Simple Iterative Technique Research Articles

The fee Ising model in the cluster variation approximation

The cluster-variation method was used to calculate the critical temperature for the fcc Ising ferromagnet in three different cluster approximations. A scheme for determing a set of independent cluster variables is presented, which considerably simplifies the minimization of the free energy. The system of equations arising from such minimization is solved, in the disordered state, by means of a simple iteration technique. The highest level of approximation treated in this work yields a critical temperature which is only 1.5% above the one estimated by the exact high-temperature expansion of the zero-field susceptibility. Furthermore, the high-temperature expansion for the specific heat gives four exact coefficients and the fifth is determined to within 0.4%.

Iterative design with deflection constraints

A procedure is developed for extending simple iterative design techniques for trusses to the case in which deflection constraints are present. For statically determinate trusses, this procedure involves modifying both the stiffness matrix and the joint load matrix in the analysis/redesign cycle; for statically indeterminate trusses, the allowable stress must also be modified.

Nonlinear identification in the presence of correlated noise using a Hammerstein model

A simple iterative technique for the estimation of parameters in a Hammerstein model is developed for the case when noise in the output data is correlated. Asymptotically unbiased estimates are obtained rapidly by employing a systematic procedure for the determination of a scalar stepping factor at each iteration.

Electron Mobility in Direct-Gap Polar Semiconductors

The electron drift mobilities of the five direct-gap III-V semiconductors GaAs, GaSb, InP, InAs, and InSb are presented as a function of temperature. Polar-mode, deformation-potential acoustic, and piezoelectric scattering are included, as well as nonparabolic conduction bands and the corresponding electron wave functions. The drift mobility follows exactly from the assumed model by a simple iterative technique of solution which retains all the advantages of variational techniques without, however, the need for excessive mathematical detail. Piezoelectric scattering is shown to be considerable in GaAs for temperatures below 100 \ifmmode^\circ\else\textdegree\fi{}K. The agreement between theory and experiment for GaAs is satisfactory.