48,245 research outputs found
Numerical evaluation of equivalence ratio measurement using OH* and CH* chemiluminescence in premixed and non-premixed methane-air flames
We provide the existence and asymptotic description of solitary wave solutions to a class of modified GreenâNaghdi systems, modeling the propagation of long surface or internal waves. This class was recently proposed by DuchĂȘne et al. (Stud Appl Math 137:356â415, 2016) in order to improve the frequency dispersion of the original GreenâNaghdi system while maintaining the same precision. The solitary waves are constructed from the solutions of a constrained minimization problem. The main difficulties stem from the fact that the functional at stake involves low order non-local operators, intertwining multiplications and convolutions through Fourier multipliers
Towards Real-Time Detection and Tracking of Spatio-Temporal Features: Blob-Filaments in Fusion Plasma
A novel algorithm and implementation of real-time identification and tracking
of blob-filaments in fusion reactor data is presented. Similar spatio-temporal
features are important in many other applications, for example, ignition
kernels in combustion and tumor cells in a medical image. This work presents an
approach for extracting these features by dividing the overall task into three
steps: local identification of feature cells, grouping feature cells into
extended feature, and tracking movement of feature through overlapping in
space. Through our extensive work in parallelization, we demonstrate that this
approach can effectively make use of a large number of compute nodes to detect
and track blob-filaments in real time in fusion plasma. On a set of 30GB fusion
simulation data, we observed linear speedup on 1024 processes and completed
blob detection in less than three milliseconds using Edison, a Cray XC30 system
at NERSC.Comment: 14 pages, 40 figure
Spectrum and Thermodynamics of the one-dimensional supersymmetric t-J model with exchange and hopping
We derive the spectrum and the thermodynamics of the one-dimensional
supersymmetric t-J model with long range hopping and spin exchange using a set
of maximal-spin eigenstates. This spectrum confirms the recent conjecture that
the asymptotic Bethe-ansatz spectrum is exact. By empirical determining the
spinon degeneracies of each state, we are able to explicitly construct the free
energy.Comment: 13 pages, Latex, (published in PRB46, 6639 (1992)
A unified constitutive model for asymmetric tension and compression creep-ageing behaviour of naturally aged Al-Cu-Li alloy
A set of unified constitutive equations is presented that predict the asymmetric tension and compression creep behaviour and recently observed double primary creep of pre-stretched/naturally aged aluminium-cooper-lithium alloy AA2050-T34. The evolution of the primary micro- and macro-variables related to the precipitation hardening and creep deformation of the alloy during creep age forming (CAF) are analysed and modelled. Equations for the yield strength evolution of the alloy, including an initial reversion and subsequent strengthening, are proposed based on a theory of concurrent dissolution, re-nucleation and growth of precipitates during artificial ageing. We present new observations of so-called double primary creep during the CAF process. This phenomenon is then predicted by introducing effects of interacting microstructures, including evolving precipitates, diffusing solutes and dislocations, into the sinh-law creep model. In addition, concepts of threshold creep stress Ïth and a microstructure-dependant creep variable H, which behave differently under different external stress directions, are proposed and incorporated into the creep model. This enables prediction of the asymmetric tension and compression creep-ageing behaviour of the alloy. Quantitative transmission electron microscopy (TEM) and related small-angle X-ray scattering (SAXS) analysis have been carried out for selected creep-aged samples to assist the development and calibration of the constitutive model. A good agreement has been achieved between the experimental results and the model. The model has the potential to be applied to creep age forming of other heat-treatable aluminium alloys
Vortex charges in high-temperature superconductors
The vortex charge in high-temperature superconductors was investigated. It was found that the vortex charge was negative when a sufficient strength of antiferromagnetic (AF) order was induced inside the vortex core. The vortex charge at optimal doping was studied as a function of magnetic field. The results showed that the AF order was absent inside the vortex core for small Coulomb repulsion.published_or_final_versio
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