4,969 research outputs found
A Contracted Path Integral Solution of the Discrete Master Equation
A new representation of the exact time dependent solution of the discrete
master equation is derived. This representation can be considered as
contraction of the path integral solution of Haken. It allows the calculation
of the probability distribution of the occurence time for each path and is
suitable as basis of new computational solution methods.Comment: For related work see
http://www.theo2.physik.uni-stuttgart.de/helbing.htm
Strain Effect in MgB2/Stainless Steel Superconducting Tape
The influence of mechanical strain on the critical current (Ic) is
investigated for MgB2/stainless steel (SUS316) superconducting tapes. The tapes
are fabricated by using 'powder in tube' method and deformation process without
any heat treatment. The tensile axial strain along tape length is successfully
induced to the sample by using a U-shape holder made of stainless steel
(SUS304). Two samples are examined at 4.2 K in 5 T (B is applied perpendicular
to the tape surface). While the initial Ic at zero external strain state (Ic0)
varies (30.4 and 33.3 A), normalized Ic (Ic/Ic0) vs. external strain relations
fall on the same curve. Linear increase of Ic is observed from zero external
strain state to 0.5% strain (107% of Ic0). Rapid and large degradation occurs
at the strain exceeding 0.4-0.5%. High durability against stress can be
expected for MgB2/stainless steel superconducting tapes.Comment: 3 pages including 2 figures, submitted to Physica
Synergistic Model of Cardiac Function with a Heart Assist Device
The breakdown of cardiac self-organization leads to heart diseases and failure, the number one cause of death worldwide. The left ventricular pressure–volume relation plays a key role in the diagnosis and treatment of heart diseases. Lumped-parameter models combined with pressure–volume loop analysis are very effective in simulating clinical scenarios with a view to treatment optimization and outcome prediction. Unfortunately, often invoked in this analysis is the traditional, time-varying elastance concept, in which the ratio of the ventricular pressure to its volume is prescribed by a periodic function of time, instead of being calculated consistently according to the change in feedback mechanisms (e.g., the lack or breakdown of self-organization) in heart diseases. Therefore, the application of the time-varying elastance for the analysis of left ventricular assist device (LVAD)–heart interactions has been questioned. We propose a paradigm shift from the time-varying elastance concept to a synergistic model of cardiac function by integrating the mechanical, electric, and chemical activity on microscale sarcomere and macroscale heart levels and investigating the effect of an axial rotary pump on a failing heart. We show that our synergistic model works better than the time-varying elastance model in reproducing LVAD–heart interactions with sufficient accuracy to describe the left ventricular pressure–volume relation
Single-atom laser generates nonlinear coherent states
The stationary state of a single-atom (single-qubit) laser is shown to be a
phase-averaged nonlinear coherent state - an eigenstate of a specific deformed
annihilation operator. The solution found for the stationary state is unique
and valid for all regimes of the single-qubit laser operation. We have found
the parametrization of the deformed annihilation operator which provides
superconvergence in finding the stationary state by iteration. It is also shown
that, contrary to the case of the usual laser with constant Einstein
coefficients describing transition probabilities, for the single-atom laser the
interaction-induced transition probabilities effectively depend on the field
intensity
Lattice deformation in an axially strained BiSrCaCuO/Ag tape conductor investigated by X-ray diffraction
The lattice deformation of a Bi-2212/Ag tape conductor is investigated as a function of an externally applied strain at 300 K. This macroscopic strain is applied in the same direction (¿axial¿) as where the current is normally passed through the conductor. A small but significant shift is observed in the position of the diffraction peak. In a limited strain regime this shift is proportional to the applied strain. The deformation of the c-axis that corresponds to the observed peak shift can be described well with an elastic grain deformation. For tensile axial strains above 0.2% and below ¿0.1% strain, the c-axis deformation is limited to an almost constant value. These two limits in the elastic behaviour divide the axial strain range into three regimes. A good correlation with the axial strain dependence of the critical current at 77 K, is obtained when the thermal contraction is taken into account. In the central strain range, where an elastic lattice deformation is observed, the critical current remains almost constant. Any tensile or compressive deformation that exceeds the elastic limits causes a more severe and irreversible reduction of the critical current
Luminary 1B DAP preflight performance evaluation
Preflight analysis of LUMINARY 1B DAP simulation and performance testing for Apollo Mission H
Ginzburg - Landau equation from SU(2) gauge field theory
The dual superconductor picture of the QCD vacuum is thought to describe
various aspects of the strong interaction including confinement. Ordinary
superconductivity is described by the Ginzburg-Landau (GL) equation. In the
present work we show that it is possible to arrive at a GL-like equation from
pure SU(2) gauge theory. This is accomplished by using Abelian projection to
split the SU(2) gauge fields into an Abelian subgroup and its coset. The two
gauge field components of the coset part act as the effective, complex, scalar
field of the GL equation. The Abelian part of the SU(2) gauge field is then
analogous to the electromagnetic potential in the GL equation. An important
aspect of the dual superconducting model is for the GL Lagrangian to have a
spontaneous symmetry breaking potential, and the existence of Nielsen-Olesen
flux tube solutions. Both of these require a tachyonic mass for the effective
scalar field. Such a tachyonic mass term is obtained from the condensation of
ghost fields.Comment: 7 pages, LATE
Stabilization, amalgamation, and curves of intersection of Heegaard splittings
We address a special case of the Stabilization Problem for Heegaard
splittings, establishing an upper bound on the number of stabilizations
required to make a Heegaard splitting of a Haken 3-manifold isotopic to an
amalgamation along an essential surface. As a consequence we show that for any
positive integer there are 3-manifolds containing an essential torus and a
Heegaard splitting such that the torus and splitting surface must intersect in
at least simple closed curves. These give the first examples of lower
bounds on the minimum number of curves of intersection between an essential
surface and a Heegaard surface that are greater than one.Comment: Version for publication. To appear in Algebraic and Geometric
Topolog
Verification test results of Apollo stabilization and control systems during undocked operations
The results are presented of analysis and simulation testing of both the Skylark 1 reaction control system digital autopilot (RCS DAP) and the thrust vector control (TVC) autopilot for use during the undocked portions of the Apollo/Soyuz Test Project Mission. The RCS DAP testing was performed using the Skylab Functional Simulator (SLFS), a digital computer program capable of simulating the Apollo and Skylab autopilots along with vehicle dynamics including bending and sloshing. The model is used to simulate three-axis automatic maneuvers along with pilot controlled manual maneuvers using the RCS DAP. The TVC autopilot was tested in two parts. A classical stability analysis was performed on the vehicle considering the effects of structural bending and sloshing when under control of the TVC autopilot. The time response of the TVC autopilot was tested using the SLFS. Results indicate that adequate performance stability margins can be expected for the CSM/DM configuration when under the control of the Apollo control systems tested
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