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The results of an experiment on measuring the characteristics of a radio signal at the input of mobile base stations of local Wi-Fi networks of an electric train on the railway are presented. The analysis of the results of the experiment carried out in the laboratory of MaximaTelecom JSC using Channel Emulator CH01 (RadioGigabit) device, together with the base stations Fruidmesh 4800. The analysis of the qualitative characteristics of signals at the entrance of the train base stations in tunnels and in open areas is given. Based on the obtained graphs, it is concluded that it is necessary to study the effect of the handover on the decrease in the input signal level, an increase in the probability of error (BER), as well as the number of retransmissions and a decrease in the channel speed. Significant fluctuations of the channel velocity in open areas due to the phenomenon of multipath propagation of radio waves are noted. All these factors create time delays for transmission of information and negatively affect the efficiency of train traffic management. The methods of reducing duration of the handover and reducing the influence of multipath are offered. [ABSTRACT FROM AUTHOR]

Internet user penetration in Indonesia is growing rapidly. Therefore, it is necessary to improve the quality of service in order to get a larger connection capacity and a high speed data access. Based on the condition, the research was carried out on planning the LTE-A network. In this research, the LTE-A network of 2300 MHz TDD frequency was planned in Nipah Mall Makassar by using parameters data from an existing operator and planned parameters. The research was conducted in several stages: existing data analysis, network planning based on capacity, and network planning based on coverage. The network planning then simulated using radio wave propagation simulator RPS5.4 to know the signal level of the antennas. The results show the network throughput in Nipah Mall is 253.8 Mbps uplink and 761.0 Mbps downlink. The number of cells required are 6 cells for uplink and 3 cells for downlink. The MAPL values are 104.94 dB uplink and 89.4 dB downlink where coverage radius are 115 m and 50 m for uplink and downlink respectively. Simulation results of RPS5.4 show the signal level both RSRP and SIR. The signal levels of RSRP range from -10 dBm to -45 dBm while the signal levels of SIR range between 10 dB and 40 dB. The signal levels both RSRP and SIR shows the planning of LTE-A network in Nipah Mall Makassar have a good signal level. [ABSTRACT FROM AUTHOR]

This article discusses the received signal reception algorithm under conditions of multipath propagation of radio waves and noise interference. Performed simulations reception system with the proposed algorithm. [ABSTRACT FROM AUTHOR]

HF communication is a kind of radio communication technology whose wavelength is between 10 meters and 100 meters and its frequency range from 3 MHz to 30 MHz. It relies on the ionospheric reflection for propagation, with long communication distance, low construction and operation costs, easy installation of equipment and other advantages. However, HF communication has the characteristics of poor stability, low transmission efficiency and weak antiinterference capability. In order to determine the loss of HF radio wave propagation on the ocean surface, we measure the loss in several aspects. Two basic models, ionospheric loss model and ocean surface loss model, are introduced to deduce the loss formula. In order to verify the reliability of the model, we calculate the maximum hop-counts before a given shortwave signal strength reaches the available signal-to-noise ratio threshold, and find that the model is in good agreement with the actual situation [ABSTRACT FROM AUTHOR]

Current research article examines the propagation pattern of seismic waves in a monoclinic strip between dissimilar monoclinic semi-infinite half - spaces. Velocity profile for incident/scattered seismic waves has been found analytically along with closed-form solutions for reflection/transmission angles. Velocity profiles for both the unconstrained and constrained geometries are plotted against propagation direction. The critical angle for each of the incident quasi-P and quasi-SV wave is computed and simulations are then performed to further study the effect of relevant parameters on phase velocities and deflection of all the scattered waves. [ABSTRACT FROM AUTHOR]

The paper demonstrates that the conditions of LF-MF-HF radio wave propagation over the "ice-sea" structure with highly inductive impedance are more favorable than over the sea without ice because of the appearance of surface electromagnetic waves (SEW). It was determined that the conditions of radio wave propagation over ice paths depend on a frequency, ice thickness and distance from the transmitter within the 100 kHz - 5 MHz range on the paths with ice thickness from 0,6 to 2,7 m. [ABSTRACT FROM AUTHOR]

We study a coupled system of equations, known as Bona-Smith system, which can be used to describe the two-way propagation of (one-dimensional) long waves of small but finite amplitude in an open channel of water of constant depth. Conservation laws are obtained using Noether's method and furthermore we present exact solutions of the system. [ABSTRACT FROM AUTHOR]

We present geometrical and kinematical analysis of Moreton waves and EIT waves observed on June 3, 2012 and Moreton waves observed on July 6, 2012. The Moreton waves were recorded in Hα images of Global Oscillation Network Group (GONG) archive and EIT waves obtained from SDO/AIA observations, especially in 193 nm channel. The observed wave of June 3 has angular span of about 70 with a broad wave front associated to NOAA active region 11496. It was found that the speed of the wave that started propagating at 17.53 UT is between 950 to 1500 km/s. Related to this wave occurrence, there was solar type II and III radio bursts. The speed of the EIT in this respect is about 247 km/sec. On the other hand, the wave of July 6 may be associated to x1.1 class flare that occurred at 23.01 UT around the 11514 active region. From the kinematical analysis, the wave propagated with the initial velocity of about 1180 km/s which is in agreement with coronal shock velocity derived from type II radio burst observation, v ≈ 1200 km/s. [ABSTRACT FROM AUTHOR]

We investigate the control of electron injection in the cascaded laser wakefield accelerators, optimization of seeding phase and the self-guided propagation of laser pulses between the two accelerators. The maximum acceleration gradient with energy spread narrowing was obtained when the seeding phase and the laser pulse propagation were optimized. [ABSTRACT FROM AUTHOR]

The ponderomotive force of a laser pulse launched into relatively rarefied plasma excites an ion acoustic wave and an electromagnetic wave inside the plasma. The ion acoustic wave induces some perturbation in the plasma density. The wave equation is written for the ion acoustic wave and the relative density perturbation δn/n is calculated as function of this wave's frequency ωA. The produced electromagnetic wave propagates through the plasma in the presence of a magnetic field both in O(ordinary) and X(extraordinary) modes. In this work estimation is made for the frequency shift of the X-mode propagation due to the density perturbation in relatively rarefied magnetized plasma. [ABSTRACT FROM AUTHOR]

Heat loads from ICRF and LH wave absorption in the SOL are characterized on JET from the de-convolution of surface temperatures measured by infrared thermography. The spatial localization, quantitative estimates, parametric dependence and physical origin of the observed heat fluxes are documented. Implications of these observations are discussed for the operation of JET with an ITER-Like Wall, featuring Beryllium tiles with reduced power handling capability. [ABSTRACT FROM AUTHOR]

The EC H&CD system of ITER tokamak is an essential tool for all the phases of ITER operation. Different levels of EC power are required through all the plasma discharge: up to 6.7 MW for assisting the breakdown and burn through, up to 20 MW for current drive and saw-teeth control from the equatorial launcher and up to 20 MW for NTM stabilization from the upper launchers. The assistance to breakdown and burn through is characterized by a very low (if not negligible) RF power absorption by the plasma. A significant level of stray radiation may also arise from partial absorption due to non-optimal plasma parameters and/or wrong injected polarization. The stray power radiated in the vacuum chamber is estimated as a first step toward mitigating potential harmful consequence to in-vessel structures and diagnostics. Power loading of the chamber walls (peek power and average power density for straight beam propagation in the empty chamber) and diffuse stray radiation effects are simulated to infer suitable strategies to avoid damage to first wall and to microwave sensitive components. [ABSTRACT FROM AUTHOR]

This paper treats self-consistently the interplay between slow magnetosonic wave penetration and edge plasma DC biasing using a two-field fluid approach. The RF and DC parts are coupled by non-linear RF and DC sheath boundary conditions at lateral boundaries of the simulation domain. Within this approach two mechanisms of RF-induced DC current flows are outlined, depending on the toroidal symmetry of the RF drive. The numerical implementation of the model using COMSOL, its validation against explicit simplified solutions and its planned improvements are discussed. [ABSTRACT FROM AUTHOR]

ELMs reduce the stored energy achieved with HHFW heating compared with the ELM free case as also occurs for NBI heating alone. This reduction can be attributed both to direct ELM ejection of stored energy and to an increase in edge density with ELMs that exceeds the onset density for perpendicular wave propagation near the antenna [1,2], and leads to significantly more edge RF power deposition. This latter effect causes a more intense RF 'hot' zone in the lower divertor scrape off region due to an increase in edge RF power propagating to the divertor from the antenna region along the magnetic field lines. Fast IR measurements of the direct ELM heat deposition at the lower divertor shows it to be peaked in the vicinity of the outer strike radius and to fall off strongly as the 'hot' zone is approached, indicating little direct ELM effect on the 'hot' zone heating. Physics studies of the 'hot' zone have begun with sweeping the RF 'hot' zone spiral over Rogowski instrumented divertor region tiles to show that the tile currents track the location of the zone. The relation of the results here to the AORSA RF code simulations including the SOL region is pointed out. [ABSTRACT FROM AUTHOR]

A steady-state tokamak reactor (SSTR) requires a high efficiency current drive system, from plug to driven mega-amps. RF systems working in the ion-cyclotron range of frequencies (ICRF) have high efficiency from plug to antenna but a limited current drive (CD) efficiency and centrally peaked CD profiles. The latter feature is not adequate for a SSTR where the current should be sufficiently broad to keep the central safety factor (possibly significantly) above 1. In addition, the fact that the fast wave (FW) is evanescent at the edge limits coupling, requiring high voltage operation, which makes the system dependent on plasma edge properties and prone to arcing, reducing its reliability. A possible way to overcome these weaknesses is to operate at higher frequency (10 times or more the cyclotron frequency). The advantages are: (1) The coupling can be much better (waves propagate in vacuum) if the parallel refractive index n∥ is kept below one, (2) The FW group velocity tends to align to the magnetic field, so the power circumnavigates the magnetic axis and can drive off-axis current, (3) Due to the latter property, n∥ can be upshifted along the wave propagation path, allowing low n∥ launch (hence good coupling, large CD efficiency) with ultimately good electron absorption (which requires higher n∥). Note however that the n∥ upshift is a self-organized feature, that electron absorption is in competition with α-particle absorption and that uncoupling of the FW from the lower hybrid resonance at the edge requires n∥ slightly above one. The latter possibly counterproductive features might complicate the picture. The different aspects of this potentially attractive off-axis FWCD scheme are discussed. [ABSTRACT FROM AUTHOR]

Fourier analysis in the poloidal direction is a standard ingredient in present-day 2D wave equation solvers describing radio frequency waves in hot tokamak plasmas. Although a powerful and elegant technique, Fourier analysis has the disadvantage that a large number of modes is needed to describe the field pattern on a magnetic surface if a short wavelength mode exists on any - even very small - subpart of the particle trajectory. The present paper examines the potential of a method that does not suffer from this drawback: a finite element technique relying on simple linear or cubic area base functions that are defined on irregular elementary surfaces of triangular shape. The wave equation is solved in its weak Galerkin variational form and for realistic 2D tokamak geometry, accounting for the toroidal curvature but assuming the toroidal angle is ignorable, allowing to study the wave pattern for each of the independent toroidal modes excited by the antenna individually. The locally uniform full hot plasma dielectric tensor to all orders in finite Larmor radius was adopted. As the main intended application is the study of fast wave behavior (heating and current drive) at arbitrary harmonics, the wave vector complex amplitude appearing in the dielectric tensor is determined through a local dispersion root evaluation. High frequency fast wave propagation and damping is provided as an illustration in view of possible application of this type of current drive in future high density reactor-like tokamaks. [ABSTRACT FROM AUTHOR]

Lower hybrid (LH) waves have the attractive property of damping strongly via electron Landau resonance on relatively fast tail electrons at (2.5-3)×vte, where vte = (2Te/me)1/2. The velocity at which damping occurs depends on the non-linear balance between quasilinear diffusion and collisions. For high efficiency current drive, a low parallel index of refraction, n∥, corresponding to a high phase velocity, is chosen. Depending on the plasma electron temperature this may put the wave propagation in a multi-pass regime. In cases of low parallel refractive index, ray tracing with no SOL has been shown to have differences with experiment [1] and collision effects in the scrape off layer may be important [2]. Using a coupled model of the full wave code, TORLH[3], and the Fokker-Planck code, CQL3D[4], the importance of full wave effects in weak and strong absorption regimes are studied. [ABSTRACT FROM AUTHOR]

The purpose of this study is to explore the important features of OFDM under different channel conditions and to analyze the outcomes. In order to procure this goal, multiple simulations are performed using GNU Octave. The simulations of OFDM transmissions are carried out under Additive White Gaussian Noise (AWGN) and/or Rayleigh fading. Besides, PACE is employed to mitigate the effects of Rayleigh fading. [ABSTRACT FROM AUTHOR]

In this chapter we aim to adapt a propagation model for Salalah city (Oman) as we examine the applicability of Okumura-Hata model in Oman in GSM frequency band. The study is a part of an ongoing work by authors, which is being carried out for an urban area on the data obtained from local operator. We accomplished the modification of the model by investigating the variation in pathloss between the measured and predicted values, according to the Okumura-Hata propagation model for a cell in Salalah city and then finding the missing experimental data with cubic regression and spline interpolation. We also verified it by applying the model for other cells. The mean square error (MSE) was calculated between measured path loss values and those predicated on the basis of Okumura-Hata model for an open area. The MSE went up to 6dB, which is an acceptable value for the signal prediction. The model showed a significant difference in an open area that allowed necessary changes to be introduced in the model. Modified equation was also re-verified for another new cell in an open area which gave acceptable results. Theoretical simulation by Okumura-Hata Model and the obtained experimental data is compared and analyzed further using a cubic regression on the set of the experimental data. Scatter plot of the experimental data on pathloss verses distance reveals a third order polynomial trend in the experimental data. Therefore, the cubic regression model was used to estimate the parameters by minimizing the sum of squares of the white noise. The coefficient of determination of this regression suggested that about 90% variation in pathloss can be explained. Theoretical simulation by Okumura-Hata Model and the obtained experimental data is compared and analyzed further using a piece-wise cubic spline to interpolate the set of the experimental data and finding the missing experimental data points. [ABSTRACT FROM AUTHOR]

Radio polarimetry is a three-dimensional statistical problem. The three-dimensional aspect of the problem arises from the Stokes parameters Q, U, and V, which completely describe the polarization of electromagnetic radiation and conceptually define the orientation of a polarization vector in the Poincaré sphere. The statistical aspect of the problem arises from the random fluctuations in the source-intrinsic polarization and the instrumental noise. A simple model for the polarization of pulsar radio emission has been used to derive the three-dimensional statistics of radio polarimetry. The model is based upon the proposition that the observed polarization is due to the incoherent superposition of two, highly polarized, orthogonal modes. The directional statistics derived from the model follow the Bingham-Mardia and Fisher family of distributions. The model assumptions are supported by the qualitative agreement between the statistics derived from it and those measured with polarization observations of the individual pulses from pulsars. The orthogonal modes are thought to be the natural modes of radio wave propagation in the pulsar magnetosphere. The intensities of the modes become statistically independent when generalized Faraday rotation (GFR) in the magnetosphere causes the difference in their phases to be large. A stochastic version of GFR occurs when fluctuations in the phase difference are also large, and may be responsible for the more complicated polarization patterns observed in pulsar radio emission. [ABSTRACT FROM AUTHOR]

An important topic in the area of airborne sound propagation is the prediction of sound propagation above an impedance ground with an atmospheric profile whose sound speed varies with height. Even if this problem is simple in concept, it leads to complications for general velocity profiles. This work illustrates the existence of a large class of realistic atmospheric profiles for which analytical solutions exist to be used as benchmark solutions for numerical methods. Spectral finite element results are discussed for sound propagation in a half-space situated above a ground surface impedance. [ABSTRACT FROM AUTHOR]

An investigation of time reversal of nonlinear and non-dissipative or dissipative plane sound waves was made. Propagation and backpropagation is time reversal invariant only when the dissipation is zero and the wave has not been shocked. A wave that has shocked has irretrievably lost part of its content. Still, if the wave and its derivatives are considered continuous there remain in theory forever information about the original signal. Factors like numerical accuracy and noise naturally set limits in practical situations. [ABSTRACT FROM AUTHOR]

Reliable characterization of the propagation environment and channel modelling of mobile satellite communication systems is necessary in order to provide better quality of service and efficient design of these systems. In this paper, the channel impairments affecting the performance and an overview of the satellite channel models are presented. The statistical distributions of the received signal that can be used to characterize the dynamic nature of these propagation channels are also presented. The main modelling parameters are investigated and simulation results show that the bit error rate (BER) performance is predominantly affected by the shadowing factor. Finally, in order to further test the channel models and the effect of the propagation environment, we investigate a novel application of using satellite diversity in conjunction with compact MIMO (multiple-input multiple-output) antenna array configurations in order to enhance the capacity of satellite communication links. [ABSTRACT FROM AUTHOR]

Future generation mobile telecommunication systems are expected to provide high data rate services and improved system performance. Long Term Evolution (LTE) is a project within the Third Generation Partnership Project (3GPP) that aims at improving the current 3G UMTS (Universal Mobile Telecommunications System) standard to cope with future requirements and to maintain competitiveness in the long term. This paper analyzes the requirements for this evolution and evaluates the performance of the Orthogonal Frequency Division Multiplexing (OFDM) UMTS-LTE system under different propagation impairments (AWGN, Pedestrian and Vehicular multipath fading channels of different speeds) in terms of bit and symbol error rates (BER and SER) for different modulation formats. [ABSTRACT FROM AUTHOR]

This paper deals with the description of the forced vibrations of air in an acoustic resonator having one closed end and the other periodically oscillating. Acoustic field in the cavity of the acoustical resonator is described as a sum of counter propagating waves with no cross-interaction. Effects of nonlinearity, absorption and detuning are taken into account. The distortions of traveling waves within the resonator length are assumed to be small, the Mach number for the moving boundary and the difference between one of the resonant frequencies and the fundamental frequency of the driving motion of the piston are also assumed to be small. The novel approximate steady state solution of the model equation using matching in the case of small dissipation is presented in this paper. The nonlinear frequency response of the resonator is calculated here for steady state oscillations for both inviscid and dissipative media. These calculations are based on the presented approximate solution. [ABSTRACT FROM AUTHOR]

Results of laboratory investigation of vibration excitation, elastic wave propagation along a stack of noise-absorbing decorative plates and reception of coherent pulse-wave signals are presented. An artificial layered structure (a stack of noise-absorbing plates of the single wavelength scale) is characterized by elastic bulk and surface wave velocities of order 40...50 m/s. Spectrum transformations of elastic surface R-wave pulses (of duration ∼50...70 ms) are observed in the experiments using a vibration source with power of several tens of milliwatt. The nonlinear medium parameter is conventionally estimated to be ∼0.1 and its high value corresponds to a medium characterized by strong acoustic nonlinearity. The analysis shows that the nature of these transformations is similar to the nonlinear effects caused by propagation of finite-amplitude acoustic waves. As distinct from R-waves, in SH-wave pulses of the same form traveling along the same surface of the artificial layered structure, the exponential amplitude decrease occurs only. [ABSTRACT FROM AUTHOR]

The brightness of the sound generated by brass instruments at high dynamic level is mainly due to the essential nonlinearity of the wave propagation in the pipe. The bright instruments such as the trumpet and the trombone (high brassiness) are different from more mellow brass instruments such as saxhorns or flugelhorns (low brassiness). The bright instruments have an almost cylindrical pipe segment just downstream of the mouthpiece. The conical bore of the saxhorns in this region implies a faster decay of the wave which reduces the nonlinear wave steepening. To investigate the differences between the brassiness of different instruments, crescendos have to be played (experiments) or simulated (theory). Then a spectral enrichment parameter, characterising the rate of spectral enrichment with increasing dynamic level, can be extracted for each instrument. A frequency-domain numerical model of brass instrument sound production is proposed as a tool to predict the spectral enrichment parameter (brassiness characterisation). It is based on generalized Burger's equations applied to weakly nonlinear wave propagation in non uniform ducts. The relevance of the present tool is evaluated by doing simulations of periodic regimes using typical brass instrument's bores, from which the spectral enrichment parameters are calculated, and compared to measured ones. [ABSTRACT FROM AUTHOR]

A computer program is developed to analyze one-dimensional elasto-plastic wave propagation in non-linear particle systems. The system is modeled by a discrete element method where the particles exhibit elastic and plastic loading and elastic unloading during compaction. The particles system is set into motion by hitting a plunger at one end while the other end is blocked. Results in form of elasto-plastic wave front propagation versus time, its peak deformations and reflection from the blocked end are shown. [ABSTRACT FROM AUTHOR]

COST (Co-operation in the field of Scientific and Technical Research) is an important instrument supporting co-operation among scientists and researchers across Europe now joining 35 member countries. Scientific projects in the COST framework are called COST Actions and have the objectives embodied in their respective Memorandum of Understanding (MoU). The main objectives of the COST Actions within the European ionospheric and radio propagation community have been: to study the influence of upper atmospheric conditions on terrestrial and Earth-space communications, to develop methods and techniques to improve existing and generate new ionospheric and propagation models over Europe for telecommunication and navigation applications and to transfer the results to the appropriate national and international organizations, institutions and industry dealing with the modern communication systems. This paper summarizes in brief the background and historical context of four ionospheric COST Actions and outlines their main objectives and results. In addition, the paper discusses the dissemination of the results and the collaboration among the participating institutions and researchers. [ABSTRACT FROM AUTHOR]

In this presentation efforts have been made to highlight the research work made on precipitation characterization and its effects on radio wave propagation particularly at frequency above 10 GHz over the Indian subcontinent. The work carried out on attenuation of radio wave due to water vapour, rain and cloud has been highlighted. To evolve better formulations suitable to tropical countries especially for Indian conditions, extensive research efforts are still needed in relation to precipitation effects on radio wave propagation. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

The sunrise effect, sunset effect, the diurnal and seasonal variations are the characteristic feature of low frequency (LF) radio wave propagated over a large distance. The normal character has been found to be perturbed during rainy days. The amplitude of 40 kHz signal transmitted from Miyakoji station, Japan and received in North-East India is remarkably attenuated after the commencement of rain. On the basis of nature of attenuation the observed records have been classified into two different forms viz., F1 and F2. An analysis in this regard is represented in this paper. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

The efficient design of reliable communication link requires the knowledge of rain fade margin to be provided in the system design to overcome the losses in the signal strength due to rain over the path. Hence there is need for the development of reliable and accurate propagation model for attenuation prediction at the operating frequency of the link at particular location. Therefore study of rain-induced effects on microwave propagation was undertaken at Guru Nanak Dev University, Amritsar. This paper describes the measurement of zenith path attenuation due to rain at Amritsar (31° 38′ N 74° 52′ E) India, using zenith looking radiometer operating at 20 GHz. The effective rain height has been obtained from the analysis of the radiometric data and point rainfall intensity. Specific attenuation for various rain rates in the present study has been evaluated from measured drop size data using lognormal drop size distribution. The average effective rain height at Amritsar has been estimated and compared to that of predicted by ITU-R model. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

An empirical model for rain attenuation has been developed based on the results of rain attenuation data collected over line-of-sight (LOS) link propagation experiment at 19.4 & 28.75 GHz at Amritsar (Latitude 31° 36′ N; Longitude 74° 56′ E) and rainfall rate measured using tipping bucket rain gauges. We present here the results of measurements of rain-induced attenuation in the vertically polarized signal propagating at 19.4 GHz over a 2.29 km LOS link during some rain events, which occurred in the monsoon season at Amritsar (India). The total attenuation over the link path measured experimentally has been compared with that obtained using Marshal & Palmer (MP) drop size distribution and Medhurst’s theoretical values and ITU-R model. Our measured results are in excellent agreement with the MP prediction. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

As is known each sea-going vessel is equipped with navigation, communication and other radio engineering facilities that serve to secure the safety of navigation and are chiefly operated at UHF-wave band. In developing these systems and calculating the energy potential for a necessary coverage range one should be well aware of the radio signal attenuation processes on a propagation path. The key parameter of this path is the (radio) wave attenuation factor V and its distance dependence V(R). A diversity of factors influencing the radio signal attenuation over the oceanic expanses, especially well pronounced and quite stable tropospheric ducts, and the lack of experimental data were the compelling reasons why the researchers of the Institute for Radiophysics and Electronics, NASU, had spent many years on comprehensive radiophysical investigations carried out in different regions of the Atlantic, Indian, Arctic and Pacific Oceans. The experimental data obtained allow creating the database of radio wave attenuation factor V. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

Two problems of the radio-occultation of Earth’s troposphere by satellite signals were analyzed: the problem of the refraction index profile reconstruction on elevation angle dependences of the refraction angle and the problem of the reconstruction of the refraction index structural characteristic profile on the transversal spatial or the frequency correlation functions of weak fluctuations of the level (amplitude logarithm) and phase. The problems are reduced to integral Fredholm equations of the first kind with self-ajoint kernels. The suggested method of the numerical solution of those equations is based on using of α — regularization methods and provides accuracy, which is sufficient for fixation of the irregular troposphere states and forecasting of the radio wave propagation conditions. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

We report the generation of extremely stable and reproducible corrugated hydrogen, nitrogen, and argon plasma waveguides up to 1.5 cm in length with corrugation period as short as 40μm and relative modulation amplitudes up to ∼20%. The waveguides are generated by projecting axially modulated Bessel beams onto uniform and extended cryogenic cluster jet flows. These waveguides are ‘slow wave’ guiding structures capable of supporting intense pulses with sub-light phase velocities, with application to direct laser acceleration of charged particles and phase-matched generation of a wide spectrum of electromagnetic radiation. These plasma structures support guided propagation at intensities limited only by our current laser energy. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Lithotripter pulses (∼7–10 μs) initiate the growth of cavitation bubbles, which collapse hundreds of microseconds later. Since the bubble growth-collapse cycle trails passage of the pulse, and is ∼1000 times shorter than the pulse interval at clinically relevant firing rates, it is not expected that cavitation will affect pulse propagation. However, pressure measurements with a fiber-optic hydrophone (FOPH-500) indicate that bubbles generated by a pulse can, indeed, shield the propagation of the negative tail. Shielding was detected within 1 μs of arrival of the negative wave, contemporaneous with the first observation of expanding bubbles by high-speed camera. Reduced negative pressure was observed at 2 Hz compared to 0.5 Hz firing rate, and in water with a higher content of dissolved gas. We propose that shielding of the negative tail can be attributed to loss of acoustic energy into the expansion of cavitation bubbles. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

The paper has three parts. In the first part a cubically nonlinear equation is derived for a transverse finite-amplitude wave in an isotropic solid. The cubic nonlinearity is expressed in terms of elastic constants. In the second part a simplified approach for a resonator filled by a cubically nonlinear medium results in functional equations. The frequency response shows the dependence of the amplitude of the resonance on the difference between one of the resonator’s eigenfrequencies and the driving frequency. The frequency response curves are plotted for different values of the dissipation and differ very much for quadratic and cubic nonlinearities. In the third part a propagating N-wave is studied, which fulfils a modified Burgers’ equation with a cubic nonlinearity. Approximate solutions to this equation are found for new parts of the wave profile. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Microwave atmospheric pressure discharge in neon sustained by surface waves in a dielectric tube is considered. The plasma column length was measured versus absorbed microwave power for different discharge conditions. This gives a view on the wave propagation characteristics. The predicted dependence of discharge length on the total flux of wave power based on the modified model of non-equilibrium plasma is compared with experimental values. Moreover, we present results of spectroscopic investigations of the electron density. The electron density was determined using the method based on the Stark broadening of Hβ spectral line. The spectroscopic results we shall use developing of a model of propagation of surface wave. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Polarization transfer in the plasma of pulsar magnetosphere is considered. It is shown that as the two natural waves of orthogonal linear polarization pass through the regions of mode coupling and cyclotron resonance, they become elliptical and non-orthogonal. Formation of pulsar polarization as a result of propagation effects implies a correlation between the ellipticity and position angle of the waves, which is proved by observations. Propagation model of pulsar polarization provides a unique possibility of diagnostics of pulsar plasma. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

We discuss the propagation of bosons and fermions in gravitational fields. The geometrical background is provided by a rotating gravitational source. Use is made of neutrino and photon wave functions that are exact to first order in the metric deviation. These are applied to the lensing of photons and neutrinos and to neutrino helicity transitions and flavor oscillations. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

The observed two-step lateral stress history in silicon carbide, SiC-B under plane shock wave propagation [N. K. Bourne, J. Millett, and I. Pickup, J. Appl. Phys. 81, 6019 (1997)] is attributed to a delayed failure in SiC-B due to propagation of a slow moving front traveling behind the main shock wave. According to this attribution, the first lower magnitude, step corresponds to the lateral stress in intact shock compressed silicon carbide as a result of the fast moving plane shock wave. The second step of higher magnitude, observed after a few hundred nanoseconds, corresponds to the lateral stress in failed silicon carbide due to propagation of the slower moving front. The current analysis, takes into account additional relevant existing results dealing with shock response of SiC-B, and shows that the suggested explanation for the observed phenomenon remains in doubt. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

One of the beamlines to become operational in the first phase at the Canadian Light Source will be dedicated to high resolution spectroscopy in the far infrared (FIR). The beamline includes three ellipsoidal mirrors and several plane mirrors that transport the beam from the bending magnet source to the FIR spectrometer. The F-number of the spectrometer is matched by the beamline optics, which relay the light via intermediate foci rather than by collimation used in mid infrared beamlines. The beamline has been designed using regular ray tracing and by propagating the electric fields generated at the magnet through the beamline optics. The fields were calculated using SRW and the propagations were performed with SRW, which assumes ideal lenses, and with a wave propagating program using the real optical surfaces. The simulations, based on wave propagation, show the significant diffraction effects at both the foci and optical surfaces due to the small electron beam, beamline aperture, and mirrors sizes. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

Based on a simple second-order thin layer asymptotic expansion for the transfer matrix, an explicit asymptotic solution for the stiffness matrix for a generally anisotropic piezoelectric thin layer is obtained. The total transfer/stiffness matrix for thick layers or multilayers is calculated with arbitrary precision by subdividing these layers into thin sublayers and combining recursively the thin layer transfer/stiffness matrices. It is shown that these methods converge to the exact solution and a hybrid transfer-stiffness matrix combination provides the smallest computational error. The new method is computationally stable, efficient and easy to implement. To solve by this method the wave propagation in a semi-space, the concept of a perfectly matched attenuating layer is introduced. The advantage of the method is that one does not need to compute the exact wave propagation solution for each anisotropic layer of the system and only the elastic constants of the layers are required. Examples are given for wave propagation in multidirectional composites and layered piezoelectric media. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

This paper reviews the status of lower hybrid current drive (LHCD) simulation and modeling. We first discuss modules used for wave propagation, absorption, and current drive with particular emphasis placed on comparing exact numerical solutions of the Fokker Planck equation in 2-D with solution methods that employ 1-D and adjoint approaches. We also survey model predictions for LHCD in past and present experiments showing detailed comparisons between simulated and observed current drive efficiencies and hard X-ray profiles. Finally we discuss several model predictions for LH current profile control in proposed next step reactor options. © 2003 American Institute of Physics [ABSTRACT FROM AUTHOR]

Electron beams propagating in the ion focused regime (Bennett pinch) are of interest for various sources of coherent electromagnetic radiation (pasotrons, ion-channel lasers, ion-channel guided free-electron lasers). The transition of a beam from a quasi-laminar state near the gun to a phase-mixed equilibrium state is accompanied with appearance of betatron oscillations. In pasotrons these oscillations play a negative role because they often result in certain beam losses due to the interception of beam electrons oscillating with large amplitudes by the chamber walls. The betatron oscillations and the beam losses can be monitored by using a weak local external magnetic field (magnetic lens) in the transition region. The results obtained show that, by using a properly designed and positioned magnetic lens, a halo in the phase-mixed beam can be greatly reduced and the beam losses can be practically eliminated. © 2003 American Institute of Physics [ABSTRACT FROM AUTHOR]

Sea clutter is the backscattered returns from a patch of the sea surface illuminated by a radar pulse. The amplitude waveforms of sea clutter and indoor radio propagation are very complicated. Can the apparent randomness of these waveforms be attributed to be generated by low-dimensional chaos? Based on the assumption that a chaotic attractor is characterized by a non-integer fractal dimension and a positive Lyapunov exponent, Haykin et al (1992) concluded that sea clutter while Tannous et al (1991) concluded that indoor radio propagation data were chaotic. However, a numerically estimated non-integral fractal dimension and a positive Lyapunov exponent may not be sufficient indication of chaos. Other researchers have also indirectly questioned the chaoticness of the sea clutter. We employ a more stringent criterion for low-dimensional chaos developed by Gao and Zheng (Phys. Rev. E, 1994) to study a two minute duration sea clutter data provided by Haykin, and indoor radio propagation data measured at UCLA, and show that these data are not chaotic. We carry out a multifractal analysis and find that sea-clutter data can be modeled as multiplicative multifractals with a lognormal envelope distribution, while the radio propagation data can be modeled as a weak multifractal in the sense of structure function technique. © 2003 American Institute of Physics [ABSTRACT FROM AUTHOR]

Path sums and Gaussian short-time propagators are used to solve two-dimensional Fokker-Planck models of lower-hybrid (LH) and electron-cyclotron (EC) current drive (CD), and are shown to be well suited to the two limiting situations where the rf quasilinear diffusion coefficient is either relatively small, D[sub rf] ≈ 0.1, or very large, D[sub rf] → ∞, the latter case enabling a special treatment. Results are given for both LHCD and ECCD in the small D[sub rf] case, whereas the limiting situation is illustrated only for ECCD. To check the accuracy of path-sum calculations, comparisons with finite difference solutions are provided. [ABSTRACT FROM AUTHOR]

A recursive algorithm has been developed for a computation of elastic wave propagation in composites. The global matrix method is applied to calculate the stiffness matrix for the unit cell. The repetition and symmetry of the cell are incorporated in a recursive scheme. Based on this method, the Floquet waves in a composite have been computed. At low frequencies, the behavior of Floquet waves is similar to that of plane waves in a homogeneous anisotropic medium. In this frequency range, the Floquet wave slowness surface can be approximated by slowness surface of plane waves defining an effective homogeneous anisotropic medium. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The objective of this paper is to show that time-reversal invariance can be exploited in acoustics to accurately control wave propagation through complex media and create a variety of useful instruments. To illustrate the robustness of time reversal mirrors, several experiments conducted in multiply scattering media, in waveguides and in reverberant cavities are presented. They show that, contrary to long-held beliefs, multi pathing and multiple scattering enhances resolution in time reversal focusing, by making the effective size of the time reversal mirror much larger than its physical size. Applications of time-reversal mirrors in pulse echo detection and particularly in nondestructive testing will be discussed. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]