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Sample records for 3-body distorted wave

  1. CMB μ distortion from primordial gravitational waves

    SciTech Connect

    Ota, Atsuhisa; Yamaguchi, Masahide; Takahashi, Tomo; Tashiro, Hiroyuki E-mail: tomot@cc.saga-u.ac.jp E-mail: gucci@phys.titech.ac.jp

    2014-10-01

    We propose a new mechanism of generating the μ distortion in cosmic microwave background (CMB) originated from primordial gravitational waves. Such μ distortion is generated by the damping of the temperature anisotropies through the Thomson scattering, even on scales larger than that of Silk damping. This mechanism is in sharp contrast with that from the primordial curvature (scalar) perturbations, in which the temperature anisotropies mainly decay by Silk damping effects. We estimate the size of the μ distortion from the new mechanism, which can be used to constrain the amplitude of primordial gravitational waves on smaller scales independently from the CMB anisotropies, giving more wide-range constraint on their spectral index by combining the amplitude from the CMB anisotropies.

  2. Phase-Conjugate Mirror Removes Wave-Front Distortions

    NASA Technical Reports Server (NTRS)

    Seery, Bernard D.; Zukowski, Barbara J. K.; Saif, Babak

    1996-01-01

    Phase-conjugate mirrors remove distortions or aberrations from wave fronts in laser beams. With help of mirrors, one obtains high-power laser beams of diffraction-limited quality. Potential applications include multistage laser systems.

  3. Optical distortion in the field of a lithotripter shock wave

    NASA Astrophysics Data System (ADS)

    Carnell, M. T.; Emmony, D. C.

    1995-10-01

    The schlieren observation of cavitation phenomena produced in the tail of a lithotripter shock wave has indicated the presence of some interesting features. The images produced appear to indicate that cavitation transients in the field of a shock wave propagate nonsymmetrically; this is not the case. The apparent lack of symmetry exhibited by the primary cavitation transients is due to a complex optical lensing effect, which is brought about by the change in refractive index associated with the pressure profile of the shock wave. Objects seen through or immersed in the shock-wave field of an electromagnetic acoustic transducer, such as cavitation, appear highly distorted because of the strong positive and negative lensing effects of the compression and rarefaction cycles of the shock wave. A modification of the schlieren technique called the scale method has been used to model the distortion introduced by the shock wave and consequently explain the cavitation distortion. The technique has also been used to quantitatively analyze and partially reconstruct the lithotripter shock wave. The combination of schlieren and scale imaging gives more information about the refractive index field and therefore the shock-wave structure itself.

  4. Distortion correction by phase conjugation using four-wave mixing

    NASA Astrophysics Data System (ADS)

    Klingenberg, Hans H.; Hall, Thomas; Riede, Wolfgang

    1996-04-01

    Pulsed energy deposition into a high power carbon-dioxide gas discharge as well as high pump energy deposition into a solid-state laser material results in a distortion of the transverse mode profile of the laser beam. In the first case the transverse field distribution is influenced by the laser induced medium perturbation and shock waves due to the inhomogeneous energy deposition into the amplifying medium. For the second case the known thermal lensing problems occur in optically pumped systems, flashlamp- and diode-pumped, respectively, under various pump power levels. The technique successfully applied in both cases for correcting the distorted phases is by means of phase conjugation. Through numerical simulations using the Fresnel-Kirchhoff diffraction theory by including the relevant beam distorting effects for the individual laser a restoration of the beam quality was found when a phase conjugate mirror (PM) was installed. These findings agree well with experimental results.

  5. A distorted wave impulse approach for atom--diatom collisions

    SciTech Connect

    Dothe, H. ); Sharma, R.D. , Hanscom Air Force Base, Massachusetts 01731-5000 )

    1993-03-15

    A formalism is derived to include the effects of the long-range attractive part of the interaction potential in the calculation of atom--diatom collision cross sections using the impulse approach (IA). These calculations have, until now, assumed the atom--diatom potential given by a sum of two atom--atom interactions, consequently yielding a poor representation of the long-range attractive part. In the distorted wave impulse approach (DWIA) the long-range attractive part, located at the center of mass of the diatom, is a spherically symmetric potential which distorts'' the incoming and outgoing waves. The DWIA formalism is used to calculate differential cross sections for the rotationally inelastic process Li[sup +]+N[sub 2]([ital v]=0, [ital j]=2)[r arrow]Li[sup +]+N[sub 2]([ital v][prime]=0, [ital j][prime]), as a function of the final rotational level [ital j][prime], at a relative kinetic energy of 4.23 eV and center of mass scattering angles of 49.2[degree] and 37.1[degree]. It is shown that differential cross sections calculated using the DWIA formalism are in much better agreement with experimentally measured ones than IA differential cross sections using atom--atom interactions expressed by either hard-core, or exponential repulsive, functions.

  6. CMB distortions from damping of acoustic waves produced by cosmic strings

    SciTech Connect

    Tashiro, Hiroyuki; Sabancilar, Eray; Vachaspati, Tanmay E-mail: Eray.Sabancilar@asu.edu

    2013-08-01

    We study diffusion damping of acoustic waves in the photon-baryon fluid due to cosmic strings, and calculate the induced μ- and y-type spectral distortions of the cosmic microwave background. For cosmic strings with tension within current bounds, their contribution to the spectral distortions is subdominant compared to the distortions from primordial density perturbations.

  7. A restoration model of distorted electron density in wave-cutoff probe measurement

    SciTech Connect

    Jun, Hyun-Su Lee, Yun-Seong

    2014-02-15

    This study investigates the problem of electron density distortion and how the density can be restored in a wave-cutoff probe. Despite recent plasma diagnostics research using a wave-cutoff probe, the problem of electron density distortion caused by plasma conditions has not been resolved. Experimental results indicate that electron density measured using the wave-cutoff method is highly susceptible to variations in the probe tip gap. This electron density distortion is caused by the bulk plasma disturbance between probe tips, and it must be removed for calculating the absolute electron density. To do this, a detailed analytic model was developed using the power balance equation near probe tips. This model demonstrates the characteristics of plasma distortion in wave-cutoff probe measurement and successfully restored the absolute value of electron density with varying probe tip gaps.

  8. Digital Distortion Caused by Traveling- Wave-Tube Amplifiers Simulated

    NASA Technical Reports Server (NTRS)

    Kory, Carol L.; Andro, Monty

    2002-01-01

    Future NASA missions demand increased data rates in satellite communications for near real-time transmission of large volumes of remote data. Increased data rates necessitate higher order digital modulation schemes and larger system bandwidth, which place stricter requirements on the allowable distortion caused by the high-power amplifier, or the traveling-wave-tube amplifier (TWTA). In particular, intersymbol interference caused by the TWTA becomes a major consideration for accurate data detection at the receiver. Experimentally investigating the effects of the physical TWTA on intersymbol interference would be prohibitively expensive, as it would require manufacturing numerous amplifiers in addition to acquiring the required digital hardware. Thus, an accurate computational model is essential to predict the effects of the TWTA on system-level performance when a communication system is being designed with adequate digital integrity for high data rates. A fully three-dimensional, time-dependent, TWT interaction model has been developed using the electromagnetic particle-in-cell code MAFIA (Solution of Maxwell's equations by the Finite-Integration-Algorithm). It comprehensively takes into account the effects of frequency-dependent AM (amplitude modulation)/AM and AM/PM (phase modulation) conversion, gain and phase ripple due to reflections, drive-induced oscillations, harmonic generation, intermodulation products, and backward waves. This physics-based TWT model can be used to give a direct description of the effects of the nonlinear TWT on the operational signal as a function of the physical device. Users can define arbitrary excitation functions so that higher order modulated digital signals can be used as input and that computations can directly correlate intersymbol interference with TWT parameters. Standard practice involves using communication-system-level software packages, such as SPW, to predict if adequate signal detection will be achieved. These models

  9. Attenuation and distortion of compression waves propagating in very long tube

    NASA Astrophysics Data System (ADS)

    Nakamura, Shinya; Sasa, Daisuke; Aoki, Toshiyuki

    2011-03-01

    A lot of phenomena related to propagating various waves are seen when the high-speed train goes through the tunnel, the gas pipeline is broken due to an accident or the air brake of the wagon operates. For instance, a compression wave generated ahead of a high-speed train entering a tunnel propagates to the tunnel exit and spouts as a micro pressure wave, which causes an exploding sound. In order to estimate the magnitude correctly, the mechanism of the attenuation and distortion of a compression wave propagating along a very long tunnel must be understood and the experimental information on these phenomena is required. An experimental investigation is carried out to clarify the attenuation and distortion of the propagating compression wave in a very long tube. Experimental results show that the strength of a compression wave decreases with distance. The attenuation and distortion of compression waves are affected by the initial waveform of the compression wave and by the unsteady boundary layer induced by the propagating wave. The shape of a compression wave becomes different with the propagating distance; that is, a shock wave appears just head of a wavefront and an overshoot on pressure distribution is observed behind a shock wave due to the transition of the unsteady boundary layer.

  10. A light-curve distortion-wave analysis of eight RS Canum Venaticorum systems

    NASA Astrophysics Data System (ADS)

    Caton, D. B.

    1986-01-01

    A program of differential U,B,V photometry of 14 RS CVn systems carried out at Rosemary Hill Observatory in 1978 - 1981 is described, and an analysis of the light curves for the characteristic distortion wave for eight of the systems is presented. The V light curves of the systems are shown. Significant waves were observed in RS CVn, RZ Eri, and RW UMa. No significant waves were found in UX Com, GK Hya, AR Lac, LX Per, or TY Pyx. Unusual light curve distortions were observed in UX Com and AR Lac.

  11. Computation of the temperature distortion in the stack of a standing-wave thermoacoustic refrigerator

    NASA Astrophysics Data System (ADS)

    Marx, David; Blanc-Benon, Philippe

    2005-11-01

    The numerical computation of the flow and heat transfer in the vicinity of a stack plate in a standing wave refrigerator is performed. Temperature distortion is observed, which appears only in the stack region, even if the acoustic standing wave outside the stack is itself sinusoidal. The distortion takes place above the whole plate surface when the length of the plate is equal to or shorter than four times the particle displacement. This condition may occur at high drive ratios and is favored by plate positions close to the velocity antinode. The thermal distortion decreases the thermoacoustic heat pumping along the plate. At high drive ratios, if the length of the plate is not large enough, the thermal distortion can typically explain a difference of about 10% between the calculated heat flux and the heat flux predicted using linear theory.

  12. Observation of Wave Packet Distortion during a Negative-Group-Velocity Transmission

    PubMed Central

    Ye, Dexin; Salamin, Yannick; Huangfu, Jiangtao; Qiao, Shan; Zheng, Guoan; Ran, Lixin

    2015-01-01

    In Physics, causality is a fundamental postulation arising from the second law of thermodynamics. It states that, the cause of an event precedes its effect. In the context of Electromagnetics, the relativistic causality limits the upper bound of the velocity of information, which is carried by electromagnetic wave packets, to the speed of light in free space (c). In anomalously dispersive media (ADM), it has been shown that, wave packets appear to propagate with a superluminal or even negative group velocity. However, Sommerfeld and Brillouin pointed out that the “front” of such wave packets, known as the initial point of the Sommerfeld precursor, always travels at c. In this work, we investigate the negative-group-velocity transmission of half-sine wave packets. We experimentally observe the wave front and the distortion of modulated wave packets propagating with a negative group velocity in a passive artificial ADM in microwave regime. Different from previous literature on the propagation of superluminal Gaussian packets, strongly distorted sinusoidal packets with non-superluminal wave fronts were observed. This result agrees with Brillouin's assertion, i.e., the severe distortion of seemingly superluminal wave packets makes the definition of group velocity physically meaningless in the anomalously dispersive region. PMID:25631746

  13. Observation of wave packet distortion during a negative-group-velocity transmission.

    PubMed

    Ye, Dexin; Salamin, Yannick; Huangfu, Jiangtao; Qiao, Shan; Zheng, Guoan; Ran, Lixin

    2015-01-01

    In Physics, causality is a fundamental postulation arising from the second law of thermodynamics. It states that, the cause of an event precedes its effect. In the context of Electromagnetics, the relativistic causality limits the upper bound of the velocity of information, which is carried by electromagnetic wave packets, to the speed of light in free space (c). In anomalously dispersive media (ADM), it has been shown that, wave packets appear to propagate with a superluminal or even negative group velocity. However, Sommerfeld and Brillouin pointed out that the "front" of such wave packets, known as the initial point of the Sommerfeld precursor, always travels at c. In this work, we investigate the negative-group-velocity transmission of half-sine wave packets. We experimentally observe the wave front and the distortion of modulated wave packets propagating with a negative group velocity in a passive artificial ADM in microwave regime. Different from previous literature on the propagation of superluminal Gaussian packets, strongly distorted sinusoidal packets with non-superluminal wave fronts were observed. This result agrees with Brillouin's assertion, i.e., the severe distortion of seemingly superluminal wave packets makes the definition of group velocity physically meaningless in the anomalously dispersive region. PMID:25631746

  14. An algorithm for the calculation of the partial wave expansion of the Coulomb-distorted plane wave

    NASA Astrophysics Data System (ADS)

    Hornyak, I.; Kruppa, A. T.

    2015-12-01

    The partial wave expansion of the Coulomb-distorted plane wave is determined by the help of the complex generalized hypergeometric function 2F2(a , a ; a + l + 1 , a - l ; z) . An algorithm for the calculation of 2F2(a , a ; a + l + 1 , a - l ; z) is created and it is implemented as a FORTRAN-90 code. The code is fast and its accuracy is 14 significant decimal digits.

  15. Tilt Modulation Distortions in Wave Topography Measured by a Scanning Radar Altimeter

    NASA Technical Reports Server (NTRS)

    Walsh, Edward J.

    1999-01-01

    Work continues on estimating tilt modulation distortions in the wave topography measured by a scanning radar altimeter. To quantify this effect, a two-dimensional simulation has been performed in the cross-track plane only which assumed that sinusoidal waves of constant wavelength propagate in the cross-track direction (and are infinitely long-crested in the along-track direction). The initial results reported earlier for a Gaussian surface scattering model indicated that when the highest reasonable value of mss is used in the simulation (the Plant limit of 0.08), the nadir values of the ratio of the apparent to actual wave height are the same as for the omnidirectional scattering case. But as the off-nadir angle increased, the apparent wave height increased and became larger than the actual wave height by about 10 degrees off-nadir. And the shorter the wavelength, the larger the apparent wave height increase. This represented a systematic over-estimate of the wave amplitude for waves propagating in the cross-track direction. For lower values of mss the situation worsened. The simulation has been improved by incorporating actual variations of backscattered power with incidence angle measured by the SRA instead of the Gaussian model. The resulting distortion was about half that originally reported. The 3-dimensional simulation to model waves propagating at various azimuthal angles relative to the cross-track plane is still in progress. The results of this model will be verified by comparing them with Scanning Radar Altimeter (SRA) data and optimum correction procedures will be developed. An assessment of the improved 2-dimensional model indicates that the distortion will generally be small in the data taken during the Southern Ocean Waves Experiment (SOWEX) presently be analyzed. But tilt modulation effects are of great concern for SRA data collected during the 1998 hurricane season since the minimum aircraft altitude was 1.5 km and it frequently flew higher. For a

  16. Amplification of Reynolds number dependent processes by wave distortion. [liquid fuel combustor stability

    NASA Technical Reports Server (NTRS)

    Ventrice, M.

    1979-01-01

    The amplification of a Reynolds number dependent process by wave distortion and the possibility of applying the results to other similar Reynolds number dependent processes were investigated. The process investigated was that associated with the operation of a constant-temperature hot-wire anemometer. The application of vaporization limited combustion, the type of combustion typically associated with liquid propellant rocket engines, was studied. A series of experiments were carried out to determine the effect of wave distortion on a Reynolds number dependent process and to establish the analogy between the anemometer process and the combustion process. Parametric trends, behavior common to different chamber geometries, and stability boundaries were identified. The results indicate a high degree of similarity between the two processes and the possibility of using the anemometer system to investigate combustion instability. The nonlinear aspects of a Reynolds number dependent process appear to be the dominant mechanisms controlling instability.

  17. Electron-impact excitation of carbon and silicon in the distorted-wave approximation

    NASA Technical Reports Server (NTRS)

    Pindzola, M. S.; Bhatia, A. K.; Temkin, A.

    1977-01-01

    The 3P to 1D electron-impact excitation cross section within the ground configuration of both neutral carbon and silicon is calculated in the distorted-wave approximation of the two-state Hartree-Fock coupled equations. An essential element of the present treatment is that orthogonality to core orbitals is not assumed in deriving equations for the scattering orbitals. A local adiabatic polarization potential is also added to the distorted-wave equations. Both elements are necessary in getting good agreement with close-coupling results for carbon to low impacting energies. The agreement is sufficiently good that predictions for silicon should be accurate to within a factor of 2.

  18. Beam distortion detection and deflectometry measurements of gigahertz surface acoustic waves.

    PubMed

    Higuet, Julien; Valier-Brasier, Tony; Dehoux, Thomas; Audoin, Bertrand

    2011-11-01

    Gigahertz acoustic waves propagating on the surface of a metal halfspace are detected using different all-optical detection schemes, namely, deflectometry and beam distortion detection techniques. Both techniques are implemented by slightly modifying a conventional reflectometric setup. They are then based on the measurement of the reflectivity change but unlike reflectometric measurements, they give access to the sample surface displacement. A semi-analytical model, taking into account optical, thermal, and mechanical processes responsible for acoustic waves generation, allows analyzing the physical content of the detected waveforms. PMID:22129002

  19. Cochlear traveling-wave amplification, suppression, and beamforming probed using noninvasive calibration of intracochlear distortion sources.

    PubMed

    Shera, Christopher A; Guinan, John J

    2007-02-01

    Originally developed to estimate the power gain of the cochlear amplifier, so-called "Allen-Fahey" and related experiments have proved invaluable for probing the mechanisms of wave generation and propagation within the cochlea. The experimental protocol requires simultaneous measurement of intracochlear distortion products (DPs) and ear-canal otoacoustic emissions (DPOAEs) under tightly controlled conditions. To calibrate the intracochlear response to the DP, Allen-Fahey experiments traditionally employ invasive procedures such as recording from auditory-nerve fibers or measuring basilar-membrane velocity. This paper describes an alternative method that allows the intracochlear distortion source to be calibrated noninvasively. In addition to the standard pair of primary tones used to generate the principal DP the noninvasive method employs a third, fixed tone to create a secondary DPOAE whose amplitude and phase provide a sensitive assay of the intracochlear value of the principal DP near its characteristic place. The method is used to perform noninvasive Allen-Fahey experiments in cat and shown to yield results in quantitative agreement with the original, auditory-nerve-based paradigm performed in the same animal. Data obtained using a suppression-compensated variation of the noninvasive method demonstrate that neither traveling-wave amplification nor two-tone suppression constitutes the controlling influence in DPOAE generation at close frequency ratios. Rather, the dominant factor governing the emission magnitude appears to be the variable directionality of the waves radiated by the distortion-source region, which acts as a distortion beamformer tuned by the primary frequency ratio. PMID:17348523

  20. Phase Inversion: Inferring Solar Subphotospheric Flow and Other Asphericity from the Distortion of Acoustic Waves

    NASA Technical Reports Server (NTRS)

    Gough, Douglas; Merryfield, William J.; Toomre, Juri

    1998-01-01

    A method is proposed for analyzing an almost monochromatic train of waves propagating in a single direction in an inhomogeneous medium that is not otherwise changing in time. An effective phase is defined in terms of the Hilbert transform of the wave function, which is related, via the JWKB approximation, to the spatial variation of the background state against which the wave is propagating. The contaminating effect of interference between the truly monochromatic components of the train is eliminated using its propagation properties. Measurement errors, provided they are uncorrelated, are manifest as rapidly varying noise; although that noise can dominate the raw phase-processed signal, it can largely be removed by low-pass filtering. The intended purpose of the analysis is to determine the distortion of solar oscillations induced by horizontal structural variation and material flow. It should be possible to apply the method directly to sectoral modes. The horizontal phase distortion provides a measure of longitudinally averaged properties of the Sun in the vicinity of the equator, averaged also in radius down to the depth to which the modes penetrate. By combining such averages from different modes, the two-dimensional variation can be inferred by standard inversion techniques. After taking due account of horizontal refraction, it should be possible to apply the technique also to locally sectoral modes that propagate obliquely to the equator and thereby build a network of lateral averages at each radius, from which the full three-dimensional structure of the Sun can, in principle, be determined as an inverse Radon transform.

  1. Four-body continuum-distorted-wave model for charge exchange between hydrogenlike projectiles and atoms

    NASA Astrophysics Data System (ADS)

    Mančev, Ivan

    2007-05-01

    The four-body continuum-distorted-wave model is formulated and used to investigate single electron capture in fast collisions of hydrogenlike projectiles with one- and multi-electron targets. The presented method of an analytical calculation of scattering integrals yields the total cross sections in terms of four-dimensional numerical quadratures. As an illustration, total cross sections are computed for electron capture processes in He+-H , He+-He , and Li2+-He collisions at intermediate and high impact energies. The contribution from the interelectron interaction during the collision is evaluated. The prior and post total cross sections are found to be in good agreement with the available experimental data.

  2. Distortion of a spherical gaseous interface accelerated by a plane shock wave.

    PubMed

    Layes, Guillaume; Jourdan, Georges; Houas, Lazhar

    2003-10-24

    The evolution of a spherical gaseous interface accelerated by a plane weak shock wave has been investigated in a square cross section shock tube via a multiple exposure shadowgraph diagnostic. Different gaseous bubbles, i.e., helium, nitrogen, and krypton, were introduced in air at atmospheric pressure in order to study the Richtmyer-Meshkov instability in the spherical geometry for negative, close to zero, and positive initial density jumps across the interface. We show that the bubble distortion is strongly different for the three cases and we present the experimental velocity and volume of the developed vortical structures. We prove that at late times the bubble velocities reach constant values which are in good agreement with previous calculations. Finally, we point out that, in our flow conditions, the gaseous bubble motion and shape are mainly influenced by vorticity and aerodynamic forces. PMID:14611354

  3. Distorted wave collision strengths for n-n(prime) transitions in hydrogenic ions

    NASA Astrophysics Data System (ADS)

    Clark, R. E. H.

    1990-05-01

    Distorted wave collision strengths have been calculated for n-n(prime) transitions in hydrogenic ions with n-n(prime) of 3-4, 3-5, 5-6, 5-7, 7-8, and 7-9. Nuclear charge numbers Z were 3, 10, and 26. For each transition at each Z, the energies, in threshold units, were 1.01, 1.2, 1.5, 1.9, 2.5, 4.0, 6.0, 10.0 and 15.0. These collision strengths should be useful in testing various semiempirical formulas for electron impact excitation collision strengths needed in plasma modeling codes. Comparison is made with two such formulas.

  4. Flexible 2D Crystals of Polycyclic Aromatics Stabilized by Static Distortion Waves

    PubMed Central

    2016-01-01

    The epitaxy of many organic films on inorganic substrates can be classified within the framework of rigid lattices which helps to understand the origin of energy gain driving the epitaxy of the films. Yet, there are adsorbate–substrate combinations with distinct mutual orientations for which this classification fails and epitaxy cannot be explained within a rigid lattice concept. It has been proposed that tiny shifts in atomic positions away from ideal lattice points, so-called static distortion waves (SDWs), are responsible for the observed orientational epitaxy in such cases. Using low-energy electron diffraction and scanning tunneling microscopy, we provide direct experimental evidence for SDWs in organic adsorbate films, namely hexa-peri-hexabenzocoronene on graphite. They manifest as wave-like sub-Ångström molecular displacements away from an ideal adsorbate lattice which is incommensurate with graphite. By means of a density-functional-theory based model, we show that, due to the flexibility in the adsorbate layer, molecule–substrate energy is gained by straining the intermolecular bonds and that the resulting total energy is minimal for the observed domain orientation, constituting the orientational epitaxy. While structural relaxation at an interface is a common assumption, the combination of the precise determination of the incommensurate epitaxial relation, the direct observation of SDWs in real space, and their identification as the sole source of epitaxial energy gain constitutes a comprehensive proof of this effect. PMID:27014920

  5. Flexible 2D Crystals of Polycyclic Aromatics Stabilized by Static Distortion Waves.

    PubMed

    Meissner, Matthias; Sojka, Falko; Matthes, Lars; Bechstedt, Friedhelm; Feng, Xinliang; Müllen, Klaus; Mannsfeld, Stefan C B; Forker, Roman; Fritz, Torsten

    2016-07-26

    The epitaxy of many organic films on inorganic substrates can be classified within the framework of rigid lattices which helps to understand the origin of energy gain driving the epitaxy of the films. Yet, there are adsorbate-substrate combinations with distinct mutual orientations for which this classification fails and epitaxy cannot be explained within a rigid lattice concept. It has been proposed that tiny shifts in atomic positions away from ideal lattice points, so-called static distortion waves (SDWs), are responsible for the observed orientational epitaxy in such cases. Using low-energy electron diffraction and scanning tunneling microscopy, we provide direct experimental evidence for SDWs in organic adsorbate films, namely hexa-peri-hexabenzocoronene on graphite. They manifest as wave-like sub-Ångström molecular displacements away from an ideal adsorbate lattice which is incommensurate with graphite. By means of a density-functional-theory based model, we show that, due to the flexibility in the adsorbate layer, molecule-substrate energy is gained by straining the intermolecular bonds and that the resulting total energy is minimal for the observed domain orientation, constituting the orientational epitaxy. While structural relaxation at an interface is a common assumption, the combination of the precise determination of the incommensurate epitaxial relation, the direct observation of SDWs in real space, and their identification as the sole source of epitaxial energy gain constitutes a comprehensive proof of this effect. PMID:27014920

  6. Distorted-wave born approximation calculations for turbulence scattering in an upward-refracting atmosphere

    NASA Technical Reports Server (NTRS)

    Gilbert, Kenneth E.; Di, Xiao; Wang, Lintao

    1990-01-01

    Weiner and Keast observed that in an upward-refracting atmosphere, the relative sound pressure level versus range follows a characteristic 'step' function. The observed step function has recently been predicted qualitatively and quantitatively by including the effects of small-scale turbulence in a parabolic equation (PE) calculation. (Gilbert et al., J. Acoust. Soc. Am. 87, 2428-2437 (1990)). The PE results to single-scattering calculations based on the distorted-wave Born approximation (DWBA) are compared. The purpose is to obtain a better understanding of the physical mechanisms that produce the step-function. The PE calculations and DWBA calculations are compared to each other and to the data of Weiner and Keast for upwind propagation (strong upward refraction) and crosswind propagation (weak upward refraction) at frequencies of 424 Hz and 848 Hz. The DWBA calculations, which include only single scattering from turbulence, agree with the PE calculations and with the data in all cases except for upwind propagation at 848 Hz. Consequently, it appears that in all cases except one, the observed step function can be understood in terms of single scattering from an upward-refracted 'skywave' into the refractive shadow zone. For upwind propagation at 848 Hz, the DWBA calculation gives levels in the shadow zone that are much below both the PE and the data.

  7. Transfer induced by core excitation within an extended distorted-wave Born approximation method

    NASA Astrophysics Data System (ADS)

    Gómez-Ramos, M.; Moro, A. M.; Gómez-Camacho, J.; Thompson, I. J.

    2015-07-01

    Background: Dynamic core-excitation effects have been found to be of importance in breakup reactions and may be of relevance when obtaining spectroscopic information from transfer reactions. Purpose: In this paper we extend the distorted-wave Born approximation (DWBA) formalism in order to allow for noncentral components in the core-core term appearing in the transition operator, which allows for dynamic core-excitation effects. Then we study these effects by applying the formalism to different (d ,p ) reactions. Methods: The expression of the nonlocal kernels required for the evaluation of the DWBA amplitudes has been extended so as to include noncentral parts in the core-core interaction. The DWBA scattering amplitude is then obtained by solving the corresponding inhomogeneous equation, with the new computed kernels, and the usual outgoing boundary conditions. A new DWBA code has been developed for this purpose. Results: For 10Be(d ,p ) 11Be , core-excitation effects are found to be almost negligible (<3 %) . The importance of this effect has been found to depend to a large extent on the excitation energy of the core. This has been confirmed in the 30Ne(d ,p ) 31Ne case, for which the excitation energy of the first 2+ state is 0.8 MeV, and the effect of core excitation increases to ≈10 % . Conclusions: We find dynamic core-excitation effects in transfer reactions to have small contributions to cross sections, in general. However, they should not be neglected, since they may modify the spectroscopic information obtained from these reactions and may become of importance in reactions with nuclei with a core with high deformation and low excitation energy.

  8. PHYSICAL FOUNDATIONS OF QUANTUM ELECTRONICS: On the distortion of a wave packet propagating in an amplifying medium

    NASA Astrophysics Data System (ADS)

    Bukhman, N. S.

    2004-04-01

    The propagation of a narrow-band signal (wave packet) in a medium with population inversion is considered. It is shown that in an optically thick medium layer the signal decomposes into the initial and amplified signals propagating at different velocities and having different durations. The initial signal propagates without distortions at the velocity c/n0 (n0 is the refractive index of the medium away from the resonance frequency) and plays the role of a precursor of the amplified signal. The amplified signal moves at a lower velocity. It lags behind the initial signal during propagation and acquires a universal Gaussian shape (irrespective of the shape of the initial signal and the spectral line profile). The appearance of the amplified signal, which substantially differs from the initial signal in all the parameters, as well as the interference between the amplified and initial signals looks like a 'extra-distortion' of the initial signal.

  9. Wave propagation and phase retrieval in Fresnel diffraction by a distorted-object approach

    SciTech Connect

    Xiao Xianghui; Shen Qun

    2005-07-15

    An extension of the far-field x-ray diffraction theory is presented by the introduction of a distorted object for calculation of coherent diffraction patterns in the near-field Fresnel regime. It embeds a Fresnel-zone construction on an original object to form a phase-chirped distorted object, which is then Fourier transformed to form a diffraction image. This approach extends the applicability of Fourier-based iterative phasing algorithms into the near-field holographic regime where phase retrieval had been difficult. Simulated numerical examples of this near-field phase retrieval approach indicate its potential applications in high-resolution structural investigations of noncrystalline materials.

  10. Expressions for Form Factors for Inelastic Scattering and Charge Exchange in Plane-Wave, Distorted-Wave, and Coupled-Channels Reaction Formalisms

    SciTech Connect

    Dietrich, F S

    2006-09-25

    This document is intended to facilitate calculation of inelastic scattering and charge-exchange cross sections in a variety of reaction models, including the plane-wave and distorted-wave approximations and the full coupled-channels treatments. Expressions are given for the coupling potentials between the relevant channels in both coordinate and momentum space. In particular, it is expected that the plane-wave calculations should be useful as a check on the correctness of coupled-channels calculations. The Fourier transform methods used to calculate the plane-wave approximation cross sections are also intended to be used to generate the transition potentials for coupled-channels codes, using a folding model with local effective interactions. Specific expressions are given for calculating transition densities for the folding model in the random phase approximation (RPA).

  11. Direct measurement of wave-front distortion induced during second-harmonic generation: application to breakup-integral compensation.

    PubMed

    Caumes, Jean Pascal; Videau, Laurent; Rouyer, Claude; Freysz, Eric

    2004-04-15

    The wave-front distortion of femtosecond laser pulses recorded with a Shack-Hartmann analyzer makes it possible to retrieve the nonlinear index of refraction of different glasses and the nonlinear phase shift induced during second-harmonic generation in beta-barium borate (BBO) crystal versus the phase mismatch. It is shown that the nonlinear phase shift induced in a 2-mm-thick BBO crystal allows compensation for up to a 2pi breakup-integral induced in a 4-cm fused-silica glass. The stability of the compensation is reported to be from 10 to 100 GW cm(-2). PMID:15119415

  12. Ferromagnetism stabilized by lattice distortion at the surface of the p-wave superconductor Sr(2)RuO(4)

    PubMed

    Matzdorf; Fang; Ismail; Zhang; Kimura; Tokura; Terakura; Plummer

    2000-08-01

    Ferromagnetic (FM) spin fluctuations are believed to mediate the spin-triplet pairing for the p-wave superconductivity in Sr(2)RuO(4). Our experiments show that, at the surface, a bulk soft-phonon mode freezes into a static lattice distortion associated with an in-plane rotation of the RuO(6) octahedron. First-principle calculations confirm this structure and predict a FM ground state at the surface. This coupling between structure and magnetism in the environment of broken symmetry at the surface allows a reconsideration of the coupling mechanism in the bulk. PMID:10926529

  13. An investigation of the open-loop amplification of Reynolds number dependent processes by wave distortion

    NASA Technical Reports Server (NTRS)

    Purdy, K. R.; Ventrice, M. B.; Fang, J.

    1972-01-01

    Analytical and experimental studies were initiated to determine if the response of a constant temperature hot wire anemometer to acoustic oscillations could serve as an analog to the response of the drop vaporization burning rate process to acoustic oscillations, and, perhaps, also as an analog to any Reynolds number dependent process. The motivation behind this study was a recent analytical study which showed that distorted acoustic oscillations could amplify the open-loop response of vaporization limited combustion. This type of amplification may be the cause of unstable combustion in liquid propellant rocket engines. The analytical results obtained for the constant temperature anemometer are similar in nature to those previously obtained for vaporization limited combustion and indicate that the response is dependent on the amount and type of distortion as well as other factors, such as sound pressure level, Mach number and hot wire temperature. Preliminary results indicate qualitative agreement between theory and experiment.

  14. Symmetry properties of the S matrix in a fully relativistic distorted-wave treatment of electron-impact ionization

    SciTech Connect

    Pyper, N. C.; Kampp, Marco; Whelan, Colm T.

    2005-05-15

    The symmetry properties of the S matrix in a fully relativistic distorted-wave treatment of electron-impact ionization are investigated. It is shown that the square modulus of the scattering matrix element in which the spin states of all four electrons are determined is not invariant under the reversal of the direction of alignment of all spins. The largest of two contributions to this noninvariance originates from the relativistic modifications of the continuum wave functions induced by the distorting potential of the target atom. A second smaller contribution is manifested on reducing the eight-dimensional matrix elements of the QED covariant propagator to purely spatial two-electron integrals. The triple differential cross section (TDCS) exhibits a spin asymmetry unless the entire scattering process occurs in a single plane. There will be a difference in the TDCS between an (e,2e) event in which the initial beam is polarized parallel or antiparallel with respect to the beam direction even if the target is unpolarized and the final spin states are not determined. The TDCS will remain unchanged if, in addition to reversal of the direction of spin alignment, one appropriate momentum component of one of the two outgoing electrons is reversed.

  15. Amplification of Reynolds number dependent processes by wave distortion. [acoustic instability of liquid propellant rocket engines

    NASA Technical Reports Server (NTRS)

    Ventrice, M. B.; Fang, J. C.; Purdy, K. R.

    1975-01-01

    A system using a hot-wire transducer as an analog of a liquid droplet of propellant was employed to investigate the ingredients of the acoustic instability of liquid-propellant rocket engines. It was assumed that the combustion process was vaporization-limited and that the combustion chamber was acoustically similar to a closed-closed right-circular cylinder. Before studying the hot-wire closed-loop system (the analog system), a microphone closed-loop system, which used the response of a microphone as the source of a linear feedback exciting signal, was investigated to establish the characteristics of self-sustenance of acoustic fields. Self-sustained acoustic fields were found to occur only at resonant frequencies of the chamber. In the hot-wire closed-loop system, the response of hot-wire anemometer was used as the source of the feedback exciting signal. The self-sustained acoustic fields which developed in the system were always found to be harmonically distorted and to have as their fundamental frquency a resonant frequency for which there also existed a second resonant frequency which was approximately twice the fundamental frequency.

  16. Laboratory-scale experiment to study nonlinear N-wave distortion by thermal turbulence.

    PubMed

    Salze, Édouard; Yuldashev, Petr; Ollivier, Sébastien; Khokhlova, Vera; Blanc-Benon, Philippe

    2014-08-01

    The nonlinear propagation of spark-generated N-waves through thermal turbulence is experimentally studied at the laboratory scale under well-controlled conditions. A grid of electrical resistors was used to generate the turbulent field, well described by a modified von Kármán model. A spark source was used to generate high-amplitude (~1500 Pa) and short duration (~50 μs) N-waves. Thousands of waveforms were acquired at distances from 250 to 1750 mm from the source (~15 to 100 wavelengths). The mean values and the probability densities of the peak pressure, the deviation angle, and the rise time of the pressure wave were obtained as functions of propagation distance through turbulence. The peak pressure distributions were described using a generalized gamma distribution, whose coefficients depend on the propagation distance. A line array of microphones was used to analyze the effect of turbulence on the propagation direction. The angle of deviation induced by turbulence was found to be smaller than 15°, which validates the use of the parabolic equation method to model this kind of experiment. The transverse size of the focus regions was estimated to be on the order of the acoustic wavelength for propagation distances longer than 50 wavelengths. PMID:25096090

  17. DISTORTED3/SCAR2 is a putative arabidopsis WAVE complex subunit that activates the Arp2/3 complex and is required for epidermal morphogenesis.

    PubMed

    Basu, Dipanwita; Le, Jie; El-Essal, Salah El-Din; Huang, Shanjin; Zhang, Chunhua; Mallery, Eileen L; Koliantz, Gregore; Staiger, Christopher J; Szymanski, Daniel B

    2005-02-01

    In a plant cell, a subset of actin filaments function as a scaffold that positions the endomembrane system and acts as a substrate on which organelle motility occurs. Other actin filament arrays appear to be more dynamic and reorganize in response to growth signals and external cues. The distorted group of trichome morphology mutants provides powerful genetic tools to study the control of actin filament nucleation in the context of morphogenesis. In this article, we report that DISTORTED3 (DIS3) encodes a plant-specific SCAR/WAVE homolog. Null alleles of DIS3, like those of other Arabidopsis thaliana WAVE and Actin-Related Protein (ARP) 2/3 subunit genes, cause trichome distortion, defects in cell-cell adhesion, and reduced hypocotyl growth in etiolated seedlings. DIS3 efficiently activates the actin filament nucleation and branching activity of vertebrate Arp2/3 and functions within a WAVE-ARP2/3 pathway in vivo. DIS3 may assemble into a WAVE complex via a physical interaction with a highly diverged Arabidopsis Abi-1-like bridging protein. These results demonstrate the utility of the Arabidopsis trichome system to understand how the WAVE and ARP2/3 complexes translate signaling inputs into a coordinated morphogenetic response. PMID:15659634

  18. Distorted-wave calculations of dielectronic recombination for C sup 3+ and O sup 5+ in small electric fields

    SciTech Connect

    Griffin, D.C. ); Pindzola, M.S.; Krylstedt, P. )

    1989-12-01

    The dielectronic recombination cross sections associated with the 2{ital s}{r arrow}2{ital p} transition in Li-like carbon and oxygen ions in the presence of small electric fields have been calculated in the distorted-wave approximation. By convoluting the product of the electron velocity and the theoretical cross section with the experimental velocity distribution, we compare our calculations with recent measurements of high-resolution recombination rates {l angle}{ital v}{sigma}({ital v}){r angle} by Andersen {ital et} {ital al}. With the exception of the magnitude of the low-energy peak due to the 2{ital p}4{ital l} resonances, the agreement between experiment and theory is excellent in C{sup 3+} for a field in the interaction region of just over 3 V/cm. In the case of O{sup 5+}, however, there is good agreement between experiment and theory for the low-Rydberg states, but there appear to be discrepancies between the measured rates and the theoretical rates for the high-Rydberg states, where the effects of fields are important.

  19. Generation of acoustic rogue waves in dusty plasmas through three-dimensional particle focusing by distorted waveforms

    NASA Astrophysics Data System (ADS)

    Tsai, Ya-Yi; Tsai, Jun-Yi; I, Lin

    2016-06-01

    Rogue waves--rare uncertainly emerging localized events with large amplitudes--have been experimentally observed in many nonlinear wave phenomena, such as water waves, optical waves, second sound in superfluid He II (ref. ) and ion acoustic waves in plasmas. Past studies have mainly focused on one-dimensional (1D) wave behaviour through modulation instabilities, and to a lesser extent on higher-dimensional behaviour. The question whether rogue waves also exist in nonlinear 3D acoustic-type plasma waves, the kinetic origin of their formation and their correlation with surrounding 3D waveforms are unexplored fundamental issues. Here we report the direct experimental observation of dust acoustic rogue waves in dusty plasmas and construct a picture of 3D particle focusing by the surrounding tilted and ruptured wave crests, associated with the higher probability of low-amplitude holes for rogue-wave generation.

  20. Relativistic description of inclusive quasielastic proton-nucleus scattering with relativistic distorted-wave impulse approximation and random-phase approximation

    SciTech Connect

    Niekerk, D. D. van; Ventel, B. I. S. van der; Titus, N. P.; Hillhouse, G. C.

    2011-04-15

    We present a fully relativistic model for polarized inclusive quasielastic proton-nucleus scattering that includes relativistic distorted waves for the projectile and ejectile (RDWIA), as well as the relativistic random-phase approximation (RPA) applied to the target nucleus. Using a standard relativistic impulse approximation treatment of quasielastic scattering and a two-body Scalar, Pseudoscalar, Vector, Axial vector, Tensor (SPVAT) form of the current operator, it is shown how the behavior of the projectile/ejectile and target can be decoupled. Distortion effects are included via a full partial-wave expansion of the relativistic wave functions. Target correlations are included via the relativistic RPA applied to mean-field theory in quantum hadrodynamics. A number of novel analytical and numerical techniques are employed to aid in this highly nontrivial calculation. A baseline plane-wave calculation is performed for the reaction {sup 40}Ca(p-vector,p-vector{sup '}) at an energy of 500 MeV and an angle {theta}{sub c.m.}=40 deg. Here it is found that the effect of isoscalar correlations is a quenching of the cross section that is expected to become more pronounced at lower energies or for higher-density targets. A RDWIA calculation shows additional reduction and if isoscalar target correlations are included this effect is enhanced.

  1. Integration of a laser doppler vibrometer and adaptive optics system for acoustic-optical detection in the presence of random water wave distortions

    NASA Astrophysics Data System (ADS)

    Land, Phillip; Robinson, Dennis; Roeder, James; Cook, Dean; Majumdar, Arun K.

    2016-05-01

    A new technique has been developed for improving the Signal-to-Noise Ratio (SNR) of underwater acoustic signals measured above the water's surface. This technique uses a Laser Doppler Vibrometer (LDV) and an Adaptive Optics (AO) system (consisting of a fast steering mirror, deformable mirror, and Shack-Hartmann Wavefront Sensor) for mitigating the effect of surface water distortions encountered while remotely recording underwater acoustic signals. The LDV is used to perform non-contact vibration measurements of a surface via a two beam laser interferometer. We have demonstrated the feasibility of this technique to overcome water distortions artificially generated on the surface of the water in a laboratory tank. In this setup, the LDV beam penetrates the surface of the water and travels down to be reflected off a submerged acoustic transducer. The reflected or returned beam is then recorded by the LDV as a vibration wave measurement. The LDV extracts the acoustic wave information while the AO mitigates the water surface distortions, increasing the overall SNR. The AO system records the Strehl ratio, which is a measure of the quality of optical image formation. In a perfect optical system the Strehl ratio is unity, however realistic systems with imperfections have Strehl ratios below one. The operation of the AO control system in open-loop and closed-loop configurations demonstrates the utility of the AO-based LDV for many applications.

  2. Does Bose-Einstein condensation of CMB photons cancel μ distortions created by dissipation of sound waves in the early Universe?

    NASA Astrophysics Data System (ADS)

    Khatri, R.; Sunyaev, R. A.; Chluba, J.

    2012-04-01

    The difference in the adiabatic indices of photons and non-relativistic baryonic matter in the early Universe causes the electron temperature to be slightly lower than the radiation temperature. Comptonization of photons with colder electrons results in the transfer of energy from photons to electrons and ions, owing to the recoil effect (spontaneous and induced). Thermalization of photons with a colder plasma results in the accumulation of photons in the Rayleigh-Jeans tail, aided by stimulated recoil, while the higher frequency spectrum tries to approach Planck spectrum at the electron temperature Tγfinal = Te < Tγinitial; i.e., Bose-Einstein condensation of photons occurs. We find new solutions of the Kompaneets equation describing this effect. No actual condensate is, in reality, possible since the process is very slow and photons drifting to low frequencies are efficiently absorbed by bremsstrahlung and double Compton processes. The spectral distortions created by Bose-Einstein condensation of photons are within an order of magnitude (for the present range of allowed cosmological parameters), with exactly the same spectrum but opposite in sign, of those created by diffusion damping of the acoustic waves on small scales corresponding to comoving wavenumbers 45 < k < 104 Mpc-1. The initial perturbations on these scales are completely unobservable today due to their being erased completely by Silk damping. There is partial cancellation of these two distortions, leading to suppression of μ distortions expected in the standard model of cosmology. The net distortion depends on the scalar power index ns and its running dns/dlnk, and may vanish for special values of parameters, for example, for a running spectrum with, ns = 1,dns/dlnk = - 0.038. We arrive at an intriguing conclusion: even a null result, non-detection of μ-type distortion at a sensitivity of 10-9, gives a quantitative measure of the primordial small-scale power spectrum.

  3. An investigation of the open-loop amplification of a Reynolds number dependent process by wave distortion

    NASA Technical Reports Server (NTRS)

    Ventrice, M. B.; Purdy, K. R.

    1974-01-01

    The response of a constant-temperature hot-wire anemometer to sinusoidal and distorted sinusoidal acoustic oscillations is examined. The output of the anemometer is dependent upon the Reynolds number of the flow over the wire. The response is a measure of the interaction between the anemometer output and the acoustic pressure in the neighborhood of the wire. It is an open-loop prediction of the characteristics of actual closed-loop operation of a system. If the open-loop response is large enough, unstable closed-loop operation is predicted. The study was motivated by a need to investigate the stability limits of liquid-propellant rockets when perturbed by pressure oscillations. The sinusoidal and distorted sinusoidal acoustic oscillations used for this study are the same as those characteristic of unstable rocket combustion. Qualitatively, the results are similar--the response of the system to pure sinusoidal acoustic vibration of the fluid surrounding the wire is small, even when the magnitude of the acoustic pressure is quite large; but the response can be increased by as much as an order of magnitude with respect to the sinusoidal case by the addition of distortion. The amplitude and phase of the distortion component, relative to the fundamental component, are the dominant factors in the increase in the response.

  4. Comparison of the rotationally adiabatic and vibrationally adiabatic distorted wave methods for the H H2(v=0, j=0)→') H chemical reactions

    NASA Astrophysics Data System (ADS)

    Clary, D. C.; Connor, J. N. L.

    Rotationally adiabatic distorted wave (RADW) and vibrationally adiabatic distorted wave (VADW) calculations of total and differential cross sections are reported for the three-dimensional H + H2(v=0, j=0) →H2(v'=0, j') + H and D + H2(v=0, j=0) →DH(v'=0, j') + H chemical reactions. Both the Porter-Karplus (PK) and the Siegbahn-Liu-Truhlar-Horowitz (SLTH) potential energy surfaces are used. The RADW results for D+H2 on the SLTH potential surface agree well with those obtained by Yung et al. In calculations using the PK surface, we obtain poor agreement with the RADW results reported for the H + H2 reaction by Choi and Tang, and for the D + H2 reaction by Tang and Choi. Reasons for these discrepancies are discussed. The absolute total RADW cross sections for the H + H2 reaction using both potential surfaces fall well below those obtained in accurate quantum calculations while the VADW total cross sections are smaller in magnitude than the RADW cross sections. The RADW and VADW results for relative rotational population distributions and for normalized differential cross sections are almost identical, and agree well with accurate quantum calculations for these quantities for the H + H2 reaction using the PK potential surface.

  5. A special method for finding body distortions that reduce the wave drag of wing and body combinations at supersonic speeds

    NASA Technical Reports Server (NTRS)

    Lomax, Harvard; Heaslet, Max A

    1956-01-01

    For a given wing and supersonic Mach number, the problem of shaping an adjoining fuselage so that the combination will have a low wave drag is considered. Only fuselages that can be simulated by singularities (multipoles) distributed along the body axis are studied. However, the optimum variations of such singularities are completely specified in terms of the given wing geometry. An application is made to an elliptic wing having a biconvex section, a thickness-chord ratio equal to 0.05 at the root, and an aspect ratio equal to 3. A comparison of the theoretical results with a wind-tunnel experiment is also presented.

  6. Amplifier Distortion

    NASA Astrophysics Data System (ADS)

    Keeports, David

    2006-12-01

    By definition, a high fidelity amplifier's instantaneous output voltage is directly proportional to its instantaneous input voltage. While high fidelity is generally valued in the amplification of recorded music, nonlinearity, also known as distortion, is desirable in the amplification of some musical instruments. In particular, guitar amplifiers exploit nonlinearity to increase both the harmonic content and sustain of a guitar's sound. I will discuss how both modifications in sound result from saturation of triode tubes and transistors. Additionally, I will describe the difference in the symmetry of saturation curves for transistors and tubes and the reason why tube guitar amplifiers are generally considered to be superior to solid-state amplifiers. Finally, I will discuss attempts to use solid-state electronics to replicate the sound of tube amplifiers.

  7. Transmission versus transflection mode in FTIR analysis of blood plasma: is the electric field standing wave effect the only reason for observed spectral distortions?

    PubMed

    Staniszewska-Slezak, Emilia; Rygula, Anna; Malek, Kamilla; Baranska, Malgorzata

    2015-04-01

    Fourier transform infrared (FTIR) microspectroscopy is assessed in terms of two techniques (i.e., transmission and transflection) as a method for rapid measurements of blood plasma. Apart from the expected effect of the electric field standing wave (EFSW), we also noticed that second-derivative IR spectra recorded in transflection mode exhibited a significant shift in the amide I band (up to 1667 cm(-1)) in comparison to the one recorded in transmission (1658 cm(-1)). This has not been reported thus far in studies of the EFSW distortion of IR spectra of biological material. The thinner the sample deposited on the low-e microscope slide, the lower the position of the amide I band found in FTIR spectra, suggesting various plasma compositions after stratification or certain changes in secondary protein conformations due to chemical and/or physical effects. There are potentially several phenomena that can occur at the surface of both IR substrates affecting the protein profile, including changes in optical properties (refractive index), variation in water content in the sample, and segregation of plasma components. All three hypotheses are discussed here, with the help of atomic force microscopy (AFM). PMID:25562064

  8. The antisymmetry of distortions

    PubMed Central

    VanLeeuwen, Brian K.; Gopalan, Venkatraman

    2015-01-01

    Distortions are ubiquitous in nature. Under perturbations such as stresses, fields or other changes, a physical system reconfigures by following a path from one state to another; this path, often a collection of atomic trajectories, describes a distortion. Here we introduce an antisymmetry operation called distortion reversal that reverses a distortion pathway. The symmetry of a distortion pathway is then uniquely defined by a distortion group; it has the same form as a magnetic group that involves time reversal. Given its isomorphism to magnetic groups, distortion groups could have a commensurate impact in the study of distortions, as the magnetic groups have had in the study of magnetic structures. Distortion symmetry has important implications for a range of phenomena such as structural and electronic phase transitions, diffusion, molecular conformational changes, vibrations, reaction pathways and interface dynamics. PMID:26572582

  9. Relativistic distorted-wave collision strengths for the 16 Δn=0 optically allowed transitions with n=2 in the 67 O-like ions with 26≤Z≤92

    SciTech Connect

    Fontes, Christopher J. Zhang, Hong Lin

    2015-01-15

    Relativistic distorted-wave collision strengths have been calculated for the 16 Δn=0 optically allowed transitions with n=2 in the 67 O-like ions with nuclear charge number Z in the range 26≤Z≤92. The calculations were made for the four final, or scattered, electron energies E{sup ′}=0.20,0.42,0.80, and 1.40, where E{sup ′} is in units of Z{sub eff}{sup 2} Ry with Z{sub eff}=Z−5.83. In the present calculations, an improved “top-up” method, which employs relativistic plane waves, was used to obtain the high partial-wave contribution for each transition, in contrast to the partial-relativistic Coulomb–Bethe approximation used in previous work by Zhang and Sampson [H.L. Zhang, D.H. Sampson, At. Data Nucl. Data Tables 82 (2002) 357]. In that earlier work, collision strengths were also provided for O-like ions, but for a more comprehensive data set consisting of all possible 45 Δn=0 transitions, six scattered energies, and the 79 ions with Z in the range 14≤Z≤92. The collision strengths covered in the present work should be more accurate than the corresponding data given by Zhang and Sampson [H.L. Zhang, D.H. Sampson, At. Data Nucl. Data Tables 82 (2002) 357] and are presented here to replace those earlier results.

  10. Quantum phase diagram of distorted J 1 - J 2 Heisenberg S  =  1/2 antiferromagnet in honeycomb lattice: a modified spin wave study.

    PubMed

    Ghorbani, Elaheh; Shahbazi, Farhad; Mosadeq, Hamid

    2016-10-12

    Using the modified spin wave method, we study the [Formula: see text] Heisenberg model with first and second neighbor antiferromagnetic exchange interactions. For a symmetric S  =  1/2 model, with the same couplings for all the equivalent neighbors, we find three phases in terms of the frustration parameter [Formula: see text]: (1) a commensurate collinear ordering with staggered magnetization (Néel.I state) for [Formula: see text], (2) a magnetically gapped disordered state for [Formula: see text], preserving all the symmetries of the Hamiltonian and lattice, which by definition is a quantum spin liquid (QSL) state and (3) a commensurate collinear ordering in which two out of the three nearest neighbor magnetizations are antiparallel and the remaining pair are parallel (Néel.II state), for [Formula: see text]. We also explore the phase diagram of a distorted [Formula: see text] model with S  =  1/2. Distortion is introduced as an inequality of one nearest neighbor coupling with the other two. This yields a richer phase diagram by the appearance of a new gapped QSL, a gapless QSL and also a valence bond crystal phase in addition to the previous three phases found for the undistorted model. PMID:27518832

  11. Relativistic distorted wave collision strengths for excitation to the 88 n = 3 and n = 4 levels in all 71 neon-like ions with 22 less than or equal to Z less than or equal to 92

    SciTech Connect

    Zhang, Hong Lin; Sampson, D. H.

    1989-02-01

    Relativistic distorted wave collision strengths are given for the 88 possible transitions between the ground level and the excited levels with n = 3 and n = 4 in the 71 neon-like ions with nuclear charge number Z in the range 22 less than or equal to Z less than or equal to 92. The calculations are made for the six final, or scattered, electron energies E' = 0.008, 0.04, 0.10, 0.21, 0.41 and 0.75, where E' is in units of Z/sub eff//sup 2/ Rydbergs with Z/sub eff/ = Z /minus/ 7.5. In addition, the transition energies and electric dipole oscillator strengths are given. 10 refs., 4 tabs.

  12. Relativistic distorted-wave collision strengths and oscillator strengths for the 185Δn=0 transitions with n=2 in the 67 C-like ions with 26≤Z≤92

    SciTech Connect

    Zhang, Hong Lin; Fontes, Christopher J.

    2015-01-15

    Relativistic distorted-wave collision strengths have been calculated for the 185 Δn=0 transitions with n=2 in the 67 C-like ions with nuclear charge number Z in the range 26≤Z≤92. The calculations were made for the six final, or scattered, electron energies E{sup ′}=0.03,0.08,0.20,0.42,0.80,  and  1.40, where E{sup ′} is in units of Z{sub eff}{sup 2} Ry with Z{sub eff}=Z−4.17. In addition, electric dipole oscillator strengths are provided. In the present collision-strength calculations, an improved “top-up” method, which employs relativistic plane waves, was used to obtain the high partial-wave contribution for each transition, in contrast to the partial-relativistic Coulomb–Bethe approximation used in previous work by Zhang and Sampson [H.L. Zhang, D.H. Sampson, At. Data Nucl. Data Tables 63 (1996) 275]. In that earlier work, collision strengths were also provided for the same 185 Δn=0 transitions in C-like ions, but for the more limited list of 46 ions with Z in the range 9≤Z≤54. The collision strengths covered in the present work, particularly those for optically allowed transitions, should be more accurate than the corresponding data given by Zhang and Sampson [H.L. Zhang, D.H. Sampson, At. Data Nucl. Data Tables 63 (1996) 275] and are presented here to replace those earlier results.

  13. Coupling of the orthorhombic distortion to the depression of the {Tc}`s due to Zn{sup 2+} doping in the ``RE-123`` HTSC`s: A (d + s)-wave picture

    SciTech Connect

    Tang, I.M.; Thongruang, R.; Charoenthai, N.

    1999-07-10

    The depressions of the {Tc}`s of the 123 REBa{sub 2}Cu{sub 3}O{sub 7} HTSC`s due to the substitution of Zn{sup 2+} ions into the Cu(2) layer are studied. The orthorhombic distortion which occurs in the 123 ceramics is assumed to induce a modification to the spin-fluctuation (SF) mediated pairing interaction which in turn causes the order parameters of these HTSC`s to be of mixed (d + s)-wave symmetry. It is shown that part of the rapid depression of the {Tc}`s caused by Zn{sup 2+} substitution into the CuO{sup 2} is due to a reduction of the SF-mediated pairing interaction. The differences in the rates of suppression of {Tc} due to Zn{sup 2+} doping in the different RE-123 HTSC`s are shown to be due to the changes in the orthorhombicity which depend on the size of the rare earth ions.

  14. L{alpha}, L{beta}, and L{gamma} x-ray production cross sections of Hf, Ta, W, Re, Os, Au, Pb, and Bi by electron impact: Comparison of distorted-wave calculations with experiment

    SciTech Connect

    Fernandez-Varea, Jose M.; Segui, Silvina; Dingfelder, Michael

    2011-02-15

    We study the emission of L{alpha}, L{beta}, and L{gamma} characteristic x rays by the impact of electrons on Hf, Ta, W, Re, Os, Au, Pb, and Bi atoms. To this end, ionization cross sections of the L{sub 1}, L{sub 2}, and L{sub 3} subshells of these atoms are calculated within the distorted-wave Born approximation. The considered energy interval spans from the ionization threshold up to 50 keV. Atomic relaxation parameters (i.e., Coster-Kronig and radiative transition probabilities, fluorescence yields, and emission rates) taken from the literature are then used to evaluate x-ray production cross sections. The theoretical predictions are compared with published experimental information. Good agreement is found for Ta, W, Os, Au, Pb, and Bi. In the case of Hf and Re, the measured cross sections are lower than the theoretical estimates by around 30%. The observed discrepancies might be attributed to the methods employed to correct the raw experimental data for the excess of detected characteristic x rays caused by the finite thickness of the sample's active layer and the presence of the thick substrate.

  15. New approach to description of (d,xn) spectra at energies below 50 MeV in Monte Carlo simulation by intra-nuclear cascade code with Distorted Wave Born Approximation

    NASA Astrophysics Data System (ADS)

    Hashimoto, S.; Iwamoto, Y.; Sato, T.; Niita, K.; Boudard, A.; Cugnon, J.; David, J.-C.; Leray, S.; Mancusi, D.

    2014-08-01

    A new approach to describing neutron spectra of deuteron-induced reactions in the Monte Carlo simulation for particle transport has been developed by combining the Intra-Nuclear Cascade of Liège (INCL) and the Distorted Wave Born Approximation (DWBA) calculation. We incorporated this combined method into the Particle and Heavy Ion Transport code System (PHITS) and applied it to estimate (d,xn) spectra on natLi, 9Be, and natC targets at incident energies ranging from 10 to 40 MeV. Double differential cross sections obtained by INCL and DWBA successfully reproduced broad peaks and discrete peaks, respectively, at the same energies as those observed in experimental data. Furthermore, an excellent agreement was observed between experimental data and PHITS-derived results using the combined method in thick target neutron yields over a wide range of neutron emission angles in the reactions. We also applied the new method to estimate (d,xp) spectra in the reactions, and discussed the validity for the proton emission spectra.

  16. Distortion in Perspective Projection

    ERIC Educational Resources Information Center

    Kelso, Robert P., Sr.

    2008-01-01

    The paper presents a unique approach in associating perspective projection with the image beheld by the eye and demonstrates that all graphical and photographic perspective projections must contain distortion when compared to the image beheld by the eye. (Contains 8 figures.)

  17. Relativistic distorted-wave collision strengths for Δn = 0 transitions in the 67 Li-like, F-like and Na-like ions with 26 ≤ Z ≤ 92

    DOE PAGESBeta

    Fontes, Christopher J.; Zhang, Hong Lin

    2016-05-04

    We calculated relativistic distorted-wave collision strength for all possible Δn=0 transitions, where n denotes the valence shell of the ground level, in the 67 Li-like, F-like and Na-like ions with Z in the range 26 ≤ Z ≤92. This choice produces 3 transitions with n=2 in the Li-like and F-like ions, and 10 transitions with n=3 in the Na-like ions. Moreover, for the Li-like and F-like ions, the calculations were made for the six final, or scattered, electron energies E'=0.008,0.04,0.10,0.21,0.41, and 0.75, where E' is in units of Zmore » $$2\\atop{eff}$$ Ry with Zeff = Z- 1.66 for Li-like ions and Zeff= Z- 6.667 for F-like ions. For the Na-like ions, the calculations were made for the six final electron energies E'=0.0025,0.015,0.04,0.10,0.21, and 0.40, with Zeff = Z- 8.34. In the present calculations, an improved “top-up” method, which employs relativistic plane waves, was used to obtain the high partial-wave contribution for each transition, in contrast to the partial-relativistic Coulomb–Bethe approximation used in previous works by Zhang, Sampson and Fontes [H.L. Zhang, D.H. Sampson, C.J. Fontes, At. Data Nucl. Data Tables 44 (1990) 31; H.L. Zhang, D.H. Sampson, C.J. Fontes, At. Data Nucl. Data Tables 48 (1991) 25; D.H. Sampson, H.L. Zhang, C.J. Fontes, At. Data Nucl. Data Tables 44 (1990) 209]. In those previous works, collision strengths were also provided for Li-, F- and Na-like ions, but for a more comprehensive set of transitions. Finally, the collision strengths covered in the present work should be more accurate than the corresponding data given in those previous works and are presented here to replace those earlier results.« less

  18. Wavefront Distortion Requirements for the LISA Mission

    NASA Astrophysics Data System (ADS)

    Bender, P. L.

    2004-12-01

    The Laser Interferometer Space Antenna (LISA) gravitational wave mission will make use of laser measurements of changes in distance between test masses in spacecraft 5 million km apart. Distortions in the far field wavefronts can interact with jitter in the transmitted beam directions to give apparent variations in the distances between the test masses. About 400 mm diameter telescopes will be used to send the laser beams between the spacecraft. Stabilization of the beam pointing directions will be done using the light from the distant spacecraft as very bright beacons to lock on to. Earlier studies of the beam pointing requirements for the LISA mission assumed only simple waveform distortions, such as cylindrical distortion or astigmatism. The analysis has now been repeated, including defocus, spherical aberration, and two components each of astigmatism and coma. These lower order aberrations are expected to be among the most damaging ones near the beam axis for a given rms wavefront distortion amplitude. This is because the higher order ones will cause the laser energy to be diffracted away from the axis more. Most of the aberration amplitude is expected to come from the optics before the telescope, rather than from the telescope itself. A total wavefront distortion amplitude of 0.05 wavelength (50 nm) rms or less appears to be adequate.

  19. Triton's Distorted Atmosphere

    NASA Technical Reports Server (NTRS)

    Elliot, J. L.; Stansberry, J. A.; Olkin, C. B.; Agner, M. A.; Davies, M. E.

    1998-01-01

    A stellar-occultation light curve for Triton shows asymmetry that can be understood if Triton's middle atmosphere is distorted from spherical symmetry. Although a globally oblate model can explain the data, the inferred atmospheric flattening is so large that it could be caused only by an unrealistic internal mass distribution or highly supersonic zonal winds. Cyclostrophic winds confined to a jet near Triton's northern or southern limbs (or both) could also be responsible for the details of the light curve, but such winds are required to be slightly supersonic. Hazes and clouds in the atmosphere are unlikely to have caused the asymmetry in the light curve.

  20. Distortions in protein helices.

    PubMed

    Geetha, V

    1996-08-01

    alpha-helices are the most common secondary structures in observed proteins. However, they are not always found in ideal helical conformation and they often exhibit structural distortions. Quantification of these irregularities become essential in understanding the packing of helices and therefore, their role in the functional characteristics of the protein. The backbone torsions phi, psi are of limited utility in this endeavor, because distorted helices often maintain the backbone geometry. The local compensatory effects are responsible for the preservation of the entire hydrogen bond network of the helical stretch. Earlier descriptions of helical linearity and curvature rest mostly on approximation, thus motivating the search for a better method for understanding and quantifying helical irregularities. We developed a method which involves the rotation and superposition of identical repeating units of the protein by the quaternion method. The set of parameters derived from the rotation-superposition algorithm helps in identifying the bends and kinks which are not necessarily induced by unusual amino acids like proline. The quantification of irregularities of observed helices might lead to a better understanding of their packing interactions. PMID:8842770

  1. Cognitive Distortions and Suicide Attempts.

    PubMed

    Jager-Hyman, Shari; Cunningham, Amy; Wenzel, Amy; Mattei, Stephanie; Brown, Gregory K; Beck, Aaron T

    2014-08-01

    Although theorists have posited that suicidal individuals are more likely than non-suicidal individuals to experience cognitive distortions, little empirical work has examined whether those who recently attempted suicide are more likely to engage in cognitive distortions than those who have not recently attempted suicide. In the present study, 111 participants who attempted suicide in the 30 days prior to participation and 57 psychiatric control participants completed measures of cognitive distortions, depression, and hopelessness. Findings support the hypothesis that individuals who recently attempted suicide are more likely than psychiatric controls to experience cognitive distortions, even when controlling for depression and hopelessness. Fortune telling was the only cognitive distortion uniquely associated with suicide attempt status. However, fortune telling was no longer significantly associated with suicide attempt status when controlling for hopelessness. Findings underscore the importance of directly targeting cognitive distortions when treating individuals at risk for suicide. PMID:25294949

  2. Analysis Of Overlay Distortion Patterns

    NASA Astrophysics Data System (ADS)

    Armitage, John D.; Kirk, Joseph P.

    1988-01-01

    A comprehensive geometrical approach is presented for the least-squares analysis of overlay distortion patterns into useful, physically meaningful systematic distortion subpatterns and an essentially non-systematic residue. A scheme of generally useful distortion sub-patterns is presented in graphic and algorithmic form; some of these sub-patterns are additions to those already in widespread use. A graphic and geometric approach is emphasized rather than an algebraic or statistical approach, and an example illustrates the value in utilizing the pattern-detecting ability of the eye-brain system. The conditions are described under which different distortion sub-patterns may interact, possibly leading to misleading or erroneous conclusions about the types and amounts of different distortions present. Examples of typical interaction situations are given, and recommendations are made for analytic procedures to avoid misinterpretation. It is noted that the lower-order distortion patterns preserve straight-line linearity, but that higher-order distortion may result in straight lines becoming curved. The principle of least-squares analysis is outlined and a simple polynomial data-fitting example is used to illustrate the method. Algorithms are presented for least-squares distortion analysis of overlay patterns, and an APL2 program is given to show how this may easily be implemented on a digital computer. The appendix extends the treatment to cases where small-angle approximation is not permissible.

  3. Memory distortion: an adaptive perspective

    PubMed Central

    Schacter, Daniel L.; Guerin, Scott A.; St. Jacques, Peggy L.

    2011-01-01

    Memory is prone to distortions that can have serious consequences in everyday life. Here we integrate emerging evidence that several types of memory distortions – imagination inflation, gist-based and associative memory errors, and post-event misinformation – reflect adaptive cognitive processes that contribute to the efficient functioning of memory, but produce distortions as a consequence of doing so. We consider recent cognitive and neuroimaging studies that link these distortions with adaptive processes, including simulation of future events, semantic and contextual encoding, creativity, and memory updating. We also discuss new evidence concerning factors that can influence the occurrence of memory distortions, such as sleep and retrieval conditions, as well as conceptual issues related to the development of an adaptive perspective. PMID:21908231

  4. Measurements of wavefront distortions of optical radiation using a shadow method

    NASA Astrophysics Data System (ADS)

    Bredikhin, Vladimir I.; Kuznetsov, S. P.

    2004-06-01

    The technique for measuring wave front distortions in optical elements by the shadow method is developed. Shadow pictures obtained for mutually perpendicular orientations of the Foucault knife-edge are the distributions of components of the gradient of the function describing the wave front relief, so that its shape can be restored by means of integration. An example of measurements of wave front distortions in large-scale optical KDP crystal elements employing the IAB 451 device is given.

  5. Probing early-universe phase transitions with CMB spectral distortions

    NASA Astrophysics Data System (ADS)

    Amin, Mustafa A.; Grin, Daniel

    2014-10-01

    Global, symmetry-breaking phase transitions in the early universe can generate scaling seed networks which lead to metric perturbations. The acoustic waves in the photon-baryon plasma sourced by these metric perturbations, when Silk damped, generate spectral distortions of the cosmic microwave background (CMB). In this work, the chemical potential distortion (μ ) due to scaling seed networks is computed and the accompanying Compton y -type distortion is estimated. The specific model of choice is the O (N ) nonlinear σ -model for N ≫1 , but the results remain the same order of magnitude for other scaling seeds. If CMB anisotropy constraints to the O (N ) model are saturated, the resulting chemical potential distortion μ ≲2 ×1 0-9 .

  6. Producing undistorted acoustic sine waves.

    PubMed

    Boutin, Henri; Smith, John; Wolfe, Joe

    2014-04-01

    A simple digital method is described that can produce an undistorted acoustic sine wave using an amplifier and loudspeaker having considerable intrinsic distortion, a common situation at low frequencies and high power. The method involves, first, using a pure sine wave as the input and measuring the distortion products. An iterative procedure then progressively adds harmonics with appropriate amplitude and phase to cancel any distortion products. The method is illustrated by producing a pure 52 Hz sine wave at 107 dB sound pressure level with harmonic distortion reduced over the audible range to >65 dB below the fundamental. PMID:25234964

  7. Stereo depth distortions in teleoperation

    NASA Technical Reports Server (NTRS)

    Diner, Daniel B.; Vonsydow, Marika

    1988-01-01

    In teleoperation, a typical application of stereo vision is to view a work space located short distances (1 to 3m) in front of the cameras. The work presented here treats converged camera placement and studies the effects of intercamera distance, camera-to-object viewing distance, and focal length of the camera lenses on both stereo depth resolution and stereo depth distortion. While viewing the fronto-parallel plane 1.4 m in front of the cameras, depth errors are measured on the order of 2cm. A geometric analysis was made of the distortion of the fronto-parallel plane of divergence for stereo TV viewing. The results of the analysis were then verified experimentally. The objective was to determine the optimal camera configuration which gave high stereo depth resolution while minimizing stereo depth distortion. It is found that for converged cameras at a fixed camera-to-object viewing distance, larger intercamera distances allow higher depth resolutions, but cause greater depth distortions. Thus with larger intercamera distances, operators will make greater depth errors (because of the greater distortions), but will be more certain that they are not errors (because of the higher resolution).

  8. Note on Redshift Distortion in Fourier Space

    NASA Astrophysics Data System (ADS)

    Cai, Yan-Chuan; Pan, Jun

    2007-02-01

    We explore features of redshift distortion in Fourier analysis of N-body simulations. The phases of the Fourier modes of dark matter density fluctuation are generally shifted by the peculiar motion along the line of sight, the induced phase shift is stochastic and has a probability distribution function (PDF) that is symmetric about the peak at zero shift and whose exact shape depends on the wave vector, except on very large scales where phases are invariant by linear perturbation theory. Analysis of the phase shifts motivates our phenomenological models for the bispectrum in redshift space. Comparison with simulations shows that our toy models are very successful in modeling bispectrum of equilateral and isosceles triangles at large scales. In the second part we compare the monopole of the power spectrum and bispectrum in the radial and plane-parallel distortion to test the plane-parallel approximation. We confirm the results of Scoccimarro that difference of power spectrum is at the level of 10%, and, in the reduced bispectrum, the difference is as small as a few percent. However, on the plane perpendicular to the line of sight of kz = 0, the difference in power spectrum between the radial and plane-parallel approximation can be more than ~10%, and even worse on very small scales. Such difference is prominent for bispectrum, especially for configurations of tilted triangles. Non-Gaussian signals under the radial distortion on small scales are systematically biased downside than are in the plane-parallel approximation, with amplitudes depending on the opening angle of the sample point to the observer. This observation gives warning to the practice of using the power spectrum and bispectrum measured on the kz = 0 plane as estimates of the real space statistics.

  9. JWST ISIM Distortion Analysis Challenge

    NASA Technical Reports Server (NTRS)

    Cifie, Emmanuel; Matzinger, Liz; Kuhn, Jonathan; Fan, Terry

    2004-01-01

    Very tight distortion requirements are imposed on the JWST's ISM structure due to the sensitivity of the telescope's mirror segment and science instrument positioning. The ISIM structure is a three dimensional truss with asymmetric gusseting and metal fittings. One of the primary challenges for ISIM's analysis team is predicting the thermal distortion of the structure both from the bulk cooldown from ambient to cryo, and the smaller temperature changes within the cryogenic operating environment. As a first cut to estimate thermal distortions, a finite element model of bar elements was created. Elements representing joint areas and metal fittings use effective properties that match the behavior of the stack-up of the composite tube, gusset and adhesive under mechanical and thermal loads. These properties were derived by matching tip deflections of a solid model simplified T-joint. Because of the structure s asymmetric gusseting, this effective property model is a first attempt at predicting rotations that cannot be captured with a smeared CTE approach. In addition to the finite element analysis, several first order calculations have been performed to gauge the feasibility of the material design. Because of the stringent thermal distortion requirements at cryogenic temperatures, a composite tube material with near zero or negative CTE is required. A preliminary hand analysis of the contribution of the various components along the distortion path between FGS and the other instruments, neglecting second order effects were examined. A plot of bounding tube longitudinal and transverse CTEs for thermal stability requirements was generated to help determine the feasibility of meeting these requirements. This analysis is a work in progress en route to a large degree of freedom hi-fidelity FEA model for distortion analysis. Methods of model reduction, such as superelements, are currently being investigated.

  10. Focal region fields of distorted reflectors

    NASA Technical Reports Server (NTRS)

    Buris, N. E.; Kauffman, J. F.

    1988-01-01

    The problem of the focal region fields scattered by an arbitrary surface reflector under uniform plane wave illumination is solved. The physical optics (PO) approximation is used to calculate the current induced on the reflector. The surface of the reflector is described by a number of triangular domain-wise 5th degree bivariate polynomials. A 2-dimensional Gaussian quadrature is employed to numerically evaluate the integral expressions of the scattered fields. No Freshnel or Fraunhofer zone approximations are made. The relation of the focal fields problem to surface compensation techniques and other applications are mentioned. Several examples of distorted parabolic reflectors are presented. The computer code developed is included, together with instructions on its usage.

  11. USA/USSR Textbook Distortions.

    ERIC Educational Resources Information Center

    Parker, Franklin

    This review of a 1981 interim report on the United States' and the Soviet Union's distortion of events in history and geography textbooks is intended to encourage educators in both countries to depict the other side more honestly, less aggressively, and more appreciative of each other's virtues and flaws. Organized into two major sections,…

  12. Analysis of pressure distortion testing

    NASA Technical Reports Server (NTRS)

    Koch, K. E.; Rees, R. L.

    1976-01-01

    The development of a distortion methodology, method D, was documented, and its application to steady state and unsteady data was demonstrated. Three methodologies based upon DIDENT, a NASA-LeRC distortion methodology based upon the parallel compressor model, were investigated by applying them to a set of steady state data. The best formulation was then applied to an independent data set. The good correlation achieved with this data set showed that method E, one of the above methodologies, is a viable concept. Unsteady data were analyzed by using the method E methodology. This analysis pointed out that the method E sensitivities are functions of pressure defect level as well as corrected speed and pattern.

  13. Detection and Rectification of Distorted Fingerprints.

    PubMed

    Si, Xuanbin; Feng, Jianjiang; Zhou, Jie; Luo, Yuxuan

    2015-03-01

    Elastic distortion of fingerprints is one of the major causes for false non-match. While this problem affects all fingerprint recognition applications, it is especially dangerous in negative recognition applications, such as watchlist and deduplication applications. In such applications, malicious users may purposely distort their fingerprints to evade identification. In this paper, we proposed novel algorithms to detect and rectify skin distortion based on a single fingerprint image. Distortion detection is viewed as a two-class classification problem, for which the registered ridge orientation map and period map of a fingerprint are used as the feature vector and a SVM classifier is trained to perform the classification task. Distortion rectification (or equivalently distortion field estimation) is viewed as a regression problem, where the input is a distorted fingerprint and the output is the distortion field. To solve this problem, a database (called reference database) of various distorted reference fingerprints and corresponding distortion fields is built in the offline stage, and then in the online stage, the nearest neighbor of the input fingerprint is found in the reference database and the corresponding distortion field is used to transform the input fingerprint into a normal one. Promising results have been obtained on three databases containing many distorted fingerprints, namely FVC2004 DB1, Tsinghua Distorted Fingerprint database, and the NIST SD27 latent fingerprint database. PMID:26353261

  14. Diffraction Analysis Of Distorted Reflector Antennas

    NASA Technical Reports Server (NTRS)

    Rahmat-Samii, Yahya; Mumford, Jeffrey H.

    1990-01-01

    Effects of systematic distortions of surfaces on radiation patterns predicted. Computer program for Diffraction Analysis of Reflector Antennas Subject to Systematic Distortions predicts performance of reflector antennas subject to sinusoidal, thermal, or gravitational distortions. Provides local interpolation algorithm readily applied to nonregular distribution of data. Developed in UNIVAC FORTRAN 77 for UNIVAC computer.

  15. Testing inflation and curvaton scenarios with CMB distortions

    NASA Astrophysics Data System (ADS)

    Clesse, Sébastien; Garbrecht, Björn; Zhu, Yi

    2014-10-01

    Prior to recombination, Silk damping causes the dissipation of energy from acoustic waves into the monopole of the Cosmic Microwave Background (CMB), resulting in spectral distortions. These can be used to probe the primordial scalar power spectrum on smaller scales than it is possible with CMB anisotropies. An enhancement of power on these scales is nevertheless required for the resulting distortions to be detectable by future experiments like PIXIE. In this paper, we examine all 49 single-field inflation models listed by Martin et al. in the Encyclopaedia Inflationaris [1] and find that only one of these may lead to a detectable level of distortions in a tuned region of its parameter space, namely the original hybrid model. Three effective multi-field scenarios are also studied: with softly and suddenly turning trajectories, and with a mild waterfall trajectory. Softly turning trajectories do not induce distortions at any detectable level, whereas a sudden turn in the field space or a mild waterfall trajectory predicts a peak (plus damped oscillations in the sudden turn case) in the scalar power spectrum, which can lead to an observable amount of CMB distortions. Finally, another scenario leading to potentially detectable distortions involves a curvaton whose blue spectrum is subdominant on CMB angular scales and overtakes the inflaton spectrum on smaller scales. In this case however, we show that the bounds from ultra compact minihaloes are not satisfied. Expectations for an ultimate PRISM-class experiment characterized by an improvement in sensitivity by a factor of ten are discussed for some models.

  16. Analysis of Brown camera distortion model

    NASA Astrophysics Data System (ADS)

    Nowakowski, Artur; Skarbek, Władysław

    2013-10-01

    Contemporary image acquisition devices introduce optical distortion into image. It results in pixel displacement and therefore needs to be compensated for many computer vision applications. The distortion is usually modeled by the Brown distortion model, which parameters can be included in camera calibration task. In this paper we describe original model, its dependencies and analyze orthogonality with regard to radius for its decentering distortion component. We also report experiments with camera calibration algorithm included in OpenCV library, especially a stability of distortion parameters estimation is evaluated.

  17. On relative distortion in fingerprint comparison.

    PubMed

    Kalka, Nathan D; Hicklin, R Austin

    2014-11-01

    When fingerprints are deposited, non-uniform pressure in conjunction with the inherent elasticity of friction ridge skin often causes linear and non-linear distortions in the ridge and valley structure. The effects of these distortions must be considered during analysis of fingerprint images. Even when individual prints are not notably distorted, relative distortion between two prints can have a serious impact on comparison. In this paper we discuss several metrics for quantifying and visualizing linear and non-linear fingerprint deformations, and software tools to assist examiners in accounting for distortion in fingerprint comparisons. PMID:25216456

  18. Spectral Distortions of the CMB Dipole

    NASA Astrophysics Data System (ADS)

    Balashev, S. A.; Kholupenko, E. E.; Chluba, J.; Ivanchik, A. V.; Varshalovich, D. A.

    2015-09-01

    We consider the distortions of the cosmic microwave background (CMB) dipole anisotropy related to primordial recombination radiation (PRR) and primordial y- and μ-distortions. The signals arise due to our motion relative to the CMB restframe and appear as a frequency-dependent distortion of the CMB temperature dipole. To leading order, the expected relative distortion of the CMB dipole does not depend on the particular observation directions and reaches the level of 10-6 for the PRR- and μ-distortions and 10-5 for the y-distortion in the frequency range 1-700 GHz. The temperature differences arising from the dipole anisotropy of the relic CMB distortions depend on the observation directions. For mutually opposite directions, collinear to the CMB dipole axis, the temperature differences due to the PRR- and μ-dipole anisotropy attain values {{Δ }}T≃ 10 {nK} in the considered range. The temperature difference arising from the y-dipole anisotropy may reach values of up to 1 μ {{K}}. The key features of the considered effect are as follow: (i) an observation of the effect does not require absolute calibration; (ii) patches of sky with minimal foreground contamination can be chosen. Future measurements of the CMB dipole distortion thus will provide an alternative method for direct detection of the PRR-, y-, and μ-distortions. The y-distortion dipole may be detectable with PIXIE at a few standard deviations.

  19. TWO NEW TIDALLY DISTORTED WHITE DWARFS

    SciTech Connect

    Hermes, J. J.; Montgomery, M. H.; Winget, D. E.; Kilic, Mukremin; Brown, Warren R.

    2012-04-10

    We identify two new tidally distorted white dwarfs (WDs), SDSS J174140.49+652638.7 and J211921.96-001825.8 (hereafter J1741 and J2119). Both stars are extremely low mass (ELM, {<=} 0.2 M{sub Sun }) WDs in short-period, detached binary systems. High-speed photometric observations obtained at the McDonald Observatory reveal ellipsoidal variations and Doppler beaming in both systems; J1741, with a minimum companion mass of 1.1 M{sub Sun }, has one of the strongest Doppler beaming signals ever observed in a binary system (0.59% {+-} 0.06% amplitude). We use the observed ellipsoidal variations to constrain the radius of each WD. For J1741, the star's radius must exceed 0.074 R{sub Sun }. For J2119, the radius exceeds 0.10 R{sub Sun }. These indirect radius measurements are comparable to the radius measurements for the bloated WD companions to A-stars found by the Kepler spacecraft, and they constitute some of the largest radii inferred for any WD. Surprisingly, J1741 also appears to show a 0.23% {+-} 0.06% reflection effect, and we discuss possible sources for this excess heating. Both J1741 and J2119 are strong gravitational wave sources, and the time-of-minimum of the ellipsoidal variations can be used to detect the orbital period decay. This may be possible on a timescale of a decade or less.

  20. Dynamic Dazzle Distorts Speed Perception

    PubMed Central

    Hall, Joanna R.; Cuthill, Innes C.; Baddeley, Roland; Attwood, Angela S.; Munafò, Marcus R.; Scott-Samuel, Nicholas E.

    2016-01-01

    Static high contrast (‘dazzle’) patterns, such as zigzags, have been shown to reduce the perceived speed of an object. It has not escaped our notice that this effect has possible military applications and here we report a series of experiments on humans, designed to establish whether dynamic dazzle patterns can cause distortions of perceived speed sufficient to provide effective defence in the field, and the extent to which these effects are robust to a battery of manipulations. Dynamic stripe patterns moving in the same direction as the target are found to increase the perceived speed of that target, whilst dynamic stripes moving in the opposite direction to the target reduce the perceived speed. We establish the optimum position for such dazzle patches; confirm that reduced contrast and the addition of colour do not affect the performance of the dynamic dazzle, and finally, using the CO2 challenge, show that the effect is robust to stressful conditions. PMID:27196098

  1. Telescopic systems with dynamic nonlinear optical correction for distortions

    SciTech Connect

    Vasil'ev, Michail V; Venediktov, Vladimir Yu; Leshchev, Alexey A

    2001-01-31

    The review of basic achievements in the field of non-linear adaptive optics is presented. In particular, schematics and properties of adaptive optical telescopes considered in which the image distortions introduced by defects of the primary mirror and other optical elements are compensated by nonlinear optical methods. The conventional methods of laser optics, such as phase conjugation and dynamic holography, make it possible both to solve the problems of classical (imaging) optics related to the building of telescopes for imaging remote objects with high resolution, which are based on large, light-weight or sectional mirrors, and create the systems that produce laser beams with the high-quality wave front. The basic designs of such telescopes are considered and the possibilities of corrections for distortions in them are analysed and confirmed by experiments. (review)

  2. Accuracy analysis of automatic distortion correction

    NASA Astrophysics Data System (ADS)

    Kolecki, Jakub; Rzonca, Antoni

    2015-06-01

    The paper addresses the problem of the automatic distortion removal from images acquired with non-metric SLR camera equipped with prime lenses. From the photogrammetric point of view the following question arises: is the accuracy of distortion control data provided by the manufacturer for a certain lens model (not item) sufficient in order to achieve demanded accuracy? In order to obtain the reliable answer to the aforementioned problem the two kinds of tests were carried out for three lens models. Firstly the multi-variant camera calibration was conducted using the software providing full accuracy analysis. Secondly the accuracy analysis using check points took place. The check points were measured in the images resampled based on estimated distortion model or in distortion-free images simply acquired in the automatic distortion removal mode. The extensive conclusions regarding application of each calibration approach in practice are given. Finally the rules of applying automatic distortion removal in photogrammetric measurements are suggested.

  3. Static stereo vision depth distortions in teleoperation

    NASA Technical Reports Server (NTRS)

    Diner, D. B.; Von Sydow, M.

    1988-01-01

    A major problem in high-precision teleoperation is the high-resolution presentation of depth information. Stereo television has so far proved to be only a partial solution, due to an inherent trade-off among depth resolution, depth distortion and the alignment of the stereo image pair. Converged cameras can guarantee image alignment but suffer significant depth distortion when configured for high depth resolution. Moving the stereo camera rig to scan the work space further distorts depth. The 'dynamic' (camera-motion induced) depth distortion problem was solved by Diner and Von Sydow (1987), who have quantified the 'static' (camera-configuration induced) depth distortion. In this paper, a stereo image presentation technique which yields aligned images, high depth resolution and low depth distortion is demonstrated, thus solving the trade-off problem.

  4. Cognitive Distortions, Humor Styles, and Depression

    PubMed Central

    Rnic, Katerina; Dozois, David J. A.; Martin, Rod A.

    2016-01-01

    Cognitive distortions are negative biases in thinking that are theorized to represent vulnerability factors for depression and dysphoria. Despite the emphasis placed on cognitive distortions in the context of cognitive behavioural theory and practice, a paucity of research has examined the mechanisms through which they impact depressive symptomatology. Both adaptive and maladaptive styles of humor represent coping strategies that may mediate the relation between cognitive distortions and depressive symptoms. The current study examined the correlations between the frequency and impact of cognitive distortions across both social and achievement-related contexts and types of humor. Cognitive distortions were associated with reduced use of adaptive Affiliative and Self-Enhancing humor styles and increased use of maladaptive Aggressive and Self-Defeating humor. Reduced use of Self-Enhancing humor mediated the relationship between most types of cognitive distortions and depressed mood, indicating that distorted negative thinking may interfere with an individual’s ability to adopt a humorous and cheerful outlook on life (i.e., use Self-Enhancing humor) as a way of regulating emotions and coping with stress, thereby resulting in elevated depressive symptoms. Similarly, Self-Defeating humor mediated the association of the social impact of cognitive distortions with depression, such that this humor style may be used as a coping strategy for dealing with distorted thinking that ultimately backfires and results in increased dysphoria. PMID:27547253

  5. Cognitive Distortions, Humor Styles, and Depression.

    PubMed

    Rnic, Katerina; Dozois, David J A; Martin, Rod A

    2016-08-01

    Cognitive distortions are negative biases in thinking that are theorized to represent vulnerability factors for depression and dysphoria. Despite the emphasis placed on cognitive distortions in the context of cognitive behavioural theory and practice, a paucity of research has examined the mechanisms through which they impact depressive symptomatology. Both adaptive and maladaptive styles of humor represent coping strategies that may mediate the relation between cognitive distortions and depressive symptoms. The current study examined the correlations between the frequency and impact of cognitive distortions across both social and achievement-related contexts and types of humor. Cognitive distortions were associated with reduced use of adaptive Affiliative and Self-Enhancing humor styles and increased use of maladaptive Aggressive and Self-Defeating humor. Reduced use of Self-Enhancing humor mediated the relationship between most types of cognitive distortions and depressed mood, indicating that distorted negative thinking may interfere with an individual's ability to adopt a humorous and cheerful outlook on life (i.e., use Self-Enhancing humor) as a way of regulating emotions and coping with stress, thereby resulting in elevated depressive symptoms. Similarly, Self-Defeating humor mediated the association of the social impact of cognitive distortions with depression, such that this humor style may be used as a coping strategy for dealing with distorted thinking that ultimately backfires and results in increased dysphoria. PMID:27547253

  6. Optimized laser turrets for minimum phase distortion

    NASA Technical Reports Server (NTRS)

    Vanderplaats, G. N.; Fuhs, A. E.; Blaisdell, G. A.

    1980-01-01

    An analysis and computer program which optimizes laser turret geometry to obtain minimum phase distortion is described. Phase distortion due to compressible, inviscid flow over small perturbation laser turrets in subsonic or supersonic flow is calculated. The turret shape is determined by a two dimensional Fourier series; in a similar manner, the flow properties are given by a Fourier series. Phase distortion is calcualted for propagation at serveral combinations of elevation and azimuth angles. A sum is formed from the set of values, and this sum becomes the objective function for an optimization computer program. The shape of the turret is varied to provide minimum phase distortion.

  7. Magneto-atmospheric waves

    NASA Technical Reports Server (NTRS)

    Thomas, J. H.

    1983-01-01

    A theoretical treatment of magneto-atmospheric waves is presented and applied to the modelling of waves in the solar atmosphere. The waves arise in compressible, stratified, electrically conductive atmospheres within gravitational fields when permeated by a magnetic field. Compression, buoyancy, and distortion of the magnetic field all contribute to the existence of the waves. Basic linearized equations are introduced to describe the waves and attention is given to plane-stratified atmospheres and their stability. A dispersion relation is defined for wave propagation in a plane-stratified atmosphere when there are no plane-wave solutions. Solutions are found for the full wave equation in the presence of either a vertical or a horizontal magnetic field. The theory is applied to describing waves in sunspots, in penumbrae, and flare-induced coronal disturbances.

  8. Segregation distortion in myotonic dystrophy.

    PubMed Central

    Magee, A C; Hughes, A E

    1998-01-01

    Myotonic dystrophy (DM) is an autosomal dominant disease which, in the typical pedigree, shows a three generation anticipation cascade. This results in infertility and congenital myotonic dystrophy (CDM) with the disappearance of DM in that pedigree. The concept of segregation distortion, where there is preferential transmission of the larger allele at the DM locus, has been put forward to explain partially the maintenance of DM in the population. In a survey of DM in Northern Ireland, 59 pedigrees were ascertained. Sibships where the status of all the members had been identified were examined to determine the transmission of the DM expansion from affected parents to their offspring. Where the transmitting parent was male, 58.3% of the offspring were affected, and in the case of a female transmitting parent, 68.7% were affected. Studies on meiotic drive in DM have shown increased transmission of the larger allele at the DM locus in non-DM heterozygotes for CTGn. This study provides further evidence that the DM expansion tends to be transmitted preferentially. PMID:9863607

  9. Traversable wormholes in distorted gravity

    NASA Astrophysics Data System (ADS)

    Garattini, Remo

    2015-07-01

    In this paper, we consider the effects of distorted gravity on the traversability of the wormholes. In particular, we consider configurations which are sustained by their own gravitational quantum fluctuations. The Ultraviolet divergences appearing to one loop are taken under control with the help of a Noncommutative geometry representation and gravity's rainbow. In this context, it will be shown that for every framework, the self-sustained equation will produce a Wheeler wormhole, namely a wormhole of Planckian size. This means that, from the point of view of traversability, the wormhole will be traversable in principle, but not in practice. For this purpose, in the context of gravity's rainbow we have considered different proposals of rainbow's functions to see if the smallness of the wormhole is dependent on the chosen form of the rainbow's function. Unfortunately, we discover that this is not the case and we suggest that the self-sustained equation can be improved to see if the wormhole radius can be enlarged or not. Some consequences on topology change are discussed.

  10. Light absorption in distorted graphene

    NASA Astrophysics Data System (ADS)

    Hernández-Ortiz, Saúl; Valenzuela, David; Raya, Alfredo; Sánchez-Madrigal, Saúl

    2016-04-01

    We model the low energy dynamics of graphene in the continuum in terms of a version of reduced quantum electrodynamics (QED) restricting fermions to a (2 + 1)-dimensional brane, while photons remain within the (3 + 1)-dimensional bulk. For charge carriers, besides the Dirac mass gap, we consider a Haldane mass term which is induced by parametrizing an effective parity 𝒫 and time-reversal 𝒯 symmetry breaking that occurs on the brane when distortions of the honeycomb array are such that the equivalence between sublattices is lost. We make use of the relativistic Kubo formula and carry out an explicit calculation of the transverse conductivity. As expected, the filling factor is a half (in natural units) for each fermion species. Furthermore, assuming that a sample of this material is radiated perpendicularly with polarized monochromatic light of frequency ω, from the modified Maxwell’s equations we address the problem of light absorption in graphene in terms of the said conductivity. We observe that light penetrating the sample changes its angle of polarization solely by effect of the induced mass, in analogy to the Faraday effect but in absence of magnetic fields. This effect might be relevant for the development of optic filters based on mechanical stretching of graphene flakes.

  11. Self-Compassion and Interpersonal Cognitive Distortions

    ERIC Educational Resources Information Center

    Akin, Ahmet

    2010-01-01

    The purpose of this study is to examine the relationships between self-compassion and interpersonal cognitive distortions. Participants were 338 university students. In this study, the Self-compassion Scale and the Interpersonal Cognitive Distortions Scale were used. The relationships between self-compassion and interpersonal cognitive distortions…

  12. Two-tone distortion in intracochlear pressure

    NASA Astrophysics Data System (ADS)

    Dong, Wei; Olson, Elizabeth S.

    2005-05-01

    Two-tone distortion was measured in the intracochlear pressure in the base of the gerbil cochlea, close to the sensory tissue, where the local motions and forces of the organ of Corti can be detected. The measurements probe both the underlying nonlinear process that generates two-tone distortion, and the filtering and spreading of the distortion products. Some of our findings are as follows: (1) The observations were consistent with previous observations of two-tone distortion in BM motion [J. Neurophysiol. 77, 2385-2399 (1997); J. Neurophysiol. 78, 261-270 (1997)]. (2) Frequency sweeps show distortion product tuning and phase-versus-frequency behavior that is similar, but not identical, to single tone tuning. (3) The decay of distortion products with distance from the basilar membrane confirms the feasibility that they could drive the stapes by a direct fluid route, as proposed by Ren [Nat. Neurosci. 7, 333-334 (2004)]. (4) The phases of the distortion products within a single family (the group of distortion products generated by a single primary pair) in some cases alternated between 0° and 180° when referenced to the phases of the primaries. This behavior is predicted by a simple compressive nonlinearity. .

  13. Temperature distortion generator for turboshaft engine testing

    NASA Technical Reports Server (NTRS)

    Klann, G. A.; Barth, R. L.; Biesiadny, T. J.

    1984-01-01

    The procedures and unique hardware used to conduct an experimental investigation into the response of a small-turboshaft-engine compression system to various hot gas ingestion patterns are presented. The temperature distortion generator described herein uses gaseous hydrogen to create both steady-state and time-variant, or transient, temperature distortion at the engine inlet. The range of transient temperature ramps produced by the distortion generator during the engine tests was from less than 111 deg K/sec (200 deg R/sec) to above 611 deg K/sec (1100 deg R/sec); instantaneous temperatures to 422 deg K (760 deg R) above ambient were generated. The distortion generator was used to document the maximum inlet temperatures and temperature rise rates that the compression system could tolerate before the onset of stall for various circumferential distortions as well as the compressor system response during stall.

  14. Combined pressure and temperature distortion effects on internal flow of a turbofan engine

    NASA Technical Reports Server (NTRS)

    Braithwaite, W. M.; Soeder, R. H.

    1979-01-01

    An additional data base for improving and verifying a computer simulation developed by an engine manufacturer was obtained. The multisegment parallel compressor simulation was designed to predict the effects of steady-state circumferential inlet total-pressure and total-temperature distortions on the flows into and through a turbofan compression system. It also predicts the degree of distortion that will result in surge of the compressor. The effect of combined 180 deg square-wave distortion patterns of total pressure and total temperature in various relative positions is reported. The observed effects of the combined distortion on a unitary bypass ratio turbofan engine are presented in terms of total and static pressure profiles and total temperature profiles at stations ahead of the inlet guide vanes as well as through the fan-compressor system. These observed profiles are compared with those predicted by the complex multisegment model. The effects of relative position of the two components comprising the combined distortion on the degree resulting in surge are discussed. Certain relative positions required less combined distortion than either a temperature or pressure distortion by itself.

  15. Compensation for 6.5 K cryogenic distortion of a fused quartz mirror by refiguring

    NASA Technical Reports Server (NTRS)

    Augason, Gordon C.; Young, Jeffrey A.; Melugin, Ramsey K.; Clarke, Dana S.; Howard, Steven D.; Scanlan, Michael; Wong, Steven; Lawton, Kenneth C.

    1993-01-01

    A 46 cm diameter, lightweight, Amersil TO8E, fused-natural-quartz mirror with a single-arch cross section was tested at the NASA-Ames Research Center Cryogenic Optical Test Facility to measure its cryogenic distortion at 6.5 K. Then the mirror was refigured with the inverse of the measured cryogenic distortion to compensate for this figure defect. The mirror was retested at 6.5 K and found to have a significantly improved figure. The compensation for cryogenic distortion was not complete, but preliminary analysis indicates that the compensation was better than 0.25 waves P-V if edge effects are ignored. The feasibility of compensating for cryogenic distortion by refiguring has thus been verified.

  16. Gravitational Effects on Distortion in Sintering

    NASA Technical Reports Server (NTRS)

    German, Randall M.

    2003-01-01

    During sintering a powder compact gains strength through low-temperature interparticle bonding, usually induced by solid-state surface diffusion, followed by further strength contributions from high-temperature densification. In cases where a liquid phase forms, sintering densification is accelerated and shape retention is sustained while open pores remain and contribute capillary forces. Unfortunately, sintering densification requires the compact become thermally softened to a point where creep strain rates reach levels near 10(exp -2)/s when the liquid forms. On the other hand, thermal softening of the powder compact substantially reduces the strength at high temperatures. Therefore, the in situ strength evolution during sintering is a primary focus to separate compact densification (as required for high performance) with minimized distortion (as required for net-shaping). With respect to gravitation effects on distortion during sintering there are two points of substantial weakness - prior to significant interparticle bonding and during final pore closure. This research is focused on understanding the competition among interparticle neck growth, densification, thermal softening, grain boundary wetting, capillary effects associated with liquid wetting and residual porosity, and gravity. Most surprising is the apparent role of gravity, where the deviatoric stress acting on the powder structure induces skeletal formation that reduces distortion. In contrast with theory, microgravity samples exhibit more distortion yet fail to fully densify. Results are presented on the experimental concepts supporting an emerging model of sintering strength evolution that enables understanding of both distortion and densification. The experiments have relied on tungsten heavy alloys, various combinations of dihedral angle, pore size, initial porosity, liquid:solid ratio, and heating rates. On Earth, the dominant factor with respect to distortion is the starting body heterogeneity

  17. Volterra distortions, spinning strings, and cosmic defects

    NASA Astrophysics Data System (ADS)

    Puntigam, Roland A.; Soleng, Harald H.

    1997-05-01

    Cosmic strings, as topological spacetime defects, show striking resemblance to defects in solid continua: distortions, which can be classified into disclinations and dislocations, are line-like defects characterized by a delta-function-valued curvature and torsion distribution giving rise to rotational and translational holonomy. We exploit this analogy and investigate how distortions can be adapted in a systematic manner from solid-state systems to Einstein - Cartan gravity. As distortions are efficiently described within the framework of an 0264-9381/14/5/017/img5 gauge theory of solid continua with line defects, we are led in a straightforward way to a Poincaré gauge approach to gravity which is a natural framework for introducing the notion of distorted spacetimes. Constructing all ten possible distorted spacetimes, we recover, inter alia, the well known exterior spacetime of a spin-polarized cosmic string as a special case of such a geometry. In a second step, we search for matter distributions which, in Einstein - Cartan gravity, act as sources of distorted spacetimes. The resulting solutions, appropriately matched to the distorted vacua, are cylindrically symmetric and are interpreted as spin-polarized cosmic strings and cosmic dislocations.

  18. Correction of walk-off induced wavefront distortion for continuous-variable applications

    NASA Astrophysics Data System (ADS)

    Zou, Hongxin; Shen, Yong; Guo, Hong

    2016-05-01

    We theoretically and experimentally investigate wave front distortion in critically phase matched continuous-wave (CW) second harmonic generation (SHG). Due to the walk-off effect in the nonlinear crystal, the generated second harmonic is extremely elliptical and quite non-Gaussian, which causes a very low matching and coupling efficiency in experiment. Cylindrical lenses and walk-off compensating crystals are adopted to correct distorted wave fronts, and obtain a good TEM00 mode efficiency. Theoretically we simulate the correction effect of 266nm laser generated with SHG. The experiment results accord well with theoretical simulation and above 80 percent TEM00 component is obtained for 266nm continuous wave laser with 4.8 degree walk-off angle in BBO crystal. After that, an optical mode cleaner is used to obtain an ideal Gaussian mode. With these treatments, the generated second harmonic can be utilized in continuous-variable regime, where almost perfect mode matching is demanded.

  19. Distortion in the frequency demodulator using feedback.

    NASA Technical Reports Server (NTRS)

    Hoffman, E.; Schilling, D. L.

    1972-01-01

    The response of a frequency demodulator using feedback (FMFB) to a frequency modulated signal is analyzed. Canonical equations of operation are obtained. Harmonic distortion is calculated for the case of a sinusoidal modulating signal. Intermodulation distortion is calculated assuming a noise-like modulation. Design curves are presented. The special case of harmonic and intermodulation distortion in a discriminator is also presented. It is shown that the results obtained in this paper by treating the discriminator as a degenerate FMFB compare favorably with those obtained by other authors. However, the results presented here do not require digital computation.

  20. Spectral distortions of the cosmic microwave background

    NASA Technical Reports Server (NTRS)

    Adams, Fred C.; Mcdowell, Jonathan C.; Freese, Katherine; Levin, Janna

    1989-01-01

    Recent experiments indicate that the spectrum of the cosmic microwave background deviates from a pure blackbody; here, spectral distortions produced by cosmic dust are considered. The main result is that cosmic dust in conjunction with an injected radiation field (perhaps produced by an early generation of very massive stars) can explain the observed spectral distortions without violating existing cosmological constraints. In addition, it is shown that Compton y-distortions can also explain the observed spectral shape, but the energetic requirements are more severe.

  1. Vacuum polarization near a distorted black hole

    NASA Astrophysics Data System (ADS)

    Frolov, V. P.; Alberto García, D.

    1983-12-01

    The vacuum polarization near a black hole distorted by the axially symmetric gravitational field of external matter is studied. The explicit expression for <φ2> at the pole of the distorted horizon is obtained. Also at Sección de Graduados, Escuela Superior de Ingeniería Mecánica y Eléctrica del IPN, México DF, México.

  2. Coulomb Distortion in the Inelastic Regime

    SciTech Connect

    Patricia Solvignon, Dave Gaskell, John Arrington

    2009-09-01

    The Coulomb distortion effects have been for a long time neglected in deep inelastic scattering for the good reason that the incident energies were very high. But for energies in the range of earlier data from SLAC or at JLab, the Coulomb distortion could have the potential consequence of affecting the A-dependence of the EMC effect and of the longitudinal to transverse virtual photon absorption cross section ratio $R(x,Q^2)$.

  3. Investigating 3-body Decays of Cluster States with the PAT-TPC

    NASA Astrophysics Data System (ADS)

    Carpenter, Lisa; Ayyad Limonge, Y.; Bazin, D.; Beceiro-Novo, S.; Bradt, J.; Cortesi, M.; Mittig, W.; Ahn, T.; Kolata, J. J.; Meisel, Z.; Bechetti, F. D.; Fritsch, A.; Howard, A.

    2016-03-01

    Recent model calculations with most advanced methods for cluster states have shown the need of experimental data to probe the structure of light exotic nuclei, including those with α-clustering, such as 14C. The Prototype Active Target Time Projection Chamber (PAT-TPC) allows us to investigate these types of structures, giving access to the full excitation function with a single beam energy. This type of experiment measures resonances in 14C that can be compared to the models. With an improved Micromegas pad plane with a circular backgammon design we are able to investigate 3-body decays in addition to 2-body scattering. The measurements were carried out by resonant alpha-scattering on 10Be beam delivered by the TwinSol facility at the University of Notre Dame. We also observed the 3-body decay of the Hoyle State in 12C from a 12N or 12B beam with the same device. Preliminary results will be presented. This work is supported by the National Science Foundation.

  4. Plasticity and Awareness of Bodily Distortion

    PubMed Central

    Zantedeschi, Marta

    2016-01-01

    Knowledge of the body is filtered by perceptual information, recalibrated through predominantly innate stored information, and neurally mediated by direct sensory motor information. Despite multiple sources, the immediate prediction, construction, and evaluation of one's body are distorted. The origins of such distortions are unclear. In this review, we consider three possible sources of awareness that inform body distortion. First, the precision in the body metric may be based on the sight and positioning sense of a particular body segment. This view provides information on the dual nature of body representation, the reliability of a conscious body image, and implicit alterations in the metrics and positional correspondence of body parts. Second, body awareness may reflect an innate organizational experience of unity and continuity in the brain, with no strong isomorphism to body morphology. Third, body awareness may be based on efferent/afferent neural signals, suggesting that major body distortions may result from changes in neural sensorimotor experiences. All these views can be supported empirically, suggesting that body awareness is synthesized from multimodal integration and the temporal constancy of multiple body representations. For each of these views, we briefly discuss abnormalities and therapeutic strategies for correcting the bodily distortions in various clinical disorders.

  5. Zero-distortion lossless data embedding

    NASA Astrophysics Data System (ADS)

    Nagaraj, Nithin; Mullick, Rakesh

    2004-05-01

    All known methods of lossless or reversible data embedding that exist today suffer from two major disadvantages: 1) The embedded image suffers from distortion, however small it may be by the very process of embedding and 2) The requirement of a special parser (decoder), which is necessary for the client to remove the embedded data in order to obtain the original image (lossless). We propose a novel lossless data embedding method where both these disadvantages are circumvented. Zero-distortion lossless data embedding (ZeroD-LDE) claims 'zero-distortion' of the embedded image for all viewing purposes and further maintaining that clients without any specialized parser can still recover the original image losslessly but would not have direct access to the embedded data. The fact that not all gray levels are used by most images is exploited to embed data by selective lossless compression of run-lengths of zeros (or any compressible pattern). Contiguous runs of zeros are changed such that the leading zero is made equal to the maximum original intensity plus the run-length and the succeeding zeros are converted to the embedded data (plus maximum original intensity) thus achieving extremely high embedding capacities. This way, the histograms of the host-data and the embedded data do not overlap and hence we can obtain zero-distortion by using the window-level setting of standard DICOM viewers. The embedded image is thus not only DICOM compatible but also zero-distortion visually and requires no clinical validation.

  6. Core-nucleus distortation in hypernuclei

    SciTech Connect

    Bodmer, A.R.; Usmani, Q.N.

    1995-08-01

    We are completing a study of the effects of the spherical distortion of the {open_quotes}core{close_quotes} nucleus by the {Lambda} in a hypernucleus. The response of the core was determined by an appropriately chosen energy-density functional which depends, in particular, on the nuclear compressibility. The forcing action of the A is determined by the nuclear density dependence of the {Lambda} binding in nuclear matter which is obtained from our work on the {Lambda} single-particle energies. Because of the strongly repulsive {Lambda}NN forces, this {Lambda} binding {open_quotes}saturates{close_quotes} at a density close to the central density of nuclei, and results in a reduced core-nucleus distortion much less than would otherwise be obtained. The effects of the core distortion then turn out to be very small even for quite light hypernuclei. This result justifies the assumption that spherical core nuclei are effectively undistorted in a hypernucleus.

  7. Minimal distortion pathways in polyhedral rearrangements.

    PubMed

    Casanova, David; Cirera, Jordi; Llunell, Miquel; Alemany, Pere; Avnir, David; Alvarez, Santiago

    2004-02-18

    A definition of minimum distortion paths between two polyhedra in terms of continuous shape measures (CShM) is presented. A general analytical expression deduced for such pathways makes use of one parameter, the minimum distortion constant, that can be easily obtained through the CShM methodology and is herein tabulated for pairs of polyhedra having four to eight vertexes. The work presented here also allows us to obtain representative model molecular structures along the interconversion pathways. Several commonly used polytopal rearrangement pathways are shown to be in fact minimum distortion pathways: the spread path leading from the tetrahedron to the square, the Berry pseudorotation that interconverts a square pyramid and a trigonal bipyramid, and the Bailar twist for the interconversion of the octahedron and the trigonal prism. Examples of applications to the analysis of the stereochemistries of several families of metal complexes are presented. PMID:14871107

  8. Dynamic Inlet Distortion Prediction with a Combined Computational Fluid Dynamics and Distortion Synthesis Approach

    NASA Technical Reports Server (NTRS)

    Norby, W. P.; Ladd, J. A.; Yuhas, A. J.

    1996-01-01

    A procedure has been developed for predicting peak dynamic inlet distortion. This procedure combines Computational Fluid Dynamics (CFD) and distortion synthesis analysis to obtain a prediction of peak dynamic distortion intensity and the associated instantaneous total pressure pattern. A prediction of the steady state total pressure pattern at the Aerodynamic Interface Plane is first obtained using an appropriate CFD flow solver. A corresponding inlet turbulence pattern is obtained from the CFD solution via a correlation linking root mean square (RMS) inlet turbulence to a formulation of several CFD parameters representative of flow turbulence intensity. This correlation was derived using flight data obtained from the NASA High Alpha Research Vehicle flight test program and several CFD solutions at conditions matching the flight test data. A distortion synthesis analysis is then performed on the predicted steady state total pressure and RMS turbulence patterns to yield a predicted value of dynamic distortion intensity and the associated instantaneous total pressure pattern.

  9. Objects exhibit body model like shape distortions.

    PubMed

    Saulton, Aurelie; Dodds, Trevor J; Bülthoff, Heinrich H; de la Rosa, Stephan

    2015-05-01

    Accurate knowledge about size and shape of the body derived from somatosensation is important to locate one's own body in space. The internal representation of these body metrics (body model) has been assessed by contrasting the distortions of participants' body estimates across two types of tasks (localization task vs. template matching task). Here, we examined to which extent this contrast is linked to the human body. We compared participants' shape estimates of their own hand and non-corporeal objects (rake, post-it pad, CD-box) between a localization task and a template matching task. While most items were perceived accurately in the visual template matching task, they appeared to be distorted in the localization task. All items' distortions were characterized by larger length underestimation compared to width. This pattern of distortion was maintained across orientation for the rake item only, suggesting that the biases measured on the rake were bound to an item-centric reference frame. This was previously assumed to be the case only for the hand. Although similar results can be found between non-corporeal items and the hand, the hand appears significantly more distorted than other items in the localization task. Therefore, we conclude that the magnitude of the distortions measured in the localization task is specific to the hand. Our results are in line with the idea that the localization task for the hand measures contributions of both an implicit body model that is not utilized in landmark localization with objects and other factors that are common to objects and the hand. PMID:25678309

  10. Analysis of Different Harmonic and Intermodulation Distortions for CATV Systems

    NASA Astrophysics Data System (ADS)

    Singh, Sandeep; Kamaljit, Singh Bhatia; Anurag, Sharma; Kaur, Harsimrat

    2015-06-01

    In this paper, after examining all the basic design issues of CATV systems, prominent distortions like harmonic and intermodulation distortions are taken into account for different order. Besides outer distortions for CATV sources, inner distortion of relative intensity to noise is disabled for current analysis.

  11. Reflective optical imaging system with balanced distortion

    SciTech Connect

    Chapman, H.N.; Hudyma, R.M.; Shafer, D.R.; Sweeney, D.W.

    1999-10-26

    An optical system compatible with short wavelength (extreme ultraviolet) radiation comprising four reflective elements for projecting a mask image onto a substrate is disclosed. The four optical elements comprise, in order from object to image, convex, concave, convex and concave mirrors. The optical system is particularly suited for step and scan lithography methods. The invention enables the use of larger slit dimensions associated with ring field scanning optics, improves wafer throughput and allows higher semiconductor device density. The inventive optical system is characterized by reduced dynamic distortion because the static distortion is balanced across the slit width.

  12. Reflective optical imaging system with balanced distortion

    DOEpatents

    Chapman, Henry N.; Hudyma, Russell M.; Shafer, David R.; Sweeney, Donald W.

    1999-01-01

    An optical system compatible with short wavelength (extreme ultraviolet) An optical system compatible with short wavelength (extreme ultraviolet) radiation comprising four reflective elements for projecting a mask image onto a substrate. The four optical elements comprise, in order from object to image, convex, concave, convex and concave mirrors. The optical system is particularly suited for step and scan lithography methods. The invention enables the use of larger slit dimensions associated with ring field scanning optics, improves wafer throughput and allows higher semiconductor device density. The inventive optical system is characterized by reduced dynamic distortion because the static distortion is balanced across the slit width.

  13. Reflective optical imaging systems with balanced distortion

    DOEpatents

    Hudyma, Russell M.

    2001-01-01

    Optical systems compatible with extreme ultraviolet radiation comprising four reflective elements for projecting a mask image onto a substrate are described. The four optical elements comprise, in order from object to image, convex, concave, convex and concave mirrors. The optical systems are particularly suited for step and scan lithography methods. The invention enables the use of larger slit dimensions associated with ring field scanning optics, improves wafer throughput, and allows higher semiconductor device density. The inventive optical systems are characterized by reduced dynamic distortion because the static distortion is balanced across the slit width.

  14. Zigzag laser with reduced optical distortion

    DOEpatents

    Albrecht, Georg F.; Comaskey, Brian; Sutton, Steven B.

    1994-01-01

    The architecture of the present invention has been driven by the need to solve the beam quality problems inherent in Brewster's angle tipped slab lasers. The entrance and exit faces of a solid state slab laser are cut perpendicular with respect to the pump face, thus intrinsically eliminating distortion caused by the unpumped Brewster's angled faces. For a given zigzag angle, the residual distortions inherent in the remaining unpumped or lightly pumped ends may be reduced further by tailoring the pump intensity at these ends.

  15. Zigzag laser with reduced optical distortion

    DOEpatents

    Albrecht, G.F.; Comaskey, B.; Sutton, S.B.

    1994-04-19

    The architecture of the present invention has been driven by the need to solve the beam quality problems inherent in Brewster's angle tipped slab lasers. The entrance and exit faces of a solid state slab laser are cut perpendicular with respect to the pump face, thus intrinsically eliminating distortion caused by the unpumped Brewster's angled faces. For a given zigzag angle, the residual distortions inherent in the remaining unpumped or lightly pumped ends may be reduced further by tailoring the pump intensity at these ends. 11 figures.

  16. Interaction of upstream flow distortions with high Mach number cascades

    NASA Technical Reports Server (NTRS)

    Englert, G. W.

    1981-01-01

    Features of the interaction of flow distortions, such as gusts and wakes with blade rows of advance type fans and compressors having high tip Mach numbers are modeled. A typical disturbance was assumed to have harmonic time dependence and was described, at a far upstream location, in three orthogonal spatial coordinates by a double Fourier series. It was convected at supersonic relative to a linear cascade described as an unrolled annulus. Conditions were selected so that the component of this velocity parallel to the axis of the turbomachine was subsonic, permitting interaction between blades through the upstream as well as downstream flow media. A strong, nearly normal shock was considered in the blade passages which was allowed curvature and displacement. The flows before and after the shock were linearized relative to uniform mean velocities in their respective regions. Solution of the descriptive equations was by adaption of the Wiener-Hopf technique, enabling a determination of distortion patterns through and downstream of the cascade as well as pressure distributions on the blade and surfaces. Details of interaction of the disturbance with the in-passage shock were discussed. Infuences of amplitude, wave length, and phase of the disturbance on lifts and moments of cascade configurations are presented. Numerical results are clarified by reference to an especially orderly pattern of upstream vertical motion in relation to the cascade parameters.

  17. A local instability of tidally distorted accretion disks

    NASA Technical Reports Server (NTRS)

    Goodman, Jeremy

    1993-01-01

    Hydrodynamic accretion disks in binary star systems have local, three-dimensional, approximately incompressible instabilities whose growth rate is linearly proportional to the tidal field of the secondary star. The instability occurs throughout the disk but is most rapid in the outer parts. The free energy for the instability derives from the tidal distortion of the disk rather than its differential rotation. The instability will excite m-parallel 1 internal waves of the type discussed by Vishniac et al. (1992), and it should facilitate return of angular momentum from the disk to the secondary star. It is closely related to a recently discovered instability that has been suggested as a mechanism for transition to turbulence in terrestrial and laboratory flows, but whether it will lead to strong turbulence in disks is as yet unclear.

  18. A symplectic integrator for the symmetry reduced and regularised planar 3-body problem with vanishing angular momentum

    NASA Astrophysics Data System (ADS)

    Rose, Danya; Dullin, Holger R.

    2013-10-01

    We construct an explicit reversible symplectic integrator for the planar 3-body problem with zero angular momentum. We start with a Hamiltonian of the planar 3-body problem that is globally regularised and fully symmetry reduced. This Hamiltonian is a sum of 10 polynomials each of which can be integrated exactly, and hence a symplectic integrator is constructed. The performance of the integrator is examined with three numerical examples: The figure eight, the Pythagorean orbit, and a periodic collision orbit.

  19. An enhanced HPIV configuration for flow measurement through thick distorting windows

    NASA Astrophysics Data System (ADS)

    Alcock, R. D.; Garner, C. P.; Halliwell, N. A.; Coupland, J. M.

    2004-04-01

    This paper reports on a new holographic particle image velocimetry configuration and analysis procedure that can be used to measure particle displacement through thick distorting windows. The technique builds upon the scanning fibre probe based object conjugate reconstruction geometry; however it avoids the requirement of using a holographic optical element to correct for window distortion of the beams. Removal of the distortion is instead accomplished by using a ray trace mapping between the wave vectors scattered by the particles at the time of each exposure and those measured by the interrogation system. The technique is ideally suited to the study of flow structure within the combustion chamber of a diesel engine, and preliminary experimental results that attempt to assess the accuracy of the technique in this situation are presented.

  20. Distortion of ultrashort pulses caused by aberrations

    NASA Astrophysics Data System (ADS)

    Horváth, Z. L.; Kovács, A. P.; Bor, Zs.

    The effect of the primary wave aberrations (spherical aberration, astigmatism and coma) on ultrashort pulses is studied by the Nijboer-Zernike theory. The results of the geometrical and the wave optical treatments are compared.

  1. Distortion invariant pattern recognition with phase filters

    NASA Technical Reports Server (NTRS)

    Rosen, Joseph; Shamir, Joseph

    1987-01-01

    A recently developed approach for pattern recognition using spatial filters with reduced tolerance requirements is employed for the generation of filters containing mainly phase information. As anticipated, the recognition levels were decreased, but they remain adequate for unambiguous identification together with appreciable amounts of distortion immunity. Furthermore, the information content of the filters is compatible with low devices like spatial light modulators.

  2. Properties of the distorted Kerr black hole

    NASA Astrophysics Data System (ADS)

    Abdolrahimi, Shohreh; Kunz, Jutta; Nedkova, Petya; Tzounis, Christos

    2015-12-01

    We investigate the properties of the ergoregion and the location of the curvature singularities for the Kerr black hole distorted by the gravitational field of external sources. The particular cases of quadrupole and octupole distortion are studied in detail. We also investigate the scalar curvature invariants of the horizon and compare their behaviour with the case of the isolated Kerr black hole. In a certain region of the parameter space the ergoregion consists of a compact region encompassing the horizon and a disconnected part extending to infinity. The curvature singularities in the domain of outer communication, when they exist, are always located on the boundary of the ergoregion. We present arguments that they do not lie on the compact ergosurface. For quadrupole distortion the compact ergoregion size is negatively correlated with the horizon angular momentum when the external sources are varied. For octupole distortion infinitely many ergoregion configurations can exist for a certain horizon angular momentum. For some special cases we can have J2/M4 > 1 and yet avoid a naked singularity.

  3. Rate-distortion theory and human perception.

    PubMed

    Sims, Chris R

    2016-07-01

    The fundamental goal of perception is to aid in the achievement of behavioral objectives. This requires extracting and communicating useful information from noisy and uncertain sensory signals. At the same time, given the complexity of sensory information and the limitations of biological information processing, it is necessary that some information must be lost or discarded in the act of perception. Under these circumstances, what constitutes an 'optimal' perceptual system? This paper describes the mathematical framework of rate-distortion theory as the optimal solution to the problem of minimizing the costs of perceptual error subject to strong constraints on the ability to communicate or transmit information. Rate-distortion theory offers a general and principled theoretical framework for developing computational-level models of human perception (Marr, 1982). Models developed in this framework are capable of producing quantitatively precise explanations for human perceptual performance, while yielding new insights regarding the nature and goals of perception. This paper demonstrates the application of rate-distortion theory to two benchmark domains where capacity limits are especially salient in human perception: discrete categorization of stimuli (also known as absolute identification) and visual working memory. A software package written for the R statistical programming language is described that aids in the development of models based on rate-distortion theory. PMID:27107330

  4. Third Order Distortion And Spectacle Lens Design

    NASA Astrophysics Data System (ADS)

    Atchison, David A.

    1986-05-01

    Third order (primary) aberration theory has had little application to the design of aspheric spectacle lenses. Such an application would be useful because: 1. Third order theory is useful in designing simple optical systems, as relatively simple equations can be used to obtain approximate magnitudes of aberrations and to show how these aberrations change with variations in design parameters without recourse to a large mass of data. 2. Aspherising one or both surfaces of spectacle lenses allows the correction of off-axis power errors in high positive power lenses where this would be otherwise impossible, and enables other factors, such as distortion correction, to be considered simultaneously with off-axis power error correction over the total range of lens powers. Third order formulae are developed for calculation of distortion in thin spectacle lenses, when one or both surfaces are conicoid aspherics. Results are presented which show the validity of using third order theory. Solutions which allow correction of rotatory or peripheral distortion, when one lens surface is a conicoid aspheric, are illustrated. A study of these solutions shows that one of the off-axis power errors (eg. oblique astigmatism) and one of the distortions can be simultaneously eliminated, but the lens forms required are too curved to be cosmetically feasible.

  5. Statistical characterization of C-arm distortion with application to intra-operative distortion correction

    NASA Astrophysics Data System (ADS)

    Chintalapani, Gouthami; Jain, Ameet K.; Taylor, Russell H.

    2007-03-01

    C-arm images suffer from pose dependant distortion, which needs to be corrected for intra-operative quantitative 3D surgical guidance. Several distortion correction techniques have been proposed in the literature, the current state of art using a dense grid pattern rigidly attached to the detector. These methods become cumbersome for intra-operative use, such as 3D reconstruction, since the grid pattern interferes with patient anatomy. The primary contribution of this paper is a framework to statistically analyze the distortion pattern which enables us to study alternate intra-operative distortion correction methods. In particular, we propose a new phantom that uses very few BBs, and yet accurately corrects for distortion. The high dimensional space of distortion pattern can be effectively characterized by principal component analysis (PCA). The analysis shows that only first three eigen modes are significant and capture about 99% of the variation. Phantom experiments indicate that distortion map can be recovered up to an average accuracy of less than 0.1 mm/pixel with these three modes. With this prior statistical knowledge, a subset of BBs can be sufficient to recover the distortion map accurately. Phantom experiments indicate that as few as 15 BBs can recover distortion with average error of 0.17 mm/pixel, accuracy sufficient for most clinical applications. These BBs can be arranged on the periphery of the C-arm detector, minimizing the interference with patient anatomy and hence allowing the grid to remain attached to the detector permanently. The proposed method is fast, economical, and C-arm independent, potentially boosting the clinical viability of applications such as quantitative 3D fluoroscopic reconstruction.

  6. Fabric geometry distortion during composites processing

    NASA Technical Reports Server (NTRS)

    Chen, Julie

    1994-01-01

    Waviness and tow misalignment are often cited as possible causes of data scatter and lower compression stiffness and strength in textile composites. Strength differences of as much as 40 percent have been seen in composites that appear to have the same basic material and structural properties -- i.e., yarn orientation, yarn size, interlacing geometry. Fabric geometry distortion has been suggested as a possible reason for this discrepancy, but little quantitative data or substantial evidence exists. The focus of this research is to contribute to the present understanding of the causes and effects of geometric distortion in textile composites. The initial part of the study was an attempt to gather qualitative information on a variety of textile structures. Existing and new samples confirmed that structures with a significant direction presence would be more susceptible to distortion due to the compaction process. Thus, uniweaves (fiber vol frac: 54-72 percent) biaxial braids (vf: 34-58 percent) demonstrated very little fabric geometry distortion. In stitched panels, only slight buckling of z-direction stitches was observed, primarily near the surface. In contrast, for structures with high compaction ratios -- e.g., large cylindrical yarns (2.5:1) orpowder towpreg (4:1) -- there were visible distortions where previously smooth and periodic undulations were transformed to abrupt changes in direction. A controlled study of the effect of forming pressure on distortion was conducted on type 162 glass plain weave fabrics. Panels (6 x 6 in) were produced via a resin infusion type setup, but with an EPON 815 epoxy resin. Pressures ranging from hand layup to 200 psi were used (vf: 34-54 percent). Photomicrographs indicated that at pressures up to 50 psi, large changes in thickness were due primarily to resin squeeze out. At higher pressures, when intimate contact was made between the layers, there was some tow flattening and in-plane shifting to optimize nesting. However

  7. Fish's Muscles Distortion and Pectoral Fins Propulsion of Lift-Based Mode

    NASA Astrophysics Data System (ADS)

    Yang, S. B.; Han, X. Y.; Qiu, J.

    As a sort of MPF(median and/or paired fin propulsion), pectoral fins propulsion makes fish easier to maneuver than other propulsion, according to the well-established classification scheme proposed by Webb in 1984. Pectoral fins propulsion is classified into oscillatory propulsion, undulatory propulsion and compound propulsion. Pectoral fins oscillatory propulsion, is further ascribable to two modes: drag-based mode and lift-based mode. And fish exhibits strong cruise ability by using lift-based mode. Therefore to robot fish design using pectoral fins lift-based mode will bring a new revolution to resources exploration in blue sea. On the basis of the wave plate theory, a kinematic model of fish’s pectoral fins lift-based mode is established associated with the behaviors of cownose ray (Rhinoptera bonasus) in the present work. In view of the power of fish’s locomotion from muscle distortion, it would be helpful benefit to reveal the mechanism of fish’s locomotion variation dependent on muscles distortion. So this study puts forward the pattern of muscles distortion of pectoral fins according to the character of skeletons and muscles of cownose ray in morphology and simulates the kinematics of lift-based mode using nonlinear analysis software. In the symmetrical fluid field, the model is simulated left-right symmetrically or asymmetrically. The results qualitatively show how muscles distortion determines the performance of fish locomotion. Finally the efficient muscles distortion associated with the preliminary dynamics is induced.

  8. JPEG 2000 Encoding with Perceptual Distortion Control

    NASA Technical Reports Server (NTRS)

    Watson, Andrew B.; Liu, Zhen; Karam, Lina J.

    2008-01-01

    An alternative approach has been devised for encoding image data in compliance with JPEG 2000, the most recent still-image data-compression standard of the Joint Photographic Experts Group. Heretofore, JPEG 2000 encoding has been implemented by several related schemes classified as rate-based distortion-minimization encoding. In each of these schemes, the end user specifies a desired bit rate and the encoding algorithm strives to attain that rate while minimizing a mean squared error (MSE). While rate-based distortion minimization is appropriate for transmitting data over a limited-bandwidth channel, it is not the best approach for applications in which the perceptual quality of reconstructed images is a major consideration. A better approach for such applications is the present alternative one, denoted perceptual distortion control, in which the encoding algorithm strives to compress data to the lowest bit rate that yields at least a specified level of perceptual image quality. Some additional background information on JPEG 2000 is prerequisite to a meaningful summary of JPEG encoding with perceptual distortion control. The JPEG 2000 encoding process includes two subprocesses known as tier-1 and tier-2 coding. In order to minimize the MSE for the desired bit rate, a rate-distortion- optimization subprocess is introduced between the tier-1 and tier-2 subprocesses. In tier-1 coding, each coding block is independently bit-plane coded from the most-significant-bit (MSB) plane to the least-significant-bit (LSB) plane, using three coding passes (except for the MSB plane, which is coded using only one "clean up" coding pass). For M bit planes, this subprocess involves a total number of (3M - 2) coding passes. An embedded bit stream is then generated for each coding block. Information on the reduction in distortion and the increase in the bit rate associated with each coding pass is collected. This information is then used in a rate-control procedure to determine the

  9. Rotating stall control in a high-speed stage with inlet distortion. Part 1: Radial distortion

    SciTech Connect

    Spakovszky, Z.S.; Weigl, H.J.; Paduano, J.D.; Schalkwyk, C.M. van; Suder, K.L.; Bright, M.M.

    1999-07-01

    This paper presents the first attempt to stabilize rotating stall in a single-stage transonic axial flow compressor with inlet distortion using active feedback control. The experiments were conducted at the NASA Lewis Research Center on a single-stage transonic core compressor inlet stage. An annular array of 12 jet-injectors located upstream of the rotor tip was used for forced response testing and to extend the compressor stable operating range. Results for radial distortion are reported in this paper. First, the effects of radial distortion on the compressor performance and the dynamic behavior were investigated. Control laws were designed using empirical transfer function estimates determined from forced response results. The transfer function indicated that the compressor dynamics are decoupled with radial inlet distortion, as they are for the case of undistorted inlet flow. Single-input-single-output (SISO) control strategies were therefore used for the radial distortion controller designs. Steady axisymmetric injection of 4 percent of the compressor mass flow resulted in a reduction in stalling mass flow of 9.7 percent relative to the case with inlet distortion and no injection. Use of a robust H{sub {infinity}} controller with unsteady nonaxisymmetric injection achieved a further reduction in stalling mass flow of 7.5 percent, resulting in a total reduction of 17.2 percent.

  10. Digital refraction distortion correction with an astigmatic coherence sensor

    NASA Astrophysics Data System (ADS)

    Marks, Daniel L.; Stack, Ronald A.; Brady, David J.

    2002-10-01

    We demonstrate the sensing and correction of an isoplanatic refractive distortion (not lens aberrations), using the complete measurement of the partially coherent field in an aperture that the previously described astigmatic coherence sensor provides. Isoplanatic distortions, and in general distortions that do not cause energy loss, maintain the orthogonality of the coherent modes. We use the fact that a common distortion will occur to all coherent modes to separate the distortion from the source behind it, rather than requiring a reference source at a different wavelength. Digital deconvolution was performed on the full four-dimensional partially coherent field for simultaneously computing the distortion and the source intensity distribution.

  11. Distortion and broadening of internal solitary wavefront in the northeastern South China Sea deep basin

    NASA Astrophysics Data System (ADS)

    Xie, Jieshuo; He, Yinghui; Lü, Haibin; Chen, Zhiwu; Xu, Jiexin; Cai, Shuqun

    2016-07-01

    Internal solitary waves (ISWs) with peculiar fronts are frequently observed in the world ocean by satellite images, though with quite few explanations. In this study a distorted and broadening ISW front across the northeastern South China Sea deep basin is presented by using synthetic aperture radar (SAR) image. To illustrate this peculiar front, a nonlinear refraction model is developed to simulate and evaluate the effects of realistic bottom topography, current, and stratification on its transformation. Simulated results in realistic oceanic environments show good agreements with this SAR-observed front. Based on separate and comparative results in different background environments, we demonstrate that the distortion is actually caused by the strong mesoscale currents at periphery of an anticyclonic eddy. Moreover, the broadening is due to the difference in change of wave half width at different rays, which is associated with the different transformation of ISWs across variable bottom topography in the deep basin.

  12. A Survey of Measurements and Measuring Techniques in Rapidly Distorted Compressible Turbulent Boundary Layers

    NASA Technical Reports Server (NTRS)

    Fernholz, H. H.; Finley, P. J.; Dussauge, J. P.; Smits, A. J.; Reshotko, E. (Editor)

    1989-01-01

    A wide range of recent work on compressible turbulent boundary layers is described. Special attention was paid to flows with rapid changes in pressure including flows with shock waves, curved walls, and expansions. The application of rapid distortion theory to flows transversing expansion and shock waves is reviewed. This is followed by an account of experiments aimed at elucidating the large scale structures present in supersonic boundary layers. The current status of laser-Doppler and hot-wire anemometry in supersonic flow is discussed, and a new interferometric technique for the determination of wall-stress is described. The use of small pressure transducers to deduce information about the structure of zero pressure-gradient and severely perturbed boundary layers is investigated. Finally, there is an extension of the data presentation of AGARDographs 223, 253 and 263 to cover rapidly distorted boundary layers.

  13. SQUARE WAVE AMPLIFIER

    DOEpatents

    Leavitt, M.A.; Lutz, I.C.

    1958-08-01

    An amplifier circuit is described for amplifying sigmals having an alternating current component superimposed upon a direct current component, without loss of any segnnent of the alternating current component. The general circuit arrangement includes a vibrator, two square wave amplifiers, and recombination means. The amplifier input is connected to the vibrating element of the vibrator and is thereby alternately applied to the input of each square wave amplifier. The detailed circuitry of the recombination means constitutes the novelty of the annplifier and consists of a separate, dual triode amplifier coupled to the output of each square wave amplifier with a recombination connection from the plate of one amplifier section to a grid of one section of the other amplifier. The recombination circuit has provisions for correcting distortion caused by overlapping of the two square wave voltages from the square wave amplifiers.

  14. Maternal transmission, sex ratio distortion, and mitochondria

    PubMed Central

    Perlman, Steve J.; Hodson, Christina N.; Hamilton, Phineas T.; Opit, George P.; Gowen, Brent E.

    2015-01-01

    In virtually all multicellular eukaryotes, mitochondria are transmitted exclusively through one parent, usually the mother. In this short review, we discuss some of the major consequences of uniparental transmission of mitochondria, including deleterious effects in males and selection for increased transmission through females. Many of these consequences, particularly sex ratio distortion, have well-studied parallels in other maternally transmitted genetic elements, such as bacterial endosymbionts of arthropods. We also discuss the consequences of linkage between mitochondria and other maternally transmitted genetic elements, including the role of cytonuclear incompatibilities in maintaining polymorphism. Finally, as a case study, we discuss a recently discovered maternally transmitted sex ratio distortion in an insect that is associated with extraordinarily divergent mitochondria. PMID:25870270

  15. Determination of geometric distortion in STIS images

    NASA Technical Reports Server (NTRS)

    Malumuth, Eliot M.; Bowers, Charles W.

    1997-01-01

    This is a report on the characterization of the geometric distortion of the Space Telescope Imaging Spectrograph (STIS) Charge Coupled Devices (CCD) and the STIS Far-Ultraviolet Multi-Anode Microchannel Arrays (FUV-MAMA) detectors when used in imaging mode. We find that the amount of the distortion is fairly small over most of the field. The maximum displacement is 1.66 pixels for the CCD and 2.71 pixels for the FUV-MAMA. This data also allows us to determine the plate scale for both cameras. For the CCD the scale is 0".05071 +/- 0".00007 /pixel. For the FUV-MAMA the scale is 0".02447 +/- 0".00001 /pixel in x and 0".02467 +/-0".00002 /pixel in y.

  16. Why do doctored images distort memory?

    PubMed

    Nash, Robert A; Wade, Kimberley A; Brewer, Rebecca J

    2009-09-01

    Doctored images can cause people to believe in and remember experiences that never occurred, yet the underlying mechanism(s) responsible are not well understood. How does compelling false evidence distort autobiographical memory? Subjects were filmed observing and copying a Research Assistant performing simple actions, then they returned 2 days later for a memory test. Before taking the test, subjects viewed video-clips of simple actions, including actions that they neither observed nor performed earlier. We varied the format of the video-clips between-subjects to tap into the source-monitoring mechanisms responsible for the 'doctored-evidence effect.' The distribution of belief and memory distortions across conditions suggests that at least two mechanisms are involved: doctored images create an illusion of familiarity, and also enhance the perceived credibility of false suggestions. These findings offer insight into how external evidence influences source-monitoring. PMID:19477661

  17. Cryogenically cooled monochromator thermal distortion predictions.

    SciTech Connect

    Tajiri, G.; Lee, W.-K.; Fernandez, P.; Mills, D.; Assoufid, L.; Amirouche, F.

    1999-10-29

    Silicon crystal monochromators at cryogenic temperatures have been used with great success at third-generation synchrotrons radiation sources. At the Advanced Photon Source (APS) the unique characteristics of silicon at liquid nitrogen temperatures (77 K) have been leveraged to significantly reduce the thermally induced distortions on beamline optical components. Finite element simulations of the nonlinear (temperature-dependent material properties) thermal stress problem were performed and compared with the experimental measurements. Several critical finite element modeling considerations are discussed for their role in accurately predicting the highly coupled thermal and structural response of the optical component's surface distortion to the high thermal heat flux. Depending on the estimated convection heat transfer coefficient, the final refined finite element model's predictions correlated well with the experimental measurements.

  18. Spatial distortion prediction system for stereoscopic images

    NASA Astrophysics Data System (ADS)

    Masaoka, Kenichiro; Hanazato, Atsuo; Emoto, Masaki; Yamanoue, Hirokazu; Nojiri, Yuji; Okano, Fumio

    2006-01-01

    We propose a system to calculate the spatial distortion in 3-D images based on the shooting, display, and viewing conditions. It can be used to predict the extent of the perceived puppet-theater effect and the cardboard effect. The magnitude of the spatial distortion and the extent of the puppet-theater and cardboard effects are displayed using a space grid whose size can be estimated based on the objects' depths, calculated from the binocular parallax of the acquired stereoscopic images. This system can also be used to predict excessive binocular parallax and excessive parallax distribution. Several cases in which puppet-theater and cardboard effects are expected to be produced are presented. We also demonstrate how the proposed system might be used to predict ratings of naturalness and quality of depth.

  19. No Core CI calculations for light nuclei with chiral 2- and 3-body forces

    NASA Astrophysics Data System (ADS)

    Maris, Pieter; Metin Aktulga, H.; Binder, Sven; Calci, Angelo; Çatalyürek, Ümit V.; Langhammer, Joachim; Ng, Esmond; Saule, Erik; Roth, Robert; Vary, James P.; Yang, Chao

    2013-08-01

    The atomic nucleus is a self-bound system of strongly interacting nucleons. In No-Core Configuration Interaction calculations, the nuclear wavefunction is expanded in Slater determinants of single-nucleon wavefunctions (Configurations), and the many-body Schrödinger equation becomes a large sparse matrix problem. The challenge is to reach numerical convergence to within quantified numerical uncertainties for physical observables using finite truncations of the infinite-dimensional basis space. We discuss strategies for constructing and solving the resulting large sparse matrices for a set of low-lying eigenvalues and eigenvectors on current multicore computer architectures. Several of these strategies have been implemented in the code MFDn, a hybrid MPI/OpenMP Fortran code for ab initio nuclear structure calculations that scales well to over 200,000 cores. We discuss how the similarity renormalization group can be used to improve the numerical convergence. We present results for excitation energies and other selected observables for 8Be and 12C using realistic 2- and 3-body forces obtained from chiral perturbation theory. Finally, we demonstrate that collective phenomena such as rotational band structures can emerge from these microscopic calculations.

  20. An accurate registration technique for distorted images

    NASA Technical Reports Server (NTRS)

    Delapena, Michele; Shaw, Richard A.; Linde, Peter; Dravins, Dainis

    1990-01-01

    Accurate registration of International Ultraviolet Explorer (IUE) images is crucial because the variability of the geometrical distortions that are introduced by the SEC-Vidicon cameras ensures that raw science images are never perfectly aligned with the Intensity Transfer Functions (ITFs) (i.e., graded floodlamp exposures that are used to linearize and normalize the camera response). A technique for precisely registering IUE images which uses a cross correlation of the fixed pattern that exists in all raw IUE images is described.

  1. Body image distortions in healthy adults.

    PubMed

    Fuentes, Christina T; Longo, Matthew R; Haggard, Patrick

    2013-10-01

    Distortions of body image have often been investigated in clinical disorders. Much of this literature implicitly assumes healthy adults maintain an accurate body image. We recently developed a novel, implicit, and quantitative measure of body image - the Body Image Task (BIT). Here, we report a large-scale analysis of performance on this task by healthy adults. In both an in-person and an online version of the BIT, participants were presented with an image of a head as an anchoring stimulus on a computer screen, and told to imagine that the head was part of a mirror image of themselves in a standing position. They were then instructed to judge where, relative to the head, each of several parts of their body would be located. The relative positions of each landmark can be used to construct an implicit perceptual map of bodily structure. We could thus measure the internally-stored body image, although we cannot exclude contributions from other representations. Our results show several distortions of body image. First, we found a large and systematic over-estimation of width relative to height. These distortions were similar for both males and females, and did not closely track the idiosyncrasies of individual participant's own bodies. Comparisons of individual body parts showed that participants overestimated the width of their shoulders and the length of their upper arms, relative to their height, while underestimating the lengths of their lower arms and legs. Principal components analysis showed a clear spatial structure to the distortions, suggesting spatial organisation and segmentation of the body image into upper and lower limb components that are bilaterally integrated. These results provide new insight into the body image of healthy adults, and have implications for the study and rehabilitation of clinical populations. PMID:23933684

  2. An Improved Distortion Solution for WFPC2

    NASA Astrophysics Data System (ADS)

    Anderson, J.

    2001-11-01

    The distortion solutions currently available for HST's WFPC2 are accurate to only about 0.05 pixel in the PC and 0.02 pixel in the WF cameras. This has in fact been the most serious limitation to accurate astrometry with WFPC2. We have improved the accuracy of these corrections by a considerable factor. The astrometric improvement is dramatic in typical fields, where stars are few. Even in crowded fields such as globular clusters, the new-found ability to make more globally based transformations offers a decided improvement over the local transformations to which we had been restricted. Our new solution comes from a re-reduction of all of the images in the Omega Cen calibration fields. These two fields have been observed repeatedly over the past seven years at a variety of orientations and offsets. The outer calibration field has been observed well over 1200 times, and the inner field more than 300 times. By studying this large data set as a whole, we can derive a much more accurate distortion solution than is possible from a single observing program at a single orientation. In particular, we (1) characterize the distortion present in each chip to 0.015 pixel in the PC and better in the WFs, (2) examine the effects of breathing on the plate scale and on the distortion, and (3) accurately determine the the astrometric transformation from one chip to another, including how the chips have moved with respect to each other over time. This work has been funded by an archival-research grant from STScI.

  3. Electrowetting lenses for compensating phase and curvature distortion in arrayed laser systems.

    PubMed

    Niederriter, Robert D; Watson, Alexander M; Zahreddine, Ramzi N; Cogswell, Carol J; Cormack, Robert H; Bright, Victor M; Gopinath, Juliet T

    2013-05-10

    We have demonstrated a one-dimensional array of individually addressable electrowetting tunable liquid lenses that compensate for more than one wave of phase distortion across a wavefront. We report a scheme for piston control using tunable liquid lens arrays in volume-bound cavities that alter the optical path length without affecting the wavefront curvature. Liquid lens arrays with separately tunable focus or phase control hold promise for laser communication systems and adaptive optics. PMID:23669829

  4. Low Distortion Welded Joints for NCSX

    SciTech Connect

    M. Denault, M Viola, W. England

    2009-02-19

    The National Compact Stellarator Experiment (NCSX) required precise positioning of the field coils in order to generate suitable magnetic fields. A set of three modular field coils were assembled to form the Half Field-Period Assemblies (HPA). Final assembly of the HPA required a welded shear plate to join individual coils in the nose region due to the geometric limitations and the strength constraints. Each of the modular coil windings was wound on a stainless steel alloy (Stellalloy) casting. The alloy is similar to austenitic 316 stainless steel. During the initial welding trials, severe distortion, of approximately 1/16", was observed in the joint caused by weld shrinkage. The distortion was well outside the requirements of the design. Solutions were attempted through several simultaneous routes. The joint design was modified, welding processes were changed, and specialized heat reduction techniques were utilized. A final joint design was selected to reduce the amount of weld material needed to be deposited, while maintaining adequate penetration and strength. Several welding processes and techniques using Miller Axcess equipment were utilized that significantly reduced heat input. The final assembly of the HPA was successful. Distortion was controlled to 0.012", well within the acceptable design tolerance range of 0.020" over a 3.5 foot length.

  5. Rapid Distortion Theory in astrophysical turbulence

    NASA Astrophysics Data System (ADS)

    Safonov, Sergey; Petrosyan, Arakel

    2016-04-01

    In this report, we study statistical properties of astrophysical turbulent plasma flows using Rapid Distortion Theory (RDT). The core assumption is that the turbulence responds to the external distortion so fast, that inertial and viscous forces result in a negligible change in velocity distribution. Thus it is assumed that the response to the external effect takes place in the time interval much smaller than turbulence decay time. This allows to linearize equations and to derive equations for second moments of turbulence. We apply RDT to incompressible turbulent MHD flows distorted with external magnetic field and linear velocity shear in cases of rotating and non-rotating plasma. It is shown that even with a strong nonlinearity many properties of turbulence can be qualitatively studied using a linear theory. A closed system of linear equations for velocity and magnetic field fluctuations is derived. Development of initially isotropic turbulence and transition to anisotropy are studied. Equations for fluid, current and cross helicity are derived. Differences in cases of rotating and non-rotating flows are discussed. Changes introduced by considering Hall effect are discussed.

  6. Distortion of conformal antennas on aircraft structures

    NASA Astrophysics Data System (ADS)

    Schippers, Harmen; van Tongeren, Hans; Verpoorte, Jaco; Vos, Guus

    2001-08-01

    Conformal antennas on aircraft allow the use of non-conventional antenna locations such as the skin of the aircraft. However, when antennas are installed at these locations they are subject to steady and unsteady aerodynamic loads. The inertial forces and these aerodynamic loads will cause deformations and vibrations of the total antenna surface. The effect of these distortions on antenna performance will be most significant on highly directional antennas. The aim of the present paper is to describe technology development for estimating the effects of surface distortion on antenna performance. The technology is applied to a Side-Looking Airborne Radar (SLAR) antenna on a reconnaissance pod mounted on a fighter type aircraft. This generic SLAR antenna is a phased array antenna covering two faces of the pod: one part on the vertical side face and one part on the lower face of the pod. Radiation patterns are computed for distorted antenna surfaces. The computational model for the determination of the disturbed radiation pattern is based on geometrical parameterisation of the Stratton-Chu integral equations.

  7. Nonlinear Hysteretic Torsional Waves.

    PubMed

    Cabaret, J; Béquin, P; Theocharis, G; Andreev, V; Gusev, V E; Tournat, V

    2015-07-31

    We theoretically study and experimentally report the propagation of nonlinear hysteretic torsional pulses in a vertical granular chain made of cm-scale, self-hanged magnetic beads. As predicted by contact mechanics, the torsional coupling between two beads is found to be nonlinear hysteretic. This results in a nonlinear pulse distortion essentially different from the distortion predicted by classical nonlinearities and in a complex dynamic response depending on the history of the wave particle angular velocity. Both are consistent with the predictions of purely hysteretic nonlinear elasticity and the Preisach-Mayergoyz hysteresis model, providing the opportunity to study the phenomenon of nonlinear dynamic hysteresis in the absence of other types of material nonlinearities. The proposed configuration reveals a plethora of interesting phenomena including giant amplitude-dependent attenuation, short-term memory, as well as dispersive properties. Thus, it could find interesting applications in nonlinear wave control devices such as strong amplitude-dependent filters. PMID:26274421

  8. Nonlinear Hysteretic Torsional Waves

    NASA Astrophysics Data System (ADS)

    Cabaret, J.; Béquin, P.; Theocharis, G.; Andreev, V.; Gusev, V. E.; Tournat, V.

    2015-07-01

    We theoretically study and experimentally report the propagation of nonlinear hysteretic torsional pulses in a vertical granular chain made of cm-scale, self-hanged magnetic beads. As predicted by contact mechanics, the torsional coupling between two beads is found to be nonlinear hysteretic. This results in a nonlinear pulse distortion essentially different from the distortion predicted by classical nonlinearities and in a complex dynamic response depending on the history of the wave particle angular velocity. Both are consistent with the predictions of purely hysteretic nonlinear elasticity and the Preisach-Mayergoyz hysteresis model, providing the opportunity to study the phenomenon of nonlinear dynamic hysteresis in the absence of other types of material nonlinearities. The proposed configuration reveals a plethora of interesting phenomena including giant amplitude-dependent attenuation, short-term memory, as well as dispersive properties. Thus, it could find interesting applications in nonlinear wave control devices such as strong amplitude-dependent filters.

  9. Automatic radial distortion correction in zoom lens video camera

    NASA Astrophysics Data System (ADS)

    Kim, Daehyun; Shin, Hyoungchul; Oh, Juhyun; Sohn, Kwanghoon

    2010-10-01

    We present a novel method for automatically correcting the radial lens distortion in a zoom lens video camera system. We first define the zoom lens distortion model using an inherent characteristic of the zoom lens. Next, we sample some video frames with different focal lengths and estimate their radial distortion parameters and focal lengths. We then optimize the zoom lens distortion model with preestimated parameter pairs using the least-squares method. For more robust optimization, we divide the sample images into two groups according to distortion types (i.e., barrel and pincushion) and then separately optimize the zoom lens distortion models with respect to divided groups. Our results show that the zoom lens distortion model can accurately represent the radial distortion of a zoom lens.

  10. Tree encoding for symmetric sources with a distortion measure

    NASA Technical Reports Server (NTRS)

    Gallager, R. G.

    1974-01-01

    A simple algorithm is developed for mapping the outputs of a source into a set of code sequences generated by a tree code. The algorithm is analyzed for the case of a source producing discrete independent equiprobable letters when the distortion measure satisfies a certain symmetry condition. It is shown that the algorithm is capable of achieving an average distortion as close as desired to the minimum average distortion for the code rate given by Shannon's rate-distortion theorem.

  11. Results of the Updated ACS/WFC Distortion Correction

    NASA Astrophysics Data System (ADS)

    Borncamp, David; Kozhurina-Platais, Vera; Avila, Roberto

    2015-03-01

    We present the results of testing an updated, interim, geometric distortion correction forthe Advanced Camera for Surveys (ACS) Wide Field Channel (WFC). This testing includes not only the updated distortion correction, but also a more robust implementation of the time dependent distortion. The updated geometric distortion correction including this time dependency can greatly improve the accuracy of the image alignment and provides a better representation of the undistorted image by as much as 0.15 pixels at the edge of the chips.

  12. Perceptual and Conceptual Distortions of Implicit Hand Maps

    PubMed Central

    Longo, Matthew R.; Mattioni, Stefania; Ganea, Nataşa

    2015-01-01

    Recent studies have revealed that human position sense relies on a massively distorted representation of hand size and shape. By comparing the judged location of landmarks on an occluded hand, Longo and Haggard (2010) constructed implicit perceptual maps of represented hand structure, showing large underestimation of finger length and overestimation of hand width. Here, we investigated the contribution of two potential sources of distortions to such effects: perceptual distortions reflecting spatial warping of the representation of bodily tissue itself, perhaps reflecting distortions of somatotopic cortical maps, and conceptual distortions reflecting mistaken beliefs about the locations of different landmarks within the body. In Experiment 1 we compared distorted hand maps to a task in which participants explicitly judged the location of their knuckles in a hand silhouette. The results revealed the conceptual distortions are responsible for at least part of the underestimation of finger length, but cannot explain overestimation of hand width. Experiment 2 compared distortions of the participant’s own hand based on position sense with a prosthetic hand based on visual memory. Underestimation of finger length was found for both hands, providing further evidence that it reflects a conceptual distortion. In contrast, overestimation of hand width was specific to representation of the participant’s own hand, confirming it reflects a perceptual distortion. Together, these results suggest that distorted body representations do not reflect a single underlying cause. Rather, both perceptual and conceptual distortions contribute to the overall configuration of the hand representation. PMID:26733842

  13. Cognitive Distortions and Autonomy among Chinese University Students

    ERIC Educational Resources Information Center

    Zhang, Li-fang

    2008-01-01

    The purpose of this study was to examine the roles of university students' cognitive distortions in their sense of autonomy. One hundred and three third-year university students from Shanghai, The People's Republic of China, responded to the Cognitive Distortion Scales [Briere, J. (2000). "Cognitive Distortion Scales: Professional manual". Lutz,…

  14. The Perceptual Distortion of Height in Intercollegiate Debate.

    ERIC Educational Resources Information Center

    Hensley, Wayne E.; Angoli, Marilyn

    Both balance and reinforcement theories were used in an examination of the perceptual distortion of height among 146 college debaters. Balance theory predicted that losers would distort winners' heights upward; reinforcement theory predicted that winners would distort losers' heights upward. The results confirmed both predictions. The possibility…

  15. The Generation of Harmonic Distortion and Distortion Products in a Computational Model of the Cochlea

    NASA Astrophysics Data System (ADS)

    Meaud, Julien; Li, Yizeng; Grosh, Karl

    2011-11-01

    It is generally agreed that the nonlinear response of the cochlea is due to the forward transduction of the outer hair cell (OHC) hair bundle (HB) and subsequent alteration of the active force applied to the cochlear structures, including the basilar membrane (BM). A mechanical-acoustical-electrical model of the cochlea with three-dimensional fluid representation, and feedback from OHC somatic motility coupled to nonlinear HB mechanotransduction is used to predict nonlinear distortion of the BM response to acoustic stimulus. An efficient alternating frequency time scheme is implemented to solve for the nonlinear stationary dynamics of the cochlea. The model is used to predict the location of maximum generation of nonlinear distortion during pure tone and two-tone stimulation as well as the propagation of the distortion components on the BM.

  16. Potential-well distortion in barrier Rf

    SciTech Connect

    King Ng

    2004-04-29

    Head-tail asymmetry has been observed in the longitudinal beam profiles in the Fermilab Recycler Ring where protons or antiprotons are stored in rf barrier buckets. The asymmetry is caused by the distortion of the rf potential well in the presence of resistive impedance. Gaussian energy distribution can fit the observed asymmetric beam profile but not without discrepancy. It can also fit the measured energy distribution. On the other hand, generalized elliptic distribution gives a better fit to the beam profile. However, it fails to reproduce the observed energy distribution.

  17. Redshift distortions of galaxy correlation functions

    NASA Technical Reports Server (NTRS)

    Fry, J. N.; Gaztanaga, Enrique

    1994-01-01

    To examine how peculiar velocities can affect the two-, three-, and four-point redshift correlation functions, we evaluate volume-average correlations for configurations that emphasize and minimize redshift distortions for four different volume-limited samples from each of the CfA, SSRS, and IRAS redshift catalogs. We present the results as the correlation length r(sub 0) and power index gamma of the two-point correlations, bar-xi(sub 0) = (r(sub 0)/r)(exp gamma), and as the hierarchical amplitudes of the three- and four-point functions, S(sub 3) = bar-xi(sub 3)/bar-xi(exp 2)(sub 2) and S(sub 4) = bar-xi(sub 4)/bar-xi(exp 3)(sub 2). We find a characteristic distortion for bar-xi(sub 2), the slope gamma is flatter and the correlation length is larger in redshift space than in real space; that is, redshift distortions 'move' correlations from small to large scales. At the largest scales (up to 12 Mpc), the extra power in the redshift distribution is compatible with Omega(exp 4/7)/b approximately equal to 1. We estimate Omega(exp 4/7)/b to be 0.53 +/- 0.15, 1.10 +/- 0.16, and 0.84 +/- 0.45 for the CfA, SSRS, and IRAS catalogs. Higher order correlations bar-xi(sub 3) and bar-xi(sub 4) suffer similar redshift distortions but in such a way that, within the accuracy of our ananlysis, the normalized amplitudes S(sub 3) and S(sub 4) are insensitive to this effect. The hierarchical amplitudes S(sub 3) and S(sub 4) are constant as a function of scale between 1 and 12 Mpc and have similar values in all samples and catalogs, S(sub 3) approximately equal to 2 and S(sub 4) approximately equal to 6, despite the fact that bar-xi(sub 2), bar-xi(sub 3), and bar-xi(sub 4) differ from one sample to another by large factors (up to a factor of 4 in bar-xi(sub 2), 8 for bar-xi(sub 3), and 12 for bar-xi(sub 4)). The agreement between the independent estimations of S(sub 3) and S(sub 4) is remarkable given the different criteria in the selection of galaxies and also the difference in the

  18. Coat forming quenching oil and distortion

    SciTech Connect

    Asada, S.

    1996-12-31

    Coat forming quenching oil which provides lubricous black coating on the treated surface of materials simultaneously with quenching is known to improve effectively surface characteristics of parts/materials treated. However, Zn-DTP added to this oil will be consumed some what at each quenching and gradual deterioration of the oil is inevitable and affecting greatly to cooling performance of the oil. To maintain long period oil stability by minimizing consumption of additive and suppressing cooling performance degradation, a new coat forming quenching oil containing petroleum type sulfonate has been developed. This is finally to contribute keeping low distortion level of treated materials in long term.

  19. The instability transition for the restricted 3-body problem. III. The Lyapunov exponent criterion

    NASA Astrophysics Data System (ADS)

    Quarles, B.; Eberle, J.; Musielak, Z. E.; Cuntz, M.

    2011-09-01

    Aims: We establish a criterion for the stability of planetary orbits in stellar binary systems by using Lyapunov exponents and power spectra for the special case of the circular restricted 3-body problem (CR3BP). The criterion augments our earlier results given in the two previous papers of this series where stability criteria have been developed based on the Jacobi constant and the hodograph method. Methods: The centerpiece of our method is the concept of Lyapunov exponents, which are incorporated into the analysis of orbital stability by integrating the Jacobian of the CR3BP and orthogonalizing the tangent vectors via a well-established algorithm originally developed by Wolf et al. The criterion for orbital stability based on the Lyapunov exponents is independently verified by using power spectra. The obtained results are compared to results presented in the two previous papers of this series. Results: It is shown that the maximum Lyapunov exponent can be used as an indicator for chaotic behaviour of planetary orbits, which is consistent with previous applications of this method, particularly studies for the Solar System. The chaotic behaviour corresponds to either orbital stability or instability, and it depends solely on the mass ratio μ of the binary components and the initial distance ratio ρ0 of the planet relative to the stellar separation distance. Detailed case studies are presented for μ = 0.3 and 0.5. The stability limits are characterized based on the value of the maximum Lyapunov exponent. However, chaos theory as well as the concept of Lyapunov time prevents us from predicting exactly when the planet is ejected. Our method is also able to indicate evidence of quasi-periodicity. Conclusions: For different mass ratios of the stellar components, we are able to characterize stability limits for the CR3BP based on the value of the maximum Lyapunov exponent. This theoretical result allows us to link the study of planetary orbital stability to chaos

  20. Geometric and rediametric distortion in spaceborne SAR imagery

    NASA Technical Reports Server (NTRS)

    Curlander, J. C.

    1982-01-01

    Distortions inherent on synthetic aperture radio (SAR) imagery and the development to date of unsupervised postprocessing rectification techniques are described. The geometric distortion can be divided into two categories: (1) distortion derived from the radar viewing geometry, this includes such effects as ground range nonlinearities, radar foreshortening and radar layover; (2) distortion introduced during the data processing, these distortions result from approximations made during the correlation such as in estimation of the target phase history, or compensation for the earth rotation. The processor induced distortions depends on the specific correlation algorithm used for image formation. The effects are addressed on the image product resulting from assumptions during the processing and it specifically considers distortions inherent in digital imagery produced by the digital image processor.

  1. Prediction of Part Distortion in Die Casting

    SciTech Connect

    R. Allen Miller

    2005-03-30

    The die casting process is one of the net shape manufacturing techniques and is widely used to produce high production castings with tight tolerances for many industries. An understanding of the stress distribution and the deformation pattern of parts produced by die casting will result in less deviation from the part design specification, a better die design and eventually more productivity and cost savings. This report presents methods that can be used to simulate the die casting process in order to predict the deformation and stresses in the produced part and assesses the degree to which distortion modeling is practical for die casting at the current time. A coupled thermal-mechanical finite elements model was used to simulate the die casting process. The simulation models the effect of thermal and mechanical interaction between the casting and the die. It also includes the temperature dependant material properties of the casting. Based on a designed experiment, a sensitivity analysis was conducted on the model to investigate the effect of key factors. These factors include the casting material model, material properties and thermal interaction between casting and dies. To verify the casting distortion predictions, it was compared against the measured dimensions of produced parts. The comparison included dimensions along and across the parting plane and the flatness of one surface.

  2. Insider censoring: Distortion of data with nondetects

    USGS Publications Warehouse

    Helsel, D.R.

    2005-01-01

    Environmental data often include low-level concentrations below reporting limits. These data may be reported as "distorting the shape of the data distribution. This results in inaccurate estimates of summary statistics and regression coefficients, distorts evaluations of whether data follow a normal distribution, and introduces inaccuracies into risk assessments and models. Insider censoring occurs when data measured as below the detection limit (

  3. Wavefront distortion and beam pointing for LISA

    NASA Astrophysics Data System (ADS)

    Bender, Peter L.

    2005-05-01

    The dc pointing directions for the LISA laser beams will be chosen to minimize the sensitivity of the measured arm lengths to jitter in the beam pointing. The earliest studies of the effects of wavefront distortion included only astigmatism and defocus, so that the desired dc beam pointing directions were on the axis for the transmitting telescopes. But, if other aberrations cause the dc pointing directions to be considerably off axis, some of the laser beam intensity will be lost. A brief study of this effect has been carried out. As examples, several cases with defocus, spherical aberration, and two components each of astigmatism and coma have been investigated. Within this class of models, pure astigmatism turned out to give the maximum sensitivity to beam pointing jitter, for a given rms wavefront distortion. Although further study is needed, it appears that the usually quoted requirements of 3 × 10-8 rad for the dc beam pointing offsets and 8 × 10-9 rad Hz-1/2 for the pointing jitter are probably reasonable choices.

  4. Reducing Field Distortion in Magnetic Resonance Imaging

    NASA Technical Reports Server (NTRS)

    Eom, Byeong Ho; Penanen, Konstantin; Hahn, Inseob

    2010-01-01

    A concept for a magnetic resonance imaging (MRI) system that would utilize a relatively weak magnetic field provides for several design features that differ significantly from the corresponding features of conventional MRI systems. Notable among these features are a magnetic-field configuration that reduces (relative to the conventional configuration) distortion and blurring of the image, the use of a superconducting quantum interference device (SQUID) magnetometer as the detector, and an imaging procedure suited for the unconventional field configuration and sensor. In a typical application of MRI, a radio-frequency pulse is used to excite precession of the magnetic moments of protons in an applied magnetic field, and the decaying precession is detected for a short time following the pulse. The precession occurs at a resonance frequency proportional to the strengths of the magnetic field and the proton magnetic moment. The magnetic field is configured to vary with position in a known way; hence, by virtue of the aforesaid proportionality, the resonance frequency varies with position in a known way. In other words, position is encoded as resonance frequency. MRI using magnetic fields weaker than those of conventional MRI offers several advantages, including cheaper and smaller equipment, greater compatibility with metallic objects, and higher image quality because of low susceptibility distortion and enhanced spin-lattice-relaxation- time contrast. SQUID MRI is being developed into a practical MRI method for applied magnetic flux densities of the order of only 100 T

  5. Engaging distortions: are we idealizing marriage?

    PubMed

    Bonds-Raacke, J M; Bearden, E S; Carriere, N J; Anderson, E M; Nicks, S D

    2001-03-01

    The present study was an investigation of the premarital status of engagement in terms of relationship satisfaction and marital expectations using the Evaluation and Nurturing Relationship Issues, Communication and Happiness (ENRICH) Marital Satisfaction Scale (EMS) and its two subscales of Idealistic Distortion (ID) and Marital Satisfaction (MS) (D. G. Fournier, D. H. Olson, & J. M. Druckman, 1983). There were 104 students (23 men and 81 women), of which 15 were married, 19 were engaged, and 70 had extended dating relationships. On average, participants had been in the relationship for 3.8 years, and the mean age was 22 years. Results demonstrated that individuals engaged to be married had significantly higher idealistic distortion scores (M = 86.89) than did either married individuals (M = 56.67) or those in extended dating relationships (M = 61.19). Finally, a negative relation was found between length of relationships and marital satisfaction subscores. Results are discussed in light of factors contributing to such idealized thinking. PMID:11403340

  6. Frequency shifts in distortion-product otoacoustic emissions evoked by swept tones.

    PubMed

    Shera, Christopher A; Abdala, Carolina

    2016-08-01

    When distortion-product otoacoustic emissions (DPOAEs) are evoked using stimuli whose instantaneous frequencies change rapidly and continuously with time (swept tones), the oscillatory interference pattern known as distortion-product fine structure shifts slightly along the frequency axis in the same direction as the sweep. By analogy with the temporal mechanisms thought to underlie the differing efficacies of up- and down-swept stimuli as perceptual maskers (e.g., Schroeder-phase complexes), fine-structure shifts have been ascribed to the phase distortion associated with dispersive wave propagation in the cochlea. This paper tests an alternative hypothesis and finds that the observed shifts arise predominantly as a methodological side effect of the analysis procedures commonly used to extract delayed emissions from the measured time waveform. Approximate expressions for the frequency shifts of DPOAE distortion and reflection components are derived, validated with computer simulations, and applied to account for DPOAE fine-structure shifts measured in human subjects. Component magnitudes are shown to shift twice as much as component phases. Procedures for compensating swept-tone measurements to obtain estimates of the total DPOAE and its components measured at other sweep rates or in the sinusoidal steady state are presented. PMID:27586726

  7. Rotating stall control in a high-speed stage with inlet distortion. Part 2: Circumferential distortion

    SciTech Connect

    Spakovszky, Z.S.; Weigl, H.J.; Paduano, J.D.; Schalkwyk, C.M. van; Suder, K.L.; Bright, M.M.

    1999-07-01

    This paper presents the first attempt to stabilize rotating stall in a single-stage transonic axial flow compressor with inlet distortion using active feedback control. The experiments were conducted at the NASA Lewis Research Center on a single-stage transonic core compressor inlet stage. An array of 12 jet injectors located upstream of the compressor was used for forced response testing and feedback stabilization. Results for a circumferential total pressure distortion of about one dynamic head and a 120 deg extent (DC(60){equals}0.61) are reported in this paper. Part 1 (Spaskovszky et al., 1999) reports results for radial distortion. Control laws were designed using empirical transfer function estimates determined from forced response results. Distortion introduces coupling between the harmonics of circumferential pressure perturbations, requiring multivariable identification and control design techniques. The compressor response displayed a strong first spatial harmonic, dominated by the well-known incompressible Moore-Greitzer mode. Steady axisymmetric injection of 4 percent of the compressor mass flow resulted in a 6.2 percent reduction of stalling mass flow. Constant gain feedback, using unsteady asymmetric injection, yielded a further range extension of 9 percent. A more sophisticated robust H{sub {infinity}} controller allowed a reduction in stalling mass flow of 10.2 percent relative to steady injection, yielding a total reduction in stalling mass flow of 16.4 percent.

  8. Inlet distortion generated forced response of a low-aspect-ratio transonic fan

    SciTech Connect

    Manwaring, S.R.; Lorence, C.B.; Wadia, A.R.; Rabe, D.C.

    1997-10-01

    This paper describes a portion of an experimental and computational program (ADLARF), which incorporates, for the first time, measurements of all aspects of the forced response of an airfoil row, i.e., the flow defect, the unsteady pressure loadings, and the vibratory response. The purpose of this portion was to extend the knowledge of the unsteady aerodynamics associated with a low-aspect-ratio transonic fan where the flow defects were generated by inlet distortions. Measurements of screen distortion patterns were obtained with total pressure rakes and casing static pressures. The unsteady pressure loadings on the blade were determined from high response pressure transducers. The resulting blade vibrations were measured with strain gages. The steady flow was analyzed using a three-dimensional Navier-Stokes solver while the unsteady flow was determined with a quasi-three-dimensional linearized Euler solver. Experimental results showed that the distortions had strong vortical, moderate entropic, and weak acoustic parts. The three-dimensional Navier-Stokes analyses showed that the steady flow is predominantly two-dimensional, with radially outward flow existing only in the blade surface boundary layers downstream of shocks and in the aft part of the suction surface. At near resonance conditions, the strain gage data showed blade-to-blade motion variations and thus, linearized unsteady Euler solutions showed poorer agreement with the unsteady loading data than comparisons at off-resonance speeds. Data analysis showed that entropic waves generated unsteady loadings comparable to vortical waves in the blade regions where shocks existed.

  9. Design of the new rigid endoscope distortion measurement system

    NASA Astrophysics Data System (ADS)

    Zhai, Xiaohao; Liu, Xiaohua; Liu, Ming; Hui, Mei; Dong, Liquan; Zhao, Yuejin; Wang, Yakun; Li, Yonghui; Zhou, Peng

    2015-08-01

    Endoscopic imaging quality affects industrial safety and medical security. Rigid endoscope distortion is of great signification as one of optical parameters to evaluate the imaging quality. This paper introduces a new method of rigid endoscope distortion measurement, which is different from the common methods with low accuracy and fussy operation. It contains a Liquid Crystal Display (LCD) to display the target, a CCD to obtain the images with distortion, and a computer to process the images. The LCD is employed instead of common white screen. The autonomous control system of LCD makes it showing the test target designed for distortion, and its parameter is known. LCD control system can change the test target to satisfy the different demand for accuracy, which avoids replacing target frequently. The test system also contains a CCD to acquire images in the exit pupil position of rigid endoscope. Rigid endoscope distortion is regarded as centrosymmetric, and the MATLAB software automatically measures it by processing the images from CCD. The MATLAB software compares target images with that without distortion on LCD and calculates the results. Relative distortion is obtained at different field of view (FOV) radius. The computer plots the curve of relative distortion, abscissa means radius of FOV, ordinate means relative distortion. The industry standard shows that, the distortion at 70% field of view is pointed on the curve, which can be taken as an evaluation standard. This new measuring method achieves advantages of high precision, high degree of intelligence, excellent repeatability and gets calculation results quickly.

  10. Power Factor Correction to Mitigate Harmonic Distortion

    NASA Astrophysics Data System (ADS)

    Kochetkov, Gary

    Many direct current (DC) devices must receive their power from the alternating current (AC) grid. Rectifiers use diodes to create DC for these devices. Due to diodes' non-linear nature however, harmonics are created and these travel back into the grid. A significant presence of harmonics causes component heating and possible malfunction. A harmonic mitigation procedure is needed. With the correct usage of transistors, the current drawn by a rectifier can be manipulated to remove almost all harmonics. This process is called power factor correction (PFC), and formally acts to reduce the total harmonic distortion (THD) of the current. To investigate this, a three phase active rectifier was computer simulated and a controller was designed to provide switching signals for the transistors. Finally, the device was constructed in the laboratory to drive a DC motor, verifying its operating principle outside of the idealities of simulation.

  11. Bulk Dirac Points in Distorted Spinels

    NASA Astrophysics Data System (ADS)

    Steinberg, Julia; Young, Steve; Zaheer, Saad; Kane, Charles; Mele, Eugene; Rappe, Andrew

    2014-03-01

    A Dirac point is characterized by four degenerate states that disperse linearly with momentum around a single point bk in the Brillouin zone. The resulting low energy theory is pseudorelativistic. A well-known example in two dimensions is graphene, which has a Fermi surface consisting exclusively of Dirac points that are responsible for many of its exotic properties. We report on an analogous Dirac-like Fermi surface in three-dimensional bulk materials in a distorted spinel structure on the basis of density functional theory (DFT) as well as tight-binding theory. The four examples we provide in this paper are BiZnSiO4, BiCaSiO4, BiMgSiO4, and BiAlInO4. A necessary characteristic of these structures is that they contain a Bi lattice which forms a hierarchy of chain-like substructures, with consequences for both fundamental understanding and materials design.

  12. Inlet distortion in engines on VSTOL aircraft

    NASA Technical Reports Server (NTRS)

    Tan, Choon S.; Greitzer, Edward M.

    1994-01-01

    This report presents the results of a research program on inlet distortion in engines on VSTOL aircraft carried out at the MIT Gas Turbine Laboratory during the period Oct. 1989 - Dec. 1993. The program focused on the development of three dimensional flow computational methodology for predicting the effects of nonuniform flow on the performance of aircraft engines in VSTOL aircraft, the development of a three dimensional instability analysis of flow in multistage axial compressors, and the preliminary applications of these newly developed methodologies for elucidating the effects of flow three dimensionality. The accomplishments of the program are brought out when the current status of predictive capabilities for three dimensional flow instabilities in compressors is assessed against that in 1989.

  13. Distortion compensation in interferometric testing of mirrors

    SciTech Connect

    Robinson, Brian M.; Reardon, Patrick J

    2009-01-20

    We present a method to compensate for the imaging distortion encountered in interferometric testing of mirrors, which is introduced by interferometer optics as well as from geometric projection errors. Our method involves placing a mask, imprinted with a regular square grid, over the mirror and finding a transformation that relates the grid coordinates to coordinates in the base plane of the parent surface. This method can be used on finished mirrors since no fiducials have to be applied to the surfaces. A critical step in the process requires that the grid coordinates be projected onto the mirror base plane before the regression is performed. We apply the method successfully during a center-of-curvature null test of an F/2 off-axis paraboloid.

  14. Uniform distortion of a heated turbulent wake

    NASA Technical Reports Server (NTRS)

    Kawall, J. G.; Keffer, J. F.

    1978-01-01

    Digital sampling and processing techniques are used to assess the effect of a uniform and constant strain rate on a slightly heated cylinder-generated wake which had undergone a prestrain development distance of 115 cylinder diameters. The wake is generated by a circular heating element (6.6-mm-diam cylinder) mounted horizontally in the center of a low-speed open return wind tunnel. The strain field is produced by a distortion duct oriented in such a way as to accentuate any periodic interface structure which might be present in the undistorted wake. Interface statistics are presented for both the undistorted (near) wake and the uniformly strained wake, and conditional (point) averages of the streamwise velocity and passive temperature fields of the strained wake. The results suggest that the interface thickness is fairly uniform along the back but decreases along the front with distance from the wake center.

  15. Primordial trispectra and CMB spectral distortions

    NASA Astrophysics Data System (ADS)

    Bartolo, Nicola; Liguori, Michele; Shiraishi, Maresuke

    2016-03-01

    We study the TTμ bispectrum, generated by correlations between Cosmic Microwave Background temperature (T) anisotropies and chemical potential (μ) distortions, and we analyze its dependence on primordial local trispectrum parameters gNL and τNL. We cross-check our results by comparing the full bispectrum calculation with the expectations from a general physical argument, based on predicting the shape of μ-T correlations from the couplings between short and long perturbation modes induced by primordial non-Gaussianity. We show that both gNL and τNL-parts of the primordial trispectrum source a non-vanishing TTμ signal, contrary to the μμ auto-correlation function, which is sensitive only to the τNL-component. A simple Fisher matrix-based forecast shows that a futuristic, cosmic-variance dominated experiment could in principle detect gNL ~ 0.4 and τNL ~ 40 using TTμ.

  16. Reduced pressure quenching oil and distortion

    SciTech Connect

    Asada, S.; Ogino, M.

    1996-12-31

    Cooling process observed in a quenching oil`s cooling curve determination by JIS silver probe method, has been divided into three stages, vapor blanket stage, boiling stage and convection stage. Under reduced pressure vaporization is accelerated and extend the vapor blanket stage which shift the position of boiling stage the fastest of cooling speed among the cooling process toward low temperature side. Taking advantage of this behavior in quenching under reduced pressure, it is possible to improve quench hardenability by controlling reduced pressure. Vapor pressure of quenching oil increases under very high vacuum and accelerates vapor blanket formation and covers the material with more vapor blanket, resulting in reduction of cooling speed. Excessive vapor blanket covering the material will lead to partially uneven quenching of the treated material caused by uneven conditions by partial decomposition. Making vapor blanket distribution more even and to optimize uniform coating condition enables to prevent heat treatment distortion caused by uneven quenching conditions.

  17. Distortions in memory for visual displays

    NASA Technical Reports Server (NTRS)

    Tversky, Barbara

    1989-01-01

    Systematic errors in perception and memory present a challenge to theories of perception and memory and to applied psychologists interested in overcoming them as well. A number of systematic errors in memory for maps and graphs are reviewed, and they are accounted for by an analysis of the perceptual processing presumed to occur in comprehension of maps and graphs. Visual stimuli, like verbal stimuli, are organized in comprehension and memory. For visual stimuli, the organization is a consequence of perceptual processing, which is bottom-up or data-driven in its earlier stages, but top-down and affected by conceptual knowledge later on. Segregation of figure from ground is an early process, and figure recognition later; for both, symmetry is a rapidly detected and ecologically valid cue. Once isolated, figures are organized relative to one another and relative to a frame of reference. Both perceptual (e.g., salience) and conceptual factors (e.g., significance) seem likely to affect selection of a reference frame. Consistent with the analysis, subjects perceived and remembered curves in graphs and rivers in maps as more symmetric than they actually were. Symmetry, useful for detecting and recognizing figures, distorts map and graph figures alike. Top-down processes also seem to operate in that calling attention to the symmetry vs. asymmetry of a slightly asymmetric curve yielded memory errors in the direction of the description. Conceptual frame of reference effects were demonstrated in memory for lines embedded in graphs. In earlier work, the orientation of map figures was distorted in memory toward horizontal or vertical. In recent work, graph lines, but not map lines, were remembered as closer to an imaginary 45 deg line than they had been. Reference frames are determined by both perceptual and conceptual factors, leading to selection of the canonical axes as a reference frame in maps, but selection of the imaginary 45 deg as a reference frame in graphs.

  18. Solar latitudinal distortions: From observations to theory

    NASA Astrophysics Data System (ADS)

    Lefebvre, S.; Rozelot, J. P.

    2004-06-01

    Solar diameters have been measured from different ground-based instruments on different sites all around the world. There are values dating back to three centuries ago, but the revival of interest began in the 1970s when it was claimed that a temporal periodic modulation had been found. The interest of such measurements, pinpointed from only two decades, may not lie in these temporal variations, but in the fact that a latitudinal heliographic dependence may exist. Such a solar shape distortion has been deduced from the analysis of solar astrolabe data sorted by heliographic latitudes, but observational evidence has also been obtained by means of a scanning heliometer (Pic du Midi Observatory). Latitudinal dependence implies sub-surfacic physical mechanisms and can be explained theoretically. Thus, in spite of the fact that ground-based observations are altered by seeing effects that may amplify or superimpose noise, it can be advanced that the solar shape is not a pure spheroid. We present here a new theory based upon the thermal-wind equation, which explains the observed distorted solar shape. Using the W parameter (called here asphericity-luminosity parameter), we show that large negative values (W ranging from around -0.075 up to -0.6) leading to a prolate Sun, are unlikely. The best range of W lies between around -0.075 and +0.6. Concerning observations, only space missions (or balloon flights) will be able to reach a clear conclusion. A space mission called PICARD is scheduled to be launched by 2008: one of its major aims is to measure these asphericities with astrometric precision.

  19. Distortion of surface plasmon polariton propagation on graphene due to chemical potential variation

    NASA Astrophysics Data System (ADS)

    Amanatiadis, Stamatios; Kantartzis, Nikolaos

    2016-04-01

    The variation of graphene chemical potential owing to surface plasmon polariton excitation and its influence on the propagation properties of the latter is systematically examined in this paper. Although the chemical potential is controlled via a constant electric field bias, the excitation of the highly confined surface wave can considerably affect it, thus disrupting the wave natural propagation. To this aim, the propagation properties of the surface wave are extracted to reliably estimate the aforesaid distortion effect with regard to frequency. Numerical results, obtained in terms of an accurate finite-difference time-domain scheme, certify this interesting convention. Furthermore, the electrodynamic forces on the free electrons of the graphene layer are calculated to justify the electrostatic assumption.

  20. Visualization of Merging Black Holes and Gravitational Waves

    NASA Video Gallery

    This visualization shows gravitational waves emitted by two black holes of nearly equal mass as they spiral together and merge. Orange ripples represent distortions of space-time caused by the rapi...

  1. Global and Local Distortion Inference During Embedded Zerotree Wavelet Decompression

    NASA Technical Reports Server (NTRS)

    Huber, A. Kris; Budge, Scott E.

    1996-01-01

    This paper presents algorithms for inferring global and spatially local estimates of the squared-error distortion measures for the Embedded Zerotree Wavelet (EZW) image compression algorithm. All distortion estimates are obtained at the decoder without significantly compromising EZW's rate-distortion performance. Two methods are given for propagating distortion estimates from the wavelet domain to the spatial domain, thus giving individual estimates of distortion for each pixel of the decompressed image. These local distortion estimates seem to provide only slight improvement in the statistical characterization of EZW compression error relative to the global measure, unless actual squared errors are propagated. However, they provide qualitative information about the asymptotic nature of the error that may be helpful in wavelet filter selection for low bit rate applications.

  2. Radial line method for rear-view mirror distortion detection

    NASA Astrophysics Data System (ADS)

    Rahmah, Fitri; Kusumawardhani, Apriani; Setijono, Heru; Hatta, Agus M.; Irwansyah, .

    2015-01-01

    An image of the object can be distorted due to a defect in a mirror. A rear-view mirror is an important component for the vehicle safety. One of standard parameters of the rear-view mirror is a distortion factor. This paper presents a radial line method for distortion detection of the rear-view mirror. The rear-view mirror was tested for the distortion detection by using a system consisting of a webcam sensor and an image-processing unit. In the image-processing unit, the captured image from the webcam were pre-processed by using smoothing and sharpening techniques and then a radial line method was used to define the distortion factor. It was demonstrated successfully that the radial line method could be used to define the distortion factor. This detection system is useful to be implemented such as in Indonesian's automotive component industry while the manual inspection still be used.

  3. A Study on the Improvement of Dynamic Loudspeaker Nonlinear Distortion

    NASA Astrophysics Data System (ADS)

    Inuzuka, Takamasa; Kasahara, Misawa; Mori, Yasuchika

    Recently, the distortion caused by signal transduction has been significantly reduced because of development of digital signal processing technology, so that sound quality has improved dramatically. However, speaker system located at the end of the sound reproduction has not changed since the basic principle of the invention, the non-linear distortion occurs mostly have been concerned about the deterioration of sound quality. It is important to eliminate this distortion in high fidelity music playback. In order to reduce the nonlinear distortion, we propose a system using disturbance observer and consider in this method.

  4. Systems and methods for mirror mounting with minimized distortion

    NASA Technical Reports Server (NTRS)

    Antonille, Scott R. (Inventor); Wallace, Thomas E. (Inventor); Content, David A. (Inventor); Wake, Shane W. (Inventor)

    2012-01-01

    A method for mounting a mirror for use in a telescope includes attaching the mirror to a plurality of adjustable mounts; determining a distortion in the mirror caused by the plurality adjustable mounts, and, if the distortion is determined to be above a predetermined level: adjusting one or more of the adjustable mounts; and determining the distortion in the mirror caused by the adjustable mounts; and in the event the determined distortion is determined to be at or below the predetermined level, rigidizing the adjustable mounts.

  5. Effects of skin elasticity on bite mark distortion.

    PubMed

    Lewis, Cheri; Marroquin, Leonor A

    2015-12-01

    Bite marks have been reported to have an evidentiary value similar to fingerprints. We believed bite mark distortion would impact the accuracy and reliability of bite mark interpretation. Inked denture-stamps were substituted for actual bite marks and were placed onto 40 participating volunteers' shoulders. Four changes in arm position were photographed using an ABFO #2 reference scale. The measurements of individual tooth widths and intercanine distances in each position were compared. The maximum tooth width distortion observed was 53.8%, whereas the maximum intercanine distance distortion was 41.9%. Distortion was found to increase with age and weight and was non-uniform across a dental arch. PMID:26451773

  6. The improvement of distortion by high-temperature oil quenching

    SciTech Connect

    Nakamura, E.; Uchida, H.; Koyama, S.

    1996-12-31

    The authors think that control of quenching distortion is very important issue from the point of view of quality control. They investigated the comparison of quenching oil and salt which are one of the major factors for distortion. By those results, the following are observed. (1) In the case of small parts, the vapor blanket cooling stage does not effect the quenching ununiformty at all. (2) The main difference between quenching oil and salt is using temperature for quenching distortion. The authors found that using quenching oil around 200 C improves the amount of quenching distortion with the lower Ms point parts.

  7. Faces distort eye movement trajectories, but the distortion is not stronger for your own face.

    PubMed

    Qian, Haoyue; Gao, Xiangping; Wang, Zhiguo

    2015-07-01

    It is currently unclear whether a person's own face has greater capacity in absorbing his/her attention than faces of others. With two visual distractor tasks, the present study assessed the extent to which a person's own face attracts his/her attention, by measuring face distractor elicited distortion of saccade trajectories. Experiment 1 showed that upright faces induced stronger distortion of saccade trajectories than inverted ones. This face inversion effect, however, was not stronger for the participant's own face than for unfamiliar other's faces. By manipulating fixation stimulus offset and using peripheral onset target, Experiment 2 further demonstrated that these observations were not contingent on saccade latency. Together, these findings suggest that a person's own face is not more salient or attention-absorbing than unfamiliar other's faces. PMID:25912608

  8. Optical compensation of distorted data image caused by interference fringe distortion in holographic data storage.

    PubMed

    Muroi, Tetsuhiko; Kinoshita, Nobuhiro; Ishii, Norihiko; Kamijo, Koji; Shimidzu, Naoki

    2009-07-01

    Photopolymer materials shrink because of photopolymerization. This shrinkage distorts the recorded interference fringes in a medium made of such material, which in turn degrades the reconstructed image quality. Adaptive optics controlled by a genetic algorithm was developed to optimize the wavefront of the reference beam while reproducing in order to compensate for the interference fringe distortion. We defined a fitness measure for this genetic algorithm that involves the mean brightness and coefficients of the variations of bit data "1" and "0". In an experiment, the adaptive optics improved the reconstructed image to the extent that data could be reproduced from the entire area of the image, and the signal to noise ratio of the reproduced data could be improved. PMID:19571923

  9. Reflector surface distortion analysis techniques (thermal distortion analysis of antennas in space)

    NASA Technical Reports Server (NTRS)

    Sharp, R.; Liao, M.; Giriunas, J.; Heighway, J.; Lagin, A.; Steinbach, R.

    1989-01-01

    A group of large computer programs are used to predict the farfield antenna pattern of reflector antennas in the thermal environment of space. Thermal Radiation Analysis Systems (TRASYS) is a thermal radiation analyzer that interfaces with Systems Improved Numerical Differencing Analyzer (SINDA), a finite difference thermal analysis program. The programs linked together for this analysis can now be used to predict antenna performance in the constantly changing space environment. They can be used for very complex spacecraft and antenna geometries. Performance degradation caused by methods of antenna reflector construction and materials selection are also taken into consideration. However, the principal advantage of using this program linkage is to account for distortions caused by the thermal environment of space and the hygroscopic effects of the dry-out of graphite/epoxy materials after the antenna is placed into orbit. The results of this type of analysis could ultimately be used to predict antenna reflector shape versus orbital position. A phased array antenna distortion compensation system could then use this data to make RF phase front corrections. That is, the phase front could be adjusted to account for the distortions in the antenna feed and reflector geometry for a particular orbital position.

  10. Transitive reasoning distorts induction in causal chains.

    PubMed

    von Sydow, Momme; Hagmayer, York; Meder, Björn

    2016-04-01

    A probabilistic causal chain A→B→C may intuitively appear to be transitive: If A probabilistically causes B, and B probabilistically causes C, A probabilistically causes C. However, probabilistic causal relations can only guaranteed to be transitive if the so-called Markov condition holds. In two experiments, we examined how people make probabilistic judgments about indirect relationships A→C in causal chains A→B→C that violate the Markov condition. We hypothesized that participants would make transitive inferences in accordance with the Markov condition although they were presented with counterevidence showing intransitive data. For instance, participants were successively presented with data entailing positive dependencies A→B and B→C. At the same time, the data entailed that A and C were statistically independent. The results of two experiments show that transitive reasoning via a mediating event B influenced and distorted the induction of the indirect relation between A and C. Participants' judgments were affected by an interaction of transitive, causal-model-based inferences and the observed data. Our findings support the idea that people tend to chain individual causal relations into mental causal chains that obey the Markov condition and thus allow for transitive reasoning, even if the observed data entail that such inferences are not warranted. PMID:26620811

  11. Cognitive Distortion in Rheumatoid Arthritis: Relation to Depression and Disability.

    ERIC Educational Resources Information Center

    Smith, Timothy W.; And Others

    1988-01-01

    Examined the relation between cognitive distortion, as measured by the Cognitive Error Questionnaire, and both self-reported and interview-rated depression and disability in 92 rheumatoid arthritis (RA) patients. Found cognitive distortion significantly associated with depression, and also related to physical disability. Discusses the results,…

  12. Audiovisual Cues and Perceptual Learning of Spectrally Distorted Speech

    ERIC Educational Resources Information Center

    Pilling, Michael; Thomas, Sharon

    2011-01-01

    Two experiments investigate the effectiveness of audiovisual (AV) speech cues (cues derived from both seeing and hearing a talker speak) in facilitating perceptual learning of spectrally distorted speech. Speech was distorted through an eight channel noise-vocoder which shifted the spectral envelope of the speech signal to simulate the properties…

  13. Quality Prediction of Asymmetrically Distorted Stereoscopic 3D Images.

    PubMed

    Wang, Jiheng; Rehman, Abdul; Zeng, Kai; Wang, Shiqi; Wang, Zhou

    2015-11-01

    Objective quality assessment of distorted stereoscopic images is a challenging problem, especially when the distortions in the left and right views are asymmetric. Existing studies suggest that simply averaging the quality of the left and right views well predicts the quality of symmetrically distorted stereoscopic images, but generates substantial prediction bias when applied to asymmetrically distorted stereoscopic images. In this paper, we first build a database that contains both single-view and symmetrically and asymmetrically distorted stereoscopic images. We then carry out a subjective test, where we find that the quality prediction bias of the asymmetrically distorted images could lean toward opposite directions (overestimate or underestimate), depending on the distortion types and levels. Our subjective test also suggests that eye dominance effect does not have strong impact on the visual quality decisions of stereoscopic images. Furthermore, we develop an information content and divisive normalization-based pooling scheme that improves upon structural similarity in estimating the quality of single-view images. Finally, we propose a binocular rivalry-inspired multi-scale model to predict the quality of stereoscopic images from that of the single-view images. Our results show that the proposed model, without explicitly identifying image distortion types, successfully eliminates the prediction bias, leading to significantly improved quality prediction of the stereoscopic images. PMID:26087491

  14. Predictors of Child Molestation: Adult Attachment, Cognitive Distortions, and Empathy

    ERIC Educational Resources Information Center

    Wood, Eric; Riggs, Shelley

    2008-01-01

    A conceptual model derived from attachment theory was tested by examining adult attachment style, cognitive distortions, and both general and victim empathy in a sample of 61 paroled child molesters and 51 community controls. Results of logistic multiple regression showed that attachment anxiety, cognitive distortions, high general empathy but low…

  15. The Relationship between Depression, Irrational Beliefs, and Cognitive Distortions.

    ERIC Educational Resources Information Center

    Chan, Florentius

    Studies have shown that depressed people have a significantly higher number of irrational beliefs and cognitive distortions than nondepressed people. The purpose of this study was to identify the causal relationship among depression, irrational beliefs, and cognitive distortions through the use of cross-lagged panel correlational analysis. On two…

  16. Cognitive Distortions, Coping Behavior, and Depression in College Students.

    ERIC Educational Resources Information Center

    Warren, Nancy J.; And Others

    1982-01-01

    This study explored the relationship of cognitive distortions and coping strategies to depression in college students. A measure of cognitive distortions (the Interpretation Inventory) and a measure of strategies for coping with depression (the Active Checklist) were developed and used for this study. Results are discussed. (CJ)

  17. Understanding Pretrial Publicity: Predecisional Distortion of Evidence by Mock Jurors

    ERIC Educational Resources Information Center

    Hope, Lorraine; Memon, Amina; McGeorge, Peter

    2004-01-01

    Prejudicial pretrial publicity (PTP) constitutes a serious source of juror bias. The current study examined differences in predecisional distortion for mock jurors exposed to negative PTP (N-PTP) versus nonexposed control participants. According to work by K. A. Carlson and J. E. Russo (2001), predecisional distortion occurs when jurors bias new…

  18. Socioeconomic Inequality and Giftedness: Suppression and Distortion of High Ability

    ERIC Educational Resources Information Center

    Ambrose, Don

    2013-01-01

    Severe socioeconomic inequality strongly suppresses and distorts the discovery of aspirations and the concomitant development of talents among the gifted. More comprehensive understanding of this suppression and distortion is available through a wide-ranging interdisciplinary search for research findings and theories that illuminate economic,…

  19. The ISOCAM field-of-view distortion correction

    NASA Technical Reports Server (NTRS)

    Ali, B.; Ott, S.; Vo, T. D.; Gastaud, R.; Okumura, K.

    2000-01-01

    We describe results from new re-analysis of the ISOCAM field-of-view distortion. In this contribution we describe the procedure for determining the distortion, the implentation and resulting effects on the ISOCAM astrometric measurements, mosaicking and flux calibration.

  20. Distortion of Probability and Outcome Information in Risky Decisions

    ERIC Educational Resources Information Center

    DeKay, Michael L.; Patino-Echeverri, Dalia; Fischbeck, Paul S.

    2009-01-01

    Substantial evidence indicates that information is distorted during decision making, but very few studies have assessed the distortion of probability and outcome information in risky decisions. In two studies involving six binary decisions (e.g., banning blood donations from people who have visited England, because of "mad cow disease"), student…

  1. Quantitative trait locus mapping can benefit from segregation distortion.

    PubMed

    Xu, Shizhong

    2008-12-01

    Segregation distortion is a phenomenon that has been observed in many experimental systems. How segregation distortion among markers arises and its impact on mapping studies are the focus of this work. Segregation distortion of markers can be considered to arise from segregation distortion loci (SDL). I develop a theory of segregation distortion and show that the presence of only a few SDL can cause the entire chromosome to distort from Mendelian segregation. Segregation distortion is detrimental to the power of detecting quantitative trait loci (QTL) with dominance effects, but it is not always a detriment to QTL mapping for additive effects. When segregation distortion of a locus is a random event, the SDL is beneficial to QTL mapping approximately 44% of the time. If SDL are present and ignored, power loss can be substantial. A dense marker map can be used to ameliorate the situation, and if dense marker information is incorporated, power loss is minimal. However, other situations are less benign. A method that can simultaneously map QTL and SDL is discussed, maximizing both use of mapping resources and use by agricultural and evolutionary biologists. PMID:18957707

  2. Cognitive Distortion and Psychological Distress in Chronic Low Back Pain.

    ERIC Educational Resources Information Center

    Smith, Timothy W.; And Others

    1986-01-01

    Indicated that cognitive distortion was associated with high scores on the Minnesota Multiophasic Personality Inventory (MMPH) Depression (D), Psychasthenia (Pt), and Schizophrenia (Sc) scales, but not the Hypochondriasis (Hs) and Hysteria (Hy) scales. Cognitive distortion is likely to be an important factor in general distress but not in…

  3. Perception of Perspective Distortions in Image-Based Rendering

    PubMed Central

    Vangorp, Peter; Richardt, Christian; Cooper, Emily A.; Chaurasia, Gaurav; Banks, Martin S.; Drettakis, George

    2013-01-01

    Image-based rendering (IBR) creates realistic images by enriching simple geometries with photographs, e.g., mapping the photograph of a building façade onto a plane. However, as soon as the viewer moves away from the correct viewpoint, the image in the retina becomes distorted, sometimes leading to gross misperceptions of the original geometry. Two hypotheses from vision science state how viewers perceive such image distortions, one claiming that they can compensate for them (and therefore perceive scene geometry reasonably correctly), and one claiming that they cannot compensate (and therefore can perceive rather significant distortions). We modified the latter hypothesis so that it extends to street-level IBR. We then conducted a rigorous experiment that measured the magnitude of perceptual distortions that occur with IBR for façade viewing. We also conducted a rating experiment that assessed the acceptability of the distortions. The results of the two experiments were consistent with one another. They showed that viewers’ percepts are indeed distorted, but not as severely as predicted by the modified vision science hypothesis. From our experimental results, we develop a predictive model of distortion for street-level IBR, which we use to provide guidelines for acceptability of virtual views and for capture camera density. We perform a confirmatory study to validate our predictions, and illustrate their use with an application that guides users in IBR navigation to stay in regions where virtual views yield acceptable perceptual distortions. PMID:24273376

  4. Motivational Distortion on 16 PF Primaries by Male Felons.

    ERIC Educational Resources Information Center

    Wallbrown, Fred H.; And Others

    1989-01-01

    Investigated motivational distortion using the 16 Personality Factor Questionnaire (16 PF) for male (n=331) criminal offenders. Results indicated that ego-strength, free-floating anxiety, ability to bind anxiety, boldness, dominance, emotional sensitivity and suspiciousness contributed most to the motivational distortion scale predictions.…

  5. Quadratic elongation: A quantitative measure of distortion in coordination polyhedra

    USGS Publications Warehouse

    Robinson, Kelly F.; Gibbs, G.V.; Ribbe, P.H.

    1971-01-01

    Quadratic elongation and the variance of bond angles are linearly correlated for distorted octahedral and tetrahedral coordination complexes, both of which show variations in bond length and bond angle. The quadratic elonga tion is dimensionless, giving a quantitative measure of polyhedral distortion which is independent of the effective size of the polyhedron.

  6. The evolved basis and adaptive functions of cognitive distortions.

    PubMed

    Gilbert, P

    1998-12-01

    This paper explores common cognitive distortions from the perspective of evolutionary psychology. It is suggested that cognitive distortions are natural consequences of using fast track defensive algorithms that are sensitive to threat. In various contexts, especially those of threat, humans evolved to think adaptively rather than logically. Hence cognitive distortions are not strictly errors in brain functioning and it can be useful to inform patients that 'negative thinking' may be dysfunctional but is a reflection of basic brain design and not personal irrationality. The evolved nature of cognitive distortions has been implicit in cognitive therapy from its early days (Beck, 1963; Ellis, 1962) but has not been fully articulated in what is now known about evolved mental processes. Many forms of cognitive distortion can be seen to use the (previously) adaptive heuristic of better safe than sorry. PMID:9875955

  7. Mechanosensitive physiology of chlamydomonas reinhardtii under direct membrane distortion

    PubMed Central

    Min, Seul Ki; Yoon, Gwang Heum; Joo, Jung Hyun; Sim, Sang Jun; Shin, Hwa Sung

    2014-01-01

    Cellular membrane distortion invokes variations in cellular physiology. However, lack of an appropriate system to control the stress and facilitate molecular analyses has hampered progress of relevant studies. In this study, a microfluidic system that finely manipulates membrane distortion of Chlamydomonas reinhardtii (C. reinhardtii) was developed. The device facilitated a first-time demonstration that directs membrane distortion invokes variations in deflagellation, cell cycle, and lipid metabolism. C. reinhardtii showed a prolonged G1 phase with an extended total cell cycle time, and upregulated Mat3 regulated a cell size and cell cycle. Additionally, increased TAG compensated for the loss of cell mass. Overall, this study suggest that cell biology that requires direct membrane distortion can be realized using this system, and the implication of cell cycle with Mat3 expression of C. reinhardtii was first demonstrated. Finally, membrane distortion can be an attractive inducer for biodiesel production since it is reliable and robust. PMID:24728350

  8. Redshift distortions of clustering: a Lagrangian approach.

    NASA Astrophysics Data System (ADS)

    Hivon, E.; Bouchet, F. R.; Colombi, S.; Juszkiewicz, R.

    1995-06-01

    We study the effects of peculiar velocities on statistical measures of galaxy clustering. These effects occur when distances to the galaxies are estimated from their redshifts. It is assumed that the clustering pattern results from the gravitational instability of initially Gaussian, small-amplitude perturbations of a Friedman-Lemaitre cosmological model. Explicit expressions are given for an arbitrary density parameter {OMEGA} of the model, both when the cosmological constant, {LAMBDA}, is zero, and when the model is spatially flat, {OMEGA}+ {LAMBDA}/3H^2^ =1. Kaiser (1987) had analyzed the redshift distortion of the two-point correlation function. This function determines the variance of the density field distribution function and can be computed using linear perturbation theory. We show here how to compute higher order moments in redshift space, paying special attention to the skewness, or third moment of the density field, and its Fourier space counterpart, the bispectrum. This calls for a weakly non-linear analysis. We rely on a perturbative expansion of particle trajectories in Lagrangian coordinates, using the formalism introduced by Moutarde et al. (1991) and further developed by Bouchet et al. (1992, 1994). This formalism extends to higher orders the Zel'dovich first order (i.e. linear) solution (1970). The lowest non-vanishing contribution to the skewness comes from the first and second-order terms in perturbation theory. Therefore, using Zel'dovich approximation would not be self-consistent and would yield inaccurate results. We show that a physically consistent and quantitatively accurate analysis of the growth skewness in redshift space can be obtained from second-order Lagrangian theory. With practical applications to redshift surveys in mind, we also study the effects of spatial smoothing of the evolved density field. The necessary formalism was developed by Juszkiewicz & Bouchet (1991) and Juszkiewicz et al. (1993a). Here we give the first complete

  9. Quantifying and Reducing Posture-Dependent Distortion in Ballistocardiogram Measurements

    PubMed Central

    Javaid, Abdul Q.; Wiens, Andrew D.; Fesmire, N. Forrest; Weitnauer, Mary A.; Inan, Omer T.

    2015-01-01

    Ballistocardiography is a non-invasive measurement of the mechanical movement of the body caused by cardiac ejection of blood. Recent studies have demonstrated that ballistocardiogram (BCG) signals can be measured using a modified home weighing scale, and used to track changes in myocardial contractility and cardiac output. With this approach, the BCG can potentially be used both for preventive screening and for chronic disease management applications. However, for achieving high signal quality, subjects are required to stand still on the scale in an upright position for the measurement; the effects of intentional (for user comfort) or unintentional (due to user error) modifications in the position or posture of the subject during the measurement have not been investigated in the existing literature. In this study, we quantified the effects of different standing and seated postures on the measured BCG signals, and on the most salient BCG-derived features compared to reference standard measurements (e.g., impedance cardiography). We determined that the standing upright posture led to the least distorted signals as hypothesized, and that the correlation between BCG-derived timing interval features (R-J interval) and the pre-ejection period, PEP (measured using ICG), decreased significantly with impaired posture or sitting position. We further implemented two novel approaches to improve the PEP estimates from other standing and sitting postures, using system identification and improved J-wave detection methods. These approaches can improve the usability of standing BCG measurements in unsupervised settings (i.e. the home), by improving the robustness to non-ideal posture, as well as enabling high quality seated BCG measurements. PMID:26058064

  10. Distortion effects in a switch array UWB radar for time-lapse imaging of human heartbeats

    NASA Astrophysics Data System (ADS)

    Brovoll, Sverre; Berger, Tor; Aardal, Åyvind; Lande, Tor S.; Hamran, Svein-Erik

    2014-05-01

    Cardiovascular diseases (CVD) are a major cause of deaths all over the world. Microwave radar can be an alternative sensor for heart diagnostics and monitoring in modern healthcare that aids early detection of CVD symptoms. In this paper measurements from a switch array radar system are presented. This UWB system operates below 3 GHz and does time-lapse imaging of the beating heart inside the human body. The array consists of eight fat dipole elements. With a switch system, every possible sequence of transmit/receive element pairs can be selected to build a radar image from the recordings. To make the radar waves penetrate the human tissue, the antenna array is placed in contact with the body. Removal of the direct signal leakage through the antennas and body surface are done by high-pass (HP) filtering of the data prior to image processing. To analyze the results, measurements of moving spheres in air and simulations are carried out. We see that removal of the direct signal introduces amplitude distortion in the images. In addition, the effect of small target motion between the collection times of data from the individual elements is analyzed. With low pulse repetition frequency (PRF) this motion will distort the image. By using data from real measurements of heart motion in simulations, we analyze how the PRF and the antenna geometry influence this distortions.

  11. Microelectrical Mechanical Systems Flow Control Used to Manage Engine Face Distortion in Compact Inlet Systems

    NASA Technical Reports Server (NTRS)

    Anderson, Bernhard H.; Miller, Daniel N.

    1999-01-01

    Turbofan engine-face flow distortion is one of the most troublesome and least understood problems for designers of modern engine inlet systems. One concern is that there are numerous sources of flow-field distortion that are ingested by the inlet or generated within the inlet duct itself. Among these are: (1) flow separation at the cowl lip during in-flight maneuvering, (2) flow separation on the compression surfaces due to shock-wave/boundary layer interactions, (3) spillage of the fuselage boundary layer into the inlet duct, (4) ingestion of aircraft vortices and wakes emanating from upstream disturbances, and (5) strong secondary flow gradients and flow separation induced by wall curvature within the inlet duct itself. Most developing aircraft (including the B70, F-111, F-14, Mig-25, Tornado, and Airbus A300) have experienced one or more of these types of problems, particularly at high Mach numbers and/or extreme maneuver conditions when flow distortion at the engine face exceeded the allowable limits of the engine.

  12. Which spectral distortions does ΛCDM actually predict?

    NASA Astrophysics Data System (ADS)

    Chluba, Jens

    2016-04-01

    Ever refined cosmological measurements have established the ΛCDM concordance model, with the key cosmological parameters being determined to percent-level precision today. This allows us to make explicit predictions for the spectral distortions of the cosmic microwave background (CMB) created by various processes occurring in the early Universe. Here, we summarize all guaranteed CMB distortions and assess their total uncertainty within ΛCDM. We also compare simple methods for approximating them, highlighting some of the subtle aspects when it comes to interpreting future distortion measurements. Under simplified assumptions, we briefly study how well a PIXIE-like experiment may measure the main distortion parameters (i.e., μ and y). Next generation CMB spectrometers are expected to detect the distortion caused by reionization and structure formation at extremely high significance. They will also be able to constrain the small-scale power spectrum through the associated μ-distortion, improving limits on running of the spectral index. Distortions from the recombination era, adiabatic cooling of matter relative to the CMB and dark matter annihilation require a higher sensitivity than PIXIE in its current design. The crucial next step is an improved modeling of foregrounds and instrumental aspects, as we briefly discuss here.

  13. High-precision camera distortion measurements with a ``calibration harp''

    NASA Astrophysics Data System (ADS)

    Tang, Zhongwei; Grompone von Gioi, Rafael; Monasse, Pascal; Morel, Jean-Michel

    2012-10-01

    This paper addresses the high precision measurement of the distortion of a digital camera from photographs. Traditionally, this distortion is measured from photographs of a flat pattern which contains aligned elements. Nevertheless, it is nearly impossible to fabricate a very flat pattern and to validate its flatness. This fact limits the attainable measurable precisions. In contrast, it is much easier to obtain physically very precise straight lines by tightly stretching good quality strings on a frame. Taking literally "plumb-line methods", we built a "calibration harp" instead of the classic flat patterns to obtain a high precision measurement tool, demonstrably reaching 2/100 pixel precisions. The harp is complemented with the algorithms computing automatically from harp photographs two different and complementary lens distortion measurements. The precision of the method is evaluated on images corrected by state-of-the-art distortion correction algorithms, and by popular software. Three applications are shown: first an objective and reliable measurement of the result of any distortion correction. Second, the harp permits to control state-of-the art global camera calibration algorithms: It permits to select the right distortion model, thus avoiding internal compensation errors inherent to these methods. Third, the method replaces manual procedures in other distortion correction methods, makes them fully automatic, and increases their reliability and precision.

  14. Which spectral distortions does ΛCDM actually predict?

    NASA Astrophysics Data System (ADS)

    Chluba, Jens

    2016-07-01

    Ever refined cosmological measurements have established the ΛCDM concordance model, with the key cosmological parameters being determined to per cent-level precision today. This allows us to make explicit predictions for the spectral distortions of the cosmic microwave background (CMB) created by various processes occurring in the early Universe. Here, we summarize all guaranteed CMB distortions and assess their total uncertainty within ΛCDM. We also compare simple methods for approximating them, highlighting some of the subtle aspects when it comes to interpreting future distortion measurements. Under simplified assumptions, we briefly study how well a PIXIE-like experiment may measure the main distortion parameters (i.e. μ and y). Next-generation CMB spectrometers are expected to detect the distortion caused by reionization and structure formation at extremely high significance. They will also be able to constrain the small-scale power spectrum through the associated μ-distortion, improving limits on running of the spectral index. Distortions from the recombination era, adiabatic cooling of matter relative to the CMB and dark matter annihilation require a higher sensitivity than PIXIE in its current design. The crucial next step is an improved modelling of foregrounds and instrumental aspects, as we briefly discuss here.

  15. Simultaneous Electromagnetic Tracking and Calibration for Dynamic Field Distortion Compensation.

    PubMed

    Sadjadi, Hossein; Hashtrudi-Zaad, Keyvan; Fichtinger, Gabor

    2016-08-01

    Electromagnetic (EM) tracking systems are highly susceptible to field distortion. The interference can cause measurement errors up to a few centimeters in clinical environments, which limits the reliability of these systems. Unless corrected for, this measurement error imperils the success of clinical procedures. It is therefore fundamental to dynamically calibrate EM tracking systems and compensate for measurement error caused by field distorting objects commonly present in clinical environments. We propose to combine a motion model with observations of redundant EM sensors and compensate for field distortions in real time. We employ a simultaneous localization and mapping technique to accurately estimate the pose of the tracked instrument while creating the field distortion map. We conducted experiments with six degrees-of-freedom motions in the presence of field distorting objects in research and clinical environments. We applied our approach to improve the EM tracking accuracy and compared our results to a conventional sensor fusion technique. Using our approach, the maximum tracking error was reduced by 67% for position measurements and by 64% for orientation measurements. Currently, clinical applications of EM trackers are hampered by the adverse distortion effects. Our approach introduces a novel method for dynamic field distortion compensation, independent from preoperative calibrations or external tracking devices, and enables reliable EM navigation for potential applications. PMID:26595908

  16. Numerical analysis of distortion characteristics of heterojunction bipolar transistor laser

    NASA Astrophysics Data System (ADS)

    Piramasubramanian, S.; Ganesh Madhan, M.; Nagella, Jyothsna; Dhanapriya, G.

    2015-12-01

    Numerical analysis of harmonic and third order intermodulation distortion of transistor laser is presented in this paper. The three level rate equations are numerically solved to determine the modulation and distortion characteristics. DC and AC analysis on the device are carried out to determine its power-current and frequency response characteristics. Further, the effects of quantum well recombination time and electron capture time in the quantum well, on the modulation depth and distortion characteristics are examined. It is observed that the threshold current density of the device decreases with increasing electron lifetime, which coincides with earlier findings. Also, the magnitude of harmonic distortion and intermodulation products are found to reduce with increasing current density and with a reduction of spontaneous emission recombination lifetime. However, an increase of electron capture time improves the distortion performance. A maximum modulation depth of 18.42 dB is obtained for 50 ps spontaneous emission life time and 1 ps electron capture time, for 2.4 GHz frequency at a current density of 2Jth. A minimum second harmonic distortion magnitude of -66.8 dBc is predicted for 50 ps spontaneous emission life time and 1 ps electron capture time for 2.4 GHz frequency, at a current density of 7Jth. Similarly, a minimum third order intermodulation distortion of -83.93 dBc is obtained for 150 ps spontaneous emission life time and 5 ps electron capture time under similar biasing conditions.

  17. Signal distortion on VHF/UHF transionospheric paths: First results from the Wideband Ionospheric Distortion Experiment

    NASA Astrophysics Data System (ADS)

    Cannon, Paul S.; Groves, Keith; Fraser, David J.; Donnelly, William J.; Perrier, Kathleen

    2006-10-01

    To the best of our knowledge, we report the first determination of ionospheric distortion, comprising the simultaneous characterization of both multipath and Doppler, on wideband, transionospheric VHF (158 MHz) and UHF (422 MHz) signals. The measurements took place as part of the test phase of the United Kingdom-United States Wideband Ionospheric Distortion Experiment during the evening (˜1000 UT) of 18 January 2005. This characterization has been achieved using the ALTAIR radar at the Ronald Reagan Ballistic Missile Defense Test Site on Kwajalein Atoll (9.395°N, 167.469°E (12.87°N, 237.16°E corrected geomagnetic)) in the Pacific, in conjunction with a low Earth orbiting, constant radar cross-section, passive satellite (calibration sphere). During the period when the two-way S4 index was above ˜0.8 on both channels, the median coherency times were 43 and 96 ms at VHF and UHF, respectively (at 1.5σ). The corresponding median coherency bandwidths were 0.8 and 2.1 MHz.

  18. Spatial distorted target recognition based on improved MACH filter

    NASA Astrophysics Data System (ADS)

    Chen, Yu; Huo, Furong; Zheng, Liqin

    2014-11-01

    Joint transform correlator (JTC) can make targets recognized and located accurately, but the bottleneck technique of JTC is how to recognize spatial distorted targets in cluttered scene. This has restricted the development of the pattern recognition with JTC to a great extent. In order to solve the problem, improved maximum average correlation height (MACH) filter algorithm is presented in this paper. The MACH algorithm has powerful capability of recognition for spatial distorted targets (rotation and scale changed etc.). The controlling parameters of the synthesized filter are optimized in this paper, which makes the filter have higher distortion tolerance and can suppress cluttered noise effectively. When improved MACH filter algorithm in frequency domain is projected to space domain, the MACH reference template image can be obtained which includes various forms of distorted target image. Based on amounts of computer simulation and optical experiments, MACH reference template is proved to have the capability of sharpening the correlation peaks and expanding recognizing scope for distorted targets in cluttered scene. MATLAB software is applied to produce MACH reference image for the detected target images and conduct simulation experiments for its powerful calculation capability of matrix. In order to prove the feasibility of MACH reference in JTC and determine the recognition scope, experiments for an aircraft target in the sky are carried out. After the original image is processed by edge extraction, a MACH filter reference template is obtained in space domain from improved MACH filter in frequency domain. From simulation experiments, the improved MACH filter is proved to have the feasibility of sharpening correlation peaks for distorted targets. Optical experiments are given to verify the effectiveness further. The experiments show the angular distortion tolerance can reach up to +/-15 degrees and scale distortion tolerance can reach up to +/-23%. Within this

  19. Opdic (optimized Peak, Distortion and Clutter) Detection Filter.

    NASA Astrophysics Data System (ADS)

    House, Gregory Philip

    1995-01-01

    Detection is considered. This involves determining regions of interest (ROIs) in a scene: the locations of multiple object classes in a scene in clutter when object distortions and contrast differences are present. High probability of detection P_{D} is essential and low P_{FA } is desirable since subsequent stages in the full system will only decrease P_{FA } and cannot increase P_{D }. Low resolution blob objects and objects with more internal detail are considered with both 3-D aspect view and depression angle distortions present. Extensive tests were conducted on 56 scenes with object classes not present in the training set. A modified MINACE (Minimum Noise and Correlation Energy) distortion-invariant filter was used. This minimizes correlation plane energy due to distortions and clutter while satisfying correlation peak constraint values for various object-aspect views. The filter was modified with a new object model (to give predictable output peak values) and a new correlated noise clutter model; a white Gaussian noise model of distortion was used; and a new techniques to increase the number of training set images (N _{T}) included in the filter were developed. Excellent results were obtained. However, the correlation plane distortion and clutter energy functions were found to become worse as N_{T } was increased and no rigorous method exists to select the best N_{T} (when to stop filter synthesis). A new OPDIC (Optimized Peak, Distortion, and Clutter) filter was thus devised. This filter retained the new object, clutter and distortion models noted. It minimizes the variance of the correlation peak values for all training set images (not just the N_{T} images). As N _{T} increases, the peak variance and the objective functions (correlation plane distortion and clutter energy) are all minimized. Thus, this new filter optimizes the desired functions and provides an easy way to stop filter synthesis (when the objective function is minimized). Tests show

  20. Die Casting Part Distortion: Prediction and Attenuation

    SciTech Connect

    Dr, R. Allen Miller

    2002-02-12

    The goal of this research was to predict the part deformation and residual stresses after ejection from the die and cooling to room temperature. A finite element model was built to achieve this goal and several modeling techniques were investigated throughout this research. Die-casting is a very complex process and the researchers are faced with a large number of hard to solve physical problems when modeling the process. Several assumptions are made in our simulation model. The first significant assumption is the instantaneous cavity filling. This means that the cavity filling stage is not considered in our model. Considering the cavity filling stage increases the modeling complexity as a result of different flow patterns. expected in the shot sleeve, gate, runner and different cavity features. The flow of gas from the cavity through the vents is another problem that is ignored in our model as a result of this assumption. Our second assumption is that the cast metal has uniform temperature distribution inside the cavity, at the starting point of simulation. This temperature is assumed to be over liquidus limit, i.e. the solid fraction is 0.0% of the cast metal. The third assumption is due to ABAQUS (commercial software used in this research) limitations. ABAQUS cannot deal with multi-phase models; therefore we use solid elements to define the casting instead of multi-phase (liquid/solid) elements. Liquid elements can carry the hydrostatic pressure from the shot sleeve and apply it on the cavity surfaces, while the solid elements do not have this capability. To compensate for this assumption we add the cavity pressure as a boundary condition and apply it on the cavity surface separately from the part. Another issue with this assumption is that, liquid casting can follow the cavity shape when it distorts. With the use of solid elements to represent the casting during its liquid state, it loses this capability to follow the cavity. Several techniques were tested to

  1. Distribution function approach to redshift space distortions

    SciTech Connect

    Seljak, Uroš; McDonald, Patrick E-mail: pvmcdonald@lbl.gov

    2011-11-01

    We develop a phase space distribution function approach to redshift space distortions (RSD), in which the redshift space density can be written as a sum over velocity moments of the distribution function. These moments are density weighted and have well defined physical interpretation: their lowest orders are density, momentum density, and stress energy density. The series expansion is convergent if kμu/aH < 1, where k is the wavevector, H the Hubble parameter, u the typical gravitational velocity and μ = cos θ, with θ being the angle between the Fourier mode and the line of sight. We perform an expansion of these velocity moments into helicity modes, which are eigenmodes under rotation around the axis of Fourier mode direction, generalizing the scalar, vector, tensor decomposition of perturbations to an arbitrary order. We show that only equal helicity moments correlate and derive the angular dependence of the individual contributions to the redshift space power spectrum. We show that the dominant term of μ{sup 2} dependence on large scales is the cross-correlation between the density and scalar part of momentum density, which can be related to the time derivative of the matter power spectrum. Additional terms contributing to μ{sup 2} and dominating on small scales are the vector part of momentum density-momentum density correlations, the energy density-density correlations, and the scalar part of anisotropic stress density-density correlations. The second term is what is usually associated with the small scale Fingers-of-God damping and always suppresses power, but the first term comes with the opposite sign and always adds power. Similarly, we identify 7 terms contributing to μ{sup 4} dependence. Some of the advantages of the distribution function approach are that the series expansion converges on large scales and remains valid in multi-stream situations. We finish with a brief discussion of implications for RSD in galaxies relative to dark matter

  2. Distortion effects on the neutron knockout from exotic nuclei in the collision with a proton target

    NASA Astrophysics Data System (ADS)

    Cravo, E.; Crespo, R.; Deltuva, A.

    2016-05-01

    Background: Reaction theory plays a major role in the interpretation of experimental data and one needs to identify and include accurately all the relevant dynamical effects in order to extract reliable structure information. The knockout of a nucleon (neutron/proton) from a high energy exotic nucleus projectile colliding with a proton target allows to get insight on the structure of its valence and inner shells. Purpose: We aim to clarify the role of the distortion on the calculated observables for nucleon knockout, in particular, the dependence of the calculated observables on the binding energy ɛb and angular momentum L of the knockout particle, and on the mass of the projectile core, Ac. We consider mainly the knockout of a neutron that may be either in the valence or in the inner shell of the projectile nucleus. Method: Exact three-body Faddeev/Alt-Grassberger-Sandhas (Faddeev/AGS) calculations are performed for the nucleon knockout from stable and exotic nuclei in the collision of 420 MeV/u projectile beams with a proton target. Results are compared with plane-wave impulse approximation (PWIA) calculations. Results: The Faddeev/AGS formalism accurately predicts: (i) a systematic nearly logarithmic dependence of the distortion parameter on the separation energy; (ii) roughly linear dependence of the ratio of the full to the PWIA cross section on the asymmetry parameter; (iii) a distinct behavior between the calculated transverse core momentum distribution from the PWIA and full Faddeev/AGS exact approach which indicates that distortion effects do not modify fully exclusive observables through a common renormalization factor. Conclusions: To extract structure information on deeper shells one needs to include distortion effects accurately. A systematic analysis enables to estimate the total cross section for knockout of a nucleon from a given shell of nuclei at/away the stability line of the nuclear landscape. The comparison with experimental results may

  3. Distortion of the cosmic background radiation by superconducting strings

    NASA Technical Reports Server (NTRS)

    Ostriker, J. P.; Thompson, C.

    1987-01-01

    Superconducting cosmic strings can be significant energy sources, keeping the universe ionized past the commonly assumed epoch of recombination. As a result, the spectrum of the cosmic background radiation is distorted in the presence of heated primordial gas via the Suniaev-Zel'dovich effect. Thiis distortion can be relatively large: the Compton y parameter attains a maximum in the range 0.001-0.005, with these values depending on the mass scale of the string. A significant contribution to y comes from loops decaying at high redshift when the universe is optically thick to Thomson scattering. Moreover, the isotropic spectral distortion is large compared to fluctuations at all angular scales.

  4. Characteristic microwave background distortions from collapsing domain wall bubbles

    NASA Technical Reports Server (NTRS)

    Goetz, Guenter; Noetzold, Dirk

    1990-01-01

    The magnitude and angular pattern of distortions of the microwave background are analyzed by collapsing spherical domain walls. A characteristic pattern of redshift distortions of red or blue spikes surrounded by blue discs was found. The width and height of a spike is related to the diameter and magnitude of the disc. A measurement of the relations between these quantities thus can serve as an unambiguous indicator for a collapsing spherical domain wall. From the redshift distortion in the blue discs an upper bound was found on the surface energy density of the walls sigma is less than or approximately 8 MeV cubed.

  5. Recovery of pyroshock data from distorted acceleration records

    NASA Technical Reports Server (NTRS)

    Smith, J. L.

    1985-01-01

    In the past, distorted pyrotechnic shock time history data was discarded completely or cleaned up by questionable means. Too often the clean up procedures introduced as much error into the data as previously existed. Techniques are presented for data recovery so that true signals are obtained and so that these recovery procedures will be completely reproducible by any scientists in any lab. Most ordnance shock data is distorted by baseline shifts or accelerometer resonances. The methodology of recovering true signals from these two types of distortion is discussed.

  6. Anisotropic magnification distortion of the 3D galaxy correlation. II. Fourier and redshift space

    SciTech Connect

    Hui Lam; Gaztanaga, Enrique; LoVerde, Marilena

    2008-03-15

    In paper I of this series we discuss how magnification bias distorts the 3D correlation function by enhancing the observed correlation in the line-of-sight (LOS) orientation, especially on large scales. This lensing anisotropy is distinctive, making it possible to separately measure the galaxy-galaxy, galaxy-magnification and magnification-magnification correlations. Here we extend the discussion to the power spectrum and also to redshift space. In real space, pairs oriented close to the LOS direction are not protected against nonlinearity even if the pair separation is large; this is because nonlinear fluctuations can enter through gravitational lensing at a small transverse separation (or i.e. impact parameter). The situation in Fourier space is different: by focusing on a small wave number k, as is usually done, linearity is guaranteed because both the LOS and transverse wave numbers must be small. This is why magnification distortion of the galaxy correlation appears less severe in Fourier space. Nonetheless, the effect is non-negligible, especially for the transverse Fourier modes, and should be taken into account in interpreting precision measurements of the galaxy power spectrum, for instance those that focus on the baryon oscillations. The lensing induced anisotropy of the power spectrum has a shape that is distinct from the more well-known redshift space anisotropies due to peculiar motions and the Alcock-Paczynski effect. The lensing anisotropy is highly localized in Fourier space while redshift space distortions are more spread out. This means that one could separate the magnification bias component in real observations, implying that potentially it is possible to perform a gravitational lensing measurement without measuring galaxy shapes.

  7. Optical phase distortion due to compressible flow over laser turrets

    NASA Technical Reports Server (NTRS)

    Fuhs, A. E.; Fuhs, S. E.

    1980-01-01

    Analytical models for optical phase distortion due to compressible flow over a laser turret are developed. Phase distortion is calculated for both blunt and small perturbation turrets. For the blunt turret, the Janzen-Rayleigh technique is used to determine the flow field. Phase distortions of 2.2 wavelengths at 3.8 microns are calculated for the blunt turret. For small perturbation turrets, a versatile analytical model is developed for a turret on a fuselage with circular cross section. With a two dimensional Fourier series representation of the turret, any shape can be considered. Both subsonic and supersonic flows can be calculated. Phase distortions of 1.2 wavelengths at 3.8 microns are calculated for one turret at high subsonic Mach number. In addition to being of value for laser turrets, the methods are applicable to reconnaissance aircraft using photographic equipment and cruise missiles using celestial navigation.

  8. Preliminary mode distortion measurements on the Jefferson Lab IRFEL

    SciTech Connect

    Stephen V. Benson; Joe Gubeli; Michelle D. Shinn

    2001-08-01

    We previously reported analytical calculations of mirror distortion in a high power FEL with a near-concentric cavity. Naive assumptions about the FEL power vs. distortion led us to believe that mirror losses were much lower than expected. Recently we have directly measured the mode size and beam quality as a function of power using a resonator with a center wavelength of 5 microns. The resonator mirrors were calcium fluoride. This material exhibits a large amount of distortion for a given power but, due to the negative slope of refractive index v temperature, adds almost no optical phase distortion on the laser output. The mode in the cavity can thus be directly calculated from the measurements at the resonator output. The presence of angular jitter produced results inconsistent with cold cavity expectations. Removing the effects of the angular jitter produces results in reasonable agreement with analytical models assuming mirror losses comparable to the original expectations.

  9. Densification and shape distortion in liquid-phase sintering

    SciTech Connect

    Liu, J.; German, R.M.

    1999-12-01

    Densification and dimensional control are important aspects of liquid-phase sintering. The capillary force and the solid bonding affect both densification and shape preservation. Capillarity, which is orientated isotropically, causes uniform shrinkage and holds grains together to preserve the component shape in the early stage of sintering. On the other hand, solid bonding resists viscous flow and inhibits densification and shape distortion. The capillary force decreases with densification and approaches zero as pores are eliminated. Thus, shape retention eventually requires solid-grain bonding. The solid-grain bonding provides compact rigidity, which is represented by compact strength. Shape distortion occurs when the compact loses its strength. For every situation, there is a critical compact strength above which no shape distortion occurs. Distortion in liquid-phase sintering indicates that the compact strength passed below a critical level.

  10. A method to estimate optical distortion using planetary images

    NASA Astrophysics Data System (ADS)

    Kouyama, Toru; Yamazaki, Atsushi; Yamada, Manabu; Imamura, Takeshi

    2013-09-01

    We developed a method to calibrate optical distortion parameters for axisymmetrical optical systems using images of a spherical target taken at a variety of distances. The method utilizes the fact that the influence of distortion on the apparent radius in the image changes with the disk size of the projected body. Because several planets can be used as the spherical target, this method enables us to obtain distortion parameters in space and by using a large number of planetary images, desired accuracy of parameters can be achieved statistically. The applicability of the method was tested by applying it to simulated planetary images and real Venus images taken by Venus Monitoring Camera onboard the ESA's Venus Express, and optical distortion was successfully retrieved with the pixel position error of less than 1 pixel. Venus is the planet most suitable for the proposed method because of its smooth, nearly spherical surface of the haze layer covering the planet.

  11. Experimental study of three exit pressure distortions on turbine performance

    NASA Astrophysics Data System (ADS)

    Gaddis, Stephen W.; Boynton, James L.

    1993-06-01

    A cold flow air test of the Space Shuttle Main Engine (SSME) High Pressure Fuel Turbopump (HPFTP) turbine was conducted with a circumferential pressure distortion at the turbine exit. The effects of three circumferential exit pressure distortions on turbine efficiency and pressure ratio, are presented. Circumferential and radial total pressure, total temperature, static pressure, and flow angle distributions at the turbine exit are also presented. Efficiency and total-to-total pressure ratio are shown to have a circumferential variation as high as 13.7 percent (or points of efficiency) and 7.1 percent, respectively. A slight pressure distortion was measured downstream of the first stage nozzle and the distortion increased across subsequent blade rows to a maximum downstream of the second stage rotor for all three plates. A brief discussion of the test facility, model, instrumentation, and test plan is given for completeness.

  12. Compensation of reflector surface distortions using conjugate field matching

    NASA Technical Reports Server (NTRS)

    Acosta, R. J.

    1986-01-01

    The feasibility of compensating for reflector surface distortions has been investigated. The performance characteristics (gain, sidelobe level, null location, beamwidth, etc.) of space communication reflector antenna systems degrade as the reflector surface distorts due to thermal effects from a varying solar flux. The technique reported here will maintain the design radiation performance independently of thermal effects on the reflector surface. With the advent of monolithic microwave integrated circuits (MMIC), a greater flexibility in array-fed reflector system design can be achieved. MMIC arrays provides independent control of amplitude and phase for each of many radiating elements of the feed array. The conjugate field matching technique provide a basis for obtaining the required element excitations under surface distortion for maintaining the design radiation performance. It is assumed that the surface characteristics (x, y, z, first derivatives, and second derivatives) under distortion are known.

  13. Characterizing, controlling, and correcting distortions in the COS FUV detector

    NASA Astrophysics Data System (ADS)

    Sahnow, David J.; Becker, George D.; Debes, John H.; Ely, Justin; Lockwood, Sean A.; Massa, Derck; Oliveira, Cristina M.; Penton, Steven V.; Proffitt, Charles; Roman-Duval, Julia; Sana, Hugues; Sonnentrucker, Paule; Taylor, Joanna

    2015-09-01

    The Far Ultraviolet (FUV) detector on the Cosmic Origins Spectrograph (COS) of the Hubble Space Telescope (HST) is subject to a variety of distortions due to its analog nature. Thermal variations of the detector and electronics stretch and shift the active area. Geometric distortions on a range of spatial scales warp the two-dimensional spectral image. Changes due to detector walk - the dependence of detected position on pulse height - add distortions that change as a function of time. The calcos calibration pipeline includes corrections for each of these effects in the calibrated spectra, but these are imperfect, and they do not help with the target acquisition process, which uses raw detector coordinates. We discuss these distortions and their effect on the data, our attempts to mitigate them, the current pipeline corrections and their success at removing the effects, and possible modifications to improve the data quality in the future.

  14. Correction of the field distortion in embedded laser marking system

    NASA Astrophysics Data System (ADS)

    Wang, Dongyun; Yu, Qiwei; Ye, Xinpiao

    2014-04-01

    Because of inherent and random errors, the pillow-shaped and barrel-shaped distortions are occurred in the embedded laser marking system. These seriously affect marking quality. However, the existed correcting approaches are almost all used on PC based laser marking controller. They require very high processing speeds of the processor which cannot be satisfied in the embedded controller. In order to find a suitable method, the causes of distortions were analyzed deeply. After that, a linear compensation method is put forward herein. It needs to determine two coefficients by standard process and tries to improve the marking quality by compensating the marking data before converted to voltage by digital-to-analogue converter. It is not complex as the PC based one, but can correct the distortions to some extent. Experiments show that this method can efficiently decrease the distortions and improve the marking quality.

  15. A method to correct coordinate distortion in EBSD maps

    SciTech Connect

    Zhang, Y.B. Elbrønd, A.; Lin, F.X.

    2014-10-15

    Drift during electron backscatter diffraction mapping leads to coordinate distortions in resulting orientation maps, which affects, in some cases significantly, the accuracy of analysis. A method, thin plate spline, is introduced and tested to correct such coordinate distortions in the maps after the electron backscatter diffraction measurements. The accuracy of the correction as well as theoretical and practical aspects of using the thin plate spline method is discussed in detail. By comparing with other correction methods, it is shown that the thin plate spline method is most efficient to correct different local distortions in the electron backscatter diffraction maps. - Highlights: • A new method is suggested to correct nonlinear spatial distortion in EBSD maps. • The method corrects EBSD maps more precisely than presently available methods. • Errors less than 1–2 pixels are typically obtained. • Direct quantitative analysis of dynamic data are available after this correction.

  16. Optical Distortion Evaluation in Large Area Windows using Interferometry

    NASA Technical Reports Server (NTRS)

    Youngquist, Robert C.; Skow, Miles; Nurge, Mark A.

    2015-01-01

    It is important that imagery seen through large area windows, such as those used on space vehicles, not be substantially distorted. Many approaches are described in the literature for measuring the distortion of an optical window, but most suffer from either poor resolution or processing difficulties. In this paper a new definition of distortion is presented, allowing accurate measurement using an optical interferometer. This new definition is shown to be equivalent to the definitions provided by the military and the standards organizations. In order to determine the advantages and disadvantages of this new approach the distortion of an acrylic window is measured using three different methods; image comparison, Moiré interferometry, and phase-shifting interferometry.

  17. Novel itinerant transverse spin waves

    NASA Astrophysics Data System (ADS)

    Feldmann, John Delaney

    In 1956, Lev Davidovich Landau put forth his theory on systems of interacting fermions, or fermi liquids. A year later, Viktor Pavlovich Silin described spin waves that such a system of fermions would support. The treatment of the contribution of the molecular field to the spin wave dispersion was a novel aspect of these spin waves. Silin predicted that there would exist a hierarchy of spin waves in a fermi liquid, one for each component of the spherical harmonic expansion of the fermi surface. In 1968, Anthony J. Leggett and Michael J. Rice derived from fermi liquid theory how the behavior of the spin diffusion coefficient of a fermi liquid could be directly experimentally observable via the spin echo effect [24]. Their prediction, that the diffusion coefficient of a fermi liquid would not decay exponentially with temperature, but rather would have a maximum at some non-zero temperature, was a direct consequence of the fermi liquid molecular field and spin wave phenomena, and this was corroborated by experiment in 1971 by Corruccini, et al. [13]. A parallel advancement in the theory of fermi liquid spin waves came with the extension of the theory to describe weak ferromagnetic metals. In 1959, Alexei Abrikosov and I. E. Dzyaloshiski put forth a theoretical description of a ferromagnetic fermi liquid [1]. In 2001, Kevin Bedell and Krastan Blagoev showed that a non-trivial contribution to the dispersion of the ferromagnetic current spin wave arises from the necessary consideration of higher harmonic moments in the distortion of the fermi surface from its ground state [8]. In the chapters to follow, the author presents new results for transverse spin waves in a fermi liquid, which arise from a novel ground state of a fermi liquid-one in which an l = 1 harmonic distortion exists in the ground state polarization. It is shown that such an instability can lead to spin waves with dispersions that are characterized by a linear dependence on the wave number at long

  18. Distorted five-dimensional electrically charged black holes

    NASA Astrophysics Data System (ADS)

    Abdolrahimi, Shohreh; Shoom, Andrey A.

    2014-01-01

    In this paper, we study distorted, five-dimensional, electrically charged (nonextremal) black holes on the example of a static and "axisymmetric" black hole distorted by external, electrically neutral matter. Such a black hole is represented by the solution derived here of the Einstein-Maxwell equations which admits an R1×U(1)×U(1) isometry group. The external matter, which is "located" at the asymptotic infinity, is not included in the solution. The space-time singularities are located behind the black hole's inner (Cauchy) horizon, provided that the sources of the distortion satisfy the strong energy condition. The inner (Cauchy) horizon remains regular if the distortion fields are finite and smooth at the outer horizon. The solution has some remarkable properties. There exists a certain duality transformation between the inner and the outer horizon surfaces which links surface gravity, electrostatic potential, and space-time curvature invariants calculated at the black hole horizons. The product of the inner and outer horizon areas depends only on the black hole's electric charge, and the geometric mean of the areas is the upper (lower) limit for the inner (outer) horizon area. The electromagnetic field invariant calculated at the horizons is proportional to the squared surface gravity of the horizons. The horizon areas, electrostatic potential, and surface gravity satisfy the Smarr formula. We formulated the zeroth and the first laws of mechanics and thermodynamics of the distorted black hole and found a correspondence between the global and local forms of the first law. To illustrate the effect of distortion, we consider the dipole-monopole and quadrupole-quadrupole distortion fields. The relative change in the Kretschmann scalar due to the distortion is greater at the outer horizon than at the inner one. By calculating the maximal proper time of free fall from the outer to the inner horizons, we show that the distortion can noticeably change the black hole

  19. Reactivity analysis of core distortion effects in the FFTF

    SciTech Connect

    Knutson, B.J.

    1982-01-01

    An improved technique for evaluating core distortion reactivity effects was developed using reactivity analyses of two core geometry models (R-Z and HEX). This technique is incorporated into a new processor code called CORDIS. The advantages of this technique over existing reactivity models are that is preserves core heterogeneity, provides a control rod insertion effect model, uses row-dependent axial shape functions, and provides a flexible and cost efficient core distortion reactivity analysis method.

  20. Nanostructure-Induced Distortion in Single-Emitter Microscopy.

    PubMed

    Lim, Kangmook; Ropp, Chad; Barik, Sabyasachi; Fourkas, John; Shapiro, Benjamin; Waks, Edo

    2016-09-14

    Single-emitter microscopy has emerged as a promising method of imaging nanostructures with nanoscale resolution. This technique uses the centroid position of an emitter's far-field radiation pattern to infer its position to a precision that is far below the diffraction limit. However, nanostructures composed of high-dielectric materials such as noble metals can distort the far-field radiation pattern. Previous work has shown that these distortions can significantly degrade the imaging of the local density of states in metallic nanowires using polarization-resolved imaging. But unlike nanowires, nanoparticles do not have a well-defined axis of symmetry, which makes polarization-resolved imaging difficult to apply. Nanoparticles also exhibit a more complex range of distortions, because in addition to introducing a high dielectric surface, they also act as efficient scatterers. Thus, the distortion effects of nanoparticles in single-emitter microscopy remains poorly understood. Here we demonstrate that metallic nanoparticles can significantly distort the accuracy of single-emitter imaging at distances exceeding 300 nm. We use a single quantum dot to probe both the magnitude and the direction of the metallic nanoparticle-induced imaging distortion and show that the diffraction spot of the quantum dot can shift by more than 35 nm. The centroid position of the emitter generally shifts away from the nanoparticle position, which is in contradiction to the conventional wisdom that the nanoparticle is a scattering object that will pull in the diffraction spot of the emitter toward its center. These results suggest that dielectric distortion of the emission pattern dominates over scattering. We also show that by monitoring the distortion of the quantum dot diffraction spot we can obtain high-resolution spatial images of the nanoparticle, providing a new method for performing highly precise, subdiffraction spatial imaging. These results provide a better understanding of the

  1. Low distortion automatic phase control circuit. [voltage controlled phase shifter

    NASA Technical Reports Server (NTRS)

    Hauge, G.; Pederson, C. W. (Inventor)

    1974-01-01

    A voltage controlled phase shifter is rendered substantially harmonic distortion free over a large dynamic input range by employing two oppositely poled, equally biased varactor diodes as the voltage controlled elements which adjust the phase shift. Control voltages which affect the bias of both diodes equally are used to adjust the phase shift without increasing distortion. A feedback stabilized phase shifter is rendered substantially frequency independent by employing a phase detector to control the phase shift of the voltage controlled phase shifter.

  2. Projection lithography with distortion compensation using reticle chuck contouring

    DOEpatents

    Tichenor, Daniel A.

    2001-01-01

    A chuck for holding a reflective reticle where the chuck has an insulator block with a non-planer surface contoured to cause distortion correction of EUV radiation is provided. Upon being placed on the chuck, a thin, pliable reflective reticle will conform to the contour of the chuck's non-planer surface. When employed in a scanning photolithography system, distortion in the scanned direction is corrected.

  3. Correlation of lattice distortion with photocatalytic activity of titanium dioxide

    SciTech Connect

    Wang Xia; Shui Miao Li Rongsheng; Song Yue

    2008-08-04

    The photocatalytic activity of titanium dioxide dispersions on X-3B pigment degradation has been investigated. A variety of factors that would influence the photocatalytic activity such as crystallite size, lattice distortion, and anatase content are discussed in detail. It is found that lattice distortion is the most important one among these factors and is expected to inhibit the hole and electron pair recombination. It determines, to some extent, the photocatalytic efficiency of titanium dioxide dispersions.

  4. Multimodal Sensory Distortions in Post-partum Exacerbation of Schizophrenia.

    PubMed

    Mehta, Urvakhsh Meherwan; Naveen Kumar, C; Venkatasubramanian, Ganesan; Thirthalli, Jagadisha

    2013-11-25

    Background: Sensory distortions of body image commonly occur during migraine, seizures, non-dominant cortical infarcts and hallucinogen abuse.Methods: We report the case of a 30-year-old woman with paranoid schizophrenia, presenting with post-partum onset multimodal sensory distortions in the absence of any neurological disorders or substance use.Results: Her symptoms involved persistent facial/body metamorphopsia (distorted images) and vocal paracousis (distorted voices), in the absence of visual hallucinations, illusions or agnosia. Neuropsychological assessments revealed deficits on visual processing tasks. Neuroimaging, electroencephalography and ophthalmological evaluation revealed no abnormalities. The multimodal sensory distortions responded to anti-psychotic treatment, paralleling improvement in other schizophrenia psychopathology, over a period of one month.Conclusion: Prominent and persistent multimodal sensory distortions like metamorphopsia and paracousis in the presence of psychotic symptoms warrant a detailed neurological and general medical work-up. These symptoms presenting in the absence of neurological or substance use disorders may be a component of schizophrenia. PMID:24275634

  5. Inlet distortion effects in aircraft propulsion system integration

    NASA Technical Reports Server (NTRS)

    Longley, J. P.; Greitzer, E. M.

    1992-01-01

    A tutorial survey of inlet flow distortion effects on engine performance and stability is presented. Inlet distortions in aero engines arise through a variety of causes. They can be essentially steady, due to non-axisymmetric intake duct geometry, or time varying, for example from flow separation off the lip of the inlet during maneuvers or shock-induced separation during supersonic flight. Whatever the cause, the result is generally a decrease in performance and, more importantly, a lessening of the stable flow range of the compressor. The distortions are generally three-dimensional. It is an extremely useful simplification to break them, at least conceptually, into radial and circumferential non-uniformities and approach each separately. Purely radial distortions can be treated by the methods that were developed for designing compressors in nominally axisymmetric inlet flow, and this type of distortion will be only briefly discussed. Circumferential non-uniformities, however, introduce additional fluid dynamic features into the analysis of compressor behavior and often have the larger impact on performance and stability. Thus we concentrate mainly on the effects of steady circumferential inlet flow distortion.

  6. Compensating for pneumatic distortion in pressure sensing devices

    NASA Technical Reports Server (NTRS)

    Whitmore, Stephen A.; Leondes, Cornelius T.

    1990-01-01

    A technique of compensating for pneumatic distortion in pressure sensing devices was developed and verified. This compensation allows conventional pressure sensing technology to obtain improved unsteady pressure measurements. Pressure distortion caused by frictional attenuation and pneumatic resonance within the sensing system makes obtaining unsteady pressure measurements by conventional sensors difficult. Most distortion occurs within the pneumatic tubing which transmits pressure impulses from the aircraft's surface to the measurement transducer. To avoid pneumatic distortion, experiment designers mount the pressure sensor at the surface of the aircraft, (called in-situ mounting). In-situ transducers cannot always fit in the available space and sometimes pneumatic tubing must be run from the aircraft's surface to the pressure transducer. A technique to measure unsteady pressure data using conventional pressure sensing technology was developed. A pneumatic distortion model is reduced to a low-order, state-variable model retaining most of the dynamic characteristics of the full model. The reduced-order model is coupled with results from minimum variance estimation theory to develop an algorithm to compensate for the effects of pneumatic distortion. Both postflight and real-time algorithms are developed and evaluated using simulated and flight data.

  7. Towards standardized assessment of endoscope optical performance: geometric distortion

    NASA Astrophysics Data System (ADS)

    Wang, Quanzeng; Desai, Viraj N.; Ngo, Ying Z.; Cheng, Wei-Chung; Pfefer, Joshua

    2013-12-01

    Technological advances in endoscopes, such as capsule, ultrathin and disposable devices, promise significant improvements in safety, clinical effectiveness and patient acceptance. Unfortunately, the industry lacks test methods for preclinical evaluation of key optical performance characteristics (OPCs) of endoscopic devices that are quantitative, objective and well-validated. As a result, it is difficult for researchers and developers to compare image quality and evaluate equivalence to, or improvement upon, prior technologies. While endoscope OPCs include resolution, field of view, and depth of field, among others, our focus in this paper is geometric image distortion. We reviewed specific test methods for distortion and then developed an objective, quantitative test method based on well-defined experimental and data processing steps to evaluate radial distortion in the full field of view of an endoscopic imaging system. Our measurements and analyses showed that a second-degree polynomial equation could well describe the radial distortion curve of a traditional endoscope. The distortion evaluation method was effective for correcting the image and can be used to explain other widely accepted evaluation methods such as picture height distortion. Development of consensus standards based on promising test methods for image quality assessment, such as the method studied here, will facilitate clinical implementation of innovative endoscopic devices.

  8. Beam-shape distortion caused by transverse wake fields

    SciTech Connect

    Chao, A.W.; Kheifets, S.

    1983-02-01

    As a particle bunch in a storage ring passes through a region with a transverse impedance, it generates a transverse wake electromagnetic field that is proportional to the transverse displacement of the bunch in the region. The field acts back on the bunch, causing various effects (such as instabilities) in the motion of the bunch. We study one such effect in which a transverse impedance causes the beam to be distorted in its shape. Observed at a fixed location in the storage ring, this distortion does not change from turn to turn; rather, the distortion is static in time. To describe the distortion, the bunch is considered to be divided longitudinally into many slices and the centers of change of the slices are connected into a curve. In the absence of transverse impedance, this curve is a straight line parallel to the direction of motion of the bunch. Perturbed by the transverse wake field, the curve becomes distorted. What we find in this paper is the shape of such a curve. The results obtained are applied to the PEP storage ring. The impedance is assumed to come solely from the rf cavities. We find that the beam shape is sufficiently distorted and hence that loss of luminosity due to this effect becomes a possibility.

  9. Comparison of methods for quantitative evaluation of endoscopic distortion

    NASA Astrophysics Data System (ADS)

    Wang, Quanzeng; Castro, Kurt; Desai, Viraj N.; Cheng, Wei-Chung; Pfefer, Joshua

    2015-03-01

    Endoscopy is a well-established paradigm in medical imaging, and emerging endoscopic technologies such as high resolution, capsule and disposable endoscopes promise significant improvements in effectiveness, as well as patient safety and acceptance of endoscopy. However, the field lacks practical standardized test methods to evaluate key optical performance characteristics (OPCs), in particular the geometric distortion caused by fisheye lens effects in clinical endoscopic systems. As a result, it has been difficult to evaluate an endoscope's image quality or assess its changes over time. The goal of this work was to identify optimal techniques for objective, quantitative characterization of distortion that are effective and not burdensome. Specifically, distortion measurements from a commercially available distortion evaluation/correction software package were compared with a custom algorithm based on a local magnification (ML) approach. Measurements were performed using a clinical gastroscope to image square grid targets. Recorded images were analyzed with the ML approach and the commercial software where the results were used to obtain corrected images. Corrected images based on the ML approach and the software were compared. The study showed that the ML method could assess distortion patterns more accurately than the commercial software. Overall, the development of standardized test methods for characterizing distortion and other OPCs will facilitate development, clinical translation, manufacturing quality and assurance of performance during clinical use of endoscopic technologies.

  10. Effects of Distortion on Mass Flow Plug Calibration

    NASA Technical Reports Server (NTRS)

    Sasson, Jonathan; Davis, David O.; Barnhart, Paul J.

    2015-01-01

    A numerical, and experimental investigation to study the effects of flow distortion on a Mass Flow Plug (MFP) used to control and measure mass-flow during an inlet test has been conducted. The MFP was first calibrated using the WIND-US flow solver for uniform (undistorted) inflow conditions. These results are shown to compare favorably with an experimental calibration under similar conditions. The effects of distortion were investigated by imposing distorted flow conditions taken from an actual inlet test to the inflow plane of the numerical simulation. The computational fluid dynamic (CFD) based distortion study only showed the general trend in mass flow rate. The study used only total pressure as the upstream boundary condition, which was not enough to define the flow. A better simulation requires knowledge of the turbulence structure and a specific distortion pattern over a range of plug positions. It is recommended that future distortion studies utilize a rake with at least the same amount of pitot tubes as the AIP rake.

  11. Dynamic Distortion Correction for Endoscopy Systems with Exchangeable Optics

    NASA Astrophysics Data System (ADS)

    Stehle, Thomas; Hennes, Michael; Gross, Sebastian; Behrens, Alexander; Wulff, Jonas; Aach, Til

    Endoscopic images are strongly affected by lens distortion caused by the use of wide angle lenses. In case of endoscopy systems with exchangeable optics, e.g. in bladder endoscopy or sinus endoscopy, the camera sensor and the optics do not form a rigid system but they can be shifted and rotated with respect to each other during an examination. This flexibility has a major impact on the location of the distortion centre as it is moved along with the optics. In this paper, we describe an algorithm for the dynamic correction of lens distortion in cystoscopy which is based on a one time calibration. For the compensation, we combine a conventional static method for distortion correction with an algorithm to detect the position and the orientation of the elliptic field of view. This enables us to estimate the position of the distortion centre according to the relative movement of camera and optics. Therewith, a distortion correction for arbitrary rotation angles and shifts becomes possible without performing static calibrations for every possible combination of shifts and angles beforehand.

  12. Remote sensing image compression assessment based on multilevel distortions

    NASA Astrophysics Data System (ADS)

    Jiang, Hongxu; Yang, Kai; Liu, Tingshan; Zhang, Yongfei

    2014-01-01

    The measurement of visual quality is of fundamental importance to remote sensing image compression, especially for image quality assessment and compression algorithm optimization. We exploit the distortion features of optical remote sensing image compression and propose a full-reference image quality metric based on multilevel distortions (MLD), which assesses image quality by calculating distortions of three levels (such as pixel-level, contexture-level, and content-level) between original images and compressed images. Based on this, a multiscale MLD (MMLD) algorithm is designed and it outperforms the other current methods in our testing. In order to validate the performance of our algorithm, a special remote sensing image compression distortion (RICD) database is constructed, involving 250 remote sensing images compressed with different algorithms and various distortions. Experimental results on RICD and Laboratory for Image and Video Engineering databases show that the proposed MMLD algorithm has better consistency with subjective perception values than current state-of-the-art methods in remote sensing image compression assessment, and the objective assessment results can show the distortion features and visual quality of compressed image well. It is suitable to be the evaluation criteria for optical remote sensing image compression.

  13. Factors associated with body image distortion in Korean adolescents

    PubMed Central

    Hyun, Mi-Yeul; Jung, Young-Eun; Kim, Moon-Doo; Kwak, Young-Sook; Hong, Sung-Chul; Bahk, Won-Myong; Yoon, Bo-Hyun; Yoon, Hye Won; Yoo, Bora

    2014-01-01

    Purpose Body image incorporates cognitive and affective components as well as behaviors related to own body perception. This study evaluated the occurrence of body image distortion and its correlates in Korean adolescents. Methods In a school-based cross-sectional survey, a total of 2,117 adolescents were recruited. They filled out self-completing questionnaires on body image distortion, eating attitudes, and behaviors (Eating Attitude Test-26) and related factors. Results Body image distortions were found in 51.8 percent of adolescents. Univariate analyses showed that boys and older adolescents had higher rates of body image distortion. In the multivariate analyses, body image distortion was associated with high risk for eating disorders (odds ratio [OR] =1.69; 95% confidence interval [CI] 1.11–2.58; P=0.015) and being over weight (OR =33.27; 95% CI 15.51–71.35; P<0.001) or obese (OR =9.37; 95% CI 5.06–17.34; P<0.001). Conclusion These results suggest that body image distortion is relatively common in Korean adolescents, which has implications for adolescents at risk of developing eating disorders. PMID:24868156

  14. The distortion tensor of magnetotellurics: a tutorial on some properties

    NASA Astrophysics Data System (ADS)

    Lilley, Frederick E. M.

    2016-05-01

    A 2 × 2 matrix is introduced which relates the electric field at an observing site where geological distortion applies to the regional electric field, which is unaffected by the distortion. For the student of linear algebra this matrix provides a practical example with which to demonstrate the basic and important procedures of eigenvalue analysis and singular value decomposition. The significance of the results can be visualised because the eigenvectors of such a telluric distortion matrix have a clear practical meaning, as do their eigenvalues. A Mohr diagram for the distortion matrix displays when real eigenvectors exist, and tells their magnitudes and directions. The results of singular value decomposition (SVD) also have a clear practical meaning. These results too can be displayed on a Mohr diagram. Whereas real eigenvectors may or may not exist, SVD is always possible. The ratio of the two singular values of the matrix gives a condition number, useful to quantify distortion. Strong distortion causes the matrix to approach the condition known as `singularity'. A closely-related anisotropy number may also be useful, as it tells when a 2 × 2 matrix has a negative determinant by then having a value greater than unity.

  15. Distortion correction for the orthogonally-splitting-imaging pose sensor

    NASA Astrophysics Data System (ADS)

    Yang, Qian; Sun, Chang-ku; Wang, Peng; Li, Wen-qiang; Liu, Xin-tong

    2015-06-01

    The orthogonally-splitting-imaging pose sensor utilizes not only large field of view spherical lenses but also two sets of cylindrical ones to realize the high-speed, high-precision and wide-field pose measurement. Notable distortion, however, results from the wide-field lenses at the same time. Therefore, to obtain the best performance of the camera model, a distortion correction method is proposed in this paper, which combines the advantages of the high-stability of the Least Square fittings based on the orthogonal polynomials and the independence of the distortion correction based on the cross-ratio invariability. In this way, the ill-conditioned fitting matrix as well as the iteration and optimization procedures in solving extrinsic and intrinsic parameters can be avoided. Due to the wide fitness of the cross-ratio invariability and the orthogonal polynomials, this distortion correction technique is also suitable to other optical set up with different imaging structure. The experiment results that the corrected grids have superior precision and reliability with their original slopes demonstrate that the distortion model on the basis of orthogonal polynomial is validated and that the distortion correction is effective.

  16. ACS/WFC Revised Geometric Distortion for DrizzlePac

    NASA Astrophysics Data System (ADS)

    Kozhurina-Platais, V.; Borncamp, D.; Anderson, J.; Grogin, N.; Hack, M.

    2015-06-01

    The goal of the ACS/WFC astrometric calibration for DrizzlePac is to provide a coordinate system free of distortion to a precision level of ˜0.1 pixels (˜ 5mas). The astrometric calibration of ACS/WFC is based on the astrometric standard field in the vicinity of globular cluster 47 Tuc. We used a polynomial model to derive the geometric distortion in the WFC channel relative to the distortion-free coordinates, which now accounts for proper motions of stars in the astrometric field. A new and straightforward representation of time-dependent distortion in the linear terms is now implemented in the IDCTAB reference file and in the STScI software DrizzlePac to obtain simultaneously the ACS/WFC geometric distortion and its time-dependent correction. As a result, the geometric distortion can be corrected down to a precision level of 0.02 pix (1mas), which allows now for improvement of the alignment and registration of the ACS/WFC images with accuracy of ˜0.05 pix (2.5mas) or better.

  17. Signal modeling of turbulence-distorted imagery

    NASA Astrophysics Data System (ADS)

    Young, S. Susan; Driggers, Ronald G.; Krapels, Keith; Espinola, Richard L.; Reynolds, Joseph P.; Cha, Jae

    2009-05-01

    Understanding turbulence effects on wave propagation and imaging systems has been an active research area for more than 50 years. Conventional atmospheric optics methods use statistical models to analyze image degradation effects that are caused by turbulence. In this paper, we intend to understand atmospheric turbulence effects using a deterministic signal processing and imaging theory point of view and modeling. The model simulates the formed imagery by a lens by tracing the optical rays from the target through a band of turbulence. We examine the nature of the turbulence-degraded image, and identify its characteristics as the parameters of the band of turbulence, e.g., its width, angle, and index of refraction, are varied. Image degradation effects due to turbulence, such as image blurring and image dancing, are revealed by this signal modeling. We show that in fact these phenomena can be related not only to phase errors in the frequency domain of the image but also a 2D modulation effect in the image spectrum. Results with simulated and realistic data are provided.

  18. More flexibility in representing geometric distortion in astronomical images

    NASA Astrophysics Data System (ADS)

    Shupe, David L.; Laher, Russ R.; Storrie-Lombardi, Lisa; Surace, Jason; Grillmair, Carl; Levitan, David; Sesar, Branimir

    2012-09-01

    A number of popular software tools in the public domain are used by astronomers, professional and amateur alike, but some of the tools that have similar purposes cannot be easily interchanged, owing to the lack of a common standard. For the case of image distortion, SCAMP and SExtractor, available from Astromatic.net, perform astrometric calibration and source-object extraction on image data, and image-data geometric distortion is computed in celestial coordinates with polynomial coefficients stored in the FITS header with the PV i_j keywords. Another widely-used astrometric-calibration service, Astrometry.net, solves for distortion in pixel coordinates using the SIP convention that was introduced by the Spitzer Science Center. Up until now, due to the complexity of these distortion representations, it was very difficult to use the output of one of these packages as input to the other. New Python software, along with faster-computing C-language translations, have been developed at the Infrared Processing and Analysis Center (IPAC) to convert FITS-image headers from PV to SIP and vice versa. It is now possible to straightforwardly use Astrometry.net for astrometric calibration and then SExtractor for source-object extraction. The new software also enables astrometric calibration by SCAMP followed by image visualization with tools that support SIP distortion, but not PV . The software has been incorporated into the image-processing pipelines of the Palomar Transient Factory (PTF), which generate FITS images with headers containing both distortion representations. The software permits the conversion of archived images, such as from the Spitzer Heritage Archive and NASA/IPAC Infrared Science Archive, from SIP to PV or vice versa. This new capability renders unnecessary any new representation, such as the proposed TPV distortion convention.

  19. Comparing Distortion Product Otoacoustic Emissions to Intracochlear Distortion Products Inferred from a Noninvasive Assay.

    PubMed

    Martin, Glen K; Stagner, Barden B; Dong, Wei; Lonsbury-Martin, Brenda L

    2016-08-01

    The behavior of intracochlear distortion products (iDPs) was inferred by interacting a probe tone (f3) with the iDP of interest to produce a "secondary" distortion product otoacoustic emission termed DPOAE(2ry). Measures of the DPOAE(2ry) were then used to deduce the properties of the iDP. This approach was used in alert rabbits and anesthetized gerbils to compare ear-canal 2f1-f2 and 2f2-f1 DPOAE f2/f1 ratio functions, level/phase (L/P) maps, and interference-response areas (IRAs) to their simultaneously collected DPOAE(2ry) counterparts. These same measures were also collected in a human volunteer to demonstrate similarities with their laboratory animal counterparts and their potential applicability to humans. Results showed that DPOAEs and inferred iDPs evidenced distinct behaviors and properties. That is, DPOAE ratio functions elicited by low-level primaries peaked around an f2/f1 = 1.21 or 1.25, depending on species, while the corresponding inferred iDP ratio functions peaked at f2/f1 ratios of ~1. Additionally, L/P maps showed rapid phase variation with DPOAE frequency (fdp) for the narrow-ratio 2f1-f2 and all 2f2-f1 DPOAEs, while the corresponding DPOAE(2ry) measures evidenced relatively constant phases. Common features of narrow-ratio DPOAE IRAs, such as large enhancements for interference tones (ITs) presented above f2, were not present in DPOAE(2ry) IRAs. Finally, based on prior experiments in gerbils, the behavior of the iDP directly measured in intracochlear pressure was compared to the iDP inferred from the DPOAE(2ry) and found to be similar. Together, these findings are consistent with the notion that under certain conditions, ear-canal DPOAEs provide poor representations of iDPs and thus support a "beamforming" hypothesis. According to this concept, distributed emission components directed toward the ear canal from the f2 and basal to f2 regions can be of differing phases and thus cancel, while these same components directed toward fdp add in

  20. Interaction of Oblique Instability Waves with Weak Streamwise Vortices

    NASA Technical Reports Server (NTRS)

    Goldstein, M. E.; Wundrow, David W.

    1994-01-01

    This paper is concerned with the effect of a weak spanwise-variable mean-flow distortion on the growth of oblique instability waves in a Blasius boundary layer. The streamwise component of the distortion velocity initially grows linearly with increasing streamwise distance, reaches a maximum, and eventually decays through the action of viscosity. This decay occurs slowly and allows the distortion to destabilize the Blasius flow over a relatively large streamwise region. It is shown that even relatively weak distortions can cause certain oblique Rayleigh instability waves to grow much faster than the usual two-dimensional Tollmien-Schlichting waves that would be the dominant instability modes in the absence of the distortion. The oblique instability waves can then become large enough to interact nonlinearly within a common critical layer. It is shown that the resulting nonlinearity is weak and that the common amplitude of the interacting oblique waves is governed by the amplitude evolution equation derived in Goldstein & Choi (1989). The implications of these results for Klebanoff-type transition are discussed.

  1. The Gaussian Shear Wave in a Dispersive Medium

    PubMed Central

    Parker, Kevin J.; Baddour, Natalie

    2014-01-01

    Within the field of “imaging the biomechanical properties of tissues,” a number of approaches analyze shear wave propagation initiated by a short radiation force push. Unfortunately, it is experimentally observed that the displacement vs. time curves in lossy tissues are rapidly damped and distorted in ways that confound any simple tracking approach. This paper addresses the propagation, decay, and distortion of pulses in lossy and dispersive media, in order to derive closed form analytic expressions for the propagating pulses. The theory identifies key terms that drive the distortion and broadening of the pulse. Furthermore, the approach taken is not dependent on any particular viscoelastic model of tissue, but instead takes a general first order approach to dispersion. Examples with a Gaussian beam pattern and realistic dispersion parameters are given along with general guidelines for identifying the features of the distorting wave that are the most compact. PMID:24412170

  2. Recovery of motion parameters from distortions in scanned images

    NASA Technical Reports Server (NTRS)

    Mulligan, Jeffrey B.

    1997-01-01

    Scanned images, such as those produced by the scanning-laser ophthalmoscope (SLO), show distortions when there is target motion. This is because pixels corresponding to different image regions are acquired sequentially, and so, in essence, are slices of different snapshots. While these distortions create problems for image registration algorithms, they are potentially useful for recovering target motion parameters at temporal frequencies above the frame rate. Stetter, Sendtner and Timberlake measured large distortions in SLO images to recover the time course of rapid horizontal saccadic eye movements. Here, this work is extended with the goal of automatically recovering small eye movements in two dimensions. Eye position during the frame interval is modeled using a low dimensional parametric description, which in turn is used to generate predicted distortions of a reference template. The input image is then registered to the distorted template using normalized cross correlation. The motion parameters are then varied, and the correlation recomputed, to find the motion which maximizes the peak value of the correlation. The location and value of the correlation maximum are determined with sub-pixel precision using biquadratic interpolation, yielding eye position resolution better than 1 arc minute. This method of motion parameter estimation is tested using actual SLO images as well as simulated images. Motion parameter estimation might also be applied to individual video lines in order to reduce pipeline delays for a near real-time system.

  3. Real-time lens distortion correction: speed, accuracy and efficiency

    NASA Astrophysics Data System (ADS)

    Bax, Michael R.; Shahidi, Ramin

    2014-11-01

    Optical lens systems suffer from nonlinear geometrical distortion. Optical imaging applications such as image-enhanced endoscopy and image-based bronchoscope tracking require correction of this distortion for accurate localization, tracking, registration, and measurement of image features. Real-time capability is desirable for interactive systems and live video. The use of a texture-mapping graphics accelerator, which is standard hardware on current motherboard chipsets and add-in video graphics cards, to perform distortion correction is proposed. Mesh generation for image tessellation, an error analysis, and performance results are presented. It is shown that distortion correction using commodity graphics hardware is substantially faster than using the main processor and can be performed at video frame rates (faster than 30 frames per second), and that the polar-based method of mesh generation proposed here is more accurate than a conventional grid-based approach. Using graphics hardware to perform distortion correction is not only fast and accurate but also efficient as it frees the main processor for other tasks, which is an important issue in some real-time applications.

  4. Parametric distortion-adaptive neighborhood for omnidirectional camera.

    PubMed

    Tang, Yazhe; Li, Youfu; Luo, Jun

    2015-08-10

    Catadioptric omnidirectional images exhibit serious nonlinear distortion due to the involved quadratic mirror. Conventional pinhole model-based methods perform poorly when directly applied to the deformed omnidirectional images. This study constructs a catadioptric geometry system to analyze the variation of the neighborhood of an object in terms of the elevation and azimuth directions in a spherical coordinate system. To accurately represent the distorted visual information, a parametric neighborhood mapping model is proposed based on the catadioptric geometry. Unlike the conventional catadioptric models, the prior information of the system is effectively integrated into the neighborhood formulation framework. Then the distortion-adaptive neighborhood can be directly calculated based on its measurable image radial distance. This method can significantly improve the computational efficiency of algorithm since statistical neighborhood sampling is not used. On the basis of the proposed neighborhood model, a distortion-invariant Haar wavelet transform is presented to perform the robust human detection and tracking in catadioptric omnidirectional vision. The experimental results verify the effectiveness of the proposed neighborhood mapping model and prove that the distorted neighborhood in the omnidirectional image follows a nonlinear pattern. PMID:26368363

  5. Thermal distortion analysis of the space station solar dynamic concentrator

    NASA Technical Reports Server (NTRS)

    Trudell, Jeffrey J.; Dalsania, Vithal; Baumeister, Joseph F.; Jefferies, Kent S.

    1988-01-01

    A method was developed to evaluate the thermal distortion of the Space Station Solar Dynamic Concentrator and the effects of thermal distortion on concentrator optical performance. The analytical method includes generating temperature distributions with TRASYS and SINDA models, interfacing the SINDA results with the SINDA-NASTRAN Interface Program (SNIP), calculating thermal distortion with a NASTRAN/PATRAN finite element model, and providing flux distribution maps within the receiver with the ray tracing OFFSET program. Temperature distributions, thermally induced slope errors, and flux distribution maps within the receiver are discussed. Results during a typical orbit indicate that temperatures of the hexagonal panels and triangular facets range between -18 and 99 C (-1 to 210 F), facet rotations are less than 0.2 mrad, and a change in facet radius due to thermal flattening is less than 5 percent. The predicted power loss with thermal distortion effects was less than 0.3 percent. The thermal distortion of the Solar Dynamic concentrator has negligible effect on the flux distribution within the receiver cavity.

  6. Simulation on Measurement Method of Geometric Distortion of Telescopes

    NASA Astrophysics Data System (ADS)

    Li, F.; Ren, S. L.

    2015-11-01

    Measuring the geometric distortion is conducive to improve the astrometric accuracy of telescopes, which is meaningful for many disciplines of astronomy, such as stellar clusters, natural satellites, asteroids, comets, and the other celestial bodies in the solar system. For this reason, researchers have developed an iterative self-calibration method to measure the geometric distortion of telescopes by observing a dense star field in the dithering mode, and have achieved many good results. However, the previous work did not constrain the density of star field or the dithering number in the observing mode, but chose relative good conditions to observe, which took up much observing time. In order to explore the validity of self-calibration method, and optimize its observing conditions, it is necessary to carry out the corresponding simulation. Firstly, we introduce the self-calibration method in detail in the present work. By the simulation method, the effectiveness of self-calibration method to give the geometric distortion is proved, and the observing conditions, such as the density of star field and dithering number, are optimized to give the geometric distortion with a high accuracy. Considering the practical application for correcting the geometric distortion, we also analyze the relation between the number of reference stars in the field of view and the astrometric accuracy by virtue of the simulation method.

  7. Distortion and flow of nematics simulated by dissipative particle dynamics.

    PubMed

    Zhao, Tongyang; Wang, Xiaogong

    2014-05-14

    In this study, we simulated distortion and flow of nematics by dissipative particle dynamics (DPD). The nematics were modeled by a binary mixture that contained rigid rods composed of DPD particles as mesogenic units and normal DPD particles as solvent. Elastic distortions were investigated by monitoring director orientation in space under influences of boundary anchoring and external fields. Static distortion demonstrated by the simulation is consistent with the prediction of Frank elastic theory. Spatial distortion profile of the director was examined to obtain static elastic constants. Rotational motions of the director under influence of the external field were simulated to understand the dynamic process. The rules revealed by the simulation are in a good agreement with those obtained from dynamical experiments and classical theories for nematics. Three Miesowicz viscosities were obtained by using external fields to hold the orientation of the rods in shear flows. The simulation showed that the Miesowicz viscosities have the order of ηc > ηa > ηb and the rotational viscosity γ1 is about two orders larger than the Miesowicz viscosity ηb. The DPD simulation correctly reproduced the non-monotonic concentration dependence of viscosity, which is a unique property of lyotropic nematic fluids. By comparing simulation results with classical theories for nematics and experiments, the DPD nematic fluids are proved to be a valid model to investigate the distortion and flow of lyotropic nematics. PMID:24832301

  8. Distortion and flow of nematics simulated by dissipative particle dynamics

    NASA Astrophysics Data System (ADS)

    Zhao, Tongyang; Wang, Xiaogong

    2014-05-01

    In this study, we simulated distortion and flow of nematics by dissipative particle dynamics (DPD). The nematics were modeled by a binary mixture that contained rigid rods composed of DPD particles as mesogenic units and normal DPD particles as solvent. Elastic distortions were investigated by monitoring director orientation in space under influences of boundary anchoring and external fields. Static distortion demonstrated by the simulation is consistent with the prediction of Frank elastic theory. Spatial distortion profile of the director was examined to obtain static elastic constants. Rotational motions of the director under influence of the external field were simulated to understand the dynamic process. The rules revealed by the simulation are in a good agreement with those obtained from dynamical experiments and classical theories for nematics. Three Miesowicz viscosities were obtained by using external fields to hold the orientation of the rods in shear flows. The simulation showed that the Miesowicz viscosities have the order of ηc > ηa > ηb and the rotational viscosity γ1 is about two orders larger than the Miesowicz viscosity ηb. The DPD simulation correctly reproduced the non-monotonic concentration dependence of viscosity, which is a unique property of lyotropic nematic fluids. By comparing simulation results with classical theories for nematics and experiments, the DPD nematic fluids are proved to be a valid model to investigate the distortion and flow of lyotropic nematics.

  9. Thermal distortion analysis of the Space Station solar dynamic concentrator

    NASA Technical Reports Server (NTRS)

    Trudell, Jeffery J.; Jefferies, Kent S.; Baumeister, Joseph F.; Dalsania, Vithal

    1988-01-01

    A method was developed to evaluate the thermal distortion of the Space Station Solar Dynamic Concentrator and the effects of thermal distortion on concentrator optical performance. The analytical method includes generating temperature distributions with TRASYS and SINDA models, interfacing the SINDA results with the SINDA-NASTRAN Interface Program (SNIP), calculating thermal distortion with a NASTRAN/PATRAN finite element model, and providing flux distribution maps within the receiver with the ray tracing OFFSET program. Temperature distributions, thermally induced slope errors, and flux distribution maps within the receiver are discussed. Results during a typical orbit indicate that temperatures of the hexagonal panels and triangular facets range between -18 and 99 C (-1 to 210 F), facet rotations are less than 0.2 mrad, and a change in facet radius due to thermal flattening is less than 5 percent. The predicted power loss with thermal distortion effects was less than 0.3 percent. The thermal distortion of the Solar Dynamic concentrator has negligible effect on the flux distribution within the receiver cavity.

  10. Development, comparison, and evaluation of software for radial distortion elimination

    NASA Astrophysics Data System (ADS)

    Papadaki, A. I.; Georgopoulos, A.

    2015-05-01

    Lately the interest of Computer Vision and Photogrammetry community has been focused on the automation of the processes of identification and elimination of the radial distortion, with the aim to correct the image coordinates and finally to obtain digital images with reliable geometric information. This effort has reached the point of development of commercial or free image processing software, claiming that it can automatically identify and remove the radial distortion from an image. In this paper in depth research has been conducted about the radial distortion and the methods of its identification and elimination. Specifically, it has been attempted to evaluate software as the aforementioned, about its effectiveness, accuracy and applicability on the elimination of the radial distortion from images. For the attainment of the desired aim, four different methods of comparison and evaluation of the performance of the software, with respect to the correction of an image, have been employed. The applied methods are (i) the optical evaluation of the produced digital images, (ii) the subtraction of the images, (iii) the comparison of the curves of the remaining radial distortion in the images and (iv) the comparison of the results from the orientation of an image pair. However, it was really important to have a benchmark for the evaluation, in order to ensure the objectivity and accuracy of the comparison. Therefore, a new reliable algorithm has been developed, which was of known and controllable accuracy. The results of these comparisons are presented and evaluated for their reliability and usefulness.

  11. Distortion definition and correction in off-axis systems

    NASA Astrophysics Data System (ADS)

    Da Deppo, Vania; Simioni, Emanuele; Naletto, Giampiero; Cremonese, Gabriele

    2015-09-01

    Off-axis optical configurations are becoming more and more used in a variety of applications, in particular they are the most preferred solution for cameras devoted to Solar System planets and small bodies (i.e. asteroids and comets) study. Off-axis designs, being devoid of central obstruction, are able to guarantee better PSF and MTF performance, and thus higher contrast imaging capabilities with respect to classical on-axis designs. In particular they are suitable for observing extended targets with intrinsic low contrast features, or scenes where a high dynamical signal range is present. Classical distortion theory is able to well describe the performance of the on-axis systems, but it has to be adapted for the off-axis case. A proper way to deal with off-axis distortion definition is thus needed together with dedicated techniques to accurately measure and hence remove the distortion effects present in the acquired images. In this paper, a review of the distortion definition for off-axis systems will be given. In particular the method adopted by the authors to deal with the distortion related issues (definition, measure, removal) in some off-axis instruments will be described in detail.

  12. Satellite measurement of ionospheric-induced vhf distortion

    SciTech Connect

    Armstrong, W.T.; Murphy, T.; Roussel-Dupre, R.; Carter, M.J.; Blevins, B.

    1992-01-01

    BLACKBEARD is a satellite RF experiment designed to study distortion and interference effects on transient transionospheric VHF signals. RF distortion will be characterized by a frequency-coherence bandwidth for different ionospheric conditions. Limitations of broad-band measurements from the frequency-coherence bandwidth of the ionosphere and broadcast interference signals will be established through these studies. Distinction between multi-path distortion resulting from large scale, coherent perturbations and small scale, random perturbations to the ionosphere will be emphasized. Ionospheric transfer function models, trans-ionospheric signal predictions, and coherence bandwidth predictions will be tested and optimized with these measurements. A global data base for both broadcast and lightning interference will also derive from these studies. This database will form the basis for interference feature extraction, signal typing, and possible neural network cataloging. The specific missions of the BLACKBEARD experiment include: perform broad-band VHF measurements of transient signals originating from a controlled pulsed ground beacon, to characterize broad-band ionospheric distortion, perform narrow-band VHF measurements of cw signals from a multi-chord interferometry ground beacon array, to characterize ionospheric structure contributing to transmission distortion, and survey power envelopes of lightning and man-made interference in selectable VHF bands, for background rejection purposes. BLACKBEARD is part of the ALEMS soft x-ray measurement satellite, a small satellite system designed for a PEGASUS launch into a 70{degrees} inclination, low earth orbit in late 1992.

  13. Satellite measurement of ionospheric-induced vhf distortion

    SciTech Connect

    Armstrong, W.T.; Murphy, T.; Roussel-Dupre, R.; Carter, M.J.; Blevins, B.

    1992-09-01

    BLACKBEARD is a satellite RF experiment designed to study distortion and interference effects on transient transionospheric VHF signals. RF distortion will be characterized by a frequency-coherence bandwidth for different ionospheric conditions. Limitations of broad-band measurements from the frequency-coherence bandwidth of the ionosphere and broadcast interference signals will be established through these studies. Distinction between multi-path distortion resulting from large scale, coherent perturbations and small scale, random perturbations to the ionosphere will be emphasized. Ionospheric transfer function models, trans-ionospheric signal predictions, and coherence bandwidth predictions will be tested and optimized with these measurements. A global data base for both broadcast and lightning interference will also derive from these studies. This database will form the basis for interference feature extraction, signal typing, and possible neural network cataloging. The specific missions of the BLACKBEARD experiment include: perform broad-band VHF measurements of transient signals originating from a controlled pulsed ground beacon, to characterize broad-band ionospheric distortion, perform narrow-band VHF measurements of cw signals from a multi-chord interferometry ground beacon array, to characterize ionospheric structure contributing to transmission distortion, and survey power envelopes of lightning and man-made interference in selectable VHF bands, for background rejection purposes. BLACKBEARD is part of the ALEMS soft x-ray measurement satellite, a small satellite system designed for a PEGASUS launch into a 70{degrees} inclination, low earth orbit in late 1992.

  14. The Far-Infrared Spectrum of Methyl Chloride: Determination and Order of Magnitude of the Sextic Centrifugal Distortion Constants in Symmetrical Tops

    NASA Astrophysics Data System (ADS)

    Demaison, J.; Bocquet, R.; Chen, W. D.; Papousek, D.; Boucher, D.; Burger, H.

    1994-07-01

    The submillimeter-wave spectra of the ground state rotational transitions of CH335Cl and CH337Cl were measured up to 1.9 THz. The far-infrared spectrum of CH335Cl was also measured in the region 35-50 cm-1 using an interferometric spectrometer (Bruker IFS 120 HR). Rotational and centrifugal distortion (up to sixth order) constants were determined for both isotopic species. The accuracy of the sextic centrifugal distortion constants is discussed. It is shown that it is possible to predict the sign and order of magnitude of the sextic constants of a symmetric-top molecule.

  15. Can Personality Type Explain Heterogeneity in Probability Distortions?

    PubMed Central

    Capra, C. Monica; Jiang, Bing; Engelmann, Jan B.; Berns, Gregory S.

    2014-01-01

    There are two regularities we have learned from experimental studies of choice under risk. The first is that the majority of people weigh objective probabilities non-linearly. The second regularity, although less commonly acknowledged, is that there is a large amount of heterogeneity in how people distort probabilities. Despite of this, little effort has been made to identify the source of heterogeneity. In this paper, we explore the possibility that personality type is linked to probability distortions. Using validated psychological questionnaires, we clustered participants into distinct personality types: motivated, impulsive, and affective. We found that the motivated viewed gambling more attractive, whereas the impulsive were the most capable of discriminating non-extreme probabilities. Our results suggest that the observed heterogeneity in probability distortions may be explained by personality profiles, which can be elicited though standard psychological questionnaires. PMID:24639891

  16. Optimized distortion correction technique for echo planar imaging.

    PubMed

    Chen, N K; Wyrwicz, A M

    2001-03-01

    A new phase-shifted EPI pulse sequence is described that encodes EPI phase errors due to all off-resonance factors, including B(o) field inhomogeneity, eddy current effects, and gradient waveform imperfections. Combined with the previously proposed multichannel modulation postprocessing algorithm (Chen and Wyrwicz, MRM 1999;41:1206-1213), the encoded phase error information can be used to effectively remove geometric distortions in subsequent EPI scans. The proposed EPI distortion correction technique has been shown to be effective in removing distortions due to gradient waveform imperfections and phase gradient-induced eddy current effects. In addition, this new method retains advantages of the earlier method, such as simultaneous correction of different off-resonance factors without use of a complicated phase unwrapping procedure. The effectiveness of this technique is illustrated with EPI studies on phantoms and animal subjects. Implementation to different versions of EPI sequences is also described. Magn Reson Med 45:525-528, 2001. PMID:11241714

  17. An Exact Formula for Calculating Inverse Radial Lens Distortions.

    PubMed

    Drap, Pierre; Lefèvre, Julien

    2016-01-01

    This article presents a new approach to calculating the inverse of radial distortions. The method presented here provides a model of reverse radial distortion, currently modeled by a polynomial expression, that proposes another polynomial expression where the new coefficients are a function of the original ones. After describing the state of the art, the proposed method is developed. It is based on a formal calculus involving a power series used to deduce a recursive formula for the new coefficients. We present several implementations of this method and describe the experiments conducted to assess the validity of the new approach. Such an approach, non-iterative, using another polynomial expression, able to be deduced from the first one, can actually be interesting in terms of performance, reuse of existing software, or bridging between different existing software tools that do not consider distortion from the same point of view. PMID:27258288

  18. Pulsar Pair Cascades in a Distorted Magnetic Dipole Field

    NASA Technical Reports Server (NTRS)

    Harding, Alice K.; Muslimov, Alex G.

    2010-01-01

    We investigate the effect of a distorted neutron star dipole magnetic field on pulsar pair cascade multiplicity and pair death lines. Using a simple model for a distorted dipole field that produces an offset polar cap (PC), we derive the accelerating electric field above the PC in space-charge-limited flow. We find that even a modest azimuthally asymmetric distortion can significantly increase the accelerating electric field on one side of the PC and, combined with a smaller field line radius of curvature, leads to larger pair multiplicity. The death line for producing pairs by curvature radiation moves downward in the P-P-dot diagram, allowing high pair multiplicities in a larger percentage of the radio pulsar population. These results could have important implications for the radio pulsar population, high energy pulsed emission, and the pulsar contribution to cosmic ray positrons.

  19. Constitutive modelling of evolving flow anisotropy including distortional hardening

    SciTech Connect

    Pietryga, Michael P.; Vladimirov, Ivaylo N.; Reese, Stefanie

    2011-05-04

    The paper presents a new constitutive model for anisotropic metal plasticity that takes into account the expansion or contraction (isotropic hardening), translation (kinematic hardening) and change of shape (distortional hardening) of the yield surface. The experimentally observed region of high curvature ('nose') on the yield surface in the loading direction and flattened shape in the reverse loading direction are modelled here by means of the concept of directional distortional hardening. The modelling of directional distortional hardening is accomplished by means of an evolving fourth-order tensor. The applicability of the model is illustrated by fitting experimental subsequent yield surfaces at finite plastic deformation. Comparisons with test data for aluminium low and high work hardening alloys display a good agreement between the simulation results and the experimental data.

  20. CMB spectral distortions and energy release in the early universe

    NASA Astrophysics Data System (ADS)

    Tashiro, Hiroyuki

    2014-06-01

    Measuring the spectral deviation of the cosmic microwave background (CMB) from the blackbody spectrum has become a focus of attention as a probe of the thermal history of the Universe. It has been more than 20 years since COBE/FIRAS's measurement, which showed excellent agreement between the CMB spectrum and a perfect blackbody spectrum. Significant developments in the technology since then have allowed us to improve the sensitivity of the absolute spectrum measurement by a factor of {˜ }10^4. Therefore, the physics related to the generation of CMB spectral distortions should now be investigated in greater detail. To probe the physics in the early universe and to open an observational window for new physics, various energy release mechanisms both in and beyond standard cosmology need to be studied. In this paper, we provide a review of the physics of CMB distortions and the energy release that creates CMB distortions in the early universe.

  1. Characterizing imaging distortion for the Intermediate Palomar Transient Factory

    NASA Astrophysics Data System (ADS)

    Shupe, David L.; Laher, Russ; Masci, Frank J.; Surace, Jason A.; Bellm, Eric Christopher; Miller, Adam; Ofek, Eran; Intermediate Palomar Transient Factory Collaboration

    2016-01-01

    The advent of time-domain surveys has put a premium on accurate astrometry determined in near-real-time. The Intermediate Palomar Transient Factory (iPTF) employs astrometric solvers from SCAMP in the Astromatic suite and from Astrometry.net. Distortion is computed by these solvers for each individual image and exposure. We present an analysis of the distortion solutions in iPTF data, and some approaches for improving astrometry for iPTF and the upcoming Zwicky Transient Facility. Additionally, Astrometry.net currently uses the SIP convention to represent distortion in FITS image headers, while the Astromatic suite uses the TPV convention. We describe a conversion between between these two conventions which has now been extended to 7th-order polynomials.

  2. Predictive Rate-Distortion for Infinite-Order Markov Processes

    NASA Astrophysics Data System (ADS)

    Marzen, Sarah E.; Crutchfield, James P.

    2016-06-01

    Predictive rate-distortion analysis suffers from the curse of dimensionality: clustering arbitrarily long pasts to retain information about arbitrarily long futures requires resources that typically grow exponentially with length. The challenge is compounded for infinite-order Markov processes, since conditioning on finite sequences cannot capture all of their past dependencies. Spectral arguments confirm a popular intuition: algorithms that cluster finite-length sequences fail dramatically when the underlying process has long-range temporal correlations and can fail even for processes generated by finite-memory hidden Markov models. We circumvent the curse of dimensionality in rate-distortion analysis of finite- and infinite-order processes by casting predictive rate-distortion objective functions in terms of the forward- and reverse-time causal states of computational mechanics. Examples demonstrate that the resulting algorithms yield substantial improvements.

  3. Cosmic Microwave Background spectral distortions from cosmic string loops

    NASA Astrophysics Data System (ADS)

    Anthonisen, Madeleine; Brandenberger, Robert; Laguë, Alex; Morrison, Ian A.; Xia, Daixi

    2016-02-01

    Cosmic string loops contain cusps which decay by emitting bursts of particles. A significant fraction of the released energy is in the form of photons. These photons are injected non-thermally and can hence cause spectral distortions of the Cosmic Microwave Background (CMB). Under the assumption that cusps are robust against gravitational back-reaction, we compute the fractional energy density released as photons in the redshift interval where such non-thermal photon injection causes CMB spectral distortions. Whereas current constraints on such spectral distortions are not strong enough to constrain the string tension, future missions such as the PIXIE experiment will be able to provide limits which rule out a range of string tensions between G μ ~ 10-15 and G μ ~ 10-12, thus ruling out particle physics models yielding these kind of intermediate-scale cosmic strings.

  4. An Exact Formula for Calculating Inverse Radial Lens Distortions

    PubMed Central

    Drap, Pierre; Lefèvre, Julien

    2016-01-01

    This article presents a new approach to calculating the inverse of radial distortions. The method presented here provides a model of reverse radial distortion, currently modeled by a polynomial expression, that proposes another polynomial expression where the new coefficients are a function of the original ones. After describing the state of the art, the proposed method is developed. It is based on a formal calculus involving a power series used to deduce a recursive formula for the new coefficients. We present several implementations of this method and describe the experiments conducted to assess the validity of the new approach. Such an approach, non-iterative, using another polynomial expression, able to be deduced from the first one, can actually be interesting in terms of performance, reuse of existing software, or bridging between different existing software tools that do not consider distortion from the same point of view. PMID:27258288

  5. Temperature effects in excitonic condensation driven by the lattice distortion

    NASA Astrophysics Data System (ADS)

    Do, Thi-Hong-Hai; Nguyen, Huu-Nha; Nguyen, Thi-Giang; Phan, Van-Nham

    2016-06-01

    The stability of the excitonic condensation at low temperature driven by a coupling of electrons to vibrational degrees of freedom in semimetal two-dimensional electronic system is discussed. In the framework of the unrestricted Hartree-Fock approximation, we derive a set of equations to determine both the excitonic condensate order parameter and lattice displacement self-consistently. By lowering temperature we find out a semimetal-insulator transition in the system if the coupling is large enough. The insulating state typifies an excitonic condensation accompanied by a finite lattice distortion. Increasing temperature, both excitonic condensate order parameter and the lattice distortion decrease and then disappear in the same manner. Microscopic analysis in momentum space strongly specifies that the excitonic condensate driven by the lattice distortion favours the BCS type.

  6. Predictive Rate-Distortion for Infinite-Order Markov Processes

    NASA Astrophysics Data System (ADS)

    Marzen, Sarah E.; Crutchfield, James P.

    2016-05-01

    Predictive rate-distortion analysis suffers from the curse of dimensionality: clustering arbitrarily long pasts to retain information about arbitrarily long futures requires resources that typically grow exponentially with length. The challenge is compounded for infinite-order Markov processes, since conditioning on finite sequences cannot capture all of their past dependencies. Spectral arguments confirm a popular intuition: algorithms that cluster finite-length sequences fail dramatically when the underlying process has long-range temporal correlations and can fail even for processes generated by finite-memory hidden Markov models. We circumvent the curse of dimensionality in rate-distortion analysis of finite- and infinite-order processes by casting predictive rate-distortion objective functions in terms of the forward- and reverse-time causal states of computational mechanics. Examples demonstrate that the resulting algorithms yield substantial improvements.

  7. Quantitative determination of bond order and lattice distortions in nickel oxide heterostructures by resonant x-ray scattering

    NASA Astrophysics Data System (ADS)

    Lu, Y.; Frano, A.; Bluschke, M.; Hepting, M.; Macke, S.; Strempfer, J.; Wochner, P.; Cristiani, G.; Logvenov, G.; Habermeier, H.-U.; Haverkort, M. W.; Keimer, B.; Benckiser, E.

    2016-04-01

    We present a combined study of Ni K -edge resonant x-ray scattering and density functional calculations to probe and distinguish electronically driven ordering and lattice distortions in nickelate heterostructures. We demonstrate that due to the low crystal symmetry, contributions from structural distortions can contribute significantly to the energy-dependent Bragg peak intensities of a bond-ordered NdNiO3 reference film. For a LaNiO3-LaAlO3 superlattice that exhibits magnetic order, we establish a rigorous upper bound on the bond-order parameter. We thus conclusively confirm predictions of a dominant spin density wave order parameter in metallic nickelates with a quasi-two-dimensional electronic structure.

  8. Intrinsic nonlinearity probed by intermodulation distortion microwave measurements on high quality MgB2 thin films

    NASA Astrophysics Data System (ADS)

    Cifariello, G.; Aurino, M.; Di Gennaro, E.; Lamura, G.; Andreone, A.; Orgiani, P.; Xi, X. X.; Villégier, J.-C.

    2006-04-01

    The two-tone intermodulation distortion arising in MgB2 thin films synthesized by hybrid physical-chemical vapor deposition is studied in order to probe the influence of the two bands on the nonlinear response of this superconductor. The measurements are carried out by using a dielectrically loaded copper cavity operating at 7GHz. Microwave data on samples having critical temperatures above 41K, very low resistivity values, and residual resistivity ratio larger than 10 are shown. The dependence of the nonlinear surface losses and of the third order intermodulation products on the power feeding the cavity and on the temperature is analyzed. At low power, the signal arising from distortion versus temperature shows the intrinsic s-wave behavior expected for this compound. Data are compared with measurements performed on Nb and YBa2Cu3O7-δ thin films using the same technique.

  9. Bounds on least-squares four-parameter sine-fit errors due to harmonic distortion and noise

    SciTech Connect

    Deyst, J.P.; Souders, T.M.; Solomon, O.M.

    1994-03-01

    Least-squares sine-fit algorithms are used extensively in signal processing applications. The parameter estimates produced by such algorithms are subject to both random and systematic errors when the record of input samples consists of a fundamental sine wave corrupted by harmonic distortion or noise. The errors occur because, in general, such sine-fits will incorporate a portion of the harmonic distortion or noise into their estimate of the fundamental. Bounds are developed for these errors for least-squares four-parameter (amplitude, frequency, phase, and offset) sine-fit algorithms. The errors are functions of the number of periods in the record, the number of samples in the record, the harmonic order, and fundamental and harmonic amplitudes and phases. The bounds do not apply to cases in which harmonic components become aliased.

  10. Anisotropic extinction distortion of the galaxy correlation function

    NASA Astrophysics Data System (ADS)

    Fang, Wenjuan; Hui, Lam; Ménard, Brice; May, Morgan; Scranton, Ryan

    2011-09-01

    Similar to the magnification of the galaxies’ fluxes by gravitational lensing, the extinction of the fluxes by comic dust, whose existence is recently detected by [B. Ménard, R. Scranton, M. Fukugita, and G. Richards, Mon. Not. R. Astron. Soc.MNRAA40035-8711 405, 1025 (2010)DOI: 10.1111/j.1365-2966.2010.16486.x.], also modifies the distribution of a flux-selected galaxy sample. We study the anisotropic distortion by dust extinction to the 3D galaxy correlation function, including magnification bias and redshift distortion at the same time. We find the extinction distortion is most significant along the line of sight and at large separations, similar to that by magnification bias. The correction from dust extinction is negative except at sufficiently large transverse separations, which is almost always opposite to that from magnification bias (we consider a number count slope s>0.4). Hence, the distortions from these two effects tend to reduce each other. At low z (≲1), the distortion by extinction is stronger than that by magnification bias, but at high z, the reverse holds. We also study how dust extinction affects probes in real space of the baryon acoustic oscillations (BAO) and the linear redshift distortion parameter β. We find its effect on BAO is negligible. However, it introduces a positive scale-dependent correction to β that can be as large as a few percent. At the same time, we also find a negative scale-dependent correction from magnification bias, which is up to percent level at low z, but to ˜40% at high z. These corrections are non-negligible for precision cosmology, and should be considered when testing General Relativity through the scale-dependence of β.

  11. Nonlinear interactions that could explain distortion product interference response areas.

    PubMed

    Fahey, P F; Stagner, B B; Lonsbury-Martin, B L; Martin, G K

    2000-10-01

    Suppression and/or enhancement of third- and fifth-order distortion products by a third tone that can have a frequency more than an octave above and a level more than 40 dB below the primary tones have recently been measured by Martin et al. [Hear. Res. 136, 105-123 (1999)]. Contours of iso-suppression and iso-enhancement that are plotted as a function of third-tone frequency and level are called interference response areas. After ruling out order aliasing, two possible mechanisms for this effect have been developed, a harmonic mechanism and a catalyst mechanism. The harmonic mechanism produces distortion products by mixing a harmonic of one of the primary tones with the other primary tone. The catalyst mechanism produces distortion products by mixing one or more intermediate distortion products that are produced by the third tone with one or more of the input tones. The harmonic mechanism does not need a third tone and the catalyst mechanism does. Because the basilar membrane frequency response is predicted to affect each of these mechanisms differently, it is concluded that the catalyst mechanism will be dominant in the high-frequency regions of the cochlea and the harmonic mechanism will have significant strength in the low-frequency regions of the cochlea. The mechanisms are dependent on the existence of both even- and odd-order distortion, and significant even- and odd-order distortion have been measured in the experimental animals. Furthermore, the nonlinear part of the cochlear mechanical response must be well into saturation when input tones are 50 or more dB SPL. PMID:11051505

  12. Critical Assessment of Correction Methods for Fisheye Lens Distortion

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Tian, C.; Huang, Y.

    2016-06-01

    A fisheye lens is widely used to create a wide panoramic or hemispherical image. It is an ultra wide-angle lens that produces strong visual distortion. The distortion modeling and estimation of the fisheye lens are the crucial step for fisheye lens calibration and image rectification in computer vision and close-range photography. There are two kinds of distortion: radial and tangential distortion. Radial distortion is large for fisheye imaging and critical for the subsequent image processing. Although many researchers have developed calibration algorithms of radial distortion of fisheye lens, quantitative evaluation of the correction performance has remained a challenge. This is the first paper that intuitively and objectively evaluates the performance of five different calibration algorithms. Upto- date research on fisheye lens calibration is comprehensively reviewed to identify the research need. To differentiate their performance in terms of precision and ease-using, five methods are then tested using a diverse set of actual images of the checkerboard that are taken at Wuhan University, China under varying lighting conditions, shadows, and shooting angles. The method of rational function model, which was generally used for wide-angle lens correction, outperforms the other methods. However, the one parameter division model is easy for practical use without compromising too much the precision. The reason is that it depends on the linear structure in the image and requires no preceding calibration. It is a tradeoff between correction precision and ease-using. By critically assessing the strengths and limitations of the existing algorithms, the paper provides valuable insight and guideline for future practice and algorithm development that are important for fisheye lens calibration. It is promising for the optimal design of lens correction models that are suitable for the millions of portable imaging devices.

  13. Heme Distortions in Sperm-Whale Carbonmonoxy Myoglobin: Correlations between Rotational Strengths and Heme Distortions in MD-Generated Structures

    SciTech Connect

    KIEFL,CHRISTOPH; SCREERAMA,NARASIMHA; LU,YI; QIU,YAN; SHELNUTT,JOHN A.; WOODY,ROBERT W.

    2000-07-13

    The authors have investigated the effects of heme rotational isomerism in sperm-whale carbonmonoxy myoglobin using computational techniques. Several molecular dynamics simulations have been performed for the two rotational isomers A and B, which are related by a 180{degree} rotation around the {alpha}-{gamma} axis of the heme, of sperm-whale carbonmonoxy myoglobin in water. Both neutron diffraction and NMR structures were used as starting structures. In the absence of an experimental structure, the structure of isomer B was generated by rotating the heme in the structure of isomer A. Distortions of the heme from planarity were characterized by normal coordinate structural decomposition and by the angle of twist of the pyrrole rings from the heme plane. The heme distortions of the neutron diffraction structure were conserved in the MD trajectories, but in the NMR-based trajectories, where the heme distortions are less well defined, they differ from the original heme deformations. The protein matrix induced similar distortions on the heroes in orientations A and B. The results suggest that the binding site prefers a particular macrocycle conformation, and a 180{degree} rotation of the heme does not significantly alter the protein's preference for this conformation. The intrinsic rotational strengths of the two Soret transitions, separated according to their polarization in the heme plane, show strong correlations with the ruf-deformation and the average twist angle of the pyrrole rings. The total rotational strength, which includes contributions from the chromophores in the protein, shows a weaker correlation with heme distortions.

  14. Distortion-rotor interaction noise produced by a drooped inlet

    NASA Technical Reports Server (NTRS)

    Smith, E. B.; Moore, M. T.; Gliebe, P. R.

    1980-01-01

    The 'drooped' inlet used on most wing mounted engines produces a wall static pressure distortion at the fan face of about plus or minus 2%. The interaction of the fan rotor with this fixed distortion pattern produces blade passing frequency and harmonic tone levels in flight which contribute to forward radiated engine noise spectra. Data from a wind tunnel test, using both a drooped inlet and an inlet with no droop, show large changes in forward radiated noise levels over a limited fan speed range. An analytical model of this fan noise mechanism is developed and is used to account for the major features of the measured results.

  15. Distortion of Crabbed Bunch Due to the Electron Cloud

    SciTech Connect

    Wang, L; Raubenheimer, T.; /SLAC

    2008-05-28

    In order to improve the luminosity, two crab cavities have been installed in KEKB HER and LER [1]. Since there is only one crab cavity in each ring, the crab cavity generates a horizontally titled bunch along the whole ring. The achieved specific luminosity with crabbed bunch is higher, but it is not as high as that from beam-beam simulation [2]. One of the suspicions is the electron cloud. The electron cloud in LER (positron beam) may distort the crabbed bunch and cause the luminosity drop. This note briefly estimates the bunch shape distortion due to the electron cloud in KEKB LER.

  16. Low thermal distortion Extreme-UV lithography reticle and method

    DOEpatents

    Gianoulakis, Steven E.; Ray-Chaudhuri, Avijit K.

    2002-01-01

    Thermal distortion of reticles or masks can be significantly reduced by emissivity engineering, i.e., the selective placement or omission of coatings on the reticle. Reflective reticles so fabricated exhibit enhanced heat transfer thereby reducing the level of thermal distortion and ultimately improving the quality of the transcription of the reticle pattern onto the wafer. Reflective reticles include a substrate having an active region that defines the mask pattern and non-active region(s) that are characterized by a surface that has a higher emissivity than that of the active region. The non-active regions are not coated with the radiation reflective material.

  17. Low thermal distortion extreme-UV lithography reticle

    DOEpatents

    Gianoulakis, Steven E.; Ray-Chaudhuri, Avijit K.

    2001-01-01

    Thermal distortion of reticles or masks can be significantly reduced by emissivity engineering, i.e., the selective placement or omission of coatings on the reticle. Reflective reticles so fabricated exhibit enhanced heat transfer thereby reducing the level of thermal distortion and ultimately improving the quality of the transcription of the reticle pattern onto the wafer. Reflective reticles include a substrate having an active region that defines the mask pattern and non-active region(s) that are characterized by a surface that has a higher emissivity than that of the active region. The non-active regions are not coated with the radiation reflective material.

  18. Low thermal distortion extreme-UV lithography reticle

    DOEpatents

    Gianoulakis, Steven E.; Ray-Chaudhuri, Avijit K.

    2002-01-01

    Thermal distortion of reticles or masks can be significantly reduced by emissivity engineering, i.e., the selective placement or omission of coatings on the reticle. Reflective reticles so fabricated exhibit enhanced heat transfer thereby reducing the level of thermal distortion and ultimately improving the quality of the transcription of the reticle pattern onto the wafer. Reflective reticles include a substrate having an active region that defines the mask pattern and non-active region(s) that are characterized by a surface that has a higher emissivity than that of the active region. The non-active regions are not coated with the radiation reflective material.

  19. Compensation of relector antenna surface distortion using an array feed

    NASA Technical Reports Server (NTRS)

    Cherrette, A. R.; Acosta, R. J.; Lam, P. T.; Lee, S. W.

    1988-01-01

    The dimensional stability of the surface of a large reflector antenna is important when high gain or low sidelobe performance is desired. If the surface is distorted due to thermal or structural reasons, antenna performance can be improved through the use of an array feed. The design of the array feed and its relation to the surface distortion are examined. The sensitivity of antenna performance to changing surface parameters for fixed feed array geometries is also studied. This allows determination of the limits of usefulness for feed array compensation.

  20. Estimation of lens distortion correction from single images

    NASA Astrophysics Data System (ADS)

    Goljan, Miroslav; Fridrich, Jessica

    2014-02-01

    In this paper, we propose a method for estimation of camera lens distortion correction from a single image. Without relying on image EXIF, the method estimates the parameters of the correction by searching for a maximum energy of the so-called linear pattern introduced into the image during image acquisition prior to lens distortion correction. Potential applications of this technology include camera identification using sensor fingerprint, narrowing down the camera model, estimating the distance between the photographer and the subject, forgery detection, and improving the reliability of image steganalysis (detection of hidden data).

  1. Compensation of reflector antenna surface distortion using an array feed

    NASA Technical Reports Server (NTRS)

    Cherrette, Alan R.; Acosta, Roberto J.; Lam, Peter T.; Lee, Shung-Wu

    1989-01-01

    The dimensional stability of the surface of a large reflector antenna is important when high gain or low sidelobe performance is desired. If the surface is distorted due to thermal or structural reasons, antenna performance can be improved through the use of an array feed. The design of the array feed and its relation to the surface distortion are examined. The sensitivity of antenna performance to changing surface parameters for fixed feed array geometries is also studied. This allows determination of the limits of usefulness for feed array compensation.

  2. Assessment and treatment of distorted schemas in sexual offenders.

    PubMed

    Beech, Anthony R; Bartels, Ross M; Dixon, Louise

    2013-01-01

    The aim of this review is to examine the literature related to the assessment and treatment of sex offenders' distorted schemas. Where appropriate, the review draws upon current insights from the field of social cognition to aid in the critical evaluation of the findings. First, the review considers the various different methodologies for assessing distorted schemas, discussing their strengths and limitations. Second, the review examines the work related to the treatment of sex offenders' schemas. Suggestions for future research, and the implications for clinical practice, are highlighted in the article. PMID:23179272

  3. Distortion-rotor interaction noise produced by a drooped inlet

    NASA Astrophysics Data System (ADS)

    Smith, E. B.; Moore, M. T.; Gliebe, P. R.

    1980-06-01

    The 'drooped' inlet used on most wing mounted engines produces a wall static pressure distortion at the fan face of about plus or minus 2%. The interaction of the fan rotor with this fixed distortion pattern produces blade passing frequency and harmonic tone levels in flight which contribute to forward radiated engine noise spectra. Data from a wind tunnel test, using both a drooped inlet and an inlet with no droop, show large changes in forward radiated noise levels over a limited fan speed range. An analytical model of this fan noise mechanism is developed and is used to account for the major features of the measured results.

  4. Isolated rotor noise due to inlet distortion or turbulence

    NASA Technical Reports Server (NTRS)

    Mani, R.

    1974-01-01

    Theoretical formulation, analysis, and results are presented that are necessary to analyze quadrupole noise generated from a loaded, subsonic rotor because of its interaction with an inflow distortion or inlet turbulence. The ratio of quadrupole to dipole noise is largely a function of the axial Mach number, wheel tip Mach number, rotor solidity, and total pressure ratio across the rotor. It is relatively independent of the specific form of the inflow distortion or inlet turbulence. Comparisons with experimental data only succeed in predicting gross levels at a given speed and fail to predict the variation of noise at fixed speed with flow and pressure ratio. Likely sources of this discrepancy are discussed.

  5. Integrated control of thermally distorted large space antennas

    NASA Technical Reports Server (NTRS)

    Tolson, Robert H.; Huang, Jen-Kuang

    1991-01-01

    The objective is to develop a control system design method that (1) recognizes the time dependence of the thermal distortion due to orbital motion and (2) controls variables that are directly related to far field performance for earth pointing space antennas. The first objective is accomplished by expanding the distortion into principal components that are orthogonal in space and time. The approach for the second objective is to expand the far zone electric field in a Zernike-Bessel series. The method accommodates tapered feeds and arbitrary polarizations. Simulations are performed for a geosynchronous radiometer to determine the effectiveness of the control system under variations in solar geometry, structure materials and thermal properties.

  6. Otoacoustic emission through waves on Reissner's membrane

    NASA Astrophysics Data System (ADS)

    Reichenbach, Tobias; Stefanovic, Aleksandra; Nin, Fumiaki; Hudspeth, A. J.

    2015-12-01

    Otoacoustic emissions are a striking manifestation of mechanical activity within the cochlea. Recent experimental work has stirred a controversy concerning how these mechanical signals propagate outward to the middle ear, from which they are emitted as airborne sounds. Here we show that Reissner's membrane, an elastic structure inside the inner ear, can sustain wave propagation and can therefore transmit otoacoustic emissions from inside the cochlea to the middle ear. We first develop a theoretical description for wave propagation on the parallel basilar and Reissner's membranes. We then describe experimental measurement of the predicted Reissner's membrane wave and its role in distortion-product otoacoustic emissions.

  7. Wave propagation analysis using the variance matrix.

    PubMed

    Sharma, Richa; Ivan, J Solomon; Narayanamurthy, C S

    2014-10-01

    The propagation of a coherent laser wave-field through a pseudo-random phase plate is studied using the variance matrix estimated from Shack-Hartmann wavefront sensor data. The uncertainty principle is used as a tool in discriminating the data obtained from the Shack-Hartmann wavefront sensor. Quantities of physical interest such as the twist parameter, and the symplectic eigenvalues, are estimated from the wavefront sensor measurements. A distance measure between two variance matrices is introduced and used to estimate the spatial asymmetry of a wave-field in the experiment. The estimated quantities are then used to compare a distorted wave-field with its undistorted counterpart. PMID:25401243

  8. Effect of visual distortion on postural balance in a full immersion stereoscopic environment

    NASA Astrophysics Data System (ADS)

    Faubert, Jocelyn; Allard, Remy

    2004-05-01

    This study attempted to determine the influence of non-linear visual movements on our capacity to maintain postural control. An 8x8x8 foot CAVE immersive virtual environment was used. Body sway recordings were obtained for both head and lower back (lumbar 2-3) positions. The subjects were presented with visual stimuli for periods of 62.5 seconds. Subjects were asked to stand still on one foot while viewing stimuli consisting of multiplied sine waves generating movement undulation of a textured surface (waves moving in checkerboard pattern). Three wave amplitudes were tested: 4 feet, 2 feet, and 1 foot. Two viewing conditions were also used; observers looking at 36 inches in front of their feet; observers looking at a distance near the horizon. The results were compiled using an instability index and the data showed a profound and consistent effect of visual disturbances on postural balance in particular for the x (side-to-side) movement. We have demonstrated that non-linear visual distortions similar to those generated by progressive ophthalmic lenses of the kind used for presbyopia corrections, can generate significant postural instability. This instability is particularly evident for the side-to-side body movement and is most evident for the near viewing condition.

  9. Rapid computation of the amplitude and phase of tightly focused optical fields distorted by scattering particles.

    PubMed

    Ranasinghesagara, Janaka C; Hayakawa, Carole K; Davis, Mitchell A; Dunn, Andrew K; Potma, Eric O; Venugopalan, Vasan

    2014-07-01

    We develop an efficient method for accurately calculating the electric field of tightly focused laser beams in the presence of specific configurations of microscopic scatterers. This Huygens-Fresnel wave-based electric field superposition (HF-WEFS) method computes the amplitude and phase of the scattered electric field in excellent agreement with finite difference time-domain (FDTD) solutions of Maxwell's equations. Our HF-WEFS implementation is 2-4 orders of magnitude faster than the FDTD method and enables systematic investigations of the effects of scatterer size and configuration on the focal field. We demonstrate the power of the new HF-WEFS approach by mapping several metrics of focal field distortion as a function of scatterer position. This analysis shows that the maximum focal field distortion occurs for single scatterers placed below the focal plane with an offset from the optical axis. The HF-WEFS method represents an important first step toward the development of a computational model of laser-scanning microscopy of thick cellular/tissue specimens. PMID:25121440

  10. Rapid computation of the amplitude and phase of tightly focused optical fields distorted by scattering particles

    PubMed Central

    Ranasinghesagara, Janaka C.; Hayakawa, Carole K.; Davis, Mitchell A.; Dunn, Andrew K.; Potma, Eric O.; Venugopalan, Vasan

    2014-01-01

    We develop an efficient method for accurately calculating the electric field of tightly focused laser beams in the presence of specific configurations of microscopic scatterers. This Huygens–Fresnel wave-based electric field superposition (HF-WEFS) method computes the amplitude and phase of the scattered electric field in excellent agreement with finite difference time-domain (FDTD) solutions of Maxwell’s equations. Our HF-WEFS implementation is 2–4 orders of magnitude faster than the FDTD method and enables systematic investigations of the effects of scatterer size and configuration on the focal field. We demonstrate the power of the new HF-WEFS approach by mapping several metrics of focal field distortion as a function of scatterer position. This analysis shows that the maximum focal field distortion occurs for single scatterers placed below the focal plane with an offset from the optical axis. The HF-WEFS method represents an important first step toward the development of a computational model of laser-scanning microscopy of thick cellular/tissue specimens. PMID:25121440

  11. Distortion and Residual Stress Control in Integrally Stiffened Structure Produced by Direct Metal Deposition

    NASA Technical Reports Server (NTRS)

    Lin, Shih-Yung; Hoffman, Eric K.; Domack, Marcia S.

    2007-01-01

    2-D thermo-mechanical model developed to characterize distortion and residual stresses in integral structure produced by DMD. Demonstrated as a tool to guide experimental development of DMD fabrication process for aero structures. Distortion and residual stresses are local to deposit. Most distortion develops during deposition of the first few layers; Little change in distortion or residual stresses after fifth deposit layer Most of distortion is localized just beneath the build. Thicker build plates and the use of build lands results in greatest decrease in levels of distortion. Pre-straining shown to reduce distortion. Difficult to implement, particularly for complex stiffener arrays. Clamp position has complex effect on distortion and stresses. Overall distortion reduced with decreasing clamp clearance. Larger clamp clearances induce bending. Use of pre-heat and active cooling show minor influence on panel distortion. Generate changes in thermal gradients in the build plate.

  12. Broad baseband nonlinear distortion mitigation using digital pre- and post-distortion in OFDM-based WDM LR-PON.

    PubMed

    Carvalho, Filipe; Cartaxo, Adolfo

    2015-03-23

    We propose a new technique for mitigation of nonlinear distortion of broadband signals due to electrical/optical conversions and fibre transmission. This technique uses memory polynomials on signals on their original format. The performance improvement is assessed experimentally for an orthogonal frequency division multiplexing signal, with 750 MHz of bandwidth (centred at 1.5 GHz) and carrying 1.25 Gbps, transmitted along a wavelength division multiplexing long-reach passive optical network. It is shown that, in back-to-back, an error vector magnitude improvement of 4.1 dB and 11.8 dB can be achieved with digital pre-distortion and digital post-distortion, respectively. With 125 km of single-mode fibre transmission, these improvements are reduced to about 1 dB and 3 dB, respectively. PMID:25837051

  13. Enhanced Modified Bark Spectral Distortion (EMBSD): An objective speech quality measure based on audible distortion and cognition model

    NASA Astrophysics Data System (ADS)

    Yang, Wonho

    The Speech Processing Lab at Temple University developed an objective speech quality measure called the Modified Bark Spectral Distortion (MBSD). The MBSD uses auditory perception models derived from psychoacoustic studies. The MBSD measure extends the Bark Spectral Distortion (BSD) method by incorporating noise making threshold to differentiate audible/inaudible distortions. The performance of the MBSD was comparable to that of the ITU-T Recommendation P.861 for various coding distortions. Based on the experiments with Time Division Multiple Access (TDMA) data that contains distortions encountered in real network applications, modifications have been made to the MBSD algorithm. These are: use of the first 15 loudness components, normalization of loudness vectors, deletion of the spreading function in the noise masking threshold calculation, and use of a new cognition model based on postmasking effects. The Enhanced MBSD (EMBSD) shows significant improvement over the MBSD for TDMA data. Also, the performance of the EMBSD is better than that of the ITU-T Recommendation P.861 and Measuring Normalizing Blocks (MNB) measures for TDMA data. The performance of the EMBSD was compared to various other objective speech quality measures with the speech data including a wide range of distortion conditions. The EMBSD showed clear improvement over the MBSD and had the correlation coefficient of 0.89 for the conditions of MNRUs, codecs, tandem cases, bit errors, and frame erasures. Mean Opinion Score (MOS) has been used to evaluate objective speech quality measures. Recognizing the procedural difference between the MOS test and current objective speech quality measures, it is proposed that current objective speech quality measures should be evaluated with Degradation Mean Opinion Score (DMOS). The Pearson product-moment correlation coefficient has been the main performance parameter for evaluation of objective speech quality measures. The Standard Error of the Estimates (SEE

  14. Multichannel nonlinear distortion compensation using optical phase conjugation in a silicon nanowire.

    PubMed

    Vukovic, Dragana; Schröder, Jochen; Da Ros, Francesco; Du, Liang Bangyuan; Chae, Chang Joon; Choi, Duk-Yong; Pelusi, Mark D; Peucheret, Christophe

    2015-02-01

    We experimentally demonstrate compensation of nonlinear distortion caused by the Kerr effect in a 3 × 32-Gbaud quadrature phase-shift keying (QPSK) wavelength-division multiplexing (WDM) transmission system. We use optical phase conjugation (OPC) produced by four-wave mixing (FWM) in a 7-mm long silicon nanowire. A clear improvement in Q-factor is shown after 800-km transmission with high span input power when comparing the system with and without the optical phase conjugation module. The influence of OSNR degradation introduced by the silicon nanowire is analysed by comparing transmission systems of three different lengths. This is the first demonstration of nonlinear compensation using a silicon nanowire. PMID:25836216

  15. Intermodulation distortion measurements of MgB2 thin films grown by HPCVD

    NASA Astrophysics Data System (ADS)

    Cifariello, G.; Aurino, M.; di Gennaro, E.; Lamura, G.; Orgiani, P.; Villegier, J.-C.; Xi, X. X.; Andreone, A.

    2006-06-01

    The two tone intermodulation distortion (IMD) arising in MgB2 thin films synthesized by hybrid physical-chemical vapour deposition (HPCVD) is studied in order to probe the influence of the two bands on the symmetry of the gap function. The measurements are carried out by using a dielectrically loaded copper cavity operating at 7 GHz. Microwave data on samples having critical temperatures above 41 K, very low resistivity values, and residual resistivity ratio larger than 10, are shown. The dependence of the nonlinear surface losses and of the third order intermodulation products on the power feeding the cavity and on the temperature is analyzed. At low power, IMD versus temperature data show the intrinsic s-wave behaviour expected for this compound

  16. Magnetic soft modes in the distorted triangular antiferromagnet -CaCr2O4

    SciTech Connect

    Toth, Sandor; Lake, Bella; Hradil, Klaudia; Rule, K; Stone, Matthew B; Islam, A. T. M. N.

    2012-01-01

    -CaCr2O4 is a spin-3/2, distorted triangular lattice antiferromagnet with a simple 120 spin structure that masks the complex pattern of exchange interactions. The magnetic excitation spectrum has been measured using inelastic neutron scattering on powder and single crystal samples. It reveals unusual low energy modes which can be explained by linear spin-wave theory assuming nearest and next-nearest neighbor interactions. The mode softening is due to the next-nearest neighbor interactions and indicates a new magnetic phase nearby as revealed by the phase diagram constructed for this system. The extracted direct exchange interactions correlate well with the Cr3+{Cr3+ distances and are in agreement with other chromium oxide delafossite compounds.

  17. Spectral distortions and anisotropies of the Cosmic Microwave Background

    NASA Astrophysics Data System (ADS)

    De Zotti, Gianfranco; Negrello, Mattia

    2015-12-01

    This contribution presents a synthetic review of the theory and the observations on spectral distortions and on anisotropies of the Cosmic Microwave Background (CMB). For a better understanding of the content of these lectures, it is useful to refer also to the figures contained in the slides available on the School's website.

  18. Distorting the metric fabric of the cognitive map.

    PubMed

    Jeffery, Kate J

    2015-06-01

    Grid cells are neurons whose regularly spaced firing fields form apparently symmetric arrays, or grids, that are thought to collectively provide an environment-independent metric framework for the brain's cognitive map of space. However, two recent studies show that grids are naturally distorted, revealing greater local environment-specific effects than previously recognized. PMID:25882915

  19. Analysis of tractable distortion metrics for EEG compression applications.

    PubMed

    Bazán-Prieto, Carlos; Blanco-Velasco, Manuel; Cárdenas-Barrera, Julián; Cruz-Roldán, Fernando

    2012-07-01

    Coding distortion in lossy electroencephalographic (EEG) signal compression methods is evaluated through tractable objective criteria. The percentage root-mean-square difference, which is a global and relative indicator of the quality held by reconstructed waveforms, is the most widely used criterion. However, this parameter does not ensure compliance with clinical standard guidelines that specify limits to allowable noise in EEG recordings. As a result, expert clinicians may have difficulties interpreting the resulting distortion of the EEG for a given value of this parameter. Conversely, the root-mean-square error is an alternative criterion that quantifies distortion in understandable units. In this paper, we demonstrate that the root-mean-square error is better suited to control and to assess the distortion introduced by compression methods. The experiments conducted in this paper show that the use of the root-mean-square error as target parameter in EEG compression allows both clinicians and scientists to infer whether coding error is clinically acceptable or not at no cost for the compression ratio. PMID:22735392

  20. CMB all-scale blackbody distortions induced by linearizing temperature

    NASA Astrophysics Data System (ADS)

    Notari, Alessio; Quartin, Miguel

    2016-08-01

    Cosmic microwave background (CMB) experiments, such as WMAP and Planck, measure intensity anisotropies and build maps using a linearized formula for relating them to the temperature blackbody fluctuations. However, this procedure also generates a signal in the maps in the form of y -type distortions which is degenerate with the thermal Sunyaev Zel'dovich (tSZ) effect. These are small effects that arise at second order in the temperature fluctuations not from primordial physics but from such a limitation of the map-making procedure. They constitute a contaminant for measurements of our peculiar velocity, the tSZ and primordial y -distortions. They can nevertheless be well modeled and accounted for. We show that the distortions arise from a leakage of the CMB dipole into the y -channel which couples to all multipoles, mostly affecting the range ℓ≲400 . This should be visible in Planck's y -maps with an estimated signal-to-noise ratio of about 12. We note however that such frequency-dependent terms carry no new information on the nature of the CMB dipole. This implies that the real significance of Planck's Doppler coupling measurements is actually lower than reported by the collaboration. Finally, we quantify the level of contamination in tSZ and primordial y -type distortions and show that it is above the sensitivity of proposed next-generation CMB experiments.

  1. Distortion of binoculars revisited: does the sweet spot exist?

    PubMed

    Merlitz, Holger

    2010-01-01

    Sixty years ago, August Sonnefeld of Zeiss reported on observations with experimental telescopes. The goal of his investigation was to determine the ideal amount of distortion applied to optical instruments that are used in combination with the human eye. His studies were inconclusive and partially contradictory. We have picked up this problem once again, adopting a modern point of view about the human imaging process, and supported by computer graphics. Based on experiments with Helmholtz checkerboards, we argue that human imaging introduces a certain amount of barrel distortion, which has to be counterbalanced through the implementation of an equally strong pincushion distortion into the binocular design. We discuss in detail how this approach is capable of eliminating the globe effect of the panning binocular and how the residual pincushion distortion affects the image when the eye is pointing off-center. Our results support the binocular designer in optimizing his instrument for its intended mode of application, and may help binocular users and astronomers better understand their tools. PMID:20035302

  2. Spontaneous perceptual facial distortions correlate with ventral occipitotemporal activity.

    PubMed

    Dalrymple, Kirsten A; Davies-Thompson, Jodie; Oruc, Ipek; Handy, Todd C; Barton, Jason J S; Duchaine, Brad

    2014-07-01

    Prosopometamorphopsia is a disorder of face perception in which faces appear distorted to the perceiver. The neural basis of prosopometamorphopsia is unclear, but may involve abnormal activity in face-selective areas in the ventral occipito-temporal pathway. Here we present the case of AS, a 44-year-old woman who reports persistent perceptual distortions of faces with no known cause. AS was presented with facial images and rated the magnitude of her distortions while activity in her core face areas and other areas in the ventral visual pathway was measured using functional magnetic resonance imaging. The magnitude of her distortions was positively correlated with signal changes in the right occipital face area (OFA) and right fusiform face area (FFA), as well as right V1-V3, and right lateral occipital cortex (LOC). There was also a trend for a significant correlation with signal in the left OFA and right inferior frontal gyrus (IFG), but not in the right or left superior temporal sulcus (STS). These results suggest that AS' prosopometamorphopsia reflects anomalous activity in face-processing network, particularly in the ventral occipitotemporal cortex. PMID:24859691

  3. Retinal image mosaicing using the radial distortion correction model

    NASA Astrophysics Data System (ADS)

    Lee, Sangyeol; Abràmoff, Michael D.; Reinhardt, Joseph M.

    2008-03-01

    Fundus camera imaging can be used to examine the retina to detect disorders. Similar to looking through a small keyhole into a large room, imaging the fundus with an ophthalmologic camera allows only a limited view at a time. Thus, the generation of a retinal montage using multiple images has the potential to increase diagnostic accuracy by providing larger field of view. A method of mosaicing multiple retinal images using the radial distortion correction (RADIC) model is proposed in this paper. Our method determines the inter-image connectivity by detecting feature correspondences. The connectivity information is converted to a tree structure that describes the spatial relationships between the reference and target images for pairwise registration. The montage is generated by cascading pairwise registration scheme starting from the anchor image downward through the connectivity tree hierarchy. The RADIC model corrects the radial distortion that is due to the spherical-to-planar projection during retinal imaging. Therefore, after radial distortion correction, individual images can be properly mapped onto a montage space by a linear geometric transformation, e.g. affine transform. Compared to the most existing montaging methods, our method is unique in that only a single registration per image is required because of the distortion correction property of RADIC model. As a final step, distance-weighted intensity blending is employed to correct the inter-image differences in illumination encountered when forming the montage. Visual inspection of the experimental results using three mosaicing cases shows our method can produce satisfactory montages.

  4. View angle tilting echo planar imaging for distortion correction.

    PubMed

    Ahn, Sinyeob; Hu, Xiaoping P

    2012-10-01

    Geometric distortion caused by field inhomogeneity along the phase-encode direction is one of the most prominent artifacts due to a relatively low effective bandwidth along that direction in magnetic resonance echo planar imaging. This work describes a method for correcting in-plane image distortion along the phase-encode direction using a view angle tilting imaging technique in spin-echo echo planar imaging. Spin-echo echo planar imaging with view angle tilting uses the addition of gradient blips along the slice-select direction, concurrently applied with the phase-encode gradient blips, producing an additional phase. This phase effectively offsets an unwanted phase accumulation caused by field inhomogeneity, resulting in the removal of image distortion along the phase-encode direction. The proposed method is simple and straightforward both in implementation and application with no scan time penalty. Therefore, it is readily applicable on commercial scanners without having any customized postprocessing. The efficacy of the spin-echo echo planar imaging with view angle tilting technique in the correction of image distortion is demonstrated in phantom and in vivo brain imaging. PMID:22213567

  5. Response of Hypervelocity Boundary Layers to Global and Local Distortion

    NASA Astrophysics Data System (ADS)

    Flaherty, William; Austin, Joanna

    2013-11-01

    Concave surface curvature can impose significant distortion to compressible boundary layer flows due to multiple, potentially coupled, effects including an adverse pressure gradient, bulk flow compression, and possible centrifugal instabilities. Approximate methods provide insight into dominant mechanisms, however few strategies are capable of treating heat transfer effects and predictions diverge significantly from the available experimental data at larger pressure gradient. In this work, we examine the response of boundary layers to global and local distortions in hypervelocity flows where thermochemical energy exchange has significant impact on boundary layer structure and stability. Experiments are carried out in a novel expansion tube facility built at Illinois. We demonstrate that reasonable estimates of the laminar heat flux augmentation may be obtained as a function of the local turning angle, even at the conditions of greatest distortion. As a model problem to study the evolution of large-scale structures under strained conditions, streamwise vortices are imposed into the boundary layer. The impact of the additional local distortion is investigated. The heat transfer scaling is found to be robust even in the presence of the imposed structures.

  6. Tidal Distortion and Disruption of Earth-Crossing Asteriods

    NASA Technical Reports Server (NTRS)

    Love, Stanley G.; Bottke, William, Jr.

    1997-01-01

    We represent results of numerical simulations that show Earth's tidal forces can both distort and disrupt Earth-crossing asteriods (ECAs) that have weak rubble-pile structures. Building on previous studies, we consider more realistic asteriod shapes and trajectories, test a variety of spin and rates and axis orientations, and employ a dissipation algorithm to more accurately treat collisions between particles.

  7. An Accurate Projector Calibration Method Based on Polynomial Distortion Representation

    PubMed Central

    Liu, Miao; Sun, Changku; Huang, Shujun; Zhang, Zonghua

    2015-01-01

    In structure light measurement systems or 3D printing systems, the errors caused by optical distortion of a digital projector always affect the precision performance and cannot be ignored. Existing methods to calibrate the projection distortion rely on calibration plate and photogrammetry, so the calibration performance is largely affected by the quality of the plate and the imaging system. This paper proposes a new projector calibration approach that makes use of photodiodes to directly detect the light emitted from a digital projector. By analyzing the output sequence of the photoelectric module, the pixel coordinates can be accurately obtained by the curve fitting method. A polynomial distortion representation is employed to reduce the residuals of the traditional distortion representation model. Experimental results and performance evaluation show that the proposed calibration method is able to avoid most of the disadvantages in traditional methods and achieves a higher accuracy. This proposed method is also practically applicable to evaluate the geometric optical performance of other optical projection system. PMID:26492247

  8. Notes on Distortions in the Market for Educational Services.

    ERIC Educational Resources Information Center

    Olson, Lawrence S.

    The document analyzes economic factors that might cause the output of educational services to diverge from the theoretical optimum because of a divergence between marginal social valuation and marginal social cost. Education contains both investment and consumption aspects. The analysis shows that the only distortion resulting from uncertainty…

  9. Body Dysmorphic Disorder: Easing the Distress of Distortion.

    ERIC Educational Resources Information Center

    Fore, Cynthia M.

    People who suffer from body dysmorphic disorder believe that their body is defected and that this defect makes them ugly. Their distorted body image can be precipitated by many internal and external factors and as a result of their imagined defect, these normal-appearing individuals exhibit self-defeating behaviors. The disorder can lead to the…

  10. A Numerical Investigation on Configurational Distortions in Nematic Liquid Crystals

    NASA Astrophysics Data System (ADS)

    Pandolfi, Anna; Napoli, Gaetano

    2011-10-01

    When subjected to magnetic or electric fields, nematic liquid crystals confined between two parallel glass plates and initially uniformly oriented may undergo homogeneous one-dimensional spatial distortions (Fréedericksz and Zolina, Trans. Faraday Soc. 29:919, 1933) or periodic distortions (Lonberg and Meyer, Phys. Rev. Lett. 55(7):718-721, 1985; and Srajer et al., Phys. Rev. Lett. 67(9):1102-1105, 1991). According to the experimental observations, periodic phases are stable configurations at intermediate intensity of the acting field, while homogeneous phases are stable at higher strengths. We present a fully nonlinear finite element approach able to describe homogeneous and periodic configurational phases in a cell of confined nematic liquid crystal with strong planar anchoring boundary conditions. Stationary configurations are obtained by setting to zero the first variation of the discretized total energy of the system. Unstable configurations are identified by evaluating the behavior of the solution under small numerical perturbations. Numerical calculations are able to describe the evolution of the configurational distortions as a function of the applied field and are able to capture the critical points between homogeneous and periodic phases. The proposed approach has been proved to be an excellent tool to predict the existence of unstable or metastable distortions, characterized by higher energy levels.

  11. Computer Software for Displaying Map Projections and Comparing Distortions.

    ERIC Educational Resources Information Center

    Wikle, Thomas

    1991-01-01

    Discusses software that educators can use to teach about distortions associated with alternative map projections. Examines the Projection, MicroCAM, World, and Atlas-GIS software programs. Suggests using the software in either introductory or more advanced courses dealing with map design or thematic cartography. Explains how to obtain the…

  12. Electromagnetic hammer removes weld distortions from aluminum tanks

    NASA Technical Reports Server (NTRS)

    Schwinghamer, R. J.

    1965-01-01

    Distortions around weld areas on sheet-aluminum tanks and other structures are removed with a portable electromagnetic hammer. The hammer incorporates a coil that generates a controlled high-energy pulsed magnetic field over localized areas on the metal surface.

  13. System for interferometric distortion measurements that define an optical path

    DOEpatents

    Bokor, Jeffrey; Naulleau, Patrick

    2003-05-06

    An improved phase-shifting point diffraction interferometer can measure both distortion and wavefront aberration. In the preferred embodiment, the interferometer employs an object-plane pinhole array comprising a plurality of object pinholes located between the test optic and the source of electromagnetic radiation and an image-plane mask array that is positioned in the image plane of the test optic. The image-plane mask array comprises a plurality of test windows and corresponding reference pinholes, wherein the positions of the plurality of pinholes in the object-plane pinhole array register with those of the plurality of test windows in image-plane mask array. Electromagnetic radiation that is directed into a first pinhole of object-plane pinhole array thereby creating a first corresponding test beam image on the image-plane mask array. Where distortion is relatively small, it can be directly measured interferometrically by measuring the separation distance between and the orientation of the test beam and reference-beam pinhole and repeating this process for at least one other pinhole of the plurality of pinholes of the object-plane pinhole array. Where the distortion is relative large, it can be measured by using interferometry to direct the stage motion, of a stage supporting the image-plane mask array, and then use the final stage motion as a measure of the distortion.

  14. Generation of Distortion Product Otoacoustic Emissions in the Gerbil Cochlea

    NASA Astrophysics Data System (ADS)

    Dong, Wei; Olson, Elizabeth S.

    2011-11-01

    Simultaneous measurements of intracochlear and ear canal pressure responses to two-tone stimulation with fixed f2/f1 ratio allowed us to probe the physical generation sites of distortion product otoacoustic emissions (DPOAEs) in the cochlea. Our results were consistent with the notion that DPOAE emerges primarily from the generator region, where the two primaries overlap.

  15. Motivational Distortion Scales for the Children's Personality Questionnaire.

    ERIC Educational Resources Information Center

    Canivez, Gary L.; Prichard, Karen K.

    1989-01-01

    Developed and cross-validated motivational distortion scales (fake bad and fake good) for the Children's Personality Questionnaire (CPQ). Findings from 12-year-old seventh- and eighth-grade students (n=58) suggest that children are sophisticated enough to respond to the CPQ in a socially desirable and socially undesirable way when asked to do so.…

  16. Improving MRI surface coil decoupling to reduce B1 distortion

    NASA Astrophysics Data System (ADS)

    Larson, Christian

    As clinical MRI systems continue to advance, larger focus is being given to image uniformity. Good image uniformity begins with generating uniform magnetic fields, which are easily distorted by induced currents on receive-only surface coils. It has become an industry standard to combat these induced currents by placing RF blocking networks on surface coils. This paper explores the effect of blocking network impedance of phased array surface coils on B1 distortion. It has been found and verified, that traditional approaches for blocking network design in complex phased arrays can leave undesirable B1 distortions at 3 Tesla. The traditional approach of LC tank blocking is explored, but shifts from the idea that higher impedance equals better B1 distortion at 3T. The result is a new design principle for a tank with a finite inductive reactance at the Larmor Frequency. The solution is demonstrated via simulation using a simple, single, large tuning loop. The same loop, along with a smaller loop, is used to derive the new design principle, which is then applied to a complex phased array structure.

  17. Pathophysiological Distortions in Time Perception and Timed Performance

    ERIC Educational Resources Information Center

    Allman, Melissa J.; Meck, Warren H.

    2012-01-01

    Distortions in time perception and timed performance are presented by a number of different neurological and psychiatric conditions (e.g. Parkinson's disease, schizophrenia, attention deficit hyperactivity disorder and autism). As a consequence, the primary focus of this review is on factors that define or produce systematic changes in the…

  18. Calculations of inlet distortion induced compressor flowfield instability

    NASA Technical Reports Server (NTRS)

    Hynes, T. P.; Chue, R.; Greitzer, E. M.; Tan, C. S.

    1987-01-01

    Calculations are presented predicting the onset of flow instability for a multistage low speed axial compressor operating in circumferentially distorted inlet flow. The most important feature of the model used is that it attempts to properly account for the fluid dynamic interaction between the spoiled and unspoiled sectors of the compressor. The calculations show that there is an approximate stability criterion, the annulus averaged slope of the compressor pressure rise characteristic equal to zero, that is valid whenever the dynamics of the compressor distorted flowfield can be considered independent of the compressor environment. This approximate criterion is used to investigate the relationship between the present model and the parallel compressor model. Further calculations are performed to investigate cases of interest when the dynamics of the flowfield are coupled to the environment. Resonant cases and cases when the distortion is unsteady are studied. In particular, it is shown that rotating distortions which propagate in the rotor direction can have a greater effect on stability margin than stationary or counter-rotational ones. Finally, it is shown that the general predictions of the model are insensitive to the details of the unsteady bladerow dynamics.

  19. Age Differences in Dreams. II: Distortion and Other Variables.

    ERIC Educational Resources Information Center

    Zepelin, Harold

    1981-01-01

    Age-related change in manifest dream content was assessed in dreams recalled from REM sleep by (N=58) men aged (27-64), and in dreams recalled from sleep at home. Evidence indicated a small age-related decline in dream distortion and family-related content. (Author)

  20. 3D magnetotelluric inversion with full distortion matrix

    NASA Astrophysics Data System (ADS)

    Gribenko, A. V.; Zhdanov, M. S.

    2014-12-01

    Distortion of regional electric fields by local structures represent one of the major problems facing three-dimensional magnetotelluric (MT) interpretation. Effect of 3D local inhomogenities on MT data can be described by a real 2x2 distortion matrix. In this project we develop a method of simultaneous inversion of the full MT impedance data for 3D conductivity distribution and for the distortion matrix. Tikhonov regularization is employed to solve the resulting inverse problem. Integral equations method is used to compute MT responses. Minimization of the cost functional is achieved via conjugate gradient method. The inversion algorithm is tested on the synthetic data from Dublin Secret Model II (DSM 2) for which multiple inversion solutions are available for comparison. Inclusion of the distortion matrix provides faster convergence and allows coarser discretization of the near-surface while achievingsimilar or better data fits as inversion for the conductivity only with finely discretized shallow regions. As a field data example we chose a subset of the EarthScope MT dataset covering Great Basin and adjacent areas of the Western United States. Great Basin data inversion identified several prominent conductive zones which correlate well with areas of tectonic and geothermal activity.

  1. Turkish Version of the Cognitive Distortions Questionnaire: Psychometric Properties

    PubMed Central

    Batmaz, Sedat; Kocbiyik, Sibel; Yuncu, Ozgur Ahmet

    2015-01-01

    Cognitive distortions are interrelated with all layers of cognitions, and they may be part of the treatment once they are accessed, identified, labeled, and changed. From both a research and a clinical perspective, it is of utmost importance to disentangle cognitive distortions from similar constructs. Recently, the Cognitive Distortions Questionnaire (CD-Quest), a brief and comprehensive measure, was developed to assess both the frequency and the intensity of cognitive distortions. The aim of the present study was to assess the psychometric properties of the Turkish version of the CD-Quest in a psychiatric outpatient sample. Demographic and clinical data of the participants were analyzed by descriptive statistics. For group comparisons, Student's t-test was applied. An exploratory principal components factor analysis was performed, followed by an oblique rotation. To assess the internal consistency of the scale Cronbach's α was computed. The correlation coefficient was calculated for test-retest reliability over a 4-week period. For concurrent validity, bivariate Pearson correlation analyses were conducted with the measures of mood severity and negatively biased cognitions. The results revealed that the scale had excellent internal consistency, good test-retest reliability, unidimensional factor structure, and evidence of concurrent and discriminant validity. PMID:26351580

  2. Hierarchical Clustering and the Concept of Space Distortion.

    ERIC Educational Resources Information Center

    Hubert, Lawrence; Schultz, James

    An empirical assesssment of the space distortion properties of two prototypic hierarchical clustering procedures is given in terms of an occupancy model developed from combinatorics. Using one simple example, the single-link and complete-link clustering strategies now in common use in the behavioral sciences are empirically shown to be space…

  3. Context-Conditioned Generalization in Adaptation to Distorted Speech

    ERIC Educational Resources Information Center

    Dahan, Delphine; Mead, Rebecca L.

    2010-01-01

    People were trained to decode noise-vocoded speech by hearing monosyllabic stimuli in distorted and unaltered forms. When later presented with different stimuli, listeners were able to successfully generalize their experience. However, generalization was modulated by the degree to which testing stimuli resembled training stimuli: Testing stimuli's…

  4. Shear waves in inhomogeneous, compressible fluids in a gravity field.

    PubMed

    Godin, Oleg A

    2014-03-01

    While elastic solids support compressional and shear waves, waves in ideal compressible fluids are usually thought of as compressional waves. Here, a class of acoustic-gravity waves is studied in which the dilatation is identically zero, and the pressure and density remain constant in each fluid particle. These shear waves are described by an exact analytic solution of linearized hydrodynamics equations in inhomogeneous, quiescent, inviscid, compressible fluids with piecewise continuous parameters in a uniform gravity field. It is demonstrated that the shear acoustic-gravity waves also can be supported by moving fluids as well as quiescent, viscous fluids with and without thermal conductivity. Excitation of a shear-wave normal mode by a point source and the normal mode distortion in realistic environmental models are considered. The shear acoustic-gravity waves are likely to play a significant role in coupling wave processes in the ocean and atmosphere. PMID:24606251

  5. Wave turbulence

    NASA Astrophysics Data System (ADS)

    Nazarenko, Sergey

    2015-07-01

    Wave turbulence is the statistical mechanics of random waves with a broadband spectrum interacting via non-linearity. To understand its difference from non-random well-tuned coherent waves, one could compare the sound of thunder to a piece of classical music. Wave turbulence is surprisingly common and important in a great variety of physical settings, starting with the most familiar ocean waves to waves at quantum scales or to much longer waves in astrophysics. We will provide a basic overview of the wave turbulence ideas, approaches and main results emphasising the physics of the phenomena and using qualitative descriptions avoiding, whenever possible, involved mathematical derivations. In particular, dimensional analysis will be used for obtaining the key scaling solutions in wave turbulence - Kolmogorov-Zakharov (KZ) spectra.

  6. Accurate Orientation Estimation Using AHRS under Conditions of Magnetic Distortion

    PubMed Central

    Yadav, Nagesh; Bleakley, Chris

    2014-01-01

    Low cost, compact attitude heading reference systems (AHRS) are now being used to track human body movements in indoor environments by estimation of the 3D orientation of body segments. In many of these systems, heading estimation is achieved by monitoring the strength of the Earth's magnetic field. However, the Earth's magnetic field can be locally distorted due to the proximity of ferrous and/or magnetic objects. Herein, we propose a novel method for accurate 3D orientation estimation using an AHRS, comprised of an accelerometer, gyroscope and magnetometer, under conditions of magnetic field distortion. The system performs online detection and compensation for magnetic disturbances, due to, for example, the presence of ferrous objects. The magnetic distortions are detected by exploiting variations in magnetic dip angle, relative to the gravity vector, and in magnetic strength. We investigate and show the advantages of using both magnetic strength and magnetic dip angle for detecting the presence of magnetic distortions. The correction method is based on a particle filter, which performs the correction using an adaptive cost function and by adapting the variance during particle resampling, so as to place more emphasis on the results of dead reckoning of the gyroscope measurements and less on the magnetometer readings. The proposed method was tested in an indoor environment in the presence of various magnetic distortions and under various accelerations (up to 3 g). In the experiments, the proposed algorithm achieves <2° static peak-to-peak error and <5° dynamic peak-to-peak error, significantly outperforming previous methods. PMID:25347584

  7. Quantification of structural distortions in the transmembrane helices of GPCRs.

    PubMed

    Deupi, Xavier

    2012-01-01

    A substantial part of the structural and much of the functional information about G protein-coupled receptors (GPCRs) comes from studies on rhodopsin. Thus, analysis tools for detailed structure comparison are key to see to what extent this information can be extended to other GPCRs. Among the methods to evaluate protein structures and, in particular, helix distortions, HELANAL has the advantage that it provides data (local bend and twist angles) that can be easily translated to structural effects, as a local opening/tightening of the helix.In this work I show how HELANAL can be used to extract detailed structural information of the transmembrane bundle of GPCRs, and I provide some examples on how these data can be interpreted to study basic principles of protein structure, to compare homologous proteins and to study mechanisms of receptor activation. Also, I show how in combination with the sequence analysis tools provided by the program GMoS, distortions in individual receptors can be put in the context of the whole Class A GPCR family. Specifically, quantification of the strong proline-induced distortions in the transmembrane bundle of rhodopsin shows that they are not standard proline kinks. Moreover, the helix distortions in transmembrane helix (TMH) 5 and TMH 6 of rhodopsin are also present in the rest of GPCR crystal structures obtained so far, and thus, rhodopsin-based homology models have modeled correctly these strongly distorted helices. While in some cases the inherent "rhodopsin bias" of many of the GPCR models to date has not been a disadvantage, the availability of more templates will clearly result in better homology models. This type of analysis can be, of course, applied to any protein, and it may be particularly useful for the structural analysis of other membrane proteins. A detailed knowledge of the local structural changes related to ligand binding and how they are translated into larger-scale movements of transmembrane domains is key to

  8. Another look at distortions of the Cosmic Microwave Background spectrum

    NASA Astrophysics Data System (ADS)

    De Zotti, G.; Negrello, M.; Castex, G.; Lapi, A.; Bonato, M.

    2016-03-01

    We review aspects of Cosmic Microwave Background (CMB) spectral distortions which do not appear to have been fully explored in the literature. In particular, implications of recent evidences of heating of the intergalactic medium (IGM) by feedback from active galactic nuclei are investigated. Taking also into account the IGM heating associated to structure formation, we argue that values of the y parameter of several × 10-6, i.e. a factor of a few below the COBE/FIRAS upper limit, are to be expected. The Compton scattering by the re-ionized plasma also re-processes primordial distortions, adding a y-type contribution. Hence no pure Bose-Einstein-like distortions are to be expected. An assessment of Galactic and extragalactic foregrounds, taking into account the latest results from the Planck satellite as well as the contributions from the strong CII and CO lines from star-forming galaxies, demonstrates that a foreground subtraction accurate enough to fully exploit the PIXIE sensitivity will be extremely challenging. Motivated by this fact we also discuss methods to detect spectral distortions not requiring absolute measurements and show that accurate determinations of the frequency spectrum of the CMB dipole amplitude may substantially improve over COBE/FIRAS limits on distortion parameters. Such improvements may be at reach of next generation CMB anisotropy experiments. The estimated amplitude of the Cosmic Infrared Background (CIB) dipole might be detectable by careful analyses of Planck maps at the highest frequencies. Thus Planck might provide interesting constraints on the CIB intensity, currently known with a simeq 30% uncertainty.

  9. Highly linear silicon traveling wave Mach-Zehnder carrier depletion modulator based on differential drive.

    PubMed

    Streshinsky, Matthew; Ayazi, Ali; Xuan, Zhe; Lim, Andy Eu-Jin; Lo, Guo-Qiang; Baehr-Jones, Tom; Hochberg, Michael

    2013-02-11

    We present measurements of the nonlinear distortions of a traveling-wave silicon Mach-Zehnder modulator based on the carrier depletion effect. Spurious free dynamic range for second harmonic distortion of 82 dB·Hz(1/2) is seen, and 97 dB·Hz(2/3) is measured for intermodulation distortion. This measurement represents an improvement of 20 dB over the previous best result in silicon. We also show that the linearity of a silicon traveling wave Mach-Zehnder modulator can be improved by differentially driving it. These results suggest silicon may be a suitable platform for analog optical applications. PMID:23481838

  10. The propagation of spark-produced N waves through turbulence

    NASA Technical Reports Server (NTRS)

    Lipkens, Bart

    1994-01-01

    A model experiment was designed and built to simulate the propagation of sonic booms through atmospheric turbulence. The setup of the model experiment is described briefly. Measurements of the N waves after they propagated across the turbulent velocity field reveal the same waveform distortion and change in rise time as for sonic booms. The data from the model experiment is used to test sonic boom models. Some models yield predictions for the waveform distortion, while others give estimates of the rise time of the sonic booms. A new theoretical model for the propagation of plane N waves through a turbulent medium is described.

  11. Heat Waves

    MedlinePlus

    Heat Waves Dangers we face during periods of very high temperatures include: Heat cramps: These are muscular pains and spasms due ... that the body is having trouble with the heat. If a heat wave is predicted or happening… - ...

  12. Spiral waves on a contractile tissue

    NASA Astrophysics Data System (ADS)

    Mesin, L.; Ambrosi, D.

    2011-02-01

    In a healthy cardiac tissue, electric waves propagate in the form of a travelling pulse, from the apex to the base, and activate the contraction of the heart. Defects in the propagation can destabilize travelling fronts and originate possible new periodic solutions, as spiral waves. Spiral waves are quite stable, but the interplay between currents and strain can distort the periodic pattern, provided the coupling is strong enough. In this paper we investigate the stability of spiral waves on a contractile medium in a non-standard framework, in which the electrical potential dictates the active strain (not stress) of the muscle. The role of conducting and contracting fibers is included in the model and periodic boundary conditions are adopted. A correlation analysis allows to evaluate numerically the range of stability of the parameters for the spiral waves, depending on the strain of the contracted fibers and on the magnitude of the stretch activated current.

  13. Centrifugal Distortion Analysis of the Millimeter-Wave Spectrum of 1,1,1,2-Tetrafluoroethane

    NASA Astrophysics Data System (ADS)

    Bizzocchi, L.; Degli Esposti, C.; Dore, L.

    1998-04-01

    The supplementary material consists of an ascii file, in which all the analysed transition frequencies of 1,1,1,2-Tetrafluoroethane (HFC 134a) are listed. Two Tables are included. Table I contains the ground state transition frequencies, and Table II contains the torsional state lines. The first page is explanatory.

  14. An experimental investigation of compressor stall using an on-line distortion indicator and signal conditioner

    NASA Technical Reports Server (NTRS)

    Costakis, W. G.; Wenzel, L. M.

    1975-01-01

    The relation of the steady-state and dynamic distortions and the stall margin of a J85-13 turbojet engine was investigated. A distortion indicator capable of computing two distortion indices was used. A special purpose signal conditioner was also used as an interface between transducer signals and distortion indicator. A good correlation of steady-state distortion and stall margin was established. The prediction of stall by using the indices as instantaneous distortion indicators was not successful. A sensitivity factor that related the loss of stall margin to the turbulence level was found.

  15. Effect of screen-induced total-pressure distortion on axial-flow compressor stability

    NASA Technical Reports Server (NTRS)

    Calogeras, J. E.; Johnsen, R. L.; Burstadt, P. L.

    1974-01-01

    An experimental investigation was made to determine the effects of screen-induced total-pressure distortions on two J85-GE-13 turbojet engines. Results were compared to those from a previous program run with a third engine. All compressors were found to be sensitive to a critical angle of circumferential distortion equal to 60 deg., and they all adhered closely to the parallel compressor model. The sensitivity of compressor exit pressure to virtually any type of distortion pattern can be determined by defining stall lines for undistorted, hub radial distorted, and tip radial distorted inflows. The effect of multiple sectors of circumferential distortion is defined.

  16. Gravity Waves

    Atmospheric Science Data Center

    2013-04-19

    article title:  Gravity Waves Ripple over Marine Stratocumulus Clouds ... Imaging SpectroRadiometer (MISR), a fingerprint-like gravity wave feature occurs over a deck of marine stratocumulus clouds. Similar ... that occur when a pebble is thrown into a still pond, such "gravity waves" sometimes appear when the relatively stable and stratified air ...

  17. Mapping flow distortion on oceanographic platforms using computational fluid dynamics

    NASA Astrophysics Data System (ADS)

    O'Sullivan, N.; Landwehr, S.; Ward, B.

    2013-10-01

    Wind speed measurements over the ocean on ships or buoys are affected by flow distortion from the platform and by the anemometer itself. This can lead to errors in direct measurements and the derived parametrisations. Here we computational fluid dynamics (CFD) to simulate the errors in wind speed measurements caused by flow distortion on the RV Celtic Explorer. Numerical measurements were obtained from the finite-volume CFD code OpenFOAM, which was used to simulate the velocity fields. This was done over a range of orientations in the test domain from -60 to +60° in increments of 10°. The simulation was also set up for a range of velocities, ranging from 5 to 25 m s-1 in increments of 0.5 m s-1. The numerical analysis showed close agreement to experimental measurements.

  18. Pulsations of an Evolved Self-consistently Distorted Star

    NASA Astrophysics Data System (ADS)

    Ouazzani, R.-M.; Dupret, M.-A.; Roxburgh, I. W.; Goupil, M.-J.

    2012-09-01

    A new two-dimensional (2D) non-perturbative method to compute accurate oscillation modes of rapidly rotating stars is presented. The 2D calculations fully take into account the centrifugal distortion of the star while the non-perturbative method includes the full influence of the Coriolis acceleration, and are used to compute oscillation modes of rapid rotators — high-order p-modes in δ Scuti stars, as well as low-order p- and g-modes in β Cephei stars. We compare the oscillation spectra obtained for centrifugally distorted polytropes with those of Reese et al. (2006), and give the first results for a realistic 2D model of a rapidly rotating 2 M⊙ evolved star computed with the method developed by Roxburgh (2006).

  19. Sleep Wrinkles: Facial Aging and Facial Distortion During Sleep.

    PubMed

    Anson, Goesel; Kane, Michael A C; Lambros, Val

    2016-09-01

    Wrinkles are just one indicator of facial aging, but an indicator that is of prime importance in our world of facial aesthetics. Wrinkles occur where fault lines develop in aging skin. Those fault lines may be due to skin distortion resulting from facial expression or may be due to skin distortion from mechanical compression during sleep. Expression wrinkles and sleep wrinkles differ in etiology, location, and anatomical pattern. Compression, shear, and stress forces act on the face in lateral or prone sleep positions. We review the literature relating to the development of wrinkles and the biomechanical changes that occur in response to intrinsic and extrinsic influences. We explore the possibility that compression during sleep not only results in wrinkles but may also contribute to facial skin expansion. PMID:27329660

  20. High thermoelectric performance of the distorted bismuth(110) layer.

    PubMed

    Cheng, L; Liu, H J; Zhang, J; Wei, J; Liang, J H; Jiang, P H; Fan, D D; Sun, L; Shi, J

    2016-07-14

    The thermoelectric properties of the distorted bismuth(110) layer are investigated using first-principles calculations combined with the Boltzmann transport equation for both electrons and phonons. To accurately predict the electronic and transport properties, the quasiparticle corrections with the GW approximation of many-body effects have been explicitly included. It is found that a maximum ZT value of 6.4 can be achieved for n-type systems, which essentially stemmed from the weak scattering of electrons. Moreover, we demonstrate that the distorted Bi layer retains high ZT values in relatively broad regions of both temperature and carrier concentration. Our theoretical work emphasizes that the deformation potential constant characterizing the electron-phonon scattering strength is an important paradigm for searching high thermoelectric performance materials. PMID:27302907

  1. Analysis and validation of laser spot weld-induced distortion

    SciTech Connect

    Knorovsky, G.A.; Kanouff, M.P.; Maccallum, D.O.; Fuerschbach, P.W.

    1999-12-09

    Laser spot welding is an ideal process for joining small parts with tight tolerances on weld size, location, and distortion, particularly those with near-by heat sensitive features. It is also key to understanding the overlapping laser spot seam welding process. Rather than attempting to simulate the laser beam-to-part coupling (particularly if a keyhole occurs), it was measured by calorimetry. This data was then used to calculate the thermal and structural response of a laser spot welded SS304 disk using the finite element method. Five combinations of process parameter values were studied. Calculations were compared to experimental data for temperature and distortion profiles measured by thermocouples and surface profiling. Results are discussed in terms of experimental and modeling factors. The authors then suggest appropriate parameters for laser spot welding.

  2. Minimizing distortion in truss structures - A Hopfield network solution

    NASA Technical Reports Server (NTRS)

    Fu, B.; Hajela, P.

    1992-01-01

    Distortions in truss structures can result from random errors in element lengths that are typical of a manufacturing process. These distortions may be minimized by an optimal selection of elements from those available for placement between the prescribed nodes - a combinatorial optimization problem requiring significant investment of computational resource for all but the smallest problems. The present paper describes a formulation in which near-optimal element assignments are obtained as minimum-energy stable states, of an analogous Hopfield neural network. This requires mapping of the optimization problem into an energy function of the appropriate Liapunov form. The computational architecture is ideally suited to a parallel processor implementation and offers significant savings in computational effort. A numerical implementation of the approach is discussed with reference to planar truss problems.

  3. Minimizing distortion in truss structures -- a Hopfield network solution

    NASA Technical Reports Server (NTRS)

    Fu, B.; Hajela, P.

    1993-01-01

    Distortions in truss structures can result from random errors in elemental lengths that are typical of a manufacturing process. These distortions may be minimized by an optimal selection of elements from those available for placement between the prescribed nodes -- a combinatorial optimization problem requiring significant investment of computational resource for all but the smallest problems. The present paper describes a formulation in which near-optimal element assignments are obtained as minimum energy, stable states, of an analogous Hopfield neural network. This requires mapping of the optimization problem into an energy function of the appropriate Lyapunov form. The computational architecture is ideally suited to a parallel processor implementation and offers significant savings in computational effort. A numerical implementation of the approach is discussed with reference to planar truss problems.

  4. The underwater camera calibration based on virtual camera lens distortion

    NASA Astrophysics Data System (ADS)

    Qin, Dahui; Mao, Ting; Cheng, Peng; Zhang, Zhiliang

    2011-08-01

    The machine view is becoming more and more popular in underwater. It is a challenge to calibrate the camera underwater because of the complicated light ray path in underwater and air environment. In this paper we firstly analyzed characteristic of the camera when light transported from air to water. Then we proposed a new method that takes the high-level camera distortion model to compensate the deviation of the light refraction when light ray come through the water and air media. In the end experience result shows the high-level distortion model can simulate the effect made by the underwater light refraction which also makes effect on the camera's image in the process of the camera underwater calibration.

  5. Stratification effects on nonlinear elastic surface waves

    NASA Astrophysics Data System (ADS)

    Parker, D. F.

    1988-01-01

    On a homogeneous elastic half-space, linear surface waves are nondispersive. In each direction, waves having any profile travel without distortion. Nonlinearity causes intermodulation between the various wavelengths so that the signal distorts. Even when nonlinearity is small, sinusoidal profiles do not remain approximately sinusoidal. The absence of dispersion means that profiles suffer cumulative distortion, until the surface slope and strain become locally unbounded. Although this behaviour is typical of many signals, there are some signals for which intermodulation is constructive. These signals can travel coherently over large distances. For seismological applications, it is important to study the effects due to stratification. Dependence of the material constants on depth modifies the nonlinear evolution equations previously derived for homogeneous media. It has a smaller effect on higher frequencies than on lower frequencies. An approximate theory for short wavelength (high frequency) signals is introduced. Calculations show that when nonlinearity is no more important than dispersion, initially sinusoidal profiles propagate with surface slope remaining finite. When dispersion is small compared to nonlinearity, certain sharp peaked profiles can travel large distances while suffering little distortion.

  6. Reduction of sextupole distortion by shuffling magnets in small groups

    SciTech Connect

    Gluckstern, R.L.; Ohnuma, S.

    1985-05-01

    A method is given for reducing the most troublesome sextupole harmonics in a ring by measuring the sextupole field in groups of magnets, and ordering them according to a predetermined prescription. The predicted result is a decrease in sextupole related distortions by a factor ..sqrt..2/(J+1)/sup 1/2/ where J magnets, covering one or more betatron periods, are measured at one time. Simulations performed for typical SSC lattices confirm the expected improvements.

  7. System overview on electromagnetic compensation for reflector antenna surface distortion

    NASA Technical Reports Server (NTRS)

    Acosta, R. J.; Zaman, A. J.; Terry, J. D.

    1993-01-01

    The system requirements and hardware implementation for electromagnetic compensation of antenna performance degradations due to thermal effects was investigated. Future commercial space communication antenna systems will utilize the 20/30 GHz frequency spectrum and support very narrow multiple beams (0.3 deg) over wide angle field of view (15-20 beamwidth). On the ground, portable and inexpensive very small aperture terminals (VSAT) for transmitting and receiving video, facsimile and data will be employed. These types of communication system puts a very stringent requirement on spacecraft antenna beam pointing stability (less than .01 deg), high gain (greater than 50 dB) and very lowside lobes (less than -25 dB). Thermal analysis performed on the advanced communication technology satellite (ACTS) has shown that the reflector surfaces, the mechanical supporting structures and metallic surfaces on the spacecraft body will distort due thermal effects from a varying solar flux. The antenna performance characteristics (e.g., pointing stability, gain, side lobe, etc.) will degrade due to thermal distortion in the reflector surface and supporting structures. Specifically, antenna RF radiation analysis has shown that pointing error is the most sensitive antenna performance parameter to thermal distortions. Other antenna parameters like peak gain, cross polarization level (beam isolation), and side lobe level will also degrade with thermal distortions. In order to restore pointing stability and in general antenna performance several compensation methods were proposed. In general these compensation methods can be classified as being either of mechanical or electromagnetic type. This paper will address only the later one. In this approach an adaptive phased array antenna feed is used to compensate for the antenna performance degradation. Extensive work has been devoted to demonstrate the feasibility of adaptive feed compensation on space communication antenna systems. This

  8. Breast tissue decomposition with spectral distortion correction: A postmortem study

    PubMed Central

    Ding, Huanjun; Zhao, Bo; Baturin, Pavlo; Behroozi, Farnaz; Molloi, Sabee

    2014-01-01

    Purpose: To investigate the feasibility of an accurate measurement of water, lipid, and protein composition of breast tissue using a photon-counting spectral computed tomography (CT) with spectral distortion corrections. Methods: Thirty-eight postmortem breasts were imaged with a cadmium-zinc-telluride-based photon-counting spectral CT system at 100 kV. The energy-resolving capability of the photon-counting detector was used to separate photons into low and high energy bins with a splitting energy of 42 keV. The estimated mean glandular dose for each breast ranged from 1.8 to 2.2 mGy. Two spectral distortion correction techniques were implemented, respectively, on the raw images to correct the nonlinear detector response due to pulse pileup and charge-sharing artifacts. Dual energy decomposition was then used to characterize each breast in terms of water, lipid, and protein content. In the meantime, the breasts were chemically decomposed into their respective water, lipid, and protein components to provide a gold standard for comparison with dual energy decomposition results. Results: The accuracy of the tissue compositional measurement with spectral CT was determined by comparing to the reference standard from chemical analysis. The averaged root-mean-square error in percentage composition was reduced from 15.5% to 2.8% after spectral distortion corrections. Conclusions: The results indicate that spectral CT can be used to quantify the water, lipid, and protein content in breast tissue. The accuracy of the compositional analysis depends on the applied spectral distortion correction technique. PMID:25281953

  9. Breast tissue decomposition with spectral distortion correction: A postmortem study

    SciTech Connect

    Ding, Huanjun; Zhao, Bo; Baturin, Pavlo; Behroozi, Farnaz; Molloi, Sabee

    2014-10-15

    Purpose: To investigate the feasibility of an accurate measurement of water, lipid, and protein composition of breast tissue using a photon-counting spectral computed tomography (CT) with spectral distortion corrections. Methods: Thirty-eight postmortem breasts were imaged with a cadmium-zinc-telluride-based photon-counting spectral CT system at 100 kV. The energy-resolving capability of the photon-counting detector was used to separate photons into low and high energy bins with a splitting energy of 42 keV. The estimated mean glandular dose for each breast ranged from 1.8 to 2.2 mGy. Two spectral distortion correction techniques were implemented, respectively, on the raw images to correct the nonlinear detector response due to pulse pileup and charge-sharing artifacts. Dual energy decomposition was then used to characterize each breast in terms of water, lipid, and protein content. In the meantime, the breasts were chemically decomposed into their respective water, lipid, and protein components to provide a gold standard for comparison with dual energy decomposition results. Results: The accuracy of the tissue compositional measurement with spectral CT was determined by comparing to the reference standard from chemical analysis. The averaged root-mean-square error in percentage composition was reduced from 15.5% to 2.8% after spectral distortion corrections. Conclusions: The results indicate that spectral CT can be used to quantify the water, lipid, and protein content in breast tissue. The accuracy of the compositional analysis depends on the applied spectral distortion correction technique.

  10. Control of Inflow Distortion in a Scarf Inlet

    NASA Technical Reports Server (NTRS)

    Gerhold, Carl H.; Clark, Lorenzo R.; Biedron, Robert T.

    2002-01-01

    The scarf inlet has the potential to reduce aircraft inlet noise radiation to the ground by reflecting it into the space above the engine. Without forward motion of the engine, the non-symmetry of the inlet causes inflow distortion which generates noise that is greater than the noise reduction of the scarf. However, acoustic evaluations of aircraft engines are often done on static test stands. A method to reduce inflow distortion by boundary layer suction is proposed and evaluated using a model of a high bypass ratio engine located in an anechoic chamber. The design goal of the flow control system is to make the inflow to the inlet circumferentially uniform and to eliminate reversed flow. This minimizes the inflow distortion and allows for acoustic evaluation of the scarf inlet on a static test stand. The inlet boundary layer suction effectiveness is evaluated both by aerodynamic and by acoustic measurements. Although the design goal is not met, the control system is found to have a beneficial effect on the engine operation, reducing blade stall and speed variation. This is quantified by two acoustic benefits, reduction both of the variability of tone noise and of the low frequency wideband noise due to the inflow distortion. It is felt that a compromise in the manufacture of the control hardware contributes to the inability of the control system to perform as expected from the analysis. The control system with sufficient authority is felt to have the potential to permit reliable acoustic testing in a static configuration of engines with non-symmetric inlets. Because the control system can improve operation of the engine, it may also have the potential to reduce noise and vibration and enhance engine longevity during low speed ground operations in the terminal area.

  11. A metasurface carpet cloak for electromagnetic, acoustic and water waves.

    PubMed

    Yang, Yihao; Wang, Huaping; Yu, Faxin; Xu, Zhiwei; Chen, Hongsheng

    2016-01-01

    We propose a single low-profile skin metasurface carpet cloak to hide objects with arbitrary shape and size under three different waves, i.e., electromagnetic (EM) waves, acoustic waves and water waves. We first present a metasurface which can control the local reflection phase of these three waves. By taking advantage of this metasurface, we then design a metasurface carpet cloak which provides an additional phase to compensate the phase distortion introduced by a bump, thus restoring the reflection waves as if the incident waves impinge onto a flat mirror. The finite element simulation results demonstrate that an object can be hidden under these three kinds of waves with a single metasurface cloak. PMID:26822429

  12. A metasurface carpet cloak for electromagnetic, acoustic and water waves

    NASA Astrophysics Data System (ADS)

    Yang, Yihao; Wang, Huaping; Yu, Faxin; Xu, Zhiwei; Chen, Hongsheng

    2016-01-01

    We propose a single low-profile skin metasurface carpet cloak to hide objects with arbitrary shape and size under three different waves, i.e., electromagnetic (EM) waves, acoustic waves and water waves. We first present a metasurface which can control the local reflection phase of these three waves. By taking advantage of this metasurface, we then design a metasurface carpet cloak which provides an additional phase to compensate the phase distortion introduced by a bump, thus restoring the reflection waves as if the incident waves impinge onto a flat mirror. The finite element simulation results demonstrate that an object can be hidden under these three kinds of waves with a single metasurface cloak.

  13. A metasurface carpet cloak for electromagnetic, acoustic and water waves

    PubMed Central

    Yang, Yihao; Wang, Huaping; Yu, Faxin; Xu, Zhiwei; Chen, Hongsheng

    2016-01-01

    We propose a single low-profile skin metasurface carpet cloak to hide objects with arbitrary shape and size under three different waves, i.e., electromagnetic (EM) waves, acoustic waves and water waves. We first present a metasurface which can control the local reflection phase of these three waves. By taking advantage of this metasurface, we then design a metasurface carpet cloak which provides an additional phase to compensate the phase distortion introduced by a bump, thus restoring the reflection waves as if the incident waves impinge onto a flat mirror. The finite element simulation results demonstrate that an object can be hidden under these three kinds of waves with a single metasurface cloak. PMID:26822429

  14. Influence of Rewetting Behavior on the Distortion of Bearing Races

    NASA Astrophysics Data System (ADS)

    Lübben, Thomas; Frerichs, Friedhelm

    2013-08-01

    Immersion quenching in evaporable fluids like oil, polymer solutions, or water is a widely used technique in heat treatment shops because this technique provides higher heat transfer coefficients than the most alternative gas quenching techniques. The disadvantages of immersion quenching in evaporating fluids are the complex heat transfer mechanisms which consist of the three phases, film boiling, nucleate boiling, and convection. Especially the transition from film to nucleate boiling—the rewetting of the sample surface—is a complex process which leads to a strong position dependence of the heat transfer coefficient of the cooled work pieces. In particular, immersion quenching of thin-walled rings can result in large changes of ovality with comparable high scattering. To understand these results, two series of experiments were performed. Rings were quenched in oil in a special quenching tank and the rewetting behavior was documented. Furthermore, bearing races were quenched in a standard tank. Before and after heat treatment, these rings were measured by a coordinate measuring system and the distortion was determined. The investigations have clearly shown that the vapor film can have an important influence on distortion generation during oil quenching. The resulting distortion can principally be explained by the observed rewetting behavior.

  15. Cartographic distortions make dielectric spacetime analog models imperfect mimickers

    NASA Astrophysics Data System (ADS)

    Fathi, Mohsen; Thompson, Robert T.

    2016-06-01

    It is commonly assumed that if the optical metric of a dielectric medium is identical to the metric of a vacuum space-time then light propagation through the dielectric mimics light propagation in the vacuum. However, just as the curved surface of the Earth cannot be mapped into a flat plane without distortion of some surface features, so too is it impossible to project the behavior of light from the vacuum into a dielectric analog residing in Minkowski space-time without introducing distortions. We study the covariance properties of dielectric analog space-times and the kinematics of a congruence of light in the analog, and show how certain features can be faithfully emulated in the analog depending on the choice of projection, but that not all features can be simultaneously emulated without distortion. These findings indicate conceptual weaknesses in the idea of using analog space-times as a basis for transformation optics, and we show that a certain formulation of transformation optics closely related to analog space-times resolves these issues.

  16. A proposed mechanism for rapid adaptation to spectrally distorted speech.

    PubMed

    Azadpour, Mahan; Balaban, Evan

    2015-07-01

    The mechanisms underlying perceptual adaptation to severely spectrally-distorted speech were studied by training participants to comprehend spectrally-rotated speech, which is obtained by inverting the speech spectrum. Spectral-rotation produces severe distortion confined to the spectral domain while preserving temporal trajectories. During five 1-hour training sessions, pairs of participants attempted to extract spoken messages from the spectrally-rotated speech of their training partner. Data on training-induced changes in comprehension of spectrally-rotated sentences and identification/discrimination of spectrally-rotated phonemes were used to evaluate the plausibility of three different classes of underlying perceptual mechanisms: (1) phonemic remapping (the formation of new phonemic categories that specifically incorporate spectrally-rotated acoustic information); (2) experience-dependent generation of a perceptual "inverse-transform" that compensates for spectral-rotation; and (3) changes in cue weighting (the identification of sets of acoustic cues least affected by spectral-rotation, followed by a rapid shift in perceptual emphasis to favour those cues, combined with the recruitment of the same type of "perceptual filling-in" mechanisms used to disambiguate speech-in-noise). Results exclusively support the third mechanism, which is the only one predicting that learning would specifically target temporally-dynamic cues that were transmitting phonetic information most stably in spite of spectral-distortion. No support was found for phonemic remapping or for inverse-transform generation. PMID:26233005

  17. Compressed image quality metric based on perceptually weighted distortion.

    PubMed

    Hu, Sudeng; Jin, Lina; Wang, Hanli; Zhang, Yun; Kwong, Sam; Kuo, C-C Jay

    2015-12-01

    Objective quality assessment for compressed images is critical to various image compression systems that are essential in image delivery and storage. Although the mean squared error (MSE) is computationally simple, it may not be accurate to reflect the perceptual quality of compressed images, which is also affected dramatically by the characteristics of human visual system (HVS), such as masking effect. In this paper, an image quality metric (IQM) is proposed based on perceptually weighted distortion in terms of the MSE. To capture the characteristics of HVS, a randomness map is proposed to measure the masking effect and a preprocessing scheme is proposed to simulate the processing that occurs in the initial part of HVS. Since the masking effect highly depends on the structural randomness, the prediction error from neighborhood with a statistical model is used to measure the significance of masking. Meanwhile, the imperceptible signal with high frequency could be removed by preprocessing with low-pass filters. The relation is investigated between the distortions before and after masking effect, and a masking modulation model is proposed to simulate the masking effect after preprocessing. The performance of the proposed IQM is validated on six image databases with various compression distortions. The experimental results show that the proposed algorithm outperforms other benchmark IQMs. PMID:26415170

  18. An Experimental Study of Fan Inflow Distortion Tone Noise

    NASA Technical Reports Server (NTRS)

    Koch, L. Danielle

    2010-01-01

    The tone noise generated when a fan ingests circumferentially distorted flow was studied by an experiment conducted with the Advanced Noise Control Fan at the NASA Glenn Research Center. The inflow was distorted by inserting cylindrical rods radially into the duct. The rods were arranged in circumferentially irregular patterns in three of the five configurations tested. Rods were held in place using a mounting ring with 30 equally spaced holes placed at an axial location one rotor chordlength upstream of the fan. Acoustic pressure was measured in the inlet and exhaust duct of the fan using the Rotating Rake fan tone measurement system. Sound power levels, calculated from the measured data, were plotted as a function of circumferential mode. An analytic description of the unsteady pressure distribution at the interaction plane between the stationary rods and the fan rotor is presented in a form suitable for representing the circumferentially irregularly placed rods. Terms in the analytical description for sound power were proven to be useful in determining the dominant circumferential modes measured in the experiment and the differences in mode power level between the configurations tested. Insight gained through this work will be useful in the development of tools to compute fan inflow distortion tone noise.

  19. Rectification of terrain induced distortions in radar imagery

    NASA Technical Reports Server (NTRS)

    Kwok, Ronald; Curlander, John C.; Pang, Shirley S.

    1987-01-01

    This paper describes a technique to generate geocoded synthetic aperture radar (SAR) imagery corrected for terrain induced geometric distortions. This algorithm transforms the raw slant range image, generated by the signal processor, into a map registered product, resampled to either Universal Transverse Mercator (UTM) or Polar Stereographic projections, and corrected for foreshortening. The technique utilizes the space platform trajectory information in conjunction with a digital elevation map (DEM) of the target area to generate an ortho-radar map with near-autonomous operation. The current procedure requires only two to three tie-points to compensate for the platform position uncertainty that results in translational error between the image and the DEM. This approach is unique in that it does not require generation of a simulated radar image from the DEM or a grid of tie-points to characterize the image-to-map distortions. Rather, it models the inherent distortions based on knowledge of the radar data collection characteristics, the signal Doppler parameters, and the local terrain height to automatically predict the registration transformation. This algorithm has been implemented on a minicomputer system equipped with an array processor and a large random-access memory to optimize the throughput.

  20. Damage to insula abolishes cognitive distortions during simulated gambling

    PubMed Central

    Clark, Luke; Studer, Bettina; Bruss, Joel; Tranel, Daniel; Bechara, Antoine

    2014-01-01

    Gambling is a naturalistic example of risky decision-making. During gambling, players typically display an array of cognitive biases that create a distorted expectancy of winning. This study investigated brain regions underpinning gambling-related cognitive distortions, contrasting patients with focal brain lesions to the ventromedial prefrontal cortex (vmPFC), insula, or amygdala (“target patients”) against healthy comparison participants and lesion comparison patients (i.e., with lesions that spare the target regions). A slot machine task was used to deliver near-miss outcomes (i.e., nonwins that fall spatially close to a jackpot), and a roulette game was used to examine the gambler’s fallacy (color decisions following outcome runs). Comparison groups displayed a heightened motivation to play following near misses (compared with full misses), and manifested a classic gambler’s fallacy effect. Both effects were also observed in patients with vmPFC and amygdala damage, but were absent in patients with insula damage. Our findings indicate that the distorted cognitive processing of near-miss outcomes and event sequences may be ordinarily supported by the recruitment of the insula. Interventions to reduce insula reactivity could show promise in the treatment of disordered gambling. PMID:24711387

  1. Two Dimensional Intermodulation Distortion Scanning of Superconducting Filter Resonators

    NASA Astrophysics Data System (ADS)

    Bischak, Michael; Remillard, Stephen

    2015-03-01

    Nonlinear superconducting conductivity produces distortion that has usually been measured globally across the entire sample. In order to fully understand the origin of non linearity, local methods must be used to examine specific points in the sample. The nonlinear Ohm's law, V =IZ(I) includes the current dependence in the impedance. The method in this work raster scans a magnetic loop probe across a sample. In order to address limited resolution, we reduced the size of the magnetic loop probe. Using the electromagnetic field solver, sonnet, two dimensional current simulations of superconducting microwave filters composed of Tl2Ba2CaCu2O8 or of YBa2Cu3O7 reveal microwave current which is bunched up at the corners and sides of the sample. Two dimensional images of third order intermodulation distortion made with the magnetic probe at the same corners and edges reveal elevated distortion in the same places. Using the magnetic probe, third order intermodulation was seen to come from the same corners and edges where the current is bunched. This research was funded by the National Science Foundation under grant number DMR-1206149.

  2. Automatic estimation and compensation of geometric distortions in video copies

    NASA Astrophysics Data System (ADS)

    Chupeau, B.; Massoudi, A.; Lefèbvre, F.

    2007-01-01

    The proliferation of pirate copies of feature films on peer-to-peer networks arouses a great interest to countermeasures such as the insertion of (invisible) forensic marks in projected movies, to deter their illegal capture. The registration of pirate copies with the original content is however a prerequisite to the recovery of such embedded messages, as severe geometric distortions often occur in illegally camcorded contents. After a brief state-of-the-art in image registration, the paper details an algorithm for video registration, focusing on the compensation of geometric distortions. Control points are automatically extracted in original and copy pictures, followed by pre- and post-matching filtering steps to discard not relevant control points and erroneous matched pairs of control points respectively. This enables the accurate numerical estimation of an 8-parameter homographic distortion model, used to register the copy frames with the original reference grid. Such an image registration algorithm is inserted into a general video registration scheme. Results are presented on both natural and synthetic test material.

  3. Calculations of inlet distortion induced compressor flow field instability

    NASA Technical Reports Server (NTRS)

    Chue, R.; Greitzer, E. M.; Tan, C. S.; Hynes, T. P.; Longley, J. P.

    1989-01-01

    Calculations of the onset of flow instability are carried out for low-speed multistage axial compressors operating with asymmetric inlet flow. The modeling of the fluid dynamic interaction between the spoiled and unspoiled sectors of the compressor is the most important feature of the calculation procedure. The calculations show that annulus average slope of the compressor pressure rise characteristic equal to zero is a useful approximate stability criterion for situations where the dynamics of the compressor flow field do not couple strongly to the compression system or the structure of the imposed distortion is not similar to that of the eigenmodes of the flow in the compressor annulus. This criterion is employed to investigate the relationship between the present model and the 'parallel compressor' model. Calculations are also presented for cases when compressor and compressor system are closely coupled, and situations in which the compressor is subjected to a rotating distortion. These first-of-a-kind computations, and the accompanying description of the physical mechanisms, show that the stability of the flow in the compressor can be adversely affected if the temporal or spatial structure of the distortion is such that resonant type responses can be evoked either from the compressor or from compressor/compression system interactions.

  4. Applying image quality in cell phone cameras: lens distortion

    NASA Astrophysics Data System (ADS)

    Baxter, Donald; Goma, Sergio R.; Aleksic, Milivoje

    2009-01-01

    This paper describes the framework used in one of the pilot studies run under the I3A CPIQ initiative to quantify overall image quality in cell-phone cameras. The framework is based on a multivariate formalism which tries to predict overall image quality from individual image quality attributes and was validated in a CPIQ pilot program. The pilot study focuses on image quality distortions introduced in the optical path of a cell-phone camera, which may or may not be corrected in the image processing path. The assumption is that the captured image used is JPEG compressed and the cellphone camera is set to 'auto' mode. As the used framework requires that the individual attributes to be relatively perceptually orthogonal, in the pilot study, the attributes used are lens geometric distortion (LGD) and lateral chromatic aberrations (LCA). The goal of this paper is to present the framework of this pilot project starting with the definition of the individual attributes, up to their quantification in JNDs of quality, a requirement of the multivariate formalism, therefore both objective and subjective evaluations were used. A major distinction in the objective part from the 'DSC imaging world' is that the LCA/LGD distortions found in cell-phone cameras, rarely exhibit radial behavior, therefore a radial mapping/modeling cannot be used in this case.

  5. Emittance and beam size distortion due to linear coupling

    SciTech Connect

    Parzen, G.

    1993-01-01

    At injection, the presence of linear coupling may result in an increased beam emittance and in increased beam dimensions. Results for the emittance in the presence of linear coupling will be found. These results for the emittance distortion show that the harmonics of the skew quadrupole field close to [nu][sub x] + [nu][sub y] are the important harmonics. Results will be found for the important driving terms for the emittance distortion. It will be shown that if these driving terms are corrected, then the total emittance is unchanged, [var epsilon][sub x] + [var epsilon][sub y] = [var epsilon][sub 1] + [var epsilon][sub 2]. Also, the increase in the beam dimensions will be limited to a factor which is less than 1.414. If the correction is good enough, see below for details, one can achieve [var epsilon][sub 1] = [var epsilon][sub x], [var epsilon][sub 2] = [var epsilon] where [var epsilon][sub 1], [var epsilon][sub 2] are the emittances in the presence of coupling, and the beam dimensions are unchanged. Global correction of the emittance and beam size distortion appears possible.

  6. Emittance and beam size distortion due to linear coupling

    SciTech Connect

    Parzen, G.

    1993-06-01

    At injection, the presence of linear coupling may result in an increased beam emittance and in increased beam dimensions. Results for the emittance in the presence of linear coupling will be found. These results for the emittance distortion show that the harmonics of the skew quadrupole field close to {nu}{sub x} + {nu}{sub y} are the important harmonics. Results will be found for the important driving terms for the emittance distortion. It will be shown that if these driving terms are corrected, then the total emittance is unchanged, {var_epsilon}{sub x} + {var_epsilon}{sub y} = {var_epsilon}{sub 1} + {var_epsilon}{sub 2}. Also, the increase in the beam dimensions will be limited to a factor which is less than 1.414. If the correction is good enough, see below for details, one can achieve {var_epsilon}{sub 1} = {var_epsilon}{sub x}, {var_epsilon}{sub 2} = {var_epsilon} where {var_epsilon}{sub 1}, {var_epsilon}{sub 2} are the emittances in the presence of coupling, and the beam dimensions are unchanged. Global correction of the emittance and beam size distortion appears possible.

  7. Distortion of homogeneous turbulence by axisymmetric strain and dilatation

    NASA Technical Reports Server (NTRS)

    Lee, Moon Joo

    1989-01-01

    Rapid distortion theory is applied to study distortion of homogeneous turbulence subject to two different axisymmetric strain modes: the axisymmetric contraction (AC, nozzle-type flow), and the axisymmetric expansion (AE, diffuser-type flow). The paper explores the differences in effects of the two axisymmetric strain modes on the anisotropy of correlations and structures of turbulence; examines the effect of dilatation on the distortion of turbulence; and provides a theoretical background for turbulence model development. It is found that velocity and vorticity fluctuations are enhanced more efficiently by contraction than by expansion; contraction produces much higher anisotropy in velocity and vorticity than expansion; root-mean-square pressure is slightly reduced during contraction, whereas it increases rapidly during expansion; and vortical structures of rodlike shape develop in a contraction flow, while disklike structures develop in an expansion flow. A simple model that reflects the dependence of turbulence evolution on structural parameters such as the Reynolds-stress anisotropy and total strain is proposed, and is shown to outperform all other models for all cases examined, regardless of the mean strain rate.

  8. A mesoscale gravity wave event observed during CCOPE. II - Interactions between mesoscale convective systems and the antecedent waves. [Cooperative Convection Precipitation Experiment

    NASA Technical Reports Server (NTRS)

    Koch, Steven E.; Golus, Robert E.; Dorian, Paul B.

    1988-01-01

    The interactions between preexisting gravity waves and convective systems were investigated using data obtained by the Cooperative Convection Precipitation Experiment observational network in Montana on July 11-12, 1981. The results indicate that strong convection substantially affects gravity waves locally by augmenting the wave amplitude, reducing its wavelength, distorting the wave shape, altering the wave phase velocity, and greatly weakening the in-phase covariance between the perturbation wind and pressure fields. These convective effects upon gravity waves are explained in terms of hydrostatic and nonhydrostatic pressure forces and gust front processes associated with thunderstorms.

  9. Elimination of threshold-induced distortion in the power spectrum of narrow-band laser speckle

    NASA Astrophysics Data System (ADS)

    Ducharme, Alfred D.; Boreman, Glenn D.; Yang, Sidney S.

    1995-10-01

    The distortion in the power spectrum of narrow-band laser speckle that results from irradiance thresholding is quantified. A method for compensation of this distortion is presented. An optimal threshold level is presented that simplifies the compensation method.

  10. Automatic estimation and correction of anisotropic magnification distortion in electron microscopes.

    PubMed

    Grant, Timothy; Grigorieff, Nikolaus

    2015-11-01

    We demonstrate a significant anisotropic magnification distortion, found on an FEI Titan Krios microscope and affecting magnifications commonly used for data acquisition on a Gatan K2 Summit detector. We describe a program (mag_distortion_estimate) to automatically estimate anisotropic magnification distortion from a set of images of a standard gold shadowed diffraction grating. We also describe a program (mag_distortion_correct) to correct for the estimated distortion in collected images. We demonstrate that the distortion present on the Titan Krios microscope limits the resolution of a set of rotavirus VP6 images to ∼7 Å, which increases to ∼3 Å following estimation and correction of the distortion. We also use a 70S ribosome sample to demonstrate that in addition to affecting resolution, magnification distortion can also interfere with the classification of heterogeneous data. PMID:26278979

  11. Nonlinear propagation and control of acoustic waves in phononic superlattices

    NASA Astrophysics Data System (ADS)

    Jiménez, Noé; Mehrem, Ahmed; Picó, Rubén; García-Raffi, Lluís M.; Sánchez-Morcillo, Víctor J.

    2016-05-01

    The propagation of intense acoustic waves in a one-dimensional phononic crystal is studied. The medium consists in a structured fluid, formed by a periodic array of fluid layers with alternating linear acoustic properties and quadratic nonlinearity coefficient. The spacing between layers is of the order of the wavelength, therefore Bragg effects such as band gaps appear. We show that the interplay between strong dispersion and nonlinearity leads to new scenarios of wave propagation. The classical waveform distortion process typical of intense acoustic waves in homogeneous media can be strongly altered when nonlinearly generated harmonics lie inside or close to band gaps. This allows the possibility of engineer a medium in order to get a particular waveform. Examples of this include the design of media with effective (e.g., cubic) nonlinearities, or extremely linear media (where distortion can be canceled). The presented ideas open a way towards the control of acoustic wave propagation in nonlinear regime. xml:lang="fr"

  12. Distortion cancellation performance of miniature delay filters for feed-forward linear power amplifiers.

    PubMed

    Roy, Manas K

    2002-11-01

    The technique of feed-forward amplitude control has been widely used in the linearization of power amplifiers for wireless communication systems. In this technique, an error signal due to third order intermodulation distortion (IMD) is extracted, amplified, and used to correct the delayed main line distorted signal. For example, a miniature prototype base station for the Global System for Mobile Communications/Code Division Multiple Access (GSM/CDMA) cellular system uses feed-forward amplifiers with bulky and expensive coaxial cables, about 20 feet in length, to provide about 25 ns of delay. This paper shows alternate space-saving approaches of achieving these delays using three different types of delay filters: electromagnetic interdigital/lumped (<2.5"), ceramic (<1.8"), and ladder-type surface acoustic wave (SAW) (0.15"). The delay lines introduce phase and amplitude imbalance and delay mismatch in the linearization loop due to fabrication tolerances. These adversely affect the IMD cancellation. Using an RF system simulation tool, this paper critically compares the IMD cancellation performance achieved using the three technologies. Simulation results show that the optimization of delay mismatch can achieve the desired cancellation more easily than other parameters. It is shown that, if the critical system parameter (phase deviation from linearity), is maintained at <2.5 degrees peak-to-peak over a 20 MHz bandwidth in the frequency range 855 MHz to 875 MHz, one can achieve 25 dB of IMD cancellation performance. This paper concludes with the suggestion of a set of realistic specifications for a miniature delay filter for the low power loop of the feed-forward amplifier. PMID:12484482

  13. Cognitive Distortions as Mediators between Life Stress and Depression in Adolescents.

    ERIC Educational Resources Information Center

    Deal, Saundra L.; Williams, John E.

    1988-01-01

    Administered measures of cognitive distortion, life stress, and depressive tendencies to 103 high school students. Findings were consistent with predictions that measures of cognitive distortion would be better predictors of depressive tendencies than were measures of life stress; cognitive distortions would affect perceived stressfulness of life…

  14. Body Image Dissatisfaction and Distortion, Steroid Use, and Sex Differences in College Age Bodybuilders.

    ERIC Educational Resources Information Center

    Peters, Mark Anthony; Phelps, LeAddelle

    2001-01-01

    Compares college age bodybuilders by sex and steroid intake on two variables: body image dissatisfaction and body image distortion. Results reveal only a significant effect for gender on body distortion. No steroid-use differences were apparent for either body image dissatisfaction or body image distortion. Analyses indicate that female…

  15. Feature maps driven no-reference image quality prediction of authentically distorted images

    NASA Astrophysics Data System (ADS)

    Ghadiyaram, Deepti; Bovik, Alan C.

    2015-03-01

    Current blind image quality prediction models rely on benchmark databases comprised of singly and synthetically distorted images, thereby learning image features that are only adequate to predict human perceived visual quality on such inauthentic distortions. However, real world images often contain complex mixtures of multiple distortions. Rather than a) discounting the effect of these mixtures of distortions on an image's perceptual quality and considering only the dominant distortion or b) using features that are only proven to be efficient for singly distorted images, we deeply study the natural scene statistics of authentically distorted images, in different color spaces and transform domains. We propose a feature-maps-driven statistical approach which avoids any latent assumptions about the type of distortion(s) contained in an image, and focuses instead on modeling the remarkable consistencies in the scene statistics of real world images in the absence of distortions. We design a deep belief network that takes model-based statistical image features derived from a very large database of authentically distorted images as input and discovers good feature representations by generalizing over different distortion types, mixtures, and severities, which are later used to learn a regressor for quality prediction. We demonstrate the remarkable competence of our features for improving automatic perceptual quality prediction on a benchmark database and on the newly designed LIVE Authentic Image Quality Challenge Database and show that our approach of combining robust statistical features and the deep belief network dramatically outperforms the state-of-the-art.

  16. Measurements of inlet flow distortions in an axial flow fan (6 and 9 blade rotor)

    NASA Technical Reports Server (NTRS)

    Barr, L. C.

    1978-01-01

    A large quantity of experimental data on inlet flow distortions in an axial flow fan were obtained. The purpose of the study was to determine the effects of design and operating variables and the type of distortion on the response of an axial flow turbomachinery rotor. Included are background information and overall trends observed in distortion attenuation and unsteady total pressure losses.

  17. Experimental evaluation of the effect of inlet distortion on compressor blade vibrations

    NASA Technical Reports Server (NTRS)

    Lubomski, J. F.

    1979-01-01

    Compressor rotor strain gage data from an engine test conducted with an inlet screen distortion were reduced and analyzed. These data are compared to data obtained from the same engine without inlet pressure distortion to determine the net effect of the distortion on the vibratory response of the compressor blades. The results obtained are presented.

  18. Quartz structure transformation under a shock wave

    NASA Astrophysics Data System (ADS)

    Vettegren', V. I.; Kuksenko, V. S.; Shcherbakov, I. P.; Mamalimov, R. I.

    2015-12-01

    The structure of a fragment formed after quartz single-crystal fracture under a shock wave has been studied using the Fourier transform infrared spectroscopy (FTIR) method. The wave is initiated by electrical breakdown of air in a hole within the single crystal. It has been found that a layer ~0.15 μm thick consisting of "diaplectic glass," i.e., quartz with a strongly distorted lattice, is formed on the fragment surface. A layer 2 μm thick with a compressed quartz lattice is located under it.

  19. Ultrasonic inspection apparatus and method using a focused wave device

    SciTech Connect

    Gieske, John H.; Roach, Dennis P.; Walkington, Phillip D.

    2001-01-01

    An ultrasonic pulse echo inspection apparatus and method for detecting structural failures. A focus lens is coupled to the transducer to focus the ultrasonic signal on an area to be inspected and a stop is placed in the focus lens to block selected ultrasonic waves. Other waves are not blocked and are transmitted through the structure to arrive at interfaces therein concurrently to produce an echo response with significantly less distortion.

  20. Minimizing distortion in truss structures via Tabu search

    NASA Technical Reports Server (NTRS)

    Kincaid, Rex K.

    1990-01-01

    The shape control of large flexible space structures is of great interest to structural designers. A related problem is to seek ways to minimize the need for active controls by careful design and construction of the space structure. A tetrahedral truss structure that is used to support a precision segmented reflector or antenna surface is considered. The structure has a hexagonal platform and is characterized by the number of rings of members in the truss. For simplicity it is assumed that a flat truss geometry exists. Hence, all structural members and ball joints are required to have the same nominal length and diameter, respectively. Inaccuracies in the length of member or diameters of joints may produce unacceptable levels of surface distortion and internal forces. In the case of a truss structure supporting an antenna, surface distortions may cause unacceptable gain loss or pointing errors. The focus is solely on surface distortion, however, internal forces may be treated in a similar manner. To test the Tabu search code for DSQRMS the appropriate influence matrices are used for a flat, two-ring tetrahedral reflector truss generated by Green and Haftka (1989). In this example there are 102 members (NMEMB) and 31 ball joints (NJOINT) of the same nominal length, respectively. Hence, all the members may be interchanged and all the joints may be interchanged. In addition, 19 positions on the surface of the truss (NNODES) were used to measure error influences. After a variety of experiments a set of good parameters was choosen for Tabu search. The sample size at each iteration is 10*NMEMB and the short term memory size is 40. In addition four pruning rules were used to accelerate the search..

  1. Distortion effects in primary calibration of low-frequency accelerometers

    NASA Astrophysics Data System (ADS)

    Scott, D. A.; Dickinson, L. P.

    2014-06-01

    According to ISO 16063-11 (1999), at frequencies below 1600 Hz primary calibration of accelerometers may employ two methods: fringe counting or sine approximation. During a recent intercomparison (APMP.AUV.V-S1) small but systematic differences were found between the results obtained by using these two methods, and by the use of different amplifier modes to drive the shaker at frequencies between 0.5 Hz and 20 Hz. The influences of distortion and noise on the two methods are explored. The results and a discussion of the differences are presented in this paper.

  2. Genome sequence of vanilla distortion mosaic virus infecting Coriandrum sativum.

    PubMed

    Adams, I P; Rai, S; Deka, M; Harju, V; Hodges, T; Hayward, G; Skelton, A; Fox, A; Boonham, N

    2014-12-01

    The 9573-nucleotide genome of a potyvirus was sequenced from a Coriandrum sativum plant from India with viral symptoms. On analysis, this virus was shown to have greater than 85 % nucleotide sequence identity to vanilla distortion mosaic virus (VDMV). Analysis of the putative coat protein sequence confirmed that this virus was in fact VDMV, with greater than 91 % amino acid sequence identity. The genome appears to encode a 3083-amino-acid polyprotein potentially cleaved into the 10 mature proteins expected in potyviruses. Phylogenetic analysis confirmed that VDMV is a distinct but ungrouped member of the genus Potyvirus. PMID:25252813

  3. Optical distortions in electron/positron storage rings

    SciTech Connect

    Brown, K.L.; Donald, M.; Servranckx, R.

    1983-01-01

    We have studied the optical distortions in the PEP electron/positron storage ring for various optical configurations using the computer programs DIMAT, HARMON, PATRICIA, and TURTLE. The results are shown graphically by tracing several thousand trajectories from one interaction region to the next using TURTLE and by tracing a few selected rays several hundred turns using the programs DIMAT and PATRICIA. The results show an interesting correlation between the calculated optical cleanliness of a particular lattice configuration and the observed operating characteristics of the machine.

  4. Wind profile estimation from point to point laser distortion data

    NASA Technical Reports Server (NTRS)

    Leland, Robert

    1989-01-01

    The author's results on the problem of using laser distortion data to estimate the wind profile along the path of the beam are presented. A new model for the dynamics of the index of refraction in a non-constant wind is developed. The model agrees qualitatively with theoretical predictions for the index of refraction statistics in linear wind shear, and is approximated by the predictions of Taylor's hypothesis in constant wind. A framework for a potential in-flight experiment is presented, and the estimation problem is discussed in a maximum likelihood context.

  5. Spacetimes with vector distortion: Inflation from generalised Weyl geometry

    NASA Astrophysics Data System (ADS)

    Beltrán Jiménez, Jose; Koivisto, Tomi S.

    2016-05-01

    Spacetime with general linear vector distortion is introduced. Thus, the torsion and the nonmetricity of the affine connection are assumed to be proportional to a vector field (and not its derivatives). The resulting two-parameter family of non-Riemannian geometries generalises the conformal Weyl geometry and some other interesting special cases. Taking into account the leading nonlinear correction to the Einstein-Hilbert action results uniquely in the one-parameter extension of the Starobinsky inflation known as the alpha-attractor. The most general quadratic curvature action introduces, in addition to the canonical vector kinetic term, novel ghost-free vector-tensor interactions.

  6. Pathophysiological distortions in time perception and timed performance

    PubMed Central

    Allman, Melissa J.

    2012-01-01

    Distortions in time perception and timed performance are presented by a number of different neurological and psychiatric conditions (e.g. Parkinson's disease, schizophrenia, attention deficit hyperactivity disorder and autism). As a consequence, the primary focus of this review is on factors that define or produce systematic changes in the attention, clock, memory and decision stages of temporal processing as originally defined by Scalar Expectancy Theory. These findings are used to evaluate the Striatal Beat Frequency Theory, which is a neurobiological model of interval timing based upon the coincidence detection of oscillatory processes in corticostriatal circuits that can be mapped onto the stages of information processing proposed by Scalar Timing Theory. PMID:21921020

  7. One dimensional wavefront distortion sensor comprising a lens array system

    DOEpatents

    Neal, D.R.; Michie, R.B.

    1996-02-20

    A 1-dimensional sensor for measuring wavefront distortion of a light beam as a function of time and spatial position includes a lens system which incorporates a linear array of lenses, and a detector system which incorporates a linear array of light detectors positioned from the lens system so that light passing through any of the lenses is focused on at least one of the light detectors. The 1-dimensional sensor determines the slope of the wavefront by location of the detectors illuminated by the light. The 1 dimensional sensor has much greater bandwidth that 2 dimensional systems. 8 figs.

  8. One dimensional wavefront distortion sensor comprising a lens array system

    DOEpatents

    Neal, Daniel R.; Michie, Robert B.

    1996-01-01

    A 1-dimensional sensor for measuring wavefront distortion of a light beam as a function of time and spatial position includes a lens system which incorporates a linear array of lenses, and a detector system which incorporates a linear array of light detectors positioned from the lens system so that light passing through any of the lenses is focused on at least one of the light detectors. The 1-dimensional sensor determines the slope of the wavefront by location of the detectors illuminated by the light. The 1 dimensional sensor has much greater bandwidth that 2 dimensional systems.

  9. Luminosity Optimization With Offset, Crossing Angle, and Distortion

    SciTech Connect

    Wu, Juhao; Raubenheimer, T.O.; /SLAC

    2005-06-15

    In a linear collider, sources of beam jitter due to kicker noise, quadrupole vibration and long-range transverse wakefields will lead to beam offsets and tilts at the Intersection Point (IP). In addition, sources of emittance dilution such as short-range transverse wakefields or dispersive errors will lead to internal beam distortions. When the IP disruption parameter is large, these beam imperfections will be amplified by a single bunch kink instability which will lead to luminosity loss. In this paper, we study the luminosity loss and then the optimization required to partially cancel the luminosity loss both analytically and with direct simulation.

  10. Advanced distortion-invariant minimum average correlation energy (MACE) filters.

    PubMed

    Casasent, D; Ravichandran, G

    1992-03-10

    The original minimum average correlation energy (MACE) filter is addressed by using a new database (strategic relocatable objects, missile launchers) and including noise performance, depression angle, and resolution effects on the number of training set images that are required. Major attention is given to our new MACE filter algorithms for distortion-invariant pattern recognition: shifted-MACE filters (to suppress large false correlation peaks), minimum variance-MACE filters (for improved noise performance), multiple symbolic encoded filters (to reduce the effect of false correlation peaks), and Gaussian-MACE filters (to improve noise performance and intraclass recognition and reduce the training set size). PMID:20720728

  11. Advanced distortion-invariant minimum average correlation energy (MACE) filters

    NASA Astrophysics Data System (ADS)

    Casasent, David; Ravichandran, Gopalan

    1992-03-01

    The original minimum average correlation energy (MACE) filter is addressed by using a new database (strategic relocatable objects and missile launchers) and including noise performance, depression angle, and resolution effects on the number of training set images that are required. Major attention is given to new MACE filter algorithms for distortion-invariant pattern recognition: shifted-MACE filters to suppress large false correlation peaks, minimum variance-MACE filters for improved noise performance, multiple symbolic encoded filters to reduce the effect of false correlation peaks, and Gaussian-MACE filters to improve noise performance and intraclass recognition and reduce the training set size.

  12. Probing correlations of early magnetic fields using μ-distortion

    SciTech Connect

    Ganc, Jonathan; Sloth, Martin S. E-mail: sloth@cp3.dias.sdu.dk

    2014-08-01

    The damping of a non-uniform magnetic field between the redshifts of about 10{sup 4} and 10{sup 6} injects energy into the photon-baryon plasma and causes the CMB to deviate from a perfect blackbody spectrum, producing a so-called μ-distortion. We can calculate the correlation (μ T) of this distortion with the temperature anisotropy T of the CMB to search for a correlation ( B{sup 2}ζ) between the magnetic field B and the curvature perturbation ζ; knowing the ( B{sup 2}ζ) correlation would help us distinguish between different models of magnetogenesis. Since the perturbations which produce the μ-distortion will be much smaller scale than the relevant density perturbations, the observation of this correlation is sensitive to the squeezed limit of ( B{sup 2}ζ), which is naturally parameterized by b{sub NL} (a parameter defined analogously to f{sub NL}). We find that a PIXIE-like CMB experiments has a signal to noise S/N≈ 1.0 × b{sub NL} ( B-tilde {sub μ}/10nG){sup 2}, where B-tilde {sub μ} is the magnetic field's strength on μ-distortion scales normalized to today's redshift; thus, a 10 nG field would be detectable with b{sub NL}=O(1). However, if the field is of inflationary origin, we generically expect it to be accompanied by a curvature bispectrum (ζ{sup 3}) induced by the magnetic field. For sufficiently small magnetic fields, the signal ( B{sup 2} ζ) will dominate, but for B-tilde {sub μ}∼> 1 nG, one would have to consider the specifics of the inflationary magnetogenesis model. We also discuss the potential post-magnetogenesis sources of a ( B{sup 2}ζ) correlation and explain why there will be no contribution from the evolution of the magnetic field in response to the curvature perturbation.

  13. Effect of rotor meridional velocity ratio on response to inlet radial and circumferential distortion

    NASA Technical Reports Server (NTRS)

    Sanger, N. L.

    1979-01-01

    Three single transonic fan stages, each having a different meridional velocity ratio across its rotor, were tested with two magnitudes of tip radial distortion and with a 90 deg circumferential distortion imposed on the inlet flow. The rotor with the lowest meridional velocity ratio (less than 0.9 at the tip) demonstrated the least degradation of performance due to these distortions. Loss and deviation angle data (as needed for performance prediction with radial distortion) calculated along actual streamlines for radially distorted flow and correlated against diffusion factor, showed consistent agreement with data calculated along design streamlines for undistorted flow.

  14. Effect of spatial inlet temperature and pressure distortion on turbofan engine stability

    NASA Technical Reports Server (NTRS)

    Mehalic, Charles M.

    1988-01-01

    The effects of circumferential and radial inlet temperature distortion, circumferential pressure distortion, and combined temperature and pressure distortion on the stability of an advanced turbofan engine were investigated experimentally at simulated altitude conditions. With circumferential and radial inlet temperature distortion, a flow instability generated by the fan operating near stall caused the high-pressure compressor to surge at, or near, the same time as the fan. The effect of combined distortion was dependent on the relative location of the high-temperature and low-pressure regions; high-pressure compressor stalls occurred when the regions coincided, and fan stalls occurred with the regions separated.

  15. Circumferential distortion modeling of the TF30-P-3 compression system

    NASA Technical Reports Server (NTRS)

    Mazzawy, R. S.; Banks, G. A.

    1977-01-01

    Circumferential inlet pressure and temperature distortion testing of the TF30 P-3 turbofan engine was conducted. The compressor system at the test conditions run was modelled according to a multiple segment parallel compressor model. Aspects of engine operation and distortion configuration modelled include the effects of compressor bleeds, relative pressure-temperature distortion alignment and circumferential distortion extent. Model predictions for limiting distortion amplitudes and flow distributions within the compression system were compared with test results in order to evaluate predicted trends. Relatively good agreement was obtained. The model also identified the low pressure compressor as the stall-initiating component, which was in agreement with the data.

  16. Spline function approximation techniques for image geometric distortion representation. [for registration of multitemporal remote sensor imagery

    NASA Technical Reports Server (NTRS)

    Anuta, P. E.

    1975-01-01

    Least squares approximation techniques were developed for use in computer aided correction of spatial image distortions for registration of multitemporal remote sensor imagery. Polynomials were first used to define image distortion over the entire two dimensional image space. Spline functions were then investigated to determine if the combination of lower order polynomials could approximate a higher order distortion with less computational difficulty. Algorithms for generating approximating functions were developed and applied to the description of image distortion in aircraft multispectral scanner imagery. Other applications of the techniques were suggested for earth resources data processing areas other than geometric distortion representation.

  17. Systematic errors in two-dimensional digital image correlation due to lens distortion

    NASA Astrophysics Data System (ADS)

    Pan, Bing; Yu, Liping; Wu, Dafang; Tang, Liqun

    2013-02-01

    Lens distortion practically presents in a real optical imaging system causing non-uniform geometric distortion in the recorded images, and gives rise to additional errors in the displacement and strain results measured by two-dimensional digital image correlation (2D-DIC). In this work, the systematic errors in the displacement and strain results measured by 2D-DIC due to lens distortion are investigated theoretically using the radial lens distortion model and experimentally through easy-to-implement rigid body, in-plane translation tests. Theoretical analysis shows that the displacement and strain errors at an interrogated image point are not only in linear proportion to the distortion coefficient of the camera lens used, but also depend on its distance relative to distortion center and its magnitude of displacement. To eliminate the systematic errors caused by lens distortion, a simple linear least-squares algorithm is proposed to estimate the distortion coefficient from the distorted displacement results of rigid body, in-plane translation tests, which can be used to correct the distorted displacement fields to obtain unbiased displacement and strain fields. Experimental results verify the correctness of the theoretical derivation and the effectiveness of the proposed lens distortion correction method.

  18. Third Wave.

    ERIC Educational Resources Information Center

    Reed, Chris

    2000-01-01

    Third Wave is a Christian charity based in Derby (England) that offers training in vocational skills, preindustrial crafts, horticultural and agricultural skills, environmental education, and woodland survival skills to disadvantaged people at city and farm locations. Third Wave employs a holistic approach to personal development in a community…

  19. Microfluidic waves.

    PubMed

    Utz, Marcel; Begley, Matthew R; Haj-Hariri, Hossein

    2011-11-21

    The propagation of pressure waves in fluidic channels with elastic covers is discussed in view of applications to flow control in microfluidic devices. A theory is presented which describes pressure waves in the fluid that are coupled to bending waves in the elastic cover. At low frequencies, the lateral bending of the cover dominates over longitudinal bending, leading to propagating, non-dispersive longitudinal pressure waves in the channel. The theory addresses effects due to both the finite viscosity and compressibility of the fluid. The coupled waves propagate without dispersion, as long as the wave length is larger than the channel width. It is shown that in channels of typical microfluidic dimensions, wave velocities in the range of a few 10 m s(-1) result if the channels are covered by films of a compliant material such as PDMS. The application of this principle to design microfluidic band pass filters based on standing waves is discussed. Characteristic frequencies in the range of a few kHz are readily achieved with quality factors above 30. PMID:21966667

  20. A New Distortion Solution for NIRC2 on the Keck II Telescope

    NASA Astrophysics Data System (ADS)

    Service, M.; Lu, J. R.; Campbell, R.; Sitarski, B. N.; Ghez, A. M.; Anderson, J.

    2016-09-01

    We present a new geometric distortion model for the narrow-field mode of the near-infrared camera (NIRC2) fed by the adaptive optics system on the W. M. Keck II telescope. The adaptive optics system and NIRC2 camera were realigned on 2015 April 13. Observations of the crowded globular cluster, M53, were obtained before and after the realignment to characterize the geometric field distortion. The distorted NIRC2 positions of M53 stars were compared with precise astrometry of this cluster from Hubble Space Telescope observations. The resulting distortion map constructed just before the realignment is consistent with the previous solution derived using data from 2007 to 2009, indicating that the distortion has been stable to ∼0.5 mas. The distortion map changed significantly after a realignment of 4.5 mas (75%) rms, and the new distortion model for post-realignment observations have a total accuracy of ∼1.1 mas.

  1. Effects of inflow distortion profiles on fan tone noise calculated using a 3-D theory

    NASA Technical Reports Server (NTRS)

    Kobayashi, H.; Groeneweg, J. F.

    1979-01-01

    Calculations of the fan tone acoustic power and modal structure generated by complex distortions in axial inflow velocity are presented. The model used treats the motor as a rotating three-dimensional cascade and calculates the acoustic field from the distortion-produced dipole distribution on the blades including noncompact source effects. Radial and circumferential distortion shapes are synthesized from Fourier-Bessel components representing individual distortion modes. The relation between individual distortion modes and the generated acoustic modes is examined for particular distortion cases. Comparisons between theoretical and experimental results for distortions produced by wakes from upstream radial rods show that the analysis is a good predictor of acoustic power dependence on disturbance strength.

  2. Thermal distortion testing of a 90-degree deployment hinge

    NASA Astrophysics Data System (ADS)

    Lininger, Lance

    2003-09-01

    Virtually all modern spacecraft have at least one (if not many) deployable items, some of which require a high degree of positional accuracy and repeatability. There are many variables that affect the deployment performance, and often the most critical and difficult variable to quantify is the affect of the thermal environment on the deployment mechanisms. Temperature changes before and after deployment can greatly affect the final deployment position and the subsequent thermal distortion of the mechanism, and it is critical to properly quantify these factors. Historically the affects of temperature change on deployment mechanisms have been evaluated via analysis due to the relative cost and difficulty in performing a test. However, during the design process of a recent Lockheed Martin deployment hinge, the engineers wanted to provide their customer with a more reliable empirical assessment. Thus, it was decided to conduct a thermal distortion and repeatability test on the hinge during the qualification phase. Testing of this nature is very rare for relatively inexpensive deployment hinges and is usually reserved for high precision, actively-latched optical hinges. Results of this testing are presented, along with lessons learned when performing the test.

  3. Flow distortion and signal loss in spiral imaging.

    PubMed

    Gatehouse, P D; Firmin, D N

    1999-05-01

    The effect of in-plane motion on the point spread function (velocity PSF) in spiral imaging is studied experimentally and derived mathematically and is shown to consist of a smoothed, trailing edge and fringes around the leading edge. The velocity PSF remains largely in phase with the static PSF, consistent with the absence of signal loss by motion-related phase shifts in central k space. However, single-shot spiral imaging gives no clear improvement in complex and turbulent flow signal uniformity compared with echo-planar imaging with early, central k-space acquisition, which requires explanation given the spiral's earlier coverage of central k space. Alternate leading-edge fringes of the spiral's velocity PSF are in antiphase to the source, and cancellation may occur when these overlap other in-phase signals. Phase variations toward peripheral k space in turbulent flow also cause distortion. It is concluded that spiral imaging may lose complex and turbulent flow signals because of complex PSF distortion. PMID:10332886

  4. Bayesian redshift-space distortions correction from galaxy redshift surveys

    NASA Astrophysics Data System (ADS)

    Kitaura, Francisco-Shu; Ata, Metin; Angulo, Raul E.; Chuang, Chia-Hsun; Rodríguez-Torres, Sergio; Monteagudo, Carlos Hernández; Prada, Francisco; Yepes, Gustavo

    2016-03-01

    We present a Bayesian reconstruction method which maps a galaxy distribution from redshift- to real-space inferring the distances of the individual galaxies. The method is based on sampling density fields assuming a lognormal prior with a likelihood modelling non-linear stochastic bias. Coherent redshift-space distortions are corrected in a Gibbs-sampling procedure by moving the galaxies from redshift- to real-space according to the peculiar motions derived from the recovered density field using linear theory. The virialized distortions are corrected by sampling candidate real-space positions along the line of sight, which are compatible with the bulk flow corrected redshift-space position adding a random dispersion term in high-density collapsed regions (defined by the eigenvalues of the Hessian). This approach presents an alternative method to estimate the distances to galaxies using the three-dimensional spatial information, and assuming isotropy. Hence the number of applications is very broad. In this work, we show the potential of this method to constrain the growth rate up to k ˜ 0.3 h Mpc-1. Furthermore it could be useful to correct for photometric redshift errors, and to obtain improved baryon acoustic oscillations (BAO) reconstructions.

  5. Peierls distortion of endohedral atoms in clathrate I

    NASA Astrophysics Data System (ADS)

    Tomono, Hidekazu; Tsumuraya, Kazuo

    2008-03-01

    The guest atom displacements in type II clathrates have been reported on experimental and theoretical points of view. The displacements are reported to be 0.6 å from the cage center of the Si28 cage to the hexagonal in the hydrogen terminated double caged Si28 cluster [1]. The distortion can be expected to occur in the type I clathrate which forms with bamboo structures in the x, y, and z directions. The guest atoms show Peiels distortion when we calculate the equilibrium distances between the two Na atoms which locate at the neighboring Si24 cages in the bamboo structure using periodic density functional calculation. The binding energy between the guest atoms is -0.10 eV/Na2. We also confirm the tendency of the Peierls distotion from the force directions of guest atoms in the double unit cells that contain four Na atoms in one dimension; We will propose the cohesion mechanism of the clathrates that the clathrates are precipitated states of the connecting endohedral atoms in the 14 group atoms. So are the hydroclathrates in which the guest molecules bind each other with chains. [1] H. Takenaka and K. Tsumuraya, Mater. Trans. 47, 63 (2006).

  6. Measuring redshift-space distortion with future SKA surveys

    NASA Astrophysics Data System (ADS)

    Raccanelli, A.; Bull, P.; Camera, S.; Blake, C.; Ferreira, P.; Maartens, R.; Santos, M.; Bull, P.; Bacon, D.; Doré, O.; Ferreira, P.; Santos, M. G.; Viel, M.; Zhao, G. B.

    2015-04-01

    The peculiar motion of galaxies can be a particularly sensitive probe of gravitational collapse. As such, it can be used to measure the dynamics of dark matter and dark energy as well the nature of the gravitational laws at play on cosmological scales. Peculiar motions manifest themselves as an overall anisotropy in the measured clustering signal as a function of the angle to the line-of-sight, known as redshift-space distortion (RSD). Limiting factors in this measurement include our ability to model non-linear galaxy motions on small scales and the complexities of galaxy bias. The anisotropy in the measured clustering pattern in redshift-space is also driven by the unknown distance factors at the redshift in question, the Alcock-Paczynski distortion. This weakens growth rate measurements, but permits an extra geometric probe of the Hubble expansion rate. In this chapter we will briefly describe the scientific background to the RSD technique, and forecast the potential of the SKA phase 1 and the SKA2 to measure the growth rate using both galaxy catalogues and intensity mapping, assessing their competitiveness with current and future optical galaxy surveys.

  7. Distortion and regulation characterization of a Mapham inverter

    NASA Technical Reports Server (NTRS)

    Sundberg, Richard C.; Brush, Andrew S.; Button, Robert M.; Patterson, Alexander G.

    1989-01-01

    Output-voltage total harmonic distortion (THD) of a 20-kHz, 6-kVA Mapham resonant inverter is characterized as a function of its switching-to-resonant frequency ratio, f(s)/f(r), using the EASY5 Engineering Analysis System. EASY5 circuit simulation results are compared with hardware test results to verify the accuracy of the simulations. The effects of load on the THD versus f(s)/f(r) is investigated for resistive, leading, and lagging power factor load impedances. The effect of the series output capacitor on the Mapham inverter output-voltage distortion and inherent load regulation is characterized under loads of various power factors and magnitudes. An optimum series capacitor value which improves the inherent load regulation to better than 3 percent is identified. The optimum series capacitor value is different from the value predicted from a modeled frequency domain analysis. An explanation is proposed which takes into account the conduction overlap in the inductor pairs during steady-state inverter operation, which decreases the effective inductance of a Mapham inverter. A fault protection and current limit method is discussed which allows the Mapham inverter to operate into a short circuit, even when the inverter resonant circuit becomes overdamped.

  8. Task 7: Endwall treatment inlet flow distortion analysis

    NASA Technical Reports Server (NTRS)

    Hall, E. J.; Topp, D. A.; Heidegger, N. J.; McNulty, G. S.; Weber, K. F.; Delaney, R. A.

    1996-01-01

    The overall objective of this study was to develop a 3-D numerical analysis for compressor casing treatment flowfields, and to perform a series of detailed numerical predictions to assess the effectiveness of various endwall treatments for enhancing the efficiency and stall margin of modern high speed fan rotors. Particular attention was given to examining the effectiveness of endwall treatments to counter the undesirable effects of inflow distortion. Calculations were performed using three different gridding techniques based on the type of casing treatment being tested and the level of complexity desired in the analysis. In each case, the casing treatment itself is modeled as a discrete object in the overall analysis, and the flow through the casing treatment is determined as part of the solution. A series of calculations were performed for both treated and untreated modern fan rotors both with and without inflow distortion. The effectiveness of the various treatments were quantified, and several physical mechanisms by which the effectiveness of endwall treatments is achieved are discussed.

  9. Assessment of camera phone distortion and implications for watermarking

    NASA Astrophysics Data System (ADS)

    Gurijala, Aparna; Reed, Alastair; Evans, Eric

    2011-02-01

    The paper presents a watermark robustness model based on the mobile phone camera's spatial frequency response and watermark embedding parameters such as density and strength. A new watermark robustness metric based on spatial frequency response is defined. The robustness metric is computed by measuring the area under the spatial frequency response for the range of frequencies covered by the watermark synchronization signal while excluding the interference due to aliasing. By measuring the distortion introduced by a particular camera, the impact on watermark detection can be understood and quantified without having to conduct large-scale experiments. This in turn can provide feedback on adjusting the watermark embedding parameters and finding the right trade-off between watermark visibility and robustness to distortion. In addition, new devices can be quickly qualified for their use in smart image applications. The iPhone 3G, iPhone 3GS, and iPhone 4 camera phones are used as examples in this paper to verify the behavior of the watermark robustness model.

  10. Entropy studies on beam distortion by atmospheric turbulence

    NASA Astrophysics Data System (ADS)

    Wu, Chensheng; Ko, Jonathan; Davis, Christopher C.

    2015-09-01

    When a beam propagates through atmospheric turbulence over a known distance, the target beam profile deviates from the projected profile of the beam on the receiver. Intuitively, the unwanted distortion provides information about the atmospheric turbulence. This information is crucial for guiding adaptive optic systems and improving beam propagation results. In this paper, we propose an entropy study based on the image from a plenoptic sensor to provide a measure of information content of atmospheric turbulence. In general, lower levels of atmospheric turbulence will have a smaller information size while higher levels of atmospheric turbulence will cause significant expansion of the information size, which may exceed the maximum capacity of a sensing system and jeopardize the reliability of an AO system. Therefore, the entropy function can be used to analyze the turbulence distortion and evaluate performance of AO systems. In fact, it serves as a metric that can tell the improvement of beam correction in each iteration step. In addition, it points out the limitation of an AO system at optimized correction as well as the minimum information needed for wavefront sensing to achieve certain levels of correction. In this paper, we will demonstrate the definition of the entropy function and how it is related to evaluating information (randomness) carried by atmospheric turbulence.

  11. The magnetic-distortion probe: Velocimetry in conducting fluids

    NASA Astrophysics Data System (ADS)

    Miralles, Sophie; Verhille, Gautier; Plihon, Nicolas; Pinton, Jean-François

    2011-09-01

    A new type of velocimeter, capable of local velocity measurements in conducting fluids, is introduced. The principle of the "magnetic-distortion probe" is based on the measurement of the induced magnetic field by the flow of a conducting fluid in the vicinity of a localized magnetic field. The new velocimeter has no moving parts, and can be enclosed in a sealed cap, easing the implementation in harsh environments, such as liquid metals. The proposed method allows one to probe both the continuous part and fluctuations of the velocity, the temporal and spatial resolution being linked to the actual geometric configuration of the probe. A prototype probe has been tested in a gallinstan pipe flow and in a fully turbulent flow of liquid gallium generated by the counter rotation of two coaxial impellers in a cylinder. The signals have been compared to a reference potential probe and show very good agreement both for time-averaged velocities and turbulent fluctuations. The prototype is shown to detect motion from a few cm s-1 to a few m s-1. Moreover, the use of the magnetic-distortion probe with large-scale applied magnetic field is discussed.

  12. Motion and distortion correction of skeletal muscle echo planar images.

    PubMed

    Davis, Andrew D; Noseworthy, Michael D

    2016-07-01

    This paper examines two artifacts facing researchers who use gradient echo (GRE) echo planar imaging (EPI) for time series studies of skeletal muscles in limbs. The first is through-plane blood flow during the acquisition, causing a vessel motion artifact that inhibits proper motion correction of the data. The second is distortion of EPI images caused by B0 field inhomogeneities. Though software tools are available for correcting these artifacts in brain EPI images, the tools do not perform well on muscle images. The severity of the two artifacts was described using image similarity measures, and the data was processed with both a conventional motion correction program and custom written tools. The conventional program did not perform well on the limb images, in fact significantly degrading image quality in some trials. Data is presented which proves that arterial pulsatile signal caused the impairment in motion correction. The new tools were shown to perform much better, achieving substantial motion correction and distortion correction of the muscle EPI images. PMID:26972774

  13. Distortion and regulation characterization of a Mapham inverter

    NASA Technical Reports Server (NTRS)

    Sundberg, Richard C.; Brush, Andrew S.; Button, Robert M.; Patterson, Alexander G.

    1989-01-01

    Output voltage Total Harmonic Distortion (THD) of a 20kHz, 6kVA Mapham resonant inverter is characterized as a function of its switching-to-resonant frequency ratio, f sub s/f sub r, using the EASY5 engineering analysis system. EASY5 circuit simulation results are compared with hardware test results to verify the accuracy of the simulations. The effects of load on the THD versus f sub s/f sub r ratio is investigated for resistive, leading, and lagging power factor load impedances. The effect of the series output capacitor on the Mapham inverter output voltage distortion and inherent load regulation is characterized under loads of various power factors and magnitudes. An optimum series capacitor value which improves the inherent load regulation to better than 3 percent is identified. The optimum series capacitor value is different than the value predicted from a modeled frequency domain analysis. An explanation is proposed which takes into account the conduction overlap in the inductor pairs during steady-state inverter operation, which decreases the effective inductance of a Mapham inverter. A fault protection and current limit method is discussed which allows the Mapham inverter to operate into a short circuit, even when the inverter resonant circuit becomes overdamped.

  14. Automatic source camera identification using the intrinsic lens radial distortion

    NASA Astrophysics Data System (ADS)

    Choi, Kai San; Lam, Edmund Y.; Wong, Kenneth K. Y.

    2006-11-01

    Source camera identification refers to the task of matching digital images with the cameras that are responsible for producing these images. This is an important task in image forensics, which in turn is a critical procedure in law enforcement. Unfortunately, few digital cameras are equipped with the capability of producing watermarks for this purpose. In this paper, we demonstrate that it is possible to achieve a high rate of accuracy in the identification by noting the intrinsic lens radial distortion of each camera. To reduce manufacturing cost, the majority of digital cameras are equipped with lenses having rather spherical surfaces, whose inherent radial distortions serve as unique fingerprints in the images. We extract, for each image, parameters from aberration measurements, which are then used to train and test a support vector machine classifier. We conduct extensive experiments to evaluate the success rate of a source camera identification with five cameras. The results show that this is a viable approach with high accuracy. Additionally, we also present results on how the error rates may change with images captured using various optical zoom levels, as zooming is commonly available in digital cameras.

  15. Atmospheric Waves

    NASA Technical Reports Server (NTRS)

    2007-01-01

    With its Multispectral Visible Imaging Camera (MVIC), half of the Ralph instrument, New Horizons captured several pictures of mesoscale gravity waves in Jupiter's equatorial atmosphere. Buoyancy waves of this type are seen frequently on Earth - for example, they can be caused when air flows over a mountain and a regular cloud pattern forms downstream. In Jupiter's case there are no mountains, but if conditions in the atmosphere are just right, it is possible to form long trains of these small waves. The source of the wave excitation seems to lie deep in Jupiter's atmosphere, below the visible cloud layers at depths corresponding to pressures 10 times that at Earth's surface. The New Horizons measurements showed that the waves move about 100 meters per second faster than surrounding clouds; this is about 25% of the speed of sound on Earth and is much greater than current models of these waves predict. Scientists can 'read' the speed and patterns these waves to learn more about activity and stability in the atmospheric layers below.

  16. Quasitravelling waves

    SciTech Connect

    Beklaryan, Leva A

    2011-02-11

    A finite difference analogue of the wave equation with potential perturbation is investigated, which simulates the behaviour of an infinite rod under the action of an external longitudinal force field. For a homogeneous rod, describing solutions of travelling wave type is equivalent to describing the full space of classical solutions to an induced one-parameter family of functional differential equations of point type, with the characteristic of the travelling wave as parameter. For an inhomogeneous rod, the space of solutions of travelling wave type is trivial, and their 'proper' extension is defined as solutions of 'quasitravelling' wave type. By contrast to the case of a homogeneous rod, describing the solutions of quasitravelling wave type is equivalent to describing the quotient of the full space of impulsive solutions to an induced one-parameter family of point-type functional differential equations by an equivalence relation connected with the definition of solutions of quasitravelling wave type. Stability of stationary solutions is analyzed. Bibliography: 9 titles.

  17. Moreton Waves

    NASA Technical Reports Server (NTRS)

    Thompson, B. J.

    1999-01-01

    "Moreton waves," named for the observer who popularized them, are a solar phenomenon also known in scientific literature as "Moreton-Ramsey wave," "flare waves," "flare-associated waves," "MHD blast waves," "chromospheric shock fronts" and various other combinations of terms which connote violently propagating impulsive disturbances. It is unclear whether all of the observations to which these terms have been applied pertain to a single physical phenomenon: there has perhaps been some overlap between the observations and the assumed physical properties of the observed occurrence. Moreton waves are ideally observed in the wings of H alpha, and appear as semi-circular fronts propagating at speeds ranging from several hundred to over a thousand km/sec. They form an arc, or "brow shape" which can span up to 180 degrees. Extrapolating the speed and locations of the arc indicates that the phenomenon's origin intersects well with the impulsive phase of the associated H alpha flare (if the flare exhibits an impulsive phase). However, the arc may not form or may not be observable until it is tens of megameters from the flaring region, and subsequently can propagate to distances exceeding 100 megameters. The high speeds and distances of propagation, plus the associated radio and energetic particle observations, provided strong evidence of a coronal, rather than a chromospheric origin. The H alpha manifestation of the wave is assumed to be the "ground track" or "skirt" of a three-dimensional disturbance.

  18. Ship waves and lee waves

    NASA Technical Reports Server (NTRS)

    Sharman, R. D.; Wurtele, M. G.

    1983-01-01

    Dynamics analogous to those of surface ship waves on water of finite depth are noted for the three-dimensional trapped lee wave modes produced by an isolated obstacle in a stratified fluid. This vertical trapping of wave energy is modeled by uniform upstream flow and stratification, bounded above by a rigid lid, and by a semiinfinite fluid of uniform stability whose wind velocity increases exponentially with height, representing the atmosphere. While formal asymptotic solutions are produced, limited quantitative usefulness is obtained through them because of the limitations of the approximations and the infinity of modes in the solution. Time-dependent numerical models are accordingly developed for both surface ship waves and internal and atmospheric ship waves, yielding a variety of results.

  19. Anomalous Centrifugal Distortion in HDO and Spectroscopic Data Bases

    NASA Astrophysics Data System (ADS)

    Coudert, L. H.

    2015-06-01

    The HDO molecule is important from the atmospheric point of view as it can be used to study the water cycle in the earth atmosphere. It is also interesting from the spectroscopic point of view as it displays an anomalous centrifugal distortion similar to that of the normal species H_2O. A model developed to treat the anomalous distortion in HDO should account for the fact that it lacks a two-fold axis of symmetry. A new treatment aimed at the calculation of the rovibrational energy of the HDO molecule and allowing for anomalous centrifugal distortion effects has been developed. It is based on an effective Hamiltonian in which the large amplitude bending ν_2 mode and the overall rotation of the molecule are treated simultaneously. Due to the lack of a two-fold axis of symmetry, this effective Hamiltonian contains terms arising from the non-diagonal component of the inertia tensor and from the Coriolis-coupling between the large amplitude bending ν_2 mode and the overall rotation of the molecule. This new treatment has been used to perform a line position analysis of a large body of infrared, microwave, and hot water vapor data involving the ground and (010) states up to J=22. For these 4413 data, a unitless standard deviation of 1.1 was achieved. A line intensity analysis was also carried out and allowed us to reproduce the strength of 1316 transitions^c with a unitless standard deviation of 1.1. In the talk, the new theoretical approach will be presented. The results of both analyses will be discussed and compared with those of a previous investigation. The new spectroscopic data base built will be compared with HITRAN 2012. Herbin et al., Atmos. Chem. Phys.~9 (2009) 9433; and Schneider and Hase, Atmos. Chem. Phys.~ 11 (2011) 11207. Coudert, Wagner, Birk, Baranov, Lafferty, and Flaud, J. Molec. Spectrosc.~251 (2008) 339. Johns, J. Opt. Soc. Am. B~2 (1985) 1340 Toth, J. Molec. Spectrosc.~162 (1993) 20 Paso and Horneman, J. Opt. Soc. Am. B~12 (1995) 1813 Toth, J

  20. Image distortion correction for micromanipulation system based on SLM microscopic vision.

    PubMed

    Wang, Yuezong; Jin, Yan; Wang, Lika

    2016-03-01

    Stereo light microscope (SLM) simulates stereo imaging principle of human eyes. Microscopic vision system based on SLM has become an important visual tool for micro measurement, micromanipulation, and microinjection. We develop a micromanipulation system based on SLM and present an image distortion correction method. We mainly correct two kinds of image distortions: lateral and vertical distortion. Distortion correction consists of two steps. First, a linear fitting algorithm for each row or column of target points is developed, and the fitting errors are calculated. If the fitting errors are smaller than a given threshold, the linear fitting results are kept and used. Otherwise polynomial fitting procedure will be used. Second, the parallelism of straight lines is corrected. The results show that a line in world coordinate frame (WCF) is not necessarily a straight line in image coordinate frame (ICF), or two parallel lines in WCF may be not parallel in ICF. Distortion correction can restore the parallel and linear relationship. For distorted left and right images, the magnitude of distortion exceeds 6 pixels and 4 pixels in the horizontal direction, and 1.2 pixels and 1.7 pixels in the vertical direction, respectively. After corrected, for left and right image, distortion can be reduced to 0.8 pixels and 0.7 pixels in the horizontal direction, and 0.96 pixels and 1.3 pixels in the vertical direction, respectively. The results show that distortion parameters obtained from the proposed method can effectively correct distorted images. PMID:26789139

  1. An experimental investigation of two large annular diffusers with swirling and distorted inflow

    NASA Technical Reports Server (NTRS)

    Eckert, W. T.; Johnston, J. P.; Simons, T. D.; Mort, K. W.; Page, V. R.

    1980-01-01

    Two annular diffusers downstream of a nacelle-mounted fan were tested for aerodynamic performance, measured in terms of two static pressure recovery parameters (one near the diffuser exit plane and one about three diameters downstream in the settling duct) in the presence of several inflow conditions. The two diffusers each had an inlet diameter of 1.84 m, an area ratio of 2.3, and an equivalent cone angle of 11.5, but were distinguished by centerbodies of different lengths. The dependence of diffuser performance on various combinations of swirling, radially distorted, and/or azimuthally distorted inflow was examined. Swirling flow and distortions in the axial velocity profile in the annulus upstream of the diffuser inlet were caused by the intrinsic flow patterns downstream of a fan in a duct and by artificial intensification of the distortions. Azimuthal distortions or defects were generated by the addition of four artificial devices (screens and fences). Pressure recovery data indicated beneficial effects of both radial distortion (for a limited range of distortion levels) and inflow swirl. Small amounts of azimuthal distortion created by the artificial devices produced only small effects on diffuser performance. A large artificial distortion device was required to produce enough azimuthal flow distortion to significantly degrade the diffuser static pressure recovery.

  2. Linear fitting interpolation based on FOV division for correcting wide angle fish-eye lens distortion

    NASA Astrophysics Data System (ADS)

    Li, An; Wu, Yi-si; Chen, Chi; Zheng, Zhen-rong

    2015-09-01

    The wide angle lens, like fish eye lens, suffers great optical distortion that causes severe deformation of the real world. A method to correct the strong distortion was presented in this work. Due to the nonlinear distribution of the distortion, linear algorithms are generally not under consideration to establish the math model of distorted-to-ideal images. However, this method employed the calibration pattern that comprised of regular array of dots to divides the full field of view (FOV) to subsections, each subsection is a small FOV, the mapping parameters between the distorted image and ideal image in each small FOV can be calculated by employing the very simple linear polynomial. Thus, applying the determined parameters to their corresponding sub-FOVs, respectively, all the ideal pixel coordinates of the distorted image can be obtained. The method employed linear polynomial characterizes the geometric deformation between the distorted and ideal images directly. Therefore, it contains both of radial distortion and tangential distortion and there is no need of concerning any intrinsic or extrinsic parameters of the optical systems. So, this algorithm reliefs the computational work that employed by conventional radial models and other mathematical models. Experiments performed on off-axis optical systems which exist complicated distortion, such as the head mounted displays (HMDs), had already yielded accurate correcting results. Likewise, in this paper, the experiments refer to the fish-eye lens also verify the effectiveness and flexibility of this method, as well, high correcting accuracy is achieved.

  3. Electron Beam Transport in Advanced Plasma Wave Accelerators

    SciTech Connect

    Williams, Ronald L

    2013-01-31

    The primary goal of this grant was to develop a diagnostic for relativistic plasma wave accelerators based on injecting a low energy electron beam (5-50keV) perpendicular to the plasma wave and observing the distortion of the electron beam's cross section due to the plasma wave's electrostatic fields. The amount of distortion would be proportional to the plasma wave amplitude, and is the basis for the diagnostic. The beat-wave scheme for producing plasma waves, using two CO2 laser beam, was modeled using a leap-frog integration scheme to solve the equations of motion. Single electron trajectories and corresponding phase space diagrams were generated in order to study and understand the details of the interaction dynamics. The electron beam was simulated by combining thousands of single electrons, whose initial positions and momenta were selected by random number generators. The model was extended by including the interactions of the electrons with the CO2 laser fields of the beat wave, superimposed with the plasma wave fields. The results of the model were used to guide the design and construction of a small laboratory experiment that may be used to test the diagnostic idea.

  4. Exchange distortion and postcollision interaction for intermediate-energy electron-impact ionization of argon

    SciTech Connect

    Prideaux, A.; Madison, D.H.; Bartschat, K.

    2005-09-15

    Measurements of fully differential cross sections for electron impact ionization of atoms have been performed for over 30 years. However, only within the last ten years has agreement between experiment and theory been achieved for ionization of hydrogen and helium. For the heavier inert gases, reasonably good agreement between experiment and theory has only been achieved for high incident energies while serious discrepancies are common for intermediate and low incident energies. It is believed that a major source of the problem stems from an improper/inadequate treatment of exchange distortion (ED) and the effects of post-collision interactions (PCIs). In this paper, two different methods for including ED are examined--one based upon the R matrix (close-coupling) approach and one originating from the single-configuration Hartree-Fock approach. In general, these two methods predict significant, but different, ED effects. The importance of PCI is studied by including the final-state Coulomb interaction directly in the final-state wave function. This procedure guarantees that PCI effects will be included to all orders of perturbation theory. For intermediate energies, PCI is an important effect and leads to an overall improvement in the agreement between experiment and theory.

  5. Half-metallicity and tetragonal distortion in semi-Heusler alloy FeCrSe

    SciTech Connect

    Huang, H. M. Luo, S. J.; Yao, K. L.

    2014-01-28

    Full-potential linearized augmented plane wave methods are carried out to investigate the electronic structures and magnetic properties in semi-Heusler alloy FeCrSe. Results show that FeCrSe is half-metallic ferromagnet with the half-metallic gap 0.31 eV at equilibrium lattice constant. Calculated total magnetic moment of 2.00μ{sub B} per formula unit follows the Slater-Pauling rule quite well. Two kinds of structural changes are used to investigate the sensitivity of half-metallicity. It is found that the half-metallicity can be retained when lattice constant is changed by −4.56% to 3.52%, and the results of tetragonal distortion indicate the half-metallicity can be kept at the range of c/a ratio from 0.85 to 1.20. The Curie temperature, cohesive energy, and heat of formations of FeCrSe are also discussed.

  6. Exchange distortion and postcollision interaction for intermediate-energy electron-impact ionization of argon

    NASA Astrophysics Data System (ADS)

    Prideaux, A.; Madison, D. H.; Bartschat, K.

    2005-09-01

    Measurements of fully differential cross sections for electron impact ionization of atoms have been performed for over 30 years. However, only within the last ten years has agreement between experiment and theory been achieved for ionization of hydrogen and helium. For the heavier inert gases, reasonably good agreement between experiment and theory has only been achieved for high incident energies while serious discrepancies are common for intermediate and low incident energies. It is believed that a major source of the problem stems from an improper/inadequate treatment of exchange distortion (ED) and the effects of post-collision interactions (PCIs). In this paper, two different methods for including ED are examined—one based upon the R matrix (close-coupling) approach and one originating from the single-configuration Hartree-Fock approach. In general, these two methods predict significant, but different, ED effects. The importance of PCI is studied by including the final-state Coulomb interaction directly in the final-state wave function. This procedure guarantees that PCI effects will be included to all orders of perturbation theory. For intermediate energies, PCI is an important effect and leads to an overall improvement in the agreement between experiment and theory.

  7. Phonon triggered rhombohedral lattice distortion in vanadium at high pressure

    PubMed Central

    Antonangeli, Daniele; Farber, Daniel L.; Bosak, Alexei; Aracne, Chantel M.; Ruddle, David G.; Krisch, Michael

    2016-01-01

    In spite of the simple body-centered-cubic crystal structure, the elements of group V, vanadium, niobium and tantalum, show strong interactions between the electronic properties and lattice dynamics. Further, these interactions can be tuned by external parameters, such as pressure and temperature. We used inelastic x-ray scattering to probe the phonon dispersion of single-crystalline vanadium as a function of pressure to 45 GPa. Our measurements show an anomalous high-pressure behavior of the transverse acoustic mode along the (100) direction and a softening of the elastic modulus C44 that triggers a rhombohedral lattice distortion occurring between 34 and 39 GPa. Our results provide the missing experimental confirmation of the theoretically predicted shear instability arising from the progressive intra-band nesting of the Fermi surface with increasing pressure, a scenario common to all transition metals of group V. PMID:27539662

  8. Statistical analysis of the 70 meter antenna surface distortions

    NASA Technical Reports Server (NTRS)

    Kiedron, K.; Chian, C. T.; Chuang, K. L.

    1987-01-01

    Statistical analysis of surface distortions of the 70 meter NASA/JPL antenna, located at Goldstone, was performed. The purpose of this analysis is to verify whether deviations due to gravity loading can be treated as quasi-random variables with normal distribution. Histograms of the RF pathlength error distribution for several antenna elevation positions were generated. The results indicate that the deviations from the ideal antenna surface are not normally distributed. The observed density distribution for all antenna elevation angles is taller and narrower than the normal density, which results in large positive values of kurtosis and a significant amount of skewness. The skewness of the distribution changes from positive to negative as the antenna elevation changes from zenith to horizon.

  9. Mosquitoes on the Wing ``Tune In'' to Acoustic Distortion

    NASA Astrophysics Data System (ADS)

    Warren, Ben; Russell, Ian

    2011-11-01

    Our current understanding of the mating game for many mosquito species is that males aggregate in noisy mating swarms and listen with their Johnston's organs (JOs) for the deeper flight tones of approaching females, to which they are attracted. As has been demonstrated, at least for the most intensely studied vector species, the mechanical resonance of the flagellum and the frequency range of the female's JO is far below that of the male's flight tones. Therefore, it has been assumed that females do not use hearing to detect the presence of males. Here we reveal that this may not be the case, and that the JOs of female Culex quinquefasciatus are exquisitely tuned to low frequency distortion products in the vibrations of the antenna due to a nonlinear interaction between her own flight tones and those of a nearby male. She can hear male flight tones by virtue of, and not despite, hearing her own flight tones.

  10. Mirror distortion measurements with an in-situ LTP

    NASA Astrophysics Data System (ADS)

    Takacs, Peter Z.; Qian, Shinan; Randall, Kevin J.; Yun, Wenbing; Li, Haizhang

    1998-11-01

    An in-situ long trace profiler developed at Brookhaven National Laboratory under the auspices of a CRADA with Continental Optical Corporation has successfully measured thermal distortion on a side-cooled mirror in a beam line at the Advanced Photon Source. The instrument scanned the central 90 mm of the 200 mm long mirror through a vacuum window while the mirror was subjected to heat loading from the synchrotron beam. Results clearly show transient effects occurring when the mirror is first illuminated that relax after about 15 minutes, in accord with finite element thermal calculations. The steady state curvature of the surface is measured to be slightly concave with an additional 5 km radius relative to the initial nominal curvature of about 1 km. The magnitude of this steady state condition was not expected and was not predicted by the calculations.

  11. Wavefront distortion optimized with volume Bragg gratings in photothermorefractive glass.

    PubMed

    Gao, Fan; Zhang, Xiang; Sun, Xiaojie; Yuan, Xiao

    2016-03-15

    The wavefront characteristics in 2D angular filtering on the basis of two orthogonal transmitting volume Bragg gratings (VBGs) is presented. The experimental results show that middle-high frequency wavefront distortions are efficiently suppressed with VBGs. The peak-valley value of the beam at a wavelength of 1053 nm reduces from 2.075λ to 0.209λ, and the root mean square value reduces from 0.207λ to 0.041λ. The wavefront power spectrum density shows that the wavefront distribution of the beam in medium and high frequencies is corrected by the VBGs. Additionally, the far-field distribution and focusing properties of the beam are improved. The beam Strehl ratio increases from 0.43 to 0.96, and the encircled energy improves from 95% energy at 4.01 mrad to 95% energy at 1.26 mrad. PMID:26977639

  12. Phonon triggered rhombohedral lattice distortion in vanadium at high pressure.

    PubMed

    Antonangeli, Daniele; Farber, Daniel L; Bosak, Alexei; Aracne, Chantel M; Ruddle, David G; Krisch, Michael

    2016-01-01

    In spite of the simple body-centered-cubic crystal structure, the elements of group V, vanadium, niobium and tantalum, show strong interactions between the electronic properties and lattice dynamics. Further, these interactions can be tuned by external parameters, such as pressure and temperature. We used inelastic x-ray scattering to probe the phonon dispersion of single-crystalline vanadium as a function of pressure to 45 GPa. Our measurements show an anomalous high-pressure behavior of the transverse acoustic mode along the (100) direction and a softening of the elastic modulus C44 that triggers a rhombohedral lattice distortion occurring between 34 and 39 GPa. Our results provide the missing experimental confirmation of the theoretically predicted shear instability arising from the progressive intra-band nesting of the Fermi surface with increasing pressure, a scenario common to all transition metals of group V. PMID:27539662

  13. Exploiting the geomagnetic distortion of inclined atmospheric showers

    NASA Astrophysics Data System (ADS)

    Billoir, Pierre; Settimo, Mariangela; Blanco, Miguel

    2016-02-01

    We propose a novel approach to the determination of the nature of ultra-high energy cosmic rays by exploiting the geomagnetic deviation of muons in nearly horizontal showers. The distribution of muons at ground level is well described by a simple parameterization providing a few shape parameters tightly correlated to Xmaxμ, the depth of maximal muon production, which is a mass indicator tightly correlated to the usual parameter Xmax, the depth of maximal development of the shower. We show that some constraints can be set on the predictions of hadronic models, especially by combining the geomagnetic distortion with standard measurements of the longitudinal profile. We discuss the precision needed to obtain significant results, and we propose a schematic layout of a detector.

  14. Distorted Graphene Sheet Structure-Derived Latent Nanoporosity.

    PubMed

    Wang, Shuwen; Ábrahám, Dániel; Vallejos-Burgos, Fernando; László, Krisztina; Geissler, Erik; Takeuchi, Kenji; Endo, Morinobu; Kaneko, Katsumi

    2016-06-01

    High surface area graphene monoliths consist mainly of single graphene layers wider than 10 nm. The interlayer porosity of high temperature treated nanoporous graphene monoliths with tuned intergraphene layer structures is evaluated by hybrid analysis of Ar adsorption at 87 K, N2 adsorption at 77 K, high resolution transmission electron microscopic observation, and small-angle X-ray scattering (SAXS) measurements. SAXS analysis results in surface areas that are 1.4 and 4.5 times larger than those evaluated by Ar adsorption for graphene monoliths nontreated and treated at 2273 K, respectively. A distorted graphene sheet structure model is proposed for the high surface area graphene monoliths on the basis of the hybrid analysis. PMID:27214125

  15. Testing dark matter clustering with redshift space distortions

    SciTech Connect

    Linder, Eric V.

    2013-04-01

    The growth rate of large scale structure can probe whether dark matter clusters at gravitational strength or deviates from this, e.g. due to self interactions. Measurement of the growth rate through redshift space distortions in galaxy redshift surveys constrains the clustering strength, and its redshift dependence. We compare such effects on growth to those from high redshift deviations (e.g. early dark energy) or modified gravity, and give a simple, highly accurate analytic prescription. Current observations can constrain the dark matter clustering strength to F{sub cl} = 0.99±0.02 of standard, if all other parameters are held fixed, but substantial covariances exist. Future galaxy redshift surveys may constrain an evolving clustering strength to 28%, marginalizing over the other parameters, or 4% if the dark energy parameters are held fixed while fitting for dark matter growth. Tighter constraints on the nature of dark matter could be obtained by combining cosmological and astrophysical probes.

  16. Highly accurate eigenvalues for the distorted Coulomb potential

    NASA Astrophysics Data System (ADS)

    Ixaru, L. Gr.; de Meyer, H.; vanden Berghe, G.

    2000-03-01

    We consider the eigenvalue problem for the radial Schrödinger equation with potentials of the form V(r)=S(r)/r+R(r) where S(r) and R(r) are well behaved functions which tend to some (not necessarily equal) constants when r-->0 and r-->∞. Formulas (14.4.5)-(14.4.8) of Abramowitz and Stegun [Handbook of Mathematical Functions, 8th ed. (Dover, New York, 1972)], corresponding to the pure Coulomb case, are here generalized for this distorted case. We also present a complete procedure for the numerical solution of the problem. Our procedure is robust, very economic and particularly suited for very large n. Numerical illustrations for n up to 2000 are given.

  17. Pulse distortion in single-mode fibers. 3: Chirped pulses.

    PubMed

    Marcuse, D

    1981-10-15

    The theory of pulse distortion in single-mode fibers is extended to include laser sources that suffer a linear wavelength sweep (chirp) during the duration of the pulse. The transmitted pulse is expressed as a Fourier integral whose spectral function is given by an analytical expression in closed form. The rms width of the transmitted pulse is also expressed in closed form. Numerical examples illustrate the influence of the chirp on the shape and rms width of the pulse. A somewhat paradoxical situation exists. A given input pulse can be made arbitrarily short by a sufficiently large amount of chirping, and, after a given fiber length, this chirped pulse returns to its original width. But at this particular distance an unchirped pulse would be only [equiation] times longer. Thus chirping can improve the rate of data transmission by only 40%. PMID:20372221

  18. Distorted mass edges at LHC from supersymmetric leptoquarks

    NASA Astrophysics Data System (ADS)

    Reuter, Jürgen; Wiesler, Daniel

    2011-07-01

    Supersymmetric (SUSY) grand unified theories based on exceptional gauge groups such as E6 have recently triggered a lot of interest. Aside from top-down motivations, they contain phenomenologically interesting states with leptoquark quantum numbers. Their SUSY partners, leptoquarkinos, will appear similar to all R-odd particles in decay cascades, but mass edges in kinematic distributions—originating from the same semiexclusive final states—will however have major differences to the corresponding edges of ordinary squarks. This distortion of standard observables bears the opportunity to detect them at the LHC, but may also pose significant confusion of underlying model assumptions, which should be handled with care and, if interpreted falsely, might even prevent a possible discovery.

  19. Testing cosmic geometry without dynamic distortions using voids

    SciTech Connect

    Hamaus, Nico; Sutter, P.M.; Lavaux, Guilhem; Wandelt, Benjamin D. E-mail: sutter@iap.fr E-mail: wandelt@iap.fr

    2014-12-01

    We propose a novel technique to probe the expansion history of the Universe based on the clustering statistics of cosmic voids. In particular, we compute their two-point statistics in redshift space on the basis of realistic mock galaxy catalogs and apply the Alcock-Paczynski test. In contrast to galaxies, we find void auto-correlations to be marginally affected by peculiar motions, providing a model-independent measure of cosmological parameters without systematics from redshift-space distortions. Because only galaxy-galaxy and void-galaxy correlations have been considered in these types of studies before, the presented method improves both statistical and systematic uncertainties on the product of angular diameter distance and Hubble rate, furnishing the potentially cleanest probe of cosmic geometry available to date.

  20. Sub-Nyquist Sampling and Moire-Like Waveform Distortions

    NASA Technical Reports Server (NTRS)

    Williams, Glenn L.

    2000-01-01

    Investigations of aliasing effects in digital waveform sampling have revealed the existence of a mathematical field and a pseudo-alias domain lying to the left of a "Nyquist line" in a plane defining the boundary between two domains of sampling. To the right of the line lies the classic alias domain. For signals band-limited below the Nyquist limit, displayed output may show a false modulation envelope. The effect occurs whenever the sample rate and the signal frequency are related by ratios of mutually prime integers. Belying the principal of a 10:1 sampling ratio being "good enough", this distortion easily occurs in graphed one-dimensional waveforms and two-dimensional images and occurs daily on television.

  1. Distortions of the cosmic microwave background spectrum by dust

    NASA Technical Reports Server (NTRS)

    Rowan-Robinson, M.; Negroponte, J.; Silk, J.

    1979-01-01

    The effects of dust in the early universe on the spectrum of the cosmic microwave background are considered, taking into account the effects of a pregalactic generation of stars. It is shown that observed distortions of the background spectrum from that of a black body at 3 K could be due to emission by silicate dust grains at a metal abundance of 0.00001 by mass and with a substantial energy input, which represent the remnants of population III stars. Attempts to fit the microwave background spectrum to the model of Rees (1978) in which the entire cosmic background is accounted for by grain emission are shown to require an implausible value for the metal abundance at early epochs, and not to agree with the millimeter and submillimeter spectrum observed by Woody and Richards (1979).

  2. Eliminating spatial distortions in Anger-type gamma cameras

    NASA Astrophysics Data System (ADS)

    Leitner, Michael; Ceeh, Hubert; Weber, Josef-Andreas

    2012-12-01

    A procedure to quantify and correct the spatial distortions inherent to Anger-type gamma cameras is presented. It consists in imaging a pattern of regularly spaced holes, assigning to each pair of lattice indices the actual position on the detector and generating a look-up matrix describing the inverse mapping. This allows one to correct the position of the distinct events either during or after the measurement with minimal computational effort. The corrected spectrum is indistinguishable from a spectrum taken with an ideal detector in a statistical sense. The effect of the increased resolution on measurements of angular correlation of positron annihilation radiation is demonstrated. The presented scheme is applicable for all types of area detectors.

  3. Local lattice distortions and thermal transport in perovskite manganites

    SciTech Connect

    Cohn, J.L.; Neumeier, J.J.; Popoviciu, C.P.; McClellan, K.J.; Leventouri, T.

    1997-10-01

    Measurements of thermal conductivity versus temperature and magnetic field are reported for perovskite manganites that exhibit ferromagnetic (FM), charge-ordering (CO), antiferromagnetic, and/or structural phase transitions. The data reveal a dominant lattice contribution to the heat conductivity with {kappa}{approximately}1{minus}2 W/mK near room temperature. The rather low values, implying a phonon mean free path on the order of a lattice spacing, are shown to correlate with static local distortions of the MnO{sub 6} octahedra. Modifications of the local structure are responsible for abrupt anomalies in the zero-field {kappa} at the FM, CO, and structural transitions, and for colossal magnetothermal resistance near the FM transition. {copyright} {ital 1997} {ital The American Physical Society}

  4. Video quality pooling adaptive to perceptual distortion severity.

    PubMed

    Park, Jincheol; Seshadrinathan, Kalpana; Lee, Sanghoon; Bovik, Alan Conrad

    2013-02-01

    It is generally recognized that severe video distortions that are transient in space and/or time have a large effect on overall perceived video quality. In order to understand this phenomena, we study the distribution of spatio-temporally local quality scores obtained from several video quality assessment (VQA) algorithms on videos suffering from compression and lossy transmission over communication channels. We propose a content adaptive spatial and temporal pooling strategy based on the observed distribution. Our method adaptively emphasizes "worst" scores along both the spatial and temporal dimensions of a video sequence and also considers the perceptual effect of large-area cohesive motion flow such as egomotion. We demonstrate the efficacy of the method by testing it using three different VQA algorithms on the LIVE Video Quality database and the EPFL-PoliMI video quality database. PMID:23008260

  5. Human Adult Cortical Reorganization and Consequent Visual Distortion

    PubMed Central

    Dilks, Daniel D.; Serences, John T.; Rosenau, Benjamin J.; Yantis, Steven; McCloskey, Michael

    2009-01-01

    Neural and behavioral evidence for cortical reorganization in the adult somatosensory system after loss of sensory input (e.g., amputation) has been well documented. In contrast, evidence for reorganization in the adult visual system is far less clear: neural evidence is the subject of controversy, behavioral evidence is sparse, and studies combining neural and behavioral evidence have not previously been reported. Here, we report converging behavioral and neuroimaging evidence from a stroke patient (B.L.) in support of cortical reorganization in the adult human visual system. B.L.’s stroke spared the primary visual cortex (V1), but destroyed fibers that normally provide input to V1 from the upper left visual field (LVF). As a consequence, B.L. is blind in the upper LVF, and exhibits distorted perception in the lower LVF: stimuli appear vertically elongated, toward and into the blind upper LVF. For example, a square presented in the lower LVF is perceived as a rectangle extending upward. We hypothesized that the perceptual distortion was a consequence of cortical reorganization in V1. Extensive behavioral testing supported our hypothesis, and functional magnetic resonance imaging (fMRI) confirmed V1 reorganization. Together, the behavioral and fMRI data show that loss of input to V1 after a stroke leads to cortical reorganization in the adult human visual system, and provide the first evidence that reorganization of the adult visual system affects visual perception. These findings contribute to our understanding of the human adult brain’s capacity to change and has implications for topics ranging from learning to recovery from brain damage. PMID:17804619

  6. Selecting Map Projections in Minimizing Area Distortions in GIS Applications

    PubMed Central

    Yildirim, Faruk; Kaya, Ahmet

    2008-01-01

    Various software for Geographical Information Systems (GISs) have been developed and used in many different engineering projects. In GIS applications, map coverage is important in terms of performing reliable and meaningful queries. Map projections can be conformal, equal-area and equidistant. The goal of an application plays an important role in choosing one of those projections. Choosing the equal-area projection for an application in which area information is used (forestry, agriculture, ecosystem etc) reduces the amount of distortion on the area, but many users using GIS ignore this fact and continue to use applications with present map sheets no matter in what map projection it is. For example, extracting area information from data whose country system's map sheet is in conformal projection is relatively more distorted, compared to an equal-area projection one. The goal of this study is to make the best decision in choosing the most proper equal-area projection among the choices provided by ArcGIS 9.0, which is a popular GIS software package, and making a comparison on area errors when conformal projection is used. In this study, the area of parcels chosen in three different regions and geographic coordinates and whose sizes vary between 0.01 to 1,000,000 ha are calculated according to Transversal Mercator (TM, 3°), Universal Transversal Mercator (UTM, 6°) and 14 different equal-area projections existing in the ArcGIS 9.0 GIS software package. The parcel areas calculated with geographical coordinates are accepted as definite. The difference between the sizes calculated according to projection coordinates and real sizes of the parcels are determined. Consequently, the appropriate projections are decided for the areas smaller and equal than 1,000 ha and greater than 1,000 ha in the GIS software package.

  7. Low color distortion adaptive dimming scheme for power efficient LCDs

    NASA Astrophysics Data System (ADS)

    Nam, Hyoungsik; Song, Eun-Ji

    2013-06-01

    This paper demonstrates the color compensation algorithm to reduce the color distortion caused by mismatches between the reference gamma value of a dimming algorithm and the display gamma values of an LCD panel in a low power adaptive dimming scheme. In 2010, we presented the YrYgYb algorithm, which used the display gamma values extracted from the luminance data of red, green, and blue sub-pixels, Yr, Yg, and Yb, with the simulation results. It was based on the ideal panel model where the color coordinates were maintained at the fixed values over the gray levels. Whereas, this work introduces an XrYgZb color compensation algorithm which obtains the display gamma values of red, green, and blue from the different tri-stimulus data of Xr, Yg, and Zb, to obtain further reduction on the color distortion. Both simulation and measurement results ensure that a XrYgZb algorithm outperforms a previous YrYgYb algorithm. In simulation which has been conducted at the practical model derived from the measured data, the XrYgZb scheme achieves lower maximum and average color difference values of 3.7743 and 0.6230 over 24 test picture images, compared to 4.864 and 0.7156 in the YrYgYb one. In measurement of a 19-inch LCD panel, the XrYgZb method also accomplishes smaller color difference values of 1.444072 and 5.588195 over 49 combinations of red, green, and blue data, compared to 1.50578 and 6.00403 of the YrYgYb at the backlight dimming ratios of 0.85 and 0.4.

  8. Distortions of glacial landform sizes by manual mapping

    NASA Astrophysics Data System (ADS)

    Hillier, John K.; Smith, Mike J.

    2016-04-01

    Mapped topographic features are important for understanding processes that sculpt the Earth's surface. Subjective manual techniques are commonly used for mapping, yet how effective they are in quantitative terms is poorly constrained. Here 12,121 outlines drawn by 25 interpreters searching for a total of 21,625 drumlins in 5 synthetic DEMs are interpreted in terms of how the manual mapping process distorts the height (H), width (W) and length (L) of the reported features. Bias in the size-frequency distributions is caused by the sub-set of the forms 'found', even assuming perfect extraction of sizes, and is governed by H driving detectability. Bias is then compounded in sizes that are extracted using the mapped outlines but, remarkably, the size-frequency distribution is not altered further when mappers' incorrect guesses (i.e. outline corresponds to no input synthetic drumlin) are then included; it seems possible that, once mappers have their 'eye in' based on the most clearly defined features, they are very effective at identifying similar morphologies. Of the metrics available to quantify the size of a population, maximum size and λ, the exponent of its tail, are the most robust to these distortions. The drumlins in the study area resemble UK drumlins, permitting extrapolation of the conclusions. These are the first results to give such granular insights into the impacts of the various stages in manually mapping glacial landforms, permitted by the development of the synthetic DEMs. Arguments will always exist about how realistic any synthetic is, but this work demonstrates another use of synthetic DEMs that may be applied more widely in geomorphology.

  9. μ distortions or running: A guaranteed discovery from CMB spectrometry

    NASA Astrophysics Data System (ADS)

    Cabass, Giovanni; Melchiorri, Alessandro; Pajer, Enrico

    2016-04-01

    We discuss the implications of a PIXIE-like experiment, which would measure μ -type spectral distortions of the cosmic microwave background (CMB) at a level of σμ=(1 /n )×10-8 , with n ≥1 representing an improved sensitivity (e.g. n =10 corresponds to PRISM). Using Planck data and considering the six-parameter Λ CDM model, we compute the posterior for μ8≡μ ×108 and find μ8=1.5 7-0.13+0.11 (68% C.L.). This becomes μ8=1.2 8-0.52+0.30 (68% C.L.) when the running αs of the spectral index is included. We point out that a sensitivity of about 3 ×PIXIE implies a guaranteed discovery: μ distortion is detected or αs≥0 is excluded (both at 95% C.L. or higher). This threshold sensitivity sets a clear benchmark for CMB spectrometry. For a combined analysis of PIXIE and current Planck data, we discuss the improvement on measurements of the tilt ns and the running αs and the dependence on the choice of the pivot. A fiducial running of αs=-0.01 (close to the Planck best fit) leads to a detection of negative running at 2 σ for 5 ×PIXIE . A fiducial running of αs=-0.02 , still compatible with Planck, requires 3 ×PIXIE to rule out αs=0 (at 95% C.L.). We propose a convenient and compact visualization of the improving constraints on the tilt, running and tensor-to-scalar ratio.

  10. Variance After-Effects Distort Risk Perception in Humans.

    PubMed

    Payzan-LeNestour, Elise; Balleine, Bernard W; Berrada, Tony; Pearson, Joel

    2016-06-01

    In many contexts, decision-making requires an accurate representation of outcome variance-otherwise known as "risk" in economics. Conventional economic theory assumes this representation to be perfect, thereby focusing on risk preferences rather than risk perception per se [1-3] (but see [4]). However, humans often misrepresent their physical environment. Perhaps the most striking of such misrepresentations are the many well-known sensory after-effects, which most commonly involve visual properties, such as color, contrast, size, and motion. For example, viewing downward motion of a waterfall induces the anomalous biased experience of upward motion during subsequent viewing of static rocks to the side [5]. Given that after-effects are pervasive, occurring across a wide range of time horizons [6] and stimulus dimensions (including properties such as face perception [7, 8], gender [9], and numerosity [10]), and that some evidence exists that neurons show adaptation to variance in the sole visual feature of motion [11], we were interested in assessing whether after-effects distort variance perception in humans. We found that perceived variance is decreased after prolonged exposure to high variance and increased after exposure to low variance within a number of different visual representations of variance. We demonstrate these after-effects occur across very different visual representations of variance, suggesting that these effects are not sensory, but operate at a high (cognitive) level of information processing. These results suggest, therefore, that variance constitutes an independent cognitive property and that prolonged exposure to extreme variance distorts risk perception-a fundamental challenge for economic theory and practice. PMID:27161500

  11. Analytical models for use in fan inflow control structure design. Inflow distortion and acoustic transmission models

    NASA Technical Reports Server (NTRS)

    Gedge, M. R.

    1979-01-01

    Analytical models were developed to study the effect of flow contraction and screening on inflow distortions to identify qualitative design criteria. Results of the study are that: (1) static testing distortions are due to atmospheric turbulence, nacelle boundary layer, exhaust flow reingestion, flow over stand, ground plane, and engine casing; (2) flow contraction suppresses, initially, turbulent axial velocity distortions and magnifies turbulent transverse velocity distortions; (3) perforated plate and gauze screens suppress axial components of velocity distortions to a degree determined by the screen pressure loss coefficient; (4) honeycomb screen suppress transverse components of velocity distortions to a degree determined by the length to diameter ratio of the honeycomb; (5) acoustic transmission loss of perforated plate is controlled by the reactance of its acoustic impedance; (6) acoustic transmission loss of honeycomb screens is negligible; and (7) a model for the direction change due to a corner between honeycomb panels compares favorably with measured data.

  12. F-15 inlet/engine test techniques and distortion methodologies studies. Volume 1: Technical discussion

    NASA Technical Reports Server (NTRS)

    Stevens, C. H.; Spong, E. D.; Hammock, M. S.

    1978-01-01

    Peak distortion data taken from a subscale inlet model were studied to determine if the data can be used to predict peak distortion levels for a full scale flight test vehicle, and to provide a better understanding of the time variant total pressure distortion and the attendant effects of Reynolds number/scale and frequency content. The data base used to accomplish this goal covered a range from Mach 0.4 to 2.5 and an angle of attack range from -10 degrees to +12 degrees. Data are presented which show that: (1) increasing the Reynolds number increases total pressure recovery, decreases peak distortion, and decreases turbulence, (2) increasing the filter cutoff frequency increases both peak distortion and turbulence, and (3) the effect of engine presence on total pressure recovery, peak distortion, and turbulence is small but favorable.

  13. Distortion-free single point imaging of multi-layered composite sandwich panel structures

    NASA Astrophysics Data System (ADS)

    Marble, Andrew E.; Mastikhin, Igor V.; MacGregor, Rod P.; Akl, Mohamad; LaPlante, Gabriel; Colpitts, Bruce G.; Lee-Sullivan, Pearl; Balcom, Bruce J.

    2004-05-01

    The results of a magnetic resonance imaging (MRI) investigation concerning the effects of an aluminum honeycomb sandwich panel on the B1 and B0 fields and on subsequent image quality are presented. Although the sandwich panel structure, representative of an aircraft composite material, distorts B0 and attenuates B1, distortion-free imaging is possible using single point (constant time) imaging techniques. A new expression is derived for the error caused by gradient field distortion due to the heterogeneous magnetic susceptibility within a sample and this error is shown not to cause geometric distortion in the image. The origin of the B0 distortion in the sample under investigation was also examined. The graphite-epoxy `skin' of the panel is the principal source of the B0 distortion. Successful imaging of these structures sets the stage for the development of methods for detecting moisture ingress and degradation within composite sandwich structures.

  14. Distortion-free single point imaging of multi-layered composite sandwich panel structures.

    PubMed

    Marble, Andrew E; Mastikhin, Igor V; MacGregor, Rod P; Akl, Mohamad; LaPlante, Gabriel; Colpitts, Bruce G; Lee-Sullivan, Pearl; Balcom, Bruce J

    2004-05-01

    The results of a magnetic resonance imaging (MRI) investigation concerning the effects of an aluminum honeycomb sandwich panel on the B1 and B0 fields and on subsequent image quality are presented. Although the sandwich panel structure, representative of an aircraft composite material, distorts B0 and attenuates B1, distortion-free imaging is possible using single point (constant time) imaging techniques. A new expression is derived for the error caused by gradient field distortion due to the heterogeneous magnetic susceptibility within a sample and this error is shown not to cause geometric distortion in the image. The origin of the B0 distortion in the sample under investigation was also examined. The graphite-epoxy 'skin' of the panel is the principal source of the B0 distortion. Successful imaging of these structures sets the stage for the development of methods for detecting moisture ingress and degradation within composite sandwich structures. PMID:15082262

  15. Effect of steady-state pressure distortion on flow characteristics entering a turbofan engine

    NASA Technical Reports Server (NTRS)

    Soeder, R. H.; Bobula, G. A.

    1979-01-01

    Flow angle, static-pressure, and total-pressure distributions were measured in the passage ahead of a turbofan engine operating with inlet pressure distortion. Distortions were generated with five screen configurations and one solid plate configuration. The screens and solid plate were circumferential and mounted on a rotatable assembly. Reynolds Number Index upstream of the distortion device was maintained at 0.5, 0.35, or 0.2, and engine corrected low-rotor speeds were held at 6000 rpm and 8600 rpm. Near the engine inlet, flow angle was largest at the hub and increased as flow approached the engine. The magnitude of static-pressure distortion measured along the inlet-duct and extended bullet nose walls increased exponentially as the flow approached the engine. Wall static-pressure distortion was also a function of distortion harmonic.

  16. High-informative version of nonlinear transformation of Langmuir waves to electromagnetic waves

    NASA Astrophysics Data System (ADS)

    Erofeev, Vasily I.; Erofeev

    2014-04-01

    The concept of informativeness of nonlinear plasma physical scenario is discussed. Basic principles for heightening the informativeness of plasma kinetic models are explained. Former high-informative correlation analysis of plasma kinetics (Erofeev, V. 2011 High-Informative Plasma Theory, Saarbrücken: LAP) is generalized for studies of weakly turbulent plasmas that contain fields of solenoidal plasma waves apart from former potential ones. Respective machinery of plasma kinetic modeling is applied to an analysis of fusion of Langmuir waves with transformation to electromagnetic waves. It is shown that the customary version of this phenomenon (Terashima, Y. and Yajima, N. 1963 Prog. Theor. Phys. 30, 443; Akhiezer, I. A., Danelia, I. A. and Tsintsadze, N. L. 1964 Sov. Phys. JETP 19, 208; Al'tshul', L. M. and Karpman, V. I. 1965 Sov. Phys. JETP 20, 1043) substantially distorts the picture of merging of Langmuir waves with long wavelengths (λ >~ c/ωpe ).

  17. Mixing of blackbodies: entropy production and dissipation of sound waves in the early Universe

    NASA Astrophysics Data System (ADS)

    Khatri, R.; Sunyaev, R. A.; Chluba, J.

    2012-07-01

    Mixing of blackbodies with different temperatures creates a spectral distortion which, at lowest order, is a y-type distortion, indistinguishable from the thermal y-type distortion produced by the scattering of cosmic microwave background (CMB) photons by hot electrons residing in clusters of galaxies. This process occurs in the radiation-pressure dominated early Universe, when the primordial perturbations excite standing sound waves on entering the sound horizon. Photons from different phases of the sound waves, having different temperatures, diffuse through the electron-baryon plasma and mix together. This diffusion, with the length defined by Thomson scattering, dissipates sound waves and creates spectral distortions in the CMB. Of the total dissipated energy, 2/3 raises the average temperature of the blackbody part of spectrum, while 1/3 creates a distortion of y-type. It is well known that at redshifts 105 ≲ z ≲ 2 × 106, comptonization rapidly transforms y-distortions into a Bose-Einstein spectrum. The chemical potential of the Bose-Einstein spectrum is again 1/3 the value we would get if all the dissipated energy was injected into a blackbody spectrum but no extra photons were added. We study the mixing of blackbody spectra, emphasizing the thermodynamic point of view, and identifying spectral distortions with entropy creation. This allows us to obtain the main results connected with the dissipation of sound waves in the early Universe in a very simple way. We also show that mixing of blackbodies in general, and dissipation of sound waves in particular, leads to creation of entropy.

  18. Asymmetry of wind waves studied in a laboratory tank

    NASA Astrophysics Data System (ADS)

    Ileykin, L. A.; Donelan, M. A.; Mellen, R. H.; McLaughlin, D. J.

    1995-03-01

    Asymmetry of wind waves was studied in laboratory tank tinder varied wind and fetch conditions using both bispectral analysis of wave records and third-order statistics of the surface elevation. It is found skewness S (the normalized third-order moment of surface elevation describing the horizontal asymmetry waves) varies only slightly with the inverse wave u*/Cm (where u* is the air friction velocity and Cm is phase speed of the dominant waves). At the same time asymmetry A, which is determined from the Hilbert transform of the wave record and characterizes the skewness of the rate of change of surface elevation, increase consistently in magnitude with the ratio u*/Cm. This suggests that nonlinear distortion of the wave profile determined by the degree of wind forcing and is a sensitive indicator of wind-wave interaction processes. It is shown that the asymmetric profile of waves can described within the frameworks of the nonlinear nonspectral concept (Plate, 1972; Lake and Yuen, 197 according to which the wind-wave field can be represented as a coherent bound-wave system consisting mainly of dominant component w. and its harmonics propagating with the same speed C. , as observed by Ramamonjiaris and Coantic (1976). The phase shift between o). harmonics is found and shown to increase with the asymmetry of the waves.

  19. Asymmetry of wind waves studied in a laboratory tank

    NASA Astrophysics Data System (ADS)

    Leykin, I. A.; Donelan, M. A.; Mellen, R. H.; McLaughlin, D. J.

    Asymmetry of wind waves was studied in laboratory tank tinder varied wind and fetch conditions using both bispectral analysis of wave records and third-order statistics of the surface elevation. It is found skewness S (the normalized third-order moment of surface elevation describing the horizontal asymmetry waves) varies only slightly with the inverse wave u*/Cm (where u* is the air friction velocity and Cm is phase speed of the dominant waves). At the same time asymmetry A, which is determined from the Hilbert transform of the wave record and characterizes the skewness of the rate of change of surface elevation, increase consistently in magnitude with the ratio u*/Cm. This suggests that nonlinear distortion of the wave profile determined by the degree of wind forcing and is a sensitive indicator of wind-wave interaction processes. It is shown that the asymmetric profile of waves can described within the frameworks of the nonlinear nonspectral concept (Plate, 1972; Lake and Yuen, 197 according to which the wind-wave field can be represented as a coherent bound-wave system consisting mainly of dominant component w. and its harmonics propagating with the same speed C. , as observed by Ramamonjiaris and Coantic (1976). The phase shift between o). harmonics is found and shown to increase with the asymmetry of the waves.

  20. Corrections to fringe distortion due to flow density gradients in optical interferometry

    NASA Technical Reports Server (NTRS)

    Cho, Y. C.; Carr, L. W.; Chandrasekhara, M. S.

    1993-01-01

    An analytical method is formulated to account for distortions of optical interferograms used for studies of flow over airfoils experiencing dynamic stall. It is shown that such distortions are generated primarily due to optical path deflections in the test flow, caused by large density gradients. Such in-flow optical path deflections are neglected in conventional optical techniques for flow studies. The present method employs a ray analysis to determine these in-flow optical path deflections, and accurately predicts the interferogram distortions.

  1. General stereoscopic distortion rectification due to arbitrary viewer motion in binocular stereoscopic display

    NASA Astrophysics Data System (ADS)

    Li, Qun; Schonfeld, Dan

    2014-03-01

    Background: In binocular stereoscopic display, stereoscopic distortions due to viewer motion, such as depth distortion, shear distortion, and rotation distortion, result in misperception of the stereo content and reduce visual comfort dramat­ ically. In the past, perceived depth distortion has been thoroughly addressed, and shear distortion has been investigated within the context of multi-view display to accommodate motion parallax. However, the impact of rotation distortion has barely been studied. Therefore, no technique is available to address stereoscopic distortions due to general viewer motion. Objective: To preserve an undistorted 3D perception from a fixed viewpoint irrespective of viewing position. Method: We propose a unified system and method that rectifies stereoscopic distortion due to general affine viewer motion and delivers a fixed perspective of the 3D scene without distortion irrespective of viewer motion. The system assumes eye tracking of the viewer and pixel-wisely adjusts the display location of the stereo pair based on tracked viewer eye location. Results: For demonstration purpose, we implement our method on controlling perceived depth in binocular stereoscopic display of red and cyan anaglyph 3D. The user first perceives the designed perspective of the 3D scene at the reference position. The user then moves to 6 different positions with various distances and angles relative to the screen. At all positions, the users report to perceive a much more consistent stereo content with the adjusted displays and at the same time, experience improved visual comfort. Novelty: We address stereoscopic distortions with a goal to maintain a fixed perspective of the stereo scene, and propose a unified solution that simultaneously rectifies the stereoscopic distortions resulted from arbitrary viewer motion.

  2. A study of the effect of group delay distortion on an SMSK satellite communications channel

    NASA Technical Reports Server (NTRS)

    Kerczewski, Robert J.

    1987-01-01

    The effects of group delay distortion on an SMSK satellite communications channel have been investigated. Software and hardware simulations have been used to determine the effects of channel group delay variations with frequency on the bit error rate for a 220 Mbps SMSK channel. These simulations indicate that group delay distortions can significantly degrade the bit error rate performance. The severity of the degradation is dependent on the amount, type, and spectral location of the group delay distortion.

  3. Summary of recent investigations of inlet flow distortion effects on engine stability

    NASA Technical Reports Server (NTRS)

    Graber, E. J., Jr.; Braithwaite, W. M.

    1974-01-01

    A review is presented of recent experimental results, analytical procedures and test techniques employed to evaluate the effects of inlet flow distortion on the stability characteristics of representative afterburning turbofan and turbojet compression systems. Circumferential distortions of pressure and temperature, separately and in combination, are considered. Resulting engine sensitivity measurements are compared with predictions based on simplified parallel compressor models and with several distortion descriptor parameters.

  4. Summary of recent investigations of inlet flow distortion effect on engine stability

    NASA Technical Reports Server (NTRS)

    Graber, E. J., Jr.; Braithwaite, W. M.

    1974-01-01

    A review is presented of recent experimental results, analytical procedures and test techniques employed to evaluate the effects of inlet flow distortion on the stability characteristics of representative afterburning turbofan and turbojet compression systems. Circumferential distortions of pressure and temperature, separately and in combination are considered. Resulting engine sensitivity measurements are compared with predictions based on simplified parallel compressor models and with several distortion descriptor parameters.

  5. Four-wave mixing of a chirped signal with bandwidth-limited pump waves in a resonant medium

    SciTech Connect

    Kabanov, V V

    1998-07-31

    An investigation is reported of the characteristic features of four-wave interaction of a chirped signal with bandwidth-limited pump waves in a resonant medium modelled by a two-level scheme. Analytic estimates are obtained and a numerical analysis is made of the combined influence of various mechanisms (spatial phase matching, a finite nonlinear response time, and phase cross-modulation) on the spectral composition and on the temporal behaviour of the fourth pulse. Conditions are found for achieving, with practically undetectable distortions, phase conjugation of a chirped signal accompanied by shortening of the pulse envelope and narrowing of the spectrum of the phase-conjugate wave. (nonlinear optical phenomena)

  6. The role of visual similarity and memory in body model distortions.

    PubMed

    Saulton, Aurelie; Longo, Matthew R; Wong, Hong Yu; Bülthoff, Heinrich H; de la Rosa, Stephan

    2016-02-01

    Several studies have shown that the perception of one's own hand size is distorted in proprioceptive localization tasks. It has been suggested that those distortions mirror somatosensory anisotropies. Recent research suggests that non-corporeal items also show some spatial distortions. In order to investigate the psychological processes underlying the localization task, we investigated the influences of visual similarity and memory on distortions observed on corporeal and non-corporeal items. In experiment 1, participants indicated the location of landmarks on: their own hand, a rubber hand (rated as most similar to the real hand), and a rake (rated as least similar to the real hand). Results show no significant differences between rake and rubber hand distortions but both items were significantly less distorted than the hand. Experiments 2 and 3 explored the role of memory in spatial distance judgments of the hand, the rake and the rubber hand. Spatial representations of items measured in experiments 2 and 3 were also distorted but showed the tendency to be smaller than in localization tasks. While memory and visual similarity seem to contribute to explain qualitative similarities in distortions between the hand and non-corporeal items, those factors cannot explain the larger magnitude observed in hand distortions. PMID:26783695

  7. Jahn-Teller distortion of neutral divacancy in Si studied by positron annihilation spectroscopy

    NASA Astrophysics Data System (ADS)

    Nagai, Y.; Inoue, K.; Tang, Z.; Yonenaga, I.; Chiba, T.; Saito, M.; Hasegawa, M.

    2003-12-01

    Jahn-Teller (JT) distortion of the diamagnetic neutral divacancy (V20) in Si is studied by positron annihilation spectroscopy. Based on the anisotropy of electron momentum distribution around the divacancies obtained by two-dimensional angular correlation of positron annihilation radiation (2D-ACAR) technique, the preferred alignment of the divacancy in a specimen by compressing uniaxial stress along the [0 1 1] axis is detected. The direction of the alignment evidences the pairing JT distortion rather than the resonant bonding distortion, which is similar to the distortion in the singly negative divacancy (V2-).

  8. Some Lower Valence Vanadium Fluorides: Their Crystal Distortions, Domain Structures, Modulated Structures, Ferrimagnetism, and Composition Dependence.

    ERIC Educational Resources Information Center

    Hong, Y. S.; And Others

    1980-01-01

    Describes some contemporary concepts unique to the structure of advanced solids, i.e., their crystal distortions, domain structures, modulated structures, ferrimagnetism, and composition dependence. (Author/CS)

  9. Three-dimensional inversion of magnetotelluric impedance tensor data and full distortion matrix

    NASA Astrophysics Data System (ADS)

    Avdeeva, A.; Moorkamp, M.; Avdeev, D.; Jegen, M.; Miensopust, M.

    2015-07-01

    Galvanic distortion of magnetotelluric (MT) data due to small-scale surficial bodies or due to topography is one of the major factors that prevents accurate imaging of the subsurface. We present a 3-D algorithm for joint inversion of MT impedance tensor data and a frequency-independent full distortion matrix that circumvents this problem. We perform several tests of our algorithm on synthetic data affected by different amounts of distortion. These tests show that joint inversion leads to a better conductivity model compared to the inversion of the MT impedance tensor without any correction for distortion effects. For highly distorted data, inversion without any distortion correction results in strong artefacts and we cannot fit the data to the specified noise level. When the distortion is reduced, we can fit the data to an RMS of one, but still observe artefacts in the shallow part of the model. In contrast, in both cases our joint inversion can fit the data within the assumed noise level and the resulting models are comparable to the inversion of undistorted data. In addition, we show that the elements of the full distortion matrix can be well resolved by our algorithm. Finally, when inverting undistorted data, including the distortion matrix in the inversion only results in a minor loss of resolution. We therefore consider our new approach a promising tool for the general analysis of field MT data.

  10. Computational method for correcting complex optical distortion based on FOV division.

    PubMed

    Li, An; Wu, Yisi; Xia, Xinxing; Huang, Yuejin; Feng, Chaoqi; Zheng, Zhenrong

    2015-03-20

    We propose a computational method for correcting complex optical distortion in off-axis optical systems, such as the optical systems found in head-mounted and head-up displays. The proposed method divides the wide field of view (FOV) into subsections, thereby allowing the distortion to be calculated for each small FOV. Instead of applying the conventional distortion model, the distortion coefficients for each small FOV can be calculated using a simple linear polynomial. In addition, in contrast to the conventional distortion coefficients that refer to the deviation between the real and paraxial image, the distortion coefficients employed by this method directly characterize the relationship between the object and its image. Thus, using the polynomial in the reverse manner repeatedly for each small FOV with the corresponding distortion coefficients, a pixel lookup table is obtained, which can be used to accurately compensate for the distortion in the optical system. This method avoids complicated computations, and there are no requirements for intrinsic or extrinsic parameters. Our experiments verified the effectiveness of the method where the root-mean-square deviation of the projected distorted straight lines was corrected from 23 to 65 pixels to approximately 1 pixel. PMID:25968533

  11. Comparative Analysis of Regions with Distorted Segregation in Three Diploid Populations of Potato

    PubMed Central

    Manrique-Carpintero, Norma C.; Coombs, Joseph J.; Veilleux, Richard E.; Buell, C. Robin; Douches, David S.

    2016-01-01

    Genes associated with gametic and zygotic selection could underlie segregation distortion, observed as alterations of expected Mendelian genotypic frequencies in mapping populations. We studied highly dense genetic maps based on single nucleotide polymorphisms to elucidate the genetic nature of distorted segregation in potato. Three intra- and interspecific diploid segregating populations were used. DRH and D84 are crosses between the sequenced doubled monoploid DM 1-3 516 R44 Solanum tuberosum Group Phureja and either RH89-039-16 S. tuberosum or 84SD22, a S. tuberosum × S. chacoense hybrid. MSX902 is an interspecific cross between 84SD22 and Ber83 S. berthaultii × 2 × species mosaic. At the 0.05 significance level, 21%, 57%, and 51% of the total markers mapped in DRH, D84, and MSX902 exhibited distorted segregation, respectively. Segregation distortion regions for DRH were located on chromosomes 9 and 12; for D84 on chromosomes 2, 3, 4, 6, 7, and 8; and on chromosomes 1, 2, 7, 9, and 12 for MSX902. In general, each population had unique segregation distortion regions and directions of distortion. Interspecific crosses showed greater levels of distorted segregation and lower recombination rates as determined from the male parents. The different genomic regions where the segregation distortion regions occurred in the three populations likely reflect unique genetic combinations producing distorted segregation. PMID:27342736

  12. Investigation of MR image distortion for radiotherapy treatment planning of prostate cancer

    NASA Astrophysics Data System (ADS)

    Chen, Z.; Ma, C.-M.; Paskalev, K.; Li, J.; Yang, J.; Richardson, T.; Palacio, L.; Xu, X.; Chen, L.

    2006-03-01

    MR imaging based treatment planning for radiotherapy of prostate cancer is limited due to MR imaging system related geometrical distortions, especially for patients with large body sizes. On our 0.23 T open scanner equipped with the gradient distortion correction (GDC) software, the residual image distortions after the GDC were <5 mm within the central 36 cm × 36 cm area for a standard 48 cm field of view (FOV). In order to use MR imaging alone for treatment planning the effect of residual MR distortions on external patient contour determination, especially for the peripheral regions outside the 36 cm × 36 cm area, must be investigated and corrected. In this work, we performed phantom measurements to quantify MR system related residual geometric distortions after the GDC and the effective FOV. Our results show that for patients with larger lateral dimensions (>36 cm), the differences in patient external contours between distortion-free CT images and GDC-corrected MR images were 1-2 cm because of the combination of greater gradient distortion and loss of field homogeneity away from the isocentre and the uncertainties in patient setup during CT and MRI scans. The measured distortion maps were used to perform point-by-point corrections for patients with large dimensions inside the effective FOV. Using the point-by-point method, the geometrical distortion after the GDC were reduced to <3 mm for external contour determination and the effective FOV was expanded from 36 cm to 42 cm.

  13. Comparative Analysis of Regions with Distorted Segregation in Three Diploid Populations of Potato.

    PubMed

    Manrique-Carpintero, Norma C; Coombs, Joseph J; Veilleux, Richard E; Buell, C Robin; Douches, David S

    2016-01-01

    Genes associated with gametic and zygotic selection could underlie segregation distortion, observed as alterations of expected Mendelian genotypic frequencies in mapping populations. We studied highly dense genetic maps based on single nucleotide polymorphisms to elucidate the genetic nature of distorted segregation in potato. Three intra- and interspecific diploid segregating populations were used. DRH and D84 are crosses between the sequenced doubled monoploid DM 1-3 516 R44 Solanum tuberosum Group Phureja and either RH89-039-16 S. tuberosum or 84SD22, a S. tuberosum × S. chacoense hybrid. MSX902 is an interspecific cross between 84SD22 and Ber83 S. berthaultii × 2 × species mosaic. At the 0.05 significance level, 21%, 57%, and 51% of the total markers mapped in DRH, D84, and MSX902 exhibited distorted segregation, respectively. Segregation distortion regions for DRH were located on chromosomes 9 and 12; for D84 on chromosomes 2, 3, 4, 6, 7, and 8; and on chromosomes 1, 2, 7, 9, and 12 for MSX902. In general, each population had unique segregation distortion regions and directions of distortion. Interspecific crosses showed greater levels of distorted segregation and lower recombination rates as determined from the male parents. The different genomic regions where the segregation distortion regions occurred in the three populations likely reflect unique genetic combinations producing distorted segregation. PMID:27342736

  14. Response of a small-turboshaft-engine compression system to inlet temperature distortion

    NASA Technical Reports Server (NTRS)

    Biesiadny, T. J.; Klann, G. A.; Little, J. K.

    1984-01-01

    An experimental investigation was conducted into the response of a small-turboshaft-engine compression system to steady-state and transient inlet temperature distortions. Transient temperature ramps range from less than 100 K/sec to above 610 K/sec and generated instantaneous temperatures to 420 K above ambient. Steady-state temperature distortion levels were limited by the engine hardware temperature list. Simple analysis of the steady-state distortion data indicated that a particle separator at the engine inlet permitted higher levels of temperature distortion before onset of compressor surge than would be expected without the separator.

  15. Effects of amplitude distortions and IF equalization on satellite communication system bit-error rate performance

    NASA Technical Reports Server (NTRS)

    Kerczewski, Robert J.; Fujikawa, Gene; Svoboda, James S.; Lizanich, Paul J.

    1990-01-01

    Satellite communications links are subject to distortions which result in an amplitude versus frequency response which deviates from the ideal flat response. Such distortions result from propagation effects such as multipath fading and scintillation and from transponder and ground terminal hardware imperfections. Bit-error rate (BER) degradation resulting from several types of amplitude response distortions were measured. Additional tests measured the amount of BER improvement obtained by flattening the amplitude response of a distorted laboratory simulated satellite channel. The results of these experiments are presented.

  16. Characterization and Correction of Geometric Distortions in 814 Diffusion Weighted Images

    PubMed Central

    Treiber, Jeffrey Mark; White, Nathan S.; Steed, Tyler Christian; Bartsch, Hauke; Holland, Dominic; Farid, Nikdokht; McDonald, Carrie R.; Carter, Bob S.

    2016-01-01

    Introduction Diffusion Weighted Imaging (DWI), which is based on Echo Planar Imaging (EPI) protocols, is becoming increasingly important for neurosurgical applications. However, its use in this context is limited in part by significant spatial distortion inherent to EPI. Method We evaluated an efficient algorithm for EPI distortion correction (EPIC) across 814 DWI scans from 250 brain tumor patients and quantified the magnitude of geometric distortion for whole brain and multiple brain regions. Results Evaluation of the algorithm’s performance revealed significantly higher mutual information between T1-weighted pre-contrast images and corrected b = 0 images than the uncorrected b = 0 images (p < 0.001). The distortion magnitude across all voxels revealed a median EPI distortion effect of 2.1 mm, ranging from 1.2 mm to 5.9 mm, the 5th and 95th percentile, respectively. Regions adjacent to bone-air interfaces, such as the orbitofrontal cortex, temporal poles, and brain stem, were the regions most severely affected by DWI distortion. Conclusion Using EPIC to estimate the degree of distortion in 814 DWI brain tumor images enabled the creation of a topographic atlas of DWI distortion across the brain. The degree of displacement of tumors boundaries in uncorrected images is severe but can be corrected for using EPIC. Our results support the use of distortion correction to ensure accurate and careful application of DWI to neurosurgical practice. PMID:27027775

  17. Tomosynthesis-detected Architectural Distortion: Management Algorithm with Radiologic-Pathologic Correlation.

    PubMed

    Durand, Melissa A; Wang, Steven; Hooley, Regina J; Raghu, Madhavi; Philpotts, Liane E

    2016-01-01

    As use of digital breast tomosynthesis becomes increasingly widespread, new management challenges are inevitable because tomosynthesis may reveal suspicious lesions not visible at conventional two-dimensional (2D) full-field digital mammography. Architectural distortion is a mammographic finding associated with a high positive predictive value for malignancy. It is detected more frequently at tomosynthesis than at 2D digital mammography and may even be occult at conventional 2D imaging. Few studies have focused on tomosynthesis-detected architectural distortions to date, and optimal management of these distortions has yet to be well defined. Since implementing tomosynthesis at our institution in 2011, we have learned some practical ways to assess architectural distortion. Because distortions may be subtle, tomosynthesis localization tools plus improved visualization of adjacent landmarks are crucial elements in guiding mammographic identification of elusive distortions. These same tools can guide more focused ultrasonography (US) of the breast, which facilitates detection and permits US-guided tissue sampling. Some distortions may be sonographically occult, in which case magnetic resonance imaging may be a reasonable option, both to increase diagnostic confidence and to provide a means for image-guided biopsy. As an alternative, tomosynthesis-guided biopsy, conventional stereotactic biopsy (when possible), or tomosynthesis-guided needle localization may be used to achieve tissue diagnosis. Practical uses for tomosynthesis in evaluation of architectural distortion are highlighted, potential complications are identified, and a working algorithm for management of tomosynthesis-detected architectural distortion is proposed. (©)RSNA, 2016. PMID:26963448

  18. Shock wave structure in heterogeneous reactive media

    SciTech Connect

    Baer, M.R.

    1997-06-01

    Continuum mixture theory and mesoscale modeling are applied to describe the behavior of shock-loaded heterogeneous media. One-dimensional simulations of gas-gun experiments demonstrate that the wave features are well described by mixture theory, including reflected wave behavior and conditions where significant reaction is initiated. Detailed wave fields are resolved in numerical simulations of impact on a lattice of discrete explosive {open_quotes}crystals{close_quotes}. It is shown that rapid distortion first occurs at material contact points; the nature of the dispersive fields includes large amplitude fluctuations of stress over several particle pathlengths. Localization of energy causes {open_quotes}hot-spots{close_quotes} due to shock focusing and plastic work as material flows into interstitial regions.

  19. Symmetry, distorted band structure, and spin-orbit coupling of group-III metal-monochalcogenide monolayers

    NASA Astrophysics Data System (ADS)

    Li, Pengke; Appelbaum, Ian

    2015-11-01

    The electronic structure of (group-III) metal-monochalcogenide monolayers exhibits many unusual features. Some, such as the unusually distorted upper valence-band dispersion we describe as a "caldera," are primarily the result of purely orbital interactions. Others, including spin splitting and wave-function spin mixing, are directly driven by spin-orbit coupling. We employ elementary group theory to explain the origin of these properties, and use a tight-binding model to calculate the phenomena enabled by them, such as the band-edge carrier effective g factors, optical absorption spectrum, conduction electron spin orientation, and a relaxation-induced upper-valence-band population inversion and spin polarization mechanism.

  20. Modeling of Millimeter-Wave Modulation Characteristics of Semiconductor Lasers under Strong Optical Feedback

    PubMed Central

    Bakry, Ahmed

    2014-01-01

    This paper presents modeling and simulation on the characteristics of semiconductor laser modulated within a strong optical feedback (OFB-)induced photon-photon resonance over a passband of millimeter (mm) frequencies. Continuous wave (CW) operation of the laser under strong OFB is required to achieve the photon-photon resonance in the mm-wave band. The simulated time-domain characteristics of modulation include the waveforms of the intensity and frequency chirp as well as the associated distortions of the modulated mm-wave signal. The frequency domain characteristics include the intensity modulation (IM) and frequency modulation (FM) responses in addition to the associated relative intensity noise (RIN). The signal characteristics under modulations with both single and two mm-frequencies are considered. The harmonic distortion and the third order intermodulation distortion (IMD3) are examined and the spurious free dynamic range (SFDR) is calculated. PMID:25383381