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Experimental and numerical study of interaction between particle loaded fluid and a rough wall with micropillars
© 2014 Elsevier Ltd. All rights reserved. Experimental and numerical studies of the behavior of a slurry in a shear flow over a rough surface with a defined micro-structure are presented. A new ring shear device was built which contains an optically transparent test chamber. Its bottom wall contains arrays of micro-cantilever force sensors simulating a defined surface roughness created by deep-etching of micro-pillars in a silicon wafer. The results of visual observation of the interaction of the suspension with the structured surface during severe deformation are shown. Observations comprise the liquid phase motion, i.e., the interaction between the liquid phase and solid particles, the movement of separate particles and their interactions with the micro-pillars. Abrupt changes in rotational motion and translational velocity of particles are observed that induce mutual collisions and successive formation and break-up of cluster structures of various types. In addition to the experiments the process was simulated with discrete element (DEM) simulations. Many characteristics found in the experiments are reproduced by the simulations. Furthermore the physical quantities of the process like contact forces or velocities can be quantified which helps us to develop more detailed models of the abrasive behavior of slurries
Distribution of Craniofacial Variables in South Dalmatian and Middle Croatian Populations
The objective of the present work was to determine some relevant craniofacial parameters,
particularly in relation to sex, for the study of the distribution of basic head
and face types, and to investigate craniofacial and morphological differences between
two population samples. The study sample comprised 100 subjects of both sex aged 18 to
30 from South Dalmatia and 200 subjects from Middle Croatia. Eight basic craniofacial
variables were measured to obtain head, forehead and face indexes. The data indicate
that average values of all variables can be used as standard craniofacial parameters
for the examined population groups. All the craniofacial variables are considerably
higher in men than in women (p < 0.05). In the South Dalmatian population mesocephalia
(48.0%) and leptoprosopia (82.0%) prevail, while in the Middle Croatian population
the brachycephalia (62.0%), and euriprosopia (73.5%) are present to a greater degree.
The most significant craniofacial and morphological differences between the
examined study samples are head width (Eu–Eu), face width (Zy–Zy), and forehead
height (Tr–N). They were found to be statistically significant in the examined Middle
Croatian population (p < 0.05). The presented measurements are highly relevant to orthodontic
diagnostics and therapy
Darboux-integration of id\rho/dt=[H,f(\rho)]
A Darboux-type method of solving the nonlinear von Neumann equation , with functions commuting with , is
developed. The technique is based on a representation of the nonlinear equation
by a compatibility condition for an overdetermined linear system. von Neumann
equations with various nonlinearities are found to possess the
so-called self-scattering solutions. To illustrate the result we consider the
Hamiltonian of a one-dimensional harmonic oscillator and
with arbitary real . It is shown that
self-scattering solutions possess the same asymptotics for all and that
different nonlinearities may lead to effectively indistinguishable evolutions.
The result may have implications for nonextensive statistics and experimental
tests of linearity of quantum mechanics.Comment: revtex, 5 pages, 2 eps figures, submitted to Phys.Lett.A
infinite-dimensional example is adde
Validation of a novel device to objectively measure adherence to long-term oxygen therapy
Sun-Kai V Lin1, Daniel K Bogen1, Samuel T Kuna2,31Department of Bioengineering; 2Department of Medicine, Pulmonary, Allergy and Critical Care Division, and Center for Sleep and Respiratory Neurobiology, University of Pennsylvania, Pennsylvania, USA; 3Department of Medicine, Philadelphia Veterans Affairs Medical Center Philadelphia, Pennsylvania, USARationale: We have developed a novel oxygen adherence monitor that objectively measures patient use of long-term oxygen therapy. The monitor attaches to the oxygen source and detects whether or not the patient is wearing the nasal cannula.Objective: The study&rsquo;s purpose was to validate the monitor&rsquo;s performance in patients with chronic obstructive pulmonary disease during wakefulness and sleep.Methods: Ten adult males with stable chronic obstructive pulmonary disease (mean &plusmn; SD FEV1 37.7 &plusmn; 14.9% of predicted) on long-term continuous oxygen therapy were tested in a sleep laboratory over a 12&ndash;13 hour period that included an overnight polysomnogram.Measurements: The monitor&rsquo;s measurements were obtained at 4-minute intervals and compared to actual oxygen use determined by review of time-synchronized video recordings.Main results: The monitor made 1504/1888 (79.7%) correct detections (unprocessed data) across all participants: 957/1,118 (85.6%) correct detections during wakefulness and 546/770 (70.9%) during sleep. All errors were false negatives, ie, the monitor failed to detect that the participant was actually wearing the cannula. Application of a majority-vote filter to the raw data improved overall detection accuracy to 84.9%.Conclusions: The results demonstrate the monitor&rsquo;s ability to objectively measure whether or not men with chronic obstructive pulmonary disease are receiving their oxygen treatment. The ability to objectively measure oxygen delivery, rather than oxygen expended, may help improve the management of patients on long-term oxygen therapy.Keywords: chronic obstructive pulmonary diseas
Von Neumann equations with time-dependent Hamiltonians and supersymmetric quantum mechanics
Starting with a time-independent Hamiltonian and an appropriately chosen
solution of the von Neumann equation we construct
its binary-Darboux partner and an exact scattering solution of
where is time-dependent and not
isospectral to . The method is analogous to supersymmetric quantum mechanics
but is based on a different version of a Darboux transformation. We illustrate
the technique by the example where corresponds to a 1-D harmonic
oscillator. The resulting represents a scattering of a soliton-like
pulse on a three-level system.Comment: revtex, 3 eps file
Covariance systems
We introduce new definitions of states and of representations of covariance
systems. The GNS-construction is generalized to this context. It associates a
representation with each state of the covariance system. Next, states are
extended to states of an appropriate covariance algebra. Two applications are
given. We describe a nonrelativistic quantum particle, and we give a simple
description of the quantum spacetime model introduced by Doplicher et al.Comment: latex with ams-latex, 23 page
Measurement of Magnetic Field in Dentistry
The principal objective was to measure the magnetic fields occurring in dental surgeries
at simultaneous subtraction of direct ground component of the magnetic field. A
specifically designed instrument with the Hall probe was used for the measurement. It
consisted of two amplifiers and a low frequency filter. Its task was to measure mean
square values of the field (RMS) dependent on the position in space. Qualitative and
quantitative analyses of the investigated variables enabled making conclusions about
the magnetic fields in dental surgeries. A number of studies have shown that many dental
instruments produce radiation with magnetic field higher than 40 G, at a significant
decrease in power of the magnetic field with increasing distance from the source. It
has also been reported that instruments of older generations produce stronger magnetic
fields than do the new ones
Translation invariant extensions of finite volume measures
We investigate the following questions: Given a measure μΛ on configurations on a subset Λ of a lattice L, where a configuration is an element of ΩΛ for some fixed set Ω, does there exist a measure μ on configurations on all of L, invariant under some specified symme- try group of L, such that μΛ is its marginal on configurations on Λ? When the answer is yes, what are the properties, e.g., the entropies, of such measures? Our primary focus is the case in which L = Zd and the symmetries are the translations. For the case in which Λ is an interval in Z we give a simple necessary and sufficient condition, local translation invariance (LTI), for extendibility. For LTI measures we construct extensions having maximal entropy, which we show are Gibbs measures; this construction extends to the case in which L is the Bethe lattice. On Z we also consider extensions supported on periodic configurations, which are analyzed using de Bruijn graphs and which include the extensions with minimal entropy. When Λ ⊂ Z is not an interval, or when Λ ⊂ Zd with d > 1, the LTI condition is necessary but not sufficient for extendibility. For Zd with d > 1, extendibility is in some sense undecidable
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Generalized early warning signals in multivariate and gridded data with an application to tropical cyclones
Tipping events in dynamical systems have been studied across many applications, often by measuring changes in variance or autocorrelation in a one-dimensional time series. In this paper, methods for detecting early warning signals of tipping events in multidimensional systems are reviewed and expanded. An analytical justification of the use of dimension-reduction by empirical orthogonal functions, in the context of early warning signals, is provided and the one-dimensional techniques are also extended to spatially separated time series over a 2D field. The challenge of predicting an approaching tropical cyclone by a tipping-point analysis of the sea-level pressure series is used as the primary example, and an analytical model of a moving cyclone is also developed in order to test predictions. We show that the one-dimensional power spectrum indicator may be used following dimension-reduction or over a 2D field. We also show the validity of our moving cyclone model with respect to tipping-point indicators.
Many dynamical systems experience sudden shifts in behavior, often referred to as tipping points or critical transitions. A volume of work is dedicated to detecting and predicting these critical transitions, often making use of generic early warning signal (EWS) indicators based on autocorrelation1,2
and increasing variance.3,4
Similar indicators based on other scaling properties of the time series, namely, detrended fluctuation analysis (DFA)5,6
and power spectrum scaling,7
have also been used. Other methods have estimated parameters to fit a model to the data, both for detecting critical transitions8–10
and for predicting future transitions dynamics
Adaptive cluster expansion for the inverse Ising problem: convergence, algorithm and tests
We present a procedure to solve the inverse Ising problem, that is to find
the interactions between a set of binary variables from the measure of their
equilibrium correlations. The method consists in constructing and selecting
specific clusters of variables, based on their contributions to the
cross-entropy of the Ising model. Small contributions are discarded to avoid
overfitting and to make the computation tractable. The properties of the
cluster expansion and its performances on synthetic data are studied. To make
the implementation easier we give the pseudo-code of the algorithm.Comment: Paper submitted to Journal of Statistical Physic
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