip broadens, and the specific plastic energy increases with increasing β‐phase content. The lower elastic limit of the β phase is likely to promote the early crazing. However, the suspected higher density of tie molecules in β spherulites provides more numerous and stiffer microfibrils. The impact strength of PP is also improved by the presence of β crystals as a result of greater energy‐absorption capabilities. However, filled samples turned out insensitive to the β phase. A discussion is made about the origins of the β‐phase‐induced improvement of the mechanical properties. The possible role of the β → α transition is also explained. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 31–42, 2002     

双连续可调偏光分束器

介绍了一种性能优良的偏光分束器。该器件由4/2波片和可调分束角棱镜组合而成,同时具备强度比和分束角连续可调的功能。文中给出了此器件的结构、原理、理论分析和性能实验研究。实验与理论相符。     

Monte Carlo studies of the square Ising model with next-nearest-neighbor interactions

We apply a new entropic scheme to study the critical behavior of the square-lattice Ising model with nearest- and next-nearest-neighbor antiferromagnetic interactions. Estimates of the present scheme are compared with those of the Metropolis algorithm. We consider interactions in the range where superantiferromagnetic (SAF) order appears at low temperatures. A recent prediction of a first-order transition along a certain range (0.5–1.2) of the interaction ratio (R=J_nnn/J_nn) is examined by generating accurate data for large lattices at a particular value of the ratio (R=1). Our study does not support a first-order transition and a convincing finite-size scaling analysis of the model is presented, yielding accurate estimates for all critical exponents for R=1. The magnetic exponents are found to obey “weak universality” in accordance with a previous conjecture.     

激发能升高级联裂变到瞬发多重碎裂的演化

分析⁴⁰Ar+¹⁵⁹Tb、¹⁹⁷Au、²⁰⁹Bi(25MeV/u)中心碰撞产生的三体碎片产物的角关联,配合Ar+Au(60MeV/u)三体出射的数据,分析非完全熔合反应产生的高激发核衰变的演化过程,证明了在25MeV/u入射能时激发核产生的三重大质量碎片是级联的两次出射的裂变形成的,其时间差尺度大约为1000fm/c,而对60MeV/u入射能下的激发核观察到重碎片在120°附近出现强的角关联,这在理论上解释为发射时间差较短,即出现了瞬发的多重碎裂.     

Local Isoperimetric Inequalities for Sectors on Surfaces and Cones

On surfaces we give conditions under which the solution of a restricted local isoperimetric problem for sectors with small solid angle is the circular sector and we characterize these surfaces. Also we study this problem for general spherical cones on hypersurfaces in higher dimensional Riemannian manifolds.