Values Of Coupling Factor Research Articles

Synthesis, characterization and studies on nonlinear optical parameters of 4-amino-5-(4-nitrophenyl)-1, 2, 4-triazole-3-thione

In this paper, we report the synthesis, characterization and third order nonlinear optical properties of a new organic NLO material of 4-amino-5-(4-nitrophenyl)-1, 2, 4-triazole-3-thione (ANIT). The material was characterized by UV–vis and FTIR studies. The third order nonlinear optical properties have been investigated in dimethyl formamide (DMF) solution at 532 nm by using the Z-scan technique with pulses of nanoseconds duration. Open aperture data demonstrates the presence of two photon absorption at this wavelength. The nonlinear absorption coefficient β, the nonlinear refractive index n2, the magnitude of effective third order susceptibility χ(3) and the second order hyperpolarizability γh have been estimated as 2.99 cm/GW, −2.53 × 10−11 esu, 2.72 × 10−13esu and 0.281 × 10−31esu respectively. The values obtained are comparable with the values obtained for 4-methoxy chalcone derivatives and dibenzylideneacetone derivatives. The value of coupling factor have been estimated to be 0.17, indicating that the nonlinearity is electronic in origin. The compound exhibits good optical limiting at 532 nm with the limiting threshold of 80 μJ/pulse. The comparatively high value obtained indicates that this material may be used in optical device applications like optical limiters and optical switches.

Influence of spinel substrate and over-layer for enhanced SAW and AO properties with KNbO3 thin film.

Surface acoustic wave (SAW) propagation characteristics have been studied using modeling calculations for a potassium niobate (KNbO3) thin film-layered structure with (001) and (110) orientation on a single crystal spinel (MgAl2O4) substrate, and a spinel buffer layer on silicon. Variation in the electromechanical coupling and acoustic attenuation has been compared. A significantly high value of coupling factor (k2max = 23%) is obtained for the (001)KNbO3/spinel structure by introducing an optimum thickness of spinel over-layer for potential wide bandwidth SAW device applications. The dispersion characteristics with the (110) KNbO3 orientation indicate an initial peak in the coupling coefficient value (k2max = 8.8%) at a relatively low KNbO3 film thickness that appears attractive for fabricating devices with thinner films. The KNbO3 film with (001) orientation is found attractive for efficient acousto-optic (AO) device application with the formation of a symmetric waveguide structure (spinel(0.5 microm)/KNbO3(1.0 microm)/spinel). A high value of k2 = 23.5% with 50% diffraction efficiency has been obtained for the spinel(0.5 microm)/KNbO3(1.0 microm)/spinel structure at 1 GHz SAW frequency and 633 nm optical wavelength at a very low input drive power of 15.4 mW.

Processing and Characterization of Piezoelectric Thick Films Screen-Printed on Silicon and Glass-Ceramic Substrates

Lead titanate modified with calcium (PT) and Pb(Zr 0.52 Ti 0.48 )O 3 (PZT) thick films (in the range 30-100 w m) have been screen-printed on various substrates: alumina, silicon, glass-ceramic and stainless steel. Different sintering aids including Li 2 CO 3 --Bi 2 O 3 --CuO and PbO--GeO 2 --SiO 2 have been tested on thick films and corresponding bulk ceramics. PT films on glass-ceramic and stainless steel substrates, previously electroded with Ag--Pd, have good properties close to the properties of the bulk ceramics: permittivity of 100-160 and d 33 of 40-55 pC/N values have been obtained. PZT films on Pt/Ti/SiO 2 /Si substrates having dielectric permittivity of 500 and piezoelectric constant d 33 of 150 pC/N with a high coupling factor value have been obtained with a good repeatability. The influence of different electrodes on the film properties and methods used for the characterization of such films clamped on substrates have been discussed.

Characterization of electromechanical coupling coefficients of piezoelectric films using composite resonators

By analyzing the resonance frequency spectrum of a composite resonator consisting of a piezoelectric ceramic film deposited on a substrate plate, the thickness extensional mode electromechanical coupling coefficient of the film, k(t)(2), can be directly calculated from the effective coupling factor values, k(eff )(2), for two special modes of the resonator. The effects of the mechanical loss in the piezoelectric films on the measurement are investigated by numerical simulation, and some guidelines for improving the accuracy of the k(t)(2) measurement are reported.

Stoechiométrie du transport du calcium par le reticulum sarcoplasmique: utilisation du p-nitrophénylphosphate comme donneur d'énergie

We have studied, under different conditions and through the hydrolysis of p-nitrophenylphosphate, the stoechiometry of the active transport of calcium by sarcoplasmic reticulum. According to a minimal kinetic model, it is possible to explain the variation of the coupling factor n(t) during the calcium accumulation in absence of precipitating agent. Under the described experimental conditions, at the beginning of the experiment, the coupling factor's value is slightly above 2.

Microwave filters with nonperiodic transmission characteristic

AbstractA microwave filter with nonuniform‐coupled transmission lines is suggested. In contrast to known transmission‐line microwave filters the transmission characteristic does not change periodically with frequency. The synthesis procedure shown reduces the design problem to the known synthesis of directional couplers with nonuniform coupling factor. A table of calculated coupling factor values of the microwave filter with an equi‐ripple passband of 0.05 dB up to 1 dB and an equi‐ripple stopband of 60 dB is given. A practical design example shows good agreement with theoretical results.

Stability of entrainment conditions for a particular form of mutually coupled Van der Pol oscillators

A commonly accepted mathematical model for the electrical activity of the gastro-intestinal tract of humans and animals comprises a set of interconnected oscillators of the Van der Pol type. The method of harmonic balance is used to obtain analytical results for the entrainment conditions of two or more Van der Pol oscillators mutually coupled between their x outputs. Two stable limit cycles are shown to exist with frequency ratios which can be adjusted by changing the coupling factor. The limit cycles have different amplitudes and phase shift in accordance with physiological data obtained from the human colon. It is shown analytically that there is a minimum value of coupling factor below which, for a given waveshape factor and frequency, only one stable limit cycle exists. This latter condition matches the measured data from the human small intestine. For oscillators having different uncoupled frequencies a hill-climbing method is used on the algebraic equations to obtain entrainment conditions and in particular the phase shift between oscillators. The analytical and hill-climbing results are compared throughout with analog simulation studies.

Some properties of p-Sip-Zn 0.5Cd 0.5Te heterojunctions. (USSR): I V Demetov and L M Panasyuk,Semiconductor Physics, No 3, Kishinev Univ 1971, 155–161 ( in Russian)

A hybrid piezoelectric composite structure is obtained by addition of nano-sized BaTiO3, SiO2 to the micro-sized PZT and polymers composition. Although the PZT material itself has excellent piezoelectric properties, PZT-based composite variety is limited. Piezoelectric properties of PZT materials can be varied with an acceptor or a donor added to the material. In addition, varieties of PZT-based sensors can be increased with doping polymers which have physical-mechanical, electrophysical, thermophysical and photoelectrical properties. The active matrix hybrid structure occurs when bringing together the unique piezoelectric properties of micro-sized PZT with electron trapping properties of nano-sized insulators (BaTiO3 or SiO2), and their piezoelectric, mechanic and electromechanic properties significantly change. In this study, the relationship between the piezoelectric constant and the coupling factor values of microstructure (PZT–PVDF) and the hybrid structure (PZT–PVDF–BaTiO3) composite are compared. The d33 value and the coupling factor of the hybrid structure have shown an average of 54 and 62% increase according to microstructure composite, respectively. In addition, the d33 value and the coupling factor of the hybrid structure (PZT–HDPE–SiO2) have exhibited about 68 and 52% increase according to microstructure composite (PZT–HDPE), respectively.

Some properties of p-Sin-CdS heterojunctions and their band models. (USSR): P A Kovalenko and L M Panasyuk,Semiconductor Physics, No 3, Kishinev Univ 1971, 132–144 ( in Russian)

A hybrid piezoelectric composite structure is obtained by addition of nano-sized BaTiO3, SiO2 to the micro-sized PZT and polymers composition. Although the PZT material itself has excellent piezoelectric properties, PZT-based composite variety is limited. Piezoelectric properties of PZT materials can be varied with an acceptor or a donor added to the material. In addition, varieties of PZT-based sensors can be increased with doping polymers which have physical-mechanical, electrophysical, thermophysical and photoelectrical properties. The active matrix hybrid structure occurs when bringing together the unique piezoelectric properties of micro-sized PZT with electron trapping properties of nano-sized insulators (BaTiO3 or SiO2), and their piezoelectric, mechanic and electromechanic properties significantly change. In this study, the relationship between the piezoelectric constant and the coupling factor values of microstructure (PZT–PVDF) and the hybrid structure (PZT–PVDF–BaTiO3) composite are compared. The d33 value and the coupling factor of the hybrid structure have shown an average of 54 and 62% increase according to microstructure composite, respectively. In addition, the d33 value and the coupling factor of the hybrid structure (PZT–HDPE–SiO2) have exhibited about 68 and 52% increase according to microstructure composite (PZT–HDPE), respectively.

An analysis of corona-generated interference in aircraft

Triboelectric charging, occurring when an aircraft is operated in precipitation, raises the aircraft potential until corona discharges occur from points of high dc field on the aircraft. These corona discharges generate noise which is coupled into receiving systems. The magnitude and spectral distribution of this radio interference, called precipitation static, depends upon three factors: 1) the strength and spectral characteristics of the source discharges, 2) the manner in which the disturbances produced by the discharges couple into the antennas, and 3) the magnitude of the discharge current and its distribution among the discharging extremities. The coupling between the antenna and the noise source is discussed using a reciprocity relationship. Because the geometry of an aircraft is complicated, and a purely theoretical approach to the determination of coupling factors is not possible, a technique developed for measuring absolute values of coupling factor as a function of frequency and position on the aircraft is described. The spectral character of the corona-noise source is studied, including a study of how the source spectrum is affected by altitude. To test the validity of the theory and the results of the laboratory work, calculations are made to predict the noise currents induced in the two test antennas employed in a flight-test program conducted on the Boeing 367-80 aircraft (prototype of the KC-135 and 707). The results of these predictions are compared with the noise spectra measured in flight.

The coupling factor of piezoelectric ceramic disks

Numerous formulae have been given for the calculation of the electromechanical coupling factor of piezoelectric disks in terms of the resonant and anti-resonant frequencies. These formulae, which are derived either on the basis of an analysis of the mechanical motions of a disk, or by considering the equivalent electrical circuit give widely divergent values of coupling factor. It is shown that when an equivalent circuit which takes account of the overtones is used, the corresponding value of coupling factor obtained is in agreement with that of the mechanical analysis. Curves, and a nomogram are given to enable coupling factor to be quickly calculated from the equations of the mechanical analysis without approximation.