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PHOTOTHERMAL DEFLECTION SPECTROSCOPY AND DETECTION

Description: The theory for a sensitive spectroscopy based on the photothermal deflection of a laser beam is developed. We consider cw and pulsed cases of both transverse and collinear photothermal deflection spectroscopy for solids, liquids, gases, and thin films. The predictions of the theory are experimentally verified, its implications for imaging and microscopy are given, and the sources of noise are analyzed. The sensitivity and versatility of photothermal deflection spectroscopy are compared with thermal lensing and photoacoustic spectroscopy.
Date: September 1, 1980
Creator: Jackson, W.; Amer, Nabil M.; Boccara, A. C. & Fournier, D.
Partner: UNT Libraries Government Documents Department

THERMAL RADIATION OF SPHERICAL AND CYLINDRICAL SOOT PARTICLES

Description: The effect of soot shape on soot radiation from flame and smoke is considered in the present study. It is realized that soot particles generally conglomerate into different shapes. while the limiting bounds are being either spherical or long chains. By modellirig the long chains as infinite cylinders, it is shown that the radiation extinction characteristics of the spherical and cylindrical soot are distinctly different, with that of the spherical particles exhibiting a cut-off wavelength phenomenon. Emissivity from a cloud of cylindrical particles is always higher than that of the spheres due to their higher extinction coefficients. Moreover, the effect of soot shape onradiation is more pronounced at typical smoke temperatures (300°K) than at flame temperatures. A simple experimental method is also proposed for determining the amount of cylindrical and spherical particles in a cloud.
Date: October 1, 1980
Creator: Lee, S. C. & Tien, C. L.
Partner: UNT Libraries Government Documents Department

STRONG COUPLING EXPANSIONS FOR NON-INTEGRABLE HAMILTONIAN SYSTEMS

Description: We present a method for studying nonintegrable Hamiltonian systems H(I,{theta})=H{sub 0}(I)+kH{sub 1}(I,{theta}) (I,{theta} are action-angle variables) in the reg1me of large k. Our central tool is the conditional probability P(I,{theta},t|I{sub 0},{theta}{sub 0},t{sub 0}) that the system is at I,{theta} at time t given that it resided at I{sub 0},{theta}{sub 0} at t{sub 0}. An integral representation is given for this conditional probability. By discretizing the Hamiltonian equations of motion in small time steps, {epsilon}, we arrive at a phase volume preserving mapping which replaces the actual flow. When the motion on the energy surface E=H(I,{theta}) is bounded we are able to evaluate physical quantities of interest for large k and fixed {epsilon}. We also discuss the representation of P(I,{theta},t|I{sub 0},{theta}{sub 0},t{sub 0}) when an external random forcing is added in order to smooth the singular functions associated with the deterministic flow. Explicit calculations of a "diffusion" coefficient are given for a non-integrable system with two degrees of freedom. The limit {epsilon}{approaches}0 , which returns us to the actual flow, is subtle and is discussed.
Date: December 1, 1980
Creator: Abarbanel, Henry D.I. & Crawford, John David
Partner: UNT Libraries Government Documents Department

DIFFUSION IN VERY CHAOTIC HAMILTONIAN SYSTEMS

Description: We study nonintegrable Hamiltonian dynamics: H(I,{theta}}) = H{sub 0}(I)+kH{sub 1}(I,{theta}) for large k; that is, far from integrability. An integral representation is given for the conditional probability P(I,{theta},t|I{sub 0},{theta}{sub 0},t{sub 0}) that the system is at I,{theta} at t, given it was at I{sub 0},{theta}{sub 0} at t{sub 0}. By discretizing time into steps of size {epsilon}, we show how to evatuate physical observables for large k, fixed {epsilon}. An explicit calculation of a diffusion coefficient in a two degree of freedom problem is reported. Passage to {epsilon} = 0, the original Hamiltonian flow, discussed.
Date: December 1, 1980
Creator: Abarbanel, Henry D.I. & Crawford, John David
Partner: UNT Libraries Government Documents Department

Source fabrication and lifetime for Li+ ion beams extracted from alumino-silicate sources

Description: A space-charge-limited beam with current densities (J) exceeding 1 mA/cm{sup 2} have been measured from lithium alumino-silicate ion sources at a temperature of #24;~1275#14;{degrees} C. At higher extraction voltages, the source appears to become emission limited with J #21;{>=} 1.5 mA/cm{sup 2}, and J increases weakly with the applied voltage. A 6.35 mm diameter source with an alumino-silicate coating, {<=}#20;0.25 mm thick, has a measured lifetime of ~#24;40 hours at ~#24;1275#14;{degrees} C, when pulsed at 0.05 Hz and with pulse length of #24;~6 μs each. At this rate, the source lifetime was independent of the actual beam charge extracted due to the loss of neutral atoms at high temperature. The source lifetime increases with the amount of alumino-silicate coated on the emitting surface, and may also be further extended if the temperature is reduced between pulses.
Date: March 5, 2012
Creator: Roy, Prabir K.; Greenway, Wayne G. & Kwan, Joe W
Partner: UNT Libraries Government Documents Department

Source fabrication and lifetime for Li{sup +} ion beams extracted from alumino-silicate sources

Description: A space-charge-limited beam with current densities (J) exceeding 1 mA/cm{sup 2} have been measured from lithium alumino-silicate ion sources at a temperature of ∼1275{degrees}C. At higher extraction voltages, the source appears to become emission limited with J ≥ 1.5 mA/cm{sup 2}, and J increases weakly with the applied voltage. A source with an alumino-silicate coating 6.35 mm in diameter and ≤0.25 mm thick, has a lifetime of ∼40 hours at ∼1275{degrees}C, when pulsed at 0.05 Hz and with pulse length of ∼6 μs each. At this rate, the source lifetime was independent of the actual beam charge extracted due to the loss of neutral atoms at high temperature. Furthermore, the source lifetime increases with the amount of alumino-silicate coated on the emitting surface, and may also be extended if the temperature is reduced between pulses.
Date: February 10, 2012
Creator: Greenway, W. G. & Kwan, J. W.
Partner: UNT Libraries Government Documents Department

A compact neutron generator using a field ionization source

Description: Field ionization as a means to create ions for compact and rugged neutron sources is pursued. Arrays of carbon nano-#12;bers promise the high #12;eld-enhancement factors required for efficient field ionization. We report on the fabrication of arrays of #12;field emitters with a density up to 10{sup 6} tips/cm{sup 2} and measure their performance characteristics using electron field emission. The critical issue of uniformity is discussed, as are efforts towards coating the nano-fibers to enhance their lifetime and surface properties.
Date: October 31, 2011
Creator: Persaud, Arun; Waldmann, Ole; Kapadia, Rehan; Takei, Kuniharu; Javey, Ali & Schenkel, Thomas
Partner: UNT Libraries Government Documents Department

THE HOT CHOCOLATE EFFECT

Description: The "hot chocolate effect" was investigated quantitatively, using water. If a tall glass cylinder is filled nearly completely with water and tapped on the bottom with a softened mallet one can detect the lowest longitudinal mode of the water column, for which the height of the water column is one quarter wavelength. If the cylinder is rapidly filled with hot tap water containing dissolved air the pitch of that mode may descend by nearly three octaves during the first few seconds as the air comes out of solution and forms bubbles. Then the pitch gradually rises as the bubbles float to the top. A simple theoretical expression for the pitch ratio is derived and compared with experiment. The agreement is good to within the ten percent accuracy of the experiments.
Date: December 1, 1980
Creator: Crawford, Frank S.
Partner: UNT Libraries Government Documents Department

LOCALITY AND REALITY

Description: Einstein's principle that no signal travels faster than suggests that observations in one spacetime region should not depend on whether or not a radioactive decay is detected in a spacelike separated region. This locality property is incompatible with the predictions of quantum theory, and this incompatibility holds independently of the questions of realism, objective reality, and hidden variables. It holds both in the pragmatic quantum theory of Bohr and in realistic frameworks. It is shown here to hold in a completed realistic quantum theory that reconciles Einstein's demand for a description of reality itself with Bohr's contention that quantum theory is complete. This completed realistic quantum theory has no hidden variables, and no objective reality in which observable attributes can become definite independently of observers. The, theory is described in some detail, with particular attention to those aspects related to the question of locality. This completed realistic quantum theory is in principle more comprehensive than Bohr.' s pragmatic quantum theory because it is not limited in principle by the requirement that the observed system be physically separated from the observing one. Applications are discussed.
Date: February 1, 1980
Creator: Stapp, Henry P.
Partner: UNT Libraries Government Documents Department

Equation of State of Classical Systems of Charged Particles

Description: Recent developments in the classical theory of fully ionized gases and strong electrolyte solutions are reviewed, and are used to discuss the equation of state at high temperature and low densities. The pressure is calculated using the ring-integral approximation, and quantitative estimates of higher correction terms are given. The effect of short-range repulsive forces is shown by comparing the results with two kinds of potential functions: hard spheres of diameter a, and "soft" spheres for which the short-range potential cancels the Coulomb potential at the origin, and decreases exponentially with distance. It is found that the use of either type of potential extends the range of validity of the ring integral approximation to considerably higher densities and lower temperatures. Since there is little difference in the results for the hard spheres and the soft spheres in this range, the latter is investigated more extensively since it is more easily handled by analytical methods. The expressions derived for the free energy of a system of charged particles can also be used in ionization equilibrium calculations, and the effect of electrostatic interactions on the equilibrium concentrations of various kinds of ions is indicated.
Date: April 26, 1962
Creator: Brush, S. G.; DeWitt, H. E. & Trulio, J. G.
Partner: UNT Libraries Government Documents Department

RECIPROCAL PASSIVE MODE-LOCKING OF A RHODAMINE 6G DYE LASER AND THE Ar+ PUMP LASER

Description: A rhodamine 6G dye laser, internally pumped within the extended cavity of an Ar{sup +} ion laser, is mode-locked when its cavity length is matched to half that of the pump laser: the 5145 {Angstrom} argon laser line is passively mode-locked by the combination of the saturable absorption and the lasing action of the dye which is in turn synchronously pumped and mode-locked. Tunable (5650 {Angstrom} to 5950 {Angstrom}) ~10 pSec pulses are generated, and the average output power is ~ 80 mW.
Date: October 1, 1980
Creator: Yasa, Zafer A. & Amer, Nabil M.
Partner: UNT Libraries Government Documents Department

Exact Solution (Within a Double Zeta Basis Set) of Schrodinger's Electronic Equation for Water

Description: Using recently developed theoretical techniques, it has been possible to achieve an exact variational solution of Schrodinger's Equation within a modest basis set of one-electron functions. The full configuration interaction for this system included a total of 256,473 {sup 1}A{sub 1} spin-and space-adapted configurations. Comparison with many-body perturbation theory proves to be quite interesting.
Date: September 1, 1980
Creator: Saxe, Paul; Schaefer, Henry F., III & Handy, Nicholas C.
Partner: UNT Libraries Government Documents Department

Surface Enhanced Second Harmonic Generation

Description: Second harmonic generation at a silver-air interface was enhanced due to surface roughness by a factor of 10{sup 4}. The local field enhancement is believed to be responsible for the effect. An unusually broad luminescence background extending far beyond the antiStokes side of the second harmonic was also observed.
Date: September 1, 1980
Creator: Chen, C. K.; de Castro, A. R. B. & Shen, Y. R.
Partner: UNT Libraries Government Documents Department

Design and Diffractive Modeling on a Single Lens Shaper

Description: This paper introduces a single lens laser beam shaper which is capable of redistributing a beam with a Gaussian profile to a super-Gaussian profile. Both geometrical and diffractive optical modelings are performed on a typical single lens shaper that shows significant reduction of destructive effects on the beam uniformity over those with sharp-edges.
Date: May 1, 2009
Creator: C. Liu, S. Zhang
Partner: UNT Libraries Government Documents Department

A new moving frame to extract scattering phases in lattice QCD

Description: We present a derivation of the finite-size formulae in a moving frame with total momentum P=(2pi/L)(e_1+e_2). These formulae allow us to calculate the S-wave and P-wave scattering phases at more energies with a fixed lattice size and thus help us to determine the resonance parameters precisely.
Date: April 1, 2011
Creator: Dru Renner,Xu Feng,Karl Jansen
Partner: UNT Libraries Government Documents Department

(Anti)symmetric matter and superpotentials from IIBorientifolds

Description: We study the IIB engineering of N=1 gauge theories with unitary gauge group and matter in the adjoint and (anti)symmetric representations. We show that such theories can be obtained as Z{sub 2} orientifolds of certain Calabi-Yau A{sub 2} fibrations, and discuss the explicit T-duality transformation to an orientifolded Hanany-Witten construction. The low energy dynamics is described by a geometric transition of the orientifolded background. Unlike previously studied cases, we show that the orientifold 5-''plane'' survives the transition, thus bringing a nontrivial contribution to the effective superpotential. We extract this contribution by using matrix model results and compare with geometric data. A Higgs branch of our models recovers the engineering of SO/Sp theories with adjoint matter through an O5-''plane'' T-dual to an O6-plane. We show that the superpotential agrees with that produced by engineering through an O5-''plane'' dual to an O4-plane, even though the orientifold of this second construction is replaced by fluxes after the transition.
Date: October 9, 2003
Creator: Landsteiner, Karl; Lazaroiu, Calin & Tatar, Radu
Partner: UNT Libraries Government Documents Department

2012 MULTIPHOTON PROCESSES GRC, JUNE 3-8, 2012

Description: The sessions will focus on:  Attosecond science;  Strong-field processes in molecules and solids;  Generation of harmonics and attosecond pulses;  Free-electron laser experiments and theory;  Ultrafast imaging;  Applications of very high intensity lasers;  Propagation of intense laser fields.
Date: March 8, 2012
Creator: Walker, Barry
Partner: UNT Libraries Government Documents Department

2012 PLASMONICS GORDON RESEARCH CONFERENCE AND GORDON RESEARCH SEMINAR, JUNE 10-15, 2012

Description: The focus of this meeting is on recent advances in science and engineering of plasmonic optics and its applications in the design of novel devices and components. The impacts of plasmonic phenomena on other disciplines such as chemistry, biology, medicine and engineering will also be discussed.
Date: June 15, 2012
Creator: Engheta, Nader
Partner: UNT Libraries Government Documents Department