Metrics for the Comparison of Acceleration Time Histories
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Abstract:
A decomposition is used to express the mean squared deviation, quantifying the dissimilarities between time histories of input (or response) quantities of multiple replicas of a soil system centrifuge test, as a unique aggregate of three discrepancy measures associated with shape, phase and frequency-shift. The shape measure quantifies the deviations associated with dissimilarities in form and amplitude. The phase measure estimates the deviations associated with differences in phase angle. The frequency-shift measure quantifies the deviations associated with differences in frequency components. These measures are illustrated using simple synthetic motions and used to assess the discrepancies among six replicas of centrifuge input motion achieved at six different facilities. The conducted analysis shows that the proposed decomposition accurately quantifies the different types of discrepancies between time histories.Keywords:
Centrifuge
Phase angle (astronomy)
Strong ground motion
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In this paper, a novel and simple method to measure the phase difference between two sinusoidal signals is presented. Basically, the method consists of subtracting two sinusoidal signals with same frequencies and measuring the resulting signal amplitude: this amplitude being a minimum whenever there is a coincidence between both signal phases. In order to test this method, an adjustable phase reference signal has been generated using a direct digital synthesizer device. Employing this reference signal, it can be demonstrated that the phase difference between two signals can be evaluated with errors smaller than 0.3° for signals with frequencies up to 1.25 MHz.
SIGNAL (programming language)
Phase difference
Direct digital synthesizer
Instantaneous phase
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Weston et al. [Philos. Trans. R. Soc. London, Ser. A 265, 595 (1969)] show the remarkable agreement between the spectra for the coefficients of variation of amplitude and phase, i.e., amplitude and phase fluctuations, for a hydrophone in shallow water. Wagstaff [J. Acoust. Soc. Am. 112, 2422 (2002)] showed the functional similarity between phase angles and pseudo-phase angles for an outdoor microphone. Pseudo-phase angles are amplitude fluctuations that have been scaled appropriately to have a similar functionality in temporally coherent signal processing as phase angles. The concepts of the two previously mentioned references are merged to exploit the similarity of phase fluctuations and amplitude fluctuations to achieve multiplicative pseudo-coherent gain. Gains in excess of 20 log(N) have been achieved (N is the number of samples averaged). 10 log(N) is considered ideal for vector averaging. It is seldom achieved, because of coherent attenuation and cancellation associated with the use of real phase angles. Results are included for wind noise in outdoor measurements. [Work supported by U.S. Army Armament Research Development and Engineering Center.]
Hydrophone
Similarity (geometry)
Phase angle (astronomy)
SIGNAL (programming language)
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This letter proposes a three-phase phase-locked loop (PLL) algorithm relying on an adaptive Clarke transform (CT) under amplitude and/or phase angle unbalanced condition. Analytical expressions for coefficients of matrix associated with the adaptive CT are derived and used to generate orthogonal signals. An auxiliary algorithm is also proposed to track the actual amplitudes and phase angle deviations. Unlike the conventional CT relying on constant coefficients, the adaptive CT can generate accurate orthogonal signals from the three-phase voltages including phase angle and/or amplitude imbalances. As a result, the proposed PLL is not affected by the unbalanced phase angles with/without amplitude imbalances. The advantages of the proposed adaptive CT-based PLL method is illustrated by both simulation and experimental results.
Phase angle (astronomy)
Constant (computer programming)
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The Phase Angle Gradient Method (PAGM) is a recent technique developed for phase retrieval based on amplitude-only measurement data. Preliminary results have shown that the PAGM is able to perform phase retrieval at 100MHz with accurate phase information based on measured fIeld components on three planar surfaces. In this paper, a performance evaluation of the PAGM under different conFigurations is conducted. Phase retrieval based on field measurements for different plane sizes and separations between the planes are studied rigorously. In addition, the PAGM is tested for different initial phase distributions. The results show that the PAGM is capable of retrieving phase information even if the separation between the measurement planes is small in terms of wavelengths.
Phase angle (astronomy)
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Measuring angle by comparing amplitude and phase is an important method in wide-band passive radar seeker technology.Because of existence of several values in phase.The system of measuring angle by comparing amplitude and phase will yield fuzziness.The long-short baselines and information of amplitude are employed to establish a method of setting stiding coarse phase according to the threshold of amplitude difference.Its validity is proved by experiment.The fuzziness is eliminated in the system of measuring angle by comparing amplitude and phase.It has certain reference and application values in actual projects.
Phase angle (astronomy)
Phase difference
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Antenna Array's Beamforms would be influenced by the imbalances of amplitude and phase in all channels. Monte Carlo Method (MCM) was adopted to simulate the beamforming pattern's variations induced by amplitude variations, phase variations and the both, respectively. Linear 8-element array beamforming with a series of amplitude variations and phase variations were simulated. An 8x8 butler matrix was also designed and used to synthesize beams. Results indicated that channels' phase variations affect the main lobe angle greatly than amplitude variations. The standard uncertainty of synthesized main lobe angle were less than 1° when the phase variation is 11.2°.
Main lobe
Phase angle (astronomy)
Side lobe
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Experimental photoacoustic spectroscopy (PAS) amplitude and phase results on an AR coated ZnSe laser window were obtained at 10.6 μm as a function of chopping frequency. The PAS signal amplitude had an f - n frequency dependence with n = 1.04. The PAS phase angle varied by 20° between 1000 Hz and 50 Hz; 7° between 1000 Hz and 100 Hz. Theoretical calculations related to the situation were performed using the Bennett-Forman and Rosencwaig-Gersho PAS theories. The Bennett-Forman theory agreed with the PAS amplitude results for r = β s u r f a c e /β b u l k ≥ 0.05 cm. A 7° phase change was obtained for r = 0.03 cm. The homogeneous sample Rosencwaig-Gersho theory did not fit either amplitude or phase angle data, yielding n = 1.5 and a phase angle of 45.0° which varied less than 0.04° over the frequency range measured.
Phase angle (astronomy)
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