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Papers by Jackson Nixon
Scripta Metallurgica, 1977
When the yield stress of copper single crystals is increased by the addition of aluminium solute ... more When the yield stress of copper single crystals is increased by the addition of aluminium solute atoms, the character of slip in the early stages of deformation changes from fine slip in pure copper (I) to sharply defined slip bands in alloy crystals when the yield stress is about 1 kg/mm 2 (2). Etch pit studies (3) of these slip bands have shown that they are characterised by a high density of ordered linear arrays of interleaved positive and negative dislocations. In some places within and near the edges of slip bands, isolated dislocation pileups on the primary glide planes may be seen. Between bands, pile-ups on secondary glide planes are also sometimes observed. Chevrier (4) and Ahearn, Haasen and Labusch (5) have analysed the distribution of dislocations in such pile-ups with a view to estimating both the stress under which they are formed and possibly the friction stress which opposes their motion and prevents them from relaxing in the unloaded crystal.
Cognitive Processing, 2006
Background MobileGIS refers to the use of geographic data in the field on mobile devices like net... more Background MobileGIS refers to the use of geographic data in the field on mobile devices like networked personal digital assistant (PDA). The main components for MobileGIS are global positioning system (GPS), mobile device i.e. mobile phone, and communication network with GIS acting as the backbone. Map generalization is the process by which small scale maps are to be derived from large scale maps. This requires the appropriate use of map generalization operations to be performed subsequent to scale reduction to reduce the graphic conflict. Method This paper looks at how human factors requirements can be considered in the context of graphic conflict reduction for MobileGIS applications. Currently, this reduction is achieved by using schematic mapping techniques. The application of schematic mapping can be thought of as a data reduction technique for large scale datasets to make it suitable for rendering in mobile applications. This work makes use of simulated annealing (SA) based technique. At the start of the optimization process SA is presented with an initial approximate solution (or state). In the case of the schematic map problem, this will be the initial network (line features with travel time, each made up of constituent vertices). The initial state is then evaluated using a cost function C; this function assigns to the input state a score that reflects how well it measures up against a set of given constraints (topological, angle, minimum edge length, clearance). If the initial cost is greater than some user defined threshold (i.e. the constraints are not met adequately) then the algorithm steps into its optimization phase. This part of the process is iterative. At each iteration, the current state (i.e. the current network) is modified to make a new, alternative, approximate solution. The current and new states are said to be neighbours. The neighbours of any given state are generated usually in an application-specific way. The iterative process continues until stopping criteria are met (e.g. a suitably good solution is found or a certain amount of time has passed). Results Prototype software for producing schematic maps tailored for MobileGIS has been developed. The software makes use of the simulated annealing optimization technique. The software is currently implemented as a VBA script within ArcGIS. This technique has been used previously to control operations of displacement, deletion, reduction and enlargement of multiple map objects to help resolve spatial conflict arising due to scale reduction. These maps are subsequently displayed within the ArcPad application on a HP iPAQ PDA and tests have been carried out using different datasets. The results of applying simulated annealing based approach for automated schematic map generation is promising and further work will be done in enhancing the software with more functionality. Conclusions Development of automated schematic map generation techniques and cartographic specification for large scale digital geographic datasets suitable for MobileGIS applications was done and various tests carried out. Spatial conflict between feature classes at the specified scale ranges are to be dealt with by applying simulated annealing metaheuristic optimization technique.
This paper looks at how human factors requirements can be considered in the context of graphic co... more This paper looks at how human factors requirements can be considered in the context of graphic conflict reduction for mobile GIS applications. Currently this reduction is achieved by using schematic mapping techniques. With the advent of high-end miniature technology as well as digital geographic data products like OSMasterMap and OSCAR, it is essential to devise proper methodologies for map generalization specifically tailored for MobileGIS applications. This paper is concerned with the problem of producing schematic maps suitable for rendering on mobile display devices (e.g. PDAs). The application of schematic mapping can be thought of as a data reduction technique for large scale datasets to make it suitable for rendering in mobile applications. These techniques have been based on computation and have not incorporated any understanding of how the simplification affects the ease of use of the maps. It is therefore desirable to devise suitable generalization techniques incorporating human factors considerations for generating schematic maps from large scale datasets for display on small display devices to be used for MobileGIS applications
Scripta Metallurgica, 1977
When the yield stress of copper single crystals is increased by the addition of aluminium solute ... more When the yield stress of copper single crystals is increased by the addition of aluminium solute atoms, the character of slip in the early stages of deformation changes from fine slip in pure copper (I) to sharply defined slip bands in alloy crystals when the yield stress is about 1 kg/mm 2 (2). Etch pit studies (3) of these slip bands have shown that they are characterised by a high density of ordered linear arrays of interleaved positive and negative dislocations. In some places within and near the edges of slip bands, isolated dislocation pileups on the primary glide planes may be seen. Between bands, pile-ups on secondary glide planes are also sometimes observed. Chevrier (4) and Ahearn, Haasen and Labusch (5) have analysed the distribution of dislocations in such pile-ups with a view to estimating both the stress under which they are formed and possibly the friction stress which opposes their motion and prevents them from relaxing in the unloaded crystal.
Cognitive Processing, 2006
Background MobileGIS refers to the use of geographic data in the field on mobile devices like net... more Background MobileGIS refers to the use of geographic data in the field on mobile devices like networked personal digital assistant (PDA). The main components for MobileGIS are global positioning system (GPS), mobile device i.e. mobile phone, and communication network with GIS acting as the backbone. Map generalization is the process by which small scale maps are to be derived from large scale maps. This requires the appropriate use of map generalization operations to be performed subsequent to scale reduction to reduce the graphic conflict. Method This paper looks at how human factors requirements can be considered in the context of graphic conflict reduction for MobileGIS applications. Currently, this reduction is achieved by using schematic mapping techniques. The application of schematic mapping can be thought of as a data reduction technique for large scale datasets to make it suitable for rendering in mobile applications. This work makes use of simulated annealing (SA) based technique. At the start of the optimization process SA is presented with an initial approximate solution (or state). In the case of the schematic map problem, this will be the initial network (line features with travel time, each made up of constituent vertices). The initial state is then evaluated using a cost function C; this function assigns to the input state a score that reflects how well it measures up against a set of given constraints (topological, angle, minimum edge length, clearance). If the initial cost is greater than some user defined threshold (i.e. the constraints are not met adequately) then the algorithm steps into its optimization phase. This part of the process is iterative. At each iteration, the current state (i.e. the current network) is modified to make a new, alternative, approximate solution. The current and new states are said to be neighbours. The neighbours of any given state are generated usually in an application-specific way. The iterative process continues until stopping criteria are met (e.g. a suitably good solution is found or a certain amount of time has passed). Results Prototype software for producing schematic maps tailored for MobileGIS has been developed. The software makes use of the simulated annealing optimization technique. The software is currently implemented as a VBA script within ArcGIS. This technique has been used previously to control operations of displacement, deletion, reduction and enlargement of multiple map objects to help resolve spatial conflict arising due to scale reduction. These maps are subsequently displayed within the ArcPad application on a HP iPAQ PDA and tests have been carried out using different datasets. The results of applying simulated annealing based approach for automated schematic map generation is promising and further work will be done in enhancing the software with more functionality. Conclusions Development of automated schematic map generation techniques and cartographic specification for large scale digital geographic datasets suitable for MobileGIS applications was done and various tests carried out. Spatial conflict between feature classes at the specified scale ranges are to be dealt with by applying simulated annealing metaheuristic optimization technique.
This paper looks at how human factors requirements can be considered in the context of graphic co... more This paper looks at how human factors requirements can be considered in the context of graphic conflict reduction for mobile GIS applications. Currently this reduction is achieved by using schematic mapping techniques. With the advent of high-end miniature technology as well as digital geographic data products like OSMasterMap and OSCAR, it is essential to devise proper methodologies for map generalization specifically tailored for MobileGIS applications. This paper is concerned with the problem of producing schematic maps suitable for rendering on mobile display devices (e.g. PDAs). The application of schematic mapping can be thought of as a data reduction technique for large scale datasets to make it suitable for rendering in mobile applications. These techniques have been based on computation and have not incorporated any understanding of how the simplification affects the ease of use of the maps. It is therefore desirable to devise suitable generalization techniques incorporating human factors considerations for generating schematic maps from large scale datasets for display on small display devices to be used for MobileGIS applications