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## A method for the measurement of the absolute value of w for X-rays in noble gases: results at 5.9 keV in xenon

Fonte: IEEE
Publicador: IEEE

Tipo: Artigo de Revista Científica

Português

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A method is described that allows the measurement of the absolute
value of the average energy to produce an ion pair, w, in noble
gases for soft X-rays and its energy dependence. It uses a specially
designed gas proportional scintillation counter working under electric
fields below the ionization threshold. The spectrum of the radiation
absorbed, and so the number of photons detected at each energy for a
period of time on the order of the minute, is measured with the
scintillation counter and, at the same time, the total primary electron
charge produced is collected in one of the grids and measured with an
electrometer. For pure xenon at 1030 mbar, a value of
w=24.2±2.5 eV is measured with 5.9-keV X-rays

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## ON THE MINIMUM ABSOLUTE VALUE of THE DISCRIMINANT of ABELIAN FIELDS of DEGREE p(2)

Fonte: World Scientific Publ Co Pte Ltd
Publicador: World Scientific Publ Co Pte Ltd

Tipo: Artigo de Revista Científica
Formato: 819-824

Português

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Let p be a prime number. A formula for the minimum absolute value of the discriminant of all Abelian extensions of Q of degree p(2) is given in terms of p.

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## Motor Preparatory Activity in Posterior Parietal Cortex is Modulated by Subjective Absolute Value

Fonte: Public Library of Science
Publicador: Public Library of Science

Tipo: Artigo de Revista Científica

Português

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Cortical motor planning is shaped by “subjective absolute value”: planning activity is strongly enhanced for large expected gains in subjects who believe they perform well; conversely, activity is higher for large expected losses in subjects who think they perform poorly.

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## Reducing the Standard Deviation in Multiple-Assay Experiments Where the Variation Matters but the Absolute Value Does Not

Fonte: Public Library of Science
Publicador: Public Library of Science

Tipo: Artigo de Revista Científica

Publicado em 30/10/2013
Português

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When the value of a quantity for a number of systems (cells, molecules, people, chunks of metal, DNA vectors, so on) is measured and the aim is to replicate the whole set again for different trials or assays, despite the efforts for a near-equal design, scientists might often obtain quite different measurements. As a consequence, some systems’ averages present standard deviations that are too large to render statistically significant results. This work presents a novel correction method of a very low mathematical and numerical complexity that can reduce the standard deviation of such results and increase their statistical significance. Two conditions are to be met: the inter-system variations of matter while its absolute value does not, and a similar tendency in the values of must be present in the different assays (or in other words, the results corresponding to different assays must present a high linear correlation). We demonstrate the improvements this method offers with a cell biology experiment, but it can definitely be applied to any problem that conforms to the described structure and requirements and in any quantitative scientific field that deals with data subject to uncertainty.

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## X-Ray Reflectivity from the Surface of a Liquid Crystal: Surface Structure and Absolute Value of Critical Fluctuations

Fonte: American Physical Society
Publicador: American Physical Society

Tipo: Artigo de Revista Científica

Português

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X-ray reflectivity from the surface of a nematic liquid crystal is interpreted as the coherent superposition of Fresnel reflection from the surface and Bragg reflection from smectic order induced by the surface. Angular dependence of the Fresnel effect yields information on surface structure. Measurement of the intensity of diffuse critical scattering relative to the Fresnel reflection yields the absolute value of the critical part of the density-density correlation function.; Engineering and Applied Sciences

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## Logarithmic and absolute-value like properties of $\pi(x)$ with applications

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Português

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We derive properties of $\pi(x)$ reminiscent of those of the logarithm and
absolute value functions. Two of these properties are similar to the relations
defining the linearity of a function. Several applications of these properties
of $\pi(x)$ are also examined.; Comment: 11 pages. Withdrawn by the author due to a problem with Theorem 3.1,
thus also invalidating all results that were based on it

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## Measurements of the absolute value of the penetration depth in high-$ T_c$ superconductors using a tunnel diode resonator

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 02/07/2000
Português

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A method is presented to measure the absolute value of the London penetration
depth, $\lambda$, from the frequency shift of a resonator. The technique
involves coating a high-$T_c$ superconductor (HTSC) with film of low - Tc
material of known thickness and penetration depth. The method is applied to
measure London penetration depth in YBa2Cu3O{7-\delta} (YBCO)
Bi2Sr2CaCu2O{8+\delta} (BSCCO) and Pr{1.85}Ce{0.15}CuO{4-\delta}$ (PCCO). For
YBCO and BSCCO, the values of $\lambda (0)$ are in agreement with the
literature values. For PCCO $\lambda \approx 2790$ \AA, reported for the first
time.; Comment: RevTex 4 (beta 4). 4 pages, 4 EPS figures. Submitted to Appl. Phys.
Lett

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## Absolute value preconditioning for symmetric indefinite linear systems

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Português

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We introduce a novel strategy for constructing symmetric positive definite
(SPD) preconditioners for linear systems with symmetric indefinite matrices.
The strategy, called absolute value preconditioning, is motivated by the
observation that the preconditioned minimal residual method with the inverse of
the absolute value of the matrix as a preconditioner converges to the exact
solution of the system in at most two steps. Neither the exact absolute value
of the matrix nor its exact inverse are computationally feasible to construct
in general. However, we provide a practical example of an SPD preconditioner
that is based on the suggested approach. In this example we consider a model
problem with a shifted discrete negative Laplacian, and suggest a geometric
multigrid (MG) preconditioner, where the inverse of the matrix absolute value
appears only on the coarse grid, while operations on finer grids are based on
the Laplacian. Our numerical tests demonstrate practical effectiveness of the
new MG preconditioner, which leads to a robust iterative scheme with minimalist
memory requirements.

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## Counting Perron Numbers by Absolute Value

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Português

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We count various classes of algebraic integers of fixed degree by their
largest absolute value. The classes of integers considered include all
algebraic integers, Perron numbers, totally real integers, and totally complex
integers. We give qualitative and quantitative results concerning the
distribution of Perron numbers, answering in part a question of W. Thurston.; Comment: This work represents, in part, the PhD thesis of the second author

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## Two CSCS-based iteration methods for absolute value equations involving Toeplitz matrix

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Português

Relevância na Pesquisa

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Recently, two kinds of HSS-based iteration methods are constructed for coping
with the absolute value equation (AVE), which is a family of non-differentiable
NP-hard problem. In present paper, we focus on developing the CSCS-based
methods for solving the absolute value equation (AVE) involving the Toeplitz
matrix, and propose the Picard-CSCS method and the nonlinear CSCS-like
iterative method. With the help of introducing a smoothing approximate
function, we give some theoretical analyses for the convergence of the
CSCS-based iteration methods for the AVE. The advantage of these methods is
that they do not require storage of coefficient matrix, and the linear
sub-systems can be solved efficiently via the fast Fourier transform (FFT).
Therefore, computational cost and computer storage may be saved in actual
implementations. Extensive numerical experiments involving the numerical
solutions of fractional diffusion equations are employed to demonstrate the
robustness and effectiveness of the proposed methods and to compare with the
recent methods.; Comment: The comments for our manuscript are highly welcome via the email.
arXiv admin note: text overlap with arXiv:1403.7013 by other authors

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## Complexity of Random Energy Landscapes, Glass Transition and Absolute Value of Spectral Determinant of Random Matrices

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Português

Relevância na Pesquisa

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Finding the mean of the total number N_{tot} of critical points for
N-dimensional random energy landscapes is reduced to averaging the absolute
value of characteristic polynomial of the corresponding Hessian. For any finite
N we provide the exact solution to the problem for a class of landscapes
corresponding to the "toy model" of manifolds in random environment. For N >>1
our asymptotic analysis reveals a phase transition at some critical value \mu_c
of a control parameter \mu from a phase with finite landscape complexity to the
phase with vanishing complexity. The same value of the control parameter is
known to correspond to an onset of glassy behaviour at zero temperature.
Finally, we discuss a method of dealing with the modulus of the spectral
determinant applicable to a broad class of problems.; Comment: Updated version, close to the published variant, but with a misprint
in Eq.(15) corrected

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## Cryptanalyzing an improved security modulated chaotic encryption scheme using ciphertext absolute value

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 28/06/2004
Português

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This paper describes the security weakness of a recently proposed improved
chaotic encryption method based on the modulation of a signal generated by a
chaotic system with an appropriately chosen scalar signal. The aim of the
improvement is to avoid the breaking of chaotic encryption schemes by means of
the return map attack introduced by Perez and Cerdeira. A method of attack
based on taking the absolute value of the ciphertext is presented, that allows
for the cancellation of the modulation scalar signal and the determination of
some system parameters that play the role of system key. The proposed improved
method is shown to be compromised without any knowledge of the chaotic system
parameter values and even without knowing the transmitter structure.; Comment: 12 pages, 8 figures, LaTeX format

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## An inexact Picard iteration method for absolute value equation

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 30/09/2015
Português

Relevância na Pesquisa

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Recently, a class of inexact Picard iteration method for solving the absolute
value equation: $Ax-|x~|=b$ have been proposed in [Optim Lett
8:2191-2202,2014]. To further improve the performance of Picard iteration
method, a new inexact Picard iteration method is proposed to solve the absolute
value equation. The sufficient conditions for the convergence of the proposed
method for the absolute value equation is given. Some numerical experiments are
given to demonstrate the effectiveness of the new method.; Comment: arXiv admin note: text overlap with arXiv:1403.7013, arXiv:1404.1678
by other authors

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## The nonlinear HSS-like iteration method for absolute value equations

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Português

Relevância na Pesquisa

45.91%

Salkuyeh proposed the Picard-HSS iteration method to solve the absolute value
equation (AVE), which is a class of non-differentiable NP-hard problem. To
further improve its performance, a nonlinear HSS-like iteration method is
proposed. Compared to that the Picard-HSS method is an inner-outer double-layer
iteration scheme, the HSS-like iteration is only a monolayer and the iteration
vector could be updated timely. Some numerical experiments are used to
demonstrate that the nonlinear HSS-like method is feasible, robust and
effective.

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## Reducing the standard deviation in multiple-assay experiments where the variation matters but the absolute value does not

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Português

Relevância na Pesquisa

45.96%

You measure the value of a quantity x for a number of systems (cells,
molecules, people, chunks of metal, DNA vectors, etc.). You repeat the whole
set of measures in different occasions or assays, which you try to design as
equal to one another as possible. Despite the effort, you find that the results
are too different from one assay to another. As a consequence, some systems'
averages present standard deviations that are too large to render the results
statistically significant. In this work, we present a novel correction method
of very low mathematical and numerical complexity that can reduce the standard
deviation in your results and increase their statistical significance as long
as two conditions are met: inter-system variations of x matter to you but its
absolute value does not, and the different assays display a similar tendency in
the values of x; in other words, the results corresponding to different assays
present high linear correlation. We demonstrate the improvement that this
method brings about on a real cell biology experiment, but the method can be
applied to any problem that conforms to the described structure and
requirements, in any quantitative scientific field that has to deal with data
subject to uncertainty.; Comment: Supplementary material at http://bit.ly/14I718S

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## Convolution based smooth approximations to the absolute value function with application to non-smooth regularization

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Português

Relevância na Pesquisa

45.91%

We present new convolution based smooth approximations to the absolute value
function and apply them to construct gradient based algorithms such as the
nonlinear conjugate gradient scheme to obtain sparse, regularized solutions of
linear systems $Ax = b$, a problem often tackled via iterative algorithms which
attack the corresponding non-smooth minimization problem directly. In contrast,
the approximations we propose allow us to replace the generalized non-smooth
sparsity inducing functional by a smooth approximation of which we can readily
compute gradients and Hessians. The resulting gradient based algorithms often
yield a good estimate for the sought solution in few iterations and can either
be used directly or to quickly warm start existing algorithms.

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## On the global convergence of the inexact semi-smooth Newton method for absolute value equation

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Português

Relevância na Pesquisa

45.91%

In this paper, we investigate global convergence properties of the inexact
nonsmooth Newton method for solving the system of absolute value equations
(AVE). Global $Q$-linear convergence is established under suitable assumptions.
Moreover, we present some numerical experiments designed to investigate the
practical viability of the proposed scheme.

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## Empirical Formula of the Absolute Value of Electrical Conductivity for Elemental Metals and Its Interpretation By Fluctuation Dissipation Theorem

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 17/01/2014
Português

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The absolute value of the electrical conductivity sigma of elemental metals
even at the room temperature range is not well theoretically understood. This
is particularly true in multivalent metals. This paper empirically found that
sigma=n_{atom}e^2tau0/mG with tau0=hbar/k_{B}T reproduces the observations
rather well for many metals as in Fig.1(b)-upper, if G is taken, by guessing to
be a summed number of electric bands counted from outer most orbitals. We find
by comparative study at the same time n_{atom}=n, namely Z=1 and m=m^* for
majority of metals for sigma. Thus the only quantity remained is tau. The
Bardeen's tau is found equal to tau0 if the deformation potential is equal to
Fermi energy, using the observationally ascertained fact that thermal acoustic
energy=the Fermi energy. Since electrons behave nearly as free electrons, the
wave function should show the minimum uncertainty relation of Delta p_{x}
Delta_{x}=hbar/2, which following the classical Fluctuation-Dissipation-Theorem
shows in fact tau0=hbar/k_{B}T.; Comment: 12 pages, 2 figures

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## On the absolute value of the air-fluorescence yield

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 17/01/2014
Português

Relevância na Pesquisa

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The absolute value of the air-fluorescence yield is a key parameter for the
energy reconstruction of extensive air showers registered by fluorescence
telescopes. In previous publications, we reported a detailed Monte Carlo
simulation of the air-fluorescence generation that allowed the theoretical
evaluation of this parameter. This simulation has been upgraded in the present
work. As a result, we determined an updated absolute value of the fluorescence
yield of 7.9+-2.0 ph/MeV for the band at 337 nm in dry air at 800 hPa and 293
K, in agreement with experimental values. We have also performed a critical
analysis of available absolute measurements of the fluorescence yield with the
assistance of our simulation. Corrections have been applied to some
measurements to account for a bias in the evaluation of the energy deposition.
Possible effects of other experimental aspects have also been discussed. From
this analysis, we determined an average fluorescence yield of 7.04+-0.24 ph/MeV
at the above conditions.; Comment: Submitted to Astroparticle Physics

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## Motor Preparatory Activity in Posterior Parietal Cortex is Modulated by Subjective Absolute Value

Fonte: Public Library of Science
Publicador: Public Library of Science

Tipo: Article; PeerReviewed
Formato: application/pdf; application/pdf; application/pdf; application/pdf; application/pdf; application/pdf; application/pdf; application/pdf; application/pdf; application/pdf; application/pdf; application/pdf

Publicado em /08/2010
Português

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For optimal response selection, the consequences associated with behavioral success or failure must be appraised. To determine how monetary consequences influence the neural representations of motor preparation, human brain activity was scanned with fMRI while subjects performed a complex spatial visuomotor task. At the beginning of each trial, reward context cues indicated the potential gain and loss imposed for correct or incorrect trial completion. FMRI-activity in canonical reward structures reflected the expected value related to the context. In contrast, motor preparatory activity in posterior parietal and premotor cortex peaked in high “absolute value” (high gain or loss) conditions: being highest for large gains in subjects who believed they performed well while being highest for large losses in those who believed they performed poorly. These results suggest that the neural activity preceding goal-directed actions incorporates the absolute value of that action, predicated upon subjective, rather than objective, estimates of one's performance.

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