802 research outputs found
Seismic Downhole, CPT, and DMT Correlations in Sand
Results from seismic cone penetration and dilatometer tests performed in a cohesionless soil are presented and compared with previously published correlations for estimating the elastic shear modulus. Poor correlations were obtained between the elastic shear modulus, the dilatometer modulus and the cone tip resistance; however, somewhat better estimates of the elastic shear modulus were obtained using the coefficient of lateral stress and total unit weight empirically determined from the dilatometer
Dissociative paraplegia after epidural anesthesia: A case report
10.1186/1752-1947-7-56Journal of Medical Case Reports7
Space-charge mechanism of aging in ferroelectrics: an exactly solvable two-dimensional model
A mechanism of point defect migration triggered by local depolarization
fields is shown to explain some still inexplicable features of aging in
acceptor doped ferroelectrics. A drift-diffusion model of the coupled charged
defect transport and electrostatic field relaxation within a two-dimensional
domain configuration is treated numerically and analytically. Numerical results
are given for the emerging internal bias field of about 1 kV/mm which levels
off at dopant concentrations well below 1 mol%; the fact, long ago known
experimentally but still not explained. For higher defect concentrations a
closed solution of the model equations in the drift approximation as well as an
explicit formula for the internal bias field is derived revealing the plausible
time, temperature and concentration dependencies of aging. The results are
compared to those due to the mechanism of orientational reordering of defect
dipoles.Comment: 8 pages, 4 figures. accepted to Physical Review
An Artificial SEI Layer Based on an Inorganic Coordination Polymer with Self-Healing Ability for Long-Lived Rechargeable Lithium-Metal Batteries
Upon immersion of a lithium (Li) anode into a diluted 0.05 to 0.20 M dimethoxyethane solution of the phosphoric-acid derivative (CFCHO)P(O)OH (HBFEP), an artificial solid-electrolyte interphase (SEI) is generated on the Li-metal surface. Hence, HBFEP reacts on the surface to the corresponding Li salt (LiBFEP), which is a Li-ion conducting inorganic coordination polymer. This film exhibits – due to the reversibly breaking ionic bonds – self-healing ability upon cycling-induced volume expansion of Li. The presence of LiBFEP as the major component in the artificial SEI is proven by ATR-IR and XPS measurements. SEM characterization of HBFEP-treated Li samples reveals porous layers on top of the Li surface with at least 3 μm thickness. Li−Li symmetrical cells with HBFEP-modified Li electrodes show a three- to almost fourfold cycle-lifetime increase at 0.1 mA cm in a demanding model electrolyte that facilitates fast battery failure (1 M LiOTf in TEGDME). Hence, the LiBFEP-enriched layer apparently acts as a Li-ion conducting protection barrier between Li and the electrolyte, enhancing the rechargeability of Li electrodes
Aging of poled ferroelectric ceramics due to relaxation of random depolarization fields by space-charge accumulation near grain boundaries
Migration of charged point defects triggered by the local random
depolarization field is shown to plausibly explain aging of poled ferroelectric
ceramics providing reasonable time and acceptor concentration dependences of
the emerging internal bias field. The theory is based on the evaluation of the
energy of the local depolarization field caused by mismatch of the
polarizations of neighbor grains. The kinetics of charge migration assumes
presence of mobile oxygen vacancies in the material due to the intentional or
unintentional acceptor doping. Satisfactory agreement of the theory with
experiment on the Fe-doped lead zirconate titanate is demonstrated.Comment: theory and experiment, 22 pages, 3 figure
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