The analysis of non steady state physiological and pathological processes concerns the abstraction, extraction, formalisation and analysis of information from physiological systems that is obscured, hidden or unable to be assessed using traditional methods. Time Series Analysis (TSA) techniques were developed and built into a software program, Easy TSA, with the aim of examining the oscillations of hormonal concentrations in respect to their temporal aspects – periodicity, phase, pulsatility. The Easy TSA program was validated using constructed data sets and used in a clinical study to examine the relationship between insulin and obesity in people without diabetes. In this study fifty-six non-diabetic subjects (28M, 28F) were examined using data from a number of protocols. Fourier Transform and Autocorrelation techniques determined that there was a critical effect of the level of BMI on the frequency, amplitude and regularity of insulin oscillations. Second, information systems formed the background to the development of an algorithm to examine glycaemic variability and a new methodology termed the Glycaemic Risk in Diabetes Equation (GRADE) was developed. The aim was to report an integrated glycaemic risk score from glucose profiles that would complement summary measures of glycaemia, such as the HbA1c. GRADE was applied retrospectively to blood glucose data sets to determine if it was clinically relevant. Subjects with type 1 and type 2 diabetes had higher GRADE scores than the non-diabetic population and the contribution of hypo- and hyperglycaemic episodes to risk was demonstrated. A prospective study was then designed with the aim to apply GRADE in a clinical context and to measure the statistical reproducibility of using GRADE. Fifty-three (Male 26, Female 27) subjects measured their blood glucose 4 times daily for twenty-one days. The results were that lower HbA1c’s correlated with an increased risk of hypoglycaemia and higher HbA1c’s correlated with an increased risk of hyperglycaemia. Some subjects had HbA1c of 7.0 but had median GRADE values ranging from 2.2 to 10.5. The GRADE score summarized diverse glycaemic profiles into a single assessment of risk. Well-controlled glucose profiles yielded GRADE scores <= 5 and higher GRADE scores represented increased clinical risk from hypo or hyperglycaemia. Third, an information system was developed to analyse data-rich multi-variable retinal images using the concept of assessment of change rather than specific lesion recognition. A fully Automated Retinal Image Differencing (ARID) computer system was developed to highlight change between retinal images over time. ARID was validated using a study and then a retrospective study sought to determine if the use of the ARID software was an aid to the retinal screener. One hundred and sixty images (80 image pairs) were obtained from Gloucestershire Diabetic Eye Screening Programme. Images pairs were graded manually and categorised according to how each type of lesion had progressed, regressed, or not changed between image A and image B. After a 30 day washout period image pairs were graded using ARID and the results compared. The comparison of manual grading to grading using ARID (Table 4.3) demonstrated an increased sensitivity and specificity. The mean sensitivity of ARID (87.9%) was increased significantly in comparison to manually grading sensitivity (84.1%) (p<0.05). The specificity of the automated analysis (87.5%) increased significantly from the specificity (56.3%) achieved by manually grading (p<0.05). The conclusion was that automatic display of an ARID differenced image where sequential photographs are available would allow rapid assessment and appropriate triage. Forth, non-linear dynamic systems analysis methods were utilised to build a system to assess the extent of chaos characteristics within the insulin-glucose feedback domain. Biological systems exist that are deterministic yet are neither predictable nor repeatable. Instead they exhibit chaos, where a small change in the initial conditions produces a wholly different outcome. The glucose regulatory system is a dynamic system that maintains glucose homeostasis through the feedback mechanism of glucose, insulin, and contributory hormones and was ideally suited to chaos analysis. To investigate this system a new algorithm was created to assess the Normalised Area of Attraction (NAA). The NAA was calculated by defining an oval using the 95% CI of glucose & Insulin (the limit cycle) on a phasic plot. Thirty non-diabetic subjects and four subjects with type 2 diabetes were analysed. The NAA indicated a smaller range for glucose and insulin excursions with the non-diabetics subjects (p<0.05). The conclusion was that the evaluation of glucose metabolism in terms of homeostatic integrity and not in term of cut-off values may enable a more realistic approach to the effective treatment and prevention of diabetes and its complications.

Modelling and simulation are essential ingredients of the analysis and design process in power electronics. It helps a design engineer gain an increased understanding of circuit operation. Accordingly, for a set of specifications given, the designer will choose a particular topology, select component types and values, estimate circuit performance etc. Typically hierarchical modelling, analysis and simulation rather than full detailed simulation of the system provides a crucial insight and understanding. The combination of these insights with hardware prototyping and experiments constitutes a powerful and effective approach to design. Obtaining the mathematical model of the power electronic systems is a major task before any analysis or synthesis or simulation can be performed. There are circuit oriented simulators which uses inbuilt mathematical models for components. Simulation with equation solver needs mathematical models for simulation which are trimmed according to user requirement. There are various methods in the literature to obtain these mathematical models. However, the issues of multi-domain system modelling and causality of the energy variables are not sufficiently addressed. Further, specifically to power converter systems, the issue of switching power models with fixed causality is not addressed. Therefore, our research focuses on obtaining solutions to the above using relatively untouched bond graph method to obtain models for power electronic systems. The power electronic system chosen for the present work is Switched Mode Power Converters (SMPC’s) and in particular PWM DC-DC converters. Bond graph is a labelled and directed graphical representation of physical systems. The basis of bond graph modelling is energy/power flow in a system. As energy or power flow is the underlying principle for bond graph modelling, there is seamless integration across multiple domains. As a consequence, different domains (such as electrical, mechanical, thermal, fluid, magnetic etc.) can be represented in a unified way. The power or the energy flow is represented by a half arrow, which is called the power bond or the energy bond. The causality for each bond is a significant issue that is inherently addressed in bond graph modelling. As every bond involves two power variables, the decision of setting the cause variable and the effect variable is by natural laws. This has a significant bearing in the resulting state equations of the system. Proper assignment of power direction resolves the sign-placing problem when connecting sub-model structures. The causality will dictate whether a specific power variable is a cause or the effect. Using causal bars on either ends of the power bond, graphically indicate the causality for every bond. Once the causality gets assigned, bond graph displays the structure of state space equations explicitly. The first problem we have encountered in modelling power electronic systems with bond graph is power switching. The essential part of any switched power electronic system is a switch. Switching in the power electronic circuits causes change in the structure of the system. This results in change in dynamic equations of the circuit according to position of the switch. We have proposed the switched power junctions (SPJ) to represent switching phenomena in power electronic systems. The switched power junctions are a generalization of the already existing 0-junction and 1-junction concepts of the bond graph element set. The SPJ’s models ideal switching. These elements maintain causality invariance for the whole system for any operational mode of the system. This means that the state vector of the resulting state equation of the system does not change for any operating mode. As SPJs models ideal power switching, the problem of stiff systems and associated numerical stability problems while simulating the system is eliminated. Further, it maintains one to one correspondence with the physical system displaying all the feasible modes of operation at the same time on the same graph. Using these elements, the switched mode power converters (SMPC's) are modelled in bond graph. Bond graph of the converter is the large signal model of the converter. A graphical procedure is proposed that gives the averaged large signal, steady state and small signal ac models. The procedure is suitable for the converters operating in both Continuous Conduction Mode (CCM) and in Discontinuous Conduction Mode (DCM). For modelling in DCM, the concept of virtual switch is used to model the converter using bond graph. Using the proposed method, converters of any complexity can be modelled incorporating all the advantages of bond graph modelling. Magnetic components are essential part of the power electronic systems. Most common parts are the inductor, transformer and coupled inductors which contain both the electric and magnetic domains. Gyrator-Permeance approach is used to model the magnetic components. Gyrator acts as an interface between electric and magnetic domain and capacitor model the permeance of the magnetic circuits. Components like inductor, tapped inductor, transformer, and tapped transformer are modelled. Interleaved converters with coupled inductor, zero ripple phenomena in coupled inductor converters as well as integrated magnetic Cuk converter are also modelled. Modelling of integrated magnetic converters like integrated magnetic forward converter, integrated magnetic boost converter are also explored. To carry out all the simulations of proposed bond graph models, bond graph toolbox is developed using MATLAB/SIMULINK. The MATLAB/SIMULINK is chosen since it is general simulation platform widely available. Therefore all the analysis and simulation can be carried out using facilities available in MATLAB/SIMULINK. Symbolic equation extraction toolbox is also developed which extracts state equations from bond graph model in SIMULINK in symbolic form.

Reliability modelling of RAID storage systems with its various components such as RAID controllers, enclosures, expanders, interconnects and disks is important from a storage system designer's point of view. A model that can express all the failure characteristics of the whole RAID storage system can be used to evaluate design choices, perform cost reliability trade-offs and conduct sensitivity analyses. We present a reliability model for RAID storage systems where we try to model all the components as accurately as possible. We use several state-space reduction techniques, such as aggregating all in-series components and hierarchical decomposition, to reduce the size of our model. To automate computation of reliability, we use the PRISM model checker as a CTMC solver where appropriate. Initially, we assume a simple 3-state disk reliability model with independent disk failures. Later, we assume a Weibull model for the disks; we also consider a correlated disk failure model to check correspondence with the field data available. For all other components in the system, we assume exponential failure distribution. To use the CTMC solver, we approximate the Weibull distribution for a disk using sum of exponentials and we first confirm that this model gives results that are in reasonably good agreement with those from the sequential Monte Carlo simulation methods for RAID disk subsystems. Next, our model for whole RAID storage systems (that includes, for example, disks, expanders, enclosures) uses Weibull distributions and, where appropriate, correlated failure modes for disks, and exponential distributions with independent failure modes for all other components. Since the CTMC solver cannot handle the size of the resulting models, we solve such models using hierarchical decomposition technique. We are able to model fairly large configurations with upto 600 disks using this model. We can use such reasonably complete models to conduct several "what-if" analyses for many RAID storage systems of interest. Our results show that, depending on the configuration, spanning a RAID group across enclosures may increase or decrease reliability. Another key finding from our model results is that redundancy mechanisms such as multipathing is beneficial only if a single failure of some other component does not cause data inaccessibility of a whole RAID group.

Water distribution systems convey drinking water from treatment plant and make available to consumers’ taps. It consists of essential components like pipes, valves, pumps, tanks and reservoirs etc. The main concern in the working of a water distribution system is to assure customer demands under a choice of quantity and quality throughout the complete life span for the probable loading situations. However, in some cases, the existing infrastructure may not be adequate to meet the customer’s requirements. In such cases, system modeling plays an important role in proper management of water supply systems. In present scenario, modeling plays a significant task in appropriate execution of water distribution system. From the angle of taking management decisions valve throttling control and pumps speed control are very important. These operational problems can be addressed by manual control or by automatic control. The problem is the use of manual controls that slow down the effectiveness of the system. It reduces the efficiency of operation of valve or pump. To improve the efficiency of such water distribution systems, an automatic control based technology has been developed that links the operation of the variable speed pump control or valve throttling control. By employing an automatic control, the pump can adjust its speed at all times to meet the actual flow requirements of each load served. In case of real system design Simulink is the most widely used tool. Commercial software package Matlab/Simulink used for creation of WDS model. The goal was to produce a model that could numerically analyze the dynamic performance of a water distribution system. A Comparison of single platform methodology (Simulink based control) and double platform methodology (Matlab and EPANET based control) has been done. Nonlinear Dynamic Inversion (DI) Control system model is developed for WDS model in Matlab/Simulink environment. Controller gain parameters are the very important value in control prospective. If the controller gain parameters are chosen incorrectly, the controlled process input can be unstable, i.e. its output diverges, with or without oscillation Tuning is the adjustment of control parameters (gains) to the optimum values for the desired control response. There are several methods for tuning controller like manual tuning (Trial and error procedure), Ziegler-Nichols method, Output Constraint Tuning (OCT) etc. Establishment of a pump operational policy by which all the reservoirs can be fed simultaneously to meet their requirements without creating undue transients. Tune the gain of DI controllers by different tuning methods and evaluate the best tuning method on the basis of controller performance. Development of meaningful additional objective is search of lower bound pump speed on the basis of control time or settling time. To bring the pump speeds in feasible range, application of constraint in pumps speed is introduced. The magnitude of constraints can be found using Monte Carlo methods. Monte Carlo methods are frequently used in simulating physical and mathematical systems. This method may be the most commonly applied statistical method in engineering and science disciplines. Another benefit is providing increased confidence that a model is robust using Monte Carlo testing. Model development for generalized control system for water distribution network provides the simplification needed for the simulation of large systems. Model development is based on the study of symmetric and non symmetric small, irregular networks, as well as large, regular and open bifurcating water distribution system. The problem considered in this section is that of flow dynamics in simple to complex, regular network which bifurcates in the form of a branching tree. In addition the control application of the flow network is investigated using valves as the manipulated variables to control branch flow rates. Communication between the network hydraulics coming from EPANET and control algorithm develop on Matlab (Programming Language) can be generalized with the help of development of general purpose control algorithm model.

Gossip is a generic protocol which was designed for spreading information between nodes in large distributed decentralised systems. This protocol can be also used for many different applications including data aggregation, topology construction, etc. This work presents and describes a framework designed for facilitating modelling and simulation of Gossip-based systems.

Der vorliegende Band der wissenschaftlichen Schriftenreihe Eingebettete Selbstorganisierende Systeme widmet sich dem Entwurf von verteilten Eingebetteten Systemen. Einsatzgebiete solcher Systeme sind unter anderem Missions- und Steuerungssysteme von Flugzeugen (Aerospace-Anwendungen) und , mit zunehmender Vernetzung, der Automotive Bereich. Hier gilt es höchste Sicherheitsstandards einzuhalten und maximale Verfügbarkeit zu garantieren. In dieser Arbeit wird diese Problematik frühzeitig im Entwurfsprozess, in der Spezifikationsphase, aufgegriffen. Es werden Implementierungsvarianten wie Hardware und Software sowie Systemkomponenten wie Berechungskomponenten und Kommunikationskomponenten unterschieden. Für die übergreifende Spezifikation wird auf Grundlage des π-Kalküls ein formales Framework, das eine einheitliche Modellierung von Teilsystemen in den unterschiedlichen Entwurfsphasen unterstützt, entwickelt. Besonderer Schwerpunkt der Untersuchungen von Herrn Förster liegt auf Erweiterungen von Systemspezifikationen. So wird es möglich, Teilkomponenten zu verändern oder zu substituieren und die Gesamtspezifikation auf Korrektheit und Konsistenz automatisiert zu überprüfen. / This volume of the scientific series Eingebettete, selbstorganisierende Systeme (Embedded Self-Organized Systems) gives an outline of the design of distributed embedded systems. Fields of application for such systems are, amongst others, mission systems and control systems of airplanes (aeronautic applications) and - with increasing level of integration - also the automotive area. In this area it is essential to meet highest safety standards and to ensure the maximum of availability. Mr Förster addresses these problems in an early state of the design process, namely the specification. Implementation versions like hardware and software are differentiated as well as system components like computation components and communication components. For a general specification Mr Förster develops a formal framework based on the pi-calculus, which supports a standardised modelling of modules in different design steps. The main focus of Mr Förster's research is the extension of system specifications. Therefore it will be possible to modify or substitute modules and to check automatically the correctness and consistency of the total specification. Mr Förster can prove the correctness of his approach and demonstrates impressively the complexity by clearly defined extension relations and formally verifiable embedding in the pi-calculus formalism. A detailed example shows the practical relevance of this research. I am glad that Mr Förster publishes his important research in this scientific series. So I hope you will enjoy reading it and benefit from it.

New Zealand Agricultural Engineering Institute / Also published as: Agricultural Engineering Thesis no. 4 / For large areas of New Zealand that suffer from agricultural drought, the only practicable way of providing irrigation is through the use of water harvesting schemes that divert winter flood water in nearby streams into off-stream storages for irrigation use in the summer. A community water harvesting scheme is presently under construction in the Glenmark area of North Canterbury which was designed using traditional methods. The objectives of this thesis were to assess the limitations of traditional design methods for water harvesting schemes using the Glenmark Scheme as a case study and to develop an improved method based on a systems modelling approach. A daily simulation model was developed that incorporated in a realistic way the engineering, hydrologic, agronomic and economic features of importance to the design of water harvesting schemes in New Zealand. The model was used to study the adequacy of the traditional methods used for the design of the Glenmark Scheme; to arrive at alternative design solutions that achieved higher levels of engineering, agronomic and economic efficiency; and to develop a better understanding of the nature of complex water harvesting systems. It was demonstrated that compounding conservatism inherent in traditional design methods resulted in scheme overdesign and that the ability of the systems model to capture the essential dynamics of the system allowed higher levels of design performance to be achieved. The experience gained in the use of the systems model led to the development of a formalised design procedure for water harvesting schemes that represents an advance on methods hitherto available.

Heutzutage gewinnt die Simulation von Gebäuden und Anlagen zunehmend an Bedeutung, um die Betriebsweise der Anlagen zu diagnostizieren bzw. zu bewerten und den Energiebedarf vorherzusagen. Dabei hängt die erzielte Genauigkeit von dem Kompliziertheitsgrad des angewendeten Simulationsprogramms ab. Deshalb ist Modellbildung und -validierung ein sehr wichtiger Bestandteil eines Softwareentwicklungsprozesses, um die Zuverlässigkeit zu sichern. Am Institut für Thermodynamik und Technische Gebäudeausrüstung liegen zahlreiche Simulationsmodelle vor. Im Rahmen dieser vorliegenden Arbeit wurden weitere benötigte Modelle (hygrisches Verhalten der Wände (vereinfachtes Verfahren), Rippenrohrwärmeüberträger, Wärmeregenerator et al.) entwickelt und in das Programm TRNSYS eingefügt sowie die vorhandenen Modelle an ihre Genauigkeit angepasst. Insbesondere sind dies die Modelle für Splitsysteme bei stetiger und nichtstetiger Regelung mit der detaillierten Betrachtung des Anlagenverhaltens sowohl beim Voll- als auch beim Teillastbetrieb. Damit ist es erstmals gelungen, das gesamte Anlagensystem der Splittechnik ausführlich zu beschreiben. Um die analytische Validierung durchführen zu können, wurden die analytischen Modelle für eine Splitanlage bei stetiger und nichtstetiger Regelung unter den vordefinierten Randbedingungen entwickelt. Zur analytischen Validierung finden auch die vorhandenen Simulationsmodelle Anwendung, so dass sich die meisten Komponenten und das Simulationsprogramm TRNSYS verifizieren ließen. Diese Validierung erfolgte im Rahmen des IEA-SHC/HVAC BESTEST TASK 22. Da an diesem TASK verschiedene Forschungsinstitutionen mit jeweils unterschiedlichen Simulationsprogrammen teilnahmen, ergab sich die beste Möglichkeit, vergleichende Tests durchzuführen. Wenn dabei ein Programm signifikante Unterschiede zu den anderen liefert, liegt dies nicht immer an Programmfehlern. Aber kollektive Erfahrungen aus diesem TASK zeigen, dass bei Abweichungen meistens Fehler bzw. fragwürdige Algorithmen gefunden wurden. Nachdem das Simulationsprogramm TRNSYS validiert war, erfolgte die Erstellung eines Konzeptes zur Fehlererkennung und Diagnose der Regelstrategien von RLTA. Das Verfahren erlaubt sowohl die Beseitigung der möglichen Fehler in der Planungsphase beim Entwurf der Regelstrategien als auch den Test der vorhandenen Regelstrategien. Dies erhöht die Zuverlässigkeit und damit die Sicherheit beim Anlagenbetrieb. Schließlich dient das Verfahren als Werkzeug zur Optimierung der Betriebsweise von RLTA. Das Regelverhalten wurde anhand typischer Fälle vorgestellt und diskutiert. Mit Hilfe des Verfahrens zur Fehlererkennung und Diagnose der Betriebsweise von RLTA ließen sich vorhandene Regelstrategien testen und verbessern.