22,846 research outputs found
Cutout reinforcements for shear loaded laminate and sandwich composite panels
This paper presents the numerical and experimental studies of shear loaded
laminated and sandwich carbon/epoxy composite panels with cutouts and
reinforcements aiming at reducing the cutout stress concentration and increasing
the buckling stability of the panels. The effect of different cutout sizes and
the design and materials of cutout reinforcements on the stress and buckling
behaviour of the panels are evaluated. For the sandwich panels with a range of
cutout size and a constant weight, an optimal ratio of the core to the face
thickness has been studied for the maximum buckling stability. The finite
element method and an analytical method are employed to perform parametric
studies. In both constant stress and constant displacement shear loading
conditions, the results are in very good agreement with those obtained from
experiment for selected cutout reinforcement cases. Conclusions are drawn on the
cutout reinforcement design and improvement of stress concentration and buckling
behaviour of shear loaded laminated and sandwich composite panels with cutouts
Rotation of Coulomb crystals in a magnetized inductively coupled complex plasma
Under suitable conditions, micron-sized dust particles introduced into inductively coupled argon plasma form a stable microscopic crystal lattice, known as a Coulomb (or plasma) crystal. In the experiment described, an external axial magnetic field was applied to various configurations of Coulomb crystal, including small crystal lattices consisting of one to several particles, and large crystal lattices with many hundreds of particles. The crystals were observed to rotate collectively under the influence of the magnetic field. This paper describes the experimental procedures and the preliminary results of this investigation
Free vibration of a three-layered sandwich beam using the dynamic stiffness method and experiment
In this paper, an accurate dynamic stiffness model for a three-layered sandwich
beam of unequal thicknesses is developed and subsequently used to investigate
its free vibration characteristics. Each layer of the beam is idealised by the
Timoshenko beam theory and the combined system is reduced to a tenth-order
system using symbolic computation. An exact dynamic stiffness matrix is then
developed by relating amplitudes of harmonically varying loads to those of the
responses. The resulting dynamic stiffness matrix is used with particular
reference to the Wittrick-Williams algorithm to carry out the free vibration
analysis of a few illustrative examples. The accuracy of the theory is confirmed
both by published literature and by experiment. The paper closes with some
concluding remarks. (c) 2007 Elsevier Ltd. All rights reserved
An event-related potential study on the information flow during prospective memory interference
Poster PresentationBACKGROUND: Electroencephalography (EEG) can examine the temporal sequence of brain activity related to a specific event, which is referred to as event-related potential (ERP). Prospective memory (PM) interference presents the interference effect of an embedded PM task on other ongoing task. In the previous functional MRI study, we found that the fusiform gyrus, left inferior parietal lobe and left frontal lobe play an essential role in PM interference effect. However, little temporal information could be retrieved from the functional MRI …published_or_final_versio
Detection of Optical Synchrotron Emission from the Radio Jet of 3C279
We report the detection of optical and ultraviolet emission from the
kiloparsec scale jet of the well-known quasar 3C~279. A bright knot, discovered
in archival V and U band {\it Hubble Space Telescope} Faint Object Camera
images, is coincident with a peak in the radio jet \sim0.6\arcsec from the
nucleus. The detection was also confirmed in Wide Field Planetary Camera-2
images. Archival Very Large Array and MERLIN radio data are also analyzed which
help to show that the high-energy optical/UV continuum, and spectrum, are
consistent with a synchrotron origin from the same population of relativistic
electrons responsible for the radio emission.Comment: 6 pages, 3 figs. accepted for publication in ApJL with minor
revision
On the numerical study of bubbly wakes generated by ventilated cavity using population balance approach
In this study, an Eulerian-Eulerian two-fluid model integrated with the population balance approach based on Multiple-Size-Group (MUSIG) model was proposed to simulate on the gas leakage bubbly wake of a ventilated cavitation problem. Three selected flow conditions with Froude number ranging from 20 to 29 have been selected for investigation. Predicted void fraction and bubble velocity profiles were validated against the experimental measurements in the high-speed water tunnel of Schauer (2003) and Wosnik (2005). Sensitivity studies on the mesh resolution and three different turbulence closures were first carried out. In comparison with experimental data, the shear stress transport (SST) turbulence model was found to be the best candidate in modelling the re-circulation motions within the cavity wake region. To consider the neighbouring effect of closely packed bubbles, an empirical equation was proposed to correlate the turbulent dispersion coefficient to the local gas void fraction. Based on the proposed empirical equation, the turbulent dispersion coefficient reduces to 0.1 when local gas void fraction is higher than 60%. In general, numerical predictions were in satisfactory agreement with the experimental data. Some discrepancies have nonetheless been found between the numerical and experimental results. The lack of exact gas leakage mechanism remains an outstanding challenge in determining the actual gas leakage rate and initial bubble size from the continuous cavity. Further effort should be also focused on combing free-surface tracking model with the present population balance approach to investigate the complex vortex structure and interaction between ventilated cavity and discrete leakage bubble
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