A5102874737- Wind and Air Flow Studies
- Underwater Acoustics Research
- Solar and Space Plasma Dynamics
- Meteorological Phenomena and Simulations
- Fluid Dynamics and Turbulent Flows
- Ionosphere and magnetosphere dynamics
- Atmospheric chemistry and aerosols
- Seismic Waves and Analysis
- Geomagnetism and Paleomagnetism Studies
- Atmospheric and Environmental Gas Dynamics
- Earthquake Detection and Analysis
- Blind Source Separation Techniques
- Atmospheric aerosols and clouds
- Particle Dynamics in Fluid Flows
- Statistical and numerical algorithms
- Seismic Imaging and Inversion Techniques
- Underwater Vehicles and Communication Systems
- Geophysical Methods and Applications
- Geophysical and Geoelectrical Methods
- Image and Signal Denoising Methods
- French Historical and Cultural Studies
- Atmospheric Ozone and Climate
- Air Quality and Health Impacts
- Historical Studies and Socio-cultural Analysis
- Speech and Audio Processing
Met Office
2015-2024
Tarumanagara University
2021
Queen's University
2010-2020
Thomson Reuters (United States)
2018
Phillips Exeter Academy
2007-2015
Carleton University
2013
Library and Archives Canada
2013
Canadian Heritage
2013
Newmont Mining (United States)
2013
Statistics Canada
2008
In the choice of an estimator for spectrum a stationary time series from finite sample process, problems bias control and consistency, or "smoothing," are dominant. this paper we present new method based on "local" eigenexpansion to estimate in terms solution integral equation. Computationally is equivalent using weishted average direct-spectrum estimates orthogonal data windows (discrete prolate spheroidal sequences) treat both smoothing problems. Some attractive features are: there no...
Random Fields is a book which I found both technically interesting and pleasure to read. The problems considered are those of describing multidimensional stochastic data (as opposed unidimensional, e.g., multivariate, time series data). presentation clear the should be useful almost anyone who uses random processes solve in engineering or science. author's approach informal and, while not careless, intended for mathematical purists. For example, index contains six references limited...
Many different random-walk models of dispersion in inhomogeneous or unsteady turbulence have been proposed and several criteria emerged to distinguish good from bad. In this paper the relationships between various are examined for a very general class it is shown that most equivalent. It also how model can be designed satisfy these exactly consistent with inertial-subrange theory. Some examples obey described. As an illustration some calculations free-convective conditions presented.
Spectrum sensing is the very task upon which entire operation of cognitive radio rests. For to fulfill potential it offers solve spectrum underutilization problem and do so in a reliable computationally feasible manner, we require sensor that detects holes (i.e., underutilized subbands spectrum), provides high spectral-resolution capability, estimates average power each subband spectrum, identifies unknown directions interfering signals. Cyclostationarity another desirable property could be...
The ability of a large-eddy simulation to represent the large-scale motions in interior turbulent flow is well established. However, concerns remain for behaviour close rigid surfaces where, with exception low-Reynolds-number flows, description must be matched some which all except larger-scale ‘inactive’ are averaged. performance simulations this near-surface region investigated and it pointed out that previous mean velocity profile matching has not had logarithmic form. A number new...
Robust estimation of power spectra, coherences, and transfer functions is investigated in the context geophysical data processing. The methods described are frequency‐domain extensions current techniques from statistical literature applicable cases where section‐averaging would be used with that contaminated by local nonstationarity or isolated outliers. paper begins a review robust theory, emphasizing principles maximum likelihood M‐estimators. These combined spectral to obtain estimates an...
Robust magnetotelluric response function estimators are now in standard use electromagnetic induction research. Properly devised and applied, these have the ability to reduce influence of unusual data (outliers) (electric field) variables, but often not sensitive exceptional predictor (magnetic data, which termed leverage points. A bounded estimator is described simultaneously limits both outliers points, has proven consistently yield more reliable estimates than conventional robust...
This paper describes some new methods for the analysis of time series and their application to find results in palaeoclimate. The statistical theory includes a quadratic inverse unbiased estimation power spectra, an associated test spectral resolution, maximum-likelihood spectrum estimates, detailed explanations topics detection periodic components. A technique estimating transfer functions is described. methodology used analyse describing global ice volume over past 700000 years as recorded...
A new stochastic model for the motion of particle pairs in isotropic high-Reynolds-number turbulence is proposed. The three-dimensional and its formulation takes account recent improvements understanding one-particle models. In particular designed so that if are initially well mixed fluid, they will remain so. contrast to previous models, leads a prediction separation probability density function which qualitative agreement with inertial subrange theory. values concentration variance from...
Analysis of instrumental temperature records beginning in 1659 shows that much the world dominant frequency seasons is one cycle per anomalistic year (the time from perihelion to perihelion, 365.25964 days), not tropical equinox equinox, 365.24220 and timing annual controlled by perihelion. The assumption were timed equinoxes has caused many statistical analyses climate data be badly biased. Coherence between changes amplitude those average show 1854 1922 there small variations, probably...
Holocene climate records are imperfect proxies for processes containing complicated mixtures of periodic and random signals. I summarize time series analysis methods such data with emphasis on the multiple-data-window technique. This method differs from conventional approaches to in that a set tapers is applied domain before Fourier transforming. The tapers, or windows, discrete prolate spheroidal sequences characterized as being most nearly band-limited functions possible among defined...
A new set of computational procedures are proposed for estimating the magnetotelluric response functions from time series natural source electromagnetic field variations. These combine remote reference method, which is effective at minimizing bias errors in response, with robust processing, useful removing contamination by outliers and other departures Gauss‐Markov optimality on regression estimates. In addition, a nonparametric jackknife estimator confidence limits introduced. The offers...
In this paper we describe a new wide-angle parabolic equation based on an operator-splitting that permits the use of marching-type Fourier transform solution method. The was first presented by Feit and Fleck [Appl. Opt. 17, 3990–3998 (1978)] for studying propagation within optical fibers. Existing computer codes which numerically solve standard ocean acoustics split-step algorithm Tappert Hardin are easily modified to accommodate capability equation. addition, since is less sensitive value...
Conventional spectrum estimates of both the smoothed-periodogram and autoregressive variety lack robustness toward outliers in original data. Outliers other local perturbations are modeled by non-Gaussian additive noise, which is zero most time. Correspondingly, conventional manifest not only inflated variances but also damaging asymptotic biases. This paper discusses robust-resistant methods estimation do suffer this way. The main approach involves "data cleaning" either one-sided or...
Abstract The use of random walk techniques in diffusion modelling has been very successful when the turbulence is not too inhomogeneous. In this paper difficulties associated with inhomogeneous are investigated, and a model developed which ensures correct steady state distribution particles phase space. requires generation numbers from non‐Gaussian distributions, makes difficult to apply cases severe inhomogeneity. An alternative presented overcomes problem where velocity Gaussian.
Summary Outliers in time series can play havoc with conventional power spectrum density estimation techniques when the features of interest consist one or more peaks relatively low amplitude. Furthermore, outliers need not be large relative to scale process order have considerable impact on estimate; they only innovations process. Following a tutorial review central notions robustness and principles guiding estimation, methods are presented for computing robust spectral densities. These...
During the 2010 eruption of Eyjafjallajökull, improvements were made to modeling procedure at Met Office, UK, enabling peak ash concentrations within volcanic cloud be estimated. In this paper we describe concentration forecasting method, its rationale and how it evolved over time in response new information user requirements. The change from solely regions also estimating required consideration emission rates, fraction surviving near‐source fall‐out, relationship between predicted mean...
Techniques for reliably estimating the power spectral density function both small and large samples of a stationary stochastic process are described. These techniques have been particularly successful in cases where range spectrum is large. The methods resistant to moderate amount contaminated or erroneous data well suited use with auxiliary tests stationarity normality. Part I concerned background theoretical considerations while examples from development analysis WT4 waveguide medium will...
[1] The Eyjafjallajökull volcano in Iceland erupted explosively on 14 April 2010, emitting a plume of ash into the atmosphere. was transported from toward Europe where mostly cloud-free skies allowed ground-based lidars at Chilbolton England and Leipzig Germany to estimate mass concentration cloud as it passed overhead. UK Met Office's Numerical Atmospheric-dispersion Modeling Environment (NAME) has been used simulate evolution during initial phase emissions, 14–16 2010. NAME captures timing...
The requirement to forecast volcanic ash concentrations was amplified as a response the 2010 Eyjafjallajökull eruption when safety limits for aviation were introduced in European area. ability provide accurate quantitative forecasts relies large extent on source term which is emissions of function time and height. This study presents estimations from derived with an inversion algorithm constrains modeled satellite observations ash. tested input two different dispersion models, run three...