Dissertations / Theses on the topic 'Foam analysis'

The aim of this thesis is to derive and solve mathematical models for the flow of liquid in a foam. A primary concern is to investigate how so-called `Marangoni stresses' (i.e. surface tension gradients), generated for example by the presence of a surfactant, act to stabilise a foam. We aim to provide the key microscopic components for future foam modelling. We begin by describing in detail the influence of surface tension gradients on a general liquid flow, and various physical mechanisms which can give rise to such gradients. We apply the models thus devised to an experimental configuration designed to investigate Marangoni effects. Next we turn our attention to the flow in the thin liquid films (`lamellae') which make up a foam. Our methodology is to simplify the field equations (e.g. the Navier-Stokes equations for the liquid) and free surface conditions using systematic asymptotic methods. The models so derived explain the `stiffening' effect of surfactants at free surfaces, which extends considerably the lifetime of a foam. Finally, we look at the macroscopic behaviour of foam using an ad-hoc averaging of the thin film models.

A graphite foam was developed at Oak Ridge National Laboratory (ORNL) by Dr. James Klett and license was granted to POCO Graphite, Inc. to manufacture and market the product as PocoFoam™. Unlike many processes currently used to manufacture carbon foams, this process yields a highly graphitic structure and overcomes many limitations, such as oxidation stabilization, that are routinely encountered in the development of carbon foam materials. The structure, thermal properties, electrical resistivity, isotropy, and density uniformity of PocoFoam™ were evaluated. These properties and characteristics of PocoFoam™ are compared with natural and synthetic graphite in order to show that, albeit similar, it is unique. Thermal diffusivity and thermal conductivity were derived from Fourier's energy equation. It was determined that PocoFoam™ has the equivalent thermal conductivity of metals routinely used as heat sinks and that thermal diffusivity is as much as four times greater than pure copper and pure aluminum. SEM and XRD results indicate that PocoFoam™ has a high degree of crystalline alignment and near theoretical d spacing that is more typical of natural flake graphite than synthetic graphite. PocoFoam™ is anisotropic, indicating an isotropy factor of 0.5, and may yield higher thermal conductivity at cryogenic temperatures than is observed in polycrystalline graphite.

Abstract In the world where every sector of industrial manufacturing is being converted toautomated systems, surface finishing processes like sanding and polishing seem to lag.This phenomenon is not surprising as these processes are complex to optimize. Therehave been projects going on with the support of European Commission to findsolutions under SYMPLEXITY (Symbiotic Human-Robot Solutions for ComplexSurface Finishing Operations). One of the projects in under this include poliMATIC(Automated Polishing for the European Tooling Industry). Halmstad University isinvolved in doing projects. This project took a portion of this study in aim to understand a foam material’s behavior used for sanding tool at the tip of a robotic arm. This is studied using a forcemeasurement system developed at Halmstad University. The project has two sectionsand starts with one; Understanding the force measurement system and upgrading innecessary ways. Two; studying how the foam material compressive hardness propertyis affected when the material is fit with sandpaper for sanding operation using theforce measurement system. The study finally revealed how the combination of thefoam with sandpaper affects the robustness of the material, and significantlyimproved the output of the system with by reducing the noise level with 40%.

Hollow glass microspheres have been used extensively in the automotive and marine industries as an additive for reducing weight and saving material costs. They are also added to paints and other materials for their reflective properties. They have shown promise for weight critical applications, but have thus far resulted in materials with low fracture toughness and impact resistance when combined with thermosetting resins in syntactic foam. The advent of commercially available microspheres with a wide range of crushing strengths, densities and adhesive properties has given new impetus to research into syntactic foam with better fracture behaviour. Current research suggests that the beneficial effects on fracture and impact resistance gained by the addition of solid reinforcements such as rubber and ceramic particles are not seen with the addition of hollow glass microspheres. The research presented in this paper has examined the mechanisms for fracture resistance in glass microsphere filled epoxy (GMFE) syntactic foams, as well as determined the effect microsphere crushing strength and adhesion strength has on the material???s fracture toughness. The flexural properties of various GMFE have also been determined. GMFE were manufactured with varying microsphere volume fraction up to 50%, and with variances in microsphere crushing strength and adhesion. The specimens were tested for Mode I fracture toughness in a three point single edge notched bending setup as described in ASTM D5045 as well as a three point flexural setup as described in ASTM D790-3. Fracture surfaces were inspected using scanning electron microscope imaging to identify the fracture mechanisms in the presence of microspheres. Results indicate a positive effect on fracture toughness resulting from new fracture areas created as tails in the wake of the microspheres in the fracture plane. Results also indicate a negative effect on fracture toughness resulting from weak microspheres or from interfacial disbonding at the fracture plane. These two effects combine to show an increase in GMFE fracture toughness as the volume fraction of microspheres is increased to between 10 ??? 20% volume fraction (where the positive effect dominates), with a reduction in fracture toughness as microspheres are added further (where the negative effect dominates).

Foam is one of the most frequently used multiphase fluids in underbalanced drilling operations because of its high carrying capacity of cuttings, compressibility property, formation fluid influx handling, etc. Foam rheology has been studied for many years. Researchers tried to explain foam behaviour by using conventional methods, i.e., determining rheological parameters of pre-defined rheological models like Power law, Bingham Plastic etc., as a function of gas ratio. However, it is known that bubble size and texture of the foam is also effective on foam behaviour. When foam is generated by using different foaming agents, even if the gas ratio is constant, different rheological parameters are observed. Therefore a more general foam characterization method that uses the bubble size and texture of foam is required. Improvements on image analysis, and computer technology allow monitoring the bubble size and texture of foam bubbles. A more comprehensive model of foam rheology definition in which the bubble size, and texture effects of the foam body is developed. Three different analysis methodologies are introduced
i) Generalized volume equalized approach, ii) Generalized volume equalized approach and image processing data, and iii) Image processing data only. The necessary information including the rheological information and image data is acquired from the experimental set-up developed for this study. It has been observed that, the pressure losses could be predicted as a function of bubble size, circularity and general rheological parameters, in &
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20 % certainty limit. It is also observed that using only the image information is possible to characterize the foam in an accurate and fast manner.

Development of new asphalt technologies to reduce both energy consumption and CO2 production has attracted great interest in recent years. The use of foam bitumen, as one of them, is attractive due to the low investment and production cost. Formation and decay of foam bitumen is a highly dynamic temperature dependent process which makes characterization difficult. In this thesis, new experimental tools were developed and applied for characterizing the foam bitumen during the hot foaming process.  One of the main goals of this study was to improve understanding and characterization of the foam bitumen formation and decay. X-ray radiography was used to study the formation and decay of foam bitumen in 2D representation. The results demonstrate that the morphology of bubble formation depends on the types of bitumen used. Moreover, theoretical investigation based on the 3D X-ray computed tomography scan dataset of bubble merging showed that the disjoining pressure increased as the gap between the bubbles in the surface layer (foam film) decreased with time and finally was ruptured.   Examining the foam bitumen stream right at the nozzle revealed that foam bitumen at a very early stage contains fragmented pieces of irregular size rather resembling a liquid than foam. The result from thermogravimetric analysis demonstrated that residual water content depends on the initial water content, and was found to be between 38 wt% and 48 wt% of the initial water content of 4 wt% to 6 wt%. Moreover the influence of viscosity and surface tension on bubble shape and rise velocity of the bubbles using level-set method was implemented in finite element method. The modeling results were compared with bubble shape correlation map from literature. The results indicated that the bubble shapes are more dependent on the surface tension parameters than to the viscosity of the bitumen, whereas the bitumen viscosity is dominant for bubble rising velocity.

QC 20160303

Pour ce travail, nous utilisons un micromodèle à haute complexité et à structure fixe pour faire une série d’expériences en variant la vitesse d’injection, la qualité de la mousse, les distributions de taille de bulles d’injection, et la méthode d’injection. Nous mettons en œuvre un suivi individuel de bulles pour associer les propriétés d’écoulement aux propriétés de taille de bulles ainsi que les caractéristiques structurelles du milieu poreux. Nous proposons de nouveaux outils pour décrire l’écoulement d’un point de vue global et local de différentes manières. Nous établissons des comportements spécifiques à chaque taille de bulle, en montrant que les bulles des mousses piégées sont plus probables d’être de taille inférieure aux tailles de bulles moyennes, alors que les mousses en mouvement accèdent elles-mêmes à différents chemins d’écoulement selon les tailles de bulles. Les bulles plus volumineuses s’écoulent en majorité dans des chemins préférentiels à haute vitesse, généralement parallèles au gradient de pression, mais les petites bulles sont transportées en supplément à l’intérieur de chemins transversaux liant les chemins préférentiels. Ailleurs, pour nos données nous démontrons l’importance supérieure de la fraction de mousse piégée vis-à-vis de la densité de bulles quant à l’explication microscopique de la viscosité apparente, malgré une contribution des deux. Nous caractérisons structurellement les zones piégées à répétition, comme étant soit des zones à faible coordination de pore, de faible taille de seuil d’entrée, d’orientation de seuil désavantageuse, ou une combinaison de ceux-ci. Les zones à fort écoulement échappent à une caractérisation en termes de paramètres de structure locale et nécessitent une considération de l’information des différents chemins traversant la totalité du modèle. À ce but, afin de décrire les zones à fort écoulement, nous développons un modèle générant des chemins, utilisant une représentation en graphe du milieux poreux, basé sur une décomposition initiale en pores et seuils, qui intègre seulement les notions de taille de seuil et d’orientation de seuil relatif au gradient de pression pour caractériser les chemins
In this work, we use of a high-complexity micromodel of fixed structure on which we perform a series of experiments with varying injection rates, foam qualities, inlet bubble size distributions and injection methods. We perform individual bubble tracking and associate flow properties with bubble size properties and structural characteristics of the medium. We propose new tools describing the local and global flow in different ways. We establish specific behaviors for different bubble sizes, demonstrating that trapped foams are more likely to have smaller than average bubble sizes, while flowing bubbles also tend to segregate in different flow paths according to bubble size. Larger bubbles tend to flow in high-velocity preferential paths that are generally more aligned with pressure gradient, but smaller bubbles tend to access in supplement transversal paths linking the different preferential paths. Furthermore, for our data we establish the pre-eminence of the trapped foam fraction over bubble density within the microscopic explanation of apparent viscosity, although both contribute to some degree. We structurally characterize consistently trapped zones as areas with either low pore coordination, low entrance throat size, unfavorable throat orientation or a combination thereof. High-flow zones however cannot be characterized in terms of local structural parameters and necessitate integration of complete path information from the entire model. In this regard, in order to capture the high-flow zones, we develop a path-proposing model that makes use of a graph representation of the model, from an initial decomposition into pores and throats, that uses only local throat size and throat orientation relative to pressure gradient to characterize paths

Thesis (MBA)--Stellenbosch University, 2001.
ENGLISH ABSTRACT: The polystyrene foam tray manufacturing industry started with a monopoly in 1954, and lasted for more than 29 years. During the last ten years the industry has grown extremely competitive, seeing many new players enter (and exit) and a reduction in industry profitability. This mini thesis attempts to analyze the polystyrene foam tray manufacturing industry in its current form and to quantify the external, new challenges it currently faces. It attempts to identify potential pitfalls for new entrants to the industry and to construct an ideal strategy suited best for the industry, based on an industry analysis. The polystyrene foam container industry background is discussed to determine its origins in South Africa. An industry and competitive analysis is done to assess the strategically relevant aspects of the industry's macro environment. A technique developed by Thompson and Strickland (1998: 68) is utilized. The scope of the macro environment in the mini-thesis was limited to the South African scenario. Ultimately, an ideal strategy, which would deal with all the relevant challenges of the industry, is proposed. The industry and competitive analysis revealed important dominant economic traits. Competition is concentrated in the country's economic hub, namely Gauteng, but regional manufacturing bases leads to extended market share in those areas. The product range spans over several hundred coloured, printed and laminated trays, but the fiercest competition across the board takes place in a few sizes white, commodity flat trays to the meat industry, which also forms the bulk of sales to the industry. The growth rate has been organic for the last few years, mainly due to the mature status of polystyrene foam tray products and the introduction of alternative (though more expensive) media. The external macro economic environment has also not been conducive to abnormally high growth (GDP in South Africa has drifted between 1% and 3% for the last few years). Five competitors exist, and two of these competitors have 80% of the market share, but are also the furthest away from the largest part of the market, namely Gauteng. Customers are divided into two groups, distributors and end users. Small competitors make extensive use of distributors (since they do not own their own distribution channels), while large competitors limit the use of distributors to limit the potential buying power of distributors. The barrier to entry for a new entrant wanting to acquire up to 5% of market share is around R 10m, which includes working capital. The industry profitability varies from losses to extreme profits in some years. This becomes a vicious circle, since the latter attracts new entrants, which in turn causes price wars. Rivalry amongst competitive sellers is excessive, specifically when new entrants appear on the scene. Price cutting, although a very blunt tool, is used almost exclusively to obtain a volume advantage. Substitute products do not really pose a threat in the South African economic situation where cost is all-important. No other packaging medium can compete with the wide range of applicability, low cost and strength of polystyrene foam. Where end-user markets are more affluent, substitute products may have a minor impact. The power of suppliers in the industry is limited, since there is a manufacturing over capacity in the country, and there are no switching costs when changing from one supplier to another. The power of buyers, specifically ones that buy in bulk (distributors and the like), is thus quite strong. The main drivers of change include excessive movement in market pricing, product innovation, technological changes, increasing globalisation of the industry and changing societal concerns. Movement in market pricing is by far the most important and has the greatest affect on industry profitability, since the complete product range is affected. The latter four drivers affect mostly branded and speciality product. Strategic group mapping, combined with an in-depth analysis of each competitor, revealed that the largest two players, Kohler Versapak and Atlantic Forming, are definitely in the strongest position from a financial point of view. Although drawbacks such a corporate red tape, shareholder pressure and geographic location exist for these competitors, sheer financial strength to survive price wars will give them an edge. With the current amount of competitors and over capacity in the market there is bound to be some consolidation in the manufacturing industry. It seems that one of the larger two players (Kohler Versapak or Atlantic Forming) may acquire one of the smaller manufacturers in a bid to stabilize market prices. The most important key success factor is the ability to produce polystyrene foam trays at the lowest possible cost. The absence of switching costs, price wars and a manufacturing over capacity are all causes of the preceding success factor. Other less important success factors are distribution related (being close to the market is an advantage) and technology related (being able to develop advanced branded and functional trays). In its current status, where there is a supply-demand imbalance, the industry does not seem attractive. Although negative external forces such as environmental pressure, are limited, growth potential is limited and competition is fierce. In summary none of the competitors have attempted to utilize other tools than pricecutting to protect market share. From a geographic location point of view, Airshield and Mainpack are positioned best, but do not possess the financial momentum to optimally utilise their location in terms of finished product distribution and raw material acquisition. Atlantic Forming and Kohler Versapak seem to have expanded their product ranges to low profit and unprofitable products, while the other competitors have stayed focused on a few high volume items. It seems that it may have been a better idea for the larger players to utilize existing resources on other profitable media rather than expanding its interests in polystyrene foam trays.
AFRIKAANSE OPSOMMING: Polistireen skuim houer vervaardiging het in 1954 met 'n monopolie begin wat vir 29 jaar staande gebly het. Gedurende die laaste tien jaar het die polistireen skuim industrie baie kompeterend geraak, met heelwat kompeterende maatskappye wat die mark betree het (en uitgetree het), en 'n gevolglike afname in industrie profyt gehad het. Hierdie minitesis poog om die polistireen skuim bakkie industrie te analiseer in sy huidige vorm en om die eksterne uitdagings wat tans bestaan, te identifiseer. Die tesis poog verder om potensiele probleme te identifiseer wat nuwe kompeterende maatskappye in die industrie mag teëkom, en dan om 'n ideale strategie saam te stel, gebasseer op 'n industrie analise. Die polistireen skuim houer industrie is bespreek, sodat die oorsprong van die industrie in Suid-Afrika bepaal kon word. 'n Industrie en kompeterende analise is gedoen om die strategies belangrike aspekte van die industrie se makro omgewing te bepaal. Vir die bogenoemde analise is 'n tegniek soos ontwikkel deur Thompson en Strickland (1998: 68) gebruik. Die omvang van die makro omgewing in hierdie minitesis is beperk tot die Suid- Afrikaanse omgewing. Die uiteindelike ideale strategie sal al die relevante uitdagings van die industrie aanspreek. Die industrie en kompeterende analise het belangrike dominante ekonomiese eienskappe blootgelê. Markgerigte kompetisie is gekonsentreerd in die land se ekonomiese enjin, naamlik Gauteng, maar streeks gebaseerde vervaardigings aanlegte lei gewoonlik tot 'n verbeterde mark aandeel in 'n spesifieke streek. Die produk reeks bestaan uit honderde gekleurde, gedrukte en gelamineerde houers, maar die grootste kompetisie vind plaas oor slegs 'n paar plat, wit vleis bakkies - wat ook die grootste volume verkope in die industrie beslaan. Die groei tempo was organies vir die laaste paar jaar, hoofsaaklik as gevolg van die volwasse stand van polistireen skuim produkte en die bekendstelling van alternatiewe produkte. Die eksterne makro ekonomiese omgewing het ook nie bygedra tot bogemiddelde groei nie (BBP in Suid-Afrika het tussen I% en 3% gewissel vir die laaste paar jaar). Vyf produseerders van polistireen skuim houers ding mee in die mark, en twee van hulle besit 80% van die totale mark aandeel, alhoewel hulle ook die verste vanaf grootste mark, naamlik Gauteng, is. Kliënte word in twee groepe verdeel, naamlik verspreiders en eind-gebruikers. Klein produseerders maak meestal gebruik van verspreiders omdat hulle nie oor hulle eie verspreidings kanale beskik nie. Groter produseerders beperk die gebruik van verspreiders om uiteindelik potensiële koopkrag van verspreiders te beperk. Vaste kapitaal, asook lopende kapitaal om ongeveer 5% van die mark te bekom, is ongeveer R10m. Die industrie profyt variëer tussen verliese tot oorgrote profyt in sommige jare. Hierdie variasie vorm 'n afbrekende sirkel, aangesien oorgrote profyt potensiële nuwe produseerders aantrek wat dan weer tot prys oorloë lei. Mededinging tussen kompeterende produseerders is oormatig sterk, spesifiek wanneer nuwe produseerders die mark betree. Alhoewel prys verlaging 'n redelike kru metode is om markaandeel te bekom, word dit amper uitsluitlik gebruik. Alternatiewe, duurder vervangings produkte is nie werklik 'n gevaar vir polistireen skuim produkte in Suid-Afrika nie, aangesien prys die belangrikste element is. Geen ander verpakkingsmedia kan meeding met die toepasbaarheid, lae koste en sterkte van polistireen skuim nie. Slegs in sekere wel-gestelde segmente van die mark kan alternatiewe produkte 'n minimale impak op die polistireen skuim mark toon. Die mag van verskaffers in die industrie is beperk, aangesien daar 'n geweldige oorkapasiteit in die land is en omdat daar geen oorskakelingskoste bestaan wanneer daar van een verskaffer tot 'n ander geskuif word nie. Die mag van kopers, en spesifiek die wat in grootmaat koop, is dus redelik sterk. Die hoofdrywers van verandering sluit in sterk beweging in mark pryse, produk innovasie, tegnologiese veranderinge, toenemende globalisering van die industrie en veranderende sosiale standaarde. Variëerende beweging van markpryse is by verre die belangrikste en het ook die grootste effek op industrie profyt, aangesien die hele produk reeks geraak word. Die laaste vier drywers affekteer meestal handelsmerk produkte en spesialiteits produkte. Strategiese groep kaarte, gekombineerd met 'n indiepte analise van elke produseerder, het aangedui dat die twee grootste kompeteerders, Kohler Versapak en Atlantic Forming, definitief in die sterkste posisie is vanaf 'n finansiële oogpunt gesien. Alhoewel negatiewe punte soos korporatiewe sloering, aandeelhouer druk en geografiese posisie teen die twee mededingers tel, sal blote finansiele mag om prys oorloë te deurstaan hulle die oorhand gee. Met die huidige hoeveelheid oorkapasiteit in die mark moet daar uiteraard konsolidasie in die vervaardigings industrie plaasvind. Dit is waarskynlik dat een van die groter spelers (Kohler Versapak of Atlantic Forming) van die kleiner mededingers mag bekom in 'n poging om die mark te stabiliseer. Die mees belangrike sleutel sukses faktor is die vermoë om polistireen skuim bakkies teen die laagste koste te vervaardig. Die afwesigheid van oorskakelingskoste, die aanwesigheid van prys oorloë en vervaardigings oorkapasiteit is almal oorsake van die genoemde sukses faktor. Ander minder belangrike sukses faktore is verspreidings verwante (om nabyaan die mark te wees is 'n voordeel) en tegnologie verwante (om handelmerk produkte en moderne funksionele produkte te kan ontwikkel) faktore. In die mark se huidige vorm is daar nie 'n vraag-aanbod balans nie, en lyk die industrie nie aantreklik nie. Alhoewel negatiewe eksterne kragte soos omgewings druk beperk is, is groei potensiaal ook beperk en kompetisie agressief. Opsommendergewys het geen van die mededingers ander metodes as prys verlaging probeer gebruik om mark aandeel te beskerm nie. Vanaf 'n geografiese oogpunt gesien, is Airshield en Mainpack die beste geposisioneer, maar hulle het nie die finansiële momentum om hulle posisie optimaal te benut in terme van klaar produk verspreiding en rou material aankope nie. Atlantic Forming en Kohler Versapak het hulle produk reeks uitgebrei na lae profit en verlies-lyende produkte, terwyl ander mededingers gefokus gebly het op 'n paar hoë volume items. Dit lyk asof dit beter sou gewees het vir die groter spelers om bestaande bronne te gebruik het op ander winsgewinde media as om verder uit te brei in polistireen skuim.

A comprehensive comparison between an air-inflated seat cushion designed for truck seats and a commonly used foam cushion is provided, using a single-axis test rig designed for dynamic seat testing. Different types of tests are conducted in order to evaluate various aspects of each type of cushion; in terms of their response to narrow-band (single frequency) dynamics, broadband input of the type that is commonly used in the trucking industry for testing seats (ISO2), and a step input for assessing the damping characteristics of each cushion. The tests were conducted over a twelve-hour period -- in four-hour intervals -- measuring the changes that occur at the seat cushion over time and assessing how these changes can affect the metrics that are used for evaluating the cushions. The tests indicated a greater stiffening of the foam cushion over time, as compared with the air-inflated cushion that showed almost no change in stiffness when exposed to a static weight for twelve hours. Furthermore, pressure measurements at the seat showed higher-pressure concentrations for the foam cushion at the bony prominence of the seat profile -- namely, the ischial tuberosities -- as compared to the air-inflated cushion. A series of tests aimed at evaluating the damping properties of each cushion showed both cushions to have nearly identical damping properties. Other methods used for evaluating the dynamic properties of the two seat cushions included those recommended by studies in the past, as well as new techniques that were developed specifically for this study. The new techniques, named Seat Pressure Distribution (SPD%) and Area Pcrms (aPcrms) for the purpose of this study, are formulated such that they can best highlight the dynamic differences between different types of seat cushions, and their effect on driver comfort. The results show that the air-inflated seat cushion can provide significant improvements in pressure distribution between the seat cushion and the driver, therefore providing a more comfortable ride and causing less fatigue.
Master of Science

The goal of this study is to design and analyze a sandwich composite panel with lightweight graphite foam core and carbon epoxy face sheets that can function as a radiator for the given payload in a satellite. This arrangement provides a lightweight, structurally efficient structure to dissipate the heat from the electronics box to the surroundings. Three-dimensional finite element analysis with MSC Visual Nastran is undertaken for modal, dynamic and heat transfer analysis to design a radiator panel that can sustain fundamental frequency greater than 100 Hz and dissipate 100 W/m2 and withstand launch loads of 10G. The primary focus of this research is to evaluate newly introduced graphite foam by Poco Graphite Inc. as a core in a sandwich structure that can satisfy structural and thermal design requirements. The panel is a rectangular plate with a cutout that can hold the antenna. The panel is fixed on all the sides. The objective is not only to select an optimum design configuration for the face sheets and core but also to explore the potential of the Poco foam core in its heat transfer capacity. Furthermore the effects of various parameters such as face sheet lay-up, orientation, thickness and material properties are studied through analytical models to validate the predictions of finite element analysis. The optimum dimensions of the sandwich panel are determined and structural and thermal response of the Poco foam is compared with existing aluminum honeycomb core.

Thesis (Ph. D.)--Case Western Reserve University, 2006.
[School of Medicine] Department of Physiology and Biophysics. Includes bibliographical references. Available online via OhioLINK's ETD Center.

Les mousses de polyuréthane (PU) hautement poreuses sont largement utilisées dans différentes industries pour dissiper l’énergie des ondes sonores et vibratoires. La propagation des ondes acoustiques dans ces matériaux poroélastiques est décrite à partir d’un ensemble de paramètres physiques connus sous le nom de paramètres de Biot (pour les matériaux isotropes, ils sont composés de 5 paramètres non acoustiques et de 4 paramètres mécaniques). Il est bien connu que les propriétés macroscopiques dépendent intrinsèquement des propriétés de la microstructure de la mousse. Ainsi, une compréhension claire des corrélations entre la structure interne des mousses de PU et leurs paramètres de Biot ainsi que la contribution de chaque paramètre, soit microscopique ou macroscopique, sur l’indicateur vibroacoustique désiré est d’un intérêt majeur au stade précoce de la conception et de l’optimisation de ces matériaux poroélastiques. Le développement d’un modèle micromacro qui corrèle les propriétés de la microstructure aux paramètres macroscopiques de Biot est donc nécessaire. Récemment, un modèle qui corrèle les propriétés de la microstructure des mousses PU hautement poreuses à leurs propriétés non acoustiques a été présenté par Doutres et coll. [24, 25]. Dans cette étude, les propriétés de la microstructure (dimensions de la cellule et taux de réticulation) sont d’abord caractérisées par un microscope électronique à balayage (SEM). Ensuite, l’effet du taux de réticulation (mesurant le pourcentage de fenêtres ouvertes), de la taille des cellules et de la densité relative sur les propriétés mécaniques de la mousse de polyuréthane a été élucidé à l’aide d’un modèle numérique. Se basant sur ce modèle, un modelé analytique existant, qui corrèle les propriétés de la microstructure de mousses PU entièrement réticulées à ses propriétés mécaniques, a été revu et corrigé pour tenir compte de l’effet important du taux de réticulation. En combinant le modèle de Doutres avec le modèle mécanique développé dans cette thèse, un modèle micro-macro complet est ainsi obtenu. Utilisant ce modèle, l’impact de la variabilité de la microstructure et la contribution de chacun des paramètres microstructuraux à la réponse vibroacoustique ont été étudiés utilisant une méthode d’analyse de sensibilité globale (FAST). La méthode FAST a été utilisée pour identifier l’impact de la microstructure sur, premièrement, les paramètres de Biot-Allard et, deuxièmement, sur les indicateurs vibroacoustiques (absorption et perte par transmission) des mousses de polyuréthane poroélastiques. Une fois les modèles micro-macro et la contribution des propriétés de la microstructure connus, la performance vibroacoustique de la mousse a été optimisée. Ainsi nous avons testé numériquement la performance acoustique de mousses homogènes et de mousses graduellement structurées (variation de propriétés suivant l’épaisseur de la mousse). Cette étude ouvre ainsi de nouvelles portes pour concevoir des mousses PU innovantes avec une microstructure modifiée et des performances vibroacoustique améliorées.
Abstract : Highly porous polyurethane (PU) foams are widely used in different industries to dissipate the energy of sound and vibration waves. Propagation of acoustic waves in such poroelastic materials is explained based on a set of physical parameters known as the Biot's parameters (for isotropic materials these are comprised of 5 non-acoustical parameters and 4 mechanical parameters). These macroscopic properties are inherently dependent on the microstructure properties of the foam. Hence, a clear understanding of correlations between the internal structure of PU foams and their Biot's parameters and the contribution of each parameter, either microscopic or macroscopic, to classical vibro-acoustic indicators is of utmost interest at the early stage of design and optimization of such poroelastic materials. In consequence, a micro macro model that correlates microstructure properties to macroscopic Biot's parameters is needed. Recently, a model that correlates the microstructure properties of highly porous PU foams to their non-acoustical properties was presented by~\citet{Doutres2011,Doutres2013}. In this study, micro-structure properties (strut length, strut thickness, and open pore content) are first characterized using a Scanning Electron Microscope (SEM). Then, a numerical study is performed to elucidate the effect of open pore content (known as reticulation rate), cell size, and relative density on the mechanical properties of polyurethane foam. Based on this study, an existing analytical model~\cite{Gong2005} that correlates fully reticulated unit cell microstructure properties of PU foams to its mechanical properties is corrected and updated to account for these important parameters. Combined with Doutres’ model, the proposed extension lead to a full micro-macro model for predicting the acoustic performance of PU foams from its microstructure. Using this model, the contribution of the unit cell parameters and effect of their variability on classical vibro-acoustic indicators (absorption and transmission loss) is investigated using a global sensitivity analysis method (FAST). The FAST method is used to identify the impact of microstructure role on, first, the Biot-Allard parameters and, second, on vibro-acoustical indicators of poroelastic polyurethane foams. Based on this sensitivity analysis study, the developed micro-macro model, is used to design both optimum homogeneous foam and functionally graded foams (properties optimally varnish along the thickness of the foam) targeting specific in absorption and/or transmission loss problems. This study opens thus a new door to design innovative PU foams with modified micro-structure and improved vibro-acoustical performance.

Today’s rapid development of powerful tools for geneexpression analysis provides unprecedented resources forelucidating complex molecular events.

The objective of this workhas been to apply, combine andevaluate tools for analysis of differential gene expressionusing atherosclerosis as a model system. First, an optimisedsolid-phase protocol for representational difference analysis(RDA) was applied to twoin vitromodel systems. Initially, The RDA enrichmentprocedure was investigated by shotgun cloning and sequencing ofsuccessive difference products. In the subsequent steps,combinations of RDA and microarray analysis were used tocombine the selectivity and sensitivity of RDA with thehigh-throughput nature of microarrays. This was achieved byimmobilization of RDA clones onto microarrays dedicated forgene expression analysis in atherosclerosis as well ashybridisation of labelled RDA products onto global microarrayscontaining more than 32,000 human clones. Finally, RDA wasapplied for the investigation of the focal localisation ofatherosclerotic plaques in mice usingin vivotissue samples as starting material.

A large number of differentially expressed clones wereisolated and confirmed by real time PCR. A very diverse rangeof gene fragments was identified in the RDA products especiallywhen they were screened with global microarrays. However, themicroarray data also seem to contain some noise which is ageneral problem using microarrays and should be compensated forby careful verification of the results.

Quite a large number of candidate genes related to theatherosclerotic process were found by these studies. Inparticular several nuclear receptors with altered expression inresponse to oxidized LDL were identified and deserve furtherinvestigation. Extended functional annotation does not liewithin the scope of this thesis but raw data in the form ofnovel sequences and accession numbers of known sequences havebeen made publicly available in GenBank. Parts of the data arealso available for interactive exploration on-line through aninteractive software tool. The data generated thus constitute abase for new hypotheses to be tested in the field ofatherosclerosis.

Keywords:representational difference analysis, geneexpression profiling, microarray analysis, atherosclerosis,foam cell formation

Rotational moulding is a low pressure, high temperature manufacturing method and is considered to be the best for making large hollow shape plastic parts. Due to its long heating cycle, mould rotation during heating and slow cooling rate, it is completely different from injection or other moulding processes. The mechanical properties of rotationally moulded plastics are totally dependent on unique heating or cooling cycles. With the growing demand for rotationally moulded plastics in load bearing and other applications, a better understanding of their fracture properties is essential. In the rotational moulding process, multilayer plastic products such as skin-foam-skin three layered sandwich structures can be manufactured in a single manufacturing step without any joints. It exhibits relatively high stiffness, strength-to-weight ratios and is used increasingly in various applications such as automotive and marine. During the lifetime of the sandwich material, it may face multiple or repeated impact events. Therefore, the aim of this work is to develop a better understanding of the fracture behaviour of rotationally moulded plastics in order to use them in skin-foam-skin sandwich structure and reduce in-service failures due to impact. Here, rotationally moulded two different commercially available Polyethylene (PE) and Polypropylene (PP) plastics are tested. Microstructural details of the plastics are investigated here. Fracture properties, particularly fracture toughness properties are studied using J-integral elastic-plastic fracture mechanics approach to identify the fracture initiation point. Impact properties are also investigated at a wide range of temperatures. PE materials are found to have better fracture properties. It is observed that with the fracture toughness plastic’s microstructure particularly crystal and amorphous region thickness are related. The understanding from these works is followed by the manufacture of rotationally moulded skin-foam–skin sandwich structure and testing of low velocity impact properties of this structure from 20 J to 100 J energy level with a drop weight impact testing machine. PE is used for both in skin and core layer and sandwich samples are manufactured at four different skin-core thickness combinations. Impact force resistance and bending stiffness are found to be increased with an increase of both skin and core layer thickness. Low velocity repeated impact properties of the rotationally moulded sandwich samples are also investigated from 20 J to 50 J energy level at the end of this project to understand the effect of repeated impact on the sandwich structure. The samples are subjected to single impact event repeatedly up-to penetration at each energy level. Impact energy-impact number curve obtained from repeated impact test provides an equation for prediction of the number of repeated impacts for the penetration of the sandwich samples at each energy level.

L'objectif de cette thèse de doctorat est d'étudier expérimentalement et numériquement le comportement thermique des mousses d'aluminium et des matériaux à changement de phase (MCP), présentés sous la forme d’un composite, afin de connaître le phénomène de stockage d’énergie thermique dans ces matériaux. Le procédé de fabrication de la mousse d'aluminium à cellules ouvertes est d’abord analysé numériquement dans le but de réduire les défauts formés durant la fabrication. Les caractéristiques de transfert de chaleur du MCP dans les mousses d'aluminium comportant différentes porosités sont ensuite étudiées en analysant les processus de fusion et la variation de températures dans ces composites. Deux modèles numériques pour la mousse d'aluminium à faible et à haute porosité sont établis afin d’évaluer la performance de stockage d'énergie des composites. Les résultats montrent que la mousse d'aluminium peut améliorer considérablement la performance de transfert de chaleur du MCP en raison de sa conductivité thermique élevée. La performance de stockage d'énergie dépend fortement de la porosité des mousses d'aluminium. Une porosité optimisée met en évidence cette performance et l’amélioration du comportement thermique. La dernière partie de la thèse porte sur une structure améliorée de la mousse par rapport à la structure uniforme: Association de l’ailette métallique et du gradient de porosité de la mousse. Cette nouvelle structure donne ainsi une performance de stockage d'énergie encore meilleure surtout dans le cas d’une source de chaleur isotherme
The objective of this Ph.D. thesis is to study the thermal behavior of the aluminum foam and phase change material (PCM) composite by both experimental and numerical methods in order to know the phenomena of storage of thermal energy in these materials. The manufacturing process of open-cell aluminum foam is firstly analyzed numerically to reduce the manufacturing defects in the samples. The heat transfer characteristics of PCM embedded in aluminum foams with different porosities are then investigated by analyzing the melting processes and the temperature variations in the composites. Two numerical models for low and high porosity aluminum foam are established to evaluate the energy storage performance of the composites. The results show that the aluminum foam can greatly improve the heat transfer performance in PCM due to its high thermal conductivity. The energy storage performance depends strongly on the porosity of the aluminum foam/PCM composite. An optimized porosity highlights this performance and improves the thermal behavior. The last part of this thesis proposes an improved structure of aluminum foam with respect to the uniform structure: Association of the metal fin and the foam with graded porosity. This new structure possesses a better energy storage performance especially in the case of the isothermal heat source

Within this paper recently developed mathematical tools for the modelling of contact problems on thin film structures [1] for multilayers and gradient coatings are adapted to allow the investigation of laminate structures of transversal isotropy. Applying series approaches using Bessel and Sinus functions complete three dimensional solutions can be found for relatively complex laminate structures allowing to model quasistatic contact, impact and bending loads. Worked into a small computer program the approach can be used to model laminate structures with up to 100 different layers on an ordinary personal computer in an acceptable calculation time. The new tool is applied to analyse a variety of load problems typically occurring in windsurfing and leading to damage of the boards consisting of a laminated shell and an polymer foam core. [1] N. Schwarzer: „Modelling of the mechanics of thin films using analytical linear elastic approaches“, habilitation thesis of the TU-Chemnitz 2004, department “Physics of solid bodies”, http://archiv.tu-chemnitz.de/pub/2004/0077

Studies involving solids-stabilised foams have been limited and few have focused on the benefits of complex systems such as those involving mixtures of more than one surfactant. Little is known about the effectiveness of using mixed surfactant systems as foam stabilisers at the bulk level. The purpose of this project was to gain further understanding and insight into foam stability, on a bulk scale, in the absence, and in the presence, of solid colloidal particles, and for systems involving single or mixed surfactants. Foams were produced using sodium dodecyl sulphate (SDS), dodecanoic acid (DA), or a mixture of both surfactants at varying molar ratios. The surface tension at a given concentration, the limiting surface tension (at high concentrations), the critical micelle concentration, foamability and foam stability were all significantly affected by the molar ratio of SDS to DA. The initial pH of mixed surfactant solutions played a role in the shift of surface tension and CMC. The higher pH values, the lower surface activity, therefore resulted in higher surface tension. At a given pH, however, the mixed surfactant solutions with higher molar ratio of SDS to DA appeared to have lower CMC. The foam stabilising ability of colloidal dispersions of four hydrous metal oxides, namely hydrous iron oxide (formed by hydrolysis of Fe(III) solutions and referred to as HFO), hydrous zinc oxide (formed by hydrolysis of Zn(II) solutions and referred to as HZO), hydrous chromium oxide (formed by hydrolysis of Cr(III) solutions and referred to as HCO), and hydrous nickel oxide (formed by hydrolysis of Ni(II) solutions and referred to as HNO) were studied at varying concentrations. Generally foam stability increased as the solid concentration increased. Foams stabilised by HNO were found to be the most stable. Foams stabilised by HFO were found to be unstable regardless of the solid concentration. It is believed that the instability of such foams is primarily due to the large aggregated size of HFO flocs. The aggregate size of hydrous metal oxides was influenced by the concentration of NaOH used to hydrolyse the metal ion solution, and by sonication treatment immediately following solid formation. However, the final pH of the colloidal dispersions did not significantly change the aggregate size. Solids stabilised foams are believed to be highly dependent on the state of hydrophobicity of the solids used, and this is in turn controlled by adjustment of the pH dependent surface charge and potential. Electrophoretic mobility is a commonly used tool to probe the potential near the surface and was used in this thesis to determine the affect of surfactant adsorption (particularly from solutions containing mixtures of SDS and DA) on surface properties of the solids. The electrophoretic mobility of all hydrous metal oxide aggregates decreased as the concentration of SDS/DA increased. Specific adsorption was evident in all cases and resulted in charge reversal for most cases. Electrophoretic mobility data for surfactant adsorption, as a function of total surfactant concentration, was consistent with a three-stage model of surfactant adsorption involving (1) electrostatic adsorption, (2) cooperative adsorption and (3) surface saturation. The influence of surfactant adsorption on electrophoretic mobility was found to be consistent with models requiring the stabilising solids to be in a controlled state of flocculation, where the zeta potential (as probed by electrophoretic mobility) must be sufficiently high to prevent total flocculation of the solid and thus collapse of the foam, but sufficiently low that the solids have some degree of hydrophobicity such that they prefer to be only partially wetted (and thus reside at the air/water interface). The total percentage adsorption of SDS/DA surfactant mixtures on both hydrous iron oxide and hydrous nickel oxide was found to be independent of time. However, the proportion of adsorption due to SDS and DA was dependent on time. Moreover, the initial and final ratio of SDS to DA adsorption did not reflect their ratio in solution. SDS adsorbed, initially, to a greater extent that would be predicted from its solution concentration, but this trend was reversed after a period of time.

Thesis (MScEng)--University of Stellenbosch, 2002.
ENGLISH ABSTRACT: The objective of this study is the assessment of the usefulness of an industrial machine vision system for laboratory studies of especially flotation froths and other foams. With this in mind it was attempted to meet three objectives. The first objective is the adjudication of the machine vision system's ability through image analysis to differentiate between characteristics of two-phase and three-phase systems. Secondly, through the use of image analysis the effect of varying surfactant concentration, as well as the addition of quartz particles on the foam/froth stability was quantified and thirdly it was attempted to define the nature of foam decay as stochastic or deterministic. While not as important in the industrial setting, the last objective is quite important when a laboratory system is concerned, even more so owing to the difficulty of quantifying the collapse or decay of foams and froths. Two experimental set-ups were used to attain above-mentioned objectives. A Leeds flotation cell was used for the flotation of the quartz with cetyltrimethylammonium bromide (CTAB) and octadecylamine (ODA) and as well as for the characterisation of the CTAB and ODA foam. A glass column was used to investigate the CTAB foam column decay. In both set-ups the foam/froth structures were monitored with an ELMO charged coupled device (CCD). The CCD was connected to a personal computer equipped with frame grabber, which captured and digitised the images. The following conclusions can be drawn from the experimental results: The machine vision system can differentiate accurately between surfactant groups of different concentration and thus groups with unique characteristics. 11 The stability of foam is highly correlated with all other foam variables extracted from the image analysis system. In particular, the movement of the foam/froth in the flotation cell has a substantial influence on the stability values obtained for the foam/froth. III As far as the experimental system was concerned, small quartz particles (- 75 urn) stabilised the froth, while coarser particles (75-106 urn, 106-150 urn and 150+ urn) destabilised the froth. IV Likewise, the decay of CTAB foam in a column was non-linear and deterministic. When observed manually, the decay of long life foams follow the same trend as short-life foams and short-life emulsions in that a specific decay constant can be calculated for a specific surfactant system. V The machine vision system is a viable alternative for current stability measurements. Firstly, no data processing need to be done to calculate a indirect stability parameter as it computes a direct stability parameter and secondly it also computes the bubble size distribution of the sample. The following recommendations are made: The experimental design of the system needs to be altered to minimise the effect the experimental environment has on results. The possibility of a different camera set-up must be investigated. The focus of the camera on the foam surface needs to be accurate as the computation of the stability value depends on the quality of the image obtained. Il The four factors that affect the stability of a flotation froth, namely solid concentration, particle size, particle type and particle hydrophobicity should be investigated in the same study. There exists many conflicting studies on this subject as many studies for different particles with a variety of sizes, hydrophobicity and concentration are performed. One study should be conducted where all four these factors are investigated under the same experimental conditions. III The method with which the image analysis system deal with fine froth need to be addressed. In laboratory systems a typical system investigated will show a dense foam with small bubble distributions as in the case of CTAB. The extent to which the grouping of fine froth as one bubble influence the instability values obtained needs to be investigated .
AFRIKAANSE OPSOMMING: Die doelwit van hierdie studie is die evaluering van die toepassing van 'n industriële masjienvisiesisteem in 'n laboratorium studie van hoofsaaklik flottasie skuim. Die doel van hierdie toepassing is drie-ledig. Die eerste doelwit is om die onderskeidingsvermoë van die masjienvisiesisteem tussen groepe met verskillende eienskappe te evalueer deur intydse beeld verwerking. Tweedens is die invloed van oppervlakmiddelkonsentrasie veranderinge asook die byvoeging van kwarts partikels op die stabiliteit van die skuim ondersoek. Derdens is die aard van die skuim verval ondersoek om vas te stelof die proses deterministies of stochasties is. Alhoewel laasgenoemde doelwit nie so belangrik is in die industriële toepassing nie, is dit van uiterse belang in die laboratorium studies, veral as gevolg van die probleme wat ondervind word in die kwantifisering van skuimverval. Twee eksperimentele opstellings is gebruik om bogenoemde doelwitte te bereik. 'n Leeds flottasiesel is gebruik vir die flottasie van kwarts met CTAB en ODA asook vir die karakterisering van CTAB en ODA skuimeienskappe. 'n Glaskolom is gebruik vir die ondersoek van die aard van skuimverval. In beide opstellings is die beelde gemonitor deur 'n ELMO CCD. Die CCD is verbind met 'n rekenaar wat toegerus is met 'n raam-vanger wat die beelde vang en digitiseer. Die volgende gevolgtrekkings kan uit die eksperimentele resultate gemaak word: Die masjienvisiesisteem differensieer akkuraat tussen oppervlakmiddel groepe van verskillende konsentrasies en dus ook tussen groepe met unieke eienskappe. 11 Die skuim stabiliteit korreleer met die ander skuim eienskappe naamlik gemiddelde area, gemiddelde omtrek, aantal borrels, fynheid van die beeld (SNE), beweging van die skuim en kleur van die skuim. Veral die beweging van die skuim in die flottasiesel het 'n beduidende invloed op die skuimstabiliteit. 111 In die genoemde eksperimentele sisteem IS gevind dat klein kwartspartikels (-75 urn) skuim stabiliseer terwyl groter partikels (75-106 urn, 106-150 urn en 150+ urn) skuim destabiliseer. IV Die verval van CTAB skuim in 'n kolom is nie-lineêr en deterministies. In die geval waar die verval van die CTAB met die hand gemeet is, is gevind dat die verval van 'n lang-lewe skuim dieselfde tendens as kort-lewe skuim en kort-lewe emulsies volg. 'n Spesifieke verval konstante kan bereken word vir 'n spesifieke oppervlakmiddel sisteem. v Die masjienvisiesisteem IS 'n werkbare alternatief in die meting van skuimstabiliteit. Anders as in bestaande stabiliteitsmetings waar 'n indirekte stabiliteitsparameter bereken moet word, bereken die sisteem 'n direkte stabiliteitsparameter asook die borrelverspreiding van die skuim monster. Die volgende aanbevelings kan gemaak word: Die eksperimentele ontwerp van die sisteem moet aangepas word om sodoende die invloed van eksperimentele kondisies op die resultate te verminder. Die moontlikheid van 'n alternatiewe kamera opstelling moet ook ondersoek word, aangesien die verkrygde stabiliteitswaardes afhanklik is van die kwaliteit van die skuimbeelde. 11 Daar is talle teenstrydige studies ten opsigte van die vier faktore wat die stabiliteit van flotasie skuim beinvloed naamlik erts tipe, partikel grootte, partikel hidrofobisiteit en vastestof konsentrasie. Hierdie faktore moet gelyktydig in 'n studie ondersoek word onder dieselfde eksperimentele kondisies. 111 Die masjienvisiesisteem groepeer fyn skuim gedeeltes saam as een borrel. Hierdie wyse van fyn skuim hantering moet aangespreek word aangesien 'n tipiese oppervlakmiddel sisteem in die laboratorium, soos in die geval van CTAB, digte skuim met 'n fyn borrelverspreiding toon. Die mate waarin die onvermoë van die sisteem om fyn borrels te herken die stabiliteitswaardes beïnvloed, moet ondersoek word.

Introduction: Microparticles (MPs) are implicated in the pathogenesis of coronary artery disease (CAD). / Aims: To determine whether circulating MPs correlate with high-risk coronary atherosclerotic plaque phenotype. / Methods: 25 patients with CAD undergoing percutaneous coronary intervention (PCI) were recruited; 13 were diagnosed to have acute coronary syndrome (ACS) & 12 with stable angina (SA). We characterized and compared coronary atherosclerotic plaque burden and vulnerable plaque phenotype by three-vessel optical coherence tomography (OCT) between ACS and SA groups. Endothelial (EMPs), platelet (PMPs), Neutrophil (NMPs), tissue factor (TFMPs) and smooth muscle (SMMPs) were quantified by flow cytometry, compared between groups pre PCI, post PCI, at days 1,7, 30 and 180. Pre and post PCI MPs measured on day 1 were correlated with OCT parameters. The levels of total and individual phenotypes of MPs were also compared based on presence or absence of thin cap fibroatheroma (TCFA) – a feature of plaque vulnerability. Procoagulant potential of MPs was determined by measuring thrombin generation assay (TGA) at above mentioned time points and compared between ACS and SA groups and also with disease free controls. / Results: OCT analysis revealed that ACS patients had more vulnerable features. The total AnnexinV+ MP (ANV+MP) levels were similar in ACS and SA groups at baseline, peaked immediately after PCI and were at their lowest on day 1. At six months CD54+EMPs [Median 9.9 (IQR 3.8,18.7) Vs. 2.6 (0.7, 5.2); p=0.008] and CD62p+PMPs [3.6 (1.2, 6.7) vs. 0.7 (0.4, 2.7); p=0.03] were significantly elevated in the ACS cohort. Patients with CAD showed abnormal thrombograms when compared to controls. Furthermore, thrombin parameters remained abnormal in ACS & SA patients at 6 months as demonstrated on AUC. Patients with TCFA exhibited enhanced thrombogenecity. / Conclusion: MPs may have a role as novel biomarkers in identifying vulnerable patients. Patients with TCFA expressed enhanced thrombogenecity irrespective of clinical presentation suggesting vulnerability.

Approved for public release; distribution is unlimited
The purpose of this project is to identify the costs and benefits associated with the application of closed-cell spray foam insulation to forward-deployed, semipermanent/nonpermanent structures, and to provide recommendations regarding future integration, use, and employment. According to the Department of Defense (DOD), forward-deployed generators, used to provide power to base support activities, are the largest single consumer of fuel throughout the battlefield. Eighty percent of the energy provided by generators is assessed to power environmental control units that run incessantly due to the poor insulating properties of the structures, according to a 2010 study conducted by the Department of the Air Force Civil Engineer Support Agency. Recent DOD policy has focused more on energy use and consumption but fails to address, and provide solutions for, major consumers of fuel throughout the battlefield. The incorporation of closed-cell, spray foam insulation into legacy DOD forward-deployed construction practices yields a significant return on investment, short-payback/break-even period, and reduces mission and personnel risk to deployed military forces.

Nowadays are foam concentrates used as the primary extinguishing agent for flammable liquid fires (especially hydrocarbons), means of transports fires, the release of chemical substances in environmental accidents, and their importance is still growing with the industrial development. All units of fire protection have foam concentrates in their equipment, so it is important that firefighters to have some necessary knowledge about their characteristics and to be able to use them effectively and safely for the environment. The basic component of foaming concentrates are surfactants. This diploma thesis analyzes foam samples which are commonly used, by methods for analysis of drinking, surface and wastewater and determines cationic, anionic and nonionic surfactants.

Optical methods play an important role in process analytical technologies (PAT). Four examples of optical process and quality sensing (OPQS) are presented, which are based on three important experimental techniques: near-infrared absorption, luminescence quenching, and a novel method, photon density wave (PDW) spectroscopy. These are used to evaluate four process and quality parameters related to beer brewing and polyurethane (PU) foaming processes: the ethanol content and the oxygen (O2) content in beer, the biomass in a bioreactor, and the cellular structures of PU foam produced in a pilot production plant.

Cette thèse porte sur les capacités d'extraction d'une mousse déposée sur un support poreux dans le but d'y déloger un contaminant ayant imprégné la porosité. Nous avons donc considéré l'imprégnation forcée de fluides dans un pore unique, étudiée pour deux cas particuliers : (i) lors de l'impact d'une goutte de liquide à l'aplomb d'un pore unique vertical cette situation visant à modéliser l'imprégnation du poreux par le contaminant, et (ii) lors de l'aspiration d'une mou sse liquide à travers le pore qui illustre la compétition d'aspiration entre la mousse et le poreux. Dans chaque cas, le diamètre du pore est inférieur à celui des gouttes ou des bulles.Pour le premier cas, nous nous sommes intéressés au volume et à la profondeur d'imprégnation pour des surfaces hydrophiles et hydrophobes. Nous établissons les diagrammes d'imprégnation en fonction du diamètre du pore et de la vitesse d'impact et un travail de modélisation nous permet de déterminer les limites entre les différentes régions de ces digrammes.Pour le second cas, nous montrons que lors de l'aspiration, la mousse entre dans le pore uniquement dans un domaine bien déterminé dans le diagramme fraction liquide, rapport de taille pore/bulle et débit d'aspiration. En dehors de ce domaine, l'aspiration peut faire entrer soit le gaz seul, soit le liquide seul. La encore, un travail de modélisation nous permet de prédire les limites des différentes zones du diagramme. Dans une dernière partie, nous revenons à un problème pratique d'imprégnation sur support textile et quantifions les capacités d'extraction d'une mousse dans cette configuration dans le but d'y déloger un contaminant

Sandwich panels comprise a thick, light-weight plastic foam such as polyurethane, polystyrene or mineral wool sandwiched between two relatively thin steel faces. One or both steel faces may be flat, lightly profiled or fully profiled. Until recently sandwich panel construction in Australia has been limited to cold-storage buildings due to the lack of design methods and data. However, in recent times, its use has increased significantly due to their widespread structural applications in building systems. Structural sandwich panels generally used in Australia comprise of polystyrene foam core and thinner (0.42 mm) and high strength (minimum yield stress of 550 MPa and reduced ductility) steel faces bonded together using separate adhesives. Sandwich panels exhibit various types of buckling behaviour depending on the types of faces used. Three types of buckling modes can be observed which are local buckling of plate elements of fully profiled faces, flexural wrinkling of flat and lightly profiled faces and mixed mode buckling of lightly profiled faces due to the interaction of local buckling and flexural wrinkling. To study the structural performance and develop appropriate design rules for sandwich panels, all these buckling failure modes have to be investigated thoroughly. A well established analytical solution exists for the design of flat faced sandwich panels, however, the design solutions for local buckling of fully profiled sandwich panels and mixed mode buckling of lightly profiled sandwich panels are not adequate. Therefore an extensive research program was undertaken to investigate the local buckling behaviour of fully profiled sandwich panels and the mixed mode buckling behaviour of lightly profiled sandwich panels. The first phase of this research was based on a series of laboratory experiments and numerical analyses of 50 foam-supported steel plate elements to study the local buckling behaviour of fully profiled sandwich panels made of thin steel faces and polystyrene foam core covering a wide range of b/t ratios. The current European design standard recommends the use of a modified effective width approach to include the local buckling effects in design. However, the experimental and numerical results revealed that this design method can predict reasonable strength for sandwich panels with low b/t ratios (< 100), but it predicts unconservative strengths for panels with slender plates (high b/t ratios). The use of sandwich panels with high b/t ratios is very common in practical design due to the increasing use of thinner and high strength steel plates. Therefore an improved design rule was developed based on the numerical results that can be used for fully profiled sandwich panels with any practical b/t ratio up to 600. The new improved design rule was validated using six full-scale experiments of profiled sandwich panels and hence can be used to develop safe and economical design solutions. The second phase of this research was based on a series of laboratory experiments and numerical analyses on lightly profiled sandwich panels to study the mixed mode buckling behaviour due to the interaction of local buckling and flexural wrinkling. The current wrinkling formula, which is a simple modification of the methods utilized for flat panels, does not consider the possible interaction between these two buckling modes. As the rib depth and width of flat plates between the ribs increase, flat plate buckling can occur leading to the failure of the entire panel due to the interaction between local buckling and wrinkling modes. Experimental and numerical results from this research confirmed that the current wrinkling formula for lightly profiled sandwich panels based on the elastic half-space method is inadequate in its present form. Hence an improved equation was developed based on validated finite element analysis results to take into account the interaction of the two buckling modes. This new interactive buckling formula can be used to determine the true value of interactive buckling stress for safe and economical design of lightly profiled sandwich panels. This thesis presents the details of experimental investigations and finite element analyses conducted to study the local buckling behaviour of fully profiled sandwich panels and the mixed mode buckling behaviour of lightly profiled sandwich panels. It includes development and validation of suitable numerical and experimental models, and the results. Current design rules are reviewed and new improved design rules are developed based on the results from this research.

La prise en considération des enjeux climatiques dans une phase préliminaire de la conception urbaine exige des outils d’aide à la conception, faciles à utiliser, rapides à exécuter, en harmonie avec le fonctionnement itératif de la conception. L’objectif de cette thèse est ainsi de produire un outil simple à utiliser en phase de design urbain permettant la prédiction de l’écoulement du vent, à une échelle locale et à hauteur de piéton, à partir des caractéristiques morphologiques urbaines. Cette lecture se fait via la construction d’un squelette du vide urbain. Ce squelette est ensuite rendu porteur d’informations qui viennent documenter les différentes composantes urbaines et leurs caractéristiques morphologiques à différentes échelles. Cette approche dynamique pour parcourir le vide urbain est aussi une approche d’analyse orientée champs pour capter et mesurer l’espace urbain au niveau d’un ensemble de capteurs virtuels ponctuels issus de l’échantillonnage du squelette. La démonstration de l’efficience des outils et méthodes proposés est faite pour trois types d’applications. La première est une production de profils de signatures morphologiques de quartiers. La seconde est une détection des différentes zones du vide urbain (rues, croisement de rues, places...). La troisième montre la capacité du squelette à renseigner sur la distribution du vent en ville
Considering climate issues in an early phase of urban design requires design tools that are easy to use, quick to execute, and in line with the iterative process of designing. This thesis aims to create a simple tool to be used during the urban design phase to predict wind flows on a local scale and at the pedestrian level, based on urban morphological characteristics. This reading occurs through the construction of an urban vacuum skeleton. The skeleton then carries information to document the different urban components and their morphological characteristics at different levels. The dynamic approach to cross the urban vacuum is also a field-oriented analytical approach to capture and measure the urban space at the level of a set of punctual virtual sensors whose skeleton is sampled. Demonstrating the efficiency of the tools and methods proposed was adapted to three types of applications. The first is a production of profiles of morphological signatures of neighborhoods. The second is a detection of the different areas of the urban void (streets, crossroads, squares...). The third shows the skeleton’s ability to provide information to learn about wind distribution in the city