Thesis (DPhil)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: In this dissertation I enquire into the status, scope and limits of human knowledge, given the fact that our perceptual and cognitive faculties are the product of evolution by natural selection. I argue that the commonsense representations these faculties provide us with yield a particular, species-specific scope on the world that does not ‘correspond’ in any straightforward way to the external world. We are, however, not bound by these commonsense representations. This particular, species-specific view of the world can be transgressed. Nevertheless, our transgressing representations remain confined to the conceptual space defined by the combinatorial possibilities of the various representational tools we possess. Furthermore, the way in which we fit representations to the external world is by means of our biologically determined epistemic orientation. Based on the fact that we are endowed with a particular set of perceptual and cognitive resources and are guided by a particular epistemic orientation, I conclude that we have a particular cognitive relation to the world. Therefore, an accurate representation for us is a particular fit (our epistemic orientation) with particular means (our perceptual and cognitive resources). / AFRIKAANSE OPSOMMING: Hierdie tesis handel oor die aard, omvang en limiete van kennis, gegewe dat ons perseptuele en kognitiewe vermoëns die resultaat van evolusie deur middel van natuurlike seleksie is. Eerstens, word daar geargumenteer dat die algemene voorstellings wat hierdie vermoëns aan ons bied ‘n partikuliere, spesie-spesifieke siening van die wêreld aan ons gee, wat nie op ‘n eenvoudige manier korrespondeer aan die werklikheid nie. Ons is egter nie gebonde aan hierdie voorstellings nie. Hierdie partikuliere, spesie-spesifieke siening van die wêreld kan oorskry word. Ons is egter wel beperk tot die konseptuele ruimte wat gedefinieër word deur die kombinatoriese moontlikhede van die voorstellingsmiddele tot ons beskikking. Verder word die manier waarop ons hierdie voorstellings aan die wêreld laat pas deur ons biologies gedetermineerde epistemiese oriëntasie bepaal. Dus, gegewe dat ons ‘n spesifieke stel perseptuele en kognitiewe vermoëns het en deur ‘n spesifieke kognitiewe epistemiese oriëntasie gelei word, staan ons in ‘n spesifieke kognitiewe verhouding tot die wêreld. ‘n Akkurate voorstelling (m.a.w. kennis vir ons) is om spesifieke vermoëns (perseptuele en kognitiewe vermoëns) op ‘n spesifieke manier (epsitemiese oriëntasie) aan die wêreld te laat pas.

Heterogeneity in modern datacenters is on the rise, in hardware resource characteristics, in workload characteristics, and in dynamic characteristics (e.g., a memoryresident copy of input data). As a result, which machines are assigned to a given job can have a significant impact. For example, a job may run faster on the same machine as its input data or with a given hardware accelerator, while still being runnable on other machines, albeit less efficiently. Heterogeneity takes on more complex forms as sets of resources differ in the level of performance they deliver, even if they consist of identical individual units, such as with rack-level locality. We refer to this as combinatorial heterogeneity. Mixes of jobs with strict SLOs on completion time and increasingly available runtime estimates in production datacenters deepen the challenge of matching the right resources to the right workloads at the right time. In this dissertation, we hypothesize that it is possible and beneficial to simultaneously leverage all of this information in the form of declaratively specified spacetime soft constraints. To accomplish this, we first design and develop our principal building block—a novel Space-Time Request Language (STRL). It enables the expression of jobs’ preferences and flexibility in a general, extensible way by using a declarative, composable, intuitive algebraic expression structure. Second, building on the generality of STRL, we propose an equally general STRL Compiler that automatically compiles STRL expressions into Mixed Integer Linear Programming (MILP) problems that can be aggregated and solved to maximize the overall value of shared cluster resources. These theoretical contributions form the foundation for the system we architect, called TetriSched, that instantiates our conceptual contributions: (a) declarative soft constraints, (b) space-time soft constraints, (c) combinatorial constraints, (d) orderless global scheduling, and (e) in situ preemption. We also propose a set of mechanisms that extend the scope and the practicality of TetriSched’s deployment by analyzing and improving on its scalability, enabling and studying the efficacy of preemption, and featuring a set of runtime mis-estimation handling mechanisms to address runtime prediction inaccuracy. In collaboration with Microsoft, we adapt some of these ideas as we design and implement a heterogeneity-aware resource reservation system called Aramid with support for ordinal placement preferences targeting deployment in production clusters at Microsoft scale. A combination of simulation and real cluster experiments with synthetic and production-derived workloads, a range of workload intensities, degrees of burstiness, preference strengths, and input inaccuracies support our hypothesis that leveraging space-time soft constraints (a) significantly improves scheduling quality and (b) is possible to achieve in a practical deployment.

Detta examenarbete redogör och belyser hur en lokalisering av förbättringsområde inom en producerande process kan ske. Rapporten har sin grund i ett sökande efter var en effektivisering kan genomföras. Hur uppnås målet och finns det metoder som kan appliceras på en diversifierad mängd områden. Många företag och verksamheter har idag ett stort behov av förbättring. Detta för att kunna överleva det allt tuffare klimatet på marknaden. En konkurrenskraftig produkt både är pris- och kvalitetsmässigt i framkant krävs för att nå marknadsandelar. Undersökningen grundar sig i en nulägesanalys på ett verkligt företag för att göra undersökningen så rättvisande som möjligt. Rapporten redogör även för en undersökning av olika metoder från tidigare forskning inom lean och theory of constraints. Genom att använda sig av verktyg som 5S, JIT och koncept i sin helhet som lean och TOC kan en lokalisering av förbättringsområden ske. Genom att studera koncept som lean och TOC lokaliseras förbättringsområden med hjälp av deras grundläggande filosofi. De delar som finns i produktionen som bör tas i beaktning är omställningar, slöserier och begränsningar. Dessa tre faktorer påverkar en process negativt om de inte lokaliseras och effektiviseras eller elimineras. Den metod som bör användas varierar från fall till fall och det är av yttersta vikt att hitta en metod som fungerar bra för den egna processen. Det första som bör göras är att bli väl påläst och vara tydlig med vad metoden ska bidra med. De metoder som denna studie har granskat och visat sig fungera i en producerande process är: 5S, JIT, SMED samt TOC:s läran om flaskhalsar och leans läran om slöserier. Metoderna bidrar med olika sätt för lokalisering av förbättringsområden. / This report describes and illustrates how to locate an area for improvement in a producing process. The report is based on a search for where the streamlining can be performed. How can we achieve the goal, and are there methods that can be applied to a diverse range of areas. Many companies and businesses today have a great need for improvement, this in order to survive the increasingly tougher climate on the market. Where you now must be able to deliver a competitive product that is both price and quality at the forefront. The study is based on a situation analysis on a real business company, with a producing process, to do the survey as accurate as possible. The report also describes a study of the different methods from previous research in lean and TOC. By using tools such as 5S, JIT and concepts in its entirety as lean and TOC can you locate each one's areas of improvement. By studying the concept of lean and TOC makes you localize areas of improvement with the help of their basic philosophy. The parts that are in production that should be taken into consideration are transitions, waste and limitations. These three factors affect the process negatively even if they are not localized and streamlined or eliminated. The method you should use will vary from case to case and it is important that you find a method that works well for one's own process. The first thing you should always do is to be well prepared and be clear about what you want the method to contribute with. The methods of this study has been reviewed and concluded that: 5S, JIT, SMED and TOC's doctrine of bottlenecks and leans doctrine of wastes will work. All these practices help with ways for locating areas of improvement.

Doctor of Philosophy / Department of Physics / Bharat Ratra / The expansion rate of the Universe changes with time, initially slowing (decelerating) when the universe was matter dominated, because of the mutual gravitational attraction of all the matter in it, and more recently speeding up (accelerating). A number of cosmological observations now strongly support the idea that the Universe is spatially flat (provided the dark energy density is at least approximately time independent) and is currently undergoing an accelerated cosmological expansion. A majority of cosmologists consider ``dark energy" to be the cause of this observed accelerated cosmological expansion. The ``standard" model of cosmology is the spatially-flat $\Lambda$CDM model. Although most predictions of the $\Lambda$CDM model are reasonably consistent with measurements, the $\Lambda$CDM model has some curious features. To overcome these difficulties, different Dark Energy models have been proposed. Two of these models, the XCDM parametrization and the slow rolling scalar field model $\phi$CDM, along with ``standard" $\Lambda$CDM, with the generalization of XCDM and $\phi$CDM in non-flat spatial geometries are considered here and observational data are used to constrain their parameter sets. In this thesis, we start with a overview of the general theory of relativity, Friedmann's equations, and distance measures in cosmology. In the following chapters we explain how we can constrain the three above mentioned cosmological models using three data sets: measurements of the Hubble parameter $H(z)$, Supernova (SN) apparent magnitudes, and the baryonic acoustic oscillations (BAO) peak length scale, as functions of redshift $z$. We then discuss constraints on the deceleration-acceleration transition redshift $z_{\rm da}$ using unbinned and binned $H(z)$ data. Finally, we incorporate the spatial curvature in the XCDM and $\phi$CDM model and determine observational constraints on the parameters of these expanded models.

O presente estudo investiga os impactos da redução nas restrições financeiras para a captação de dívidas no mercado de capitais brasileiro sobre o financiamento e os investimentos de companhias brasileiras de capital aberto e fechado, não financeiras. Empiricamente, o estudo interpreta que a Instrução CVM nº 476, vigente a partir do ano de 2009, que trata das ofertas públicas de valores mobiliários distribuídas com esforços restritos, pode ter reduzido as restrições financeiras enfrentadas por sociedades anônimas brasileiras, dado que tal mudança regulatória, comparativamente ao mecanismo tradicional para o acesso ao mercado de capitais nacional, reduziu os custos de emissão de debêntures (valor mobiliário em foco) no mercado de capitais nacional, tornou o acesso ao capital mais rápido e reduziu uma barreira regulatória para as sociedades anônimas fechadas, impedidas de realizar emissões públicas de debêntures no mercado de capitais nacional antes da CVM 476. Sobre o financiamento, foram propostas as hipóteses de que a CVM 476, isto é, a redução nas restrições financeiras, possibilitou que as companhias aumentassem sua alavancagem total, devido ao aumento da alavancagem de longo prazo. Sobre os investimentos, foram propostas hipóteses relacionadas ao caixa e aos investimentos em ativos de longo prazo. Em relação ao caixa, a hipótese propõe que a CVM 476 possibilitou que as companhias mantivessem menores saldos em caixa, devido à redução no componente de restrição financeira da política de caixa. Sobre os investimentos em ativos de longo prazo, a hipótese propõe que a CVM 476 possibilitou que companhias aumentassem tais investimentos, pois poderiam tornar-se menos dependentes da geração interna de recursos e de outras fontes de capitais. É esperado que tais efeitos sejam maiores para as sociedades anônimas de capital fechado, pois, a priori, espera-se que tais companhias sejam mais restritas financeiramente do que as abertas, especialmente no que se refere ao acesso ao mercado de capitais nacional. Para investigar as hipóteses, foram realizadas duas abordagens empíricas. Na primeira, as emissões de debêntures pela CVM 476 foram adicionadas aos modelos como a variável explicativa de interesse, sendo representada por uma variável binária que indica a emissão das debêntures, no ano da emissão. Na segunda abordagem, a CVM 476 é tratada como um experimento natural que pode ter provocado um choque exógeno nas restrições financeiras, ou seja, uma diminuição nas restrições financeiras enfrentadas pelas sociedades anônimas brasileiras de capital aberto e fechado (as companhias tratadas), de modo que, nesta abordagem, as empresas de responsabilidade limitada são definidas como grupo de controle. Os resultados são compatíveis com as hipóteses relativas ao financiamento, isto é, a CVM 476 possibilitou o aumento da alavancagem total e de longo prazo das companhias, de modo que há evidências que tais efeitos sejam maiores para as sociedades anônimas fechadas. Por outro lado, não foram encontradas evidências robustas que indiquem que a CVM 476 possibilitou, de forma ampla, ajustes no caixa e nos investimentos em ativos de longo prazo de companhias afetadas pela Instrução / This study analyses the effects of reducing financing constraints to debt issuance in Brazilian bond market on financing and investments of Brazilian public and private non-financial companies. Empirically, this study interprets that CVM Act nº 476, in force since 2009, which deals with public issuance of securities issued with restricted efforts, may have reduced financing constraints faced by Brazilian companies, since this Act, compared to the traditional mechanism to access Brazilian bond market, reduced issuance costs of debentures in domestic bond market, made the access to capital faster and reduced a regulatory barrier for private companies, restricted from conducting public issues of debentures in domestic bond market before CVM 476. The hypotheses related to financing propose that CVM 476, that is, the reduction in financing constraints, allowed companies to increase total leverage, due to the increase in long-term leverage. Regarding investments, hypotheses related to cash holdings and investments in long-term assets were proposed. The hypothesis concerning cash proposes that CVM 476 allowed companies to maintain lower cash holdings, due to the reduction in financing constraint component of the cash policy. Regarding investments in long-term assets, the hypothesis proposes that CVM 476 allowed companies to increase their investments, since they could become less dependent on internally generated cash flow and other sources of capital. These effects are expected to be greater for private companies, since these companies are expected to be more financially constrained than public companies, especially with regard to the access to the domestic bond market. Two empirical approaches were employed to investigate the hypotheses. In the first one, debentures issues according to CVM 476 were added to the models as the explanatory variable of interest, and is represented by a dummy variable that indicates the issuance of the debentures, in the year of the issue. In the second approach, CVM 476 is analyzed as a natural experiment that may have caused an exogenous shock in financing constraints, that is, a decrease in financing constraints faced by Brazilian public and private companies (treatment group) and, in this approach, limited liability firms are defined as the control group. The results are compatible with the hypotheses regarding financing, that is, CVM 476 made possible the increase in total and long-term leverage of the companies, and there is evidence that these effects are greater for private companies. On the other hand, no robust evidence was found that indicate the CVM 476 made possible extensive adjustments in cash holdings and investments in long-term assets of the companies treated by CVM 476.

Student Number 9705165A Master of Arts in Forced Migration Studies Faculty of Humanities / Objective: To identify and investigate barriers faced by Somali forced migrants when accessing health care in Johannesburg. In particular, the study seeks to compare perceptions of health personnel and migrants as to the nature of such access constraints. Design and Methods: The study made use of semi-structured and in-depth interviews with a snowball sample of health personnel and migrants. Ten health personnel were interviewed and twenty migrants (ten male and ten female). Results: Constraints of language and xenophobia were identified by both health personnel and forced migrant interviewed. Constraints related to the shortage of resources and the poor functioning of the referral system are experienced by all users of the public health system, irrespective of their nationality. No mention was made of traditional or allopathic medicine. Conclusions: There exists a gap between the access to health care guaranteed in the Refugees Act and practices at facility level. There are many similarities across interviews in the constraints identified by migrants and some agreement in the constraints identified by migrants and health personnel. These results confirm that migrants experience a fairly severe level of constraint when attempting to utilize formal health care services in Johannesburg.

O intento do trabalho é verificar se empresas com ações negociadas na Bovespa enfrentam restrição ao crédito. A análise de painel com base em dados de balanço patrimonial para o período de 2001 a 2005 revelou que, diferentemente do que se esperava, empresas de grande porte apresentam maior dependência dos fluxos de caixa para efetivar seus investimentos. Todavia, há argumentos teóricos na literatura que fundamentam esses resultados, bem como outras evidências empíricas semelhantes. / The paper focuses on evaluating whether Brazilian listed firms have faced financial constraints. Relying on data over the period 2001-2005, a panel data analysis was carried out, but the evidence raised turned out differently from the initially expected: large firms are more sensitive to cash flows to undertake their investment than smaller ones. Nonetheless, the recent literature provides theoretical rationale to deal with those findings as well as empirical evidence consistent with them.

O intento do trabalho é verificar se empresas com ações negociadas na Bovespa enfrentam restrição ao crédito. A análise de painel com base em dados de balanço patrimonial para o período de 2001 a 2005 revelou que, diferentemente do que se esperava, empresas de grande porte apresentam maior dependência dos fluxos de caixa para efetivar seus investimentos. Todavia, há argumentos teóricos na literatura que fundamentam esses resultados, bem como outras evidências empíricas semelhantes. / The paper focuses on evaluating whether Brazilian listed firms have faced financial constraints. Relying on data over the period 2001-2005, a panel data analysis was carried out, but the evidence raised turned out differently from the initially expected: large firms are more sensitive to cash flows to undertake their investment than smaller ones. Nonetheless, the recent literature provides theoretical rationale to deal with those findings as well as empirical evidence consistent with them.

<p>In order to design robust controllers, H-infinity synthesis is a common tool to use. The controllers that result from these algorithms are typically of very high order, which complicates implementation. However, if a constraint on the maximum order of the controller is set, that is lower than the order of the plant, the problem is no longer convex and it is then relatively hard to solve. These problems become very complex, even when the order of the system to be controlled is low.</p><p>The approach used in the thesis is based on formulating the constraint on the maximum order of the plant as a polynomial equation. By using the fact that the polynomial is non-negative on the feasible set, the problem is reformulated as an optimization problem where the nonconvex polynomial function is to be minimized over a convex set defined by linear matrix inequalities.</p><p>To solve this optimization problem, two methods have been proposed. The first method is a barrier method and the second one is a method based on a primal-dual framework. These methods have been evaluated on several problems and compared with a well-known method found in the literature. To motivate this choice of method, we have made a brief survey of available methods available for solving the same or related problems.</p><p>The proposed methods emerged as the best methods among the three for finding lower order controllers with the same or similar performance as the full order controller. When the aim is to find the lowest order controller with no worse than +50% increase in the closed loop H-infinity norm, then the three compared methods perform equally well.</p>

Aircrafttrajectory optimization is traditionally used forminimizing fuel consumption or time when going from one flightstate to another. This thesis presents a possible approach toincorporate tactical constraints in aircraft trajectoryoptimization. The stealth technology of today focuses on making thetactics already in use more effective. Since tactics andstealth are closely interrelated, new and better results may beobtained if both aspects are considered simultaneously. Simplyreducing the radar cross section area in some directionswithout considering tactical aspects may result in little, ifany, improvement. Flight tests have been performed in cooperation withEricsson Microwave Systems and the Swedish Air Force FlightAcademy. The aircraft used was the subsonic jet trainer Saab105, designated SK60 by the Swedish Air Force. The results showa decrease of 40% in the time interval between the instant theaircraft was first detected until it could pass above the radarstation. This corresponds to a reduced radar cross section(RCS) in the direction from the aircraft to the radar of almost90%, if classical RCS reduction techniques would have beenapplied. If a modern aircraft with stealth properties would be used,the proposed methodology is believed to increase the possibleimprovements further. This is because the variation of themagnitude of RCS in different directions is greater for a shapeoptimized aircraft, which is the property exploited by thedeveloped method. The methods presented are indeed an approach utilizing theideas of the network centric warfare (NCW) concept. Themethodology presented depends on accurate information about theadversary, while also providing up-to-date information to theother users in the information network. The thesis focuses on aircraft but the methods are generaland may be adapted for missiles, shipsor land vehicles. Theproposed methods are also economically viable since they areuseful for existing platforms without costly modifications. Themethods presented are not limited to radar threats only. Thereasons for using radar in this thesis are the availablenon-classified data and that radar is known to pose a majorthreat against aircraft.