Magnetic Coupling of a Rotating Black Hole with Advection-Dominated Accretion Flows

A model of magnetic coupling (MC) of a rotating black hole (BH) with advection- dominated accretion flow (MCADAF) is proposed. It turns out that MCADAF providers a natural explanation for the transition radius between ADAF and SSD, and could be used to interpret the highest luminosity of GX 339-4 in hard-state. A very steep emissivity index can be produced in the innermost part of the MCADAF,which is consistent with the recent XMM-Newton observations of the nearby bright Seyfert 1 galaxy MCG-6-30-15 and with two X-ray binaries (XRBs): XTE J1655-500 and GX 339-4. In addition, we estimate the BH spins in Seyfert 1 galaxy MCG-6-30-15 and in the two XRBs based on this model.Comment: 18 pages, 9 figures,acceptted by New Astronom

Locally Unitarily Invariantizable NEPv and Convergence Analysis of SCF

We consider a class of eigenvector-dependent nonlinear eigenvalue problems (NEPv) without the unitary invariance property. Those NEPv commonly arise as the first-order optimality conditions of a particular type of optimization problems over the Stiefel manifold, and previously, special cases have been studied in the literature. Two necessary conditions, a definiteness condition and a rank-preserving condition, on an eigenbasis matrix of the NEPv that is a global optimizer of the associated optimization problem are revealed, where the definiteness condition has been known for the special cases previously investigated. We show that, locally close to the eigenbasis matrix satisfying both necessary conditions, the NEPv can be reformulated as a unitarily invariant NEPv, the so-called aligned NEPv, through a basis alignment operation -- in other words, the NEPv is locally unitarily invariantizable. Numerically, the NEPv is naturally solved by an SCF-type iteration. By exploiting the differentiability of the coefficient matrix of the aligned NEPv, we establish a closed-form local convergence rate for the SCF-type iteration and analyze its level-shifted variant. Numerical experiments confirm our theoretical results.Comment: 38 pages, 11 figure

A new pick-type theorem on the hexagonal lattice

AbstractLet L be the lattice of all vertex points in a tiling of the plane by regular hexagons of unit area. Suppose the vertices of a planar polygon P are points of the lattice L, and points of L occur frequently along the edges of P. Then the area of P is A(P)=14b+12i+112c-1, where b is the number of lattice points on the boundary of P, i is the number of lattice points in the interior of P, and c is the boundary characteristic of P

Building an ontological knowledgebase for bridge maintenance

The operation stage has the biggest potential value in the bridge life cycle management, and it often critically influences the overall cost of the bridge. As such, changes in the efficiency of the project's operation stage could be of significant benefit to the overall project. However, current approaches in the operation stage often lack the effective support of computer-aided tools. This research presents a holistic method based on an ontology to achieve automatic rule checking and improve the management and communication of knowledge related to bridge maintenance. The developed ontology can also facilitate a smarter decision-making process for bridge management by informing engineers of choices with different considerations. Three approaches; semantic validation, syntactical validation, and case study validation, have been adopted to evaluate this ontology and demonstrate how the developed ontology can be used by engineers when dealing with different issues. The results showed that this approach can create a holistic knowledge base that can integrate various domain knowledge to enable bridge engineers to make more comprehensive decisions rather than a single objective-targeted delivery

Nature Of CIO Position Power: Evidence From China

This paper extends the power theory established in western management literature to study Chinese CIOs’ position power. By conducting case study on six logistics companies, we investigate what CIO position power includes, how CIOs acquire the position power, and determining factors of CIO position power. We find Chinese CIOs typically have three kinds of legitimate position power (i.e., power of participating IT assessment activities, IT-enabled business process power, and data administration power) and coercive/punishment position power. They gain legitimate position power and coercive/punishment position power through different ways. In addition, we find that firm strategic orientation, CEO’s IT competency, and CIO tenure are factors that determine the nature of CIO position power