4,801 research outputs found
New twisted intermetallic compound superconductor: A concept
Method for processing Nb3Sn and other intermetallic compound superconductors produces a twisted, stabilized wire or tube which can be used to wind electromagnetics, armatures, rotors, and field windings for motors and generators as well as other magnetic devices
Method of fabricating a twisted composite superconductor
A method of producing a twisted, stabilized wire or tube superconductor which can be used to wind electromagnets, armatures, rotors, field windings for motors and generators, and other magnetic devices which use a solenoid, toroidal, or other type winding is reported. At least one groove is formed along the length of a wire substrate which is then twisted into a helix and a layer of intermetallic superconducting material is formed in the groove. This layer can be formed by depositing the desired intermetallic compound into the groove or by diffusing one component of the superconductor into the groove formed in a substrate composed of the other component. The superconductor prepared by this method comprises a non-superconductor wire twisted into the shape of a helix, having at least one groove containing a layer of superconductor material along the length of the wire
Developing a Normative Framework to Access Small-Firm Entry Strategies: A Resource-Based View
The decision to pursue growth opportunities is often complex and multidimensional. Small businesses pursuing these opportunities must consider many important criteria, such as resource requisites, timing and how to enter new markets. Unfortunately, there are not many systemic tools available to make these difficult decisions. One area of literature that may assist small businesses in deciding how to enter new markets is the resource-based view of a firm. The resource-based view of a firm complements current strategic management thought by refocusing efforts on the long-term accumulations of assets rather than short-term resource allocations. We synthesize concepts from the resource-based view with the literature on alternative entry strategies to develop a normative framework for small-business decision makers. Specifically, from the resource-based view, we consider: I) different types of distinctive competencies - tangible/intangible resources owned by a firm and capabilities/processes used by a firm; 2) the degree to which these distinctive competencies can be sustained given certain environmental attributes, such as ease of imitation, abilities of competitors and industry dynamism. The interrelationships between distinctive competence and environmental sustainability are then used to identify appropriate strategies to enter new markets
Shear-melting of a hexagonal columnar crystal by proliferation of dislocations
A hexagonal columnar crystal undergoes a shear-melting transition above a
critical shear rate or stress. We combine the analysis of the shear-thinning
regime below the melting with that of synchrotron X-ray scattering data under
shear and propose the melting to be due to a proliferation of dislocations,
whose density is determined by both techniques to vary as a power law of the
shear rate with a 2/3 exponent, as expected for a creep model of crystalline
solids. Moreover, our data suggest the existence under shear of a line hexatic
phase, between the columnar crystal and the liquid phase
Center-stabilized Yang-Mills theory: confinement and large volume independence
We examine a double trace deformation of SU(N) Yang-Mills theory which, for
large and large volume, is equivalent to unmodified Yang-Mills theory up to
corrections. In contrast to the unmodified theory, large volume
independence is valid in the deformed theory down to arbitrarily small volumes.
The double trace deformation prevents the spontaneous breaking of center
symmetry which would otherwise disrupt large volume independence in small
volumes. For small values of , if the theory is formulated on with a sufficiently small compactification size , then an analytic
treatment of the non-perturbative dynamics of the deformed theory is possible.
In this regime, we show that the deformed Yang-Mills theory has a mass gap and
exhibits linear confinement. Increasing the circumference or number of
colors decreases the separation of scales on which the analytic treatment
relies. However, there are no order parameters which distinguish the small and
large radius regimes. Consequently, for small the deformed theory provides
a novel example of a locally four-dimensional pure gauge theory in which one
has analytic control over confinement, while for large it provides a simple
fully reduced model for Yang-Mills theory. The construction is easily
generalized to QCD and other QCD-like theories.Comment: 29 pages, expanded discussion of multiple compactified dimension
Winter climate variability and snowpack in the West
Snowpack is an important source of water supply in the western United States. This study examines the seasonal variability of an extensive history of snow observations over the western United States and Canada. It links variations in snowpack to variations in atmospheric circulation, surface temperature, and precipitation
M.I.T./Canadian Vestibular Experiments on the Spacelab-1 Mission. Part 1: Sensory Adaptation to Weightlessness and Readaptation to One-G: An Overview
Experiments on human spatial orientation were conducted on four crewmembers of Space Shuttle Spacelab Mission 1. The conceptual background of the project, the relationship among the experiments, and their relevance to a 'sensory reinterpretation hypothesis' are presented. Detailed experiment procedures and results are presented in the accompanying papers in this series. The overall findings are discussed as they pertain to the following aspects of hypothesized sensory reinterpretation in weightlessness: (1) utricular otolith afferent signals are reinterpreted as indicating head translation rather than tilt, (2) sensitivity of reflex responses to footward acceleration is reduced, and (3) increased weighting is given to visual and tactile cues in orientation perception and posture control. Results suggest increased weighting of visual cues and reduced weighting of graviceptor signals in weightlessness
Debye screening in strongly coupled N=4 supersymmetric Yang-Mills plasma
Using the AdS/CFT correspondence, we examine the behavior of correlators of
Polyakov loops and other operators in N=4 supersymmetric Yang-Mills theory at
non-zero temperature. The implications for Debye screening in this strongly
coupled non-Abelian plasma, and comparisons with available results for thermal
QCD, are discussed.Comment: 21 pages, 5 figures, significantly expanded discussion of Polyakov
loop correlator and static quark-antiquark potentia
ROSAT PSPC Observations of the Richest () ACO Clusters
We have compiled an X-ray catalog of optically selected rich clusters of
galaxies observed by the PSPC during the pointed GO phase of the ROSAT mission.
This paper contains a systematic X-ray analysis of 150 clusters with an optical
richness classification of from the ACO catalog (Abell, Corwin, and
Olowin 1989). All clusters were observed within 45' of the optical axis of the
telescope during pointed PSPC observations. For each cluster, we calculate: the
net 0.5-2.0 keV PSPC count rate (or upper limit) in a 1 Mpc radius
aperture, 0.5-2.0 keV flux and luminosity, bolometric luminosity, and X-ray
centroid. The cluster sample is then used to examine correlations between the
X-ray and optical properties of clusters, derive the X-ray luminosity function
of clusters with different optical classifications, and obtain a quantitative
estimate of contamination (i.e, the fraction of clusters with an optical
richness significantly overestimated due to interloping galaxies) in the ACO
catalog
Effective theories for real-time correlations in hot plasmas
We discuss the sequence of effective theories needed to understand the
qualitative, and quantitative, behavior of real-time correlators
in ultra-relativistic plasmas. We analyze in detail the case where A is a
gauge-invariant conserved current. This case is of interest because it includes
a correlation recently measured in lattice simulations of classical, hot,
SU(2)-Higgs gauge theory. We find that simple perturbation theory, free kinetic
theory, linearized kinetic theory, and hydrodynamics are all needed to
understand the correlation for different ranges of time. We emphasize how
correlations generically have power-law decays at very large times due to
non-linear couplings to long-lived hydrodynamic modes.Comment: 28 pages, Latex, uses revtex, epsf macro packages [Revised version: t
-> sqrt{t} in a few typos on p. 10.
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