Amplitude response of Fabry-Perot frequency discriminators

The amplitude noise responses of optical-frequency-discriminating systems, based on Fabry-Perot cavities with intensity noise compensation, are analyzed considering also the effect of the resonator transient. From the point of view of amplitude noise immunity, systems based on transmission or reflection alone behave in a quite similar way within the discriminator bandwidth, whereas a proper combination of both these signals not only increases the sensitivity to frequency noise but also allows for higher rejection to amplitude noise.     

Linear frequency tuning of SAW resonators

Frequency tuning in SAW (surface acoustic wave) resonator-stabilized oscillators is normally accomplished via utilization of a voltage-controlled phase shifter. The design of abrupt junction varactor diode-inductor networks which employ impedance transformation techniques to obtain linear frequency tuning of two-port SAW resonators is reported. The approach is similar to that previously developed for linear tuning of bulk wave, quartz crystal resonators. This technique uses varactor diode parallel inductance to provide a linear reactance versus voltage network, which is effectively connected in series with the resonator motional impedance in order to tune the effective resonator center frequency. Typical tuning ranges are significantly larger than those achievable using the phase shifter approach, and are on the order of 400 ppm for the 320-MHz resonator used.     

Synthesis and bulk acoustic wave properties on the dual mode frequency shift of solidly mounted resonators

This study focused on the fabrication and the theoretical analysis of solidly mounted resonators (SMR) concerning dual-mode frequency responses and their frequency shift of bulk acoustic wave (BAW) resonance. For this device fabrication, RF/DC magnetron sputtering and photolithography were employed to constitute the required multilayer structure. For the theoretical analysis, the dualmode frequency shift was characterized by the Sauerbrey's formula, and a modified formula was carried out following the trend for the large frequency shift. In the fabrication of the SMR device, Mo/SiO2 was chosen to construct the Bragg reflector as the high/low acoustic impedance materials, respectively, and aluminum nitride (AlN) was used as a piezoelectric layer. To investigate the characteristics of BAW on the dual-mode frequency shift, the c-axis tilted angle of AlN was altered as well as the various mass loading on the SMR. Based on the experimental results, the dual-resonance frequencies showed a nonlinear decreasing trend with a linear increase of the mass loading. Therefore, a modified formula was carried out. Furthermore, the ratio of the longitudinal-resonant frequency to the shear-resonant frequency remained at a range around 1.76 despite the various c-axis tilted angles of AlN and gradual mass loading on the SMR. The electromechanical coupling coefficient, k2(eff), of the shear resonance rose with the increase of the c-axis tilted angle of AlN.     

Calculation of the characteristics of countercurrent axisymmetric jets

On the basis of analysis and generalization of experimental data, a method is proposed for calculating the parameters of the interaction of two coaxial jets flowing in opposite directions from circular nozzles of different diameters.Notation d, D diameter of the nozzles for the small- and large-diameter jets - density - x, y coordinates - u, U averaged longitudinal component of velocity of the small- and large-diameter jets - L_ax distance between nozzles - q relative impulse - G mass rate of the medium - 2r width of the jet - _i, L_i lengths of the flow zones of the small- and large-diameter jets, where i=1, 2 - range of the jet - 2B distance between corresponding points of lines of maximum velocity of the large-diameter jet Indices 0 initial state - m maximum value - ax value on the axis - d large-diameter jet - y_0.5 distance from the axis to the point at which the velocity is equal to half the velocity on the axis Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 56, No. 5, pp. 725–729, May, 1989.     

Calculation of a two-phase flow in an axisymmetric nozzle

A system of differential equations is presented to describe a two-phase flow through an axisymmetric supersonic nozzle. The results for the solution of this system on a Minsk-14 computer are given. The theoretical results are compared qualitatively with the experimental data.     

Mg2Ni系储氢合金的制备及其性能研究

采用感应熔炼法制备出两种镁基储氢合金,即Mg2Ni和Mg2Ni0.9Zr0.1;对两种合金进行扩散退火处理,并对退火处理前后的金相显微组织进行了比较研究;最后对这两种合金进行了X射线衍射实验和吸放氢性能测试实验.研究结果表明该方法制备出的镁基储氢合金活化性能优良;扩散退火能显著改善镁基储氢合金的显微组织和储氢性能.     

Design and properties of STW asynchronous resonators on quartz

In a surface transverse wave (STW) asynchronous resonator, grating phase shifters are placed between interdigital transducers and reflectors to obtain the incident and reflected waves in phase, and the resonance frequency is located near the center frequency of the reflectors. In this paper, the scattering matrix method is used for design of such resonators with one dominant longitudinal mode. At a frequency of about 509.5 MHz, insertion loss, and loaded and unloaded quality factors of about 6 dB, 5,300 and 11,000, respectively, were obtained. The measured and calculated parameters of this resonator are in good agreement. Design guidelines and comparison of synchronous and asynchronous resonators are presented. Compared to synchronous resonators, low spurious signals' level, location of the resonance frequency near the center frequency of the reflectors, and simple design method make the asynchronous resonators more attractive for manufacture and practical applications.     

Calculation of a turbulent monodisperse flow in an axisymmetric channel

A stationary isothermal model of the aerodynamics of a two-phase flow in an axisymmetric channel has been constructed with allowance for the turbulent and pseudoturbulent mechanisms underlying the transfer of the solid phase momentum. The equations of dispersed phase motion are closed at the level of the equations for the second moments of the pulsation velocities of particles, whereas the equation of momentum transfer of the carrier is closed on the basis of a one-parameter model of turbulence extended to the case of two-phase turbulent flows. The results of calculations are compared with experimental data. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 5, pp. 844–855, September–October, 2008.     

Scattering analysis of two-port SAW resonators

Linear equations derived from the scattering matrix approach to the two-port resonator were solved, and analytical expressions for the normalized SAW amplitudes were obtained. Asynchronous and synchronous resonators were analyzed numerically. It was shown that the output of the two-port resonator is a sum of two signals. In the case of the asynchronous resonator, these signals are in phase at a resonance frequency; for the synchronous resonator, they are in phase quadrature, which causes the higher insertion loss of the synchronous resonator     

Non-linear dynamic analysis of axisymmetric shells

Incremental equations of motion are derived from a Lagrangian variational formulation for the large displacement elastic-plastic and elastic-viscoplastic dynamic analysis of deformable bodies. The material constitutive behaviour is described in terms of the symmetric Piola–Kirchhoff stress and Lagrangian strain tensors. Degenerate isoparametric elements, permitting relaxation of the Kirchhoff–Love hypothesis, are used in a finite element formulation specialized for the analysis of shells of revolution subjected to axisymmetric loading. The linearized incremental equations of motion are solved using direct integration procedures, with added accuracy obtained from application of equilibrium correction at each step. The effectiveness of the numerical techniques is illustrated by the dynamic response analyses carried out on a shallow spherical cap subjected to uniform external step pressure loadings.     

Waveguide coupling of SAW resonators with different properties

In contrast to conventional transversely coupled resonator filters, waveguide coupling of two one-port resonators with different resonance frequencies is described. The different resonance frequencies are implemented by different central finger gaps or gratings differing by a scaling factor. Consequently, the equivalent fingers and reflecting strips of different resonators are shifted with respect to each other, and the waveguide modes are, therefore, no longer independent of each other. This effect is called mutual coupling of waveguide modes and requires a new type of modeling. The main characteristics of the new modeling method are described. The advantage of the design principle consists of a wider bandwidth without changing the waveguide parameters and different input and output impedance.     

Automatic frequency tuning circuits of passive hydrogen frequency standards

Translated from Izmeritel'naya Tekhnika, No. 7, pp. 27–28, July, 1991.     

Sensitivity analysis and shape optimization of axisymmetric structures

An efficient method is developed for sensitivity analysis in shape optimization of axisymmetric structures. The technique of isoparametric mapping is used to generate the finite element mesh from a small set of master elements and master nodes. Co-ordinates of selected master nodes are used as design variables. Shape function values of master elements at derived finite element nodes obtained during the isoparametric mapping process are utilized to calculate the gradients of weight and response of the structures with respect to the design variables. Analytic formulations of the gradients are developed for sensitivity analysis of axisymmetric structures. An optimization procedure using a sequential linear programming method is applied to effectively utilize the calculated gradients. Numerical examples of optimum design of disks subject to thermo-mechanical loadings are presented.     

Deconvolution of axisymmetric flame properties using Tikhonov regularization

We present a method based on Tikhonov regularization for solving one-dimensional inverse tomography problems that arise in combustion applications. In this technique, Tikhonov regularization transforms the ill-conditioned set of equations generated by onion-peeling deconvolution into a well-conditioned set that is less susceptible to measurement errors that arise in experimental settings. The performance of this method is compared to that of onion-peeling and Abel three-point deconvolution by solving for a known field variable distribution from projected data contaminated with an artificially generated error. The results show that Tikhonov deconvolution provides a more accurate field distribution than onion-peeling and Abel three-point deconvolution and is more stable than the other two methods as the distance between projected data points decreases.