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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

Borges, F. I. G. M.; Conde, C. A. N.
Fonte: IEEE Publicador: IEEE
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
45.96%
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

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

Interlando, J. Carmelo; Dantas Lopes, Jose Othon; Da Nobrega Neto, Trajano Pires; Flores, Andre Luiz
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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45.91%
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.

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

Iyer, Asha; Lindner, Axel; Kagan, Igor; Andersen, Richard A.
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
45.91%
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.

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

Echenique-Robba, Pablo; Nelo-Bazán, María Alejandra; Carrodeguas, José A.
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 30/10/2013 Português
Relevância na Pesquisa
45.96%
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.

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

Pershan, Peter S.; Als-Nielsen, J.
Fonte: American Physical Society Publicador: American Physical Society
Tipo: Artigo de Revista Científica
Português
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45.91%
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

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

Benyaminov, Boris B.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
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45.91%
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

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

Prozorov, R.; Giannetta, R. W.; Carrington, A.; Fournier, P.; Greene, R. L.; Hinks, D. G.; Banks, A. R.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 02/07/2000 Português
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45.91%
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

Absolute value preconditioning for symmetric indefinite linear systems

Vecharynski, Eugene; Knyazev, Andrew V.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
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46.18%
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.

Counting Perron Numbers by Absolute Value

Calegari, Frank; Huang, Zili
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
45.91%
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

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

Gu, Xian-Ming; Huang, Ting-Zhu; Li, Hou-Biao; Wang, Sheng-Feng; Carpentieri, Bruno
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
46.04%
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

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

Fyodorov, Yan V.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
46%
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

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

Alvarez, G.; Montoya, F.; Romera, M.; Pastor, G.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 28/06/2004 Português
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45.91%
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

An inexact Picard iteration method for absolute value equation

Miao, Shu-Xin; Xiong, Xiang-Tuan; Wen, Jin
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 30/09/2015 Português
Relevância na Pesquisa
46.12%
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

The nonlinear HSS-like iteration method for absolute value equations

Qi, Ya-E; Zhu, Mu-Zheng
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.

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

Echenique-Robba, Pablo; Nelo-Bazán, María Alejandra; Carrodeguas, José A.
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

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

Voronin, Sergey; Ozkaya, Gorkem; Yoshida, Davis
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.

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

Cruz, J. Y. Bello; Ferreira, O. P.; Prudente, L. F.
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.

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

Hirayama, Tadashi
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 17/01/2014 Português
Relevância na Pesquisa
45.91%
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

On the absolute value of the air-fluorescence yield

Rosado, J.; Blanco, F.; Arqueros, F.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 17/01/2014 Português
Relevância na Pesquisa
46.09%
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

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

Iyer, Asha; Lindner, Axel; Kagan, Igor; Andersen, Richard A.
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
Relevância na Pesquisa
46.08%
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.