Broad-Band Polarization Characteristics on Transmission and Reflection of Metal Array Structures in Terahertz Region

SUMMARY We tested the capability of seismic noise to monitor the stability conditions of a small rock block that we forced to fail in four following stages. Ambient vibrations were recorded with a broad-band 3C seismometer placed on top of the block and were processed to analyse their spectral and polarization characteristics with diverse algorithms. To analyse the spectral content of the records, we applied the multitaper method while seismic noise polarization features were investigated by means of the singular value decomposition of the Hermitian spectral density matrix. Numerical modelling was found to add limited value because of the uncertainty in estimating correctly spatial and mechanical features of the rock bridges between the block and the rock mass. Nevertheless, a modelling exercise we performed is in agreement with previous post-failure observations according to which unstable rocks may be coupled to the stable rock mass by rock bridges covering only a few per cent of the total surface of the fractures. Our analyses confirm that, when approaching final collapse, there is a trend of the block eigenmodes towards lower frequencies and show that polarized bands become narrower.

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Linear Polarization Properties of Pulsars at 35 & 327 MHz

International Astronomical Union Colloquium ◽

10.1017/s0252921100059595 ◽

2000 ◽

Vol 177 ◽

pp. 245-246

Author(s):

Ashish Asgekar ◽

A. A. Deshpande

Keyword(s):

Fourier Analysis ◽

Radio Telescope ◽

Faraday Rotation ◽

Linear Polarization ◽

Broad Band ◽

Spectral Domain ◽

Spectral Modulation ◽

Polarization Characteristics

Faraday Rotation of the plane of polarization of broad-band signals, during propagation through the intervening medium, manifests as quasi-sinusoidal spectral modulations when observed with a telescope sensitive to a single linear polarization. Such a modulation can be exploited to study linear polarization characteristics of pulsars (Suleimanova, Volodin, & Shitov, 1988; Smirnova & Boriakoff 1997, Ramkumar & Deshpande 1999 (RD99)). We have used our data on a few bright pulsars at 35 MHz (Asgekar & Deshpande 1999, elsewhere in this volume) and data obtained at 327 MHz using Ooty Radio Telescope (see RD99 for details), to study average linear polarization properties using this technique. The data obtained over 256 frequency channels were re-sampled in the spectral domain to make the Faraday modulation appear periodic, and then a simple Fourier analysis was performed to look for (ACF) features associated with the possible spectral modulation (see RD99 for the analysis details).

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Chapter 19 Polarization characteristics of metallic photonic crystals in terahertz region

Nanophotonics - Integrating Photochemistry, Optics and Nano/Bio Materials Studies, Proceedings of the 1st International Nanophotonics Symposium Handai - Handai Nanophotonics ◽

10.1016/s1574-0641(04)80024-x ◽

2004 ◽

pp. 313-330 ◽

Cited By ~ 1

Author(s):

F. Miyamaru ◽

M. Hangyo

Keyword(s):

Photonic Crystals ◽

Terahertz Region ◽

Metallic Photonic Crystals ◽

Polarization Characteristics

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Chronic Laser Exposure Effects on Rabbit Retina

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100093523 ◽

1972 ◽

Vol 30 ◽

pp. 54-55

Author(s):

Burton B. Silver ◽

Theodore Lawwill

Keyword(s):

Laser Irradiation ◽

Laser Light ◽

Broad Band ◽

Argon Laser ◽

Atropine Sulfate ◽

Ultrastructural Changes ◽

Laser Exposure ◽

Rabbit Retina ◽

Histological Changes ◽

Threshold Doses

Dutch-belted 1 to 2.5 kg anesthetized rabbits were exposed to either xenon or argon laser light administered in a broad band, designed to cover large areas of the retina. For laser exposure, the pupil was dilated with atropine sulfate 1% and pheny lephrine 10%. All of the laser generated power was within a band centered at 5145.0 Anstroms. Established threshold for 4 hour exposures to laser irradiation are in the order of 25-35 microwatts/cm2. Animals examined for ultrastructural changes received 4 hour threshold doses. These animals exhibited ERG, opthalmascopic, and histological changes consistent with threshold damage.One month following exposure the rabbits were killed with pentobarbitol. The eyes were immediately enucleated and dissected while bathed in 3% phosphate buffered gluteraldehyde.

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Atomic-level imaging of the surface structure of Ag2O

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100113160 ◽

1984 ◽

Vol 42 ◽

pp. 656-657

Author(s):

William Krakow

Keyword(s):

High Vacuum ◽

Atomic Level ◽

Ultra High Vacuum ◽

Research Groups ◽

Resolution Electron ◽

Surface Reconstructions ◽

Order Of Magnitude ◽

High Resolution Electron Microscope ◽

Saturated Structure ◽

Transmission And Reflection

In recent years electron microscopy has been used to image surfaces in both the transmission and reflection modes by many research groups. Some of this work has been performed under ultra high vacuum conditions (UHV) and apparent surface reconstructions observed. The level of resolution generally has been at least an order of magnitude worse than is necessary to visualize atoms directly and therefore the detailed atomic rearrangements of the surface are not known. The present author has achieved atomic level resolution under normal vacuum conditions of various Au surfaces. Unfortunately these samples were exposed to atmosphere and could not be cleaned in a standard high resolution electron microscope. The result obtained surfaces which were impurity stabilized and reveal the bulk lattice (1x1) type surface structures also encountered by other surface physics techniques under impure or overlayer contaminant conditions. It was therefore decided to study a system where exposure to air was unimportant by using a oxygen saturated structure, Ag2O, and seeking to find surface reconstructions, which will now be described.

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Real-ear Masking Calibration for Portable Pure-Tone Audiometers

Language Speech and Hearing Services in Schools ◽

10.1044/0161-1461.1504.289 ◽

1984 ◽

Vol 15 (4) ◽

pp. 289-294

Author(s):

Martin S. Robinette ◽

Robert H. Brey

Keyword(s):

Pure Tone ◽

Broad Band ◽

Resistive Network ◽

Many Instruments

A transformer mixing network is described which allows the calibration of broad-band masking for portable audiometers that lack a built-in mixing network. For many instruments the transformer network is preferable to the resistive network previously published.

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