Highly flexible all-optical wavelength conversion at 2.488 Gbits/s using a multi-output-wavelength laser

An integrated multiwavelength grating cavity (MGC) laser fabricated by selective area regrowth is demonstrated. In addition to allowing wavelength conversion, the device can perform various important network functions such as space switching and multiplexing. The use of the device for these functions offers several advantages from a wavelength division multiplexing (WDM) network, such as flexibility, reduced component count, size, and the associated cost reduction.

Engineering development of the Lancaster flexible bag.

Describes progress in the last 12 months which has established bag designs and fabrication techniques, giving greater confidence in the life and cost of these components. A quarter scale bag is under construction. Extensive tank testing has also established life time bending moment and mooring load envelopes, enabling hull and mooring design to proceed. A computer simulation programme has been used to check tank model results and to establish turbine and generator operating conditions. This has allowed generation and transmission component design to proceed, and suggests a high operating efficiency can be maintained with a simple control regime. Simple solutions in minor areas such as valve design and damage stability control add to the picture of steady progress in establishing the Lancaster Flexible Bag 's feasibility.

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.

Carbon nanotube based cathodes for microwave amplifiers

We have studied two different kinds of electron tubes using a cold field emission cathode as the electron source. This cathode is an array of vertically aligned multiwall carbon nanotubes. The first device is a triode. With this device, we demonstrated the modulation at 32 GHZ of a 1.4 A/cm2 peak current density with a 82% modulation ratio. The second device is a traveling wave tube. For this device, the objective is to test a cathode delivering a 2 A/cm 2 electron beam. ©2009 IEEE.

Carbon nanotube based photocathodes for high frequency amplifiers

The combination of high frequency, high power, high efficiency capabilities is a feature of vacuum tube technology. For most of applications, large bandwidths are required, and therefore the modulation method should also allow large bandwidth operation. Optically modulated cold cathodes, avoiding the use of resonant cavities, should satisfy this requirement. This is the reason why we have developed carbon nanotube based photocathode.© 2009 IEEE.

Flexible array sensors based on zinc oxide nanowires for touch displays

Recent efforts towards the fabrication of touch sensing systems are presented, in which zinc oxide nanowire arrays are embedded in a polymer matrix to produce an engineered composite material. In the future, these sensor systems will be fully flexible and multi-touch as intended for Nokia's 'Morph' concept device.

Refractive index evaluation of multi-walled carbon nanotube arrays

Transmission terahertz time-domain spectroscopy (THz-TDS) measurements of carbon nanotube arrays are presented. A relatively thin film with vertically aligned multi-walled carbon nanotubes has been prepared and measured using THz-TDS. Experimental results were obtained from 80GHz to 2.5THz, and the sample has been characterized by extracting the relative permittivity of the carbon nanotubes. A combination of the Maxwell-Garnett and Drude models within the frequency range provide a good fit to the measured permittivity.

Fabrication and mechanical property of carbon nanotube/metal composites

Carbon nanotubes (CNTs) are known to exhibit extraordinary mechanical properties such as high tensile strength, the highest Young modulus etc. These, combining with their large aspect ratio, make CNTs an excellent additive candidate to complement or substitute traditional carbon black or glass fiber fillers for the development of nano-reinforced composites. CNTs have thus far been used as additives in polymers, ceramics and metals to be pursued on practical applications of their composites. © 2010 IEEE.

Stabilization of carbon nanotube field emitters

Carbon nanotubes (CNTs) have been determined to be field emitters of high quality, but CNTs produced by chemical vapour deposition can produce emission currents with high instability and noise. This work finds that adsorbates and amorphous carbon deposited during the growth process are the primary contributors to field emission instability, and shows that burning off the amorphous carbon in air at 450 °C removes the amorphous carbon, resulting in stabilities of better than 3 per cent over 1 h. This work removes one of the major barriers to the use of CNTs in field emission devices.

Hydrodynamic pressures behind flexible and rigid dams

During earthquakes, hydrodynamic pressures are generated by the impounded reservoir on the dam face. The magnitude and distribution of the hydrodynamic pressures vary with factors such as frequency and intensity of earthquake-induced ground motion, depth of impounded reservoir, stiffness of dam and geological conditions. It is difficult to obtain experimental data on hydrodynamic pressures from the field owing to uncertainties associated with earthquake loading. This paper aims at using dynamic centrifuge modelling to measure hydrodynamic pressures behind both relatively stiff and flexible model dams. Comparisons of the experimental data with theoretical hydrodynamic pressures show that Westergaard's equation gives a conservative estimation of hydrodynamic pressures. Comparison with Chopra's method revealed that it underpredicts hydrodynamic pressures for low reservoir depths but gives reasonably good predictions for higher depths of reservoir. It is concluded that dynamic centrifuge modelling may be an effective experimental method to estimate the hydrodynamic pressures acting on a dam. © 2010 Thomas Telford Ltd.

Building flexible user interfaces for solving PDEs

FEniCS is a collection of software tools for the automated solution of differential equations by finite element methods. In this note, we describe how FEniCS can be used to solve a simple nonlinear model problem with varying levels of automation. At one extreme, FEniCS provides tools for the fully automated and adaptive solution of nonlinear partial differential equations. At the other extreme, FEniCS provides a range of tools that allow the computational scientist to experiment with novel solution algorithms. © 2010 American Institute of Physics.