Analysis of subspace fitting and ML techniques for parameterestimation from sensor array data

It is shown that the multidimensional signal subspace method, termed weighted subspace fitting (WSF), is asymptotically efficient. This results in a novel, compact matrix expression for the Cramer-Rao bound (CRB) on the estimation error variance. The asymptotic analysis of the maximum likelihood (ML) and WSF methods is extended to deterministic emitter signals. The asymptotic properties of the estimates for this case are shown to be identical to the Gaussian emitter signal case, i.e. independent of the actual signal waveforms. Conclusions concerning the modeling aspect of the sensor array problem are drawn     

A view of three decades of linear filtering theory

Developments in the theory of linear least-squares estimation in the last thirty years or so are outlined. Particular attention is paid to early mathematica[ work in the field and to more modern developments showing some of the many connections between least-squares filtering and other fields.     

Displacement structure approach to discrete-trigonometric-transform based preconditioners of G.Strang type and of T.Chan type

In this paper adisplacement structure technique is used to design a class of newpreconditioners for theconjugate gradient method applied to the solution of large Toeplitz linear equations. Explicit formulas are suggested for the G.Strang-type and for the T.Chan-type preconditioners belonging to any of 8 classes of matrices diagonalized by the correspondingdiscrete cosine or sine transforms. Under the standard Wiener class assumption theclustering property is established for all of these preconditioners, guaranteeing a rapid convergence of the preconditioned conjugate gradient method. The formulas for the G.Strang-type preconditioners have another important application: they suggest a wide variety of newO(m logm) algorithms for multiplication of a Toeplitz matrix by a vector, based on any of the 8 DCT’s and DST’s. Recentlytransformations of Toeplitz matrices to Vandermonde-like or Cauchy-like matrices have been found to be useful in developing accuratedirect methods for Toeplitz linear equations. Here it is suggested to further extend the range of the transformation approach by exploring it foriterative methods; this technique allowed us to reduce the complexity of each iteration of the preconditioned conjugate gradient method to 4 discrete transforms per iteration. This work was supported in part by ARO contract DAAH04-96-1-0176, NSF contract CCR-962811 and also by DARPA contract F49620-95-1-0525. The views and conclusions contained in these documents are those of the author(s) and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of the National Science Foundation, the Advanced Research Projects Agency, the Army Research office, or the U.S. Government.     

On linear H∞ equalization of communicationchannels

As an alternative to existing techniques and algorithms, we investigate the merit of the H^∞ approach to the linear equalization of communication channels. We first give the formulation of all causal H^∞ equalizers using the results of and then look at the finite delay ease. We compare the risk-sensitive H^∞ equalizer with the MMSE equalizer with respect to both the average and the worst-case BER performances and illustrate the improvement due to the use of the H^∞ equalizer     

Effect of metalloids on crystallization and magnetic behaviour of FeCoSiB based metallic glass

A series of amorphous iron-cobalt alloys with varying metalloid, boron and silicon contents were studied for their thermal stability and magnetic behaviour. The crystallization temperature and thermal stability increased with the silicon content. Good soft magnetic properties were observed for the materials with nominal composition, (Fe_0.79Co_0.21)77Si_12.2B_10.8. The magnetic properties were further improved by annealing.     

New algorithms for reconfiguring VLSI/WSI arrays

In this paper we present new algorithms for reconfiguring arrays of identical Processing Elements (PEs) in the presence of faults. In particular, we consider a well-studied reconfiguration model which consists of a rectangular array of PEs with spare columns of PEs on one side. In the presence of faulty PEs, reconfiguration is achieved by constructing alogical array using only the healthy non-spare and spare PEs. Note that one can always successfully reconfigure the array as long as the number of faulty PEs is no more than the number of spare PEs. The general objective, however, is to derive a logical array such that the geometric distances betweenlogical neighbors (i.e., PEs that are connected in the reconfigured array) are kept small. This criterion is motivated by the fact that shorter interconnects reduce the communication delays among the PEs, and also lead to less routing hardware. The problem of determining a reconfiguration that minimizes the length of the longest interconnect ishard and several researchers have presented sub-optimal algorithms that seem to have satisfactory performance. In this paper we develop anew efficient algorithm that can reconfigure any array with arbitrary patterns of faulty PEs. Furthermore we show that our algorithm performs better than most of the other algorithms developed for similar models.This work was supported in part by the SDIO/IST U.S. Army Research Office through Contract DAAL03-90-G-0108.     

A note on the complementary model of Weinert and Desai

We use elementary concepts of linear least-squares estimation to obtain a direct derivation of the so-called complementary model of Weinert and Desai [1].     

Crystallization Study of Cu_(56)Zr_7Ti_(37) Metallic Glass by Electrical Resistivity Measurement

In this paper,the crystallization behaviour of amorphous Cu56Zr7Ti37 alloy using thermal electrical resistivity(TER) and differential scanning calorimetry(DSC) studies has been described.Isochronal TER and DSC measurements indicate that crystallization occurs in two stages.Isothermal crystallization studies of the alloy by TER show that the kinetics conforms to Johnson-Mehl-Avrami model.Avrami exponents derived from kinetics,between 1.1 and 1.2,imply that the crystallization processes are diffusion controlled with near zero nucleation.Activation energy has been found to increase with the transformed volume fraction.A plausible explanation has been presented by separating the contributions due to nucleation and crystal growth towards total activation energy.