Influence of lattice temperature on SOI MOSFET's output characteristics

An explanation for the observed variations in the output behaviour of SOI transistors with different buried oxide thicknesses is presented. At low drain bias, the temperature effects are relatively insignificant while at high drain bias, the temperature effects dominate the nonlinear behaviour of the output characteristics.

MOS and bipolar gated thyristor: A thyristor with IGBT switching characteristics

The IGBT has become the device of choice in many high-voltage-power electronic applications, by virtue of combining the ease of MOS gate control with an acceptable forward voltage drop. However, designers have retained an interest in MOS gated thyristor structures which have a turn-off capability. These offer low on-state losses as a result of their latching behaviour. Recently, there have been various proposals for dual-gate devices that have a thyristor on-state with IGBT-like switching. Many of these dual gated structures rely on advanced MOS technology, with inherent manufacturing difficulties. The MOS and bipolar gated thyristor offers all the advantages of dual gated performance, while employing standard IGBT processing techniques. The paper describes the MBGT in detail, and presents experimental and simulation results for devices based on realistic commercial processes. It is shown that the MBGT represents a viable power semiconductor device technology, suitable for a diverse range of applications. © IEE, 1998.

Improving discharge characteristics of indirect integral collector storage systems with multi-element storage

Desired performance of unpressurized integral collector storage systems hinges on the appropriate selection of storage volume and the immersed heat exchanger. This paper presents analytical results expressing the relation between storage volume, number of heat exchanger transfer units and temperature limited performance. For a system composed of a single storage element, the limiting behavior of a perfectly stratified storage element is shown to be superior to a fully-mixed storage element, consistent with more general analysis of thermal storage. Since, however, only the fully-mixed limit is readily obtainable in a physical system, the present paper also examines a division of the storage volume into separate compartments. This multi-element storage system shows significantly improved discharge characteristics as a result of improved elemental area utilization and temperature variation between elements, comparable in many cases to a single perfectly-stratified storage element. In addition, the multi-element system shows increased robustness with respect to variations in heat exchanger effectiveness and initial storage temperature.

The influence of peel angle on the mechanics of peeling flexible adherends with arbitrary load-extension characteristics

The peel test is commonly used to determine the strength of adhesive joints. In its simplest form, a thin flexible strip which has been bonded to a rigid surface is peeled from the substrate at a constant rate and the peeling force which is applied to the debonding surfaces by the tension in the tape is measured. Peeling can be carried out with the peel angle, i.e. the angle made by the peel force with the substrate surface, from any value above about 10° although peeling tests at 90 and 180° are most common. If the tape is sufficiently thin for its bending resistance to be negligibly small then as well as the debonding or decohesion energy associated with the adhesive in and around the point of separation, the relation between the peeling force and the peeling angle is influenced both by the mechanical properties of the tape and any pre-strain locked into the tape during its application to the substrate. The analytic solution for a tape material which can be idealised as elastic perfectly-plastic is well established. Here, we present a more general form of analysis, applicable in principle to any constitutive relation between tape load and tape extension. Non-linearity between load and extension is of increasing significance as the peel angle is decreased: the model presented is consistent with existing equations describing the failure of a lap joint between non-linear materials. The analysis also allows for energy losses within the adhesive layer which themselves may be influenced by both peel rate and peel angle. We have experimentally examined the application of this new analysis to several specific peeling cases including tapes of cellophane, poly-vinyl chloride and PTFE. © 2005 Elsevier Ltd. All rights reserved.

Photonics and lasing in liquid crystal materials

Owing to fundamental reasons of symmetry, liquid crystals are soft materials. This softness allows long length-scales, large susceptibilities and the existence of modulated phases, which respond readily to external fields. Liquid crystals with such phases are tunable, self-assembled, photonic band gap materials; they offer exciting opportunities both in basic science and in technology. Since the density of photon states is suppressed in the stop band and is enhanced at the band edges, these materials may be used as switchable filters or as mirrorless lasers. Disordered periodic liquid crystal structures can show random lasing. We highlight recent advances in this rapidly growing area, and discuss future prospects in emerging liquid crystal materials. Liquid crystal elastomers and orientationally ordered nanoparticle assemblies are of particular interest. © 2006 The Royal Society.

Random lasing in a bistable smectic A liquid crystal

In this work, we examine the phenomenon of random lasing from the smectic A liquid crystal phase. We summarise our results to date on random lasing from the smectic A phase including the ability to control the output from the sample using applied electric fields. In addition, diffuse random lasing is demonstrated from the electrohydrodynamic instabilities of a smectic A liquid crystal phase that has been doped with a low concentration of ionic impurities. Using a siloxane-based liquid crystal doped with ionic impurities and a laser dye, nonresonant random laser emission is observed from the highly scattering texture of the smectic A phase which is stable in zero-field. With the application of a low frequency alternating current electric field, turbulence is induced due to motion of the ions. This is accompanied by a decrease in the emission linewidth and an increase in the intensity of the laser emission. The benefit in this case is that a field is not required to maintain the texture as the scattering and homeotropic states are both stable in zero field. This offers a lower power consumption alternative to the electric-field induced static scattering sample.