Variation Of Phase Difference Research Articles

Flow visualization of coaxial jet excited with varying phase differences

Flow visualization of coaxial jet excited with varying phase differences

Improved technique for measuring refractive index and thickness of a transparent plate

The phase difference between s- and p-polarizations of a circularly polarized heterodyne light beam reflected from a transparent plate is measured. The measured data is substituted into the specially derived equations and the refractive index can be calculated. Next, the variations of phase difference between s- and p-polarizations due to the wavelength shift and the extraction of the plate in a modified Michelson interferometer are measured. Then, its thickness can be calculated based on the measured value of refractive index, the variations of phase difference, and the specified value of wavelength shift.

Measurement of wavelength shift by using surface plasmon resonance heterodyne interferometry

A linearly polarized light is incident on a surface plasmon resonance (SPR) apparatus at the resonant angle, the surface plasmons are excited. Small wavelength shifts will introduce phase difference variations between s- and p-polarizations of the reflected light. These phase difference variations can be measured accurately by using heterodyne interferometry. Based on these facts, a novel method for measuring small wavelength shifts is proposed. It has the advantages of both common-path interferometry and heterodyne interferometry.

An ultra-broad-band reflection-type phase-shifter MMIC with series and parallel LC circuits

An ultra-broad-band reflection-type phase shifter is proposed. Theoretically, the proposed phase shifter has frequency-independent characteristics in the case of 180/spl deg/ phase shift. The phase shifter is composed of a 3-dB hybrid coupler and a pair of novel reflective terminating circuits. The reflective terminating circuit switches two states of series and parallel LC circuits. Using an ideal circuit model without parasitic circuit elements, we have derived the determining condition of frequency independence of circuit elements. Extending the concept, we can also obtain a broad-band phase shifter for other phase difference as well. In this case, for a given phase difference and an operating frequency, we also derive a condition to obtain minimum variation of phase difference around the operating frequency. This enables the broad-band characteristics for arbitrary phase difference. The fabricated 180/spl deg/ reflective terminating circuit monolithic microwave integrated circuit (MMIC) has achieved a phase difference of 183/spl deg/ /spl plusmn/ 3 over 0.5-30 GHz. The 180/spl deg/ phase-shifter MMIC has demonstrated a phase shift of 187/spl deg/ /spl plusmn/ 7/spl deg/ over 0.5-20 GHz. The 90/spl deg/ reflective terminating circuit MMIC has performed a phase difference of 93/spl deg/ /spl plusmn/ 7/spl deg/ over 4-12 GHz.

A composite optical waveguide-based polarimetric interferometer for chemical and biological sensing applications

A new polarimetric interferometer has been developed on the basis of the phase difference between transverse electric (TE)/sub 0/ and transverse magnetic (TM)/sub 0/ modes in a composite optical waveguide (OWG). The composite OWG consists of a single-mode potassium ion-exchanged planar waveguide overlaid with a high-index thin film that has two tapered ends and supports only the TE/sub 0/ mode. Applying tapered velocity coupling theory, we found that the TE/sub 0/ and TM/sub 0/ modes coexisting in the potassium ion-exchanged layer were separated in the thin film region of the composite OWG: the TE/sub 0/ mode was coupled into the thin film while the TM/sub 0/ mode was confined in the potassium ion-exchanged layer. Interference occurs between TE- and TM-polarized output components when a single output beam is passed through a 45/spl deg/-polarized analyzer. The phase difference /spl phi/ between both orthogonal output components is very sensitive to the superstrate index n/sub c/ in the thin film region. Our experimental results indicate that a slight change of /spl Delta/n/sub c/=3.71/spl times/10/sup -6/ results in the phase-difference variation of /spl Delta//spl phi/=1/spl deg/ for a 5-mm-long TiO/sub 2//K/sup +/ composite OWG with a 34-nm-thick TiO/sub 2/ film. Such a simple polarimetric interferometer can be applied to chemical or biological sensors by modifying the upper film surface of the composite OWG with a chemically or biologically active substance.

Vacuum measurement using total-internal-reflection heterodyne interferometry

Based on the effect that the phase difference between s- and p-polarizations at the total-internal-reflection is changed with the variation of the air refractive index, which is related to the air pressure, a new optical method for measuring the air pressure of a vacuum cavity is proposed. From the experimental curve of the phase difference variation measured by the heterodyne interferometry and the calibrated pressure measurement of a vacuum cavity, an empirical formula is derived. With this empirical formula, the measurable range of this new optical method is 760 to 0.1 torr.

Common-path heterodyne interferometric detection scheme for measuring wavelength shift

When a linearly polarized light passes through a uniaxial crystal, small wavelength shifts will introduce phase difference variations between s- and p-polarizations. These phase difference variations can be measured accurately by heterodyne interferometry. Based on these facts, a common-path heterodyne interferometric detection scheme for measuring wavelength shift is proposed. This scheme has the advantages of both common-path interferometry and heterodyne interferometry.

Some aspects of the nonlocal electrodynamics of infinite Josephson junctions

We derive the basic equations of nonlocal Josephson electrodynamics, valid for any ratios of the characteristic scale of phase-difference variations and junction thickness. The spectrum of generalized Swihart waves is obtained. We also study the effect of finite surface resistance of the superconducting electrodes on the dynamics of vortex structures characteristic of nonlocal electrodynamics.

Implications of the Gaussian intensity distribution of laser beams on the performance of the phase Doppler technique. Sizing uncertainties

The influence of the Gaussian intensity distribution of the incident laser beams on sizing measurements by phase-Doppler velocimetry has been investigated using geometrical optics approximation, considering the interference between contributions from reflection at the external surface of a droplet, refraction through the droplet and those refracted after one and two reflections at the inner surface of the droplet. The results have considered the use of forward-(scattering angles between 30 and 75°), back-(scattering angles between 140 and 180°) and side-(scattering angles between 80 and 130°) scattered light to size transparent non-absorbing spherical droplets in the range of relative refractive indices between 1.33 and 1.4 and normal, or oblique trajectories relative to the fringes of the velocimeter. The results have demonstrated the influence of phase and amplitude validations and the logic of the signal processor on sizing uncertainties. The Gaussian intensity profile of the laser beams caused variations of phase difference and associated amplitude of the signal with droplet trajectory and, for the optical arrangement of the current work, the resulting sizing uncertainties after amplitude and phase validations were between 5 and 10% for forward-scattered light collected at 30° and +9%/−100% and +20%/−16% for back-scattered light collected at 150° for droplet-to-probe diameter ratios of 1.67 and 0.24, respectively. For side-scattered light, the phase validation logic is not valid and the sizing uncertainties after amplitude validation were +19%/−26% and ±5% for droplet-to-probe diameter ratios of 1.67 and 0.24, respectively, and scattering angle of 104°. Although these sizing errors correspond to optical arrangements, which may not be available in commercially available phase Doppler systems, experimental results from Willman et al. ( Proc. 7th Int. Symp. on Applications of Laser Technologies to Fluid Mechanics, 1994) using commercial instruments indicate similar errors. Sizing with forward-scattered light is preferable overall, but for flows with limited optical access, sizing with side-scattered light is preferable to back-scattered light due to lower sizing errors. Droplet refractive index influences the response curves and for refractive indices of 1.33 and 1.4, back-scattered light should be collected between scattering angles of 145 and 160° and of 155 and 160°, respectively, and that for side-scattered light at around 120 and 104°, respectively, and for both arrangements the collection optics are required to be within a small range of angles around the bisector plane of the beams.

Automatic alignment of optical interferometers

We present a description of a system for automatic alignment of optical interferometers. The technique relies on using differential phase modulation to permit the detection of the phase difference between two fundamental-mode Gaussian beams at the output of an interferometer. Measurements of the spatially varying phase difference between the two beams by use of one or more multielement photodiodes permits information to be derived about the mismatch in overlap between the phase fronts at the output of the interferometer.

Evaluation of computerized analysis of the propagation of human duodenojejunal contractions

Abstract Detection of peristalsis in the human small intestine has been limited in the past by both the available measurement techniques and the complexity of this activity. Recent developments in ambulant recording have provided a means of monitoring the occurrence of intestinal contractions at multiple sites in the small bowel, but the problem of complexity remains. Using digital data recorded from an intra‐luminal strain‐gauge transducer in the proximal gut, an algorithm was implemented to identify and classify contractile events within the small bowel. By modelling propagated activity the effect of varying transducer spacing and the number of transducers used was assessed. The question of variability of apparent velocity of peristaltic contractions was examined using successive cross‐correlation calculations to extract underlying phase differences between samples of 512 minutes of manometric recording over 150 mm of human small bowel. The effective velocity was found to have a median value of 14 mm sec‐1 and an inter quartile range of 12–18 mm see‐1). It is proposed that, in dynamically tracking variations in phase difference between adjacent recording sites, cross‐correlation techniques should be used to control the parameters used for the recognition of propagated contractile events and thereby improve the specificity of this process.

Interaural time sensitivity in medial superior olive of cat

1. We studied the sensitivity of cells in the medial superior olive (MSO) of the anesthetized cat to variations in interaural phase differences (IPDs) of low-frequency tones and in interaural time differences (ITDs) of tones and broad-band noise signals. Our sample consisted of 39 cells histologically localized to the MSO. 2. All but one of the cells had characteristic frequencies less than 3 kHz, and 79% were sensitive to ITDs and IPDs. More than one-half (56%) of the cells responded to monaural stimulation of either ear, and both the binaural and monaural responses were highly phase locked. All of the cells that were sensitive to IPDs and monaurally driven by either ear responded in accord with that predicted by the coincidence model of Jeffress, as judged by comparisons of the phases at which the monaural and binaural responses occurred. The optimal IPDs were tightly clustered between 0.0 and 0.2 cycles. Most cells exhibited facilitation of the response at favorable ITDs and inhibition at unfavorable ITDs compared with the monaural responses. 3. Cells in the MSO exhibited characteristic delay, as judged by a linear relationship between the mean interaural phase and stimulating frequency. Characteristic phases were clustered near 0 indicating the most cells responded maximally when the two input tones were in phase. With the use of the binaural beat stimulus we found no differential selectivity for either the direction or speed of interaural phase changes. 4. The cells were also sensitive to ITDs of broad-band noise signals. The ITD curve in response to broad-band noise was similar to that predicted by the composite curve, which was calculated by linearly summating the tonal responses over the frequencies in the response area of the cell. Most (93%) of the peaks of the composite curves were between 0 and +400 microseconds, corresponding to locations in the contralateral sound field. Moreover, computer cross correlations of the monaural spike trains were similar to the ITD curve generated binaurally for both correlated and uncorrelated noise signals to the two ears. Thus our data suggest that the cells in the MSO behave much like cross-correlators. 5. By combining data from different animals and lcoating each cell on a standard MSO, we found evidence for a spatial map of ITDs across the anterior-posterior (A-P) axis of the MSO.(ABSTRACT TRUNCATED AT 400 WORDS)

Canonic coupling of oscillators in a chain

The phenomenon of coupling of several sinusoidal oscillators is discussed. The oscillators are arranged in a chain, and each oscillator affects its next neighbour in the chain and is affected by it. The coupling is, therefore, bilateral and its main effect is due to variations in phase differences between neighbouring oscillators. The simple approach to the treatment of the behaviour of the coupling and the relative simplicity of the models of oscillators participating in the system enables an analytical solution to be found for many of the details of system dynamics without a need to resort to complicated approximate methods. The results are supported by computer simulation. The present work follows a previous successful treatment of simpler systems (a system of two coupled oscillators and a system of oscillators coupled in a ring). The paper concludes by considering the possible application of the present results for analyzing some technological and natural systems.

Chromatic dispersion characterization in short single-mode fibers by spectral scanning of phase difference in a Michelson interferometer

Chromatic dispersion characteristics around zero-dispersion wavelength have been measured in short samples of single-mode fibers by a spectral scanning of the interference signal in a Michelson interferometer. The propagative refractive index is directly obtained from the phase-difference variations with the wavelength between a light beam propagated through the fiber and a reference beam. The optimum operative conditions of the interferometer for obtaining the unequivocal analysis of experimental signals are discussed. The accuracy of the results obtained shows the reliability of the method for a complete dispersion characterization.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A Possible New Type of Simultaneously Incommensurate and Ferroelectric Phases

A previous paper [J. Phys. Soc. Jpn. 54 (1985) 4213] indicated the possibility of a transition from an incommensurate phase having constant phase differences to an incommensurate phase having varying phase differences. Following that paper, this paper indicates that the latter phase, viz., the incommensurate phase of the varying phase difference type should be ferroelectric. Since this phase is not semicommensurate, it is a new type of simultaneously incommensurate and ferroelectric phase. Its polar direction agrees with the incommensurate direction and hence differs from the polar direction of the corresponding commensurate ferroelectric phase. The expressions of the temperature dependences of spontaneous polarization and susceptibility are deduced.

Canonic coupling of oscillators in a ring

AbstractThe paper deals with the phenomenon of coupling of several sinusoidal oscillators. The oscillators are arranged in a ring, and each oscillator affects its next neighbour in the ring. The coupling is unilateral and its main effect is due to variations in phase differences between neighbouring oscillators. The simple approach to the treatment of the behaviour of the coupling and the relative simplicity of the models of oscillators participating in the system enable an analytical solution of the problem to be found without a need to resort to complicated approximate methods. The results are supported by computer simulations. Several modes of dynamic behaviour of the system are identified. The number of possible modes increases with the number of oscillators in the ring. The paper concludes by demonstrating that the present results possess a potential of being useful in analysing some technological and natural systems.

Possibility of the Transition from an Incommensurate Phase Having Constant Phase Differences to an Incommensurate Phase Having Varying Phase Differences

The order parameter, Q ( x ), for incommensurate transitions can, as is well known, be expressed as a sum of harmonics of the form Q n e i n h x , where n is an integer. Let θ n =arg Q n . For | n |>1, let η n =θ n - n θ 1 . Two different types of incommensurate phases are conceivable. In one, the phase differences η n s 's (subscript s means spontaneous) are constant against variation of temperature T . In the other, η n s 's vary with T . The constant phase difference type is usual, but the varying phase difference type is also possible. On cooling, it is possible that an incommensurate phase of the constant phase difference type, which succeeds the prototypic phase, is changed to an incommensurate phase of the varying phase difference type by second-order transition. A detailed account of this transformation is given.

Phase dynamics and radiated power of dc SQUIDS

The time variation of the quantum phase difference and the radiated power of two resistively shunted junctions in a superconducting loop are analyzed using a first harmonic approximation method. It is shown explicitly that an output coupling impedance connected across the junctions plays an important role in determining the output power as well as the cutoff frequency in the radiation spectrum. The radiated power of an array of dc SQUIDs is compared with the power output of a synchronized series array in a resonant cavity. WithN superconducting weak links coupled to a fixed load, the SQUID array suffers an output power saturation for largeN; our analysis shows that it is very difficult to obtain radiated power higher than a few microwatts. On the other hand, a cavity-coupled large array gives an output power proportional toN with a narrow linewidth, suggesting that it could be very useful in practice.

Intermittency in Josephson junctions

Numerical and analog solutions to a differential equation describing an rf-driven Josephson junction were obtained; variations of the quantum phase difference across the junction and its time derivative provide clear examples for the existence of intermittency in this nonlinear system. A critical exponent is determined in agreement with theoretical predictions.

Chromospheric Oscillations Observed with OSO 8. II. Average Phase Spectra for SI II.

view Abstract Citations (26) References (8) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Chromospheric Oscillations Observed with OSO 8. II. Average Phase Spectra for SI II. White, O. R. ; Athay, R. Grant Abstract Time series of intensity and Doppler-shift fluctuations in the Si II emission lines λ1816.93 and λ1817.45 are Fourier analyzed to determine the frequency variation of phase differences between intensity and velocity and between these two lines formed 300 km apart in the middle chromosphere. Average phase spectra show that oscillations between 2 and 9 mHz in the two lines have time delays from 35 to 40s, which is consistent with the upward propagation of sound waves at 8. 7.5 km s-1. In this same frequency band near 3 mHz, maximum brightness leads maximum blueshift by 600. At frequencies above 11 mHz where the power spectrum is flat, the phase differences are uncertain, but approximately 65% of the cases indicate upward propagation. At these higher frequencies, the phase lead between intensity and blue Doppler shift ranges from 0° to 180° with an average value of 90°. However, the phase estimates in this upper band are corrupted by both aliasing and randomness inherent to the measured signals. Phase differences in the two narrow spectral features seen at 10.5 and 27 mHz in the power spectra are shown to be consistent with properties expected for aliases of the wheel rotation rate of the spacecraft wheel section. Publication: The Astrophysical Journal Supplement Series Pub Date: March 1979 DOI: 10.1086/190575 Bibcode: 1979ApJS...39..347W full text sources ADS |