AlGaN/GaN HEMTs-an overview of device operation and applications

Wide bandgap semiconductors are extremely attractive for the gamut of power electronics applications from power conditioning to microwave transmitters for communications and radar. Of the various materials and device technologies, the AlGaN/GaN high-electron mobility transistor seems the most promising. This paper attempts to present the status of the technology and the market with a view of highlighting both the progress and the remaining problems.     

The Effect of Boundary Conditions on Gas-phase Synthesised Silver Nanoparticles

We have prepared spherical non-agglomerated silver nanoparticles by an evaporation–condensation–dilution/cooling technique. Silver was evaporated from a crucible in a tubular flow reactor. A porous tube diluter was used to quench the carrier gas at the outlet of the reactor to enhance the formation of small particles and to suppress agglomeration and other particle growth mechanisms. The number size distribution of the prepared particles was measured with a differential mobility analyser–condensation nucleus counter combination and the size and the shape of the particles were analysed with transmission electron microscope. The system was modelled using a sectional aerosol dynamics computer code to estimate the importance of different aerosol processes. In all conditions the particles obtained were non-agglomerated and spherical. The mean particle diameter varied from 4 to 10-nm depending on boundary conditions. From the modelling studies it can be concluded that the nucleation rate is the most important parameter controlling the final particle size.     

Malaysia's Multimedia Super Corridor Cluster: communication linkages among stakeholders in a national system of innovation

As the wave of globalization washes over geographical boundaries, the world steps into the era of a new knowledge-based economy with governments striving to encourage innovation in industry especially through national systems of innovation. A national system of innovation (NSI) is considered important because how a nation utilizes and exploits its NSI will determine whether it can compete and ride the wave of globalization or be carried by it and thrashed onto the shores of the new economy. This paper seeks to highlight the linkages developed for enabling communication among the various NSI stakeholders for achieving goals in one such effort, viz. the Multimedia Super Corridor (MSC) Cluster of Malaysia. The MSC offers a vision to create a global multimedia climate through an integrated environment of interlinked elements and attributes. The government of Malaysia, realising the significance of the NSI as a way to better utilize, exploit, and enhance systems, is making efforts to this effect. The efforts include bringing together various stakeholder organizations under the "Multimedia Flagship Applications" to develop flagship applications. This is for the development of information technology applications to pave the way toward a knowledge-based economy. The MSC Cluster is presented here as a physical manifestation of the NSI, and it gives an idea as to how policy makers can design linkages for communication among the various stakeholders to further national innovative performance and competitiveness in general.     

Refractive index profiling-state of the art

Problems associated with different calibration techniques and some instrumental effects that can determine instrumental accuracy are discussed. It is shown how transmission effects can be observed and used to generate a correction curve for refracted near-field instruments. High-quality fiber slices needed for axial interferometry were used to obtain refractive index differences on suitable fibers to ±1% with the measurements traceable to national standards. Interferometry was used to calibrate a multiple-step fiber which is available in 10-m lengths with a certificate of calibration. The limitations of the technique are discussed, and preliminary results of a study on the effects of residual stress and stress relief on measurements are given. Comparisons are made between measurements made by axial interferometry and refracted near field on a range of fibers. It is shown that commercial profilers can produce reliable measurements of refractive index difference, absolute refractive index, profile shape, and numerical aperture that agree well with measurements by other techniques     

HPTLC Determination of Swertiamarin and Amarogentin in Swertia Species from the Western Himalayas

JPC – Journal of Planar Chromatography – Modern TLC - A high-performance thin-layer chromatographic (HPTLC) method has been established for simple and rapid quantification of two...     

New linear codes over F/sub 5/ obtained by tripling method and improvements on bounds

One of the most important problems of coding theory is to construct codes with the best possible minimum distance. We further generalize the method first introduced by Gulliver and Harada (see Des., Codes Cryptogr, vol. 22, no. 1, p.89-96, 2001) and later generalized by the present authors, and obtain new linear codes which improve the best known minimum-distance bounds of certain linear codes. We have found eight new linear codes over F/sub 5/ with improved minimum distances. We introduce a generalized version of a Gray map, then we give definitions of quasi- and nearly quasi-cyclic codes. We conclude by giving the parameters of new linear codes with their generator matrices.     

Impact of die-to-die and within-die parameter fluctuations on themaximum clock frequency distribution for gigascale integration

A model describing the maximum clock frequency (FMAX) distribution of a microprocessor is derived and compared with wafer sort data for a recent 0.25-μm microprocessor. The model agrees closely with measured data in mean, variance, and shape. Results demonstrate that within-die fluctuations primarily impact the FMAX mean and die-to-die fluctuations determine the majority of the FMAX variance. Employing rigorously derived device and circuit models, the impact of die-to-die and within-die parameter fluctuations on future FMAX distributions is forecast for the 180, 130, 100, 70, and 50-nm technology generations. Model predictions reveal that systematic within-die fluctuations impose the largest performance degradation resulting from parameter fluctuations. Assuming a 3σ channel length deviation of 20%, projections for the 50-nm technology generation indicate that essentially a generation of performance gain can be lost due to systematic within-die fluctuations. Key insights from this work elucidate the recommendations that manufacturing process controls be targeted specifically toward sources of systematic within-die fluctuations, and the development of new circuit design methodologies be aimed at suppressing the effect of within-die parameter fluctuations     

Bounds of age replacement time

An age replacement policy with a planned replacement time t₀ is considered. Five approximations which give upper or lower bounds of an optimum time t₀¹ and are computed more easily than t₀¹ are derived. A numerical example shows, when the failure time has a Weibull distribution, that some approximations are fairly good.     

Generalized fractional programming duality: A parametric approach

Using a parametric approach, duality is presented for a minimax fractional programming problem that involves several ratios in the objective function.The first author is thankful to Natural Science and Engineering Research Council of Canada for financial support through Grant A-5319, and the authors are thankful to the anonymous referees for useful suggestions.