A unified approach to smoothing formulas

Based on various approaches, several different solutions to the smoothing problem have been given. The relationships between these solutions are not immediate, although they solve the same problem. Making use of a certain framework from scattering theory, we derive two families of solutions, with equations evolving forwards and backwards in time, respectively. Within these families three major previous approaches are obtained as special cases, and their relationships are clarified. The set of solutions also contains as a fourth special case a (new) backwards analog of the innovations solution. The Mayne-Fraser two-filter formula belongs to the set of backwards solutions, and within this framework certain difficulties with its interpretation can be resolved.     

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.     

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.     

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     

A spline-theoretic approach to minimum-energy control

The problem of minimum-energy control of linear systems with linear functional constraints on the output is considered from a spline-theoretic viewpoint. It is shown that constrained minimum-energy control and spline interpolation are dual projection problems: if the given system is driven by the minimum-energy control, the system output will be the spline that interpolates the output constraints. This duality result is used to obtain a simple formula for the exact optimal control under very general constraints.     

MIMO linear equalization with an H/sup /spl infin// criterion

In this paper, we study the problem of linearly equalizing the multiple-input multiple-output (MIMO) communications channels from an H/sup /spl infin// point of view. H/sup /spl infin// estimation theory has been recently introduced as a method for designing filters that have acceptable performance in the face of model uncertainty and lack of statistical information on the exogenous signals. In this paper, we obtain a closed-form solution to the square MIMO linear H/sup /spl infin// equalization problem and parameterize all possible H/sup /spl infin//-optimal equalizers. In particular, we show that, for minimum phase channels, a scaled version of the zero-forcing equalizer is H/sup /spl infin//-optimal. The results also indicate an interesting dichotomy between minimum phase and nonminimum phase channels: for minimum phase channels the best causal equalizer performs as well as the best noncausal equalizer, whereas for nonminimum phase channels, causal equalizers cannot reduce the estimation error bounds from their a priori values. Our analysis also suggests certain remedies in the nonminimum phase case, namely, allowing for finite delay, oversampling, or using multiple sensors. For example, we show that H/sup /spl infin// equalization of nonminimum phase channels requires a time delay of at least l units, where l is the number of nonminimum phase zeros of the channel.     

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.     

Some new algorithms for recursive estimation in constant, linear, discrete-time systems

Certain recently developed fast algorithms for recursive estimation in constant continuous-time linear systems are extended to discrete-time systems. The main feature is the replacement of the Riccati-type difference equation that is generally used for such problems by another set of difference equations that we call of Chandrasekhar-type. The total number of operations in the new algorithm is in general less than with the Riccati-equation based Kalman filter, with significant reductions being obtained in several important special cases. The algorithms are derived via a factorization of increments of the Riccati equation variable, a method that can be extended to nonsymmetric Riccati equations as well.