Difference-frequency System Research Articles

Выбор рациональных параметров вибрационной очистки поверхностей просеивания при классификации материалов

В работе приводится динамическая схема вибрационной очистки поверхностей просеивания при классификации сыпучего материала. На основе анализа динамических свойств системы вибрационной очистки разработана методика и программа расчета рациональных параметров прерывистого силового возмущения. Исследованы коэффициенты динамичности системы для различных областей частот колебаний вибровозбудителя: низких и резонансных частот, высоких частот

ChemInform Abstract: Measurements and Calculations of Oscillations and Phase Relations in the Driven Gas-Phase Combustion of Acetaldehyde

Oscillations in light emission and species concentrations, are measured as periodic perturbations are simultaneously applied to the input rates of acetaldehyde and oxygen in the gas‐phase combustion of acetaldehyde in a continuous‐flow stirred tank reactor for conditions where the autonomous reaction itself is oscillatory. The experimental results are compared with the predictions of a five‐variable thermokinetic model. We measure periodic responses in the fundamental entrainment band (ratio of frequency of perturbation to frequency of response equal to unity) for four different values of phase shift between the acetaldehyde and oxygen perturbation wave forms as we vary the frequency and amplitude of the external periodic perturbations. Outside of the entrainment bands we find quasiperiodic response. We determine the phases of the light emission and six species concentrations, as measured with a mass spectrometer, with respect to the periodic perturbation, the variation of these phases across the fundamental entrainment band for different values of reactant phase shift and for different amplitudes of perturbation, and the effects of the phase shift between the two input perturbations on the light emission response of the system for different frequencies of perturbation. Both the experiments and calculations predict a widening of the entrainment band with an increase in perturbation amplitude, and the same variation in bandwidths for the four values of reactant phase shift studied. The experiments and calculations also predict the same general trends in light phase and species phases (difference between the light emission and species concentrations with respect to the perturbing wave form) as the band is traversed for different amplitudes of perturbation and for different values of reactant phase shift. Some discrepancies in the species phases exist; however, the similarities which exist between the experiments and the calculations provide further substantiation for the model. We find that changing the phase shift between reactant inflows from 0° to 360° produces a sharp change in light phase near 180°, in both the experiments and calculations. In general, we also find that the light emission remains entrained near the total flux minimum of the perturbing wave form, and we attribute this correlation to the net heat loss which arises from the reactant flux through the reactor.

NON-LINEAR RESPONSE OF TORSIONALLY COUPLED BASE ISOLATED STRUCTURE TO HARMONIC EXCITATION

Effect of base isolation on the response of torsionally coupled system under harmonic base excitation is investigated with the help of a 3-D idealized model of building. The base isolator of the building allows translational as well as rotational displacements at the base level of the building model. The hysteretic force deformation characteristics of the bearing are modeled by coupled non-linear differential equations. The responses of the base isolated system are compared with that of the fixed base system in order to study the effectiveness of base isolation. The investigation showa (i) the response of base isolated system for different frequencies of base excitation with respect to fixed base frequencies of the system, (ii) the difference in the response obtained by considering and ignoring the interaction between the restoring forces of the elastomeric bearings and (iii) the effect of torsional coupling on the effectiveness of base isolation.

Measurements and calculations of oscillations and phase relations in the driven gas-phase combustion of acetaldehyde

Oscillations in light emission and species concentrations, are measured as periodic perturbations are simultaneously applied to the input rates of acetaldehyde and oxygen in the gas-phase combustion of acetaldehyde in a continuous-flow stirred tank reactor for conditions where the autonomous reaction itself is oscillatory. The experimental results are compared with the predictions of a five-variable thermokinetic model. We measure periodic responses in the fundamental entrainment band (ratio of frequency of perturbation to frequency of response equal to unity) for four different values of phase shift between the acetaldehyde and oxygen perturbation wave forms as we vary the frequency and amplitude of the external periodic perturbations. Outside of the entrainment bands we find quasiperiodic response. We determine the phases of the light emission and six species concentrations, as measured with a mass spectrometer, with respect to the periodic perturbation, the variation of these phases across the fundamental entrainment band for different values of reactant phase shift and for different amplitudes of perturbation, and the effects of the phase shift between the two input perturbations on the light emission response of the system for different frequencies of perturbation. Both the experiments and calculations predict a widening of the entrainment band with an increase in perturbation amplitude, and the same variation in bandwidths for the four values of reactant phase shift studied. The experiments and calculations also predict the same general trends in light phase and species phases (difference between the light emission and species concentrations with respect to the perturbing wave form) as the band is traversed for different amplitudes of perturbation and for different values of reactant phase shift. Some discrepancies in the species phases exist; however, the similarities which exist between the experiments and the calculations provide further substantiation for the model. We find that changing the phase shift between reactant inflows from 0° to 360° produces a sharp change in light phase near 180°, in both the experiments and calculations. In general, we also find that the light emission remains entrained near the total flux minimum of the perturbing wave form, and we attribute this correlation to the net heat loss which arises from the reactant flux through the reactor.