Дисертації з теми "MWEL"

Dans ce mémoire, nous nous penchons sur les expressions polylexicales (EP) et leurs relations avec l’analyse syntaxique, la tâche qui consiste à déterminer les relations syntaxiques entre les mots dans une phrase donnée. Le défi que posent les EP dans ce contexte, par rapport aux expressions linguistiques régulières, provient de leurs propriétés parfois inattendues qui les rendent difficiles à gérer dans te traitement automatique des langues. Dans nos travaux, nous montrons qu’il est pourtant possible de profiter de ce cette caractéristique des EP afin d’améliorer les résultats d’analyse syntaxique. Notamment, avec les grammaires d’arbres adjoints (TAGs), qui fournissent un cadre naturel et puissant pour la modélisation des EP, ainsi qu’avec des stratégies de recherche basées sur l’algorithme A* , il est possible d’obtenir des gains importants au niveau de la vitesse sans pour autant détériorer la qualité de l’analyse syntaxique. Cela contraste avec des méthodes purement statistiques qui, malgré l’efficacité, ne fournissent pas de solutions satisfaisantes en ce qui concerne les EP. Nous proposons un analyseur syntaxique novateur qui combine les grammaires TAG avec La technique A*, axé sur la prédiction des EP, dont les fonctionnalités permettent des applications à grande échelle, facilement extensible au contexte probabiliste
In this thesis, we focus on multiword expressions (MWEs) and their relationships with syntactic parsing. The latter task consists in retrieving the syntactic relations holding between the words in a given sentence. The challenge of MWEs in this respect is that, in contrast to regular linguistic expressions, they exhibit various irregular properties which make them harder to deal with in natural language processing. In our work, we show that the challenge of the MWE-related irregularities can be turned into an advantage in practical symbolic parsing. Namely, with tree adjoining grammars (TAGs), which provide first-cLass support for MWEs, and A* search strategies, considerable speed-up gains can be achieved by promoting MWE-based analyses with virtually no loss in syntactic parsing accuracy. This is in contrast to purely statistical state-of-the-art parsers, which, despite efficiency, provide no satisfactory support for MWEs. We contribute a TAG-A* -MWE-aware parsing architecture with facilities (grammar compression and feature structures) enabling real-world applications, easily extensible to a probabilistic framework

Detailed thermodynamic, kinetic, geometric, and cost models are developed, implemented, and validated for the synthesis/design and operational analysis of hybrid solid oxide fuel cell (SOFC) – gas turbine (GT) – steam turbine (ST) systems ranging in size from 1.5 MWe to 10 MWe. The fuel cell model used in this thesis is based on a tubular Siemens-Westinghouse-type SOFC, which is integrated with a gas turbine and a heat recovery steam generator (HRSG) integrated in turn with a steam turbine cycle. The SOFC/GT subsystem is based on previous work done by Francesco Calise during his doctoral research (Calise, 2005). In that work, a HRSG is not used. Instead, the gas turbine exhaust is used by a number of heat exchangers to preheat the air and fuel entering the fuel cell and to provide energy for district heating. The current work considers instead the possible benefits of using the exhaust gases in an HRSG in order to produce steam which drives a steam turbine for additional power output. Four different steam turbine cycles are considered in this M.S. thesis work: a single-pressure, a dual-pressure, a triple-pressure, and a triple-pressure with reheat. The models have been developed to function both at design (full load) and off-design (partial load) conditions. In addition, different solid oxide fuel cell sizes are examined to assure a proper selection of SOFC size based on efficiency or cost. The thermoeconomic analysis includes cost functions developed specifically for the different system and component sizes (capacities) analyzed. A parametric study is used to determine the most viable system/component syntheses/designs based on maximizing total system efficiency or minimizing total system life cycle cost.
Master of Science

Dans un reacteur a eau pressurisee rep, quand un accident de reactivite se produit, apres ejection d'une grappe de controle, le flux augmente et genere une energie importante dans le combustible. Ceci produit une reactivite negative qui tend a reduire la reactivite introduite: c'est l'effet doppler. Par consequent, la puissance du reacteur decroit, bien avant la chute des barres par l'arret d'urgence, une seconde plus tard. L'abaque de surete elaboree dans cette etude est propre au rep 1300 mwe. Elle est effectuee par le modele de cinetique ponctuelle, utilisant une modelisation simplifiee de transfert de chaleur. Certaines hypotheses ont ete adoptees confirmant le conservatisme dans le trace des abaques dont les calculs sont bases sur les temperatures limites de la gaine et du combustible. Leurs valeurs sont prises dans le rapport de surete du palier p4. Le schema de calcul utilise est decrit par les etapes suivantes: a) calculs statiques, b) calculs de cinetique, c) calculs de thermique. Dans un rep, la temperature limite qui assure l'integrite du combustible doit etre inferieure a la temperature de fusion au centre de la pastille du combustible pour le transitoire initie par l'ejection d'une grappe de controle (range en classe 4 dans le rapport de surete). Elle est egale a 2800c (valeur theorique pour l'oxyde d'uranium). Dans le trace d'abaques, on a pris 2675c pour prendre en compte les incertitudes du schema de calcul utilise. L'analyse basee sur les calculs de cinetique tridimensionnelle pour les trois niveaux de puissance effectues par le code cronos1 (50% pn, 38% pn, 18% pn) pour le rep 1300 mwe, pilote en mode gris et gere par tiers, montre que les temperatures maximales atteintes pendant le transitoire initie par l'ejection de grappe de controle ne depassent pas les limites de surete, grace aux caracteristiques physiques de ce reacteur et a son systeme de protection

Analytical ultracentrifugation (AUC) has made an important contribution to polymer and particle characterization since its invention by Svedberg (Svedberg and Nichols 1923; Svedberg and Pederson 1940) in 1923. In 1926, Svedberg won the Nobel price for his scientific work on disperse systems including work with AUC. The first important discovery performed with AUC was to show the existence of macromolecules. Since that time AUC has become an important tool to study polymers in biophysics and biochemistry. AUC is an absolute technique that does not need any standard. Molar masses between 200 and 1014 g/mol and particle size between 1 and 5000 nm can be detected by AUC. Sample can be fractionated into its components due to its molar mass, particle size, structure or density without any stationary phase requirement as it is the case in chromatographic techniques. This very property of AUC earns it an important status in the analysis of polymers and particles. The distribution of molar mass, particle sizes and densities can be measured with the fractionation. Different types of experiments can give complementary physicochemical parameters. For example, sedimentation equilibrium experiments can lead to the study of pure thermodynamics. For complex mixtures, AUC is the main method that can analyze the system. Interactions between molecules can be studied at different concentrations without destroying the chemical equilibrium (Kim et al. 1977). Biologically relevant weak interactions can also be monitored (K ≈ 10-100 M-1). An analytical ultracentrifuge experiment can yield the following information: • Molecular weight of the sample • Number of the components in the sample if the sample is not a single component • Homogeneity of the sample • Molecular weight distribution if the sample is not a single component • Size and shape of macromolecules & particles • Aggregation & interaction of macromolecules • Conformational changes of macromolecules • Sedimentation coefficient and density distribution Such an extremely wide application area of AUC allows the investigation of all samples consisting of a solvent and a dispersed or dissolved substance including gels, micro gels, dispersions, emulsions and solutions. Another fact is that solvent or pH limitation does not exist for this method. A lot of new application areas are still flourishing, although the technique is 80 years old. In 1970s, 1500 AUC were operational throughout the world. At those times, due to the limitation in detection technologies, experimental results were obtained with photographic records. As time passed, faster techniques such as size exclusion chromatography (SEC), light scattering (LS) or SDS-gel electrophoresis occupied the same research fields with AUC. Due to these relatively new techniques, AUC began to loose its importance. In the 1980s, only a few AUC were in use throughout the world. In the beginning of the 1990s a modern AUC -the Optima XL-A - was released by Beckman Instruments (Giebeler 1992). The Optima XL-A was equipped with a modern computerized scanning absorption detector. The addition of Rayleigh Interference Optics is introduced which is called XL-I AUC. Furthermore, major development in computers made the analysis easier with the help of new analysis software. Today, about 400 XL-I AUC exist worldwide. It is usually applied in the industry of pharmacy, biopharmacy and polymer companies as well as in academic research fields such as biochemistry, biophysics, molecular biology and material science. About 350 core scientific publications which use analytical ultracentrifugation are published every year (source: SciFinder 2008 ) with an increasing number of references (436 reference in 2008). A tremendous progress has been made in method and analysis software after digitalization of experimental data with the release of XL-I. In comparison to the previous decade, data analysis became more efficient and reliable. Today, AUC labs can routinely use sophisticated data analysis methods for determination of sedimentation coefficient distributions (Demeler and van Holde 2004; Schuck 2000; Stafford 1992), molar mass distributions (Brookes and Demeler 2008; Brookes et al. 2006; Brown and Schuck 2006), interaction constants (Cao and Demeler 2008; Schuck 1998; Stafford and Sherwood 2004), particle size distributions with Angstrom resolution (Cölfen and Pauck 1997) and the simulations determination of size and shape distributions from sedimentation velocity experiments (Brookes and Demeler 2005; Brookes et al. 2006). These methods are also available in powerful software packages that combines various methods, such as, Ultrascan (Demeler 2005), Sedift/Sedphat (Schuck 1998; Vistica et al. 2004) and Sedanal (Stafford and Sherwood 2004). All these powerful packages are free of charge. Furthermore, Ultrascans source code is licensed under the GNU Public License (http://www.gnu.org/copyleft/gpl.html). Thus, Ultrascan can be further improved by any research group. Workshops are organized to support these software packages. Despite of the tremendous developments in data analysis, hardware for the system has not developed much. Although there are various user developed detectors in research laboratories, they are not commercially available. Since 1992, only one new optical system called “the fluorescence optics” (Schmidt and Reisner, 1992, MacGregor et al. 2004, MacGregor, 2006, Laue and Kroe, in press) has been commercialized. However, except that, there has been no commercially available improvement in the optical system. The interesting fact about the current hardware of the XL-I is that it is 20 years old, although there has been an enormous development in microelectronics, software and in optical systems in the last 20 years, which could be utilized for improved detectors. As examples of user developed detector, Bhattacharyya (Bhattacharyya 2006) described a Multiwavelength-Analytical Ultracentrifuge (MWL-AUC), a Raman detector and a small angle laser light scattering detector in his PhD thesis. MWL-AUC became operational, but a very high noise level prevented to work with real samples. Tests with the Raman detector were not successful due to the low light intensity and thus high integration time is required. The small angle laser light scattering detector could only detect latex particles but failed to detect smaller particles and molecules due to low sensitivity of the detector (a photodiode was used as detector). The primary motivation of this work is to construct a detector which can measure new physico-chemical properties with AUC with a nicely fractionated sample in the cell. The final goal is to obtain a multiwavelength detector for the AUC that measures complementary quantities. Instrument development is an option for a scientist only when there is a huge potential benefit but there is no available commercial enterprise developing appropriate equipment, or if there is not enough financial support to buy it. The first case was our motivation for developing detectors for AUC. Our aim is to use today’s technological advances in microelectronics, programming, mechanics in order to develop new detectors for AUC and improve the existing MWL detector to routine operation mode. The project has multiple aspects which can be listed as mechanical, electronical, optical, software, hardware, chemical, industrial and biological. Hence, by its nature it is a multidisciplinary project. Again by its nature it contains the structural problem of its kind; the problem of determining the exact discipline to follow at each new step. It comprises the risk of becoming lost in some direction. Having that fact in mind, we have chosen the simplest possible solution to any optical, mechanical, electronic, software or hardware problem we have encountered and we have always tried to see the overall picture. In this research, we have designed CCD-C-AUC (CCD Camera UV/Vis absorption detector for AUC) and SLS-AUC (Static Light Scattering detector for AUC) and tested them. One of the SLS-AUC designs produced successful test results, but the design could not be brought to the operational stage. However, the operational state Multiwavelength Analytical Ultracentrifuge (MWL-AUC) AUC has been developed which is an important detector in the fields of chemistry, biology and industry. In this thesis, the operational state Multiwavelength Analytical Ultracentrifuge (MWL-AUC) AUC is to be introduced. Consequently, three different applications of MWL-AUC to the aforementioned disciplines shall be presented. First of all, application of MWL-AUC to a biological system which is a mixture of proteins lgG, aldolase and BSA is presented. An application of MWL-AUC to a mass-produced industrial sample (β-carotene gelatin composite particles) which is manufactured by BASF AG, is presented. Finally, it is shown how MWL-AUC will impact on nano-particle science by investigating the quantum size effect of CdTe and its growth mechanism. In this thesis, mainly the relation between new technological developments and detector development for AUC is investigated. Pioneering results are obtained that indicate the possible direction to be followed for the future of AUC. As an example, each MWL-AUC data contains thousands of wavelengths. MWL-AUC data also contains spectral information at each radial point. Data can be separated to its single wavelength files and can be analyzed classically with existing software packages. All the existing software packages including Ultrascan, Sedfit, Sedanal can analyze only single wavelength data, so new extraordinary software developments are needed. As a first attempt, Emre Brookes and Borries Demeler have developed mutliwavelength module in order to analyze the MWL-AUC data. This module analyzes each wavelength separately and independently. We appreciate Emre Brookes and Borries Demeler for their important contribution to the development of the software. Unfortunately, this module requires huge amount of computer power and does not take into account the spectral information during the analysis. New software algorithms are needed which take into account the spectral information and analyze all wavelengths accordingly. We would like also invite the programmers of Ultrascan, Sedfit, Sedanal and the other programs, to develop new algorithms in this direction.
Die analytische Chemie versucht die chemische Zusammensetzung, chemische und physikalische Eigenschaften von biologischen oder künstlichen Materialien zu bestimmen. Mit der Entwicklung deren Methoden können genauere Informationen über die Umweltverschmutzung, das Ozonloch, Proteinfunktionen und Wechselwirkungen im menschlichen Körper erlangt werden. Es sind eine Vielzahl von analytischen Techniken vorhanden, die durch Verbesserungen in der Mikroelektronik, Mechanik, Informatik und Nanotechnologie einer markanten Entwicklung unterworfen wurden. In dieser Arbeit wurde versucht die Detektionskapazität der analytischen Ultrazentrifuge zu erhöhen. Die analytische Ultrazentrifuge (AUZ) ist eine gut bekannte, sehr leistungsstarke Trennungsmethode. AUZ benutzt die Zentrifugalkraft zum Trennen von Stoffen. Die Probe kann für die Messung gelöst oder in einer Flüssigkeit dispergiert werden. Makromoleküle, Proteine und kolloidale Systeme in Lösung können in einer AUZ Zelle zwischen 1000-60000 Rotationen pro Minute zentrifugiert werden, wie beispielsweise in der kommerziellen Beckmann AUZ. Die Rotationsbeschleunigung entspricht 73-262mal der Erdschwerebeschleunigung (= 9.81 m s-2) für eine radiale Position von 6.5 Zentimeter. Diese Kraft ist der Schlüsselfaktor für die Fähigkeit der AUZ sogar kleine Moleküle und Ionen zu trennen. Die Experimente wurden bei kontrollierter Rotationsgeschwindigkeit und Temperatur ausgeführt. Drei verschiedene, neue Detektoren wurden im Rahmen dieser Arbeit konstruiert und getestet. Diese Detektoren haben die analytischen Informationen sehr verbessert. Dies wurde für Proteine, halbleitende Nanopartikel sowie auch für industrielle Produkte gezeigt.

Thesis (MEng)--Stellenbosch University, 2014.
ENGLISH ABSTRACT: Central receiver power plants generate renewable electricity by exploiting the energy provided by the sun. The conditions experienced in the Northern Cape region of South Africa provide the ideal conditions for the development of these plants. Without a storage medium these plants have capacity factors in the range of 25-30%. The inclusion of a thermal energy storage medium provides the ability to increase the capacity factors of these plants. Although storage increases the costs, it results in better utilisation of the power block and a decrease in the levelised electricity cost (LEC). Eskom intends building a 100MWe central receiver dry cooled power plant in the Upington region. This research identifies the appropriate storage medium and ideal storage capacity to achieve the lowest LEC. A literature survey was performed to identify the different methods of storage that are available. The different storage methods were evaluated and the best storage medium for a central receiver power plant based on the developments of the various storage technologies was identified. To determine the costs associated with a central receiver power plant, data published by NREL was used. Different plant parameters were required to evaluate the costs. A power plant model based on efficiencies and energy balances was created to determine the required plant parameters. It provided the ability to determine the effect of changing different plant parameters on the LEC and estimate the plant output. The power block parameters were initially varied to determine the most efficient power block configuration. Once the most efficient power block configuration was identified the solar field and storage parameters were varied to determine the plant configuration which resulted in the lowest LEC. The most efficient power block configuration of 0.4206 was found for a system comprising of six feedwater heaters with the feedwater temperature of 230°C, main steam pressure 140 bar and an exit steam generator salt temperature of 290°C. A solar multiple of 3.0 with 16 hours of storage resulted in a LEC of R1.41/kWh with no system constraints. A capacity factor constraint of 60% resulted in a solar multiple of 1.8 with 8 hours of storage and a LEC of R1.78/kWh.
AFRIKAANSE OPSOMMING: Sonkragaanlegte met sentrale ontvangers wek hernubare elektrisiteit op deur sonenergie te ontgin. Die klimaat in die Noord Kaap-streek van Suid-Afrika is ideaal vir die oprigting van hierdie aanlegte. Sonder ’n bergingsmedium is die kapasiteitsfaktore van sulke aanlegte ongeveer 25-30%. Met die insluiting van ’n bergingsmedium vir termiese energie kan die kapasiteitsfaktore egter verhoog word. Hoewel berging aanlegkoste verhoog, lei dit terselfdertyd tot beter aanwending van die kragblok en ’n afname in die konstante eenheidskoste van elektrisiteit (LEC). Eskom beplan om ’n droogverkoelde kragaanleg van 100 MW met ’n sentrale ontvanger in die Upington-streek op te rig. Hierdie navorsing was dus daarop toegespits om die mees geskikte bergingsmedium en ideale bergingskapasiteit te bepaal om die laagste moontlike LEC uit die aanleg te verkry. ’n Literatuurstudie is onderneem om die verskeie beskikbare bergingsmetodes te bestudeer. Die verskillende metodes is beoordeel, waarna die beste bergingsmedium vir ’n kragaanleg met ’n sentrale ontvanger op grond van die ontwikkelings in die verskillende bergingstegnologieë bepaal is. Om die koste van ’n kragaanleg met ’n sentrale ontvanger te bepaal, is gepubliseerde data van die Amerikaanse Nasionale Laboratorium vir Hernubare Energie (NREL) gebruik. Verskillende aanlegparameters was egter nodig om die koste te beoordeel. Dié parameters is gevolglik bepaal deur ’n kragaanlegmodel op grond van doeltreffendheidsfaktore en energiebalanse te skep. Sodoende kon vasgestel word watter uitwerking veranderinge in die verskillende parameters op die LEC sou hê, en kon die aanleguitset geraam word. Die kragblokparameters is aanvanklik afgewissel om die doeltreffendste kragbloksamestel te bepaal. Nadat dít bepaal is, is die sonenergieveld en bergingsparameters weer afgewissel om vas te stel watter aanlegsamestel die laagste LEC tot gevolg sou hê. Die beste termiese benuttingsgraad is behaal vir ʼn stoom siklus met ses water verhitters en ʼn water temperatuur van 230 °C by die ketel se inlaat, ʼn stoom druk van 140 bar, en sout uitlaat temperatuur van 290 °C. ʼn Vermenigvuldigingsfaktor van drie vir die heliostaat veld, en 16 uur termiese energie storing gee ʼn opwekkingskoste van R 1.41/kW/h indien daar geen beperkings op die grootte of koste van die stelsel geplaas word nie. Indien die kapitaal uitgawe ʼn perk van 60 % op die kapasitiet van die stelsel plaas, verander die optimale ontwerpspunt na ʼn vermenigvuldigingsfaktor van 1.8, en die termiese stoorkapasitiet verlaag na 8 uur. In hierdie geval is die opwekkingskoste R 1.78/kWh.

It already seems preposterous to be able to sufficiently meet global food demand of the expected nine billion people by 2050 while at the same time maintain our emissions levels below 2ᵒC by the end of the century. This is more so for a continent such as Africa where much of this population is expected to arise from considering the fact that the continent is ranked to have the highest proportion of food insecure population. In order to overcome this challenge, we will need a total revolution of our agricultural production systems to systems that not only focus on increasing food production but also build our resilience to climate change. An example of one such practice is System of Rice Intensification (SRI) which is acclaimed to increase rice production while at the same time reducing the pressure on scarce water resources, minimizing agricultural greenhouse gases emissions and improving the farmers' households' adaptive capacity to climate change impacts by increasing their income. However, despite the success attributed to SRI, its uptake across Sub Saharan Africa is arguably low. This is puzzling considering the high proportion of food insecurity in the region and the region's susceptibility to damage from increased severity and frequency of climate extreme events such as droughts and floods due to its geographical positioning and the limited adaptive capacity of its people. In this work, the researcher sought to understand the barriers and enablers to the adoption of the System of Rice intensification in Mwea irrigation scheme (MIS) in Kenya. The findings show that most barriers to the uptake of SRI in MIS occur during the dissemination of SRI. Further critical barriers to the uptake of SRI in MIS were identified as follows: lack of formal SRI training, high costs of rice production, failure to involve key stakeholder institutions such as SACCOs while marketing SRI and farmer's age. Moreover, the study also depicted that most barriers to SRI adoption were intertwined, thus focusing on a single barrier would be myopic. Furthermore, enablers to the uptake of SRI in MIS are tied to the benefits of SRI pre-empted by lead farmers. This correlation implies that the benefits of SRI are key motivators for SRI adoption. Other enablers include training. However, informal training on SRI through social networks which play a crucial role at disseminating climate adaptation activities amongst small scale farmers, is marked with a lot of inconsistencies which makes it a barrier for SRI uptake. In this regard, we advise that SRI trainers clearly highlight the activities involved in SRI and their resultant benefits during initial SRI information dissemination.

L'ensemble des travaux présentés dans cette étude est lié à l’accident d'éjection de grappe de contrôle dans un REP 900 MWe recyclant du plutonium et fonctionnant en mode gris. Cet accident, considéré de classe IV dans le rapport de sûreté, provient de la rupture de l'enceinte de pression du mécanisme de grappe. Il a pour conséquence l'introduction rapide d'une réactivité, dans le cœur qui provoque un transitoire violent de puissance où la tenue du combustible peut être mise en cause. Deux aspects importants constituent le cadre particulier dans lequel cette étude a été effectuée : le recyclage du plutonium dans les REP 900 MWe et leur fonctionnement en mode gris. Ils sont à la base des difficultés principales rencontrées dans cette étude. Notre objectif était donc d'évaluer qualitativement et quantitativement l'évolution des paramètres physiques pendant l'accident de façon à trouver le ou les scénarios les plus sévères et à pouvoir ainsi estimer la gravité des conséquences. Nous avons traité le problème en deux étapes : tout d'abord, examen de tous les scénarios possibles à l'aide d'un schéma de calcul 2D+1D+OD de façon à trouver ceux susceptibles d'être les plus pénalisants ; puis constitution d'un schéma de calcul précis composé de calculs 3D statiques, de cinétique neutronique et de thermique pour examiner les scénarios retenus dans la première étape.

L'étude comporte deux sujets principaux concernant le calcul d'un REP1300 : - d'une part, la représentation hétérogène d'assemblages dans le calcul de transport. - d'autre part, la mise au point d'une nouvelle proposition pour le calcul des constantes nucléaires d'assemblages barrés utilisables dans les calculs de diffusion homogènes. Dans la représentation hétérogène des assemblages on utilise les conditions de symétrie et les groupements de plusieurs cellules physiques pour réduire l'emplacement de mémoire et le temps de calcul. L'utilisation des conditions de symétrie s'avère physiquement justifiée et représente un gain de temps de calcul de 40% par rapport à la représentation complète de l'assemblage. D'autre part, en conservant le spectre correct et en tenant compte des limites du code de transport APOLL01, des groupements à 9, 24 et 22 cellules ont été retenus respectivement pour des assemblages standard, barre grise et noires. Ils sont de 20, 27 et 24 cellules pour les assemblages empoisonnés respectivement 8, 12 et 16 crayons de pyrex. La qualité du groupement augmente l'évolution du combustible et avec l'augmentation de l'enrichissement et plus généralement avec le durcissement du spectre. Dans l'élaboration des constantes nucléaires homogènes des assemblages équipés de grappes absorbantes, un nouveau schéma de calcul est nécessaire car l'utilisation des constantes nucléaires homogènes obtenues en milieu infini conduit à une surestimation de l'efficacité des barres de 6 à 10%. Les constantes barrées homogènes calculées en milieu infini sont donc ajustées par un facteur tenant compte simultanément de l'influence de l'environnement et de l'équivalence transport-diffusion. Une étude de la sensibilité des facteurs d'ajustement aux différents changements d'états du réacteur montre que le calcul de ces facteurs, en début de vie, est suffisant et qu'ils peuvent être utilisés pendant tout le fonctionnement du cœur. Ces facteurs dépendent essentiellement de la nature de la barre. L'obtention de constantes nucléaires ajustées devient alors une opération simple. Cette procédure permet d'améliorer les études tridimensionnelles du cœur avec barres au cours du fonctionnement tout en conservant des coûts de calcul acceptables.

There is an increasing concern over mercury emissions from coal-fired boilers. Coal-fired power generation accounts for approximately 33% of total mercury emission in the United States. Once it is emitted into the atmosphere and deposited on land or water, mercury can transform into methylmercury, an organic form. Mercury can then enter the food chain, which poses a potential threat to human health and the environment. To study the relationship between particulate bound mercury and fly ash properties, fly ash samples were collected from the mechanical hopper (MHP) and the electrostatic precipitator (ESP) of a 100 MWe pulverized coal-fired boiler and analyzed for particulate mercury concentration (Hgp), unburned carbon, loss on ignition (LOI), elemental content and specific surface area (SSA). Different types of software, such as Microsoft Excel, Minitab and Origin, were applied to build the regression models to evaluate the relationship between Hgp and fly ash properties. The results of the analysis indicate that the amount of mercury emissions is dependent on the properties of the fly ash at the MHP and ESP as well as the amount of fly ash removed by air pollution control devices (APCD). Their relationship can be described as: Hgp (MHP), ppm = 0.0230 + 0.00838 Carbon (MHP), % + 0.00385 LOI (MHP), % Hgp (ESP), ppm = -0.0180 + 0.0670 Carbon (ESP), % + 0.0448 LOI (ESP), % The SSA of ESP ash is larger than MHP ash, which can help explain why Hgp at the ESP is higher than at the MHP. For the multiple metal oxides in fly ash, all the regression results indicate the trace elements have a very weak relationship with Hgp. There is no significant effect from trace elements on mercury absorption. Further study of Hgp catalyst mechanism and absorption phenomenon is ongoing. The function of various emission control technologies such as SCR and hot-side ESP in some coal-fired power plants are being evaluated.

L'etat du vieillissement de la cuve (dommages par irradiation) qui determine en grande partie la duree de vie du fonctionnement d'un reacteur nucleaire est fonction de la dose recue. Pour la determination de cette dose on utilise deux schemas de calcul: un schema exact utilisant le code tripoli qui resout l'equation de boltzmann par la methode de monte-carlo et un schema simplifie base sur la methode d'attenuation en ligne droite. Les avantages de la deuxieme methode rapide (reproduction des resultats facilement) et deterministe (les effets de difference sont possibles) par rapport a la premiere longue et statistique rendent son developpement necessaire. Les qualifications de ces methodes se font par comparaison avec l'experience que nous approchons ainsi: pour la premiere methode, par la verification de la programmation de tipoli (representativite du choc) et son alignement avec les codes sn, et, pour la deuxieme methode, par sa modification afin d'utiliser des coefficients d'attenuation lineaires variables a l'interieur de chaque milieu, pour mieux representer les effets de spectre et de reflexion. Dans le cadre de la verification des donnees physiques de base et de leur mode de representation, on presente une etude de l'influence de la mise en groupe des sections efficaces et du nombre de groupes, ainsi qu'une etude de l'influence de l'origine des sections efficaces

This study applies major principles of cognitive linguistics to the task of developing a novel model of the bilingual dictionary called the dictionary for productive comprehension (DPC). Based on conceptual analysis and coherent network representation of entry words, multi-word expressions, and constructions, the DPC provides access to the conventional linguistic knowledge of native speakers. In seeing linguistic units as contentful symbolic forms, the DPC is designed with a view of language as a lexicogrammatical continuum. By constructing the bilingual dictionary at the intersections of the two languages’ concepts under clearly specified conditions of their neutralization, it is given theoretical status. However, the main purport of this study is in the realm of applied lexicography. Among its tasks are: operationalizing conceptual analysis by establishing heuristically viable discovery procedures; working out guidelines for converting conceptual networks into the microstructure of dictionary entries, and for organizing its macrostructure as a natural-language thesaurus of lexicalized and lexicogrammatical concepts; laying a foundation for selecting and locating MWEs, proverbial expressions and constructions in a principled way, and suggesting approaches to organizing the constructicon, the part of the dictionary that contains schematic constructions. The DPC model offers effective remedies for the two major faults of the conventional bilingual dictionary, i.e. unrecognizability of the SL entry as a coherent whole by the TL user, and, consequently, inability to suggest precise cognitive orientations for the user's own production of an equivalent TL text. It proves that the bilingual dictionary can be something other than an inventory of disparate senses, a boundless set of translation equivalents, or an eclectic mixture of the two. By maintaining conceptual integrity of linguistic units, DPC affords the user a means of grasping the essence of a foreign word, MWE, or construction as if they were units of one’s native speech, as well as a generative potential with regard to translating into the TL. At the same time, by making conventional linguistic knowledge of the native speaker explicit, DPC serves the purpose of a learner’s dictionary.

O método envolve a avaliação da geração termoelétrica regionalizada, em pequena escala e a partir dos resíduos agrícolas existentes em fontes locais de pós-colheita, beneficiamento e transformação da produção primária. O trabalho está apoiado na adequação técnico-tecnológica, na viabilidade econômico-financeira, no inventário geo-referenciado da disponibilidade de biomassa e na aproximação multicriteríal de apoio a decisão. Para subsidiar as informações com dados, fez-se uma varredura das principais tecnologias existentes, sua disponibilidade e custo, e aplicou-se um questionário específico, dirigido ao diagnóstico energético das empresas trabalhadas, todas do setor arrozeiro. Esses números, que alimentam as simulações efetuadas para os casos reais, são amostrados em um Município tomado como representativo da média das regiões do Estado do Rio Grande do Sul. As avaliações econômicas utilizam-se de dois índices: a TIR e o Payback, ambos descontados a uma taxa empregada como mínima de atratividade econômica. O pequeno volume investido e as grandes oscilações dos indicadores, conduzem a instabilidade da análise, em que pequenas variações, relativas ao valor total do investimento expresso em termos de fluxo de caixa, causam grandes alterações nos valores finais da TIR. Um maior prazo de financiamento e percentual de participação nos itens financiados é desejável para alavancar projetos termoelétricos dessa natureza. Alternativas tecnológicas, como de gaseificação, e associação de empresas geradoras de resíduo potencialmente combustível, são recomendáveis especialmente para escalas inferiores a 200 kW, de potência instalada. O método multicriterial mostrou-se útil, especialmente se acompanhado da tecnologia do sistema de infomações geográficas (SIG). É uma eficiente e valiosa ferramenta para avaliação de projetos e para hierarquizqão de preferências das possióilidades existentes, apresentando uma priorização que pode, ou não, ser adotada para o estabelecimento de políticas de incentivo. É, ainda, perfeitamente aplicável a projetos de geração termoelétrico de pequeno porte, especialmente em co&guração de auto consumo, em empresas que se utilizem dos resíduos agrícolas próprios, próximos, ou em conjunto com outras unidades, abrindo caminhos para a gestão ambienta1 dos resíduos através da geração de biotermoeletricidade.
The study develops an evaluation of the regionalised thermoelectrical power generation, in small scale using the local existent agricultural residues like those fiom crops, benefiting and transformation procedures of the primary production. The work is based on the techniciantechnological settle down, the economic-hancial viability, the geo referenciated inventory of the residual biomass disponibility, and in the multicriterial decision aid approach. To provide the system with information data, a survey of the main existent technologies are made, and the readiness and cost are saved. Also a spesc questionnaire was applied, intended to obtain an energy diagnosis of the worked companies, all of thern dealing with rice. Those numbers feed the simulations that are made based on real cases, sampled in a county taken as representative of the average areas of the State of Rio Grande do Sul - Brazil. The economic evaluations make use of two indexes: the real discount rate (RDR) and the Payback, both discounted for a minimum economic attractiveness. The small amount invested and the great oscillations of the indexes, conduce to a moderate instabiity of the analysis, where small variations of the whole investrnent, expressed in cash flow terms, cause great alterations in the final values of RDR. Increasing the h c i n g perbd and percentage of participation in the financed items is desirable to improve thermoelectrical project competitiveness. Technological advancing like gaseification, and association of some companies that are potentidy fbel residue generators, are altematives to power plants, especially recornmended for scales lower than 200 kWe. The multicriterial method seems to be very usem, especially if accompanied of the geographical information system (GIS) methodology. It is an efficient and valuable to01 in the evaluation of projects and in the preferences hierarchization of the existing possibilities, presenting a priorization scale that can or not, be adopted for incentive policy. It is also perfectly applicable to small scale power generation projects, especially in self consumer contiguration, and in companies that used their own or nearby agricultural residues, or together with other enterprise, so open opportunities for the residues administration by the biothermoelechicity generation way.

Abstract A WATERSHED MOMENT: IMPLEMENTING STATE ENVIRONMENTAL LITERACY POLICY INTO A CENTRAL VIRGINIA SCHOOL DISTRICT By Melinda J. VanDevelder, Ph.D. A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at Virginia Commonwealth University. Virginia Commonwealth University, 2018 Director: Charol Shakeshaft, Ph.D., Professor, Department of Educational Leadership Policy goals may be impossible to achieve at the classroom level (Ravitch, 2014), as policy depends on those who implement it (Lipsky, 1980). The purpose of this research was to investigate how the voluntary environmental educational executive order, EO42, was implemented and executed in a Central Virginia Public School district. The requirements of EO42 were former Virginia Governor MacAuliffe’s response to a multi-state policy he signed called the 2014 Chesapeake Bay Watershed Agreement, which called for all Virginia public education schools to implement Meaningful Watershed Educational Experiences (MWEEs) with students at the elementary, middle, and high school levels. Interviews of state educational and environmental policy-makers indicated EO42 was a hurried process that came without funding and which was done, in large part, to make a political statement. An interview of the Central County Public School’s science specialist portrays the practices used with local environmental outreach educators in order to prepare 64 middle and high school science teachers to implement MWEE lessons required by EO42 for the 2015-2016 school year. A 2 x 2 Chi-squared analysis done on data collected from teacher surveys indicated a statistically significant difference [Chi-squared (1 d.f.) = 4.17, p < 0.05] between teachers’ professional development attendance and teachers’ perceived ability to complete a MWEE lesson with their students. Analyzed teacher survey data also indicates that teachers who had attempted MWEEs in prior years were more likely to attempt a MWEE with their students [t (61) = -2.846, p = 0.006] than were teachers who had not. Though 83% of teachers reported completing a MWEE with the majority of their students, analysis of teacher-reported lessons indicated that only 22% of teachers completed the four components required of a MWEE (environmental issue definition, an outdoor field experience, an action project, and project synthesis and conclusion). Results indicate that there is much work to be done when introducing new policy into secondary schools (Ball, Maguire, & Braun, 2012).

In natural languages, words can occur in single units called simplex words or in a group of simplex words that function as a single unit, called multiword expressions (MWEs). Although MWEs are similar to simplex words in their syntax and semantics, they pose their own sets of challenges (Sag et al. 2002). MWEs are arguably one of the biggest roadblocks in computational linguistics due to the bewildering range of syntactic, semantic, pragmatic and statistical idiomaticity they are associated with, and their high productivity. In addition, the large numbers in which they occur demand specialized handling. Moreover, dealing with MWEs has a broad range of applications, from syntactic disambiguation to semantic analysis in natural language processing (NLP) (Wacholder and Song 2003; Piao et al. 2003; Baldwin et al. 2004; Venkatapathy and Joshi 2006).
Our goals in this research are: to use computational techniques to shed light on the underlying linguistic processes giving rise to MWEs across constructions and languages; to generalize existing techniques by abstracting away from individual MWE types; and finally to exemplify the utility of MWE interpretation within general NLP tasks.
In this thesis, we target English MWEs due to resource availability. In particular, we focus on noun compounds (NCs) and verb-particle constructions (VPCs) due to their high productivity and frequency.
Challenges in processing noun compounds are: (1) interpreting the semantic relation (SR) that represents the underlying connection between the head noun and modifier(s); (2) resolving syntactic ambiguity in NCs comprising three or more terms; and (3) analyzing the impact of word sense on noun compound interpretation. Our basic approach to interpreting NCs relies on the semantic similarity of the NC components using firstly a nearest-neighbor method (Chapter 5), then verb semantics based on the observation that it is often an underlying verb that relates the nouns in NCs (Chapter 6), and finally semantic variation within NC sense collocations, in combination with bootstrapping (Chapter 7).
Challenges in dealing with verb-particle constructions are: (1) identifying VPCs in raw text data (Chapter 8); and (2) modeling the semantic compositionality of VPCs (Chapter 5). We place particular focus on identifying VPCs in context, and measuring the compositionality of unseen VPCs in order to predict their meaning. Our primary approach to the identification task is to adapt localized context information derived from linguistic features of VPCs to distinguish between VPCs and simple verb-PP combinations. To measure the compositionality of VPCs, we use semantic similarity among VPCs by testing the semantic contribution of each component.
Finally, we conclude the thesis with a chapter-by-chapter summary and outline of the findings of our work, suggestions of potential NLP applications, and a presentation of further research directions (Chapter 9).

Text mining is involved in a broad scope of applications in diverse domains that mainly, but not exclusively, serve political, commercial, medical and academic needs. Along with the rapid development of the Internet technology in recent thirty years and the advent of online social media and network in a decade, text data is obliged to entail features of online social data streams, for example, the explosive growth, the constantly changing content and the huge volume. As a result, text mining is no longer merely oriented to textual content itself, but requires consideration of surroundings and combining theories and techniques of stream processing and social network analysis, which give birth to a wide range of applications used for understanding thoughts spread over the world , such as sentiment analysis, mass surveillance and market prediction. Automatically discovering sequences of words that represent appropriate themes in a collection of documents, topic detection closely associated with document clustering and classification. These two tasks play integral roles in revealing deep insight into the text content in the whole text mining framework. However, most existing detection techniques cannot adapt to the dynamic social context. This shows bottlenecks of detecting performance and deficiencies of topic models. In this thesis, we take aim at text data stream, investigating novel techniques and solutions for robust text mining to tackle arising challenges associated with the online social context by incorporating methodologies of stream processing, topic detection and document clustering and classification. In particular, we have advanced the state-of-theart by making the following contributions: 1. A Multi-Window based Ensemble Learning (MWEL) framework is proposed for imbalanced streaming data that comprehensively improves the classification performance. MWEL ensures that the ensemble classifier is maintained up to date and adaptive to the evolving data distribution by applying a multi-window monitoring mechanism and efficient updating strategy. 2. A semi-supervised learning method is proposed to detect latent topics from news streams and the corresponding social context with a constraint propagation scheme to adequately exploit the hidden geometrical structure as supervised information in given data space. A collective learning algorithm is proposed to integrate the textual content into the social context. A locally weighted scheme is afterwards proposed to seek an improvement of the algorithm stability. 3. A Robust Hierarchical Ensemble (RHE) framework is introduced to enhance the robustness of the topic model. It, on the one hand, reduces repercussions caused by outliers and noises, and on the other overcomes inherent defects of text data. RHE adapts to the changing distribution of text stream by constructing a flexible document hierarchy which can be dynamically adjusted. A discussion of how to extract the most valuable social context is conducted with experiments for the purpose of removing some noises from the surroundings and efficiency of the proposed.

Thesis (M.S.)--University of Wisconsin--Madison, 2002.
Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaf 151).

Research Thesis  Submitted  in  Fulfilment  of  the  Requirements  for  the  Degree  of  Doctor  of   Philosophy  in  Economics, School of Economic & Business Sciences Faculty of Commerce, Law and Management University of Witwatersrand, Johannesburg, SA
The world is facing a sustainability crisis due to depletion and degradation of environmental and natural resources faster than they can be generated. Many of these resources are not partitioned by private property rights, and are held as state property, common property, or as open-access. Common Property Resources (CPRs) have two distinct attributes: (1) limited or nontrivial exclusion (it is difficult to exclude multiple individuals or users from appropriating from the resource) and (2) substractability (the resource features rivalry in consumption), meaning that appropriation by one reduces the overall resource availability and thus, subtracts from what can be appropriated by others. Examples include fisheries, grazing lands, irrigation systems, and ground water basins. Because no one has property rights or control over such resources, users of CPRs are frequently assumed to be caught in an inescapable dilemma - overexploitation of the resource. Thus, unlike the ‘invisible hand’ of Adam Smith in competitive markets, in the case of CPRs the self-interested behavior does not yield economic efficiency or optimal outcome or Pareto optimality. This study sought to understand the evolution of management dynamics and operation of governance structures developed by resource users and other stakeholders in three large scale CPRs in Kenya. The objectives are to (1) examine the evolution of management dynamics. (2) Examine the management model applied and its functioning. (3) Explore the governance structures and challenges of implementing them. (4) Explore critical variables related to user groups, institutional arrangements and external environment in the resource system. (5) Suggest measures to improve on the management and governance of the resource system. In addition, the study gives a comparative analysis of the management models applied in the three CPR systems. The general theoretical literature on CPRs has focused mainly on two basic but important conditions or categories. First, small scale communally owned and governed resources, in ii terms of the physical or geographical size of the resource system with well-defined boundaries. Secondly, group or users size, characterized by small numbers with similar identities and interests. This study therefore, contributes to literature by using large scale CPR case studies in terms of physical size of resource system and number of users and examining the evolution and dynamics in the management model and governance structures. A Qualitative Research (QR) methodology is adopted and analytical tools of institutional analysis and an empirical foundation based on field data applied. A survey research design is used. Both primary and secondary data was sourced and a pilot study was conducted to test reliability of research instruments. Data is documented, compiled and presented in form of tables, figures and general descriptions. Data analysis and synthesising is done by working through the data to arrive at a conclusion to answer the research questions and achieve the purpose of the study. The study findings show that management and governance issues in the three CPRs have evolved over time both in terms of the scale and involvement of other stakeholders in decision making process in the resource system. Specifically, the collaborations among state agencies, other stakeholders and resource users through their associations has enabled monitoring and enforcement not only be effective but also legitimate and consequently, lead to sustainable resource use. The management models used in the three CPR case studies are identified as the Partnership Fisheries Management (PFM) in Lake Victoria fishery, Participatory Irrigation Management (PIM) in Mwea Rice Irrigation Scheme and Holistic Management Framework (HMF) in Laikipia group grazing lands. The governance structures applied in the three CPRs are generally position, boundary, choice or authority, aggregation, information, payoff and scope rules. The degree of application of each set of rules however, depends on the nature of the resource system. They are designed, developed, implemented, monitored, enforced, sanctioned and arbitrated by the resource users, state lead agencies, departments and ministries iii and other stakeholders or actors. Each of these actors are involved in varying degrees in the various phases depending on their role and interest in the resource system. The management and governance structures can be strengthened and improved by enhancing certain administrative, health, safety, environmental issues and increased state support and involvement in the resource system. The co-management model design which is applied in the three CPRs yield various benefits to the resource-dependent community, public, state and resource system because it incorporates state and local (resource users) managers in decision making. However, the degree of participation of other stakeholders, challenges faced and other internal and external factors, depend on the nature of CPR, ownership and control of the CPR by resource users and the technical infrastructural investments required for the operation of the system. These results add to existing knowledge on Sustainable Development (SD) environment nexus by providing facts to multidisciplinary environmental and natural resources scholars regarding the dynamics of large scale CPR systems. Provide an in depth understanding of CPR management issues for the formulation of national strategies for SD, fisheries, Arid and Semi-Arid Lands (ASALs), and irrigation farming. Lastly, they provide ways of responding to increasing challenges of shared water resources (Lake Victoria) in addition to strengthening of relations within the East African Community (EAC). Key words: Actors, bio-physical and community attributes Common Property Resources, governance structures, institutions, large scale, management models, resource users, resource systems
GR2018

Degree: PhD Department: Engineering
1997, South African’s major power utility, recognised the need to improve the understanding of fly ash formation and slag deposition of South African coals. This requirement is due to the predicted quality changes of power station feedstocks and the limited research into the slagging propensity of South African coals. This research seeks to develop an analytical technique and a fly ash formation model for predicting the slagging propensity of coals. The research will establish if the models based on Carboniferous coals can be applied to South African Permian coals. A water-cooled suction pyrometer with a custom designed slag probe was used to obtain samples of fly ash and slag from within a 200 MWe pulverised fuel boiler. Simultaneously, samples of pulverised fuel feedstock were collected. The mineral attributes in the pulverised fuel and the phases in fly ash and slag deposit were quantified by CCSEM. The analytical procedure, CCSEM, has been developed with a novel procedure for identifying minerals and C-bearing phases. The new fly ash formation model assumes that the mineral attributes of the combusting pulverised fuel particle controls the size and elemental signature of the resultant fly ash particle(s). The new model has shown that the inherent mineral attributes controls the physical and chemical characteristics of the initial fly ash phases. Thereafter, conditions (stoichiometric, temperature and turbulence) within the combustion chamber promote the physical and/or chemical interaction of the initial fly ash particles. Slag deposits are enriched in Ca- and Fe-bearing alumino-silicates. The new slagging propensity index is based on either predicting or measuring the proportion of Ca- and Fe-bearing alumino-silicates. iv The numerous fly ash formation models, based on Carboniferous coals are not necessarily valid for South African coals. It is not the integrity of the actual fly ash formation mechanisms that is questioned, but rather the experimental scale on which the models are based. This research has produced an analytical technique and a fly ash formation model to predict the slagging propensity of coals. This forms a platform for further research into the role that organically bound cations, combustion conditions and boiler configuration has on the formation of Ca- and Fe-bearing alumino-silicates.