Optimal estimation retrieval is a nonlinear regression scheme to determine the conditions statistically most-likely to produce a given measurement, weighted against any a priori knowledge. The technique is applied to three problems within the field of lidar data analysis. A retrieval of the aerosol backscatter and either the extinction or lidar ratio from two-channel Raman lidar data is developed using the lidar equations as a forward model. It produces profiles consistent with existing techniques at a resolution of 10-1000 m and uncertainty of 5-20%, dependent on the quality of data. It is effective even when applied to noisy, daytime data but performs poorly in the presence of cloud. Two of the most significant sources of uncertainty in that retrieval are the nonlinearity of the detectors and the instrument's calibration (known as the dead time and overlap function). Attempts to retrieve a nonlinear correction from a pair of lidar profiles, one attenuated by a neutral density filter, are not successful as uncertainties in the forward model eliminate any information content in the measurements. The technique of Whiteman et al. [1992] is found to be the most accurate. More successful is a retrieval of the overlap function of a Raman channel using a forward model combining an idealised extinction profile and an adaptation of the equations presented in Halldórsson and Langerholc [1978]. After refinement, the retrieval is shown to be at least as accurate, and often superior to, existing methods of calibration from routine measurements, presenting uncertainties of 5-15%. These techniques are then applied to observations of ash over southern England from the Eyjafjallajökull eruption of April 2010. Lidar ratios of 50-60 sr were observed when the plume first appeared, which reduced to 20-30 sr after several days within the planetary boundary layer, indicating an alteration of the particles over time.

This thesis studies the optimal control of vehicular systems, focusing on the solution of minimum-lap-time problems for a Formula 1 car. The basic optimal control theory is summarised as an infinite-dimensional extension of optimisation theory. The relevant numerical techniques for optimisation and integral approximation are compared in view of the application to vehicle systems. The classical brachistochrone problem is revisited from an optimal control perspective, with two vehicle-relevant generalisations. Closed-form solutions are derived for both the optimal trajectory and transit time. Problems involving a steerable disc rolling on the interior surface of a hemisphere are studied. For three-dimensional problems of this type, which involve rolling bodies and nonholonomic constraints, numerical solutions are used. The identification of 3D race track models from measured GPS data is treated as a problem in the differential geometry of curves and surfaces. Curvilinear coordinates are adopted to facilitate optimal control solutions. The track is specified in terms of three displacement-dependent curvatures and two edge variables. The differential model is smoothed using numerical optimal control techniques. The Barcelona track is considered as an illustrative example. The minimum-lap-time problem for a Formula 1 car on a flat track is solved using direct transcription. The driven line and multiple car setup parameters are optimised simultaneously. It is shown that significant lap-time reductions can be obtained from track-specific setup parameter optimisation. Reduced computing times are achieved using a combination of analytical derivatives, model non-dimensionalisation and problem scaling. The optimal control of the car on a 3D track is studied; the results are compared with flat-track solutions. Contemporary kinetic energy-recovery systems are studied and compared with future hybrid kinetic-thermal energy-recovery systems. It is demonstrated that these systems can produce contemporary lap time using approximately two-thirds of the fuel required by present-day vehicles.

Three non-peripherally substituted liquid crystalline bisphthalocyanine (Pc) compounds have been studied to examine the role of central metal ions lutetium (Lu), and gadolinium (Gd) and substituent chain lengths, i.e. octyl (C8H17) and hexyl (C6H13), in determining the physical properties. For the octyl substituted Pc molecules, the head-to-tail or Jaggregates within the as-deposited spun films produced a redshift of the optical absorption Q bands in relation to their 0.01 mgml-1 solutions. Annealing at 80˚C produced a well-ordered discotic liquid crystalline (LC) mesophase causing additional redshifts irrespective of the metal ion in case of C8LuPc2 and C8GdPc2. Formation of face-to-face or H-aggregated monomers led to blueshifts of the Q bands with respect to solution spectra for C6GdPc2, both as-deposited and annealed films. Stretching and bending vibrations of pyrrole, isoindole, and metal-nitrogen bonds in Pc rings showed Raman bands at higher energy for smaller metal ion. However, no change was observed for the difference in chain lengths. As-deposited C8LuPc2 and C6GdPc2 produced comparable Ohmic conductivity, of the value 67.55 Scm-1 and 42.31 Scm-1, respectively. C8GdPc2 exhibited two orders of magnitude less conductivity than the other two due to the size effect of the central ion and side chain length. On annealing, an increase of Ohmic conductivity was noticed in the isostructural octyl substituted phthalocyanines on contrary to a reduced conductivity in hexyl substituted one. An optical band shift of the C8LuPc2 and C8GdPc2 thin films occurred on oxidation by bromine vapour. Oxidations of Pc-coated ITO were also achieved by applying potential at 0.88 V and 0.96 V electrochemically for the C8LuPc2 and C8GdPc2 compounds, respectively. To explore the applications of these compounds in biosensing, in situ interaction studies between bromine oxidised compounds and biological cofactors nicotinamide adenine dinucleotide (NADH) and L-ascorbic acid (vitamin C) were carried out using optical absorption spectroscopy. Thin films of a non-peripherally octyl substituted LC lead phthalocyanine was exposed to 99.9 % pure hydrogen sulfide gas to produce hybrid nanocomposites consisting of lead sulphide quantum dots embedded in the analogous metal free phthalocyanine matrix. Trapping of charge carriers caused hysteresis in the current-voltage characteristics of the film on interdigitated gold electrodes. The charge hopping distance was found to be 9.05 nm, more than the percolation limit and responsible for forming two well-defined conducting states with potential application as a memristor.

Heavy duty powertrains are complex systems with components from various domains, different response times during transient operations and different efficient operating ranges. To ensure efficient transient operation of a powertrain, e.g. with low fuel consumption or short transient duration, it is important to come up with proper control strategies. In this dissertation, optimal control theory is used to calculate and analyze efficient heavy duty powertrain controls during transient operations in different applications. This is enabled by first developing control ready models, usable for multi-phase optimal control problem formulations, and then using numerical optimal control methods to calculate the optimal transients. Optimal control analysis of a wheel loader operating in a repetitive loading cycle is the first studied application. Increasing fuel efficiency or reducing the operation time in such repetitive loading cycles sums up to large savings over longer periods of time. Load lifting and vehicle traction consume almost all of the power produced by a diesel engine during wheel loader operation. Physical models are developed for these subsystems where the dynamics are described by differential equations. The model parameters are tuned and fuel consumption estimation is validated against measured values from real wheel loader operation. The sensitivity of wheel loader trajectory with respect to constrains such as the angle at which the wheel loader reaches the unloading position is also analyzed. A time and fuel optimal trajectory map is calculated for various unloading positions. Moreover, the importance of simultaneous optimization of wheel loader trajectory and the component transients is shown via a side to side comparison between measured fuel consumption and trajectories versus optimal control results. In another application, optimal control is used to calculate efficient gear shift controls for a heavy duty Automatic Transmission system. A modeling and optimal control framework is developed for a nine speed automatic transmission. Solving optimal control problems using the developed model, time and jerk efficient transient for simultaneous disengagement of off-going and engagement of in-coming shift actuators are obtained and the results are analyzed. Optimal controls of a diesel-electric powertrain during a gear shift in an Automated Manual Transmission system are calculated and analyzed in another application of optimal control. The powertrain model is extended by including driveline backlash angle as an extra state in the system. This is enabled by implementation of smoothing techniques in order to describe backlash dynamics as a single continuous function during all gear shift phases. Optimal controls are also calculated for a diesel-electric powertrain corresponding to a hybrid bus during a tip-in maneuver. It is shown that for optimal control analysis of complex powertrain systems, minimizing only one property such as time pushes the system transients into extreme operating conditions far from what is achievable in real applications. Multi-objective optimal control problem formulations are suggested in order to obtain a compromise between various objectives when analyzing such complex powertrain systems.

International Telemetering Conference Proceedings / October 28-31, 1996 / Town and Country Hotel and Convention Center, San Diego, California / This paper will discuss the design and use of Optimal Ratio Combiners in modern telemetry applications. This will include basic design theory, operational setups, and various types of combiner configurations. The paper will discuss the advantages of pre-detection vs. post-detection combining. Finally, the paper will discuss modern design techniques.

ITC/USA 2005 Conference Proceedings / The Forty-First Annual International Telemetering Conference and Technical Exhibition / October 24-27, 2005 / Riviera Hotel & Convention Center, Las Vegas, Nevada / To correctly demodulate a signal sent through a multiple-input multiple-output (MIMO) channel, a receiver may use training to learn the channel parameters. The choice of training parameters can significantly impact system performance. Training too often yields low throughput while training infrequently produces poor channel estimates and increased transmission errors. Previous work on optimal training parameters has focused on the block fading Rayleigh model. This work examines a more general case; finding the training parameters that maximize throughput for a continuously varying channel. Training parameters that maximize a lower bound on channel capacity are determined via simulation, and general guidelines are presented for selecting optimal training parameters.

Thesis (PhD)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: A flood event in the town of Mariental, in 2006, raised a sudden awareness regarding the state of dam safety in Namibia. Although damage was caused at the town, the flood was not extreme; it was approximately a one in fifty year event. The concern, however, was the increase in risk imposed on the town due to the temporary malfunctioning of the back-up power system: should the secondary back-up system also have failed, the embankment could have overtopped with subsequent failure; a catastrophe. The Rational Quantitative Optimal (RQO) approach, presented in this dissertation, provides a robust risk evaluation model which produces a definitive result for the reduction of risk from the overtopping of earth-fill dams. The model is based on principles of risk, but an assessment of a portfolio of dams provides discrete optimal results, not expressed in terms of probability. All the steps that the methodology comprises have been developed exhaustively and propose to address concerns raised by dam owners and decision makers regarding risk-based dam safety: a transparent framework for decision making related to public safety, which will also appeal to the technically minded portfolio manager looking for a purely quantitative procedure to assist in the decision making process. The RQO process is applied mechanistically, not requiring judgement from the decision maker. It thus addresses the concern raised by dam owners regarding the probability of risk assessment being judgmental. Risk in this dissertation is associated with embankment dams and concomitant external erosion, which globally is the single largest cause of failure of these dams. This specific failure mechanism, in particular, is a threat in Namibia, since other mechanisms, such as internal erosion, poses very little risk to the type of embankment dams typically found in Namibia. Therefore, for practical purposes, the extreme flood hydrology in Namibia is revisited and applied to real dams in the RQO model. Extreme flood hydrology in Namibia has, for the past thirty years, largely been based on the South African Department of Water Affairs Technical Report 137 (TR 137) of 1988; This report proposes an empirically established upper limit of flood peaks, called the Regional Maximum Flood (RMF), which is associated with an annual recurrence interval of 10 000 years, as shown in this study from probabilistic analysis which included palaeoflood data. The updated flood model incorporates thirty years of additional systematic data, as well as palaeoflood data that has resulted from a new approach. The new data have provided an increase in the K‒value boundaries for some of the regional flood zones. A revised graphical distribution of the K‒value zones for Namibia is presented and is proposed as a replacement for the current model. / AFRIKAANSE OPSOMMING: ‘n Vloed in die dorp Mariental, in 2006, het belangstelling in damveiligheid in Namibia aangewakker. Alhoewel skade aangerig is aan die dorp, was dit nie ‘n besonderse groot vloed nie; dit was ‘n vloed met ongeveer ‘n vyftig jaar herhalingsperiode. Kommer met betrekking tot die voorval spruit uit die toename in risiko weens die bystand kragaanleg wat gefaal het toe dit nodig was. Indien die tweede bystand stelsel ook nie gewerk het nie, kon die dam se wal oorstroom het, wat tot katastrofiese faling van die dam kon gelei het. Die Rasionele Kwantitatiewe Optimale benadering (RQO) vir damveiligheid, wat verlaging in risiko teen oorstroming van grondvul damme teweegbring word hier voorgestel. Die model is gebaseer op beginsels van risiko analise, maar die resultaat vir ‘n portefeulje van damme word uitgedruk nie in waarskynlikheidsterme nie, maar in terme van ‘n diskrete optimale antwoord. Die metode is in diepte ontwikkel en spreek onsekerhede aan waarvoor dam-eienaars en besluitnemers te staan gekom het; ‘n deursigtige besluitnemings proses wat die veiligheid van die publiek eerste stel, en wat ook aanklank sal vind by ‘n tegnies georiënteerde bestuurder wat ‘n kwantitatiewe oplossing soek vir besluitneming by ‘n portefeulje van damme. Die RQO proses is meganisties in sy toepassing; dit verg geen oordeel van die besluitnemer nie. Sodoende spreek dit ‘n bekommernis aan wat menige dam-eienaars het oor die onpartydigheid of onbevooroordeeldheid in risiko besluitneming. Risiko word in hierdie studie geassosiëer met grondvul damme en eksterne erosie. Eksterne erosie is op internasionale vlak die grootste enkele oorsaak van faling van grondvuldamme. Hierdie falingsmeganisme is ook die grootste risiko van faling wat in Namibia voorkom, aangesien interne erosie nie by rotsvul damme, wat tipies in Namibia gebou word, ‘n groot risiko inhou nie. Dus, vir die praktiese toepassing van die RQO metode, word die ekstreme vloedhidrologie van Namibië ook onder oënskou geneem. Die afgelope dertig jaar is vloedhidrologie in Namibie hoofsaaklik gebaseer op die streeksmaksimum vloed metode wat deur Kovács (1988), van die destydse Suid Afrikaanse Departement van Waterwese, opgestel is vir lande in suidelike Afrika. Dit is beskryf in die tegniese verslag, die TR 137 van 1988, van die Departement van Waterwese, Suid Afrika. TR 137 stel ‘n streeksverbonde empiries-gebaseerde boonste limiet vir vloede voor, die sogenaamde Streeks Maksimum Vloed (SMV). Hierdie studie het gevind dat die SMV vloede tipies ‘n 10 000 jaar herhalingsperiode het deur ‘n waarskynlikheidsontleding te doen van die vloeirekords en palaeovloeddata. Die opgedateerde SMV vloedmodel vir Namibie sluit in dertig jaar se addisionele aaneenlopend-gemete data, asook nuwe palaeovloed data. Die nuwe data vergroot die areas van sommige van die die K-sones, wat die streeksvloed sones voorstel. ‘n Hersiene kaart met die nuwe K-sone grense daarop aangedui word deur hierdie navorsing aangebied en word voorgestel as ‘n vervanging van die Kovács-SMV-kaart van Namibië van 1988.

Self-assembly is a process of non-intrusive transformation of a system from a disordered to an ordered state. For engineering purposes, self-assembly of microscopic objects can benefit significantly from macroscopic guidance and control. This dissertation is concerned with controlling self-assembly in binary monolayers of electrically charged particles that follow basic laws of statistical mechanics. First, a simple macroscopic model is used to determine an optimal thermal control for self-assembly. The model assumes that a single rate-controlling mechanism is responsible for the formation of spatially ordered structures and that its rate follows an Arrhenius form. The model parameters are obtained using molecular dynamics simulations. The optimal control is derived in an analytical form using classical optimization methods. Two major lessons were learned from that work: (i) isothermal control was almost as effective as optimal time-dependent thermal control, and (ii) neither electrostatic interactions nor thermal control were particularly effective in eliminating voids formed during self-assembly. Accordingly, at the next stage, the focus is on temperature-pressure control under isothermal-isobaric conditions. In identifying optimal temperature and pressure conditions, several assumptions, that allow one to relate the optimal conditions to the phase diagram, are proposed. Instead of verifying the individual assumptions, the entire approach is verified using molecular dynamics simulations. It is estimated that under optimal isothermal-isobaric conditions the rate of self-assembly is about five time faster than that under optimal temperature control conditions. It is argued that the proposed approach of relating optimal conditions to the phase diagram is applicable to other systems. Further, the work reveals numerous and useful parallels between self-assembly and crystal physics, which are important to exploit for developing robust engineering self-assembly processes. / text

The main result is a new original algorithm: CONDOR ("COnstrained, Non-linear, Direct, parallel Optimization using trust Region method for high-computing load, noisy functions"). The aim of this algorithm is to find the minimum x* of an objective function F(x) (x is a vector whose dimension is between 1 and 150) using the least number of function evaluations of F(x). It is assumed that the dominant computing cost of the optimization process is the time needed to evaluate the objective function F(x) (One evaluation can range from 2 minutes to 2 days). The algorithm will try to minimize the number of evaluations of F(x), at the cost of a huge amount of routine work. CONDOR is a derivate-free optimization tool (i.e., the derivatives of F(x) are not required. The only information needed about the objective function is a simple method (written in Fortran, C++,...) or a program (a Unix, Windows, Solaris,... executable) which can evaluate the objective function F(x) at a given point x. The algorithm has been specially developed to be very robust against noise inside the evaluation of the objective function F(x). This hypotheses are very general, the algorithm can thus be applied on a vast number of situations. CONDOR is able to use several CPU's in a cluster of computers. Different computer architectures can be mixed together and used simultaneously to deliver a huge computing power. The optimizer will make simultaneous evaluations of the objective function F(x) on the available CPU's to speed up the optimization process. The experimental results are very encouraging and validate the quality of the approach: CONDOR outperforms many commercial, high-end optimizer and it might be the fastest optimizer in its category (fastest in terms of number of function evaluations). When several CPU's are used, the performances of CONDOR are currently unmatched (may 2004). CONDOR has been used during the METHOD project to optimize the shape of the blades inside a Centrifugal Compressor (METHOD stands for Achievement Of Maximum Efficiency For Process Centrifugal Compressors THrough New Techniques Of Design). In this project, the objective function is based on a 3D-CFD (computation fluid dynamic) code which simulates the flow of the gas inside the compressor.

La théorie du contrôle optimal s'est très rapidement développée depuis quelques années. Différentes méthodes ont été proposées pour aborder le problème. Nous développons ci-dessous une méthode due essentiellement à M. Hestenes