1,655 research outputs found
Anomalous change in leakage and displacement currents after electrical poling on lead-free ferroelectric ceramics
We report the polarization, displacement current and leakage current behavior
of a trivalent nonpolar cation Al cation substituted lead free ferroelectric
NBT-BT electroceramics with tetragonal phase and P4mm space group symmetry.
Nearly three orders of magnitude decrease in leakage current were observed
under electrical poling, which significantly improves microstructure,
polarization, and displacement current. Effective poling neutralizes the domain
pinning, traps charges at grain boundaries and fills oxygen vacancies with free
charge carriers in matrix, thus saturated macroscopic polarization in contrast
to that in upoled samples. E-poling changes bananas type polarization loops to
real ferroelectric loops.Comment: 18 pages, 5 figure
MIDAS, prototype Multivariate Interactive Digital Analysis System for large area earth resources surveys. Volume 1: System description
A third-generation, fast, low cost, multispectral recognition system (MIDAS) able to keep pace with the large quantity and high rates of data acquisition from large regions with present and projected sensots is described. The program can process a complete ERTS frame in forty seconds and provide a color map of sixteen constituent categories in a few minutes. A principle objective of the MIDAS program is to provide a system well interfaced with the human operator and thus to obtain large overall reductions in turn-around time and significant gains in throughput. The hardware and software generated in the overall program is described. The system contains a midi-computer to control the various high speed processing elements in the data path, a preprocessor to condition data, and a classifier which implements an all digital prototype multivariate Gaussian maximum likelihood or a Bayesian decision algorithm. Sufficient software was developed to perform signature extraction, control the preprocessor, compute classifier coefficients, control the classifier operation, operate the color display and printer, and diagnose operation
Polyfluorene as a model system for space-charge-limited conduction
Ethyl-hexyl substituted polyfluorene (PF) with its high level of molecular
disorder can be described very well by one-carrier space-charge-limited
conduction for a discrete set of trap levels with energy 0.5 eV above
the valence band edge. Sweeping the bias above the trap-filling limit in the
as-is polymer generates a new set of exponential traps, which is clearly seen
in the density of states calculations. The trapped charges in the new set of
traps have very long lifetimes and can be detrapped by photoexcitation. Thermal
cycling the PF film to a crystalline phase prevents creation of additional
traps at higher voltages.Comment: 13 pages, 4 figures. Physical Review B (accepted, 2007
MIDAS, prototype Multivariate Interactive Digital Analysis System, Phase 1. Volume 2: Diagnostic system
The MIDAS System is a third-generation, fast, multispectral recognition system able to keep pace with the large quantity and high rates of data acquisition from present and projected sensors. A principal objective of the MIDAS Program is to provide a system well interfaced with the human operator and thus to obtain large overall reductions in turn-around time and significant gains in throughout. The hardware and software generated in Phase I of the over-all program are described. The system contains a mini-computer to control the various high-speed processing elements in the data path and a classifier which implements an all-digital prototype multivariate-Gaussian maximum likelihood decision algorithm operating 2 x 105 pixels/sec. Sufficient hardware was developed to perform signature extraction from computer-compatible tapes, compute classifier coefficients, control the classifier operation, and diagnose operation. Diagnostic programs used to test MIDAS' operations are presented
Self-consistent model of unipolar transport in organic semiconductor diodes: accounting for a realistic density-of-states distribution
A self-consistent, mean-field model of charge-carrier injection and unipolar
transport in an organic semiconductor diode is developed utilizing the
effective transport energy concept and taking into account a realistic
density-of-states distribution as well as the presence of trap states in an
organic material. The consequences resulting from the model are discussed
exemplarily on the basis of an indium tin oxide/organic semiconductor/metallic
conductor structure. A comparison of the theory to experimental data of a
unipolar indium tin oxide/poly-3-hexyl-thiophene/Al device is presented.Comment: 6 pages, 2 figures; to be published in Journal of Applied Physic
Crosstalk Cascades for Frame-rate Pedestrian Detection
Cascades help make sliding window object detection fast,
nevertheless, computational demands remain prohibitive for numerous applications. Currently, evaluation of adjacent windows proceeds independently; this is suboptimal as detector responses at nearby locations and scales are correlated. We propose to exploit these correlations by
tightly coupling detector evaluation of nearby windows. We introduce two opposing mechanisms: detector excitation of promising neighbors and inhibition of inferior neighbors. By enabling neighboring detectors to communicate, crosstalk cascades achieve major gains (4-30x speedup) over cascades evaluated independently at each image location. Combined
with recent advances in fast multi-scale feature computation, for which we provide an optimized implementation, our approach runs at 35-65 fps
on 640 x 480 images while attaining state-of-the-art accuracy
First record of Anastrepha fraterculus and Ceratitis capitata (Diptera, Tephritidae) on Arecaceae in Brazil.
Luttinger-liquid-like transport in long InSb nanowires
Long nanowires of degenerate semiconductor InSb in asbestos matrix (wire
diameter is around 50 \AA, length 0.1 - 1 mm) were prepared. Electrical
conduction of these nanowires is studied over a temperature range 1.5 - 350 K.
It is found that a zero-field electrical conduction is a power function of the
temperature with the typical exponent .
Current-voltage characteristics of such nanowires are found to be nonlinear and
at sufficiently low temperatures follows the power law . It
is shown that the electrical conduction of these nanowires cannot be accounted
for in terms of ordinary single-electron theories and exhibits features
expected for impure Luttinger liquid. For a simple approximation of impure LL
as a pure one broken into drops by weak links, the estimated weak-link density
is around per cm.Comment: 5 pages, 2 figure
Characterization of the first true coaxial 18-fold segmented n-type prototype detector for the GERDA project
The first true coaxial 18-fold segmented n-type HPGe prototype detector
produced by Canberra-France for the GERDA neutrinoless double beta-decay
project was tested both at Canberra-France and at the Max-Planck-Institut fuer
Physik in Munich. The main characteristics of the detector are given and
measurements concerning detector properties are described. A novel method to
establish contacts between the crystal and a Kapton cable is presented.Comment: 21 pages, 16 Figures, to be submitted to NIM
Electrochromic Properties of TungstenMolybdenum Oxide Electrodes
Tungsten oxide and molybdenum doped tungsten oxide electrochromic films have been electrochemically prepared from a metal peroxide bath and experimentally tested. They were characterized by electrical and optical methods, using cyclic voltammograms and calculating the charge capacity as a function of the number of deposition cycles. The color of the electrochromic WO 3 film is strongly altered by doping it with molybdenum. Electrochromic W-Mo oxide films were fabricated by adding different percentages of molybdenum to tungsten oxide, ranging from 0.5% to 7% weight of deposition solution. Normal optical transmittance was also measured and evidence is given of different behavior of the switching for oxidation and reduction cycle, so that coloration occurs in a shorter time than the bleaching. The time constant of the process tends to increase as a function of the molybdenum oxide doping concentration
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