100,835 research outputs found
Insensitivity of visual short-term memory to irrelevant visual information
Several authors have hypothesised that visuo-spatial working memory is functionally analogous to verbal working memory. Irrelevant background speech impairs verbal short-term memory. We investigated whether irrelevant visual information has an analogous effect on visual short-term memory, using a dynamic visual noise (DVN) technique known to disrupt visual imagery (Quinn & McConnell, 1996a). Experiment 1 replicated the effect of DVN on pegword imagery. Experiments 2 and 3 showed no effect of DVN on recall of static matrix patterns, despite a significant effect of a concurrent spatial tapping task. Experiment 4 showed no effect of DVN on encoding or maintenance of arrays of matrix patterns, despite testing memory by a recognition procedure to encourage visual rather than spatial processing. Serial position curves showed a one-item recency effect typical of visual short-term memory. Experiment 5 showed no effect of DVN on short-term recognition of Chinese characters, despite effects of visual similarity and a concurrent colour memory task that confirmed visual processing of the characters. We conclude that irrelevant visual noise does not impair visual short-term memory. Visual working memory may not be functionally analogous to verbal working memory, and different cognitive processes may underlie visual short-term memory and visual imagery
Improved parallelization techniques for the density matrix renormalization group
A distributed-memory parallelization strategy for the density matrix
renormalization group is proposed for cases where correlation functions are
required. This new strategy has substantial improvements with respect to
previous works. A scalability analysis shows an overall serial fraction of 9.4%
and an efficiency of around 60% considering up to eight nodes. Sources of
possible parallel slowdown are pointed out and solutions to circumvent these
issues are brought forward in order to achieve a better performance.Comment: 8 pages, 4 figures; version published in Computer Physics
Communication
A parallel algorithm for Hamiltonian matrix construction in electron-molecule collision calculations: MPI-SCATCI
Construction and diagonalization of the Hamiltonian matrix is the
rate-limiting step in most low-energy electron -- molecule collision
calculations. Tennyson (J Phys B, 29 (1996) 1817) implemented a novel algorithm
for Hamiltonian construction which took advantage of the structure of the
wavefunction in such calculations. This algorithm is re-engineered to make use
of modern computer architectures and the use of appropriate diagonalizers is
considered. Test calculations demonstrate that significant speed-ups can be
gained using multiple CPUs. This opens the way to calculations which consider
higher collision energies, larger molecules and / or more target states. The
methodology, which is implemented as part of the UK molecular R-matrix codes
(UKRMol and UKRMol+) can also be used for studies of bound molecular Rydberg
states, photoionisation and positron-molecule collisions.Comment: Write up of a computer program MPI-SCATCI Computer Physics
Communications, in pres
Serial digital decoder Patent
Serial digital decoder design with square circuit matrix and serial memory storage unit
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