The purpose of this essay is to explore how different means are used to create indeterminate meaning in Henry James’s novella The Turn of the Screw. It suggests that the indeterminacy creates gaps in the text which the reader is required to fill in during the reading process, and that this indeterminacy is achieved chiefly through the use of an unreliable narrator and of ambiguity in the way the narrator relates the events that take place. The reliability of the narrator is called into question by her personal qualities as well as by narrative factors. Personal qualities that undermine the narrator’s reliability are youth, inexperience, nervousness, excitability and vanity. Narrative factors that damage the narrator’s reliability concern the story as manuscript, the narrator’s role in the story she narrates, and her line of argumentation. The ambiguity in the way events are reported is produced by ambiguous words, dismissed propositions and omissions. The essay demonstrates how the unreliable narrator and the ambiguity combine to make the reader question the narrator’s account and supply his or her own interpretation of key elements in the story, that is, how they invite the reader to “co-author” the text.

Twin-screw pumps are economical alternatives to the conventional multiphase system and are increasingly used in the oil and gas industry due to their versatility in transferring the multiphase mixture with varying Gas Void Fraction (GVF). Present work focuses on the experimental and numerical analysis of twin-screw pumps for different operating conditions. Experimental evaluation aims to understand steady state and transient behavior of twin-screw pumps. Detailed steady state evaluation helped form better understanding of twin-screw pumps under different operating conditions. A comparative study of twin-screw pumps and compressors contradicted the common belief that compressor efficiency is better than the efficiency of twin-screw pumps. Transient analysis at high GVF helped incorporate necessary changes in the design of sealflush recirculation loop to improve the efficiency of the pump. The effect of viscosity of the sealflush fluid at high GVF on pump performance was studied. Volumetric efficiency was found to be decreased with increase in viscosity. Flow visualization was aimed to characterize phase distribution along cavities and clearances at low to high GVF. Dynamic pressure variation was studied along the axis of the screw which helped correlate the GVF, velocity and pressure distribution. Complicated fluid flow behavior due to enclosed fluid pockets and interconnecting clearances makes it difficult to numerically simulate the pump. Hence design optimization and performance prediction incorporates only analytical approach and experimental evaluation. Current work represents an attempt to numerically simulate a multiphase twin-screw pump as a whole. Single phase 3D CFD simulation was performed for different pressure rise. The pressure and velocity profile agreed well with previous studies. Results are validated using an analytical approach as well as experimental data. A two-phase CFD simulation was performed for 50% GVF. An Eulerian approach was employed to evaluate multiphase flow behavior. Pressure, velocity, temperature and GVF distributions were successfully predicted using CFD simulation. Bubble size was found to be most dominant parameter, significantly affecting phase separation and leakage flow rate. Better phase separation was realized with increased bubble size, which resulted in decrease in leakage flow rate. CFD results agreed well with experimental data for the bubble size higher than 0.08 mm.

No description available.

A large number of studies have concentrated on golf swing biomechanics, ranging from planar rigid-link models to 3D kinematic analysis. A promising technique, instantaneous screw axis (ISA) theory, has not been covered in the literature and could provide a better true segment rotation approximation. The objectives of this study are to identify ISA location and orientation, as well as segment angular velocity, of the major body segments involved in the golf swing. For all subjects, it was found that the magnitude of maximum angular velocities increased from the most proximal segment (the pelvis) to the most distal segment (the left arm), in accordance with the summation of speeds principle. Furthermore, most subjects achieved their maximum angular velocities in the desired kinematic sequence, where the first maxima was achieved by the most proximal segment and followed by the more distal segments in the kinematic chain.

No description available.

A large number of bone fractures are treated with stabilisation devices that utilise metal wires or screws, which traverse the bone and are connected to an external frame or internal plate. Clinically, fixation devices are required to be able to: sustain loads; minimise patient discomfort and possible implant loosening; and promote healing. In the recent years locking plates have become increasingly popular for osteoporotic or complex fractures, which can be difficult to manage. It, however, remains unclear as to how these devices need to be configured for optimum clinical performance. This thesis investigates the mechanics of locking plates, factors that influence their performance and provides guidance to optimise the placement of screws. Finite element simulation and analytical models were developed and validated using lab-based experimental models. The local behaviour around the screw-bone interface is considered and the implications of different modelling assumptions assessed. A novel method of simulating the effect of radial interference due to pilot-hole size is proposed. Different screw types are evaluated: osteoporotic bone is found to be particularly susceptible to the screw tightening preload used in compression screws; far-cortical locking screws are found to slightly reduce device stiffness but substantially increase strain levels around screw holes. Finite element simulations show that many of the local effects, such as preloads and contact modelling, can profoundly influence the prediction of strains around screws but do not generally influence the global load-displacement behaviour; the screw-plate connection and bone/plate material and geometric properties are found to have an influence on global stiffness predictions. The key determinants of load-displacement behaviour evaluated through models are the loading and restraint conditions, which explain the huge range of stiffness predictions in the literature (three orders of magnitude). An analytical model based on 7 bone-plate construct parameters is developed. Despite its simplicity, the model is found to be able to predict the axial stiffness for experimental tests conducted and for 16 other cases from five previous studies with an average error of 20%. The manner of load application, not considered in the literature, is shown to dramatically alter predictions of plate stress, strains within the bone and conclusions regarding screw placement. Even with the inclusion of muscles forces, the choice of restraint condition dominates the mechanical behaviour. Using the models, the influence of screw position is systematically evaluated in varying bone qualities under axial loading and torsion and guidance for optimising fixation is developed.

This thesis concerns the construction of a detailed, compartmental population balance model for twin-screw granulation using the stochastic weighted particle method. A number of new particle mechanisms are introduced and existing mechanisms augmented including immersion nucleation, coagulation, breakage, consolidation, liquid penetration, primary particle layering and transport. The model’s predictive power is assessed over a range of liquid-solid mass feed ratios using existing experimental data and is demonstrated to qualitatively capture key experimental trends in the physical characteristic of the granular product. As part of the model development process, a number of numerical techniques for the stochastic weighed method are constructed in order to efficiently solve the population balance model. This includes a new stochastic implementation of the immersion nucleation mechanism and a variable weighted inception algorithm that dramatically reduces the number of computational particles (and hence computational power) required to solve the model. Optimum operating values for free numerical parameters and the general convergence properties of the complete simulation algorithm are investigated in depth. The model is further refined though the use of distinct primary particle and aggregate population balances, which are coupled to simulate the complete granular system. The nature of this coupling permits the inclusion of otherwise computational prohibitive mechanisms, such as primary particle layering, into the process description. A new methodology for assigning representative residence times to simulation compartments, based on screw geometry, is presented. This residence time methodology is used in conjunction with the coupled population balance framework to model twin-screw systems with a number of different screw configurations. The refined model is shown to capture key trends attributed to screw element geometry, in particular, the ability of kneading elements to distribute liquid across the granular mass.

A aplicação da madeira como material estrutural na construção civil é amplamente difundida em coberturas residenciais e comerciais, construção de residências ou em obras de grande porte como pontes. Freqüentemente ocorre a necessidade de ligações entre peças estruturais. Uma das possibilidades de ligação é a utilização de parafusos auto-atarraxantes solicitados por esforços de tração, diferente da maioria dos casos de ligações, nas quais pinos estão solicitados por forças laterais. Um tipo particular de parafuso auto-atarraxante é o torx, que possui rosca em toda a sua extensão, possibilitando uma outra forma de arranjo de ligação que facilita a execução das ligações entre as peças estruturais. Este parafuso possui uma grande resistência que traz à industrialização das estruturas de madeiras. O objetivo desta pesquisa é determinar, de maneira experimental, a resistência de ligações utilizando parafusos torx auto-atarraxantes submetidos a esforços axiais de tração, em peças de madeira, avaliando a influência de diversos fatores, tais como: direção de fixação dos parafusos em relação às fibras, efeito de grupo teor de umidade, massa específica da madeira e espaçamentos entre parafusos. Foram utilizadas as espécies: Pinus Taeda (Pinus taeda L.), Eucalipto Grandis (Eucalyptus grandis) e Cupiúba (Goupia glabra). / Timber as a structural material civil in construction is widely used in framework, construction of houses or larger construction as bridges. The use of connections among structural members is frequently required. One of the connection possibilities is the use of lag screws in axial withdrawal load, differently from most cases of connections in which they are laterally loaded. A peculiar type of lag screw is the torx, which possesses thread along its extension, making possible another form of connection arrangement that facilitates the execution of the connections among the structural pieces. This lag screw has a high strength and facilitates the industrialization of timber structures. The aim of this research is to determine, in an experimental way, the strength of connections using torx lag screws in withdrawal loads, evaluating the influence of several factors, such as direction of the lag screws in relation to grain, group effect, moisture content, density of wood and spacings among screws. The species used were: Pinus Taeda (Pinus taeda L.), Eucalipto Grandis (Eucalyptus grandis) and Cupiúba (Goupia glabra).

O objetivo do estudo foi avaliar a influência do diâmetro do orifício piloto e a freqüência da colocação dos implantes no torque de inserção e na resistência ao arrancamento. Foram utilizados parafusos de 5, 6 e 7mm do sistema USS de fixação vertebral, os quais foram inseridos nos corpos de prova de madeira, poliuretana, polietileno e osso bovino. Para inserção dos implantes foram confeccionados com broca orifícios piloto com diâmetros menor, igual e maior que o diâmetro interno do parafuso. O torque de inserção dos parafusos avaliado nos corpos de prova de madeira foi mensurado por meio de torquímetro com capacidade de 5Nm, e nos demais corpos de prova foi utilizado torquímetro de 2Nm. Os ensaios mecânicos de arrancamento dos parafusos foram realizados utilizando máquina universal de ensaio Emic? e Software Tesc 3.13 para análise dos resultados, utilizando células de carga com capacidade de 2000 N e 20000 N, selecionadas de acordo com a resistência mecânica de cada corpo de prova, e com velocidade de aplicação de força de 2 mm/min. Os valores do torque de inserção dos parafusos de 5, 6 e 7mm de diâmetro externo, nos diferentes materiais, apresentaram maiores valores de torque na primeira inserção, com exceção dos corpos de prova de poliuretana com orifício piloto de 5,5mm. O diâmetro do orifício piloto em relação ao diâmetro interno do parafuso apresentou influência no torque de inserção dos implantes, nos diferentes corpos de prova, observando maior torque de inserção nos corpos de prova com orifício piloto menor que o diâmetro interno do parafuso e menor torque de inserção nos corpos de prova com diâmetro do orifício piloto maior que o diâmetro interno do parafuso. A força máxima de arrancamento nos parafusos de 5, 6 e 7mm de diâmetro externo, inseridos nos diferentes corpos de prova, apresentaram maiores valores na primeira inserção nos diferentes diâmetros de orifício piloto. O diâmetro do orifício piloto em relação ao diâmetro interno do parafuso apresentou influência na força máxima de arrancamento dos implantes, nos diferentes corpos de prova, observando maior força de arrancamento nos corpos de prova com orifício piloto menor que o diâmetro interno do parafuso e menor força de arrancamento nos corpos de prova com diâmetro do orifício piloto maior que o diâmetro interno do parafuso. Podemos concluir que a freqüência de colocação dos implantes influencia na qualidade da ancoragem. A realização de menor freqüência de colocação dos implantes proporciona uma melhor fixação. A perfuração do orifício piloto com instrumental de menor diâmetro, em relação ao diâmetro interno do parafuso, tende a apresentar melhor fixação do parafuso que a perfuração com diâmetro maior. / The aim of the study was to evaluate the influence of the diameter of the pilot hole and the frequency of screw placement on pullout out resistance and insertion torque of the pedicle screw. Pedicle screws of 5, 6 and 7mm of the USS system for vertebral fixation were inserted into wood, polyurethane, polyethylene and bovine bone. The pilot hole for screw insertion was drilled with small, equal and wider than the internal diameter of the screw. The insertion torque was measured in the wood test bodies used a torquímetro with capacity of 5Nm, and other test bodies was used a torquimetro of 2Nm. Mechanical pullout assays were performed using a universal testing machine rehearsals of screws pullout were accomplished using universal machine Emic® and Software Tesc 3.13 for analysis of the results. Load cells were using with capacity of 2000 N and 20000 N, selected in agreement with the mechanical resistance of each test bodies. A constant displacement rate of 2mm/min was applied until failure. The values of the insertion torque of the screws of 5, 6 and 7mm of external diameter, in the different materials, they presented highest insertion torque in the first insert, in the different materials, except for the polyurethane test bodies with pilot hole of 5,5mm. The diameter of the pilot hole in relation to the internal diameter of the screw exerts an influence in the torque of insert of the implants. We observed highest insert torque in the test bodies with smaller pilot hole than the internal diameter of the screw and smaller insert torque in the proof bodies with diameter of the wider pilot hole than the internal diameter of the screw. The pullout resistance of the screws of 5, 6 and 7mm of external diameter performed highest values in the first screw insert, in the different diameters of pilot hole and test bodies. The diameter of the pilot hole in relation to the internal diameter of the screw exerts an influence in the pullout resistance of the implants. The highest pullout resistance was observed in the test bodies with smaller pilot hole than the internal diameter of the screw. The smaller pullout resistance was observed in the test bodies with diameter of the larger pilot hole than the internal diameter of the screw. We can conclude that the frequency of placement of the implants influences in the quality of the anchorage. The accomplishment of smaller frequency of placement of the implants provides a better fixation. The perforation of the pilot hole with instrumental of smaller diameter, in relation to the internal diameter of the screw, tends to present better fixation of the screw than the perforation with larger diameter.

Implants such as intramedullary nails or cancellous screws are used to mechanically stabilize fractures in bone. They provide reinforcement to the bone if they find good purchase in cancellous bone. Not all implants hold enough loads for mechanical stability and pull-out or cut-out may happen in some cases. This is linked to the interface between the bone and the implant. Computer modelling techniques are used to investigate both the effects of cut-out in a femur model, and the pull-out forces of cancellous bone screws. The bone geometry was based on CT scanned cancellous bone and converted using Mimics® software. The finite element models were produced in ANSYS®. Simple bone models were used to examine a fractured femur under standard gait loading. These models were continuum models and idealised the screw to bone interface in order to ease computational demand. The models were used to investigate the ideal positions of intramedullary devices lag screws on an anterior-posterior view of the implant location. In accordance with literature, an inferior-central or central-central position was the best position of the lag screw, while a superior-anterior or inferior-anterior position was adverse. The introduction of multi-scale modelling in order to investigate cut-out with a discrete bone model was not achieved. Discrete cancellous bone models were used to examine some of the cancellous screw characteristics, including pitch, inner diameter and proximal half angle, while a cancellous screw was also studied using a model of cancellous bone with a range of bone densities. The calculated reaction force for a pull-out of 0.2mm shows the influence of some parameters. Change in the proximal half angle increased the stiffness and strength by about 15% in line with the experimental findings of others, while apparent density changes of 2.5% increased the forces threefold. A significant reduction in reaction force was observed when a particular screw geometry in lower apparent density bone was modelled and rotated through 180° on a plane. Examination of the geometry of the bone/screw interface shows that in certain positions there is very little cancellous bone to support the implant. This will lead to low strength and is very difficult to predict. The same models were used to examine the effect of increasing bone stiffness adjacent to the implant and the use of a cement layer to augment the screw model. The increasing stiffness concluded that an increase in pull-out stiffness can be achieved, even in low quality bone, while the cement augmentation showed a significant increase in pull-out strength, though it was idealised as bonded to the bone and screw.