Generalized Stokes Vectors and Generalized Power Spectra for Second-Order Stationary Vector-Processes

1981 ◽  
Vol 40 (1) ◽  
pp. 137-149 ◽  
Author(s):  
J. C. Samson ◽  
J. V. Olson
Keyword(s):  
Power Spectra ◽  
Second Order ◽  
Stokes Vectors ◽  
Stationary Vector

G-INFLATION: INFLATION WITH THE MOST GENERAL SECOND-ORDER FIELD EQUATIONS

2012 ◽  
Vol 10 ◽  
pp. 77-84
Author(s):  
TSUTOMU KOBAYASHI ◽  
MASAHIDE YAMAGUCHI ◽  
JUN'ICHI YOKOYAMA
Keyword(s):  
Power Spectra ◽  
Second Order ◽  
Stability Criteria ◽  
Cosmological Perturbations ◽  
Field Equations ◽  
Special Cases ◽  
Single Field ◽  
The Stability

In this talk, we have discussed generalized Galileons as a framework to develop the most general single-field inflation models ever, (Generalized) G-inflation, containing previous examples such as k-inflation, extended inflation, and new Higgs inflation as special cases. We have also investigated the background and perturbation evolution in this model, calculating the most general quadratic actions for tensor and scalar cosmological perturbations to give the stability criteria and the power spectra of primordial fluctuations.

scholarly journals K-inflationary power spectra at second order

2013 ◽  
Vol 2013 (06) ◽  
pp. 021-021 ◽  
Author(s):  
Jérôme Martin ◽  
Christophe Ringeval ◽  
Vincent Vennin
Keyword(s):  
Power Spectra ◽  
Second Order

Spatial nonlinearities in the instantaneous perception of textures with identical power spectra

1980 ◽  
Vol 290 (1038) ◽  
pp. 83-94 ◽  
Keyword(s):  
Order Statistics ◽  
Power Spectra ◽  
Building Blocks ◽  
Second Order ◽  
Perceptual System ◽  
Higher Order Statistics ◽  
Line Segments ◽  
Second Order Statistics ◽  
Local Structures ◽  
Perception System

In 1962, Julesz observed that texture pairs with identical second-order statistics but different third- and higher-order statistics were usually not discriminable without scrutiny. Since second-order (dipole) statistics determine the autocorrelation functions and hence the power spectra, this observation also meant that in preattentive perception of texture the phase (position) spectra were ignored. In the last two decades many new classes of texture pairs with identical power spectra have been invented that were not effortlessly discriminable; however, recently (Caelli & Julesz 1978; Caelli et al . 1978; Julesz et al . 1978) several counterexamples were found. In these texture pairs with identical power spectra some local structures of ‘quasi-collinearity’, ‘corner’, ‘closure’ and ‘granularity’ yielded strong discrimination. These features can be regarded as the fundamental building blocks of form, that is, the essential nonlinearities of the preattentive perceptual system. Here, it will be shown that these counterexamples are not independent of each other, but can be described by two elementary units: bars (line segments) and their terminators. Furthermore, the preattentive texture perception system can count the number of terminators but ignores their positions.

Springing Response Statistics of Tethered Platforms in Random Waves

2006 ◽  
Author(s):  
P. S. Teigen ◽  
O. Gaidai ◽  
A. Naess
Keyword(s):  
Volterra Series ◽  
Series Representation ◽  
Power Spectra ◽  
Second Order ◽  
Random Waves ◽  
Sea State ◽  
Sum Frequency ◽  
Wave Forcing ◽  
Spring System ◽  
Mass Spring

The paper investigates the wave forcing and motion response of a small size TLP, with particular focus on sum frequency effects related to the restrained modes, heave, roll and pitch. The fluid loading is obtained from a second order diffraction code, and the stochastic response in a random sea state is estimated using a Volterra series representation of the response process. Although the wave loading is assumed to be a second order process, the dynamical system as such is a damped, linear mass-spring system. Numerical results are presented both in terms of power spectra and as extreme value predictions. In the latter case three different methods are compared and evaluated.

scholarly journals Study of second-order wind statistics in the mesosphere and lower thermosphere region from multistatic specular meteor radar observations during the SIMONe 2018 campaign

2020 ◽  
Author(s):  
Harikrishnan Charuvil Asokan ◽  
Jorge L. Chau ◽  
Raffaele Marino ◽  
Juha Vierinen ◽  
Fabio Vargas ◽  
...  
Keyword(s):  
Gravity Waves ◽  
Spread Spectrum ◽  
Lower Thermosphere ◽  
Power Spectra ◽  
Geographic Area ◽  
Second Order ◽  
Small Scale ◽  
Meteor Radar ◽  
Mesosphere And Lower Thermosphere ◽  
Field Correlation

Abstract. In recent years, multistatic specular meteor radars (SMRs) have been introduced to study the Mesosphere and Lower Thermosphere (MLT) dynamics. In this paper, the statistics of mesoscale MLT power spectra are explored through observations from a campaign using the SIMONe (Spread-spectrum Interferometric Multistatic meteor radar Observing Network) approach conducted in northern Germany in 2018 (hereafter SIMONe 2018). The seven-day SIMONe 2018 comprised of fourteen multistatic SMR links and allows to build a substantial database of specular meteor trail events, collecting more than one hundred thousand detections per day within a geographic area of ~ 500 km x 500 km. The two methods we propose to obtain the power spectra in frequency range are (1) Wind field Correlation Function Inversion (WCFI), which utilizes two-point correlations of specular meteor observations, and (2) Mean Wind Estimation (MWE), which determines the MLT winds and gradients from specular meteor observations. Monte Carlo simulations of a gravity wave spectral model were implemented to validate and compare both methods. The simulation analyses suggest that the WCFI is the viable option among them to study the second-order statistics of the MLT winds that helps to capture the energy of small-scale wind fluctuations. Characterization of the spectral slope at different MLT altitudes has been conducted on the SIMONe 2018, and it provides evidence that gravity waves with periods smaller than seven hours and greater than two hours are dominated by waves with horizontal wavelength significantly larger than 500 km, which might be associated to secondary gravity waves. We believe that the presented methods can help us bridge the observational gap between large and small-scale mesospheric wind fluctuations and also improve the capabilities of SMRs.

Disappearance Voltage Determinations Using a Convergent Beam

1971 ◽  
Vol 29 ◽  
pp. 184-185
Author(s):  
W. L. Bell
Keyword(s):  
Second Order ◽  
Objective Method ◽  
Uniform Thickness ◽  
Rocking Curve ◽  
Crystal Perfection ◽  
Kikuchi Line ◽  
Central Maximum ◽  
Diffraction Patterns ◽  
Convergent Beam ◽  
Beam Technique

Disappearance voltages for second order reflections can be determined experimentally in a variety of ways. The more subjective methods, such as Kikuchi line disappearance and bend contour imaging, involve comparing a series of diffraction patterns or micrographs taken at intervals throughout the disappearance range and selecting that voltage which gives the strongest disappearance effect. The estimated accuracies of these methods are both to within 10 kV, or about 2-4%, of the true disappearance voltage, which is quite sufficient for using these voltages in further calculations. However, it is the necessity of determining this information by comparisons of exposed plates rather than while operating the microscope that detracts from the immediate usefulness of these methods if there is reason to perform experiments at an unknown disappearance voltage.The convergent beam technique for determining the disappearance voltage has been found to be a highly objective method when it is applicable, i.e. when reasonable crystal perfection exists and an area of uniform thickness can be found. The criterion for determining this voltage is that the central maximum disappear from the rocking curve for the second order spot.

Image formation analysis of thick biological specimens using three-dimensional power-spectra of through focus series

1994 ◽  
Vol 52 ◽  
pp. 124-125
Author(s):  
Karen F. Han
Keyword(s):  
Inelastic Scattering ◽  
Imaging Techniques ◽  
Mass Density ◽  
Relative Proportion ◽  
Three Dimensional ◽  
Power Spectra ◽  
Image Formation ◽  
Energy Filtering ◽  
Ewald Sphere ◽  
Nonlinear Imaging

The primary focus in our laboratory is the study of higher order chromatin structure using three dimensional electron microscope tomography. Three dimensional tomography involves the deconstruction of an object by combining multiple projection views of the object at different tilt angles, image intensities are not always accurate representations of the projected object mass density, due to the effects of electron-specimen interactions and microscope lens aberrations. Therefore, an understanding of the mechanism of image formation is important for interpreting the images. The image formation for thick biological specimens has been analyzed by using both energy filtering and Ewald sphere constructions. Surprisingly, there is a significant amount of coherent transfer for our thick specimens. The relative amount of coherent transfer is correlated with the relative proportion of elastically scattered electrons using electron energy loss spectoscopy and imaging techniques.Electron-specimen interactions include single and multiple, elastic and inelastic scattering. Multiple and inelastic scattering events give rise to nonlinear imaging effects which complicates the interpretation of collected images.

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