482 resultados para Finite field
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The concept of market-driven rather than product-driven quality management has been given prominence through the report of a recent inquiry into the performance of the Hong Kong construction industry. The report submitted to the Government of Hong Kong in 2001 establishes a new vision of ‘an integrated industry that is capable of continuous improvement towards excellence in the market-driven environment’. Given the current economic downturn, major contractors are facing many challenges to realize this new quality oriented vision. This paper addresses the critical and timely issue of applying quality management to the project delivery process in Hong Kong. The paper attempts to capture and critically examine management perceptions of quality management aspects as applied to a local large-scale road construction project. Based on the analysis of questionnaire feedback and face-to-face interviews, the paper reveals key attributes of a successful application of quality management approaches, and identifies a mechanism for facilitating such implementation.
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Transport processes within heterogeneous media may exhibit non-classical diffusion or dispersion; that is, not adequately described by the classical theory of Brownian motion and Fick's law. We consider a space fractional advection-dispersion equation based on a fractional Fick's law. The equation involves the Riemann-Liouville fractional derivative which arises from assuming that particles may make large jumps. Finite difference methods for solving this equation have been proposed by Meerschaert and Tadjeran. In the variable coefficient case, the product rule is first applied, and then the Riemann-Liouville fractional derivatives are discretised using standard and shifted Grunwald formulas, depending on the fractional order. In this work, we consider a finite volume method that deals directly with the equation in conservative form. Fractionally-shifted Grunwald formulas are used to discretise the fractional derivatives at control volume faces. We compare the two methods for several case studies from the literature, highlighting the convenience of the finite volume approach.
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Effective digital human model (DHM) simulation of automotive driver packaging ergonomics, safety and comfort depends on accurate modelling of occupant posture, which is strongly related to the mechanical interaction between human body soft tissue and flexible seat components. This paper presents a finite-element study simulating the deflection of seat cushion foam and supportive seat structures, as well as human buttock and thigh soft tissue when seated. The three-dimensional data used for modelling thigh and buttock geometry were taken on one 95th percentile male subject, representing the bivariate percentiles of the combined hip breadth (seated) and buttock-to-knee length distributions of a selected Australian and US population. A thigh-buttock surface shell based on this data was generated for the analytic model. A 6mm neoprene layer was offset from the shell to account for the compression of body tissue expected through sitting in a seat. The thigh-buttock model is therefore made of two layers, covering thin to moderate thigh and buttock proportions, but not more fleshy sizes. To replicate the effects of skin and fat, the neoprene rubber layer was modelled as a hyperelastic material with viscoelastic behaviour in a Neo-Hookean material model. Finite element (FE) analysis was performed in ANSYS V13 WB (Canonsburg, USA). It is hypothesized that the presented FE simulation delivers a valid result, compared to a standard SAE physical test and the real phenomenon of human-seat indentation. The analytical model is based on the CAD assembly of a Ford Territory seat. The optimized seat frame, suspension and foam pad CAD data were transformed and meshed into FE models and indented by the two layer, soft surface human FE model. Converging results with the least computational effort were achieved for a bonded connection between cushion and seat base as well as cushion and suspension, no separation between neoprene and indenter shell and a frictional connection between cushion pad and neoprene. The result is compared to a previous simulation of an indentation with a hard shell human finite-element model of equal geometry, and to the physical indentation result, which is approached with very high fidelity. We conclude that (a) SAE composite buttock form indentation of a suspended seat cushion can be validly simulated in a FE model of merely similar geometry, but using a two-layer hard/soft structure. (b) Human-seat indentation of a suspended seat cushion can be validly simulated with a simplified human buttock-thigh model for a selected anthropomorphism.
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We present a rigorous validation of the analytical Amadei solution for the stress concentration around an arbitrarily orientated borehole in general anisotropic elastic media. First, we revisit the theoretical framework of the Amadei solution and present analytical insights that show that the solution does indeed contain all special cases of symmetry, contrary to previous understanding, provided that the reduced strain coefficients b11 and b55 are not equal. It is shown from theoretical considerations and published experimental data that the b11 and b55 are not equal for realistic rocks. Second, we develop a 3D finite element elastic model within a hybrid analytical–numerical workflow that circumvents the need to rebuild and remesh the model for every borehole and material orientation. Third, we show that the borehole stresses computed from the numerical model and the analytical solution match almost perfectly for different borehole orientations (vertical, deviated and horizontal) and for several cases involving isotropic, transverse isotropic and orthorhombic symmetries. It is concluded that the analytical Amadei solution is valid with no restriction on the borehole orientation or the symmetry of the elastic anisotropy.
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Field-effect transistors (FETs) fabricated from undoped and Co2+-doped CdSe colloidal nanowires show typical n-channel transistor behaviour with gate effect. Exposed to microscope light, a 10 times current enhancement is observed in the doped nanowire-based devices due to the significant modification of the electronic structure of CdSe nanowires induced by Co2+-doping, which is revealed by theoretical calculations from spin-polarized plane-wave density functional theory.
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Urban and regional planners, in the era of globalization, require being equipped with necessary skill sets to better deal with complex and rapidly changing economic, sociocultural, political, and environmental fabrics of cities and their regions. To provide such skill sets, urban and regional planning curriculum of Queensland University of Technology, Brisbane, Australia, offers planning practice in the international context. This article, first, reports the findings of pedagogic analyses of the international field trips conducted to Malaysia, Korea, Turkey, and Taiwan. The article, then, discusses the opportunities and constraints of exposure of students to planning practice beyond the Australian context.
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Biological systems involving proliferation, migration and death are observed across all scales. For example, they govern cellular processes such as wound-healing, as well as the population dynamics of groups of organisms. In this paper, we provide a simplified method for correcting mean-field approximations of volume-excluding birth-death-movement processes on a regular lattice. An initially uniform distribution of agents on the lattice may give rise to spatial heterogeneity, depending on the relative rates of proliferation, migration and death. Many frameworks chosen to model these systems neglect spatial correlations, which can lead to inaccurate predictions of their behaviour. For example, the logistic model is frequently chosen, which is the mean-field approximation in this case. This mean-field description can be corrected by including a system of ordinary differential equations for pair-wise correlations between lattice site occupancies at various lattice distances. In this work we discuss difficulties with this method and provide a simplication, in the form of a partial differential equation description for the evolution of pair-wise spatial correlations over time. We test our simplified model against the more complex corrected mean-field model, finding excellent agreement. We show how our model successfully predicts system behaviour in regions where the mean-field approximation shows large discrepancies. Additionally, we investigate regions of parameter space where migration is reduced relative to proliferation, which has not been examined in detail before, and our method is successful at correcting the deviations observed in the mean-field model in these parameter regimes.
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Light Gauge Steel Framing (LSF) walls are made of cold-formed, thin-walled steel lipped channel studs with plasterboard linings on both sides. However, these thin-walled steel sections heat up quickly and lose their strength under fire conditions despite the protection provided by plasterboards. A new composite wall panel was recently proposed to improve the fire resistance rating of LSF walls, where an insulation layer was used externally between the plasterboards on both sides of the wall frame instead of using it in the cavity. A research study using both fire tests and numerical studies was undertaken to investigate the structural and thermal behaviour of load bearing LSF walls made of both conventional and the new composite panels under standard fire conditions and to determine their fire resistance rating. This paper presents the details of finite element models of LSF wall studs developed to simulate the structural performance of LSF wall panels under standard fire conditions. Finite element analyses were conducted under both steady and transient state conditions using the time-temperature profiles measured during the fire tests. The developed models were validated using the fire test results of 11 LSF wall panels with various plasterboard/insulation configurations and load ratios. They were able to predict the fire resistance rating within five minutes. The use of accurate numerical models allowed the inclusion of various complex structural and thermal effects such as local buckling, thermal bowing and neutral axis shift that occurred in thin-walled steel studs under non-uniform elevated temperature conditions. Finite element analyses also demonstrated the improvements offered by the new composite panel system over the conventional cavity insulated system.
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This practice-based presentation explores the role of fashion as an agent for social inclusion and ethical design practice in communities. The Stitchery Collective is an artist-run initiative based in Brisbane, Australia. Operating at the intersection of craft and design, the fashion-based initiative challenges the assumption that fashion is designed, produced and consumed exclusively in the commercial sector. As a not-for-profit cooperative, the stitchery collective is the first and only fashion organisation in Australia to attract funding under the national and state artist-run-initiative scheme. The collective approach extends to the stitchery design practice, facilitated by individual practitioners working within the organisation who devise programs in the context of collaborative and socially engaged design. Working under the banner of a question, Can fashion be more than pretty clothes for pretty people? the stitchery works to extend the cultural field of fashion practice in the 21st century. The premise of dress as a ‘significant creative or cultural expression’ has informed the expanded definition of fashion practice, as adopted by the stitchery. This alternative classification has fostered partnerships with numerous community groups, including those marginalised in the contemporary fashion context such as recent migrants and refugees. Community engagement programs span design, sewing and up-cycling workshops, sustainability lectures, clothing swaps and public education seminars, supported by partnerships with various cultural, government and educational institutions. In 2011, the stitchery travelled to the Venice Biennale’s 3rd International Children’s Carnival, hosting a workshop series and installation to promote design for sustainability. The proven potential for design to connect community members has motivated the stitchery to question the opportunity for fashion practice to, perhaps uncharacteristically, operate under the banner of ‘design for social good’. Acknowledging craft and design as relational fields, this presentation expands fashion as a tool for social innovation and sustainable practice. The stitchery dislocates the consumer status of fashion with small-scale, localised projects; moving beyond fashion as a dictum of social class to an alternative model that is accessible, conscious, flexible, connected and sustainable. As an undefined post-industrial future approaches, the non-commercial status of the stitchery practice might work to present an image of the active post-consumer. How can the stitchery propose a resilient model of design for the future?
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Growing food presents diverse challenges and opportunities within the urban environment. As cities develop, population density rises, land prices rise, and the opportunity to use land for traditional farming and gardening diminishes. Counter to this trend there are a growing number of both community gardens, city farms, guerrilla gardening, rooftop and vertical gardens, pot plants, windowsill herbs, and other balcony or backyard gardens cropping up in different cities, all with a purpose to produce food. This workshop brings to-gether practitioners and researchers in the field of urban agriculture and Hu-man-Computer Interaction to explore and opportunities for technology design to support the different forms of growing practice and foster local food production in cities. This 1-day workshop will serve as an active forum for researchers and practi-tioners across various fields including, but not limited to, agriculture and gar-dening, education, urban planning, human-computer interaction, and communi-ty engagement. This workshop has three distinct points of focus: i) Individual and small-scale gardening and food production, and how to connect like minded people who are involved in these practices to share their knowledge ii) Com-munities involved in urban agriculture, either through community gardens, city farms, or grassroots movements, often dependant on volunteer participation, providing the challenge of managing limited resources iii) Environmental and sociocultural sustainability through urban agriculture. The participants will have an opportunity to present their own work. This will be followed by a visit to a nearby city farm, which will provide a local context for a group design exercise. Finally the workshop will conclude with panel dis-cussions to review opportunities for further research and collaborations beyond the conference. For more information, please visit the workshop website, at http://www.urbaninformatics.net/resources/interact2013cfp/
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LiFePO4 is a commercially available battery material with good theoretical discharge capacity, excellent cycle life and increased safety compared with competing Li-ion chemistries. It has been the focus of considerable experimental and theoretical scrutiny in the past decade, resulting in LiFePO4 cathodes that perform well at high discharge rates. This scrutiny has raised several questions about the behaviour of LiFePO4 material during charge and discharge. In contrast to many other battery chemistries that intercalate homogeneously, LiFePO4 can phase-separate into highly and lowly lithiated phases, with intercalation proceeding by advancing an interface between these two phases. The main objective of this thesis is to construct mathematical models of LiFePO4 cathodes that can be validated against experimental discharge curves. This is in an attempt to understand some of the multi-scale dynamics of LiFePO4 cathodes that can be difficult to determine experimentally. The first section of this thesis constructs a three-scale mathematical model of LiFePO4 cathodes that uses a simple Stefan problem (which has been used previously in the literature) to describe the assumed phase-change. LiFePO4 crystals have been observed agglomerating in cathodes to form a porous collection of crystals and this morphology motivates the use of three size-scales in the model. The multi-scale model developed validates well against experimental data and this validated model is then used to examine the role of manufacturing parameters (including the agglomerate radius) on battery performance. The remainder of the thesis is concerned with investigating phase-field models as a replacement for the aforementioned Stefan problem. Phase-field models have recently been used in LiFePO4 and are a far more accurate representation of experimentally observed crystal-scale behaviour. They are based around the Cahn-Hilliard-reaction (CHR) IBVP, a fourth-order PDE with electrochemical (flux) boundary conditions that is very stiff and possesses multiple time and space scales. Numerical solutions to the CHR IBVP can be difficult to compute and hence a least-squares based Finite Volume Method (FVM) is developed for discretising both the full CHR IBVP and the more traditional Cahn-Hilliard IBVP. Phase-field models are subject to two main physicality constraints and the numerical scheme presented performs well under these constraints. This least-squares based FVM is then used to simulate the discharge of individual crystals of LiFePO4 in two dimensions. This discharge is subject to isotropic Li+ diffusion, based on experimental evidence that suggests the normally orthotropic transport of Li+ in LiFePO4 may become more isotropic in the presence of lattice defects. Numerical investigation shows that two-dimensional Li+ transport results in crystals that phase-separate, even at very high discharge rates. This is very different from results shown in the literature, where phase-separation in LiFePO4 crystals is suppressed during discharge with orthotropic Li+ transport. Finally, the three-scale cathodic model used at the beginning of the thesis is modified to simulate modern, high-rate LiFePO4 cathodes. High-rate cathodes typically do not contain (large) agglomerates and therefore a two-scale model is developed. The Stefan problem used previously is also replaced with the phase-field models examined in earlier chapters. The results from this model are then compared with experimental data and fit poorly, though a significant parameter regime could not be investigated numerically. Many-particle effects however, are evident in the simulated discharges, which match the conclusions of recent literature. These effects result in crystals that are subject to local currents very different from the discharge rate applied to the cathode, which impacts the phase-separating behaviour of the crystals and raises questions about the validity of using cathodic-scale experimental measurements in order to determine crystal-scale behaviour.
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The research reported here addresses the problem of athlete off-field behaviours as they influence sports’ sponsors, particularly the achievement of sponsorship objectives. The question arises because of incidents of sponsorship contract cancellation following news-media reporting of athletes’ off-field behaviours. Two studies are used to investigate the research question; the first establishes the content of news-media reports, and the second tests the effects of news’ reports on athlete, team and sponsor evaluations using an experimental design. Key assumptions of the research are that sponsorship objectives are principally consumer-based and mediated. Models of sponsorship argue that sponsors aim to reach and influence consumers through sponsees. Assuming this pathway exists is central to sponsorship activities. A corollary is that other mediators, in this case the news-media, may also communicate (uncontrollable) messages such that a consumer audience may be told of negative news that may then be associated with the sponsor. When sponsors cancel contracts it is assumed that their goal is to control the links between their brand and a negative referent. Balance theory is used to discuss the potential effects of negative off-field behaviours of athletes on sponsor’s objectives. Heider’s balance theory (1958) explains that individuals prefer to evaluate linked individuals or entities consistently. In the sponsorship context this presents the possibility that a negative evaluation of the athlete’s behaviour will contribute to correspondingly negative evaluations of the athlete’s team and sponsors. A content analysis (Study 1) was used to survey the types of athlete off-field behaviours commonly reported in a newspaper. In order to provide a local context for the research, articles from the Courier Mail were sampled and teams in the National Rugby League (NRL) competition were the focus of the research. The study identified nearly 2000 articles referring to the NRL competition; 258 of those refer to off-field incidents involving athletes. The various types of behaviours reported include assault, sexual assault allegations, driving under the influence of alcohol, illicit drug use, breaches of club rules, and positive off-field activities (i.e., charitable activities). An experiment (Study 2) tested three news’ article stimuli developed from the behaviours identified in Study 1 in a between-subjects design. A measure of Identification with the Team was used as a covariate variable in the Multivariate Analysis of Covariance analysis. Social identity theory suggests that when an individual identifies with a group, their attitudes and behaviours towards both in- and out-group members are modified. Use of Identification with the Team as a covariate acknowledges that respondents will evaluate behaviours differently according to the attribution of those behaviours to an in- or out-group member. Findings of the research suggest that the news’ article stimuli have significant, large effects on evaluations of athlete off-field behaviour and athlete Likability. Consistent with pretest results, charitable fundraising is regarded as extremely positive; the athlete, correspondingly, is likable. Assault is evaluated as extremely negative, and the athlete as unlikable. DUI scores reveal that the athlete’s behaviour is very negative; however, the athlete’s likability was evaluated as neutral. Treatment group does not produce any significant effects on team or sponsor variables. This research also finds that Identification with the Team has significant, large effects on team variables (Attitude toward the Brand and Corporate Image). Identification also has a significant large effect on athlete Likability, but not on Attitude toward the Act. Identification with the Team does not produce any significant effects on sponsor variables. The results of this research suggest that sponsor’s consumer-based objectives are not threatened by newspaper reports linking athlete off-field behaviour with their brand. Evaluations of sponsor variables (Attitude toward the Sponsor’s Brand and Corporate Image) were consistently positive. Variance in that data, however, cannot be attributed to experimental stimuli or Identification with the Team. These results argue that respondents may regard sponsorships, in principle, as good. Although it is good news for sponsors that negative evaluations of athletes will not produce correspondingly negative evaluations of consumer-based sponsorship objectives, the results indicate problems for sponsorship managers. The failure of Identification with the Team to explain sponsor variable variance indicates that the sponsor has not been evaluated as a linked entity in a relationship with the sporting team and athlete in this research. This result argues that the sponsee-mediated affective communication path that sponsors aim use to communicate with desirable publics is not necessarily a path available to them.
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Due to their small collecting volume diodes are commonly used in small field dosimetry. However the relative sensitivity of a diode increases with decreasing small field size. Conversely, small air gaps have been shown to cause a significant decrease in the sensitivity of a detector as the field size is decreased. Therefore this study uses Monte Carlo simulations to look at introducing air upstream to diodes such that they measure with a constant sensitivity across all field sizes in small field dosimetry. Varying thicknesses of air were introduced onto the upstream end of two commercial diodes (PTW 60016 photon diode and PTW 60017 electron diode), as well as a theoretical unenclosed silicon chip using field sizes as small as 5 mm × 5 mm . The metric D_(w,Q)/D_(Det,Q) used in this study represents the ratio of the dose to a point of water to the dose to the diode active volume, for a particular field size and location. The optimal thickness of air required to provide a constant sensitivity across all small field sizes was found by plotting D_(w,Q)/D_(Det,Q) as a function of introduced air gap size for various field sizes, and finding the intersection point of these plots. That is, the point at which D_(w,Q)/D_(Det,Q) was constant for all field sizes was found. The optimal thickness of air was calculated to be 3.3 mm, 1.15 mm and 0.10 mm for the photon diode, electron diode and unenclosed silicon chip respectively. The variation in these results was due to the different design of each detector. When calculated with the new diode design incorporating the upstream air gap, k_(Q_clin 〖,Q〗_msr)^(f_clin 〖,f〗_msr ) was equal to unity to within statistical uncertainty (0.5 %) for all three diodes. Cross-axis profile measurements were also improved with the new detector design. The upstream air gap could be implanted on the commercial diodes via a cap consisting of the air cavity surrounded by water equivalent material. The results for the unclosed silicon chip show that an ideal small field dosimetry diode could be created by using a silicon chip with a small amount of air above it.
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Ab initio density functional calculations were performed to study finite-length zigzag (7, 0) @ (16, 0) double-walled carbon nanotubes (DWCNTs) with H-termination at the open ends. We find that such a DWCNT nanodot displays a very large magnetic moment at the zigzag edges and the ground state displays symmetric anti-ferromagnetic coupling. When an external electric field is applied along the direction of tube axis, a gap is opened for one spin channel, whereas another spin channel remains metallic, i.e. half metallicity occurs. Our results suggest an important new avenue for the development of CNT-based spintronic materials with enhanced properties.