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We consider the problem of finding an approximate minimizer of a general quadratic function subject to a two-norm constraint. The Steihaug-Toint method minimizes the quadratic over a sequence of expanding subspaces until the iterates either converge to an interior point or cross the constraint boundary. The benefit of this approach is that an approximate(More)
Iterative methods are proposed for certain augmented systems of linear equations that arise in interior methods for general nonlinear optimization. Interior methods define a sequence of KKT equations that represent the symmetrized (but indefinite) equations associated with New-ton's method for a point satisfying the perturbed optimality conditions. These(More)
Optimization for complex systems in engineering often involves the use of expensive computer simulation. By combining statistical emulation using treed Gaussian processes with pattern search optimization, we are able to perform robust local optimization more efficiently and effectively than using either method alone. Our approach is based on the(More)
We describe an asynchronous parallel derivative-free algorithm for linearly constrained optimization. Generating set search (GSS) is the basis of our method. At each iteration , a GSS algorithm computes a set of search directions and corresponding trial points and then evaluates the objective function value at each trial point. Asynchronous versions of the(More)
— High-frequency backscatter radio systems operate in the dyadic backscatter channel, a pinhole channel whose envelope probability density function and bit-error-rate performance are strongly affected by link envelope correlation – the envelope correlation between the forward and backscatter links of the dyadic backscatter channel. This paper shows that(More)
A novel approach for pairing RFID-enabled devices is introduced and evaluated in this work. Two or more devices are moved simultaneously through the radio field in close proximity of one or more RFID readers. Gesture recognition is applied to identify the movements of the devices, to mark them as a pair. This application is of interest for social networks(More)
—Passive, backscatter radio frequency identification (RFID) systems are often range limited by the power incident on the radio frequency (RF) tag. We have demonstrated an increase in the power incident on the RF tag using transmit diversity in a monostatic backscatter channel. Transmit diversity was achieved by phase conjugating the forward link of the(More)