Analysis of modified SMI method for adaptive array weight control

An adaptive array is applied to the problem of receiving a desired signal in the presence of weak interference signals which need to be suppressed. A modification, suggested by Gupta, of the sample matrix inversion (SMI) algorithm controls the array weights. In the modified SMI algorithm, interference suppression is increased by subtracting a fraction F of the noise power from the diagonal elements of the estimated covariance matrix. Given the true covariance matrix and the desired signal direction, the modified algorithm is shown to maximize a well-defined, intuitive output power ratio criterion. Expressions are derived for the expected value and variance of the array weights and output powers as a function of the fraction F and the number of snapshots used in the covariance matrix estimate. These expressions are compared with computer simulation and good agreement is found. A trade-off is found to exist between the desired level of interference suppression and the number of snapshots required in order to achieve that level with some certainty. The removal of noise eigenvectors from the covariance matrix inverse is also discussed with respect to this application. Finally, the type and severity of errors which occur in the covariance matrix estimate are characterized through simulation

Addressing the Quality Change Issue in the Consumer Price Index

macroeconomics, consumption, consumer price index, quality change, CPI bias, retail, substitution bias

Life expectancy of shingle beaches: measuring in situ abrasion

In situ abrasion of shingle beach material is a neglected area of study in coastal geomorphology, with reduction in beach volumes normally attributed to longshore and offshore drift. Results from field abrasion experiments conducted on flint shingle beaches on the East Sussex coast, southern England, show that in situ reductions in volume of beach material may be more significant than has been thought. Two beaches composed almost entirely of flint shingle were seeded with hard quartzite from a Devon beach and less resistant limestone from a South Wales beach that are readily distinguishable from the flint. The seeding commenced in January 2001. The pebbles, similar in size and shape to the natural flint shingle, were left in the surf zone at two sites. Prior to exposure the pebbles were engraved with a code number and weighed. At regular intervals those that could be re-found were re-weighed and returned to the beach. Abrasion rates were calculated for each pebble as percentage weight loss per tide. By the end of October 2001, more than 700 measurements of abrasion rates had been made from a total of 431 pebbles. Average limestone abrasion rates (0.0266% loss of weight per tide) were three times greater than those of quartzite (0.0082% per tide). Measurable abrasion rates were recorded over just a few tidal cycles, not only in severe wave conditions but also in much calmer weather. The maximum abrasion rates recorded exceeded 1% per tide for limestone

The Impact of Hosting a Major Sport Event on the South African Economy

The impact of the sporting industry on economic decision making has increased dramatically since the global media explosion in the 1980s. Tourism and advertising revenues generated by these mega-events have become a major boost to the economies of hosting nations. In addition, globalisation has placed great emphasis on the importance of foreign direct investment (FDI), especially to developing countries. This paper seeks to examine the impact of the pre-event phase expenditure attributed to the hosting of the 2010 FIFA World Cup on the South African economy. In this phase, expenditure is mainly geared towards the construction and improvement of infrastructure required to successfully host the event. Using a Computable General Equilibrium (CGE) model developed specifically for the South African economy, the impact of the pre-event phase on the local economy is measured. It is found that there is a positive impact on most macroeconomic variables, including GDP and employment. With the potential economic benefits of the event and post-event phases of the World Cup also taken into account, it can be concluded with relative certainty that the impact of hosting a mega-event on the South African economy is beneficial towards achieving higher economic growth and development. In addition to analysing the impact of the 2010 FIFA World Cup, the outcomes are also used to briefly examine the feasibility of South Africa’s bid to host the 2011 IRB World Cup and the 2016 Olympic Games.computable general equilibrium, mega-events, economic development

Joint design for improved fatigue life of diffusion-bonded box-stiffened panels

Simple photoelastic models were used to identify a cross-section geometry that would eliminate the severe stress concentrations at the bond line between box stiffeners diffusion bonded to a panel skin. Experimental fatigue-test data from titanium test specimens quantified the allowable stress in terms of cycle life for various joint geometries. It is shown that the effect of stress concentration is reduced and an acceptable fatigue life is achieved

Neutralization of chemokines RANTES and MIG increases virus antigen expression and spinal cord pathology during Theiler's virus infection.

The role of chemokines during some viral infections is unpredictable because the inflammatory response regulated by these molecules can have two, contrasting effects-viral immunity and immunopathologic injury to host tissues. Using Theiler's virus infection of SJL mice as a model of this type of disease, we have investigated the roles of two chemokines-regulated on activation, normal T cell-expressed and secreted (RANTES) chemokine and monokine induced by IFN-gamma (MIG)-by treating mice with antisera that block lymphocyte migration. Control, infected mice showed virus persistence, mild inflammation and a small degree of demyelination in the white matter of the spinal cord at 6 weeks post-infection. Treatment of mice with RANTES antiserum starting at 2 weeks post-infection increased both viral antigen expression and the severity of inflammatory demyelination at 6 weeks post-infection. MIG antiserum increased the spread of virus and the proportion of spinal cord white matter with demyelination. Overall, viral antigen levels correlated strongly with the extent of pathology. At the RNA level, high virus expression was associated with low IL-2 and high IL-10 levels, and RANTES antiserum decreased the IL-2/IL-10 ratio. Our results suggest that RANTES and MIG participate in an immune response that attempts to restrict viral expression while limiting immunopathology and that anti-chemokine treatment poses the risk of exacerbating both conditions in the long term