954 resultados para Multi-phase Modelling


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The issue of trust in Internet-based business-to-consumer electronic commerce has been explored from a number of difference perspectives. The current body of research is diverse and fragmented. This paper critically reviews recently published models pertaining to trust in business to consumer e-commerce. For analytical purposes we categorize the literature in three main streams: technological, design and sociological/psychological. Based on our analysis and our own empirical observations we raise four main areas of concern that warrant further research attention: an oversimplification of the trust concept, a uni-directional view of trust, discipline centered approaches to modelling trust and a lack of empirical grounding and testing. In the light of these concerns we recommend avenues for further research.

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Spectral element method is very efficient in modelling high-frequency stress wave propagation because it works in the frequency domain. It does not need to use very fine meshes in order to capture high frequency wave energy as the time domain methods do, such as finite element method. However, the conventional spectral element method requires a throw-off element to be added to the structural boundaries to act as a conduit for energy to transmit out of the system. This makes the method difficult to model wave reflection at boundaries. To overcome this limitation, imaginary spectral elements are proposed in this study, which are combined with the real structural elements to model wave reflections at structural boundaries. The efficiency and accuracy of this proposed approach is verified by comparing the numerical simulation results with measured results of one dimensional stress wave propagation in a steel bar. The method is also applied to model wave propagation in a steel bar with not only boundary reflection, but also reflections from single and multiple cracks. The reflection and transmission coefficients, which are obtained from the discrete spring model, are adopted to quantify the discontinuities. Experimental tests of wave propagation in a steel bar with one crack of different depths are also carried out. Numerical simulations and experimental results show that the proposed method is effective and reliable in modelling wave propagation in one-dimensional waveguides with reflections from boundary and structural discontinuities. The proposed method can be applied to effectively model stress wave propagation for structural damage detection.

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This multi-disciplinary investigation found that: i) in Triodia-mallee the Mallee Emu-wren requires vegetation greater than 16-18 years since last burned, with high coverage of mature growth-phase Triodia scariosa (spinifex) and, ii) the species is panmictic with relatively low genetic diversity and evidence of genetic drift and bottlenecks.

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A simple biofilm model was developed to describe the growth of bacteria in drinking water biofilms and the subsequent interactions with disinfectant residuals incorporating the important processes, such as attachment of free bacteria to the biofilm on a wall surface, detachment of bacteria from the biofilm, growth of biofilm bacteria with chloramine inhibition, chloramine decay in the bulk water phase, and chloramine decay due to biofilm bacteria and wall surfaces. The model is useful in evaluating the biological stability of different waters, as it can predict concentration of organic substances in water. In addition, the model can be used to predict the bacterial growth and biofilm decay in distribution systems. A model of this kind is a useful tool in developing system management strategies to ultimately improve drinking water quality.

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Natural rubber (NR)/multi-walled carbon nanotube (MWCNTs) composites were prepared bycombining self-assembly and latex compounding techniques. The acid-treated MWCNTs (H2SO4: HNO3=3:1,volume ratio) were self-assembled with poly (diallyldimethylammonium chloride) (PDDA) through electrostaticadhesion. In the second assembling, NR/MWCNTs composites were developed by mixing MWCNTs/PDDAsolution with NR latex. The results show that MWCNTs are homogenously distributed throughout the NRmatrix as single tube and present a great interfacial adhesion with NR phase when MWCNTs contents areless than 3 wt%. Moreover, the addition of the MWCNTs brings about the remarkable enhancement in tensilestrength and crosslink density compared with the NR host, and the data peak at 2 wt% MWCNTs loadings.When more MWCNTs are loaded, aggregations of MWCNTs are gradually generated, and the tensile strengthand crosslink both decrease to a certain extent.

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Introducing haptic interface to conduct microrobotic intracellular injection has many beneficial implications. In particular, the haptic device provides force feedback to the bio-operator's hand. This paper introduces a 3D particle-based model to simulate the deformation of the cell membrane and corresponding cellular forces during microrobotic cell injection. The model is based on the kinematic and dynamic of spring – damper multi particle joints considering visco-elastic fluidic properties. It simulates the indentation force feedback as well as cell visual deformation during the microinjection. The model is verified using experimental data of zebrafish embryo microinjection. The results demonstrate that the developed cell model is capable of estimating zebrafish embryo deformation and force feedback accurately.

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Use of hydrogen as a temporary alloying element in Ti alloys is an attractive approach to improve the mechanical properties of the materials, enhance processability and thereby reduce manufacturing costs. In this paper, the hydrogen diffusion process and the phase transformation both between Ti particles and in Ti sheets were simulated to analyze the mechanism of hydrogen diffusion in different phases (α-Ti, β-Ti and TiHx). With the simulation based on the kinetics and thermodynamics, quantitative behaviors of the hydrogen diffusion and the phase transformation were analyzed. The simulation results provide an insight into the diffusion process and improve the fundamental understanding of the mechanism of diffusion and phase transformation.

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For fluid-filled closed cell composites widely distributed in nature, the configuration evolution and effective elastic properties are investigated using a micromechanical model and a multiscale homogenization theory, in which the effect of initial fluid pressure is considered. Based on the configuration evolution of the composite, we present a novel micromechanics model to examine the interactions between the initial fluid pressure and the macroscopic elasticity of the material. In this model, the initial fluid pressure of the closed cells and the corresponding configuration can be produced by applying an eigenstrain at the introduced fictitious stress-free configuration, and the pressure-induced initial microscopic strain is derived. Through a configuration analysis, we find the initial fluid pressure has a prominent effect on the effective elastic properties of freestanding materials containing pressurized fluid pores, and a new explicit expression of effective moduli is then given in terms of the initial fluid pressure. Meanwhile, the classical multiscale homogenization theory for calculating the effective moduli of a periodical heterogeneous material is generalized to include the pressurized fluid "inclusion" effect. Considering the coupling between matrix deformation and fluid pressure in closed cells, the multiscale homogenization method is utilized to numerically determine the macroscopic elastic properties of such composites at the unit cell level with specific boundary conditions. The present micromechanical model and multiscale homogenization method are illustrated by several numerical examples for validation purposes, and good agreements are achieved. The results show that the initial pressure of the fluid phase can strengthen overall effective bulk modulus but has no contribution to the shear modulus of fluid-filled closed cell composites.

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Background : Osteoporosis affects over 220 million people worldwide, and currently there is no 'cure' for the disease. Thus, there is a need to develop evidence-based, safe and acceptable prevention strategies at the population level that target multiple risk factors for fragility fractures to reduce the health and economic burden of the condition.

Methods :
The 'Osteo-cise: Strong Bones for Life' study will investigate the effectiveness and feasibility of a multi-component targeted exercise, osteoporosis education/awareness and behavioural change program for improving bone health and muscle function, and reducing falls risk in community-dwelling older adults at an increased risk of fracture. Men and women aged 60 years or above will participate in an 18-month randomised controlled trial comprising a 12-month structured and supervised community-based program and a 6-month 'research to practise' translational phase. Participants will be randomly assigned to either the 'Osteo-cise' intervention or a self-management control group. The intervention will comprise a multi-modal exercise program incorporating high velocity progressive resistance training, moderate impact weight-bearing exercise and high challenging balance exercises performed three times weekly at local community-based fitness centres. A behavioural change program will be used to enhance exercise adoption and adherence to the program. Community-based osteoporosis education seminars will be conducted to improve participant knowledge and understanding of the risk factors and preventative measures for osteoporosis, falls and fractures. The primary outcomes measures, to be collected at baseline, 6, 12, and 18 months, will include DXA-derived hip and spine bone mineral density measurements and functional muscle power (timed stair-climb test). Secondary outcomes measures include: MRI-assessed distal femur and proximal tibia trabecular bone micro-architecture, lower limb and back maximal muscle strength, balance and function (four square step test, functional reach test, timed up-and-go test and 30-second sit-to-stand), falls incidence and health-related quality of life. Cost-effectiveness will also be assessed.

Discussion :
The findings from the Osteo-cise: Strong Bones for Life study will provide new information on the efficacy of a targeted multi-modal community-based exercise program incorporating high velocity resistance training, together with an osteoporosis education and behavioural change program for improving multiple risk factors for falls and fracture in older adults at risk of fragility fracture. Trial Registration: Australian New Zealand Clinical Trials Registry reference ACTRN12609000100291

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In this paper, a neural network (NN)-based multi-agent classifier system (MACS) utilising the trust-negotiation-communication (TNC) reasoning model is proposed. A novel trust measurement method, based on the combination of Bayesian belief functions, is incorporated into the TNC model. The Fuzzy Min-Max (FMM) NN is used as learning agents in the MACS, and useful modifications of FMM are proposed so that it can be adopted for trust measurement. Besides, an auctioning procedure, based on the sealed bid method, is applied for the negotiation phase of the TNC model. Two benchmark data sets are used to evaluate the effectiveness of the proposed MACS. The results obtained compare favourably with those from a number of machine learning methods. The applicability of the proposed MACS to two industrial sensor data fusion and classification tasks is also demonstrated, with the implications analysed and discussed.

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Mathematical modelling is one of the current focuses in the Singapore Mathematics Curriculum Framework. A multi-tiered teaching experiment using design research methodology was conducted to build teachers’ capacity in designing, facilitating, and evaluating learning during mathematical modelling tasks for Primary 5 students (aged 10-11). This paper illustrates the use of the retrospective analysis phase within design research cycles to activate a critical moment of teacher learning involving the interplay between questioning and listening during her first attempt at facilitating a mathematical modelling task. The teacher affirmed her deliberate focuses in the use of questions to (a) refine students’ models, (b) encourage articulation of student ideas in self-evaluation of the models, and (c) clarify and understand student reasoning. However, she also discovered the importance of interpretative listening in conjunction with questioning to promote more sophisticated mathematisation processes in model development. Implications from the use of the retrospective analysis phase on activating critical moments of learning during teacher education will be discussed.

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This paper investigates the location and velocity estimation problem involving multiple targets using the phase difference and frequency shift of the returned Doppler modulated signal. The minimal receiver configuration that addresses the data association and missing information problem is presented for the case of linear arrays. Non-linearly modeled Doppler radar measurements are used to obtain an accurate estimate of the target dynamics progressively in a linear framework utilizing a recently developed robust state estimation approach.

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Until recently, the limited use of modelling activities in Singapore mathematics classrooms despite the incorporation of mathematical modelling in the curriculum since 2003 could be due to a lack of concerted efforts in teacher preparation. Explicit guidelines have recently been developed by the Ministry of Education (CPDD, 2012) with a view to harness the potentials of modelling activities for fostering 21st Century Competences in students. This paper illustrates how a multi-tiered teaching experiment using design research methodology was conducted to build teachers' capacity in facilitating and designing modelling tasks using a case study involving an experienced teacher in a primary 5 (aged 10-11) mathematics classroom. Implications on the identification of teacher competencies to be focused upon during teacher development in incorporating mathematical modelling in Singapore classrooms will be drawn.

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Objectives
This paper reports the quantitative findings of the first phase of a larger program of ongoing research: Feedback Incorporating Review and Simulation Techniques to Act on Clinical Trends (FIRST2ACTTM). It specifically aims to identify the characteristics that may predict primary outcome measures of clinical performance, teamwork and situation awareness in the management of deteriorating patients.

Design
Mixed-method multi-centre study.

Setting
High fidelity simulated acute clinical environment in three Australian universities.

Participants
A convenience sample of 97 final year nursing students enrolled in an undergraduate Bachelor of Nursing or combined Bachelor of Nursing degree were included in the study.

Method
In groups of three, participants proceeded through three phases: (i) pre-briefing and completion of a multi-choice question test, (ii) three video-recorded simulated clinical scenarios where actors substituted real patients with deteriorating conditions, and (iii) post-scenario debriefing. Clinical performance, teamwork and situation awareness were evaluated, using a validated standard checklist (OSCE), Team Emergency Assessment Measure (TEAM) score sheet and Situation Awareness Global Assessment Technique (SAGAT). A Modified Angoff technique was used to establish cut points for clinical performance.

Results
Student teams engaged in 97 simulation experiences across the three scenarios and achieved a level of clinical performance consistent with the experts' identified pass level point in only 9 (1%) of the simulation experiences. Knowledge was significantly associated with overall teamwork (p = .034), overall situation awareness (p = .05) and clinical performance in two of the three scenarios (p = .032 cardiac and p = .006 shock). Situation awareness scores of scenario team leaders were low overall, with an average total score of 41%.

Conclusions
Final year undergraduate nursing students may have difficulty recognising and responding appropriately to patient deterioration. Improving pre-requisite knowledge, rehearsal of first response and team management strategies need to be a key component of undergraduate nursing students' education and ought to specifically address clinical performance, teamwork and situation awareness.

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The relative strengths of individual units, described as attributes, determine the outcome during unit conflicts involving units in the armies of opponents in large strategy games. We describe a process for developing predictive models of the outcome for such conflicts where combat involves single unit adversaries where each unit is defined in terms of 4 fundamental attributes. These attributes: range, speed, health and damage are common to unit descriptions in many successful real-time strategy games. Our analysis process identifies three phases of game play with invariant properties that hold throughout each phase. We demonstrate the utility of this analysis by creating a model that predicts game outcomes. Predictions are validated against the game simulation. The game outcomes are explicitly related to the attributes of the two units involved, highlighting the significance and role of each attribute.