Diffusion and Internal Friction in Na-Rb Silicate Glasses

The internal friction and self-diffusion coefficients of sodium and rubidium ions for (l-X)Na₂O-XRb₂O-3SiO₂ glasses were measured. Diffusion was measured by radioactive isotopes and a thin-sectioning technique at 350° to 500°C. Internal friction was measured at −140° to 500°C and 0.05 to 6000 Hz. The maximum height for the mixed-alkali internal friction peak occurs at the composition at which the Na and Rb diffusion coefficients are equal. It is concluded that the mechanism responsible for the mixed-alkali peak is a coupled, cooperative rearrangement of sodium and rubidium ions, with the slower moving ion controlling the rate of rearrangement. This mechanism should also apply to other mixed-alkali silicate glasses since the internal friction for these systems is similar.     

DETERMINATION of RESIDENCE TIME DISTRIBUTION of NONSETTLING FOOD PARTICLES IN VISCOUS FOOD CARRIER FLUIDS USING HALL EFFECT SENSORS

Hall effect sensors were used to determine residence time distributions for diced carrot particles in 4% Colflo 67 carrier fluid. Four sensors at either end of a 3.2 m long 2 in. IDF tube viscometer allowed residence times to be measured for carrot particles incorporating a ceramic magnet. Mean particle residence times were greater than mean bulk residence time for 8 mm diced carrots, whereas 15 mm carrots showed trials in which particles travelled faster than the bulk fluid. Increasing concentration of 15 mm diced carrots from 3.25, 6.30, 9.16 to 11.85% w/w resulted in decreasing mean particle residence times from 17.6, 17.0, 15.9 to 14.3 s, with minimum residence times of 16.4, 16.2, 14.8 and 13.4 s, respectively. This sensing technique operates through stainless steel, providing applications for UHT foods containing particles. In addition, the technique was not affected by high particle concentration, and will operate for any distribution of particle size, shape or type.     

Novel microscopy-based approaches to study the film formation mechanism and associated mechanical response in polymer lattices

In this paper, we present the results from novel microscopy-based approaches aimed at providing further insight into the mechanism of film formation and associated mechanical response in polymer lattices. Firstly, a ‘simple’ methodology, combining the use of variable pressure scanning electron microscopy and a recently introduced enhanced coolstage (–50 to +50°C), was successfully developed and not only used to study dynamic processes, e.g. different stages of latex film formation, but also for high-resolution imaging of ‘freeze-dried’ structures. By using the enhanced freeze-drying capability of the system, it was also possible to preserve the structure and features of the studied system with minimum shrinkage and distortion and in the case of polymer lattices at a desired stage of film formation. Moreover, specimens can then be readily imaged, without the need of conductive coatings and at much lower chamber gas pressures, thus minimizing the beam skirting effects and allowing higher resolutions to be achieved. The second and final part of our study consider the mechanical response of the studied latex dried under different conditions, with the particular emphasis on the effects of drying rate [% relative humidity (RH)]. Atomic force microscopy force distance curve measurements revealed that while the %RH did not have an effect on the structures formed, it did have an effect on the adhesive properties of the studied system. It is strongly believed that the methodologies developed and used here can be applied to other material systems, including biologicals and pharmaceuticals.     

用于反射型显示器的光致发光增强技术

摘译电子书市场受众的逐渐增加,极大地促进了人们对低耗、日光下可读反射型显示器的关注。目前的反射显示器通常是黑白的,如亚马逊公司的Kindle电子书使用的是E-Ink Vizplex成像膜;或者仅仅能显示暗淡色域     

Liquid-Phase-Assisted Transformation of Seeded γ-Alumina

α-Al₂O₃-seeded, boehmite-derived γ-Al₂O₃ was transformed in the presence of V₂O₅, resulting in a 205°C decrease in the α-Al₂O₃ transformation temperature and a 74% reduction in the apparent activation energy for the γ- to α-Al₂O₃ transformation at temperatures greater than 850°C. These changes are attributed to the lowered energy barrier for nucleation by seeding and the lowered activation energy for material transport through the liquid relative to the unseeded, solid-state transformation. Growth of the transforming alumina yielded fine-grained α-Al₂O₃ particles which exhibited a highly faceted morphology. It is proposed that the combined control of both nucleation and growth during liquid-phase-assisted transformation provides a potentially powerful technique for tailoring powder characteristics in many material systems which undergo nucleation and growth processes.     

Trying to Do Group Theory with Undergraduates and Computers

This paper discusses the author's efforts to use computers and software as a catalyst for engaging undergraduates in the process of doing mathematics in the context of finite group theory. Examples of questions that have been used to motivate undergraduate research and a classroom case study are presented.     

现实与虚幻之间

1997年初我继续学习历程之前，我决定不再欣赏。而是批判甚至挖掘建筑消极的特性。我不完全成功，但这段经历让我思考一系列的问题：什么是现实？什么是虚拟？假的比真的更好吗？这些问题将我引向对建筑自疑的更高领域，当我看当代的建筑案例时，我开始流连于诚实和欺骗之间。