51,832 research outputs found
Weak-Light, Zero to -\pi Lossless Kerr-Phase Gate in Quantum-well System via Tunneling Interference Effect
We examine a Kerr phase gate in a semiconductor quantum well structure based
on the tunnelling interference effect. We show that there exist a specific
signal field detuning, at which the absorption/amplification of the probe field
will be eliminated with the increase of the tunnelling interference.
Simultaneously, the probe field will acquire a -\pi phase shift at the exit of
the medium. We demonstrate with numerical simulations that a complete 180^\circ
phase rotation for the probe field at the exit of the medium is achieved, which
may result in many applications in information science and telecommunication
Development of an integrated BEM approach for hot fluid structure interaction
A comprehensive boundary element method is presented for transient thermoelastic analysis of hot section Earth-to-Orbit engine components. This time-domain formulation requires discretization of only the surface of the component, and thus provides an attractive alternative to finite element analysis for this class of problems. In addition, steep thermal gradients, which often occur near the surface, can be captured more readily since with a boundary element approach there are no shape functions to constrain the solution in the direction normal to the surface. For example, the circular disc analysis indicates the high level of accuracy that can be obtained. In fact, on the basis of reduced modeling effort and improved accuracy, it appears that the present boundary element method should be the preferred approach for general problems of transient thermoelasticity
Development of an integrated BEM approach for hot fluid structure interaction: BEST-FSI: Boundary Element Solution Technique for Fluid Structure Interaction
As part of the continuing effort at NASA LeRC to improve both the durability and reliability of hot section Earth-to-orbit engine components, significant enhancements must be made in existing finite element and finite difference methods, and advanced techniques, such as the boundary element method (BEM), must be explored. The BEM was chosen as the basic analysis tool because the critical variables (temperature, flux, displacement, and traction) can be very precisely determined with a boundary-based discretization scheme. Additionally, model preparation is considerably simplified compared to the more familiar domain-based methods. Furthermore, the hyperbolic character of high speed flow is captured through the use of an analytical fundamental solution, eliminating the dependence of the solution on the discretization pattern. The price that must be paid in order to realize these advantages is that any BEM formulation requires a considerable amount of analytical work, which is typically absent in the other numerical methods. All of the research accomplishments of a multi-year program aimed toward the development of a boundary element formulation for the study of hot fluid-structure interaction in Earth-to-orbit engine hot section components are detailed. Most of the effort was directed toward the examination of fluid flow, since BEM's for fluids are at a much less developed state. However, significant strides were made, not only in the analysis of thermoviscous fluids, but also in the solution of the fluid-structure interaction problem
Electromagnetic decays of vector mesons as derived from QCD sum rules
We apply the method of QCD sum rules in the presence of external
electromagnetic fields to the problem of the electromagnetic
decays of various vector mesons, such as , and . The induced condensates obtained previously
from the study of baryon magnetic moments are adopted, thereby ensuring the
parameter-free nature of the present calculation. Further consistency is
reinforced by invoking various QCD sum rules for the meson masses. The
numerical results on the various radiative decays agree very well with the
experimental data.Comment: To appear in Phys. Lett.
Optical study of phase transitions in single-crystalline RuP
RuP single crystals of MnP-type orthorhombic structure were synthesized by
the Sn flux method. Temperature-dependent x-ray diffraction measurements reveal
that the compound experiences two structural phase transitions, which are
further confirmed by enormous anomalies shown in temperature-dependent
resistivity and magnetic susceptibility. Particularly, the resistivity drops
monotonically upon temperature cooling below the second transition, indicating
that the material shows metallic behavior, in sharp contrast with the
insulating ground state of polycrystalline samples. Optical conductivity
measurements were also performed in order to unravel the mechanism of these two
transitions. The measurement revealed a sudden reconstruction of band structure
over a broad energy scale and a significant removal of conducting carriers
below the first phase transition, while a charge-density-wave-like energy gap
opens below the second phase transition.Comment: 5 pages, 6 figure
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