A new sensorless method for switched reluctance motor drives

This paper describes a new method for indirect sensing of the rotor position in switched reluctance motors (SRMs) using pulse width modulation voltage control. The detection method uses the change of the derivative of the phase current to detect the position where a rotor pole and stator pole start to overlap, giving one position update per energy conversion. As no a priori knowledge of motor parameters is required (except for the numbers of stator and rotor poles), the method is applicable to most SRM topologies in a wide power and speed range and for several inverter topologies. The method allows modest closed-loop dynamic performance. To start up the motor, a feedforward stepping method is used which assures robust startup (even under load) from standstill to a predefined speed at which closed-loop sensorless operation can be applied. Experimental results demonstrate the robust functionality of the method with just one current sensor in the inverter, even with excitation overlap, and the sensorless operation improves with speed. The method is comparable to the back-EMF position estimation for brushless DC motors in principle, performance and cost. A detailed operation and implementation of this scheme is shown, together with steady-state and dynamic transient test results

Current Status of Simulations

As the title suggests, the purpose of this chapter is to review the current status of numerical simulations of black hole accretion disks. This chapter focuses exclusively on global simulations of the accretion process within a few tens of gravitational radii of the black hole. Most of the simulations discussed are performed using general relativistic magnetohydrodynamic (MHD) schemes, although some mention is made of Newtonian radiation MHD simulations and smoothed particle hydrodynamics. The goal is to convey some of the exciting work that has been going on in the past few years and provide some speculation on future directions.Comment: 15 pages, 14 figures, to appear in the proceedings of the ISSI-Bern workshop on "The Physics of Accretion onto Black Holes" (8-12 October 2012

Selected nucleon form factors and a composite scalar diquark

A covariant, composite scalar diquark, Fadde'ev amplitude model for the nucleon is used to calculate pseudoscalar, isoscalar- and isovector-vector, axial-vector and scalar nucleon form factors. The last yields the nucleon sigma-term and on-shell sigma-nucleon coupling. The calculated form factors are soft, and the couplings are generally in good agreement with experiment and other determinations. Elements in the dressed-quark-axial-vector vertex that are not constrained by the Ward-Takahashi identity contribute ~20% to the magnitude of g_A. The calculation of the nucleon sigma-term elucidates the only unambiguous means of extrapolating meson-nucleon couplings off the meson mass-shell.Comment: 12 pages, REVTEX, 5 figures, epsfi

Comparison of ibuprofen release from minitablets and capsules containing ibuprofen: β-Cyclodextrin complex

NOTICE: this is the author’s version of a work that was accepted for publication in European Journal of Pharmaceutics and Biopharmaceutics. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Eur J Pharm Biopharm. 2011 May;78(1):58-66. Epub 2010 Dec 30.Mixtures containing ibuprofen (IB) complexed with b-cyclodextrin (bCD) obtained by two complexation methods [suspension/solution (with water removed by air stream, spray- and freeze-drying) and kneading technique] were processed into pharmaceutical dosage forms (minitablets and capsules). Powders (IB, bCD and IBbCD) were characterized for moisture content, densities (true and bulk), angle of repose and Carr’s index, X-ray and NMR. From physical mixtures and IBbCD complexes without other excipients were prepared 2.5-mm-diameter minitablets and capsules. Minitablets were characterized for the energy of compaction, tensile strength, friability, density and IB release (at pH 1.0 and 7.2), whereby capsules were characterized for IB release. The results from the release of IB were analyzed using different parameters, namely, the similarity factor (f2), the dissolution efficiency (DE) and the amounts released at a certain time (30, 60 and 180 min) and compared statistically (a = 0.05). The release of IB from the minitablets showed no dependency on the amount of water used in the formation of the complexes. Differences were due to the compaction force used or the presence of a shell for the capsules. The differences observed were mostly due to the characteristics of the particles (dependent on the method considered on the formation of the complexes) and neither to the dosage form nor to the complex of the IB

Comparison Of Methanolysis Of A Series Of P-benzyloxybenzoyl Chlorides With That Of Benzoyl, P-phenoxybenzoyl, And P-methoxybenzoyl Chlorides

The kinetics of the methanolysis (solvolysis) of a series of p-benzyloxybenzoyl chlorides have been compared with values for benzoyl, p-methoxybenzoyl. and p-phenoxybenzoyl chloride. Small rate differences between benzoyl chloride and the other compounds stem from counterbalancing large changes in enthalpies and entropies of activation, ascribed to different degrees of SN1 character in the reactions. Differences within the benzyloxy-series are ascribed to effects of substituents on the inductive effect of the benzene ring of the benzyloxy-group. Data have been analysed in terms of the Hammett equation. Values of σ for the p-benzyloxy-group were obtained from both kinetic and acidity measurements : both are considerably less than the literature value, which we regard as suspect. A coefficient of transmission of electronic effects across a p-benzyloxy-group was determined as 0.17.141648165

Intrinsic Decoherence Dynamics in Smooth Hamiltonian Systems: Quantum-classical Correspondence

A direct classical analog of the quantum dynamics of intrinsic decoherence in Hamiltonian systems, characterized by the time dependence of the linear entropy of the reduced density operator, is introduced. The similarities and differences between the classical and quantum decoherence dynamics of an initial quantum state are exposed using both analytical and computational results. In particular, the classicality of early-time intrinsic decoherence dynamics is explored analytically using a second-order perturbative treatment, and an interesting connection between decoherence rates and the stability nature of classical trajectories is revealed in a simple approximate classical theory of intrinsic decoherence dynamics. The results offer new insights into decoherence, dynamics of quantum entanglement, and quantum chaos.Comment: 12 pages, 7 figures, to appear in Physical Review

Finding Faint Intermediate-mass Black Holes in the Radio Band

We discuss the prospects for detecting faint intermediate-mass black holes, such as those predicted to exist in the cores of globular clusters and dwarf spheroidal galaxies. We briefly summarize the difficulties of stellar dynamical searches, then show that recently discovered relations between black hole mass, X-ray luminosity and radio luminosity imply that in most cases, these black holes should be more easily detected in the radio than in the X-rays. Finally, we show upper limits from some radio observations of globular clusters, and discuss the possibility that the radio source in the core of the Ursa Minor dwarf spheroidal galaxy might be a $\sim 10,000-100,000 M_\odot$ black hole.Comment: 10 pages, no figures, to appear in From X-ray Binaries to Quasars: Black Hole Accretion on All Mass Scales, ed. T. J. Maccarone, R. P. Fender, and L. C. Ho (Dordrecht: Kluwer

Popular attitudes to memory, the body, and social identity : the rise of external commemoration in Britain, Ireland, and New England

A comparative analysis of samples of external memorials from burial grounds in Britain, Ireland and New England reveals a widespread pattern of change in monument style and content, and exponential growth in the number of permanent memorials from the 18th century onwards. Although manifested in regionally distinctive styles on which most academic attention has so far been directed, the expansion reflects global changes in social relationships and concepts of memory and the body. An archaeological perspective reveals the importance of external memorials in articulating these changing attitudes in a world of increasing material consumption