Water supply system planning is concerned about the design of water supply infrastructure for distributing water from sources to users. Population growth, economic development and diminishing freshwater supplies are posing growing challenges for water supply system planning in many urban areas. Besides the need to exploit alternative water sources to the conventional surface and groundwater supplies, such as reclaimed water, a systematic point of view has to be taken for the efficient management of all potential water resources, so that issues of water supply, storage, treatment and reuse are not considered separately, but rather in the context of their interactions. The focus of this dissertation is to develop mathematical models and optimization algorithms for water supply system planning, where the interaction of different system components is explicitly considered. A deterministic nonlinear programming model is proposed at first to decide pipe and pump sizes in a regional water supply system for satisfying given potable and non-potable user demands over a certain planning horizon. A branch-and-bound algorithm based on the reformulation-linearization technique is then developed for solving the model to global optimality. To handle uncertainty in the planning process, a stochastic programming (SP) model and a robust optimization (RO) model are successively proposed to deal with random water supply and demand and the risk of facility failure, respectively. Both models attempt to make the decision of building some additional treatment and recharge facilities for recycling wastewater on-the-site. While the objective of the SP model is to minimize the total system design and expected operation cost, the RO model tries to achieve a favorable trade-off between system cost and system robustness, where the system robustness is defined in terms of meeting given user demands against the worst-case failure mode. The Benders decomposition method is then applied for solving both models by exploiting their special structure.

Šiais laikais naujos technologijos sudaro vis didesnę mūsų gyvenimo dalį, bet jų jau greičiausiai neįsivaizduotume savęs. Tačiau ne visi naujų tachnologijų kūriniai tarnauja ilgai, taip pat kaip ne visi jie veikia teisingai. Tam, kad nustatytume, jog įrenginys veikia teisingai raikalinga atlikti testavimą. Mažėjant schemų dydžiams, augant metalo tankiui ir didėjant lustų veikimo greičiui, vėlinimų testavimas tampa būtinybe tam, kad palaikyti kokybę susijusią su schemos veikimo greičių sutrikimais. Vėlinimo gedimų tyrimas atsako į klausimą ar schema veikia teisingai be didelių nuostolių. Šiame darbe aptarsime vėlinimo gedimų atsiradimo priežastis bei galimas juos įtakojančias sąlygas. Taip pat analizuosime vėlinimo gedimų testavimo modelius, metodus, jų privalumus, trūkumus ir galimus trūkumų sprendimus. Tyrimui pilnai atlikti inicijuosime eksperimentą, siekdami išsiaiškinti tiesioginės ir netiesioginės įtakos poveikį vėlinimų gedimų funkciniam testui. / Nowadays new technologies contains the bigger part of our lifes, we couldnt imagine our selves without them. Otherwise, not all creations of new technologies are serving so long, also not all of them are serving right and effectively. When the system size degrees, the metal grows, and the time working on chips grows – the delay fault testing becomes very important part of system creation process. The delay fault test answers to the question does the system works right and without any big loses. The test process has important point in Delay test has been investigated for many years. We can say that test process contains on these steps: setting the purpose of the test, designing the test, controlling the test process, perform the test and analyze test results. Also we will shortly discuss about basic gauge of testing process. The main point of this paper is to analyze the models of delay faults test processes. To see the best and the worst sides of delay faults and represent experimental test to demonstrate the the robust and non-robust test advantagies in delay fault test.

Observers are used in the monitoring and control of dynamical systems to deduce the values of unmeasured states. Designing an observer requires having an accurate model of the plant — if the model parameters are characterized imprecisely, the observer may not provide reliable estimates. An interval observer, which comprises an upper and lower observer, bounds the plant's states from above and below, given the range of values of the imprecisely characterized parameters, i.e., it defines an interval in which the plant's states must lie at any given instant. We propose a linear programming-based method of interval observer design for two cases: 1) only the initial conditions of the plant are uncertain; 2) the dynamical parameters are also uncertain. In the former, we optimize the transient performance of the interval observers, in the sense that the volume enclosed by the interval is minimized. In the latter, we optimize the steady state performance of the interval observers, in the sense that the norm of the width of the interval is minimized at steady state. Interval observers are typically designed to characterize the widest interval that bounds the states. This thesis proposes an interval observer design method that utilizes additional, but still-incomplete information, that enables the designer to identify tighter bounds on the uncertain parameters under certain operating conditions. The number of bounds that can be refined defines a class of systems. The definition of this class is independent of the specific parameters whose bounds are refined. Applying robust optimization techniques, under a cardinality constrained model of uncertainty, we design a single observer for an entire class of systems. These observers guarantee a minimum level of performance with respect to the aforementioned metrics, as we optimize the worst-case performance over a given class of systems. The robust formulation allows the designer to tune the level of uncertainty in the model. If many of the uncertain parameter bounds can be refined, the nominal performance of the observer can be improved, however, if few or none of the parameter bounds can be refined, the nominal performance of the observer can be designed to be more conservative.

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No description available.

In this work VLE data was measured on three different pieces of equipment. Measurements were undertaken in the laboratory of Professor Gmehling in Oldenburg, Germany using two different static cells and in the Thermodynamics Research Unit (TRU), University of Natal, South Africa using a specially designed dynamic still. The three pieces of equipment used are as follows: i.) Static apparatus of Rarey and Gmehling (1993), ii.) Static apparatus of Kolbe and Gmehling (1985) as modified by Fischer and Wilken (2001), and, iii.) Dynamic apparatus ofHarris et al. (2003b). In total 370 data points were measured; fourteen sets of VLE data and eight vapour pressure data sets were measured. The work undertaken in Germany measured the systems hexane (1) + N-methylformarnide (2), benzene (1) + N-methylformamide (2), cWorobenzene (1) + N-methylformarnide (2) and acetonitrile (1) + N-methylformamide (2), at 363.15 K using the equipment of Rarey and Gmehling (1993). The systems CO2 (1) + Napthalene (2) at T = 372.45 K, 403.85 K and 430.65 K and CO2 (1) + Benzoic acid (2) at T= 403.28 K, 432.62 K and 458.37 K were measured on the equipment of Kolbe and GmeWing (1985) (as modified by Fischer and Wilken (2001)). Apart from the CO2 (1) + Napthalene (2) system at T = 372.45 K, all the above-mentioned data are new data. The equipment designed in the TRU was designed to operate between 300 and 700 K and between 1 kPa and 30 MPa. The equipment is of the dynamic recirculating VLE still type (DRVS) and is based on the principles of low-pressure stills. The still is constructed from uniquely machined Stainless-steel components and standard commercial Stainless-steel tubing and valves and is computer controlled to operate either isobarically or isothermally. Vapour pressures were measured on the new equipment for n-heptane, n-decane, n-dodecane, n-hexadecane, l-octadecene, 1-hexadecanol and d,l-menthol at low pressures and for acetone at high pressures. These vapour pressure measurements were used as test systems and ranged from 1.00 kPa to 1 000 kPa and from 308.33 K to 583.90 K. Cyclohexane (1) + ethanol (2) at 40 kPa and n-dodecane (1) + l-octadecene (2) at 26.66 kPa were measured as two isobaric VLE test systems. The VLE data measured for d,l-menthol (1) + l-isomenthol (2) at T= 448.15 K and n-dodecane (1) + l-octadecene (2) at P = 3.0 kPa represent new data measured on the equipment. All the VLE systems were modeled. Two data reduction methods were investigated: i.) the combined (r-rf) method, and, ii.) the direct method (H) method. Several different Gibbs excess models (Wilson, NRTL and UNIQUAC), equations of state (PengRobinson and virial) and mixing rules (Huron-Vidal, Wong-Sandler and Twu-Coon) were used in different combinations to find the best fit for the data. The Maher and Smith (1979) method was used to determine infinite dilution activity coefficients from the very smooth data of the N-methylformamide systems. Excess properties were determined for the CO2 (1) + Napthalene (2) and the CO2 (1) + Benzoic acid (2) systems. Although the equipment of Hams et al. (2003b) was able to measure data at high temperatures and elevated pressures, the precission of the data was not as good as was expected. Measuring the system temperature at elevated temperatures was especially problematic. The problem is attributed to the large mass of Stainless-steel used in the construction of the apparatus. To rectify this problem it is suggested that the equipment be modified to be lighter in weight and only capable of measuring VLE at moderate pressures (less than 3 MPa). / Thesis (Ph.D.)-University of Natal, Durban, 2004.

Large boilers have typically been designed for continuous operation from 60-100% load. With restructuring of electrical supply and in some cases because of local fuel supply constraints, some of these boilers are run for only two shifts per day and this entails warm start ups. A reasonable objective is to bring the plant online as quickly as possible within the equipments constraint and without risk of tripping major plant equipment such as feed pumps and circulation pumps. The project required the development of a model accurate enough to represent the boiler thermal dynamics. The thesis compares the simulated model results with the measured results from a Benson boiler from Majuba power station. The developed model is then used to investigate gain scheduled and robust control approaches to the design of the control system for collector vessel level and evaporator flow rate. Once the control problems are clearly understood, an investigation into fast start up is undertaken. The subject of the start up of Benson boilers has limited open literature. This is because flexibility in plant operation has only recently become an important issues with electricity utilities. The limited research in the field of robust control of start up of Benson boiler has made the extensive work done by both Eitelberg and Boje [2001,2002,2004] state of the art. Most of the research done in this thesis follows from the work done by Eitelberg and Boje. / Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2005.

This thesis aims to verify the use of quantitative feedback theory (QFT) as a viable tool for designing power system stabilisers (PSS) for a single machine infinite bus system. The result of the QFT design is verified by simulation of the linear and nonlinear models representing the power system, and also by experimental procedures carried out in a laboratory. QFT falls into the classical control category, and is a frequency domain design method. It is an alternative to other design methods such as root locus and Hoo . The QFT design procedure can be extended to a multimachine system and QFT designs of MIMO systems has gained impetus. From theory, through simulation, and to the final laboratory testing on a single machine, infinite bus system, it will be shown that the application of QFT to robust PSS design does indeed work. QFT is a design method that allows the designer to choose a set of realistic operating points and to produce a design that include those points. Other methods allow the designer to produce a design for single operating point, and one has no idea how the design performs at the other operating points. / Thesis (M.Sc.Eng.)-University of Natal, Durban, 2003.

This thesis investigates the design of damping controllers to alleviate the problem of low frequency electro-mechanical oscillations in power systems. The operating point and network parameters of power systems are continually changing, resulting in changes in system dynamics. The conventional controller design methodology has therefore come under increasing scrutiny for its lack of considerations for robustness. The thesis first outlines the conventional design of a power system stabilizer (PSS) and then applies two robust techniques (Hoo and Quantitative Feedback Theory, QFT) to the design problem. The single machine infinite bus (SMIB) model is used to illustrate the procedure for all three design techniques. The final design is undertaken to illustrate the more important problem of robust multi-machine PSS design using QFT. The design requires linearised models of the multi-machine system. A brief discussion is given on how these can be obtained. An introduction to decentralized control design in QFT is included to support the multi-machine design. Chapter three proceeds through the design steps required to generate a conventional PSS. The technique is shown to be simple for a given set of operating conditions. The controller is shown to be adequately robust over the given set of operating conditions albeit not by design. Chapter four introduces a design technique that directly addresses robustness issues during the controller design. For a restricted range of operating conditions the designed controller demonstrates the desired robustness and performance characteristics. The inherent difficulties with Hoo in PSS design become more apparent as the operating range is extended. Chapter five introduces the second robust controller design technique. QFT is shown to be more adept at dealing with increased operating ranges and changing specifications in the single-machine infinite-bus case. The controller is easy to generate and performs well over the entire range of operating conditions. QFT is also applied to the controller design for a four-machine study system. The design is a marginally more complex than in the single machine case but is still easily accomplished. This thesis confirms previous attempts at solving the design problem using the methods outlined above. The performance of all controllers is assessed for small and large disturbances using non-linear time domain simulations with models developed using PSCAD/EMTDC and MATLAB. / Thesis (M.Sc.)-University of Natal,Durban, 2002.

The distribution of liquid gazes (or cryogenic liquids) using bulks and tractors is a particular aspect of a fret distribution supply chain. Traditionally, these optimisation problems are treated under certainty assumptions. However, a large part of real world optimisation problems are subject to significant uncertainties due to noisy, approximated or unknown objective functions, data and/or environment parameters. In this research we investigate both robust and stochastic solutions. We study both an inventory routing problem (IRP) and a production planning and customer allocation problem. Thus, we present a robust methodology with an advanced scenario generation methodology. We show that with minimal cost increase, we can significantly reduce the impact of the outage on the supply chain. We also show how the solution generation used in this method can also be applied to the deterministic version of the problem to create an efficient GRASP and significantly improve the results of the existing algorithm. The production planning and customer allocation problem aims at making tactical decisions over a longer time horizon. We propose a single-period, two-stage stochastic model, where the first stage decisions represent the initial decisions taken for the entire period, and the second stage representing the recovery decision taken after an outage. We aim at making a tool that can be used both for decision making and supply chain analysis. Therefore, we not only present the optimized solution, but also key performance indicators. We show on multiple real-life test cases that it isoften possible to find solutions where a plant outage has only a minimal impact.