31,124 research outputs found
Numerical analysis of the Iosipescu specimen for composite materials
A finite element analysis of the Iosipescu shear tests for unidirectional and cross-ply composites is presented. It is shown that an iterative analysis procedure must be used to model the fixture-specimen kinematics. The correction factors which are needed to compensate for the nonuniformity of stress distribution in calculating shear modulus are shown to be dependent on the material orthotropic ratio and the finite element loading models. Test section strain distributions representative of typical graphite-epoxy specimens are also presented
Interstitial gas and density-segregation in vertically-vibrated granular media
We report experimental studies of the effect of interstitial gas on
mass-density-segregation in a vertically-vibrated mixture of equal-sized bronze
and glass spheres. Sufficiently strong vibration in the presence of
interstitial gas induces vertical segregation into sharply separated bronze and
glass layers. We find that the segregated steady state (i.e., bronze or glass
layer on top) is a sensitive function of gas pressure and viscosity, as well as
vibration frequency and amplitude. In particular, we identify distinct regimes
of behavior that characterize the change from bronze-on-top to glass-on-top
steady-state.Comment: 4 pages, 5 figures, submitted to PRL; accepted in PRE as rapid
communication, with revised text and reference
THOR 2.0: Major Improvements to the Open-Source General Circulation Model
THOR is the first open-source general circulation model (GCM) developed from
scratch to study the atmospheres and climates of exoplanets, free from Earth-
or Solar System-centric tunings. It solves the general non-hydrostatic Euler
equations (instead of the primitive equations) on a sphere using the
icosahedral grid. In the current study, we report major upgrades to THOR,
building upon the work of Mendon\c{c}a et al. (2016). First, while the
Horizontally Explicit Vertically Implicit (HEVI) integration scheme is the same
as that described in Mendon\c{c}a et al. (2016), we provide a clearer
description of the scheme and improved its implementation in the code. The
differences in implementation between the hydrostatic shallow (HSS),
quasi-hydrostatic deep (QHD) and non-hydrostatic deep (NHD) treatments are
fully detailed. Second, standard physics modules are added: two-stream,
double-gray radiative transfer and dry convective adjustment. Third, THOR is
tested on additional benchmarks: tidally-locked Earth, deep hot Jupiter,
acoustic wave, and gravity wave. Fourth, we report that differences between the
hydrostatic and non-hydrostatic simulations are negligible in the Earth case,
but pronounced in the hot Jupiter case. Finally, the effects of the so-called
"sponge layer", a form of drag implemented in most GCMs to provide numerical
stability, are examined. Overall, these upgrades have improved the flexibility,
user-friendliness, and stability of THOR.Comment: 57 pages, 31 figures, revised, accepted for publication in ApJ
Safety Assessment of Moso Bamboo Column Under Fire by Using Bamboo as Protection Layer
Global warming issue has forced the construction world including architecture to find the green material in order to minimize CO2 which damages to the nature. In the beginning, wood was one of the green material but it has long growth cycle. Lately, bamboo has been chosen for its fast growing cycle and resuming some wood properties, also known as local material and eco-friendly –benign to the nature. Generally, wood and bamboo are composed by carbon-based compound. So, they are combustible and flammable when they are exposed to the fire. Up to now, there are not so many studies regarding the fire behavior of raw round bamboo which is used as the structure. To investigate the effectiveness of bamboo protection layer, the nine-trunk bamboos will be tied up to construct the column. A one bamboo will be placed in the middle and surrounded by the other eight-bamboos –as the protection layer of the center. All of them are with no-fire retardant. By doing this, it is possible to obtain knowledge upon bamboo on its natural properties. Specimen will be exposed to the fire inside the furnace up to 700° C. The temperature changing on the specimen will be measured by thermocouples which are installed inside and outside the wall of main bamboo in the center part. The main bamboo is expected to have lower temperature than its auto-ignition temperature, so that the structure will be able stand out during the fire until the occupants able to be evacuated safely
Orbital symmetry fingerprints for magnetic adatoms in graphene
In this paper, we describe the formation of local resonances in graphene in
the presence of magnetic adatoms containing localized orbitals of arbitrary
symmetry, corresponding to any given angular momentum state. We show that
quantum interference effects which are naturally inbuilt in the honeycomb
lattice in combination with the specific orbital symmetry of the localized
state lead to the formation of fingerprints in differential conductance curves.
In the presence of Jahn-Teller distortion effects, which lift the orbital
degeneracy of the adatoms, the orbital symmetries can lead to distinctive
signatures in the local density of states. We show that those effects allow
scanning tunneling probes to characterize adatoms and defects in graphene.Comment: 15 pages, 11 figures. Added discussion about the multi-orbital case
and the validity of the single orbital picture. Published versio
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