2,794 research outputs found
Analysis of tooling boss weld failure in the lower bulkhead of the S-1C-S fuel tank
Failure analysis of tooling boss weld in lower bulkhead of Saturn 1C stage fuel tan
Analysis of failed contacts from methode connector, FD-744-3S-SF
Methode contact cracking failure and subsequent production quality contro
Existence, Regularity, and Properties of Generalized Apparent Horizons
We prove a conjecture of Tom Ilmanen's and Hubert Bray's regarding the
existence of the outermost generalized apparent horizon in an initial data set
and that it is outer area minimizing.Comment: 16 pages, thoroughly revised, no major changes, to appear in Comm.
Math. Phy
Entropy-driven enhanced self-diffusion in confined reentrant supernematics
We present a molecular dynamics study of reentrant nematic phases using the
Gay-Berne-Kihara model of a liquid crystal in nanoconfinement. At densities
above those characteristic of smectic A phases, reentrant nematic phases form
that are characterized by a large value of the nematic order parameter
. Along the nematic director these "supernematic" phases exhibit a
remarkably high self-diffusivity which exceeds that for ordinary, lower-density
nematic phases by an order of magnitude. Enhancement of self-diffusivity is
attributed to a decrease of rotational configurational entropy in confinement.
Recent developments in the pulsed field gradient NMR technique are shown to
provide favorable conditions for an experimental confirmation of our
simulations.Comment: 10 pages, 5 figure
Multilayer approximation for a confined fluid in a slit pore
A simple Lennard-Jones fluid confined in a slit nanopore with hard walls is
studied on the basis of a multilayer structured model. Each layer is
homogeneous and parallel to the walls of the pore. The Helmholtz energy of this
system is constructed following van der Waals-like approximations, with the
advantage that the model geometry permits to obtain analytical expressions for
the integrals involved. Being the multilayer system in thermodynamic
equilibrium, a system of non-linear equations is obtained for the densities and
widths of the layers. A numerical solution of the equations gives the density
profile and the longitudinal pressures. The results are compared with Monte
Carlo simulations and with experimental data for Nitrogen, showing very good
agreement.Comment: 6 pages, 5 figures
The Meservey-Tedrov effect in FSF double tunneling junctions
Double tunneling junctions of ferromagnet-superconductor-ferromagnet
electrodes (FSF) show a jump in the conductance when a parallel magnetic field
reverses the magnetization of one of the ferromagnetic electrodes. This change
is generally attributed to the spin-valve effect or to pair breaking in the
superconductor because of spin accumulation. In this paper it is shown that the
Meservey-Tedrov effect causes a similar change in the conductance since the
magnetic field changes the energy spectrum of the quasi-particles in the
superconductor. A reversal of the bias reverses the sign in the conductance
jump
The role of string-like, supramolecular assemblies in reentrant supernematic liquid crystals
Using a combination of isothermal-isobaric Monte Carlo and microcanonical
molecular dynamics we investigate the relation between structure and
self-diffusion in various phases of a model liquid crystal using the
Gay-Berne-Kihara potential. These molecules are confined to a mesoscopic
slit-pore with atomically smooth substrate surfaces. As reported recently [see
M. G. Mazza {\em et al.}, Phys. Rev. Lett. {\bf 105}, 227802 (2010)], a
reentrant nematic (RN) phase may form at sufficiently high pressures/densities.
This phase is characterized by a high degree of nematic order and a
substantially enhanced self-diffusivity in the direction of the director
which exceeds that of the lower-density nematic and an
intermittent smectic A phase by about an order of magnitude. Here we
demonstrate that the unique transport behavior in the RN phase may be linked to
a confinement-induced packing effect which causes the formation of
supramolecular, string-like conformations. The strings consist of several
individual molecules that are capable of travelling in the direction of
as individual "trains" consisting of chains of molecular "cars".
Individual trains run in parallel and may pass each other at sufficiently high
pressures.Comment: 24 page
Disorder-induced pseudodiffusive transport in graphene nanoribbons.
We study the transition from ballistic to diffusive and localized transport in graphene nanoribbons in the presence of binary disorder, which can be generated by chemical adsorbates or substitutional doping. We show that the interplay between the induced average doping (arising from the nonzero average of the disorder) and impurity scattering modifies the traditional picture of phase-coherent transport. Close to the Dirac point, intrinsic evanescent modes produced by the impurities dominate transport at short lengths giving rise to a regime analogous to pseudodiffusive transport in clean graphene, but without the requirement of heavily doped contacts. This intrinsic pseudodiffusive regime precedes the traditional ballistic, diffusive, and localized regimes. The last two regimes exhibit a strongly modified effective number of propagating modes and a mean free path which becomes anomalously large close to the Dirac point
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