In this note, we study anEk/Em/1 queueing model where interarrival and service times are Erlang distributions with parametersk andm respectively. We prove that the roots of the characteristic polynomial associated with Erlang distributions are simple if the arrival and service rates are real. Based on this result, a general solution space of vectors for stationary probabilities is easily constructed. 相似文献
The character of the molecular orbitals can be better accounted for in terms of molecular adapted atomic orbitals and the Fock matrix expanded in these atomic orbital sets. A clean‐cut and unique criterion for the diradicals and the covalent bonds can be given for the molecular orbitals in both restricted and unrestricted Hartree‐Fock wavefunctions. Instead of the picture that overlap charge migrates into the bonding region, the new analysis displays another picture that the charge densities for the electrons with α and β spins give rise to two opposite spin density shifts. If the α one shifts from atom A toward atom B then it is vice versa for the β one. The spin density shifts proceed until the bonding molecular orbitals form. 相似文献
We investigate the tunneling conductance on the surface of topological insulator ferromagnet (F)/insulator (I)/superconductor (S) junction where superconducting type is either s- or d-wave paring. Topological insulators (TI) are insulating in bulk but conducting on the surface with the Dirac-fermion-like carriers. In contrast to the Dirac fermions in graphene, relativistic mass of the Dirac fermions in TI can be easily caused by applying magnetic field perpendicular to its surface. In this work, we emphatically focus on the effect of the magnetically-induced relativistic mass on the tunneling conductance of a TI-based F/I/S junction. We find that, due to the effect of spinless fermions as carriers in TI, the behavior of the tunneling conductance in a TI-based NIS junction resembles that in a nonmagnetic graphene-based NIS junction. In case of the d-wave paring F/I/S junction, increasing magnetically-induced relativistic mass changes the zero bias conductance dip (peak) to a zero bias conductance peak (dip). This behavior cannot be observed in a graphene-based F/I/S junction. 相似文献
The Josephson currents through real vector potential (RVP) and pseudo vector potential (PVP) barriers in graphene are investigated. In graphene, the pseudo vector potential may be caused by a local strain. The comparison of supercurrents induced by the two type-barriers is focused. As a result, we find that not only will the RVP induce a transition Josephson current from the 0→π state but also causes the difference in the phases of the order parameters of the two superconducting graphene layers to shift from φ→2φ. The critical current is PVP-independent around the neutrality point while it strongly depends on the RVP. The vector potential dependence of critical current is found to be perfectly linear for both PVP and RVP barriers. 相似文献
The X‐ray crystal structures of the polyfluorinated complexes [5,5′‐bis(HCF2CF2CF2CF2CH2OCH2)‐2,2′‐bpy]MI2 ( 55‐8F‐PtI 2 and 55‐8F‐PdI 2 where M = Pt and Pd, respectively) were obtained. These two structures are found to show not only two different types of intramolecular, six‐membered cyclic C–H···F–C interactions (F2C–H···F–C and HC–H···F–C) as important structural features but also alternating fluorinated and non‐fluorinated layers. The F2C–H···F–C interactions, which are close to the metal core, are much better structurally characterized in this type of complexes with fluorous ponytails at the 5,5′ positions than those previously reported at the 4,4′ positions. The molecular planes of (bpy)MI2 are extended by self‐matching, using two C–H···I hydrogen bonds and one C–H···F–C blue‐shifting hydrogen bond. The F2C–H···F–C hydrogen bonds interact at the supramolecular level such that one polyfluorinated ponytail of the title compounds is transoid without an intramolecular C–H···F–C interaction, while the other polyfluorinated ponytail is cisoid with an intramolecular C–H···F–C interaction. Why one ponytail is cisoidal while the other is transoidal will be explained. Furthermore, the second type of C–H···F–C interactions involving the methylene H atom has been identified for the first time. In addition, these two metal structures are studied by density functional theory (DFT). 相似文献
Polyaniline‐polypyrrole (PANI‐PPy) nanofibers with high aspect ratios have been synthesized by a one‐step, surfactant‐assisted chemical oxidative polymerization from mixtures of aniline (An) and pyrrole (Py) monomers. PANI‐PPy nanofibers synthesized with an excess of either PANI or PPy show similar spectral (UV‐vis and FT‐IR) characteristics as the individual homopolymers, whereas nanofibers from an equimolar mixture of An and Py display unique spectral characteristics. PANI‐PPy nanofibers undergo a spontaneous redox reaction with metal ions to produce metal nanoparticles with various morphologies and/or sizes. These findings may open new opportunities for synthesizing functional polymer nanofibers and metal nanoparticles with controllable sizes and/or morphologies.