Cette thèse est un travail empirique sur la dispersion des prix, c'est-à-dire le fait qu'un bien identique puisse être vendu à des prix différents, en violation de la célèbre loi du prix unique. L'approche s'inscrit dans une littérature initiée par Stigler (1961), qui note que "la dispersion des prix est (...) la mesure de l'ignorance dans le marché". Il en découle que de simples observations de prix peuvent révéler beaucoup d'information sur le fonctionnement d'un marché.Le premier chapitre étudie l'impact de la création d'une enseigne à bas prix sur le marché français de la distribution de carburant. Cette création implique que de nombreuses stations sont confrontées à une baisse de prix importante d'un proche concurrent. La réaction agrégée mesurée au niveau national est faible, mais masque des hausses et des baisses en proportions équivalentes. L'hétérogénéité des réactions souligne l'importante segmentation du marché. Le second chapitre, utilisant le même jeu de de données, examine la pertinence de modèles qui identifient la dispersion des prix à des équilibres en stratégies mixtes. Empiriquement, on observe que l'ordre des prix des stations concurrentes tend en effet à varier dans le temps, et que sa volatilité croit lorsque la distance qui sépare les points de vente augmente. La dispersion est donc croissante d'un coût recherche supporté par les consommateurs. Par ailleurs, l'enseigne des stations détermine largement leur stratégie de prix. Les stations qui pratiquent les prix les plus bas sont relativement plus susceptibles de maintenir des prix parfaitement alignés sur ceux des proches concurrents, tandis que la dispersion mesurée entre les stations plus onéreuses est corrélée positivement avec le coût du diesel et le nombre de stations présentes sur le marché. Ainsi, les résultats renforcent la thèse de la coexistence d'un marché proche d'une concurrence à la Bertrand avec un marché moins concurrentiel, où des stations tirent parti de frictions importantes.Le dernier chapitre s'intéresse à la grande distribution, s'appuyant sur des données collectées sur un comparateur de prix en ligne. J'observe que les comparaisons réalisées entre chaînes de magasins par le site sont relativement peu informatives compte tenu de l'hétérogénéité des résultats au niveau local. L'échantillon de produits retenu peut en outre conduire à des résultats largement différents. La volatilité des comparaisons augmente avec la distance séparant les supermarchés, ce qui, comme dans le cas du carburant, dénote la présence de coûts de recherche. A l'échelle locale, le niveau des prix ne croit pas avec la concentration approximée par les parts de marché, ce qui conduit à remettre en question la pertinence de cet indicateur en matière de politique publique. La dispersion est positivement corrélée au niveau des prix, ce qui suggère que l'imperfection de l'information permet effectivement aux supermarchés de pratiquer des prix plus élevés qu'en concurrence parfaite. / This thesis is an empirical study of price dispersion, namely the fact that a homogenous good can typically be purchased at various prices, in violation of the famous law of one price. The approach belongs to a literature initiated by Stigler (1961), which notes that “price dispersion is (...) the measure of ignorance in the market”. A noteworthy consequence is that simple price observations can be very informative about competition in a market.The first chapter analyses the impact of the creation of a discount chain on the French retail gasoline market. This creation implies that many gas stations are confronted with a sharp price decrease by a competitor. The aggregate reaction, measured at the national level, is weak but it conceals increases and decreases in equivalent proportions The heterogeneity of measured reactions highlights an important market segmentation. Using the same data, the second chapter explores the relevance of models which identify price dispersion with an equilibrium in mixed strategies. Empirically, the rank of competing gas stations is indeed observed to vary over time, and its volatility is positively correlated with the distance that separates the outlets. Dispersion thus increases with a search cost incurred by customers. The chain affiliation of gas stations largely determines their pricing strategies. Retailers which have low price policies are more likely than others to keep prices aligned with nearby competitors, while dispersion measured between more expensive gas stations is positively correlated with diesel cost and the number of sellers in the market. Results thus provide further support the coexistence of a market close to Bertrand competition with a less competitive market, where gas stations take advantage of significant frictions.The last chapter focuses on grocery stores, using data collected from an online price comparison website. Aggregate national chain comparisons that are displayed on the website are found to provide information of little value to consumers given the heterogeneity observed within store level comparison results. These can furthermore vary significantly depending on the set of compared products. Volatility tends to increase with the distance that separates supermarkets, which, as in the case of gasoline, suggests that search cost influence competition. Within local markets, the measured concentration is negatively correlated with price levels, which leads to question its effective relevance in terms of public policies. Price dispersion is found to increase with market price levels, which is consistent with sellers taking advantage of consumer search costs to post higher prices.

Cette thèse est consacrée à l’étude du comportement global des solutions de l’équation des ondes énergie-critique. On s’intéresse tout spécialement à la description de la dynamique du système dans l’espace de l’énergie. Nous développons une variante de la méthode d’énergie qui permet de construire des solutions explosives de type II, instables. Ensuite, par une démarche similaire, nous donnons le premier exemple d’une solution radiale de l’équation des ondes énergie-critique qui converge dans l’espace de l’énergie vers une superposition de deux états stationnaires (bulles). En appliquant notre méthode au cas de l’équation des ondes des applications harmoniques (wave map), nous obtenons des solutions de type bulle-antibulle, en toute classe d’équivariance k > 2. Pour l’équation des ondes énergie-critique radiale, nous étudions également le lien entre la vitesse de l’explosion de type II et la limite faible de la solution au moment de l’explosion. Finalement, nous montrons qu’il est impossible qu’une solution radiale converge vers une superposition de deux bulles ayant les signes opposés. / In this thesis we study the global behavior of solutions of the energy-criticalfocusing nonlinear wave equation, with a special emphasis on the description of the dynamics in the energy space. We develop a new approach, based on the energy method, to constructing unstable type II blow-up solutions. Next, we give the first example of a radial two-bubble solution of the energy-critical wave equation. By implementing this construction in the case of the equivariant wave map equation, we obtain bubble-antibubble solutions in equivariance classes k > 2. We also study the relationship between the speed of a type II blow-up and the weak limit of the solution at the blow-up time. Finally, we prove that there are no pure radial two-bubbles with opposite signs for the energy-critical wave equation.

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The dispersion quality of nanoinclusions within a matrix material is often overlooked when relating the effect of nanoscale structures on functional performance and processing/property relationships for nanocomposite materials. This is due in part to the difficulty in visualizing the nanoinclusion and ambiguity in the description of dispersion. Understanding the relationships between the composition of the nanofiller, matrix chemistry, processing procedures and resulting dispersion is a necessary step to tailor the physical properties. A method is presented that incorporates high-contrast imaging, an emerging scanning electron microscopy technique to visualize conductive nanofillers deep within insulating materials, with various image processing procedures to allow for the quantification and validation of dispersion parameters. This method makes it possible to quantify the dispersion of various single wall carbon nanotube (SWCNT)-polymer composites as a function of processing conditions, composition of SWCNT and polymer matrix chemistry. Furthermore, the methodology is utilized to show that SWCNT dispersion exhibits fractal-like behavior thus allowing for simplified quantitative dispersion analysis. The dispersion analysis methodology will be corroborated through comparison to results from small angle neutron scattering dispersion analysis. Additionally, the material property improvement of SWCNT nanocomposites are linked to the dispersion state of the nanostructure allowing for correlation between dispersion techniques, quantified dispersion of SWCNT at the microscopic scale and the material properties measured at the macroscopic scale. / Ph. D.

Thesis is divided into two parts. The first part is written rather in theoretical way. It deals with general formation of the dispersion mathematically and verbally. It focuses on the chromatic and polarization mode dispersion. Different types of optical fibers for category G.65X are mentioned as well in connection with the ITU-T. Further attention is drawn first to compensation and then the measurement both of the mentioned dispersions. The thesis describes also analyzers and their main features. The second part is devoted to practical measurements of polarization mode dispersion. In the beginning there are described the components used for construction of the optical measurements and topologies. It is followed by an analysis of an each optical link. The results of these measurement methods and their mutual comparisons are at the end of this section. Measurements in temperature chamber is the subject of a further practical part, which from the beginning captures the essential features of the temperature chamber. This is followed by a description of the measurements, analyses and final valuation depending on the amount of polarization mode dispersion versus the temperature.

The work deals with dispersive effects of single mode fibers. We learn about the chromatic dispersion, the main attention is paid to the Polarization Mode Dispersion. We clarify the root cause origin of the Polarization Mode Dispersion describing parameters and its effect on transmitted data. Further on, the works dedicates to measure methods of the Polarization Mode Dispersion which is the interferometric method or the POTDR method. We explain the ways of the PMD removal at contemporary optic routes and options of PMD compensation by using compensators of various types. There is also mentioned the possibility of profiting from the soliton transmission. The last chapter deals with measuring of a real optic route. It includes measured data and its evaluation due to the ITU-T demands.

In this thesis, the m-arity tree networks have been investigated to derive equations for their nodes, links and required wavelengths. The relationship among all parameters such as leaves nodes, destinations, paths and wavelengths has been found. Three situations have been explored, firstly when just one server and the leaves nodes are destinations, secondly when just one server and all other nodes are destinations, thirdly when all nodes are sources and destinations in the same time. The investigation has included binary, ternary, quaternary and finalized by general equations for all m-arity tree networks. Moreover, a multicast technology is analysed in this thesis to transmit data carried by specific wavelengths to several clients. Wavelengths multicast switching is well examined to propose split-convert-split-convert (S-C-S-C) multicast switch which consists of light splitters and wavelengths converters. It has reduced group delay by 13% and 29% compared with split-convert (S-C) and split-convert-split (S-C-S) multicast switches respectively. The proposed switch has also increased the received signal power by a significant value which reaches 28% and 26.92% compared with S-C-S and S-C respectively. In addition, wavelengths allocation algorithms in multicast technology are proposed in this thesis using tree networks topology. Distributed scheme is adopted by placing wavelength assignment controller in all parents’ nodes. Two distributed algorithms proposed shortest wavelength assignment (SWA) and highest number of destinations with shortest wavelength assignment (HND-SWA) algorithms to increase the received signal power, decrease group delay and reduce dispersion. The performance of the SWA algorithm was almost better or same as HND-SWA related to the power, dispersion and group delay but they are always better than other two algorithms. The required numbers of wavelengths and their utilised converters have been examined and calculated for the researched algorithms. The HND-SWA has recorded the superior performance compared with other algorithms. It has reduced number of utilised wavelengths up to about 19% and minimized number of the used wavelengths converters up to about 29%. Finally, the centralised scheme is discussed and researched and proposed a centralised highest number of destinations (CHND) algorithm with static and dynamic scenarios to reduce network capacity decreasing (Cd) after each wavelengths allocation. The CDHND has reduced (Cd) by about 16.7% compared with the other algorithms.

Wage structure has shown to be crucial for firms and workers. However, there existwage dispersion for identical workers in labor markets. The paper measures the effectof industry and firm size on wages in Sweden. The results show that both industry andfirm size have significant effects on wages. Regarding the explanation factors, thefinding is that human capital factors can explain a portion of the industry wagedifferentials, but have less impact on wage differentials across firm size. However,compensating differentials and union organization are not the determinants of theindustry wage differentials and firm size-wage effects. In addition, unobservedindividual characteristics can partly explain firm size effect on wages, but cannotexplain industry wage differentials based on our samples.

Despite expectations in the late 1990s that the Internet would lead to frictionless commerce, empirical research shows that electronic commerce is characterized by persistent price dispersion. This paper examines reasons why online price dispersion exists in the books, CDs, and consumer electronics retail sectors. The Internet allows for multi-channel retailing, and it influences supply, demand, and market-related factors for both retailers and consumers. These factors shape retailers’ price-setting abilities which, in turn, shape their pricing strategies. I find that different pricing strategies result in online price dispersion, and I ultimately predict that retail e-commerce markets, which are oligopolistic in nature, will continue to exhibit persistent price dispersion. In particular, price dispersion will decrease the most in the CDs sector, followed by the books and then the consumer electronics sectors.

With the advance of combinational chemistry and high throughput screening, an increasing number of pharmacologically active compounds have been discovered and developed. A significant proportion of those drug candidates are poorly water-soluble, thereby exhibiting limited absorption profiles after oral administration. Therefore, advanced formulation and processing technologies are demanded in order to overcome the biopharmaceutical limits of poorly water-soluble drugs. A number of pharmaceutical technologies have been investigated to address the solubility issue, such as particle size reduction, salt formation, lipid-based formulation, and solubilization. Within the scope of this dissertation, two of the pharmaceutical technologies were investigated names thin film freezing and hot-melt extrusion. The overall goal of the research was to improve the oral bioavailability of poorly water-soluble drugs by producing amorphous solid dispersion systems with enhanced wetting, dissolution, and supersaturation properties. In Chapter 1, the pharmaceutical applications of hot-melt extrusion technology was reviewed. The formulation and process development of hot-melt extrusion was discussed. In Chapter 2, we investigated the use of thin film freezing technology combined with template emulsion system to improve the dissolution and wetting properties of itraconazole (ITZ). The effects of formulation variables (i.e., the selection of polymeric excipients and surfactants) and process variables (i.e., template emulsion system versus cosolvent system) were studied. The physic-chemical properties and dissolution properties of thin film freezing compositions were characterized extensively. In Chapter 3 and Chapter 4, we investigated hot-melt extrusion technology for producing amorphous solid dispersion systems and improving the dissolution and absorption of ITZ. Formulation variables (i.e., the selection of hydrophilic additives, the selection of polymeric carriers) and process variables (i.e., the screw configuration of hot-melt extrusion systems) were investigated in order to optimize the performance of ITZ amorphous solid dispersions. The effects of formulation and process variables on the properties of hot-melt extrusion compositions were investigated. In vivo studies revealed that the oral administration of advanced ITZ amorphous solid dispersion formulations rendered enhanced oral bioavailability of the drug in the rat model. Results indicated that novel formulation and processing technologies are viable approaches for enhancing the oral absorption of poorly water-soluble drugs. / text