In this thesis, a single image dehazing method based on modified dark channel prior and haze (fog) density detection is proposed. Dark channel prior dehazing algorithm is achieved good results for some haze images. However, we observed that haze images contain low and high haze density. Thus, the region of low haze density is unnecessary to dehaze. To solve this problem, we first defined the HSV distance, pixel-based dark channel prior and pixel-based bright channel prior to estimate the haze density. Further to enhance the dehazing performance of dark channel prior, the atmospheric light value and dehazing weighting is revised based on the HSV distance. Then the new transmission map is obtained. After that, a bilateral filter is applied to refine the transmission map, which can provide the higher accuracy of transmission map. Finally, the haze-free image is recovered by combining the input image and the refined transmission map. As a result, high-quality haze-free image can be recovered with lower computational complexity, which can be naturally extended to video dehazing.

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L'hydrolyse enzymatique des protéines thermosensibles des moûts ou des vins a été envisagée comme une technique alternative à l'utilisation des bentonites dans le cadre de la protection des vins vis à vis de la de la casse protéique.Le Laboratoire d'Œnologie et de Chimie Appliqué possède une collection de levures issues du vignoble champenois dont certaines possèdent une activité protéasique exocellulaire.Dans un premier temps, 40 de ces levures, fermentaires et non-fermentaires, ont été présélectionnées. La quantification de leur activité protéasique exocellulaire a été réalisée et nous a conduit à ne retenir que 10 d'entres elles. Ces 10 levures ont fait l'objet d'une identification précise et parmi elles l'une s'est avérée être une Saccharomyces cerevisiae.Cette souche, baptisée S.cerevisiae PlR1, est en mesure d'exprimer son activité protéasique exocellulaire au cours de la fermentation alcoolique.Les conditions de l'expression de cette activité ont été étudiées de même qu'ont été déterminées les principales caractéristiques de la protéase libérée.Par la suite nous nous sommes attachés à étudier dans quelle mesure cette activité protéasique exocellulaire était capable d'hydrolyser les protéines du moût et à identifier les protéines concernées. / The hydrolysis of thermosensitive proteins of grape juice has been proposed as one of the potential alternative methods to the use of bentonite to prevent haze formation in wine.The Laboratory of Enology and Applied Chemistry owns a collection of yeast isolated from the Champenois vineyard, with some yeast showing an exocellular prototeolytic activity.Out of this yeast collection, 40 yeast strains, either fermentative or non fermentative, were selected first. Based on the determination of their exocellular proteolytic activity, 10 yeast strains (out of the 40 yeast strains selected) were further used for this study. Those 10 yeast strains have been carefully identified, being one of them a Saccharomyces cerevisiae.This wild yeast strain, named S. cerevisiae PlR1, is able to express its exocellular proteolytic activity during the alcoholic fermentation.Parameters required for optimal proteolytic activity were determined. Characterization of the secreted protease was also done.It was then searched whether this proteolytic activity can affect must proteins and a tentative identification of the hydrolyzed proteins was carried out.

abstract: A new nanoparticle deposition technique, Aerosol Impaction-Driven Assembly (AIDA), was extensively characterized for material structures and properties. Aerogel films can be deposited directly onto a substrate with AIDA without the long aging and drying steps in the sol-gel method. Electron microscopy, pore size analysis, thermal conductivity, and optical measurements show the nanoparticle (NP) films to be similar to typical silica aerogel. Haze of nanoparticle films modeled as scattering sites correlates strongly with pore size distribution. Supporting evidence was obtained from particle sizes and aggregates using electron microscopy and small-angle X-ray scattering. NP films showed interlayers of higher porosity and large aggregates formed by tensile film stress. To better understand film stress and NP adhesion, chemical bonding analyses were performed for samples annealed up to 900 °C. Analysis revealed that about 50% of the NP surfaces are functionalized by hydroxyl (-OH) groups, providing for hydrogen bonding. Ellipsometric porosimetry was used to further understand the mechanical properties by providing a measure of strain upon capillary pressure from filling pores. Upon annealing to 200 °C, the films lost water resulting in closer bonding of NPs and higher Young’s modulus. Upon further annealing up to 900 °C, the films lost hydroxyl bonds while gaining siloxane bonds, reducing Young’s modulus. The application of ellipsometric porosimetry to hydrophilic coatings brings into question the validity of pore size distribution calculations for materials that hold onto water molecules and result in generally smaller calculated pore sizes. Doped hydrogenated microcrystalline silicon was grown on crystalline silicon NPs, as a test case of an application for NP films to reduce parasitic absorption in silicon heterojunction solar cells. Parasitic absorption of blue light could be reduced because microcrystalline silicon has a mix of direct and indirect bandgap, giving lower blue absorption than amorphous silicon. Using Ultraviolet Raman spectroscopy, the crystallinity of films as thin as 13 nm was determined rapidly (in 1 minute) and non-destructively. A mono-layer of nanocrystals was applied as seeds for p-doped microcrystalline silicon growth and resulted in higher crystallinity films. Applications of the method could be explored for other nanocrystalline materials. / Dissertation/Thesis / Doctoral Dissertation Materials Science and Engineering 2020

The development of a new catalyst system by The Dow Chemical Company has resulted in the production of isotactic polypropylene and propylene/ethylene copolymers with a unique defect and comonomer distribution. This work investigated the morphology and optical properties of cast and compression molded films made from the homopolymer and copolymers with up to 20 mol% ethylene comonomer. The defect distribution of the Dow Chemical copolymers resulted in materials with lower crystallinity than Ziegler-Natta or metallocene-made materials of similar ethylene content. These materials exhibited a gamma-phase crystal content ranging from 0-95%, depending on ethylene content, processing condition, and catalyst type. The gamma-phase crystal content of quiescently crystallized copolymer films was found to significantly influence their bulk optical properties, presumably through a change in the spherulite birefringence. The bulk haze, clarity, and transparency of a homopolymer film were degraded through annealing treatments, which decreased the fraction of gamma-phase crystallinity and increased the thickness of existing lamellae, resulting in an increased intensity of scattered light and a corresponding degradation in the optical properties of the film. The haze, clarity, transparency, and gloss of the copolymer films were found to improve at higher comonomer content and higher cooling rates. The variation in the length scale and degree of disorder in the bulk morphology of films processed under different conditions was shown to correlate with the optical quality of the films, with smaller scale morphologies scattering less light and resulting in films with better optical properties. It was also shown that no single metric can completely describe the optical quality of a polymer film; the relative importance of haze, transparency, and gloss, which depends on the intended application of the film, was discussed. The influence of surface scattering from the films was controlled through the compression molding of films using substrates of different surface roughness. The contribution of light scattered from the surface of the films was isolated and found to play a significant role in the degradation of optical quality. / Ph. D.

An investigation was carried out on a three stage method (extrusion/annealing/uniaxial-stretching) (MEAUS) utilized to produce semicrystalline polymeric microporous membranes. The two semicrystalline polymers studied were selected based on a set-of-prerequisites proposed for the formation of highly porous membranes via the method in question. The prerequisites included "fast" crystallization kinetics, presence of an ac relaxation, ability to form a planar stacked lamellar morphology with a "good" crystalline orientation upon melt-extrusion, and rapid heat transfer of the film during extrusion. The first polymer was isotactic poly(4-methyl-1-pentene) (PMP), and the second was polyoxymethylene (POM). Three PMP resins were studied, which differed in weight average molecular weight. Three POM resins were also investigated where two of resins were characterized by relatively narrow molecular weight distributions (MWD) ca 2 while the third POM resin possessed a MWD ca 5.9. The melt-extruded film morphologies and orientation values were a consequence of the melt-relaxation times as a result of the resin characteristics and/or the melt-extrusion conditions. Following the extrusion stage, the effect of annealing (second stage) on film properties was investigated. The annealing variables investigated included the temperature, time, and level of extension applied during annealing. The annealed films were then subjected to the uniaxially stretching stage (third stage) consisting of a cold and hot step, respectively, where deformation was along the extrusion direction. The variables of interest included the cold and hot stretch temperature and extension level. It was found that starting precursor morphology and orientation, annealing conditions, and stretching variables impact the final film microporous morphology and permeability. Additionally, the proposed prerequisites were verified in both the PMP and POM film series. In addition to the MEAUS study, a comprehensive investigation was conducted of the optical properties of blown and cast films made from conventional Ziegler-Natta catalyzed linear low density polyethylene (LLDPE) as well as metallocene-catalyzed LLDPE resins. From this work, it was determined that in PE blown and cast films made using conventional processing conditions, the optical haze properties are adversely affected due to enhanced surface roughness caused by the formation of spherulitic-like superstructures in polymer melts that possess fast relaxing and low melt elasticity rheological characteristics. This optical property study was also published in J. Appl. Polym. Sci., 77(13), 2845, (2000). / Ph. D.

Harmattan and Dust (sand) storms together with anthropogenic activities including the use of firewood and kerosene as fuel for cooking, and diesel/petrol generators for electricity generation are potential sources of particulate and gaseous pollutants in homes in Damaturu town, Nigeria. Other activities like the burning of locally produced incense and mosquito coils as well as the use of aerosol sprays are further possible sources of indoor pollution, which may result in exposure of people to a range of pollutants through inhalation, by ingestion of settled dusts as well as dermal contact. Local people associate occurrence of dust events with adverse health effects and hence there is a need for an understanding of the composition of the settled and airborne dusts in order to assess the possible associated health risks. The first phase of the study involved selection and development of methods of dust sampling and analysis. For validation of the methods employed and to establish a broad understanding of the characteristics of the settled dusts, an initial survey study was conducted involving the application of thermal desorption/gas chromatography/mass spectrometry (TD/GC/MS) analysis for organic compound analysis, scanning electron microscopy (SEM), inductively coupled plasma-mass spectrometry (ICP-MS) for analysis of metals, and microbiological analysis. Airborne samples were also collected using sorbent tubes to determine organic compounds in air during activities such as cooking with kerosene, gas, and firewood as well as during electricity generation with fossil fuels. Carbon monoxide (CO) and ultrafine particles (UFPs) monitored simultaneously during some of the household activities. The study involved a novel method of extracting organic chemical emissions from dust by heating of the dusts directly in a micro chamber (μ-CTETM) and collection of emissions on sampling tubes. The method provided a relatively quick way of collecting chemical emissions from dusts that are readily available for release. The sampled tubes were analysed by TD/GC/MS. The conventional solvent extraction of the dusts was also carried out and the extracts were analysed by liquid injection-GC/MS and results of the two methods compared. The study determined a number of constituents (metals, SVOCs, phthalates and physical properties) of dusts collected from households in Damaturu during different weather events and from different indoor/outdoor locations; and compared with some UK samples. The samples investigated include dusts deposited; during two notable dusty-weather events (Harmattan and Storm) as well as when there was no notable dust event; during human activities; and dusts from different types of buildings (modern and traditional homes) as well as inside and outside homes. A standard reference material for organic chemicals (SRM 2585) was also analysed. The physical characterization of the settled house dust samples analysed revealed the various shapes and sizes, and elemental composition of the constituents, which included respirable particles. The microbial analysis also indicated the presence of the spores of a host of fungi and bacterial species; and the possible contributions of household activities to the increased production of pollutants (UFP and CO) ascertained. The μ-CTE extraction of the house dusts by heating with TD/GC/MS analysis of the emissions as well as the solvent extraction-GC/MS revealed the presence of many organic chemical compounds with different analytical retention times and varying concentrations in the dust samples. Chemicals of interest quantified: benzene, hexanal, nonanal, diethyl phthalate (DEP), diisobutylphthalate (DIBP), dibutylphthalate (DBP), and diethylhexylphthalate (DEHP). A host of other chemicals commonly present in the analysed samples identified using the NIST library associated with the MS system software. These chemicals included naphthalene and C10-C16 aliphatic and aromatic hydrocarbons, which would need confirmation by running the pure compound samples. There was an observed higher concentration of the chemicals in the solvent extracts than the μ-CTE extracted dust. The higher concentration of the chemicals in the solvent extracts expected due to the aggressive removal of the chemicals by the organic solvent whereas in the case of thermal extraction only the readily available chemicals (loosely bound to the matrix) released by increases in temperature were removed. Generally, the concentrations of the chemicals found were higher in the indoor than in the outdoor dust samples. In the analysis of the dusts collected during weather events; higher chemical concentrations observed in the samples collected during Harmattan period than the other periods. The Harmattan dust period may pose increased exposures to dust and possible health risks. More exposure is expected to occur in the traditional homes compared with the modern homes due to the higher concentrations of the chemicals in both the indoors and the outdoors and this may be especially important to women and children who spend most of their times at home. Metal analysis involved microwave-assisted digestion of the dust samples followed by ICP-MS analysis. The total quant method of metal analysis for a general profiling indicated the presence of more than 50 elemental contaminants in house dust. The results of the quantitative analysis for six target metals: Cd, Cr, Cu, Ni, Pb, and Zn showed their presence in all indoor and the outdoor dust samples. The mean concentrations showed that the metals were in higher concentrations in the indoor dusts than in the outdoor dusts. The quantitative analysis carried out indicated higher metal contents in the storm dusts than the dusts during the other periods. Results of the dusts collected from modern and traditional homes indicated the presence of the metals in higher concentrations in the dusts from traditional homes than the dusts from the modern homes. The estimated mean concentrations of the metals and phthalates inadvertently ingested as a constituent of dust indicated that some of the pollutants could exceed the tolerable daily intake (TDI) due to high exposures to dust expected to be the case in Damaturu. The results of the investigation of the dust composition, combined with information on exposure to dust and pollutants, show that dusts are a risk to the health of people in the Damataru community. Recommendations are made for more studies to provide a better understanding of dust ingestion and exposure to some phthalates and heavy metals in particular and the possible health risks. To the best of my knowledge, this is the first ever research study of airborne and settled dusts undertaken in North-Eastern Nigeria.

Study on nanoparticle additives in multiphase systems (liquid, polymer) are of immense interest in developing new product applications. Critical challenges for nanoparticle additives include their synthesis, formulation and characterization. These challenges are addressed in three application areas: nanofluids for engine lubrication, ultrathin nanocomposites for optical devices, and nanoparticle size distribution characterization. Nanoparticle additives in oligomer mixtures can be used to develop extended temperature range motor oils. A model system includes poly(α-olefin) based oligomers with a modest fraction of poly(dimethylsiloxane) oligomers along with graphite as nanoparticle additive. Partition coefficients of each oligomer are determined since the oligomer mixture phase separated at temperatures less than -15 °C. Also, the surface of graphite additive is quantitatively analyzed and modified via silanization for each oligomer. Thus, upon separation of the oligomer mixture, each functionalized graphite additive migrates to its preferred oligomers and forms a uniform dispersion. Similarly, nanoparticle additives in polymer matrices can be used to develop new low haze ultrathin film optical coatings. A model system included an acrylate monomer as the continuous phase with monodisperse or bidisperse mixtures of silica nanoparticles deposited on glass and polycarbonate substrates. Surface (root mean squared roughness, Wenzel’s contact angle) and optical properties (haze) of these self assembled experimental surfaces were compared to simulated surface structures. Manipulating the size ratios of silica nanoparticle mixtures varied the average surface roughness and the height distributions, producing multimodal structures with different packing fractions. In both nanofluid and nanocomposite applications, nanoparticle additives tend to aggregate/agglomerate depending on various factors including the state of nanoparticles (powder, dispersion). A set of well-characterized ceria and titania nanoparticle products from commercial sources along with in-lab synthesized nanoparticles were studied via fractal theory. Fractal coefficients were obtained through two-dimensional images (from electron microscopy) and particle size distributions (from electron microscopy and dynamic light scattering). For some arbitrary collections of aggregated nanoparticle materials, the fractal coefficients via two-dimensional images correlated well to the average primary particle size. This complementary tool could be used along with conventional nanoparticle characterization techniques when not much is known about the nanoparticle surfaces to characterize agglomeration or aggregation phenomena.

Aerosols change the Earth's energy balance. Black carbon (BC) aerosols are a product of incomplete combustion of fossil fuels and biomass burning and cause a net warming through aerosol radiation interactions (ari) and aerosol cloud interactions (aci). BC aerosols have potentially strong implications on the Arctic climate, yet the net global climate effect of BC is very uncertain. Best estimates assume a net warming effect, roughly half to that of CO2. However, the time scales during which CO2 emissions affect the global climate are on the order of hundreds of years, while BC is a short-lived climate pollutant (SLCP) with atmospheric life times of days to weeks. Climate models or atmospheric transport models struggle to emulate the seasonality and amplitude of BC concentrations in the Arctic, which are low in summer and high in winter/spring during the so called Arctic haze season. The high uncertainties regarding BC's climate impact are not only related to ari and aci, but also due to model parameterizations of BC lifetime and transport, and the highly uncertain estimates of global and regional BC emissions. Given the high uncertainties in technology-based emission inventories (EI), there is a need for an observation-based assessment of sources of BC in the atmosphere. We study short-term and long-term observations of elemental carbon (EC), the mass-based analog of optically-defined BC. EC aerosol concentrations and carbon-isotope-based (δ13C and ∆14C) sources were constrained (top-down) for three Arctic receptor sites in Abisko (northern Sweden), Tiksi (East Siberian Russia), and Zeppelin (on Svalbard, Norway). The radiocarbon (∆14C) signature allows to draw conclusion on the EC sources (fossil fuels vs. biomass burning) with high accuracy (&lt;5% variation). Stable carbon isotopic fingerprints (δ13C) give qualitative information of the consumed fuel type, i.e. coal, C3-plants (wood), liquid fossil fuels (diesel) or gas flaring (methane and non-methane hydrocarbons). These fingerprints can be used in conjunction with Bayesian statistics, to estimate quantitative source contributions of the sources. Finally, our observations were compared to predictions from a state of the art atmospheric transport model (coupled to BC emissions), conducted by our collaborators at NILU (Norwegian Institute for Air Research). Observed BC concentrations showed a high seasonality throughout the year, with elevated concentrations in the winter, at all sites. The highest concentrations were measured on Svalbard during a short campaign (Jan-Mar 2009) focusing on BC pollution events. Long-term observations showed that Svalbard (2013) had overall the lowest annual BC concentrations, followed by Abisko (2012) and Tiksi (2013). Isotope constraints on BC combustion sources exhibited a high seasonality and big amplitude all across the Eurasian Arctic. Uniform seasonal trends were observed in all three year-round studies, showing fractions of biomass burning of 60-70% in summer and 10-40% in winter. Europe was the major source region (&gt;80%) for BC emissions arriving at Abisko and the main sources were liquid fossil fuels and biomass burning (wood). The model agreed very well with the Abisko observations, showing good model skill and relatively well constrained sources in the European regions of the EI. However, for the Svalbard and East Siberian Arctic observatories the model-observation agreement was not as good. Here, Russia, Europe and China were the major contributors to the mostly liquid fossil and biomass burning BC emissions. This showed that the EI still needs to be improved, especially in regions where emissions are high but observations are scarce (low ratio of observations to emitted pollutant quantity). Strategies for BC mitigation in the (Eurasian) Arctic are probably most efficient, if fossil fuel (diesel) emissions are tackled during winter and spring periods, all across Eurasia. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 3: Manuscript.</p>

This thesis sets out to examine the making of femininity in hip-hop, with a special focus on the performances of three artists - Mykki Blanco, Angel Haze, and Brooke Candy - and their representations made through music videos and lyrics. The thesis is structured around critical femininity studies, and created through a somatechnics perspective. I am investigating how femininity and the feminine body is made through and in relation to technology and different expressions of race, class, and sexuality. By questioning how structures of femininity is made and re-made through a somatechnical perspective, this thesis offers alternatives to interpret feminine representations in hip-hop, and bases its conversation in both culture studies and critical femininity studies. In the paper‘s conclusion, questions regarding active feminist resistance in hip-hop are raised, with hope to widen the discussions about female identified artists and their performances in this specific discourse.