1,687 research outputs found
Compressible flow structures interaction with a two-dimensional ejector: a cold-flow study
An experimental study has been conducted to examine the interaction of compressible flow structures such as
shocks and vortices with a two-dimensional ejector geometry using a shock-tube facility. Three diaphragm pressure
ratios ofP4
=P1 = 4, 8, and 12 have been employed, whereP4
is the driver gas pressure andP1
is the pressure within
the driven compartment of the shock tube. These lead to incident shock Mach numbers of Ms = 1:34, 1.54, and 1.66,
respectively. The length of the driver section of the shock tube was 700 mm. Air was used for both the driver and
driven gases. High-speed shadowgraphy was employed to visualize the induced flowfield. Pressure measurements
were taken at different locations along the test section to study theflow quantitatively. The induced flow is unsteady
and dependent on the degree of compressibility of the initial shock wave generated by the rupture of the diaphragm
PCE: Piece-wise Convex Endmember Detection
DOI: 10.1109/TGRS.2010.2041062 This item also falls under IEEE copyright. "© 2010 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works."A new hyperspectral endmember detection method
that represents endmembers as distributions, autonomously partitions the input data set into several convex regions, and simultaneously
determines endmember distributions and proportion values for each convex region is presented. Spectral unmixing methods that treat endmembers as distributions or hyperspectral images as piece-wise convex data sets have not been previously developed
Mechanical Response of He- Implanted Amorphous SiOC/ Crystalline Fe Nanolaminates
This study investigates the microstructural evolution and mechanical response of sputter-deposited amorphous silicon oxycarbide (SiOC)/crystalline Fe nanolaminates, a single layer SiOC film, and a single layer Fe film subjected to ion implantation at room temperature to obtain a maximum He concentration of 5 at. %. X-ray diffraction and transmission electron microscopy indicated no evidence of implantation-induced phase transformation or layer breakdown in the nanolaminates. Implantation resulted in the formation of He bubbles and an increase in the average size of the Fe grains in the individual Fe layers of the nanolaminates and the single layer Fe film, but the bubble density and grain size were found to be smaller in the former. By reducing the thicknesses of individual layers in the nanolaminates, bubble density and grain size were further decreased. No He bubbles were observed in the SiOC layers of the nanolaminates and the single layer SiOC film. Nanoindentation and scanning probe microscopy revealed an increase in the hardness of both single layer SiOC and Fe films after implantation. For the nanolaminates, changes in hardness were found to depend on the thicknesses of the individual layers, where reducing the layer thickness to 14 nm resulted in mitigation of implantation-induced hardening
Strong-field approximation for Coulomb explosion of H_2^+ by short intense laser pulses
We present a simple quantum mechanical model to describe Coulomb explosion of
H by short, intense, infrared laser pulses. The model is based on the
length gauge version of the molecular strong-field approximation and is valid
for pulses shorter than 50 fs where the process of dissociation prior to
ionization is negligible. The results are compared with recent experimental
results for the proton energy spectrum [I. Ben-Itzhak et al., Phys. Rev. Lett.
95, 073002 (2005), B. D. Esry et al., Phys. Rev. Lett. 97, 013003 (2006)]. The
predictions of the model reproduce the profile of the spectrum although the
peak energy is slightly lower than the observations. For comparison, we also
present results obtained by two different tunneling models for this process.Comment: 8 pages, 4 figure
An analytic model of rotationally inelastic collisions of polar molecules in electric fields
We present an analytic model of thermal state-to-state rotationally inelastic
collisions of polar molecules in electric fields. The model is based on the
Fraunhofer scattering of matter waves and requires Legendre moments
characterizing the "shape" of the target in the body-fixed frame as its input.
The electric field orients the target in the space-fixed frame and thereby
effects a striking alteration of the dynamical observables: both the phase and
amplitude of the oscillations in the partial differential cross sections
undergo characteristic field-dependent changes that transgress into the partial
integral cross sections. As the cross sections can be evaluated for a field
applied parallel or perpendicular to the relative velocity, the model also
offers predictions about steric asymmetry. We exemplify the field-dependent
quantum collision dynamics with the behavior of the Ne-OCS() and
Ar-NO() systems. A comparison with the close-coupling calculations
available for the latter system [Chem. Phys. Lett. \textbf{313}, 491 (1999)]
demonstrates the model's ability to qualitatively explain the field dependence
of all the scattering features observed
A new record of the puffer fish Takifugu oblongus (Bloch, 1786) from the northern Persian Gulf, Iran
The new record of a puffer fish “Takifugu oblongus Bloch, 1786” (Tetraodontiformes, Tetraodontidae) is recorded for the first time the muddy shores of the inter-tidal zone of Bandar-e-Abbas city, in the northern Persian Gulf, Iran in March 2011. The morphological features of Takifugu oblongus are described. This species has previously been recorded from Indo-West Pacific, South Africa to Indonesia, Japan, China, and Korea (locality type). This finding considerably extends our knowledge of the distribution of Takifugu oblongus
Dark matter spike around Bumblebee black holes
The effects of dark matter spike in the vicinity of the supermassive black
hole, located at the center of M87 (the Virgo A galaxy), are investigated
within the framework of the so-called Bumblebee Gravity. Our primary aim is to
determine whether the background of spontaneous Lorentz symmetry breaking has a
significant effect on the horizon, ergo-region, and shadow of the Kerr
Bumblebee black hole in the spike region. For this purpose, we first
incorporate the dark matter distribution in a Lorentz-violating spherically
symmetric space-time as a component of the energy-momentum tensors in the
Einstein field equations. This leads to a space-time metric for a Schwarzschild
Bumblebee black hole with a dark matter distribution in the spike region and
beyond. Subsequently, this solution is generalized to a Kerr Bumblebee black
hole through the use of the Newman-Janis-Azreg-A\"inou algorithm. Then,
according to the available observational data for the dark matter spike density
and radius, and the Schwarzschild radius of the supermassive black hole in
Virgo A galaxy, we examine the shapes of shadow and demonstrate the influence
of the spin parameter , the Lorentz-violating parameter and the
corresponding dark matter halo parameters and on the
deformation and size of the shadow
Suspended liquid particle disturbance on laser-induced blast wave and low density distribution
The impurity effect of suspended liquid particles on the laser-induced gas breakdown was experimentally investigated in quiescent gas. The focus of this study is the investigation of the influence of the impurities on the shock wave structure as well as the low density distribution. A 532 nm Nd:YAG laser beam with an 188 mJ/pulse was focused on the chamber filled with suspended liquid particles 0.9 ± 0.63 μm in diameter. Several shock waves are generated by multiple gas breakdowns along the beam path in the breakdown with particles. Four types of shock wave structures can be observed: (1) the dual blast waves with a similar shock radius, (2) the dual blast waves with a large shock radius at the lower breakdown, (3) the dual blast waves with a large shock radius at the upper breakdown, and (4) the triple blast waves. The independent blast waves interact with each other and enhance the shock strength behind the shock front in the lateral direction. The triple blast waves lead to the strongest shock wave in all cases. The shock wave front that propagates toward the opposite laser focal spot impinges on one another, and thereafter a transmitted shock wave (TSW) appears. The TSW interacts with the low density core called a kernel; the kernel then longitudinally expands quickly due to a Richtmyer-Meshkov-like instability. The laser-particle interaction causes an increase in the kernel volume which is approximately five times as large as that in the gas breakdown without particles. In addition, the laser-particle interaction can improve the laser energy efficiency
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