Journal Article•
Mathematical Analysis of Random Noise-Conclusion
About: This article is published in Bell System Technical Journal.The article was published on 1945-01-01 and is currently open access. It has received 807 citations till now.
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TL;DR: In this paper, multivariate linear regression is used to downscale reanalysis-based mid-tropospheric predictors (wind components and speed, temperature, and geopotential height) to historical wind observations at 44 surface weather stations during the four calendar seasons.
Abstract: Multivariate linear regression is used to downscale reanalysis-based midtropospheric predictors (wind components and speed, temperature, and geopotential height) to historical wind observations at 44 surface weather stations during the four calendar seasons. The model performance is assessed as a function of statistical feature of the wind, averaging time scale of the wind statistics, and wind regime (as defined by how variable the vector wind is relative to its mean amplitude).Despite large differences in predictability characteristics between sites, several systematic results are observed: consistent with recent studies, a strong anisotropy of predictability for vector quantities is often observed, although no obvious relation is found between large-scale topographic features and the anisotropy orientation or magnitude. The predictability of time-averaged quantities increases with decreasing averaging time scale. In general, the predictability of mean vector wind components is superior to that o...
16Â citations
TL;DR: In this paper, large samples are synthesized through autoregressive, fast fractional noise, and broken line models, based on a practically significant pentad time unit, for four stations in the British Wye catchment.
Abstract: Large samples are synthesized through autoregressive, fast fractional noise, and broken line models, based on a practically significant pentad time unit, for four stations in the British Wye catchment. Hydrologic characteristics such as the numbers, durations, and magnitudes of droughts and floods are assessed by means of the crossing properties at critical levels in the time series. If a Gaussian distribution is applied to the stochastic component, crossing properties other than surplus run lengths are unrealistic. Compatibility with historical properties is achieved by the incorporation of approximately twice the coefficient of skewness estimated from the original data through a transformation to a gamma function. Also there is agreement in serial correlograms and coefficients of skewness. In this way neither negative numbers nor outliers are generated through autoregressive models, but run lengths at extreme levels in data from all models need adjustment, and a closer fitting distribution function is desirable.
16Â citations
TL;DR: In this paper, the variations in the quantity of wave power available to a wave energy converter by filtering out short-period waves have been examined, and two new parameters namely, R and S are defined to quantify the effect of this filtering on the variation of wave to-wave period and height.
16Â citations
TL;DR: In this paper, an analysis of the error introduced into estimates of avalanche photodiode (APD) laser-rangefinder performance by assuming Gaussian distribution of the APD multiplication gain is presented.
Abstract: An analysis is presented of the error introduced into estimates of avalanche photodiode (APD) laser-rangefinder performance by assuming Gaussian distribution of the APD multiplication gain. The amplitude of current pulses emitted by an APD obeys the McIntyre distribution, the tails of which diverge from the Gaussian distribution having the same mean and variance. Because extinction of false alarms requires setting a discrimination threshold far into the tail of an analog photoreceiver’s output distribution, the threshold level required to achieve a specified false alarm rate (FAR) using an APD-based photoreceiver is often not accurately predicted by the standard FAR model of Rice. Characteristics of APD-based photoreceivers are calculated using the McIntyre distribution and are compared with characteristics calculated using the Gaussian approximation.
16Â citations
01 Jan 1960
TL;DR: In this article, it is suggested that estimates of maximum wind speeds associated with gusts may be conveniently based on the level of the mean wind speed, assuming that the fluctuations in wind speed are approximately Gaussian and that the average turbulent intensity is about 0.25.
Abstract: Estimates of wind forces on structures are traditionally based on the assumption that the wind speed is invariant with space and time. However, air flow within the lower layers of the atmosphere is almost always turbulent due to fluctuations in wind velocity that comprise a very broad spectrum of characteristic lengths and amplitudes. In view of the fundamental dynamic nature of the problem, ultimate resolution depends upon satisfactory knowledge of the spectra and cospectra of the wind-velocity fluctuations. Recent measurements of these properties of turbulent structure are summarized, and application of these data to the problem of estimating wind forces is discussed. It is suggested that estimates of maximum wind speeds associated with gusts may be conveniently based on the level of the mean wind speed, assuming that the fluctuations in wind speed are approximately Gaussian and that the average turbulent intensity is about 0.25. Until additional measurements of the basic properties of turbulent structure are available, it appears unlikely that the power-spectral-analysis techniques can replace the conventional steady-state procedure.
16Â citations