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Particular Frequency (particular + frequency)

Distribution by Scientific Domains

Engineering	50%

Selected Abstracts

Raman Spectroscopy of Laser-Shocked Nitrobenzene

PROPELLANTS, EXPLOSIVES, PYROTECHNICS, Issue 6 2002
Naoshi Kozu
A technique for in situ Raman spectroscopy of laser-shocked nitrobenzene was developed. Raman spectra of shocked nitrobenzene are obtained up to ,3.5,GPa, and peak shifts at particular frequencies are observed. The shifts are plotted as a function of density and compared with the data under isothermal compression. Both data provide the same results. This indicates that the numbers of peak shifts of nitrobenzene depend solely on material density. [source]

Coupling between dissimilar rectangular dielectric waveguides

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 2 2003
H. Cory
Abstract The coupling between two identically excited, dissimilar rectangular dielectric waveguides, whose axes are parallel, is studied as a function of frequency and of the geometrical and the electrical properties of the structure. It is found that, for a given permittivity ratio, the power transfer between the guides is maximal, but not complete, at some particular frequency. It is also found that, for a given frequency, the power transfer between the guides is complete for the appropriate combination of permittivity and size of the guides, thus the same propagation coefficient is achieved for both. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 136,139, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10996 [source]

LES of a Confined Configuration using Oscillating Inflow Conditions

PROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2003
Michael Düsing
In actual turbulent flow problems, in particular in gas turbine combustion chambers, flows are three dimensional, recirculating and turbulent in confined and complex geometries. Instationarities due to turbulence, combustion instabilities and oscillating inflow conditions require a highly time and spatial resolving procedure. 3D Large Eddy Simulations (LES) are therefore used in this work to study two confined coaxial air jets with oscillating velocity inflow conditions. The influences of the inflow, in particular frequency (f = 0 ÷ 1600 [Hz]) and amplitude, on the velocity are analysed. [source]

Seasonal unit root tests and the role of initial conditions

THE ECONOMETRICS JOURNAL, Issue 3 2008
David I. Harvey
Summary, In the context of regression-based (quarterly) seasonal unit root tests, we examine the impact of initial conditions (one for each quarter) of the process on test power. We investigate the behaviour of the well-known OLS detrended HEGY seasonal unit root tests together with their quasi-differenced (QD) detrended analogues, when the initial conditions are not asymptotically negligible. We show that the asymptotic local power of a test at a given frequency depends on the value of particular linear (frequency specific) combinations of the initial conditions. Consistent with previous findings in the nonseasonal case, the QD detrended test at a given spectral frequency dominates on power for relatively small values of this combination, while the OLS detrended test dominates for larger values. Since, in practice, the seasonal initial conditions are not observed, in order to maintain good power across both small and large initial conditions, we develop tests based on a union of rejections decision rule; rejecting the unit root null at a given frequency (or group of frequencies) if either of the relevant QD and OLS detrended HEGY tests rejects. This procedure is shown to perform well in practice, simultaneously exploiting the superior power of the QD (OLS) detrended HEGY test for small (large) combinations of the initial conditions. Moreover, our procedure is particularly adept in the seasonal context since, by design, it exploits the power advantage of the QD (OLS) detrended HEGY tests at a particular frequency when the relevant initial condition is small (large) without imposing that same method of detrending on tests at other frequencies. [source]