Design of 2-D recursive digital filters satisfying prescribed magnitude and constant group delay response

Generation of the 2-variable very-strictly-Hurwitz polynomial (VSHP) using properties of derivatives of even or odd parts of Hurwitz polynomials and their applications in designing 2-D recursive digital filters satisfying prescribed magnitude and constant group delay response is described.     

Austenite stabilization in stainless steel by hydrogen

It has been found that stabilization of austenite by hydrogen is governed not by its amount but by the manner of its introduction into the austenite just prior to transformation into martensite. In this case stabilization is to be understood as a decreasing tendency to transformation into martensite. The experimental results obtained using an appropriate material (steel No. 1.4576) show that cathodic impregnation brings about a stabilization of austenite as defined above.     

Heat transfer in boundary layer flow of a micropolar fluid past a curved surface with suction and injection

Van Dyke's singular perturbation technique has been used to study the heat transfer in the flow of a micropolar fluid past a curved surface with suction and injection. The conditions for similar solutions of the thermal boundary layer equations have been obtained. In addition to the usual “no slip” condition for velocity, the two types of boundary conditions used for microrotation are: (i) no relative spin on the boundary; (ii) the anti-symmetric part of the stress tensor vanishes at the boundary. The effect of suction or injection on velocity, microrotation, temperature, skin friction coefficient, wall couple stress coefficient, displacement and momentum thicknesses, rate of heat transfer and adiabatic wall temperature have been studied. It is observed that with the increase of injection velocity, the thickness of the boundary layer is increased and the local drag is reduced. A comparison with the results obtained for a Newtonian fluid reveals that the microelements present in the fluid reduce the velocity and frictional drag, and cool the boundary.     

Evaluation of performance criteria of the CSI-IM drive system

The stability, sensitivity, and static velocity error coefficient of an induction motor (IM) drive fed by a current-source inverter (CSI) are analyzed to obtain the necessary information for the design of a practical system. These analyses are considered useful for determining an appropriate subsystem to compensate for performance deficiencies     

Effect of pretreatment on the anodic behaviour of lead alloys for use in electrowinning operations. I

Lead alloys are widely used as anodes in electrowinning operations, for the recovery of metals such as zinc, copper and chromium. When lead alloys are used as such it takes a long time for the build up of a compact, adherent and protective lead dioxide film. During the initial period prior to the build up of the compact layer of lead dioxide, the rate of anodic dissolution is very high, leading to a decrease in the purity of the cathode deposit. In order to minimize the duration of the conditioning of the anode, it is customary to build up a compact lead dioxide layer by pretreating the anodes in suitable electrolytes. An attempt is made to evaluate the performance of the pretreated electrodes by potentiodynamic methods.     

Convulsions with meningiomas: incidence and significance

In a study of a consecutive series of 127 surgically treated meningiomas, it was found that 29% of the patients had reported with convulsions as their initial symptom. In this group, surgical excision of the meningioma stopped the convulsions in about half of the patients, but the others continued to have seizures after their operations. Among those patients with meningiomas who did not have preoperative convulsions, about one-sixth (15 patients) developed postoperative seizures. Patients in both groups required prolonged anticonvulsant medication. Factors predisposing to the occurrence of postoperative seizures were the site of the tumor, faulty surgical technique, and a preoperative history of seizures.     

Thermal and optical properties of Cd1-x Zn x S thin films by photoacoustics

Ternary compounds Cd_1-x Zn _x S for various Zn concentration in thin films are synthesized by spray pyrolysis and studied by photoacoustics technique for thermal and optical properties. The thermal diffusivity as a function of the alloy composition measured by photoacoustics shows a maximum at x = 0.6. The optical band gap increases with zinc concentration and the continuous change indicates the formation of solid solution.