Dissertations / Theses on the topic 'Si ratios'

The external silicon cycle during the Precambrian (4.5-0.5 Ga) is not well understood despite its key significance to apprehend ancient dynamics at the surface of the Earth. In the absence of silicifying organisms, external silicon cycle dramatically differs from nowadays. Our current understanding of Precambrian oceans is limited to the assumption that silicon concentrations were close to saturation of amorphous silica. This thesis aims to bring new insights to different processes that controlled the geochemical silicon cycle during the Archaean (3.8-2.5 Ga). Bulk rock Ge/Si ratio and Si isotopes (δ30Si) offer ideal tracers to unravel different processes that control the Si cycle given their sensitivity to fractionation under near-surface conditions.

First, this study focuses on Si inputs and outputs to ocean over a limited time period (~2.95 Ga Pongola Supergroup, South Africa) through the study of a palaeosol sequence and a contemporaneous banded iron formation. The palaeosol study offers precious clues in the comprehension of Archaean weathering processes and Si transfer from continent to ocean. Desilication and iron leaching were shown to be the major Archaean weathering processes. The occurrence of weathering residues issued of these processes as major component in fine-grained detrital sedimentary mass (shales) attests that identified weathering processes are widely developed and suggest an important dissolved Si flux from continent to the ocean. In parallel, banded iron formations (BIFs), typically characterised by alternation of iron-rich and silica-rich layers, represent an extraordinary record of the ocean-derived silica precipitation throughout the Precambrian. A detailed study of a 2.95 Ga BIF with excellent stratigraphic constraints identifies a seawater reservoir mixed with significant freshwater and very limited amount of high temperature hydrothermal fluids as the parental water mass from which BIFs precipitated. In addition, the export of silicon promoted by the silicon adsorption onto Fe-oxyhydroxides is evidenced. Then, both Si- and Fe-rich layers of BIFs have a common source water mass and a common siliceous ferric oxyhydroxides precursor. Thus, both palaeosols and BIFs highlight the significance of continental inputs to ocean, generally under- estimated or neglected, as well as the close link between Fe and Si cycles.

In a second time, this study explores secular changes in the Si cycle along the Precambrian. During this timespan, the world ocean underwent a progressive decrease in hydrothermal inputs and a long-term cooling. Effects of declining temperature over the oceanic Si cycle are highlighted by increasing δ30Si signatures of both chemically precipitated chert and BIF through time within the 3.8-2.5 Ga time interval. Interestingly, Si isotope compositions of BIF are shown to be kept systematically lighter of about 1.5‰ than contemporaneous cherts suggesting that both depositions occurred through different mechanisms. Along with the progressive increase of δ30Si signature, a decrease in Ge/Si ratios is attributed to a decrease in hydrothermal inputs along with the development of large and widespread desilication during continental weathering.

Le cycle externe du silicium au précambrien (4.5-0.5 Ga) reste mal compris malgré sa position clé dans la compréhension des processus opérant à la surface de la Terre primitive. En l’absence d’organismes sécrétant un squelette externe en silice, le cycle précambrien du silicium était vraisemblablement très différent de celui que nous connaissons à l’heure actuelle. Notre conception de l’océan archéen est limitée à l’hypothèse d’une concentration en silicium proche de la saturation en silice amorphe. Cette thèse vise à une meilleure compréhension des processus qui contrôlaient le cycle géochimique externe du silicium à l’archéen (3.8-2.5 Ga). Dans cette optique, le rapport germanium/silicium (Ge/Si) et les isotopes stables du silicium (δ30Si) représentent des traceurs idéaux pour démêler les différents processus contrôlant le cycle du Si.

Dans un premier temps, cette étude se focalise sur les apports et les exports de silicium à l’océan sur une période de temps restreinte (~2.95 Ga Pongola Supergroup, Afrique du Sud) via l’étude d’un paléosol et d’un dépôt sédimentaire de précipitation chimique quasi-contemporain. L’étude du paléosol apporte de précieux indices quant aux processus d’altération archéens et aux transferts de silicium des continents vers l’océan. Ainsi, la désilicification et le lessivage du fer apparaissent comme des processus majeurs de l’altération archéenne. La présence de résidus issus de ces processus d’altération en tant que composants majeurs de dépôts détritiques (shales) atteste de la globalité de ces processus et suggère des flux significatifs en silicium dissout des continents vers l’océan. En parallèle, les « banded iron formations » (BIFs), caractérisés par une alternance de niveaux riches en fer et en silice, représentent un enregistrement extraordinaire et caractéristique du précambrien de précipitation de silice à partir de l’océan. Une étude détaillée d’un dépôt de BIFs permet d’identifier une contribution importante des eaux douces dans la masse d’eau à partir de laquelle ces roches sont précipitées. Par ailleurs, un mécanisme d’export de silicium via absorption sur des oxyhydroxydes de fer est mis en évidence. Ainsi, les niveaux riches en fer et riche en silice constituant les BIFs auraient une même origine, un réservoir d’eau de mer mélangée avec des eaux douces et une contribution minime de fluides hydrothermaux de haute température, et un même précurseur commun. Dès lors, tant les paléosols que les BIFs mettent en évidence l’importance des apports continentaux à l’océan, souvent négligés ou sous estimés, ainsi que le lien étroit entre les cycles du fer et du silicium.

Dans un second temps, cette étude explore l’évolution du cycle du silicium au cours du précambrien. Durant cette période, l’océan voit les apports hydrothermaux ainsi que sa température diminuer. Dans l’intervalle de temps 3.8-2.5 Ga, les effets de tels changements sur le cycle du silicium sont marqués par un alourdissement progressif des signatures isotopiques des cherts et des BIFs. Le fort parallélisme entre l’évolution temporelle des compositions isotopiques des deux précipités met en évidence leur origine commune, l’océan. Cependant, les compositions isotopiques des BIFs sont systématiquement plus légères d’environ 1.5‰ que les signatures enregistrées pas les cherts. Cette différence est interprétée comme le reflet de mécanismes de dépôts différents. L’alourdissement progressif des compositions isotopiques concomitant à une diminution des rapports Ge/Si reflètent une diminution des apports hydrothermaux ainsi que la mise en place d’une désilicification de plus en plus importante et/ou généralisée lors de l’altération des continents.

Doctorat en Sciences
info:eu-repo/semantics/nonPublished

On retrouve dans les météorites primitives des grains qui se sont condensés dans différents environnements stellaires et sont restés intacts après la formation du système solaire. L'identification du site d'origine de ces grains pré-solaires est effectuée grâce à la comparaison entre les abondances isotopiques mesurées et celles prédites par les modèles stellaires. Nous présentons dans ce manuscrit les analyses de deux expériences effectuées à l'installation ALTO avec le spectromètre magnétique split-pole, visant à réduire les incertitudes associées à deux réactions jouant un rôle dans la production des isotopes utilisés pour identifier les grains de novæ. Ces derniers sont caractérisés par des abondances extrêmes en ¹³C, ¹⁵N et ³⁰Si, mais la découverte dans certains grains d'isotopes caractéristiques de la nucléosynthèse dans les supernovæ à effondrement de coeur (CCSN) a remis en question cette origine. La première étude concerne l'impact du taux de la réaction ¹³N(a,p)¹⁶O sur les abondances en ¹³C prédites par de récents modèles de CCSN. Nous procédons à une ré-évaluation du taux de cette réaction en utilisant une méthode Monte Carlo pour obtenir des incertitudes statistiques. Les largeurs partielles alpha des états du noyau composé ¹⁷F sont déterminées en se basant sur les propriétés des états analogues du noyau miroir ¹⁷O qui ont été mesurées en utilisant la réaction de transfert alpha ¹³C(7Li,t)¹⁷O. Nous nous intéressons ensuite à la réaction ³⁰P(p,g)³¹S, qui est une des dernières réactions dont l'incertitude du taux a un impact important sur les prédictions faites par les modèles de novæ classiques, notamment des abondances en ³⁰Si. Pour réduire les incertitudes sur les propriétés spectroscopiques du noyau composé ³¹S, une étude de la réaction ³¹P(³He,t)³¹S a été effectuée. Les tritons et les protons de décroissance venant des états peuplés du ³¹S ont été détectés simultanément à l'aide du spectromètre et de détecteurs silicium à pistes. L'étude des corrélations angulaires proton est présentée et les rapports de branchement extraits
Primitive meteorites contain several types of dust grains that condensed in different stellar environments and survived destruction in the early Solar System. The stellar sources where these presolar grains come from are identified through comparisons between measurements of isotopic abundances and predictions by stellar models. In this manuscript is presented a detailed analysis of two experiments performed at the ALTO facility, using the split-pole magnetic spectrometer, aiming at reducing the nuclear uncertainties associated to two reactions which rate uncertainty affects the synthesis of isotopes used to identify putative novae grains. These grains are characterised by extremely high ¹³C, ¹⁵N and ³⁰Si isotopic abundances, but isotopic signatures found in a few grains indicate also a possible core-collapse supernovae (CCSN) origin. We first study the impact of the ¹³N(a,p)¹⁶O reaction rate uncertainty on ¹³C abundances predicted by recent CCSN models. We perform a re-evaluation of this reaction rate using a Monte Carlo approach to obtain meaningful statistical uncertainties. Alpha partial widths of states in the ¹⁷F compound nucleus are determined using the spectroscopic informations of the analog states in the ¹⁷O mirror nucleus that were measured using the ¹³C(7Li,t)¹⁷O alpha-transfer reaction. We then study the ³⁰P(p,g)³¹S reaction, which is one of the few remaining reactions which rate uncertainty has a strong impact on classical novae model predictions, in particular for ³⁰Si abundances. To reduce the nuclear uncertainties associated to this reaction, we studied the ³¹P(³He,t)³¹S reaction. Triton and proton decays from the populated states in ³¹S were detected simultaneously using the spectrometer and silicon strip detectors. The study of the angular correlations of proton decays is presented and branching ratios are extracted

This masters thesis investigates the possibility to estimate the ethanol content in the fuel using ion currents. Flexible fuel cars can be run on gasoline-ethanol blends with an ethanol content from0 to 85 percentage. It is important for the engine control system to have information about the fuel. In todays cars the measurements of the fuel blend are done by a sensor. If it is possible to do this with ion currents this can be used to detect if the sensor is broken, and then estimate the ethanol content until the sensor gets fixed. The benefit

of using ion currents is that the signal is measured directly from the spark plug and therefore no extra hardware is needed. To be able to see how the ethanol ratio affects the ion currents, the dependencies of the operating point have been investigated. This has been done by a literature review and by measurements in a Saab 9-3. Engine speed, load, ignition timing, lambda and spark plugs effects on the ion currents are especially studied. A black box model for the ion currents dependence on operating point is developed. This model describes the engine speed, load and ignition timing dependencies well, but it can not be used to estimate the ethanol ratio.

Emission from cars today is one of the biggest environmental issues, hence stringent government standards have been introduced to decrease emission. Car companies do not only have to satisfy government standards, but also meet consumer demands on increased fuel economy and good drivablility. This report will introduce controllers designed to control the air/fuel ratio in an SI engine. The engine model used is simplified. The engine components modelled include the inlet manifold, fuel dynamics, combustion and exhaust sensor.

Nonlinearities and delays are inherent in the engine dynamics and as such a Smith Predictor is utilised as the basis for controller structure to compensate for the delays. Here the Smith Predictor is combined with feedforwarding of the mass air charge, which is estimated from both the inlet and combustion models. Therefore different ways of merging the estimates are also explored.

A real engine was not accesible, thus simulators were implemented using data sets provided by General Motors. Model errors were introduced to test the controllers performance. The proposed methods should be tested on a real engine to ensure that this isa viable approach, as the simulations show it maybe promising to use in practice.

More stringent Euro 6 and LEV III emission standards will immediately begin execution on 2014 and 2015 respectively. Accurate air/fuel ratio control can effectively reduce vehicle emission. The simulation of engine dynamic system is a very powerful method for developing and analysing engine and engine controller. Currently, most engine air/fuel ratio control used look-up table combined with proportional and integral (PI) control and this is not robust to system uncertainty and time varying effects. This thesis first develops a simulation package for a port injection spark-ignition engine and this package include engine dynamics, vehicle dynamics as well as driving cycle selection module. The simulations results are very close to the data obtained from laboratory experiments. New controllers have been proposed to control air/fuel ratio in spark ignition engines to maximize the fuel economy while minimizing exhaust emissions. The PID control and fuzzy control methods have been combined into a fuzzy PID control and the effectiveness of this new controller has been demonstrated by simulation tests. A new neural network based predictive control is then designed for further performance improvements. It is based on the combination of inverse control and predictive control methods. The network is trained offline in which the control output is modified to compensate control errors. The simulation evaluations have shown that the new neural controller can greatly improve control air/fuel ratio performance. The test also revealed that the improved AFR control performance can effectively restrict engine harmful emissions into atmosphere, these reduce emissions are important to satisfy more stringent emission standards.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005.
Includes bibliographical references (p. 133-135).
A set of experiments was performed to investigate the effects of air-fuel ratio, inlet boost pressure, hydrogen rich fuel reformate, and compression ratio on engine knock behavior. For each condition the effect of spark timing on torque output was measured. Knock limited spark advance was then found for a range of octane number (ON) for each of three fuel types; primary reference fuels (PRFs), toluene reference fuels (TRFs), and test gasolines. A new combustion phasing parameter based on the timing of 50% mass fraction burned, ternled "combustion retard", was found to correlate well to engine performance. Increasing air- fuel ratio increases the combustion retard required to just avoid knock for PRFs and has little effect for TRFs. Combustion retard also increases more with inlet pressure and decreases more with reformate addition for PRFs than for TRFs. Both fuel types responded similarly to increased compression ratio. The trends for gasoline are about halfway between PRFs and TRFs. Experiments were also performed to determine the response of mid-load indicated efficiency to air-fuel ratio, load, and compression ratio. At a compression ratio of 9.8:1, relative net efficiency improvement is about 2.5% per unit compression ratio. Efficiency peaks at about 14:1 with a maximum benefit of 6-7%. Detailed chemical kinetics were combined with a cylinder pressure based end-gas modeling methodology to successfully predicted the response of PRFs to compression ratio and air-fuel ratio, and the response of TRFs to boost. The difference between the response of PRFs and TRFs to air-fuel ratio was also captured.
(cont.) Constant volume chemistry modeling found that hydrogen slows alkane autoignition reactions by consuming hydroxy radicals in the end gas. Reforming 30% of the fuel entering an engine decreases the required fuel quality 10 ON or more, which would allow increased compression ratio or increased turbocharging without increasing combustion retard. A simplified analysis indicates that increasing compression ratio and downsizing the engine to maintain constant maximum torque would increase fuel efficiency by about 9%. Turbocharging and downsizing would increase fuel efficiency by about 16%.
by Michael D. Gerty.
S.M.

The combination of MFI zeolite nano-sheets with competitive adsorption of water (H2O) in hydrocracking of long-chain paraffins presents a promising opportunity to produce diesel with high yield and with high cetane number. Thus, in wet hydrocracking of a long-chain paraffin (n-hexadecane (n-C16)) over MFI nano-sheets, it was investigated whether catalytic activity increased with increasing number of Brønsted acid (H + ) sites (decreasing silicon-to-aluminium (Si/Al) ratio), while secondary cracking remained completely suppressed. Also, it was investigated whether more Al atoms could be incorporated into the framework of MFI nano-sheets by modifying the new synthesis method. It was demonstrated that the new synthesis method, which utilizes C22H45–N + (CH3)2–C6H12–N + (CH3)2–C6H13 (C22-6-6) as structure-directing agent (SDA), could be extended to various Si/Al ratios in the range 25 – 100. The nano-sheets exhibited extra-framework Al (EFAl) species. Nano-sheets with Si/Al = 75 exhibited an oddly large amount of EFAl species compared to the other nano-sheets. For nano-sheets with Si/Al = 75, a high fraction of the EFAl species may have formed during calcination of the ammonium form and may encompass flexible Al species with predominantly Al in octahedral coordination (AlVI). Nano-sheets were loaded with 0.9 wt% platinum (Pt) via incipient wetness impregnation (IWI). Pt/nano-sheets with Si/Al = 25, 50 and 100 exhibited similar and high Pt dispersion (γPt). In contrast, Pt/nano-sheets with Si/Al = 75 exhibited a very low γPt, which was probably a result of the abundance, nature and/or location of EFAl species present in the support. In dry hydrocracking of n-C16, the catalytic activity increased with decreasing Si/Al ratio, strongly suggesting that the number of H+ sites increased with decreasing Si/Al ratio. Nano-sheets with Si/Al = 75 most likely contained AlVI species associated with Brønsted acidity, supporting the presence of flexible AlVI species. In wet hydrocracking of n-C16, at a constant and sufficiently high γPt, the activity increased with increasing number of H+ sites (decreasing Si/Al ratio), while secondary cracking remained completely suppressed. Pt/nano-sheets with Si/Al = 75 displayed a lower activity than 2 Pt/nano-sheets with Si/Al = 100, which may be a result of the very low γPt of Pt/nano-sheets with Si/Al = 75, underlining the importance of high γPt. For Pt/nano-sheets with Si/Al = 25, 50 and 100, H2O favoured linear cracking products at low cracking yields. In contrast, for Pt/nano-sheets with Si/Al = 75, H2O favoured branched cracking products, which may be a result of Pt sites on the external surface of the support being too far from the H+ sites inside the micropores. The new synthesis method could be extended to a modified SDA, namely C22H45–N + (CH3)2–C6H12–N + (CH3)2–C3H7 (C22-6-3), at various Si/Al ratios in the range 25 – 100. Replacing the terminal –C6H13 group in C22-6-6 with –C3H7 resulted in an increase in the framework Al (FAl) content of MFI nano-sheets with Si/Al ≥ 50, with the increase being the most pronounced for nano-sheets with Si/Al = 50. This was due to the increased occupancy of the zeolite framework by the hydrophilic region of C22-6-3 in comparison to the hydrophilic region of C22-6-6 under the given set of synthesis conditions, since –C3H7 was less bulky than –C6H13. Calcined nano-sheets were loaded with 1 wt% Pt via competitive ion exchange (CIE). In dry and wet hydrocracking of n-C16, the activity increased with decreasing Si/Al ratio and in wet hydrocracking, secondary cracking was not completely suppressed up to high conversions. This was probably due to the presence of additional H+ sites generated after SDA removal. H2O favoured linear cracking products at low cracking yields. Sodium (Na+ ) ion-exchanged nano-sheets were loaded with 1 wt% Pt via CIE. The average Pt size (dPt) of the Pt/Na+ nano-sheets were larger than the dPt of the Pt/calcined nano-sheets, which may be a result of the nature and/or location of EFAl species present in the Na+ supports. In dry and wet hydrocracking of n-C16, differences in activity were observed and in wet hydrocracking, secondary cracking was not completely suppressed up to high conversions. This was probably due to insufficient intimacy between H+ sites and Pt sites such that the rate was controlled by diffusion of olefinic intermediates from H+ sites to Pt sites and vice versa. H2O favoured linear cracking products at low cracking yields.

La distillation fractionnée des coupes pétrolières brutes se révèle insuffisante, pour répondre seule aux besoins en carburants et génère de fortes quantités de distillats à longue chaîne carbonée (C20-C50). Cette coupe d’hydrocarbures peu valorisable est ainsi transformée en molécules hydrocarbonées plus légères, par le biais de deux procédés : le craquage catalytique en lit fluidisé ou l’hydrocraquage. Ce dernier permet le craquage sélectif des hydrocarbures essentiellement en gazole et kérosène. Les catalyseurs acides utilisés sont « bifonctionnels » : une matrice zéolithique USY (zéolithe Y ultra-stabilisée) favorise le craquage des hydrocarbures, pendant qu’un sulfure mixte ou un métal noble greffé catalyse les réactions d’hydrogénation et de déshydrogénation. L’objectif de ce travail de thèse consiste à maximiser la sélectivité en distillats moyens, en diminuant le temps de séjour des molécules d’hydrocarbures dans la structure zéolithique, afin de réduire les réactions de surcraquage. Pour cela, il a été choisi de synthétiser directement des nanocristaux de zéolithe Y sans agent organique structurant, avec un rapport Si/Al le plus élevé possible. Cette propriété leur confère une meilleure stabilité lors des post-traitements, indispensables pour atteindre le rapport Si/Al des zéolithes USY actuellement utilisées. Grâce à l’élaboration d’une nouvelle stratégie de synthèse, des nanocristaux compris entre 20 et 90 nm avec un rapport Si/Al variant de 2,2 à 2,6 ont été obtenus. Puis, l’obtention de la forme protonée de ces nanocristaux (90 nm) a été étudiée et des mesures d’acidité ont également été effectuées
The fractionated distillation of crude oil is not sufficient to cover all the fuel needs and produces large amounts of long chain carbon distillates (C20-C50). Thus, these hydrocarbons are transformed into lighter hydrocarbon molecules by two processes: fluid catalytic cracking or hydrocracking. The latter allows the selective cracking of hydrocarbons essentially in gas oil and kerosene. The acid catalysts used are “bifunctional”: a zeolite matrix USY (ultra-stabilized zeolite Y) performs the hydrocarbons cracking, at the same time a sulfide or a noble metal catalyzes hydrogenation and dehydrogenation reactions. The aim of this work is to maximize the selectivity to middle distillates by decreasing the residence time of hydrocarbon molecules in the zeolite framework. For this, it was chosen to directly synthesize zeolite Y nanocrystals with the highest possible Si/Al ratio, in a SDA-free medium. This property gives them a better stability during the post-treatments essential to reach the Si/Al ratio of the currently used USY zeolite. Thanks to a new synthesis strategy, nanocrystals between 20 and 90 nm with a Si/Al ratio varying from 2.2 to 2.6 were obtained. Then, the protonated form of these nanocrystals (90 nm) was studied and acidity measurements were also carried out

This thesis is devoted to the development of nano-focusing refractive optics for high energy X-rays using planar microelectronic technology. The availability of such optics is the key for the exploitation of high brilliance third and fourth generation X-ray sources. Advancements in the quality of optics available are commensurate with advancements in the fabrication technology. The fabrication process directly influences the quality and performance, so must be understood and controlled. In the first part of this thesis, the development of high aspect ratio Si kinoform lenses is examined. It is shown that control of the re-entrance angle is critical for successful fabrication; in fact, a large re-entrance angle can destroy the lens during the fabrication process. Through an etch study, it was found that as aspect ratio increases, control of the re-entrance angle becomes harder. To control the re-entrance angle for very high aspect ratios, a novel approach based on sacrificial structures was proposed and initial results presented. The second part is dedicated to an experimental study of refractive lenses made from diamond. Due to its low atomic number, relatively high density and very high thermal conductivity, diamond is one of the most desirable lens materials for refractive X-ray optics. However, due to its extreme hardness, it is very difficult to structure into a form suitable for X-ray lenses. To overcome this difficulty a Si moulding technique was used and focusing down to a 400 nm wide spot was achieved. Several obstacles were encountered and successfully overcome. The hardest obstacle was to obtain selective void-free filling in the Si moulds. Several methods were investigated. A method based on a sacrificial oxide layer and an Electrostatic Self-Assembly process was found to be the most useful. The approach discovered in this thesis is not limited to X-ray lenses, but can be applied to a wide variety of high aspect ratio MEMS requiring void-free diamond filling and smooth sidewalls.

This work concerns a systematic study of IC engine operation with 100% biogas as fuel (as opposed to the dual-fuel mode) with particular emphasis on operational issues and the quest for high efficiency strategies. As a first step, a commercially available 1.2 kW genset engine is modified for biogas operation. The conventional premixing of air and biogas is compared with a new manifold injection strategy. The effect of biogas composition on engine performance is also studied. Results from the genset engine study indicate a very low overall efficiency of the system. This is mainly due to the very low compression ratio (4.5) of the engine. To gain further insight into factors that contribute to this low efficiency, thermodynamic engine simulations are conducted. Reasonable agreement with experiments is obtained after incorporating estimated combustion durations. Subsequently, the model is used as a tool to predict effect of different parameters such as compression ratio, spark timing and combustion durations on engine performance and efficiency. Simulations show that significant improvement in performance can be obtained at high compression ratios. As a step towards developing a more efficient system and based on insight obtained from simulations, a high compression ratio (9.2) engine is selected. This engine is coupled to a 3 kW alternator and operated on 100% biogas. Both strategies, i.e., premixing and manifold injection are implemented. The results show very high overall (chemical to electrical) efficiencies with a maximum value of 22% at 1.4 kW with the manifold injection strategy. The new manifold injection strategy proposed here is found to be clearly superior to the conventional premixing method. The main reasons are the higher volumetric efficiency (25% higher than that for the premixing mode of supply) and overall lean operation of the engine across the entire load range. Predictions show excellent agreement with measurements, enabling the model to be used as a tool for further study. Simulations suggest that a higher compression ratio (up to 13) and appropriate spark advance can lead to higher engine power output and efficiency.

Ion current sensing, where information about the combustion process in an SI-engine is gained by applying a voltage over the spark gap, is currently used to detect and avoid knock and misfire. Several researchers have pointed out that information on peak pressure location and air/fuel ratio can be gained from the ion current and have suggested several ways to estimate these parameters.

Here a simplified Bayesian approach was taken to construct a lowpass-like filter or estimator that makes use of prior information to improve estimates in crucial areas. The algorithm is computationally light and could, if successful, improve estimates enough for production use.

The filter was implemented in several variants and evaluated in a number of simulated cases. It was found that the proposed filter requires a number of trade-offs between variance, bias, tracking speed and accuracy that are difficult to balance. For satisfactory estimates and trade-off balance the prior information must be more accurate than was available.

It was also found that similar a task, constructing a general Bayesian estimator, has already been tackled in the area of particle filtering and that there are promising and unexplored possibilities there. However, particle filters require computational power that will not be available to production engines for some years.

Vid jonströmsmätning utvinns information om förbränningsprocessen i en bensinmotor genom att en spänning läggs över gnistgapet och den resulterande strömmen mäts. Jonströmsmätning används idag för knack- och feltändningsdetektion. Flera forskare har påpekat att det finns än mer information i jonströmmen, bl.a. om bränsleblandningen och cylindertrycket och har även föreslagit metoder för att utvinna och använda den informationen för skattning av dessa parametrar.

Här presenteras en förenklad Bayesisk metod i form av en lågpassfilter-liknande skattare som använder förkunskap till att förbättra estimat på relevanta områden. Algoritmen är beräkningsmässigt lätt och kan, om den är framgångsrik, leverera skattningar av förbränningsparametrar som är tillräckligt bra för att användas för sluten styrning av en bensinmotor.

Skattaren, eller filtret, implementerades i flera varianter och utvärderades i ett antal simulerade fall. Resultaten visade på att flera svåra avvägningar måste göras mellan förbättring i varians, avvikelse och följning eftersom förbättring i den ena ledde till försämring i de andra. För att göra dessa avvägningar och få goda skattningar krävs bättre förhandskunskap och mätdata än vad som var tillgängligt.

Bayesisk skattning är ett stort befintligt område inom statistik och signalbehandling och den mest generella skattaren är partikelfiltret som har många intressanta tillämpningar och möjligheter. De har hittills inte använts inom skattning av förbränningsparametrar och har således go potential för framtida utveckling. De är dock beräkningsmässigt tunga och kräver beräkningsresurser utöver vad som är tillgängliga i ett motorstyrsystem idag.

>Magister Scientiae - MSc
Ethylene and propylene are greatly used for their importance as feedstocks for producing useful materials. Due to rise in prices and the demand of ethylene and propylene, the need to increase the selective production of these light olefins is necessary. To achieve this, zeolites, specifically ZSM-5 has been used to investigate catalytic cracking of several types of hydrocarbons for the production of these light olefins. This study focuses on developing hierarchical macro and/or mesoporous ZSM-5 zeolites with variable Si/Al ratios. The synthesized materials were then evaluated on their performance via catalytic cracking of hexane, dodecane and tyre derived oil [TDO] to produce light olefins, particularly ethylene and propylene.

In this thesis, exergy based SI engine model optimisation (EBSIEMO) is studied and evaluated. A four-stroke bi-fuel spark ignition (SI) engine is modelled for optimisation of engine performance based upon exergy analysis. An artificial neural network (ANN) is used as an emulator to speed up the optimisation processes. Constrained particle swarm optimisation (CPSO) is employed to identify parameters such as equivalence ratio and ignition time for optimising of the engine performance, based upon maximising 'total availability'. In the optimisation process, the engine exhaust gases standard emission were applied including brake specific CO (BSCO) and brake specific NOx (BSNOx) as the constraints. The engine model is developed in a two-zone model, while considering the chemical synthesis of fuel, including 10 chemical species. A computer code is developed in MATLAB software to solve the equations for the prediction of temperature and pressure of the mixture in each stage (compression stroke, combustion process and expansion stroke). In addition, Intake and exhaust processes are calculated using an approximation method. This model has the ability to simulate turbulent combustion and compared to computational fluid dynamic (CFD) models it is computationally faster and efficient. The selective outputs are cylinder temperature and pressure, heat transfer, brake work, brake thermal and volumetric efficiency, brake torque, brake power (BP), brake specific fuel consumption (BSFC), brake mean effective pressure (BMEP), concentration of CO2, brake specific CO (BSCO) and brake specific NOx (BSNOx). In this model, the effect of engine speed, equivalence ratio and ignition time on performance parameters using gasoline and CNG fuels are analysed. In addition, the model is validated by experimental data using the results obtained from bi-fuel engine tests. Therefore, this engine model was capable to predict, analyse and useful for optimisation of the engine performance parameters. The exergy based four-stroke bi-fuel (CNG and gasoline) spark ignition (SI) engine model (EBSIEM) here is used for analysis of bi-fuel SI engines. Since, the first law of thermodynamic (the FLT), alone is not able to afford an appropriate comprehension into engine operations. Therefore, this thesis concentrates on the SI engine operation investigation using the developed engine model by the second law of thermodynamic (the SLT) or exergy analysis outlook (exergy based SI engine model (EBSIEM)) In this thesis, an efficient approach is presented for the prediction of total availability, brake specific CO (BSCO), brake specific NOx (BSNOx) and brake torque for bi-fuel engine (CNG and gasoline) using an artificial neural network (ANN) model based on exergy based SI engine (EBSIEM) (ANN-EBSIEM) as an emulator to speed up the optimisation processes. In the other words, the use of a well trained an ANN is ordinarily much faster than mathematical models or conventional simulation programs for prediction. The constrained particle swarm optimisation (CPSO)-EBSIEM (EBSIEMO) was capable of optimising the model parameters for the engine performance. The optimisation results based upon availability analysis (the SLT) due to analysing availability terms, specifically availability destruction (that measured engine irreversibilties) are more regarded with higher priority compared to the FLT analysis. In this thesis, exergy based SI engine model optimisation (EBSIEMO) is studied and evaluated. A four-stroke bi-fuel spark ignition (SI) engine is modelled for optimisation of engine performance based upon exergy analysis. An artificial neural network (ANN) is used as an emulator to speed up the optimisation processes. Constrained particle swarm optimisation (CPSO) is employed to identify parameters such as equivalence ratio and ignition time for optimising of the engine performance, based upon maximising 'total availability'. In the optimisation process, the engine exhaust gases standard emission were applied including brake specific CO (BSCO) and brake specific NOx (BSNOx) as the constraints. The engine model is developed in a two-zone model, while considering the chemical synthesis of fuel, including 10 chemical species. A computer code is developed in MATLAB software to solve the equations for the prediction of temperature and pressure of the mixture in each stage (compression stroke, combustion process and expansion stroke). In addition, Intake and exhaust processes are calculated using an approximation method. This model has the ability to simulate turbulent combustion and compared to computational fluid dynamic (CFD) models it is computationally faster and efficient. The selective outputs are cylinder temperature and pressure, heat transfer, brake work, brake thermal and volumetric efficiency, brake torque, brake power (BP), brake specific fuel consumption (BSFC), brake mean effective pressure (BMEP), concentration of CO2, brake specific CO (BSCO) and brake specific NOx (BSNOx). In this model, the effect of engine speed, equivalence ratio and ignition time on performance parameters using gasoline and CNG fuels are analysed. In addition, the model is validated by experimental data using the results obtained from bi-fuel engine tests. Therefore, this engine model was capable to predict, analyse and useful for optimisation of the engine performance parameters. The exergy based four-stroke bi-fuel (CNG and gasoline) spark ignition (SI) engine model (EBSIEM) here is used for analysis of bi-fuel SI engines. Since, the first law of thermodynamic (the FLT), alone is not able to afford an appropriate comprehension into engine operations. Therefore, this thesis concentrates on the SI engine operation investigation using the developed engine model by the second law of thermodynamic (the SLT) or exergy analysis outlook (exergy based SI engine model (EBSIEM)) In this thesis, an efficient approach is presented for the prediction of total availability, brake specific CO (BSCO), brake specific NOx (BSNOx) and brake torque for bi-fuel engine (CNG and gasoline) using an artificial neural network (ANN) model based on exergy based SI engine (EBSIEM) (ANN-EBSIEM) as an emulator to speed up the optimisation processes. In the other words, the use of a well trained an ANN is ordinarily much faster than mathematical models or conventional simulation programs for prediction. The constrained particle swarm optimisation (CPSO)-EBSIEM (EBSIEMO) was capable of optimising the model parameters for the engine performance. The optimisation results based upon availability analysis (the SLT) due to analysing availability terms, specifically availability destruction (that measured engine irreversibilties) are more regarded with higher priority compared to the FLT analysis.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
The aim of this work is analyze the rates of modalization in the discursive genre advice letter, in order to observe how they help in the construction of self image. We are interested in the analysis of images that the authors of letters build in their discourses. As second objective, we intend to verify if the discourses of the letters break with the traditional stereotype of female figure and its social role or pointed traditional roles. The corpus of that work is compound for six advice letters published in the column Consultório Sentimental of Veja.com Magazine and signed by the columnist Betty Milan. The analysis is made based in the rules of Bakhtin about the genres of discourse, the notion of ethos discoursed by Amossy (2005) and Maingueneau (2001, 2005, 2008) and of Kerbrat-Orecchioni (1980) about the rates of modalization. The studies of Bakhtin were used to analyze the advice letters while genre of discourse, considering theirs constituents (theme, style, and composition) and theirs authors. As the studies about media and social construction of genre, we intend to point the role of media in the spread of social roles of women and men in social relations. These are built in the interaction among women, men and society.
Este trabalho tem como objetivo analisar os índices de modalização presentes no gênero discursivo carta de aconselhamento a fim de observar como eles auxiliam na construção da imagem de si. Estamos interessadas na análise da imagem que as autoras dessas cartas constroem no seu discurso. Como segundo objetivo, pretendemos verificar se os discursos dessas cartas rompem com o estereótipo tradicional da figura feminina e seu papel social ou pontuam papéis tradicionais. O corpus deste trabalho é composto por seis cartas de aconselhamento, publicadas na coluna Consultório Sentimental da revista Veja.com e assinada pela colunista Betty Milan. A análise foi realizada com base nos preceitos de Bakhtin acerca dos gêneros do discurso, da noção de ethos discutida por Amossy (2005) e Maingueneau (2001, 2005, 2008) e de Kerbrat-Orecchioni (1980) acerca dos índices de modalização. Os estudos de Bakhtin foram usados para analisar as cartas de aconselhamento enquanto gêneros do discurso, considerando seus constituintes (tema, estilo e composição) e sua autoria. Com os estudos sobre mídia e construção social de gênero pretendemos apontar o papel da mídia na veiculação dos papéis sociais de mulheres e homens nas relações sociais. Estas são construídas na interação entre mulheres, homens e sociedade.

Thesis (Ph.D.); Submitted to the University of California, Berkeley, CA (US); 24 Nov 2004.
Published through the Information Bridge: DOE Scientific and Technical Information. "LBNL--56751" McGuire, John Andrew. USDOE Director. Office of Science. Office of Basic Energy Sciences. Materials Science and Engineering Division (US) 11/24/2004. Report is also available in paper and microfiche from NTIS.

Orientador: Thales Rocha de Mattos Filho
Tese(doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba
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Resumo: Ratos albinos machos foram utilizados para investigar os efeitos de antagonista específico de receptores Hl periféricos, Terfenadina e receptores H2, Cimetidina sobre as concentrações dos elementos Ca, P, Mg, Si, B e Sr, através de Espectroscopia de Emissão Atômica com Plasma Induzido (ICP-AES), no soro destes animais durante a regeneração hepática após hepatectomia parcial. Setenta e três ratos divididos em três grupos foram sacrificados respectivamente 6, 24 e 360 h após a técnica cirúrgica. Cada grupo contendo 4 subgrupos receberam doses de Terfenadina (2mg/kg/dia), Cimetidina (20mg/kg/dia), Terfenadina (2mg/kg/dia) + Cimetidina (20mg/kg/dia) e NaCl 0,9% (Controle), intraperitonealmente durante o tempo do experimento. Os resultados obtidos sugerem que os níveis de P, Mg e Sr não sofrem alterações no soro durante a regeneração hepática, com os níveis de Ca apresentando um significante turnover nos grupos tratados e Si e especialmente, B tendo importantes alterações
Abstract: Adult male albino rats (Wistar strain) were used to investigate the effects of selective antagonist of only peripheral histamine Hl-receptors, Terfenadine and histamine H2-receptors antagonist, Cimetidine on the serum concentrations of elements Ca, P, Mg, Si, B and Sr, by Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES) during liver regeneration after partial hepatectomy. Seventy-three animals were randomly divided into three groups and were sacrificed respectively 6, 24 and 360 h postoperatively. Each group was divided into four sub-groups that received doses of Terfenadine (2mg/kg/day), Cimetidine (20mg/kg/day), Terfenadine (2mg/kg/day) + Cimetidine (20mg/kg/day) and NaCl 0,9% (Control), intraperitoneal^ during the experimentation. The results obtained suggested that P, Mg and Sr levels not modified in rat serum during liver regeneration, with Ca levels' exhibiting a significant turnover in the treated groups and Si, specially, Boron showing important changes
Doutorado
Farmacologia
Doutor em Ciências

Today, with various technology and business standards, organizations face rapid changes in both internal and external environments. To be able to rapidly respond to such changing environments, integration of software systems has entered among the top priorities of many organizations. However, despite extended use of software integration, methods for estimating the business value of implementing such integration are still missing. Besides presenting a conceptual model to define the benefits of systems integration and related causal relationships, this study proposes a method for measuring such benefits in monetary terms. In particular, we  demonstrate how a mathematical programming technique called Data Envelopment Analysis (DEA) can be used to evaluate the business value of software integration. Our method is illustrated using data from 12 organizations. The results indicate significant productivity gains by integrating software systems, which represent the value of software integration in organizations.

PRC is no longer seen only as a "world factory". It gains on importace as an global trading partner and many foreign companies try to succeed in Chinese market as importers of their products. Also Czech businesses have already penetrated Chinese market, invested there or are seriously considering expansion to the market. Main objectives of the thesis are to review and characterize main risks, obstacles and barriers which Czech entrepreneurs have to deal with when entering the Chinese market and suggestions how to obviate them.

La formation du noyau sur Terre se produit par différenciation métal-silicate dans un océan magmatique. Ce processus d'équilibrage permet d'éliminer les éléments sidérophiles du manteau jusqu'au noyau, en fixant la composition en éléments traces des deux réservoirs. Des expériences de cloisonnement métal-silicate à haute pression et à haute température peuvent être utilisées pour faire correspondre les abondances observées et, comme le cloisonnement des éléments est fonction de P, T, fO2 et de la composition, elles limitent davantage les conditions thermochimiques de la formation du noyau. Dans cette thèse, des expériences de partitionnement métal-silicate superliquide des éléments sidérophiles et lithophiles (Ni, Cr, V, Nb, Ta et W) ont été réalisées dans des cellules d'enclumes de diamant chauffées au laser dans des conditions P-T jusqu'à 94 GPa et 4500K. Dans ces conditions P-T extrêmes, on constate que (1) aucun effet mesurable de la concentration de nickel sur le partage du Ni, du Cr et du V, l'alliage Fe-Ni est chimiquement idéal sur une large gamme de concentrations de Ni (3.5 à 48.7 % en poids) ; (2) Nb, Ta et W deviennent plus siderophile avec la température et en interaction avec l'oxygène du métal alors que Nb et W deviennent moins siderophile sous pression. En nous basant sur le paramétrage de nos résultats à haute teneur en P en fonction de P, T, fO2 et de la composition, nous avons modélisé une formation de noyaux à plusieurs stades et montré que le rapport Nb/Ta sous-chondritique dans le manteau peuvent s'expliquer soit en oxydant soit en réduisant les conditions de formation du noyau.Après le dernier événement de différenciation noyau-manteau, le noyau de la Terre est considéré comme fixé. On a récemment proposé que le SiO2 puisse se cristalliser à partir d'un alliage liquide de Fe-Si-O au sommet du noyau pendant le refroidissement séculaire, et flotter en raison de sa flottabilité négative, modifiant ainsi sa composition avec le temps. Nous avons étudié ici le champ liquidus des binaires Fe-Si, Fe-O et ternaires Fe-Si-O à la pression d'enveloppe du manteau du noyau et une gamme de températures en utilisant la dynamique moléculaire ab initio, englobant toutes les valeurs plausibles pour le noyau à travers le temps géologique. Nous constatons que les liquides restent bien mélangés avec des propriétés ternaires identiques au mélange de propriétés binaires. Des simulations en deux phases du SiO2 solide et du Fe liquide montrent une dissolution à des températures égales ou supérieures à 4100 K, ce qui suggère que la cristallisation du SiO2 ainsi que l'immiscibilité du liquide dans le Fe-Si-O sont peu probables dans le noyau terrestre
Core formation on Earth occurs by metal-silicate differentiation in a magma ocean. This equilibration process strips siderophile elements from the mantle to the core, setting the trace-element composition of both reservoirs. High-pressure and high-temperature metal-silicate partitioning experiments can be used to match the observed abundances, and because element partitioning is a function of P, T, fO2 and composition, further constrain the thermochemical conditions of core formation. In this thesis, superliquidus metal-silicate partitioning experiments of both siderophile and lithophile elements (Ni, Cr, V, Nb, Ta and W) have been performed in laser-heated diamond anvil cells at P-T conditions up to 94 GPa and 4500 K. At these extreme P-T conditions, it is found that (1) no measurable effect of nickel concentration on the partitioning of Ni, Cr and V, the Fe-Ni alloy is chemically ideal over a broad range of Ni concentrations (3.5 to 48.7 wt%); (2) Nb, Ta and W become more siderophile with temperature and by interacting with oxygen in the metal, whereas Nb and W become less siderophile with pressure. Based on the parameterization of our high-P results as a function of P, T, fO2 and composition, we have modelled a multi-stage core formation and shown that subchondritic Nb/Ta ratio in the mantle can be explained by either oxidizing or reducing core-forming conditions. After the last event of core-mantle differentiation, the Earth’s bulk core is considered frozen from then onwards. It was recently proposed that SiO2 could crystallize from a Fe-Si-O liquid alloy at the top of the core during secular cooling, and float out due to its negative buoyancy, hence changing core composition over time. Here we investigated the liquidus field of Fe-Si, Fe-O binaries and Fe-Si-O ternaries at core-mantle boundary pressure and a range of temperatures using ab initio molecular dynamics, encompassing any plausible values for the core through geological time. We find that the liquids remain well mixed with ternary properties identical to the mixing of binary properties. Two‐phase simulations of solid SiO2 and liquid Fe show dissolution at temperatures at and above 4100 K, suggesting that SiO2 crystallization as well as liquid immiscibility in Fe–Si–O is unlikely to occur in Earth's core

La partie principale de cette these est consacree a l'etude du compose a fermions lourds uir#2si#2. L'elaboration de monocristaux de grande purete chimique en a ete une etape importante. L'etude et la mise au point d'un nouveau four de tirage czochralski a chauffage tri-arcs sont decrites. Cet appareillage, entierement concu en technique ultravide, a permis la synthese de monocristaux dont les caracteristiques sont meilleures que celles publiees, jusqu'a ce jour. La recherche de nouveaux intermetalliques ternaires proches, dans le diagramme d'equilibre, des composes a fermions lourds de formule generale 1-2-2 est egalement abordee. Trois nouvelles familles de composes ont ete ainsi mises en evidence: m#2t#3x, m#6t#1#6x#7 et m#4t#1#3x#9 (avec m = terre rare ou uranium, t = element de transition et x = silicium ou germanium). Leurs proprietes cristallographiques et physiques ont ete etudiees. Les composes des deux premieres familles sont paramagnetiques de type pauli. Ceux de la troisieme sont, en revanche, tous ordonnes, avec des comportements magnetiques varies. En particulier, nos mesures revelent que u#4ir#1#3si#9 et u#4ir#1#3ge#9 sont deux nouveaux fermions lourds presentant trois transitions magnetiques. Les etudes realisees au cours de ce travail sur uir#2si#2 confirment toute la complexite de ce compose a fermions lourds. Les caracterisations structurales de nos monocristaux ont mis en evidence, pour la premiere fois, l'existence de substitutions d'iridium, par du silicium, sur les deux sites cristallographiques de l'iridium. Les sites de silicium ne sont pas affectes par ce melange, ce qui n'avait jamais ete soupconne. L'influence du recuit et de la stoechiometrie sur les proprietes de uir#2si#2 est egalement presentee. Les etudes par diffraction des neutrons ont montre que uir#2si#2 est antiferromagnetique de type i, que la densite d'aimantation est isotrope et presque uniquement portee par l'uranium et qu'il existe une contribution positive supplementaire attribuable aux electrons de conduction

La premiere partie de cette these est consacree a l'etude des structures magnetiques des monopnictures et des monochalcogenures de neptunium. Dans la seconde partie, nous avons etudie les excitations magnetiques des solutions solides de u(ru#1#-#xrh#x)#2si#2. Par la determination des structures magnetiques de npp et de npbi, nous avons termine la serie des monopnictures de neptunium. Tous ces composes ont une structure magnetique avec un vecteur de propagation et des composantes de fourier selon les axes quatre. En utilisant cette propriete, nous avons etabli un modele de type annni qui nous a permis de suivre l'evolution des integrales d'echange avec le pnictogene. Les monochalcogenures de neptunium ont tous une structure antiferromagnetique de type ii. Cependant, nps presente une transition du premier ordre, tandis que la transition magnetique de npse et npte est du second ordre. En utilisant des proprietes de symetrie du cristal, les resultats de spectroscopie mossbauer ainsi que les resultats de diffraction neutronique, nous avons determine des solutions possibles pour les structures magnetiques de nps et npse. Ces solutions sont multi-k et assez compliquees. Pour npte, l'etude du facteur de forme et l'evolution thermique du moment magnetique ont montre que ce compose avait un comportement magnetique tres particulier. Nous avons utilise trois methodes pour etudier les solutions solides de u(ru#1#-#x-rh#x)#2si#2s: chaleur specifique, diffraction elastique et inelastique de neutrons. Par un modele simple, nous avons pu relier la dependance en temperature du gap des excitations antiferromagnetiques a l'anomalie de la chaleur specifique a t#n. Les excitations magnetiques ont ete decrites comme etant dues a un champ cristallin a deux niveaux couples par une interaction anisotrope de type rkky. Nous avons vu aussi que l'evolution du moment magnetique avec la concentration de rhodium est tres particuliere: la temperature de transition decroit, alors que la valeur du moment a basse temperature augmente

碩士
中山醫學大學
公共衛生學系碩士班
99
Al2O3 supported catalyst has been used as oxidative catalyst for CO gaseous pollutant removal widely. Although Al2O3 supported catalyst shows the good catalytic activity, the catalytic oxidation is limited with high reaction temperature required. By comparing with a conventional heat-treated catalyst, the photocatalyst may operate at room temperature in the atmospheric pressure without heating. The photocatalytic reaction is a simple and operating easily method, and then the application of photocatalyst is broadly with less energy consuming. Recently, the researches showed that the TiO2 photocatalyst were supported on the silica substrate over gaseous catalytic reaction and the penetration coefficient of light was improved. However, the porosity of silica substrate was low. The low specific surface area contributed to bad dispersion of TiO2, and the photocatlytic activity was decreased. This study prepared three catalysts (30%Si-70%Ti, 70%Si-30%Ti, 100%Ti) by the hydrothermal method, and then Pt/Si-Ti catalyst was prepared by the microwave heating method. CO was chosen as the reactant for photocatalytic reaction, and the different reaction parameters were studied, such as different ratio of Si/Ti, the effect of Pt, and different light sources. Catalyst properties were analyzed by X-ray powder diffractometer (XRD), Field Emission SEM (FESEM), and Trasmission electron microscope (TEM). FESEM and TEM were used to study the particle size and dispersion of catalysts, and the crystal phase was analyzed by the XRD. The experimental results indicated that the main crystal phase of Si-Ti photocatalyst preparted by the hydrothermal method was rutile. For photocatalytic reaction, the catalytic activity was improved by the metal Pt. Under UV light or visible light, 99% CO removal efficiency was carried out over Pt/30%Si-70%Ti or Pt/100%Ti. The optimum reaction conditions for CO removal over Pt/30%Si-70%Ti were O2 concentration 10%, room temperature, CO concentration 500 ppm, and space velocity 375,000 h-1.

碩士
國立交通大學
應用化學系碩博士班
105
In this study, we took the Ga-Si-B-Ca-Sr system as a reference to understand the sealing materials for solid oxide fuel cell (SOFC). By changing the compositions ratios of Al/Si, La/Si, B/Si, and Ga/Si, different glass samples were synthesized. The effects of composition on the property of the sealing materials were discussed. It was found that nitrate precursors in aqueous solution were easier to make raw materials that created eutectic form and homogeneous reaction in high temperature region. In the Al series, Al2O3 as a network modifier, make the glass transition temperature (Tg), the melting temperature (Tm), the starting point of crystallization temperature (Tx), the crystallization temperature (Tc) and the softening point (Ts) decrease, the coefficient of thermal expansion (CTE) increase. The La series exhibited low thermal vibration, high coordination number, and large radius but weak bonding energy, which increased Tg, Tm and CTE and reduced Tx, Tc and Ts. For B series, the boron element makes structure unstable and cause “Borate Volatility”, which reduced Tg, Tm and Ts, whereas Tx, Tc and CTE were increased. In the Ga series, the, Tg, Tm, Tx, Tc and Ts were increased and CTE increased, which may due to their low thermal vibration, large Ga/Si ratio ( > 1), and weak Ga-O bonding energy. All products in this study exhibit good adhesion with LSGM film at 850oC, but it was found that La and Si may diffuse across the glass-SOFC interface. The effect of La and Si diffusion remains uncertain and will be further studied. In this study, YP052 (12Ga-10Si-2K-2Ca-4Sr-6B-2La-4Al) most reached our goal. It does not crystallize after a long time at the operating temperature and adhere with LSGM well. If we reduce the pre-sintering temperature, YP052 is expected to have less crystallization and better sealing ability. The leak rate could be measured and discussed after the leakage test system established.

碩士
國立臺灣科技大學
化學工程技術研究所
86
W2NX thin films were grown onto Si<100>substrates under different sputtering conditions of N2/Ar flow ratios by RF magnetron sputtering method. Surface profiler and scanning electron microscopy (SEM) were used to obtain the thickness of thin films. The structure, orientation and morphology of these films were investigated using X-ray diffraction (XRD)and atomic force microscopy (AFM). By means of X-ray photoelectron spectroscopy (XPS), the composition of thin films were verified. AES depth profile analysis shows the diffusion of Cu in Cu/W2N1.26/Si structure at different deposition temperatures. 　　The thickness of W2NX thin films was measured using surface profiler and SEM and the deposition rate was found to decrease with increasing N2/Ar flow ratio. Also, the following results were found by XRD and XPS with increasing N2 flow rate: (1)The phase transfer is βw→co-exist αw and βw →αw →W2N. (2)N/W ratio has a maximun value of 0.63. (3) The binding energy of W4f in W2N is 31.8 eV. According to the AES depth profile analysis, the Cu/W2N1.26/Si struture is stable after 30 minutes annealing at 500℃. However, it also shows that N/W ratio decreased with increasling anneaing temperature.

碩士
國立臺北科技大學
車輛工程系所
98
The targeted developments for future vehicles are how to reduce fuel consumption, pollutant emission while maintaining high level of engine performance. To deal with those issues, fuel system has been taken great concerns by scientists for a long period of time. As we know, Port Fuel Injection system (PFI) and Gasoline Direct Injection system (GDI) are popular techniques which are being used on commercial vehicles. This paper presents the possible improvement of engine performance by applying effect of swirl motion on lean-limit of semi-direct injection SI engine. The fuel goes into cylinder directly through intake valve near the middle intake stroke to make richer mixture around the spark plug, which is called semi-direct injection (SDI). Thus, this system includes high swirl charge, injection during intake valve opening, and air-assisted fuel injection. The modifications of intake port by using baffle plate and the other by closing one intake valve for the 125 cc, 4-valve, port-fuel-injection (PFI) engine to increase swirl ratio of in-cylinder air motions which helped to form rich mixture around spark plug, and lean mixture at other location. The swirl motion were measured on steady flow bench. Therefore, This paper was also as investigated effect of swirl ratio on performance of lean burn SDI comparing to original PFI engine. Additionally, in-cylinder swirl motion which was made by swirl generator in the intake port was used to reach stratified charge. The SDI engine then was tested under lean conditions at 4500 rpm and 5300 rpm. Engine torque, fuel consumption, exhaust emissions, and engine combustion characteristics were investigated. Experimental results indicated that lean-limit was extended to maximum air-fuel ratio 26.28 (lambda = 1.8) at swirl ratio 3.5 while brake specific fuel consumption and coefficient of cycle variation were decreased. In addition, analysis on engine exhausted gas showed the decrease of CO and HC emissions. However, NOx emission increased sharply near stoichiometric air fuel ratio (AFR) and decreased with the rise of AFR at lean combustion comparing to original PFI engine.

碩士
臺灣大學
光電工程學研究所
96
In this thesis, correlation between N2O/SiH4 fluence ratio and O/Si composition ratio for optimizing Si nanocrystal precipitation in Si-rich SiOx grown by low-plasma PECVD is demonstrated. The O/Si composition ratio of SiOx can be adjustable from 1.38 to 0.88 by detuning N2O fluence and N2O/SiH4 ratio to obtain a nonlinearly Gaussian-like dependency with near-infrared photoluminescence (PL). By reducing N2O/SiH4 ratio, abundant Si-H bonds with absorption at 870 and 2250 cm-1 assist small-size Si nanocrystal precipitation and prevent outer surface re-oxidation. Maximum PL at 760 nm at O/Si=1.24 with corresponding Si concentration of 44.64 atom.% is obtained at N2O/SiH4 ratio of 5.5. In particular, the N2O fluence remains as small as 25 sccm to restrict oxygen desorption and to complete SiH4 decomposition, thus minizing the hydrogen passivation on dangling bonds at Si nanocrystal surface. The N2O:SiH4 fluence is decreased to 5:1 and the optimized annealing are achieved as short as 15 min at 1100oC in comparison with typical 1-hr process. HRTEM analysis reveals such tiny Si nanocrystals exhibit diameter of only 1.5±0.2 nm. From FTIR results, we conclude that the ultra-low fluence PECVD can completely decompose the Si from SiH4 with minimum hydrogen passivation, which facilitates the precise control of Si nanocrystal size and greatly enhances the blue PL intensity. The blue-light EL pattern is observed at 290 V for the MOSLED made on SiOx grown at N2O fluence as low as 25 sccm. The maximum emitting power is about 333~500 nW for the blue-light MOSLED as compared to that of 270 nW for red-light MOSLED associated with a PI slope of 0.37 mW/A. Higher output power of MOSLED on low-N2O-fluence grown SiOx is attributed to the smaller Si nanocrystals with larger density.

碩士
國立東華大學
應用物理研究所
96
Using atomic force microscope (AFM) anodic nano-oxide bumps were locally tip-induced on a native SiO2 layer of Si(111) in contact mode. To study the anodic growth mechanism and the ratios of O and Si, wavelength dispersion spectroscopy (WDS) and scanning photoelectron spectromicroscopy (SPEM) were exploited. From the semi-quantitative WDS spectra, the nano-oxide bump contains more oxygen than the native SiO2 layer, indicating that the ratio of O and Si of the nano-oxide bump is greater than 2. From the quantitative SPEM spectra, the components of Si4+O4, Si3+O3, Si2+O2, and Si can be separated. From the intensity ratios of Si4+O4, Si3+O3, Si2+O2, and Si, we can easily and exactly obtain the ratio of O and Si of the nano-oxide bump. The higher nano-oxide bumps get the larger ratios of O and Si.

碩士
國立屏東科技大學
機械工程系所
104
1.The microstructure of as-forged brass with lower (0.23 and 0.25) Si/Mn ratios is a αCu matrix with some Mn5Si3 precipitates. However, when heated at or above 820°C, the Mn5Si3 precipitates would be not found. 2.When aged above the temperature ranging between 760 and 790℃, some βCu-phase would be occurred on the brass with lower Si/Mn ratios(0.23, 0.25) resulting to being duplex phase matrix. However, the microstructure of the brass with higher Si/Mn ratiow(0.36) would be a single βCu phase. 3.During the high-temperature heated treatment, both of the size and amount of Mn5Si3 precipitates would be growth. In addition, when aged at lower temperature, some niddle-like precipitates are formed within the αCu matrix. Based on the kikuchi maps, these niddle-like precipitates could be analyzed to a Orthorhombic structure, of which the lattice parameters being a=0.486nm, b=0.443nm and c=1.095nm. 4.The amount of the Mn5Si3 precipitates and niddle-like precipitates formed within the αCu matrix could be consistent with the Si/Mn ratios. Addituionally, the contents of the Fe alloy element would play an important role on the precipitations during the aging processes.

碩士
國立東華大學
應用物理研究所
95
We present the results of the electrical resistivity, thermal conductivity, as well as Seebeck coefficient measurements on the stoichiometric CaAl2Si2 and non-stoichiometric CaAl1.75Si2.25, CaAl1.9Si2.1, CaAl2.1Si1.9, and CaAl2.25Si1.75 compounds in the temperature range between 10 and 300 K. It has been found that the magnitude of electrical resistivity decreases for the non-stoichiometric samples, attributed to the shift of Fermi energy from the dip of the density of states as a consequence of the change of Al/Si ratio. From the thermal conductivity results, we correlated the extent of disorder and Al/Si ratio with various thermal scattering mechanisms in the investigated temperature range. In addition, a systematic change in the magnitude of Seebeck coefficient as a function of Al/Si concentration has been observed. These results have been associated with the effect of hole/electron doping on the Fermi level density of states. A detailed analysis of the electrical resistivity and Seebeck coefficient suggest the presence of two types charge carriers and the temperature dependent changes in their mobility.

碩士
嘉南藥理大學
觀光事業管理系
103
After the opening of Hsuehshan Tunnel, the traffic volume increases drastically and Jiaosi has become popular tourist attractions in recent years. In addition to the research of distribution of water volume in Jiaosi hot springs area, this thesis discusses the total amount control is in accordance with hot spring resource distribution in Jiaosi hot springs area by monitoring data. This study is used the rainfall and evaporation data in 2012 to estimation the Jiaosi cold water dischange. volume and hot springs area with rainfall and evaporation data in 2012. This thesis designs the proportion experiment of mixing indoor and field cold and hot water to estimate the different mixing proportion of cold and hot water districts with different temperatures. Which can estimate hot water and hot spring volume in every district of Jiaosi hot springs area through temperature and empirical formulas The results show that the daily cold water volume was 5,733 m3 and hot water was 1,989 CMD, hot spring water was 7,722 CMD in 2012, while nearby the temperature method empirical of Chen (2014). The cold water was 4,500 CMD and the hot water was 1,086 CMD, hot spring water volume in Jiaosi hot spring area was 5,586 CMD in 2013. The estimates of hot water volume were as follows: Tangwei Station (41%), Tourist Center Station (24%), Park Station (10%) and Parking Lot Shen Station (9%). Accounting for only 48% of the total area, the four districts own 84% of the total hot water volume. Dazhong Road Station (8%), Qilidanqian Station (5%) and New Xiaoshen Station (3%) only have 16% of hot water volume. The total hot spring volume should be subregional control is reasonable.

Future internal combustion engines demand higher efficiency but progression towards this is limited by the phenomenon called knock. A possible solution for reaching high efficiency will be to improve the anti-knock quality of the fuels by blending high-octane fuel with a low-octane fuel. In this study, the non-linear blending effect by blending oxygenated/non-oxygenated fuels of high octane number with low octane fuels were studied in three different combustion modes: Spark ignition (SI), Homogeneous Charge Compression ignition (HCCI) and Compression Ignition (CI). For SI combustion, RON and MON was used for the fuel rating, for HCCI combustion, Lund Chevron HCCI fuel number and for rich combustion conditions, Derived Cetane Number (DCN) was used to understand the fuel auto-ignition behavior. A Cooperative Fuel Research (CFR) engine was used for SI and HCCI mode whereas Ignition Quality Tester (IQT) was used for CI mode. The non-linear blending behavior was described using the concept of blending octane number. Five octane additives including ethanol, methanol, 1-butanol, toluene and iso-octane were used in this study, of which ethanol and methanol gave the strongest octane enhancement effect whereas iso-octane resulted in the weakest octane enhancement. The base fuel composition and octane number also had an important role in the blending behavior of the fuels. The non-linear blending of fuels highlighted that some of the blended fuels behaved similarly in both SI and HCCI combustion mode, therefore the study was further extended to understand the pre-spark heat release or Low temperature heat release (LTHR) in both the combustion modes. Knock occurs in SI due to end-gas auto-ignition and for HCCI, the combustion is controlled by auto-igniting of the complete charge inside the cylinder. Therefore fundamentally the combustion process in the end gas region of SI and HCCI combustion modes is controlled by auto-ignition. In this respect, HCCI combustion was used as an alternative path to understand the end-gas auto-ignition in SI engine using the standard CFR engine. Pre-spark heat release or low temperature reactions were detected in both the combustion modes.

碩士
中興大學
材料工程學系所
95
Recently﹐the recording of blue-ray write-once disk are mainly made by a-Si/Cu . However﹐due to the advances of the blue-ray disk technique day by day﹐the multi-layers is developed successfully . Therefore﹐we need to further increase the data transfer rate﹐but must change the film structure or use the other material to instead of a-Si . In this study﹐different thickness ratio of a-Ge/Ni、a-Si/a-Ge/Ni and a-Ge/Ni/a-Si recording film by an ion beam assisted deposition(IBAD) system was adopted as the recording layer for the blue-ray write-once disk . Learnt by the experimental result﹐a-Ge(20 nm)/ Ni(1 nm) of recording film only the phase variety of two stages happen, the first stage will have obvious reflectivity increment between 400~440 ℃, the second stage is in the anneal temperature after raising to 500 ℃. Take place the droop of reflectivity. Between 400~440 ℃ reflectivity varieties change for the amorphous Ge crystallization, the reflectivity after 540 ℃ droop for crystallize melting of Ge. Ge(20 nm)/Ni(2 nm) record film has the reflectivity of four stages and changes in the anneal process. The first stage is forming Ni5 Ge3 phase by Ni and Ge inter-diffusion . The variety of second stage is the Ni5 Ge3 and Ge wedge bonding to become NiGe phase. The third stage goes to 390 ℃ for the anneal or so then will have the crystallize germanium . The Ge of the fourth stage occurrence melts to cause of reflectivity droop. And a-Si/a-Ge/Ni at the phase change generated by the anneal temperature of below 500 ℃ all and a-Ge(20 nm)/Ni(2 nm) record film homology, and can generate in above 500 ℃ the second-time reflectivity increment .Suggest being because forming Ni-Si compound cause. So we infer it when can apply blue-ray write-once disk , can because of reflectivity again increase of the phenomemon raise between as-deposition and data write of reflectivity difference. For the a-Ge/Ni/a-Si record film, after 580 ℃ anneal transactions, become the gradient of the reflectivity rising of crystallize Ge reduces after 580 ℃ anneal transactions and occurrence reflectivity again increase of the phenomemon of gradient droop. On the other hand in element depth composition analysis, we find Ni and Ge will produced inter-diffusion but a-Si and a-Ge will be not easy. Also find that the Ni atom will spread into a Si substrate after anneal. In activation energy analysis, the add of amorphous Si layer that can reduce amorphous Ge to change crystallize Ge phase change activation energy but will raise phase variety temperature. The affix of besides amorphous Si layer can also reduce the phase of the Ni5Ge3 phases change activation energy, while the Ni5Ge3 change the activation energy smaller record film forming NiGe phase of the phase change the activation energy is also lower. The residual stress analyzes, understand all as-deposited of record membranes in order to compress stress.If there are more remain stress in the recording films, the heat which is needed to " relaxation " the stress is higher. So that delays the phase change temperature which produce Ni5Ge3.