Tesi sul tema "Design optimal"

Several types of pupil modulation have been reported to decrease the aberration variance of the modulation-transfer-function (MTF) in aberration-tolerant hybrid optical-digital imaging systems. It is common to enforce restorability constraints on the MTF, requiring trade of aberration-tolerance and noise-gain. In this thesis, instead of optimising specific MTF characteristics, the expected imaging-error of the joint design is minimised directly. This method is used to compare commonly used phase-modulation functions. The analysis shows how optimal imaging performance is obtained using moderate phasemodulation, and more importantly, it shows the relative merits of different functions. It is shown that the technique is readily integrable with off-the-shelf optical design software, which is demonstrated with the optimisation of a wide-angle reflective system with significant off-axis aberrations. The imaging error can also be minimised for amplitudeonly masks. It is shown that phase aberrations in an imaging system can be mitigated using binary amplitude masks. This offers a low-cost, transmission-mode alternative to phase correction as used in active and adaptive optics. More efficient masks can be obtained by the optimisation of the imaging fidelity.

In this bachelor thesis we report on our numerical investigations into the optimal design of protective multi-layer coatings subject to an external force of Hertzian form. In view of mechanical reliablity and durability of the substrate and the coating we aim to find the best composition of given materials with the least computational effort. Numerical studies are carried out using the simulation software ELASTICA being the first non-FEM approach for the computation of stress fields within multi-layer coated, elastic materials. We thereby made use of the massive parallel computer CLiC (Chemnitzer Linux Cluster) where we ran our Windows based application in a Wine Environment. The outcome of the optimization is in general very sensitive towards the input parameters(i.e., material properties) which are not always available in the desired accuracy. However, the scheme outlined in this work is shown to produce very good results and could contribute a great deal to find optimal solutions for real applications
Diese Bachelorarbeit befasst sich mit numerischen Untersuchungen zum optimalen Design von schützenden Mehrschichtbeschichtungen, die einer externen, Hertzschen Last ausgesetzt sind. Hinsichtlich der mechanischen Zuverlässigkeit und Haltbarkeit von Substrat und Beschichtung, versuchen wir die beste Zusammensetzung von gegebenen Materialien mit möglichst geringem Rechenaufwand zu finden. Die numerischen Berechungen wurden mit der Simulationssoftware ELASTICA durchgeführt, welches das erste kommerzielle, nicht-FEM-basierte Programm zur Berechnung von Stressfeldern innerhalb mehrfach beschichteter, elastischer Materialien darstellt. Dafür benutzten wir auf dem massiven Parrallelrechner CLiC (Chemnitzer Linux Cluster) unsere Windows basierte Anwendung unter der Emulationssoftware Wine. Das Ergebnis der Optimierung hängt im allgemeinen sehr stark von der Qualität der Eingangsparameter (z.B. Materialeigenschaften) ab, welche nicht immer in der erwünschten Genauigkeit vorliegen. Es wird gezeigt, dass die in dieser Arbeit vorgestellte Vorgehensweise sehr gute Resultate liefert und für reale Anwendungen einen äusserst ressourcenschonenden Lösungsweg darstellt

The optimum values for the section variables like channel side slope,bottom width,depth and radius for triangular,rectangular, trapezoidal and circular channels are computed by minimizing the cost of the channel section.Manning &rsquo
s uniform flow formula is treated as a constraint for the optimization model.The cost function is arranged to include the cost of lining,cost of earthwork and the increment in the cost of earthwork with the depth below the ground surface.The optimum values of section variables are expressed as simple functions of unit cost terms.Unique values of optimum section variables are obtained for the case of minimum area or minimum wetted perimeter problems.

Doctor of Philosophy (Economics)
Auctions are an ancient economic institution. Since Vickrey (1961), the development of auction theory has lead to an extremely detailed description of the often desirable characteristics of these simple selling procedures, in the process explaining their enduring popularity. Given the pervasiveness of auctions, the question of how a seller should engineer the rules of these mechanisms to maximize her own profits is a central issue in the organization of markets. The seminal paper of Myerson (1981) shows that when facing buyers with Independent Private Values (IPVs) a standard auction with a specifically selected reserve price (or prices) is optimal, that is, maximizes a seller's expected profits among all conceivable selling mechanisms. In this model, it is assumed that the buyers have perfect information as to the existence of gains from trade. We shall argue that the consequences of this assumption for the design of the optimal auction are not well understood, which motivates our analysis. The three essays of this thesis relax the `known seller valuation' assumption by examining the optimal auction program when the seller (and principal) holds private information representing her reservation value for the good. In the first essay we provide an original technique for comparing ex ante expected profits across mechanisms for a seller facing N>1 potential buyers when all traders hold private information. Our technique addresses mechanisms that cannot be ranked point-by-point through their allocation rules using the Revenue Equivalence Theorem. We find conditions such that the seller's expected profits increase in the slope of each buyer's allocation probability function. This provides new intuition for the fact that a principal does not benefit from holding private information under risk neutrality. Monopoly pricing induces steep probability functions so the seller/principal benefits from announcing a fixed price, and implicitly her private information. An application is presented for the well known k double auction of the bilateral trade literature. In the second and third essays of this thesis, we extend the above framework to allow for informational externalities. Specifically, we allow for the situation in which the seller's private information represents a common value component in buyers' valuations. Thus the seller's private information (say regarding the quality of the good) is of interest to bidders independently of any strategic effects. In recent work Cai, Riley and Ye (2007) have demonstrated that a seller who holds private information about the quality of a good faces an extra consideration in designing an auction; the reserve price signals information to bidders. In a separating equilibrium signalling is costly in the sense that reserves are higher than would be optimal under complete information. We examine the returns to the seller in an English auction from using different types of secret reserve regimes. We find that immediate disclosure of a reserve is preferable to announcement after the auction in the form of a take-it-or-leave-it offer to the winning bidder. Sale occurs less often during the auction for a given reserve price strategy under secret reserve regimes, which increases the incentive for the seller to report more favourable information though the reserve price offer. Separating equilibria involving later announcement therefore generate even lower expected profits to the seller (signalling is more costly) than under immediate disclosure. In the third essay we compare the benchmark signalling equilibrium of immediate disclosure to a screening regime which we call the Right of Refusal. In this extreme form of a secret reserve the seller never announces the reserve price, she simply accepts or rejects the auction price. We find that the Right of Refusal dominates immediate disclosure if the seller's valuation is a sufficient statistic for the private information of interest. Thus a seller with market-relevant private preference information can benefit from not exercising monopoly price setting power. The result also provides conditions under which a competitive screening equilibrium is more efficient than a signalling mechanism. Broadly speaking, screening is better when the common value aspect in the preferences of the informed and uninformed parties are `aligned', and potential gains from trade to the uninformed party are significant. We believe this conclusion to be of particular interest to the design of privatization schemes.

This thesis concerns the approximation of optimally controlled partial differential equations for inverse problems in optimal design. Important examples of such problems are optimal material design and parameter reconstruction. In optimal material design the goal is to construct a material that meets some optimality criterion, e.g. to design a beam, with fixed weight, that is as stiff as possible. Parameter reconstrucion concerns, for example, the problem to find the interior structure of a material from surface displacement measurements resulting from applied external forces. Optimal control problems, particularly for partial differential equations, are often ill-posed and need to be regularized to obtain good approximations. We here use the theory of the corresponding Hamilton-Jacobi-Bellman equations to construct regularizations and derive error estimates for optimal design problems. The constructed Pontryagin method is a simple and general method where the first, analytical, step is to regularize the Hamiltonian. Next its Hamiltonian system is computed efficiently with the Newton method using a sparse Jacobian. An error estimate for the difference between exact and approximate objective functions is derived, depending only on the difference of the Hamiltonian and its finite dimensional regularization along the solution path and its L² projection, i.e. not on the difference of the exact and approximate solutions to the Hamiltonian systems. Another treated issue is the relevance of input data for parameter reconstruction problems, where the goal is to determine a spacially distributed coefficient of a partial differential equation from partial observations of the solution. It is here shown that the choice of input data, that generates the partial observations, affects the reconstruction, and that it is possible to formulate meaningful optimality criteria for the input data that enhances the quality of the reconstructed coefficient. In the thesis we present solutions to various applications in optimal material design and reconstruction.
Denna avhandling handlar om approximation av optimalt styrda partiella differentialekvationer för inversa problem inom optimal design. Viktiga exempel på sådana problem är optimal materialdesign och parameterskattning. Inom materialdesign är målet att konstruera ett material som uppfyller vissa optimalitetsvillkor, t.ex. att konstruera en så styv balk som möjligt under en given vikt, medan ett exempel på parameterskattning är att hitta den inre strukturen hos ett material genom att applicera ytkrafter och mäta de resulterande förskjutningarna. Problem inom optimal styrning, speciellt för styrning av partiella differentialekvationer,är ofta illa ställa och måste regulariseras för att kunna lösas numeriskt. Teorin för Hamilton-Jacobi-Bellmans ekvationer används här för att konstruera regulariseringar och ge feluppskattningar till problem inom optimaldesign. Den konstruerade Pontryaginmetoden är en enkel och generell metod där det första analytiska steget är att regularisera Hamiltonianen. I nästa steg löses det Hamiltonska systemet effektivt med Newtons metod och en gles Jacobian. Vi härleder även en feluppskattning för skillnaden mellan den exakta och den approximerade målfunktionen. Denna uppskattning beror endast på skillnaden mellan den sanna och den regulariserade, ändligt dimensionella, Hamiltonianen, båda utvärderade längst lösningsbanan och dessL²-projektion. Felet beror alltså ej på skillnaden mellan den exakta och denapproximativa lösningen till det Hamiltonska systemet. Ett annat fall som behandlas är frågan hur indata ska väljas för parameterskattningsproblem. För sådana problem är målet vanligen att bestämma en rumsligt beroende koefficient till en partiell differentialekvation, givet ofullständiga mätningar av lösningen. Här visas att valet av indata, som genererarde ofullständiga mätningarna, påverkar parameterskattningen, och att det är möjligt att formulera meningsfulla optimalitetsvillkor för indata som ökar kvaliteten på parameterskattningen. I avhandlingen presenteras lösningar för diverse tillämpningar inom optimal materialdesign och parameterskattning.
QC 20100712

Psycholinguistic accounts of language production have traditionally been informed by evidence from highly constrained, non-interactive experimental tasks, such as picture description and sentence completion. These studies are informative about the mechanisms and representations that underlie production, but they tell us little about the impact of communicative context on those basic processes. This thesis examines language behaviour in more naturalistic situations, where the speaker is talking to a co-present addressee. This kind of setting more closely reflects production outside the laboratory, where speakers need to make themselves understood if communication is to be successful. In particular, the thesis investigates whether speakers follow a principle of ‘optimal design’ at the level of grammatical encoding. Optimal design can be interpreted in different ways; speakers may say things that are easy to produce, maximising efficiency for themselves. Alternatively, they might aim to produce messages that are easy for an audience to understand (or they might trade off between these goals). The thesis focuses on whether speakers take addresses’ perspectives into account when they formulate syntactic structure and word order. Referential communication paradigms were used to investigate language production during collaborative tasks. Speakers described picture cards or other objects so that an addressee could pick out the intended referent from an array. The structure of the array was manipulated such that particular syntactic structures or word orders would be easier for the addressee to interpret than others. The research suggests that grammatical stages of language production can be sensitive to information about an addressee’s perspective. Speakers show evidence of optimal design in their choice of syntax and word order, but only when it is obvious how they can make their utterances easy to understand.

The variogram plays a central role in the analysis of geostatistical data. A valid variogram model is selected and the parameters of that model are estimated before kriging (spatial prediction) is performed. These inference procedures are generally based upon examination of the empirical variogram, which consists of average squared differences of data taken at sites lagged the same distance apart in the same direction. The ability of the analyst to estimate variogram parameters efficiently is affected significantly by the sampling design, i.e., the spatial configuration of sites where measurements are taken. In this paper, we propose design criteria that, in contrast to some previously proposed criteria oriented towards kriging with a known variogram, emphasize the accurate estimation of the variogram. These criteria are modifications of design criteria that are popular in the context of (nonlinear) regression models. The two main distinguishing features of the present context are that the addition of a single site to the design produces as many new lags as there are existing sites and hence also produces that many new squared differences from which the variograrn is estimated. Secondly, those squared differences are generally correlated, which inhibits the use of many standard design methods that rest upon the assumption of uncorrelated errors. Several approaches to design construction which account for these features are described and illustrated with two examples. We compare their efficiency to simple random sampling and regular and space-filling designs and find considerable improvements. (author's abstract)
Series: Forschungsberichte / Institut für Statistik

This thesis studies the design of Bayesian revenue-optimal auctions for a class of problems in which buyers have general (non-linear and multi-parameter) preferences. This class includes the classical linear single-parameter problem considered by Myerson (1981), for which he provided a simple characterization of revenue proving optimality of a mechanism, leading to numerous applications in theory and practice. However, for fully general preferences no generic and practical solution is known (various negative computational or structural results exist for special cases), even for the problem of designing a mechanism for a single agent. This thesis sets to identifies key conditions implying that the optimal mechanism is practical. Our main results are different in that they identify different conditions implying different notions of practicality, but are all similar in adopting a modular view to the problem that separates the task of designing a solution for the single-agent problem as the main module, from the task of combining these modules to form an optimal multi-agent mechanism. For multi-parameter linear settings, we specify a large class of distributions over values that implies that the optimal single-agent mechanism is posted pricing, and the optimal multi-agent mechanism maximizes \emph{virtual values} for players' favorite items (e.g., when agents are identical, second price auction with reserve for favorite items). More generally, we specify a condition called revenue-linearity (defined beyond multi-parameter linear settings) that implies that optimizing agents' marginal revenue maximizes revenue. Finally, adopting efficient computability as the notion of practicality, we show that for any setting in which single-agent solutions are efficiently computable, multi-agent solutions are also computable.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2012.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 121-123).
Reference trajectory design for atmospheric reentry vehicles can be accomplished through trajectory optimization using optimal control techniques. However, this method generally focuses on nominal vehicle performance and does not include robustness considerations during trajectory design. This thesis explores the use of linear covariance analysis to directly include trajectory robustness in the design process. The covariance matrix can be propagated along a trajectory to provide the expected errors about the nominal trajectory in the presence of uncertainties. During the optimization process, the covariance matrix is used as a performance metric to be minimized, directly penalizing expected errors so that the trajectory is shaped to reduce its sensitivity to uncertainties. This technique can penalize the open-loop covariance of the trajectory or the closed-loop covariance with the inclusion of a feedback guidance law. This covariance shaping technique is applied to reference trajectory design for a generic small reentry vehicle. A baseline trajectory is generated without any robustness considerations, along with an open-loop covariance shaped trajectory and a closed-loop covariance shaped trajectory, which uses a feedback guidance law based on a linear quadratic regulator scheme. Uncertainties in initial conditions, atmospheric density, aerodynamic coefficients, and unmodeled dynamics are applied to each trajectory and performance is analyzed using linear covariance analysis and Monte Carlo simulations. The results show that when the vehicle is flown closed-loop with feedback, shaping using the open-loop covariance produces a trajectory that is less robust than the baseline trajectory, while shaping using the closed-loop covariance generates a trajectory with reduced sensitivity to uncertainty for more robust performance.
by Benjamin R. Saunders.
S.M.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Economics, 2009.
Includes bibliographical references (p. 157-166).
This dissertation consists of three chapters analyzing the optimal design of insurance contracts. I consider three relevant contexts that change the central trade-off between the provision of insurance and the provision of incentives. The first chapter analyzes the role of biased beliefs for the optimal design of static and dynamic insurance contracts. Biased risk perceptions change the perceived value of insurance and the perceived returns to avoiding these risks. I show empirically that unemployed workers overestimate how quickly they will find work, but underestimate the return to their search efforts. I analyze how these biases drive a wedge between social and private insurance, and between naive and optimal policy implementation. The second chapter analyzes the role of training for the design of unemployment insurance. A worker's human capital falls upon displacement and depreciates during unemployment. Training counters the decrease in human capital, but also changes the willingness of the unemployed to search. I characterize the optimal unemployment insurance contract and analyze the optimal timing of unemployment benefits and training programs during unemployment. The third chapter analyzes the role of heterogeneity in risk perceptions for the optimal design of screening contracts in a model with moral hazard and adverse selection. I show how optimists receive less insurance than pessimists and I contrast the distortions in insurance coverage that arise with competing and monopolistic insurers.
(cont.) Heterogeneity in beliefs strengthens the case for government intervention in insurance markets and can explain the negative correlation between risk occurrence and insurance coverage found in empirical studies.
by Johannes Spinnewijn.
Ph.D.

Thesis (MEng)--Stellenbosch University, 2015.
ENGLISH ABSTRACT: Currently the three main algae strains that are manufactured commercially are Chlorella, Spirulina and Dunaliela salina, which are produced for biomass and bioproducts. Photobioreactors (PBR) allow the exploitation of over 50 000 known microalgae species with over 15 000 novel compounds having been chemically identified to date. Many of these algae could be sources of high-value products which are produced using a method that delivers them from renewable resources. Designing an optimal photobioreactor is a complex process because a large array of variables is included in the design, with several of the variables interacting with each other directly. The interactions of most of these variables have not been established. The initial information that is available is inadequate because most photobioreactors have been tested on a laboratory scale and the information given does not include the manufacturing materials, the size of tubing used and other design variables. Before designing a photobioreactor, it is important to understand the best conditions for the production of algae because these have a direct influence on the requirements. In order to produce algae biomass under the specific conditions, one has to investigate current photobioreactors that have been designed in order to establish whether they are capable of optimum production under the production conditions; determine possible factors that could influence the production negatively and how they could be prevented; and undertake a cost analysis to determine whether the production of algae is an economically viable process using the specific reactor. All of these criteria have to be met for a photobioreactor to be viable in the production of algae biomass. Currently a Bubble column reactor is considered to be the best design for a photobioreactor and also the most scalable. Due to the limited information available, testing was conducted to determine the effect of: 1) different manufacturing materials, 2) the gas dispersion unit, 3) the diameters of the tubing and 4) the density. Bubble column reactors were used to test the effects of the four variables and were considered to be the most important aspects in the design. For testing these variables and their interaction, Chlorella Vulgaris was used because it is one of the most popular algae species used for production currently. As temperature and the availability of light play a large role in the production of algae, all testing was done in a laboratory environment to ensure small temperature changes and the constant availability of light. The reactors that were tested were made of PVC couplings, with the clear tubing used being made of either PVC or acrylic tubing. Enriched air was supplied at a 5% volume per volume ratio of CO2, with a flow rate of 0.02 volume per volume per minute (vvm) for the 50 mm diameter reactors and 0.36 vvm for the 90 and 110 mm diameter reactors. Two gas dispersion units were used to determine whether they would have any effect on the production. The gas dispersion units create small bubbles to ensure a high surface area to volume ratio and thereby they allow for maximum CO2 and O2 mass transfer. A growth rate of 0.14 gram per litre per day was found to yield the best production of all the reactors and configurations that were tested. The 50 mm diameter reactors showed the best growth followed by the 110 mm diameter reactors. The 90 mm diameter reactors all had a negative growth rate which appeared to be due to an insufficient gas flow rate. The 50 mm reactors had the best growth rate of 0.14 and 0.10 grams per litre per day for the acrylic tubing, while 0.08 grams per litre per day was achieved with PVC tubing. The 110 mm reactors had a highest growth rate of 0.05 grams per litre per day with PVC tubing. It was found that the 50 mm and 90 mm reactors showed a better performance with acrylic tubing while the 110 mm reactors showed a better performance with PVC tubing. The gas dispersion unit is affected by the gas flow rate, the density, the diameter of the tubing and the material that is used. The gas dispersion units’ effect is dependent on the diameter of the reactor seeing that the 50 mm reactor shows better performance with the small unit, while the 110 mm reactor shows better performance with the large unit, due to the gas flow rate that is required in the reactors. Because the gas flow rate and gas dispersion unit directly affect the agitation, the optimal density is affected directly due to the availability of light and therefore the tubing material. The gas dispersion units should fit properly into the reactor and be capable of handling the gas flow rate that is required. The diameter of the tubing does not show any effect but could have an effect under different testing conditions and could not be conclusively eliminated. The density of algae does have an effect, although most reactors showed a better production rate at a higher culture density. The scale up of the bubble column reactor creates a dead zone when a module is constructed. The scale up of a bubble column reactor could range from increasing the vertical tubing length, increasing the diameter of the tubing to adding vertical tubing to a module. The dead zone is formed at the bottom of the reactor where the module interconnects the vertical growth tubes, because these fittings are not constructed from a clear material, due to cost of such a construction. The dead zone that is created causes a large portion of algae to form a sediment, which directly affects the production of the system because it is in a dark zone of the reactor. Improved results would be obtained if the algae were kept at a homogeneous density that would ensure maximum expose to light. The ratio of gas flow rate to reactor volume and diameter of the tubing was found to be crucial. It is suspected that the 90 mm tubing reactor had a negative growth rate as this ratio was not correct. The 50 mm reactors had to be run at a much lower reactor volume per volume gas flow rate which could consist of air, carbon dioxide enriched air or other gases as required. The inclusion of the tubing diameter in the ratio is of vital importance and should be studied further. A cost analysis shows that the bubble column reactors under the tested conditions are not financially viable. A large component of the cost is carbon dioxide and medium, which is a composition of nutrients. This could be removed if a free source were obtained, which would make the system financially viable. These sources could include waste water and flue gas from industrial processes. It is recommended that a gas dispersion tube be positioned at the bottom of the reactor to ensure that no sedimentation occurs and that there is a homogeneous culture, and to maximise the production capabilities of a bubble column reactor. It is also recommended that the gas flow rate inside the reactor be studied to obtain a ratio where the volume of the reactor, the height of the reactor and the diameter of the tubing are included to obtain a sufficient rate of flow.
AFRIKAANSE OPSOMMING: Tans is daar drie belangrike alg stamme wat kommersieel geproduseer word, Chlorella, Spirulina en Dunaliela salina. Fotobioreaktors het meegebring dat meer as 50 000 bekende alg spesies met meer as 15 000 komponente tot op datum chemies geïdentifiseer is. Baie van hierdie alge kan hoë waarde produkte wees, wat met behulp van hernubare metodes geproduseer kan word. Die ontwerp van 'n optimale fotobioreaktor is 'n komplekse proses aangesien 'n groot verskeidenheid veranderlikes ingesluit moet word wat ‘n invloed op mekaar kan hê. Die interaksie van meeste van hierdie veranderlikes is nog nie vasgestel nie. Die inligting oor hierdie onderwerp is beperk aangesien die meeste fotobioreaktors in 'n laboratorium getoets is en dus nie die vervaardigingsmateriale, die grootte van buise en ander ontwerp veranderlikes insluit nie. Voordat 'n fotobioreaktor ontwerp kan word, moet die ideale alg produksie toestande verstaan word, aangesien dit 'n direkte impak op die produksie vereistes kan hê. Om alg biomassa onder spesifieke omstandighede te produseer, moet die bestaande fotobioreaktor ontwerpe ondersoek word. Daar moet vasgestel word of die bepaalde ontwerp oor die kapasiteit beskik om optimale produksie te lewer; identifisering van faktore wat produksie negatief kan beïnvloed en hoe dit voorkom kan word; en 'n koste ontleding moet gedoen word om te bereken of die produksie van alge met die geidentifiseerde ontwerp 'n ekonomies lewensvatbare proses is. Daar moet aan al die vereistes voldoen word om te bepaal of 'n fotobioreaktor lewensvatbaar is vir die produksie van alg biomassa. 'n Borrel-kolom reaktor ontwerp word tans as die beste ontwerp vir 'n fotobioreaktor geag, asook die mees aanpasbare ontwerp. As gevolg van die beperkte inligting wat beskikbaar is, is navorsing gedoen om die invloed van verskillende faktore te bepaal, naamlik: vervaardigingsmateriaal, gasverspreidingseenheid, buisdeursnee en digtheid. Borrel-kolom reaktors is gebruik om die vier belangrikste veranderlikes in die ontwerp te toets. Om die veranderlikes en hul interaksie te toets, is Chlorella vulgaris gebruik, aangesien dit een van die gewildste alg spesies is vir die produksie van biomassa. As gevolg van die belangrike rol wat temperatuur en lig beskikbaarheid in die produksie van alge speel, is al die toetse in 'n laboratorium-omgewing gedoen om temperatuur wisseling te beperk en konstante lig beskikbaarheid te verseker. Die reaktors wat getoets is, is vervaardig uit PVC koppelstukke, met die deurskynende buise wat uit PVC of akriel vervaardig is. Verrykte lug is verskaf op 'n 5% volume per volume verhouding CO2, met 'n vloei tempo van 0,02 volume per volume per minuut (vvm) vir die 50 mm deursnee reaktors en 0,36 vvm vir die 90 mm en 110 mm reaktors. Twee gasverspreidingseenhede is gebruik om hulle invloed op die produksie te bepaal. Die gasverspreidingseenhede skep kleiner borrels, om 'n hoë oppervlak area tot volume verhouding te skep en daardeur 'n maksimum CO2 en O2 massa-oordrag te verseker. 'n Groeikoers van 0,14 gram per liter per dag is gevind as die beste produksie van al die reaktors en konfigurasies wat getoets is. Die 50 mm deursnee reaktors het die beste groei getoon, gevolg deur die 110 mm deursnee reaktors. Die 90 mm deursnee reaktors het 'n negatiewe groeikoers getoon, wat moontlik toegeskryf kan word aan onvoldoende gas vloei tempo. Die 50 mm reaktors het die beste groeikoers van 0,14 en 0,10 gram per liter per dag vir die akriel buise getoon, terwyl ‘n 0,08 gram per liter per dag behaal is met 'n PVC buis. Die 110 mm reaktors het die hoogste groeikoers aangedui van 0,05 gram per liter per dag met 'n PVC buis. Daar is bevind dat die 50 mm en 90mm reaktors 'n beter prestasie met akriel buise gehad het, terwyl die 110 mm reaktors 'n beter prestasie met 'n PVC buis gehad het. Die gasverspreidingseenheid word beinvloed deur die gas vloei tempo, digtheid, buisdeursnee en die vervaardigingsmateriaal wat gebruik word. Die gasverspreidingseenhede word verder beinvloed deur die reaktor se buisdeursnee aangesien die 50 mm reaktor ‘n beter prestasie getoon het met die kleiner gas eenheid, terwyl die 110 mm reaktor ‘n beter prestasie getoon het met die groter gas eenheid, as gevolg van die gas vloei tempo wat vereis is. Die gas vloei tempo en gasverspreidingseenheid het ‘n direkte invloed op die groei van die kultuur, dus is die optimale digtheid afhanklik van die lig beskikbaarheid en dus die vervaardigingsmateriaal van die buise. Die gasverspreidingseenhede moet stewig in die reaktor pas en in staat wees om die gas vloei tempo wat vereis word te kan hanteer. Hoewel die deursnee van die buise nie 'n invloed getoon nie, kan dit 'n invloed onder verskillende toets omstandighede toon en kon nie finaal uitgeskakel word. Die digtheid van die alge het wel 'n effek, hoewel die meeste reaktors ‘n beter produksie tempo op 'n hoër kultuur digtheid toon. Die groter skaal borrel-kolom reaktor ontwikkel 'n dooie sone indien ‘n module saamgestel word. Die groter skaal borrel-kolom reaktor kan insluit: die verhoging van die vertikale buis lengte, 'n toename in deursnee van die buise en toevoeging van vertikale buise in die module. Die dooie sone het gevorm aan die onderkant van die reaktor waar die module se vertikale groei buise met mekaar verbind is. Hierdie area is uit nie-deurskynende materiaal vervaardig as gevolg van die konstruksie koste. Die dooie sone het veroorsaak dat groot hoeveelhede van die alge ‘n sediment gevorm het en ‘n direkte invloed op die produksie van die stelsel gehad het aangesien dit 'n donker sone in die reaktor gevorm het. Beter resultate kan verwag word indien die alge op 'n homogeniese digtheid gehou kan word om maksimum lig blootstelling te verseker. Daar is bevind dat die verhouding van gas vloei tempo tot reaktor volume en buisdeursnee deurslaggewend is. Die negatiewe groeikoers in die 90 mm reaktor word toegeskryf daaraan dat hierdie verhouding nie korrek was nie. Die 50 mm reaktors het op 'n laer reaktor volume per volume gas vloei tempo gefunksioneer wat kan bestaan uit die lug, verrykte lug of ander gasse soos benodig. Dit dui daarop dat die insluiting van die buis deursnee in hierdie verhouding van kardinale belang is en verder bestudeer moet word. 'n Koste ontleding toon dat die borrel-kolom reaktors onder hierdie getoets omstandighede nie finansieel lewensvatbaar is nie. 'n Groot deel van die koste is die medium, wat 'n samestelling van voedingstowwe is, en koolstofdioksied koste. Om finansieel lewensvatbaar te raak, moet hierdie kostes deur 'n gratis bron vervang word. Die bronne kan bestaan uit afval water en oortolige CO2 uit industrie. Daar word aanbeveel dat 'n gasverspreidingsbuisie aan die onderkant van die reaktor geplaas word. Dit sal verseker dat geen sediment vorm nie en 'n homogeniese kultuur gehandhaaf kan word om maksimum produksie in 'n borrel-kolom reaktor te handhaaf. Verder word aanbeveel dat die gas vloei tempo binne die reaktor verder bestudeer word om 'n verhouding tussen die volume van die reaktor, die hoogte van die reaktor en die deursnee van die buise te bepaal deur sodoende 'n voldoende tempo van vloei te verkry.

Morphing structures change their geometric configuration to achieve a wide range of performance goals. For morphing aircraft these include alleviating drag, or altering aerofoil lift. The design of structures capable of realising these goals is a highly multidisciplinary problem. Optimally morphing a compliant structure involves finding the distribution of actuation which best achieves a desired configuration change. In this work, the location and magnitude of discrete actuators are optimised, to minimise both aerodynamic and geometric objective functions. A range of optimisation methods, including differential and stochastic techniques, has been implemented to search optimally the large, nonlinear, and often discontinuous design spaces associated with such problems. The optimal design of morphing systems is investigated through consideration of a morphing shock control bump and an adaptive leading edge. CFD is implemented to evaluate the aerodynamic performance of optimiser-controlled morphing structures. A bespoke grid-generation algorithm is developed, capable of producing a mesh for all possible geometries, with low levels of cell skewness and orthogonality at the fluid-structure boundaries. Structural compliance – a prerequisite for morphing – allows significant displacement of the structure to occur, but simultaneously enables the possibility of detrimental aeroelastic effects. Static aeroelasticity is catered for, at significant computational expense, via coupling of the structural and aerodynamic models within individual optimisation function evaluations. Morphing geometry is investigated to reduce computational design requirements, and provide an objective starting point for an aeroelastic optimisation. The requirements of morphing between aerodynamic shapes are evaluated using geometry-based objective functions. Displacements and curvatures are compared between an optimiser-controlled structure and the target morph, and the differences minimised to effect the required shape change. In addition to enabling optimal problem definition, these geometric objective functions allow conclusions on the feasibility of a morph to be drawn a priori.

Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2002.
Includes bibliographical references (leaves 92-95). Also available in electronic version. Access restricted to campus users.

Auctions are an ancient economic institution. Since Vickrey (1961), the development of auction theory has lead to an extremely detailed description of the often desirable characteristics of these simple selling procedures, in the process explaining their enduring popularity. Given the pervasiveness of auctions, the question of how a seller should engineer the rules of these mechanisms to maximize her own profits is a central issue in the organization of markets. The seminal paper of Myerson (1981) shows that when facing buyers with Independent Private Values (IPVs) a standard auction with a specifically selected reserve price (or prices) is optimal, that is, maximizes a seller's expected profits among all conceivable selling mechanisms. In this model, it is assumed that the buyers have perfect information as to the existence of gains from trade. We shall argue that the consequences of this assumption for the design of the optimal auction are not well understood, which motivates our analysis. The three essays of this thesis relax the `known seller valuation' assumption by examining the optimal auction program when the seller (and principal) holds private information representing her reservation value for the good. In the first essay we provide an original technique for comparing ex ante expected profits across mechanisms for a seller facing N>1 potential buyers when all traders hold private information. Our technique addresses mechanisms that cannot be ranked point-by-point through their allocation rules using the Revenue Equivalence Theorem. We find conditions such that the seller's expected profits increase in the slope of each buyer's allocation probability function. This provides new intuition for the fact that a principal does not benefit from holding private information under risk neutrality. Monopoly pricing induces steep probability functions so the seller/principal benefits from announcing a fixed price, and implicitly her private information. An application is presented for the well known k double auction of the bilateral trade literature. In the second and third essays of this thesis, we extend the above framework to allow for informational externalities. Specifically, we allow for the situation in which the seller's private information represents a common value component in buyers' valuations. Thus the seller's private information (say regarding the quality of the good) is of interest to bidders independently of any strategic effects. In recent work Cai, Riley and Ye (2007) have demonstrated that a seller who holds private information about the quality of a good faces an extra consideration in designing an auction; the reserve price signals information to bidders. In a separating equilibrium signalling is costly in the sense that reserves are higher than would be optimal under complete information. We examine the returns to the seller in an English auction from using different types of secret reserve regimes. We find that immediate disclosure of a reserve is preferable to announcement after the auction in the form of a take-it-or-leave-it offer to the winning bidder. Sale occurs less often during the auction for a given reserve price strategy under secret reserve regimes, which increases the incentive for the seller to report more favourable information though the reserve price offer. Separating equilibria involving later announcement therefore generate even lower expected profits to the seller (signalling is more costly) than under immediate disclosure. In the third essay we compare the benchmark signalling equilibrium of immediate disclosure to a screening regime which we call the Right of Refusal. In this extreme form of a secret reserve the seller never announces the reserve price, she simply accepts or rejects the auction price. We find that the Right of Refusal dominates immediate disclosure if the seller's valuation is a sufficient statistic for the private information of interest. Thus a seller with market-relevant private preference information can benefit from not exercising monopoly price setting power. The result also provides conditions under which a competitive screening equilibrium is more efficient than a signalling mechanism. Broadly speaking, screening is better when the common value aspect in the preferences of the informed and uninformed parties are `aligned', and potential gains from trade to the uninformed party are significant. We believe this conclusion to be of particular interest to the design of privatization schemes.

There are two main approaches to designing road pricing schemes. The first is judgmental in nature and focuses on the acceptability and practicality of the scheme. The second is based on theory concentrating on the optimality and performance of the scheme. This research aimed to integrate these two approaches into a single framework and to develop a tool to aid the decision maker in designing a practical and optimal road pricing scheme. A review of the practical design criteria and a survey with six local authorities in the U. K. were conducted to clarify the concept of the judgmental design. A simple charging scheme like a charging cordon is believed to be the most practical charging regime due to its simple structure. The decision on the boundary and structure of the cordon is based largely on public acceptability and possible adverse impacts. Road pricing is used to serve several objectives including congestion reduction, revenue generation, and increase in efficiency of the transport system. The framework for the theoretical optimal toll design problem adopted was a Stackelberg game where the travellers' behaviour were assumed to follow the concept of Wardrop's user equilibrium. This problem can also be formed as a Mathematical Program with Equilibrium Constraint (MPEC). After reviewing various methods for solving the MPEC problem, three possible methods (the merit function method, improved cutting plane algorithm, and Genetics Algorithm (GA) based algorithm) were developed and tested with the optimal toll problem. The GA based algorithm was found to be the most appropriate for the development of the design algorithm with practical constraints. Three different features of the judgmental design were included into the optimisation algorithm: the closed cordon formation, constraints on the outcomes of the scheme, and the allowance for multiple objectives. An algorithm was developed to find the optimal cordon with an optimal uniform toll. It is also capable of designing a scheme with multiple cordons. The algorithms for solving the constrained optimal cordon design problem and the multiobjective cordon design problem were also developed. The algorithm developed for the multiobjective problem allows the application of the posterior and progressive preference articulation approach by generating the set of non-dominated solutions. The algorithms were tested with a network of Edinburgh. The results revealed several policy implications. Adopting a judgmental cordon with a simple uniform toll may be less effective. A variable optimised toll around the judgmental cordon can generate around 70% more benefit than the optimal uniform toll. The optimised location of a cordon generated about 80% higher benefit compared to the best judgmental cordon. Additional constraints such as a maximum of total travel time decreased the level of the benefit of the scheme by 90%. Different objectives may require different designs for the charging cordon scheme. The welfare maximisation cordon should focus on those trips contributing most to the social welfare function which are mainly in the congested areas with an appropriate toll level. The revenue maximisation cordon should impose a higher number of crossing points and minimise possible diversion routes to avoid the tolls which should be high. The equity cordon should cover a wider area of the network with low toll level to ensure a good distribution of the cost and benefit to all origin-destination pairs. The algorithms developed can offer support to the decision maker in developing a charging cordon scheme by formalising the process of charging cordon design. This will increase the transferability of the technique and the transparency of the decision process.

Magíster en Gestión de Operaciones. Ingeniero Civil Matemático
En este trabajo estudiamos un par de problemas de la teoría de paradas óptimas, y mostramos cómo aplicar estos resultados en el diseño de mecanismos. Consideramos dos versiones modificadas de la famosa desigualdad del profeta [10, 16, 17]: una no-adaptativa donde la regla de parada debe ser decidida de antemano, y una adaptativa --- que corresponde a la configuración clásica de la desigualdad del profeta ---, pero en el caso restringido cuando las distribuciones de las variables aleatorias están idénticamente distribuidas [13]. Para la primera situación, encontramos un factor de garantía para la regla de parada con respecto al máximo esperado de la secuencia de variables aleatorias y demostramos que es la mejor posible; para el segundo, probamos que una conjetura sobre cuál es el mejor factor posible es verdadera [14]. Cerramos esta tesis extendiendo estos resultados para resolver el problema de un vendedor que enfrenta a muchos compradores potenciales y debe diseñar una subasta secuencial para maximizar sus ingresos. El tipo de mecanismos que consideramos para estudiar este problema de pricing son los mecanismos posted price, y los resultados que obtenemos toman la forma de factores de aproximación con respecto al valor de la subasta óptima [19].
In this work we study a pair of problems in optimal stopping theory, and show how to apply these results in mechanism design. We consider two modified versions of the famous prophet inequality [10, 16, 17]: a non-adaptive where the stop rule must be decided beforehand, and an adaptive one --- which corresponds to the classical prophet inequality setting ---, but when the distributions of the random variables are identical [13]. For the first set-up, we find a new factor guarantee with respect to the expected maximum of the random variables sequence and prove it is the best possible; for the second, we prove that a conjecture about the best possible factor achievable is true [14]. We close this dissertation by extending these results to solve the problem of a seller that faces many potential buyers and must design a sequential auction in order to maximize its revenue. The type of mechanisms we consider to study this pricing problem are the posted price mechanisms, and the results we get are in the form of approximation factors guarantees with respect to the optimal auction [19].
Este trabajo ha sido parcialmente financiado por Conicyt y el Núcleo Milenio Información y Coordinación en Redes

Compliant actuators are mechanical devices that extend the traditional architecture of robotic joints (motor – transmission – load) by introducing in the power transmission chain some degree of compliance, in the form of off-the-shelf springs or elastic and deformable components. Depending on where and how these compliant elements are inserted in the transmission, many different architectures of compliant actuators arise. The objective of this work is to analyze these different architectures from a theoretical point of view, derive new optimal design techniques and methodologies and, finally, apply these techniques to design new prototypes of robotic actuators devoted to specific applications.

Advances in optical coherent transmissions and electrical compensation technologies have stimulated the exploration of novel optical network architectures. Filterless optical backbone networks (F-OBNs) eliminate or minimize the usage of active photonic reconfigurable components, which is also referred to as passive OBN. By introducing passive splitters and combiners to interconnect the fiber links, this type of networks have been proposed as a cost- and energy-efficient alternative to active optical switching networks. However, F-OBN suffers from a constraint on wavelength reuse due to its broadcast nature. Consequently, this architecture always requires more resources, i.e. higher number of wavelengths, than the active optical switching networks. To address this issue, another passive approach for optical core network, i.e., semi-filterless OBN (SF-OBN) has been introduced. By utilizing passive colored components, e.g., Fiber Bragg Grating (FBG), red/blue filters, etc., at some selected nodes, the SF-OBN is able to improve the wavelength usage while keeping the similar level on cost and energy consumption as FOBN. In this thesis project, an optimization model for wavelength assignment and filter placement in SF-OBN has been developed. F-OBN can be considered as a special case without any filter in SF-OBN. Using integer linear programming (ILP) formulation, the model aims to minimize the total number of wavelengths required in the network given the number of filters. Furthermore, wavelength usage, cost and energy consumption in active optical switching, F-OBN and SF-OBN have been compared in order to evaluate the performance of the each network architecture.

This thesis solves estimation and control problems in computational neuroscience, mathematically dealing with the first-passage times of diffusion stochastic processes. We first derive estimation algorithms for model parameters from first-passage time observations, and then we derive algorithms for the control of first-passage times. Finally, we solve an optimal design problem which combines elements of the first two: we ask how to elicit first-passage times such as to facilitate model estimation based on said first-passage observations. The main mathematical tools used are the Fokker-Planck partial differential equation for evolution of probability densities, the Hamilton-Jacobi-Bellman equation of optimal control and the adjoint optimization principle from optimal control theory. The focus is on developing computational schemes for the solution of the problems. The schemes are implemented and are tested for a wide range of parameters.

Thesis (Ph. D.) -- University of Maryland, College Park, 2004.
Thesis research directed by: Electrical Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

Thesis (M. S.)--Biomedical Engineering, Georgia Institute of Technology, 2009.
Committee Co-Chair: Butera, Robert; Committee Co-Chair: Paninski, Liam; Committee Member: Isbell, Charles; Committee Member: Rozell, Chris; Committee Member: Stanley, Garrett; Committee Member: Vidakovic, Brani.

Within the telecommunication business there are a lot of different hardware designs made for outside locations. Many of these outdoor products contain sensitive electronic equipment and all of these designs must be able to function in extreme environments. They might be mounted on the ground, on a wall or on masts at varying altitudes. They need to be enclosed and protected against blizzards, moisture, sandstorms, earthquakes, dust and similar contaminations or nature phenomena in order to assure a reliable and proper function of the device.

To delimit this thesis the focus is completely set on outdoor enclosures with hinged doors. The sealing solution for the enclosure door is crucial because it is the weakest link in the environmental protection. The aim with this thesis is to find a robust yet versatile sealing solution for Ericsson outdoor cabinets.

The sealing solution does not only concern the gasket design, it is in fact the entire principle when it comes to seal the door. Interesting features are choice of locking system, the positions of the hinges and other details which might affect the sealing of the enclosure door.

The project includes the whole product development process from pre-study to concept development and evaluation of proposal design. The pre-study contain extensive literature research, benchmark and a state of the art investigation. A number of concepts are generated, screened, compared and ranked with systematic concept development methods. At last, one final concept is selected for further development. The chosen sealing solution is refined and a functional model is made. A simple prototype of the sealing solution is designed, manufactured and tested to validate the functionality of the concept.

An economical analysis is performed in order to approximate the manufacturing cost of the gasket proposed in the sealing solution and to compare the unit price for different batch sizes. The water intrusion test indicates that the solution seems promising and that the result is a simple and robust sealing solution that easily can be implemented on various enclosure types.

Inom telecom-industrin finns det många typer av hårdvara som är konstruerad för att placeras utomhus. Många av dessa utomhusprodukter innehåller känslig elektronisk utrustning och alla dessa konstruktioner måste fungera i extrema miljöer. De kan monteras på marken, på väggar eller på master på olika höjder. De måste vara täta och skyddade mot snöstormar, fukt, sandstormar, jordbävningar, damm och liknande föroreningar eller naturfenomen för att säkerställa en tillförlitlig och korrekt funktion hos anordningen.

För att begränsa detta examensarbete är fokus helt inställt på utomhusskåp med gångjärnsupphända dörrar. Tätningslösningen för skåpdörren är kritisk eftersom den utgör den svagaste länken i väderskyddet. Målet med detta examensarbete är att hitta en robust men samtidigt mångsidig lösning för Ericssons utomhuskabinet.

Tätningslösningen handlar inte enbart om packningsutformningen utan den täcker faktiskt hela principen för hur dörren tätas. Intressanta delar är val av lås-lösning, placeringen av gångjärnen och andra detaljer som kan påverka tätningen av skåpsdörren.

Projektet behandlar hela produktutvecklingsprocessen från förstudie till konceptutveckling och utvärdering av föreslagen konstruktion. Förstudien innehöll en utförlig litteraturstudie, en ”benchmark” och en ”state of the art” undersökning. Ett antal koncept genererades, kontrollerades, jämfördes och rankades med hjälp av systematiska konceptutvecklingsmetoder. Till sist valdes ett slutgiltigt koncept ut för vidare utveckling. Den valda tätningslösningen förfinades och en funktionsmodell byggdes. En enkel prototyp av tätningslösningen konstruerades, tillverkades och testades för att validera funktionen hos konceptet.

En ekonomisk analys utfördes för att uppskatta tillverkningskostnaden för den föreslagna packningen i tätningslösningen och för att jämföra enhetspriset för olika seriestorlekar. Ett vattentäthetstest visar att lösningen verkar lovande och att resultatet är en enkel och robust tätningslösning som på ett enkelt sätt kan implementeras på olika skåpstyper.

The main area of emphasis in this study is to investigate the methods and technology for aerodynamic configuration sizing of missiles and to develop a software platform in MATLAB®
environment as a design tool which has an ability of optimizing the external configuration of missiles for a set of flight requirements specified by the user through a graphical user interface. A genetic algorithm based optimization tool is prepared by MATLAB is expected to help the designer to find out the best external geometry candidates in the conceptual design stage. Missile DATCOM software package is employed to predict the aerodynamic coefficients needed in finding the performance merits of a missile for each external geometry candidate by integrating its dynamic equations of motion. Numerous external geometry candidates are rapidly eliminated according to objectives and constraints specified by designers, which provide necessary information in preliminary design. In this elimination, the external geometry candidates are graded according to their flight performances in order to discover an optimum solution. In the conceptual design, the most important performance objectives related to the external geometry of a missile are range, speed, maneuverability, and control effectiveness. These objectives are directly related to the equations of motion of the missile, concluding that the speed and flight range are related to the total mass and the drag-to-lift ratio acting on missile. Also, maneuverability depends on the normal force acting on missile body and mass whereas the control effectiveness is affected by pitching moment and mass moment of inertia of missile. All of the flight performance data are obtained by running a two degree-of-freedom simulation. In order to solve the resulting multi-objective optimization problem with a set of constraint of linear and nonlinear nature and in equality and inequality forms, genetic-algorithm-based methods are applied. Hybrid encoding methods in which the integer configuration variables (i.e., nose shape and control type) and real-valued geometrical dimension (i.e., diameter, length) parameters are encoded in the same individual chromosome. An external configuration design tool (EXCON) is developed as a synthesis and external sizing tool for the subsonic cruise missiles. A graphical user interface (GUI), a flight simulator and optimization modules are embedded into the tool. A numerical example, the re-configuration problem of an anti-ship cruise missile Harpoon, is presented to demonstrate the accuracy and feasibility of the conceptual design tool. The optimum external geometries found for different penalty weights of penalty terms in the cost function are compared according to their constraint violations and launch mass values. By means of using EXCON, the launch mass original baseline Harpoon is reduced by approximately 30% without deteriorating the other flight performance characteristics of the original Harpoon.

At present the office real estate market in Sweden faces new challenges since the economic and real estate crisis of 2008-2010 years. Since the time of economic and real estate crisis of 2008-2010 years, the office real estate market has started to face new challenges. For example, office vacancy rates have increased significantly and challenges how to find the tenant for office premises became very actual. At the same time the demand for high quality office premises still exists on the market but with new requirements to the standards of the office working space. It is happening because the employees’ needs and requirements become more oriented to the comfort and safety of the working place. The employers try to keep and motivate employees by providing the most efficient and comfortable office space to work in and balance on cost-quality issues at the same time. In order to influence on demand from tenants’ and empower tenant search process the landlords have to use new, more competitive methods. The external design of the building and internal design of the office space in particular become more and more significant in leasing, sub-leasing and buying premises property purchase at the real estate office market. It is also useful and important because tenants can change the interior and design project upon their business needs and company’s strategies. The aim of this research paper is to set up the hypothesis that the office’s space design has a significant influence on tenant search process, plays the key role in so-called optimal office for tenant and tests above mentioned hypothesis by the empirical research study (method of questionnaire) among real “market players”-tenant representatives, consulting agencies and property owners. The location for the research and analysis activities is selected as Stockholm and Stockholm’s region, time frame is September - October 2010.

This thesis considers the optimal design of integrated batch processes, where plant design and scheduling as well as the detailed operating procedure of the individual processing steps are considered simultaneously. The State-Task Network (STN) representation of process recipes is augmented to facilitate a detailed characterisation of both the materials handled in a process and the transient behaviour of batch processes. Based on this STN characterisation, a mathematical formulation for the design of batch processes is presented. This results in a multistage optimal control problem with continuous variables corresponding to both the control variables in individual processing steps and the scheduling decisions. The optimisation objective is the maximisation of the net profit of the process, comprising material, utility and annualised capital cost. A decomposition approach is proposed for solving this problem. The approach is illustrated through a number of examples of significant complexity in the process recipe as well as the process model describing each unit operation. The above methodology is also extented to address the problem of designing processes that have to operate under limited resource availability. It also deals with the determination of the equipment requirements for the design or retrofit of batch plants.

A substantial proportion of biodiversity occurs on private land. In attempting to halt the decline of this biodiversity, voluntary contracts with private landowners have become a cornerstone of conservation investments. Taking a theoretical modelling approach, I investigate several issues in the design of voluntary conservation investments. First, I consider the implications for conservation of the informational advantage that landowners have in contract negotiations. I find that landowners have the potential to use their private information on conservation costs to make conservation considerably more expensive than suggested by estimates of opportunity costs relied on in previous studies. Next, I consider how cost structures affect the optimal distribution of nature reserves, showing that common cost structures used in conservation studies could lead to ineffective and inefficient reserves designs. Following on from this, by mapping the trade-off between conservation improvements and the increasing costs of achieving those improvements over various species distributions, I find that conservation will be most cost-effective when species are highly nested and conservation targets include widespread species. Finally, I analyse how socio-economic and ecological uncertainty affects the choice between short or long conservation contracts and reveal that socio-economic factors have a greater impact on contract choice than those of an ecological nature. Several important conclusions follow from these results. First, conservation science must deal with the complexities of conservation planning problems. Simplifications, such as assuming conservation costs equal opportunity costs, can result in distorted conservation priorities and unrealistic expectations. Second, incorporating in analyses the uncertainties inherent in conservation planning, such as uncertainties in cost and the future ecological condition of sites, is crucial for developing effective conservation strategies. Finally, the results reinforce the conclusion of other recent studies that variation in socio-economic aspects of conservation can be more important for effective conservation planning than variation in indicators of biodiversity.

We consider optimal design for changepoint problems with particular attention paid to situations where the only possible change is in the mean. Optimal design for changepoint problems has only been addressed in an unpublished doctoral thesis, and in only one journal article, which was in a frequentist setting. The simplest situation we consider is that of a stochastic process that may undergo a, change at an unknown instant in some interval. The experimenter can take n measurements and is faced with one or more of the following optimal design problems: Where should these n observations be taken in order to best test for a change somewhere in the interval? Where should the observations be taken in order to best test for a change in a specified subinterval? Assuming that a change will take place, where should the observations be taken so that that one may best estimate the before-change mean as well as the after-change mean? We take a Bayesian approach, with a risk based on squared error loss, as a design criterion function for estimation, and a risk based on generalized 0-1 loss, for testing. We also use the Spezzaferri design criterion function for model discrimination, as an alternative criterion function for testing. By insisting that all observations are at least a minimum distance apart in order to ensure rough independence, we find the optimal design for all three problems. We ascertain the optimal designs by writing the design criterion functions as functions of the design measure, rather than of the designs themselves. We then use the geometric form of the design measure space and the concavity of the criterion function to find the optimal design measure. There is a straightforward correspondence between the set of design measures and the set of designs. Our approach is similar in spirit, although rather different in detail, from that introduced by Kiefer. In addition, we consider design for estimation of the changepoint itself, and optimal designs for the multipath changepoint problem. We demonstrate why the former problem most likely has a prior-dependent solution while the latter problems, in their most general settings, are complicated by the lack of concavity of the design criterion function.
Nous considérons, dans cette dissertation, les plans d'expérience bayésiens optimauxpour les problèmes de point de rupture avec changement d'espérance. Un cas de pointde rupture avec changement d'espérance à une seule trajectoire se présente lorsqu'uneséquence de données est prélevée le long d'un axe temporelle (ou son équivalent) etque leur espérance change de valeur. Ce changement, s'il survient, se produit à unendroit sur l'axe inconnu de l'expérimentateur. Cet endroit est appelé "point derupture". Le fait que la position du point de rupture soit inconnue rend les tests etl'inférence difficiles dans les situations de point de rupture à une seule trajectoire.

This paper describes the so-called moving local regression, a special nonparametric statistical tool, which is firstly discussed thoroughly from analysis point of view. It avoids some drawbacks of its most serious alternatives: spline and kernel methods. The former lack computational simplicity and calculation speed, the latter may introduce high bias due to local constancy. The methods incorporation into the design framework is given, including the derivation of the necessary formulae. A Kiefer-Wolfowitz type equivalence theorem is formulated. Some geometrical examples illuminate the interrelations of the basic ingredients of the method and establish empirical relations to parametric techniques. (author's abstract)
Series: Forschungsberichte / Institut für Statistik

The structural nature of the world often provides a clear guide to where sought objects are likely to appear, as well as the kind of objects they may repeatedly appear in the presence of. The relationship between the targets, distractors and the landscape provides context, which ensures efficient search. This thesis will explore the dynamics of how knowledge of the environment ahead will inform search on future presentation of those scenes, as well as explore how several factors between individuals (such as cognitive resources, or tendencies towards anxiety) may influence search and learning processes. This thesis reports three studies using a new eye movement experimental paradigm termed the repeated scenes search task (RSST). This task presented scenes taken on a route around a suburban neighbourhood as search arrays, while participants searched for target superimposed in naturalistic locations. The scenes were presented on 8 occasions in each experiment, and performance improved with number of repeats. In the experimental chapters the influence of scene order on search was examined with targets appearing in several contingencies with relation to scene identity and compared between the scenes appearing in a consistent or randomised order. Subtle benefits to search were found when scenes were presented in a consistent order. The influence of boosting WM and inducing a state of anxiety upon participant responses (via more efficient eye movements) were also examined. The impact of these findings upon the general literature and with regard to individuals searching in dangerous environments are discussed, with the key finding that attentional networks, working memory and a state of anxiety are important factors to consider in search through familiar environments.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2013.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 63-64).
Myerson's seminal work provides a computationally efficient revenue-optimal auction for selling one item to multiple bidders. Generalizing this work to selling multiple items at once has been a central question in economics and algorithmic game theory, but its complexity has remained poorly understood. We answer this question by showing that a revenue-optimal auction in multi-item settings cannot be found and implemented computationally efficiently, unless ZPP = P # p. This is true even for a single additive bidder whose values for the items are independently distributed on two rational numbers with rational probabilities. Our result is very general: we show that it is hard to compute any encoding of an optimal auction of any format (direct or indirect, truthful or non-truthful) that can be implemented in expected polynomial time. In particular, under well-believed complexity-theoretic assumptions, revenue-optimization in very simple multi-item settings can only be tractably approximated. We note that our hardness result applies to randomized mechanisms in a very simple setting, and is not an artifact of introducing combinatorial structure to the problem by allowing correlation among item values, introducing combinatorial valuations, or requiring the mechanism to be deterministic (whose structure is readily combinatorial). Our proof is enabled by a flow interpretation of the solutions of an exponential-size linear program for revenue maximization with an additional supermodularity constraint.
by Christos Tzamos.
S.M.