Modeling of voids/cracks and their interactions

Numerical modeling of a two-dimensional elastic body containing multiple voids/cracks to study the interaction between these defects can be  significantly simplified by developing special finite elements, each containing an internal circular/elliptic hole or a slit crack. These finite elements are developed using complex potentials and the conformal mapping technique. The elements developed can be divided into two categories, namely, the semi-analytic-type and hybrid-type elements. The latter element type is an improved version of the former due to the implementation of displacement continuity along the inter-element boundary. All the proposed elements can be easily combined with the conventional displacement elements, such as isoparametric elements, to analyze the above-mentioned problems without using complicated finite element meshes. Numerical examples have been employed to illustrate the modeling of voids/cracks and their interactions. The results obtained using the semi-analytic-type elements are in good agreement with the theoretical results, and the corresponding results obtained using the hybrid-type elements show an improvement of the agreement with the theoretical results. However, the former element type is much easier to construct.

Efficient Coxian duration modelling for activity recognition in smart environment with the hidden semi-Markov model

In this paper, we exploit the discrete Coxian distribution and propose a novel form of stochastic model, termed as the Coxian hidden semi-Makov model (Cox-HSMM), and apply it to the task of recognising activities of daily living (ADLs) in a smart house environment. The use of the Coxian has several advantages over traditional parameterization (e.g. multinomial or continuous distributions) including the low number of free parameters needed, its computational efficiency, and the existing of closed-form solution. To further enrich the model in real-world applications, we also address the problem of handling missing observation for the proposed Cox-HSMM. In the domain of ADLs, we emphasize the importance of the duration information and model it via the Cox-HSMM. Our experimental results have shown the superiority of the Cox-HSMM in all cases when compared with the standard HMM. Our results have further shown that outstanding recognition accuracy can be achieved with relatively low number of phases required in the Coxian, thus making the Cox-HSMM particularly suitable in recognizing ADLs whose movement trajectories are typically very long in nature.

Analytic prediction of structural stress-strain relations of microstructured metal

Nanostructured and ultra-fine grained metals have higher strength but extremely limited ductility compared to coarse grained metals. However, their ductility can be greatly improved by introducing a specific range of grain sizes in the microstructures. In the paper, multiscale unit cell approach (UCA) is developed and applied to predict the averaged stress-strain relations of the multiscale microstructure metals. The unit cell models are three-phase structured at different scale lengths of 100 nm, 1 μm and 10 μm with different volume fractions and periodic boundary conditions. The contributions of multi-scale microstructures to the macroscopic structural properties of metals are also studied using a analytic approach—two-step mean-field method (TSMF), where three microstructural parameters are introduced and thus mechanical properties such as strength and ductility are presented as a function of these parameters. For verification of these proposed numerical and theoretical algorithms, the structural properties of the pure nickel with three-grain microstructures are studied and the results from FEA and the proposed theory have good agreement.

Multi-attribute preference modelling and regional land-use planning

Forest management policy decisions are complex due to the multiple-use nature of goods and services from forests, difficulty in monetary valuation of ecological services and the involvement of a large number of stakeholders. Multi-attribute decision techniques can be used to synthesise stakeholder preferences related to regional forest planning because it can accommodate conflicting, multidimensional, incommensurable and incomparable objectives. The objective of this paper is to examine how the Analytical Hierarchy Process (AHP) can be used to incorporate stakeholder preferences in determining optimal forest land-use choices. The Australian Regional Forest Agreement Programme is taken as an illustrative case for the analysis. The results show that the AHP can formalise public participation in decision making and increase the transparency and the credibility of the process.

Characterising material and process variation effects on springback robustness for a semi-cylindrical sheet metal forming process

Variation in the incoming sheet material and fluctuations in the press setup is unavoidable in many stamping plants. The effect of these variations can have a large influence on the quality of the final stamping, in particular, unpredictable springback of the sheet when the tooling is removed. While stochastic simulation techniques have been developed to simulate this problem, there has been little research that connects the influence of the noise sources to springback. This paper characterises the effect of material and process variation on the robustness of springback for a semi-cylindrical channel forming operation, which shares a similar cross-section profile as many automotive structural components. The study was conducted using the specialised sheet metal forming package AutoForm^TM Sigma, for which a series of stochastic simulations were performed with each of the noise sources incrementally introduced. The effective stress and effective strain scatter in a critical location of the part was examined and a response window, which indicates the respective process robustness, was defined. The incremental introduction of the noise sources allows the change in size of the stressstrain response window to be tracked. The results showed that changes to process variation parameters, such as BHP and friction coefficient, directly affect the strain component of the stressstrain response window by altering the magnitude of external work applied to forming system. Material variation, on the other hand, directly affected the stress component of the response window. A relationship between the effective stressstrain response window and the variation in springback was also established.

Mathematical modelling of deep bed filtration

Numerous mathematical models have been developed to evaluate both initial and transient stage removal efficiency of deep bed filters. Microscopic models either using trajectory analysis or convective-diffusion equations were used to compute the initial removal efficiency. These models predicted the removal efficiency under favorable filtration conditions quantitatively, but failed to predict the removal efficiency under unfavorable conditions. They underestimated the removal efficiency under unfavorable conditions. Thus, semi-empirical formulations were developed to compute initial removal efficiencies under unfavorable conditions. Also, correction for the adhesion of particles onto filter grains improved the results obtained for removal efficiency from the trajectory analysis. Macroscopic models were used to predict the transient stage removal efficiency of deep bed filters. O’Melia and Ali’s model assumed that the particle removal is due to filter grains as well as the particles that are already deposited onto the filter grain. Thus, semi-empirical models were used to predict the ripening of filtration. Several modifications were made to the model developed by O’Melia and Ali to predict the deterioration of particle removal during the transient stages of filtration. Models considering the removal of particles under favorable conditions and the accumulation of charges on the filter grains during the transient stages were also developed. This paper evaluates those models and their applicability under different operating conditions of filtration.

Mathematical modelling of downflow floating medium filter (DFF) with in-line flocculation arrangement

A laboratory-scale set-up consisting of rapid mixing device and floating medium filter was used to study the use of a downflow floating medium filter (DFF) with an in-line flocculation arrangement as a static flocculator and a prefilter. The semi-empirical mathematical model formulated incorporates flocculation within the filter, particle/floc attachment onto the filter and the detachment of flocs from the medium. The mathematical model for filtration takes into account the expansion of the filter bed. The removal efficiency of DFF and headless development were successfully simulated for different conditions of filtration velocity, filter depth and influent suspended solids (SS). The values of attachment coefficient a(p)β and headless coefficient β1 were found to be independent of filtration velocity, filter depth and influent SS concentration.

Analytic study on pure bending of metal sheets

In this work, analytical models of pure bending are developed to simulate a particular type of bend test and to determine possible errors arising from approximations used in analyzing experimental data. Analytical models proposed for steels include a theoretical solution of pure bending and a series of finite element models, based on the von Mises yield function, are subjected to different stress and strain conditions. The results show that for steel sheets the difference between measured and calculated results of the moment-curvature behaviour is small and the numerical results from the finite element models indicate that experimental results obtained from the test are acceptable in the range of the pure bending operation. Further for magnesium alloys, which exhibit unsymmetrical yielding, the algorithm of the yield function with a linear isotropic hardening model is implemented by programming a user subroutine in Abaqus for bending simulations of magnesium. The simulations using the proposed user subroutine extract better results than those using the von Mises yield function.

Development of an expert system modelling the construction process

The construction industry in the UK needs to improve its performance and provide clients with an improved level of satisfaction. The inefficient design and construction process is usually criticised as one of the main causes of poor performance.

A new construction process system, CONstruction Best Practice System (CONBPS), has been developed based on the use of an expert system. CONBPS is based on the traditional procurement strategy as it is probably the most popular procurement method in the UK and yet it is subject to most criticism. This model clearly identifies the roles and responsibilities of the major parties within the building team and identifies the activities and the key issues within the project cycle. The completed model reflects the full project cycle from inception to completion.

The prototype of this system has been demonstrated to the construction participants for their comments. The practitioners included architects, quantity surveyors, planning supervisors, private and public clients. The method of collecting data was through the use of semi-structured interviews.

Following feedback from practitioners, the CONBPS has been updated. This version is more robust; besides, it is more practical and user-friendly as it incorporates the comments from practitioners, who are also the potential users.

The primary aim of this paper is to discuss the development of the updated CONBPS. The improvement of the updated CONBPS includes the information for constructing the system, the computerised functions, system structure, knowledge representation structure and the system operation.

Adaptation to climate change in regional Australia : a decision-making framework for modelling policy for rural production

A decision-making framework was developed and applied in regional Australia to identify adaptation issues arising in agricultural systems and rural production as a consequence of climate change. Australian agriculture is very susceptible to the adverse impacts of climate change, with major shifts in temperature and rainfall projected. An advantage of the framework is that it provides a suite of tools to aid in the formulation of strategies for sustainable regional development and adaptation. The decision-making framework uses a participatory approach that integrates land suitability analysis with uncertainty analysis and spatial optimisation to determine optimal agricultural land use (at a regional scale) for current and possible future climatic conditions. It thus provides a robust analytic approach to (i) recognise regions under threat of productivity declines, (ii) identify alternative cropping systems better adapted to likely future climatic conditions and (iii) investigate policy actions to improve the sub-optimal situations created by climate change. The decision-making framework and its methods were applied in a case study of the South West Region of Victoria.

TeeVML : tool support for semi-automatic integration testing environment emulation

Software environment emulation provides a means for simulating an operational environment of a system. This process involves approximation of systems’ external behaviors and their communications with a system to be tested in the environment. Development of such an environment is a tedious task and involves complex low level coding. Model driven engineering is an avenue to raise the level of abstraction beyond programming by specifying solution directly using problem domain concepts. In this paper we propose a novel domain-specific modeling tool to generate complex testing environments. Our tool employs a suite of domain-specific visual modeling languages for modelling emulation environment at a high level of abstraction. These high level specifications are then automatically transformed to runtimeenvironment for application integration testing, boosting development productivity and ease of use.

Concordance in phylogeography and ecological niche modelling identify dispersal corridors for reptiles in arid Australia

Aim: Using the rock-specialist agamid Ctenophorus caudicinctus as a model, we test hypothesized biogeographical dispersal corridors for lizards in the Australian arid zone (across the western sand deserts), and assess how these dispersal routes have shaped phylogeographical structuring. Location: Arid and semi-arid Australia. Methods: We sequenced a c. 1400 bp fragment of mtDNA (ND2) for 134 individuals of C. caudicinctus as well as a subset of each of the mtDNA clades for five nuclear loci (BDNF, BACH1, GAPD, NTF3, and PRLR). We used phylogenetic methods to assess biogeographical patterns within C. caudicinctus, including relaxed molecular clock analyses to estimate divergence times. Ecological niche modelling (Maxent) was employed to estimate the current distribution of suitable climatic envelopes for each lineage. Results: Phylogenetic analyses identified two deeply divergent mtDNA clades within C. caudicinctus - an eastern and western clade - separated by the Western Australian sand deserts. However, divergences pre-date the Pleistocene sand deserts. Phylogenetic analyses of the nuclear DNA data sets generally support major mtDNA clades, suggesting past connections between the western C. c. caudicinctus populations in far eastern Pilbara (EP) and the lineages to the east of the sand deserts. Ecological niche modelling supports the continued suitability of climatic conditions between the Central Ranges and the far EP for C. c. graafi. Main conclusions: Estimates of lineage ages provide evidence of divergence between eastern and western clades during the Miocene with subsequent secondary contact during the Pliocene. Our results suggest that this secondary contact occurred via dispersal between the Central Ranges and the far EP, rather than the more southerly Giles Corridor. These events precede the origins of the western sand deserts and divergence patterns instead appear associated with Miocene and Pliocene climate change.