535 research outputs found
Pyroelectric response of ferroelectric nanoparticles: size effect and electric energy harvesting
The size effect on pyroelectric response of ferroelectric nanowires and
nanotubes is analyzed. The pyroelectric coefficient strongly increases with the
wire radius decrease and diverges at critical radius Rcr corresponding to the
size-driven transition into paraelectric phase. Size-driven enhancement of
pyroelectric coupling leads to the giant pyroelectric current and voltage
generation by the polarized ferroelectric nanoparticles in response to the
temperature fluctuation. The maximum efficiency of the pyroelectric energy
harvesting and bolometric detection is derived, and is shown to approach the
Carnot limit for low temperatures.Comment: 17 pages, 4 figures, 1 Appendi
Analytical Model of Soil Pulverization and Tillage Tools
AbstractThe paper deals with the pulverization (fracture) model that is not based on soil elastic properties but on the physical processes of the wedge interaction with soil. The presented model agrees with the experimental data better than other models, including those based on soil elastic properties, and the tests of flat tillage tools with a variable cutting angle have proved this
Effect of the Intrinsic Width on the Piezoelectric Force Microscopy of a Single Ferroelectric Domain Wall
Intrinsic domain wall width is a fundamental parameter that reflects bulk
ferroelectric properties and governs the performance of ferroelectric memory
devices. We present closed-form analytical expressions for vertical and lateral
piezoelectric force microscopy (PFM) profiles for the conical and disc models
of the tip, beyond point charge and sphere approximations. The analysis takes
into account the finite intrinsic width of the domain wall, and dielectric
anisotropy of the material. These analytical expressions provide insight into
the mechanisms of PFM image formation and can be used for quantitative analysis
of the PFM domain wall profiles. PFM profile of a realistic domain wall is
shown to be the convolution of its intrinsic profile and resolution function of
PFM.Comment: 25 pages, 5 figures, 3 tables, 3 Appendices, To be submitted to J.
Appl. Phy
Mesoscopic mechanism of the domain wall interaction with elastic defects in ferroelectrics
The role of elastic defects on the kinetics of 180-degree uncharged
ferroelectric domain wall motion is explored using continuum time-dependent LGD
equation with elastic dipole coupling. In one dimensional case, ripples, steps
and oscillations of the domain wall velocity appear due to the wall-defect
interactions. While the defects do not affect the limiting-wall velocity vs.
field dependence, they result in the minimal threshold field required to
activate the wall motions. The analytical expressions for the threshold field
are derived and the latter is shown to be much smaller than the thermodynamic
coercive field. The threshold field is linearly proportional to the
concentration of defects and non-monotonically depends on the average distance
between them. The obtained results provide the insight into the mesoscopic
mechanism of the domain wall pinning by elastic defects in ferroelectrics.Comment: 18 pages, 6 figures, 1 appendi
Optical spectroscopy of DPVs and the case of LP Ara
We present preliminary results of our spectroscopic campaign of a group of
intermediate mass interacting binaries dubbed "Double Periodic Variables"
(DPVs), characterized by orbital light curves and additional long photometric
cycles recurring roughly after 33 orbital periods (Mennickent et al. 2003,
2005). They have been interpreted as interacting, semi-detached binaries
showing cycles of mass loss into the interstellar medium (Mennickent et al.
2008, Mennickent & Kolaczkowski 2009). High resolution Balmer and helium line
profiles of DPVs can be interpreted in terms of mass flows in these systems. A
system solution is given for LP Ara, based on modeling of the ASAS V-band
orbital light curve and the radial velocity of the donor star.Comment: To be published in the proceedings book of the IAUS 272, Cambridge
University Press. Editors C. Neiner, G. Wade, G. Meynet and G. Peter
Reliability of AC thick-film electroluminescent lamps
The reliability of AC thick-film EL devices has been studied. The AC thickfilm
EL devices were fabricated by Novatech Inc. using the industrial print screen
technology. The analysis of reasons for failure has been proposed. The dependence of EL
lamp parameters on physical properties of the device EL layers was found. Our analysis
of the breakdown spot showed that improvement of reliability can be reached using the
additional dielectric layer between the phosphor layer and transparent electrode, high
concentration of phosphor powder 70 % and binder 30 %, balanced resistance between
the electric circuit and EL lamp. The thickness of the phosphor layer was equal to H =
(1 + √3/2)D (hexagonal packing), where D is the mean diameter of phosphor particles.
The reliability dependence of EL lamp on a water adsorption property of packaging
material was revealed
Domain structure formation by using Scanning Probe Microscopy: equilibrium polarization distribution and effective piezoelectric response calculations
In the paper we adopt the analytical Landau-Ginzburg-Devonshire theory to
describe the ferroelectric domain structure formation using Scanning Probe Microscopy.
We calculate the effective local piezoresponse of the domain structure within the
decoupling approximation using the conventional relation between piezoelectric tensor
components and the spontaneous polarization vector. The depth profile of the
polarization distribution was derived from the nonlinear Landau-Ginzburg-Devonshire
equation. We demonstrate that depending on the material parameters such as the intrinsic
domain wall width and probe apex geometry, the shape of the nucleating nanodomains
induced by the probe can be either oblate or prolate. The derived analytical expressions
for the polarization redistribution caused by the biased probe are valid for both first and
second order ferroelectrics
Domain Dynamics in Piezoresponse Force Microscopy: Quantitative Deconvolution and Hysteresis Loop Fine Structure
Domain dynamics in the Piezoresponse Force Spectroscopy (PFS) experiment is
studied using the combination of local hysteresis loop acquisition with
simultaneous domain imaging. The analytical theory for PFS signal from domain
of arbitrary cross-section is developed and used for the analysis of
experimental data on Pb(Zr,Ti)O3 polycrystalline films. The results suggest
formation of oblate domain at early stage of the domain nucleation and growth,
consistent with efficient screening of depolarization field within the
material. The fine structure of the hysteresis loop is shown to be related to
the observed jumps in the domain geometry during domain wall propagation
(nanoscale Barkhausen jumps), indicative of strong domain-defect interactions.Comment: 17 pages, 3 figures, 2 Appendices, to be submmited to Appl. Phys.
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A priori probabilistic model for the reliability of an "organised structure"
The basic possibility to create information model of the certain product (a semiconductor electronic device, or its element: p-n junction, quantum well, etc.) has been considered. Each product may be represented uniquely as a certain sequence of the Numbers set by technical requirements, drawings and process charts. The set Number may be realised only with a certain probability, therefore, the Number (N) in the initial engineering data is set with a maximum deviation from a mean value, i.e., the tolerance ±ΔN. During operation or storage, such processes as wear or ageing destroy the product deforming the tolerance of the set sequence of numbers, what is accompanied by inevitable increase of entropy. Hence, each product is endowed with the information negentropy, which may be calculated and may serve as initial value when solving an adequate equation of production of the thermodynamic entropy. As a particular example, the simplified model has been considered: a semiconductor plate covered on each side with insulator, which degrades during storage. The equality of a square of the tolerance and the real Number dispersion determined by the probability with which the Number realises with the set tolerance was taken as the base approximation
Endocrine Disruptors and Leydig Cell Function
During the past decades, a large body of information concerning the effects of endocrine disrupting compounds (EDCs) on animals and humans has been accumulated. EDCs are of synthetic or natural origin and certain groups are known to disrupt the action of androgens and to impair the development of the male reproductive tract and external genitalia. The present overview describes the effects of the different classes of EDCs, such as pesticides, phthalates, dioxins, and phytoestrogens, including newly synthesized resveratrol analogs on steroidogenesis in Leydig cells. The potential impact of these compounds on androgen production by Leydig cells during fetal development and in the adult age is discussed. In addition, the possible role of EDCs in connection with the increasing frequency of abnormalities in reproductive development in animals and humans is discussed
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