Non-resonant Frequencies Research Articles

Frequency conversion involving Raman-like processes above the ionization threshold

Resonant and nonresonant frequency conversion probabilities for processes taking place above and below the ionization threshold in hydrogen are compared. The frequency of the emitted radiation is different from any characteristic frequencies of the medium and cannot be resonantly reabsorbed. It is shown how particular resonances can enhance emission processes while keeping unchanged the losses coming from lowest order ionization.

Electromagnetic acoustic transducer for in-plane and plane-normal velocity measurements

A new electromagnetic acoustic transducer (EMAT) is developed that measures velocities and absolute surface displacements in-plane and plane-normal to the direction of wave propagation. This transducer is flexible in shape and design to conform with irregular surfaces and has unique characteristics of nonresonant frequency response. Tests show that the sensitivity of this EMAT can be increased by increasing the applied magnetic field. Because this transducer is mode selective and nonresonent, its response can be related uniquely to the wave motion. This property is highly desirable for research purposes, though generally not wanted in field monitoring situations.

Enhanced production of tunable VUV radiation by phase-matched frequency tripling in krypton and xenon

Nonresonant frequency tripling of intense dye laser radiation in negative dispersive Kr ( \lambda = 1203-1235 A ) is efficiently enhanced by phase matching with the positive dispersive tare gas Ar or Xe. Phase matching of Kr with Ar improved the efficiency of the conversion of 3648 A to L_{\alpha} = 1216 A by more than two orders of magnitude. At L_{\alpha}, 16 W ( 4 \cdot 10^{10} photons/pulse) could be generated with 1.5 MW pulses of a frequency doubled dye laser. The optimum conversion is limited by absorption of the VUV in the rare gas mixture and by dielectric breakdown. In mixtures of Kr and Xe, the dependence of the VUV on the density of the two gas components indicates a phase difference between their contributions to the induced third-order polarization. Measurements of the VUV output of different Kr-Xe mixtures provide a determination of the ratio of the third-order nonlinear susceptibilities χ Kr /χ Xe and of the wave vector mismatches per atom C Kr /C Xe at wavelengths \lambda = 1205-1230 A Besides frequency tripling in Kr, third-harmonic generation of blue dye laser light ( \lambda = 4208-4406 A) has been investigated in Xe phase matched with Kr. The peak power of the tunable VUV at \lambda = 1403-1469 A exceeded 30 W ( 8.7 \cdot 10^{10} photons/pulse).

Conversion from 3371 to 1124 Å by nonresonant optical frequency tripling in compressed krypton gas

The 1-MW 3-nsec output from a commercial nitrogen laser has been frequency tripled in krypton to generate vacuum-ultraviolet 1124-A radiation. Conversion efficiencies of up to 10(-6) and optimum krypton gas pressures as high as 4-5 atm were found. Preliminary experiments using a para-terphenyl dye laser have yielded tunable radiation in the 1116-1165-A region.

Nonlinear and parametric effects in atomic rf spectroscopy

Nonlinear phenomena occurring during interaction between an atom and a strong rf of resonant or nonresonant frequency are reviewed. The account is given in both semiclassical and consistently quantummechanical languages. The concept of an atom dressed by the radiation field in which not only the optical-frequency but also the radio-frequency is quantized is presented in detail. The results are summarized of theoretical and experimental studies of multiphoton transitions, radiative shifts of normal magnetic resonance lines, parametric resonance, and coherent resonances under the conditions of optical pumping. The influence of nonresonance rf fields on magnetic properties and the rate of magnetic relaxation of atoms is discussed.

High-order mode coupler for millimetre wavelengths

A new type of injection filter has been developed that can be used for local-oscillator injection in millimetre-wave mixers and other narrowband diplexing applications. The insertion loss for nonresonance frequencies is typically less than 0.25 dB. For the selected resonant modes, the coupler acts as a 3 dB power divider. Insertion losses of 1.5 dB or less can be reached at these frequencies.

Resonance effects in stepping motors

The mechanism of resonance-induced maloperation of stepping motors is studied, and a simple analytical method is presented enabling resonance frequency bands, and the damping factors necessary to suppress resonance, to be predicted. Emphasis is placed on the determination of the equivalent linearised torque/displacement characteristic for practical use. Experimental results for the bands of resonance-induced maloperation of a 3-stack stator, variablereluctance type of motor confirm the approach. The occurrence of reverse running in a highly stable, double-speed mode at certain, nonresonant frequencies is reported and briefly commented on.

Strong-Field Electromagnetic Wave Interaction with Anisotropic Plasmas

Investigations of strong-field electromagnetic wave interactions with plasmas have been conducted. In the nonresonant frequency regions, the electron velocity distribution function is Maxwellian and considerations based on Maxwellian theory agree with experiment. At resonant and near-resonant frequencies considerations based on an electron velocity distribution which is non-Maxwellian explain the observations if enhanced electron diffusion is absent. However, at near-resonant frequencies, enhanced electron diffusion due to strong fields can be of great significance in reducing the electron density.

Periodic solutions of quasi-linear systems with several degrees of freedom in presence of arbitrary frequencies: PMM vol.36, n≗2, 1972. pp. 349–357

Methods of constructing periodic solutions of quasi-linear(autonomous or non-autonomous) systems of second order equations, based on the Poicare method, are given in a condensed form. A general case of simple or multiple frequencies of the generating system in the presence of critical (resonant).null and noncritical (nonresonant) frequencies is considered. It is assumed that the amplitude equaions have only simple solutions. Two methods of obtaining the coefficients of expansions of the required functions into series in terms of a small parameter are given for the autonomous systems. Unlike the book by Malkin [1] in which the author considers the systems of first order equations and having obtained the fundamental amplitudes constructs the solutions by successive integration of the equations, the present paper gives for each case a ready formula for computing several approximations.

Wave-Particle Energy Transfer and Wave-Amplitude Limiting Effects for a Flutelike High-Frequency Mode

The change of energy and phase of a particle gyrating in a homogeneous magnetic field and a perpendicularly propagating electrostatic wave is calculated analytically for resonant and nonresonant frequencies in the regime where the wavelength 2πk⊥−1 is of the order of the gyroradius a. This new result provides a quantitative basis for a simple wave-particle interaction model and resolves certain discrepancies between previously obtained results and numerical calculations of the ranges of k⊥a for which instability is possible. The long-time behavior of the particle motion is discussed using a stroboscopic orbit theory. Significant modifications of the particle orbits by a single wave, which necessitate the use of a “strong turbulence” theory, are shown to occur if eδψ/KT⊥∼(2π)1/2(K⊥a)−1/2(ω−lΩ) /ω, where eδψ/KT⊥ is the ratio of wave potential energy to perpendicular particle kinetic energy and l is the harmonic number.

Scattering of Phonons by Bound Donor Electrons in Doped Germanium

In the present work the scattering of phonons by bound donor electrons is calculated for resonance and nonresonance frequencies using Kwok's approach, and the results are applied to explain the phonon conductivity of doped Ge.

Transient response of networks employed in protective relaying

Series and parallel combinations of resistance and inductance are investigated theoretically under maximum-transient conditions, to find alternative representations of the replica impedance employed in distance-protection applications for which the line current is converted to an equivalent voltage. When the primary-system-impedance angle exceeds the replica-impedance angle, the parallel configuration is shown to develop a significantly reduced transient component of the output voltage, and a lower transient flux is required in the core of the energising current transformer. The parallel-tuned-filter circuit is employed in differential current-protection schemes to allow a reduction in the transient component of the relaying quantity derived via a current transformer. The circuit parameters are investigated with a view to minimising the transient-flux requirements of the current transformer and developing an output approaching proportionality with the a.c. component of the primary current. The treatment includes energisation at nonresonant frequencies.

Investigation of the Vibrational Properties of a J9 Transducer in Water by an Optical Interferometric Technique

The magnitude and phase of the mechanical and radiation impedance of a USRL J9 transducer at nonresonant frequencies have been directly measured under free-field conditions by an optical interferometric technique. The requisite facility and technique (measurement of vibrational amplitude as a function of drive current) are described. The mode shape of the transducer in air and in water is also shown. [Work supported by Code 468 of the Office of Naval Research, U. S. Navy.]

Evaporative water loss in birds—II. A modified method for determination by direct weighing

1. 1. A direct weighing method of determining avian evaporative water loss under conditions of controlled temperature and humidity was developed. 2. 2. Ambient water vapor pressure and evaporative water loss are inversely related in Excalfactoria chinensis at 32,25 and 15°C. 3. 3. Evaporative water loss at a given temperature in E. chinesis is proportional to the water lossa vapor pressure gradient between the environment and evaporative surfaces. 4. 4. Maximum rates of gular flutter in a variety of species are roughly inversely related to the size of the gular area. 5. 5. Panting and gular fluttering may occur at rates determined by the resonant characteristics of thoratic cavity and gular region, respectively, or at apparent nonresonant frequencies.

О ДВИЖЕНИИ ЧАСТИЦ В НЕРЕЗОНАНСНЫХ В. Ч. И МАГНИТОСТАТИЧЕСКИХ ПОЛЯХ

The smoothed motion of a particle along the lines of force of a magnetic field in the presence of a high-frequency field is analyzed. Small gradients of all the fields and non-resonant frequency of the h.f. field are assumed. A certain conservativeness of motion is derived which permits further development of the kinetic theory. A qualitative evaluation of the possibility of trapping a rapid cluster of plasma by means of a h.f. field is made.

Die exakte Bestimmung der Elektronendichteverteilung in einem endlichen, anisotropen Plasma

AbstractIf a microwave cavity containing an anisotropic, inhomogeneous plasma is excited with a nonresonant frequency ω, the electron density distribution inside the plasma can be obtained from a knowledge of the tangential electrical field on a surface enclosing the plasma. The main step is the derivation of an integralequation relating the tangential field to the highfrequency plasma current. An experimental setup is discussed. The obtainable precision is limited by the noise like density fluctuations in the plasma itself and is about 1% for \documentclass{article}\pagestyle{empty}\begin{document}$\frac{{\delta N}}{{\bar N}}$\end{document} for a spatial resolution in the same order of magnitude.

On the motion of a satellite about its center of mass under the action of gravitational moments

We investigate analytically and numerically the variation of the obliquity (the axial tilt) of a hypothetical exo-Earth. A large number of exoplanets was discovered recently; since not much information is available about the masses and orbits of the stars and planets comprising a planetary exo-system, unlike for the planets of the Solar system, the problem is considered in a general setup. The exo-Earth is assumed to be rigid, axially symmetric and almost spherical, the difference between the largest and the smallest principal moments of inertia being a small parameter of the problem. Assuming the orbits of the celestial bodies to be quasiperiodic, we apply time averaging to study rotation of the exo-Earth at times large compared to the respective periods. In the present paper, we consider the case of non-resonant frequencies; we intend to study resonances in the future. In addition, we investigate numerically how the range of obliquity of the exo-Earth in a particular system comprised of a star and two planets varies on modifying the geometry of the orbits, the mass of the second planet and the initial obliquity.

The effect of acoustic vibration on forced convective heat transfer

AbstractIn an effort to study the effect of acoustic vibration on forced convective heat transfer, sound at resonant frequencies of 198, 256, and 322 c./sec., as well as sound at nonresonant frequencies, was imposed on air flowing at Reynolds numbers of 560 to 5,900 in the core of a horizontal, double pipe, steam to air, heat exchanger. Increases in Nusselt number of up to 51% in the nominally laminar region and up to 27% in the nominally turbulent region were obtained. The improvement peaked sharply at resonance and increased with both amplitude and resonant frequency. A qualitative dual mechanism is suggested, and correlations for the experimental results are presented.

Resonance Transitions Induced by Perturbations at Two or More Different Frequencies

Resonance transition probabilities for a system in the presence of oscillatory perturbations at two or more different frequencies are discussed. It is shown that if resonance transitions are induced by a perturbation at one frequency, then the presence of the other perturbations at nonresonant frequencies alters the resonance frequency for the first perturbation. Theoretical expressions for the alteration of the resonance frequency are derived. Various applications of the derived formulas are discussed, including resonance experiments with more than one oscillatory field, molecular beam experiments in a nonuniform constant field, evaluation of "collision-narrowing" effects in nuclear paramagnetic resonance, etc. The effects of the extraneous oscillatory perturbations are shown to be especially important if their frequencies are close to Bohr frequencies for the perturbation.

X.Additional experiments on moving-coil reproducers and on flexible disks

Abstract In this paper various details of moving-coil reproducers are discussed. The modulus of elasticity of paper is determined and used to compare the stiffness of conical sheets and disks of the same radius. A series of experiments is outlined, showing the influence of reinforcing certain portions of the diaphragm. The combination modes of a reed-driven paper disk are treated, and by comparison with theory, heterogeneity of the paper is disclosed. The exact solution of a lossless reed-driven disk vibrating in vacuo is given, due allowance being made for variation in the apparent mass of the reed itself. The case of a coil-driven circular aluminium disk is examined experimentally, and the frequency band occupied by the first symmetrical mode is shown to be only 5 cycles. With constant current in the coil, the output at resonance is some 2000 times greater than at non-resonant frequencies. The influence of the magnetic field upon the output and upon the coil impedance of a reproducer is analysed. The output criterion of the magnet is stipulated in terms of total gap area, air-gap flux density, and the coil space factor. It is shown that the oscillation of a coil driven by an alternating current in a non-uniform magnetic field is accompanied by a motion of translation. This is akin to the process of rectification.