Hyperbranched polymers containing oxazoline monomers and succinic anhydride: Applications in fast drying,low solvent coating formulations

Melt-polycondensation of succinic acid anhydride with oxazoline-based diol monomers gave hyperbranched polymers with carboxylicacids terminal groups. ¹H NMR and quantitative ¹³C NMR spectroscopy coupled with DEPT-135 ¹³C NMR experiment showed high degrees of branching (over 60%). Esterification of the acid end groups by addition of citronellol at 160 °C produced novel white spirit soluble resins which were characterized by Fourier transform-infrared (FTIR) spectroscopy, gel permeation chromatography (GPC), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Blends of the new hyperbranched materials with commercial alkyd resins resulted in a dramatic, concentration dependent drop in viscosity. Solvent-borne coatings were formulated containing the hyperbranched polymers. Dynamic mechanical analysis studies revealed that the air drying rates of the new coating systems were enhanced compared with identical formulations containing only commercial alkyd resins.     

HTPC的多声道利器——爱必特HAD X-Plosion 7.1声卡测评

自己组装HTPC已经逐渐成为影音发烧友中的潮流,不过许多HTPC系统只注重于显卡的配置,而忽略了声卡的配置,虽然视频效果不错,可是音效则让人不敢恭维,难免给人一种“头重脚轻”的感觉。爱必特推出的“颠覆者7．1”声卡则是让HTPC达到家庭影院音效的不错选择。     

The effect of terrain on radio propagation in urban microcells

A model based on the geometrical theory of diffraction is proposed for predicting radio propagation in urban microcells in the presence of undulating terrain. Comparisons with data show that the model is appropriate for predicting shadowing by terrain, but the effect of terrain fluctuations which do not obscure the line of sight is smaller than the model predicts. It is also shown that the presence of buildings lining the streets, while causing considerable variations over short distances, has only a small effect on the large-scale trend of the average signal     

Inhomogeneous ladder networks,part I

In this paper the theory of orthogonal polynomials is taken as the starting point for developing the theory of semi-infinite inhomogeneous ladder networks of two element kinds. It is shown that the transfer impedance of the ladder network, suitably normalized, is just the Green's function of a self-adjoint difference operator of ‘Sturm–Liouville’ type. An integral representation for this Green's function is given, and is evaluated in product form. The theory is illustrated with a number of examples based on classical orthogonal polynomials, the use of which enables all the calculations to be carried through explicitly.     

Conjecture in system theory

This letter proves that a time-invariant infinite-dimensional linear network cannot have identical behaviour to a time-varying finite-dimensional network, the proof depending heavily on advanced concepts in system theory.     

Emerging Broadband Access Technologies

This paper briefly outlines the wide variety of emerging technologies that are set to challenge the traditional copper pair access network for new services. Features such as capacity and geographical coverage of the alternatives are discussed.     

Lightly branched comb polyesters: Application in fast drying solvent-borne coating formulations

Novel oxazoline-based comb-polymers possessing linoleyl or oleic side chains have been synthesized and used to produce low viscosity coatings. Inclusion of the polymers in model paint formulations results in coatings that exhibit faster drying times than commercially available alkyd resin formulations. The comb polymers were produced from diol substituted oxazoline monomers that were synthesized through a scalable, solvent free protocol and purified by simple recrystallisation. Co-polymerisation of the oxazolines with adipic acid at 160 °C in the bulk resulted in the targeted polyester comb type polymers. The polymers were soluble in a range of organic solvents and compatible with commercial alkyd resins. Model paint formulations containing up to 40 wt% of the linoleyl-based comb polymers exhibited a dramatic reduction in viscosity (from 35 to 13 Poise at 25 °C) with increasing quantities of polymer added. Dynamic mechanical analysis (DMA) studies revealed that the drying rate of the model paint formulations containing the comb polymers was enhanced when compared with that of commercial alkyd resins.