Modification of Polypropylene/High Density Polyethylene Blend Using Nanokaolinite Clay and E-Glass Fibre: Preparation, Characterization and Micromechanical Modelling

Upgrading two widely used standard plastics, polypropylene (PP) and high density polyethylene (HDPE), and generating a variety of useful engineering materials based on these blends have been the main objective of this study. Upgradation was effected by using nanomodifiers and/or fibrous modifiers. PP and HDPE were selected for modification due to their attractive inherent properties and wide spectrum of use. Blending is the engineered method of producing new materials with tailor made properties. It has the advantages of both the materials. PP has high tensile and flexural strength and the HDPE acts as an impact modifier in the resultant blend. Hence an optimized blend of PP and HDPE was selected as the matrix material for upgradation. Nanokaolinite clay and E-glass fibre were chosen for modifying PP/HDPE blend. As the first stage of the work, the mechanical, thermal, morphological, rheological, dynamic mechanical and crystallization characteristics of the polymer nanocomposites prepared with PP/HDPE blend and different surface modified nanokaolinite clay were analyzed. As the second stage of the work, the effect of simultaneous inclusion of nanokaolinite clay (both N100A and N100) and short glass fibres are investigated. The presence of nanofiller has increased the properties of hybrid composites to a greater extent than micro composites. As the last stage, micromechanical modeling of both nano and hybrid A composite is carried out to analyze the behavior of the composite under load bearing conditions. These theoretical analyses indicate that the polymer-nanoclay interfacial characteristics partially converge to a state of perfect interfacial bonding (Takayanagi model) with an iso-stress (Reuss IROM) response. In the case of hybrid composites the experimental data follows the trend of Halpin-Tsai model. This implies that matrix and filler experience varying amount of strain and interfacial adhesion between filler and matrix and also between the two fillers which play a vital role in determining the modulus of the hybrid composites.A significant observation from this study is that the requirement of higher fibre loading for efficient reinforcement of polymers can be substantially reduced by the presence of nanofiller together with much lower fibre content in the composite. Hybrid composites with both nanokaolinite clay and micron sized E-glass fibre as reinforcements in PP/HDPE matrix will generate a novel class of high performance, cost effective engineering material.

Development of directly modulated high speed telecommunication lasers based on surface defined feedback gratings

High-speed semiconductor lasers are an integral part in the implemen- tation of high-bit-rate optical communications systems. They are com- pact, rugged, reliable, long-lived, and relatively inexpensive sources of coherent light. Due to the very low attenuation window that exists in the silica based optical fiber at 1.55 μm and the zero dispersion point at 1.3 μm, they have become the mainstay of optical fiber com- munication systems. For the fabrication of lasers with gratings such as, distributed bragg reflector or distributed feedback lasers, etching is the most critical step. Etching defines the lateral dimmensions of the structure which determines the performance of optoelectronic devices. In this thesis studies and experiments were carried out about the exist- ing etching processes for InP and a novel dry etching process was de- veloped. The newly developed process was based on Cl2/CH4/H2/Ar chemistry and resulted in very smooth surfaces and vertical side walls. With this process the grating definition was significantly improved as compared to other technological developments in the respective field. A surface defined grating definition approach is used in this thesis work which does not require any re-growth steps and makes the whole fabrication process simpler and cost effective. Moreover, this grating fabrication process is fully compatible with nano-imprint lithography and can be used for high throughput low-cost manufacturing. With usual etching techniques reported before it is not possible to etch very deep because of aspect ratio dependent etching phenomenon where with increasing etch depth the etch rate slows down resulting in non-vertical side walls and footing effects. Although with our de- veloped process quite vertical side walls were achieved but footing was still a problem. To overcome the challenges related to grating defini- tion and deep etching, a completely new three step gas chopping dry etching process was developed. This was the very first time that a time multiplexed etching process for an InP based material system was demonstrated. The developed gas chopping process showed extra ordinary results including high mask selectivity of 15, moderate etch- ing rate, very vertical side walls and a record high aspect ratio of 41. Both the developed etching processes are completely compatible with nano imprint lithography and can be used for low-cost high-throughput fabrication. A large number of broad area laser, ridge waveguide laser, distributed feedback laser, distributed bragg reflector laser and coupled cavity in- jection grating lasers were fabricated using the developed one step etch- ing process. Very extensive characterization was done to optimize all the important design and fabrication parameters. The devices devel- oped have shown excellent performance with a very high side mode suppression ratio of more than 52 dB, an output power of 17 mW per facet, high efficiency of 0.15 W/A, stable operation over temperature and injected currents and a threshold current as low as 30 mA for almost 1 mm long device. A record high modulation bandwidth of 15 GHz with electron-photon resonance and open eye diagrams for 10 Gbps data transmission were also shown.

Zum Querkrafttragverhalten von UHPC-Balken mit kombinierter Bewehrung aus Stahlfasern und Stabstahl

Ultrahochfester Beton besitzt aufgrund seiner Zusammensetzung eine sehr hohe Druckfestigkeit von 150 bis über 200 N/mm² und eine außergewöhnlich hohe Dichtigkeit. Damit werden Anwendungen in stark belasteten Bereichen und mit hohen Anforderungen an die Dauerhaftigkeit des Materials ermöglicht. Gleichzeitig zeigt ultrahochfester Beton bei Erreichen seiner Festigkeit ein sehr sprödes Verhalten. Zur Verhinderung eines explosionsartigen Versagens werden einer UHPC-Mischung Fasern zugegeben oder wird eine Umschnürung mit Stahlrohren ausgebildet. Die Zugabe von Fasern zur Betonmatrix beeinflusst neben der Verformungsfähigkeit auch die Tragfähigkeit des UHPC. Das Versagen der Fasern ist abhängig von Fasergeometrie, Fasergehalt, Verbundverhalten sowie Zugfestigkeit der Faser und gekennzeichnet durch Faserauszug oder Faserreißen. Zur Sicherstellung der Tragfähigkeit kann daher auf konventionelle Bewehrung außer bei sehr dünnen Bauteilen nicht verzichtet werden. Im Rahmen des Schwerpunktprogramms SPP 1182 der Deutschen Forschungsgemeinschaft (DFG) wurden in dem dieser Arbeit zugrunde liegenden Forschungsprojekt die Fragen nach der Beschreibung des Querkrafttragverhaltens von UHPC-Bauteilen mit kombinierter Querkraftbewehrung und der Übertragbarkeit bestehender Querkraftmodelle auf UHPC untersucht. Neben einer umfassenden Darstellung vorhandener Querkraftmodelle für Stahlbetonbauteile ohne Querkraftbewehrung und mit verschiedenen Querkraftbewehrungsarten bilden experimentelle Untersuchungen zum Querkrafttragverhalten an UHPC-Balken mit verschiedener Querkraftbewehrung den Ausgangspunkt der vorliegenden Arbeit. Die experimentellen Untersuchungen beinhalteten zehn Querkraftversuche an UHPC-Balken. Diese Balken waren in Abmessungen und Biegezugbewehrung identisch. Sie unterschieden sich nur in der Art der Querkraftbewehrung. Die Querkraftbewehrungsarten umfassten eine Querkraftbewehrung aus Stahlfasern oder Vertikalstäben, eine kombinierte Querkraftbewehrung aus Stahlfasern und Vertikalstäben und einen Balken ohne Querkraftbewehrung. Obwohl für die in diesem Projekt untersuchten Balken Fasergehalte gewählt wurden, die zu einem entfestigenden Nachrissverhalten des Faserbetons führten, zeigten die Balkenversuche, dass die Zugabe von Stahlfasern die Querkrafttragfähigkeit steigerte. Durch die gewählte Querkraftbewehrungskonfiguration bei ansonsten identischen Balken konnte außerdem eine quantitative Abschätzung der einzelnen Traganteile aus den Versuchen abgeleitet werden. Der profilierte Querschnitt ließ einen großen Einfluss auf das Querkrafttragverhalten im Nachbruchbereich erkennen. Ein relativ stabiles Lastniveau nach Erreichen der Höchstlast konnte einer Vierendeelwirkung zugeordnet werden. Auf Basis dieser Versuchsergebnisse und analytischer Überlegungen zu vorhandenen Querkraftmodellen wurde ein additiver Modellansatz zur Beschreibung des Querkrafttragverhaltens von UHPCBalken mit einer kombinierten Querkraftbewehrung aus Stahlfasern und Vertikalstäben formuliert. Für die Formulierung der Traganteile des Betonquerschnitts und der konventionellen Querkraftbewehrung wurden bekannte Ansätze verwendet. Für die Ermittlung des Fasertraganteils wurde die Faserwirksamkeit zugrunde gelegt. Das Lastniveau im Nachbruchbereich aus Viendeelwirkung ergibt sich aus geometrischen Überlegungen.

Goal sketching and the business case

This paper describes how the business case can be characterized and used to quickly make an initial and structurally complete goal-responsibility model. This eases the problem of bringing disciplined support to key decision makers in a development project in such a way that it can be instantiated quickly and thereafter support all key decision gateways. This process also greatly improves the understanding shared by the key decision makers and helps to identify and manage load-bearing assumptions.

Distributed water ingress and water potential measurements using fibre optics

We report on a distributed moisture detection scheme which uses a cable design based on waterswellable hydrogel polymers. The cable modulates the loss characteristic of light guided within a multi-mode optical fibre in response to relative water potentials in the surrounding environment. Interrogation of the cable using conventional optical time-domain reflectometry (OTDR) instruments allows water ingress points to be identified and located with a spatial resolution of 50 cm. The system has been tested in a simulated tendon duct grouting experiment as a means of mapping the extent of fill along the duct during the grouting process. Voided regions were detected and identified to within 50 cm. A series of salt solutions has been used to determine the sensor behaviour over a range of water potentials. These experiments predict that measurements of soil moisture content can be made over the range 0 to – 1500 kPa. Preliminary data on soil measurements have shown that the sensor can detect water pressure changes with a resolution of 45 kPa. Applications for the sensor include quality assurance of grouting procedures, verification of waterproofing barriers and soil moisture content determination (for load-bearing calculations).

Thinking out of the box – skills for work

Since the Dearing Report .1 there has been an increased emphasis on the development of employability and transferable (‘soft’) skills in undergraduate programmes. Within STEM subject areas, recent reports concluded that universities should offer ‘greater and more sustainable variety in modes of study to meet the changing demands of industry and students’.2 At the same time, higher education (HE) institutions are increasingly conscious of the sensitivity of league table positions on employment statistics and graduate destinations. Modules that are either credit or non-credit bearing are finding their way into the core curriculum at HE. While the UK government and other educational bodies argue the way forward over A-level reform, universities must also meet the needs of their first year cohorts in terms of the secondary to tertiary transition and developing independence in learning.

Jämförelsestudie avseende stomsystem : Ramverk eller fackverk/balk/pelar-system

Projektet omfattade en jämförelsestudie avseende stomsystem. Studien undersökte ramverk och fackverk/balk/pelar-system och genomfördes självständigt med stöttning av Ramböll AB´s kontor i Falun. Syftet var främst att undersöka vilka skillnader det finns mellan tvåledsramar och fackverk/balk/pelar-system för lätta hallbyggnader och försöka få klarhet i varför fackverk/balk/pelar-system är det dominerande systemet i Sverige eftersom övriga Europa har tagit en annan utveckling och domineras av tvåledsramar. Studien undersöker skillnaderna mellan systemen i en hallbyggnad med förutbestämda mått i stål.Inledningsvis gjordes en litteraturstudie för att få en bredare bakgrund av systemen och en bättre förståelse om förutsättningarna för varje system. Efter litteraturstudien kunde sedan ett typhus och beräkningsunderlag för jämförelsestudien tas fram. Även en enkätstudie gjordes med syftet att skapa en tydlig bild av vilket stomsystem konstruktörer i Sverige oftast väljer och varför. Resultatet av studien visade att tvåledsramar ger en ökad kostnad jämfört med fackverk/balk/pelar-system i materialåtgång och framställning samt att beräkningarna blir mer komplicerade. Skulle fortsatta studier göras med dessa system i byggnader med andra mått skulle det kanske gå att få fram speciella mått på byggnader där kostnaden för tvåledsramar blir densamma som för fackverk/balk/pelar-system och därför är ett likvärdigt alternativ som stomsystem.En viktig slutsats från projektet är att tvåledsramar används mycket mer sällan än fackverk/balk/pelar-system som stomsystem i lätta hallbyggnader i Sverige på grund av att kostnaderna blir mycket högre med tvåledsramar och att det är ett mer komplicerat system i beräkningsarbetet. De viktigaste slutsatserna från jämförelsestudien går att sammafatta som följande: Tvåledsramar är dyrare att använda. Tvåledsramar är ett mer komplicerat system beräkningsmässigt. Traditionen av att använda tvåledsramar finns inte och därför används inte systemet.

Estudo da viabilidade técnica para a Bolívia de painéis de gesso reforçados com fibra de vidro para paredes internas não portantes

Na construção civil, nos países em desenvolvimento como a Bolívia, continua-se usando técnicas e materiais na execução de paredes, similar a décadas passadas. Os painéis de gesso reforçados com fibra de vidro são uma alternativa de simplificação e agilização na execução das paredes internas não portantes. A presente dissertação objetiva mostrar a viabilidade técnica e econômica dos painéis para paredes internas, na Bolívia; para tanto realizou-se uma avaliação dos recursos disponíveis (gesso), com relação às reservas, produção e custos. A técnica adotada na produção dos painéis é a de pré-mistura, que permite a moldagem dos painéis manual ou mecanicamente com equipamentos simples e de baixo custo. O estudo do compósito de gesso reforçado com fibra de vidro (GRG) foi realizado com gesso brasileiro e com gesso boliviano, verificando-se o seu comportamento mecânico com diferentes teores de fibra de vidro. Verificou-se aumento da resistência a tração na flexão e diminuição da resistência a compressão com o aumento do teor de fibra de vidro. A avaliação do comportamento mecânico dos painéis foi feita através dos ensaios de impacto (corpo mole e corpo duro). Nos ensaios de corpo mole, verificou-se aumento da resistência com o aumento do teor de fibra de vidro. Os teores de 0,75% e 1,5% se mostraram suficientes para que os painéis de GRG satisfaçam os requisitos de desempenho para divisórias internas respectivamente para o gesso brasileiro e boliviano. O comportamento dos painéis nos ensaios de impacto de corpo duro foi satisfatório, tanto para painéis com fibra como para painéis sem fibra de vidro. No estudo preliminar de custos, verificou-se uma redução em torno de 36% para os painéis de GRG em relação às paredes intemas tradicionalmente usadas na Bolívia.

Plásticos reforçados a base de tecidos híbridos: efeitos da anisotropia e geometria normativa na caracterização mecânica e da fratura

As most current studies, reinforced plastics have been, in recent years, a viable alternative in building structural elements of medium and large, since the lightness accompanied by high performance possible. The design of hybrid polymer composites (combination of different types of reinforcements) may enable structural applications thereof, facing the most severe service conditions. Within this class of composite materials, reinforced the underlying tissues hybrid high performance are taking space when your application requires high load bearing and high rigidity. The objective of this research work is to study the challenges in designing these fabrics bring these materials as to its mechanical characterization and fracture mechanisms involved. Some parameters associated with the process and / or form of hybridization stand out as influential factors in the final performance of the material such as the presence of anisotropy, so the fabric weave, the process of making the same, normative geometry of the specimens, among others. This sense, four laminates were developed based hybrid reinforcement fabrics involving AS4 carbon fiber, kevlar and glass 49-E as the matrix epoxy vinyl ester resin (DERAKANE 411-350). All laminates were formed each with four layers of reinforcements. Depending on the hybrid fabric, all the influencing factors mentioned above have been studied for laminates. All laminates were manufactured industrially used being the lamination process manual (hand-lay-up). All mechanical characterization and study of the mechanism of fracture (fracture mechanics) was developed for laminates subjected to uniaxial tensile test, bending in three and uniaxial compression. The analysis of fracture mechanisms were held involving the macroscopic, optical microscopy and scanning electron microscopy

Influence of Implant Design on the Biomechanical Environment of Immediately Placed Implants: Computed Tomography-Based Nonlinear Three-Dimensional Finite Element Analysis

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Leaf emergences in Microlepis oleaefolia (DC.) Triana (Melastomataceae) and their probable function: An anatomical and ultrastructural study

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Friction and wear properties of functionally graded aluminum matrix composites

Aluminum matrix composites are currently considered as promising materials for tribological applications in the automotive, aircraft and aerospace industries due to their great advantage of a high strength-to-weight ratio. A superior combination of surface and bulk mechanical properties can be attained if these composites are processed as functionally graded materials (FGM's). In this work, homogeneous aluminum based matrix composite, cast by gravity, and aluminum composites with functionally graded properties, obtained by centrifugal cast, are tested against nodular cast iron in a pin-on-disc tribometer. Three different volume fractions of SiC reinforcing particles in each FGM were considered in order to evaluate their friction and wear properties. The sliding experiments were conducted without lubrication, at room temperature, under a normal load of 5 N and constant sliding speed of 0.5 ms-1. The worn surfaces as well as the wear debris were characterized by SEM/EDS and by atomic force microscopy (AFM). The friction coefficient revealed a slightly decrease (from 0.60 to 0.50) when FGM's are involved in the contact instead of the homogeneous composite. Relatively low values of the wear coefficient were obtained for functionally graded aluminum matrix composites (≈10-6 mm3N-1 m-1), which exhibited superior wear resistance than the homogeneous composite and the opposing cast iron surface. Characterization of worn surfaces indicated that the combined effect of reinforcing particles as load bearing elements and the formation of protective adherent iron-rich tribolayers has a decisive role on the friction and wear properties of aluminum matrix composites.

Failure of miniplate osteosynthesis for the management of atrophic mandibular fracture

Fractures of the severely atrophic (<10 mm) edentulous mandible are not common, and these fractures with a vertical height of 10 mm or less have long been recognized as being particularly problematic. Although there are advances in the treatment of the atrophic mandibular fracture, the treatment remains controversial. There are some options for treatment planning because of using small miniplates to large reconstruction plates. However, when the fixation method fails, it causes malunion, nonunion, and/or infection, and sometimes it has been associated with large bone defects. The authors describe a clinical report of a failed miniplate fixation for atrophic mandibular fracture management. The authors used a load-bearing reconstruction plate combined with autogenous bone graft from iliac crest for this retreatment. The authors show a follow-up of 6 months, with union of the fracture line and no complication postoperatively. © 2013 by Mutaz B. Habal, MD.

Atributos físicos do solo em áreas de plantio direto com e sem escarificação

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Implant-supported rehabilitation after treatment of atrophic mandibular fractures: report of two cases

Objective The objective of this article is to present options of rehabilitation with dental implants in two cases of severely atrophic mandibles (<10 mm) after rigid internal fixation of fractures. Patients and method Two patients who sustained fractures in severely atrophic mandibles with less than 10 mm of bone height were treated by open reduction and internal fixation through a transcervical access. Internal fixation was obtained with 2.4-mm locking reconstruction plates. The first patient presented satisfactory bone height at the area between the mental foramens and after 2 years, received flapless guided implants in the anterior mandible and an immediate protocol prosthesis. The second patient received a tent pole iliac crest autogenous graft after 2 years of fracture treatment and immediate implants. After 5 months, a protocol prosthesis was installed in the second patient. Results In both cases, the internal fixation followed AO principles for load-bearing osteosynthesis. Both prosthetic devices were Branemark protocol prosthesis. The mandibular reconstruction plates were not removed. Both patients are rehabilitated without complications and satisfied with esthetic and functional results. Conclusion With the current techniques of internal fixation, grafting, and guided implants, the treatment of atrophic mandible fractures can achieve very good results, which were previously not possible.