9 resultados para Control framework

em University of Queensland eSpace - Australia


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In this paper, a new control design method is proposed for stable processes which can be described using Hammerstein-Wiener models. The internal model control (IMC) framework is extended to accommodate multiple IMC controllers, one for each subsystem. The concept of passive systems is used to construct the IMC controllers which approximate the inverses of the subsystems to achieve dynamic control performance. The Passivity Theorem is used to ensure the closed-loop stability. (c) 2005 Elsevier Ltd. All rights reserved.

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Fault diagnosis has become an important component in intelligent systems, such as intelligent control systems and intelligent eLearning systems. Reiter's diagnosis theory, described by first-order sentences, has been attracting much attention in this field. However, descriptions and observations of most real-world situations are related to fuzziness because of the incompleteness and the uncertainty of knowledge, e. g., the fault diagnosis of student behaviors in the eLearning processes. In this paper, an extension of Reiter's consistency-based diagnosis methodology, Fuzzy Diagnosis, has been proposed, which is able to deal with incomplete or fuzzy knowledge. A number of important properties of the Fuzzy diagnoses schemes have also been established. The computing of fuzzy diagnoses is mapped to solving a system of inequalities. Some special cases, abstracted from real-world situations, have been discussed. In particular, the fuzzy diagnosis problem, in which fuzzy observations are represented by clause-style fuzzy theories, has been presented and its solving method has also been given. A student fault diagnostic problem abstracted from a simplified real-world eLearning case is described to demonstrate the application of our diagnostic framework.

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Pressure on boards to improve corporate performance and management oversight has led to a series of inquiries and reports advocating governance reform. These reports largely reflect an agency perspective of governance and seek to ensure greater board independence from and control of management. While board independence is important to good governance, we contend that frameworks, models and advice centred on one element of governance ignore the complexity of how boards work. We develop a holistic board framework based upon the concept of board intellectual capital to address this concern. Our framework proposes a series of inputs (e.g. company history, company constitution, legal environment) that lead to a particular mix of board intellectual capital. We contend that the balance of the different elements of board intellectual capital will lead to a series of board behaviours. Further, the board needs to mobilise its intellectual capital to carry out a series of roles. The exact nature of these roles will depend on the company's requirements. Thus, the governance outputs of organisational performance, board effectiveness and director effectiveness will depend on the match between the board's intellectual capital and the roles required of it. We conclude by demonstrating the benefits of this framework as a diagnostic tool. We outline how boards wishing to improve their governance systems can diagnose common governance problems by evaluating their own board's capabilities in relation to the different components of the framework.

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Adsorption of pure nitrogen, argon, acetone, chloroform and acetone-chloroform mixture on graphitized thermal carbon black is considered at sub-critical conditions by means of molecular layer structure theory (MLST). In the present version of the MLST an adsorbed fluid is considered as a sequence of 2D molecular layers, whose Helmholtz free energies are obtained directly from the analysis of experimental adsorption isotherm of pure components. The interaction of the nearest layers is accounted for in the framework of mean field approximation. This approach allows quantitative correlating of experimental nitrogen and argon adsorption isotherm both in the monolayer region and in the range of multi-layer coverage up to 10 molecular layers. In the case of acetone and chloroform the approach also leads to excellent quantitative correlation of adsorption isotherms, while molecular approaches such as the non-local density functional theory (NLDFT) fail to describe those isotherms. We extend our new method to calculate the Helmholtz free energy of an adsorbed mixture using a simple mixing rule, and this allows us to predict mixture adsorption isotherms from pure component adsorption isotherms. The approach, which accounts for the difference in composition in different molecular layers, is tested against the experimental data of acetone-chloroform mixture (non-ideal mixture) adsorption on graphitized thermal carbon black at 50 degrees C. (C) 2005 Elsevier Ltd. All rights reserved.

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Water quality is a key concern in the current global environment, with the need to promote practices that help to protect water quality, such as riparian zone management, being paramount. The present study used the theory of planned behaviour as a framework for understanding how beliefs influence decisions about riparian zone management. Respondents completed a survey that assessed their behavioural, normative, and control beliefs in relation to intentions to manage riparian zones on their property. The results of the study showed that, overall, landholders with strong intentions to manage their riparian zones differed significantly in terms of their beliefs compared to landholders who had weak intentions to manage their riparian zones. Strong intentions to manage riparian zones were associated with a favourable cost-benefit analysis, greater perceptions of normative support for the practice and lower perceptions of the extent to which barriers would impede management of riparian zones. It was also evident that willingness to comply with the recommendations of salient referents, beliefs about the benefits of riparian zone management and perceptions of the extent to which barriers would impede riparian zone management were most important for determining intentions to manage riparian zones. Implications for policy and extension practice are discussed. (c) 2005 Elsevier Ltd. All rights reserved.

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Our research described in this paper identifies a three part premise relating to the spyware paradigm. Firstly the data suggests spyware is proliferating at an exponential rate. Secondly ongoing research confirms that spyware produces many security risks – including that of privacy/confidentiality breaches via illicit data collection and reporting. Thirdly, anti-spyware controls are improving but are still considered problematic for several reasons. Our research then concludes that control measures to counter this very significant challenge should merit compliance auditing – and this auditing may effectively target the vital message passing performed by all illicit data collection spyware. Our research then evolves into an experiment involving the design and implementation of a software audit tool to conduct the desired compliance auditing. The software audit tool is positioned at the protected network’s gateway. The software audit tool uses ‘phone-home’ IP addresses as spyware signatures to detect the presence of the offending software. The audit tool also has the capability to differentiate legitimate message passing software from that produced by spyware – and ‘learn’ both new spyware signatures and new legitimate message passing profiles. The testing stage of the software has proven successful – albeit using very limited levels of network message passing variety and frequency.