Mechanical countermeasures to subsynchronous torsional instability[in turbogenerators]

A mechanical countermeasure is presented that uses a fluid coupling to drive a flywheel at the end of a turbogenerator shaft, resulting in increased torsional damping for the shaft. The effect of varying the flywheel inertia and the fluid coupling's characteristics on the mechanical damping is presented. The application of such a countermeasure to subsynchronous resonance requires studies to determine the size of the coupling and flywheel that would be required to offset any negative electrical damping that may exist due to series compensation on the transmission system     

Dual parallel modulation schemes for low-distortion analog opticaltransmission

The use of two integrated-optical modulators operated in parallel to attain low-distortion analog optical transmission is examined. This static feedforward approach achieves significantly improved linearity at the expense of small increases in the required optical power and moderate increases in the required drive voltage. A novel variation that uses the unique characteristics of an integrated-optical modulator to correct the dominant quadratic distortion of a directly modulated laser is proposed     

Laser surface hardening of thin steel slabs

The transformation hardening of steels by surface heating by a c.w. laser beam has been studied. We examined the surface treatment of thin steel slabs by a suitable mathematical model of the thermal transient induced by laser beam heating. The laser parameters for surface hardening of such samples and the resulting microstructures are discussed. Hardening depths calculated from the mathematical model fit well with experimental results.     

Simulating the propagation of displacement discontinuities in a regularized strain‐softening medium

A numerical model is developed which allows the inclusion of displacement discontinuities in a strain‐softening medium, independent of the finite element mesh structure. Inelastic deformations develop in the continuum and, when a critical threshold of inelastic deformation is reached, a displacement discontinuity is inserted. Discontinuities are introduced using the partition of unity concept which allows discontinuous functions to be added to the standard finite element basis. It is shown that the introduction of displacement discontinuities at the later stages of the failure process can lead to a failure mode that is fundamentally different than that using a continuum model only. This combined continuum‐discontinuous model is better able to describe the entire failure process than a continuum or a discrete model alone and treats mode‐I and mode‐II failure in a unified fashion. Copyright © 2001 John Wiley & Sons, Ltd.     

Data fusion of electrophysiological and haemodynamic signals forventricular rhythm tracking

Demonstrates how the cause of the ventricular contraction (VC), reflected by its electrophysiological precursors (ECG), and its related effect on the haemodynamic system [characterized by the systemic arterial pressure (SAP), sometimes called the mean systolic arterial pressure (MSAP)] can be fused together for a ventricular rhythm (VR) tracking purpose. Data fusion of heterogeneous signals, such as ECG and SAP, appears to be an interesting alternative to overcome the relative drawbacks of signal processing on univariate channels. Behind the clinical aim of providing a more robust VR signal, this article exemplifies how to manage such heterogeneous data when asynchronous events represent the same VC. From an engineering perspective, the main objectives of this article are, firstly, to present a formal representation of the problem of VR tracking and, secondly, to introduce a novel signal processing architecture that is able to manage and fuse cardiovascular data that are both asynchronous and heterogeneous. The evaluation of the performance of this signal processing system uses a very noisy data set extracted from the IMPROVE data library