Fourier analysis of two-run-times-two-frame phase shift algorithm

For fan/compressor design, quantifying distortion transfer and generation bladerow by bladerow through a fan/compressor is important to understand the flow physics and predict performance. What is needed are descriptors capable of describing distortion profiles with both high and low distortion content and account for the reshaping of distortion profiles. Four key parameters were identified as desirable to quantitatively capture distortion transfer, generation and effects on performance: distortion magnitude, shape, severity and phase. A set of distortion descriptors based on Fourier analysis are shown to quantitatively capture distortion magnitude, shape and phase change across bladerows. These Fourier descriptors are modal amplitude, total amplitude, and phase shift. When used together, these Fourier descriptors can be used to qualitatively describe any conceivable profile shape for any parameter.

Download Full-text

Phase Shift Measurement of a Retarder Based on Fourier Analysis

Acta Optica Sinica ◽

10.3788/aos20082801.0105 ◽

2008 ◽

Vol 28 (1) ◽

pp. 105-109

Author(s):

赵廷生 Zhao Tingsheng ◽

李国华 Li Guohua ◽

彭捍东 Penh Handong ◽

周文平 Zhou Wenping

Keyword(s):

Phase Shift ◽

Fourier Analysis ◽

Shift Measurement

Download Full-text

The LDE-Type Flare Occurrence (1969-1993)

International Astronomical Union Colloquium ◽

10.1017/s0252921100025458 ◽

1994 ◽

Vol 144 ◽

pp. 279-282

Author(s):

A. Antalová

Keyword(s):

Time Series ◽

Fourier Analysis ◽

Sunspot Cycle ◽

List Type ◽

Type Number ◽

Solar Cycles ◽

Type Iv ◽

Long Duration ◽

Cycle Maximum ◽

Flare Index

AbstractThe occurrence of LDE-type flares in the last three cycles has been investigated. The Fourier analysis spectrum was calculated for the time series of the LDE-type flare occurrence during the 20-th, the 21-st and the rising part of the 22-nd cycle. LDE-type flares (Long Duration Events in SXR) are associated with the interplanetary protons (SEP and STIP as well), energized coronal archs and radio type IV emission. Generally, in all the cycles considered, LDE-type flares mainly originated during a 6-year interval of the respective cycle (2 years before and 4 years after the sunspot cycle maximum). The following significant periodicities were found:• in the 20-th cycle: 1.4, 2.1, 2.9, 4.0, 10.7 and 54.2 of month,• in the 21-st cycle: 1.2, 1.6, 2.8, 4.9, 7.8 and 44.5 of month,• in the 22-nd cycle, till March 1992: 1.4, 1.8, 2.4, 7.2, 8.7, 11.8 and 29.1 of month,• in all interval (1969-1992):a)the longer periodicities: 232.1, 121.1 (the dominant at 10.1 of year), 80.7, 61.9 and 25.6 of month,b)the shorter periodicities: 4.7, 5.0, 6.8, 7.9, 9.1, 15.8 and 20.4 of month.Fourier analysis of the LDE-type flare index (FI) yields significant peaks at 2.3 - 2.9 months and 4.2 - 4.9 months. These short periodicities correspond remarkably in the all three last solar cycles. The larger periodicities are different in respective cycles.

Download Full-text

Object Wave Determination by Single-Sideband Methods

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100071776 ◽

1973 ◽

Vol 31 ◽

pp. 266-267

Author(s):

Kenneth H. Downing ◽

Benjamin M. Siegel

Keyword(s):

Phase Shift ◽

Carbon Films ◽

Object Wave ◽

Electron Wave ◽

Phase Object ◽

Heavy Atoms ◽

Single Sideband ◽

Thin Carbon ◽

Additional Phase Shift ◽

Additional Phase

Under the “weak phase object” approximation, the component of the electron wave scattered by an object is phase shifted by π/2 with respect to the unscattered component. This phase shift has been confirmed for thin carbon films by many experiments dealing with image contrast and the contrast transfer theory. There is also an additional phase shift which is a function of the atomic number of the scattering atom. This shift is negligible for light atoms such as carbon, but becomes significant for heavy atoms as used for stains for biological specimens. The light elements are imaged as phase objects, while those atoms scattering with a larger phase shift may be imaged as amplitude objects. There is a great deal of interest in determining the complete object wave, i.e., both the phase and amplitude components of the electron wave leaving the object.

Download Full-text

A Many-Beam Technique for Enhanced Resolution of Partial Dislocations

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100096485 ◽

1972 ◽

Vol 30 ◽

pp. 646-647

Author(s):

J. M. Oblak ◽

B. H. Kear

Keyword(s):

Phase Shift ◽

Field Method ◽

Dark Field ◽

Bright Field ◽

Field Technique ◽

Weak Beam ◽

Partial Dislocations ◽

Enhanced Resolution ◽

Nickel Base ◽

Beam Technique

The “weak-beam” and systematic many-beam techniques are the currently available methods for resolution of closely spaced dislocations or other inhomogeneities imaged through strain contrast. The former is a dark field technique and image intensities are usually very weak. The latter is a bright field technique, but generally use of a high voltage instrument is required. In what follows a bright field method for obtaining enhanced resolution of partial dislocations at 100 KV accelerating potential will be described.A brief discussion of an application will first be given. A study of intermediate temperature creep processes in commercial nickel-base alloys strengthened by the Ll2 Ni3 Al γ precipitate has suggested that partial dislocations such as those labelled 1 and 2 in Fig. 1(a) are in reality composed of two closely spaced a/6 <112> Shockley partials. Stacking fault contrast, when present, tends to obscure resolution of the partials; thus, conditions for resolution must be chosen such that the phase shift at the fault is 0 or a multiple of 2π.

Download Full-text

Observation of surface morphology by reflection electron holography

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100154652 ◽

1989 ◽

Vol 47 ◽

pp. 536-537

Author(s):

N. Osakabe ◽

J. Endo ◽

T. Matsuda ◽

A. Tonomura

Keyword(s):

Phase Shift ◽

Surface Morphology ◽

High Sensitivity ◽

High Energy ◽

Path Difference ◽

Transmission Mode ◽

Electron Holography ◽

Dynamical Process ◽

High Vertical Resolution ◽

Amplification Technique

Progress in microscopy such as STM and TEM-TED has revealed surface structures in atomic dimension. REM has been used for the observation of surface dynamical process and surface morphology. Recently developed reflection electron holography, which employes REM optics to measure the phase shift of reflected electron, has been proved to be effective for the observation of surface morphology in high vertical resolution ≃ 0.01 Å.The key to the high sensitivity of the method is best shown by comparing the phase shift generation by surface topography with that in transmission mode. Difference in refractive index between vacuum and material Vo/2E≃10-4 owes the phase shift in transmission mode as shownn Fig. 1( a). While geometrical path difference is created in reflection mode( Fig. 1(b) ), which is measured interferometrically using high energy electron beam of wavelength ≃0.01 Å. Together with the phase amplification technique , the vertivcal resolution is expected to be ≤0.01 Å in an ideal case.

Download Full-text