Capacity Estimation in Multiple-Chip-Rate DS/CDMA Systems Supporting Multimedia Services

This paper is concerned with capacity estimation in multiple-chip-rate (MCR)DS/CDMA systems supporting multimedia services with different informationrates and quality requirements. Considering both power spectral density (PSD)over a radio frequency (RF) band and the effect of RF input filtering onthe receiver, capacity that satisfies the requirementof the bit energy-to-interference PSD ratio is derived.The optimum value of the received power which causes the leastinterference for other users while maintaining an acceptablequality-of-service(QoS) requirement is also derived. The results show that system performanceisstrongly affected by a selected channel assignment strategy. Therefore, it is critical to efficiently assign radio resources in MCR-DS/CDMA systems that support high capacity and a low blocking rate.     

Evaluating the Sensitivity of Attic Radiant Barrier Performance to Climate Parameters

By employing a calibrated and tested computer model, simulations of ceiling heat transfer in typical residential attics located in 12 locations across the United States were obtained to study the sensitivity of attic radiant barrier performance to local climate parameters. For each location, the net ceiling heat flux over the summer cooling season was computed for an attic with and for an attic without an installed radiant barrier. The net reduction of heat flux induced by the radiant barrier was computed and then related to climate variables. Among the local environmental parameters, the local ambient air temperature, local ambient humidity, and latitude had significant effects on the performance of radiant barriers. It was concluded that the installation of radiant barriers would be most beneficial in regions with high outdoor air temperatures and high relative humidity.     

Effects of ageing treatments on transformation temperatures and precipitation kinetics in a Cu-Zn-Al shape-memory alloy

The effects of ageing treatments on transformation temperatures, hardness, and precipitation kinetics in a Cu-14.2Zn-8.5Al (wt%) shape-memory alloy were investigated. Quench-ageing treatment temperatures varied from 100 to 500° C with times up to 200 h after the solution treatment. The martensitic transformation temperature, M _s, of the hot-rolled material was decreased from 55 to 51 °C by the solution treatment. The temperature hysteresis (A _f-M _f) was 50° C for the hot-rolled condition, but was reduced to 30° C after the solution treatment. The maximum hardness for material aged at 500° C was lower than that for that aged at 300 or 400° C. The apparent activation energy for hardness increase in this alloy was 110 kJ mol^–1, compared with 72 kJ mol^–1 for the similar copper-based shape-memory alloy Cu-21.2 Zn- 6.0 Al. The ordering temperatures for B₂ and DO₃ superlattices were in the neighbourhood of 480 and 260° C, respectively. The tensile ductility and yield strength of this alloy were significantly reduced by the ageing treatment at 400° C.     

Measurement of Torsion from Multitemporal Images of the Eye Using Digital Signal Processing Techniques

Two methods of measuring ocular torsion from digital images of the eyes were developed and tested. One method measures torsion from the translation of two landmarks using a rectilinear coordinate system. The second method measures torsion from the translation of two landmarks using a polar coordinate system. The center for the polar sampling is the center of the pupil. After thresholding and filtering the images, landmark translation is measured from the interpolated peak in the normalized cross correlation of the reference landmark with the image.     

Stable single-frequency fiber ring laser for 25-GHz ITU-T grids utilizing saturable absorber filter

A stable single-frequency fiber ring laser is proposed that operates in a single mode for more than an hour by incorporating unpumped erbium-doped fiber (EDF) as a saturable absorber filter and optimizing the length of EDF used as gain medium. This laser can be continuously tuned to 25-GHz spacing that precisely matches the ITU-T grids by temperature control of etalon filter. This laser had a signal-to-source spontaneous emission ratio higher than 70 dB, and lasing frequencies of 361 channels was matched to ITU-T grids with excellent flatness. Frequency offset from the ITU-T grid was less than 0.14 GHz. The linewidth and the relative intensity noise value was less than 1.3 kHz and 130 dB/Hz (above 250 kHz), respectively.