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A 2,6-dimethylphenol-dipentene dicyanate ester (DPCY) was synthesized from the reaction of 2,6-dimethylphenol-dipentene adduct and cyanogen bromide. The proposed structure was confirmed by Fourier transform infrared (FTIR), elemental analysis, mass, and nuclear magnetic resonance (NMR) spectra. DPCY was then cured by itself or cured with bisphenol A dicyanate ester (BADCY). Thermal properties of cured epoxy resins were studied using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), dielectric analysis (DEA), and thermogravimetric analysis (TGA). These data are compared with those of BADCY. The cured DPCY exhibits a lower dielectric constant (2.61 at 1 MHz), dissipation factor (29.3 mU at 1 MHz), thermal stability (5% degradation temperature and char yield are 429 degreesC and 17.64%, respectively), glass transition temperature (246 degreesC by TMA and 258 T by DMA), coefficient of thermal expansion (33.6 ppm before Tg and 134.1 ppm after Tg), and moisture absorption (0.95% at 48 h) than those of BADCY, but higher moduli (5.12 GPa at 150 degreesC and 4.60 GPa at 150 degreesC) than those of the bisphenol A system. The properties of cured cocyanate esters lie between cured BADCY and DPCY, except for moduli. Moduli of some cocyanate esters are even higher than those of cured BADCY and DPCY. A positive deviation from the Fox equation was observed for cocyanate esters. (C) 2004 Wiley Periodicals, Inc

Recently, mobile location estimation is drawing considerable attention in the field of wireless communications.Among different mobile location estimation methods, the one which estimates the location of mobile stations with reference to the wave propagation model is drawing much attention. This approach, in principle, makes use of the most primitive property of wave propagation -signal strength, to perform location estimation. Hence this approach should be able to apply to different kinds of cellular network. We found out that in estimating mobile location with reference to signal strength, the azimuth gain of directional antenna and environmental factors can help to improve the accuracy. In this paper, we report our study of a Directional Propagation Model (DPM) which enhanced the traditional propagation model with these factors. We experimented our model with 3,703 sets of real life data collected from a major mobile phone operator of Hong Kong. Results show that the DPM models have significant improvement over other existing location methods in terms of accuracy and stability.

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