Showing papers by "University of Bedfordshire published in 1971"

New Methods for Measurement of Complex Permittivity up to 13 GHz and their Application to the Study of Dielectric Relaxation of Polar Liquids Including Aqueous solutions

Abstract: High frequency dielectric measurements, until recently the exclusive prerogative of point-by-point frequency domain methods, can now be made with very reasonable precision in the time domain. These novel methods which are an extension of the earlier reported Time Domain Reflectometry technique yield dielectric information over a range equivalent in frequency to about 10 MHz to 13 GHz. The theoretical basis of these methods is given and their accuracy demonstrated by reference to measurements on water and ethanol. An example of their application to aqueous systems is also given. Hochfrequenzmessungen an Dielektrika, die bisher nur durch “Punkt-fur-Punkt”-Methoden im Frequenzgebiet (frequency domain) ausfuhrbar waren, konnen jetzt mit guter Prazision im Zeitgebiet (time domain) ausgefuhrt werden. Diese neuen Methoden, die eine Verbesserung fruher berichteter Zeitgebiet-Reflektionsmethoden darstellen, gestatten die Ermittlung dielektrischen Verhaltens fur einen Frequenzbereich von etwa 10 MHz bis 13 GHz. Die theoretische Basis dieser Methode wird erlautert und ihre Prazision dargelegt durch Messungen an Wasser und an Athanol. Ein Beispiel ihrer Anwendung auf wasserenthaltende Systeme wird vorgelegt.

The importance of instrumental tilt on measurements of atmospheric turbulence

Abstract: This note discusses the equations that govern the dependence of observed turbulence characteristics on instrumental tilt and then considers the magnitudes of the effects within the constant stress layer.

Cyclic stress-strain relations from bending and push-pull tests:

Abstract: Cyclic plastic-straining tests have been conducted in push-pull on cylindrical specimens and in uniform bending on rectangular-section bars of mild steel (B.S. 1501–161 Grade 28A) and of stainless steel (En 58J). The mild-steel specimens were tested at room temperature and 350°C, the stainless-steel specimens at room temperature and 650°C. It is found that there is good correspondence between cyclic stress-strain relations (the cyclic semi-range of strain and the corresponding cyclic semi-range of stress) derived from bending tests, when an expression analogous to that developed by Nadai for monotonic straining is used, and those obtained more directly from push-pull tests.

Impedance bridge apparatus having lead wire resistance compensation means

Abstract: A bridge circuit for the comparison of the values of electrical impedances. The novel feature is that an additional source of electrical energy is provided which is connected into the bridge circuit in such a way as to ensure that the current through or the voltage across the impedances are in a predetermined ratio. This prevents for example, the resistances of the lead wires affecting the accuracy of the bridge.

Strain localization in beams under cyclic plastic straining at room and elevated temperature

Abstract: Deflection-controlled tests have been conducted on beams subjected to uniform bending and two forms of non-uniform bending in which strain localization occurs. The materials tested were mild steel to B.S. 1501–161 Grade 28A at room temperature and 350°C and stainless steel En 58J at room temperature and 650°C.For materials which show a settled cyclic stress-strain relation (the cyclic semi-range of strain and the corresponding cyclic semi-range of stress) estimates may be made of life in deflection cycling for beams under strain-localization conditions if the strains are calculated from the cyclic relations and the corresponding endurances are obtained from strain-cycling tests in uniform bending. On the basis of the present and previous results, it is believed that this procedure will give predictions which are on the side of safety. In the present work the predictions were often unduly safe. For materials which strain-harden severely, an elastic analysis may sometimes be adequate for an assessme...

Implement carrying linkage means

Abstract: A three-point linkage for an implement-carrying tractor has one link horizontally moveable against resilience, and has a linkage whereby manual control is exercised differentially to drag load, upon the valve which controls the draft-controlling ram.