35 resultados para updates
em Aston University Research Archive
Resumo:
This paper presents a forecasting technique for forward electricity/gas prices, one day ahead. This technique combines a Kalman filter (KF) and a generalised autoregressive conditional heteroschedasticity (GARCH) model (often used in financial forecasting). The GARCH model is used to compute next value of a time series. The KF updates parameters of the GARCH model when the new observation is available. This technique is applied to real data from the UK energy markets to evaluate its performance. The results show that the forecasting accuracy is improved significantly by using this hybrid model. The methodology can be also applied to forecasting market clearing prices and electricity/gas loads.
Resumo:
Purpose – This study seeks to provide valuable new insight into the timeliness of corporate internet reporting (TCIR) by a sample of Irish-listed companies. Design/methodology/approach – The authors apply an updated version of Abdelsalam et al. TCIR index to assess the timeliness of corporate internet reporting. The index encompasses 13 criteria that are used to measure the TCIR for a sample of Irish-listed companies. In addition, the authors assess the timeliness of posting companies’ annual and interim reports to their web sites. Furthermore, the study examines the influence of board independence and ownership structure on the TCIR behaviour. Board composition is measured by the percentage of independent directors, chairman’s dual role and average tenure of directors. Ownership structure is represented by managerial ownership and blockholder ownership. Findings – It is found that Irish-listed companies, on average, satisfy only 46 per cent of the timeliness criteria assessed by the timeliness index. After controlling for size, audit fees and firm performance, evidence that TCIR is positively associated with board of director’s independence and chief executive officer (CEO) ownership is provided. Furthermore, it is found that large companies are faster in posting their annual reports to their web sites. The findings suggest that board composition and ownership structure influence a firm’s TCIR behaviour, presumably in response to the information asymmetry between management and investors and the resulting agency costs. Practical implications – The findings highlight the need for improvement in TCIR by Irish-listed companies in many areas, especially in regard to the regular updates of information provided on their web sites. Originality/value – This study represents one of the first comprehensive examinations of the important dimension of the TCIR in Irish-listed companies.
Resumo:
Jill Poole's best-selling Casebook on Contract Law provides a clear and well-structured explanation of the principles and rules of contract law through a comprehensive selection of case law, addressing all aspects encountered on undergraduate courses. The coverage in this new edition has been revised to incorporate all recent significant decisions and judgments made by the House of Lords and the Court of Appeal. Extracts have been chosen from a wide range of historical and contemporary cases to illustrate the reasoning processes of the court and how legal principles are developed, thus enabling cases to be analysed and discussed independently while, taken as a whole, the chapters provide a sound understanding of the modern law of contract. Succinct author commentary focuses the reader on the key elements within the extracts, while thought-provoking questions are posed throughout to develop a more in-depth appreciation of the subject. Online resource centre Student resources - Updates - Guidance on answering questions - Guidance on reading cases - Questions and answers.
Resumo:
This ninth edition of the established Textbook on Contract Law by Jill Poole provides a wide-ranging and straightforward exposition of contract law. The text opens with an overview of the main issues surrounding contract law which places the subject in its wider context, then goes on to give a clear explanation of all the major areas of contract law encountered on undergraduate courses. Features of the book includes chapter summaries to draw key themes and issues together; examples and questions to encourage a deeper understanding of the often complex points of law; and extensive further reading lists of both texts and articles to guide students towards the most relevant and up-to-date resources available. Online resource centre Lecturer resources - Testbank of 150 multiple-choice questions Student resources - Guidance on answering questions in contract law - Questions and answers - Student questions - Updates - Web links
Resumo:
Jill Poole's best-selling "Casebook on Contract Law" provides a clear and well-structured exposition of the principles and rules through a comprehensive selection of case law, addressing all aspects encountered on undergraduate courses. Extracts have been chosen from a wide range of historical and contemporary cases to illustrate the reasoning processes of the court, why decisions are made and how legal principles are developed - enabling cases to be analyzed and discussed independently while, taken as a whole, the chapters provide a sound understanding of the modern law of contract. Succinct author commentary focuses the reader on the key elements within the extracts, while thought-provoking questions are posed throughout to develop more in-depth analysis. This book is accompanied by a specifically designed companion web site which provides: Questions in contract law; Guidance on answering questions; Guidance on reading cases; Questions and answers; and Updates.
Resumo:
Jill Poole's best-selling Casebook on Contract Law provides a clear and well-structured explanation of contractual principles through a comprehensive selection of case law, addressing all aspects encountered on undergraduate courses. The coverage in this new edition has been revised to incorporate all recent significant decisions and judgments made by the House of Lords and the Court of Appeal. The extracts have been selected from a wide range of historical and contemporary cases and illustrate the reasoning processes of the court, the grounds justifying the decisions, and how legal principles are developed. Readers can discuss and analyse individual cases while, taken as a whole, the chapters provide a sound appreciation of the modern law of contract. Succinct author commentary focuses the reader on the key elements within the extracts, while thought-provoking questions are posed throughout to develop more in-depth analysis. Online Resource Centre Student resources - Updates - Guidance on answering questions - Guidance on reading cases - Questions and answers.
Resumo:
This is a new edition of the established Textbook on Contract Law by Professor Jill Poole. Designed specifically for undergraduates new to the subject, this title offers a well-structured and straightforward account of the modern law of contract. The text opens with an overview of the key theories and issues surrounding contract contract law which places the subject in its wider context, then goes on to a detailed treatment of all key topics, offering succinct explanations of complex ideas. Other features of the book include chapter summaries that draw key themes and issues together, selected further reading lists, and useful web links to guide students towards the most relevant and up-to-date resources available. Online Resource Centre Lecturer resources - Testbank Student resources - Guidance on answering questions in contract law - Questions and answers - Student questions - Updates - Web links.
Resumo:
In 2002, we published a paper [Brock, J., Brown, C., Boucher, J., Rippon, G., 2002. The temporal binding deficit hypothesis of autism. Development and Psychopathology 142, 209-224] highlighting the parallels between the psychological model of 'central coherence' in information processing [Frith, U., 1989. Autism: Explaining the Enigma. Blackwell, Oxford] and the neuroscience model of neural integration or 'temporal binding'. We proposed that autism is associated with abnormalities of information integration that is caused by a reduction in the connectivity between specialised local neural networks in the brain and possible overconnectivity within the isolated individual neural assemblies. The current paper updates this model, providing a summary of theoretical and empirical advances in research implicating disordered connectivity in autism. This is in the context of changes in the approach to the core psychological deficits in autism, of greater emphasis on 'interactive specialisation' and the resultant stress on early and/or low-level deficits and their cascading effects on the developing brain [Johnson, M.H., Halit, H., Grice, S.J., Karmiloff-Smith, A., 2002. Neuroimaging of typical and atypical development: a perspective from multiple levels of analysis. Development and Psychopathology 14, 521-536].We also highlight recent developments in the measurement and modelling of connectivity, particularly in the emerging ability to track the temporal dynamics of the brain using electroencephalography (EEG) and magnetoencephalography (MEG) and to investigate the signal characteristics of this activity. This advance could be particularly pertinent in testing an emerging model of effective connectivity based on the balance between excitatory and inhibitory cortical activity [Rubenstein, J.L., Merzenich M.M., 2003. Model of autism: increased ratio of excitation/inhibition in key neural systems. Genes, Brain and Behavior 2, 255-267; Brown, C., Gruber, T., Rippon, G., Brock, J., Boucher, J., 2005. Gamma abnormalities during perception of illusory figures in autism. Cortex 41, 364-376]. Finally, we note that the consequence of this convergence of research developments not only enables a greater understanding of autism but also has implications for prevention and remediation. © 2006.
Resumo:
Cascaded multilevel inverters-based Static Var Generators (SVGs) are FACTS equipment introduced for active and reactive power flow control. They eliminate the need for zigzag transformers and give a fast response. However, with regard to their application for flicker reduction in using Electric Arc Furnace (EAF), the existing multilevel inverter-based SVGs suffer from the following disadvantages. (1) To control the reactive power, an off-line calculation of Modulation Index (MI) is required to adjust the SVG output voltage. This slows down the transient response to the changes of reactive power; and (2) Random active power exchange may cause unbalance to the voltage of the d.c. link (HBI) capacitor when the reactive power control is done by adjusting the power angle d alone. To resolve these problems, a mathematical model of 11-level cascaded SVG, was developed. A new control strategy involving both MI (modulation index) and power angle (d) is proposed. A selected harmonics elimination method (SHEM) is taken for switching pattern calculations. To shorten the response time and simplify the controls system, feed forward neural networks are used for on-line computation of the switching patterns instead of using look-up tables. The proposed controller updates the MI and switching patterns once each line-cycle according to the sampled reactive power Qs. Meanwhile, the remainder reactive power (compensated by the MI) and the reactive power variations during the line-cycle will be continuously compensated by adjusting the power angles, d. The scheme senses both variables MI and d, and takes action through the inverter switching angle, qi. As a result, the proposed SVG is expected to give a faster and more accurate response than present designs allow. In support of the proposal there is a mathematical model for reactive powered distribution and a sensitivity matrix for voltage regulation assessment, MATLAB simulation results are provided to validate the proposed schemes. The performance with non-linear time varying loads is analysed and refers to a general review of flicker, of methods for measuring flickers due to arc furnace and means for mitigation.
Resumo:
The modelling of mechanical structures using finite element analysis has become an indispensable stage in the design of new components and products. Once the theoretical design has been optimised a prototype may be constructed and tested. What can the engineer do if the measured and theoretically predicted vibration characteristics of the structure are significantly different? This thesis considers the problems of changing the parameters of the finite element model to improve the correlation between a physical structure and its mathematical model. Two new methods are introduced to perform the systematic parameter updating. The first uses the measured modal model to derive the parameter values with the minimum variance. The user must provide estimates for the variance of the theoretical parameter values and the measured data. Previous authors using similar methods have assumed that the estimated parameters and measured modal properties are statistically independent. This will generally be the case during the first iteration but will not be the case subsequently. The second method updates the parameters directly from the frequency response functions. The order of the finite element model of the structure is reduced as a function of the unknown parameters. A method related to a weighted equation error algorithm is used to update the parameters. After each iteration the weighting changes so that on convergence the output error is minimised. The suggested methods are extensively tested using simulated data. An H frame is then used to demonstrate the algorithms on a physical structure.
Resumo:
This paper uses a meta-Malmquist index for measuring productivity change of the water industry in England and Wales and compares this to the traditional Malmquist index. The meta-Malmquist index computes productivity change with reference to a meta-frontier, it is computationally simpler and it is circular. The analysis covers all 22 UK water companies in existence in 2007, using data over the period 1993–2007. We focus on operating expenditure in line with assessments in this field, which treat operating and capital expenditure as lacking substitutability. We find important improvements in productivity between 1993 and 2005, most of which were due to frontier shifts rather than catch up to the frontier by companies. After 2005, the productivity shows a declining trend. We further use the meta-Malmquist index to compare the productivities of companies at the same and at different points in time. This shows some interesting results relating to the productivity of each company relative to that of other companies over time, and also how the performance of each company relative to itself over 1993–2007 has evolved. The paper is grounded in the broad theory of methods for measuring productivity change, and more specifically on the use of circular Malmquist indices for that purpose. In this context, the contribution of the paper is methodological and applied. From the methodology perspective, the paper demonstrates the use of circular meta-Malmquist indices in a comparative context not only across companies but also within company across time. This type of within-company assessment using Malmquist indices has not been applied extensively and to the authors’ knowledge not to the UK water industry. From the application perspective, the paper throws light on the performance of UK water companies and assesses the potential impact of regulation on their performance. In this context, it updates the relevant literature using more recent data.
Resumo:
The need for low bit-rate speech coding is the result of growing demand on the available radio bandwidth for mobile communications both for military purposes and for the public sector. To meet this growing demand it is required that the available bandwidth be utilized in the most economic way to accommodate more services. Two low bit-rate speech coders have been built and tested in this project. The two coders combine predictive coding with delta modulation, a property which enables them to achieve simultaneously the low bit-rate and good speech quality requirements. To enhance their efficiency, the predictor coefficients and the quantizer step size are updated periodically in each coder. This enables the coders to keep up with changes in the characteristics of the speech signal with time and with changes in the dynamic range of the speech waveform. However, the two coders differ in the method of updating their predictor coefficients. One updates the coefficients once every one hundred sampling periods and extracts the coefficients from input speech samples. This is known in this project as the Forward Adaptive Coder. Since the coefficients are extracted from input speech samples, these must be transmitted to the receiver to reconstruct the transmitted speech sample, thus adding to the transmission bit rate. The other updates its coefficients every sampling period, based on information of output data. This coder is known as the Backward Adaptive Coder. Results of subjective tests showed both coders to be reasonably robust to quantization noise. Both were graded quite good, with the Forward Adaptive performing slightly better, but with a slightly higher transmission bit rate for the same speech quality, than its Backward counterpart. The coders yielded acceptable speech quality of 9.6kbps for the Forward Adaptive and 8kbps for the Backward Adaptive.
Resumo:
Competition in the 3PL market continues to intensify as providers compete to win and retain clients. 3PL providers are required to reduce costs while offering tailored innovative logistical solutions in order to remain competitive. 3PL providers can reduce costs through the consolidation of assets and introduction of cross-docking activities. Innovative logistical services can be tailored to each client via the introduction of real-time data updates. This paper highlights that RFID enabled RTE can assist in improvements of both these areas through increased network visibility. A framework is presented where the 3PL provider focuses on asset reduction, asset utilisation, real-time data employment and RTE cycle time reduction in order to enhance competitiveness. © 2011 IEEE.
Resumo:
Relations between spatial attention and motor intention were investigated by means of an EEG potential elicited by shifting attention to a location in space as well as by the selection of a hand for responding. High-density recordings traced this potential to a common frontoparietal network activated by attentional orienting and by response selection. Within this network, parietal and frontal cortex were activated sequentially, followed by an anterior-to-posterior migration of activity culminating in the lateral occipital cortex. Based on temporal and polarity information provided by EEG, we hypothesize that the frontoparietal activation, evoked by directional information, updates a task-defined preparatory state by deselecting or inhibiting the behavioral option competing with the cued response side or the cued direction of attention. These results from human EEG demonstrate a direct EEG manifestation of the frontoparietal attention network previously identified in functional imaging. EEG reveals the time course of activation within this network and elucidates the generation and function of associated directing-attention EEG potentials. The results emphasize transient activation and a decision-related function of the frontoparietal attention network, contrasting with the sustained preparatory activation that is commonly inferred from neuroimaging.
Resumo:
This research was concerned with identifying factors which may influence human reliability within chemical process plants - these factors are referred to as Performance Shaping Factors (PSFs). Following a period of familiarization within the industry, a number of case studies were undertaken covering a range of basic influencing factors. Plant records and site `lost time incident reports' were also used as supporting evidence for identifying and classifying PSFs. In parallel to the investigative research, the available literature appertaining to human reliability assessment and PSFs was considered in relation to the chemical process plan environment. As a direct result of this work, a PSF classification structure has been produced with an accompanying detailed listing. Phase two of the research considered the identification of important individual PSFs for specific situations. Based on the experience and data gained during phase one, it emerged that certain generic features of a task influenced PSF relevance. This led to the establishment of a finite set of generic task groups and response types. Similarly, certain PSFs influence some human errors more than others. The result was a set of error type key words, plus the identification and classification of error causes with their underlying error mechanisms. By linking all these aspects together, a comprehensive methodology has been forwarded as the basis of a computerized aid for system designers. To recapitulate, the major results of this research have been: One, the development of a comprehensive PSF listing specifically for the chemical process industries with a classification structure that facilitates future updates; and two, a model of identifying relevant SPFs and their order of priority. Future requirements are the evaluation of the PSF listing and the identification method. The latter must be considered both in terms of `useability' and its success as a design enhancer, in terms of an observable reduction in important human errors.