Third Order Low Frequency Sinusoidal Oscillators Employing CFOAs and Grounded Capacitors

E×B guiding-centre (GC) motion in a special configuration of three low-frequency electrostatic waves can be considered as a paradigmatic Hamiltonian system for studying adiabatic motion and separatrix crossings. A peculiarity of this system is that a single initial condition gives rise to two stroboscopic phase-space trajectories. According to the classical Hamiltonian theory, the proportion of points on the stroboscopic trajectories is a function of the time evolution of the surfaces enclosed by the separatrices in the phase space. This behaviour is qualitatively observed in test-particle numerical experiments. The ability of numerical integration methods like the ‘classical’ fourth-order Runge–Kutta integration scheme or a third-order symplectic integrator to reproduce the statistics is analysed.

Download Full-text

Quadratic Electro-Optical Characterization of Molecular Nonlinear optical Materials

MRS Proceedings ◽

10.1557/proc-109-251 ◽

1987 ◽

Vol 109 ◽

Cited By ~ 2

Author(s):

John C. Luong ◽

N. F. Borrelli ◽

A. R. Olszeuski

Keyword(s):

Optical Materials ◽

Nonlinear Optical ◽

Second Harmonic ◽

Low Frequency ◽

Second Order ◽

Third Order ◽

Kerr Coefficient ◽

Molecular Compounds ◽

Order Susceptibility

ABSTRACTA convenient method of measuring the nonlinear optical properties of molecular compounds is described. The method involves measuring the quadratic electro-optical coefficient of a polymer composite containing a variable concentration of the candidate NLO material. The X(3) (ω) value obtained by this low-frequency Kerr measurement, after local-field corrections, can be compared to the nonresonant third-order susceptibility measured by degenerate-four-wave-mixing technique on selective samples. We find that the choice of the polymer matrix dictates the contribution of second-order susceptibility to the Kerr coefficient. Therefore, our method can also be extended to the measurement of second-order susceptibility, analogous to the technique of field-induced second-harmonic-generation.

Download Full-text

Realization of SIMO biquad filters and quadrature sinusoidal oscillators using OTRAs

Journal of Engineering Research ◽

10.36909/jer.icari.15277 ◽

2021 ◽

Author(s):

Garima Garima ◽

◽

Pragati Kumar ◽

Data Ram Bhaskar ◽

◽

...

Keyword(s):

Quality Factor ◽

Experimental Validation ◽

Low Frequency ◽

Spice Simulation ◽

Sinusoidal Oscillators ◽

Input Multiple Output ◽

Condition Of Oscillation ◽

Single Input ◽

Simulation Results ◽

Quality Factor Q

In this communication, two single-input multiple-output (SIMO) type biquad filters employing operational transresistance amplifiers (OTRAs) have been presented. Various parameters of the proposed filter circuits viz. pole frequency (ɷ), pole quality factor (Q) and the gain are independently controllable. The proposed filter configurations can also be converted into low frequency oscillators with fully uncoupled control of condition of oscillation and frequency of oscillation with quadrature output voltages. The active and passive sensitivities of the proposed circuits have been found to be small. SPICE simulation results and experimental validation of the proposed circuits employing OTRAs realized with AD844 type CFOAs have also been presented.

Download Full-text

The Investigation of Temperature Effect on Dynamic Characteristics of Rubber Isolator

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.138-139.575 ◽

2011 ◽

Vol 138-139 ◽

pp. 575-580

Author(s):

De Bao Han

Keyword(s):

Interpolation Method ◽

Dynamic Properties ◽

Low Frequency ◽

Model Parameters ◽

Force Model ◽

Third Order ◽

Restoring Force ◽

First Order ◽

The Third ◽

Rubber Isolator

This article focuses on the temperature dependent dynamic properties of rubber isolator. First, a set of experimental device was designed to conduct the experimental investigation. Then, a polynomial model of hysteretic used as an isolator restoring force model was proposed and the model parameters were identified using the displacement-restoring force loop from experiment by the optimal least-squares arithmetic. Finally, the Hermite interpolation method was utilized to add the number of identified parameters, such that curvatures that represent the first order stiffness, the third order stiffness and damping varied with frequency, amplitude under different temperature were obtained. The analysis results indicated that the first order stiffness varies weakly with the temperature increasing, and there is an area of the first order stiffness varied drastically. The third order stiffness have a strong nonlinear area within the low frequency and little amplitude, the third order stiffness magnitude increases with the temperature increasing firstly, then decreases while the temperature over 50°C. There is a sensitive area as the amplitude less than 1.5mm, the damping decreases rapidly with the augmenting of vibration amplitude, and the rate of decreasing is less gradually with the temperature rising.

Download Full-text

New technique for detection of changes in QRS morphology of ECG signals

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1983.244.4.h560 ◽

1983 ◽

Vol 244 (4) ◽

pp. H560-H566

Author(s):

S. L. Blumlein ◽

G. Harvey ◽

V. K. Murthy ◽

L. J. Haywood

Keyword(s):

Low Frequency ◽

New Technique ◽

Frequency Noise ◽

Third Order ◽

Ecg Signals ◽

Qrs Morphology ◽

Ectopic Beats ◽

The Difference ◽

A New Technique ◽

Electrocardiogram Ecg

With the use of the electrocardiogram (ECG) as a prototype signal, a new technique was devised for detecting signals embedded in noise. Averaged "normal" digitized ECG signals formed a template to which subsequent ECG QRS complexes were compared. The difference between the averaged template signals and subsequent normal beats was white noise, whereas the difference between the template and ectopic beats consisted of nonrandom signal variation. The template to new signal comparison for the zero-, first-, second-, and third-order differences utilized an approximate F test. Accurate detection of abnormal signals associated with high- and low-frequency noise is accomplished with this method, and the practical clinical utility of the method is under study.

Download Full-text

The effect of the ionosphere on ultra-low-frequency radio-interferometric observations

Astronomy and Astrophysics ◽

10.1051/0004-6361/201833012 ◽

2018 ◽

Vol 615 ◽

pp. A179 ◽

Cited By ~ 17

Author(s):

F. de Gasperin ◽

M. Mevius ◽

D. A. Rafferty ◽

H. T. Intema ◽

R. A. Fallows

Keyword(s):

Signal To Noise Ratio ◽

Low Frequency ◽

Systematic Errors ◽

Electron Content ◽

Satellite Measurements ◽

Third Order ◽

Low Frequencies ◽

Total Electron ◽

Main Driver ◽

Systematic Effects

Context. The ionosphere is the main driver of a series of systematic effects that limit our ability to explore the low-frequency (<1 GHz) sky with radio interferometers. Its effects become increasingly important towards lower frequencies and are particularly hard to calibrate in the low signal-to-noise ratio (S/N) regime in which low-frequency telescopes operate. Aims. In this paper we characterise and quantify the effect of ionospheric-induced systematic errors on astronomical interferometric radio observations at ultra-low frequencies (<100 MHz). We also provide guidelines for observations and data reduction at these frequencies with the LOw Frequency ARray (LOFAR) and future instruments such as the Square Kilometre Array (SKA). Methods. We derive the expected systematic error induced by the ionosphere. We compare our predictions with data from the Low Band Antenna (LBA) system of LOFAR. Results. We show that we can isolate the ionospheric effect in LOFAR LBA data and that our results are compatible with satellite measurements, providing an independent way to measure the ionospheric total electron content (TEC). We show how the ionosphere also corrupts the correlated amplitudes through scintillations. We report values of the ionospheric structure function in line with the literature. Conclusions. The systematic errors on the phases of LOFAR LBA data can be accurately modelled as a sum of four effects (clock, ionosphere first, second, and third order). This greatly reduces the number of required calibration parameters, and therefore enables new efficient calibration strategies.

Download Full-text