Dissertations / Theses on the topic 'Rigid foam'

Train speeds and heavy haul axle loads are constantly increasing the forces and stresses experienced by track structures. This is especially true for track transitions that generate high dynamic forces on both the track and vehicles as a result of differing track stiffness values on either side of the track transition. Reducing differential settlement between the two track structures at a track transition is one method of improving the life of the track and increasing maintenance intervals. Ballast attrition and breakdown at these track transition zones is also of major concern as ballast fouling can lead to reduced drainage performance of the ballast as well as a potential loss of strength as the ballast becomes increasingly fouled. In this study rigid polyurethane foam was used as a means to reinforce ballast. Various tests were conducted using a dynamic load hydraulic load frame in a large ballast box test at heavy haul axle loads. Unreinforced, reinforced and 50 % reinforced ballast layers of 300 mm depth were tested to approximately 5,000,000 load cycles. The results showed that rigid polyurethane foam reinforced ballast exhibited in the order of 60 % less settlement for a fully reinforced layer and 42 % less settlement for a half reinforced layer. The increase in layer stiffness with increasing load cycles was also observed for the reinforced ballast layers which is contrast with the decrease in layer stiffness for conventional unreinforced ballast. The use of rigid polyurethane foam (RPF) to reinforce ballast has a number of benefits which could result in better track geometry and longer maintenance cycles resulting in lower overall costs.
Dissertation (MEng)--University of Pretoria, 2015.
tm2016
Civil Engineering
MEng
Unrestricted

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1987.
MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING.
Bibliography: leaves 69-71.
by Thanasis C. Triantafillou.
M.S.

Cellulose nanowhisker (CNW) prepared by acid hydrolysis of softwood Kraft pulp was incorporated as nanofiller in rigid polyurethane (PU) foam synthesis. The density, morphology, chemical structure, mechanical properties and thermal behavior of the products were characterized. The nanocomposites exhibited better performance especially at high CNW¡¯s content which was probably due to the high specific strength and aspect ratio of CNW, the hydrogen bonding and crosslinking between CNW and polymer matrix, a higher crosslinking density compared to the control, and the function of CNW as an insulator and mass transfer insulator. Lignin polyol was synthesized through oxypropylation and used for rigid PU foam preparation. The density, morphology, chemical structure, compressive property and thermal behavior of the product were characterized. Lingin-based rigid PU foam showed improved compressive property compared to its commercial counterpart. Ethanol organosolv lignin-based PU showed a slightly stronger compressive property than Kraft lignin-based PU. The enhancement was primarily attributed to the rigid phenolic structure and the high hydroxyl functionality of lignin. Lignin-based PU generated more char than common PUs which was possibly related to the better flame retardant property. This study provided an alternative way to valorize the two most abundant biopolymers and resulted in relatively environmentally benign rigid PU nanocomposite foam.

Automotive crash has garnered significant attention in the recent years with increasing fatality and safety concerns. Substantial effort and great amount of time and expertise has been directed towards the issues related to crashworthiness such as impact, rollover scenarios and restraint performance. Automotive rollover is one of those important concerns for the auto industry as the fatality rates and death causing conditions are vital compared to other crashes. In the past few decades, research has been focused towards developing efficient roof structure by implementing crashworthy structures, to protect or at least reduce the severity of the accident to the occupants of the vehicle during an event of a rollover. Studies have been carried in this area in developing efficient crashworthy structures. As the technology is evolving, researchers have found that thin walled tubes filled with foam materials possess high energy absorption properties compared to empty crashworthy structures. Further research in this has area led to the interference of nanotechnology, which implements emerging techniques in developing advanced materials for engineering applications. Scientists were able to develop low density, lightweight foams with high energy-absorption characteristics with these techniques. The purpose of this thesis is to analyze and evaluate the performance of low density carbon nanofoam (CNF) as an energy absorbing material in improving the roof strength of the vehicle. The LS- DYNA code, a non-linear dynamic finite element solver is utilized to accomplish this study. First, a three- point bending test simulation is carried as component level testing to analyze the behavior of foam materials. Then, the energy absorbing characteristics of a hollow tube is studied and the results are compared with regular polyurethane (PU) foam and carbon nanofoam inserts into the hollow tube, under similar conditions. Finally, PU foam and CNF is applied into the critical areas of roof supporting structures as two different conditions and static roof crush and dynamic inverted drop test simulations are conducted depicting an actual rollover scenario to study the crashworthy behavior of the vehicle roof with and without the foam. This study highlights that carbon nanofoam is found to be more effective compared to the regular polyurethane foam exhibiting better energy absorption characteristics.
Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering

Ce travail de thèse porte sur le développement d’une nouvelle génération de mousses polymères biosourcées capables de satisfaire la fonction d’âme alvéolaire et structurale de pièces automobiles. Les formulations époxy choisies comme base polymère reposent sur deux différents prépolymères époxy, l’huile de lin époxydée (ELO) et le glycérol époxydé (GE). Ces derniers, associés en proportions variables, sont réticulés avec deux différents durcisseurs : l’isophorone diamine (IPDA) ou l’anhydride méthyl tétrahydrophtalique (MTHPA). Les formulations ternaires « ELO – GE – durcisseur » ont été caractérisées selon une approche multi-techniques (DSC, TGA, rhéométrie dynamique et en mode permanent) permettant d’établir des relations structure-propriétés fiables. Puis, la production d’une mousse a été possible grâce à la maîtrise d’une réaction chimique qui se déroule parallèlement à la réticulation de la résine époxy. Le bicarbonate de sodium et de potassium ont été retenus comme agents moussants. Afin d’améliorer les performances finales des mousses, la proportion de GE au sein des formulations polymère à base IPDA a été augmentée. Mais, une telle modification induit la dégradation thermique du système à cause de l’exothermicité élevée de la réaction de réticulation. L’introduction d’un absorbeur d’exothermicité, permet grâce à sa décomposition endothermique de contrôler l’excès de chaleur dégagée et par la même d’empêcher la dégradation. Une dernière classe de durcisseurs a également été étudiée et donne après optimisation des mousses dotés d’excellentes propriétés ultimes. Ainsi, une large gamme de mousses biosourcées rigides et légères pouvant être mises en œuvre dans un temps très court a été développée
This thesis focuses on the development of a new generation of bio-based polymer foams able to produce low density core in sandwich structure for automotive applications. The polymer formulations used in this research contain two different epoxy compounds, epoxidized linseed oil (ELO) and the epoxidized glycerol (GE). Combined in varying proportions, they were cured with two different hardeners, isophorone diamine (IPDA) or methyl tetrahydrophthalic anhydride (MTHPA). Ternary formulations “ELO – GE – hardener” were characterized by a multi-techniques approach (DSC, TGA, rheometry in steady or dynamic mode) in order to establish structure-property relationships. The production of polymeric-foam materials was carried out by tuning a chemical reaction which takes place during curing. Sodium bicarbonate and potassium bicarbonate were used as harmless foaming agents. In order to improve the final performances of the foams, the ratio GE/ELO was increased in the reactive formulations based on IPDA hardener. But, such modification provokes also the thermal degradation of the system because of the high exothermicity of the curing reaction. The introduction of “exothermicity regulators” that undergo endothermic transformations allowed to control the excess of released heat and consequently, to prevent the material degradation. A last class of hardener was also studied and made it possible after optimization the production of foams with good ultimate properties. To conclude, a large range of biobased and lightweight rigid foams able to be produced in a few minutes was developed

Les mousses rigides constituent une classe très importante de matériaux de par leur large champ d’applications et de leur poids économique considérable. Le développement de mousses à base de tannins a permis d’obtenir des matériaux issus à 90% de produits naturels. Dans ce travail, un type de tannins très réactif dit « procyanidine », a été employé. Les formulations et la technologie de fabrication de mousses rigides ont été développées à partir de tannins extraits d’écorce de pin et d’épicéa. Dans un premier temps, la composition et la réactivité des tannins ont été étudiées. Ensuite, l’étude du processus de moussage des résines à base de ces tannins a permis l’élaboration d’une large gamme de mousses rigides tannin-furanique. Leur excellente résistance au feu, leur résistance mécanique et leur haute performance thermique en font des matériaux d’isolation de haute qualité. Ces mousses peuvent également être employées comme absorbeurs acoustiques. De plus, de nouveaux solides cellulaires à base de tannins et de protéine ont également été développés, proposant ainsi un nouveau type de matériaux issu de produits naturels
Rigid foams contitute a very important class of materials considering their wide application range and their considerable economic impact. The development of tannin-based foams provided materials made from 90% natural products.In this work, a type of tannins highly reactive, namely « procyanidin », was used. First, tannins composition and reactivity were studied. Then, the foaming process investigation of tannin-based resins leads to a wide pannel of tannin-furanic rigid foams. Their excellent fire resistance, mechanical resistance and high thermal performance make them high quality insulation materials. These foams are also suitable for other applications such acoustic absorption. Thus, new cellular solids from tannin and protein were also developped, offering a new type of materials derived from natural products

The thesis deals with the processes that occur in the course of the manufacturing of rigid polyurethane-polyisocyanurate (PU-PIR) foams, their properties and technology. It deals above all with principles of foam nucleation and stability. The purpose of understanding these principles is their possible use for improving thermo-insulating properties of the material. The experimental part of the thesis studies the influence of additives and ultrasound on the PU-PIR foam properties. It has been found that low molecular weight compounds with perfluorinated chain leads to decreasing foam cell size and its lower thermal conductivity. The additives mentioned act probably on the surfactants principle by facilitating nucleation and stabilizing growing centres of bubbles. They probably form also part of blowing agents mixture inside the foam cells which cause lowering of thermal conductivity as well. Compounds with similar chemical structure have unique influence on the properties of rigid PU-PIR foams. Further research ought to be focused on cheaper modes of producing perfluorinated compounds.

Este trabalho teve como objetivo o estudo da espuma rígida de poliuretano (PU) derivada de óleo de mamona para aplicação como forro na isolação térmica de sistemas de cobertura. Dentro deste objetivo foram caracterizadas as suas propriedades termomecânicas e avaliado o seu comportamento térmico quando aplicada como forro em células de teste em quatro situa-ções diferentes. As caracterizações termomecânicas da espuma rígida de poliuretano derivada de óleo de mamona foram realizadas utilizando as técnicas Termogravimétrica (TGA), Dinâ-mico-Mecânica (DMA), e Método do Fio Quente Paralelo. A técnica Termogravimétrica (TGA) possibilitou o estudo da decomposição da espuma e uma avaliação de sua cinética. A cinética de decomposição foi realizada em quatro diferentes razões de aquecimento e os resul-tados foram avaliados utilizando o método baseado no modelo de Ozawa-Flynn-Wall no qual foi possível estimar o tempo de vida da espuma rígida de poliuretano para vários valores de temperatura constante. Por meio da utilização da técnica Dinâmico-Mecânica (DMA) foi pos-sível determinar a temperatura de transição vítrea da espuma e os módulos viscoelásticos de armazenamento (E) e de perda (E) assim como os valores de Tan Delta. O Método do Fio Quente Paralelo proporcionou a determinação do valor da condutividade térmica da espuma, que a classificou como um material muito isolante (1).A espuma rígida de poliuretano apre-sentou propriedades termomecânicas compatíveis para utilização como isolante térmico em temperaturas abaixo da ambiente, e em temperaturas acima de 100 oC. O estudo comparativo entre quatro células de teste para análise do comportamento térmico do forro foi feito com a coleta de dados em canteiro experimental. Os resultados obtidos comprovaram a eficiência da espuma rígida de poliuretano derivada do óleo de mamona na redução da entrada de calor durante o período de radiação solar global máxima e a atenuação da perda de calor no período sem influência da radiação solar
This work aimed to study the rigid foam polyurethane (PU) derived from castor oil for appli-cation as lining in thermal insulation systems coverage. Within this objective we have charac-terized the thermomechanical properties and assessed its thermal behavior when applied as lining cells testing in four different situations. The rigid foam polyurethanes thermo characte-rizations, derived from castor oil, were performed using the Thermogravimetric Analysis (TGA), Dynamic Mechanical Analysis (DMA), and Hot Parallel Wire Method. The Thermo-gravimetric Analysis (TGA) has enabled the study of the foams decomposition and an evalu-ation of its kinetics. The decomposition kinetics was carried out in four various heating rea-sons and the results were evaluated using the method based on Ozawa-Flynn-Wall model which it was possible to estimate the rigid foam polyurethanes lifetime for various constant temperature values. By Dynamic Mechanical Analysis (DMA) has been possible to determine the foams glass transition temperature and the viscoelastics modules, storing module (E\') and loss module (E) well as the values of Tan Delta. The Hot Parallel Wire Method provided the valuation of foams thermal conductivity which ranked as a very insulating material (1). The rigid foam polyurethane has been shown to thermomechanical compatible for used as an insu-lator heat at temperatures below ambient, and temperatures above 100 oC. The four test cells comparative study for linings thermal behavior analysis was made with the collecting data from experimental plot. Results obtained proved the rigid foam polyurethane efficiency, de-rived from castor oil, in reducing the input heat during the maximum solar radiation and at-tenuation of heat loss in the period with no influence of solar radiation.

The morphology and elastic properties of foams are investigated using models accounting for the cellular structure. Different modeling approaches are evaluated and compared to the cellular structures of real foams. The aim is to find an approach that produces realistic models that can be adjusted to match morphology measures taken form real foams. The elastic properties are computed using finite element analysis and the results are compared with both experimental results from mechanical testing and existing analytical models. A generalization of the existing analytical models is suggested for better agreement with the modeling results. In Paper A Voronoi and equilibrium foam models are generated and investigated. The Voronoi models are found to have a high content of short edges and small faces while conversion into equilibrium foams eliminates such small geometrical features. It is also seen that different seed point distribution algorithms generally result in different model topologies. In Paper B the relations between the sphere packing fraction and the resulting degree of volumetric polydispersity are studied as well as the relations between polydispersity and a number of morphology parameters. Both Voronoi and equilibrium foams are investigated and compared with data from real foams. Such comparisons indicate that the used method is somewhat limited in terms of polydispersity but provides a controlled way of varying the foam morphology. In Paper C equilibrium models are used to study the inuence of polydispersity, relative density and distribution of solid on the elastic properties of foams. It is found that the elastic moduli are very weakly coupled to the polydispersity while the inuence from the relative density and distribution of solid is considerably stronger. Existing analytical models from the literature are fitted to the results and generalizations are suggested for better agreement over the investigated range of relative density and distribution of solid. In Paper D equilibrium foam models with prescribed polydispersity are generated, analyzed and compared to real foams. The polydispersity of real foams is measured in micro-CT images and the results are applied to the models. The elastic properties are computed and the results are compared with experimental results and previous models with significantly lower polydispersity. No clear relation is found between the elastic properties and the polydispersity of equilibrium foams.

QC 20150505

The theoretical part summarizes the chemical recycling processes of polyurethane and polyisocyanurate insulation foams and methods of polyols preparation from their alcoholysates. Emphasis is placed on the use of microwave heating during depolymerization, as a perspective energy source for chemolysis processes. The practical part is focused on optimization of recyclates preparation derived from polyisocyanurate foams and polyethylene terephthalate by microwave enhanced glycerolysis. Recyclates obtained were verified for their workability and applicability in blends with virgin polyols in polyisocyanurate foam manufacture process.

Die Anwendung von textilbewehrtem Beton ermöglicht vorgefertigte, filigrane und leichte Betonkonstruktionen von hoher Dauerhaftigkeit und Oberflächenqualität. Stand der Technik in der Anwendung sind hinterlüftete Fassadenplatten mit Dicken von 20-35 mm und Größen von bis zu 12,3 m², die aufgrund der geringen Querschnittssteifigkeiten nur mit metallischen oder monolithischen Aussteifungen realisierbar sind. Steife, tragfähige und dennoch leichte Querschnitte lassen sich mit Sandwichkonstruktionen erreichen, die große Spannweiten und zusätzliche Einsparpotentiale im Betoneinsatz und der Gesamtbauteilstärke ermöglichen. Insbesondere selbsttragende Sandwichkonstruktionen bieten ein hohes Anwendungspotenzial im Fassadenbereich. Der vorliegende Beitrag berichtet über Lastannahmen, Tragverhalten, Herstellung und Anwendung beim Hallenneubau des Instituts für Textiltechnik, RWTH Aachen.

The primary goal of this dissertation is to develop point-based rigid and non-rigid image registration methods that have better accuracy than existing methods. We first present point-based PoIRe, which provides the framework for point-based global rigid registrations. It allows a choice of different search strategies including (a) branch-and-bound, (b) probabilistic hill-climbing, and (c) a novel hybrid method that takes advantage of the best characteristics of the other two methods. We use a robust similarity measure that is insensitive to noise, which is often introduced during feature extraction. We show the robustness of PoIRe using it to register images obtained with an electronic portal imaging device (EPID), which have large amounts of scatter and low contrast. To evaluate PoIRe we used (a) simulated images and (b) images with fiducial markers; PoIRe was extensively tested with 2D EPID images and images generated by 3D Computer Tomography (CT) and Magnetic Resonance (MR) images. PoIRe was also evaluated using benchmark data sets from the blind retrospective evaluation project (RIRE). We show that PoIRe is better than existing methods such as Iterative Closest Point (ICP) and methods based on mutual information. We also present a novel point-based local non-rigid shape registration algorithm. We extend the robust similarity measure used in PoIRe to non-rigid registrations adapting it to a free form deformation (FFD) model and making it robust to local minima, which is a drawback common to existing non-rigid point-based methods. For non-rigid registrations we show that it performs better than existing methods and that is less sensitive to starting conditions. We test our non-rigid registration method using available benchmark data sets for shape registration. Finally, we also explore the extraction of features invariant to changes in perspective and illumination, and explore how they can help improve the accuracy of multi-modal registration. For multimodal registration of EPID-DRR images we present a method based on a local descriptor defined by a vector of complex responses to a circular Gabor filter.

The sponsors of this project have been using the rigid heavily-crosslinked polyurethane foam detailed in this study for load-bearing applications. One of the main requirements of this material is that it must possess excellent recovery properties following extensive compressive periods over several years. For such long loading regimes, there is need for detailed understanding of the compressive behaviour of this material, and its subsequent recovery upon release. More recently, there has been a growing interest in replacing the polyurethane foam with an alternative cellular plastic that possesses similar, if not identical, compressive recovery and behaviour. Attention was focused on the other primary polymer contingent, a polyethylene foam. A polyimide foam was also considered as it was already being used in applications similar to those of the polyurethane foam. The structures of the foams were investigated by means of Differential Scanning Calorimetry, Scanning Electron Microscopy and Image Analysis. The deformation mechanisms that occur during the application of a compressive force were examined visually via a scanning electron microscope compression rig. The mechanical analysis involved stress-strain testing whereby three stages of compression were identified (‘linear elastic, stress plateau and densification’), as described in the literature. Quadratic relationships were found to exist between the foam density and the ‘elastic modulus, plateau modulus and the compressive strength’ respectively. Such relationships had previously been found to exist in the literature, but not for the rigid variety of foam at such a broad range of densities. Further analysis included a detailed study of the recovery of the polyurethane (100 kg m[sup]-3 to 800 kg m[sup]-3) foams, a lightly-crosslinked polyethylene foam and a non-crosslinked polyimide foam. The foam samples were compressed by strains which spanned their linear elastic and stress plateau regimes i.e. by 2.5% to 35% for periods ranging from 3 days up to one year at ambient temperature. This analysis was also undertaken at elevated temperature as a means of accelerating the ageing process. Recovery of all of the samples was monitored for a minimum of 100 days at ambient temperature following release. Recovery of all of the foams tested was found to occur in two stages; an initial rapid recovery within the first day following release followed by a much slower recovery phase over a period of approximately 100 days. The initial rapid recovery was attributed to the recovery of the bulk polymer whilst the recovery of the cellular structure was associated with the ensuing slower recovery phase. In addition, recovery of the foams was found to be dependent more upon the compressive strain than on other parameters, such as compressive period and foam density. For compressive periods exceeding two weeks, recovery is almost independent of the latter parameters.

Mestrado em Engenharia Química
A temática do presente trabalho insere-se na procura de agentes expansores mais eficientes para espumas de poliuretano. Nesta perspectiva, são apresentadas medições da condutividade térmica de misturas binárias de gases contendo X3 e um alcano, utilizando o Método Transiente do fio Aquecido. A calibração do aparelho foi efectuada através da medição da condutividade térmica de azoto, por comparação com valores da literatura (NIST). Foram estudados dois sistemas binários para possível aplicação como agentes expansores: X1 + X3 e X2 + X3. Foram realizadas medidas de condutividade térmica em três misturas de composições diferentes de cada um dos referidos sistemas na gama de pressão entre 1 e 5 bar e temperaturas entre 300 e 400K. Para a correlação dos resultados experimentais foi utilizado o Modelo Generalizado de Wassiljewa, tendo sido também estudada a dependência do parâmetro ε com a pressão e temperatura. Concluiu-se que o Modelo Generalizado de Wassiljewa apresenta um bom ajuste aos valores experimentais da condutividade térmica de ambos os sistemas estudados, tendo-se verificado que o parâmetro ε apresenta sempre um valor próximo da unidade. O sistema X2 + X3 é aquele que apresenta valores condutividade térmica mais promissores para aplicação como agente expansor de espumas de poliuretano. ABSTRACT: The present work aims at finding a suitable, highly efficient blowing agent for polyurethane rigid foams. In this framework, measurements of the thermal conductivity of binary gas mixtures using the Transient Hot-wire Method are presented. The calibration of the apparatus was performed using nitrogen and the results were compared with values from the literature (NIST). Two binary systems were studied as possible blowing agents: X1 + X3 and X2 + X3. Three different compositions were measured within a pressure range 1 to 5 bar and temperatures between 300 and 400K. The obtained thermal conductivity data was correlated using the Extended Wassiljewa Model and the dependence of the ε parameter with pressure and temperature was addressed. The Extended Wassiljewa model performs very well in the description of thermal conductivity of both systems and the ε parameter presents always a value close to unity. In conclusion, the X2+ X3 system is the one that seem to be more promissing for the proposed aplication.

Medical image registration consists of finding spatial correspondences between two images or more. It is a powerful tool which is commonly used in various medical image processing tasks. Even though medical image registration has been an active topic of research for the last two decades, significant challenges in the field remain to be solved. This thesis addresses some of these challenges through extensions to the Free-Form Deformation (FFD) registration framework, which is one of the most widely used and well-established non-rigid registration algorithm. Medical image registration is a computationally expensive task because of the high degrees of freedom of the non-rigid transformations. In this work, the FFD algorithm has been re-factored to enable fast processing, while maintaining the accuracy of the results. In addition, parallel computing paradigms have been employed to provide near real-time image registration capabilities. Further modifications have been performed to improve the registration robustness to artifacts such as tissues non-uniformity. The plausibility of the generated deformation field has been improved through the use of bio-mechanical models based regularization. Additionally, diffeomorphic extensions to the algorithm were also developed. The work presented in this thesis has been extensively validated using brain magnetic resonance imaging of patients diagnosed with dementia or patients undergoing brain resection. It has also been applied to lung X-ray computed tomography and imaging of small animals. Alongside with this thesis an open-source package, NiftyReg, has been developed to release the presented work to the medical imaging community.

Cellular materials are all around us. They can be found in nature as in bone, wood, leaves and even in our food. In the last fifty years, man has produced many synthetic cellular materials: firstly with polymeric foams and more recently with foamed metals, ceramics and glass. Polymer foams are used in a variety of applications ranging from coffee mugs to the feet of the Apollo Lunar Module, for which they were used as shock absorbers. This project was aimed at understanding the recovery from long-term compression of rigid polymer foams. Understanding the dynamics involved in the recovery process of foams is very important, especially in the automotive industry where it determines safety of the driver, passengers and pedestrians, for example, in car bumpers. In this study, foam samples were compressed by strains which spanned their linear elastic and stress plateau regions, i.e. 2.5% - 35% for one month at various temperatures. Recovery occurred in two stages, designated phase 1 and phase 2. Phase 1 is the initial recovery, which dominates the full recovery process and is complete within hours or days. Phase 2 is a lesser recovery occurring over a much longer period of approximately 100 days. The initial recovery is associated with the polymer itself, whilst phase 2 recovery is associated with the cellular structure. Recovery of all samples was monitored for a minimum of 100 days at ambient temperature. Tests were also carried out to see how the environmental surroundings affect the polymer recovery. The different polymer foams which were investigated were: • Polyethylene • Polyetherimide • Polyurethane • Polysulphone The polymers tested all showed very different responses to the changes in temperature. All polymers investigated at different compressive strains demonstrated reproducible Arrhenius plot slopes under different conditions and hence a reasonably reproducible set of values of recovery process. Analyses were based on the final total recovery of the thickness as the most reliable parameter of recovery. It has been demonstrated that the mechanism of polymer deformation and recovery probably does not involve chain scission but backbone vibration; that the best parameter for characterising the recovery process is the final total dimensional recovery of the sample; and that subtle environmental changes have a large effect on the recovery from compression, although temperature and humidity are not responsible.

The mechanical and mesoscopic structural properties of rigid cellular foam made of polystyrene have been investigated. Basic properties (e.g., density, total and available porosity, permeability, surface area, isotropicity, and cell size and cell wall thickness distributions) were measured. In most cases, alternative methods were used to determine which methods were most appropriate for the type of samples we studied. Standard compression and deflection mechanical tests were performed. The stress-strain curves and related mechanical properties were found to agree with standard cellular structural models of open-cell foams. We investigated the effects of small (~<5 atm) hydrostatic stress applied to foam samples for long periods of time (~one day). We observed large changes (up to a factor of three) in the stress-strain diagrams, Young's modulus, elastic collapse stress, ultimate strength, resilience, Poisson's ratio, permeability, penetration depth, and available porosity. Effects were most pronounced above 2 atm applied pressure differential, but were observed even for 1 atm loads. Short-term exposure to loads up to ten times as large did not cause comparable changes. These changes were interpreted as resulting from observed changes in the mesoscopic structure occurring near the surface using standard cellular structural models. This work was originally motivated by applications of foam as an inflating agent and structural component of fiber-epoxy composite tubular struts to be used in innovative space structures. The key recommendations of this study, regarding such applications, are to closely monitor the effects on the mechanical properties of polystyrene foam of: (1) cell structure and density inhomogeneities, and (2) pressure differentials which may be encountered during deployment and curing.

Image registration seeks pointwise correspondences between the same or analogous objects in different images. Conventional registration methods generally impose continuity and smoothness throughout the image. However, there are cases in which the deformations may involve discontinuities. In general, the discontinuities can be of different types, depending on the physical properties of the tissue transitions involved and boundary conditions. For instance, in the respiratory motion the lungs slide along the thoracic cage following the tangential direction of their interface. In the normal direction, however, the lungs and the thoracic cage are constrained to be always in contact but they have different material properties producing different compression or expansion rates. In the literature, there is no generic method, which handles different types of discontinuities and considers their directional dependence. The aim of this thesis is to develop a general registration framework that is able to correctly model different types of tissue transitions with a general formalism. This has led to the development of the eXtended Free Form Deformation (XFFD) registration method. XFFD borrows the concept of the interpolation method from the eXtended Finite Element method (XFEM) to incorporate discontinuities by enriching B-spline basis functions, coupled with extra degrees of freedom. XFFD can handle different types of discontinuities and encodes their directional-dependence without any additional constraints. XFFD has been evaluated on digital phantoms, publicly available 3D liver and lung CT images. The experiments show that XFFD improves on previous methods and that it is important to employ the correct model that corresponds to the discontinuity type involved at the tissue transition. The effect of using incorrect models is more evident in the strain, which measures mechanical properties of the tissues.

Das Ziel dieser Dissertation ist die Erforschung einer gewissen Invariante von Singularitäten über einem Grundkörper k von positiver Charakteristik. Sei x \in X ein singulärer Punkt auf einem k-Schema. Dann ist die lokale rigide Kohomologie im Grad i definiert als H^i_{rig, {x}}(X), also als die rigide Kohomologie von X mit Träger in der Teilmenge {x}. In Kapitel 2 zeigen wir, dass die lokale rigide Kohomologie tatsächlich eine Invariante ist. Das heißt: Sind x'' \in X'' und x \in X kontaktäquivalente singuläre Punkte auf k-Schemata, dann sind die Vektorräume H_{rig, {x}}(X) und H_{rig, {x''}}(X'') zueinander isomorph. Dieser Isomorphismus ist kompatibel mit der Wirkung des Frobenius auf der rigiden Kohomologie. In den Kapiteln 3 und 4 beschäftigen wir uns mit gewichtet homogenen Singularitäten von Hyperflächen. Der Hauptsatz des dritten Kapitels besagt, dass die lokale rigide Kohomologie einer solchen Singularität isomorph ist zu dem G-invarianten Teil von H_{rig}(\Proj^{n-1}_k \setminus \widetilde{S}_{\infty}). Hier bezeichnet \widetilde{S}_{\infty} \subset \Proj^{n-1}_k eine gewisse glatte projektive Hyperfläche und G ist eine endliche Gruppe, die auf der rigiden Kohomologie des Komplements wirkt. Dank einem Algorithmus von Abbott, Kedlaya und Roe ist es möglich, den Frobenius-Automorphismus auf H_{rig}(\Proj^{n-1}_k \setminus \widetilde{S}_{\infty}) annähernd zu berechnen. In Kapitel 4 formulieren wir eine Anpassung dieses Algorithmus, mithilfe derer Berechnungen auf dem G-invarianten Teil gemacht werden können. Der angepasste Algorithmus kann vollständig mithilfe gewichtet homogener Polynome formuliert werden, was für unsere Anwendungen sehr natürlich scheint. In Kapitel 5 formulieren wir einige Vermutungen und offene Probleme, die mit den Ergebnissen der früheren Kapitel zusammenhängen.
The goal of this thesis is to study a certain invariant of isolated singularities over a base field k of positive characteristic. This invariant is called the local rigid cohomology. For a singular point x \in X on a k-scheme, the i-th local rigid cohomology is defined as H^i_{rig, {x}}(X), the i-th rigid cohomology of X with supports in the subset {x}. In chapter 2 we show that the local rigid cohomology is indeed an invariant. That is: if x'' \in X'' and x \in X are contact-equivalent singularities on k-schemes, then the local rigid cohomology spaces H_{rig, {x}}(X) and H_{rig, {x''}}(X'') are isomorphic. The isomorphism that we construct is moreover compatible with the Frobenius action on rigid cohomology. In chapters 3 and 4 we focus our attention on weighted homogeneous hypersurface singularities. Our goal in chapter 3 is to show that for such a singularity, the local rigid cohomology may be identified with the G-invariants of a certain rigid cohomology space $H_{rig}(\Proj^{n-1}_k \setminus \widetilde{S}_{\infty}). Here \widetilde{S}_{\infty} \subset \Proj^{n-1}_k is a smooth projective hypersurface, and G is a certain finite group acting on the rigid cohomology of its complement. It is known that the rigid cohomology of a smooth projective hypersurface is amenable to direct computation. Indeed, an algorithm by Abbott, Kedlaya and Roe allows one to approximate the Frobenius on such a rigid cohomology space. In chapter 4 we will modify this algorithm to deal with the G-invariant part of cohomology. The modified algorithm can be formulated entirely in terms of weighted homogeneous polynomials, which seems natural for our applications. Chapter 5 is a collection of conjectures and open problems that are related to the earlier chapters.

A mathematical dynamic model is derived for the compliant constant-force mechanism, based on the pseudo-rigid-body model simplification of the device. The compliant constant-force mechanism is a slider mechanism incorporating large-deflection beams, which outputs near-constant-force across the range of its designed deflection. The equation of motion is successfully validated with empirical data from five separate mechanisms, comprising two configurations of compliant constant-force mechanism. The dynamic model is cast in generalized form to represent all possible configurations of compliant constant-force mechanism. Deriving the dynamic equation from the pseudo-rigid-body model is useful because every configuration is represented by the same model, so a separate treatment is not required for each configuration. An unexpected dynamic trait of the constant-force mechanism is discovered: there exists a range of frequencies for which the output force of the mechanism accords nearer to constant-force than does the output force at static levels.

There are many collisions on the roads every day. Automotive companies do number of different types of crash-tests to reduce the consequences of these collisions. Crash-tests are supposed to uncover problems of tested vehicles. Then it is possible to propose constructional changes to reduce the consequences of different types of collisions. Indipendent organisations then test productional vehicles according to their standarts and evaluate safety of these vehicles. One of these crash-tests is the small overlap test which is being done by Insurance Institute for Highway Safety. The small overlap test will be the subject of this thesis. Computational modelling of small overlap test is realised for basic variant and for variants with changes. There is also comparison of basic variant and variants with changes.

The present dissertation analyzes some of the internal tensions in our current constitutional democracies. I start from the consideration of the characteristics that currently define our constitutional realities. I attempt to account about the means we have to guarantee and satisfy the purposes and values of constitutionalism as a political project. Namely, the written and rigid form of our Constitutions and the judicial review, and the tension that prima facie they have with the ideal of collective or democratic self-government. In the same way, I argue how we can overcome this tension through the express adherence to the postulates that justify the rigid contemporary constitutionalism, I mean, towards a model of strong constitutionalism. Besides, I try to show how from an adequate perspective these same postulates should be understood as a necessary means to make sense of any authentically democratic form of government.
El presente trabajo de tesis doctoral analiza algunas de las tensiones internas a nuestras actuales democracias constitucionales. En particular, partiendo de la consideración de los caracteres que actualmente definen a nuestras actuales realidades constitucionales, trata de dar cuenta de los medios que tenemos para tratar de garantizar y satisfacer los fines y valores del constitucionalismo como proyecto político, esto es, de la forma escrita y rígida de nuestras actuales Constituciones y del control judicial de constitucionalidad, y la tensión prima facie que los mismos presentan respecto del ideal del auto-gobierno colectivo o democrático. Del mismo modo, trata de argumentar cómo podemos superar esta tensión, desde la expresa adhesión hacia los postulados que justifican el constitucionalismo rígido contemporáneo, es decir, hacia un modelo de constitucionalismo fuerte. También, busca lograr demostrar cómo, vistas adecuadamente las cosas, estos mismos postulados deben ser entendidos como un medio necesario para salvaguardar la propia viabilidad y dotar de sentido a cualquier forma de gobierno genuinamente democrática.

Tese de mestrado em Química Tecnológica, apresentada à Universidade de Lisboa, através da Faculdade de Ciências, 2016
O mercado dos poliuretanos encontra-se, de momento, em expansão. No ano de 2012, a Asia foi o maior produtor de poliuretano, tendo sido responsável pela produção de cerca de 10 milhões de toneladas, seguida pela Europa com uma produção anual de 4 milhões de toneladas. No ano de 2013 a produção mundial de latas de espuma de poliuretano atingiu as 600 mil toneladas, sendo esperado que em 2018 a sua produção a nível mundial atinja as 820 mil toneladas [1]. No que diz respeito às espumas de poliuretano de um componente, o mercado tem apresentado um crescimento anual, sendo mais notório em mercados emergentes. No ano de 2013 foram produzidas mundialmente 535 milhões de latas e estima-se que em 2018 sejam produzidas cerca de 668 milhões de latas [1]. As espumas de poliuretano de um componente têm tido uma utilização crescente na indústria de construção civil, por exemplo na fixação e vedação em portas e janelas, preenchimento de buracos, isolamento em edifícios, etc. Ao contrário das espumas de poliuretano de dois componentes, em que os polióis e os isocianatos não são armazenados em conjunto, no caso de espumas de poliuretano de um componente, estes encontram-se misturados e reagidos numa lata pressurizada, juntamente com os gases propulsores. À mistura, no interior de uma lata pressurizada, composta pelos polióis e o isocianato é dado o nome de quasi-pré-polímero, sendo que o processo de cura será apenas completo após a dispensa (“spray”) da espuma, quando ocorre contacto com a humidade do ar, formando-se uma espuma de poliuretano-poliureia rígida. Deste modo, a velocidade de cura deste tipo de espuma encontra-se fortemente dependente da humidade do meio em que foi feito o spray, levando a que seja mais lenta que no caso das espumas de poliuretano de dois componentes. O estágio que me foi proporcionado pela empresa Greenseal Research, teve como principal objetivo o desenvolvimento de microcápsulas à base de sílica, inorgânicas e organicamente modificadas (híbridas), contendo um composto encapsulado, com o intuito de serem aplicadas em espumas de poliuretano de um componente, numa tentativa de aumentar a velocidade do seu processo de cura. O composto a encapsular, glicerol, contém grupos O-H que vão contribuir para o processo de cura. Durante o processo de spray do poliuretano, as microcápsulas deverão ser quebradas mecanicamente, devido à diferença de pressão a que se encontram no interior da lata e a pressão a que são sujeitas no exterior. Após a quebra das microcápsulas, o composto encapsulado é libertado, entrando em contacto com o pré-polímero e, em conjunto com a humidade do meio ambiente, contribuir para o processo de cura da espuma, acelerando-o. Foram sintetizadas e caracterizadas diversas microcápsulas ao longo deste trabalho. Para a sua síntese foi utilizada a técnica sol-gel, combinada com a tecnologia das emulsões. Esta técnica baseia-se na polimerização de um percursor (alcóxido), previamente hidrolisado, em torno das gotículas das micro-emulsões, que contém o composto a encapsular. Observou-se que a polimerização ocorre do exterior para o interior da gotícula, levando à formação de uma cápsula que contem no seu interior o composto desejado. Através desta técnica foi possível sintetizar tanto microcápsulas inorgânicas, a partir do percursor tetraetilortossilicato, TEOS, como microcápsulas híbridas, utilizando para isso os percursores metil-trietoxisilano (MTES) e (3-glicidiloxi-propil)trimetoxi-silano (GPTMS), com funcionalidade orgânica metil e glicidilóxi, respetivamente, em conjunto com o tetraetilortosilicato. Foram também sintetizadas microcápsulas de sílica com uma dupla parede utilizando, em adição ao tetraetilortossilicato, um aminosilano. Para além das sínteses referidas, foram ainda sintetizadas microcápsulas às quais se adicionaram outros constituintes, como silicones e pó de cortiça, na tentativa de estas adquirirem algumas características dos compostos adicionados, obtendo-se as propriedades desejadas. Foram ainda feitos estudos de vários parâmetros reacionais, como a possibilidade de adição de dois tensioactivos, um em cada fase da emulsão (dispersa e contínua), a adição de um catalisador, a quantidade de tensioactivo a adicionar, entre outros, numa tentativa de conseguir otimizar o processo de encapsulação e as características das cápsulas, diminuir os custos de produção das mesmas e ainda tentar aumentar o rendimento da reação. Na fase de incorporação das microcápsulas nas latas de espuma foi necessário ter em atenção alguns aspetos, de modo a garantir que a qualidade e tempo de vida do material dentro da lata não diminuíssem com a adição das microcápsulas. Foi assim necessário garantir que as microcápsulas não se encontrassem agregadas, nem apresentarem grandes dimensões, o que poderia levar à ocorrência de acumulação das mesmas com consequente obstrução do “nozzle” logo após o primeiro “spray”, impossibilitando uma posterior utilização da lata. Foi ainda necessário garantir que o composto encapsulado não estava a ser libertado do interior das cápsulas, o que, caso acontecesse, levaria à cura antecipada do pré-polímero ainda dentro da lata, inviabilizando o produto. A libertação do glicerol prévia ao “spray”, pode ocorrer quer por saída do mesmo através dos poros da cápsula, quer por quebra das microcápsulas no interior da lata. Durante o estágio foram utilizadas diversas técnicas de caracterização químicas e físicas. A técnica “microscopia electrónica de varrimento”, permitiu caracterizar as microcápsulas ao nível morfológico, ou seja se estas são mononucleadas, polinucleadas ou se do tipo matriz porosa, perceber se existe e qual o nível de aglomeração das microcápsulas e ainda ter uma noção da sua dimensão e da sua gama de tamanhos. A técnica de espectroscopia de infravermelho por transformada de Fourier permitiu a deteção de grupos químicos específicos nas microcápsulas, o que possibilitou confirmar a existência de determinados compostos e assim a ocorrência de algumas reações químicas durante a síntese. Esta técnica foi ainda importante pois permitiu ter uma noção da quantidade do composto encapsulado, por comparação da banda correspondente aos grupos O-H e das restantes bandas relativas ao glicerol, entre espectros de diferentes sínteses. No entanto a análise termogravimétrica foi fundamental para obter uma noção quantitativa do glicerol encapsulado. Foram ainda feitos alguns testes, previamente desenvolvidos na Greenseal Research, que permitiram perceber se as microcápsulas apresentavam lixiviação e ainda qual a contribuição das mesmas para o processo de cura das espumas. As microcápsulas de sílica apresentam uma forma esférica perfeita, pouca aglomeração e são as cápsulas que apresentam maior quantidade de glicerol encapsulado, no entanto são de grandes dimensões e apresentam um grau de lixiviação não aceitável para a aplicação, levando a uma diminuição significativa do tempo de vida da lata. Comparativamente, as microcápsulas que foram obtidas com os percursores metil-trietoxisilano e (3-glicidiloxi-propil)trimetoxi-silano não apresentam uma forma esférica perfeita e encontram-se mais aglomeradas, no entanto, no geral, apresentam tamanhos mais pequenos e foi observada menos lixiviação. Ainda, em alguns casos, as microcápsulas híbridas aparentam conter uma quantidade de glicerol idêntica à observada nas microcápsulas de sílica. Finalmente, as microcápsulas de sílica com uma dupla parede de amino-sílica apresentam-se como uma boa opção para a aplicação em espumas de poliuretano, uma vez que são poli-nucleadas, apresentam uma forma esférica perfeita, baixa aglomeração, reduzida lixiviação e promovem uma significativa aceleração da cura das espumas. No entanto foi observado que a utilização de um “nozzle” durante o spray, contribui para uma maior quebra das microcápsulas e consequente libertação do composto encapsulado, uma vez que, especialmente as microcápsulas mais pequenas, têm dificuldade em ser quebradas pela diferença de pressão. Na fase final do estágio foi realizado um estudo prévio ao “scale-up”, i.e. a quantidade de reagentes foi aumentada para o dobro, da síntese de microcápsulas de sílica com uma segunda parede de amino-silica. Após diversas tentativas, é possível considerar que o “scale-up” foi bem conseguido, tendo sido obtidas microcápsulas idênticas às da síntese prévia ao “scale-up” e um aumento da quantidade de microcápsulas obtidas para aproximadamente o dobro. Com a utilização de um “nozzle” durante o processo de “spray”, foi observada uma diminuição no tempo de cura da espuma de cerca de 30 minutos com a aplicação das microcápsulas, por comparação com a espuma de referência, o que corresponde a uma diminuição de 44% no tempo necessário para a cura da espuma. Como estudos futuros, poder-se-ia tentar obter microcápsulas de sílica com uma dupla parede de amino-silica, do tipo “core-shell”, numa tentativa de conseguir encapsular maior quantidade de glicerol, ao mesmo tempo que se mantém a resistência mecânica típica destas cápsulas. Ainda, poderia ser interessante, tentar encapsular um catalisador, em conjunto com o glicerol, de modo a tornar a aceleração do processo de cura, das espumas contendo microcápsulas, ainda mais significativa.
The main purpose of this work was to produce microcapsules, with an encapsulated curing agent, to incorporate in one component polyurethane foams, in order to accelerate the foam curing process. During this work, inorganic silica based microcapsules and also those organically modified (hybrid composition) were produced, by an approach that combines the micro-emulsion technique with the sol-gel method. Varied newly developed shell compositions have been screened and assessed. In particular, the addition of silicones and cork powder to the synthesis was studied, in an attempt to combine and achieve desired properties. Also, several reactional parameters were studied, in order to optimize the microencapsulation process and microcapsule features, reduce the synthesis costs and increase the reaction yield. In a final part of this work, a “pre-scale-up” of a previous selected synthesis was made. All the microcapsules were subjected to physical and chemical characterization technics. Scanning electron microscope, SEM, analysis was used to characterize the microcapsules regarding their morphology, size and agglomeration. The Fourier transform infrared spectroscopy, FTIR, characterization was useful to understand the molecular structure of the shell, in order to confirm the presence of certain reactional groups. The FTIR technique has also enabled to compare, between different syntheses, the amount of glycerol that was encapsulated, however the thermogravimetric analysis, TGA, characterization was fundamental to have a precise notion of its amount. The other characterization techniques employed in this work had been previously developed at Greenseal Research and were aimed at studying the leaching of the encapsulated compound, as well as evaluating the effect of the microcapsules on the OCF foams. The hybrid (organically modified) microcapsules did not have a perfect spherical shape and most of them were agglomerated. Nevertheless, they exhibited a lower leaching, when comparing with inorganic silica based ones, and, in some cases, the amount of encapsulated glycerol was almost the same. Finally, the silica based microcapsules with a second shell of amino-functional silica were found to be the best choice to apply in polyurethane foams, since the microcapsules had a perfect spherical shape, were not very aggregated, were poly-nucleated, did not exhibit significant leaching and led to a significant increase in the curing rate.

碩士
中國文化大學
材料科學與製造研究所
87
The open cell rigid polyurethane (PU) foam for vacuum insulation panel which have high thermal resistance and without any CFCs or HCFCs blowing agent have been studied in this research. The objectives were to find the optimization composition of open cell rigid polyurethane raw material and the foam physical properties. The effect factors of composition and properties include the ratio of isocynate and polyether; stirring speed, mixing temperature and additives. The solid fraction was found to increase as the mixing temperature increasing. The ratio of isocynate and polyether between 1.1 and 1.2, the solid fraction was less then other ratios. In this research, the ratio of open cell was found almost 100%, however, there had non-uniformity cell size, over reaction those problem.

碩士
中國文化大學
造紙印刷研究所
85
The open cell rigid polyurethane (PU) foam for vacuum insulationpanel (VIP) which contain non-CFCs or non-HCFCs and with high thermal resistancehave been studied in this research. The objective was to identify factorswhich influence the batch manufacture efficiency and the thermal conductivityperformance of the PU vacuum insulation panels.The thermal conductivity performancesof vacuum insulation panels were experimentally investigated. the changeof thermal conductivity of PU VIPs are as functions of drying pretreatmenttemperature and time, PU foam cell size, the encapsulation barrier, getter, evacuation pressure.The VIPs have a low thermal conductivity (7.1 mW/mK), underthe 120oC, 10 minutes pretreatment, 14 mTorr evacuation pressure, the compositionof CPP/Al/PET laminated film bag and with zeolite and active carbon mixturegetters, which insulation effectiveness is four times better than those formerCFCs blowing rigid PU foam.

碩士
中國文化大學
材料科學與製造研究所
88
The objectives of this research are to identify the factors which influence the physical properties of open cell rigid polyurethane foam and find the model of thermal conductivity of PU foam. The physical properties performances of the open cell rigid PU foam were experimently inuestigated. The effect factors for the physical properties of PU foam include the ratio of isocynate , polyether and water mixing temperature, and the additives. The model of thermal conductivity of PU foam is fowrd as below： The thermal conductivities data between the thereotical caculation of model and experinently inuertigated are within 12%.

碩士
國立成功大學
航空太空工程學系
84
Auxetic foam is a new material which exhibits a negative Poisson's Ratio. It gets fatter when stretched and thinner when compressed. This novel propertyresults from its re-entrant cell shape. Auxetic foam has been fabricated by heating and compressing to force the cell rib into permanent buckle and deformation, and then the cells were converted from convex shape to re-entrantshape. The Poisson's ratio is such a fundamentally important property of a material that a negative Poisson's ratio will significantly affect the material's mechanical performance. A method of fabricating rigid auxetic foamswas developed. The microstructures, material properties, and deformation underloading of conventional foam and auxetic foam were compared by experiments. It was shown that auxetic foams have higher ultimate strength and energy absorption. Therefore, auxetic foams will be nice core materials which can enhance the impact resistance of sandwich plate.

A sampling-window based approach was developed to collect and analyze the gases evolved during fire performance testing using the cone calorimeter. For this purpose, a Fourier Transform Intra-red (FTIR) Spectroscopy system and a Novatec analyzer were coupled to the cone calorimeter. An experimental gas sampling apparatus was designed and constructed and a sampling-window based method was developed. The sampling-window based method was initially tested using blue Styrofoam samples, then a small number of intumescent materials were also examined. Using the new integrated system, spectral scans were taken with an FTIR using 30s, 45s and 60s sampling windows, during off-gasing, fire growth, steady heat release rate, and fire decay stages of cone calorimeter testing. By focusing the sampling window on a specific stage of fire development the tests indicated that high concentrations of toxic gases were evolved during sample off-gasing, before ignition. In contrast to other methods that are designed to obtain total toxic gas yield over the full course of a cone calorimeter fire performance test, the sampling-window method here allows for a greater understanding of fire gas evolution at the various stages of fire growth and development. With the cone calorimeter coupled with a preconfigured “out of the box” lightweight portable ambient air analyzer and the sampling-window based approach developed, the fire gases associated with the polystyrene (blue Styrofoam) could be identified along with a number of the fire gases typically associated with the intumescent foam. For further analysis of fire gases produced, a calibrated, lab quality FTIR, with a higher resolution than the preconfigured “out of the box” lightweight portable ambient air analyzer may be required. However the system configuration and methodology would remain the same as developed here. The sampling-window based approach developed is useful for use in the development of other gas sampling techniques and can be used with other complimentary techniques such as Gas Chromatography (GC) and Mass Spectroscopy (MS). In such a combined Cone Calorimeter-GC-MS system, the GC is used to separate the various fire gases while the MS is used to identify all the components at a molecular level, and provide a more concise analysis of evolved fire gases. It is therefore recommended that the GC-MS technique also be developed for the cone calorimeter and used to compliment the FTIR technique developed in this study.

碩士
中原大學
土木工程研究所
99
In structures, the connections of beam and column were often semi-rigid connection. Hence, this article introduced the general connections in steel structures, and illustrated how the Eurocode3 (EC3) and scholars discriminate the strength of connections. This article also shows the relationship of moment-curvature of steel structure connection models, and simulated the reaction of semi-rigid connection, and use flexible spring to control horizontal and vertical direction, and use rotate spring to control rotate direction. and then considered the internal force and internal moment of spring in Vector Form Intrinsic Finite Element (VFIFE, V-5), and could simulate the stress behavior and P–Δ effect of semi-rigid steel connections. This article use exact solution to shows the accuracy of the simulation of flexible and rotate spring, and verify the feasibility of simulation, and probe the effect of nonlinear spring into the feasibility of simulation of semi-rigid connections of beams and columns.

A research report submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in partial fulfillment of the requirements for the degree of Master of Science in Engineering Johannesburg, 2017
The development of methods which are better able to predict the effect of large scale emergent roughness elements on the flow characteristics requires a better understanding of the drag coefficient under conditions likely to occur in the field. A laboratory investigation was carried out with newly developed equipment to quantify the drag force on various shaped cylinders, as well as the drag on an individual cylinder surrounded by an array of cylinders. The relationship between the drag coefficient and cylinder Reynolds number for a single circular cylinder was found to be of similar form but larger in magnitude than the established relationship for an infinitely long cylinder; the relationship departs from the infinite cylinder relationship for low cylinder Reynolds numbers. Contrary to previous research, the results for the multiple cylinder investigation did not reveal a clear relationship between the cylinder density and drag coefficient. Equations were developed and verified with existing laboratory data. These should be improved and extended by further research for field use.
MT2017

Rigid polyurethane foam is a polymeric material which is widely used for thermal insulation in building construction and other applications. Given recent emphasis on energy conservation and efficiency, there has been continuous growth in its use over the years. This raises significant fire safety concerns since polyurethanes are inherently very flammable and prone to release toxic gases as the foam thermally decomposes and burns. To improve fire safety characteristics by reducing ignitability and flammability of the foams, various flame retardants (FR) have been introduced into base foam formulations. But with the introduction of FR agents, there has been rising concern within the fire safety community and general public regarding the overall benefits versus detrimental impacts of even commonly used FR agents. In the case of rigid polyurethane foam, however, such an assessment is difficult as there are few cross comparisons in the literature that detail the impacts of different concentrations of common fire retardants, such as brominated, phosphorus-based and expandable graphite agents, on the fire behavior, smoke development and toxic gas production for even single base foam formulations. The present experimental work focuses on a systematic evaluation of these factors using three common, commercial fire retardants added in concentrations of 0%wt, 10%wt and 20%wt to a single formulation of rigid polyurethane foam. Cone calorimeter and smoke density tests are used to simulate well ventilated and poorly ventilated fire conditions during material fire performance assessment, while FTIR, Novatech P 695 gas analyzers and TD-GC/MS methods are used to investigate the gases evolved during oxidative pyrolysis and combustion of the samples. Concentration measurements of principal fire gases such as CO, CO2, reduced O2, and NOx are combined with more detailed investigation of the volatile organic compounds generated during the fire testing. Use of gas absorption sampling followed by off-line Thermal Desorption/Gas Chromatography/Mass Spectrometry (TD-GC-MS) analysis for identification of toxic gases has proven of significant benefit in this application. The full set of data obtained provides a more comprehensive identification of the evolved products during three characteristic periods in the combustion process. As such, it expands current knowledge and provides valuable new insight and understanding of thermal degradation, combustion and smoke development, as well as overall fire performance, of fire retarded rigid polyurethane foams in well-ventilated and poorly ventilated environments.

碩士
國立成功大學
土木工程學系
105
Lightweight foam is a special kind of material with high porosity, good thermal insulation and excellent energy absorption. Foam has been widely used in lightweight structural engineering. However, due to the limitation in manufacturing, there are a variety of microstructural defects in commercially-available foams, thus reducing their engineering properties. In practice, hollow sphere foams are employed to replace the traditional foams with some microstructural defects resulting from production process. Because of the regularly-stacking microstructure of hollow sphere foams, their physical and engineering properties can be predicted more accurately. In the study, the difference in the uniaxial compressive stress-strain curves between the single-sized and dual-sized hollow sphere foams with the same relative density is discussed in detail. The commercially available finite element software ABAQUS is utilized here to conduct a series of numerical analyses. The stress-strain curves of hollow sphere foams between two rigid plates under uniaxial compression are obtained numerically. In running numerical analysis, a prescribed displacement is imposed on the rigid plates, the corresponding stresses on hollow sphere foams are calculated numerically. Furthermore, the resulting stress-strain curves of hollow sphere foams are presented and then compared to evaluate the effects of relative density and cell geometry. Numerical results show that the Young's modulus, yield strength and strain energy of dual-sized hollow sphere foams are consistently larger than those of single-sized hollow sphere foams with the same relative density.

碩士
國立成功大學
機械工程學系碩博士班
101
Spatial generalizations of planar kinematics allow us to take advantage of well-known theories in planar kinematics and extend them to their counterparts in spatial kinematics. It is known that the planar slider, the revolute-prismatic dyad, is the degeneration of the spatial cylindrical-cylindrical dyad with their axes intersected perpendicularly. We refer to this special cylindrical-cylindrical dyad as the spatial slider. This thesis investigates the spatial generalizations of the solution spaces of the planar slider mechanisms. This thesis is divided into two parts: the first part is about the rigid-body guidance problem, while the second part is about the path-generation problem. For the spatial generalization of the rigid-body guidance problem, the maximum number of design positions is four for both planar and spatial sliders. Previous research only provided numerical solutions of spatial sliders for maximum number of design positions. This thesis seeks to find all solutions in a closed form. This thesis utilizes the concept of equivalent screw triangle to obtain the equations for synthesis. It then simplifies the equations and employs the dialytic elimination method to find the closed-form solution, which is a univariate ninth-degree polynomial equation. Among the nine solutions, two are infinite roots, and one is the displacement screw of position 1 and position 2. Therefore, there are at most six real finite solutions. For the spatial generalization of the path generation problem, previous research demonstrates that spatial line guidance is the generalization of planar point guidance. The path-generation problem of planar double-slider linkage has not been studied completely. This thesis shows that the maximum number of specified lines (points) is seven for both spatial and planar problems. The maximum number of specified lines for the spatial slider-crank linkage has been shown to be eight, which is the same as the planar case. We also utilize the concept of equivalent screw triangle to obtain the equations for synthesis. These equations are too complicated to be solved analytically; therefore, we can only obtain numerical solutions. Numerical examples with animations using CAD programs are provided to confirm the validity of the results. This thesis solves complete- and incomplete-specified displacement synthesis problems and demonstrates the correspondence between the planar and spatial slider mechanisms. Closed-form solutions and numerical solutions are provided in this thesis. The results given in thesis may lead to the discovery of more spatial generalizations of planar kinematic theories.