6,409 research outputs found
Energy absorption by polymer crazing
During the past thirty years, a tremendous amount of research was done on the development of crazing in polymers. The phenomenon of crazing was recognized as an unusual deformation behavior associated with a process of molecular orientation in a solid to resist failure. The craze absorbs a fairly large amount of energy during the crazing process. When a craze does occur the surrounding bulk material is usually stretched to several hundred percent of its original dimension and creates a new phase. The total energy absorbed by a craze during the crazing process in creep was calculated analytically with the help of some experimental measurements. A comparison of the energy absorption by the new phase and that by the original bulk uncrazed medium is made
Violating conformal invariance: Two-dimensional clusters grafted to wedges, cones, and branch points of Riemann surfaces
We present simulations of 2-d site animals on square and triangular lattices
in non-trivial geomeLattice animals are one of the few critical models in
statistical mechanics violating conformal invariance. We present here
simulations of 2-d site animals on square and triangular lattices in
non-trivial geometries. The simulations are done with the newly developed PERM
algorithm which gives very precise estimates of the partition sum, yielding
precise values for the entropic exponent (). In particular, we studied animals grafted to the tips of wedges
with a wide range of angles , to the tips of cones (wedges with the
sides glued together), and to branching points of Riemann surfaces. The latter
can either have sheets and no boundary, generalizing in this way cones to
angles degrees, or can have boundaries, generalizing wedges. We
find conformal invariance behavior, , only for small
angles (), while for
. These scalings hold both for wedges and cones. A heuristic
(non-conformal) argument for the behavior at large is given, and
comparison is made with critical percolation.Comment: 4 pages, includes 3 figure
Experimental Studies of Low-field Landau Quantization in Two-dimensional Electron Systems in GaAs/AlGaAs Heterostructures
By applying a magnetic field perpendicular to GaAs/AlGaAs two-dimensional
electron systems, we study the low-field Landau quantization when the thermal
damping is reduced with decreasing the temperature. Magneto-oscillations
following Shubnikov-de Haas (SdH) formula are observed even when their
amplitudes are so large that the deviation to such a formula is expected. Our
experimental results show the importance of the positive magneto-resistance to
the extension of SdH formula under the damping induced by the disorder.Comment: 9 pages, 3 figure
SiFTO: An Empirical Method for Fitting SNe Ia Light Curves
We present SiFTO, a new empirical method for modeling type Ia supernovae (SNe
Ia) light curves by manipulating a spectral template. We make use of
high-redshift SN observations when training the model, allowing us to extend it
bluer than rest frame U. This increases the utility of our high-redshift SN
observations by allowing us to use more of the available data. We find that
when the shape of the light curve is described using a stretch prescription,
applying the same stretch at all wavelengths is not an adequate description.
SiFTO therefore uses a generalization of stretch which applies different
stretch factors as a function of both the wavelength of the observed filter and
the stretch in the rest-frame B band. We compare SiFTO to other published
light-curve models by applying them to the same set of SN photometry, and
demonstrate that SiFTO and SALT2 perform better than the alternatives when
judged by the scatter around the best fit luminosity distance relationship. We
further demonstrate that when SiFTO and SALT2 are trained on the same data set
the cosmological results agree.Comment: Modified to better match published version in Ap
Cover Crop System to Control Charcoal Rot in Soybeans
This research compares methods of controlling charcoal rot in soybean cultivars from three maturity groups commonly grown in southeast Kansas. The results indicate that a mustard plant that produces high levels of glucosinolates can be used as a cover crop to reduce the charcoal rot disease in soybeans
Cover Crop System to Control Charcoal Rot in Soybeans
This research compares methods of controlling charcoal rot in soybean cultivars from three maturity groups commonly grown in southeast Kansas. The results indicate that a mustard plant that produces high levels of glucosinolates can be used as a cover crop to reduce the charcoal rot disease in soybeans
Direct CP and T Violation in Baryonic B Decays
We review the direct CP and T violation in the three-body baryonic B decays
in the standard model. In particular, we emphasize that the direct CP violating
asymmetry in is around 22% and the direct
violating asymmetry in \bar B^0 \ra \Lambda \bar p \pi^+ can be as large as
12%, which are accessible to the current B factories at KEK and SLAC as well as
SuperB and LHCb.Comment: 6 pages, Talk given at 4th International Conference on Flavor Physics
(ICFP 2007), Beijing, China, 24-28 Sep 200
Corrugated Silicon Platelet Feed Horn Array for CMB Polarimetry at 150 GHz
Next generation cosmic microwave background (CMB) polarization anisotropy
measurements will feature focal plane arrays with more than 600 millimeter-wave
detectors. We make use of high-resolution photolithography and wafer-scale etch
tools to build planar arrays of corrugated platelet feeds in silicon with
highly symmetric beams, low cross-polarization and low side lobes. A compact
Au-plated corrugated Si feed designed for 150 GHz operation exhibited
performance equivalent to that of electroformed feeds: ~-0.2 dB insertion loss,
<-20 dB return loss from 120 GHz to 170 GHz, <-25 dB side lobes and <-23 dB
cross-polarization. We are currently fabricating a 50 mm diameter array with 84
horns consisting of 33 Si platelets as a prototype for the SPTpol and ACTpol
telescopes. Our fabrication facilities permit arrays up to 150 mm in diameter.Comment: 12 pages; SPIE proceedings for Millimeter, Submillimeter, and
Far-Infrared Detectors and Instrumentation for Astronomy V (Conference 7741,
June 2010, San Diego, CA, USA
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