Expansive soils are a worldwide problem especially in the regions where climate is arid or semi arid. These soils swell when they are exposed to water and shrink when they dry. Cyclic swelling and shrinkage of clays and associated movements of foundations may result in cracking of structures. Several methods are used to decrease or prevent the swelling potential of such soils like prewetting, surcharge loading, chemical stabilization etc. Among these, one of the most widely used method is using chemical admixtures (chemical stabilization). Cyclic wetting and drying affects the swell &ndash / shrink behaviour of expansive soils. In this research, the effect of cyclic swell &ndash / shrink on swell percentage of a chemically stabilized expansive soil is investigated. Class C Fly Ash is used as an additive for stabilization of an expansive soil that is prepared in the laboratory environment by mixing kaolinite and bentonite. Fly ash was added to expansive soil with a predetermined percentage changing between 0 to 20 percent. Hydrated lime with percentages changing between 0 to 5 percent and sand with 5 percent were also used instead of fly ash for comparison. Firstly, consistency limits, grain size distributions and swell percentages of mixtures were determined. Then to see the effect of cyclic swell &ndash / shrink on the swelling behavior of the mixtures, swell &ndash / shrink cycles applied to samples and swell percentages were determined. Swell percentage decreased as the proportion of the fly ash increased. Cyclic swell-shrink affected the swell percentage of fly ash stabilized samples positively.

The present study suggests new insights into topographic characterisation of engineering polymer surfaces towards to physical-chemical and mechanistic understanding of wetting phenomena on rough surfaces. Non-contact chromatic confocal imaging was chosen and justified as the optimal measuring method to study and correlate surface topography and surface properties of Sheet Moulding Compounds (SMC) as well as polyester and cotton fabrics. Before topographical characterisation, an adequate selection of optimal sampling conditions (cut-off length and resolution) were done by a systematic procedure proposed for periodic and non-periodic surfaces. Topographical characterisation of the surfaces was realized by an innovative methodology, separately considering different length scales in dependence on the surface morphologies of the materials. For SMC materials, the influence of moulding conditions (pressure, moulding time, metallic mold topography, metallic mold form, prepregs placement procedure, glass fibres content and orientation) on resulting macro-, meso- and micro-topography was studied. A model to conceptualize the influence of the most important moulding conditions on topographic characteristics and, as a consequence, on the quality of the resulting surface was presented. To quantify the effect of surface modification, a new parameter (Surface Relative Smooth) was suggested, developed and validated, which can be used for the characterisation of changes due to surface modifications for every solid material. A very important and innovative part of the present study is the development of new concepts for topographic characterisation of textile materials using different length scales, that makes possible to consider and analyse separately their specific morphologies caused by weave, yarn and filament/fibres, and to investigate the influence of topography on wettability by modification processes, e.g. construction parameters, thermosetting, impregnation with Soil Release Polymers (SRP) and wash-dry cycles. The present study showed, how construction parameters of polyester textiles, such as fineness of filaments and yarn, warp and weft densities as well as the type of weave, control the surface topography - characterised as meso-porosity (spaces between yarns) and micro-porosity (spaces between filaments) - and as a consequence strongly influence their capillarity. On the basis of experimental results, revealing differences in three basic types of woven fabrics – plain, twill and Panama – in respect to water penetration, the concept of an innovative novel wicking model was developed. Additionally, the influence of thermosetting and impregnation of polyester fabrics with Soil Release Polymers on topography, wetting and cleanability of three woven plain polyester fabrics, having different wefts, were studied. To characterise the soiling behaviour, an ‘spot analysis method’ was suggested, allowing wetting dynamics studies of liquids on fabrics with anisotropic surface properties. This method is applicable also to surfaces with anisotropic roughness characteristics and to porous media. The effect of wash-dry cycles on topography, spreading, wetting and soiling of woven plain and knitted cotton fabrics was in addition investigated. In all cases studied, the topographical characterisation and interpretation of results on different length scales contributed to a better understanding of wetting phenomena. A mathematical model for a virtual construction of textile surfaces to predict effects resulting from topographic changes on the behaviour of polymer and textiles surfaces was developed. Woven plain textiles and SMC surfaces were mathematically synthesized by a combination of various harmonic waves, i.e. Fourier synthesis. Topographic and technical construction parameters were taken into account to build their virtual topographies. In the case of textile surfaces, the effect of wash-dry cycles for cotton fabrics and thermosetting of polyester fabrics on their meso- and micro-morphology was investigated on the basis of the real topography of a given textile surface. The model allows to predict changes in the porosity of resulting textile materials, their wettability and soiling behaviour. The method presented provides possibilities to simulate controlled changes in textile construction parameters and to study their effect on the resulting topography. / Die vorliegende Arbeit vermittelt neue Einblicke in die topographische Charakterisierung technisch relevanter Polymeroberflächen mit dem Ziel, die Mechanismen der Benetzungsphänomene auf rauen Oberflächen besser zu verstehen. Eine 3D-Abbildung der Oberflächentopographie wurde mit einem konfokalen Mikroskop mit chromatischer Kodierung zwecks optimaler Charakterisierung duromerer Verbundwerkstoffsystemen (SMS: Sheet Moulding Compounds) sowie Polyester- und Baumwolltextilien berührungsfrei durchgeführt. Zur topographischen Oberflächencharakterisierung wurde eine systematische Prozedur vorgeschlagen, welche es erlaubt, eine entsprechende Auswahl von optimalen Messbedingungen, wie die Bewertungslänge (cut-off length) und Auflösung, für Oberflächen mit periodischer und nicht-periodischer Rauheit zu treffen. Die topographische Charakterisierung von Oberflächen wurde methodologisch weiter entwickelt, indem die Oberflächen auf verschiedenen Längenskalen je nach Morphologie untersucht werden können. Für duromere Verbundwerkstoffsysteme wurde der Einfluss von den Bedingungen des Formpressens (Druck, Zeit, Topographie und Form des metallischen Werkzeugs, Einbringen des Prepregs, Glasfasergehalt und -orientierung) auf die resultierende makro-, meso- und mikroskopische Topographie studiert. Eine modellmäßige Beschreibung des Einflusses der wichtigsten Charakteristiken des Herstellungsprozesses duromerer Verbundwerkstoffsysteme auf ihre topographische Charakteristiken und demzufolge auf die Qualität des Endproduktes wurde konzipiert. Zur Quantifizierung des Effekts der Oberflächenmodifizierung wurde einen neuen Parameter – Surface Relative Smooth – vorgeschlagen und dessen Nutzung für jedes beliebige Feststoffkörpers verifiziert. Das Hauptaugenmerk bei der Durchführung der Arbeit wurde auf die Entwicklung neuer Konzepte zur topographischen Charakterisierung textiler Materialien gelegt, welche die Nutzung mehrerer Längenskalen in Betracht ziehen. Dies ermöglicht die spezifische Morphologien textiler Strukturen zu berücksichtigen und jede Struktur, welche durch die Gewebeart, die Art der Fasern und des Garns entstanden ist, gesondert bezüglich ihr Einflusses auf die Benetzbarkeit infolge der Modifizierung (Konstruktionsparameter, Thermofixierung, Imprägnierung mit Soil-Release- Polymeren, Waschen/Trocknen-Zyklen) zu analysieren. In der vorliegenden Arbeit wird gezeigt, wie die Konstruktionsparameter von Polyestertextilien, wie z.B. die Filament- und Garnfeinheit, Kett- und Schussdichte sowie die Gewebebindung Einfluss auf die Oberflächentopographie und als Folge auf ihre Kapillarität nehmen, und zwar als Mesoporosität (Abstände zwischen Garnwindungen) und als Mikroporosität (Abstände zwischen einzelnen Filamenten). Auf der Basis von umfangreichen experimentellen Daten, welche die Unterschiede zwischen verschiedenen Bindungsarten (Leinwand, Köper, Panama) offenbaren, wurde ein neues Modell zur Beschreibung der Penetration von Flüssigkeiten in die textile Strukturen entwickelt. Außerdem wurde der Einfluss der Thermofixierung und Imprägnierung von Polyester Materialen mit Soil-Release-Polymeren auf die Topographie, Benetzbarkeit und Auswaschbarkeit für die drei wichtigsten Gewebearten untersucht, welche die gleiche Anzahl von Schussfäden haben. Für die Charakterisierung des Anschmutzungsverhaltens von Textilen wurde eine so genannte Fleck-Analysierungsmethode (spot analysis method) vorgeschlagen, welche es erlaubt, benetzungsdynamische Eigenschaften von Flüssigkeiten an Oberflächen mit anisotroper Topographie zu studieren. Diese Methode ist geeignet auch für Oberflächen mit anisotropen Rauheitsstrukturen und für poröse Materialien. Der Effekt von Waschen/Trocken-Zyklen auf die Topographie, Spreitung, Benetzung und Anschmutzung von Leinwandgewebe und Gestricke aus Baumwolle wurde zusätzlich untersucht. In allen Spezialfällen diente die topographische Charakterisierung und die Interpretation der Ergebnisse auf verschiedenen Längenskalen zur besseren Verständnis von Benetzungsphänomenen. Ein mathematisches Modell für die virtuelle Konstruktion von textilen Oberflächen wurde entwickelt, die das Studium der Effekte infolge topographischer Änderungen auf das Verhalten von Polymer- und Textiloberflächen ermöglicht. Oberflächen von Leingeweben und duromeren Verbundwerkstoffsystemen wurden mit der Fourier-Synthese unter Zuhilfenahme verschiedener harmonischer Wellen mathematisch abgebildet. Die Topographie- und Konstruktionsparameter wurden bei der Fourier-Synthese zur Konstruktion virtueller Topographien genutzt. Im Falle der textilen Materialein wurde der Effekt von Waschen/Trocknen-Zyklen für die Baumwolltextilien sowie der Thermofixierung von Polyestertextilien auf ihre Meso- und Mikromorphologie auf der Basis gemessener Parameter für jede Topographie modelliert. Dieses Modell erlaubt auch die Vorhersage der Änderungen in der Porosität von resultierenden textilen Strukturen, ihres Benetzungs- und Anschmutzungsverhaltens. Mit dieser Methode ist es möglich, gewünschte Änderungen von textilen Konstruktionsparametern einzustellen und ihre Effekte auf die Topographie zu untersuchen.

Zu Beginn der Arbeit werden thermodynamische, strukturelle und statistische Grundlagen und Modelle wiedergegeben, die einerseits Entmischungssysteme und andererseits flüssige Ober- und Grenzflächen betreffen. Hieran schließt sich eine umfangreiche Darstellung der Meßmethode an, die die theoretischen Zusammenhänge für die Beschreibung der Formen flüssiger Grenzflächen sowie eine Darstellung aller experimentell möglichen Kraftmeßkurven und deren Auswertung beinhaltet. Weiterhin folgt die Darstellung der Dichte-, Dichtedifferenz-, und Grenzflächenspannungsmeßergebnisse separat für die Systeme Ga-Hg, Ga-Pb, Al-Pb und Al-In. Die Temperaturabhängigkeit und die Absolutwerte der Grenzflächenspannung werden mit den vorgestellten Modellen verglichen. Im Anschluß daran werden die Oberflächenspannungsmeßergebnisse für das System Ga-Pb vorgestellt, dies geschieht unter Bezugnahme auf Benetzungsphänomene, Adsorptionserscheinungen und Keimbildungsprozesse. In einem relativ selbständigen Kapitel am Ende der Arbeit werden experimentelle Ergebnisse zur Durchmischung und Entmischung wiedergegeben und mit theoretischen Ergebnissen zum diffusionsgesteuerten Durchmischungsprozeß verglichen.

Water infiltration into the unsaturated zone especially in a shallow water table environment is affected by air compression ahead of the wetting front and air counterflow. Neglecting air compression in infiltration modeling can overestimate infiltration and infiltration rates, whereas not accounting for air counterflow can underestimate infiltration and infiltration rates due to unrealistic buildup of air pressure resistance ahead of the wetting front. A method, derived on the basis of the Green and Ampt (1911) infiltration model, is introduced to simulate air compression and air counterflow during infiltration into a shallow water table. The method retains the simplicity of the Green and Ampt (1911) model but adds the air pressure resistance term ahead of the wetting front. Infiltration equations are derived on the basis of the Green and Ampt (1911) and Sabeh’s (2004) infiltration model which accounts for air compression and air counterflow. The difference between this method and Sabeh’s (2004) model is that air counterflow, air compression, and infiltration are decoupled and updated with each wetting front increment whereas Sabeh’s (2004) method uses time step as a decoupling mechanism. Air compression ahead of the wetting front is predicted using the perfect gas law. Laboratory experiments showed that the introduced method is reasonably accurate when modeling cumulative infiltration values. Results of laboratory experiments were compared to results of the modeled infiltration methods: original Green and Ampt (1911) model and Green and Ampt with air compression and counterflow. The advantage of this new method is its simplicity. The new method uses parameters that are generally needed for modeling infiltration with the Green and Ampt (1911) approach. Disadvantages of the model are assumptions of the uniform water content and the uniform pressure. Another shortcoming of the model is that it does not account for air compression and air counterflow prior to ponding. Laboratory experiments described in this work and a proposed model can be further used for modeling and studying infiltration with air effects. In addition, this work can be of use to someone studying irrigation techniques of rice or other crops.

No description available.

No description available.

Membrane processes can cover a wide range of separation problems [with a specific membrane (membrane structure) required for every problem]. Thus, there are membranes available that differ in their structure and consequently in the functionality. Therefore membrane characterization is necessary to ascertain, which membrane may be used for a certain separation. Membranes of pore size ranging from 100nm to 1μm with a uniform pore size are very important in membrane technology. An optimum performance is achieved when the membrane is as thin as possible having a uniform pore size. Here in this thesis, membranes were synthesized by particle assisted wetting using mono-layers of silica colloids as templates for pores along with polymerizable organic liquids on water surface. The pore size reflects the original shape of the particles. Thus it is possible to tune the pore size by varying the particle size. This method is effective to control pore sizes of membranes by choosing silica particles of suitable size. This approach gives a porous structure that is very thin, but unfortunately limited in mechanical stability. Thus there is a need for support which is robust and can withstand the various mechanical stresses. A small change in the membrane or defect in the layered structure during the membrane formation can have drastic effect on the assembly. Lateral homogeneity of the layer generated by the particle assisted wetting can be judged by examination of its reflectivity, but once it is transferred on any solid support this option is no more. So a method is needed to detect the cracks or the inhomogenity of the membrane which can be detected even after the transfer. To tackle this problem a very simple and novel technique for characterizing the membrane by fluorescence labeling and optical inspection was developed in this thesis. The idea was to add a fluorescent dye which is poorly water soluble to the spreading solution comprising of the particles and the monomer. If the dye survived the photo-cross linking, then it would be embedded in the cross-linked polymer and would serve as a marker. Defects and inhomogenity would show up as cracks and spots. By the method that we have developed, we can detect our membrane from the support and spot defects.

Flexographic printing is a common printing method in the packaging field. The printing method is characterized primarily by the flexible printing plate and the low viscosity inks which make it suitable for use on almost any substrate. The object of this study was to obtain further knowledge of the some important mechanisms of flexographic printing and how they influence the print quality. The thesis deals with printing primarily on board and liner but also on newsprint with water-borne ink using a full-scale flexographic central impression (CI) printing press. Several printing trials have been performed with a focus on the chemical interaction between the ink and substrate and the physical contact between the ink-covered printing plate and the substrate. Multicolour printing exposes the substrate to water from the water-containing ink. The emphasis was to investigate the relation between print quality and water-uptake of the paper surface with heat and water. Printing trials was carried out on substrates possessing a hydrophobic, and also a rather hydrophilic surface using a regular commercial water-borne ink. The favorable effect which water or surfactant solution had on the hydrophobic substrate with regard to print mottle could depend on its surface compressibility in combination with the hydrophobic nature of its surface that could affect the wetting properties. Conventional printing involves physical contact between plate and ink and between ink and substrate. A method for measuring the dynamic nip pressure using thin load cells is presented. Print quality was influenced by the plate material. A correction procedure taking into account the size of the sensor was developed in order to estimate the maximum dynamic pressure in the printing nip. An attempt was made to identify essential mechanical and chemical parameters, and also geometrical properties of the plate that affected print quality. Laboratory printing trials were carried out and a multivariate analysis was applied for evaluation of print quality data. The impact of the plate properties on print quality was evident. The essential properties of the plate that influence print quality were the small-scale roughness and long-scale roughness.

A project studied wetting of iron, nickel and platinum by molten MnO-SiO2 (MS) and CaO-Al2O3-SiO2 (CAS) slags of eutectic composition to contribute to understanding of wetting behaviour of solid metal-molten oxide systems relevant to steelmaking. Novel results of dynamic wetting behaviour by the sessile drop method were obtained under strongly reducing atmosphere (oxygen partial pressure 10-20 -- 10-18 atm). Terminal contact angles (after 240 min) for MS slag were: for iron substrates -5??2??(1350??C), 9+-2?? (1390??C), 6+-2 (1450??C); nickel -- 3+-2??(1350 and 1390??C); and platinum --15+-2??(1350 and 1390??C), 12+-2??(1450??C). Contact angles with CAS slag were: iron -- 55+-2??(1350??C), 60+-2?? (1390??C), 44+-2?? (1450??C); nickel -- 59+-2??(1350??C), 60+-2?? (1390??C); and platinum -- 15+-2?? (1350, 1390 and 1450??C). Values for interfacial tension, work of adhesion, spreading parameter (S) and interaction coefficient (Ф) were also determined. Work of adhesion for all three substrates with MS slag changed in a very narrow range 910 - 930 mJ/m2. Interfacial tension with this slag was 1,480 mN/m for Ni at 1350-1390??C, and 1,880-1,890 mN/m for Pt in the temperature range 1,350-1,450??C. For iron, interfacial tension was 1,720 mN/m at 1350??C (γ-Fe); it decreased to 1590-1580 mN/m with increasing temperature to 1390 and 1450??C (-Fe). Lower work of adhesion and higher interfacial tension was found for metals with CAS slag. Wetting properties of Pt substrate with MS slag were close to that with CAS slag, while Fe and Ni substrates showed better wetting by MS slag in comparison with CAS slag. This was attributed to higher reactivity of Fe and Ni with MS slag, particularly reduction of MnO. Although MnO was also reduced in reaction with Pt, oxygen adsorption in contact with both slags was a major factor governing wettability of Pt. Dissolution of manganese in nickel and platinum substrates at elevated temperatures modified the interface chemistry, causing formation of a liquid alloy phase. Degree of silica reduction from MS slag was much smaller in comparison with MnO reduction (negligible for Pt); it was very minor from CAS slag. Concentration profiles of Mn and Si across the interface and along the metal surface were used to estimate diffusion coefficients. Diffusion along metal surfaces was generally higher by 1 to 2 orders of magnitude than across the interface. Reduction of oxides and adsorption of oxygen modify the metal-oxide interface, making wetting dynamic. They have a profound on interfacial properties.

[pt] No presente trabalho, pretende-se avaliar os efeitos de ciclos de umedecimento e secagem na resistência ao cisalhamento do solo. Este estudo é de grande importância, particularmente,para os solos brasileiros, já que se encontram em uma região tropical, onde verifica-se a ocorrência de períodos bem definidos de chuvas e estiagem. Sabe-se que, longos períodos de chuvas podem saturar o solo, assim como durante a estiagem,pode ocorrer uma maior evaporação do que infiltração de água, o que leva o solo a uma condição não saturada, provocando o surgimento de uma nova componente de resistência, a coesão aparente. Na natureza, estes dois períodos não ocorrem de maneira uniforme, fazendo com que o solo atinja valores de sucção diferentes, dependendo do seu umedecimento e secagem. Assim sendo, ciclos de umedecimento e secagem e o nível de sucção atingido correspondente, podem afetar o comportamento mecânico do solo. Afim de verificar a influência de tais ciclos de umedecimento e secagem, determinou-se a resistência ao cisalhamento do solo, por meio de ensaios de cisalhamento direto com sucção controlada no equipamento desenvolvido na PUC-Rio. O umedecimento e a secagem do solo,foram simulados, em laboratório, através da diminuição e aumento da sucção, respectivamente. Utilizou-se o solo maduro do campo experimental II da PUC-Rio, peneirado e compactado em laboratório.Foram realizadas várias séries de ensaios, em que se modificavam os procedimentos realizados em relação aos níveis de sucção aplicados. A partir dos resultados obtidos,verificou-se a influência dos ciclos de umedecimento e secagem e dos níveis de sucção atingidos em cada caso, na resistência ao cisalhamento do solo, bem como na variação de volume total e de água nas amostras, durante o cisalhamento. / [en] This work intends to evaluate the effects of wetting and drying cycles on soil shear strength. It is a study of great importance, specially for brazilian soils, since they are found in a tropical area, where there are periods well defined of raining and dryness.It is well known that long raining periods can saturate the soil, as well as during dryness it can occur a bigger evaporation than infiltration of water, what brings soil to an unsaturated state. Unsaturated soils have an additional strength component: the apparent cohesion. In nature, raining and dryness do not occur uniformly, because of that, the soil suction can reach different values, depending on its wetting and drying, thus being, wetting and drying cycles and the corresponding suction levels can affect the mechanical behaviour of soil.Aiming at verify the influence of such cycles of wetting and drying, soil shear strength was obtained through laboratory tests of direct shear with controlled suction, using PUC-Rio s developed equipment. Soil wetting and drying had been simulated in laboratory, reducing and increasing suction. Mature soil brought from the experimental field II of PUC-Rio, sifted and compact in laboratory, was used.Many series of laboratory tests had been carried out, modifying procedures related to applied suction levels. From the gotten results the influence, of wetting and drying cycles and reached levels of suction, was verified. Such influence also occurred, on total and water volume changes, during the shear.