1,939 research outputs found
Analyzing and Modeling the Performance of the HemeLB Lattice-Boltzmann Simulation Environment
We investigate the performance of the HemeLB lattice-Boltzmann simulator for
cerebrovascular blood flow, aimed at providing timely and clinically relevant
assistance to neurosurgeons. HemeLB is optimised for sparse geometries,
supports interactive use, and scales well to 32,768 cores for problems with ~81
million lattice sites. We obtain a maximum performance of 29.5 billion site
updates per second, with only an 11% slowdown for highly sparse problems (5%
fluid fraction). We present steering and visualisation performance measurements
and provide a model which allows users to predict the performance, thereby
determining how to run simulations with maximum accuracy within time
constraints.Comment: Accepted by the Journal of Computational Science. 33 pages, 16
figures, 7 table
Heuristic Solutions for Loading in Flexible Manufacturing Systems
Production planning in flexible manufacturing system deals with the efficient organization of the production resources in order to meet a given production schedule. It is a complex problem and typically leads to several hierarchical subproblems that need to be solved sequentially or simultaneously. Loading is one of the planning subproblems that has to addressed. It involves assigning the necessary operations and tools among the various machines in some optimal fashion to achieve the production of all selected part types. In this paper, we first formulate the loading problem as a 0-1 mixed integer program and then propose heuristic procedures based on Lagrangian relaxation and tabu search to solve the problem. Computational results are presented for all the algorithms and finally, conclusions drawn based on the results are discussed
The co-incident flow of work pieces and cutting tools in a restricted category of flexible machining cells
The work reported in this thesis describes research carried out into the detailed design
and operation of Flexible Machining Cells (FMC) incorporating automated work and tool
flow, dual flow. Three modes of cell management are considered for dual flow cells,
where the author examines both their operational and economic performance.
A framework is defined for investigating these dual flow cells, and a structured approach
providing a novel and detailed modelling capability is described. The question of how
this approach compares to single flow modelling and the additional or alternative
requirements for dual flow modelling is examined via the following key areas; the
specification of material handling requirements, tool transportation and issue and finally,
the control required to examine the interaction between the two flows operating
concurrently.
The framework is tested for its industrial applicability via an industrial case study. A
major aim of this study is to examine the view that a hybrid cell management strategy,
competitive management, could outperform the other strategies examined.
The aim of this methodology is to provide a solution for the control of FMCs. Emphasis
is placed on the ease of control and how the loading and control rules selection can
maximise economic enhancement of a cells performance
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