Thermodynamics of Magnetised Kerr-Newman Black Holes

The thermodynamics of a magnetised Kerr-Newman black hole is studied to all orders in the appended magnetic field $B$. The asymptotic properties of the metric and other fields are dominated by the magnetic flux that extends to infinity along the axis, leading to subtleties in the calculation of conserved quantities such as the angular momentum and the mass. We present a detailed discussion of the implementation of a Wald-type procedure to calculate the angular momentum, showing how ambiguities that are absent in the usual asymptotically-flat case may be resolved by the requirement of gauge invariance. We also present a formalism from which we are able to obtain an expression for the mass of the magnetised black holes. The expressions for the mass and the angular momentum are shown to be compatible with the first law of thermodynamics and a Smarr type relation. Allowing the appended magnetic field $B$ to vary results in an extra term in the first law of the form $-\mu dB$ where $\mu$ is interpreted as an induced magnetic moment. Minimising the total energy with respect to the total charge $Q$ at fixed values of the angular momentum and energy of the seed metric allows an investigation of Wald's process. The Meissner effect is shown to hold for electrically neutral extreme black holes. We also present a derivation of the angular momentum for black holes in the four-dimensional STU model, which is ${\cal N}=2$ supergravity coupled to three vector multiplets.Comment: 27 page

Automatic adaptive multi-point moment matching for descriptor system model order reduction

We propose a novel automatic adaptive multi-point moment matching algorithm for model order reduction (MOR) of descriptor systems. The algorithm implements both adaptive frequency expansion point selection and automatic moment order control via a transfer function based error metric. Without a priori information of the system response, the proposed algorithm guarantees a much higher global accuracy compared with standard multi-point moment matching without adaptation. The moments are computed via a generalized Sylvester equation which is subsequently solved by a newly proposed generalized alternating direction implicit (GADI) method. Numerical examples then confirm the efficacy of the proposed schemes. © 2013 IEEE.published_or_final_versio

Study on the application of a new multiepoxy reinforcement agent for sheep leather

Content: Leather is a kind of natural biomass composite material which is made of animal skin as material by a series of chemical and physical processing. Its main structure is Collagen fibers of three-dimensional network structure. As we all know sheep leather always exist a common problem with low strength, while the strength of leather depended on the woven degree of collagen fibers. Through the past decades, many methods have been tried to improve the properties of sheep leather. The most commonly used methods are retanning. However, the strength enhancement of sheep leather is extremely limited by retanning, although the fullness and softness may be improved. In this study, a new type of multi-epoxy reinforcement agent (IGE) and IGE with the synergistic effect of polyamine (IGE-PA) were used to enhance the strength of sheep leather in tanning and fatliquoring process. Comparing with chromium tanned leather, it was found that under the optimized conditions (dosage: 10%, pH: 8, Temperature: 35℃ for penetration and 45℃ for fixation, tanning time: 10 h) with IGE as the main tanning agent, the tearing strength was increased 56.8%. While when the polyamine as the synergetic agent for IGE, the tearing strength was significantly increased 87.9%. While IGE and IGE-PA were used in fatliquoring process, it has significant reinforcement effect for tetrakis hydroxymethyl phosphonium (THP) salt tanned leather. It was found that under the optimized conditions (Dosage: 2.5%, pH: 7-8, Temperature: 50℃, Time: 2h) with IGE in fatliquoring process, the tear strength was increased 50.24%, while the IGE-PA was used, the tear strength was increased 64.3%. Furthermore, TGA results showed that decomposition temperatures of IGE and IGE-PA enhanced leather were all higher than traditional chromium tanned leather. In addition, SEM results showed that IGE and IGE-PA enhanced leather obtained better opened-up fiber structure. Take-Away: 1. A new type of multi-epoxy tanning agent (IGE) has reinforcement effect for sheep leather especially in tear strength. 2. IGE with the synergistic effect of polyamine (IGE-PA) were used in tanning process, which has a significant enhancement for the sheep leather. 3. IGE and IGE-PA can be also used in fatliquoring process to enhance the strength of sheep leather

Solution of two channel spin-flavor Kondo model

We investigate a model where an impurity couples to both the spin and the flavor currents of the two channel conduction electrons. This model can be used as a prototype model of a magnetic impurity tunneling between two sites in a metal and of some heavy fermion systems where the ground state of the impurity has a fourfold degeneracy. The system is shown to flow to a doubly degenerate non fermi-liquid(NFL) fixed point; the thermodynamic quantities show NFL behaviors, but the transport quantities show fermi liquid (FL) behaviors . A spin-flavor coupling double tensor term is shown to drive the system to one of the two singlet FL fixed points. The relation with SU(4) Coqblin-Schrieffer model is studied. The implications on the possible experiments are given.Comment: 11 pages, REVTEX, no figures. To appear in Phys. Rev. B (Rapid Comm.) July 1, 199

Photolithographic micromolding of ceramics using plasma etched polyimide patterns

Features as fine as 4 μm with high aspect ratio were produced from ceria‐zirconia ceramic using a thick plasma‐etched polyimide layer as a micromold.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70009/2/APPLAB-63-24-3379-1.pd

Universal thermal and electrical conductivity from holography

It is known from earlier work of Iqbal, Liu (arXiv:0809.3808) that the boundary transport coefficients such as electrical conductivity (at vanishing chemical potential), shear viscosity etc. at low frequency and finite temperature can be expressed in terms of geometrical quantities evaluated at the horizon. In the case of electrical conductivity, at zero chemical potential gauge field fluctuation and metric fluctuation decouples, resulting in a trivial flow from horizon to boundary. In the presence of chemical potential, the story becomes complicated due to the fact that gauge field and metric fluctuation can no longer be decoupled. This results in a nontrivial flow from horizon to boundary. Though horizon conductivity can be expressed in terms of geometrical quantities evaluated at the horizon, there exist no such neat result for electrical conductivity at the boundary. In this paper we propose an expression for boundary conductivity expressed in terms of geometrical quantities evaluated at the horizon and thermodynamical quantities. We also consider the theory at finite cutoff outside the horizon (arXiv:1006.1902) and give an expression for cutoff dependent electrical conductivity, which interpolates smoothly between horizon conductivity and boundary conductivity . Using the results about the electrical conductivity we gain much insight into the universality of thermal conductivity to viscosity ratio proposed in arXiv:0912.2719.Comment: An appendix added discussing relation between boundary conductivity and universal conductivity of stretched horizon, version to be published in JHE