Direct numerical integration of coupled one-dimensional Schrödinger equations

Physical problems which can usually be described with the help of sets of coupled second-order differential equations are outlined. In the case of scattering problems, the direct numerical integration of these equations is the unique method of obtaining a solution. For bound-state calculations this integration is in direct competition with powerful conventional techniques such as the variational principle and the standard matrix diagonalization. We are developing two methods for solving by direct integration the eigenvalue problem associated with sets of coupled one-dimensional Schrödinger equations. These methods are successfully used to calculate the bound states of nuclear three- and four-body systems with two-body pure central forces.     

Elastic-plastic state of torispherical heads

The value of the permissible pressure in torispherical heads is usually judged from the size of the permanent deformations after the first load cycle. The difficulty always lies in the determination of the maximum permanent strain caused by the pressure, as the strain depends on the changes of the elastic-plastic state. The elastic-plastic state of the heads can be, for example, found and well followed by the finite element method. Values obtained in this way are naturally valid only for the case examined. However, by extending the numerical investigations and by appropriately processing and evaluating the results certain regularities and generalizations can be recognized. On this basis certain approximations can be made, leading to a very simple and reliable calculation process.     

Significance of mental factors in paroxysmal ventricular tachycardias]

In this paper is reported on two cases of paroxysmal ventricular tachycardia. The clinical and paraclinical examinations did not reveal any organic heart disease, the psychological one, however, found a very severe neurotic personality disorder. Antiarrhythmic drugs were ineffective in both cases. Meanwhile one female patient went through a brief psychotherapy which dismissed the arrhythmia.     

Time analysis of composite beams with partial interaction using available modelling techniques: A comparative study

This paper presents a comparison of available numerical structural formulations for the short- and long-term analysis of composite beams with partial shear interaction. The finite difference method, the finite element method, the direct stiffness method and the exact analytical model have been considered, and both the instantaneous analysis and the time analysis based on the age-adjusted effective modulus method (AEMM) have been carried out. For modelling based on the first two of these formulations, a spatial discretisation and a discretisation in the time domain are required, while only the time discretisation needs to be specified for the direct stiffness method. The results obtained using these formulations are compared qualitatively and their accuracy is estimated, adopting the exact analytical model as a benchmark reference with the objective of establishing the minimum spatial discretisations required to keep the error within an acceptable tolerance. These comparisons are carried out for simply supported beams, propped cantilevers and fixed ended beams, from which the qualitative behaviour of these formulations in the modelling of continuous beams can also be deduced.     

Cost and time calculation in rough NC turning

The aim of this work is to present the calculation procedure for the optimum cutting conditions (cutting speed and used feed) in high speed turning through an NC rough turning cycle with complex profile. The considered optimization criteria are minimum production time and cost. A simple method for determining the variable machined length, the average workpiece diameter and the optimum number of passes is mentioned. Developed models of cutting time and cost were validated based on experimetal tests. Different models have been programmed in a Visual–Basic interface, allowing the operator to find rapidly optimum values of cutting parameters and an estimation of cutting operation cost.     

Paul de Gara, M.D.: President John F. Kennedy''s allergist

We report an artefact seen on MRI in a patient with a cerebellopontine angle syndrome due to an epidermoid cyst. Even minute nonferromagnetic metallic particles such as gold can cause large artefacts.