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Harmonic Analysis (harmonic + analysis)

Distribution by Scientific Domains
Engineering37%

Selected Abstracts

A multiproxy climate record from a raised bog in County Fermanagh, Northern Ireland: a critical examination of the link between bog surface wetness and solar variability,

JOURNAL OF QUATERNARY SCIENCE, Issue 7 2007
Graeme T. Swindles
Abstract A proxy climate record from a raised bog in County Fermanagh, Northern Ireland, is presented. The record spans the interval between 2850,cal.,yr,BC and cal. yr AD 1000 and chronological control is achieved through the use of tephrochronology and 14C dating, including a wiggle-match on one section of the record. Palaeoclimatic inferences are based on a combination of a testate amoebae-derived water table reconstruction, peat humification and plant macrofossil analyses. This multiproxy approach enables proxy-specific effects to be identified. Major wet shifts are registered in the proxies at ca. 1510,cal.,yr,BC, 750,cal.,yr,BC and cal. yr AD 470. Smaller magnitude shifts to wetter conditions are also recorded at ca. 380,cal.,yr,BC, 150,cal.,yr,BC, cal. yr AD 180, and cal. yr AD 690. It is hypothesised that the wet shifts are not merely local events as they appear to be linked to wider climate deteriorations in northwest Europe. Harmonic analysis of the proxies illustrates statistically significant periodicities of 580, 423,373, 307 and 265 years that may be related to wider Holocene climate cycles. This paper illustrates how the timing of climate changes registered in peat profiles records can be precisely constrained using tephrochronology to examine possible climatic responses to solar forcing. Relying on interpolated chronologies with considerable dating uncertainty must be avoided if the climatic responses to forcing mechanisms are to be fully understood. Copyright © 2007 John Wiley & Sons, Ltd. [source]

A technique of waveform judgment for harmonic analysis on distribution lines

ELECTRICAL ENGINEERING IN JAPAN, Issue 2 2009
Tadao Aizawa
Abstract Most general-purpose analyzers for harmonic analysis on distribution lines are designed to sample the data of one or two power supply periods. In other words, these analyzers process waveforms and display the results based on the assumption that the analyzed waveforms contain no noninteger components, such as subharmonics and interharmonics. When waveforms containing noninteger components are analyzed with these general-purpose analyzers, the results often indicate components that are not actually present. This paper proposes a technique of waveform judgment and explains its method of application. The technique allows noninteger components to be recognized in analyzed waveforms from the properties of Lissajous figures, and clarifies the types of components and the time windows necessary for appropriate analysis. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 166(2): 32, 38, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20536 [source]

Testing of insulation systems with respect to high-frequency voltage stress

EUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 5 2002
M. Paede
Due to the increasing use of power electronics high frequency working voltages are occurring rather frequently. This means a very high stress for any kind of insulatation. This situation is further aggravated by decreasing dimensions due to miniaturization. Therefore this situation has to be taken into account during dimensioning and testing. Different test methods with respect to withstand and partial discharge inception are described. The necessary test equipment and the dimensioning of the test circuits are specified. The aspects of periodic non-sinusoidal voltages are taken into account by harmonic analysis. [source]

Assessment of regional geomagnetic field modelling methods using a standard data set: spherical cap harmonic analysis

GEOPHYSICAL JOURNAL INTERNATIONAL, Issue 3 2000
Z. Düzgit
Various methods that take account of the potential nature of the field have been proposed for modelling geomagnetic data on a regional scale. Several of these have been applied to a standard data set based on annual mean values from observatories in Europe. Here, we examine some of the properties of spherical cap harmonic analysis when applied to this data set, and compare the quality of fit with that of the other models. It is found that, for this data set, rectangular polynomial analysis provides a compact fit to main field data, but that in most other cases, for both main field and anomaly data, spherical cap harmonic analysis provides the better fit. Although relatively insensitive to chosen cap size, spherical cap harmonic analysis deteriorates more rapidly than the other methods when the number of coefficients is reduced. [source]

Restricted algebras on inverse semigroups I, representation theory

MATHEMATISCHE NACHRICHTEN, Issue 16 2006
Massoud Amini
Abstract The relation between representations and positive definite functions is a key concept in harmonic analysis on topological groups. Recently this relation has been studied on topological groupoids. This is the first in a series of papers in which we have investigated a similar relation on inverse semigroups. We use a new concept of "restricted" representations and study the restricted semigroup algebras and corresponding C *-algebras. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Redshift-space distortions in the PSCz galaxy catalogue

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2001
A.N. Taylor
We apply a spherical harmonic analysis to the Point Source Redshift Survey (PSCz), to compute the real-space galaxy power spectrum and the degree of redshift distortion caused by peculiar velocities. We employ new parameter eigenvector and hierarchical data compression techniques, allowing a much larger number of harmonic modes to be included, and correspondingly smaller error bars. Using 4644 harmonic modes, compressed to 2278, we find that the IRAS redshift-space distortion parameter is and the amplitude of galaxy clustering on a scale of is . Combining these we find the amplitude of mass perturbations is . While this is compatible with results from the cosmic microwave background (CMB), with a small degree of tilt, it disagrees with the amplitude of matter perturbations estimated from the abundance of clusters by a factor of 2, independent of cosmology. A preliminary model fitting analysis combining the CMB with either the PSCz or cluster abundances shows that the cosmological matter density parameter , and the IRAS bias parameter . However, the cluster abundances suggest that and , while the PSCz requires and . Given the physics of galaxy formation is poorly constrained, we conclude that IRAS galaxies and mass are only partially correlated. [source]