The method of angular lines to solve cylindrical electromagnetic boundary-value problems

A method for solving cylindrical electromagnetic boundary-value problems is presented. The method is semidiscrete. The wave equation is written in cylindrical coordinates and a differential-discretizing process is used in angular direction, and in the radial direction the analytic solutions are used. The new method is called the method of angular lines (MAL). To confirm the validity of MAL Dirichlet- and Neumann-type boundary-value problems of a two-dimensional scalar wave equation are investigated. The results show good agreement with previously published results. Advantages and disadvantages of the method are discussed. © 1995 John Wiley & Sons, Inc.     

Current oscillations due to filamentary double injection in diodes with deep levels

Current oscillations occurring in the positive differential resistance region of the d.c. I–V characteristics of Au-compensated n-type silicon pin diodes have been investigated. The experimental results strongly suggest that the current oscillations are caused by the formation of unstable filaments prior to the occurrence of stable filaments which are connected with the negative differential resistance region typical for double injection diodes with deep levels. On the basis of this model the degree of modulation could be increased up to 30% in our diodes.     

Einfluß unterschiedlicher Aufheizgeschwindigkeiten und Haltedauern auf das Rekristallisationsverhalten verschiedener unlegierter Stähle

Untersuchungen über das Rekristallisationsverhalten von Stahldrähten aus den Stahlsorten St 37, C 35, C 70, D 12-2, D 15-2, D 35-2 nach Verformungsgraden von 10 bis 50% bei unterschiedlichen Rekristallisationsbedingungen mit Aufheizgeschwindigkeiten zwischen 6 und 350 °C/s, Glühtemperaturen zwischen 300 und 700 °C und einer Haltedauer zwischen 60 und 1000 s. Beschreibung der Induktiverwärmungsanlage. Ermittlung der Festigkeitskennwerte wie Zugfestigkeit, Streckgrenze, Bruchdehnung, Brucheinschnürung sowie des Gefüges und der Korngröße nach den verschiedenen Glühungen.     

Image guide couplers with isotropic and anisotropic coupling elements

Among other waveguide elements directional couplers are required in integrated millimeterwave circuits in image guide technique. Hereby an I-guide is used which consists of a dielectric slab between two conducting plates on which the electric field is perpendicularily. Flat coupling behaviour and better isolation can be reached by use of a dielectric coupling element and absorber materials. Thereby the frequency dependence is reduced significantly. Further the coupling can be steered by an additional premagnetized ferrite slab. In this way switched couplers can be realized.     

Synthesis of Microporous Carbon Nanofibers and Nanotubes from Conjugated Polymer Network and Evaluation in Electrochemical Capacitor

One‐dimensional fibers and tubes are constructed through the oriented carbon‐carbon cross‐linking reactions towards rigid conjugated polymer networks. As the result, a template‐free and one‐step synthesis of CNTs and CNFs is achieved through a simple carbonization of the as‐formed carbon‐rich tubular and fiberlike polyphenylene precursors under argon. Microporous CNTs and CNFs with a surface area up to 900 m² g^–1 are obtained, together with HR‐TEM characterizations indicating the formation of intrinsic microporous structure in these rigid carbon‐rich networks. The primary electrochemical experiments reveal their promising applications as advanced electrodes in electrochemical double‐layered capacitor (EDLC).