Inversion of low-frequency subsurface data in a finite-depth ocean

AbstractLet:[▿2+k2+k2v(x)]u=−δ(x−y) in L=R2 × [0,h],u= 0 at x3 = 0, ux3 = 0 at x3 = h, u(x,y,k) satisfies the limiting absorption principle. Letu(x,y,k) be known for all x,y∈ P ≔ {x:x3 = d}, where 0< d<h is a small fixed number (subsurface data), and allk∈ (0,k0),k0 > 0 is a small number. These data determine v(x) uniquely and an analytical procedure is given for finding v(x) given the above data. It is assumed that v(x), the inhomogeneity in the refraction coefficient (of the ocean of depth h), is an arbitrary compactly supported square integrable function

Anomalous Heat Conduction and Anomalous Diffusion in Low Dimensional Nanoscale Systems

Thermal transport is an important energy transfer process in nature. Phonon is the major energy carrier for heat in semiconductor and dielectric materials. In analogy to Ohm's law for electrical conductivity, Fourier's law is a fundamental rule of heat transfer in solids. It states that the thermal conductivity is independent of sample scale and geometry. Although Fourier's law has received great success in describing macroscopic thermal transport in the past two hundreds years, its validity in low dimensional systems is still an open question. Here we give a brief review of the recent developments in experimental, theoretical and numerical studies of heat transport in low dimensional systems, include lattice models, nanowires, nanotubes and graphenes. We will demonstrate that the phonon transports in low dimensional systems super-diffusively, which leads to a size dependent thermal conductivity. In other words, Fourier's law is breakdown in low dimensional structures

Longitudinal scaling property of the charge balance function in Au + Au collisions at 200 GeV

We present measurements of the charge balance function, from the charged particles, for diverse pseudorapidity and transverse momentum ranges in Au + Au collisions at 200 GeV using the STAR detector at RHIC. We observe that the balance function is boost-invariant within the pseudorapidity coverage [-1.3, 1.3]. The balance function properly scaled by the width of the observed pseudorapidity window does not depend on the position or size of the pseudorapidity window. This scaling property also holds for particles in different transverse momentum ranges. In addition, we find that the width of the balance function decreases monotonically with increasing transverse momentum for all centrality classes.Comment: 6 pages, 3 figure

Measurement of the Bottom contribution to non-photonic electron production in p+pp+p collisions at s\sqrt{s} =200 GeV

The contribution of $B$ meson decays to non-photonic electrons, which are mainly produced by the semi-leptonic decays of heavy flavor mesons, in $p+p$ collisions at $\sqrt{s} =$ 200 GeV has been measured using azimuthal correlations between non-photonic electrons and hadrons. The extracted $B$ decay contribution is approximately 50% at a transverse momentum of $p_{T} \geq 5$ GeV/$c$. These measurements constrain the nuclear modification factor for electrons from $B$ and $D$ meson decays. The result indicates that $B$ meson production in heavy ion collisions is also suppressed at high $p_{T}$.Comment: 6 pages, 4 figures, accepted by PR

Production of Υ(nS) mesons in Pb+Pb and pp collisions at 5.02 TeV

A measurement of the production of vector bottomonium states, Υ ( 1S ) , Υ ( 2S ) , and Υ ( 3S ) , in Pb + Pb and p p collisions at a center-of-mass energy per nucleon pair of 5.02 TeV is presented. The data correspond to integrated luminosities of 1.38 nb − 1 of Pb + Pb data collected in 2018, 0.44 nb − 1 of Pb + Pb data collected in 2015, and 0.26 fb − 1 of p p data collected in 2017 by the ATLAS detector at the Large Hadron Collider. The measurements are performed in the dimuon decay channel for transverse momentum p μ μ T &lt; 30 GeV , absolute rapidity | y μ μ | &lt; 1.5 , and Pb + Pb event centrality 0–80%. The production rates of the three bottomonium states in Pb + Pb collisions are compared with those in p p collisions to extract the nuclear modification factors as functions of event centrality, p μ μ T , and | y μ μ | . In addition, the suppression of the excited states relative to the ground state is studied. The results are compared with theoretical model calculations

Tomographic reconstructions using map algorithms - application to the SPIDR mission

The spectral image of an astronomical scene is reconstructed from noisy tomographic projections using maximum a posteriori (MAP) and filtered backprojection (FBP) algorithms. Both maximum entropy (ME) and Gibbs prior are used in the MAP reconstructions. The scene, which is a uniform background with a localized emissive source superimposed on it, is reconstructed for a broad range of source counts. The algorithms are compared regarding their ability to detect the source in the background. Detectability is defined in terms of a contrast-to-noise ratio (CNR) which is a Monte Carlo ensemble average of spatially averaged CNRs for the individual reconstructions. Overall, MAP was found to yield improved CNR relative to FBP. Moreover, as a function of the total source counts, the CNR varies distinctly different for source and background regions. This may be important in separating a weak source from the background

Two-dimensional region-of-interest reconstruction: analyzing the difference between virtual fanbeam and DBP-Hilbert reconstructions

This work addresses theoretical advances classical (2D) tomographic image reconstruction. During the past several years, inversion formulas have been established that allow ROI reconstruction from incomplete (yet sufficient) data. Such reconstructions have important consequences in certain practical situations, such as truncated projections. The precise relationship between the largest ROI that can be reconstructed and the incompleteness of the sinogram is a complex question which has still not been completely answered in the 2D case. These relationships are inherent to the system and have consequences for iterative/statistical reconstruction methods, because they describe which part of the reconstructed image is determined completely by the data; the other parts of the image will have been more heavily influenced by the regularization method or by the nature of the objective function. Our understanding of the nature of reconstruction from incomplete yet sufficient data relies mainly on formulas obtained from the virtual fanbeam (VFB) method and from the DBP-Hilbert method. The purpose of this work is to provide a structure in which to examine the inherent differences in these two approaches. Using a common reconstruction problem, we reformulate VFB and DBP-Hilbert reconstruction formulas into weight functions that are applied in the sense of an inner product to the sinogram. A common regularization is used for the Hilbert transform in both methods. Unlike the usual Fourier windows used in analytic methods, the regularization we used is applied locally to the singularity to avoid the regularization obscuring the nature of the reconstruction. The weight functions clearly show how truncated projections are being correctly handled. The dissimilarity in the weight functions of the two methods illustrates fundamental differences in managing incomplete data, and suggests that many other such methods exist. ©2009 IEEE.SCOPUS: cp.pinfo:eu-repo/semantics/publishe