3,203 research outputs found
Nanoindentation of the a and c domains in a tetragonal BaTiO3 single crystal
Nanoindentation in conjunction with piezoresponse force microscopy was used to study domain switching and to measure the mechanical properties of individual ferroelectric domains in a tetragonal BaTiO3 single crystal. It was found that nanoindentation has induced local domain switching; the a and c domains of BaTiO3 have different elastic moduli but similar hardness. Nanoindentation modulus mapping on the a and c domains further confirmed such difference in elasticity. Finite element modeling was used to simulate the von Mises stress and plastic strain profiles of the indentations on both a and c domains, which introduces a much higher stress level than the critical value for domain nucleation
The Sensitivity of the IceCube Neutrino Detector to Dark Matter Annihilating in Dwarf Galaxies
In this paper, we compare the relative sensitivities of gamma-ray and
neutrino observations to the dark matter annihilation cross section in
leptophilic models such as have been designed to explain PAMELA data. We
investigate whether the high energy neutrino telescope IceCube will be
competitive with current and upcoming searches by gamma-ray telescopes, such as
the Atmospheric Cerenkov Telescopes (ACTs) (HESS, VERITAS and MAGIC), or the
Fermi Gamma Ray Space Telescope, in detecting or constraining dark matter
particles annihilating in dwarf spheroidal galaxies. We find that after ten
years of observation of the most promising nearby dwarfs, IceCube will have
sensitivity comparable to the current sensitivity of gamma-ray telescopes only
for very heavy (m_X > 7 TeV) or relatively light (m_X < 200 GeV) dark matter
particles which annihilate primarily to mu+mu-. If dark matter particles
annihilate primarily to tau+tau-, IceCube will have superior sensitivity only
for dark matter particle masses below the 200 GeV threshold of current ACTs. If
dark matter annihilations proceed directly to neutrino-antineutrino pairs a
substantial fraction of the time, IceCube will be competitive with gamma-ray
telescopes for a much wider range of dark matter masses.Comment: 7 pages, 3 figures. v2: references added and minor revisions. v3: as
published in PRD
Modeling Wireless Signal Transmission Performance Path Loss for ZigBee Communication Protocol in Residential Houses
Low-cost and high performance wireless technologies make it a reality to develop a wireless HVAC control system for multi-zone environmental control in residential houses to improve individual comfort and reduce energy consumption. The lack of understanding on signal transmission performance of wireless sensor network in residential houses limited the application of wireless sensor networks, especially the new ZigBee protocol. This paper is to establish path loss models for predicting wireless data transmission performance in residential houses for ZigBee protocol. Factors affecting the wireless data transmission in residential indoor environment include free space separation, walls, floors, and wireless device inteference. Effects of these factors on the path loss in residential indoor environment were evaluated through empirical testing using received signal strength indicator (RSSI) value measured by commercial ZigBee modules and an embedded microcontroller-based data acquisition system. The model for the effects of walls on the same floor was able to predict 73.6% of the system variability. The measured RSSI data were made versus 1mW transmission source and therefore the RSSI-based path loss models were able to accurately predict the performance of wireless signal of stronger or weaker power transmission systems
Exceptional and Anisotropic Transport Properties of Photocarriers in Black Phosphorus
We show that black phosphorus has room-temperature charge mobilities on the
order of 10 cmVs, which are about one order of magnitude
larger than silicon. We also demonstrate strong anisotropic transport in black
phosphorus, where the mobilities along the armchair direction are about one
order of magnitude larger than zigzag direction. A photocarrier lifetime as
long as 100 ps is also determined. These results illustrate that black
phosphorus is a promising candidate for future electronic and optoelectronic
applications.Comment: 5 pages, 4 figure
High-Energy Neutrino Signatures of Dark Matter Decaying into Leptons
Decaying dark matter has previously been proposed as a possible explanation
for the excess high energy cosmic ray electrons and positrons seen by PAMELA
and the Fermi Gamma-Ray Space Telescope (FGST). To accommodate these signals
however, the decays must be predominantly leptonic, to muons or taus, and
therefore produce neutrinos, potentially detectable with the IceCube neutrino
observatory. We find that, with five years of data, IceCube (supplemented by
DeepCore) will be able to significantly constrain the relevant parameter space
of decaying dark matter, and may even be capable of discovering dark matter
decaying in the halo of the Milky Way.Comment: 4 pages, 1 figur
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