33,719 research outputs found
The role of the cytoskeleton in the motility of coccidian sporozoites
Imperial Users onl
Boundary-detection algorithm for locating edges in digital imagery
The author has identified the following significant results. Initial development of a computer program which implements a boundary detection algorithm to detect edges in digital images is described. An evaluation of the boundary detection algorithm was conducted to locate boundaries of lakes from LANDSAT-1 imagery. The accuracy of the boundary detection algorithm was determined by comparing the area within boundaries of lakes located using digitized LANDSAT imagery with the area of the same lakes planimetered from imagery collected from an aircraft platform
Experience with a vectorized general circulation weather model on Star-100
A version of an atmospheric general circulation model was vectorized to run on a CDC STAR 100. The numerical model was coded and run in two different vector languages, CDC and LRLTRAN. A factor of 10 speed improvement over an IBM 360/95 was realized. Efficient use of the STAR machine required some redesigning of algorithms and logic. This precludes the application of vectorizing compilers on the original scalar code to achieve the same results. Vector languages permit a more natural and efficient formulation for such numerical codes
Noise-induced dynamical transition in systems with symmetric absorbing states
We investigate the effect of noise strength on the macroscopic ordering
dynamics of systems with symmetric absorbing states. Using an explicit
stochastic microscopic model, we present evidence for a phase transition in the
coarsening dynamics, from an Ising-like to a voter-like behavior, as the noise
strength is increased past a nontrivial critical value. By mapping to a thermal
diffusion process, we argue that the transition arises due to locally-absorbing
states being entered more readily in the high-noise regime, which in turn
prevents surface tension from driving the ordering process.Comment: v2 with improved introduction and figures, to appear in PRL. 4 pages,
4 figure
Suppression of combustion oscillations with mechanical devices Interim report
Static rocket thrust chamber simulator for cylindrical cold flow-type apparatus desig
p-Wave stabilization of three-dimensional Bose-Fermi solitons
We explore bright soliton solutions of ultracold Bose-Fermi gases, showing
that the presence of p-wave interactions can remove the usual collapse
instability and support stable soliton solutions that are global energy minima.
A variational model that incorporates the relevant s- and p-wave interactions
in the system is established analytically and solved numerically to probe the
dependencies of the solitons on key experimental parameters. Under attractive
s-wave interactions, bright solitons exist only as meta-stable states
susceptible to collapse. Remarkably, the presence of repulsive p-wave
interactions alleviates this collapse instability. This dramatically widens the
range of experimentally-achievable soliton solutions and indicates greatly
enhanced robustness. While we focus specifically on the boson-fermion pairing
of 87Rb and 40K, the stabilization inferred by repulsive p-wave interactions
should apply to the wider remit of ultracold Bose-Fermi mixtures.Comment: 9 pages, 6 figure
Estimation of Costs of Phosphorus Removal In Wastewater Treatment Facilities: Adaptation of Existing Facilities
As part of a wider enquiry into the feasibility of offset banking schemes as a means to implement pollutant trading within Georgia watersheds, this is the second of two reports addressing the issue of estimating costs for upgrades in the performance of phosphorus removal in point-source wastewater treatment facilities. Earlier, preliminary results are presented in Jiang et al (2004) (Working Paper # 2004-010 of the Georgia Water Planning and Policy Center). The present study is much more detailed and employs an advanced software package (WEST®, Hemmis nv, Kortrijk, Belgium) for simulating a variety of treatment plant designs operating under typical Georgia conditions. Specifically, upgrades in performance, in a single step, from a plant working at an effluent limit of less than 2.0 mg/l phosphorus to one working with limits variously ranging between less than 1.0 mg/l to less than 0.05 mg/l phosphorus are simulated and the resulting costs of the upgrade estimated.Five capacities of plant are considered, from 1 MGD to 100 MGD. Three strategic, alternative designs for the facility are considered: the basic activated sludge (AS) process with chemical addition, the Anoxic/Oxic (A/O) arrangement of the AS process, and the Anaerobic/Aerobic/Oxic (A/A/O) arrangement of the AS process. Upgrades in performance are consistent with the logical alternatives for adapting these options. Cost comparisons are made primarily on the basis of the incremental cost of the upgrade, i.e., from the base-case, reference plant to that performing at the higher level, as expressed through the incremental Total Annual Economic Cost (TAEC; in /kg).For the most stringent upgrade, for example, to a plant generating an effluent with less than 0.05 mg/l phosphorus, these marginal costs -- the cost of the additional phosphorus removed as a result of the upgrade -- amount to something of the order of 150-425 $/kg, with the upper bound being associated with the smallest plant configuration (1 MGD). Working Paper Number 2005-001
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