Laboratory evaluation of a field-portable dielectric/soil-moistureprobe

An evaluation of an L-band dielectric soil-moisture probe conducted to examine its capabilities, calibration, and performance under laboratory conditions is discussed. Results indicated that the probe can estimate the real part of the dielectric constant over a wide range of values. The imaginary part of the dielectric constant was overestimated. Since the soil moisture estimate is made using only the real part of the dielectric constant, the probe should produce reliable estimates of soil moisture. Studies utilizing a variety of soils, ranging from a loamy sand to a clay loam, produced results which were not as variable as those predicted by the dielectric models     

DAME: Searching Large Data Sets Within a Grid-Enabled Engineering Application

The use of search engines within the Internet is now ubiquitous. This work examines how Grid technology may affect the implementation of search engines by focusing on the Signal Data Explorer application developed within the Distributed Aircraft Maintenance Environment (DAME) project. This application utilizes advanced neural-network-based methods (Advanced Uncertain Reasoning Architecture (AURA) technology) to search for matching patterns in time-series vibration data originating from Rolls-Royce aeroengines (jet engines). The large volume of data associated with the problem required the development of a distributed search engine, where data is held at a number of geographically disparate locations. This work gives a brief overview of the DAME project, the pattern marching problem, and the architecture. It also describes the Signal Data Explorer application and provides an overview of the underlying search engine technology and its use in the aeroengine health-monitoring domain.     

Sparse Approximations of the LMMSE Channel Estimation in OFDM with Transmitter Diversity

The linear minimum mean-squared error (LMMSE) channel estimation for orthogonal frequency-division multiplexing (OFDM) systems requires a large number of complex multiplications. We evaluate a simplified LMMSE channel estimation algorithm in a transmit diversity environment by applying a significant weight catching (SWC) technique to the LMMSE fixed weighting matrix. The SWC technique itself is based on modifying the smoothing matrix by leaving the Γ largest values in each row and turning the rest to zeros. This allows the computational complexity of the full LMMSE processor to be reduced by more than 50%. In the well known LMMSE by singular value decomposition (SVD) technique the sparse approximation is accomplished by zeroing out all but the r largest singular values. LMMSE by SVD is the preferred approximation technique for low delay spread channels. However, in channels with large delay spreads, LMMSE by SWC is a better choice in terms of computational complexity and estimation accuracy Igor Tolochkoreceived his Dipl.-Eng. Degree in Electrical Engineering from Polytechnic Institute, Riga, Latvia in 1987 and PhD from Victoria University, Melbourne, Australia in 2005. He was a senior and later principal design engineer in mobile communications at the Riga Semiconductor Institute Alpha (1988 – 1993). During 1993 – 1998, he was involved in research and development activities in communications with different companies in Riga and Melbourne, Australia. From 1998 to 2002, he was with Ericsson Australia as a senior design engineer. Currently, he works for NEC Australia Pty. Ltd. as a senior design engineer in 3G Mobile Department. His current research interests include digital signal processing, indoor and outdoor wireless communications and error control coding. Michael Faulkner(M'84) received the B.Sc. (Eng) from Queen Mary College, London University, UK, in 1970, the M.E. degree from the University of New South Wales, Australia in 1978, and the PhD from University of Technology Sydney in 1993. From 1972 to 1975 he was with STC (now Alcatel) Australia. From 1975 to 1977 he as with the University of New South Wales, and since then as a lecturer and now professor at Victoria University of Technology, Melbourne, Australia where he is director of the Telecommunications and Micro-electronics research centre. Between 1988 and 2000 he spent four periods at Lund University, Sweden. He was co-recipient of the IEE's 1997 IERE prize for a paper on amplifier linearisation. His current interests are, signal processing, radio technology, radio systems and MIMO/OFDM.     

Criteria for nearly omnidirectional radiation patterns for printed antennas

Radiation from printed antennas is investigated with emphasis placed on producingbar{E}- andbar{H}-plane radiation patterns that are as nearly omnidirectional as possible. This is achieved using criteria which are derived for a nonzero radiation field extending down to the layer surface (radiation into the horizon). It is determined that this phenomenon arises when a surface wave pole coincides with a branch point in the complex plane. A simple ray optics interpretation is given for the phenomenon, and graphs are presented to easily enable design of printed antenna geometry to achieve nearly omnidirectionalbar{E}- orbar{H}-plane patterns.     

Combined michelson and polarimetric fibre-optic interferometric sensor

A fibre-optic interferometric sensor utilising a highly birefringent fibre sensing element has been configured such that both Michelson and polarimetric outputs are simultaneously available. This device therefore offers the high resolution of a Michelson interferometer in conjunction with the increased dynamic range of a polarimetric device. The results of preliminary experiments in which the system was used as a temperature sensor are presented.     

An asymptotic extraction technique for evaluating Sommerfeld-type integrals

An asymptotic extraction process is developed which leads to an efficient method for the evaluation of the electric field from a Hertzian dipole in a layered geometry. This technique allows for a rapidly converging expression for the electric field which remains well behaved as the source and observation heightsz', zcoincide. A useful application of this method is in the calculation of mutual impedance between printed dipoles.     

Microstrip dipoles on electrically thick substrates

Certain basic radiation properties of microstrip dipoles on electrically thick substrates are investigated, and a comparison is made with the case of dipoles printed on a dielectric half-space. It is concluded that the microstrip dipole radiation properties become sensitive to substrate loss as the substrate thickness increases, with the half-space properties obtained for an adequate amount of loss. Asymptotic formulas for radiated power and efficiency are given for both the thick substrate and half-space problems, showing the behavior with increasing dielectric constant. The method of moments is used to extend the analysis to center-fed strip dipoles, and a method of improving both the efficiency and gain of a printed antenna by using a superstrate layer is discussed.     

Microstructure and protein digestibility of beef: The effect of cooking conditions as used in stews and curries

Beef meat was cooked at 373 K for 10 and 30 min to investigate the effect of the cooking conditions generally used during beef stew and curry preparation on protein digestibility. The cooked meats, along with a raw control, were digested using an in vitro digestion model to simulate gastric and small-intestinal conditions. Samples taken at different digestion times were analyzed using SDS-PAGE, RP-HPLC, ninhydrin assays for amino N and transmission electron microscopy. Simulated gastric conditions quickly led to the loss of basic sarcomere structure in raw meat myofibrils whereas the sarcomere structure of the compact cooked meat myofibrils remained intact after 30 min of gastric digestion. Prolonged cooking of meat (30 min) resulted in incomplete digestion of small MW (<10 kDa) peptides, as observed from SDS-PAGE. This agreed with the amount of ninhydrin-reactive amino N released during digestion, which decreased with an increase in cooking time. The RP-HPLC peak areas of the major identified amino acids (tryptophan, tyrosine and phenylalanine) also decreased with an increase in cooking time. This suggested the formation of “limit peptides” during prolonged cooking of beef, which were not further broken down into free amino acids by digestive enzymes and therefore might not be bioavailable.     

Implications of the recent reductions in natural gas prices for emissions of CO2 from the US power sector

CO(2) emissions from the US power sector decreased by 8.76% in 2009 relative to 2008 contributing to a decrease over this period of 6.59% in overall US emissions of greenhouse gases. An econometric model, tuned to data reported for regional generation of US electricity, is used to diagnose factors responsible for the 2009 decrease. More than half of the reduction is attributed to a shift from generation of power using coal to gas driven by a recent decrease in gas prices in response to the increase in production from shale. An important result of the model is that, when the cost differential for generation using gas rather than coal falls below 2-3 cents/kWh, less efficient coal fired plants are displaced by more efficient natural gas combined cycle (NGCC) generation alternatives. Costs for generation using NGCC decreased by close to 4 cents/kWh in 2009 relative to 2008 ensuring that generation of electricity using gas was competitive with coal in 2009 in contrast to the situation in 2008 when gas prices were much higher. A modest price on carbon could contribute to additional switching from coal to gas with further savings in CO(2) emissions.     

Long-term aging of copper added to soils

Aging refers to the processes by which the mobility and bioavailability/toxicity of metals added to soil decline with time. Although long-term aging is a key process that needs to be considered in the risk assessment of metals in field soils, the long-term aging of Cu added to soils has not been studied in detail. In this study, the effects of aging on Cu isotopic exchangeability, total Cu in soil pore water, pore water free Cu2+ activity, and "available" Cu measured by the technique of diffusive gradient in thin film (DGT-Cu) were investigated in 19 European soils at two total Cu concentrations shown to inhibit plant (tomato) growth by 10 and 90%. After addition of Cu, the soils were leached, incubated outdoors, and sampled regularly over a 2-year period. The results showed that when water soluble Cu was added to soils, concentrations of Cu determined by each of the techniques tended to decrease rapidly initially, followed by further decreases at slow rates. Soil pH was a vital factor affecting the aging rate of Cu added to soils. The relatively low solubility products and low isotopic exchangeabilities of Cu in calcareous soils immediately after addition of soluble Cu2+ suggested Cu2+ probably precipitated in these soils as Cu2(OH)2CO3 (malachite) and Cu(OH)2. Isotopic dilution was found to be a robust technique for measuring rates of long-term aging reactions. A semi-mechanistic model was developed to describe the rate and extent of Cu aging across soils as affected by soil pH and other physicochemical parameters. Although not measured directly, it is inferred from soil physicochemical controls on Cu aging that processes of precipitation/nucleation of Cu in soils and hydrolysis of Cu2+ followed by a diffusion process controlled the decrease in Cu availability with time. The model was validated by testing it against field soils with different contamination histories and was found to successfully predict the isotopic exchangeability of Cu added to soils based on two parameters: soil pH and time.