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On‐body propagation channels show significant polarization selectivity that has dominant impacts on the on‐body link quality in wireless body area networks. For on‐body relay channels over long distances across the body, the antenna polarization configurations of the relaying nodes are crucial to determine the relay performance, thereby requiring polarization optimization schemes. In this article, narrow band flat‐fading on‐body channels at 2.484 GHz are measured to analyse their polarization distribution above the skin under static postures. The measured on‐body channels show full‐space polarization convergence and dispersion, which are modelled by an extended 3 by 3 channel polarization matrix, and a statistical channel model is also proposed. Multi‐hop polarized on‐body relay channels are analysed on the relay link capacity, which shows polarization dependency between adjacent hop channels when relaying nodes are mounted by linearly polarized antennas. Both regular and iterative polarization selection algorithms are then designed to optimise the antenna polarization configuration of the nodes. Simulations based on the proposed polarization distribution model show significant link capacity increases for two‐hop and tfhree‐hop on‐body relay channels by the optimization algorithms. The results confirm the necessity of proper polarization selection schemes for on‐body relay channels. [ABSTRACT FROM AUTHOR]

We search for indications of waves in the 25 - 2000 MHz radio spectrum of the 1 August 2010 event (SOL2010-08-01T08:57:00L075C013), where fast propagating waves in the solar corona with periods of 181, 69, and 40 seconds were detected in UV observations. Using the wavelet technique, we construct a new type of oscillation map for selected periods in the whole domain of the radio spectrum. While an oscillation with a period of 181 seconds was recognized in the whole 25 - 2000 MHz radio spectrum, oscillations with periods of 69 and 40 seconds were only confirmed in the 250 - 870 MHz frequency range. In the 800 - 2000 MHz range we found periods of 50 and 80 seconds. Moreover, in the 250 - 870 MHz frequency range, an oscillation with a period of about 420 seconds was detected. We also made maps of phases of the 181-second oscillations in order to analyze their frequency drift. At the beginning of the radio event, the phase of the 181-second oscillation in the 2000 - 500 MHz frequency range drifts toward lower frequencies. On the other hand, we found that the phase is nearly synchronous at frequencies 25 - 500 MHz. While the phase drift at higher frequencies can be interpreted as being caused by the UV wave, the synchronization of the phase on lower frequencies is explained by the fast electron beams, whose acceleration is modulated by the UV wave. Owing to this modulation, the electron beams are accelerated with the period of the UV wave (181 seconds). These beams propagate upward through the solar corona and generate the 25 - 500 MHz radio emission with the 181-second period. The 25 - 500 MHz radio emission, which corresponds to a large interval of heights in the solar corona, is nearly synchronous because of the high beam velocity ( ${\approx}\,\mathrm{c}/3$ , where c is the light speed). [ABSTRACT FROM AUTHOR]

The IceCube experiment has recently reported the observation of 28 high-energy (>30 TeV) neutrino events, separated into 21 showers and 7 muon tracks, consistent with an extraterrestrial origin. In this Letter, we compute the compatibility of such an observation with possible combinations of neutrino flavors with relative proportion (αe:αμ:ατ)⊕. Although the 7:21 track-to-shower ratio is naively favored for the canonical (1:1:1)⊕ at Earth, this is not true once the atmospheric muon and neutrino backgrounds are properly accounted for. We find that, for an astrophysical neutrino E-2 energy spectrum, (1:1:1)⊕ at Earth is disfavored at 81% C.L. If this proportion does not change, 6 more years of data would be needed to exclude (1:1:1)⊕ at Earth at 3σ C.L. Indeed, with the recently released 3-yr data, that flavor composition is excluded at 92% C.L. The best fit is obtained for (1:0:0)⊕ at Earth, which cannot be achieved from any flavor ratio at sources with averaged oscillations during propagation. If confirmed, this result would suggest either a misunderstanding of the expected background events or a misidentification of tracks as showers, or even more compellingly, some exotic physics which deviates from the standard scenario. [ABSTRACT FROM AUTHOR]

Heat was used as a tracer to measure infiltration rates from a recharge basin. The propagation of diurnal oscillation of surface water temperature into the basin bed was monitored along a transect using Fiber Optic Distributed Temperature Sensing (FODTS). The propagation rate was related to downward specific discharge using standard theory of heat advection and dispersion in saturated porous media. An estimate of the temporal variation of heat propagation was achieved using a wavelet transform to find the phase lag between the surface temperature diurnal oscillation and the correlated oscillation at 0.33 and 0.98 m below the bed surface. The wavelet results compared well to a constant velocity model of thermal advection and dispersion during periods of relatively constant discharge rates. The apparent dispersion of heat was found to be due primarily to hydrodynamic mechanisms rather than thermal diffusion. Specific discharge estimates using the FODTS technique also compared well to water balance estimates over a four month period, although there were occasional deviations that have yet to be adequately explained. The FODTS technique is superior to water balance in that it produces estimates of infiltration rate every meter along the cable transect, every half hour. These high resolution measurements highlighted areas of low infiltration and demonstrated the degradation of basin efficiency due to source waters of high suspended solids. FODTS monitoring promises to be a useful tool for diagnosing basin performance in an era of increasing groundwater demand. [ABSTRACT FROM AUTHOR]

Mechanisms for the northward propagation (NP) of the boreal summer intraseasonal oscillation (BSISO) and associated Asian summer monsoon (ASM) are investigated using data from the interim ECMWF Re-Analysis (ERA-Interim, herein called ERAI) and the superparameterized Community Climate System Model (SP-CCSM). Analyzed mechanisms are 1) destabilization of the lower troposphere by sea surface temperature anomalies, 2) boundary layer moisture advection, and boundary layer convergence associated with 3) SST gradients and 4) barotropic vorticity anomalies. Mechanism indices are regressed onto filtered OLR anomaly time series to study their relationships to the intraseasonal oscillation (ISO) and to equatorial Rossby (ER) waves. Northward propagation in ERAI and SP-CCSM is promoted by several mechanisms, but is dominated by boundary layer moisture advection and the barotropic vorticity effect. SST-linked mechanisms are of secondary importance but are nonnegligible. The magnitudes of NP mechanisms vary from the Indian Ocean to the west Pacific Ocean, implying that NP is accomplished by different mechanisms across the study area. SP-CCSM correctly simulates observed NP mechanisms over most of the ASM domain except in the Arabian Sea during the early stages of the monsoon life cycle. Reduced NP in the Arabian Sea arises from weaker-than-observed easterly shear, reducing the effectiveness of the barotropic vorticity mechanism. The ability of SP-CCSM to correctly simulate NP mechanisms in other regions results from the model's ability to simulate reasonable mean wind and moisture fields, a realistic spectrum of variability, and the capability of convection to respond to boundary layer changes induced by large-scale NP mechanisms. [ABSTRACT FROM AUTHOR]

Abstract: In this work, the large-wave simulation (LWS) method is adapted for application in spilling wave breaking over a constant slope beach. According to LWS, large scales of velocities, pressure and free-surface elevation are numerically resolved, while the corresponding unresolved scale effects are taken into consideration by a subgrid scale (SGS) model for wave and eddy stresses. The model may be not fully applicable in very shallow water, close to the shoreline, where the unresolved, turbulent, free-surface oscillation is of the same order with the water depth. Time integration of the Euler equations is achieved by a two-stage fractional scheme, combined with a hybrid scheme for spatial discretization, consisting of finite difference and pseudospectral approximation methods. Model parameters are calibrated by comparison to available experimental data of free-surface elevation and velocities in the surf zone for cross-shore incoming waves. The action of the wave SGS stresses in the outer coastal and surf zones initiates breaking and generates appropriate vorticity, in the form of an eddy structure (surface roller), at the breaking wavefront. At incipient breaking, both advection and gravity contribute to the vorticity flux at the free surface, while only after the full development of the surface roller, the effect of advection becomes stronger. The SGS model is also utilized to simulate propagation, refraction and breaking of oblique incoming waves. The gradual breaking and dissipation of wave crestlines and the surface roller structure along the breaking wavefront are automatically captured without any empirical input, such as data for the roller shape or the wave propagation angle at breaking. [Copyright &y& Elsevier]

The article discusses the presence of strong solitonlike splashes of the large-amplitude electromagnetic wave field within the nonradiative propagation. It mentions that the wave amplitude in the splashes region can rise by magnitude order. It adds that new features can be revealed by soluble model problems in the wave propagation and in oscillation dynamics.

Traditional methods used to predict the ground-wave field strength at low frequency are not applicable for terrains with serious irregularities because of the analytical approximations. In this paper, the two dimensional finite-difference time-domain (FDTD) algorithm is applied to calculate the field strength of the low frequency (LF) ground wave propagating over irregular terrains. The propagation characteristics are studied as functions of the mountain's gradient, height, and width, respectively. We also focus on studying the cases with multiple mountains in the path. Moreover, the error of the traditional integral equation method is analyzed by comparisons. The results show that when the mountain's gradient and height are high, additional oscillations in the field strength will appear in front of and in the mountain region due to the wave reflection and scattering. At last, measurements of the Loran-C signals are taken along a real path between Pucheng and Tongchuan in Shaanxi province, China. It is found that most of the measured and FDTD results have good agreements while some still have big errors owing to the model approximation. The FDTD method gets better precision than the integral equation method in the irregular terrain. [ABSTRACT FROM AUTHOR]

Random networks of symmetrically coupled, excitable elements can self-organize into coherently oscillating states if the networks contain loops (indeed loops are abundant in random networks) and if the initial conditions are sufficiently random. In the oscillating state, signals propagate in a single direction and one or a few network loops are selected as driving loops in which the excitation periodically circulates. We analyze the mechanism, describe the oscillating states, identify the pacemaker loops, and explain key features of their distribution. [ABSTRACT FROM AUTHOR]

The article reports on the demonstrations of the application of radio waves for chartering the large-scale structure of the universe. It examines the density patter called baryonic acoustic oscillations (BAOs) as a way of describing the universe's expansion. It also discusses that the expansion is accelerating under the influence of a dark energy.

In a dispersive medium, the appearance of the steady-state part of the signal is preceded by oscillations known as precursors. These early oscillations are the product of the interrelated effects of phase dispersion and frequency dependent attenuation. Inside water, the attenuation rate of the Brillouin precursor is sub-exponential, following the inverse square-root of the distance traveled. Based on that, a near-optimal pulse that could achieve this attenuation rate, and, hence, would lend itself to underwater detection and communication applications, was recently proposed. The "optimality" of this pulse is shown to be related to the temporal support of the pulse and its spectral characteristics, rather than its shape. A family of alternative pulses is found to have the low attenuation feature of the "optimal" pulse, as they eventually evolve into the Brillouin precursor itself shortly after they enter water. In addition, this work considers the practical case when such a pulse would be generated in air, would impinge onto an air-water interface and then propagate inside water. It is shown how the presence of the interface affects the attenuation rate of the pulse inside water and a simple way to recover its low attenuation rate is suggested. The finite-difference time-domain technique is employed in all the simulations. [ABSTRACT FROM AUTHOR]

Abstract: Calcium ions are an important second messenger in living cells. Calcium signals in form of waves serve as a means of intercellular communication and thus represent a vibrant subject for experimental and theoretical investigations. Here we study the role of cellular variability on the occurrence of Ca2+ wave propagation in a net of diffusively coupled cells. Dynamics of individual cells is simulated by a mathematical model for Ca2+ oscillations. Structural diversity of cells is introduced via variations of the bifurcation parameters, which signify cell sensitivity for external stimulation. Remarkably, for sufficient values of variability Ca2+ waves emerge, which are mostly ordered for intermediate variability strength. We analyze the spatial profile via the autocorrelation function, which confirms a resonance-like response due to the cellular variability. Thus, the reported phenomenon is a novel observation of diversity-induced spatial coherence resonance in a tissue-like media. [Copyright &y& Elsevier]

The influence of the Indian Ocean dipole (IOD) on the poleward propagation of boreal summer intraseasonal oscillations (BSISOs) is examined using observed datasets. This study finds that coherent (incoherent) poleward propagation of precipitation anomalies from 5°S to 25°N are observed during negative (positive) IOD years. Disorganized poleward propagation of BSISO in the south equatorial Indian Ocean is observed during positive IOD years. The rationale behind such an anomaly in the poleward propagation of BSISO in contrasting IOD years is identified based on the theory of northward-propagating BSISO, which suggests the influential role of air–sea interaction on the genesis and propagation of BSISO. It is found that the mean structure of moisture convergence and meridional specific humidity distribution undergoes radical changes in contrasting IOD years, which in turn influences the meridional propagation of BSISO. This study assumes significance, considering the critical role of BSISO in modulating the seasonal mean summer monsoon rainfall. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the evolution of classical wave propagation in the canonical acoustic black hole by a numerical method and discuss the details of the tail phenomenon. The oscillating frequency and damping time scale both increase with the angular momentum l. For lower l, numerical results show the lowest WKB approximation gives the most reliable result. We also find that the time scale of the interim region from ringing to tail is not affected obviously by changing l. [ABSTRACT FROM AUTHOR]

Using the method of unidirectional waves, we numerically solve a wave equation that describes the vector propagation of a femtosecond laser pulse of few optical cycles in a uniaxial crystal. Propagation of the pulse in the direction normal to the optical axis is studied, taking into account both the second- and third-order nonlinearity of the crystal. Conversion efficiency as a function of crystal length, pump intensity, and pulse duration is studied. As an example, the propagation of a femtosecond laser pulse of τ = 10 fs duration at λ = 810 nm in a 12-μm thick LiNbO3 crystal is numerically modeled. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 280–285, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10742 [ABSTRACT FROM AUTHOR]

Part II. Investigates how the quassi biennial oscillation (QBO) influence on wave propagation and temperatures affects the Antarctic ozone hole. Correlation between QBO and ozone hole severity; Ozone response to QBO; Discussion and conclusions.

A comprehensive design for high-power DFB lasers is discussed. An anti-reflection/high-reflection facet structure and optimized coupling between forward and backward propagation waves in continuous corrugation-type devices are shown in to be essential for thus purpose. By applying the forementioned optimization to 1.5 µm DFB laser parameters, a maximum output power of 45 mW and a quantum efficiency of 37 percent are obtained at 20°C. The devices oscillate in a single-longitudinal-mode with a side-mode suppression ratio of more than 30 dB under 1 GHz sinusoidal modulation. [ABSTRACT FROM AUTHOR]

This paper theoretically analyzes the effect of an inverted atmospheric layer, nonuniform in the lateral direction, on wave propagation by means of the coupled mode theory. A grounded duct, an inverted atmospheric model, was employed in which a 2n power N profile (height) is located under standard atmosphere and the lowest layer with a linear profile. In terms of distance, the depth of the lowest layer is assumed to vary slowly with distance. The nonuniform atmosphere varying continuously in the distance is replaced by a staircase approximation. Numerical examples are given for the coupling coefficient of the neighboring atmospheres. The coupled mode becomes maximum immediately before the trapping mode and the mode conversion is more conspicuous for a larger n. The spatial distributions of the propagation characteristics are shown in the nonuniform duct made of uniform, nonuniform, and uniform sections in the distance direction. It was found that the variation of the received electric field changes significantly according to the change in duct height in the distance direction and that the effect of the order n is extremely significant. [ABSTRACT FROM AUTHOR]