1,721,037 research outputs found
Noise Dependence of Correlation and Structure Functions on Mean Count Rate and Sampling Time
Full text linkExperimental results for the noise of photon-correlation and photon-structure functions are presented. The noise dependences on the mean count rate and on the sampling time are investigated by means of a specifically built linear fluctuation analyzer, and the results are compared with theoretical predictions. The predicted mean count rate dependence and sampling time dependence of the noise are confirmed by the experimental analysis. Some discrepancies between analytical expressions and experimental results are observed in the crossover predictions. The results show that the structure function has better noise performance for relatively high mean count rates and for long sampling times, which strongly suggests a wider use of this statistical estimator in measurements requiring good accuracy, as in the case of uniform sampling
A Low Cost Correlator Employing a Personal Computer
Full text linkThe intention of this paper is to describe the design of a 16-bit correlation setup employing a personal computer (PC) used in intensity fluctuation spectroscopy. It is based on a hardware acquisition board which counts the photons detected in the selected sampling time. The calculation of the correlation coefficients is achieved with a PC by means of a suitable software program. This arrangement permits one to obtain various kinds of information from the recorded data, i.e., it is possible to evaluate other statistical estimators instead of the usual correlation function. Experimental tests of the apparatus have been obtained by measuring the light scattered by a liquid suspension of polystyrene latex spheres
Experimental Analysis of the noise in photon correlation and photon structure functions
Full text linkWe present an experimental analysis of the variance of photon-correlation and photon-structure functions obtained from dynamic light-scattering measurements. The results are compared with theoretical predictions. The noise evaluation of the statistical estimators has been obtained by using a fluctuation analyzer, specifically built for this purpose, which uses linearly spaced sampling time. The noise dependences on the experimental bounds (mean count rate and sampling time) are investigated. The predicted behavior of the estimator variances has been confirmed. However, the measured accuracies of correlation and structure functions show a discrepancy between their analytical expressions and the experimental results in the high-intensity limit of the scattered light. The results confirm that the structure function has better noise performance for relatively high mean count rates. This strongly suggests a wider use of this statistical estimator in measurements requiring a good accuracy, such as in the analysis of polydispersed microparticle size distribution, in the case of uniform sampling
Experimental analysis of the noise of statistical estimators used in correlation spectroscopy
No full textDeviazione frattale del moto browniano in sospensioni di particelle sferiche ad elevata concentrazione
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