Analysis of Moderate and Intense Rainfall Rates Continuously Recorded Over Half a Century and Influence on Microwave Communications Planning and Rain-Rate Data Acquisition

This paper is concerned with the statistical investigation of a massive data bank of 49 years of rainfall rateRcontinuously recorded in Barcelona using a rain-rate gauge with ten seconds response time. With radio communications in mind, the paper addresses and reviews in detail: 1) reliable statistical model forR, 2) number of years required to obtain a database from which to derive a reliableR-distribution, and 3) the CCIR worst-month concept. The research has shown that the generalized Paretoaexp(-muR)/R^{b}gives nearly perfect fit for all ranges ofRfollowed closely by the gamma distribution, and the simpler square root (R^{1/2}) normal distribution gives excellent fit too. The log-normal distribution was unsatisfactory forR geq 60mm/h. The spread of the yearly distribution ofP(R)is cube root normally distributed([P(R)]^{1/3})and between 7 and 10 years are required before a reliable average distributionP(R)can be obtained. The study of theP(R)return time in years is also presented. High resolution ofP(R)is presented looking at the evolution of the annualP(R)in terms of the hourly and monthly contributing parts revealing statistical features such as the location in time of rain rates above 50 mm/h. Finally, the study shows that the calendar month contribution toP(R)remains at all times well below the synthetic CCIR worst month and recommendations are then given about its use.     

The multivariable model-based control of the non-alumina electrolyte variables in aluminum smelting cells

This paper investigates the application of multivariable model-based control to improve the regulatory control of electrolyte temperature, aluminum fluoride concentration, liquidus temperature, superheat, and electrolyte height. Also examined are therappropriateness of different control structures and the possible inclusion of recently developed sensors for alumina concentration and individual cell duct flowrate, temperature, and heat loss. For the smelter in this study, the maximum improvement possible with a multivariable model-based controller is predicted to be 30–40% reduction in standard deviation in electrolyte temperature, aluminum fluoride concentration, liquidus temperature, and superheat, and around half this for electrolyte height. Three control structures were found to be appropriate; all are different than the existing control structure, which was found to be suboptimal. Linear Quadratic Gaussian controllers were designed for each control structure and their predicted performance compared. Comalco Research.     

The synthesis,swelling behaviour and rheological properties of chemically crosslinked thermosensitive copolymers based on <Emphasis Type="Italic">N</Emphasis>-isopropylacrylamide

In this contribution thermosensitive polymer matrices based on N-isopropylacrylamide have been developed. The hydrogels were prepared by photopolymerisation of N-isopropylacrylamide and 1-vinyl-2-pyrrolidinone in appropriate amounts of distilled water. The monomers were cured using a UV-light sensitive initiator called 1-hydroxycyclohexylphenylketone. These copolymers were crosslinked using ethylene glycol dimethacrylate and poly(ethylene glycol) dimethacrylate with molecular weights 600 and 1,000, at 0.1 wt% of the total monomer content. The chemical structure of the xerogels was characterised by means of Fourier transform infrared spectroscopy (FTIR) and the transition temperature of the hydrogels was determined using modulated differential scanning calorimetry (MDSC). By altering the feed ratio, hydrogels were synthesised to have lower critical solution temperatures (LCST) around 37 °C. This ability to shift the phase transition temperature of the gels provides excellent flexibility in tailoring transitions for specific uses. The samples synthesised with PEG1000DMA crosslinking agents absorbed over 18 times their weight in water, while maintaining good gel integrity thus falling marginally short of being characterised as superabsorbent. Each of the samples showed similar deswelling behaviour at 37 °C. Rheological studies showed that increasing the molecular weight of the crosslinking agent caused an increase in hydrogel strength.     

Book reviews

TOWARDS COSMOPOLIS: Planning for Multicultural Cities. Leonie Sandercock. John Wiley & Sons, Chichester, UK, 1998. ISBN 0471971987 (paperback). 258 pp.; bibliography. RRP $41.15.

THE MYTH OF THE POWERLESS STATE: Governing the Economy in a Global Era. Linda Weiss. Polity/Blackwell, Cambridge, 1998. ISBN 0745615821 (paperback). 260 pp.; index and bibliography. RRP $37.95.

SOCIAL CHANGE, SUBURBAN LIVES: An Australian Newtown 1960s to 1990s. Lois Bryson and Ian Winter. Allen & Unwin, Sydney, 1998. ISBN 1864486996 (paperback). 238 pp.; index and bibliography. RRP $29.95.

CONTESTING THE AUSTRALIAN WAY: States, Markets and Civil Society. Paul Smyth and Bettina Cass (eds). Cambridge University Press, Cambridge, 1998. ISBN 0521633060 (hardback). 280 pp.; bibliography and index. RRP $90.00.

THE ECOLOGICAL CITY AND THE CITY EFFECT: Essays on the Urban Planning Requirements for the Sustainable City. Franco Archibugi. Ashgate, Aldershot, UK, 1997. ISBN 1859726534 (hardback). 243 pp.; bibliography and index. RRP $96.50.

CITIES FOR TOMORROW: Integrating Land Use, Transport and the Environment. Hans L. Westerman. Austroads, Sydney, 1998. ISBN 0855885033 (paperback). Resource Document 202 pp.; Better Practice Guide. 394 pp.; index. RRP $180.00.

EAST WEST PERSPECTIVES ON 21ST CENTURY URBAN DEVELOPMENT: Sustainable Eastern and Western Cities in the New Millennium. John Brotchie, Peter Newton, Peter Hall and John Dickey (eds). Ashgate, Aldershot, UK, 1999. ISBN 1840143177 (hardback). 432 pp.; bibliography and index. RRP $122.00.

MADE IN LANCASHIRE: A History of Regional Industrialisation. Geoffrey Timmins. Manchester University Press, Manchester, 1998. ISBN 0719045398. 334 pp.; bibliography and index. RRP $145.00.     

Thermodynamic properties and defect structure of semiconducting compound phases: Tin telluride

Defect equilibria for binary semiconducting compound phases which exhibit ionized native donor and acceptor defects were considered, and equations describing the pressure-temperature-composition relationships for these compound phases were derived. These equations were used to analyze experimental data from the literature for tin telluride. Excellent agreement was obtained between calculated thermodynamic and phase boundary values and experimental data. The approach presented is readily extended to obtain equations for the thermodynamic properties of ternary and higher order semiconducting compound phases.     

Preliminary investigation of bioadvantaged polymers as sustainable alternatives to petroleum-derived polymers for asphalt modification

Due to recent volatility in the petroleum market, the possibility of using sustainable alternative materials as substitutes has gained great interest and viability. The purpose of this research is fourfold: to demonstrate how bioadvantaged polymers are produced using non-food soybean oil and showcase their economic and environmental value; to evaluate how they perform rheologically in asphalt against commonly used petroleum-derived polymers; to optimize the formulation of the bioadvantaged polymer for warm climate regions pavement applications based on the grading results, and to verify the modification effects of optimized bioadvantaged polymer by running performance grade tests. The study on economic and environmental implications demonstrated that poly(styrene-acrylated epoxidized soybean oil) (PS-PAESO) is more cost-effective, environmentally friendly, and safer to produce than styrene-butadiene (SB) polymer. The commercially produced petroleum-derived SB diblock polymer was used for comparison, while the laboratory produced bioadvantaged polymers were targeted at 1.25 MDa molecular weight of PS-PAESO diblock copolymers that consist of PAESO with various polystyrene (PS) molecular weights and contents. The effectiveness and rheological performance of the polymer modified asphalt binders were evaluated through binder investigations. Rheology test results indicated that the bioadvantaged polymers improved the stiffness, elasticity, and rutting resistance of the neat asphalt binder. Best-fit prediction models were developed through response surface modeling to optimize the PS-PAESO formulation in terms of PS content and molecular weight and the models were verified to be highly accurate based on the grading results. It was found that lower polystyrene content in PS-PAESO polymer could be beneficial in the improvement of critical high temperatures.     

A physical alpha-power law MOSFET model

A new compact physics-based alpha-power law MOSFET model is introduced to enable projections of low power circuit performance for future generations of technology by linking the simple mathematical expressions of the original alpha-power law model with their physical origins. The new model, verified by HSPICE simulations and measured data, includes: 1) a subthreshold region of operation for evaluating the on/off current tradeoff that becomes a dominant low power design issue as technology scales, 2) the effects of vertical and lateral high field mobility degradation and velocity saturation, and 3) threshold voltage roll-off. Model projections for MOSFET CV/I indicate a 2X-performance opportunity compared to the National Technology Roadmap for Semiconductors (NTRS) extrapolations for the 250, 180, and 150 nm generations subject to maximum leakage current estimates of the roadmap. NTRS and model calculations converge at the 70 nm technology generation, which exhibits pronounced on/off current interdependence for low power gigascale integration     

A minimum total power methodology for projecting limits on CMOS GSI

A circuit design methodology minimizing total power drain of a static complementary metal-oxide-semiconductor (CMOS) random logic network for a prescribed performance, operating temperature range, and short channel threshold voltage rolloff is investigated. Physical, continuous, smooth, and compact “transregional” MOSFET drain current models that consider high-field effects in scaled devices and permit tradeoffs between saturation drive current and subthreshold leakage current are employed to model CMOS circuit performance and power dissipation at low voltages. Transregional models are used in conjunction with physical short channel MOSFET threshold voltage rolloff models and stochastic interconnect distributions to project optimal supply voltages, threshold voltages, and device channel widths minimizing total power dissipated by CMOS logic circuits for each National Technology Roadmap for Semiconductors (NTRS) technology generation. Optimum supply voltage, corresponding to minimum total power dissipation, is projected to scale to 510 mV for the 50-nm 10-GHz CMOS generation in the year 2012. Techniques exploiting datapath parallelism to further scale the supply voltage are shown to offer decreasing reductions in power dissipation with technology scaling