Diffusion of ethylene glycol accompanied by reactions in poly(ethylene terephthalate) melts

Diffusion coefficients of ethylene glycol (EG) have been measured in poly(ethylene terephthlate) (PET) melts by a quartz-spring sorption apparatus. A simple mathematical model was developed to investigate the sorption behavior accompanied by chemical reactions of EG and PET at high temperatures. Diffusion coefficients are deduced from experimental data for an asymptotically thin sample in order to minimize the effects of reactions. The diffusion coefficient of EG is strongly dependent on the vapor pressure of EG and temperature but not on the molecular weight of PET in this experimental range (degree of polymerization 80–120). The diffusion coefficient of EG in PET melt at 265°C is 2.58 × 10^?7 cm²/s at the limit of zero concentration of EG. The activation energy for diffusion is 38.4 kcal/gmol, and the heat of solution for sorption is ?44.9 kcal/gmol. The concentrations of the volatile materials resulting from reactions in PET-EG system were analyzed with gas chromatography. In addition, a fit of the current model to experimental data yields frequency factors for the polymerization reaction (k₁) and the acetaldehyde formation reaction (k₂) to be 5.84 × 10⁸ cm³/mol ? min and 3.90 × 10¹¹ min^?1, respectively.     

JSOG中水蒸汽含量的模拟计算

氧碘化学激光（简称 COIL）系统中，水是影响激光功率输出的最重要的原因之一。气流中的水不仅对激发态碘原子有严重的猝灭作用，另外对碘分子解离、超音速流动特性也有很坏的负面作用。单重态氧发生器的BHP（Basic Hydrogen Peroxide ）溶液是最主要的水蒸汽源。利用传质模型对射流式单重态氧发生器（简称JSOG）中产生的水蒸汽进行了计算，所得的数值结果与实验测量结果基本相符。根据模拟结果，对发生器的设计及实验条件进行了优化。     

Experimental investigation of supersonic radiation propagation in low-density plastic and copper-doped foams

1 Introduction The investigation of supersonic radiation wave transporting in low density foam pro-duced by thermal radiation is of crucial importance in inertial confinement fusion (ICF) research[1]. When the intense radiation flux is incident in the media, first, a supersonic heat wave is formed which propagates into the undisturbed material. In time, due to the increasing mass of heated material, it slows down and is overtaken by a shock wave,thus becoming of the ablative type. Normally, …     

Electrokinetic control of fluid in plastified laser-printed poly(ethylene terephthalate)-toner microchips

The application of plastified laser-printed poly(ethylene terephthalate)(PET)-toner microchips to capillary electrophoresis was investigated. Electroosmotic flow was observed in the direction of the cathode for the buffer system studied (phosphate, pH 3–10). Average electroosmotic mobilities of 1.71×10^–4 to 4.35×10^–4 cm² V^–1 s^–1 were observed from pH 3 to 10. This variation suggests that silica fillers in the toner and on the surface of the polymer dominate the zeta potential of the material, which is also confirmed by XPS measurements. Dopamine and catechol were used as model analytes for microchip electrophoresis in combination with electrochemical detection. Results show that these two analytes can be efficiently separated and detected electrochemically with the plastified laser-printed PET-toner microchips.     

应用核磁共振进行聚驱后泡沫驱油特性研究

采用并联岩心进行聚驱后泡沫驱油实验,利用核磁共振技术,对驱替后岩心的不同直径孔隙内的流体分布进行了研究,得到了水驱、聚合物驱、泡沫驱替阶段的驱出油的孔径范围以及剩余油分布.实验结果表明,与水驱和聚合物驱相比,泡沫驱增大了波及的孔径的范围.泡沫可以在水驱和聚驱易发生窜流的大孔径通道形成封堵,从而波及到了水驱和聚驱未波及到的孔径,不但大幅度的提高了低渗岩心的采收率,也驱出了部分高渗岩心的小孔径的油.     

Chromotropic acid-functionalized polyurethane foam: A new sorbent for on-line preconcentration and determination of cobalt and nickel in lettuce samples

A chromotropic acid-functionalized polyurethane foam has been developed for use in an on-line preconcentration system for cobalt and nickel determination. The packing material was prepared by covalent coupling of chromotropic acid with the polyurethane foam through an azo group. Co and Ni ions were sorbed in the mini-column, from which they could be eluted directly to the nebulizer-burner system of a flame atomic absorption spectrometer. Elution of cobalt and nickel from the mini-column can be accomplished with 0.50 and 0.75 M HCl solutions, respectively. The enrichment factors obtained were 22 (Co) and 27 (Ni), for 60 s preconcentration time, and 57 (Co) and 59 (Ni), if a preconcentration time of 180 s was used. Under the optimum conditions, the proposed procedure allowed the determination of metals with detection limits of 0.43 (cobalt) and 0.52 microg/L (nickel), respectively, on using preconcentration periods of 180 s. The accuracy of the developed procedure was evaluated by analysis of the certified reference materials NIST 1515 Apple Leaves and NIST 1570a Spinach Leaves. The method was applied to the analysis of lettuce samples. The contents of cobalt in the samples analyzed varied from 0.75 to 0.98 microg/g. Nickel was not detected in the lettuce samples.     

Comments on ultra-high-energy photons and D-foam models

We revisit the constraints that the non-observation of ultra-high-energy photons due to the GZK cutoff can impose on models of Lorentz violation in photon propagation, following recent work by Maccione, Liberati and Sigl (2010) [arXiv:1003.5468] that carries further an earlier analysis by the present authors [J. Ellis et al., Phys. Rev. D 63 (2001) 12402, hep-th/0012216]. We argue that the GZK cutoff constraint is naturally evaded in the D-brane model of space–time foam presented recently by the present authors [J. Ellis et al., Phys. Lett. B 665 (2008) 412, arXiv:0804.3566], in which Lorentz-violating effects on photon propagation are independent of possible effects during interactions. We also note a novel absorption mechanism that could provide a GZK-like cutoff for photons in low-scale string models.     

Lattice Boltzmann 3D flow simulations on a metallic foam

In this paper a lattice Boltzmann method (LBM) is used to simulate isothermal incompressible flow in a RCM-NCX-1116 metallic foam. The computational technique is a multiple relaxation time (MRT) lattice Boltzmann equation model. Computer aided X-ray micro-tomography is used to obtain 3D images of the metallic foam, providing the geometry and information required for LB simulations of a single phase flow.Pressure drops are computed and successfully compared to experimental measures and correlated with Ergun’s equation. Invariance of Ergun’s parameters A and B with the sampling rate of the images is observed.     

Morphology and Pore Size Distribution of Biocompatible Interconnected Porous Poly(L-lactic acid) Foams with Nanofibrous Structure Prepared by Thermally Induced Liquid–Liquid Phase Separation

Biocompatible, highly interconnected microporous poly(L-lactic acid) (PLLA) foams with nanofibrous structure, containing pores with average diameter below 1 μm and fibers with diameters of 10² nm scale, were prepared through the thermally induced liquid–liquid phase separation (TIPS) method consisting of quenching of the PLLA solution, freeze extraction with ethanol, and vacuum drying. Diverse foam morphologies were obtained by systematically changing parameters involved in the TIPS process, such as polymer concentration, solvent composition, and quenching temperatures. The morphology of different foams was examined by scanning electron microscopy to characterize the pore size and the pore size distribution. The results showed that most porous foams had a nanofibrous structure with interconnected open pores. In the case of using tetrahydrofuran (THF) as solvent, the higher the PLLA concentration, the smaller the average pore diameter and the narrower the pore size distribution. In the case of using the mixed solvents of THF/DOX (1,4-dioxane) with higher than 6/4 volume ratio, there appeared a maximum value of average pore diameter and a widest pore size distribution at 0.09 g/mL PLLA concentration. The average pore diameter of the foams increased with increasing DOX content in the mixed solvent and ranged from 0.2 to 0.9 μm depending on the process parameters. When the DOX content reached 60% by volume, the morphology of the foams contained some large closed pores with diameter ranging from 1 to 10 μm. By decreasing the quenching temperature, the average pore diameter of foams decreased and the pore size distribution became narrower. All the pore size distribution fit F-distribution equations.     

Study on Phase‐Change Characteristics of PET‐PEG Copolymers

Polyethylene glycol (PEG) was selected as a phase‐change material (PCM) and the phase‐change fibers of its copolymers with polyethylene terephalate (PET), PET‐PEG, were successfully prepared by melt spinning. The PET‐PEG copolymers have solid‐solid phase change characteristics at 10–60°C without obvious liquid substance appearing, while PET/PEG blends will lose their phase‐change characteristics since the PEG of the blends may melt and leak under high temperature. By controlling the molecular weight and relavent proportion of PEG added, the phase‐change temperature range and the enthalpy can be adjusted.