Some new results on binary linear block codes

Certain properties of the parity-check matrix H of (n, k) linear codes are used to establish a computerised search procedure for new binary linear codes. Of the new error-correcting codes found by this procedure, two codes were capable of correcting up to two errors, three codes up to three errors, four codes up to four errors and one code up to five errors. Two meet the lower bound given by Helgert and Stinaff, and seven codes exceed it. In addition, one meets the upper bound. Of the even-Hamming-distance versions of these codes, eight meet the upper bound, and the remaining two exceed the lower bound.     

Online digital filtering

The advantages of the recursive digital filter as a real-time signal processor are stated, and, as an example, a fourth-order Cheby?shev lowpass filter has been synthetised and programmed into an online computer. Typical responses are shown for pulse, step and low-frequency mixed sinusoidal signals.     

An extended UTD analysis for RCS computations involving higher order curved surfaces

An extended utd (eutd) solution is developed for the scattering and diffraction of high frequency em fields from higher order (polynomial and spline defined) curved surfaces. The new solution is computationally efficient and overcomes the difficulties of the classic go/gtd/utd solutions near ray caustics and caustic terminations. The approach for constructing the eutd solution is based on a spatial domain radiation integral representation for the scattered field which is then reduced using a uniform asymptotic procedure. Further heuristic modifications are also made and correct the go induced current assumption near the shadow boundaries. New uniform reflection, first order edge diffraction, and zero-curvature diffraction coefficients are then derived and involve higher order phase integrals as canonical functions. Numerical results involving third and fourth order polynomial strips are provided and compare favorably with reference moment method results. abs]Fr|Résumé Une théorie uniforme de la diffraction étendue (eutd) est développée pour la diffraction ? un champ électromagnétique à haute fréquence sur des surfaces de courbure complexe. La nouvelle résolution est intéressante du point de vue du temps de calcul et permet ? éviter les difficultés classiques des méthodes gtd/utd près de certaines caustiques. ? approche prise pour la construction de ? eutd est basée sur une représentation intégrate dans le domaine spatial du champ diffracté, réduite par une procédure asymptotique uniforme. Des modifications heuristiques sont faites qui corrigent le courant ? optique géométrique près de la frontière ? ombre. Des expressions uniformes sont alors déduites qui demandent le calcul ? intégrates de termes possédant une phase ? ordre élevé. Des résultats numériques sont donnés et comparés avec ceux obtenus par une méthode des moments.     

Wave active filters

A method is described and implemented for the derivation of active RC filters from analogue passive filters of the lossless ladder doubly terminated kind. The method is based on scattering-parameter formulation and the active RC filters thus derived are referred to as wave active filters.     

A sparse and condensed QP formulation for predictive control of LTI systems

The computational burden that model predictive control (MPC) imposes depends to a large extent on the way the optimal control problem is formulated as an optimization problem. We present a formulation where the input is expressed as an affine function of the state such that the closed-loop dynamics matrix becomes nilpotent. Using this approach and removing the equality constraints leads to a compact and sparse optimization problem to be solved at each sampling instant. The problem can be solved with a cost per interior-point iteration that is linear with respect to the horizon length, when this is bigger than the controllability index of the plant. The computational complexity of existing condensed approaches grow cubically with the horizon length, whereas existing non-condensed and sparse approaches also grow linearly, but with a greater proportionality constant than with the method presented here.     

A Parallel Recursive Shortest Spanning Tree Algorithm for Image Segmentation in Distributed Computing Environment

The recursive shortest spanning tree (RSST) algorithm has been used for various image and video coding systems. The speed is very demanding for such applications. However, the RSST algorithm is too complex to perform in a reasonable time. This motivates the present work. A distributed algorithm that constructs a recursive shortest spanning tree for image segmentation with a fixed number of processors is presented in this paper. Using a tailored data partition strategy to assign jobs to processors in our proposed parallel recursive shortest spanning tree (PRSST) algorithm, we derive a new lower bound ofO(n) for one processor with ann-pixel image. The complexity of the proposed algorithm is cost-optimal and the total number of messages required isO(c) for images of any size, wherecis a small constant. The objective quality of segmented images produced by our PRSST has maximum 1.5 dB difference from those generated by Morris's RSST algorithm for images of the size of 128 by 128 and 150 by 150 pixels.     

Improvement for solving the mix-up problem in constant modulusarrays

The authors propose an efficient and computationally fast algorithm for solving the mix-up problem in complex arrays. The Lagrange multiplier theory is used in the optimisation of the constant modulus algorithm (CMA) cost function and the input data are processed in blocks. Furthermore, a simplification of the CMA cost function is proposed that leads to a robust algorithm for solving this problem. Simulations are presented to support the analysis     

Mechanical and high pressure tribological properties of nanocrystalline Ti(N,C) and amorphous C:H nanocomposite coatings

This paper reports on the mechanical and high pressure tribological properties of nanocrystalline (nc-) Ti(N,C)/amorphous (a-) C:H deposited, using low temperature (～ 200 °C) DC reactive magnetron sputtering. The mechanical properties are affected by the nc-Ti(N,C)/a-C:H phase fraction ratio. For increasing C contents (from 31 to 47 at.%) an increase of the a-C:H phase content and a degradation of the nanocrystalline phase occurs leading to a reduction in nanoindentation hardness (H) values (from 15 to 9 GPa) and reduced modulus (Er) values (from 150 to 80 GPa). A strong correlation between H/E ratio and wear performance was exhibited by the coatings. The synthesized coatings survived up to 100 m sliding distance when tested using pin-on-disc sliding configuration at > 4.5 GPa contact pressures and the measured friction coefficient values were similar for all films (μ ～ 0.21–0.25).