O solo é um importante recurso natural e a sua conservação é essencial para uma produção sustentável. A qualidade de um solo, por sua vez, pode ser definida como a capacidade deste em exercer sua função em um ecossistema e pode ser descrita por meio de parâmetros físicos, químicos e biológicos. Os atributos físicos do solo descrevem a organização de sua estrutura, de modo que esta é responsável pela movimentação e disponibilidade da solução do solo para as plantas e depende da dimensão, forma e arranjo de suas partículas sólidas e de seus poros. Portanto, a discussão dos mecanismos de movimento e retenção da água no solo é relevante na inferência da sua qualidade física. A curva de retenção da água no solo é o gráfico da umidade do solo em função do potencial mátrico da água no solo, a qual é uma ferramenta importante na avaliação da qualidade física do solo. No Brasil, os Latossolos são de grande importância, devido a sua extensão e potencial produtivo. Estes solos são muito intemperizados, com elevada estabilidade de agregados e podem ser originados a partir de materiais distintos, o que interfere na resposta física. Portanto, o objetivo geral deste trabalho foi avaliar a qualidade físico-hídrica do solo por meio da análise da curva de retenção da água em três Latossolos, verificando entre dois modelos empíricos de ajuste (BROOKS; COREY, 1964; VAN GENUCHTEN, 1980). Também foram avaliadas a frequência de distribuição do tamanho de poros e a utilização do índice S como indicador da qualidade física do solo. Foram coletadas amostras indeformadas de três áreas para confecção das curvas de retenção de água no solo: (1) Latossolo Vermelho Amarelo Distrófico típico (pousio); (2) Latossolo Vermelho Distrófico típico álico (cana-de-açúcar); (3) Latossolo Vermelho Distrófico típico (cana-de-açúcar). Os resultados mostraram que a curva de retenção de água foi influenciada pela densidade do solo, porosidade, textura e conteúdo de carbono orgânico; o ajuste da curva de retenção de água no solo pelos dois modelos utilizados foi semelhante, porém o modelo de van Genuchten (1980) apresentou-se ligeiramente melhor que o modelo de Brooks e Corey (1964), principalmente nos pontos próximos à saturação; a frequência de distribuição de poros e o índice S foram sensíveis em diferenciar a qualidade estrutural de solos devido à textura e ao manejo. / Soil is an important natural resource and its conservation is essential for sustainable production. The quality of a soil can be defined as its ability to exert its function in an ecosystem and can be described by means of physical, chemical and biological parameters. The soil physical attributes describe the organization of its structure, that is responsible for the moviment and availability of soil solution for plants and it depends on the size, shape and arrangement of its solid particles and pores. Therefore, the discussion of the mechanisms of soil water movement and retention is important in inferring its physical quality. The soil water retention curve is an important tool to evaluate soil quality, is the graph of soil water content as a function of soil water matric potential. In Brazil, the Oxisols are of great importance due to their extent and productive potential. These soils are highly weathered, with high aggregate stability and can originate from different materials, which interfer on the physical response. Therefore, the aim of this work was to evaluate the physical-hydric quality of the soil by means of the soil water retention curve of three Oxisols, by using two empirical adjustment models (BROOKS; COREY, 1964; VAN GENUCHTEN, 1980). Pore-size distribution frequency and the use of the S index as an indicator of physical soil quality were also evaluated. Undisturbed soil samples were collected from three areas to obtain the soil water retention curves: (1) Typic Hapludox (fallow land), (2) Rhodic Hapludox (sugarcane), (3) Rhodic Hapludox (sugarcane). The results showed that the soil water retention curve was influenced by the soil bulk density, soil porosity, soil texture and soil organic carbon content. The fitness of the soil water retention curve by the two models was similar, however the van Genuchten\'s model (1980) was slightly better than the model of Brooks and Corey (1964), especially in the points near saturation; the pore-size distribution frequency and the S index were sensitive in differentiating the structural quality of soil due to the texture and management.

O solo é um importante recurso natural e a sua conservação é essencial para uma produção sustentável. A qualidade de um solo, por sua vez, pode ser definida como a capacidade deste em exercer sua função em um ecossistema e pode ser descrita por meio de parâmetros físicos, químicos e biológicos. Os atributos físicos do solo descrevem a organização de sua estrutura, de modo que esta é responsável pela movimentação e disponibilidade da solução do solo para as plantas e depende da dimensão, forma e arranjo de suas partículas sólidas e de seus poros. Portanto, a discussão dos mecanismos de movimento e retenção da água no solo é relevante na inferência da sua qualidade física. A curva de retenção da água no solo é o gráfico da umidade do solo em função do potencial mátrico da água no solo, a qual é uma ferramenta importante na avaliação da qualidade física do solo. No Brasil, os Latossolos são de grande importância, devido a sua extensão e potencial produtivo. Estes solos são muito intemperizados, com elevada estabilidade de agregados e podem ser originados a partir de materiais distintos, o que interfere na resposta física. Portanto, o objetivo geral deste trabalho foi avaliar a qualidade físico-hídrica do solo por meio da análise da curva de retenção da água em três Latossolos, verificando entre dois modelos empíricos de ajuste (BROOKS; COREY, 1964; VAN GENUCHTEN, 1980). Também foram avaliadas a frequência de distribuição do tamanho de poros e a utilização do índice S como indicador da qualidade física do solo. Foram coletadas amostras indeformadas de três áreas para confecção das curvas de retenção de água no solo: (1) Latossolo Vermelho Amarelo Distrófico típico (pousio); (2) Latossolo Vermelho Distrófico típico álico (cana-de-açúcar); (3) Latossolo Vermelho Distrófico típico (cana-de-açúcar). Os resultados mostraram que a curva de retenção de água foi influenciada pela densidade do solo, porosidade, textura e conteúdo de carbono orgânico; o ajuste da curva de retenção de água no solo pelos dois modelos utilizados foi semelhante, porém o modelo de van Genuchten (1980) apresentou-se ligeiramente melhor que o modelo de Brooks e Corey (1964), principalmente nos pontos próximos à saturação; a frequência de distribuição de poros e o índice S foram sensíveis em diferenciar a qualidade estrutural de solos devido à textura e ao manejo. / Soil is an important natural resource and its conservation is essential for sustainable production. The quality of a soil can be defined as its ability to exert its function in an ecosystem and can be described by means of physical, chemical and biological parameters. The soil physical attributes describe the organization of its structure, that is responsible for the moviment and availability of soil solution for plants and it depends on the size, shape and arrangement of its solid particles and pores. Therefore, the discussion of the mechanisms of soil water movement and retention is important in inferring its physical quality. The soil water retention curve is an important tool to evaluate soil quality, is the graph of soil water content as a function of soil water matric potential. In Brazil, the Oxisols are of great importance due to their extent and productive potential. These soils are highly weathered, with high aggregate stability and can originate from different materials, which interfer on the physical response. Therefore, the aim of this work was to evaluate the physical-hydric quality of the soil by means of the soil water retention curve of three Oxisols, by using two empirical adjustment models (BROOKS; COREY, 1964; VAN GENUCHTEN, 1980). Pore-size distribution frequency and the use of the S index as an indicator of physical soil quality were also evaluated. Undisturbed soil samples were collected from three areas to obtain the soil water retention curves: (1) Typic Hapludox (fallow land), (2) Rhodic Hapludox (sugarcane), (3) Rhodic Hapludox (sugarcane). The results showed that the soil water retention curve was influenced by the soil bulk density, soil porosity, soil texture and soil organic carbon content. The fitness of the soil water retention curve by the two models was similar, however the van Genuchten\'s model (1980) was slightly better than the model of Brooks and Corey (1964), especially in the points near saturation; the pore-size distribution frequency and the S index were sensitive in differentiating the structural quality of soil due to the texture and management.

La connaissance de la dynamique des matières en suspension (MES) et des turbidités en milieu côtier est un élément clé pour comprendre les écosystèmes marins. Les processus de floculation/défloculation représentent des mécanismes essentiels contrôlant la dynamique des caractéristiques physiques des MES et, par conséquent, leur devenir dans l’environnement. Cette thèse a pour objectif de mieux comprendre la caractérisation des MES et leur variabilité de l’échelle tidale à l’échelle annuelle en mer côtière, en réponse aux différents forçages hydrodynamiques, hydrologiques et biologiques ayant lieu à l’interface entre estuaire et baie. À cette fin, des capteurs optiques et acoustiques ont été déployés in situ, lors de 6 campagnes en mer réalisées en 2016, en vue de caractériser et de quantifier les MES dans la colonne d’eau, à la sortie de l’embouchure de l’estuaire de Seine (France). Une analyse critique des mesures granulométriques issues du LISST-100X est proposée. Un travail de quantification des incertitudes de mesure associées à l’estimation de la concentration en MES a mis en avant le risqué lié à un rinçage insuffisant des filtres et a conduit à définir une masse minimum à filtrer, de l'ordre de 10 mg, quelle que soit la concentration. Ce travail a notamment permis de proposer une méthode d’estimation d’un volume optimal de filtration basée sur une mesure préalable de turbidité de référence. Les mesures à haute fréquence ont montré que la dynamique des caractéristiques physiques des MES en termes de concentration et de taille médiane sont contrôlées par le cycle advection-floculation-sédimentation-remise en suspension. Ces résultats ont permis de hiérarchiser les paramètres de contrôle des processus de floculation. La turbulence a été identifiée comme le principal paramètre de contrôle à l’échelle tidale et semi-lunaire, la taille médiane maximale des flocs étant inversement corrélée à l’intensité des courants. À l’échelle saisonnière, la variation des caractéristiques des MES (taille, densité, vitesse de chute) est liée à la variabilité du contenu en matière organique (MO), avec une floculation favorisée quand le taux de MO particulaire augmente. Ces flocs plus grands et moins denses sont également plus résistants à la fragmentation induite par cisaillement turbulent. Ces travaux ont également permis de discuter le concept de structuration fractale des flocs.La dynamique de la dimension fractale, déterminée en combinant des données in situ de concentration en MES et de distribution en classe de taille, peut traduire des variations de composition des MES, mais peut aussi résulter d'incertitudes de mesure associées aux instruments. Ces dernières sont discutées dans cette thèse. La variabilité saisonnière des caractéristiques des MES est plus prononcée au large que dans la zone sous influence de l’estuaire de Seine. À partir des observations ponctuelles en Baie de Seine et d’une série de mesure long terme dans la zone côtière belge acquise par le laboratoire RBINS, les méthodes acoustiques et optiques sont combinées. Ces dernières ont mis en avant une augmentation de la rétrodiffusion acoustique lorsque la densité moyenne des flocs diminue. / The knowledge of suspended particulate matter (SPM) and turbidity dynamics in coastal waters is essential for studying marine ecosystems. Flocculation/deflocculation processes are crucial mechanisms controlling the dynamics of SPM physical characteristics and thus, the fate of these SPM in the environment. This PhD thesis focuses on the SPM characteristics and their dynamics in coastal waters, from tidal to annual scales, in response to hydrodynamic, hydrological and biological forcing that take place at the interface between estuaries and coastal seas. To this end, optical and acoustic sensors were deployed in situ through 6 field campaigns in 2016, in order to characterize and quantify SPM in the water column, near the mouth of the Seine estuary (France). A critical analysis of LISST-100X measurements in coastal waters is presented. The quantification of uncertainties on SPM concentration measurements is investigated: it highlights the crucial effect of salt retention, and the need for a minimum mass to filter, around 10 mg. A method for estimating an optimal filtration volume based on a reference turbidity measurement is proposed. High frequency measurements show that the dynamics of SPM and median diameter are controlled by the advection-flocculationsedimentation-resuspension cycle.These results allow to classify the factors controlling flocculation processes. Turbulence is identified as the main factor at the semi-diurnal and semi-lunar tidal scales, as the maximum median size of flocs decreases when the tidal currents intensify.At the seasonal scale, the variation of SPM characteristics (size, density, settling velocity) is correlated to the variability of the organic matter (OM) content: in particular, flocculation is enhanced by an increase of the particular OM fraction. The resulting larger and lesser dense flocs are also more resistant to the fragmentation induced by shear. This work also investigates the fractal approach applied to flocs. The fractal dimension variability, calculated by combining in situ data of SPM concentration and particle size distribution, can be associated to variations of the SPM composition, but can also result from uncertainties linked to instrument limitations. The latter are discussed in this PhD thesis. The seasonal variability of SPM characteristics is more pronounced offshore than at the mouth of the Seine estuary. From short-term observations in the Seine Bay and from long-term series in the Belgian coastal zone provided by the RBINS, optical turbidity and acoustic backscatter measurements are combined. They highlight an increase of the acoustic backscatter intensity when mean floc density.

This dissertation focuses on the formation, growth and discontinuance of business populations and firms in Sweden during the 20th century. It addresses some key issues in the domain of economic and social sciences, and in particular entrepreneurship and small business research: if and when firms grow, stagnate and decline, as well as how long firms survive and when they are likely to disband. Previous research has primarily analyzed these questions from a short time frame. Further, an individual or firm-oriented focus is commonly assumed. In that, alternative or complementary explanations to the growth and survival of firms may be disregarded. In contrast to much previous research, this dissertation assumes a micro-to-macro, longitudinal and demographic population approach. The period of investigation is over one hundred years. In addressing the growth and survival of firms, it takes into account the impact of firm-specific structural factors (such as firm age and size), generation (cohort) effects, as well as the influence of macroeconomic, exogenous factors. Further, the relationship between managerial/ownership succession and firm performance is also addressed. Both cross-sectional and longitudinal databases are employed in the dissertation. Its main empirical material consists of unique longitudinal data on new business firms, traced at the firm level from their birth to their termination. More specifically, seven birth cohorts – generations – of approximately 2,200 firms founded in 1899, 1909, 1912, 1921, 1930, 1942 and 1950 are included. The main findings show that ownership/management succession in firms had a quite weak correlation with firm performance and survival. At least at an aggregate level, and with some exceptions, it is debatable if the loss and replacement of owner-managers in small and in larger firms have any observable effects on firm performance. Furthermore, macroeconomic phenomena influence the conditions of individual firms as well as populations/aggregates of businesses. Both the growth and termination of firms and firm populations are found to be related to real economic (environmental) conditions; e.g. favorable macroeconomic conditions implied that firms grew in size. At the same time, under certain circumstances, the influence of structural variables (firm age and size) – as suggested in much previous research – is found to be of importance. As concerns firm growth, as well as firm termination, the economic environment and structural factors interact. These findings challenges individual or firm-level research that mainly focus on personal traits and behaviors in explaining firm success and failure. Other previous assumptions are also challenged when taking a longer time perspective into consideration. For decades, organization and business research have acknowledged a liability of newness and of size for business firms. While this might be true under some conditions, this liability of newness is falsified in the study: the termination behavior of some firm generations did not correspond with these assumptions. Thus, the perspectives and methodology applied in the dissertation complement earlier approaches in entrepreneurship and small business research.

<p>The project was conducted on a small-scale catchment at Goedertrou in the Riebeek- Kasteel district. The focus of this study was to address some of the hydrological processes active in the research catchment, namely infiltration, run-off and sediment mobilisation on different soil types. It was done to investigate the origin of Berg River pollutants. To answer the overall question about what influence the natural salt load of the Berg River, a number of subprojects have been identified, one of which is to understand the hydrological processes in the soil mantle and vadose zone. Hence, the study aimed to answer the research questions mentioned and discussed in section 1.3 of Chapter 1. Considering the results, it could be suggested that decayed root systems from the rows of plants, soil cracks, small channels and openings created by small animals, as well as slope orientation and, therefore, soil composition, all played a major role in influencing the ability of the soil to absorb the simulated rainfall. In this study, the factors that influenced run-off are micro topography, soil moisture, root system, animal activities in soil profile, soil crack dimensions and the hydraulic conductivity. The main factors that played a major role to influence sediments mobilisation are strongly believed to be the micro topography within the ring, slope gradient and length, vegetation cover and rainfall-simulation intensity. After using different techniques, the results show that farmers must be aware that with storm rainfall, particles smaller than 65 &mu / m are subject to mobilisation. It is important to let land-users know that they need proper and appropriate methods for land-use.</p>

Die vorliegende Arbeit befasst sich mit Untersuchung der gekoppelten Einflüsse ‎von Gasart, Porengröße und Porengrößenverteilung auf die effektive ‎Wärmeleitfähigkeit nicht-durchströmter poröser Materialien (Dämmstoffe). Diese ‎Zusammenhänge sind bisher nur ansatzweise bekannt und für eine spätere ‎praktische Anwendung von zunehmend großer Bedeutung. Um dies zu erreichen ‎wurden 12 verschiedene hoch poröse Materialien (Porosität höher als 70 %) ‎ausgewählt, die unterschiedlichen Porengrößenverteilungen im Makro- Mikro- und ‎Nanobereich haben. Die effektive Wärmeleitfähigkeit wurde hauptsachlich in zwei ‎unterschiedlichen Messverfahren untersucht. Die Messungen erfolgt bei normalem ‎Druck in vier Gas Atmosphären ‎(Kr, Ar, N2 and He) bei Temperaturen bis maximal 900 °C. Kritische Analyse zum ‎jeweiligen Messverfahren und Auswertungsalgorithmus wurden durchgeführt. Ein ‎mathematisches Model basiert auf die Porengrößenverteilung mit Berücksichtigung ‎des Knudsen Effekts wurde entwickelt um die Änderung der effektiven ‎Wärmeleitfähigkeit beim Wechsel der Gas Atmosphäre auszuwerten. Diese führt zu ‎besser Ergebnisse als die ausgewertet Ergebnisse von den vorhandenen Modellen ‎aus der Literatur. ‎ / In the present work, the influences of exchanging the filling gas accompanied with Knudsen effect on effective thermal conductivity were investigated with experiments and physical mathematical modeling. This work is thought to be the first intensive study in this area of the research, which includes twelve different porous insulation materials. Analysis of the huge number of experimental results leaded to new observations regarding various coupling effects. An improved model for predicting the change in effective thermal conductivity due to exchanging the filling gas has been developed with regards to the Knudsen effect based on models for rarefied gases and parallel arrangements models for effective thermal conductivity.

Zu den wenigen Methoden, die sich für eine prozessnahe Charakterisierung von dispersen Stoffsystemen bezüglich der Partikelgrößenverteilung eignen, zählt die Schalldämpfungsspektroskopie. Dennoch ist ihr Einsatz in der industriellen Praxis auf einen überschaubaren Bereich an Messaufgaben und Stoffsystemen beschränkt. Insbesondere findet sie kaum Einsatz für die Partikelgrößenanalyse von submikronen Emulsionen. Die vorliegende Arbeit macht es sich deshalb zum Ziel, ausgehend von grundsätzlichen Überlegungen die Eignung der Schalldämpfungsspektroskopie zur prozessnahen Charakterisierung des Dispersitätszustandes von submikronen Emulsionen zu bewerten und zu verbessern. Schwerpunkte der Arbeit sind die modellhafte Beschreibung des Schalldämpfungsverhaltens von hoch konzentrierten Partikelsystemen im Submikrometerbereich, die Abschätzung des Einflusses von Emulgatoren auf die Schalldämpfung, die Erkennbarkeit von Einzelheiten der Partikelgrößenverteilung, die Sensitivität berechneter Partikelgrößenverteilungen bezüglich der Partikelkonzentration und der verschiedenen Stoffeigenschaften sowie die Auswertung von Schalldämpfungsspektren bei Unkenntnis dieser Modellparameter. Die angesprochenen Aspekte werden am Beispiel typischer Charakterisierungsaufgaben diskutiert. / The ultrasonic spectroscopy is one of few measurement methods applicable to the online characterization of disperse systems with regard to particle size distribution. However, its application in industrial practise is restricted to a rather low number of measurement tasks and material systems. In particular it is hardly used for the particle size analysis of submicron emulsions. This thesis therefore aims to the evaluation of the ultrasonic spectroscopy regarding its applicability to the online characterization of submicron emulsions. Main issues of the thesis are the modelling of sound attenuation in dense particle systems, the estimation on the influence that surfactant layers exert on sound attenuation, the resolution at which size distribution can be measured, the sensitivity of calculated size distributions to model parameters (particle concentration and material properties) and the analysis of measured attenuation spectra by unknown model parameters. The meanining of these issues are illustrated for typical characterization tasks.

Im Rahmen dieser Arbeit erfolgte eine Analyse des Einflusses von Harnstoff-SCR-Technik auf die Partikelemission. Zudem wurde mit der Partikelkonfektionierung durch motorische Maßnahmen eine Möglichkeit zur Verbesserung der katalytischen Partikeloxidation aufgezeigt und untersucht. Untersuchungen mit einem Nfz-Dieselmotor zeigen, dass im Teillastbetrieb mit einem Harnstoff-SCR-System eine deutliche Partikelminderung möglich ist. Sie basiert im Wesentlichen auf der Oxidation organisch löslicher Bestandteile der Partikel im Katalysator. Reduktionsmitteldosierung drängt die Oxidation leicht zurück, die SCR erweist sich als zur Partikeloxidation konkurrierend. Die Charakteristik der Partikelgrößenverteilung wird durch das SCR-System nicht wesentlich verändert, jedoch kann analog zur emittierten Partikelmasse auch die Partikelanzahl deutlich abgesenkt werden. Eine Analyse hinsichtlich der Partikelbestandteile in unterschiedlichen Partikelgrößenklassen hat gezeigt, dass der Anteil organisch löslicher Substanzen mit zunehmender Partikelgröße absinkt. Durch Veränderung des Einspritzbeginns des Kraftstoffs ist die Konfektionierung der Partikelemission im Sinne besserer katalytischer Oxidation möglich. Dabei wird durch Frühverstellung der Anteil organisch löslicher Komponenten der Partikel deutlich erhöht, gleichzeitig ist eine intensive Nanopartikelbildung zu beobachten. Ein Katalysator auf V2O5/WO3/TiO2-Basis ist sehr gut zur Oxidation sowohl der Nanopartikel als auch des größten Teils der organisch löslichen Komponenten geeignet. Damit wird insgesamt eine deutliche Partikelminderung erzielt. Abgasrückführung behindert die Partikelkonfektionierung zunächst deutlich. Durch die dabei jedoch mögliche noch weitere Verlagerung des Einspritzzeitpunktes nach &amp;quot;früh&amp;quot; kann der negative Einfluss aber weitgehend kompensiert werden, so dass eine ähnlich gute Partikelminderung wie im Betrieb ohne AGR bei gleichzeitiger Minderung der Stickoxidemission möglich ist.

Ziel dieser Arbeit war es, die Auswirkungen der im Kühlmittel von Leichtwasserreaktoren zur Reaktivitätssteuerung eingesetzten Borverbindungen auf Siedeprozesse – und damit indirekt auf die Wärmeabfuhr der Brennelemente – zu untersuchen. Bei den Siedeversuchen, die Gegenstand der vorliegenden Arbeit sind, wurde besonders auf eine realitätsnahe Annäherung an die Reaktorparameter Wert gelegt. Als Unterstützung zur Interpretation der Ergebnisse dienten eigene Messungen von signifikanten physikalischen Stoffdaten an wässrigen Borsäure- und Pentaboratlösungen. Die Siedeprozesse wurden in einer eigens für diese Analysen konzipierten und errichteten Versuchsanlage SECA unter Verwendung eines Leitfähigkeitsgittersensors sowie einer Hochgeschwindigkeitskamera bei Drücken von maximal 40 bar und Temperaturen bis zu 250 °C untersucht. Entsprechend der in den Untersuchungen gewonnenen Erkenntnis wird für reale Reaktoren fol-gendes angenommen: Die Anwesenheit von Borsäure hat keinen Einfluss auf großvolumige Sie-devorgänge im betrachteten Störfallszenario eines Druckwasserreaktors, und die Auswirkungen auf das unterkühlte Sieden sind vernachlässigbar gering. Es ist nicht zu erwarten, dass der Wärmeübergang von den Brennelementen an das Kühlmittel beeinflusst wird. Bei einer Einspeisung von Pentaborat in Siedewasserreaktoren kann jedoch davon ausgegangen werden, dass der Wärmeübergang durch eine Verkleinerung der Blasen verbessert wird. Weitere Untersuchungen bezüglich des Austrages von Pentaborat an der Phasengrenze sowie der Bildung von Schäumen sind jedoch notwendig, und es ist den Fragen nachzugehen, ob sich diese Schäume auch bei der Einspeisung von Pentaborat in einen Siedewasserreaktor bilden können und welche Auswirkungen diese auf die oberhalb des Kerns befindlichen Dampfabscheiderzyklone und Dampftrockner haben.

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