1,471 research outputs found
The characteristics of electronic training collars for dogs
A wide range of electronic dog training collars (e-collars) is available in the UK, yet there is no means by which purchasers can meaningfully compare their electrical characteristics at the point of sale. In this research the electrical characteristics of 13 models of e-collar were examined and an approach to ranking the strength of the electrical stimuli was developed. The electrical impedance of dogs’ necks was measured so that e-collars could be tested under realistic conditions. This impedance was found to be about 10kΩ for wet dogs and 640kΩ for dry dogs. Two copies of each of eight e-collar models and one copy of a further five models were tested. The stimuli generated by these collars comprised sequences of short high voltage pulses. There were large differences between e-collar models in the peak voltage, number of pulses and duration of the pulses but little variation between the duplicates. The peak voltage varied with the impedance of the dog, from 6000V at an impedance of 500kΩ to 100V at 5kΩ. The highest voltages were generated for only a few millionths of a second. A stimulus strength ranking index (SSRI) was developed based on the subjective response of human subjects to electrical stimuli. This index is used to compare the strength of e-collars with diverse electrical characteristics. It shows a wide range in the stimulus strengths of collars and that the relationships between ‘momentary’ and ‘continuous’ stimuli for various models differ significantly
Pressure-Induced Anomalous Phase Transitions and Colossal Enhancement of Piezoelectricity in PbTiO
We find an unexpected tetragonal-to-monoclinic-to-rhombohedral-to-cubic phase
transition sequence induced by pressure, and a morphotropic phase boundary in a
pure compound using first-principles calculations. Huge dielectric and
piezoelectric coupling constants occur in the transition regions, comparable to
those observed in the new complex single-crystal solid-solution piezoelectrics
such as Pb(MgNb)O-PbTiO, which are expected to
revolutionize electromechanical applications. Our results show that
morphotropic phase boundaries and giant piezoelectric effects do not require
intrinsic disorder, and open the possibility of studying this effect in simple
systems.Comment: 4 pages, to appear in Phys. Rev. Let
Brain abscess due to the fungi hormodendrum
Brain abscess caused by fungal infection is rare, only very few examples having been recorded in the English language literature. Perhaps the most comprehensive review is that of Craig and Gates,l who investigated all cases of brain abscess occurring in the Mayo Clinic during the years 1915-1945. During this 30-year period there were 104 examples of metastatic brain abscess, only 5 of which were caused by fungal infection. Two of these were caused by Actinomyces species, two by Coccidioides immitis and one by Monilia albicans. Apart from this series only i olated cases have. been reported, mainly due to Actinomyces, Blastomyces or Torula species. Eckhardt and Pilcher described a case caused by Nocardia asteroides. Binford et al.a rep.orted the case history of a patient with a metastatic brain abscess caused by the fungus Cladosporium (Hormodendrum) trichoides. King and Collette4 described a seoond example of brain abscess due to this fungus and the former authors demonstrated the identity of the fungus isolated by King and Collette with that which they had isolated. The case history reported here is a further example of a brain abscess due to a fungus of the Hormodendrum group and is, as far as we are aware, only the third case described
CaCu_3Ti_4O_12/CaTiO_3 Composite Dielectrics: A Ba/Pb-free Ceramics with High Dielectric Constants
We have measured dielectric properties of CaCuTiO
( = 0, 0.1, 0.5, 1, 1.5, 2, 2.9 and 3), and have found that
CaCuTiO (a composite of CaCuTiO and
CaTiO) exhibits a high dielectric constant of 1800 with a low dissipation
factor of 0.02 below 100 kHz from 220 to 300 K. These are comparable to (or
even better than) those of the Pb/Ba-based ceramics, which could be attributed
to a barrier layer of CaTiO on the surface of the CaCuTiO
grains. The composite dielectric ceramics reported here are environmentally
benign as they do not contain Ba/Pb.Comment: 4 pages, 4 figures, Appl. Phys. Lett. (scheduled on July 25, 2005
Ferroelectric Phase Transitions in Ultra-thin Films of BaTiO3
We present molecular dynamics simulations of a realistic model of an
ultrathin film of BaTiO sandwiched between short-circuited electrodes to
determine and understand effects of film thickness, epitaxial strain and the
nature of electrodes on its ferroelectric phase transitions as a function of
temperature. We determine a full epitaxial strain-temperature phase diagram in
the presence of perfect electrodes. Even with the vanishing depolarization
field, we find that ferroelectric phase transitions to states with in-plane and
out-of-plane components of polarization exhibit dependence on thickness; it
arises from the interactions of local dipoles with their electrostatic images
in the presence of electrodes. Secondly, in the presence of relatively bad
metal electrodes which only partly compensate the surface charges and
depolarization field, a qualitatively different phase with stripe-like domains
is stabilized at low temperature
An empowerment intervention for Indigenous communities: An outcome assessment
© 2015 Kinchin et al. Background: Empowerment programs have been shown to contribute to increased empowerment of individuals and build capacity within the community or workplace. To-date, the impact of empowerment programs has yet to be quantified in the published literature in this field. This study assessed the Indigenous-developed Family Wellbeing (FWB) program as an empowerment intervention for a child safety workforce in remote Indigenous communities by measuring effect sizes. The study also assessed the value of measurement tools for future impact evaluations. Methods: A three-day FWB workshop designed to promote empowerment and workplace engagement among child protection staffwas held across five remote north Queensland Indigenous communities. The FWB assessment tool comprised a set of validated surveys including the Growth and Empowerment Measure (GEM), Australian Unity Wellbeing Index, Kessler psychological distress scale (K10) and Workforce engagement survey. The assessment was conducted pre-intervention and three months post-intervention. Results: The analysis of pre-and post-surveys revealed that the GEM appeared to be the most tangible measure for detecting positive changes in communication, conflict resolution, decision making and life skill development. The GEM indicated a 17 % positive change compared to 9 % for the Australian Unity Wellbeing Index, 5 % for the workforce engagement survey and less than 1 % for K10. Conclusions: This study extended qualitative research and identified the best measurement tool for detecting the outcomes of empowerment programs. The GEM was found the most sensitive and the most tangible measure that captures improvements in communication, conflict resolution, decision making and life skill development. The GEM and Australian Unity Wellbeing Index could be recommended as routine measures for empowerment programs assessment among similar remote area workforce
Optimal configuration of microstructure in ferroelectric materials by stochastic optimization
An optimization procedure determining the ideal configuration at the
microstructural level of ferroelectric (FE) materials is applied to maximize
piezoelectricity. Piezoelectricity in ceramic FEs differ significantly from
that of single crystals because of the presence of crystallites (grains)
possessing crystallographic axes aligned imperfectly. The piezoelectric
properties of a polycrystalline (ceramic) FE is inextricably related to the
grain orientation distribution (texture). The set of combination of variables,
known as solution space, which dictates the texture of a ceramic is unlimited
and hence the choice of the optimal solution which maximizes the
piezoelectricity is complicated. Thus a stochastic global optimization combined
with homogenization is employed for the identification of the optimal granular
configuration of the FE ceramic microstructure with optimum piezoelectric
properties. The macroscopic equilibrium piezoelectric properties of
polycrystalline FE is calculated using mathematical homogenization at each
iteration step. The configuration of grains characterised by its orientations
at each iteration is generated using a randomly selected set of orientation
distribution parameters. Apparent enhancement of piezoelectric coefficient
is observed in an optimally oriented BaTiO single crystal. A
configuration of crystallites, simultaneously constraining the orientation
distribution of the c-axis (polar axis) while incorporating ab-plane
randomness, which would multiply the overall piezoelectricity in ceramic
BaTiO is also identified. The orientation distribution of the c-axes is
found to be a narrow Gaussian distribution centred around . The
piezoelectric coefficient in such a ceramic is found to be nearly three times
as that of the single crystal.Comment: 11 pages, 7 figure
Phase diagram of Pb(Zr,Ti)O3 solid solutions from first principles
A first-principles-derived scheme, that incorporates ferroelectric and
antiferrodistortive degrees of freedom, is developed to study
finite-temperature properties of PbZr1-xTixO3 solid solutions near its
morphotropic phase boundary. The use of this numerical technique (i) resolves
controversies about the monoclinic ground-state for some Ti compositions, (ii)
leads to the discovery of an overlooked phase, and (iii) yields three
multiphase points, that are each associated with four phases. Additional
neutron diffraction measurements strongly support some of these predictions.Comment: 10 pages, 2 figure
Metal-Ferroelectric-Metal heterostructures with Schottky contacts I. Influence of the ferroelectric properties
A model for Metal-Ferroelectric-Metal structures with Schottky contacts is
proposed. The model adapts the general theories of metal-semiconductor
rectifying contacts for the particular case of metal-ferroelectric contact by
introducing: the ferroelectric polarization as a sheet of surface charge
located at a finite distance from the electrode interface; a deep trapping
level of high concentration; the static and dynamic values of the dielectric
constant. Consequences of the proposed model on relevant quantities of the
Schottky contact such as built-in voltage, charge density and depletion width,
as well as on the interpretation of the current-voltage and capacitance-voltage
characteristics are discussed in detail.Comment: 14 pages with 4 figures, manuscript under revision at Journal of
Applied Physics for more than 1 year (submitted May 2004, first revision
September 2004, second revision May 2005
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