Offset-QAM based coherent WDM for spectral efficiency enhancement

Optically multiplexed multi-carrier systems with channel spacing reduced to the symbol rate per carrier are highly susceptible to inter-channel crosstalk, which places stringent requirements for the specifications of system components and hinders the use of high-level formats. In this paper, we investigate the performance benefits of using offset 4-, 16-, and 64-quadrature amplitude modulation (QAM) in coherent wavelength division multiplexing (CoWDM). We compare this system with recently reported Nyquist WDM and no-guard-interval optical coherent orthogonal frequency division multiplexing, and show that the presented system greatly relaxes the requirements for device specifications and enhances the spectral efficiency by enabling the use of high-level QAM. The achieved performance can approach the theoretical limits using practical components.

Solar thermal collectors for use in hybrid solar-biomass power plants in India

This thesis examined solar thermal collectors for use in alternative hybrid solar-biomass power plant applications in Gujarat, India. Following a preliminary review, the cost-effective selection and design of the solar thermal field were identified as critical factors underlying the success of hybrid plants. Consequently, the existing solar thermal technologies were reviewed and ranked for use in India by means of a multi-criteria decision-making method, the Analytical Hierarchy Process (AHP). Informed by the outcome of the AHP, the thesis went on to pursue the Linear Fresnel Reflector (LFR), the design of which was optimised with the help of ray-tracing. To further enhance collector performance, LFR concepts incorporating novel mirror spacing and drive mechanisms were evaluated. Subsequently, a new variant, termed the Elevation Linear Fresnel Reflector (ELFR) was designed, constructed and tested at Aston University, UK, therefore allowing theoretical models for the performance of a solar thermal field to be verified. Based on the resulting characteristics of the LFR, and data gathered for the other hybrid system components, models of hybrid LFR- and ELFR-biomass power plants were developed and analysed in TRNSYS®. The techno-economic and environmental consequences of varying the size of the solar field in relation to the total plant capacity were modelled for a series of case studies to evaluate different applications: tri-generation (electricity, ice and heat), electricity-only generation, and process heat. The case studies also encompassed varying site locations, capacities, operational conditions and financial situations. In the case of a hybrid tri-generation plant in Gujarat, it was recommended to use an LFR solar thermal field of 14,000 m2 aperture with a 3 tonne biomass boiler, generating 815 MWh per annum of electricity for nearby villages and 12,450 tonnes of ice per annum for local fisheries and food industries. However, at the expense of a 0.3 ¢/kWh increase in levelised energy costs, the ELFR increased saving of biomass (100 t/a) and land (9 ha/a). For solar thermal applications in areas with high land cost, the ELFR reduced levelised energy costs. It was determined that off-grid hybrid plants for tri-generation were the most feasible application in India. Whereas biomass-only plants were found to be more economically viable, it was concluded that hybrid systems will soon become cost competitive and can considerably improve current energy security and biomass supply chain issues in India.

Trigeneration using biomass energy for sustainable development

Purpose: The paper aims to design and prove the concept of micro-industry using trigeneration fuelled by biomass, for sustainable development in rural NW India. Design/methodology/approach: This is being tested at village Malunga, near Jodhpur in Rajasthan. The system components comprise burning of waste biomass for steam generation and its use for power generation, cooling system for fruit ripening and the use of steam for producing distilled water. Site was selected taking into account the local economic and social needs, biomass resources available from agricultural activities, and the presence of a NGO which is competent to facilitate running of the enterprise. The trigeneration system was designed to integrate off-the-shelf equipment for power generation using boilers of approximate total capacity 1 tonne of fuel per hour, and a back-pressure steam turbo-generator (200 kW). Cooling is provided by a vapour absorption machine (VAM). Findings: The financial analysis indicates a payback time of less than two years. Nevertheless, this is sensitive to market fluctuations and availabilities of raw materials. Originality/value: Although comparable trigeneration systems already exist in large food processing industries and in space heating and cooling applications, they have not previously been used for rural micro-industry. The small-scale (1-2 m3/h output) multiple effect distillation (3 effect plus condenser) unit has not previously been deployed at field level. © Emerald Group Publishing Limited.

Uncertainty propagation in the model web:a case study with e-Habitat

eHabitat is a Web Processing Service (WPS) designed to compute the likelihood of finding ecosystems with equal properties. Inputs to the WPS, typically thematic geospatial "layers", can be discovered using standardised catalogues, and the outputs tailored to specific end user needs. Because these layers can range from geophysical data captured through remote sensing to socio-economical indicators, eHabitat is exposed to a broad range of different types and levels of uncertainties. Potentially chained to other services to perform ecological forecasting, for example, eHabitat would be an additional component further propagating uncertainties from a potentially long chain of model services. This integration of complex resources increases the challenges in dealing with uncertainty. For such a system, as envisaged by initiatives such as the "Model Web" from the Group on Earth Observations, to be used for policy or decision making, users must be provided with information on the quality of the outputs since all system components will be subject to uncertainty. UncertWeb will create the Uncertainty-Enabled Model Web by promoting interoperability between data and models with quantified uncertainty, building on existing open, international standards. It is the objective of this paper to illustrate a few key ideas behind UncertWeb using eHabitat to discuss the main types of uncertainties the WPS has to deal with and to present the benefits of the use of the UncertWeb framework.

Two-dimensional viscoelastic discrete triangular system with negative-stiffness components

Potential applications of high-damping and high-stiffness composites have motivated extensive research on the effects of negative-stiffness inclusions on the overall properties of composites. Recent theoretical advances have been based on the Hashin-Shtrikman composite models, one-dimensional discrete viscoelastic systems and a two-dimensional nested triangular viscoelastic network. In this paper, we further analyze the two-dimensional triangular structure containing pre-selected negative-stiffness components to study its underlying deformation mechanisms and stability. Major new findings are structure-deformation evolution with respect to the magnitude of negative stiffness under shear loading and the phenomena related to dissipation-induced destabilization and inertia-induced stabilization, according to Lyapunov stability analysis. The evolution shows strong correlations between stiffness anomalies and deformation modes. Our stability results reveal that stable damping peaks, i.e. stably extreme effective damping properties, are achievable under hydrostatic loading when the inertia is greater than a critical value. Moreover, destabilization induced by elemental damping is observed with the critical inertia. Regardless of elemental damping, when the inertia is less than the critical value, a weaker system instability is identified.

Anomalies in stiffness and damping of a 2D discrete viscoelastic system due to negative stiffness components

The recent development of using negative stiffness inclusions to achieve extreme overall stiffness and mechanical damping of composite materials reveals a new avenue for constructing high performance materials. One of the negative stiffness sources can be obtained from phase transforming materials in the vicinity of their phase transition, as suggested by the Landau theory. To understand the underlying mechanism from a microscopic viewpoint, we theoretically analyze a 2D, nested triangular lattice cell with pre-chosen elements containing negative stiffness to demonstrate anomalies in overall stiffness and damping. Combining with current knowledge from continuum models, based on the composite theory, such as the Voigt, Reuss, and Hashin-Shtrikman model, we further explore the stability of the system with Lyapunov's indirect stability theorem. The evolution of the microstructure in terms of the discrete system is discussed. A potential application of the results presented here is to develop special thin films with unusual in-plane mechanical properties. © 2006 Elsevier B.V. All rights reserved.

Bidirectional transport between the trans-Golgi network and the endosomal system

The exchange of proteins and lipids between the trans-Golgi network (TGN) and the endosomal system requires multiple cellular machines, whose activities are coordinated in space and time to generate pleomorphic, tubulo-vesicular carriers that deliver their content to their target compartments. These machines and their associated protein networks are recruited and/or activated on specific membrane domains where they select proteins and lipids into carriers, contribute to deform/elongate and partition membrane domains using the mechanical forces generated by actin polymerization or movement along microtubules. The coordinated action of these protein networks contributes to regulate the dynamic state of multiple receptors recycling between the cell surface, endosomes and the TGN, to maintain cell homeostasis as exemplified by the biogenesis of lysosomes and related organelles, and to establish/maintain cell polarity. The dynamic assembly and disassembly of these protein networks mediating the exchange of membrane domains between the TGN and endosomes regulates cell-cell signalling and thus the development of multi-cellular organisms. Somatic mutations in single network components lead to changes in transport dynamics that may contribute to pathological modifications underlying several human diseases such as mental retardation.

Design and development of agent-based procurement system to enhance business intelligence

The purpose of this research is to propose a procurement system across other disciplines and retrieved information with relevant parties so as to have a better co-ordination between supply and demand sides. This paper demonstrates how to analyze the data with an agent-based procurement system (APS) to re-engineer and improve the existing procurement process. The intelligence agents take the responsibility of searching the potential suppliers, negotiation with the short-listed suppliers and evaluating the performance of suppliers based on the selection criteria with mathematical model. Manufacturing firms and trading companies spend more than half of their sales dollar in the purchase of raw material and components. Efficient data collection with high accuracy is one of the key success factors to generate quality procurement which is to purchasing right material at right quality from right suppliers. In general, the enterprises spend a significant amount of resources on data collection and storage, but too little on facilitating data analysis and sharing. To validate the feasibility of the approach, a case study on a manufacturing small and medium-sized enterprise (SME) has been conducted. APS supports the data and information analyzing technique to facilitate the decision making such that the agent can enhance the negotiation and suppler evaluation efficiency by saving time and cost.

Retrieving designs from a sketch using an automated GT coding and classification system

While the retrieval of existing designs to prevent unnecessary duplication of parts is a recognised strategy in the control of design costs the available techniques to achieve this, even in product data management systems, are limited in performance or require large resources. A novel system has been developed based on a new version of an existing coding system (CAMAC) that allows automatic coding of engineering drawings and their subsequent retrieval using a drawing of the desired component as the input. The ability to find designs using a detail drawing rather than textual descriptions is a significant achievement in itself. Previous testing of the system has demonstrated this capability but if a means could be found to find parts from a simple sketch then its practical application would be much more effective. This paper describes the development and testing of such a search capability using a database of over 3000 engineering components.

A flexible, extensible object oriented real-time near photorealistic visualization system:the system framework design

In this paper we describe a novel, extensible visualization system currently under development at Aston University. We introduce modern programming methods, such as the use of data driven programming, design patterns, and the careful definition of interfaces to allow easy extension using plug-ins, to 3D landscape visualization software. We combine this with modern developments in computer graphics, such as vertex and fragment shaders, to create an extremely flexible, extensible real-time near photorealistic visualization system. In this paper we show the design of the system and the main sub-components. We stress the role of modern programming practices and illustrate the benefits these bring to 3D visualization. © 2006 Springer-Verlag Berlin Heidelberg.

Asynchrony and the grouping of vowel components:captor tones revisited

Asynchrony is an important grouping cue for separating sound mixtures. A harmonic incremented in level makes a reduced contribution to vowel timbre when it begins before the other components. This contribution can be partly restored by adding a captor tone in synchrony with, and one octave above, the leading portion of the incremented harmonic [Darwin and Sutherland, Q. J. Exp. Psychol. A 36, 193-208 (1984)]. The captor is too remote to evoke adaptation in peripheral channels tuned to the incremented harmonic, and so the restoration effect is usually attributed to the grouping of the leading portion with the captor. However, results are presented that contradict this interpretation. Captor efficacy does not depend on a common onset, or harmonic relations, with the leading component. Rather, captor efficacy is influenced by frequency separation, and extends to about 1.5 oct above the leading component. Below this cutoff, the captor effect is equivalent to attenuating the leading portion of the incremented harmonic by about 6 dB. These results indicate that high-level grouping does not govern the captor effect. Instead, it is proposed that the partial restoration of the contribution of an asynchronous component to vowel timbre depends on broadband inhibition within the central auditory system. © 2006 Acoustical Society of America.

Independent detectors for expansion and rotation, and for orthogonal components of deformation

It is well known that optic flow - the smooth transformation of the retinal image experienced by a moving observer - contains valuable information about the three-dimensional layout of the environment. From psychophysical and neurophysiological experiments, specialised mechanisms responsive to components of optic flow (sometimes called complex motion) such as expansion and rotation have been inferred. However, it remains unclear (a) whether the visual system has mechanisms for processing the component of deformation and (b) whether there are multiple mechanisms that function independently from each other. Here, we investigate these issues using random-dot patterns and a forced-choice subthreshold summation technique. In experiment 1, we manipulated the size of a test region that was permitted to contain signal and found substantial spatial summation for signal components of translation, expansion, rotation, and deformation embedded in noise. In experiment 2, little or no summation was found for the superposition of orthogonal pairs of complex motion patterns (eg expansion and rotation), consistent with probability summation between pairs of independent detectors. Our results suggest that optic-flow components are detected by mechanisms that are specialised for particular patterns of complex motion.

Magnetic drive system for a new centrifugal rotary blood pump

The purpose of this investigation was to design a novel magnetic drive and bearing system for a new centrifugal rotary blood pump (CRBP). The drive system consists of two components: (i) permanent magnets within the impeller of the CRBP; and (ii) the driving electromagnets. Orientation of the magnets varies from axial through to 60° included out-lean (conical configuration). Permanent magnets replace the electromagnet drive to allow easier characterization. The performance characteristics tested were the axial force of attraction between the stator and rotor at angles of rotational alignment, Ø, and the corresponding torque at those angles. The drive components were tested for various magnetic cone angles, ?. The test was repeated for three backing conditions: (i) non-backed; (ii) steel-cupped; and (iii) steel plate back-iron, performed on an Instron tensile testing machine. Experimental results were expanded upon through finite element and boundary element analysis (BEM). The force/torque characteristics were maximal for a 12-magnet configuration at 0° cone angle with steel-back iron (axial force = 60 N, torque = 0.375 Nm). BEM showed how introducing a cone angle increases the radial restoring force threefold while not compromising axial bearing force. Magnets in the drive system may be orientated not only to provide adequate coupling to drive the CRBP, but to provide significant axial and radial bearing forces capable of withstanding over 100 m/s2 shock excitation on the impeller. Although the 12 magnet 0° (?) configuration yielded the greatest force/torque characteristic, this was seen as potentially unattractive as this magnetic cone angle yielded poor radial restoring force characteristics.

Oxidation studies of a novel barrier polymer system

The thermal oxidation of two model compounds representing the aromatic polyamide, MXD6 (poly m-xylylene adipamide) have been investigated. The model compounds (having different chemical structures, viz, one corresponding to the aromatic part of the chain and the other to the aliphatic part), based on the structure of MXD6 were prepared and reactions with different concentrations of cobalt ions examined with the aim of identifying the role of the different structural components of MXD6 on the mechanism of oxidation. The study showed that cobalt, in the presence of sodium phosphite (which acts as an antioxidant for MXD6 and the model compounds), increases the oxidation of the model compounds. It is believed that the cobalt acts predominantly as a catalyst for the decomposition of hydroperoxides, formed during oxidation of the models in the melt phase, to free radical products and to a lesser extent as a catalyst for the initiation of the oxidation reaction by complex formation with the amide, which is more likely to take place in the solid phase. An oxidation cycle has been proposed consisting of two parts both of which will occur, to some extent under all conditions of oxidation (in the melt and in the solid phase), but their individual predominance must be determined by the prevailing oxygen pressure at the reaction site. The different aspects of this proposed mechanism were examined from extensive model compound studies, and the evidence based on the nature of product formation and the kinetics of these reactions. Main techniques used to compare the rates of oxidation and the study of kinetics included, oxygen absorption, FT-IR, UV and TGA. HPLC was used for product separation and identification.