Multiple paths through a network

The most sophisticated iterative algorithm for balancing network congestion for a given set of desired vehicle movement from origins to destinations can generate thousands of paths of equal cost to connect a single O-D pair. Some sets of paths are combinations of minor variations on one main path, while other sets contain various degrees of difference, possibly up to complete independence. Present methods for comparing paths do not take into account the multi-dimensional nature of similarities and differences between paths, or the different character of sets of paths - especially from a geographic point of view. I develop a battery of methods of making comparisons, and apply them to illustrative sets of paths identified in the highly disaggregated Chicago network. I begin a discussion of how these comparisons might be used to throw light on problems of network aggregation and of discrete choice of route among populations of users.

Multiple paths through a network

The most sophisticated iterative algorithm for balancing network congestion for a given set of desired vehicle movement from origins to destinations can generate thousands of paths of equal cost to connect a single O-D pair. Some sets of paths are combinations of minor variations on one main path, while other sets contain various degrees of difference, possibly up to complete independence. Present methods for comparing paths do not take into account the multi-dimensional nature of similarities and differences between paths, or the different character of sets of paths - especially from a geographic point of view. I develop a battery of methods of making comparisons, and apply them to illustrative sets of paths identified in the highly disaggregated Chicago network. I begin a discussion of how these comparisons might be used to throw light on problems of network aggregation and of discrete choice of route among populations of users

Algorithmic and technical improvements: Optimal solutions to the (Generalized) Multi-Weber Problem

Rosing has recently demonstrated a new method for obtaining optimal solutions to the (Generalized) Multi-Weber Problem and proved the optimality of the results. The method develops all convex hulls and then covers the destinations with disjoint convex hulls. This paper seeks to improve implementation of the algorithm to make such solutions economically attractive. Four areas are considered: sharper decision rules to eliminate unnecessary searching, bit pattern matching as a method of recording a history and eliminating duplication, vector intrinsic functions to speed up comparisons, and profiling a program to maximize operating efficiency. Computational experience is also presented

An exploratory randomized controlled trial of assisted practice for improving sit-to-stand in stroke patients in the hospital setting

Objectives: To evaluate the amount of practice achieved and assess potential for effects on performance of 30 minutes of daily training in sit-to-stand. Design: Randomized controlled pilot study. Setting: Stroke rehabilitation unit, UK. Participants: Eighteen stroke patients needing 'stand by' help to sit-to-stand. Interventions: In addition to usual rehabilitation the experimental group (n=9) practised sit-to-stand and leg strengthening exercises for 30 minutes, on weekdays for two weeks, with a physiotherapy assistant. The control group received arm therapy. Main outcome measures: Frequency of sit-to-stands per day. Performance measures: rise time, weight taken through the affected foot at 'thighs off', number of attempts needed to achieve three successful sit-to-stands and the number of sit-to-stands performed in 60 seconds. Outcome was measured one and two weeks after baseline assessment. Results: Sit-to-stand frequency averaged 18 per day. Thirty minutes of practice in sit-to-stand resulted in a mean of 50 (SD 17.2) extra stands per day. There was a significant mean difference of 10% body weight taken through the affected foot after one week of intervention: The control group had reduced weight through the affected leg while the training group increased weight (F1,16 = 11.1, P=0.004, 95% confidence interval (CI) - 16.61 to - 3.72). No significant differences between groups were found on other measures. Results two weeks after baseline were inconclusive due to loss of five participants. Conclusions: Task-specific practice given for 30 minutes a day appears promising for patients learning to sit-to-stand. © SAGE Publications 2008

Selective Laser Sintering Preparation and Tribological Testing of Nanostructured Tungsten Carbide-Cobalt Composites

This paper describes the results to date ofresearch done to compare and contrast the tribological properties ofnanostructured tungsten carbide-cobalt composites consolidated by selective laser sintering (SLS) and conventional grain size composites ofthe same chemical composition consolidated by conventional commercial methods. The powder preprocessing and selective laser sintering methods will briefly be described. The tribological testing methods will be discussed, and the tribological properties ofthe selective laser sintered and commercially consolidated materials will be compared. It will be seen that the nanosized WC-Co composites have far superior harness and wear resistance compared to their microsized counterparts.Mechanical Engineerin

Selective Area Laser Deposition - A Method of Solid Freeform Fabrication

Mechanical Engineerin

Spatial and spatio-temporal patterns in a cell-haptotaxis model

We investigate a cell-haptotaxis model for the generation of spatial and spatio-temporal patterns in one dimension. We analyse the steady state problem for specific boundary conditions and show the existence of spatially hetero-geneous steady states. A linear analysis shows that stability is lost through a Hopf bifurcation. We carry out a nonlinear multi-time scale perturbation procedure to study the evolution of the resulting spatio-temporal patterns. We also analyse the model in a parameter domain wherein it exhibits a singular dispersion relation