975 research outputs found
Design of a General-Purpose MIMO Predictor with Neural Networks
A new multi-step predictor for multiple-input, multiple-output (MIMO) systems is proposed. The output prediction of such a system is represented as a mapping from its historical data and future inputs to future outputs. A neural network is designed to learn the mapping without re quiring a priori knowledge of the parameters and structure of the system. The major problem in de veloping such a predictor is how to train the neural network. In case of the back propagation algorithm, the network is trained by using the network's output error which is not known due to the unknown predicted future system outputs. To overcome this problem, the concept of updating, in stead of training, a neural network is introduced and verified with simulations. The predictor then uses only the system's historical data to update the configuration of the neural network and always works in a closed loop. If each node can only handle scalar operations, emulation of an MIMO mapping requires the neural network to be excessively large, and it is difficult to specify some known coupling effects of the predicted system. So, we propose a vector-structured, multilayer perceptron for the predictor design. MIMO linear, nonlinear, time-invariant, and time-varying systems are tested via simulation, and all showed very promising performances.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68861/2/10.1177_1045389X9400500206.pd
An evaluation of the Wii Nunchuk as an alternative assistive device for people with intellectual and physical disabilities using switch controlled software
Many people with intellectual disabilities also have physical difficulties which prevent them from using standard computer control devices. Custom made alternative devices for those with special needs can be expensive and the low unit turnover makes the prospect unattractive to potential manufacturers. One solution is to explore the potential of devices used in contemporary gaming technology, such as the Nintendo Wii. The Wii Nunchuk has the potential to replace joystick functions with the advantages of not being surface bound and easier for some individuals to grasp. This study evaluated the feasibility of using the Nunchuk by comparing its performance as a switch with the participant's usual switch. Twenty three volunteers aged between 17 and 21 with intellectual and physical disabilities completed a Single Switch Performance Test using the new device and their familiar device. For most functions of the switch, there was no significant difference between the participants' performance using the Nunchuck and their familiar device. Additional analysis found that some participants' performance did improve whilst using the Nunchuck, but this was not significantly related to physical or cognitive ability. Those whose performance was better with the Nunchuk were more likely to hold it in the conventional way than were those who had better performance with their familiar device. This merits it being offered as a possible alternative to currently available switches for those with physical difficulties affecting their grip
Thermoelectric power of MgBBe
We investigated thermoelectric power of MgBBe (,
0.2, 0.3, 0.4, and 0.6). decreases systematically with , suggesting
that the hole density increases. Our band calculation shows that the increase
occurs in the -band. With the hole-doping, decreases.
Implication of this phenomenon is discussed within the BCS framework. While the
Mott formula explains only the linear part of at low temperature,
incorporation of electron-phonon interaction enables us to explain over
wide temperature range including the anomalous behavior at high temperature.Comment: 4 pages, 4 figure
Liouville Correspondences between Integrable Hierarchies
In this paper, we study explicit correspondences between the integrable Novikov and Sawada-Kotera hierarchies, and between the Degasperis-Procesi and Kaup-Kupershmidt hierarchies. We show how a pair of Liouville transformations between the isospectral problems of the Novikov and Sawada-Kotera equations, and the isospectral problems of the Degasperis-Procesi and Kaup-Kupershmidt equations relate the corresponding hierarchies, in both positive and negative directions, as well as their associated conservation laws. Combining these results with the Miura transformation relating the Sawada-Kotera and Kaup-Kupershmidt equations, we further construct an implicit relationship which associates the Novikov and Degasperis-Procesi equations
Observation of nano-indent induced strain fields and dislocation generation in silicon wafers using micro-raman spectroscopy and white beam x-ray topography
In the semiconductor manufacturing industry, wafer handling introduces micro-cracks at the wafer edge. During heat treatment these can produce larger, long-range cracks in the wafer which can cause wafer breakage during manufacture. Two complimentary techniques, micro-Raman spectroscopy (μRS) and White Beam Synchrotron X-ray Topography (WBSXRT) were employed to study both the micro-cracks and the associated strain fields produced by nano-indentations in Si wafers, which were used as a means of introducing controlled strain in the wafers. It is shown that both the spatial lateral and depth distribution of these long range strain fields are relatively isotropic in nature. The Raman spectra suggest the presence of a region under tensile strain beneath the indents, which can indicate a crack beneath the indent and the data strongly suggests that there exists a minimum critical applied load below which cracking will not initiate
Vacancy-assisted domain-growth in asymmetric binary alloys: a Monte Carlo study
A Monte Carlo simulation study of the vacancy-assisted domain-growth in
asymmetric binary alloys is presented. The system is modeled using a
three-state ABV Hamiltonian which includes an asymmetry term, not considered in
previous works. Our simulated system is a stoichiometric two-dimensional binary
alloy with a single vacancy which evolves according to the vacancy-atom
exchange mechanism. We obtain that, compared to the symmetric case, the
ordering process slows down dramatically. Concerning the asymptotic behavior it
is algebraic and characterized by the Allen-Cahn growth exponent x=1/2. The
late stages of the evolution are preceded by a transient regime strongly
affected by both the temperature and the degree of asymmetry of the alloy. The
results are discussed and compared to those obtained for the symmetric case.Comment: 21 pages, 9 figures, accepted for publication in Phys. Rev.
Electromigration-Induced Flow of Islands and Voids on the Cu(001) Surface
Electromigration-induced flow of islands and voids on the Cu(001) surface is
studied at the atomic scale. The basic drift mechanisms are identified using a
complete set of energy barriers for adatom hopping on the Cu(001) surface,
combined with kinetic Monte Carlo simulations. The energy barriers are
calculated by the embedded atom method, and parameterized using a simple model.
The dependence of the flow on the temperature, the size of the clusters, and
the strength of the applied field is obtained. For both islands and voids it is
found that edge diffusion is the dominant mass-transport mechanism. The rate
limiting steps are identified. For both islands and voids they involve
detachment of atoms from corners into the adjacent edge. The energy barriers
for these moves are found to be in good agreement with the activation energy
for island/void drift obtained from Arrhenius analysis of the simulation
results. The relevance of the results to other FCC(001) metal surfaces and
their experimental implications are discussed.Comment: 9 pages, 13 ps figure
Measurements of the Composite Fermion masses from the spin polarization of 2-D electrons in the region
Measurements of the reflectivity of a 2-D electron gas are used to deduce the
polarization of the Composite Fermion hole system formed for Landau level
occupancies in the regime 1<\nu<2. The measurements are consistent with the
formation of a mixed spin CF system and allow the density of states or
`polarization' effective mass of the CF holes to be determined. The mass values
at \nu=3/2 are found to be ~1.9m_{e} for electron densities of 4.4 x 10^{11}
cm^{-2}, which is significantly larger than those found from measurements of
the energy gaps at finite values of effective magnetic field.Comment: 4 pages, 3 fig
Transverse Momentum Dependent Parton Distribution/Fragmentation Functions at an Electron-Ion Collider
We present a summary of a recent workshop held at Duke University on Partonic
Transverse Momentum in Hadrons: Quark Spin-Orbit Correlations and Quark-Gluon
Interactions. The transverse momentum dependent parton distribution functions
(TMDs), parton-to-hadron fragmentation functions, and multi-parton correlation
functions, were discussed extensively at the Duke workshop. In this paper, we
summarize first the theoretical issues concerning the study of partonic
structure of hadrons at a future electron-ion collider (EIC) with emphasis on
the TMDs. We then present simulation results on experimental studies of TMDs
through measurements of single spin asymmetries (SSA) from semi-inclusive
deep-inelastic scattering (SIDIS) processes with an EIC, and discuss the
requirement of the detector for SIDIS measurements. The dynamics of parton
correlations in the nucleon is further explored via a study of SSA in D (`D)
production at large transverse momenta with the aim of accessing the unexplored
tri-gluon correlation functions. The workshop participants identified the SSA
measurements in SIDIS as a golden program to study TMDs in both the sea and
valence quark regions and to study the role of gluons, with the Sivers
asymmetry measurements as examples. Such measurements will lead to major
advancement in our understanding of TMDs in the valence quark region, and more
importantly also allow for the investigation of TMDs in the sea quark region
along with a study of their evolution.Comment: 44 pages 23 figures, summary of Duke EIC workshop on TMDs accepted by
EPJ
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