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1
Morton, Jeremy Andrew. "Advancement of Online Systems in Engineering by Expert TA." NCSU, 2006. http://www.lib.ncsu.edu/theses/available/etd-05182006-121854/.
Повний текст джерелаАнотація:
This dissertation introduces a new online system called Expert TA. The system was developed based on the hypothesis that expressions are key elements in engineering problems and that the treatment of expressions is critical to the advancement of online systems. This dissertation identifies ergonomic problems with expression entry that Expert TA overcomes through the use of a problem-customize integrated expression editor, called a palate. Then the dissertation shows, using an expression analyzer that operates in the background of Expert TA, that specific mathematical mistakes within an entered expression can now be located. Emulating standard instructional practices, detailed feedback pertaining to specific mistakes and grading on the basis of specific mistakes is now possible.
2
SHARMA, KRITIKA. "TO DECIPHERTHE ROLE OF TA SYSTEMS IN MYCOBACTERIUM TUBERCULOSIS." Thesis, DELHI TECHNOLOGICAL UNIVERSITY, 2021. http://dspace.dtu.ac.in:8080/jspui/handle/repository/18461.
Повний текст джерелаАнотація:
Mycobacterium tuberculosis is the bacteria responsible for the disease of the
infamous Tuberculosis (TB). mtb is the major human pathogens prevalent in
developing countries, with an appropriate number of 2 million deaths per year. This
disease is treatable but the hurdles we face, this project helps in giving the new
approach and better perspective. Latent Tb is the phase when the bacteria exits in
one person’s body and unable to replicate properly due to healthy and good
immunity response. But it shows its pathogenicity when the immune response gets
degraded. The reason can be any other physiological condition or aging. Even after
any person is responding regardless having any physiological conditions, the case
of patient can be treated. But problem arises when patient’s body stop responding
regarding the treatment. To overcome the growing problem of MDR, XDR varieties
and eradication of the latent form of TB, novel ways of more rapid treatment are the
need of the hour. The complete sequence of the genome of Mtb (H37Rv) has been
achieved, but more deep knowledge and understanding of different classes of toxin
and antitoxin systems needs to be studies. Mycobacterium tuberculosis is known to
be the causative agent in tuberculosis. Tuberculosis is the disease in which lungs get
affected along with other parts. 87% new cases had been recorded in TB burden
countries. Among which out of 30 countries, 8 countries hold the two thirds of the
cases. India was among the 8 countries. More than 2 million cases were recoded in
past two years. And this data is keep increasing in recent years. Immunology plays
a paramount role in this disease. The person who gets affected by the mtb infection
is expected to express inflammatory response which causes the breakdown of the
lungs matrix and formation of lung cavities. But many underlying immunological
dysfunction like aids and diabetes etc. creates variation in formation of lung
cavities. The fatality in TB is increased by the drug resistant TB. It means that the
person stops responding to the treatment. Over the past decade, there has been a
sharp increase in the disease, with the emergence of MDR and EDR varieties of TB.
Toxin-Antitoxin systems are potential therapeutic domain in antibiotic resistance.
TA systems are present in the bacteria. These TA systems can be classified into six
classes. They are prone to the unfavorable conditions. We can manipulate these TA
regions to loosen up its harmful effect and will make it less fatal in the cause of
tuberculosis.
3
Lo, Hong Rui. "System characterisation and identification of non-linear systems (with particular reference to hysteretic systems)." Thesis, University of Southampton, 1988. https://eprints.soton.ac.uk/52277/.
Повний текст джерелаАнотація:
System identification is the process of building mathematical models of dynamical systems based on observed data. Many effective techniques have been developed for linear systems. For non-linear systems, some progress has been achieved, but techniques for practical use and which can deal with a large class of systems are limited. In particular few identification techniques have been found in the literature which can be applied to hysteretic systems. This thesis is devoted to the development of a system identification technique which can be applied to a relatively large class of non-linear systems, including hysteretic systems. The key to this technique is to select an appropriate subset of the state vector describing the system and generate a non-linear surface in this subspace which characterises the non-linearity. For non-hysteretic systems, this space is the normal state space. For hysteretic systems, the selection of the appropriate space usually needs some prior knowledge about the system. The procedure involves estimating the non-linear component as a function of time. This is approached via a deconvolution method, and a section of this thesis shows how an optimal deconvolution method may be used. The method of creating the surface is described, and identification is then conducted by analysing and fitting the surface. The success of identification is obviously affected by the quality of the surface, which is, in turn, affected by factors such as the type and the level of the excitation, the frequency range and the magnitude of the spectrum of the process, and errors in the signal processing. These problems are discussed in the application of this technique to several simulated non-linear systems (including both non-hysteretic and hysteretic types) and also to the practical case of a cable type vibration isolator.
4
Vafiadis, Konstantinos G. "Systems and control problems in early systems design." Thesis, City University London, 2003. http://openaccess.city.ac.uk/7661/.
Повний текст джерелаАнотація:
This thesis is concerned with the evaluation of properties of early design models, the control structure selection and the representation and properties of composite system models. The work is motivated by the need to introduce a Systems and Control Theory based framework for early design stages of the overall system design of engineering processes, and in particular chemical processes, such as process synthesis and control structure selection. The overall spirit of the work is that engineering design is an evolutionary process, the different stages of which shape the structure of the resulting system models and precondition the potential for design at the next stage. The work identifies a number of key problems in the overall design, which are of a generic, systemic character, and then deals with working out solutions for such problems. The results contribute in the development of a framework for systems integration using as criteria and tools, those provided by Systems and Control Theory. The work aims to provide a control theoretic dimension to the rules and practices currently used in the specific application areas. The thesis contributes in the development of a Systems and Control conceptual and tools framework for integrated design of engineering processes by providing results in the following areas: - Specification of a number of generic problems in the field of integrated design and identification of relevant control theoretic concepts and tools. - Study of Model Orientation for linear implicit state-space models and definition of classes of oriented realisations. - Development of solutions to two problems of Structural Identification for uncertain early process models related to infinite zero structure and McMillan degree. - Development of a generic representation of composite systems that allows the study of transition from the aggregate to composite system properties, as a generalised Control Design and characterisation of some key system properties. -Specification of a framework for integrated Control Structure Selection and development of software for many approaches of the "interaction analysis" indicators. The results contribute in the area of development of the systems and control ideas for the problems of systems integration and early design. The work emphasises the strong links between Modelling, Selection of Control Structures and Control Structural methodologies.
5
Hitchins, Derek K. "Conceiving systems." Thesis, City University London, 1990. http://openaccess.city.ac.uk/7668/.
Повний текст джерелаАнотація:
The thesis is concerned with the development of innovative, robust design concepts for a class of systems called Information Decision Action (IDA) Systems. IDA systems are typified by Command and Control (C2) and Command, Control, Communications and Intelligence (C3I) systems as used by police, emergency services and the military - the two titles refer respectively to the human activity and the technological systems. The class of systems is much wider, however, and includes, financial, traffic control, business and even governmental systems where information is gathered, used as a basis for human decision-forming, and results in action, all in real, or near-real time. IDA system complexity stems largely from the dominance of robust human activity systems within the overall system, and also from the employment of often-rigid, technology-based, decision support systems which are unable to adapt as swiftly as the humans they serve. The thesis is in two parts. In the first part, the author presents a perspective on "hard" and "soft" systems and the gradual move by so-called "hard" systems engineers towards softer concepts in the search for more satisfactory IDA systems. This progression is presented partly by anecdote, supported by some of the author's papers showing the development of his contribution to understanding of, and partly by an exposition of the essential themes inherent in, IDA systems. Keynote papers in the first part are: MOSAIC: Concepts for the Deployment of Air Power in Europe and The Human Element in C3 I: The first of these presents a highly-survivable alternative to the present force and C2 deployment approaches which have evolved little since World War IT; the second considers the human and his social behaviour as keys to understanding IDA systems. Other papers develop the themes and show their application to systems in which the author has had major involvement The second part is concerned with the process of conceiving and creating IDA systems and it too draws on published papers as direct support for the thesis. Keynote papers here are A General Theory of Command and Control, a unique recent paper which proposes a set of design axioms for an idealized IDA system, the award-winning Managing Systems Creation which presents an engineering framework for Creating Systems, and SEAMS (Systems Engineering, Analysis and Management Support) which signals a major design initiative to develop engineering frameworks into company-wide IT environments. The second part also introduces a complete Conceiving System, called the Seven-Step Continuum (SSC), describes some prototype tools developed by the author to perform some of the tasks of design conception and - in Chapter 9, which is a paper within the thesis - shows results from using the SSC, its methods and tools, in practice. The second part closes with a look forward to the building of flexible future systems which can adapt to their environment.
6
Whitmore, Guy Matthew. "Coordinate reference systems for high precision geodesy." Thesis, University of Nottingham, 1994. http://eprints.nottingham.ac.uk/29037/.
Повний текст джерелаАнотація:
The advent of the Global Positioning System (GPS) meant that, for the first time, the geodetic and geophysical community has a tool for measurements on a global, continental and national scale. Global GPS networks are already competing with VLBI and SLR for the measurement of inter-continental baselines and earth rotation parameters. The development of the 'high accuracy fiducial GPS technique', as described in this thesis, has produced results comparable with mobile VLBI and SLR systems, but in shorter observational periods and at lower costs. Combined with global GPS networks, which have the potential to provide time-tagged fiducial station coordinates at the observational epochs, coordinates can be determined in a global reference frame. The results in this thesis, from a fiducial GPS campaign to monitor the vertical land movement at tide gauge sites in the UK, demonstrate that millimetric precisions and accuracies can be obtained in all three components over baselines of hundreds of kilometers. The combination of GPS with existing 2-d classical triangulation networks for mapping, engineering surveying and navigation has caused many problems, since the GPS observations are 3-d and of a superior quality. In Europe these problems have been overcome by the establishment of a new high precision reference framework, EUREF, based on fiducial GPS carried out in 1989. This thesis also describes the determination of coordinates for the UK EUREF stations and their application for geodetic control in Great Britain.
7
Butt, Aaron Trevor. "Identification and characterisation of toxin-antitoxin systems (TA) in Burkholderia pseudomallei." Thesis, University of Exeter, 2013. http://hdl.handle.net/10871/9303.
Повний текст джерелаАнотація:
The aim of this study was to identify and characterise type II toxin-antitoxin (TA) systems in Burkholderia pseudomallei, the causative agent of the human disease melioidosis. 8 putative TA systems were identified within the genome of B. pseudomallei K96243. 5 of these were located witihn genome islands. Of the candidate toxins, BPSL0175 (RelE1) or BPSS1060 (RelE2) caused growth to cease when expressed in Escherichia coli, whereas expression of BPSS0390 (HicA) or BPSS1584 (HipA) (in an E. coli ΔhipBA background) caused a reduction in the number of culturable bacteria. HicA also caused growth arrest in B. pseudomallei K96243 ΔhicAB. These toxin induced phenotypes were enhanced by an <3kDa extracellular factor that accumulated in the spent medium during growth. Expression of the cognate antitoxins could restore growth and culturability of cells. Expression of hicA in E. coli gave an increased number of persister cells in response to ciprofloxacin or ceftazidime. Site directed mutagenesis studies identified two key residues within the HicA toxin that were essential for both the reduced culturability and increased persistence phenotypes. Deletion of hicAB from B. pseudomallei K96243 did not affect persister cell or survival frequencies compared to the wild type following treatment with a variety of stress conditions. Deletion of the ΔhipBA locus from B. pseudomallei K96243 also had no affect on bacterial persistence or survival under the conditions tested.
8
Lathi, Deepak. "Impulse measurements in earthing systems." Thesis, Cardiff University, 2012. http://orca.cf.ac.uk/44776/.
Повний текст джерелаАнотація:
The behaviour of earth electrodes at power frequency conditions is well known. Several studies are going on at present, to understand the behaviour of earthing systems at transient impulse and high frequency conditions. The study of impulse measurements in earthing systems was carried out during this project, to understand the soil electromagnetic behaviour towards high frequency and variable AC/DC/impulse current magnitudes. Several measurement techniques and instrumentation used for the measurement of the earthing systems were surveyed. The limitations and the advantages of each approach have been identified, and the range of application determined. Extensive experiments were performed on the practical earth electrodes at the Cardiff University test site at Llanrumney, and at the Dinorwig power station earthing facilities. These experiments have revealed that there is reduction of impedance of earth electrodes over the frequency range 20Hz to 120kHz. Moreover, a pronounced effect of DC current magnitude was observed on the earth resistance of the electrodes over the range of 1mA to 500mA. The numerical modelling of the test configurations did not show the reduction in earth impedance over the frequency range 20Hz to 120kHz. To understand the different trends shown by the experiments and simulation, and the effect of frequency and current magnitude, a geological literature survey was carried out. This survey revealed that when the soil water electrolyte solution is subjected to high frequency electrical currents, it exhibits conductivity dispersion phenomenon. Conductivity dispersion is a phenomenon where conductivity of the clay water electrolyte solution increases by about 30% over a frequency range 20Hz to 100kHz. The geological literature survey also revealed that the polarisation effect in the soil water electrolyte is responsible for the non-linear current effect. Moreover, during this project, a new technique of FFT from impulse, was proposed to measure the earth electrode impedance, over a frequency range which is an inherent component of the impulse signals. The FFT from impulse signals, showed a good agreement of the measured earth impedance of the earth electrodes, with the measured earth impedance using the variable frequency scan method. FFT from impulse technique has an advantage over the variable frequency scan method, from the point of view of the time required for the measurement and the simplicity of the test source, for the measurement of the earth electrode impedance. Such a technique, could have impact on the testing at high current magnitudes, where impulse generation is much easier. Finally, the future scope of work is presented to explore the measurement of earth electrode impedance above the frequency of 120kHz and current magnitudes above 5A.
9
Soltanahmadi, Abbasali. "Dynamics of flexible riser systems." Thesis, City, University of London, 1988. http://openaccess.city.ac.uk/20155/.
Повний текст джерелаАнотація:
This thesis is concerned with the static and dynamic analyses and the model testing of deep sea flexible riser systems which are the key components associated with semi-submersible oil platforms. A numerical method based on explicit integration of Newton's second law is developed to predict the 3-dimensional dynamic behaviour of the riser due to the hydrodynamic loadings induced by wave and current motion. In this analysis the effects of waves and currents from separate directions, vessel movements, vortex-shedding and structural damping are included. The material damping for the riser is modelled by a single Kelvin system and the hydrodynamic loadings are assessed from the modified Morison equation. The effect of vortex-shedding on the riser is modelled by considering the interaction of drag-inertia and lift forces due to wave and current motion. The drag coefficient being modified ~ the vortex-shedding effects which are predicted by calculating the maximum response of the flexible riser in the lift force direction. The formfinding and static analysis of the riser when subject to structural self-weight and other static loadings is carried out by the method of Dynamic Relaxation using kinetic damping. The method is well suited to computer aided design procedures in which various shapes for the riser catenary have to be investigated together with the effects of boundary support conditions and alternative arrangements of mooring buoys. The theories described above are implemented into three computer programs. The first program deals with the formfinding of the riser and the second investigates the dynamic behaviour of the riser due to non-linear current and wave loadings. The third program is concerned with the static solution of the riser due to current loading. The latter is employed when the hydrodynamic force consists of current loading only and therefore the dynamic solution is not desired. The iterative use of the first and third programs allows potential designs to be quickly investigated. The results predicted by the numerical analyses are compared with those obtained from two series of model tests in wave flumes. The tests were scaled from prototype situations using Froud number criteria. The first set of tests used a small scale flexible chain model with negligible material damping and structural bending stiffness and no induced vortex shedding; the aim of these tests being only to validate the assessment of the hydrodynamic forces on the riser. '!he second set investigated the response of a larger scale model which induced vortex-shedding and in which the riser system had significant structural damping. The comparison of experimental and computed results showed close agreement. The developed computer programs were also validated numerically by comparing the predicted results with those obtained from the well known riser program "FLEXRISER".
10
Bingley, R. M. "Electronic theodolite intersection systems." Thesis, University of Nottingham, 1990. http://eprints.nottingham.ac.uk/14248/.
Повний текст джерелаАнотація:
The development of electronic surveying instruments, such as electronic theodolites, and concurrent advances in computer technology, has revolutionised engineering surveying; one of the more recent examples being the introduction of Electronic Theodolite Intersection Systems (ETISs). An ETIS consists of two or more electronic theodolites and a computer, with peripheral hardware and suitable software. The theoretical principles on which they are based have been known for a long time, but intersection has seldom been used as a method of measurement. The main reasons for its re-evaluation were the introduction of one-second electronic theodolites and the ability to interface these on-line to a computer. The last decade has seen the development of several commercially available systems and probably even more in-house developed systems. Such systems are capable of performing real-time, non-contact, three-dimensional coordinate determination to a high accuracy, enabling their use in a wide variety of applications. This thesis details all aspects of ETISs. Initially, the theoretical principles on which the systems are based are developed. The components of a system are then detailed and a review of current commercially available systems and their applications is given. The thesis then concentrates on the development of an ETIS by the author and details its' application in both industrial measurement and deformation monitoring. Finally, the thesis concludes with a discussion on the factors affecting the accuracies attainable with ETISs.
11
Salahat, Mohammed Hasan. "Information systems development through an integrated framework." Thesis, University of Huddersfield, 2016. http://eprints.hud.ac.uk/id/eprint/34432/.
Повний текст джерелаАнотація:
Information systems are essential entities for several organizations who strive to successfully run their business operations. One of the major problems faced by the organizations is that many of these information systems fail, and thus the organizations do not achieve their required targets in time. Many of the reasons for the information system failures documented in the literature are related to development methodologies or frameworks that are unable to handle both ‘hard’ and ‘soft’ system aspects. In general, the hard issues of the system are considered more significant than the soft issues, however, all the methodologies must be able to deal with all the system and business aspects. This thesis investigates the possibility of developing and evaluating a multimethodology framework that can be used for information systems development in an academic and business environment. The research explores the applicability of such a framework that comprehends both ‘soft’ and ‘hard’ system aspects in order to eliminate information system failures. Different software development approaches are investigated, including the dominant ‘domain-driven design’ (DDD) approach. A new multimethodological framework entitled ‘Systemic Soft Domain Driven Design’ (SSDDDF) has been developed by combining ‘soft system methodology’ as a guiding methodology, ‘unified modelling language’ as a business domain modelling approach, and a domain-driven design implementation pattern. This framework is intended as an improvement of the DDD approach. Soft and hard techniques are integrated through mapping from the ‘consensus primary task model’ of the soft approach to the ‘use cases’ of the hard approach. In addition, ‘soft language’ is introduced as a complement to DDD’s ‘ubiquitous language’, for facilitating the communication between the different stakeholders of a project. The implementation pattern (e.g., Naked Objects) is included for generating code from domain models. The framework has been evaluated as an information systems development approach through different undergraduate and postgraduate projects. Feedback from the developers has been positive and encouraging for further improvements in the future. The SSDDD framework has also been compared to different ISD methodologies and frameworks among of these DDD as an approach to ISD. The results of this comparison show that SSDDDF has advantages over DDD and significant improvements to DDD have been achieved. Finally, the research suggests an agenda for further improvements of the framework, while suggesting the development of different pattern languages.
12
Phoomboplab, Tirawat. "Self-resilient production systems : framework for design synthesis of multi-station assembly systems." Thesis, University of Warwick, 2012. http://wrap.warwick.ac.uk/59325/.
Повний текст джерелаАнотація:
Product design changes are inevitable in the current trend of time-based competition where product models such as automotive bodies and aircraft fuselages are frequently upgraded and cause assembly process design changes. In recent years, several studies in engineering change management and reconfigurable systems have been conducted to address the challenges of frequent product and process design changes. However, the results of these studies are limited in their applications due to shortcomings in three aspects which are: (i) They rely heavily on past records which might only be a few relevant cases and insufficient to perform a reliable analysis; (ii) They focus mainly on managing design changes in product architecture instead of both product and process architecture; and (iii) They consider design changes at a station-level instead of a multistation level. To address the aforementioned challenges, this thesis proposes three interrelated research areas to simulate the design adjustments of the existing process architecture. These research areas involve: (i) the methodologies to model the existing process architecture design in order to use the developed models as assembly response functions for assessing Key Performance Indices (KPIs); (ii) the KPIs to assess quality, cost, and design complexity of the existing process architecture design which are used when making decisions to change the existing process architecture design; and (iii) the methodology to change the process architecture design to new optimal design solutions at a multi-station level. In the first research area, the methodology in modeling the functional dependence of process variables within the process architecture design are presented as well as the relations from process variables and product architecture design. To understand the engineering change propagation chain among process variables within the process architecture design, a functional dependence model is introduced to represent the design dependency among process variables by cascading relationships from customer requirements, product architecture, process architecture, and design tasks to optimise process variable design. This model is used to estimate the level of process variable design change propagation in the existing process architecture design Next, process yield, cost, and complexity indices are introduced and used as KPIs in this thesis to measure product quality, cost in changing the current process design, and dependency of process variables (i.e, change propagation), respectively. The process yield and complexity indices are obtained by using the Stream-of-Variation (SOVA) model and functional dependence model, respectively. The costing KPI is obtained by determining the cost in optimizing tolerances of process variables. The implication of the costing KPI on the overall cost in changing process architecture design is also discussed. These three comprehensive indices are used to support decision-making when redesigning the existing process architecture. Finally, the framework driven by functional optimisation is proposed to adjust the existing process architecture to meet the engineering change requirements. The framework provides a platform to integrate and analyze several individual design synthesis tasks which are necessary to optimise the multi-stage assembly processes such as tolerance of process variables, fixture layouts, or part-to-part joints. The developed framework based on transversal of hypergraph and task connectivity matrix which lead to the optimal sequence of these design tasks. In order to enhance visibility on the dependencies and hierarchy of design tasks, Design Structure Matrix and Task Flow Chain are also adopted. Three scenarios of engineering changes in industrial automotive design are used to illustrate the application of the proposed redesign methodology. The thesis concludes that it is not necessary to optimise all functional designs of process variables to accommodate the engineering changes. The selection of only relevant functional designs is sufficient, but the design optimisation of the process variables has to be conducted at the system level with consideration of dependency between selected functional designs.
13
Pantelous, Athanasios. "Solutions properties and techniques for implicit systems." Thesis, City University London, 2013. http://openaccess.city.ac.uk/3513/.
Повний текст джерелаАнотація:
In economic theory, input-output analysis has been developed for the description of the production of a multi-sector economy. An input-output model is a quantitative economic technique that represents the interdependencies between different branches of a national economy or different regional economies. In the region of input-output economics, many models were established to describe the real economics.
14
Huang, Danguang. "Flexible design of urban water distribution systems." Thesis, University of Birmingham, 2011. http://etheses.bham.ac.uk//id/eprint/2948/.
Повний текст джерелаАнотація:
Urban water distribution systems (UWDS) are highly inter-connected and under many uncertainties from water demand, pipe roughness, and component failure. Accurate projections of these uncertainties are almost impossible, and thus it may not be a proper method to design the system to meet its performance criteria for the forecasted scenario. The system is designed for the deterministic not for the uncertainties, as a result it may not be efficient or effective to be operated under different future scenarios. Flexible design is shown as a useful strategy to cost-effectively respond to uncertainties because of its consideration of uncertainties in advance, and has been successfully applied in many engineering systems. The objective of flexible design is to identify flexibility sources in UWDS and embed them into the system design to respond to uncertainties. The thesis discussed different terms to define the property of the system to respond to uncertainties and proposed a definition of flexibility for UWDS. It then proposed different measures to indicate flexibility value and introduced an efficient method to handle numerous uncertain parameters in the model. It also develops an efficient method to identify high value flexibility sources based on the Flexibility Index. Finally the thesis presents a flexibility-based optimisation model that enable water engineers to compare different flexible design alternatives and generate optimal solutions. A definition of flexibility in UWDS is proposed to illustrate broadly its property to respond to uncertainties, since it is not so useful, or at least in this thesis to distinguish similar terms to define the property of the system to respond to uncertainties. Identified flexibility sources by the proposed method is not useful for the flexibility-based optimization model to design a system, but it might be a powerful tool to locate the weak points in the system or provide better update options during rehabilitation of the system. The computational efficiency of the proposed flexibility-based optimisation model was demonstrated by dramatic decreasing on the number of the required hydraulic simulation in the case study. Flexible designs in the case study are more expensive than inflexible design, but have better hydraulic performance under uncertainties.
15
Abdul, Hamid Haziah. "Transients in reactors for power systems compensation." Thesis, Cardiff University, 2012. http://orca.cf.ac.uk/45202/.
Повний текст джерелаАнотація:
This thesis describes new models and investigations into switching transient phenomena related to the shunt reactors and the Mechanically Switched Capacitor with Damping Network (MSCDN) operations used for reactive power control in the transmission system. Shunt reactors and MSCDN are similar in that they have reactors. A shunt reactor is connected parallel to the compensated lines to absorb the leading current, whereas the MSCDN is a version of a capacitor bank that has been designed as a C-type filter for use in the harmonic-rich environment. In this work, models have been developed and transient overvoltages due to shunt reactor deenergisation were estimated analytically using MathCad, a mathematical program. Computer simulations were then undertaken using the ATP/EMTP program to reproduce both single-phase and three-phase shunt reactor switching at 275 kV operational substations. The effect of the reactor switching on the circuit breaker grading capacitor was also examined by considering various switching conditions. The main original achievement of this thesis is the clarification of failure mechanisms occurring in the air-core filter reactor due to MSCDN switching operations. The simulation of the MSCDN energisation was conducted using the ATP/EMTP program in the presence of surge arresters. The outcome of this simulation shows that extremely fast transients were established across the air-core filter reactor. This identified transient event has led to the development of a detailed air-core reactor model, which accounts for the inter-turn RLC parameters as well as the stray capacitances-to-ground. These parameters are incorporated into the transient simulation circuit, from which the current and voltage distribution across the winding were derived using electric field and equivalent circuit modelling. Further analysis of the results has revealed that there are substantial dielectric stresses imposed on the winding insulation that can be attributed to a combination of three factors. (i) First, the surge arrester operation during the MSCDN energisation, which causes steep voltage change at the reactor terminal. (ii) Second, the nonuniform voltage distribution, resulting in high stresses across the top inter-turn windings. (iii) Third, the rapid rate-of-change of voltage in the assumed worst-case reactor winding location. This is accompanied by a high dielectric (displacement) current through the inter-turn winding insulation. Work within this investigation proposes that a synergistic effect of high electric field and high dielectric current occurring at worst energisation, followed by the thermal effects of steady state operation contributes to the failure of air-core reactors used on the 400 kV MSCDN.
16
Carugo, Dario. "Development of microfluidic systems for therapeutic applications." Thesis, University of Southampton, 2012. https://eprints.soton.ac.uk/348835/.
Повний текст джерелаАнотація:
The development of a microfluidic-based strategy is presented for investigating the functional behaviour of hydrogel spherical beads which are employed in the clinic as embolic agents and drug delivery systems for the treatment of hypervascularised tumours and arteriovenous malformations. For this purpose, biomimetic microchannel networks were designed and fabricated by micromilling technology. Microdevices architecture reproduced characteristic features of microcirculatory arteriolar systems. The miniaturisation allowed for coupling with microscope-based technology and in situ visualisation of particles/cells behaviour. The flow dynamics of red blood cells (RBCs) suspensions within the aforementioned biomimetic microfluidic devices was investigated, by using in-house developed micro-Particle Image Velocimetry (μ-PIV) methods and image analysis techniques to quantify fluid velocity fields, cell-free layer width and RBCs spatial distribution. Results demonstrated the potential of the developed microfluidic devices for reliably reproducing peculiar properties of RBCs flow behaviour within human microcirculatory systems, including the relationship between cell-depletion layer width and microvessel diameter, and the dependence of RBCs distribution on the local Reynolds number. These findings opened the way for the application of the developed microfluidic devices as a biomimetic platform for investigating the performance of embolic beads. The flow behaviour of hydrogel beads within biomimetic microfluidic environments was investigated by adopting a two-steps approach, in which beads hydrodynamics was firstly studied within straight microchannels (Step I) and subsequently within network-like microchannel constructs (Step II). For this purpose, microscopy-based analysis techniques were developed in order to quantify bead radial position and axial velocity. Results demonstrated that bead flow behaviour depended on a complex interplay between the governing physical parameters, which included fluid rheology, fluid inertia (i.e., Reynolds number) and particle relative dimension (i.e., degree of confinement). Notably, it has been demonstrated that for a given combination of such parameters beads underwent oscillatory dynamics which have been thoroughly characterised experimentally. Further, beads partitioning at bifurcations, penetration efficacy and spatial location of the embolic events within biomimetic microchannel networks were investigated. The experimental observations presented here can provide relevant insight into the mechanisms governing the spatial distribution of embolic beads within tumour vascular systems. Finally, the spatiotemporal dynamics of drug elution from hydrogel embolic beads was investigated within the aforementioned biomimetic microchannel networks. Both on-chip analysis and off-chip analysis techniques were developed for quantifying the kinetics of drug elution and the amount of eluted drug from single embolic beads. Results revealed that drug elution from hydrogel embolic beads depended on the local hydrodynamics at the embolic site and on the location of the embolic event within the vascular network (i.e., proximal or distal embolisation). A numerical model was developed in order to better understand the role played by flow dynamics environment on the spatial distribution of the eluted drug at biomimetic bifurcations. In conclusion, the results of this study have established that microfluidics could be potentially employed as an alternative to animal models for investigating the performance and functional behaviour of hydrogel beads used in cancer therapy and targeted drug delivery.
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Weckendorf, Jan. "Dynamic response of structural timber flooring systems." Thesis, Edinburgh Napier University, 2009. http://researchrepository.napier.ac.uk/Output/2962.
Повний текст джерелаАнотація:
The dynamic response of structural timber flooring systems can cause vibrational serviceability problems in terms of discomfort experienced by the occupants. A unified method to control timber floor vibrations has not been established to-date. The vibration problem is manifold. The complexity and the limited amount of research with respect to timber floor vibrations have shown an urgent need for further investigations. This thesis has focused on the effects of structural and non-structural modifications on the dynamic performance of timber flooring systems by using experimental data from sixty-seven full-scale flooring systems for analytical investigations so as to identify structural configurations and vibration parameters, which are promising to further the design against disturbing vibrations. The collected data have also been used to identify weaknesses of current design criteria and to build and validate a finite element (FE) model for eigenproblem analyses of timber I-joist floors. The experimental work has been carried out with support from industry, and part of the investigations with respect to the design criteria has been conducted as Visiting Scientist within a Short Term Scientific Mission of COST Action E55 at VTT - Technical Research Centre of Finland in Espoo, Finland. The significant effects of floor make-up and different configurations on their dynamic response are examined, with specific interest to stiffen dynamically sensitive locations targeted, and the most promising designs (configurations) are identified. The important effects of damping on the dynamic performance of flooring systems are addressed by determination of damping ratios from the full-scale experimental work. The results were then used to perform a series of statistical studies to identify and recommend more appropriate damping ratios for design of bare light-weight timber flooring structures based on a number of distinct structural properties. The computer-based finite element analysis has been successfully used to model a series of timber flooring systems incorporating timber I-joists for predicting modal parameters and their relative changes due to structural modifications. The analysis has demonstrated the significant influence of assigning spring stiffness at the supports and at the interface of deck and joists on the floor responses. Overall, this research has helped to achieve a much broader knowledge and greater understanding of dynamic response and vibrational characteristics of timber flooring systems, and has made a contribution to identifying improved structural design and furthering vibration prediction and assessment. Undertaking of any such measures and future work as suggested in this thesis could significantly contribute to the improvement of the structural design and the design to Eurocode 5 if results are incorporated in future revisions. This would lead to fewer nuisances for residential occupants and enhanced quality of life.
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Харченко, Н. А., С. В. Дацько та В. С. Костенко. "Особенности обеспечения надежности в сетях абонентского доступа на базе PON". Thesis, ХНУРЕ, 2018. https://nure.ua/konferencii-ta-workshops/mizhnarodnij-molodizhnij-forum-radioelektronika-i-molod-u-hhi-stolitti.
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Alblalaihid, Khalid. "Active suspension structure for micro-scale probing systems." Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/33734/.
Повний текст джерелаАнотація:
The continued trends of product miniaturisation and increased part complexity have led to a requirement for highly accurate coordinate metrology, suitable for small parts. Coordinate metrology of such parts is performed on a micro-coordinate measurement machine (micro-CMMs), for which a specialised micro-scale probing system is required. These probing systems consist of a probe onto which a stylus is mounted. The probe provides significant flexibility allowing the stylus tip to be easily deflected during contact with a surface. Achieving an optimum stiffness for the probe represents a significant design challenge, and often leads to undesirable compromises. For example, as stylus tip size reduces the contact pressure for a given load increases, requiring the probe stiffness to be kept as low as possible to prevent damage to the part surface; however, for a more robust probing system the stiffness should be increased. This thesis presents an improved tactile micro-probing system that makes use of an active suspension structure that can be tuned to have either low or high stiffness as required for each phase of a measurement. Development of the probe includes analytical and numerical modelling for a range of solutions as well as empirical investigations into the manufacture of a smart suspension structure for a prototype probing system. Modelling results demonstrate significant stiffness reduction is possible by using the concept of adjusting the internal strain of suspension beam elements. In principle stiffness may be reduced down to zero at the point of beam buckling. It is also shown that such a probing system can provide isotropic stiffness for a range of different styli lengths. A prototype of the suspension structure was fabricated using a chemical etching process and 6.6 mm long stylus. The stiffness of the structure was assessed by measuring the modal frequencies of the suspension structure that correspond to vertical and lateral probe motion. Using this method, results show it is possible to reduce the frequency of the vertical mode and the torsional mode by 70 % and 33 %, respectively. Using finite element analysis it is shown that this equates to a reduction in vertical and lateral stiffness to 12 % and 46 % of their initial value, respectively, representing a ratio of the vertical to lateral stiffness of 1.7, which is close to the isotropic stiffness. A novel control system is presented that monitors and controls stiffness, allowing easy switching between “stiff” and “flexible” modes. During switching, the stylus tip undergoes a displacement or approximately 18 μm, however, the control system is able ensure a consistent flexible mode tip deflection to within 12 nm in the vertical axis. Combining stage errors with the probing system linearity error, the stylus tip zero offset position error and the probing system measurement repeatability, gives an estimate of a combined uncertainty for the probing system or of 58 nm (coverage factor, k = 2), which demonstrates the potential of this innovative variable stiffness micro-scale probe system.
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Hendawy, Zeinab Mohamed. "Mathematical algorithms for optimisation of large scale systems." Thesis, City University London, 1989. http://openaccess.city.ac.uk/8248/.
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This research is concerned with the problem of optimisation of steady state large scale systems using mathematical models. Algorithms for on-line optimisation of interconnected industrial processes are investigated. The research is concerned with two different kinds of algorithms which are based on the structure of the model used and the way of incorporating the real process information in order to compensate for model-reality differences. The first class of algorithms are developed from the price method with global feedback information which is mainly based on the normal Lagrangian function. Two existing algorithms are examined: The double iterative price correction mechanism and the augmented interaction balance method. Both methods use a double iterative coordination strategy and global feedback measurements from the real process. They are based respectively on the normal and the augmented Lagrangian functions. Hence, the first algorithm can only be recommended for application to convex problems. An algorithm, namely the augmented price correction mechanism, has been developed to extend the applicability of the previous price correction mechanism to non-convex problems. It is also applicable to convex problems with the advantage of reducing the number of times that information is required from the real process. The second class of algorithms is known as integrated system optimisation and parameter estimation (ISOPE) • The model used contains uncertain parameters and the algorithm solves the optimisation and parameter estimation tasks repeatedly until no furthur improvement is obtained. Developed ISOPE algorithms are involved in this research to cover the problems with output dependent constraints. Simulation results show superiority of the double iterative algorithm over that of single loop method in considerably reducing the number of times that information is required from the real process and hence saving on-line computing time. It is hoped that this work will provide useful information for implementing and furthur developing on-line steady state optimisation techniques.
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Chen, Zhangqi. "A Comprehensive Study of Diffusion and Modulus of Binary Systems within the Ti-Mo-Nb-Ta-Zr System." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1562224291399741.
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Ooi, Chia Ai. "Balancing control for grid-scale battery energy storage systems." Thesis, Cardiff University, 2016. http://orca.cf.ac.uk/93020/.
Повний текст джерелаАнотація:
Grid-scale battery energy storage systems (BESSs) are becoming increasingly attractive as the connection of a BESS has been shown to improve the dynamic behaviours of the power grid. A key problem with BESSs is the potential for poor utilisation of mismatched cells and reliability issues resulting from the use of a large number of cells in series. This thesis proposes a technique for state-of-charge balancing of many thousands of cells individually (i.e. not in packs) using a tightly integrated power electronic circuit coupled with a new control system design. Cells are organised in a hierarchical structure consisting of modules, sub-banks, banks and phases. The control strategy includes five levels of balancing: balancing of cells within a module, balancing of modules within a sub-bank, sub-banks within a bank, banks in a phase and balancing between phases. The system seeks to maximise the accessible state-of-charge range of each individual cell, thereby enhancing the overall capacity of the system. The system is validated in simulation for a 380 kWh BESS using 2835 lithium-ion cells where charge balancing is demonstrated for mismatched cells. A ‘peak sharing’ concept is implemented to manage voltage constraints so that alternative modules assume a portion of the load when certain modules are not capable of meeting the demand. An experimental validation has been performed to demonstrate the effectiveness of the balancing control. This work is intended to address the challenges of eventual scaling towards a 100 MWh+ BESS, which may be composed of hundreds of thousands of individual cells.
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El, Mghairbi Ahmed. "Assessment of earthing systems and enhancement of their performance." Thesis, Cardiff University, 2012. http://orca.cf.ac.uk/32579/.
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This thesis reports on the evaluation of performance and behaviour of earth electrode systems subjected to DC, AC and transient current injections with different rise times and shapes. The performance of the earth electrode system when injected with currents at the power frequency is now well understood, but the response of the system under high frequency and transient conditions is yet to be fully clarified. This thesis contributes to the better understanding of complex earthing systems such as earth grids and wind turbine earthing system behaviour under high frequency and transient conditions including voltage distributions along the length of the electrode. The frequency and time domain responses of earth electrodes (vertical and horizontal earth electrodes and earth grids) were quantified for soil resistivity ranged from 10Ωm to 10kΩm. Practical wind turbine earthing system models were developed to account for the additional effects of the above–ground tower structure of the wind turbine and also to consider the benefits of various enhancements to the earthing system. Simulations using 1/5μs and 8/20μs impulse currents were carried out, and a number of parameters were quantified; these include the earth potential rise and the voltage distributions at ground surface level. In particular, the contribution of mitigating techniques, such as rings and rods were derived. The computations allowed determination of touch and step voltages. The results show that the performance of an earth electrode depends on a number of factors such as soil resistivity and permittivity and electrode dimensions, and it was found that significant inductive effects dominate at high frequency. Thus, the ability of a horizontal earth electrode to reduce the earth potential rise is limited because, beyond a certain length known as the effective length, no further reduction is obtained. The effective length was determined experimentally by incrementally increasing the length of the test electrode. The experimental and simulation results show reasonably close agreement. Furthermore, reasonable prediction of the effective length may be possible using simple empirically derived equations. The thesis proposes a new method to increase the effective length of in-ground horizontal earth electrodes and the effective area of earth grids. It is proposed that an additional insulated parallel an above ground conductor is bonded to the horizontal electrode at suitable points along its length. Field tests show that the addition to such enhancement reduces inductance effects and helps dissipation of injected currents, so that a greater length of buried earth conductor is utilised, and this contributes to an additional reduction in the earth impedance. Hence, the earth potential rise at the point of current injection is reduced. Enhancing the earthing system in this way results in a significant reduction in the transient potentials developed at the base of the turbine structure. These TEPR reductions produce associated reductions in touch and step voltages.
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Kruisbrink, A. C. H. "The dynamic behaviour of check valves in pipeline systems." Thesis, City University London, 1996. http://openaccess.city.ac.uk/8269/.
Повний текст джерелаАнотація:
A semi-empirical method is developed to describe the dynamic behaviour of check valves in pipeline systems. The method is based on parameterized valve models and dimensionless valve characteristics, which may be obtained from experiments. The check valve is considered as a black box with certain input and output characteristics. The check valve closure and associated pressure surges are the dominant phenomena. Undamped check valves may be considered as a special case of damped check valves. Much attention is paid to the description of the hydrodynamic (fluid) forces on the internal, moving valve elements. These elements may be considered as translating or rotating bodies with (at least) one plane of symmetry. The equations of motion for the constrained, unsteady motion of such a body in an unconfined, unsteady fluid flow are based on the dynamical theory of Kirchhoff, extended to an unsteady fluid flow. The equivalent equations for a body in a confined fluid are based on Lagrange's method of generalized coordinates. A general (dimensionless) valve equation of motion is developed, which is valid for most of the existing check valve types. Basic differential equations are derived for the transient flow in a pipe with constant initial flow deceleration. The equations are applied to describe the check valve closure under reflection free and reflecting boundary conditions in the form of dimensionless, analytical equations. The theory is based on conventional waterhammer theory. The pipe and valve equations are coupled via the integral form of the momentum equation. The uncoupled and coupled, (dimensionless) pipe and valve equations show formally which (dimensionless) variables and valve, system and fluid parameters are relevant to the dynamic behaviour of check valves in pipeline systems. In that sense they are used in a dimensional analysis to develop (dimensionless) valve characteristics and dynamic scale laws. Based on the dimensionless valve characteristics, models for undamped and damped check valves are developed and implemented in the waterhammer computer code CVWP (Check Valve Waterhammer Program). Experiments are performed in the test facility at Delft Hydraulics to measure several valve characteristics of weakly and strongly damped check valves. The dynamic scale laws are validated by means of numerical simulations. The valve models are validated against experimental data. The study has been performed within the Check Valve Research Project (CVRP).
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Elliott, Bruce Jeffrey. "Benefits of adopting systems engineering approaches in rail projects." Thesis, University of Birmingham, 2014. http://etheses.bham.ac.uk//id/eprint/5322/.
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Systems Engineering (SE) is being increasingly used in rail projects. However, it is not entirely clear what exactly the return on investing in SE is or how to maximise this return. This thesis describes research into the relationship between the adoption of SE in rail projects and project outcomes. Using project cost and duration and system performance to measure the benefits of adopting SE is found to be problematic. Theoretical reasons and practical experience lead the writer to believe that many of the benefits of adopting SE on projects are enjoyed as a consequence of reducing change latency - the unnecessary delay in deciding to make a change. A tentative theory of how SE can reduce change latency is proposed and tested against data collected from nine rail projects. The data corroborate several causal mechanisms in the theory but also suggest that change latency depends upon other factors. For practitioners considering whether to apply SE on a project, the research findings provide encouragement but also a warning that the full benefits of applying SE will only be enjoyed if other pre-requisites for sound decision making are in place. The findings also provide guidance on how to adapt SE practices when applying them to rail projects, in order to maximise the benefits. The writer argues that change latency is a valuable metric for both practitioners and researchers and that formulating and refining explicit theories about the manner in which SE delivers benefits can assist researchers to build upon each other’s work.
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Vinai, Giovanni Maria. "Scalabilité et amélioration des propriétés de couplage d'échange pour TA-MRAM." Thesis, Grenoble, 2013. http://www.theses.fr/2013GRENY035/document.
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Le couplage d’échange entre une couche ferromagnétique (F) et une couche antiferromagnétique (AF) permet de piéger l’aimantation de la couche ferromagnétique. Ce phénomène est largement utilisé dans des systèmes magnétiques complexes, telles que les vannes de spins, ou les mémoires MRAM, où il permet de constituer des couches de références, normalement insensibles aux cycles d’écriture des couches de stockage. On remarque aux petites dimensions, lorsque la taille des cellules diminue en dessous de la centaine de nm, des renversements partiels ou complets des électrodes de référence, dus à un basculement du réseau de spins dans l’AF. L’objectif de cette thèse est de comprendre ces phénomènes de renversement, de les quantifier en fonction de la dimension latérale des dispositifs, et de présenter des solutions viables afin d’accroître la stabilité des systèmes de stockage. Ce travail essentiellement expérimental, comprenant dépôts, lithogravure et caractérisations, se déroulera pour la majeure partie au sein du laboratoire SPINTEC (UMR8191). L’étudiant sera cependant amené à collaborer avec plusieurs entités du pôle grenoblois, notamment pour les mesures magnéto-optiques, les analyses cristallographiques, ainsi que pour une partie de simulation atomistique ; il devra aussi s’intéresser à l’intégration industrielle de ses études en rendant compte de ses résultats, en les discutant, afin que Crocus Technology en bénéficie directement. La thèse, se déroulant sur trois ans, explorera les points suivants : i) Etude de la stabilité thermique en fonction de la taille des motifs (0-15mois) L’étudiant déposera par pulvérisation cathodique des bicouches F/AF (AF=FeMn, PtMn ou IrMn) qui seront gravées sur la plate forme de technologie amont (PTA) localisée sur le site du CEA/Grenoble. Il caractérisera par des mesures d’effet kerr ou de magnétotransport les propriétés magnétiques des bicouches, notamment les distributions de TB, de champ d’échange, en fonction de la taille des motifs. Il participera aux analyses cristallographiques en collaboration avec le Service général des rayons X et le laboratoires d'Etude des Matériaux par Microscopie Avancée (LEMMA) (du CEA/Grenoble/INAC/SP2M). Ces analyses qui donneront des renseignements sur les tailles de grains et leur distribution seront utilisées pour comprendre les mesures magnétiques dans un premier temps, et seront un point de départ pour optimiser via des recuits, ou l’ajout d’éléments d’addition, la stabilité des systèmes aux dimensions réduites, typiquement <100nm. ii) Etude du couplage inter-grain dans l’AF (15-22mois) L’étudiant réalisera des mesures de trainage magnétique et déterminera les volumes de nucléation dans l’AF et les comparera aux données cristallographiques. Il essaiera de déterminer l’importance de ce couplage dans la stabilité des points mémoire en jouant sur son intensité (recuits, éléments d’addition…), ceci participant de l’optimisation de l’anisotropie d’échange aux petites dimensions présentée dans la partie précédente. iii) Volet de simulations atomistiques (22-30mois) L’étudiant collaborera avec le laboratoire LSIM et notamment F. Lançon afin de simuler, grâce à un code de calcul développé localement, l’impact de la cristallographie (taille de grains, couplage inter-grains, désordre interfacial et rugosité) sur les propriétés de l’anisotropie d’échange dans les systèmes F/AF de taille réduite. Ces simulations permettront de comprendre les mesures expérimentales réalisées en parallèle et d’ouvrir de nouvelles voies exploratoires pour optimiser les valeurs de champ d’échange en vue de leur intégration dans les dispositifsExchange coupling between a ferromagnetic (F) and an antiferromagnetic (AF) layer is responsible of a higher coercivity and of a shift in the hysteresis loop. This phenomenon is widely used in magnetic systems like spin-valves and MRAM to set the reference layer, that remains fixed during the writing processes of the storage layer. It has been noticed that, for systems with reduced lateral size , the magnetization of the reference layer can (completely or partially) reverse because of spin switches in the AF layer. The aim of this thesis project is the understanding of these reversal phenomena, the quantification as a function of lateral dimension and the proposal of feasable solutions in order to increase the stability of the storage layer. The thesis will be maily experimental, including deposition, lithography and characterization processes. The main part of the thesis will be spent at SPINTEC (UMR8191) laboratories. The student will also collaborate with other research groups in Grenoble, in particular for magneto-optical measurements, crystallographic analysis, and atomic simulations. He will also manage the industrial integration of his studies, by sharing and discussing his results with Crocus Technology. The thesis, during a period of three years, will cover the following subjects: i) Study of the termal stability as a function of lateral size (0-15 months). The student will deposit F/AF bilayers being AF FeMn, PtMn or IrMn) by magnetron sputtening. These layers will be etched at Pthe TA cleanroom facility, in CEA-Grenoble. TB and exchange field distributions will be characterized by Kerr effect and magnetotrasport measurements as a function of lateral size. He will collaborate to the crystallographic analysis with the X-ray general service and the 'laboratoires d'Etude des Matériaux par Microscopie Avancée' (LEMMA) (CEA/Grenoble/INAC/SP2M). These analysis, that will give informations about grain size and distribution, will help the understanding of the magnetic measurements and will be a starting point for an optimization, through annealing steps or additional elements, of the stability of systems with reduced lateral size (typically below 100nm). ii) Study of AF inter-grain coupling (15-22 months) The student will perform magnetic training measurements. He will determine the nucleation volumes in the AF and compare them with the crystallographic results. He will manage to establish the importance of this coupling in the stability of magnetic memories and to vary its intensity (annealing, additional elements). This study will contribute to optimize the exchange anisotropy at reduced dimensions presented in the previous point. iii) Atomic simulations (22-30 months) The student will collaborate with LSIM laboratory, in particular with F.Lançon. He will simulate the impact of crystallography (grain size, inter-grain coupling, interfacial disorder, rugosity) on exchange anisotropy properties in F/AF systems with reduced lateral size. Simulations will be performed with a code developped in the lab. These simulations will help in understanding the experimental measures performed previously, and will give new suggestions in the optimization process of the exchange field for technological integration
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Abuazoum, Latifa Abdalla. "Advanced model updating methods for generally damped second order systems." Thesis, University of Nottingham, 2011. http://eprints.nottingham.ac.uk/12063/.
Повний текст джерелаАнотація:
This thesis is mostly about the analysis of second order linear vibrating systems. The main purpose of this study is to extend methods which have previously been developed for either undamped or proportionally damped or classically damped systems to the general case. These methods are commonly used in aerospace industries. Ground vibration testing of aircraft is performed to identify the dynamic behaviour of the structure. New aircraft materials and joining methods - composite materials and/or novel adhesive bonding approaches in place of riveted or welded joints - cause higher levels of damping that have not been seen before in aircraft structure. Any change occurring in an original structure causes associated changes of the dynamic behaviour of the structure. Analytical finite element analyses and experimental modal testing have become essential tools for engineers. These techniques are used to determine the dynamic characteristics of mechanical structures. In Chapters 3 and 4, structural analysis and modal testing have been carried out an aircraft-like structure. Modal analysis techniques are used to extract modal data which are identified from a single column of the frequency response matrix. The proposed method is presented for fitting modal peaks one by one. This technique overcomes the difficulty due to the conventional methods which require a series of measured FRFs at different points of excitation. New methods presented in this thesis are developed and implemented initially for undamped systems in all cases. These ideas are subsequently extended for generally damped linear systems. The equations of motion of second order damped systems are represented in state space. These methods have been developed based on Lancaster Augmented Matrices (LAMs) and diagonalising structure preserving equivalences (DSPEs). In Chapter 5, new methods are developed for computing the derivatives of the non-zeros of the diagonalised system and the derivatives of the diagonalising SPEs with respect to modifications in the system matrices. These methods have provided a new approach to the evaluation and the understanding of eigenvalue and eigenvector derivatives. This approach resolves the quandary where eigenvalue and eigenvector derivatives become undefined when a pair of complex eigenvalues turns into a pair of real eigenvalues or vice-versa. They also have resolved when any one or more of the system matrices is singular. Numerical examples have illustrated the new methods and they have shown that the method results overcome certain difficulties of conventional methods. In Chapter 6, Möbius transformations are used to address a problem where the mass matrix is singular. Two new transformations are investigated called system spectral transformation SSTNQ and diagonalising spectral/similarity transformation DSTOQ. The transformation SSTNQ maps between matrices of two systems having the same short eigenvectors and their diagonalised system matrices. The transformation DSTOQ maps between two diagonalising SPE‟s having identical eigenvalues. Modal correlation methods are implemented to evaluate and quantify the differences between the output results from these techniques. Different cross orthogonality measures represent a class of methods which are recently performed as modal correlation for damped systems. In Chapter 7, cross orthogonality measures and mutual orthogonality measures are developed for undamped systems. These measures are defined in terms of real matrices - the diagonalising structure preserving equivalences (DSPEs). New methods are well developed for ill-conditioned system such that they work for all occasions and not only for cases where mass matrix is non-singular. Also a measure of the residuals is introduced which does not demand invertibility of diagonalised system matrices. Model updating methods are used in order to update models of systems by matching the output results from analytical system models with the experimentally obtained values. In Chapter 8, both cross-orthogonality measures and mutual-orthogonality measures are developed and used in the model updating of generally damped linear systems. Model updating based on the mutual orthogonality measures exhibits monotonic convergence from every starting position. That is to say, the ball of convergence has an infinite radius whereas updating procedures based on comparing eigenvectors exhibit a finite ball of convergence. Craig Bampton transformations are one of component methods which are used to reduce and decouple large structure systems. In Chapter 9 Craig Bampton transformations are developed for undamped systems and extended for damped second order systems in state space. Craig Bampton transformations are generalised and presented in SPEs forms. The two parts of the Craig Bampton transformations are extended in the full sizes of the substructure. The extended Craig Bampton transformations are modified to format each block of transformed substructure matrices as LAMs matrices format. This thesis generalises and develops the methods mentioned above and illustrates these concepts with an experimental modal test and some examples. The thesis also contains brief information about basic vibration properties of general linear structures and literature review relevant to this project.
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Zhang, Jie. "Expert systems in on-line process control and fault diagnosis." Thesis, City University London, 1991. http://openaccess.city.ac.uk/7682/.
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In this research expert systems for on-line process control and fault diagnosis have been investigated and the majority of the research is on using expert systems in on-line process fault diagnosis. Several on-line expert systems, including a rule based controller and several fault diagnosis systems, have been developed in this research and are reported in this thesis. The research results obtained demonstrate that rule based controllers can be used in situations where mathematical models for the controlled process cannot be obtained or are very difficult to obtain. The research on on-line fault diagnosis emphasises deep knowledge based approaches. Two avenues in deep knowledge based approaches, namely causal search and qualitative modelling based diagnosis, have been investigated. In the approach of causal search the research results reveal that diagnostic efficiency can be achieved through structural decomposition. A systematic approach for developing diagnostic rules based on structural decomposition is presented in this thesis. Much of the research has been done on qualitative model based fault diagnosis. A qualitative reasoning method which utilizes knowledge on the quantitative relations among variables to reduce ambiguity and can cope with a wider range of situations than Raiman's Order of Magnitude Reasoning is investigated. In the qualitative model based diagnosis the function of the qualitative model is to predict the behaviour of the process under various hypotheses and, therefore, to verify these hypotheses. Further research concerning self-reasoning has been done for the qualitative model based diagnosis approach. Self-reasoning is achieved by backward tracing through the model of the diagnosis system and makes this diagnosis system more intelligent. Self-learning of heuristic rules based on qualitative modelling is investigated and heuristic rules can add efficiency to model based diagnosis. During investigating self-learning of heuristic rules, the good learning property of neural networks is recognised and, neural networks based on-line fault diagnoses are also investigated. The research results reveal that neural networks based diagnosis systems are easy to develop and perform robustly provided that the training data are available.
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Nistazakis, Emmanouil. "Process and systems based methodologies related to control structure selection." Thesis, City University London, 1998. http://openaccess.city.ac.uk/7711/.
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This thesis is concerned with an important aspect of process control design, that is, the synthesis of the control structures. A review of the rapidly growing process methodologies' literature is presented and this leads to the identification of wider issues and new problems which are referred to as global instrumentation and forms the main subject of this thesis. The main objective has been the integration of existing process based tools and methodologies with a much more general approach of a systems and control theory character. The problem of Global Process Instrumentation concerns the selection of systems of measurement and actuation variables, found during the synthesis/design and operation of large-scale industrial processes/systems. The role of traditional instrumentation was considered but the emphasis has been on the systems aspects. In fact, instrumentation leads to the shaping of the final system and thus, is crucial in defining the control quality properties and operability characteristics of the final design. The development of these system aspects led to the emergence of an integrated framework for Global Instrumentation. An attempt was also made to abstract some results and formulate generic issues and problems, that would provide a wider scenario for activities in the future. Development of CAD to support the selection of control structures has been a major task undertaken here. The system aspects of Global Instrumentation are demonstrated by studying two specific problems that involve the study of the structural properties of interconnected systems as a function of local selection of sensors and actuators and the problem of well-conditioning badly structured transfer functions. The role of selection of inputs and outputs, on the overall shaping of composite structure properties, at the subsystem level, was examined, and the significance of an assumption related to interconnections, referred to as the completeness assumption, was investigated. Specifically, the significance of the deviations from the completeness, was the subject of the investigation. Matrix Pencil Theory was used to examine the controllability, observability and zero structure related properties of composite systems under partial or total loss of inputs/outputs at the subsystem level. Selecting subsets of the original sets of inputs, outputs to guarantee full rank transfer function, was also an issue that was examined. The above problems were presented as part of an integrated design philosophy that aims to explore the system structure. An integrated approach to the overall problem of control structure selection was formulated and open issues and problems were identified. It was based on the assumption that there exists a progenitor model of the linear type for the process, which, however, may not be well defined. Structural analysis of the system theoretic framework, the interaction measures and the results for evaluation of alternative decentralisation schemes were then used, to specify a step by step approach to the control structure selection. The problem of handling alternative criteria was also considered and basic elements of a system procedure were given. There are many open issues, which were identified and are still open and thus the proposed structural approach should be considered as the first step to the development of an integrated methodology that involves the following major steps: (a) Classification of system model variables and definition of well structured progenitor model. (b) Definition of effective input, output structure based on operability, controllability criteria. (c) Determining the structure of the control scheme by evaluation of alternative decentralised structures. An important part of the integrated methodology for control structure selection is the - so called - interaction analysis. It consists of a number of diagnostics and structural tests that help to restrict the choice of the best scheme. Several of these tests/methodologies were reviewed and some of them were further expanded. The outcomes obtained by these methodologies provided promising results. These results gave the motivation for the construction of a complete CAD package, the "Interaction Analysis Toolbox", written in MATLAB®t. This Toolbox provides many tools and diagnostics that can be applied during the design stages, for the evaluation of the various alternative control structures.
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Álvarez, Martín José Alberto. "Adaptive multivariable intermittent control : theory, development, and applications to real-time systems." Thesis, University of Glasgow, 2018. http://theses.gla.ac.uk/30633/.
Повний текст джерелаАнотація:
Intermittent Control, as a control scheme that switches between open and closed-loop configurations, has been suggested as an alternative model to describe human control and to explain the intermittency observed during sustained control tasks. Additionally, IC might be beneficial in the following scenarios: 1 - in the field of robotics, where open-loop evolution could be used for computationally intensive tasks such as constrained optimisation routines, 2 - in an adaptation context, helping to detect system and environmental variations. Based on these ideas, this thesis explored the application of real-time multivariable intermittent controllers in humanoid robotics as well as adaptive versions of IC implemented on inverted pendulum structures.
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Tan, Kay Chen. "Evolutionary methods for modelling and control of linear and nonlinear systems." Thesis, University of Glasgow, 1997. http://theses.gla.ac.uk/8473/.
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The aim of this work is to explore the potential and enhance the capability of evolutionary computation for the development of novel and advanced methodologies for engineering system modelling and controller design automation. The key to these modelling and design problems is optimisation. Conventional calculus-based methods currently adopted in engineering optimisation are in essence local search techniques, which require derivative information and lack of robustness in solving practical engineering problems. One objective of this research is thus to develop an effective and reliable evolutionary algorithm for engineering applications. For this, a hybrid evolutionary algorithm is developed, which combines the global search power of a "generational" EA with the interactive local fine-tuning of Boltzmann learning. It overcomes the weakness in local exploration and chromosome stagnation usually encountered in pure EAs. A novel one-integer-one-parameter coding scheme is also developed to significantly reduce the quantisation error, chromosome length and processing overhead time. An "Elitist Direct Inheritance" technique is developed to incorporate with Bolzmann learning for reducing the control parameters and convergence time of EAs. Parallelism of the hybrid EA is also realised in this thesis with nearly linear pipelinability. Generic model reduction and linearisation techniques in L2 and L∞ norms are developed based on the hybrid EA technique. They are applicable to both discrete and continuous-time systems in both the time and the frequency domains. Superior to conventional model reduction methods, the EA based techniques are capable of simultaneously recommending both an optimal order number and optimal parameters by a control gene used as a structural switch. This approach is extended to MIMO system linearisation from both a non-linear model and I/O data of the plant. It also allows linearisation for an entire operating region with the linear approximate-model network technique studied in this thesis. To build an original model, evolutionary black-box and clear-box system identification techniques are developed based on the L2 norm. These techniques can identify both the system parameters and transport delay in the same evolution process. These open-loop identification methods are further extended to closed-loop system identification. For robust control, evolutionary L∞ identification techniques are developed. Since most practical systems are nonlinear in nature and it is difficult to model the dominant dynamics of such a system while retaining neglected dynamics for accuracy, evolutionary grey-box modelling techniques are proposed. These techniques can utilise physical law dominated global clearbox structure, with local black-boxes to include unmeasurable nonlinearities as the coefficient models of the clear-box. This unveils a new way of engineering system modelling. With an accurately identified model, controller design problems still need to be overcome. Design difficulties by conventional analytical and numerical means are discussed and a design automation technique is then developed. This is again enabled by the hybrid evolutionary algorithm in this thesis. More importantly, this technique enables the unification of linear control system designs in both the time and the frequency domains under performance satisfaction. It is also extended to control along a trajectory of operating points for nonlinear systems. In addition, a multi-objective evolutionary algorithm is developed to make the design more transparent and visible. To achieve a step towards autonomy in building control systems, a technique for direct designs from plant step response data is developed, which bypasses the system identification phase. These computer-automated intelligent design methodologies are expected to offer added productivity and quality of control systems.
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Zhang, Yang. "Development of BDD models for decision support in phased mission systems." Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/32431/.
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Autonomous systems are becoming increasingly commonplace, with applications either existing or suggested in many different industries. As levels of autonomy increase, the need for these systems to interpret with environments in which they operating and make decisions about their own future actions following internal failures or external threats. In the past, reliability analysis methods have been suggested as having the potential to provide information that could be used in a real-time decision support tool for autonomous systems in changing environments. Real-time support is particularly important in systems such as unmanned aerial vehicles (UAV), where any delay in making a decision following a failure occurrence or the emergence of a threat could be catastrophic. Reliability Analysis can be used to calculate the failure probability of a mission such as that performed by a UAV by modelling the mission as a sequence of tasks known as a phased mission. Binary Decision Diagram models have shown great potential for analysing phased mission systems since they can produce accurate mission and phase failure probabilities in reasonably short time frames. Although research to date has shown that Binary Decision Diagrams appear to have the most promise for performing the real-time analysis that would be required as an input to a decision making tool for phased mission systems, the analysis as it stands still falls some way short of being near-instant, as it must be for decisions to be made quickly when required. In common with many systems, phased mission systems can contain components that fail in multiple failure modes. It is therefore important that multiple failure modes are modelled while developing the Binary Decision Diagram tools and techniques considered in this research. The research presented in this thesis aims to address the deficiencies seen in previous methods by investigating the Binary Decision Diagram techniques and suggesting how the techniques can be developed for use within a decision support tool where fast, accurate decision making is required. The novelty of the research is as follows: 1. Different Binary Decision Diagram models for phased mission systems are reviewed and three new Binary Decision Diagram models are proposed to improve the efficiency and accuracy of analysis for phased mission systems containing multiple failure mode components. 2. Since the size of a Binary Decision Diagram has a significant effect on the time required to quantify it and the Binary Decision Diagram size is influenced by variable ordering, nine different variable ordering schemes are investigated for phased mission systems. Eight of them are extended from fault tree analysis of single phase systems containing single failure mode components and one is newly-developed specially for use within a decision support tool. 3. Due to the potential time limitation for decision making, approximation methods are investigated to evaluate the failure probabilities in phased mission systems while trading off between accuracy and analysis efficiency. Three new approximation models are developed and their analysis efficiency advantage over the exact analysis is demonstrated testing on a large number of sample phased mission systems. A performance indicator is developed in order to facilitate the choice of approximation method taking into account accuracy and efficiency requirements. The benefits of the developed methods are demonstrated through the consideration of a case study.
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Li, Chung Wai. "On-line distributed hierarchical control and optimisation of large scale systems." Thesis, City University London, 1990. http://openaccess.city.ac.uk/7528/.
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This research is concerned with the application of closed-loop coordination techniques for on-line steady state optimisation and control of large scale systems using a micro-computer based system. A two-level hierarchical computer structure consisting of a coordinator at the supremal (upper) level and two local decision units at the infimal (lower) level had been established. Parallel computation were performed at the local decision unit level once the coordination parameters had been received from the supremal level. A steady state system model consisting of two interconnected subprocesses, simulated oy an analogue computer, was used to investigate the coordination methods for closed-loop hierarchical control. First-order time constants were introduced to the interaction inputs and the controls within the simulated subprocesses. Investigations had been carried out to study closed loop control using the Interaction Prediction and Interaction Balance coordination method. Special attention was given to the study of the problems associated with synchronisation of the local decision units for closed-loop control. Stability aspects of both coordination methods when subjected to disturbances in the controls and interconnections had been investigated~ Problems relating to system transient and local. decision asynchronisation, as well as their effects on system stability and convergence of the two tasks, namely the local decision task and the coordinator task had also been investigated. Methods for dealing with these problems had been suggested. The sub-optimality, convergency and robustness properties of each coordination method had been discussed. This research has demonstrated that the Interaction Prediction coordination methods are best suited for on-line distributed optimising control of large scale interconnected systems. Using the local feedback scheme, complete decentralisation at the local decision level operated asynchronou.sly can be achieved with the Interaction Prediction coordination method.
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Aziz, Mohd Ismail bin Abd. "Development of hierarchical optimal control algorithms for interconnected nonlinear dynamical systems." Thesis, City University London, 1999. http://openaccess.city.ac.uk/7753/.
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The main concern of this thesis is to develop and advance the knowledge of new hierarchical algorithms for optimal control of interconnected nonlinear systems. To achieve this, four basic hierarchical structures are developed by taking into account the manner in which real process measurements taken from interaction inputs are incorporated and utilized in the model-based optimal control problem. The structures are iterative in nature, and are derived using the dynamic integrated system optimization and parameter estimation (DISOPE) technique to take into account model-reality differences that may have been deliberately introduced to facilitate the solution of the complex nonlinear problem or due to uncertainty in the model used for computation. Three of the four basic hierarchical structures are used as a basis for developing hierarchical optimal control algorithms using a linear quadratic model formulation. Two approaches are used in the coordination problem of the algorithms, price coordination approach and the direct coordination approach. The algorithms are then implemented using two techniques, the single loop and the double loop techniques. All the algorithms are implemented in software and a simulation study is carried out using two examples to investigate their effectiveness and convergence properties. The optimality of the solution provided by the structures and the algorithms described in this research work are established. In addition, convergence analysis is carried out to provide sufficient convergence conditions of the double loop algorithms. Suggestions for future research as a continuation of the work presented in this thesis are also made.
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Brown, Daniel. "The management of Trihalomethanes in water supply systems preferred access arrangement." Thesis, University of Birmingham, 2009. http://etheses.bham.ac.uk//id/eprint/364/.
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The formation of potentially harmful trihalomethanes (THM) when using chlorine as a disinfectant in potable water supplies has led to tighter regulatory controls and hence a need for better models for THM management. The prediction of THM concentration is difficult due to the complex and changing hydrodynamic and chemical regimes found in water treatment works (WTWs) and distribution systems. The purpose of the study is to increase understanding of THM formation and chlorine decay through six water treatment works (WTWs) and distribution systems operated by Severn Trent Water Ltd and ultimately develop an efficient, robust, cost effective model for chlorine decay and THM formation. With knowledge of the bulk chlorine decay characteristics and the THM productivity of the water, this model offers a simple and straightforward tool which can be readily applied to WTWs and distribution systems alike to provide an initial assessment of the risks of total THM formation at different sites, and to identify sites and systems at risk of compliance failure. Relying only on the measurement of analytically undemanding parameters (in particular, chlorine and its decay with time), under appropriate circumstances this model offers advantages of simplicity and cost-effectiveness over other, more complex models. The model can thus be applied to assess the chemical risk under different scenarios allowing for informed decision making.
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Lampakis, Elias G. "Algebraic synthesis methods for linear multivariable control systems." Thesis, City, University of London, 1995. http://openaccess.city.ac.uk/19007/.
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The mathematical formulation of various control synthesis problems (such as Decentralized Stabilization Problem (DSP), Total Finite Settling Time Stabilization for discrete time linear systems (TFSTS), Exact Model Matching Problem (EMMP), Decoupling and Noninteracting Control Problems) via the algebraic framework of Matrix Fractional Representation (MFR) - i.e. the representation of the transfer matrices of the system as matrix fractions over the ring of interest - results to the study of matrix equations over rings, such as : A . X + B . Y = C , (X. A + Y . B =C) (1) A· X = B , (y. A = B) (2) A·X·B = C (3) A·X + Y·B = C, X·A + B·Y = C, A·X·B + C·Y·D = E (4). The main objective of this dissertation is to further investigate conditions for existence and characterization of certain types of solutions of equation (1) ; develop a unifying algebraic approach for solvability and characterization of solutions of equations (1) - (4), based on structural properties of the given matrices, over the ring of interest. The standard matrix Diophantine equation (1) is associated with the TFSTS for discrete time linear systems and issues concerning the characterization of solutions according to the Extended McMillan Degree (EMD) (minimum EMD, or fixed EMD) of the stabilizing controllers they define, are studied. A link between the issues in question and topological properties of certain families of solutions of (1) is established . Equation (1) is also studied in association with the DSP and Diagonal DSP (DDSP) for continuous time linear systems. Conditions for characterizing block diagonal solutions of (1) (which define decentralized stabilizing controllers) are derived and a closed form description of the families of diagonal and two blocks diagonal decentralized stabilizing controllers is introduced. The set of matrix equations (1) - (4) is assumed over the field of fractions of the ring of interest , ℛ , (mainly a Euclidean Domain (ED) and thus a Principal Ideal Domain (PID)) and solvability as well as parametrization of solutions over ℛ is investigated under the unifying algebraic framework of extended non square matrix divisors, projectors and annihilators of the known matrices over ℛ . In practice the ring of interest is either the ring of polynomials ℝ [s] , or the rings of proper ℝ_pr(s) and especially proper and stable rational functions R_op(s). The importance of R_op(s) is highlighted early in the thesis and further computational issues arising from its structure as an ED are considered.
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Windows-Yule, Christopher R. K. "Convective and segregative mechanisms in vibrofluidised granular systems." Thesis, University of Birmingham, 2015. http://etheses.bham.ac.uk//id/eprint/5988/.
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Granular materials display a host of fascinating behaviours both remarkably similar to and strikingly different from those exhibited by classical solids, liquids and gases. Due to the ubiquity of granular materials, and their far-reaching importance in multitudinous natural and industrial processes, an understanding of their dynamics is of the utmost importance to modern society. In this thesis, we analyse in detail two phenomena, one from each of the above categories: granular convection, a behaviour directly analogous to the Rayleigh-Benard cells observable in classical fluids, and granular segregation, a phenomenon without parallel in classical, molecular physics, yet which is known to greatly impact various physical and industrial systems. Through this analysis, conducted using a combination of the experimental positron emission particle tracking technique and discrete particle method simulations, we aim to improve our knowledge of these processes on a fundamental level, gaining insight into the factors which may influence them, and hence how they may be effectively controlled, augmented or eliminated.
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Williams, Oludare Adebayo. "Beyond lean : a framework for fit production systems." Thesis, Cardiff University, 2013. http://orca.cf.ac.uk/48274/.
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Western manufacturing companies are facing a challenging environment fraught with strong competition from India, China and other emerging economies. In this context, the effectiveness of the traditional production concepts of leanness and agility is being challenged. Against this background, the need for new manufacturing paradigms is set to provide new knowledge, techniques, and concepts useful for managers to address the difficulties of today’s business environment. This work extends the concept of production management beyond the achievement of efficiency short-term goals into the realms of strategic thinking by creating both the framework and the indices for an integrated production system. This research presents fit manufacturing as a new production model for a holistic manufacturing strategy that links the short-term goals of manufacturing effectiveness and efficiency embodied in lean and agile production strategies with the long-term objective of sustainable enterprise management. The research extends the concept of integration beyond ordinary manufacturing functions into the realms of strategic thinking. The thesis gives an operational definition for the concept of fit manufacturing by describing the structural and operational characteristics of the production philosophy. It proposes the central theme of fit xxiii manufacturing as a manufacturing strategy essential to creating an integrated view of the factory – inside out and vice-versa. The idea of an overall fitness index combining measures of leanness, agility and economic sustainability is put forward and justified and the necessary conditions for fitness are derived. A case study showing an application of these different measures and the overall production fitness index is presented. This research has shown that the fit production model combines the strengths of lean and agile manufacturing, with the long-term sustainability and viability of the enterprise. The model can be used to assess the performance of the production process, to evaluate investment proposals such as adding a new product line or increasing the overall capacity of the factory, and to build the enterprise of the future.
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Park, Mun Gyu. "RAMS management of railway systems." Thesis, University of Birmingham, 2014. http://etheses.bham.ac.uk//id/eprint/4750/.
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Railway RAMS is an engineering discipline that integrates reliability, availability, maintainability and safety characteristics into an inherent design property through systems engineering. This research is to establish a systematic approach of RAMS management for the railway systems engineering through the establishment of the engineering concepts, methods, techniques and tools. For this purpose, the research focuses on three subjects and a case study. Firstly, this research provides a RAMS management systems included railway systems engineering and RAMS management processes so that railway organisations can decide a strategic policy, control functions and coordinate activities related to RAMS management. Secondly, this research provides railway risk assessment methods to assess all of the potential hazards that threaten the railway’s operational objectives and control them within the possible acceptable criteria. Thirdly, this research provides the method that develops RAMS performance specifications appropriate to the RAMS requirements and operational contexts in order to develop RAMS design and its acceptance criteria for implementing the detailed design and/or contract. Finally, this research presents a case study for the risk assessment, using the data collected from the railway industry to demonstrate the proposed risk assessment method and to investigate the RAMS performance of the railway systems and their major failure causes.
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Raper, Adrian. "An expert systems approach to model based signal processing of shock phenomena." Thesis, University of Southampton, 1988. https://eprints.soton.ac.uk/52268/.
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Expert systems have been proposed as a means of storing and applying a human expert's knowledge and problem solving skills. This would be a valuable facility in the area of signal processing as analysts already rely on computers for numerical manipulation of data. This research describes the successful conception and realising of software to assist a technically competent person in directing, applying and interpreting of signal processing algorithms with particular reference to the interpretation of measured responses to shock excitation. If a structure has been excited by some driving force, a measured response contains information about parts of the structure involved in the movement. An analyst given the measurement and asked to underdtand and explain the process that caused it will interpret the signal by building a model. The model is initially an empty shell but is made specific to the data by extracting information from the signal or prior knowledge. Information in the signal is stored in two ways; the numeric data values that represent the measured variable and the patterns visible to the eye when the data values are plotted against time. The information from the numeric values is extracted using algorithms which emphasise the previously hidden information. The design of the expert system has a model of the vibration process at its heart and aims to make it specific to the data just as the analyst does. There are three sections to the program, choice of a model, defining the components of the model and finally producing a report of the analysis. The first and third sections use rule based inference but the middle section is founded on a new architecture tuned for model building. It is a blackboard control structure organised to represent a linear system model. Knowledge sources are attached to each component and are scheduled by the user. A graphical interface is provided through which the user can view any part of the model in signal or symbolic format. Software is provided that creates the signals that form a view of the model and keeps the linear system causal. There are two main areas of knowlege application that give the program unique powers. One is in characterising features in the measurement emphasised by some algorithm as parameters of one of the components. The other is in finding a comparison whereby the accuracy of the parameter, in terms of how well it lets the model mimic the measurement, is established. Both these procedures are dominated by exploiting the user's ability to find patterns in noisy signals. This is particularly true when the model can generate different views of a signal. One statistical method of assessing a parameter value is explored and that is an adaptation of the maximum likelihood function used to find the confidence of epoch locations.
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Sempewo, Jotham Ivan. "Transitioning of urban water distribution systems." Thesis, University of Birmingham, 2013. http://etheses.bham.ac.uk//id/eprint/4227/.
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The upgrade of urban water distribution systems (UWDS) amidst uncertain global change pressures is a challenging problem. To deal with this dilemma water utilities require approaches that enable UWDS to be transitioned at a minimal technical and socio-economic impact as uncertainties become known. A review of approaches for upgrading UWDS shows that existing cost models are skewed towards operation and maintenance costs without consideration for future transitionability. This thesis describes approaches for the sustainable transition of UWDS and their application on case studies. The thesis develops a conceptual framework for the analysis of UWDS transitions. It then develops a Socio-economic Impact Indicator (SII) framework based on Multi Criteria Decision Analysis and the Analytical Hierarchical Process to estimate impacts in an urban area due to UWDS transitions. It also develops an approach for modelling socio-technical transitions based on multinomial logistic regression. The thesis then develops an UWDS transition design approach that considers not only operation and maintenance costs (leakage and burst costs) but also transitionability and future socio-technical impacts costs. The developed approaches have been tested on case studies as proof of concept. Maximum cost saving can be realised when existing UWDS are upgraded with consideration of future UWDS transitionability.
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Kyaw, Si Thu. "Finite element modelling of stresses and failure within plasma spray thermal barrier coating systems." Thesis, University of Nottingham, 2013. http://eprints.nottingham.ac.uk/27952/.
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Air plasma sprayed thermal barrier coating (APS TBC) systems are usually applied to engine components to reduce the temperature of the substrate and increase the efficiency of engines. However, failure of these coatings leads to oxidation and corrosion of the substrate. Therefore, a thorough understanding of the coating failure is necessary to predict the lifetime of coated components. This project has carried out stress analysis and prediction of subsequent failure of APS TBC systems associated with sintering of the TBC, oxidation of the bond coat (BC), substrate geometry, undulations at the coating interfaces and coating fracture toughness. Stress analysis is crucial for predicting TBC failure as stresses in the vicinity of the coating interfaces cause cracks and subsequent coating delamination. The Finite element (FE) method was used for stress analysis of TBC systems at high temperature stage and at cooling stage after operation. Initially, FE model of an axisymmetric unit cell representing the slice of a coated cylinder was used. Different radii for cylinders were used to investigate the significance of substrate curvature on coating stresses. The effect of asperities at the coating interface on residual stresses was observed using 3D models. The models were built based on the actual geometries of asperities, which were extracted from 3D SEM images of the coating interfaces. An Arrhenius approach was utilised to implement changes in mechanical and physical properties of TBC due to sintering. BC oxidation and related changes in its composition were also implemented. The accuracy of assumptions for FE models was validated by comparing the evaluated stresses against experimental results by project partners. Finally, the effects of stresses and fracture toughness of the coatings and coating interfaces on failure of the TBC system were studied, using cohesive surface modelling and extended finite element modelling (XFEM) methods.
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Qin, Shunde. "Shear behaviour of corroded reinforced concrete T-beams repaired with fibre reinforced polymer systems." Thesis, University of Birmingham, 2016. http://etheses.bham.ac.uk//id/eprint/6990/.
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This study investigates the shear behaviour of corrosion-damaged reinforced concrete Tbeams repaired with fibre reinforced polymer (FRP) systems. Nine beams with different corrosion levels (0% (uncorroded), 7% and 12%) and different strengthening methods were tested. Both the embedded Carbon-FRP rods and externally bonded Carbon-FRP sheets were effective in enhancing the shear strength of tested beams. The test beams were modelled using nonlinear three dimensional half models in the finite element (FE) package TNO Diana. The shear force capacity, shear force-deflection graphs and crack patterns at failure were used to validate the FE models. Reasonable agreement was obtained between the experimental and numerical results. A parametric study investigating the effect of concrete strength, steel-to-CFRP shear reinforcement ratio and shear span-to-effective depth ratio was carried out. The FE predictions suggest that the embedded CFRP shear contribution decreases with the increase in steel-to-CFRP shear reinforcement ratio and shear span-to-effective depth ratio. Finally, the FE predictions were compared with the predictions of Concrete Society TR55 design guidance. The results suggest that TR55 overestimates the shear strength enhancement offered by embedded CFRP rods.
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Al-Shaqi, Riyad. "Ambient assisted living systems for older people with Alzheimer's." Thesis, Cardiff University, 2016. http://orca.cf.ac.uk/96487/.
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The older people population in the world is increasing as a result of advances in technology, public health, nutrition and medicine. People aged sixty or over were more than 11.5% of the global population in 2012. By 2050, this percentage is expected to be doubled to two billion and around thirty-three countries will have more than ten million people aged sixty or more each. With increasing population age around the word, medical and everyday support for the older people, especially those who live with Alzheimer’s who can't be trusted for consistence interaction with their environment, attract the attention of scientists and health care providers. Existing provisions are often deemed inadequate; e.g.; current UK housing services for the older people are inadequate for an aging population both in terms of quality and quantity. Many older people prefer to spend their remaining life in their home environment; over 40% of the older people have concerns about having to move into a care home when they become old and nearly 70% of them worry about losing their independence or becoming dependent on others. There is, therefore, a growing interest in the design and implementation of smart and intelligent Ambient Assisted Living (AAL) systems that can provide everyday support to enable the older people to live independently in their homes. Moreover, such systems will reduce the cost of health care that governments have to tackle in providing assistance for this category of citizens. It also relieves relatives from continuous and often tedious supervision of these people around the clock, so that their life and commitments are not severely affected. Hence, recognition, categorization, and decision-making for such peoples’ everyday life activities is very important to the design of proper and effective intelligent support systems that are able to provide the necessary help for them in the right manner and time. Consequently, the collection of monitoring data for such people around the clock to record their vital signs, environmental conditions, health condition, and activities is the entry level to design such systems. This study aims to capture everyday activities using ambient sensory II information and proposes an intelligent decision support system for older people living with Alzheimer’s through conducting field study research in the Kingdom of Saudi Arabia within their homes and health care centres. The study considers the older people, who live with Alzheimer’s in Kingdom of Saudi Arabia. Since Alzheimer’s is a special form of dementia that can be supported in early stages with the ambient assistive systems. Further, the results of the field study can also be generalized to societies, which are interested in the mental and cognitive behaviour of older people. This generalization is related to the existence of common similarities in their daily life. Moreover, the approach is a generalized approach. Hence it can also be utilized on a new society which is conducting the same field study. This study initially presents a real-life observation process to identify the most common activities for these patients’ group. Then, a survey analysis is carried out to identify the daily life activities based on the observation. The survey analysis is accomplished using a U-test (Mann-Whitney). According to the analysis, it has been found that these people have fourteen common activities. However, three of these activities such as sleeping, walking (standing) and sitting cover about 72% of overall activities. Therefore, this study focuses on the recognition of these three common activities to demonstrate the effectiveness of the research. The activity recognition is carried out using a common image processing technique, called Phase-Correlation and Log-Polar (PCLP) transformation. According to results, the techniques predicted human activities of about 43.7%. However, this ratio is low to utilise for further analysis. Therefore, an Artificial Neural Network (ANN)- based PCLP model is developed to increase the accuracy of activity recognition. The enhanced PCLP transformation method can predict nearly 80% of the evaluated activities. Moreover, this study also presents a decision support system for Alzheimer’s people, which will provide these people with a safe environment. The decision support system utilises an extended sensory-based system, including a vision sensor, vital signs sensor and environmental sensor with expert rules. The proposed system was implemented on an older people patient with 87.2% accuracy.
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Marian, Laurentiu. "The tuned mass damper inerter for passive vibration control and energy harvesting in dynamically excited structural systems." Thesis, City University London, 2016. http://openaccess.city.ac.uk/14884/.
Повний текст джерелаАнотація:
A novel passive vibration control configuration, namely the Tuned-Mass-Damper-Inerter (TMDI) is proposed in this work. The TMDI combines the “inerter”, a mechanical two-terminal flywheel device developing resisting forces proportional to the relative acceleration of its terminals, with the well-known and widely used in various passive vibration control applications Tuned-Mass-damper (TMD). Introduced as a generalization of the TMD, the TMDI takes advantage of the “mass amplification effect” of the inerter to achieve enhanced performance compared to the classical TMD. For linear harmonically excited primary systems, analytical closed-form expressions are derived for optimal TMDI design/tuning parameters using the well-established and widely applied for the case of the classical TMD semi-empirical fixed-point theory. It is shown that for the same attached mass the TMDI system is more effective than the classical TMD to suppress vibrations close to the natural frequency of the uncontrolled primary system, while it is more robust to de-tuning effects. Moreover, it is analytically shown that optimally designed TMDI outperforms the classical TMD in minimizing the displacement variance of undamped linear single-degree-of-freedom (SDOF) white-noise excited primary systems. For this particular case, optimal TMDI parameters are derived in closed-form as functions of the additional oscillating mass and the inerter constant. Furthermore, pertinent numerical data are furnished, derived by means of a numerical optimization procedure, for classically damped mechanical cascaded chain-like primary systems base excited by stationary colored noise. This exemplifies the effectiveness of the TMDI over the classical TMD to suppress the fundamental mode of vibration for linear MDOF structures. It is concluded that the incorporation of the inerter in the proposed TMDI configuration can either replace part of the TMD vibrating mass to achieve lightweight passive vibration control solutions, or improve the performance of the classical TMD for a given TMD mass. The TMDI is further applied for passive vibration control of seismically excited building structures. An input non-stationary stochastic process compatible with the elastic design spectrum of the European aseismic code provisions (EC8) is assumed. The effectiveness of the proposed TMDI configuration over the classical TMD is assessed by performing response history analyses for an ensemble of EC8 spectrum compatible field recorded strong ground motions. The optimally tuned TMDI solution achieves considerable reduction of the peak average top floor displacement and peak average top floor accelerations of the considered primary structures compared to the one achieved by the optimally designed classical TMD, assuming the same additional mass in both cases. Furthermore, the TMDI configuration achieves significant reduction in the maximum displacement of the additional oscillating mass. In this study, the primary structures are assumed to behave linearly in alignment with current trends in performance based requirements for minimally damaged structures protected by passive control devices. Furthermore, optimally designed TMDI is applied for vibration suppression and energy harvesting via an electromagnetic device which transforms the mechanical kinetic energy into electrical energy. Unlike the case of traditional energy harvesting enabled TMD systems, the amount of available energy to be harvested by the herein proposed TMDI-based harvester is leveraged by changing the intensity of the mass amplification effect of the inerter, through mechanical gearing, without changing the weight of the TMDI system. Therefore, the inclusion of the inerter adds a “degree of freedom” or a design parameter to the classical TMD-based harvesters allowing to control the trade-off between vibration suppression and energy harvesting in a more flexible manner. Overall, the herein reported numerical data and analytical work provide evidence that the TMDI offers a novel promising solution for passive vibration control and energy harvesting. Most importantly, it opens several new research paths involving numerical/parametric work, as well as, prototyping, experimental testing and field deployment.
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Billstein, Hedda, and Sofie Näslund. "Att ta fram kundnyttor med användningen av ett digitalt verksamhetssystem : En fallstudie av CANEA." Thesis, Uppsala universitet, Institutionen för samhällsbyggnad och industriell teknik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-444955.
Повний текст джерелаАнотація:
Informationsteknik (IT) har i samband med ett växande behov att transformera verksamheter till digitala fått en större betydelse för beslutsfattande i företag, då utvecklings- och investeringsinitiativ i allt större utsträckning inkluderar specifika IT element. Likafullt kvarstår utmaningar med att motivera nyttor av en investering i digitala verksamhetssystem. Utmaningarna indikerar ett behov av att tydliggöra nyttor med användningen av ett digitalt verksamhetssystem. Syftet med studien var att utforska nyttor och relevanta nyckeltal relaterade till användningen av ett företags digitala verksamhetssystem. Fortsatt var syftet att göra en ansats i att ta fram innehåll till en generell nyttokalkyl för användning av ett integrerat verksamhetssystem, vilken kan åskådliggöra faktiska nyttor och mätbara effekter samt användas vid försäljning av produkten. En kvalitativ fallstudie genomfördes på CANEA, där fem medarbetare på olika hierarkiska nivåer intervjuades och forskning inom ämnesområdet insamlades. Det har påvisats att investeringar i digitala verksamhetssystem genererar både kvantitativa- och kvalitativa nyttor. Likaså har det påvisats att forskningen antyder att det inledningsvis kan vara fördelaktigt att inkludera finansiella nyttor i en nyttokalkyl för investeringar i digitala verksamhetssystem. Fortsatt har det indikerats att kalkylen behöver inkludera både kvantitativa-, kvalitativa- och finansiella nyckeltal. Givet till kalkylens utformning och design har studiens resultat implicerat att val av output för respektive nyckeltal bör anpassas till organisationen och systemet i fråga.In connection with a growing need to transform businesses into digital, information technology (IT) has become increasingly important for decision-making in companies, as development and investment initiatives increasingly include specific IT elements. Nevertheless, challenges remain in motivating the benefits of investing in digital business systems. The challenges indicate a need to clarify the benefits of using a digital business system. The purpose of the study was to explore benefits and relevant key figures related to the use of a company's digital business system. The aim of the study was furthermore to make an effort to produce a content proposal for a general benefit calculation for the use of an integrated business system, which can illustrate actual benefits and measurable effects andbe used in the sale of the product. A qualitative case study was conducted at CANEA, where five employees at different hierarchical levels were interviewed and research in the subject area was collected. It has been shown that investments in digital business systems generate both quantitative and qualitative benefits. Similarly, it has been shown that research suggests that it may initially be beneficial to include financial benefits in a benefit calculation for investments in digital business systems. The result has continued to indicate that the calculation needs to include both quantitative, qualitative and financial key figures. Given the design and design of the calculation, the results of the study have indicated that the choice of output for each key figure should be adapted to the organization and system in question.
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Azolibe, Ifeanyi. "Architecture of a cyber-physical system for aircraft fuel control systems tests." Thesis, University of Glasgow, 2016. http://theses.gla.ac.uk/8503/.
Повний текст джерелаАнотація:
The aircraft fuel control system makes sure an engine has the precise amount of fuel required to generate power and thrust for every stage of flight. It therefore plays a role in determining the economics of flight. In order to maintain the economic equilibrium of performance and flight safety, it undergoes a Maintenance Repair or Overhaul (MRO) service after several hours of operation. A critical aspect of the MRO service is the test performed to validate the airworthiness of a fuel control system before it returns to service. The test of aircraft fuel control systems is human-centric by design. The operator uses a network of test systems to generate in-flight conditions similar to what the Unit-Under-Test (UUT) experiences on-board an aircraft engine, then performs tests to validate and verify its airworthiness. Thereafter, test results are recorded for regulatory compliance reasons after each test is performed successfully. An analysis of the test specification for the UUT involved in this study revealed 90% of an operator’s touch-time is automatable. The functions of control, data processing, data entry and supervision must be achieved automatically if they are to be performed autonomously by a cyber-physical test system. But the automation of these activities at the micro level does not guarantee their autonomous execution at a macro level by such a cyber-physical system composed of the network of test systems. Therefore, knowledge of a multidisciplinary array of fundamental concepts and how they can be fused to execute the test of aircraft fuel control systems autonomously, have been developed as presented in this thesis. For the function of process control, the response of the processes used to set test conditions is ~ 50Hz, five times the rate of process responses reported in typical process industries where automation of process control have been achieved. As a result of this fundamental knowledge, the design of the architectures for the functions of control and data processing is an asynchronous one. Noting that none of the data is fed back through a network like the case of Networked Control Systems or Supervisory Control and Data Acquisition Systems. The realization of the control functions for each process used to set test conditions is based on control laws synthesized through modelling of their respective actuation mechanisms. Of the three models developed, a 2nd order model has been identified as been representative of the dynamic and steady-state characteristics of each actuation mechanism. A typical actuation mechanism contains a high number of masses and springs whose physical modelling resulted in a model of 12th order. This model is highly unrepresentative of the transient and steady-state response observed in the process due to difficulty in estimating the internal parameters of respective actuators. A linear model synthesized from the calibration data of each actuation mechanism has also been investigated and found to be too ideal. Its response is unrepresentative of the dynamic characteristics of the actuation mechanisms. The processes used to generate test conditions have been set simultaneously using a network of PID controllers. The controllers’ gains are an order of ten less than what they were for the sequential set up of test conditions due the fact that there are interactions between the processes inside a UUT. Fundamentally however, this Thesis demonstrates an asynchronous architecture for the control function, which enables a pseudo steady-state execution of tests. In-practice, this has the potential to reduce the time it takes to perform a test by one-third. The function of supervision has been developed in the form of a Fault Detection Isolation and Recovery capability within the cyber-physical test system. The architecture for this function is designed based on minimalizing the constraint of the period of recoverability (PoR), where the deviations from normal operation need to be detected, the outcomes they could result to—diagnosed and recovery strategies executed to prevent test systems or the UUT deviate from normal operation, using measurements acquired in a time < PoR. Oscillations and offsets have been identified as the major causes of deviations in subsystems during the test of the aircraft fuel control system in this study. In order to diagnose a deviation, a fuzzy inference engine has been developed over a Fault Tree Analysis approach because it makes the automation of domain knowledge needed to realize the supervision function effective. Nevertheless, the contributions of this thesis are the knowledge gaps it uncovers and the formalized approaches it proposes in the form of architectures to plug these gaps. It provides a direction on how to actualize not only the concept of automation, but the realization of a cyber-physical system to test an aircraft fuel control systems. It is the architecture of a singular system capable of executing the functions performed by an operator autonomously, and surpassing what can be achieved in the case of simultaneous process control, automated detection and isolation of a critical deviations under the period of recoverability, that is the fundamental contribution of this thesis. So that in the not so distant future the test of aircraft fuel control systems can be performed by machines.
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Bates, Ronald Anthony. "The robust design of complex systems." Thesis, City, University of London, 1995. http://openaccess.city.ac.uk/17421/.
Повний текст джерелаАнотація:
Robust Engineering Design has evolved as an important methodology for the integration of quality with the process of design. The methodology encompasses the disciplines of experimental design, model building and optimization. First an experiment is conducted on a system (or a simulation of the system), second a model is built to emulate the system and finally the emulation model is used to optimize the system design. Applying these methods to large problems can be difficult and time-consuming because of the complexity of most design problems. It is the goal of this thesis to introduce methods which reduce problem complexity and so make the application of Robust Engineering Design (RED) methodology easier for large design problems. By drawing from methods used in systems theory and circuit optimization several techniques are presented with the aim of reducing the complexity of performing experiments for Robust Engineering Design. A common framework for experimentation is created by combining a commercial circuit simulator with established methods for experimental design and model building. This provides the basis for experimentation in subsequent chapters. A method of design optimization with respect to quality is presented to complete the model-based Robust Engineering Design cycle. Three approaches to reducing problem complexity are adopted. First a method of system decomposition is applied directly to an electronic circuit to reduce the size of experiment required for RED. Second a method of modelling system response functions is described which integrates the action of the circuit simulator with the model building process. Third information about system topology is used in the design of experiments to enhance the model-building process. Conclusions are drawn about the effectiveness of the approaches described with respect to the impact on problem complexity.
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Lulec, Andac. "Solution Of Sparse Systems On Gpu Architecture." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613355/index.pdf.
Повний текст джерелаАнотація:
The solution of the linear system of equations is one of the core aspects of Finite Element Analysis (FEA) software. Since large amount of arithmetic operations are required for the solution of the system obtained by FEA, the influence of the solution of linear equations on the performance of the software is very significant.
In recent years, the increasing demand for performance in the game industry caused significant improvements on the performances of Graphical Processing Units (GPU). With their massive floating point operations capability, they became attractive sources of performance for the general purpose programmers. Because of this reason, GPUs are chosen as the target hardware to develop an efficient parallel direct solver for the solution of the linear equations obtained from FEA.
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Ben, Hamdin Hanya Abdusalam Mohamed. "Boundary element and transfer operator methods for multi-component wave systems." Thesis, University of Nottingham, 2012. http://eprints.nottingham.ac.uk/12446/.
Повний текст джерелаАнотація:
In this thesis, exact and semiclassical approaches are derived for predicting wave energy distributions in coupled cavities with variable material properties. These approaches are attractive because they can be extended to more complex built-up systems. For the exact treatment, we describe a multi-component boundary element method. We point out that depending on the boundary conditions and the number of interfaces between sub-components, it may be advantageous to use a normal derivative method to set up the integral kernels. We describe how the arising hypersingular integral kernels can be reduced to weakly singular integral and then using the piecewise constant collocation method. The normal derivative method can be used to minimise the number of weakly-singular integrals thus leading to BEM formulations which are easier to handle. The second component of this work concerns a novel approach for finding an exact formulation of the transfer operator. This approach is demonstrated successfully for a disc with boundary conditions changing discontinuously across the boundary. Such an operator captures the diffraction effects related to the change of boundary conditions. So it incorporates boundary effects such as diffraction and surface waves. A comparison between the exact results from the BEM against the exact transfer operator shows good agreement between both categories. Such an exact operator converges to the semiclassical Bogomolny transfer operator in the semiclassical limit. Having seen how the exact transfer operator behaves for a unit disc, a similar approach is adapted for the coupled cavity configuration resulting in the semiclassical transfer operator. Our formulation for the transfer operator is applicable not only for the quantization of a system, but also to recover the Green function.