2,905 research outputs found
Cyclic debonding of adhesive joints
Bonded lap joints were manufactured and tested under static and fatigue loading. Specimens were designed to fail in the bondline, and all fatigue tests included monitoring the crack growth to failure. Test specimens included aluminum details joined by two different adhesives. Specimens also included titanium and boron-epoxy details joined by an epoxy laminating resin. Additonal program variables included bondline thickness, adherend and spice plate thickness, specimen width, and specimen fabrication procedure. Adhesive aging was found to be generally detrimental to the lives of most of the specimens bonded with one adhesive system. Adhesive material was found to have a major influence on debond rate. Co-cured titanium/boron-epoxy specimens were found to resist debonding better than specimens fabricated with a sequential cure. Splice plate thickness and test section width were found to have little effect on debond rate. The data also suggested the existence of an optimum bondline thickness
Quantum paramagnetic ground states on the honeycomb lattice and field-induced transition to N\'eel order
Motivated by recent experiments on BiMnO(NO), and a
broader interest arising from numerical work on the honeycomb lattice Hubbard
model, we have studied the effect of a magnetic field on honeycomb lattice spin
models with quantum paramagnetic ground states. For a model with frustrating
second-neighbor exchange, , we use a Lindemann-like criterion within spin
wave theory to show that N\'eel order melts beyond a critical . The
critical increases with a magnetic field, implying the existence of a
field-induced paramagnet-N\'eel transition over a range of . We also study
bilayer model using a spin- generalization of bond operator mean field
theory. We show that there is a N\'eel-dimer transition for various spin values
with increasing bilayer coupling, and that the resulting interlayer dimer state
undergoes a field induced transition into a state with transverse N\'eel order.
Finally, we study a spin-3/2 model which interpolates between the Heisenberg
model and the Affleck-Kennedy-Lieb-Tasaki (AKLT) parent Hamiltonian. Using
exact diagonalization, we compute the fidelity susceptibility to locate the
Neel-AKLT quantum critical point, obtain the spin gap of the AKLT parent
Hamiltonian, and argue that AKLT state also undergoes field-induced Neel
ordering.Comment: 8 pages, revised longer version of arXiv:1012.0316. Corrected factor
of 2 error in Eq.[16], replotted Fig.[4] and revised the critical
needed to stabilize interlayer dimer state. We thank S. V. Isakov for
discussions which uncovered this erro
Magnetic field dependence of charge stripe order in La2-xBaxCuO4 (x~1/8)
We have carried out a detailed investigation of the magnetic field dependence
of charge ordering in La2-xBaxCuO4 (x~1/8) utilizing high-resolution x-ray
scattering. We find that the charge order correlation length increases as the
magnetic field greater than ~5T is applied in the superconducting phase (T=2K).
The observed unusual field dependence of the charge order correlation length
suggests that the static charge stripe order competes with the superconducting
ground state in this sample.Comment: 4 pages, 4 figure
Charge-transfer exciton in La2CuO4 probed with resonant inelastic x-ray scattering
We report a high-resolution resonant inelastic x-ray scattering study of
La2CuO4. A number of spectral features are identified that were not clearly
visible in earlier lower-resolution data. The momentum dependence of the
spectral weight and the dispersion of the lowest energy excitation across the
insulating gap have been measured in detail. The temperature dependence of the
spectral features was also examined. The observed charge transfer edge shift,
along with the low dispersion of the first charge transfer excitation are
attributed to the lattice motion being coupled to the electronic system. In
addition, we observe a dispersionless feature at 1.8 eV, which is associated
with a d-d crystal field excitation.Comment: 5 pages, 4 figure
The Medicare Prospective Payment System: Impact on the Frail Elderly and an Alternative Reimbursement Formula
The Medicare Prospective Payment System: Impact on the Frail Elderly and an Alternative Reimbursement Formula
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