Materials which form the surface and subcutaneous layers of an extrudate experience large deformations when they traverse the die land. This, when added to the inhomogeneity caused by the dead metal zone, leads to con...
详细信息
Materials which form the surface and subcutaneous layers of an extrudate experience large deformations when they traverse the die land. This, when added to the inhomogeneity caused by the dead metal zone, leads to considerable modifications to the deformation parameters when compared to the remainder of the extrusion. The distribution of structure is therefore greatly inhomogeneous. Reference to both empirical and physical models of the recrystallisation process indicates that nucleation and growth will differ at these locations in those aluminium alloys that are usually solution treated and aged subsequent to the deformation process. Since static recrystallisation has a significant influence on many of the properties of the extrudate, it is therefore essential to provide the methodology to predict these variations. In the work presented, a physical model, for AA2024, based on dislocation density, subgrain size and misorientation is modified and integrated into the commercial finite element method (FEM) code, FORGE, to study the microstructure changes. Axi-symmetrical and shape extrusion are presented as examples. The evolution of the substructure influencing static recrystallisation is studied. The predicted results show an agreement with the experimental measurement. The distribution of equivalent strain, temperature compensated strain rate and temperatures are also presented to aid interpretation. Importantly the properties of hard alloys improve as the temperature of the extrusion is raised. This phenomenon is discussed and theoretically justified. This paper also presents some innovative work where the physically based models, and the Cellular Automata (CA) method, are combined to simulate the static recrystallisation process. The FEM is adopted to provide the initial morphology and state variables for the structure models, such as the equivalent strain, the temperature and the equivalent strain rate. The subgrain size, and dislocation densities are calculated
The accurate simulation of anatomical joint models is important for both medical diagnosis and realistic animation applications. Quaternion algebra has been increasingly applied to model rotations providing a compact ...
详细信息
The accurate simulation of anatomical joint models is important for both medical diagnosis and realistic animation applications. Quaternion algebra has been increasingly applied to model rotations providing a compact representation while avoiding singularities. This paper describes the application of artificial neural networks topologically evolved using genetic algorithms to model joint constraints directly in quaternion space. These networks are trained (using resilient back propagation) to model discontinuous vector fields that act as corrective functions ensuring invalid joint configurations are accurately corrected. The results show that complex quaternion-based joint constraints can be learned without resorting to reduced coordinate models or iterative techniques used in other quaternion based joint constraint approaches.
This study examines a selection of off-the-shelf forecasting and forecast combination algorithms with a focus on assessing their practical relevance by drawing conclusions for non-expert users. Some of the methods hav...
详细信息
ISBN:
(纸本)2930307080
This study examines a selection of off-the-shelf forecasting and forecast combination algorithms with a focus on assessing their practical relevance by drawing conclusions for non-expert users. Some of the methods have only recently been introduced and have not been part in comparative empirical evaluations before. Considering the advances of forecasting techniques, this analysis addresses the question whether we need human expertise for forecasting or whether the investigated methods provide comparable performance.
The article reviews two books including 'Greener by degrees: exploring sustainability through higher education curricula,' edited by Carolyn Roberts and Jane Roberts, and 'design for sustainability: a prac...
The article reviews two books including 'Greener by degrees: exploring sustainability through higher education curricula,' edited by Carolyn Roberts and Jane Roberts, and 'design for sustainability: a practical approach,' by Tracy Bhamra and Vicky Lofthouse.
Nature is an information sourcebook of behaviour, function, colour and shape which can inspire visual design and invention. Studying the form and functional characteristics of a natural object can provide inspiration ...
详细信息
Nature is an information sourcebook of behaviour, function, colour and shape which can inspire visual design and invention. Studying the form and functional characteristics of a natural object can provide inspiration for product design and help to improve the marketability of manufactured products. The inspiration can be triggered either by direct observation or captured by three-dimensional （3D） digitising techniques to obtain superficial information （geometry and colour）. An art designer often creates a concept in the form of a two-dimensional （2D） sketch while engineering methods lead to a point cloud in 3D. Each has its limitations in that the art designer commonly lacks the knowledge to build a final product from a 2D sketch and the engi- neering designer＇s 3D point clouds may not be very beautiful. We propose a method for Product design from Nature （PDN）, coupling aesthetic intent and geometrical characteristics, exploring the interactions between designers and nature＇s systems in PDN. We believe that this approach would considerably reduce the lead time and cost of product design from nature.
In recent years a considerable amount of natural computing research has been undertaken to exploit the analogy between, say, searching a given problem space for an optimal solution and the natural process of foraging ...
In recent years a considerable amount of natural computing research has been undertaken to exploit the analogy between, say, searching a given problem space for an optimal solution and the natural process of foraging for food. Such analogies have led to useful solutions in areas such as optimisation, prominent examples being ant colony systems and particle swarm optimisation. However, these solutions often rely on well defined fitness landscapes that are not always be available in more general search scenarios. This paper surveys a wide variety of behaviours observed within the natural world, and aims to highlight general cooperative group behaviours, search strategies and communication methods that might be useful within a wider computing context, beyond optimisation, where information from the fitness landscape may be sparse, but new search paradigms could be developed that capitalise on research into biological systems that have developed over millennia within the natural world.
Voice over Internet Protocol (VoIP) is an important service with strict Quality-of-Service (QoS) requirements in Wireless Local Area Networks (WLANs). The popular Distributed Coordination Function (DCF) of IEEE 802.11...
详细信息
Over the last decade there has been a shift in emphasis from interface usability to interface appeal. Very few studies, however, have examined the link between the two. The current study examined the possibility that ...
Over the last decade there has been a shift in emphasis from interface usability to interface appeal. Very few studies, however, have examined the link between the two. The current study examined the possibility that aesthetic appeal may affect user performance. In a visual search task designed to mimic user searches of interface displays, participants were asked to search for a target icon in an array of distractors. Target icons were varied orthogonally along two dimensions, complexity (which is known to affect visual search for icons in displays) and aesthetic appeal. The results showed that visually simple icons were found faster than visually complex icons, replicating previous findings. More importantly, aesthetic appeal interacted with icon complexity, significantly reducing search times for complex but not simple icons. These findings provide empirical evidence to support the idea that aesthetic appeal can influence performance.
Until recently the guiding tenet in human-computer interaction was that any interface must be easy to learn and use. However, it has been increasingly recognized that the appeal of the interface to the user and their ...
Until recently the guiding tenet in human-computer interaction was that any interface must be easy to learn and use. However, it has been increasingly recognized that the appeal of the interface to the user and their enjoyment of it is also important. The aim of the current study was to examine the nature of the relationships between icon characteristics, user performance, and aesthetic appeal. When participants were asked to rate the appeal of a corpus of icons, it was found that the same icon characteristics predicted appeal as those predicting user performance. The theoretical and practical implications of the remarkable similarity in the factors determining appeal and usability are discussed.
Currently, in any Mobile Ad Hoc Network (MANET), one routing protocol routes the packets to their destination no matter what the network's context is! This 'one size fits all' approach is far from optimum....
详细信息
Currently, in any Mobile Ad Hoc Network (MANET), one routing protocol routes the packets to their destination no matter what the network's context is! This 'one size fits all' approach is far from optimum. This paper introduces a novel intelligent routing protocol selector for MANET. The intelligent selector learns the network's performance and behaviour then chooses the optimum routing protocol according to the network's context, e.g.: number of nodes and mobility. The selector recommends the optimum network context depending on the current network situation. The selector is adaptable to the variations in the network environment by predicting four important parameters that indicate the changes in the network context. The intelligent selector system can deploy any protocol to its best advantages by testing the network's context and employing the most suitable protocol for that situation.
暂无评论