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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Energy absorption for crashworthiness in carbon-fibre braided composite structures

Lazarus, Simon David January 2004 (has links)
In this investigation the effects of material, structural and testing parameters of carbon epoxy braided composite tubes were analysed with respect to their performance in crush and impact conditions. An original method of manufacturing the composite tubes with vacuum infusion together with an expandable foam core to form multi-cellular structures was used. Low cost, 24k tow carbon fibre braids were used and their performance was compared with that of the more expensive l2k tow size fibres. The specimens produced were axially crushed at constant quasi-static low velocities and at higher impact velocities using an instrumented falling weight machine. Load displacement data gathered from such tests were used to evaluate the test specimens with respect to their specific energy absorption values. The effects of a number of parameters including fibre tow size, braid architecture, resin content and loading type were evaluated. From the experimental results analysed from the test specimens it can be concluded that: - The 24k fibre showed lower specific energy absorption values than specimens made from l2k fibre. Epoxy resin content rather than epoxy resin type can significantly affect the specific energy absorption values. In general, specimens tested in impact loading exhibited lower specific energy absorption values than the same specimens test in quasi-static crush. A reasonably good correlation between global density and specific energy absorption for the type of structures examined was found
2

Rock behaviour of the Bushveld Merensky Reef and the design of crush pillars

Watson, Bryan Philip 03 May 2011 (has links)
PhD, Faculty of Engineering and the Built Environment, University of the Witwatersrand, 2010 / The aim of this investigation was to provide a proper design procedure for Merensky crush pillars, based primarily on underground measurements. Three sites with a variety of geotechnical conditions were selected. An interaction between the pillars and the rock mass around the stopes was shown by the literature, relevant laboratory tests and numerical modelling. During the investigations, nonlinear rock behaviour was observed at one of the sites. Further studies revealed that nonlinear behaviour also occurred in samples extracted from high stress conditions at the other sites, but the rock mass was not nonlinear at these sites. A methodology for determining stress from strain measured in nonlinear rock was established. The research also established that there is an approximately linear relationship between peak pillar strength and w/h ratio at ratios between about 1.2 and 8. The so called ‘squat’ effect is not observed because pillar failure is not contained within the pillar but extends into the foundations. A linear peak pillar strength formula was established from back analyses of underground pillar failures and was confirmed by numerical modelling. Pillar behaviour was established from underground measurements on one stability pillar and six crush pillars, which included peak and residual strengths. Also, stable and unstable loading conditions were established from an analysis of pillar bursts and the minimum strata stiffness for stable pillar failure was determined. This stiffness is only achieved near the advancing face and pillars that fail in the back areas are likely to burst. For this reason, pillar design needs to include the peak strength as large pillars may be too strong and fail in the back area. The residual strength also needs to be considered as the load-bearing capacity of these pillars needs to satisfy the criterion of 1 MPa across the stope to prevent back-breaks. This translates into a pillar stress of between 8 MPa and 13 MPa if the pillar lines are spaced 30 m apart. The peak and residual requirements have been included in a design chart, and the relationship between w/h ratio and residual strength is provided in a graph for easy design.
3

From rifting to current collision, vertical movement and propagation of deformation in the Zagros belt, Iran : insights from section balancing and detrital low-temperature thermochronology / Du rifting à la collision actuelle, étude des mouvements verticaux et de la propagation de la déformation dans la chaîne du Zagros, Iran : apports des coupes équilibrées et de la thermochronologie détritique basse température

Wrobel-Daveau, Jean-Christophe 10 November 2011 (has links)
Mon travail dans la chaîne du Zagros (Iran) a été double. D'une part, d'après des évidences de terrain dans la "Crush Zone" de Kermanshah, j'ai pu décrire des "Carbonates allochtones" (pré-rift) "Crétacé-moyens" et des sédiments pélagiques liasiques (syn-à post-rift), tous deux exposés sur du manteau serpentinisé. Ceci nous a conduit à proposer l'existence de manteau exhumé le long de failles de détachement dans ce domaine, au moins pendant la phase tardive de rifting, et très probablement un renouvellement de ce processus plusieurs fois au cours de l'histoire de la Téthys. Ceci induit une nouvelle compréhension de la géométrie initiale de la paléo-marge Arabe et des relations structuralles actuelles dans ce domaine. Dans ce schéma, la plate-forme Bisotoun était initialement situé entre le bassin sub-océanique sur manteau exhumé d'Harsin (au sud-ouest) et la Néo-Téthys (au nord-est). D'autre part, j'ai modélisé l'évolution cinématique conduisant à la formation de la ZFTB, à partir de la quantification des mouvements verticaux basée sur la thermochronologie détritiques basse température [AFTA et (U-Th) / He sur apatite et de zircon] et la construction de coupes équilibrées. La construction de deux principaux transects régionaux à l'échelle crustale dans le Lurestan et le Zagros Central, basé sur une description détaillée du style structural, a notamment permis de souligner l'absence probable du décollement basal régional "Hormuz" sous le Lurestan, la présence d'un duplex sédimentaires sous la structure du Mongasht dans le Zagros central et l'existence probable de grabens crustaux inversés à l'avant de la chaîne. La combinaison d'un modèle cinématique forward basé sur des contraintes géométriques et des méthodes thermochronologiques a permis de proposer une propagation vers l'avant de l'exhumation au sein de la marge Arabe entre 14 et 2 Ma. Cette chronologie a finalement été étendu aux régions voisines du Fars et du Kurdistan irakien, sur la base de la modification de deux autres section, apportant ainsi un nouvel aperçu de l'évolution régionale du Zagros. / My work in the Zagros belt (Iran) has been twofold. On the one hand, based on field evidence cropping out in the Kermanshah Crush Zone, I described “Mid-Cretaceous” carbonate “extensional allochthons” (pre-rift) and Liassic pelagic sediments (syn- to post-rift), both exposed above serpentinised mantle. This led us to propose the occurrence of mantle exhumation along detachment faults in this area, at least during the late stage of rifting, and most likely a renewal of this process several times during the history of the Tethys. This induced a new understanding of the initial geometry of the Arabian paleo-margin and of the current structural relationships in this area. In this view, the Bisotoun platform was initially located between the Harsin mantlefloored sub-oceanic-basin (to the south-west) and the Neo-Tethys (to the north-east). On the other hand, I modeled the kinematic evolution leading to the formation of the Zagros Fold-Thrust Belt (ZFTB), based on the quantification of the vertical movements with detrital low temperature thermochronology [AFT and (U-Th)/He on apatite and zircon] and section balancing. The construction of two main regional crustal-scale cross-sections in the Lurestan and the Central Zagros, based on a detailed description of the structural style, has notably permitted to emphasize the possible absence of the regional basal Hormuz décollement under the Lurestan, the presence of a sedimentary duplex under the Mongasht structure in the Central Zagros and the probable existence of inverted crustal grabens at the front of the belt. The combination of a geometric forward kinematic model and thermochronological methods has permitted to propose a forward propagation of the exhumation of the Arabian margin from 14 to 2 Ma. This chronology has finally been extended to the neighboring regions of the Fars and of the Iraqi Kurdistan, on the base of the modification of two other cross-sections, thus bringing a new regional overview of the Zagros evolution.
4

Prehospital omvårdnad vid risk för crush syndrom

Jonsson, Uno January 2012 (has links)
Sammanfattning. Bakgrund:Crush syndrome eller traumatisk rahbdomyolys är vanligt vid större naturkatastrofer som tex jordbävningar. Det kan också uppkomma när personer utsätts för tryck mot musklerna vid tex stroke, intoxikationer, byggnadsras, industriolyckor. Inom ambulanssjukvården i Sverige har vi inte någon behandlingsplan för detta tillstånd och därför kan det finnas en risk att dessa patienter inte får rätt omvårdnad. Syfte:Studiens syfte var att belysa ambulanssjuksköterskans omvårdnad vid risk för Crush syndrome. Metod:En litteraturstudie gjordes för att granska redan publicerat forskningsmaterial. Sökningarna gjordes i databaserna Cinahl och Pubmed. Fem artiklar inkluderades och innehållet analyserades med manifest innehållsanalys. Resultat:De patienter som riskerar att få Crush syndrom har följande symtom: skada på muskelmassa, förlängd kompression, komprimerad lokal cirkulation, puls >120 och onormal urinfärg. Den viktigaste omvårdnadsåtgärden som kan vara livräddande för personen är insättande av intravenös kristalloid vätska samtidigt som personen losstages. Den vätska som rekommenderas är vanlig natriumklorid. Klinisk implikation:Ett förslag på omvårdnadsplan presenteras. Nyckelord:crush syndrome, prehospital care, prehospital omvårdnad, klämsklador, muskelskador, / Abstrakt. Background: Crush syndrome or traumatic rehbdomyolys is common in major natural disaster such as earthquakes. It can also arise when people are exposed on the muscle at such stroke, poisoning, structural collapse, industrial accidents. In prehospital care in Sweden we have no treatment plan for this condition and therefore it may be a risk that these patients not receiving the proper care. Purpose:The aim of this study was to illuminate the ambulance nurses care at risk of Crush syndrome. Method:A literature review was done to examine already published research material. The searches was made in the databases Cinahl and Pubmed. Five articles were included and the contents analyzed by manifest content analysis. Results:The patients who are at risk of Crush syndrome has the following symptoms: damage to the muscle mass, prolonged compression, compressed local circulation, heart rate > 120 and abnormal urine color. The most important nursing action that can be lifesaving is initiation of  intravenous crystalloid fluid while the person being detached. The fluid recommended is the usual sodium chloride. Clinical implication: A proposal for the nursing care plan are presented. Keywords:crush syndrome, prehospital care, crushing, muscle damage,
5

INCORPORATION OF BIO BASED FLAX FIBER REINFORCED POLYMER SKINS FOR PACKAGING ENHANCEMENTS

Sufia Suleman Sukhyani (11679325) 20 December 2021 (has links)
This thesis provides an approach to incorporate natural composites like Flax Fiber using a resin with 30% bio-content to enhance the packaging boxes made of corrugated cardboard. The objective of introducing natural composite skins is to reduce/eliminate the compressive loading subjected to the boxes while stacking in warehouses.
6

Incorporation of Bio Based Flax Fiber Reinforced Polymer Skins for Packaging Enhancements

Sukhyani, Sufia 12 1900 (has links)
Indiana University-Purdue University Indianapolis (IUPUI) / This thesis provides an approach to incorporate natural composites like Flax Fiber using a resin with 30% bio-content to enhance the packaging boxes made of corrugated cardboard. The objective of introducing natural composite skins is to reduce/eliminate the compressive loading subjected to the boxes while stacking in warehouses.
7

Lesão por esmagamento do nervo isquiático de ratos: estudo da vascularização / Crush injury of the rat sciatic nerve: vascularization study.

Pachioni, Celia Aparecida Stellutti 30 May 2006 (has links)
Este trabalho teve como objetivo estudar as alterações microvasculares intraneurais agudas em nervo isquiático de rato submetido à esmagamento por diferentes cargas. Foram utilizados sessenta ratos machos da linhagem Wistar, distribuídos em dois grupos experimentais de acordo com o protocolo de injeção de vasos e subdivididos de acordo com a carga de esmagamento. Os nervos isquiáticos direitos de cada grupo experimental foram isolados e submetidos ao esmagamento com diferentes cargas (0,5 Kg, 1 Kg, 5 Kg, 10 kg e 15 kg) por 10 minutos e os nervos isquiáticos esquerdos foram utilizados como controle. Após o esmagamento, 30 animais foram submetidos ao Protocolo I, que constou de: cateterização da aorta abdominal, perfusão manual da solução composta de tinta da China e gelatina 5% em formol 10%, dissecação e retirada dos nervos direitos e esquerdos, desidratação e diafanização para análise longitudinal dos vasos intraneurais. Os outros trinta animais foram submetidos ao Protocolo II, que constou de: cateterização da aorta abdominal e perfundidos com solução composta de tinta da China e gelatina 5% em soro fisiológico e, após, mantidos em freezer -20°C por uma hora. Em seguida os nervos foram dissecados e retirados em toda a sua extensão, cortados em 3 fragmentos, congelados em isopentano em gelo seco e armazenados em freezer -70°C, seccionados em cortes transversais semi-seriados em criostato para análise e contagem dos vasos intraneurais. Os resultados mostraram regiões de hematoma endoneural e epineural nas diferentes cargas utilizadas indicando que as forças de esmagamento foram suficientes para lesar os vasos intraneurais do nervo isquiático, especialmente com cargas elevadas. A análise morfométrica mostrou um comportamento diferente nas três regiões estudadas, constatando menor número de vasos na região do esmagamento e não nas regiões acima e abaixo da mesma. Estes resultados sugerem lesão localizada dos vasos intraneurais que foi proporcional à carga de esmagamento, causando hematoma endoneural e epineural, o que criará um microambiente desfavorável para a regeneração das fibras nervosas que também foram lesadas nesse modelo. / The objective of this work was to study the acute intraneurial microvascular changes in the rat sciatic nerve submitted to a crush injury by different loads. Sixty Wistar male rats were used and distributed into two experimental groups according to vessel injection protocol and subdivided according to the crush load. The right sciatic nerves of each experimental group were isolated and submitted to crush by different loads (0,5 Kg, 1 Kg, 5 Kg, 10 kg and 15 kg) for ten minutes. The left sciatic nerves were used as controls. After the crush, thirty animals were submitted to Protocol I, which consisted of: abdominal aorta catheterization, manual perfusion withf a solution composed of China ink and gelatin 5% in formaldehyde 10%. After that the right and left nerves were collected, fixed in formaldehyde10%, dehydrated and diaphanized for longitudinal analysis of the intraneurial vessels. The other thirty animals were submitted to Protocol II, which consisted of: abdominal aorta catheterization, as described above and perfused with a solution of China ink and gelatin 5% in physiologic saline and then placed in a freezer at -20°C for one hour. After that the nerves were dissected and removed in their entire length, cut into three fragments, frozen in isopentane and dry ice and placed in a freezer at -70°C, cut in semi-serial histological transverse sections for analysis and intraneurial vessel quantification.The results showed endoneurial and epineurial haematoma areas in the different groups, indicating that the crush forces were enough to damage the intraneurial vessels, specially with high loads. The morphometrical analysis showed a different profile in the three fragments, with smaller number of vessels in the crush region then above and below, suggesting that the damage to intraneurial vessels was proportional to the crush load, causing endoneurial and epineurial haematoma, which creates an unfavorable microenvironment for the regeneration of the nerve fibers that were also damaged in that model.
8

Understanding and predicting alcohol yield from wheat

Misailidis, Nikiforos January 2010 (has links)
Bioethanol is a promising renewable biofuel and wheat is currently the main candidate asthe feedstock for its production in the UK context. The quality of the numerous varieties ofwheat developed in the past by plant breeders has been well examined in terms of bread, biscuitand pasta producing industries. In general, the end-use quality determination of wheat in termsof alcohol yield is less investigated. This work focused on understanding and predicting thealcohol yield from wheat according to its physical, physicochemical and chemicalcharacteristics. The research ran alongside the GREEN Grain project and utilised its wheatsamples, which consist of a range of wheat varieties, agronomic regimes and growing sitesfrom four harvests years 2005-2008. The combined dataset consists of a diverse range ofchemical, physicochemical and physical characteristics of the GREEN Grain wheats. An initial multivariate analysis (PCA) indicated that the first principal component, whichexplains most of the variability of the wheat characteristics, is related with the classification ofwheat as hard or soft. High alcohol yielding wheats typically have high starch, mealiness andalbumin+globulin fraction, and also low protein, gliadin fraction and hardness. They also havelarger and more spherical kernels. Analysis of Variance (ANOVA) was applied in order to identify differences between thevarieties, the sites and the application or not of N fertiliser. The ANOVA showed that theapplication of N fertiliser increases all the protein components, although it increases the Gliadinand the LMW glutenins more. N fertiliser also yields smaller (TGW, width, depth) and moreelongated kernels. High alcohol yielding varieties tend to be softer with lower protein andlarger and more spherical kernels. This consistent variability allowed prediction of the alcoholyield based on easily measured parameters. The following model, based on the SKCS reportedvalues plus protein, could predict the alcohol yield with an R2 of about 78%:Alcohol yield = 466.62 - 5.07 × Protein - 0.21 × hardness + 11.6 × diameter ±6.94 l/dry tonIt is frequently hypothesised that larger and more rounded kernels produce more alcoholbecause they have a smaller relative amount of the unfermentable outer layers. In an effort totest this hypothesis, the pericarp thicknesses and the crease characteristics of the wheat sampleswere measured. It was found that pericarp thickness and crease dimensions vary with kernelsize, with significant differences between varieties. A physical model was developed thatconsiders these differences and calculates the endosperm to non-endosperm ratio. None of thevariables obtained by the physical model could be related to alcohol yield. The SKCS fundamental data were further analysed in an effort to improve the alcoholyield predictability. It was found that the averaged Crush Response Profiles are morereproducible than the hardness index itself. It was shown that the initial peak does not occurbecause of the "shell" (i.e. the bran layers) as suggested in the literature, but because of thecrease. Examination of the effects of moisture content on the aCRPs showed that their 1stquarter is equivalent to the stress-strain plots of dedicated rheological tests. The remaining partsof the curve relate to the post-failure behaviour of the kernels and with hardness as used incereal science. The aCRP parameters could improve the alcohol yield predictability of theGREEN Grain wheats to an R2 of about 82.3% and a standard error of the regression of6.3 l/dry ton. Further standardisation and calibration with respect to the moisture content and tothe size of the kernels could improve the predictions even further. Textural testing of cereals is constrained by the complexity of the wheat kernel structureand exacerbated by the between-kernel variation. The current work has demonstrated howSKCS data can be interpreted more insightfully in order to improve end-use quality predictions. The aCRP parameters clearly contain rheological information about wheats. Further research toestablish their examination by more standardised methodologies will allow effectiveinvestigation of connections between the rheological properties, chemical characteristics,processing behaviour and end-use quality prediction of wheat.
9

Nerve Regeneration Using Lysophosphatidylcholine and Nerve Growth Factor

Wood, Ryan LaVar 01 June 2016 (has links)
Peripheral nerve damage affects hundreds of thousands of people every year. This study tested the effectiveness of using lysophosphatidylcholine (LPC) in combination with nerve growth factor (NGF) to increase the healing rate of damaged left sciatic nerves in female rats. The rats were randomly divided into eight groups: Sham, Right Sciatic, Crush, LPC, LPC-NGF, Crush- LPC, Crush-NGF, and Crush-LPC-NGF. The healing of the nerves was measured by monitoring gait, electrophysiological parameters (compound muscle action potential amplitudes and nerve conductance velocities) and morphological parameters (total fascicular area, total myelinated fiber counts, fiber densities, fiber diameters, and g-ratio). Gait and electrophysiological parameters were measured three times a week. Morphological parameters were measured at three weeks and at six weeks. The LPC and LPC-NGF groups were not statistically different from the controls (Sham and Right Sciatic) at either of the morphological time points but were statistically different from the controls for the first three weeks for the electrophysiological parameters and gait. The LPC-NGF group did not differ from the LPC group at any time point for any of the parameters. Crush, Crush-LPC, Crush-NGF, and Crush-LPC-NGF groups statistically differed from the controls at week 3 for all parameters and only in the electrophysiological parameters at week 6. Crush-LPC, Crush-NGF, and Crush-LPC-NGF did not differ from each other or from the Crush group. The combination of LPC and NGF did not prove to be an effective treatment for peripheral nerve damage. Future work is recommended to test multiple injections of LPC and NGF.
10

Mechanics of Light Weight Proppants: A Discrete Approach

Kulkarni, Mandar 2012 May 1900 (has links)
Proppants are a specific application of granular materials used in oil/gas well stimulation. Employment of hard and soft particle mixtures is one of the many approaches availed by the industry to improve fracture resistance and the stability of the granular pack in the hydraulic fracture. Current industrial practices of proppant characterization involve long term and expensive conductivity tests. However, the mechanics governing the proppant pack response, in particular the effects due to material, shape and size of particles on the pack porosity, stiffness and particle fragmentation are not understood clearly. The present research embodies analytical and experimental approach to model hard (ceramic) and soft (walnut shell and/or pure aluminum) proppant mixtures by taking into account polydispersity in size, shape and material type of individual particles. The hydraulic fracture condition is represented through confined compression and flowback loads. The particle interactions clearly illustrate changes in pore space as a function of pressure, mixture composition and friction. Single particle compression tests on individual particles are carried out to obtain mechanical properties which are incorporated into the finite element models and are further correlated with the compression/crush response of the mixture. The proppant pack stiffness and particle fragmentation depends strongly on the mixture composition as illustrated in the models and experiments. The flowback models demonstrated that the formation of a stable arch is essential to pack stability. Additional variables that enhance flowback resistance are identified as: addition of softer particles to a pack, softer rock surfaces and higher inter-particle friction. The computational studies also led to the discovery of better, and more efficient pack compositions such as - short and thin pure Al needles/ceramic and the pistachio shells/ceramic mixtures. These analytical results have generated great interest and are engaged in the design of experiments to formulate future proppant pack mixtures at Baker Hughes Pressure Pumping, Tomball, TX.

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