An improved optimal bit allocation method for sub-band coding

This paper presents an improved optimal bit allocation method for sub-band coding. To speed up the allocation process, a coarse bit range for each sub-band is firstly obtained using the log–variance method, and then an optimal searching routine is applied to produce the final solution. Good features are showed in the simulations for evaluating the proposed method.     

Survey of aflatoxins in beer sold in Canada

Between March 1998 and March 2002, 304 samples of domestic (Canadian) and imported beers from 36 countries were picked up for the determination of aflatoxins B₁, B₂, G₁ and G₂. Twelve samples were positive with aflatoxins greater than the limit of quantitation (LOQ) (aflatoxin B₁, 4.4 ng l^-1; aflatoxin B₂, 3.4 ng l^-1; aflatoxin G₁, 11.2 ng l^-1; and aflatoxin G₂, 6.2 ng l^-1). Five samples from Mexico, two samples from Spain and one from Portugal contained aflatoxin B₁. Four samples from India contained aflatoxins B₁ and B₂. The remaining samples contained less than the LOQ for aflatoxins B₁, B₂, G₁ and G₂. The analytical method for this survey was based on that of Scott and Lawrence (Scott PM, Lawrence GA. 1997. Determination of aflatoxins in beer. Journal of AOAC International 80:1229-1234.). Aflatoxins B₁, B₂, G₁ and G₂ were determined at parts per trillion (ng l^-1) levels in beer by immunoaffinity column cleanup followed by derivatization with trifluoroacetic acid and reversed-phase liquid chromatography with fluorescence detection.     

WTFM, software for well test analysis in fractured media combining fractional flow with double porosity and leakance approaches

The identification of the hydraulic characteristics and transport properties of fractured reservoirs requires the development of specific models that account for (i) the medium heterogeneity, e.g. the presence of major conductive fractures that delimit capacitive matrix blocks, with weakly open, dead end or isolated fractures, and (ii) for the geometrical arrangement of the major conductive fractures network, which dominates the flow at the scale of the well tests.Well Tests in Fractured Media (WTFM) software takes into account these two main features by combining radial flow generalized to fractional dimension, with the theory of double-porosity, including diffusivity in the second porosity, transient inter-porosity flow and inter-porosity skin effect, and with leakance. The implementation of this nD model, with n fractional, extends usefully the domain of application of the usual 1D/2D/3D double-porosity/leakance models for a large range of connection levels of fracture networks. Although the fractures geometry and properties are not considered one by one, or by directional families, they are taken into account by averaged properties and by the impact that the whole network has on the hydrodynamic behaviour. The accuracy of the coupled transient behaviours analysis is augmented by taking into account wellbore storage and skin effects. All together, the use of these different options allows matching a wide range of pumping test curves, characteristics of distinctive behaviours, with a limited number of parameters. Distinctive well test experiments, in both sedimentary and crystalline rocks, are presented for enlightening how the pertinent use of the model options improves predictions.     

Modified planar inverted F antenna

The design of a modified planar inverted F antenna (PIFA) which is more compact (antenna length <λ₀/8 and antenna height <0.01 λ₀) and has a much wider antenna bandwidth (greater than 10 times that of a simple PIFA) is demonstrated. The reduction in antenna length is achieved by meandering the radiating patch, while the enhanced bandwidth with low antenna height is obtained using a chip-resistor load in place of the shorting post. A typical design of the modified PIFA in the 800 MHz band has been implemented, and experimental results are presented and discussed     

High-power, low-threshold BH lasers operating at 1.52 ?m grown entirely by MOVPE

BH laser devices with efficient optical and current confinement have been grown using a new all-MOVPE growth technique. The devices produced operated with CW threshold currents as low as 14 mA and output powers of up to 28 mW at 20°C. In initial experiments, over 70% of the working devices tested had threshold currents of less than 30 mA, substantiating the view that MOVPE is a highly promising technique for the large-scale production of complex optoelectronic devices.     

Finite prism analysis of plates and shells

The finite prism technique introduced by Zienkiewicz and Too⁴ is extended to include 12-node prism elements and, more importantly, a novel offset beam element. The use of 12-node prism elements enables parabolic strain distributions to be simulated, this being useful for structures which have strongly tapered cross-sections. The offset beam element is used to simulate flexure and torsion of a beam whose centroid is offset from the main structure. The element is specified completely at the nodes of adjacent prism elements and so is not really an ‘element’ in the usual sense. The analysis is applied to thin and thick plates and to shells, with and without edge beams. It is shown to be more versatile than the finite strip method and it requires smaller computer resources than the finite element method. Experimental verification of the analysis is obtained by comparison with measurements for a double-T bridge deck tested by Loo¹⁴.     

Simultaneous transmission of speech and data using an adaptive cancelling technique

A new scheme to transmit data and analogue speech simultaneously over an analogue transmission line is presented. The transmitter simply combines speech and modulated voice-band data signals together while the receiver uses an adaptive cancelling technique to recover these signals from the received composite. The scheme works for phase-dispersive channels and without bandwidth expansion.     

Influence of Head Geometry on Bolted Joint Behavior

Numerical models of single-fastener bolted lap joints are developed in which the effect of the head angle and height on joint elongation are studied for three fastener sizes, three panel materials, and several panel thicknesses. Baseline 100° bolt-head angle numerical models are calibrated and validated with experimental data. These baseline models are then modified to predict the load-elongation behavior of lap joints with five different head angles and four different head heights. The numerical predictions are summarized in graphical form. The results show that the fastener head height has a much greater influence on joint-slip resistance than does the angle, with the shallower heads providing the greatest resistance to joint elongation under load.