Dissertationen zum Thema „Snow particles“

The simplest form of a snow particle is a hexagonal prism which can grow into a stellar crystal by growing branches from the six corners of the prism. The snow particle is affected by the temperature and supersaturation in the air, giving its unique form. Manual classification of snow particles based on shape is tedious work. Convolutional Neural Network (CNN) can therefor be of great assistance and are common in automatic image processing. From a data set consisting of 3165 images sorted into 15 shape classes, a sub set of 2193 images and 7 classes was used. The selected classes had the highest number of snow particle images and were used to train, validate and test on. Four data sets were constructed and eight models were used to classify the snow particles into seven classes. To reduce the amount of training data needed pretrained versions of neural networks AlexNet and ResNet50 were used with a technique called transfer learning. The 2193 images make up the first data set, Data set 1. To handle unbalanced classes in the first data set Synthetic Minority Oversampling Technique (SMOTE) was used to increase the number of snow particles in classes with few examples, creating Data set 2. A third data set was constructed to mimic a real world application. The data for training and validation was increased with SMOTE, while the test data only consisted of real snow particles. The performance of both ResNet50 and AlexNet on the data met the requirements for a practical application. However, ResNet50 had a higher overall accuracy, 72%, compared to AlexNet 69% on the evaluated data set. A t-test was conducted with a significance of p < 1·10−8. To enhance the shape of the snow particles a Euclidean Distance Transform (EDT) was used, creating Data set 4. However, this did not increase the accuracy of the trained model. To increase the accuracy of the models more training data of snow particles is needed, especially for classes with few examples. A larger data set would also allow more classes to be included in the classification.

The Deepwater Horizon oil spill that started on April 20, 2010, in the Gulf of Mexico was the largest marine oil spill in the history of the petroleum industry. There was an unexpected and prolonged sedimentation event of oil-associated marine snow to the seafloor due to the oil spill. The sedimentation event occurred because of the coagulation process among oil associated marine particles. Marine scientists are developing models for the coagulation process of marine particles and oil, in order to estimate the amount of oil that may reach the seafloor along with marine particles. These models, used certain assumptions regarding the shape and the texture parameters of marine particles. Such assumptions may not be based on accurate information or may vary during and after the oil spill. The work performed here provided a quantitative analysis of the assumptions used in modeling the coagulation process of marine particles. It also investigated the changes in model parameters (shape and texture) during and after the Deepwater Horizon oil spill in different seasons (spring and summer). An Interactive Visualization Application was developed for data exploration and visual analysis of the trends in these parameters. An Interactive Statistical Analysis Application was developed to create a statistical summary of these parameter values.

Thesis (Ph.D.)--City University of Hong Kong, 2009.
"Submitted to Department of Electronic Engineering in partial fulfillment of the requirements for the degree of Doctor of Philosophy." Includes bibliographical references.

Atmospheric particulate matter (PM) is linked to various adverse environmental and health impacts. PM in the atmosphere reduces visibility, alters precipitation patterns by acting as cloud condensation nuclei (CCN), and changes the Earth’s radiative balance by absorbing or scattering solar radiation in the atmosphere. The long-range transport of pollutants leads to increase in PM concentrations even in remote locations such as polar regions and mountain ranges. One significant effect of PM on the earth’s climate occurs while light absorbing PM, such as Black Carbon (BC), deposits over snow. In the Arctic, BC deposition on highly reflective surfaces (e.g. glaciers and sea ices) has very intense effects, causing snow to melt more quickly. Thus, characterizing PM sources, identifying long-range transport pathways, and quantifying the climate impacts of PM are crucial in order to inform emission abatement policies for reducing both health and environmental impacts of PM. Chemical transport models provide mathematical tools for better understanding atmospheric system including chemical and particle transport, pollution diffusion, and deposition. The technological and computational advances in the past decades allow higher resolution air quality and weather forecast simulations with more accurate representations of physical and chemical mechanisms of the atmosphere. Due to the significant role of air pollutants on public health and environment, several countries and cities perform air quality forecasts for warning the population about the future air pollution events and taking local preventive measures such as traffic regulations to minimize the impacts of the forecasted episode. However, the costs associated with the complex air quality forecast models especially for simulations with higher resolution simulations make “forecasting” a challenge. This dissertation also focuses on applications, performance analysis, and optimization of meteorology and air quality modeling forecasting models. This dissertation presents several modeling studies with various scales to better understand transport of aerosols from different geographical sources and economic sectors (i.e. transportation, residential, industry, biomass burning, and power) and quantify their climate impacts. The simulations are evaluated using various observations including ground site measurements, field campaigns, and satellite data. The sector-based modeling studies elucidated the importance of various economical sector and geographical regions on global air quality and the climatic impacts associated with BC. This dissertation provides the policy makers with some implications to inform emission mitigation policies in order to target source sectors and regions with highest impacts. Furthermore, advances were made to better understand the impacts of light absorbing particles on climate and surface albedo. Finally, for improving the modeling speed, the performances of the models are analyzed, and optimizations were proposed for improving the computational efficiencies of the models. Theses optimizations show a significant improvement in the performance of Weather Research and Forecasting (WRF) and WRF-Chem models. The modified codes were validated and incorporated back into the WRF source code to benefit all WRF users. Although weather and air quality models are shown to be an excellent means for forecasting applications both for local and hemispheric scale, further studies are needed to optimize the models and improve the performance of the simulations.

The main focus of this thesis was the simulation of a powder-snow avalanche flow. The simulation were implemented using the particle-based simulation solution SPH, from a mathematical model describing powder-snow flow dynamics. The simulation was accelerated by applying the computational power of the GPU, in order to provide a faster simulation time than would have been achieved on the CPU.

Ce travail est consacré à l'étude du givrage atmosphérique des structures par accrétion de neige collante qui peut conduire à des dommages sévères aux structures. Les particules à la base de ce type d'accrétions sont caractérisées par un mélange d'eau et glace quantifié dans cette étude par un paramètre sans dimension : la teneur en eau liquide: TEL définie comme le ratio de la masse liquide sur la masse totale de la particule. La définition de la TEL considérée dans ce travail est différente de celle utilisée en aéronautique. Dans cette étude, la neige collante a été reproduite avec une températures ambiante négative. L'approche expérimentale, mise en oeuvre dans une soufflerie climatique, est consacrée à l'étude de l'effet de la TEL sur l'accrétion de neige sur une structure de test. La TEL est ajustée en modifiant la température ambiante. Les résultats sont synthétisés par le coefficient β défini comme le ratio entre le flux massique de l'accrétion, et le flux massique de neige incidente. Un premier modèle numérique évalue les conditions aux limites pour le modèle d'accrétion : c. à. D. La distribution en taille des particules à l'amont de la structure et la TEL associée. La première partie du modèle numérique d'accrétion concerne l'analyse du comportement des particules à proximité de la structure expérimentale quantifié par le nombre de Stokes. La capacité des particules à impacter la structure est synthétisé par le coefficient de collision n1. L'analyse du coefficient expérimental β, en fonction de n1 est développée. Ceci permet l'étude de la capacité des particules à s'accrocher à la surface en fonction de la TEL. Le résultat est évalué par le coefficient de collage n2. La seconde partie expose une approche pour modéliser la forme d'accrétion, par le coefficient de collage n2, en s'appuyant sur l'angle d'impact entre la particule et la surface. Des perspectives sont proposées
The present work aims at studying the atmospheric phenomenon of wet-snow accretion to structures. This phenomenon may induce severe damages to structures. Freezing particles which generate wet-snow accretions are characterized by a mixed phase ice/water. The particle state in this framework is quantified by a dimensionless parameter: the liquid water content LWC defined as the ratio of the particle liquid mass to the whole particle mass. This LWC definition is different form the aeronautical one. In this work, wet snow is produced with an ambient temperature below 0°C. Both experimental and numerical approaches are undertaken to investigate the subject. The experimental approach, undertaken in a climatic wind tunnel, is based on the LWC effect on the accretions obtained on a test structure. The particle LWC is tuned by adjusting the ambient temperature of the test chamber. The results are synthesized by a coefficient β defined as the ratio of the accretion mass flux to the snow mass flux. A first numerical model assesses the boundary conditions of the accretion model, i. E. The particle size distribution upstream the structure and the associated LWC. The first part of accretion model concerns the study of the particle behavior close to the structure which is quantified with a Stokes number. The efficiency of particles to impact the structure is synthesized by a dimensionless parameter n1. The analysis of the experimental coefficient β according to n1 is developed. This allows to study the efficiency of particles to stick on the structure as a function of the LWC. The result is synthesized by the n2 coefficient. The second part concerns an attempt to model the accretion shape by the sticking efficiency n2 as a function of the particle-surface angle of impact. A series of perspectives are presented

The Sudbury Neutrino Observatory solved the solar neutrino problem, confirming neutri- nos have non-zero masses. Massive neutrinos raise questions about the nature of neutrinos, implying physics beyond the standard model and potentially a solution to the observed matter-antimatter asymmetry in the universe. The Sudbury Neutrino Observatory is be- ing upgraded, with the goal of probing the nature of neutrino masses. The experiment will also study reactor, geo, supernovae and solar neutrinos. The upgrade is characterised by changing the target mass from heavy water to scintillator. Using scintillator allows for the lowering of the energy threshold, but this increases sensitivity to backgrounds. To meet the requirements of the physics on detector performance, a detailed optical calibration is needed. Due to increased background sensitivity, a new external LED-based calibration system has been developed and the existing laser calibration system has been modified to meet radiopurity requirements. This thesis describes the the development and imple- mentation of both of these calibration systems. With a study of the potential use of the LED system to monitor the detector's structure, enabling a better definition of the fiducial volume by reducing the effects of external backgrounds. An assessment of the impact of these systems on the detector performance will be presented.

Marine aggregates are an important means of carbon transfers downwards to the deep ocean as well as an important nutritional source for benthic organism communities that are the ultimate recipients of the flux. During these last 10 years, data on size distribution of particulate matter have been collected in different oceanic provinces using an Underwater Video Profiler. The cruise data include simultaneous analyses of particle size distributions as well as additional physical and biological measurements of water properties through the water column. First, size distributions of large aggregates have been compared to simultaneous measurements of particle flux observed in sediment traps. We related sediment trap compositional data to particle size (d) distributions to estimate their vertical fluxes (F) using simple power relationships (F=Ad^b). The spatial resolution of sedimentation processes allowed by the use of in situ particle sizing instruments lead to a more detailed study of the role of physical processes in vertical flux. Second, evolution of the aggregate size distributions with depth was related to overlying primary production and phytoplankton size-distributions on a global scale. A new clustering technique was developed to partition the profiles of aggregate size distributions. Six clusters were isolated. Profiles with a high proportion of large aggregates were found in high-productivity waters while profiles with a high proportion of small aggregates were located in low-productivity waters. The aggregate size and mass flux in the mesopelagic layer were correlated to the nature of primary producers (micro-, nano-, picophytoplankton fractions) and to the amount of integrated chlorophyll a in the euphotic layer using a multiple regression technique on principal components. Finally, a mesoscale area in the North Atlantic Ocean was studied to emphasize the importance of the physical structure of the water column on the horizontal and vertical distribution of particulate matter. The seasonal change in the abundance of aggregates in the upper 1000 m was consistent with changes in the composition and intensity of the particulate flux recorded in sediment traps. In an area dominated by eddies, surface accumulation of aggregates and export down to 1000 m occured at mesoscale distances (<100 km).

L'une des propriétés les plus fascinantes de la neige est sa blancheur, capable de transformer complètement un paysage en quelques heures. Cette couleur vient de la capacité unique de la neige à réfléchir le rayonnement solaire dans les longueurs d'onde visibles, c'est-à-dire son fort albédo. Cette particularité de la neige est d'une importance cruciale pour le bilan énergétique de surface et par conséquent pour un large éventail de questions sociales, écologiques et climatiques. La blancheur de la neige peut, cependant, être altérée par la présence d'impuretés absorbantes. Dans les Alpes européennes, deux types d'impuretés absorbantes impactent significativement l'évolution saisonnière du manteau neigeux : le carbone suie et les poussières minérales du Sahara. Cette thèse vise à mieux comprendre et modéliser le dépôt, l'évolution et l'impact de ces impuretés absorbantes sur les manteaux neigeux saisonniers des Alpes françaises. À cette fin, trois problématiques principales sont abordées : * Quels types d'impuretés absorbantes sont présents dans un manteau neigeux saisonnier alpin et en quelle quantité? Avec quelle incertitude peut-on estimer leurs concentrations à partir de mesures? * Quels impacts radiatifs ont les dépôts d'impuretés absorbantes sur l'évolution du manteau neigeux et comment varient t-ils d'une année à l'autre? * Peut-on modéliser cet impact en se servant des modèles de manteau neigeux et des modèles atmosphériques de chimie-aérosols? Tout d'abord, une représentation explicite du dépôt et de l'évolution des impuretés absorbantes a été implémentée dans le modèle détaillé de manteau neigeux SURFEX/ISBA-Crocus. Ces nouveaux développements permettent de modéliser l'assombrissement de la surface de la neige par les impuretés absorbantes (impact direct) ainsi que leurs interactions avec le métamorphisme de la neige (impacts indirects). Les simulations de l'enneigement au Col de Porte, forcées par des flux de dépôt d'impuretés absorbantes provenant du modèle atmosphérique de chimie-aérosols ALADIN-Climate, mettent en évidence un raccourcissement de la saison de neige allant jusqu'à 9 jours en raison du carbone suie et des poussières minérales sahariennes. Ensuite, une campagne de terrain de deux ans a été menée au site d'étude du Col du Lautaret. Pendant deux saisons d'hiver, la concentration en impuretés absorbantes ainsi que les propriétés physiques et optiques du manteau neigeux ont été mesurées chaque semaine. Ce jeu de données unique est d'abord utilisé pour ouvrir la voie à une nouvelle méthode visant à estimer le profil vertical de concentration en impuretés absorbantes dans la neige à partir de mesures de profils d'irradiance spectrale. L'évaluation de cette méthode par rapport aux mesures chimiques met en évidence la difficulté d'établir un lien entre la chimie de la neige et ses propriétés optiques. Une seconde étude compare ensuite les mesures d'albédos spectraux, les mesures chimiques d'impuretés absorbantes et des simulations du manteau neigeux.[...]
One of the most fascinating properties of snow is its whiteness, and its ability to fully transform a landscape in a couple of hours. This color is due to the unique ability of snow to reflect solar radiation in the visible wavelengths, i.e. its high albedo. This particularity of snow is of crucial importance for the surface energy budget and consequently for a wide range of social, ecological and climatic issues. However, the whiteness of the snow cover can be altered by the presence of Light Absorbing Particles (LAPs) on and close below its surface. In the European Alps, two types of LAPs are suspected to have a significant impact on the evolution of seasonal snow: Black Carbon (BC) and Saharan mineral dust. This thesis aims at a better understanding and modelling of the deposition, evolution and impact of LAPs on the seasonal snowpack in the French Alps. To this aim, three main questions are addressed: * What types of LAPs are present in a seasonal alpine snowpack and in what quantity? How well can we estimate their concentration in snow based on measurements? * What is the impact of LAPs on snowpack evolution and how does this impact vary in time? * Are we able to model this impact using state-of-the-art atmospheric chemical transport models and detailed snowpack models? First, an explicit representation of LAPs was implemented in the detailed snowpack model SURFEX/ISBA-Crocus. These new developments enable to account for darkening of the snow surface by LAPs (direct impact) as well as their interactions with snow metamorphism (indirect impacts). Snowpack simulations at Col de Porte (1326 m a.s.l.) using LAP deposition fluxes from an atmospheric model highlight a shortening of the snow season by up to 9 days due to BC and dust. Second, a two-year field campaign was conducted at Col du Lautaret study site (2058 m a.s.l, French Alps). During two winter seasons, concentrations of LAPs as well as physical and optical properties of the snowpack were measured weekly from the onset to the total melt-out of the snowpack. This unique dataset was first used to pave the way for a novel method to estimate vertical profiles of LAP concentration in snow from spectral irradiance profile measurements. This method was evaluated against chemical measurements pointing out difficulties to relate snow chemistry to its radiative properties. A second study was then dedicated to the comparison of spectral albedo measurements, chemical measurements of LAPs near the surface and snowpack simulations. This latter study corroborates the issue previously mentioned and points out a gap in the current understanding of chemical measurements of BC in snow. The impact of LAPs at Col du Lautaret over the two years was evaluated using the ensemble modeling framework of SURFEX/ISBA-Crocus. We estimated that the shortening of the snow season due to LAPs was around 10±5 and 11±1 days for both seasons respectively. The studies of the impact of LAP carried out at a single location during this thesis pave the way for a larger scale study of the impacts of LAP deposition across the Alps over longer periods

The SNO+ experiment will use a liquid scintillator based detector to study solar, geo, and reactor neutrinos and double beta decay. This thesis discusses the effect of backgrounds on the measurement of neutrinoless double beta decay and describes analysis techniques developed to reduce their impact. Details of the modeling of the photomultiplier tubes in the SNO+ Monte Carlo RAT are first described and comparisons are made with the SNO Monte Carlo SNOMAN. SNOMAN has been extensively verified with calibration sources and RAT is shown to be in good agreement. The event reconstruction techniques are then presented and predict an achievable 15cm position and 7% energy resolution. The backgrounds are discussed and pileup backgrounds identified, including many previous unknown pileup backgrounds. Techniques to reject the pileup background are presented and shown to give over 99% rejection in the region of the double beta decay end point (3-4MeV), below the irreducible background from solar neutrinos. Finally the resulting limit on the effective Majorana neutrino mass SNO+ could achieve in 2015 is predicted to be 270meV and this is compared with other experiments that are underway.

The SNO+ experiment is primarily looking for neutrinoless double-beta decay, an unobserved, lepton number violating radioactive decay. This is achieved by loading liquid scintillator with tellurium whose isotope 130Te decays via double beta decay with a Q-value of 2527 keV. An optical calibration system, located outside the scintillator, has been developed to help meet the radiopurity requirements of the experiment. This thesis describes the hardware component of the optical calibration system which calibrates the timing and charge response of the photomultiplier tube array of SNO+. A set of quality assurance tests showed that the system was at the required standard for installation. Data taken with SNO+ and the optical calibration system showed that the system was stable enough for photomultiplier tube calibration, identified resolvable issues with the SNO+ data acquisition system and allowed measurement of single photoelectron spectra. Data quality checks have been developed to ensure data is of calibration standard. The sensitivity of SNO+ to neutrinoless double-beta decay with nearly 800 kg of 130Te and five years data taking is investigated with a comprehensive evaluation of systematic uncertainties. Two new methods for acquiring a greater sensitivity to neutrinoless double-beta decay were developed; a one dimensional fit in event energy and a multidimensional fit in event energy and position. A simple event counting analysis, developed previously by the collaboration, was shown to be sensitive to systematic uncertainties. A fit in an extended energy range was shown to constrain the systematics and achieve a half-life sensitivity of 9.30x1025 yr corresponding to a 5.6% improvement over the counting analysis which neglected systematic uncertainties. The multidimensional analysis with systematics included achieved a 20% improvement over the counting analysis with a half-life sensitivity of 1:06 x 1026 yr, corresponding to an effective Majorana mass between 52 to 125 meV.

SNO+ is a liquid scintillator experiment whose physics goals include measurements of solar neutrinos, reactor anti-neutrinos, geo neutrinos and double beta decay. During an initial water phase, it will also search for invisible modes of nucleon decay. This thesis investigates methods of improving the detector's sensitivity to the baryon and lepton violating processes of neutrinoless double beta decay and invisible nucleon decay. It does this through an improved scintillator model, allowing the sensitivity of the detector with different loading techniques to be evaluated, through a new background rejection technique, capable of increasing the active volume of the detector, and with the development of improved position fitters, achieving resolutions of approximately 10 cm in scintillator and 25 cm in water. The sensitivity of SNO+ to invisible modes of nucleon decay is explored, predicting, after one month of data, a limit of t > 1.38 x 10³⁰ years on the decay of neutrons and of t > 1.57 x 10³⁰ years on the decay of protons.

Cette thèse porte sur la caractérisation du transport sur un lit granulaire cohésif en considérant le cas du sable et de la neige. Une approche numérique pour étudier le processus de l'érosion par impact sur un empilement cohésif a permis de quantifier l'effet de la cohésion sur le processus Splash. Pour quantifier l'effet de la cohésion le transport de particules par un écoulement d'air, nous avons choisi une approche expérimentale en soufflerie. L'étude du transport sur un lit de sable sec a permis de caractériser la transition du régime de saltation vers un régime collisionnel lorsque le nombre de Shields atteint S=0.3. Dans le cas du transport de sable humide, la vitesse seuil d'arrachement des grains du lit augmente avec la teneur en eau tandis que la vitesse seuil d'impact est du même ordre de grandeur que le seuil dynamique obtenu dans le cas sec. Ces résultats suggèrent qu'une fois que les grains sont arrachés au sol, ils ont un comportement similaire au transport sur sol sec. Sur un lit rigide de neige, la longueur caractéristique de décroissance augmente quadratiquement avec la vitesse de friction de l’air mais également avec le diamètre de la particule. Les caractéristiques de transport éolien de neige sur neige cohésive sont proches de celle sur neige rigide. On note une nette diminution, en soufflerie, de la quantité de neige transportée qui peut toutefois être significativement augmentée du fait de l’effet érosif d’un flux entrant. Sur un lit cohésif, dans le cas du sable humide et de la neige, le flux transporté tend vers la saturation mais la longueur de la soufflerie ne permet pas de l'atteindre
This thesis deals with the cohesion effect on the aeolian grain transport. We consider the sand and snow case. A numerical approach to the erosion process by impact allows us to quantify the cohesion effect on the Splash process. Then we adopt wind tunnel experiment to study the effect of the cohesion on the transport. We show over a dry sand bed a transition from the saltation regime to a collision one at a Shields number of 0.3. Over a wet sand bed, the aerodynamic threshold increases with the water content whereas the impact threshold is in the same order of magnitude compare to the dry case. Over a hard snow bed, the characteristic decay height shows a quadratic dependence with the air friction speed and increases with the particle diameter. The characteristics of the aeolian transport over a cohesive snow bed are close to those over a hard one. There is a sharp decrease of the transported snow flux which can increase significantly when the wind tunnel is fed with an incoming snow flux. Our results indicate the mass flow rate aims to a saturation. However the saturation is not reached with the wind-tunnel length we work over wet sand and cohesive snow bed

SNO+, the successor of the Sudbury Neutrino Observatory, is an upcoming low energy neutrino experiment, located in the 2 km deep laboratory SNOLAB, Canada. The spheric acrylic vessel in the detector center will contain 780 t of LAB. The main goal of SNO+ is the search for the neutrinoless double beta decay of 130Te, using a novel scintillator in which natural Te is bound with an initial loading of 0.3% via water and a surfactant. Within this thesis, the first measurement of the Alpha-particle and proton quenching parameters of loaded and unloaded LAB is described. These parameters are crucial for an efficient background suppression, necessary to reach a sensitivity above the current limit in 76Ge of T1/2(0v) > 2.1 x 10^(25) y (90% C.L.). For 0.3% Te-loading, the quenching parameter obtained is kB = (0.0070 +/- 0.0004) cm/MeV for Alpha-particles and kB = (0.0090 +/- 0.0003) cm/MeV for protons. Additionally, the spectral sensitivity of SNO+ to supernova electron anti-neutrinos and muon and tau (anti-)neutrinos is determined for the first time, using inverse beta decay and v-p elastic scattering with the measured quenching parameters. The obtained sensitivity to the mean energy of electron anti-neutrinos is E = 15.47^(+1.54)_(-2.43) MeV and of muon and tau (anti-)neutrinos is E = 17.81^(+3.49)_(-3.09) MeV
SNO+, der Nachfolger des Sudbury Neutrino Observatorys, ist ein bevorstehendes Niederenergie-Neutrino-Experiment im 2 km tiefen Untergrundlabor SNOLAB in Kanada. Die Acryl-Kugel im Zentrum des Detektors wird mit 780 t LAB gefüllt werden. Das Hauptziel von SNO+ ist die Suche nach dem neutrinolosen Doppelbetazerfall von 130Te mit einem neuartigen Szintillator, in dem natürliches Te mit einer Anfangskonzentration von 0.3% über Wasser und ein Tensid gebunden wird. In dieser Arbeit wird erstmals die Messung der Alpha-Teilchen und Proton Quenching Parameter in diesem und in normalem LAB beschrieben. Die Parameter sind unverzichtbar für eine effiziente Untergrund Unterdrückung, die notwendig ist um auf das bestehende Limit in 76Ge von T1/2(0v) > 2.1 x 10^(25) y (90% C.L.) sensitiv zu sein. Der ermittelte Quenching Parameter bei 0.3% Te beträgt kB = (0.0070 +/- 0.0004) cm/MeV für Alpha-Teilchen und kB = (0.0090 +/- 0.0003) cm/MeV für Protonen. Zusätzlich wird erstmals die spektrale Sensitivität von SNO+ auf Supernova Elektron Anti-Neutrinos und Muon and Tau (Anti-)Neutrinos bestimmt über den inversen Betazerfall und die elastische v-p Streuung zusammen mit den gemessenen Quenching Parametern. Die ermittelte Sensitivität auf die mittlere Energie der Elektron Anti-Neutrinos ist E = 15.47^(+1.54)_(-2.43) MeV und der Muon und Tau (Anti-)Neutrinos ist E = 17.81^(+3.49)_(-3.09) MeV

ABSTRACT SYNTHESIS AND CHARACTERIZATION OF ETHANOL ELECTRO-OXIDATION CATALYSIS Demir-Kivrak, Hilal Ph.D., Department of Chemical Engineering Supervisor : Prof. Dr. Deniz Ü
ner Co-supervisor : Dr. Sadig Kuliyev October 2010, 196 pages In this study, the role of defects, the role of Sn in relation to defects, and the role of oxide phase of tin in ethanol electro-oxidation reaction were investigated. Firstly, adsorption calorimetry measurements were conducted on monometallic (1%Pt, 2%Pt, and 5%Pt) and bi-metallic (5% Pt-Sn) &gamma
-Al2O3 supported Pt catalysts. It was observed that while saturation coverage values decreased, intermediate heats remained same for Pt-Sn catalysts by the increasing amount of tin. The effect of particle size was investigated on Pt/C (pH=5), Pt/C (pH=11) catalysts at different scan rates. At high scan rates (quite above diffusion limitations), current per site activities were nearly the same for 20% Pt/C (E-Tek), Pt/C (pH=11), and Pt/C (pH=5) catalysts, which explained as electro-oxidation reaction takes place at the defects sites. Furthermore, the effect of support on ethanol electro-oxidation was investigated on CNT supported Pt catalyst. Results indicate that only the metal v dispersions improved ethanol electro-oxidation reaction and support did not have any effect on ethanol electro-oxidation reaction. Results on the 20% Pt-Sn/C (15:1 to 1:1 Pt: Sn atomic ratios) and 20% Pt-SnO2/C (6:1 and 1:1) catalysts indicated that ethanol electro-oxidation activity increased by increasing tin amount. For 20% Pt-Sn/C catalysts, Pt-Sn (6:1)/C indicated best activity. On the other hand, 20% Pt-SnO2 (6:1)/C catalyst was better than Pt-Sn (6:1)/C in terms of ethanol electro-oxidation activity due to the fact that there was low contact between Pt and tin oxide particles.

Uzorci zemljišta iz povšinskog sloja dubine 0 - 10 cmprikupljeni su sa 121 lokacije na gradskom području NovogSada. Ispitivano područje obuhvatilo je površinu (4 x 5)km²,koja je podeljena na mrežna polja veličine (400 x 400) m² i u          svakom polju uzet je po jedan uzorak. Za 121 uzorakgradskog zemljišta Novog Sada ispitana su fizičko-hemijskasvojstva zemljišta, ukupni i pristupačni sadržaj metala (As,Co, Cr, Cu, Mn, Ni, Pb, Zn) i njihova prostorna raspodela.Konturne mape prostorne raspodele metala u zemljištudobijene su korišćenjem interpolacijske metode običnogkriginga. Za pojedine uzorke izvršeno je razdvajanje česticapo veličinama frakcionisanjem u vodi pomoću sita različitihveličina i identifikovani su minerali prisutni u frakciji prah +glina. Aktivnosti radionuklida „unsupported” ²¹⁰Pb i ¹³⁷Csodređene su za jedan deo uzoraka zemljišta u Novom Sadu iza uzorke zemljišta pored fabrike akumulatora u Somboru.Ispitana je i vertikalna distribucija stabilnog i radioaktivnogPb u zemljištu.Na 14 lokacija u Novom Sadu prikupljeno je 35 uzorakasnega direktno sa asfaltnih puteva i sa zemljanih površina uokolini puteva i na pešačkim ostrvima. Raspodela čestica poveličinama i ukupne koncentracije metala (Al, Ca, Cu, Fe, K,Na, Mn, Ni, Pb, Zn) određene su analizom filtriranih uzoraka,a za 4 uzorka ispitana je morfologija čestica i urađenasemikvantitativna analiza čestica u suvoj materiji.Prilikom obrade rezultata merenja primenjene su metodedeskriptivne statistike i multivarijacione statističke analize ucilju identifikacije izvora zagađenja i određivanja povezanostiizmeđu samih metala i drugih parametara.
A total of 121 surface soil samples were collected across the central part of Novi Sad covering a surface area (4 km x 5 km). The physicochemical properties, pseudo total and available metal concentrations (As, Co, Cr, Cu,  Mn, Ni, Pb, and Zn) were determined. Contour maps of spatial distribution of the investigated metals were obtained using ordinary  kriging interpolation method. Separation of different particle size fractions by wet sieving  and identification of minerals in the clay and silt fraction for some soil samples were performed.  Specific activities of radionuclides “unsupported” ²¹⁰Pb and ¹³⁷Cs were measured in forty soil samples collected in urban area of Novi Sad and industrial area of Sombor (near a battery manufacturer).  Vertical distribution of stable and radioactive  Pb for  two samples from the industrial soil was examined.Thirty five snow samples were collected at fourteen locations near crossroads in Novi Sad. The samples were taken directly from the road surface and from the ground surface in the vicinity of roads and on pedestrian islands. Particle size distribution and  total concentration of the metals (Al, Ca, Cu, Fe, K, Na, Mn, Ni, Pb, Zn) were  determined for filtered samples. Semi-quantitative analysis of the particles was  conducted and morphology of the particles was examined for dry matter of four snow samples. Methods of descriptive and multivariate statistics and geostatistics were carried out for  the analysis and interpretation of the data.

碩士
國立中山大學
機械與機電工程學系研究所
101
Due to the increased awareness of living and industrial safety, carbon monoxide detectors must be geared towards better portability and sensitivity. Metal oxide semiconductor sensors should possess advantages such as heat and corrosion resistance, low cost materials, and ease of miniaturization. This thesis applied ball milled and powdered ZnO and SnO2 to manufacture into paste, then used the screen printing method deposited ZnO and SnO2 paste film and silver electrode on glass substrate. The influence on sensing film materials, temperature, time of heat treatment, and temperature of measurement was investigated. The samples were fabricated and measured by setting up self-measurement apparatus. The data was analyzed the changes of resistance under different air and carbon monoxide environments. This is followed by analysis of both surface topography and microstructure of the sensing film under OM and SEM. Experiment reveals that samples under different annealing process yield different surface morphology and micro structure while at the beginning of the heat treatment, epoxy evaporates from the sample brought about porous structure. Annealing at higher temperature sample will have more rough surface and better sensitivity in detecting carbon monoxide. After epoxy removed, heat treatment mechanism is then switched to sinter ZnO and SnO2 powders. the longer the samples are sintered, the lower the sensitive. Sensing films composited with ZnO and SnO2 will have better carbon monoxide sensitivity at 300oC but its sensitivity decays at a faster rate than samples working at 250 oC despite the slightly weaker sensitivity. Sensing films with pure ZnO will have higher sensitivity compared to pure SnO2 one. With the increase of SnO2 proportion, carbon monoxide sensitivities of detectors decreases, however, its life time can be improve significantly.

Deeper understanding and technological progress in materials physics demand exploration of soft and hard matter at their relevant length scales. This research focuses on the nanometer length scale investigation of structural changes required for membrane fusion in virus nanoparticles and nano-spectroscopic investigation of layered material surfaces implementing scattering type scanning near-field optical microscopy (s-SNOM). Spectroscopy and imaging experiments were deployed to investigate the chemical and structural modifications of the viral protein and lipid bilayer under various environmental pH variations. It has been shown that breakage of viral membrane could occur even without the presence of a targeting membrane, if the environment pH is lowered. This is in contrary to the current viral fusion model, which requires virus binding to a host cell membrane for forming the fusion pore to release the viral genome. The fusion inhibitor compound 136 can effectively prevent the membrane breakage induced by low pH. The chemical surface stability and degradation of black phosphorus (BP) under ambient conditions have been studied using s-SNOM. We found that the degraded area and volume on the surface of black phosphorus increase with time slowly at the start of degradation and enlarge rapidly (roughly exponentially) afterward and reach saturation growth following S-shaped growth curve (sigmoid growth curve). The theoretical model presented suggests that the degraded sites in the adjacent surrounding causes the experimentally observed exponential growth of degraded area at the initial stage. By studying the BP surfaces coated by Al2O3, boron nitride (BN) and hybrid BN/Al2O3 layers through the period up to 6 months, it has been concluded that ~5 nm thin hybrid layer of BN/Al2O3 helps the surface passivation of BP flakes of thickness ~30 nm. This is supported by the electrical characterization results of BP field effect transistor coated with a BN/Al2O3 layer. We have performed infrared nano-spectroscopy on muscovite mica exfoliated on silicon and silicon dioxide substrates. We show that the near-field profile in s-SNOM can penetrate down to several hundreds of nanometers and enable spectroscopy of buried structures. We found spectral broadening of mica as its thickness increases revealing clearly the effect of size on the absorption response.

Thesis (Ph. D.)--Florida State University, 2007.
Advisor: Hong Li, Florida State University, College of Arts and Sciences, Dept. of Chemistry and Biochemistry. Title and description from dissertation home page (viewed May 21, 2008). Document formatted into pages; contains xiii, 93 pages. Includes bibliographical references.

The SNO+ experiment is a kilo-tonne scale liquid scintillator detector located at SNOLAB in Sudbury, Ontario, Canada. As the successor to the Sudbury Neutrino Observatory, SNO+ will use linear alkylbenzene (LAB) as the scintillator to study neutrinos. During the solar phase, ux measurements will be made of low energy neutrinos originating in the Sun. In another phase, 800 kg of tellurium will loaded into the scintillator to search for neutrinoless double beta decay. Measurements will also be made of neutrinos coming from nearby nuclear reactors and from inside Earth's mantle and crust. To enable these multiple physics goals, a sensitive calibration procedure must be carried out in order to fully understand the detector. The optical and energy responses of the detector will be measured with calibration sources deployed throughout the acrylic vessel. These sources must be connected to the observatory deck above the vessel by gas capillaries, optical bres, and signal wires housed in specially designed submersible umbilical cables. The design and fabrication of these umbilical cables is presented. Development work on a deployed radon calibration source will also be described.
Thesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2014-05-30 15:56:19.906