92,907 research outputs found
An advanced meshless method for time fractional diffusion equation
Recently, because of the new developments in sustainable engineering and renewable energy, which are usually governed by a series of fractional partial differential equations (FPDEs), the numerical modelling and simulation for fractional calculus are attracting more and more attention from researchers. The current dominant numerical method for modeling FPDE is Finite Difference Method (FDM), which is based on a pre-defined grid leading to inherited issues or shortcomings including difficulty in simulation of problems with the complex problem domain and in using irregularly distributed nodes. Because of its distinguished advantages, the meshless method has good potential in simulation of FPDEs. This paper aims to develop an implicit meshless collocation technique for FPDE. The discrete system of FPDEs is obtained by using the meshless shape functions and the meshless collocation formulation. The stability and convergence of this meshless approach are investigated theoretically and numerically. The numerical examples with regular and irregular nodal distributions are used to validate and investigate accuracy and efficiency of the newly developed meshless formulation. It is concluded that the present meshless formulation is very effective for the modeling and simulation of fractional partial differential equations
Joint Symbol-Level Precoding and Reflecting Designs for IRS-Enhanced MU-MISO Systems
Intelligent reflecting surfaces (IRSs) have emerged as a revolutionary solution to enhance wireless communications by changing propagation environment in a cost-effective and hardware-efficient fashion. In addition, symbol-level precoding (SLP) has attracted considerable attention recently due to its advantages in converting multiuser interference (MUI) into useful signal energy. Therefore, it is of interest to investigate the employment of IRS in symbol-level precoding systems to exploit MUI in a more effective way by manipulating the multiuser channels. In this article, we focus on joint symbol-level precoding and reflecting designs in IRS-enhanced multiuser multiple-input single-output (MU-MISO) systems. Both power minimization and quality-of-service (QoS) balancing problems are considered. In order to solve the joint optimization problems, we develop an efficient iterative algorithm to decompose them into separate symbol-level precoding and block-level reflecting design problems. An efficient gradient-projection-based algorithm is utilized to design the symbol-level precoding and a Riemannian conjugate gradient (RCG)-based algorithm is employed to solve the reflecting design problem. Simulation results demonstrate the significant performance improvement introduced by the IRS and illustrate the effectiveness of our proposed algorithms
Market timing with aggregate accruals
We propose a market-timing strategy that aims to exploit aggregate accruals' return forecasting power. Using several performance measures of the aggregate accruals-based market-timing strategy, such as excess portfolio return, Sharpe ratio, and Jensen's alpha, we find robust evidence that, relative to the passive investment strategy of buying and holding the stock market, the market-timing strategy delivers superior performance that is both statistically and economically significant. Specifically, on average, the market-timing strategy beats the SP500 index by 6 to 22 percentage points (annualized) after controlling for transaction costs over the 1980-2004 period.© 2009 Palgrave Macmillan.postprin
The Sarbanes-Oxley act and corporate investment: A structural assessment
We assess the impact of the Sarbanes-Oxley Act of 2002 on corporate investment in an investment Euler equation framework. We allow a dummy for the passage of the Act to affect the rate at which managers discount future investment payoffs. Using generalized method of moments estimators, we find that the rate U.S. firm managers apply to discount investment projects rises significantly after 2002, while the discount rate for U.K. firms remains unchanged. The effects of the legislation on corporate investment are asymmetric, and are much more significant among relatively small firms. We also find that well-governed firms, firms with a credit rating, and accelerated filers of Section 404 of the Act have become more cautious about investment. © 2010 Elsevier B.V.postprin
Corrections to Tribimaximal Mixing from Nondegenerate Phases
We propose a seesaw scenario that possible corrections to the tribimaximal
pattern of lepton mixing are due to the small phase splitting of the
right-handed neutrino mass matrix. we show that the small deviations can be
expressed analytically in terms of two splitting parameters( and
) in the leading order. The solar mixing angle favors a
relatively smaller value compared to zero order value (), and the
Dirac type CP phase chooses a nearly maximal one. The two Majorana
type CP phases and turn out to be a nearly linear dependence.
Also a normal hierarchy neutrino mass spectrum is favored due to the stability
of perturbation calculations.Comment: 19 pages 6 figures, Accepted by Mod. Phy. Lett.
Geometric entanglement from matrix product state representations
An efficient scheme to compute the geometric entanglement per lattice site
for quantum many-body systems on a periodic finite-size chain is proposed in
the context of a tensor network algorithm based on the matrix product state
representations. It is systematically tested for three prototypical critical
quantum spin chains, which belong to the same Ising universality class. The
simulation results lend strong support to the previous claim [Q.-Q. Shi, R.
Or\'{u}s, J. O. Fj{\ae}restad, and H.-Q. Zhou, New J. Phys \textbf{12}, 025008
(2010); J.-M. St\'{e}phan, G. Misguich, and F. Alet, Phys. Rev. B \textbf{82},
180406R (2010)] that the leading finite-size correction to the geometric
entanglement per lattice site is universal, with its remarkable connection to
the celebrated Affleck-Ludwig boundary entropy corresponding to a conformally
invariant boundary condition.Comment: 4+ pages, 3 figure
Supersymmetric Modified Korteweg-de Vries Equation: Bilinear Approach
A proper bilinear form is proposed for the N=1 supersymmetric modified
Korteweg-de Vries equation. The bilinear B\"{a}cklund transformation of this
system is constructed. As applications, some solutions are presented for it.Comment: 8 pages, LaTeX using packages amsmath and amssymb, some corrections
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