In a recent study, an environment-friendly material, corrugated cardboard, was used as a building block for the vibration isolator with a preliminary study. The present thesis was motivated to advance technology for improving the design of such a corrugated cardboard vibration isolator with a focus on the modeling of its stiffness and damping. In particular, this study has performed the following works: (1) improving the FE (finite element) model of the stiffness of the corrugated cardboards by more accurately identifying the material parameters in the cardboard material constitutive equation; (2) analyzing the effect of the error in geometry of the corrugated cardboards in the FE model; (3) developing the Rayleigh damping model of the corrugated cardboards and evaluating its accuracy. Several conclusions were drawn from this study: (1) the parameter identification procedure based on the inverse analysis is feasible for improving the accuracy of the model of the stiffness of the cardboard. (2) The FE model of the cardboards with a greater in-plane geometrical deflection has less vertical compressive stiffness. The geometrical deflections of the corrugated cardboards also change the condition of the contact friction stress and the compressive deformation. (3) Rayleigh damping model is accurate enough for calculating the damping of the corrugated cardboards. The contributions of the thesis include: (1) provision of a more accurate model for the compressive stiffness the corrugated cardboards, (2) finding that the friction between the cardboard and the vibrator and the geometrical error of the cardboards have a significant influence over the accuracy of the FE model, (3) finding that in practice the foregoing influence can significantly degraded the performance of the cardboards as a vibrator isolator, and (4) provision of a model for the compressive damping of the corrugated cardboards.

Rapid delivery of backfill to support underground openings attracted many mines to adopt paste backfilling methods. As a precaution to prevent liquefaction and to improve the mechanical performance of backfills, a small portion of a binder is added to the paste to form the cemented paste backfill (CPB). Recently, adding sand to mine tailings (MT) in CPB mixes has attracted attention since it enhances the flow and mechanical characteristics of the pastefill. This thesis investigates the effects of adding sand to CPB on the undrained mechanical behavior of the mixture (CPBS) under monotonic and cyclic loads. Liquefaction investigations took place at the earliest practically possible age. Beyond this age, the present research focused on characterizing the evolution of stiffness and obtaining the values of the stiffness parameters that could be useful for designing and modeling backfilling systems. The liquefaction investigation involved monotonic compression and extension triaxial tests. Neither flow nor temporary liquefaction was observed for all cemented and uncemented specimens under monotonic compression, while temporary liquefaction was observed for all specimens under monotonic extension. The addition of binder and sand to MT was found to slightly strengthen the pastefill in compression while weakening it in extension. Under cyclic loading, the addition of sand negatively impacted the cyclic resistance. However, binder was found to be more effective in the presence of sand. All specimens exhibited a cyclic mobility type of response. The evolution of effective stiffness parameters for two CPB-sand mixtures was monitored in a non-destructive triaxial test for five days. Self-desiccation was found to not be influential on the development of early age stiffness. Moreover, a framework is suggested to predict the undrained stiffness at degrees of saturation representative of the field. The credibility of the proposed test in providing stiffness parameters at representative strain levels of the field was verified.

Glaucoma is a common cause of blindness worldwide, yet the etiology of the disease is unclear. A leading hypothesis is that elevated intraocular pressure (IOP) affects the biomechanical environment within the tissues of the optic nerve head (ONH), and that the altered biomechanical environment contributes to optic nerve damage and consequent loss of vision. The biomechanical environment of the ONH is strongly dependent on the biomechanical properties of sclera, particularly scleral stiffness. However there is significant variability in reported stiffness data for human sclera. Therefore, our research goal was to measure the stiffness of human sclera and incorporate this information into finite element models of the human eye to characterize and quantify the biomechanical environment within and around the optic nerve head region at different IOP levels. Human sclera adjacent to the optic nerve head showed highly nonlinear, nearly isotropic and heterogeneous stiffness which was found to be substantially lower than that previously assumed, particularly at lower levels of IOP. The products c*c1 and c*c2, measures of stiffness in the latitudinal and longitudinal directions from the Fung constitutive model, were 2.9 ± 2.0 MPa and 2.8 ± 1.9 MPa, respectively, and were not significantly different (two-sided t-test; p = 0.795). Scleral stiffness was not statistically different between left and right eyes of an individual (p = 0.952) and amongst the quadrants of an eye (p = 0.412 and p = 0.456 in latitudinal and longitudinal directions, respectively). Three stress-strain relationships consistent with the 5th, 50th and 95th percentiles of the measured scleral stiffness distribution were selected as representatives of compliant, median and stiff scleral properties and were implemented in a generic finite element model of the eye using a hyperelastic five-parameter Mooney-Rivlin material model. Models were solved for IOPs of 15, 25 and 50 mmHg. The magnitudes of strains at the optic nerve head region were substantial at even the lowest applied IOP (15 mmHg) and increased at elevated IOPs (e.g. the third principal strain in the compliant model reached as much as 5.25% in the lamina cribrosa at 15mmHg and 8.84% in the lamina cribrosa at 50 mmHg). Scleras that are “weak”, but still within the physiologic range, are predicted to lead to appreciably increased optic nerve head strains and could represent a risk factor for glaucomatous optic neuropathy. As IOP increased from 15 to 50 mmHg, principal strains in the model with a compliant sclera increased at a lower rate than in the model with a stiff sclera. We quantified the biomechanical environment within and around the optic nerve head region using a range of experimentally measured mechanical properties of sclera and at different IOPs. We showed that IOP-related strains within optic nerve head tissues can reach potentially biologically significant levels (capable of inducing a range of effects in glial cells) even at average levels of IOP and for typical human scleral biomechanical properties.

Rapid delivery of backfill to support underground openings attracted many mines to adopt paste backfilling methods. As a precaution to prevent liquefaction and to improve the mechanical performance of backfills, a small portion of a binder is added to the paste to form the cemented paste backfill (CPB). Recently, adding sand to mine tailings (MT) in CPB mixes has attracted attention since it enhances the flow and mechanical characteristics of the pastefill. This thesis investigates the effects of adding sand to CPB on the undrained mechanical behavior of the mixture (CPBS) under monotonic and cyclic loads. Liquefaction investigations took place at the earliest practically possible age. Beyond this age, the present research focused on characterizing the evolution of stiffness and obtaining the values of the stiffness parameters that could be useful for designing and modeling backfilling systems. The liquefaction investigation involved monotonic compression and extension triaxial tests. Neither flow nor temporary liquefaction was observed for all cemented and uncemented specimens under monotonic compression, while temporary liquefaction was observed for all specimens under monotonic extension. The addition of binder and sand to MT was found to slightly strengthen the pastefill in compression while weakening it in extension. Under cyclic loading, the addition of sand negatively impacted the cyclic resistance. However, binder was found to be more effective in the presence of sand. All specimens exhibited a cyclic mobility type of response. The evolution of effective stiffness parameters for two CPB-sand mixtures was monitored in a non-destructive triaxial test for five days. Self-desiccation was found to not be influential on the development of early age stiffness. Moreover, a framework is suggested to predict the undrained stiffness at degrees of saturation representative of the field. The credibility of the proposed test in providing stiffness parameters at representative strain levels of the field was verified.

The research presented in this thesis is to evaluate the feasibility of demountable shear connectors as an alternative to welded shear connectors in composite structures through push off tests and composite beam tests. Push off tests were conducted to examine the shear strength, stiffness and ductility of demountable shear connectors in composite structures. The experimental results showed that demountable shear connectors in composite structures have very similar shear capacity to welded shear connectors. The shear capacity was compared against the prediction methods used for the welded shear connections given in Eurocode 4 and AISC 360-10 and the methods used for bolted connections in Eurocode 3 and ACI 318-08. It was found that the AISC 360-10 and ACI 318-08 methods overestimated the shear capacity in some cases. The Eurocode method is conservative and can be utilised to predict the shear capacity of demountable connectors in composite structures. The experimental studies of two identical composite beams using demountable shear connectors and welded shear connectors showed very similar moment capacity. However, the specimen with demountable shear connectors was more ductile compared to the welded specimen. The experimental study suggests that the methods available in Eurocode 4 and BS 5950 for predicting moment capacity and mid span deflection can be adopted for composite beam with demountable shear connectors. In addition, a finite element analysis of push off test and beam test with demountable shear connectors was also conducted for parametric studies and results are used to evaluate the behaviour of composite structures.

BACKGROUND: Arterial stiffness (AS), or loss of elastic compliance of large arteries, is an independent risk factor for cardiovascular events1. A recent study demonstrated that single nucleotide polymorphisms (SNPs) in a genetic locus downstream of the gene Bcl11b are associated with AS2. However, how this genetic locus and Bcl11b regulate AS is unknown. OBJECTIVES: To determine the molecular mechanisms by which Bcl11b effects the aortic wall and AS. METHODS: Vascular smooth muscle (VSM) cells were isolated from aortas of wildtype (WT) mice and mice with VSM-specific Bcl11b deletion (BKO). mRNA levels of Bcl11b, vascular contractile markers (myosin heavy chain 11 (MYH11), smooth muscle -actin (ACTA2), and myocardin (MYOCD)) and a cell proliferation marker (Ki67) were measured in WT and BKO VSM cells isolated from murine aortas. VSM cell contractility in response to angiotensin II (angII), a contractile stimulus, was measured in WT and BKO VSM cells using an optimized collagen gel contractility assay. RESULTS: BKO VSM cells had decreased expression of contractile markers compared to WT cells, which resulted in impaired collagen gel contraction in response to angII. CONCLUSIONS: Bc111b is expressed in aortic smooth muscle cells and it regulates the expression of VSM contractile proteins. Our data strongly supports the hypothesis that Bcl11b regulates AS by regulating the contractile function of VSM cells in the aortic wall. / 2019-07-11T00:00:00Z

This candidate thesis reports the findings of a study on an objective method for measuring grip stiffness in carton board packages with different geometries and material properties. Syntouch Biotac and a tensile tester were used as an objective method for measuring grip stiffness. In this project tests were carried out on packages with three different grammages and two different geometries. For each grammage and geometry, ten packages were tested. The study identifies that the applied method for the measurement of grip stiffness works to measure the change in grip stiffness regardless of where a load was applied on a package. Furthermore, the method demonstrates reasonable results. Finally, the study concluded that the objective testing method could distinguish between different material properties and geometries of the cartons being measured. / En studie om en objektiv metod för mätning av greppstyvhet hos kartongförpackningar med olika geometrier och materialegenskaper rapporteras här. Syntouch Biotac och en provdragare användes som objektiv metod för mätning av greppstyvhet. I detta projekt utfördes tester på förpackningar med tre olika materialegenskaper (ytvikter) samt två olika geometrier. För varje ytvikt och geometri testades tio förpackningar. Studien visar att den maskinbaserade metoden för mätning av greppstyvhet fungerar för att mäta förändring i greppstyvhet oberoende av på var tryck appliceras på förpackningen. Dessutom påvisade studien rimliga resultat. I studien kom författarna även fram till att den maskinbaserade metoden kan skilja olika materialegenskaper och geometrier åt, vilket är verifierar metoden.

abstract: Robotic joints can be either powered or passive. This work will discuss the creation of a passive and a powered joint system as well as the combination system being both powered and passive along with its benefits. A novel approach of analysis and control of the combination system is presented. A passive and a powered ankle joint system is developed and fit to the field of prosthetics, specifically ankle joint replacement for able bodied gait. The general 1 DOF robotic joint designs are examined and the results from testing are discussed. Achievements in this area include the able bodied gait like behavior of passive systems for slow walking speeds. For higher walking speeds the powered ankle system is capable of adding the necessary energy to propel the user forward and remain similar to able bodied gait, effectively replacing the calf muscle. While running has not fully been achieved through past powered ankle devices the full power necessary is reached in this work for running and sprinting while achieving 4x’s power amplification through the powered ankle mechanism. A theoretical approach to robotic joints is then analyzed in order to combine the advantages of both passive and powered systems. Energy methods are shown to provide a correct behavioral analysis of any robotic joint system. Manipulation of the energy curves and mechanism coupler curves allows real time joint behavioral adjustment. Such a powered joint can be adjusted to passively achieve desired behavior for different speeds and environmental needs. The effects on joint moment and stiffness from adjusting one type of mechanism is presented. / Dissertation/Thesis / Doctoral Dissertation Mechanical Engineering 2017

Humans have a complex musculoskeletal arrangement which gives them great behavioural flexibility. As well as simply moving their legs, they can modulate the impedance of them. Variable impedance has become a large field in robotics, and tailoring the impedance of a robot to a particular task can improve efficiency, stability, and potentially safety. Locomotion of a bipedal robot is a perfect example of a task for which variable impedance may provide such advantages, since it is a dynamic movement which involves periodic ground impacts. This thesis explores the creation of two novel bipedal robots with variable impedance joints. These robots aim to achieve some of the benefits of compliance, while retaining the behavioural flexibility to be truly versatile machines. The field of variable impedance actuators is explored and evaluated, before the design of the robots is presented. Of the two robots, BLUE (Bipedal Locomotion at the University of Edinburgh) has a 700mm hip rotation height, and is a saggital plane biped. miniBLUE has a hip rotation height of 465mm, and includes additional joints to allow hip adduction and abduction. Rapid prototyping techniques were utilised in the creation of both robots, and both robots are based around a custom, high performance electronics and communication architecture. The human walking cycle is analysed and a simple, parameterised representation developed. Walking trajectories gathered from human motion capture data, and generated from high level gait determinants are evaluated in dynamic simulation, and then on BLUE. With the robot being capable of locomotion, we explore the effect of varying stiffness on efficiency, and find that changing the stiffness can have an effect on the energy efficiency of the movement. Finally, we introduce a system for goal-based teleoperation of the robots, in which parameters are extracted from a user in a motion capture suit and replicated by the robot. In this way, the robot produces the same overall locomotion as the human, but with joint trajectories and stiffnesses that are more suited for its dynamics.

Submitted by Simone Souza (simonecgsouza@hotmail.com) on 2017-10-13T16:36:18Z No. of bitstreams: 1 DISS_2014_Rainy da Conceição Soares.pdf: 11654773 bytes, checksum: 5a6226e8b1e735f46252986260c5691e (MD5) / Approved for entry into archive by Jordan (jordanbiblio@gmail.com) on 2017-11-07T12:05:07Z (GMT) No. of bitstreams: 1 DISS_2014_Rainy da Conceição Soares.pdf: 11654773 bytes, checksum: 5a6226e8b1e735f46252986260c5691e (MD5) / Made available in DSpace on 2017-11-07T12:05:07Z (GMT). No. of bitstreams: 1 DISS_2014_Rainy da Conceição Soares.pdf: 11654773 bytes, checksum: 5a6226e8b1e735f46252986260c5691e (MD5) Previous issue date: 2014-05-09 / CNPq / Há muito tempo sabe-se que a resistência da madeira varia com seu teor de umidade. Com o aumento do teor de umidade da madeira observa-se uma diminuição em sua resistência mecânica, esta variação na resistência é mais sensível para baixos teores de umidade, e é praticamente desprezível para elevados teores de umidade. Decorre deste fato, que para comparar a resistência de duas espécies, ou peças, a uma determinada solicitação, é necessário estabelecer-se um teor de umidade de referência, pois uma espécie de menor resistência, com baixo teor de umidade, pode aparentar maior resistência que uma espécie sabidamente mais resistente, porém com elevado teor de umidade. A atual norma brasileira para o projeto de estruturas de madeira adota, para referência, o teor de umidade de 12%, para o qual devem ser reportados todos os resultados de ensaios. A hipótese deste trabalho é a de que reportar resultados de ensaios feitos em madeira verde, ao teor de umidade de referência, pode produzir erros bem superior a 10%, portanto, inaceitáveis ao calculo de estruturas de madeira. O procedimento adequado seria fazer uma secagem inicial, em clima padrão (Temperatura de 202oC e umidade relativa de 655%), até estabilização da massa, ou seja, até atingir a umidade de equilíbrio com o ambiente, antes de fazer os ensaios. O objetivo deste trabalho foi mostrar que os resultados de ensaios realizados com madeira muito úmida, ou seja, com teor de umidade acima do limite de saturação das fibras, não podem ser adequadamente corrigidos para o teor de umidade de referencia de 12%, pois o erro cometido nessa correção pode superar 10%. Para isto, foram comparados resultados, corrigidos ao teor de umidade de referência, de ensaios realizados em madeira seca ao ar e condicionada (valores já próximos a 12% de umidade) com os obtidos em madeira muito úmida, no caso saturada em água. Para dar consistência estatística foram utilizadas 10 espécies diferentes de madeira. De cada espécie foram realizados ensaios de compressão paralela (resistência e rigidez), cisalhamento e densidade aparente, nas três condições de umidade já definidas. Utilizando-se como variável o “erro relativo”, tomando por base o valor corrigido, por expressões já validadas na literatura para o intervalo de umidade entre 10 e 20%, a partir da situação “madeira condicionada”, foi aplicado o teste de Tukey, cujos resultados indicam que as correções feitas a partir das situações “madeira condicionada” e “madeira seca ao ar” são estatisticamente equivalentes e diferem das correções feitas a partir da situação “madeira saturada”. Conclui-se, dessa forma, que para reportar valores à umidade de referência não se pode partir de ensaios em madeira com elevado teor de umidade, os corpos-de-prova devem estar condicionados ou secos ao ar. / For a long time it is known that the wood strength varies with its moisture content. Increasing wood moisture content occurs a decrease in its mechanical strength, this variation in resistance is more sensitive to low levels of moisture content, and is practically negligible to high levels of moisture content. Happens from this fact, that to compare two species strength, or wooden pieces, to a specific request, it is necessary to establish a reference moisture content, because a lower strength species, with low moisture content, can to present higher strength that a greatest strength species, but with higher moisture content. The current Brazilian Code for the timber structures design adopts for reference, the 12% moisture content, to which all tests results must be reported. The hypothesis of this work is that when reporting results of tests made in wood green, to the 12% moisture content, the errors can be superior to 10%, therefore, unacceptable to timber structures design. The proper procedure would be to make an initial drying, on standard weather, until mass stabilization, that is, until it reaches the moisture content equilibrium with the environment, before making the tests. The objective of this work was to show that the results of tests conducted with very wet wood, i.e. with moisture content above the fibers saturation limit, cannot be adequately corrected for the 12% reference moisture content, because the error committed in this correction can overcome 10%. To this, results of tests conducted in air-dried wood and conditioned (values already close to 12% moisture content) were compared with those obtained in very wet wood, in this case wood saturated in water. These results were previously reported at reference moisture content. For statistical consistency were used 10 different species of wood. Of each species were conducted tests of compression parallel to the fibers (strength and stiffness), shear strength and specific gravity, on the three defined conditions for moisture. Using as variable the “relative error”, on the basis of the corrected value by expressions, already validated in the literature for the moisture interval between 10 and 20%, from the situation “conditioned wood”, Tukey test was applied and the results indicate that the corrections made from the situations "conditioned wood" and " air-dried wood" are statistically equivalents, but differ from corrections made from the situation "saturated wood". It is concluded, therefore, that to report tests results to the moisture content reference, these results can’t be obtained from tests on high moisture content wood. The specimens must be conditioned or air-dried before.