Spatial Characteristics Of Radiation Research Articles

Quasi-real-time estimation of a loudspeaker direction from sound pressure level ratio among four channels

This paper describes a quasi-real-time estimation method of loudspeaker direction under Gaussian noise environment. Our estimation method is based on sound pressure level ratio among four channels when the loudspeaker is surrounded by four microphones. Performance of our method tends to be better when acoustic spatial radiation characteristics of sound source is skewed. Preliminary experiments show that an offline processing version of our method is more than 99% accurate in acoustically clean environments. In this paper, we discuss the noise robustness of our method through simulation experiments. Loudspeaker direction is estimated from 0.34s segments of Japanese sentences every 0.01s, that is quasi-real-time processing. Those segments are contaminated by Gaussian noise at 0dB, 10dB, 20dB. We demonstrate that the proposed method is robust to Gaussian noise. The results show that accuracies of proposed method (Prop2) are 96.9%, 98.2%, 98.4% at the band the center frequency of which is 2000Hz.

Application of the equivalent source method to preserve and reproduce the spatial characteristics of the sound source

Many works have been done to make a database of sound sources' radiation patterns, such as musical instruments. However, the conventional approaches were mainly based on the farfield measurement at some selected points on the spherical surface. A huge amount of data was presented in every spherical coordinate's angular direction. To overcome the problem, a method based on the equivalent source method(ESM) is proposed to record and exchange information on the spatial radiation characteristics from a sound source. By utilizing the principle of acoustical holography, complicated radiation patterns and strengths of an actual source can be approximately described by expanding the spherical harmonics in various orders. Such a method enables preserving the radiation pattern information of sound sources keeping only details on the position coordinate of equivalent sources and the coefficient of each order of spherical harmonics, which can be regarded as a standard format. If the proposed approach is used, a more precise and large amount of information can be stored with a smaller size of data than the conventional dataset.

Effect of Laser Intensity on an Electron’s Optimal Position and Spatial Radiation Characteristics in a Linearly Polarized Tightly Focused Laser Field

Effect of Laser Intensity on an Electron’s Optimal Position and Spatial Radiation Characteristics in a Linearly Polarized Tightly Focused Laser Field

Noise footprint assessment at a vertiport for different approach and departure procedures of a tilt-wing air-taxi

Community noise at vertiports is one of the most important questions related to upcoming urban air mobility (UAM) operations. While fixed-wing and/or fixed-rotor aircraft can mainly be treated by their changing operational parameters, such as rotor or propeller rpm, tilt-wing or tilt-engine configurations are more difficult to simulate because of their constantly changing noise emission and spatial radiation characteristics. The work presented in this paper is providing an overview of the noise situation at a virtual vertiport which is being approached and departed by a tilt-wing air-taxi in different ways. Several different departure procedures are simulated with the same generic air-taxi. For the noise emission semi-empiric methods were used. During the air-taxi's descent and climb, different tilt configurations are included, mainly defined by the time dependent engine's tilt-angle, but also related to different approach paths. Each approach or departure procedure is generating individually time dependent changing noise emission characteristics which are used for noise footprint mapping around the touch-down or lift-off point. Different noise metrics are computed, including some which are representative to indicate noise annoyance among the vertiport's neighborhood. It is expected that each procedure will generate its own specific community noise situation in the vicinity of the vertiport, and thus may provide an early recommenddation for later operations. The results are compared towards each other. Additionally, a simulated certification flyover according to ICAO Chapter 13 - which is about the noise certification of tilt-rotor aircraft - is set into relation to the vertiport's community noise.

Influence of high-energy electron’s initial position on its spatial radiation characteristics during interaction with a linearly polarized tightly focused laser

Influence of high-energy electron’s initial position on its spatial radiation characteristics during interaction with a linearly polarized tightly focused laser

Circular, Plane-Directional Radiation from the Edges of Light-Excited Layer of a Laser Dye Solution with the Regular Geometric Form

Homogeneous light excitation of the Rhodamine 6G laser dye alcohol solution layer of rectangular and circular geometric form by the second harmonic of Nd:YAG (532 nm) laser is realized. A circular, plane-directed radiation from the edges of the excited layer with a small, vertical, divergence was obtained. Was investigated experimentally the spectral and spatial characteristics of radiation. The investigated layer is a part of the dye solution that is in direct

Nonlinear Thomson scattering from a tightly focused circularly polarized laser with varied initial phases

Within the frame of classical electrodynamics, nonlinear Thomson scattering by an electron of a tightly focused circularly polarized laser has been investigated. The electron motion and spatial radiation characteristics are studied numerically when the electron is initially stationary. The numerical analysis shows that the direction of the maximum radiation power is in linear with the initial phase of the laser pulse. Furthermore, we generalize the rule to the case of arbitrary beam waist, peak amplitude and pulse width. Then the radiation distribution is studied when the electron propagates in the opposite sense with respect to the laser pulse and the linear relationship still holds true. Last we pointed out the limitation of the single electron model in this paper.

Spatial Characteristics of Radiation Initiated by a Discharge over the Ferrite Surface

Spatial Characteristics of Radiation Initiated by a Discharge over the Ferrite Surface

Spatial radiation features of circularly polarized tightly focused laser beams colliding with electrons

In the framework of laser-matter interaction and nonlinear Thomson scattering, we investigate the three-dimensional (3D) motion trajectories and spatial radiation characteristics of the colliding motion electrons with tightly focused circularly polarized Gaussian pulses at different intensities. Combined with the 3D spatial images and the analysis of specific two-dimensional unfolded images, we discover that the amplitude of the motion trajectory increases steadily with increasing laser intensity, the peak radiation power increases rapidly, and the peak radiation azimuth decreases slowly. In addition, by studying the electron motion under the high-intensity () laser field, we find that the electron motion is retrograde twice when interacting with pulsed laser once. Lastly, by extracting the direction and energy of spatial radiation, we indicate that the existence of a specific laser intensity can make the peak radiation azimuth and which intienity provides the maximum conversion rate of laser energy to the peak power of radiation.

Acoustic spatial radiation characteristics of a violin made of Japanese cedar wood produced in Nara Prefecture

Acoustic spatial radiation characteristics of a violin made of Japanese cedar wood produced in Nara Prefecture

Spectral and Spatial Features of Radiation Emitted by a Cholesteric Liquid-Crystal Laser

Spectral and spatial characteristics of radiation emitted by a laser operating on the Bragg structure arising in cholesteric liquid crystals (CLCs) have been studied, as well as their variations with a change of the planar CLC orientation. A defect in the helical structure of the CLC formed by a ternary mixture of cholesterol viscous esters is revealed at the mutually orthogonal orientations of the CLC director at the substrates. This defect manifests itself as a local dip in the selective reflection band, which agrees with the behavior of the defect mode in the photonic crystal. Such a defect in the helical structure stimulates the selection of longitudinal modes with the indices N = ±1, so that the single-mode lasing regime is realized. A spatial ring structure in the laser radiation is found to arise, when higher longitudinal modes are generated.

Spatial, temporal and spectral emission characteristics from electron oscillation driven by an intense circularly polarized few-cycle laser pulse

The spatial, temporal and spectral emission characteristics of radiation generated from electron oscillations driven by an intense circularly polarized few-cycle laser pulse have been investigated theoretically and numerically using a single electron model. For a femtosecond driving laser pulse with duration of one optical cycle, the maximal radiation emitted by the electron comprises only one electromagnetic pulse having durations much shorter than the optical cycle and belonging to the attosecond range. It is discovered that the influence of the initial phase on the process of full spatial characteristics of the radiation is apparent for intense few-cycle laser pulse. The characteristics can be used to measure the initial phase of intense circularly polarized few-cycle laser pulse in experiments.

Relativistic motion and spatial characteristics of radiation from an electron driven by an intense few-cycle laser pulse

Relativistic motion and full spatial characteristics of radiation from an electron driven by an intense few-cycle laser pulse have been investigated theoretically and numerically with a single electron model. It is discovered that the influence of the initial phase on the process of relativistic motion and spatial characteristics of the radiation is apparent for intense few-cycle laser pulse. The characteristics can be used to measure the initial phase of intense few-cycle laser pulse in experiment.

Spatial characteristics of radiation from lightning discharges

The results of measurements of levels of electric and magnetic radiation fields from lightning discharges are presented. Lightning discharges occurred in the region of the terrestrial surface bounded by a sector of ∼90° with a radius of ∼30–300 km. A power spatial dependence of the electromagnetic radiation field components of lightning discharges is established. The results of measurements are interpreted using fractal geometry methods.

Experimental study of electromagnetic radiation from a faster-than-light vacuum macroscopic source

The effect which manifests itself in the form of directed electromagnetic pulses (EMP) initiated by an X-ray incident obliquely upon a conducting surface has been confirmed and investigated experimentally in detail. A planar accelerating diode comprising a metallic cathode and grid anode was initiated with an oblique short soft-X-ray pulse from a point laser-plasma source. Then a source of directed EMP—a current of accelerated photoelectrons—was formed whose boundary ran along the anode external surface with a faster-than-light velocity. The plasma was formed when short-pulse ( ∼ 0.3 ns ) laser radiation from ISKRA-5 facility was focused on a plane Au target. The amplitude-in-time and spatial characteristics of radiation emitted by the faster-than-light source have been measured. Parameters of the accelerated electron current have been measured too.

Temporal and Spatial Characteristics of Radiation from Large Scale Pool Fires

Temporal and Spatial Characteristics of Radiation from Large Scale Pool Fires

High Luminance Lasers for Atmospheric Sounding

Consider the applicability of a traveling wave amplifier for enhancing power parameters of radiation, while retaining the stability and spectral line width of the source. That should allow increasing the radiation efficiency of a cavity lidar. The advantage of a traveling wave amplifier is its ability to leave the spectral and spatial characteristics of radiation practically unchanged, in contrast to other types of amplifiers. The paper presents results of experimental investigations of the source - amplifier system for various lengths of the amplifier.

Influence of Ar on the emission characteristics of an electron-beam-controlled CO2laser

An investigation was made of the influence of Ar on the energy, temporal, and spatial characteristics of radiation from a pulsed atmospheric-pressure electron-beam-controlled CO2 laser pumped by pulses of 15–30 μs duration. Complete replacement of helium with argon in a CO2–N2–He active mixture resulted in a considerable reduction in the output energy because of the low rate of filling the lower active level. When He was partially replaced with Ar, a typical output energy from a CO2:N2:He = 1:2:3 mixture could be obtained at a lower electron-beam current density or electric field strength. Argon caused degradation in the radiation divergence.

Spatial characteristics of a beam and quality of phase conjugation of radiation from a CO2laser with InAs in its resonator

An investigation was made of the spatial characteristics of radiation from a CO2 laser with InAs in a stable resonator. Inhomogeneities of the spatial distribution of the radiation intensity observed in the near-field zone were due to diffraction of the radiation by the smallest aperture inside the resonator because of formation of a nonlinear diverging lens in InAs. The beam emerging from the laser had the properties of a converging wave. In spite of the characteristics of the spatial distribution of the laser radiation, the system with InAs inside the resonator ensured a nearly 100% phase conjugation, i.e., the fronts of the waves counterpropagating in the resonator were conjugate.

Investigation of spatial characteristics of radiation emitted by an electron-beam-controlled CO2laser with intracavity apodization

A study was made of the influence of smoothing of the edge of an exit mirror in an unstable resonator on the dynamics of the spatial structure of the radiation emitted by an electron-beam-controlled CO2 laser. Numerical methods and experiments demonstrated that the self-interaction effects in the active medium of this laser were reduced by amplitude smoothing of the unstable resonator mirrors. Even when traditional working mixtures were used, the level of light-induced inhomogeneities in the active medium (and the divergence of the output radiation governed by these inhomogeneities) decreased strongly when teeth were formed along the perimeter of a metal exit window in the unstable resonator.