199,498 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
: An Excellent Candidate of Tetraquarks
We analyze various possible interpretations of the narrow state
which lies 100 MeV above threshold. This interesting state
decays mainly into instead of . If this relative branching
ratio is further confirmed by other experimental groups, we point out that the
identification of either as a state or more generally
as a state in the representation is probably
problematic. Instead, such an anomalous decay pattern strongly indicates
is a four quark state in the representation
with the quark content . We discuss its
partners in the same multiplet, and the similar four-quark states composed of a
bottom quark . Experimental searches of other members
especially those exotic ones are strongly called for
Resonant systems for dynamic evaluation of pressure transducers
Tests were conducted with contrived inlet modulated sinusoidal pressure generator to study possible use in calibrating pressure sensors. Results indicate concept is feasible and applicable to transducer evaluation
Melt conditioned direct chill casting (MC-DC) of wrought Al-alloys
Melt Conditioned Direct Chill (MC-DC) casting is a new development for producing high-quality billets and slabs. In the MC-DC process, liquid metal is continuously fed into a MCAST (melt conditioning by advanced shear technology) machine, where the liquid metal is subjected to high shear rate and high degree of turbulence provided by a twin screw mechanism at temperatures either above or below the alloy liquidus, and the conditioned liquid metal is then fed continuously into a Direct Chill (DC) caster to produce billets or slabs. The MC-DC process is applicable to both Aland Mg-alloys. In this paper we present our experimental investigations of the effects of processing parameters on the microstructural and compositional uniformity of 5xxx and 7xxx series Al-alloys. It has been confirmed by our experiments that the MC-DC process can produce billets and slabs with fine and uniform microstructure, uniform chemical compositions and much reduced cast defects, such as porosity and cracks
Helium Recombination Lines as a Probe of Abundance and Temperature Problems
The paper presents a simplified formula to determine an electron temperature,
Te(He I), for planetary nebulae (PNe) using the He I 7281/6678 line flux ratio.
In our previous studies of Te(He I) (Zhang et al. 2005), we used the He I line
emission coefficients given by Benjamin et al. (1999). Here we examine the
results of using more recent atomic data presented by Porter et al. (2005). A
good agreement is shown, suggesting that the effect of uncertainties of atomic
data on the resultant Te(He I) is negligible. We also present an analytical
formula to derive electron temperature using the He I discontinuity at 3421 A.
Our analysis shows that Te(He I) values are significantly lower than electron
temperatures deduced from the Balmer jump of H I recombination spectra, Te(H
I), and that inferred from the collisionally excited [O III] nebular-to-auroral
forbidden line flux ratio, Te([O III]). In addition, Te(H I) covers a wider
range of values than either Te(He I) or Te([O III]). This supports the
two-abundance nebular model with hydrogen-deficient material embedded in
diffuse gas of a ``normal'' chemical composition (i.e. ~solar).Comment: 5 pages, 3 figures. To appear in the RevMexAA proceedings of "The
Ninth Texas-Mexico Conference on Astrophysics
Localization of fermionic fields on braneworlds with bulk tachyon matter
Recently, Pal and Skar in [arXiv:hep-th/0701266] proposed a mechanism to
arise the warped braneworld models from bulk tachyon matter, which are endowed
with a thin brane and a thick brane. In this framework, we investigate
localization of fermionic fields on these branes. As in the 1/2 spin case, the
field can be localized on both the thin and thick branes with inclusion of
scalar background. In the 3/2 spin extension, the general supergravity action
coupled to chiral supermultiplets is considered to produce the localization on
both the branes as a result.Comment: 9 pages, no figure
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