Guided propagation of surface acoustic waves and piezoelectric field enhancement in ZnO/GaAs systems

The characteristics and dispersion of the distinct surface acoustic waves (SAWs) propagating in ZnO/GaAs heterostructures have been studied experimentally and theoretically. Besides the Rayleigh mode, strong Sezawa modes, which propagate confined in the overlayer, arise due to the smaller sound velocity in ZnO than in the substrate. The design parameters of the structure providing the strongest piezoelectric field at a given depth within the layered system for the different modes have been determined. The piezoelectric field of the Rayleigh mode is shown to be more than 10 times stronger at the interface region of the tailored ZnO/GaAs structure than at the surface region of the bulk GaAs, whereas the same comparison for the first Sezawa mode yields a factor of 2. This enhancement, together with the capacity of selecting waves with different piezoelectric and strain field depth profiles, will facilitate the development of SAW-modulated optoelectronic applications in GaAs-based systems. © 2011 American Institute of Physics.

Morphological decomposition in Arabic ASR systems

In recent years, the use of morphological decomposition strategies for Arabic Automatic Speech Recognition (ASR) has become increasingly popular. Systems trained on morphologically decomposed data are often used in combination with standard word-based approaches, and they have been found to yield consistent performance improvements. The present article contributes to this ongoing research endeavour by exploring the use of the 'Morphological Analysis and Disambiguation for Arabic' (MADA) tools for this purpose. System integration issues concerning language modelling and dictionary construction, as well as the estimation of pronunciation probabilities, are discussed. In particular, a novel solution for morpheme-to-word conversion is presented which makes use of an N-gram Statistical Machine Translation (SMT) approach. System performance is investigated within a multi-pass adaptation/combination framework. All the systems described in this paper are evaluated on an Arabic large vocabulary speech recognition task which includes both Broadcast News and Broadcast Conversation test data. It is shown that the use of MADA-based systems, in combination with word-based systems, can reduce the Word Error Rates by up to 8.1 relative. © 2012 Elsevier Ltd. All rights reserved.

Modelling information requirements in complex engineering services

Services based around complex engineering equipment and systems provide substantial challenges in both the long-term management of the equipment and the need for guaranteed delivery of the related service. One of the challenges for an organisation providing these services is the management of the information that is required to design, deliver and subsequently assess the success of the service. To assist in this process this paper develops a model for capturing, organising and assessing information requirements for these Complex Engineering Services in which information required to support key decisions in the life cycle of the service is identified. The model – referred to as The 12-Box Model for Service Information Requirements – is embedded in a three-phase procedure for providing an assessment of information requirements of a service contract which also provides insight into the capabilities of available information systems in supporting the contract. An illustrative example examining service information in an aircraft availability contract is used to demonstrate the use of the 12-Box Model and associated assessment procedure.

The application of STEM and in situ controlled dehydration to bacterial systems using ESEM.

Transmission imaging with an environmental scanning electron microscope (ESEM) (Wet STEM) is a recent development in the field of electron microscopy, combining the simple preparation inherent to ESEM work with an alternate form of contrast available through a STEM detector. Because the technique is relatively new, there is little information available on how best to apply this technique and which samples it is best suited for. This work is a description of the sample preparation and microscopy employed by the authors for imaging bacteria with Wet STEM (scanning transmission electron microscopy). Three different bacterial samples will be presented in this study: first, used as a model system, is Escherichia coli for which the contrast mechanisms of STEM are demonstrated along with the visual effects of a dehydration-induced collapse. This collapse, although clearly in some sense artifactual, is thought to lead to structurally meaningful morphological information. Second, Wet STEM is applied to two distinct bacterial systems to demonstrate the novel types of information accessible by this approach: the plastic-producing Cupriavidus necator along with wild-type and ΔmreC knockout mutants of Salmonella enterica serovar Typhimurium. Cupriavidus necator is shown to exhibit clear internal differences between bacteria with and without plastic granules, while the ΔmreC mutant of S. Typhimurium has an internal morphology distinct from that of the wild type.

Centrifuge modelling on long-term behaviour of tunnels in transitional ground

Long-term settlement of tunnels has caused concerns about its influence on tunnel safety and serviceability. Aiming to investigate the long-term behaviour of tunnels against the background of Shanghai metro line, two cases of centrifuge modelling were conducted, with efforts to expose the mechanism affecting the consolidation of the ground. Evenly layered ground and transitional ground strata were set for each case separately and the settlement, lining load and pore water pressure were checked against elapsed time up to 20 years. The results verified some previous findings concerning the settlement and lining load development trend, however, it was also shown that the transitional ground made the tunnel response more complicated. The research is expected to provide some basis for further research on other affecting factors, such as lining permeability. © 2010 Taylor & Francis Group, London.

Development of teaching resources for physical modelling community

Physical modelling of interesting geotechnical problems has helped clarify behaviours and failure mechanisms of many civil engineering systems. Interesting visual information from physical modelling can also be used in teaching to foster interest in geotechnical engineering and recruit young researchers to our field. With this intention, the Teaching Committee of TC2 developed a web-based teaching resources centre. In this paper, the development and organisation of the resource centre using Wordpress. Wordpress is an open-source content management system which allows user content to be edited and site administration to be controlled remotely via a built-in interface. Example data from a centrifuge test on shallow foundations which could be used for undergraduate or graduate level courses is presented and its use illustrated. A discussion on the development of wiki-style addition to the resource centre for commonly used physical model terms is also presented. © 2010 Taylor & Francis Group, London.

Clustering user data for user modelling in the GUIDE multi-modal set-top box

Chapter 20 Clustering User Data for User Modelling in the GUIDE Multi-modal Set- top Box PM Langdon and P. Biswas 20.1 ... It utilises advanced user modelling and simulation in conjunction with a single layer interface that permits a ...

The application of STEM and in situ controlled dehydration to bacterial systems using ESEM

Transmission imaging with an environmental scanning electron microscope (ESEM) (Wet STEM) is a recent development in the field of electron microscopy, combining the simple preparation inherent to ESEM work with an alternate form of contrast available through a STEM detector. Because the technique is relatively new, there is little information available on how best to apply this technique and which samples it is best suited for. This work is a description of the sample preparation and microscopy employed by the authors for imaging bacteria with Wet STEM (scanning transmission electron microscopy). Three different bacterial samples will be presented in this study: first, used as a model system, is Escherichia coli for which the contrast mechanisms of STEM are demonstrated along with the visual effects of a dehydration-induced collapse. This collapse, although clearly in some sense artifactual, is thought to lead to structurally meaningful morphological information. Second, Wet STEM is applied to two distinct bacterial systems to demonstrate the novel types of information accessible by this approach: the plastic-producing Cupriavidus necator along with wild-type and δmreC knockout mutants of Salmonella enterica serovar Typhimurium. Cupriavidus necator is shown to exhibit clear internal differences between bacteria with and without plastic granules, while the δmreC mutant of S. Typhimurium has an internal morphology distinct from that of the wild type. © 2012 Wiley Periodicals, Inc.

Gigabit NRZ, CAP and optical OFDM systems over POF links using LEDs

Simulations have been performed to compare the system capacity and power dissipation of NRZ, CAP-64 and 64-QAM-OFDM systems over FEC enhanced POF links using LEDs, for both unidirectional and bidirectional transmission. It is shown that CAP-64 outperforms NRZ and 64-QAM-OFDM in terms of system capacity and supports a record high 3.5Gb/s bidirectional and 2.1Gb/s unidirectional transmissions over 50m POF. The CAP-64 transceiver consumes similar power compared with NRZ whilst the 64-QAM-OFDM transceiver consumes about twice as much. © 2012 Optical Society of America.

Comparisons between gigabit NRZ, CAP and optical OFDM systems over FEC enhanced POF links using LEDs

Simulations have been performed to compare the link power budget and power dissipation of carrierless amplitude and phase modulation-64 (CAP-64) and 64-quadrature amplitude modulation-orthogonal frequency division multiplexing (64-QAM-OFDM) systems over feedforward error correction (FEC) enhanced plastic optical fibre (POF) links using light emitting diodes (LEDs). It is shown that CAP-64 outperforms 64-QAM-OFDM and supports record high 2.1Gb/s over 50m POF transmission. The CAP-64 and 64-QAM-OFDM links consume similar powers which are 2 (2.5) times of that of NRZ for the single POF link (twin POF links) case. © 2012 IEEE.