Simple adaptively modulated optical OFDM modems using subcarrier modulation with input/output reconfigurability

Three novel designs of adaptively modulated optical orthogonal frequency division multiplexing modems using subcarrier modulation (AMOOFDM-SCM) are proposed, for the first time, each of which requires a single IFFT/FFT operation. These designs has a number of salient advantages including a significantly simplified modem configuration due to the involvement of a single IFFT/FFT operation, input/output reconfigurability, dynamic bandwidth allocation capability, cost reduction and system flexibility and performance robustness to variations in transmission link conditions. Investigations show that these three modems are capable of supporting >60Gb/s AMOOFDM-SCM signal transmission over 20km, 40km and 60km single-mode fibre-based intensity modulation and direct detection transmission links without optical amplification and chromatic dispersion compensation. Copyright © 2010 The authors.

Ultrafast sputtered ZnO thin films with high kT for acousticwave device applications

The fabrication of high frequency acoustic wave devices requires thedevelopment of thin films of piezoelectric materials with improved morphologicaland electro-acoustical properties. In particular, the crystalline orientationof the films, surface morphology, film stress and electrical resistivity are keyissues for the piezoelectric response. In the work reported here, ZnO thinfilms were deposited at high rates (>50 nm/min) using a novel process knownas the High Target Utilisation Sputtering (HiTUS). The films deposited possessexcellent crystallographic orientation, high resistivity (>109ωm), and exhibit surface roughness and film stress one order of magnitudelower than films grown with standard magnetron sputtering. The electromechanicalcoupling coefficient of the films, kT, was precisely calculated byimplementing the resonant spectrum method, and was found to be at least 6%higher than any previously reported kT of magnetron sputtered filmsto the Authors' knowledge. The low film stress of the film is deemed as one ofthe most important factors responsible for the high k T valueobtained. © 2010 IEEE.

Theoretical model for dicke superradiance in a semiconductor laser device

A theoretical model for Dicke superradiance (SR) in diode lasers is proposed using the travelling wave method with a spatially resolved absorber and spectrally resolved gain. The role of electrode configuration and optical bandwidth are compared and contrasted as a route to enhance femtosecond pulse power. While pulse duration can be significantly reduced through careful absorber length specification, stability is degraded. However an increased spectral gain bandwidth of up to 150 nm is predicted to allow pulsewidth reductions of down to 10 fs and over 500-W peak power without further degradation in pulse stability. © 2011 IEEE.

ANALYTICAL DEVICE FOR TEST FLUIDS, COMPRISES A CONDUCTIVE POLYMER COMPOSITION

A sensor for chemical species or biological species or radiation presenting to test fluid a polymer composition comprises polymer and conductive filler metal, alloy or reduced metal oxide and having a first level of electrical conductance when quiescent and being convertible to a second level of conductance by change of stress applied by stretching or compression or electric field, in which the polymer composition is characterised by at least one of the features in the form of particles at least 90% w/w held on a 100 mesh sieve; and/or comprising a permeable body extending across a channel of fluid flow; and/or affording in-and-out diffusion of test fluid and/or mechanically coupled to a workpiece of polymer swellable by a constituent of test fluid.

A controller for a miniature intra-aortic ventricular assist device.

Two control algorithms have been developed for a minimally invasive axial-flow ventricular assist device (VAD) for placement in the descending aorta. The purpose of the device is to offload the left ventricle and to augment lower body perfusion in patients with moderate congestive heart failure. The VAD consists of an intra-aortic impeller with a built-in permanent magnet rotor and an extra-aortic stator. The control algorithms, which use pressure readings upstream and downstream of the VAD to determine the pump status, have been tested in a mock circulatory system under two conditions, namely with or without afterload sensitivity. The results give an insight into controller design for an intra-aortic blood pump working in series with the heart.

Design method of an innovative motor for an intra-aortic ventricular assist device

A permanent-magnet motor has been designed for an innovative axial-flow ventricular assist device (VAD), to be placed in the descending aorta, intended to offload the left ventricle and augment renal perfusion in patients with congestive heart failure (CHF). For this application, an intra-aortic impeller with a built-in permanent magnet rotor is driven by an extraaortic stator working in synchronism with the natural heart. To meet this need, a two-dimensional analytical model has been developed in the MATLAB environment to estimate machine parameters; finite element analysis (FEA) has been used to refine the results. A prototype blood pump equipped with an innovative motor designed from the procedure above has been tested in a mock loop representing the human circulatory system. The performance of VAD incorporating the motor is presented. © 2009 IEEE.