12,659 research outputs found
Thermal conductivity in the vortex state of the superconductor UPd_2Al_3
The magneto-thermal conductivity kappa is calculated for the vortex state of
UPd_2Al_3 by assuming horizontal gap nodes. The Green's function method we
employed takes into account the effects of supercurrent flow and Andreev
scattering on the quasiparticles due to Abrikosov's vortex lattice order
parameter. The calculated angular dependence of kappa_{yy} for field rotation
theta_0 in the ac-plane depends strongly on field strength H, impurity
scattering, anisotropy of the Fermi velocity, and temperature. For finite
temperatures and the clean unitary scattering limit we get qualitative
agreement with recent experiments for all four proposed gap functions having
horizontal line nodes at ck_z = 0, pi/4, and pi/2.Comment: 12 pages, 3 figures with several part
Teamwork and organizational innovation: the moderating role of the HRM context
Evidence is accumulating on the role of teams in shaping a variety of business outcomes, but our knowledge on the effect of teamwork on organizational innovation is still evolving. This study examines whether the extent to which two staff groups are organized in teams (production staff and management/administrative staff) affects organizational innovation and whether human resource management (HRM) systems, which can be of facilitating or con- straining nature, enhance the teamwork/innovation relationships. Hypotheses were tested with lagged and longitudinal data derived from 18 to 45 organizations from the UK manufacturing sector. Results suggest that the more widespread the use of teamwork in organizations, the higher the level of organizational innovation. Furthermore, this effect depends, particularly for production teams, on the overall quality of the HRM systems that exist in their organizations. Teamwork/innovation relationships are further moderated (for management and administrative teams) by an HRM practice that provides teams with time for thoughtful reflection. Thus, HRM systems can be of more or less facilitating or constraining nature for teams in organizations
Isomonodromic deformatiion with an irregular singularity and hyperelliptic curve
In this paper, we extend the result of Kitaev and Korotkin to the case where
a monodromy-preserving deformation has an irregular singularity. For the
monodromy-preserving deformation, we obtain the -function whose
deformation parameters are the positions of regular singularities and the
parameter of an irregular singularity. Furthermore, the -function is
expressed by the hyperelliptic function moving the argument \z and
the period \B, where and the positions of regular singularities move
and \B, respectively.Comment: 23 pages, 2 figure
Exchange Enhancement of the Electron-Phonon Pair Interaction
The critical temperature of high- superconductors is determined, at
least in part, by the electron-phonon coupling. We include the effect of an
exchange interaction between the electrons and calculate the renormalization of
the bare phonon frequencies and the electron-phonon verticies in a random phase
approximation and obtain a strongly enhanced attractive phonon-induced
electron-electron interaction. Using Fast Fourier Transform techniques, the
weak-coupling selfconsistency equation for the order parameter is solved in the
2D first Brillouin zone for the Emery tight-binding band with different band
fillings. The enhancement of arises primarily from the softening of the
phonon frequencies rather than the vertex renormalization.Comment: (2 pages, postscript file, hardcopies available from the authors
On higher genus Weierstrass sigma-function
The goal of this paper is to propose a new way to generalize the Weierstrass
sigma-function to higher genus Riemann surfaces. Our definition of the odd
higher genus sigma-function is based on a generalization of the classical
representation of the elliptic sigma-function via Jacobi theta-function.
Namely, the odd higher genus sigma-function (for u\in
\C^g) is defined as a product of the theta-function with odd half-integer
characteristic , associated with a spin line bundle , an
exponent of a certain bilinear form, the determinant of a period matrix and a
power of the product of all even theta-constants which are non-vanishing on a
given Riemann surface.
We also define an even sigma-function corresponding to an arbitrary even spin
structure. Even sigma-functions are constructed as a straightforward analog of
a classical formula relating even and odd sigma-functions. In higher genus the
even sigma-functions are well-defined on the moduli space of Riemann surfaces
outside of a subspace defined by vanishing of the corresponding even
theta-constant.Comment: to be published in Physica
Ultradiscretization of the solution of periodic Toda equation
A periodic box-ball system (pBBS) is obtained by ultradiscretizing the
periodic discrete Toda equation (pd Toda eq.). We show the relation between a
Young diagram of the pBBS and a spectral curve of the pd Toda eq.. The formula
for the fundamental cycle of the pBBS is obtained as a colloraly.Comment: 41 pages; 7 figure
Derivation of diagnostic models based on formalized process knowledge
Β© IFAC.Industrial systems are vulnerable to faults. Early and accurate detection and diagnosis in production systems can minimize down-time, increase the safety of the plant operation, and reduce manufacturing costs. Knowledge- and model-based approaches to automated fault detection and diagnosis have been demonstrated to be suitable for fault cause analysis within a broad range of industrial processes and research case studies. However, the implementation of these methods demands a complex and error-prone development phase, especially due to the extensive efforts required during the derivation of models and their respective validation. In an effort to reduce such modeling complexity, this paper presents a structured causal modeling approach to supporting the derivation of diagnostic models based on formalized process knowledge. The method described herein exploits the Formalized Process Description Guideline VDI/VDE 3682 to establish causal relations among key-process variables, develops an extension of the Signed Digraph model combined with the use of fuzzy set theory to allow more accurate causality descriptions, and proposes a representation of the resulting diagnostic model in CAEX/AutomationML targeting dynamic data access, portability, and seamless information exchange
Characterisation of dispersions within annealed HVOLF thermally sprayed AlSnCu coatings
High velocity oxy-liquid fuel (HVOLF) AlSnCu coatings are characterised following annealing for up to 5 hours at 300Β°C. A combination of statistical analysis of BSE images and TEM observations demonstrate the decrease in the number of sub-micron and nanoscale Sn particles with annealing, commensurate with a decrease in the coating microhardness. TEM evidence further suggests the coarsening of nanoscale Sn through a mechanism of a liquid phase migration within the Al matrix. EELS and EFTEM additionally allow the identification of the precipitation of theta'
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