25,507 research outputs found
Excitation of nonlinear ion acoustic waves in CH plasmas
Excitation of nonlinear ion acoustic wave (IAW) by an external electric field
is demonstrated by Vlasov simulation. The frequency calculated by the
dispersion relation with no damping is verified much closer to the resonance
frequency of the small-amplitude nonlinear IAW than that calculated by the
linear dispersion relation. When the wave number increases,
the linear Landau damping of the fast mode (its phase velocity is greater than
any ion's thermal velocity) increases obviously in the region of in which the fast mode is weakly damped mode. As a result, the deviation
between the frequency calculated by the linear dispersion relation and that by
the dispersion relation with no damping becomes larger with
increasing. When is not large, such as , the nonlinear IAW can be excited by the driver with the linear frequency
of the modes. However, when is large, such as
, the linear frequency can not be applied to exciting the
nonlinear IAW, while the frequency calculated by the dispersion relation with
no damping can be applied to exciting the nonlinear IAW.Comment: 10 pages, 9 figures, Accepted by POP, Publication in August 1
A new solution algorithm for solving rule-sets based bilevel decision problems
Copyright © 2012 John Wiley & Sons, Ltd. Copyright © 2012 John Wiley & Sons, Ltd. Bilevel decision addresses compromises between two interacting decision entities within a given hierarchical complex system under distributed environments. Bilevel programming typically solves bilevel decision problems. However, formulation of objectives and constraints in mathematical functions is required, which are difficult, and sometimes impossible, in real-world situations because of various uncertainties. Our study develops a rule-set based bilevel decision approach, which models a bilevel decision problem by creating, transforming and reducing related rule sets. This study develops a new rule-sets based solution algorithm to obtain an optimal solution from the bilevel decision problem described by rule sets. A case study and a set of experiments illustrate both functions and the effectiveness of the developed algorithm in solving a bilevel decision problem
An algorithm for solving rule sets-based bilevel decision problems
Bilevel decision addresses the problem in which two levels of decision makers each tries to optimize their individual objectives under certain constraints, and to act and react in an uncooperative and sequential manner. Given the difficulty of formulating a bilevel decision problem by mathematical functions, a rule sets-based bilevel decision (RSBLD) model was proposed. This article presents an algorithm to solve a RSBLD problem. A case-based example is given to illustrate the functions of the proposed algorithm. Finally, a set of experiments is analyzed to further show the functions and the effectiveness of the proposed algorithm. © 2011 Wiley Periodicals, Inc
Rule sets based bilevel decision model
Bilevel decision addresses the problem in which two levels of decision makers, each tries to optimize their individual objectives under constraints, act and react in an uncooperative, sequential manner. Such a bilevel optimization structure appears naturally in many aspects of planning, management and policy making. However, bilevel decision making may involve many uncertain factors in a real world problem. Therefore it is hard to determine the objective functions and constraints of the leader and the follower when build a bilevel decision model. To deal with this issue, this study explores the use of rule sets to format a bilevel decision problem by establishing a rule sets based model. After develop a method to construct a rule sets based bilevel model of a real-world problem, an example to illustrate the construction process is presented. Copyright © 2006, Australian Computer Society, Inc
Anti-Stokes scattering and Stokes scattering of stimulated Brillouin scattering cascade in high-intensity laser-plasmas interaction
The anti-Stokes scattering and Stokes scattering in stimulated Brillouin
scattering (SBS) cascade have been researched by the Vlasov-Maxwell simulation.
In the high-intensity laser-plasmas interaction, the stimulated anti-Stokes
Brillouin scattering (SABS) will occur after the second stage SBS rescattering.
The mechanism of SABS has been put forward to explain this phenomenon. And the
SABS will compete with the SBS rescattering to determine the total SBS
reflectivity. Thus, the SBS rescattering including the SABS is an important
saturation mechanism of SBS, and should be taken into account in the
high-intensity laser-plasmas interaction.Comment: 6 pages, 5 figure
A Supervised ML Applied Classification Model for Brain Tumors MRI.
Brain Tumor originates from abnormal cells, which is developed uncontrollably. Magnetic resonance imaging (MRI) is developed to generate high-quality images and provide extensive medical research information. The machine learning algorithms can improve the diagnostic value of MRI to obtain automation and accurate classification of MRI. In this research, we propose a supervised machine learning applied training and testing model to classify and analyze the features of brain tumors MRI in the performance of accuracy, precision, sensitivity and F1 score. The result presents that more than 95% accuracy is obtained in this model. It can be used to classify features more accurate than other existing methods
Enhanced superconductivity at the interface of W/SrRuO point contact
Differential resistance measurements are conducted for point contacts (PCs)
between tungsten tip approaching along the axis direction and the
plane of SrRuO single crystal. Three key features are found.
Firstly, within 0.2 mV there is a dome like conductance enhancement due to
Andreev reflection at the normal-superconducting interface. By pushing the W
tip further, the conductance enhancement increases from 3\% to more than 20\%,
much larger than that was previously reported, probably due to the pressure
exerted by the tip. Secondly, there are also superconducting like features at
bias higher than 0.2 mV which persists up to 6.2 K, resembling the enhanced
superconductivity under uniaxial pressure for bulk SrRuO crystals
but more pronounced here. Third, the logarithmic background can be fitted with
the Altshuler-Aronov theory of tunneling into quasi two dimensional electron
system, consistent with the highly anisotropic electronic system in
SrRuO.Comment: prb style, 9 pages, 8 fig
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