Statistics of low-frequency normal-mode amplitudes in an ocean with random sound-speed perturbations : shallow-water environments

Author Posting. © Acoustical Society 2012. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 131 (2012): 1749-1761, doi:10.1121/1.3666002.Second- and fourth-moment mode-amplitude statistics for low-frequency ocean sound propagation through random sound-speed perturbations in a shallow-water environment are investigated using Monte Carlo simulations and a transport theory for the cross-mode coherence matrix. The acoustic observables of mean and mean square intensity are presented and the importance of adiabatic effects and cross-mode coherence decay are emphasized. Using frequencies of 200 and 400 Hz, transport theory is compared with Monte Carlo simulations in a canonical shallow-water environment representative of the summer Mid-Atlantic Bight. Except for ranges less than a horizontal coherence length of the sound structure, the intensity moments from the two calculations are in good agreement. Corrections for the short range behavior are presented. For these frequencies the computed mode coupling rates are extremely small, and the propagation is strongly adiabatic with a rapid decay of cross-mode coherence. Coupling effects are predicted to be important at kilohertz frequencies. Decay of cross-mode coherence has important implications for acoustic interactions with nonlinear internal waves: For the case in which the acoustic path is not at glancing incidence with a nonlinear internal-wave front, adiabatic phase randomizing effects lead to a significantly reduced influence of the nonlinear waves on both mean and mean square intensity.This work was supported by the Office of Naval Research and the Naval Undersea Warfare Center’s Under- Sea Warfare chair at the Naval Postgraduate School

Acoustic and oceanographic observations and configuration information for the WHOI moorings from the SW06 experiment

This document describes data, sensors, and other useful information pertaining to the moorings that were deployed from the R/V Knorr from July 24th to August 4th, 2006 in support of the SW06 experiment. The SW06 experiment was a large, multi-disciplinary effort performed 100 miles east of the New Jersey coast. A total of 62 acoustic and oceanographic moorings were deployed and recovered. The moorings were deployed in a “T” geometry to create an along-shelf path along the 80 meter isobath and an across-shelf path starting at 600 meters depth and going shoreward to a depth of 60 meters. A cluster of moorings was placed at the intersection of the two paths to create a dense sensor-populated area to measure a 3-dimensional physical oceanography. Environmental moorings were deployed along both along-shelf and across-shelf paths to measure the physical oceanography along those paths. Moorings with acoustic sources were placed at the outer ends of the “T” to propagate various signals along these paths. Five single hydrophone receivers were positioned on the across shelf path and a vertical and horizontal hydrophone array was positioned at the intersection of the “T” to get receptions from all the acoustics assets that were used during SW06.Funding was provided by the Office of Naval Research under Contract No. N00014-04-1014

Entropy and scintillation analysis of acoustical beam propagation through ocean internal waves

Author Posting. © Acoustical Society of America, 2005. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 117 (2005): 1611-1623, doi:10.1121/1.1854571.Parabolic equation numerical simulations of waveguide acoustical beam propagation in an ocean of Garrett–Munk internal waves are used to examine the range evolution of beam properties such as beamwidth (both spectral and spatial), Shannon entropy, and scintillation index, as a function of beam angle. Simulations are carried out at 250- and 125-Hz acoustic frequencies. The ray trajectories associated with these beams are predominantly chaotic or exponentially sensitive to initial conditions and/or medium perturbations. At long range near saturation, the finite-frequency beams show a constant rate of change of Shannon entropy with range, independent of acoustic frequency. This full-wave rate of entropy is of the same order of magnitude as the average rate of entropy for the ray trajectories associated with this beam. Finite-range Lyapunov exponents provide the estimates of ray entropy rate or Kolmogorov–Siani entropy. The correspondence between full-wave and ray entropies suggests a full-wave manifestation of ray chaos, but only once statistical saturation is obtained. In spite of this correspondence, the simulated acoustical beams expand diffusively not exponentially (or explosively)

Two-particle correlations in azimuthal angle and pseudorapidity in inelastic p + p interactions at the CERN Super Proton Synchrotron

Results on two-particle ΔηΔϕ correlations in inelastic p + p interactions at 20, 31, 40, 80, and 158 GeV/c are presented. The measurements were performed using the large acceptance NA61/SHINE hadron spectrometer at the CERN Super Proton Synchrotron. The data show structures which can be attributed mainly to effects of resonance decays, momentum conservation, and quantum statistics. The results are compared with the Epos and UrQMD models.ISSN:1434-6044ISSN:1434-605

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe

Biological Earth observation with animal sensors

Space-based tracking technology using low-cost miniature tags is now delivering data on fine-scale animal movement at near-global scale. Linked with remotely sensed environmental data, this offers a biological lens on habitat integrity and connectivity for conservation and human health; a global network of animal sentinels of environmen-tal change

Synthesis and Anti-Knock Properties of Furfural Derivatives

Исследовательским методом оценены октановые числа растворов диэтилацеталя фурфурола и фурфуриламина в прямогонном бензине и установлены линейные зависимости октанового числа растворов изученных веществ от их концентрации. Рассчитаны октановые числа смешения диэтилацеталя фурфурола (106,0±3,8) и фурфуриламина (193,5±7,7). Предложен новый метод препаративного синтеза диэтилацеталя фурфурола прямым взаимодействием спирта и альдегида. Для смещения равновесия реакции пары воды из газовой фазы над раствором реагирующих веществ удаляются оксидом кальция. Оценена окислительная стабильность растворов фурфуриламина в прямогонном бензине: по показателю «индукционный период» (более 1000 мин) она соответствует требованиям ГОСТ 2084-77 при концентрации фурфуриламина менее 5 мас. %.Research octane numbers (RON) of the furfural diethyl acetal and furfurylamine solutions in straight-run gasoline were measured, and the liner dependences between the solution octane numbers and concentrations of furfural derivatives were found. Blending research octane numbers (BRON) for furfural diethyl acetal (106.0±3.8) and furfurylamine (193.5±7.7) are calculated. A novel method of syntheses of furfural diethylacetal by the direct interaction of the alcohol and the aldehyde is developed. To shift the reaction equilibrium a water vapour from gas phase over the reaction mass is removed by calcium oxide. Oxidative stability of the furfurylamine solutions in straight-run gasoline (test for induction period) was estimated. It corresponds to the GOST 2084-77 conditions at the furfurylamine concentrations less than 5 wt. % and exceeds value of 1000 mi

The Use of Carbon-Containing Compounds to Prepare Functional and Structural Composite Materials: A Review

The review presents data on the synthesis, properties of carbon-containing compounds, and their application in the technology of obtaining functional and structural composites. Such materials are widely used in recent years due to their good physical and mechanical properties. The review discusses in detail the influence of the chemical composition of various carbon-containing substances and the size of the dispersed phase on the mechanical and physical properties of produced metal matrix composite. The review also concerns methods for the modern synthesis of graphene, carbon nanotubes, and metallic functional and structural composites with reinforcing carbon-containing compounds. Additionally, the results of metal matrix composite modeling are presented. They show that the improved mechanical properties of CNT–Al composites can be attributed to three factors: CNT hardening, matrix grain refinement, and layered architecture