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Tsunami Deposit Study Using 2D ERI Technique in Thoothukudi Shoreline, Tamil Nadu, India
A. Antony Ravindran
Online Journal of Earth Sciences , 2012, DOI: 10.3923/ojesci.2011.22.25
Abstract: The aim of the study is about beaches in the study area acts like a sponge but the groundwater along the beach is very dynamic. The flow direction of the beach groundwater is mainly governed by the physical and geological characteristics of the beaches as well as the waves and tide conditions in the sea. The Indian Ocean Tsunami 2004 was affected and sediment deposited in the Thoothukudi shoreline. Through the 2D Electrical Resistivity Imaging (ERI) Technique, an attempt is made to understand the interface zone of the seawater intrusion and the land groundwater along the beach groundwater table and Tsunami deposits in the Thoothukudi shoreline. The profiles survey were carried out using the help of equipment like CRM-500, Multicore cable, electrodes and Res 2DINV Software. The measuring profiles are predetermined as a interval of electrodes in m and cm scales. From four profiles study is to determine the salt water and clay tsunami deposit range of apparent resistivity from 1-5 Ω m-1, sandy 10-100 Ω m-1.
The Case for a 30m Diameter Submillimeter Telescope on the Antarctic Plateau
Antony A. Stark
Physics , 2003,
Abstract: A large single-dish submillimeter-wave telescope equipped with a focal plane array containing ~10^4 bolometers and costing about $120M could locate most protogalaxies in the southern sky within a year of operation.
The AST/RO Survey of the Galactic Center Region
Antony A. Stark
Physics , 2003,
Abstract: AST/RO is a 1.7m diameter submillimeter-wave telescope at the geographic South Pole. A key AST/RO project is the mapping of C I and CO J=4-3 and J=7-6 emission from the inner Milky Way (Martin et al. 2003). These data are released for general use.
Design Considerations for Large Detector Arrays on Submillimeter-wave Telescopes
Antony A. Stark
Physics , 2000, DOI: 10.1117/12.390436
Abstract: The emerging technology of large (~ 10,000 pixel) submillimeter-wave bolometer arrays presents a novel optical design problem---how can such arrays be fed by diffraction-limited telescope optics where the primary mirror is less than 100,000 wavelengths in diameter? Standard Cassegrain designs for radiotelescope optics exhibit focal surface curvature so large that detectors cannot be placed more than 25 beam diameters from the central ray. The problem is worse for Ritchey-Cretien designs, because these minimize coma while increasing field curvature. Classical aberrations, including coma, are usually dominated by diffraction in submillimeter-wave single dish telescopes. The telescope designer must consider (1) diffraction, (2) aberration, (3) curvature of field, (4) cross-polarization, (5) internal reflections, (6) the effect of blockages, (7) means of beam chopping on- and off-source, (8) gravitational and thermal deformations of the primary mirror, (9) the physical mounting of large detector packages, and (10) the effect of gravity and (11) vibration on those detectors. Simultaneous optimization of these considerations in the case of large detector arrays leads to telescopes that differ considerably from standard radiotelescope designs. Offset optics provide flexibility for mounting detectors, while eliminating blockage and internal reflections. Aberrations and cross-polarization can be the same as on-axis designs having the same diameter and focal length. Trade-offs include the complication of primary mirror homology and an increase in overall cost. A dramatic increase in usable field of view can be achieved using shaped optics. Solutions having one to six mirrors will be discussed, including a possible six-mirror design for the proposed South Pole 10m telescope.
AST/RO: A Small Submillimeter Telescope at the South Pole
Antony A. Stark
Physics , 2001,
Abstract: Understanding of star formation in the Universe is advancing through submillimeter-wave observations of the Milky Way and other galaxies. Technological constraints on such observations require a mixture of telescope sizes and observational techniques. For some purposes, small submillimeter-wave telescopes are more sensitive than large ones. The Antarctic Submillimeter Telescope and Remote Observatory (AST/RO) is a small, wide-field instrument located at an excellent observatory site. By observing the Milky Way and Magellanic Clouds at arcminute resolution, it provides a context for interpreting observations of distant galaxies made by large interferometric telescopes. AST/RO also provides hands-on training in submillimeter technology and allows testing of novel detector systems.
Meeting the Optical Requirements of Large Focal-Plane Arrays
Antony A. Stark
Physics , 2003,
Abstract: Technological advances will allow the placement of many Terahertz detectors at the focal plane of a single telescope. For a telescope of a given diameter and wavelength of operation, there is a limit to the number of usable detectors imposed by diffraction and optical aberrations. These effects can be ameliorated through an optical design where the magnification of the telescope's secondary mirror is small and the detector package is therefore located near the secondary mirror. A field mirror can be used to flatten the image, and the focal reducer which matches the detector to the telescope can also provide an image of the aperture for placement of filters and stops. A design concept is presented for the South Pole Telescope which comprises a 10-meter diameter off-axis paraboloidal primary mirror, a Gregorian secondary mirror, a tertiary chopper, dewar widow, Lyot stops, band-pass filter, and space behind the focal plane for cryogenics. The telescope is bilaterally symmetric, and all apertures are unblocked. The field of view is one degree in diameter, so this telescope can feed an array of several tens of thousands of detectors at Terahertz frequencies.
Millimeter and Submillimeter Observations from the South Pole
Antony A. Stark
Physics , 2001, DOI: 10.1063/1.1475608
Abstract: During the past decade, a year-round observatory has been established at the geographic South Pole by the Center for Astrophysical Research in Antarctica (CARA). CARA has fielded several millimeter- and submillimeter-wave instruments: AST/RO (the Antarctic Submillimeter Telescope and Remote Observatory, a 1.7-m telescope outfitted with a variety of receivers at frequencies from 230 GHz to 810 GHz, including PoleSTAR, a heterodyne spectrometer array), Python (a degree-scale CMB telescope), Viper (a 2-m telescope which has been outfitted with SPARO, a submillimeter-wave bolometric array polarimeter, ACBAR, a multi-channel CMB instrument, and Dos Equis, a HEMT polarimeter), and DASI (the Degree-Angular Scale Interferometer). These instruments have obtained significant results in studies of the interstellar medium and observational cosmology, including detections of the 1 degree acoustic peak in the CMB and the Sunyaev-Zel'dovich effect. The South Pole environment is unique among observatory sites for unusually low wind speeds, low absolute humidity, and the consistent clarity of the submillimeter sky. The atmosphere is dessicated by cold: at the South Pole's average annual temperature of -49 C, the partial pressure of saturated water vapor is only 1.2% of what it is at 0 C. The low water vapor levels result in exceptionally low values of sky noise. This is crucial for large-scale observations of faint cosmological sources---for such observations the South Pole is unsurpassed.
Comparative Spectroscopic Studies on Pure, 10 and 50 mol% Glycine Mixed L-Valinium Picrate Crystals  [PDF]
Antony A. Joseph, John David I. Ebenezar, Ramachandra C. Raja
Journal of Minerals and Materials Characterization and Engineering (JMMCE) , 2014, DOI: 10.4236/jmmce.2014.21002
Abstract: Nonlinear optical crystals of pure, 10 and 50 mol% glycine mixed L-valinium picrate have been grown from saturated aqueous solution by slow evaporation method at a temperature of 36℃ using a constant temperature bath of accuracy of ±0.01℃. The synthesized organic optical material has been purified by repeated recrystallization. The cell parameters were calculated using single crystal X-ray diffraction technique which confirmed the crystal system. Optical behavior was examined by UV-Vis-NIR spectrometer in the range from 190 nm to 1100 nm, which revealed the absence of absorption in the entire visible region. Functional groups and modes of vibration were identified by FT-IR spectrometer in the range between 400 cm-1 and 4000 cm-1. The 1H- and 13C NMR spectra of grown crystals were recorded using D2O as solvent on a Bruker 300 MHz (Ultrashield) TM instrument at 23℃ (300 MHz for 1H NMR and 75 MHz for 13C NMR) to confirm the molecular structure. The second harmonic generation conversion efficiency was investigated by Kurtz powder method using Nd: YAG laser as a source to explore the NLO characteristics.
Theoretical Studies of [2,3]-Sigmatropic Rearrangements of Allylic Selenoxides and Selenimides
Craig A. Bayse,Sonia Antony
Molecules , 2009, DOI: 10.3390/molecules14093229
Abstract: Density-functional theory is used to model the endo and exo transition states for [2,3]-sigmatropic rearrangement of allylic aryl-selenoxides and -selenimides. The endo transition state is generally preferred for selenoxides if there is no substitution at the 2 position of the allyl group. Based upon the relative energies of the endo and exo transition states, enantioselectivity of rearrangements is expected to be greatest for molecules with substitutions at the 1- or (E)-3- position of the allyl group. Ortho substitution of a nitro group on the ancillary selenoxide phenyl ring reduces the activation barriers, increases the difference between the endo and exo activation barriers and shifts the equilibrium toward products.
Separation of zeros and a Hermite interpolation based frame algorithm for band limited functions
A. Antony Selvan,R. Radha
Mathematics , 2015,
Abstract: It is shown that if a non-zero function $f\in B_\sigma$ has infinitely many double zeros on the real axis, then there exists at least one pair of consecutive zeros whose distance apart is greater than $\dfrac{\pi}{\sigma}\tau^{1/4}$, $\tau\approx5.0625$. A frame algorithm is provided for reconstructing a function $f\in B_\sigma$ from its nonuniform samples $\{f^{(j)}(x_i):j=0,1,\dots, k-1, i\in\mathbb{Z}\}$ with maximum gap condition, $\sup\limits_i(x_{i+1}-x_i)=\delta<\dfrac{1}{\sigma}c_k^{1/2k}$, where $c_k$ is a Wirtinger-Sobolev constant, using Hermite interpolation.
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