While existing off-policy evaluation (OPE) methods typically estimate the value of a policy, in real-world applications, OPE is often used to compare and rank policies before deploying them in the real world. This is also known as the offline policy ranking problem. While one can rank the policies based on point estimates from OPE, it is beneficial to estimate the full distribution of outcomes for policy ranking and selection. This paper introduces Probabilistic Offline Policy Ranking that works with expert trajectories. It introduces rigorous statistical inference capabilities to offline evaluation, which facilitates probabilistic comparisons of candidate policies before they are deployed. We empirically demonstrate that POPR is effective for evaluating RL policies across various environments.

The focus of this dissertation is on improving decision-maker trade-offs and the development of a new constrained methodology for multiple response surface optimization. There are three key components of the research: development of the necessary conditions and assumptions associated with constrained multiple response surface optimization methodologies; development of a new constrained multiple response surface methodology; and demonstration of the new method. The necessary conditions for and assumptions associated with constrained multiple response surface optimization methods were identified and found to be less restrictive than requirements previously described in the literature. The conditions and assumptions required for a constrained method to find the most preferred non-dominated solution are to generate non-dominated solutions and to generate solutions consistent with decision-maker preferences among the response objectives. Additionally, if a Lagrangian constrained method is used, the preservation of convexity is required in order to be able to generate all non-dominated solutions. The conditions required for constrained methods are significantly fewer than those required for combined methods. Most of the existing constrained methodologies do not incorporate any provision for a decision-maker to explicitly determine the relative importance of the multiple objectives. Research into the larger area of multi-criteria decision-making identified the interactive surrogate worth trade-off algorithm as a potential methodology that would provide that capability in multiple response surface optimization problems. The ISWT algorithm uses an ε-constraint formulation to guarantee a non-dominated solution, and then interacts with the decision-maker after each iteration to determine the preference of the decision-maker in trading-off the value of the primary response for an increase in value of a secondary response. The current research modified the ISWT algorithm to develop a new constrained multiple response surface methodology that explicitly accounts for decision-maker preferences. The new Modified ISWT (MISWT) method maintains the essence of the original method while taking advantage of the specific properties of multiple response surface problems to simplify the application of the method. The MISWT is an accessible computer-based implementation of the ISWT. Five test problems from the multiple response surface optimization literature were used to demonstrate the new methodology. It was shown that this methodology can handle a variety of types and numbers of responses and independent variables. Furthermore, it was demonstrated that the methodology can be successful using a priori information from the decision-maker about bounds or targets or can use the extreme values obtained from the region of operability. In all cases, the methodology explicitly considered decision-maker preferences and provided non-dominated solutions. The contribution of this method is the removal of implicit assumptions and includes the decision-maker in explicit trade-offs among multiple objectives or responses.

Call number: LD2668 .T4 1961 A33

Call number: LD2668 .T4 1961 S85

ABSTRACT This study investigates the usefulness of spin-off historical and pro forma financial statements on the market’s ability to predict the firm’s future earnings. This study evaluates the spin-off historical and pro forma financial statements required for a Securities and Exchange Commission (SEC) regulation (Form 10-12(b). The study evaluates the question Are spin-off financial statements that reflect the firm’s adoption of the accounting required for the regulation (SEC form 10-12(b)) predictive of future earnings and thus useful? According to Statement of Financial Accounting Concepts No. 8 (SFAC8), the objective of general purpose financial reporting is that financial statements are useful to investors in making decisions about providing resources to the firm. Financial information is capable of making a difference in decisions if they have predictive value, confirmatory value or both. This is a quantitative, positivist, empirical archival study of final SEC Forms 10-12(b) for spin-off firms filed for listing on a public exchange of either NYSE or NASDAQ from the period of 2000 to 2014. The study evaluates if spin-off financial statements (historical and pro forma) are predictive, confirmatory or both. This study compares the performance of these companies to their peer group to assess if the results of this population are significantly different from the performance of the peer group in predicting future earnings. There were large variances between the historical, pro forma and Year 1 key financial statement elements. Variances ranged between 4% to over 500%. The difference in means in the population were significant between historical and pro forma net income as well as the change in shareholders equity and between historical and Year 1 shareholders’ equity. There was a significant difference in the leverage metric between historical leverage ratio and Year 1’s leverage ratio of the firms. The study found that the peer financial metrics were predictive of future earnings but the historical spin statements are not as predictive as their peer group. There was a significant difference in the predictability between the peer group and the historical spin metrics. The research supports the usefulness of the pro forma information. The research does not appear to support the usefulness of the historical information. Thus, the study provides the first empirical evidence that spin-off financial statements provide less information to the market. This is a new approach to study the application of accounting standards.

International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, Nevada / The space shuttle has been flying for seventeen years and NASA plans to fly it for many more. To meet the requirement of supporting future flights, NASA has undertaken a Shuttle Upgrades Program to improve various shuttle components. The avionics on the solid rocket booster (SRB) is one of the areas being upgraded. To develop avionics hardware, the environments that they are to encounter during flight must be defined to a higher degree of fidelity than is currently available. This paper describes the effort to determine these environments via the use of a commercial off the shelf data acquisition system.

International Telemetering Conference Proceedings / October 28-31, 1996 / Town and Country Hotel and Convention Center, San Diego, California / We have long used standards to guide the development process of software systems. Standards such as POSIX, X-Windows, SQL have become part of the language of software developers and have guided the coding of systems that are intended to be portable and interoperable. Standards also have a role to play in the integration of commercial off-the-shelf (COTS) products. At NASA's Goddard Space Flight Center, we have been participating on the Renaissance Team, a reengineering effort that has seen the focus shift from custom-built systems to the use of COTS to satisfy prime mission functions. As part of this effort, we developed a process that identified standards that are applicable to the evaluation and integration of products and assessed how those standards should be applied. Since the goal is to develop a set of standards that can be used to instantiate systems of differing sizes and capabilities, the standards selected have been broken into four areas: global integration standards, global development standards, mission development standards, and mission integration standards. Each of the areas is less restrictive than the preceding area in the standards that are allowed. This paper describes the process that we used to select and categorize the standards to be applied to Renaissance systems.

Thesis (MSc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Damping-off of rooibos (Aspalathus linearis), which is an important indigenous crop in South Africa, causes serious losses in rooibos nurseries and is caused by a complex of pathogens of which oomycetes, mainly Pythium, are an important component. The management of damping-off in organic rooibos nurseries is problematic, since phenylamide fungicides may not be used. Therefore, alternative management strategies such as rotation crops, compost and biological control agents, must be investigated. The management of damping-off requires knowledge, which currently is lacking, of the Pythium species involved, and their pathogenicity towards rooibos and two nursery rotation crops (lupin and oats). Pythium species identification can be difficult since the genus is complex and consists of more than 120 species. Species identification is, however, greatly facilitated by analyses of the internal transcribed spacer (ITS) regions. These regions, have also been used to divide the genus into 11 phylogenetic clades (A to K), with some clades, such as clade G, still being poorly characterised. The first aim of the study was to characterize 12 Pythium clade G isolates that were obtained from damped-off rooibos seedlings, along with six known clade G species. Subsequently, oligonucleotides were designed for differentiating two rooibos associated groups that may represent new taxons, for future use in DNA macro-array analyses. Phylogenetic analyses of the ITS region and a combined phylogeny of four gene regions (ITS, -tubulin and, COX1 and COX2 [cytochrome c oxidase subunits I and II]) identified five sub-clades within Pythium clade G. The rooibos isolates formed two groups, Rooibos group I (RB I) and II (RB II) that clustered into two groups within sub-clade 1 with good support (64%-89% bootstrap, 1.00 probability). The Pythium RB I isolates had P. iwayamai as its nearest neighbour, and may represent a new species. The Pythium RB II isolates had P. canariense and P. violae as their closest relatives and may, along with other isolates contained in the RB II sub-clade, represent several new species. Morphological analyses of the rooibos isolates were inconclusive, since the isolates all contained similar morphological characteristics that did not correspond to the description of known Pythium species. The Pythium RB I and II isolates were all non-pathogenic toward rooibos, lupin and oats seedlings. For each of the two rooibos groups, one newly developed oligonucleotide was able to differentiate the isolates from clade G reference isolates using DNA macro-array analyses. The second aim of the study was to determine the oomycetes species associated with rooibos in nurseries and in a native rooibos site, and their pathogenicity towards rooibos and two nursery rotation crops (lupin and oats). Since some isolates were shown to be nonpathogenic, another aim was to determine whether these isolates, along with the previously characterised non-pathogenic Pythium RB I and RB II isolates, could suppress pathogenic oomycetes. Characterisation of isolates from 19 nurseries and one native rooibos site revealed the presence of five Pythium species (P. acanthicum, P. irregulare, P. mamillatum, P. myriotylum, and P. pyrilobum) and Phytophthora cinnamomi. In nurseries, P. irregulare was the most common species (81%) followed by P. myriotylum (14%). Similarly, P. irregulare was also the most prevalent species (57%) in native rooibos, but P. pyrilobum (26%) was second most prevalent. Pathogenicity studies on rooibos showed that all species, except P. acanthicum, were highly virulent causing 100% damping-off. On lupin, P. acanthicum was also the only non-pathogenic species, with the other species being less virulent on lupin than on rooibos. Only P. irregulare, P. myriotylum, and P. pyrilobum were pathogenic towards oats, and were also less virulent on oats than on rooibos. On lupin and oats, not all off the isolates from a specific species was pathogenic. Non-pathogenic Pythium species (P. acanthicum, Pythium RB I and II) was only effective at suppressing disease on the less susceptible crops of lupin and oats, but not on rooibos. The third aim of the study was to investigate the management of rooibos damping-off using two composts (A and B), and composts combined with non-pathogenic Pythium species. Evaluation of the suppression by composts of Ph. cinnamomi and 29 Pythium isolates, which represented the four pathogenic Pythium rooibos species, showed that both composts were able to suppress some, but not all of the pathogenic Pythium isolates. Both composts were very effective at, and the highest percentage control was achieved, with suppression of Ph. cinnamomi. Most isolates of P. mamillatum and P. pyrilobum were suppressed by composts, whereas most P. irregulare (> 62%) and P. myriotylum (>50%) isolates were not suppressed. Non-pathogenic Pythium species combined with either of the two composts were able to significantly reduce damping-off caused by P. irregulare or a combination of pathogenic species (P. irregulare, P. mamillatum, P. myriotylum, P. pyrilobum, and Ph. cinnamomi), compared to than when only the pathogens were present. In the absence of non-pathogenic species, neither of the composts was able to suppress the aforementioned pathogenic isolates. This study has improved our knowledge of the oomycete species that are involved in rooibos damping-off, and has identified possible management strategies for use in organic nurseries. Several oomycete species are involved in causing damping-off and their differential virulence, and responses to being suppressed by composts, will require the use of integrated management strategies. Management strategies that showed promise include the combined use of compost and non-pathogenic Pythium taxons. The use of oats, which is susceptible to fewer oomycete isolates than rooibos, could also be valuable as a rotation crop. Altogether, knowledge obtained in this study can be used to (i) optimize integrated management strategies for organic nurseries, (ii) elucidate the mechanisms involved in disease suppression and (ii) develop molecular techniques, such as DNA macro-arrays and quantitative PCR (qPCR) for the rapid assessment of the species involved, and the quantification of inoculum in nursery soils. / AFRIKAANSE OPSOMMING: Omvalsiekte van rooibos (Aspalathus linearis), wat ‘n belangrike inheemse gewas in Suid-Afrika is, veroorsaak ernstige verliese in rooiboskwekerye, en word deur ‘n kompleks van patogene veroorsaak, waarvan oömysete, hoofsaaklik Pythium, ’n belangrike komponent is. Die bestuur van omvalsiekte in organiese rooiboskwekerye is problematies, aangesien fenielamied fungisiedes nie gebruik mag word nie. Alternatiewe bestuurstrategieë, soos rotasie-gewasse, kompos en biologiese beheer-agente, moet dus ondersoek word. Die bestuur van omvalsiekte vereis kennis, wat tans ontbreek, naamlik die Pythium spesies wat betrokke is, hul patogenisiteit teenoor rooibos, en twee kwekery rotasie-gewasse (lupiene en hawer). Pythium spesie-identifikasie kan moeilik wees aangesien die genus kompleks is en uit meer as 120 spesies bestaan. Spesie-identifikasie word egter grootliks vergemaklik deur analise van die interne getranskribeerde spasieerder (ITS) areas. Hierdie areas is ook gebruik om die genus in 11 filogenetiese “clades” (A tot K) te verdeel, met sommige “clades”, soos “clade” G, wat steeds swak gekarakteriseer is. Die eerste doelwit van die studie was om 12 Pythium “clade” G isolate te karakteriseer, wat vanaf omvalsiekte rooibossaailinge verkry is, tesame met ses bekende “clade” G spesies. Gevolglik is oligonukleotiede ontwerp ten einde twee rooibosgeassosieerde groepe, wat nuwe taksons kan verteenwoordig, te onderskei, en vir toekomstige gebruik in DNS makro-“array” analise. Filogenetiese analise van die ITS area en ‘n gekombineerde filogenie van vier geen-areas (ITS, -tubulien en, COX1 en COX2 [sitokroom c oksidase sub-eenhede I en II]) het vyf sub-“clades” binne Pythium “clade” G geïdentifiseer. Die rooibos isolate het twee groepe gevorm, Rooibos groep I (RB I) en II (RB II) wat twee groepe binne sub-“clade” 1 gevorm het, met goeie ondersteuning (64%-89% “bootstrap”, 1.00 waarskynlikheid). Die Pythium RB I isolate het P. iwayamai as sy naaste verwant, en mag ‘n nuwe spesie verteenwoordig. Die Pythium RB II isolate het P. canariense en P. violae as hul naaste verwante en mag, tesame met ander isolate wat in die RB II sub-“clade” ingesluit word, verskeie nuwe spesies verteenwoordig. Morfologiese analise van die rooibos-isolate was onbeslis, aangesien die isolate almal soortgelyke morfologiese kenmerke bevat het, wat nie met die beskrywing van bekende Pythium spesies ooreengestem het nie. Die Pythium RB I en II isolate was almal nie-patogenies teenoor rooibos-, lupien- en hawersaailinge. Vir elk van die twee rooibosgroepe, was een nuut-ontwikkelde oligonukleotied in staat om die isolate van “clade” G verwysingsisolate te differensieer, deur die gebruik van DNS makro-“array” analise. Die tweede doelwit van die studie was om die oömysete spesies wat met rooibos in kwekerye en in ‘n inheemse rooibos-area geassosieer word, te bepaal, en hul patogenisiteit teenoor rooibos en twee kwekery rotasie-gewasse (lupien en hawer). Aangesien van die isolate nie-patogenies was, was ’n ander doelwit om te bepaal of hierdie isolate, tesame met die voorheen gekarakteriseerde nie-patogeniese Pythium RB I en RB II isolate, patogeniese oömysete kan onderdruk. Karakterisering van isolate van 19 kwekerye en een inheemse rooibos-area, het op die teenwoordigheid van vyf Pythium spesies (P. acanthicum, P. irregulare, P. mamillatum, P. myriotylum, en P. pyrilobum) en Phytophthora cinnamomi gedui. P. irregulare was die mees algemene spesie (81%) in kwekerye, gevolg deur P. myriotylum (14%). Soortgelyk was P. irregulare ook die mees algemene spesie (57%) in inheemse rooibos, maar P. pyrilobum (26%) was tweede mees algemeen. Patogenisiteitstudies op rooibos het getoon dat alle spesies, behalwe P. acanthicum, hoogs virulent was en 100% omvalsiekte veroorsaak het. Op lupien was P. acanthicum ook die enigste nie-patogeniese spesie, terwyl die ander spesies minder virulent op lupien as op rooibos was. Slegs P. irregulare, P. myriotylum en P. pyrilobum was patogenies teenoor hawer, en was ook minder virulent op hawer as op rooibos. Op lupien en hawer was nie alle isolate van ‘n spesifieke spesie patogenies nie. Nie-patogeniese Pythium spesies (P. acanthicum, Pythium RB I en II) was slegs effektief om siekte op die minder vatbare gewasse, lupien en hawer, te onderdruk, maar nie op rooibos nie. Die derde doelwit van die studie was om die bestuur van rooibos omvalsiekte te ondersoek, deur die gebruik van twee tipes kompos (A en B), en kompos gekombineer met nie-patogeniese Pythium spesies. Evaluasie van die onderdrukking deur kompos van Ph. cinnamomi en 29 Pythium isolate, wat die vier patogeniese Pythium rooibosspesies verteenwoordig het, het getoon dat beide tipes kompos in staat was om sommige, maar nie al die patogeniese Pythium isolate, te onderdruk nie. Beide tipes kompos was baie effektief, en die hoogste persentasie beheer was met die onderdrukking van Ph. cinnamomi verkry. Meeste isolate van P. mamillatum en P. pyrilobum is deur kompos onderdruk, terwyl meeste P. irregulare (> 62%) en P. myriotylum (>50%) isolate nie onderdruk is nie. Nie-patogeniese Pythium spesies, in kombinasie met enige van die twee tipes kompos, was in staat om betekenisvol omvalsiekte veroorsaak deur P. irregulare, of in ’n kombinasie met patogeniese spesies (P. irregulare, P. mamillatum, P. myriotylum, P. pyrilobum, en Ph. cinnamomi), te verminder, in vergelyking met wanneer slegs die patogene aanwesig was. In die afwesigheid van nie-patogeniese spesies, was nie een van die tipes kompos in staat om die voorafgenoemde patogeniese isolate te onderdruk nie. Hierdie studie het ons kennis rakende die oömysete spesies betrokke in rooibos omvalsiekte verbeter, en het moontlike bestuurstrategieë geïdentifiseer wat in organiese kwekerye gebruik kan word. Verskeie oömysete spesies is betrokke in die oorsaak van omvalsiekte, en hul verskille in virulensie, en reaksies op onderdrukking deur kompos, sal die gebruik van geïntegreerde bestuurstrategieë vereis. Bestuurstrategieë wat belofte toon, sluit die gekombineerde gebruik van kompos en nie-patogeniese Pythium taksons in. Die gebruik van hawer, wat vir minder oömysete isolate as rooibos vatbaar is, kan ook waardevol as ‘n rotasie-gewas wees. Tesame, kan kennis wat in die studie opgedoen is gebruik word om (i) geïntegreerde bestuurstrategieë vir organiese kwekerye te optimaliseer, (ii) die meganismes betrokke in siekte-onderdrukking te bepaal, en (iii) molekulêre tegnieke, soos DNS makro- “arrays” en kwantitatiewe PKR (qPKR) te ontwikkel vir die vinnige bepaling van die spesies betrokke, en die kwantifisering van inokulum in kwekery-gronde.

Ett företags kapitalstruktur är förhållandet mellan företagets eget kapital och skulder. Det finns huvudsakligen två teorier som förklarar företagens val av kapitalstruktur, trade off-teorin som utgår från en optimal skuldsättningsgrad och pecking order-teorin som utgår från företagets lönsamhet. Tidigare forskning ger ingen entydig bild av vilken teori som bäst förklarar kapitalstrukturen hos företag, dessutom saknas forskning på svenska företag. Syftet med denna studie är att undersöka vilken av teorierna som bäst förklarar större svenska företags kapitalstruktur. Vidare är syftet att undersöka om teorierna förklarar kapitalstrukturen olika bra beroende på vilken bransch som studeras. En multipel regressionsmodell med fem oberoende variabler som förklarar skuldsättningsgraden används. Resultatet visar på att det inte går att säkerställa vilken av teorierna som bäst förklarar kapitalstrukturen hos svenska större företag då vi finner stöd för båda teorierna. Vidare ger resultatet stöd för att de två teoriernas tillämpbarhet varierar beroende på vilken bransch som undersöks.

The electrical efficiency of telecommunication power supplies is increasing to meet customer demands for lower total cost of ownership. Increased capital cost can now be justified if it enables sufficiently large energy savings, allowing the use of topologies and devices previously considered unnecessarily complex or expensive. Silicon carbide Schottky diodes have already been incorporated into commercial power supplies as expensive, but energy saving components. This thesis pursues the next step of considering silicon carbide transistors for use in telecommunications power converters. A range of silicon carbide transistors was considered with a primary focus on recently developed, normally-off, junction field effect transistors. Tests were devised and performed to uncover a number of previously unpublished characteristics of normally-off silicon carbide JFETs. Specifically, unique reverse conduction and associated gate current draw relationships were measured as well as the ability to block small reverse voltages when a negative gate-source voltage is applied. Reverse recovery-like characteristics were also measured and found to be superior to those of silicon MOSFETs. These characteristics significantly impact the steps that are required to maximize efficiency with normally-off SiC JFETs in circuits where synchronous rectification or bidirectional blocking is performed. A gate drive circuit was proposed that combines a number of recommendations to achieve rapid and efficient switching of normally-off SiC JFETs. Specifically, a low transient output impedance was provided to achieve rapid turn-on and turn-off transitions as well as a high dc output impedance to limit the steady state drive current while sustaining the turned-on state. A prototype circuit was constructed using building blocks that are typically found in single chip MOSFET drivers. The circuit was shown to operate well from a single supply, alleviating the need for a split supply such as that required by many published JFET drive circuits. This demonstrated a proof of concept for a single chip JFET driver solution. An active power factor correction circuit topology was extensively modelled and a prototype designed and tested to verify the model. The circuit was able to operate at switching frequencies in excess of 100kHz when using SiC JFETs, whereas silicon MOSFETs could only achieve switching frequencies of several kHz before switching losses became excessive. The circuit was designed as the dc equivalent for a 2kW, 230V AC input power converter with a split +/-400V dc output. A commercial single phase telecommunications power converter was modified to utilise normally-off SiC JFETs in its power factor correction circuit. The converter was tested and found to achieve similar electrical efficiency with 1200V SiC JFETs to that achieved with 600V silicon MOSFETs. The performance of the 1200V SiC JFETs in this application was also compared to that of 900V silicon MOSFETs and found to be superior. Finally, a prototype three-phase cyclo-converter was modified to use 1200V normallyoff SiC JFETs in place of 600V silicon MOSFETs and found to achieve similar electrical efficiency to the silicon MOSFETs in a 208V three phase system. These results strongly indicate that the 1200V SiC JFETs would provide better performance than 900V silicon MOSFETs in a 400V three phase system (that had been considered for commercial development).