4,059 research outputs found
Hydrogen induced fracture characteristics of single crystal nickel-based superalloys
A stereoscopic method for use with x ray energy dispersive spectroscopy of rough surfaces was adapted and applied to the fracture surfaces single crystals of PWA 1480E to permit rapid orientation determinations of small cleavage planes. The method uses a mathematical treatment of stereo pair photomicrographs to measure the angle between the electron beam and the surface normal. One reference crystal orientation corresponding to the electron beam direction (crystal growth direction) is required to perform this trace analysis. The microstructure of PWA 1480E was characterized before fracture analysis was performed. The fracture behavior of single crystals of the PWA 1480E nickel-based superalloy was studied. The hydrogen-induced fracture behavior of single crystals of the PWA 1480E nickel-based superalloy was also studied. In order to understand the temperature dependence of hydrogen-induced embrittlement, notched single crystals with three different crystal growth orientations near zone axes (100), (110), and (111) were tensile tested at 871 C (1600 F) in both helium and hydrogen atmospheres at 34 MPa. Results and conclusions are given
Topological Mott Insulators
We consider extended Hubbard models with repulsive interactions on a
Honeycomb lattice and the transitions from the semi-metal phase at half-filling
to Mott insulating phases. In particular, due to the frustrating nature of the
second-neighbor repulsive interactions, topological Mott phases displaying the
quantum Hall and the quantum spin Hall effects are found for spinless and
spinful fermion models, respectively. We present the mean-field phase diagram
and consider the effects of fluctuations within the random phase approximation
(RPA). Functional renormalization group analysis also show that these states
can be favored over the topologically trivial Mott insulating states.Comment: 5 Pages, 4 figure
Local density of states of a d-wave superconductor with inhomogeneous antiferromagnetic correlations
The tunneling spectrum of an inhomogeneously doped extended Hubbard model is
calculated at the mean field level. Self-consistent solutions admit both
superconducting and antiferromagnetic order, which coexist inhomogeneously
because of spatial randomness in the doping. The calculations find that, as a
function of doping, there is a continuous cross over from a disordered ``pinned
smectic'' state to a relatively homogeneous d-wave state with pockets of
antiferromagnetic order. The density of states has a robust d-wave gap, and
increasing antiferromagnetic correlations lead to a suppression of the
coherence peaks. The spectra of isolated nanoscale antiferromagnetic domains
are studied in detail, and are found to be very different from those of
macroscopic antiferromagnets. Although no single set of model parameters
reproduces all details of the experimental spectrum in BSCCO, many features,
notably the collapse of the coherence peaks and the occurence of a low-energy
shoulder in the local spectrum, occur naturally in these calculations.Comment: 9 pages, 5 figure
The first Chinese student space shuttle getaway special program
The first Chinese Getaway Special program is described. Program organization, the student proposal evaluation procedure, and the objectives of some of the finalist's experiments are covered. The two experiments selected for eventual flight on the space shuttle are described in detail. These include: (1) the control of debris in the cabin of the space shuttle; and (2) the solidification of two immiscible liquids in space
Improving the security of quantum direct communication with authentication
Two protocols of quantum direct communication with authentication [Phys. Rev.
A {\bf 73}, 042305 (2006)] are recently proposed by Lee, Lim and Yang. In this
paper we will show that in the two protocols the authenticator Trent should be
prevented from knowing the secret message of communication. The first protocol
can be eavesdropped by Trent using the the intercept-measure-resend attack,
while the second protocol can be eavesdropped by Trent using single-qubit
measurement. To fix these leaks, I revise the original versions of the
protocols by using the Pauli-Z operation instead of the original
bit-flip operation . As a consequence, the protocol securities are improved.Comment: Any suggestion,comment or help is welcome
Secure Direct Communication Based on Secret Transmitting Order of Particles
We propose the schemes of quantum secure direct communication (QSDC) based on
secret transmitting order of particles. In these protocols, the secret
transmitting order of particles ensures the security of communication, and no
secret messages are leaked even if the communication is interrupted for
security. This strategy of security for communication is also generalized to
quantum dialogue. It not only ensures the unconditional security but also
improves the efficiency of communication.Comment: To appear in Phys. Rev.
Radial differential mobility analyzer
The present invention provides a differential mobility analyzer for the classification of aerosols, comprising a chamber having two generally parallel faces and means to confine gases in the chamber, one of the faces having a generally arcuate, annular sheath air channel having an axis of symmetry, other of the faces having a generally arcuate, annular aerosol channel having an axis of symmetry generally coincident with the axis of symmetry of the sheath air channel, a first one of the faces having a sample flow aperture generally aligned with the axis of symmetry of the sheath air channel, a second one of the faces having an excess flow aperture generally aligned with the axis of symmetry of the sheath air channel, and means for maintaining an electric potential difference between the faces
- …