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Sample records for 2f1-f2 distortion product

  1. The generation mechanisms and repeatability of 2F1-F2 distortion product otoacoustic emissions: study on normally hearing subjects.

    PubMed

    Parazzini, M; Wilson, H K; Bell, S; Tognola, G; Ravazzani, P; Lutman, M E

    2006-01-01

    The 2F1-F2 distortion product otoacoustic emission (DPOAE) is considered to consist of two generation mechanisms, the so-called place-fixed and wave-fixed mechanisms, depending on the frequency ratio F2/F1. The general assumption is that for a small frequency ratio there is a predominantly place-fixed emission mechanism, while with a larger frequency ratio there is a predominantly wave-fixed mechanism. There is also a lack of published data on the repeatability of the two components when separated. One aim of this study was therefore to identify the wave-fixed and place-fixed components of the 2F1-F2 DPOAE using a time-window separation method. The second aim was to quantify the test-retest repeatability of the separated 2F1-F2 DPOAE components in a group of normally hearing subjects. Results confirmed the presence of wave-fixed and place-fixed components for 2F1-F2 and a predominance of place or wave-fixed DPOAE as a function of frequency ratio. This pattern varied somewhat among subjects. Moreover, regardless of which component was stronger for any F2/F1, both components were highly repeatable across time within individual ears.

  2. Cochlear microphonic evidence for mechanical propagation of distortion products (f2-f1) and (2f1-f2)

    NASA Astrophysics Data System (ADS)

    Gibian, G. L.

    1980-03-01

    Cochlear microphonic (CM) data were obtained from the second and third turns of the chinchilla cochlea. Fluid-filled glass micropipettes were used to record from scala media, and nichrome wire electrodes were used to record differentially between scala vestibuli and scala tympani. Validity of our results is supported in part by the sensitivity and sharp tuning of the CM and, in the case of the scala media recordings, by the presence of a normal DC endolymphatic potential. It was observed, with sound pressure levels (SPL) as low as 25 dB, that these distortion products in CM display tuning similar to the single-tone response. The tuning similarities observed in the present CM study are consistent with previous neural studies. From these tuning similarities, it is concluded that our CM data reflect the presence of mechanically propagated distortion products at low SPLs.

  3. Parameters to Maximize 2f2-f1 Distortion Product Otoacoustic Emission Levels

    ERIC Educational Resources Information Center

    Horn, Jennifer H.; Pratt, Shiela R.; Durrant, John D.

    2008-01-01

    Purpose: Past research has established parameters for the 2f1-f2 distortion product otoacoustic emissions (DPOAEs) that enhance response levels (e.g., L1 - L2 = 10 dB; f2/f1 = 1.22; L1, L2 = 65, 55 dB SPL). These same parameters do not optimize 2f2-f1 DPOAEs. Therefore, this study was conducted to evaluate more completely those parameters that…

  4. Low-frequency distortion product otoacoustic emissions in two species of kangaroo rats: implications for auditory sensitivity.

    PubMed

    Shaffer, L A; Long, G R

    2004-01-01

    Low-frequency distortion-product otoacoustic emissions were measured in two species of kangaroo rats to test the prediction that a large footdrumming species (e.g., Dipodomys spectabilis) would have greater distortion-product otoacoustic emission amplitude than a small non-footdrumming species (e.g., Dipodomys merriami), indicating better hearing sensitivity at low frequencies. Equal-level (65 dB SPL) stimulus tones ( f(1), f(2)), presented over a ( f(1)) range of 200-1000 Hz, were used to evoke the 2 f(1)- f(2) distortion-product otoacoustic emission. Mean 2 f(1)- f(2) levels for D. merriami showed good correspondence to previously published audiograms for that species. Mean 2 f(1)- f(2) levels and 95% confidence intervals indicated species differences below 400 Hz, supporting the theory that low-frequency hearing sensitivity is better in large kangaroo rat species. These results suggest that the size-related divergence in footdrumming behavior may be related to differential auditory sensitivity.

  5. 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

  6. Transmission of cochlear distortion products as slow waves: a comparison of experimental and model data.

    PubMed

    Vetešník, Aleš; Gummer, Anthony W

    2012-05-01

    There is a long-lasting question of how distortion products (DPs) arising from nonlinear amplification processes in the cochlea are transmitted from their generation sites to the stapes. Two hypotheses have been proposed: (1) the slow-wave hypothesis whereby transmission is via the transverse pressure difference across the cochlear partition and (2) the fast-wave hypothesis proposing transmission via longitudinal compression waves. Ren with co-workers have addressed this topic experimentally by measuring the spatial vibration pattern of the basilar membrane (BM) in response to two tones of frequency f(1) and f(2). They interpreted the observed negative phase slopes of the stationary BM vibrations at the cubic distortion frequency f(DP) = 2f(1) - f(2) as evidence for the fast-wave hypothesis. Here, using a physically based model, it is shown that their phase data is actually in accordance with the slow-wave hypothesis. The analysis is based on a frequency-domain formulation of the two-dimensional motion equation of a nonlinear hydrodynamic cochlea model. Application of the analysis to their experimental data suggests that the measurement sites of negative phase slope were located at or apical to the DP generation sites. Therefore, current experimental and theoretical evidence supports the slow-wave hypothesis. Nevertheless, the analysis does not allow rejection of the fast-wave hypothesis.

  7. Distortion product otoacoustic emissions provide clues to hearing mechanisms in the frog

    NASA Astrophysics Data System (ADS)

    Vassilakis, Pantelis; Narins, Peter M.

    2003-10-01

    Cubic distortion product otoacoustic emissions (DPOAEs) were recorded from 10 Rana pipiens and 10 Rana catesbeiana, 5 males and 5 females each. The I/O curves obtained from the amphibian papilla (AP) of both species are very similar to the respective mammalian curves, indicating that, like in the mammalian cochlea, there may be an amplification process active in the frog AP. The DPOAE level dependence on primary levels is also similar to the mammalian case, suggesting a mechanical structure in the frog inner ear may be functioning analogously to the mammalian basilar membrane. DPOAE audiograms were obtained for primary frequencies spanning the animals hearing range and levels determined by the previous experiments. R. catesbeiana produce stronger emissions than R. pipiens and, consistent with previously reported sexual dimorphism in the mammalian and anuran auditory systems, females from both species produce stronger emissions than males. Additionally, the 2f1-f2 DPOAE is generated primarily at the DPOAE frequency place, while the 2f2-f1 DPOAE is generated primarily at a frequency place between the primaries. This difference in mammalian and frog DPOAEs may be linked to an anatomical difference that results in the acoustic energy following opposite paths through the mammalian and frog inner ears. [Work supported by NIH Grant No. DC-00222 to Peter M. Narins.] a)Currently at De Paul Univ., School of Music, Chicago, IL 60614.

  8. Effects of aspirin on distortion product otoacoustic emission suppression in human adults: A comparison with neonatal data

    NASA Astrophysics Data System (ADS)

    Abdala, Carolina

    2005-09-01

    One of the distortion product otoacoustic emission (DPOAE) paradigms used to study cochlear function is DPOAE (2f1-f2) ipsilateral suppression. Newborns do not have adultlike DPOAE suppression. At 6000 Hz, infants show excessively narrow DPOAE suppression tuning and shallow growth of suppression for low-frequency suppressor tones. The source of this immaturity is not known but the outer hair cell (OHC) is one possible locus. In the present study, DPOAE suppression was measured at f2=1500 and 6000 Hz from two groups with impaired OHC function in an attempt to model the observed immaturity in neonates: adults with aspirin-induced OHC dysfunction and subjects with sensorineural hearing loss (SNHL). Their DPOAE suppression results were compared to those obtained from a group of term newborns to address whether infant DPOAE suppression resembles suppression from individuals with known OHC dysfunction. Results indicate that aspirin systematically alters DPOAE suppression in adults at f2=6000 Hz, but not 1500 Hz. However, neither aspirin-induced OHC dysfunction nor naturally occurring SNHL produces ``neonatal-like'' DPOAE suppression at either test frequency. This finding does not support the hypothesis that non-adultlike DPOAE suppression characterizing newborns can be explained by minor impairments or alterations of OHC function.

  9. Time-domain demonstration of distributed distortion-product otoacoustic emission components

    PubMed Central

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

    2013-01-01

    Distortion-product otoacoustic emissions (DPOAEs) were measured in rabbits as time waveforms by employing a phase-rotation technique to cancel all components in the final average, except the 2f1-f2 DPOAE. Subsequent filtering allowed the DPOAE waveform to be clearly visualized in the time domain. In most conditions, f2 was turned off for 6 ms, which produced a gap so that the DPOAE was no longer generated. These procedures allowed the DPOAE onset as well as the decay during the gap to be observed in the time domain. DPOAEs were collected with L1 = L2 = 65-dB sound pressure level primary-tone levels for f2/f1 ratios from 1.25 to 1.01 in 0.02 steps. Findings included the appearance of complex onsets and decays for the DPOAE time waveforms as the f2/f1 ratio was decreased and the DPOAE level was reduced. These complexities were unaffected by interference tones (ITs) near the DPOAE frequency place (fdp), but could be removed by ITs presented above f2, which also increased DPOAE levels. Similar outcomes were observed when DPOAEs were measured at a sharp notch in the DPOAE level as a function of the f2 primary tone frequency, i.e., DP-gram. Both findings were consistent with the hypothesis that the DPOAE-ratio function, and some notches in the DP-gram, are caused by interactions of distributed DPOAE components with unique phases. PMID:23862812

  10. Temperature dependence of distortion-product otoacoustic emissions in tympanal organs of locusts.

    PubMed

    Möckel, Doreen; Kössl, Manfred; Lang, Julian; Nowotny, Manuela

    2012-09-15

    Distortion-product otoacoustic emissions (DPOAEs) in tympanal organs of insects are vulnerable to manipulations that interfere with the animal's physiological state. Starting at a medium temperature, we raised and lowered the locust's body temperature within the range of 12 to 35°C by changing the temperature of the surrounding air, while recording DPOAEs. These experimental manipulations resulted in reversible amplitude changes of the 2f(1)-f(2) emission, which were dependent on stimulus frequency and level. Using low f(2) frequencies of up to 10 kHz, a temperature increase (median +8-9°C) led to an upward shift of DPOAE amplitudes of approximately +10 dB, whereas a temperature decrease (median -7°C) was followed by a reduction of DPOAE amplitudes by 3 to 5 dB. Both effects were only present in the range of the low-level component of DPOAE growth functions below L2 levels (levels of the f(2) stimulus) of approximately 30 dB SPL. DPOAEs evoked by higher stimulus levels as well as measurements using higher stimulation frequencies above 10 kHz remained unaffected by any temperature shifts. The Arrhenius activation energy was calculated from the -10 dB SPL thresholds (representing the low-level component) of growth functions, which had been measured with 8 and 10 kHz as f(2) frequencies and amounted to up to ~34 and 41 kJ mol(-1), respectively. Such activation energy values provide a hint that the dynein-tubulin system within the scolopidial receptors could play an essential part in the DPOAE generation in tympanal organs.

  11. Distortion product otoacoustic emission level maps from normal and noise-damaged cochleae.

    PubMed

    Meinke, Deanna K; Clavier, Odile H; Norris, Jesse; Kline-Schoder, Robert; Allen, Lindsay; Buckey, Jay C

    2013-01-01

    Distortion product otoacoustic emission (DPOAE) level mapping may be useful for detecting noise-induced hearing loss (NIHL) early. Employing DPOAE mapping effectively requires knowledge of the optimal mapping parameters to use for detecting noise-induced changes. The goal of this project was to show the map regions that differ most between normal and noise-damaged cochlea to determine the optimal mapping parameters for detecting NIHL. DPOAE level maps were generated for the 2f 1 -f 2 and the 2f 2 -f 1 DPOAEs for 17 normal hearing male subjects and 19 male subjects with NIHL. DPOAEs were measured in DPOAE frequency steps of approximately 44 Hz from 0.5 kHz to 6 kHz using constant f 2 /f 1 ratios incremented in 0.025 steps from 1.025 to 1.5 using both unequal-level (L1,L2 = 65,55 dB sound pressure level (SPL)) and equi-level (L1,L2 = 75,75 dB SPL) stimulus paradigms. Maximal responses for the 2f 2 -f 1 emission at L1,L2 = 65,55 dB SPL were found at lower ratios compared to previous studies. The map regions where NIHL eliminated or reduced DPOAE magnitude were identified. DPOAE level mapping using higher-level, equi-level primaries produced significantly more detectable emissions particularly for the 2f 2 -f 1 emission. The data from this study can be used to optimize DPOAE level mapping parameters for tracking noise-exposed subjects longitudinally.

  12. Distortion product otoacoustic emissions in geriatric dogs.

    PubMed

    Strain, G M; Rosado Martinez, A J; McGee, K A; McMillan, C L

    2016-10-01

    Recordings of distortion product otoacoustic emissions (DPOAE) were taken from 28 geriatric dogs aged 12.2 ± 2.2 years and 15 control dogs aged 5.9 ± 3.0 years (mean ± standard deviation) to demonstrate frequency-specific changes in cochlear responses. Recordings were performed for primary frequencies of 2-12 kHz in 2 kHz increments. Brainstem auditory evoked response (BAER) recordings were also made from geriatric dogs for comparison with DPOAE responses. Significant decreases in DPOAE response amplitudes were observed at frequencies of 6-12 kHz in geriatric dogs compared to control dogs, reflecting loss of cochlear outer hair cells along the length of the cochlea. Significant decreases in response amplitudes were not seen at frequencies of 2 or 4 kHz. Decreases in BAER response amplitudes subjectively paralleled the depressed DPOAE amplitudes. No significant linear regression relationships were found for DPOAE response amplitude vs. age despite the progressive nature of age-related hearing loss. The reductions in response at all frequencies starting at the age where dogs are considered geriatric indicate that age-related hearing loss begins earlier in the life span. DPOAE recordings provide a means to assess cochlear function across different portions of the auditory spectrum for assessing hearing loss associated with aging, and potentially for losses from other causes of decreased auditory function.

  13. Level dependence of the nonlinear-distortion component of distortion-product otoacoustic emissions in humans.

    PubMed

    Zelle, Dennis; Thiericke, John P; Dalhoff, Ernst; Gummer, Anthony W

    2015-12-01

    Distortion-product otoacoustic emissions (DPOAEs) emerge when presenting two primary tones with different frequencies f1 and f2 to the cochlea and are commonly used in diagnosis and research to evaluate the functional state of the cochlea. Optimal primary-tone stimulus levels accounting for the different level dependencies of the traveling-wave amplitudes of the two primary tones near the f2-tonotopic place on the basilar membrane are often used to maximize DPOAE amplitudes. However, parameters defining the optimal levels can be affected by wave interference between the nonlinear-distortion and coherent-reflection components of the DPOAE. Here, the components were separated in the time domain using a pulsed stimulus paradigm and optimal levels determined. Based on the amplitude dependence of the nonlinear-distortion components on primary-tone stimulus levels, level parameters yielding maximum DPOAE amplitudes were derived for six normal-hearing adults and compared to data recorded with continuous two-tone stimulation. The level parameters resulting from analysis of the nonlinear-distortion components show dependence on stimulus frequency and small standard deviations. DPOAE input/output functions derived for optimal levels exhibit larger slopes, wider dynamic range and less variability across subjects than those derived for conventional stimulus and analysis conditions, potentially increasing their reliability and sensitivity for assessing cochlea function.

  14. Periodogram based tests for distortion product otoacoustic emissions.

    PubMed

    Craigmile, Peter F; King, Wayne M

    2004-07-01

    Distortion product otoacoustic emissions (DPOAEs) are an important nonbehavioral measure of cochlear function, which provides a close analogue of the behavioral pure-tone audiogram. DPOAEs are sinusoidal distortion products (DPs) produced by nonlinearities in the healthy cochlea. Detection of DPs is accomplished in the Fourier domain with a periodogram based test. The test compares the power in the DP periodogram bin to a noise estimate derived from a certain number of the surrounding bins. Statistical properties of this test to date have only been examined by constructing receiver operator characteristics curves derived from DPOAE measurements in normal and hearing impaired individuals. In this paper the null distribution of this order-statistic based test is explicitly derived, and via simulations intended to mimic the nonwhite features of real-ear noise measurements, the power of the test is demonstrated. These simulations demonstrate that a local F test is more powerful than this DPOAE test, with critical values that are easier to calculate. Although the power of both tests increase with an increasing number of bins, the improvement is negligible at around four bins. Since the power of both tests decrease at lower DP frequencies, it is not recommended to use a large number of bins.

  15. Sources of variability in distortion product otoacoustic emissions

    PubMed Central

    Garner, Cassie A.; Neely, Stephen T.; Gorga, Michael P.

    2008-01-01

    The goal of this study was to determine the extent to which the variability seen in distortion product otoacoustic emissions (DPOAEs), among ears with normal hearing, could be accounted for. Several factors were selected for investigation, including behavioral threshold, differences in middle-ear transmission characteristics either in the forward or the reverse direction, and differences in contributions from the distortion and reflection sources. These variables were assessed after optimizing stimulus parameters for individual ears at each frequency. A multiple-linear regression was performed to identify whether the selected variables, either individually or in combination, explained significant portions of variability in DPOAE responses. Behavioral threshold at the f2 frequency and behavioral threshold squared at that same frequency explained the largest amount of variability in DPOAE level, compared to the other variables. The combined model explained a small, but significant, amount of variance in DPOAE level at five frequencies. A large amount of residual variability remained, even at frequencies where the model accounted for significant amounts of variance. PMID:18681596

  16. 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.

  17. Distortion Product Otoacoustic Emissions Evoked by Tone Complexes

    PubMed Central

    Meenderink, Sebastiaan W. F.

    2010-01-01

    Distortion product otoacoustic emissions (DPOAEs) are traditionally evoked by two-tone stimuli. In this study, emission data from Mongolian gerbils are reported that were obtained with stimuli consisting of six to 10 tones. The stimuli were constructed by replacing one of the tones of a tone pair by a narrowband multitone complex. This produced rich spectra of the ear canal sound pressure in which many of the third-order DPOAEs originated from the interaction of triplets of stimulus components. A careful choice of the stimulus frequencies ensured that none of these DPOAE components coincided. Three groups of DPOAEs are reported, two of which are closely related to DPOAEs evoked by tone pairs. The third group has no two-tone equivalent and only arises when using a multitone stimulus. We analyzed the relation between multitone-evoked DPOAEs and DPOAEs evoked by tone pairs, and explored the new degrees of freedom offered by the multitone paradigm. PMID:20838846

  18. The origin of the distortion product otoacoustic emission fine structure

    NASA Astrophysics Data System (ADS)

    Piskorski, Pawel

    Distortion-product otoacoustic emissions (DPOAEs) are sounds detected in the ear canal which are generated by the nonlinear processes in the inner ear (cochlea) in response to the external stimulation of two or more tones (primaries). Their generation region in the cochlea can be systematically changed by varying the primary frequencies, and they are currently being evaluated for possible clinical use in screening for hearing defects. The phase and amplitude of various orders of DPOAEs of frequencies, f/sb [dp]=f1-n(f2-f1),/ (n=1,2,/...), were measured in human subjects for two- tone stimuli of frequencies f1 and f2 (>f1). A number of experimental paradigms (fixed primary ratio f2/f1, fixed f1, fixed f2, and fixed f/sb [dp]) were used to investigate the nature of peaks and valleys (fine structure) of DPOAEs in their phase and amplitude dependence on the primary frequencies. This fine structure must be taken into account in any potential clinical applications of DPOAEs. The experimental results largely support a model in which the fine structure stems from interference at the base of the cochlea between distortion product (DP) components coming from the primary DPOAE source region (around the f2 tonotopic place) and components coming from the DP tonotopic place (via reflection of an apically moving DP wave). The spectral periodicity of the fine structures for several orders of apical DPOAEs corresponds to a tonotopic displacement of about 0.4 mm along the basilar membrane (BM) (0.4 bark). In agreement with the reaction model, this spectral spacing is also characteristic of synchronous evoked and spontaneous otoacoustic emission spectra as well as the microstructure of the hearing threshold. Approximate analytic expressions for the mechanisms which are responsible for the fine structure are used to interpret the data.

  19. Distortion product otoacoustic emissions in young adult and geriatric cats.

    PubMed

    Strain, George M; McGee, Kain A

    2017-03-01

    Recordings of distortion product otoacoustic emissions (DPOAEs) were taken from 15 geriatric cats (mean age ± standard deviation, SD, 13.6 ± 2.7 years; range 10.2-19.4 years) and 12 young adult control cats (mean ± SD 4.6 ± 0.5 years; range 3.4-5 years) to identify frequency-specific age-related changes in cochlear responses. Recordings were performed for primary frequencies from 2 to 12 kHz in 2 kHz increments. Cats were considered to be geriatric > 11.9 ± 1.9 years of age. Brainstem auditory evoked response (BAER) recordings were also made for subjective comparison with DPOAE responses. No differences in DPOAE response amplitudes were observed at any tested frequency in geriatric cats compared to control cats, reflecting an apparent absence of loss of cochlear outer hair cells along the length of the cochlea. No linear regression relationships were found for DPOAE response amplitude versus age in geriatric cats, despite the progressive nature of age-related hearing loss in other species. The absence of reductions in response at any of the tested frequencies in cats within the age span where cats are considered to be geriatric indicates that age-related hearing loss, if it does develop in cats, begins later in the life span of cats than in dogs or human beings.

  20. Temperature dependence of anuran distortion product otoacoustic emissions.

    PubMed

    Meenderink, Sebastiaan W F; van Dijk, Pim

    2006-09-01

    To study the possible involvement of energy-dependent mechanisms in the transduction of sound within the anuran ear, distortion product otoacoustic emissions (DPOAEs) were recorded in the northern leopard frog over a range of body temperatures. The effect of body temperature depended on the stimulus levels used and on the hearing organ under investigation. Low-level DPOAEs from the amphibian papilla (AP) were reversibly depressed for decreased body temperatures. Apparently, DPOAE generation in the AP depends on metabolic rate, indicating the involvement of active processes in the transduction of sound. In contrast, in the other hearing organ, the basilar papilla (BP), the effects of body temperature on DPOAEs were less pronounced, irrespective of the stimulus levels used. Apparently, metabolic rate is less influencing DPOAE generation. We interpret these results as evidence that no amplifier is involved in sound transduction in the BP. The passive functioning of the anuran BP would place this hearing organ in a unique position within tetrapod hearing, but may actually be beneficial to ectothermic species because it will provide the animal with a consistent spectral window, regardless of ambient or body temperature.

  1. Latencies of extracted distortion-product otoacoustic source components

    NASA Astrophysics Data System (ADS)

    Zelle, Dennis; Thiericke, John P.; Gummer, Anthony W.; Dalhoff, Ernst

    2015-12-01

    Distortion product otoacoustic emissions (DPOAEs) evolve as a byproduct of the nonlinear amplification process of two stimulus tones f2 ≥ f1 in the cochlea. According to a prevailing model, DPOAEs comprise a nonlinear-generation and a coherent-reflection component. Recently, we introduced a new technique using short f2 pulses which enables the extraction of both source components in the time domain by nonlinear least-square curve fitting to decompose the DPOAE response into pulse basis functions (PBFs). The analysis of the extracted DPOAE source components in the time domain enables determination of their latencies which may be used to estimate cochlear frequency tuning. Short-pulse DPOAEs were acquired from 16 subjects for f2 = 1.5, 2, 3, and 4 kHz using six primary-tone levels with L2 = 25 - 65 dB SPL. For the extracted nonlinear-generation and coherent-reflection components, latencies decrease with increasing stimulus frequency and level. The obtained latency values are in accordance with the expected behavior of the cochlear amplifier and may provide an additional diagnostic parameter to assess frequency tuning.

  2. Transient Evoked and Distortion Product Otoacoustic Emissions in a Group of Neonates

    PubMed Central

    Silva, Giovanna Cesar; Delecrode, Camila Ribas; Kemp, Adriana Tahara; Martins, Fabiana; Cardoso, Ana Claudia Vieira

    2015-01-01

    Introduction The most commonly used method in neonatal hearing screening programs is transient evoked otoacoustic emissions in the first stage of the process. There are few studies comparing transient evoked otoacoustic emissions with distortion product, but some authors have investigated the issue. Objective To correlate the results of transient evoked and distortion product otoacoustic emissions in a Brazilian maternity hospital. Methods This is a cross-sectional, comparative, and prospective study. The study included 579 newborns, ranging from 6 to 54 days of age, born in a low-risk maternity hospital and assessed for hearing loss. All neonates underwent hearing screening by transient evoked and distortion product otoacoustic emissions. The results were analyzed using the Spearman correlation test to relate the two procedures. Results The pass index on transient evoked otoacoustic emissions was 95% and on distortion product otoacoustic emissions was 91%. The comparison of the two procedures showed that 91% of neonates passed on both procedures, 4.5% passed only on transient evoked otoacoustic emissions, 0.5% passed only on distortion product otoacoustic emissions, and 4% failed on both procedures. The inferential analysis showed a significant strong positive relationship between the two procedures. Conclusion The failure rate was higher in distortion product otoacoustic emissions when compared with transient evoked; however, there was correlation between the results of the procedures. PMID:26157501

  3. Interpretation of standard distortion product otoacoustic emission measurements in light of the complete parametric response.

    PubMed

    Mills, David M

    2002-10-01

    Emission characteristics (at 2f1-f2) are measured in Mongolian gerbil as a function of the independent variation of all four stimulus parameters, the frequencies (f1 and f2) and the intensities (L1 and L2) of the two stimulus tones. The main five-dimensional display chosen is a logarithmic grid of frequencies, where for each frequency pair there is a contour map of the emission amplitude as a function of the two stimulus levels. The feature which leads to the greatest complexity in the proper interpretation of emission responses is the widespread presence of "notches" in these contour maps. Notches are lines of relative minima in the emission amplitude, and are found at either: (1) constant L1, but only in regions where L1 > L2; or (2) at constant L2, only where L2 > or = L1. Notches are not found at any other orientations, and are associated with emission phase shifts of about 180 degrees as the notch line is traversed. These notch characteristics are explained by phase cancellation in a simple cochlear amplifier model in which there is a change, as a function of the stimulus level alone, of relevant characteristics of the cochlear response to a single tone. Only one mechanism of emission generation is required to explain the observed patterns, i.e., there is no need to invoke different "active" and "passive" mechanisms. Unless properly accounted for, the presence of notches adversely affects all of the standard emission measurements, i.e., all methods which cover a restricted parameter set such as DPgrams, input-output or "growth" functions, and frequency ratio functions. Conversely, because the notch location appears approximately invariant in the cochlea, notches potentially make it possible to use certain emission growth functions to estimate forward and reverse middle-ear transfer functions.

  4. Estimating the operating point of the cochlear transducer using low-frequency biased distortion products

    PubMed Central

    Brown, Daniel J.; Hartsock, Jared J.; Gill, Ruth M.; Fitzgerald, Hillary E.; Salt, Alec N.

    2009-01-01

    Distortion products in the cochlear microphonic (CM) and in the ear canal in the form of distortion product otoacoustic emissions (DPOAEs) are generated by nonlinear transduction in the cochlea and are related to the resting position of the organ of Corti (OC). A 4.8 Hz acoustic bias tone was used to displace the OC, while the relative amplitude and phase of distortion products evoked by a single tone [most often 500 Hz, 90 dB SPL (sound pressure level)] or two simultaneously presented tones (most often 4 kHz and 4.8 kHz, 80 dB SPL) were monitored. Electrical responses recorded from the round window, scala tympani and scala media of the basal turn, and acoustic emissions in the ear canal were simultaneously measured and compared during the bias. Bias-induced changes in the distortion products were similar to those predicted from computer models of a saturating transducer with a first-order Boltzmann distribution. Our results suggest that biased DPOAEs can be used to non-invasively estimate the OC displacement, producing a measurement equivalent to the transducer operating point obtained via Boltzmann analysis of the basal turn CM. Low-frequency biased DPOAEs might provide a diagnostic tool to objectively diagnose abnormal displacements of the OC, as might occur with endolymphatic hydrops. PMID:19354389

  5. Noise Levels during Aerobics and the Potential Effects on Distortion Product Otoacoustic Emissions

    ERIC Educational Resources Information Center

    Torre, Peter, III; Howell, Jennifer C.

    2008-01-01

    The purpose of this study was to measure noise levels during aerobics classes and to examine how outer hair cell (OHC) function, using distortion product otoacoustic emissions (DPOAEs), may be affected by this exposure. Fifty individuals (48 women and 2 men, ages 19-41 years) participated in 50-min aerobics classes. Noise levels were measured…

  6. Production and Perception of Distortion in Word-Initial Friction Duration

    ERIC Educational Resources Information Center

    Jovicic, Slobodan T.; Kasic, Zorca; Punisic, Silvana

    2010-01-01

    The purpose of the present study was to investigate (a) the distortion in production of word-initial friction duration in fricative /[esh]/, and (b) the perceptual discrimination between typical (normal) and atypical (prolonged or lengthened) friction duration. In the first experiment 80 school aged children pronounced word /[esh]uma/, 40 of them…

  7. Distortion products and backward-traveling waves in nonlinear active models of the cochlea

    PubMed Central

    Sisto, Renata; Moleti, Arturo; Botti, Teresa; Bertaccini, Daniele; Shera, Christopher A.

    2011-01-01

    This study explores the phenomenology of distortion products in nonlinear cochlear models, predicting their amplitude and phase along the basilar membrane. The existence of a backward-traveling wave at the distortion-product frequency, which has been recently questioned by experiments measuring the phase of basilar-membrane vibration, is discussed. The effect of different modeling choices is analyzed, including feed-forward asymmetry, micromechanical roughness, and breaking of scaling symmetry. The experimentally observed negative slope of basilar-membrane phase is predicted by numerical simulations of nonlinear cochlear models under a wide range of parameters and modeling choices. In active models, positive phase slopes are predicted by the quasi-linear analytical computations and by the fully nonlinear numerical simulations only if the distortion-product sources are localized apical to the observation point and if the stapes reflectivity is unrealistically small. The results of this study predict a negative phase slope whenever the source is distributed over a reasonably wide cochlear region and/or a reasonably high stapes reflectivity is assumed. Therefore, the above-mentioned experiments do not contradict “classical” models of cochlear mechanics and of distortion-product generation. PMID:21568417

  8. Stability of the Medial Olivocochlear Reflex as Measured by Distortion Product Otoacoustic Emissions

    ERIC Educational Resources Information Center

    Mishra, Srikanta K.; Abdala, Carolina

    2015-01-01

    Purpose: The purpose of this study was to assess the repeatability of a fine-resolution, distortion product otoacoustic emission (DPOAE)-based assay of the medial olivocochlear (MOC) reflex in normal-hearing adults. Method: Data were collected during 36 test sessions from 4 normal-hearing adults to assess short-term stability and 5 normal-hearing…

  9. Modeling two-tone suppression and distortion product on basilar membrane

    NASA Astrophysics Data System (ADS)

    Murakami, Yasuki; Ishimitsu, Shunsuke

    2015-12-01

    This paper reveals mechanisms of two-tone suppression (2TS) and distortion product (DP) on the basilar membrane (BM) using a model. Computational simulation is conducted with an active and nonlinear transmission line model including a nonlinear outer hair cell model that shows compressive property in two dimensionally where two tones are input. To evaluate the cochlear model, over all responses of BM model are used. For simultaneous input pairs, the response is suppressed by a stronger tone, or distorted where levels of a pair are equaled. Cubic distortion produced by a simple nonlinear feedback system including the OHC model appears similar to DPs in the cochlear model. These results suggest that two dimensional property of the OHC and its feedback generate 2TS and DPs. This further suggests the importance of the overall responses for investigating mechanisms of cochlear nonlinearities without fluid coupling in the cochlea.

  10. The influence of transducer operating point on distortion generation in the cochlea

    NASA Astrophysics Data System (ADS)

    Sirjani, Davud B.; Salt, Alec N.; Gill, Ruth M.; Hale, Shane A.

    2004-03-01

    Distortion generated by the cochlea can provide a valuable indicator of its functional state. In the present study, the dependence of distortion on the operating point of the cochlear transducer and its relevance to endolymph volume disturbances has been investigated. Calculations have suggested that as the operating point moves away from zero, second harmonic distortion would increase. Cochlear microphonic waveforms were analyzed to derive the cochlear transducer operating point and to quantify harmonic distortions. Changes in operating point and distortion were measured during endolymph manipulations that included 200-Hz tone exposures at 115-dB SPL, injections of artificial endolymph into scala media at 80, 200, or 400 nl/min, and treatment with furosemide given intravenously or locally into the cochlea. Results were compared with other functional changes that included action potential thresholds at 2.8 or 8 kHz, summating potential, endocochlear potential, and the 2 f1-f2 and f2-f1 acoustic emissions. The results demonstrated that volume disturbances caused changes in the operating point that resulted in predictable changes in distortion. Understanding the factors influencing operating point is important in the interpretation of distortion measurements and may lead to tests that can detect abnormal endolymph volume states.

  11. Simultaneous Intracochlear Pressure Measurements from Two Cochlear Locations: Propagation of Distortion Products in Gerbil.

    PubMed

    Dong, Wei

    2016-12-01

    Sound energy propagates in the cochlea through a forward-traveling or slow wave supported by the cochlear partition and fluid inertia. Additionally, cochlear models support traveling wave propagation in the reverse direction as the expected mechanism for conveying otoacoustic emissions out of the cochlea. Recently, however, this hypothesis has been questioned, casting doubt on the process by which otoacoustic emissions travel back out through the cochlea. The proposed alternative reverse travel path for emissions is directly through the fluids of the cochlea as a compression pressure in the form of a fast wave. In the present study, a custom-made micro-pressure sensor was used in vivo in the gerbil cochlea to map two-tone-evoked pressure responses at distinct longitudinal and vertical locations in both the scala tympani and scala vestibuli. Analyses of the magnitude and phase of intracochlear pressure responses at the primary tone and distortion product frequencies were used to distinguish between fast and slow waves in both the forward- and reverse-propagation directions. Results demonstrated that distortion products may travel in both forward and reverse directions post-generation and the existence of both traveling and compression waves. The forward-traveling component appeared to duplicate the process of any external tone, tuned to the local characteristic-frequency place, as it increased compressively and nonlinearly with primary-tone levels. A compression wave was evidenced at frequencies above the cutoff of the recording site. In the opposite direction, a reverse-traveling wave played the major role in driving the stapes reversely and contributed to the distortion product otoacoustic emission. The compression wave may also play a role in reverse propagation when distortion products are generated at a region close to the stapes.

  12. Source of level dependent minima in rabbit distortion product otoacoustic emissions

    PubMed Central

    Fahey, P. F.; Stagner, B. B.; Martin, G. K.

    2008-01-01

    Sharp level dependent minima (commonly called nulls or notches) in the distortion product otoacoustic emissions (DPOAEs) have been postulated to be due to two different mechanisms. It is shown here that the level dependent nulls in rabbit 2f1−f2 DPOAEs carry the signature of the mixing of a third order nonlinear term with a fifth order nonlinear term. This suggests that the minima are not due to the mixing of signals from two different physical sites of origin, but rather are due to the nature of the nonlinearity itself. Model simulations show that null production is indifferent to several properties of nonlinear input∕output functions. PMID:19206797

  13. Using a third tone to probe the physiological generation site of distortion product otoacoustic emissions in gerbil

    NASA Astrophysics Data System (ADS)

    Dong, Wei

    2015-12-01

    The generation of distortion product otoacoustic emissions (DPOAEs) has been summarized using a two-mechanism theory consisting of nonlinear distortion and linear coherent reflection. However, the precise generation site in the cochlea is still unclear. The current study in gerbils used a third tone in different cochlear regions to probe the cochlear origin site of DPOAEs. DPOAEs and their intracochlear sources, distortion products (DPs), were simultaneously measured. Our results suggest that the major generation site of DPOAEs evoked by an f2/f1 ratio of 1.25 extends basal to the primary f2 place, which is consistent with notions about the location of the cochlear amplifier.

  14. Quantitative indices for the assessment of the repeatability of distortion product otoacoustic emissions in laboratory animals.

    PubMed

    Parazzini, Marta; Galloni, Paolo; Brazzale, Alessandra R; Tognola, Gabriella; Marino, Carmela; Ravazzani, Paolo

    2006-08-01

    Distortion product otoacoustic emissions (DPOAE) can be used to study cochlear function in an objective and non-invasive manner. One practical and essential aspect of any investigating measure is the consistency of its results upon repeated testing of the same individual/animal (i.e., its test/retest repeatability). The goal of the present work is to propose two indices to quantitatively assess the repeatability of DPOAE in laboratory animals. The methodology is here illustrated using two data sets which consist of DPOAE subsequently collected from Sprague-Dawley rats. The results of these experiments showed that the proposed indices are capable of estimating both the repeatability of the true emission level and the inconsistencies associated with measurement error. These indices could be a significantly useful tool to identify real and even small changes in the cochlear function exerted by potential ototoxic agents.

  15. Wideband detection of middle ear muscle activation using swept-tone distortion product otoacoustic emissions.

    PubMed

    Henin, Simon; Long, Glenis R; Thompson, Suzanne

    2014-07-01

    The measurement of efferent-induced suppression of otoacoustic emissions (OAEs) using contralateral acoustic stimulation (CAS) is complicated by potential contamination by the middle ear muscle reflex (MEMR), particularly at moderate to high CAS levels. When logarithmically sweeping primaries are used to measure distortion product otoacoustic emissions, the level and phase of the primaries at the entrance of the ear canal may be monitored simultaneously along with the OAEs elicited by the swept-tones. A method of detecting MEMR activation using swept-tones is presented in which the differences in the primaries in the ear canal with and without CAS are examined, permitting evaluation of MEMR effects over a broad frequency range. A range of CAS levels above and below expected contralateral acoustic reflex thresholds permitted evaluation of conditions with and without MEMR activation.

  16. [High-resolution distortion-product otoacoustic emissions: method and clinical applications].

    PubMed

    Janssen, T; Lodwig, A; Müller, J; Oswald, H

    2014-10-01

    Unlike pure tone thresholds that assess both peripheral and central sound processing, distortion-product otoacoustic emissions (DPOAEs) selectively mirror the functioning of the cochlear amplifier. High resolution DPOAEs are missing in the toolbox of routine audiometry due to the fact that high resolution DPOAE measurements are more time-consuming when compared to normal clinical DP grams with rough frequency resolution. Measurements of high resolution DPOAEs allow an early assessment of beginning sensory cell damage due to sound overexposure or administration of ototoxic drugs. When using a rough grid, sensory cell damage would be overlooked as in the early state damage only appears at some distinct cochlear sites. A review is given on the method and application of high resolution DPOAEs.

  17. Overcoming residual stresses and machining distortion in the production of aluminum alloy satellite boxes.

    SciTech Connect

    Younger, Mandy S.; Eckelmeyer, Kenneth Hall

    2007-11-01

    Distortion frequently occurs during machining of age hardening aluminum alloys due to residual stresses introduced during the quenching step in the heat treatment process. This report quantifies, compares, and discusses the effectiveness of several methods for minimizing residual stresses and machining distortion in aluminum alloys 7075 and 6061.

  18. Age-related Shifts in Distortion Product Otoacoustic Emissions Peak-ratios and Amplitude Modulation Spectra

    PubMed Central

    Lai, Jesyin; Bartlett, Edward L.

    2015-01-01

    Amplitude modulation (AM) is an important temporal cue for precise speech and complex sound recognition. However, functional decline of the auditory periphery as well as degradation of central auditory processing due to aging can reduce the salience and resolution of temporal cues. Age-related deficits in central temporal processing have previously been observed at more rapid AM frequencies and various AM depths. These centrally observed changes result from cochlear changes compounded with changes along the ascending auditory pathway. In fact, a decrease in ability to detect temporally modulated sounds accurately could originate from changes in cochlear filtering properties and in cochlear mechanics due to aging. Nonetheless, few studies have examined cochlear mechanisms in AM detection. To assess integrity of the mechanical properties of the auditory periphery, distortion product otoacoustic emissions (DPOAEs) are a tool commonly used in clinics and in research. In this study, we measured DPOAEs to reveal age-related changes in peak f2/f1 ratio and degradation in AM detection by basilar membrane vibration. Two tones (f1 and f2, f2>f1) at various f2/f1 ratios and simultaneous presentation of one AM and one pure tone were used as stimuli to evoke DPOAEs. In addition of observing reduced DPOAE amplitudes and steeper slopes in the input-output DPOAE functions, higher peak f2/f1 ratios and broader f2/f1 tuning were also observed in aged animals. Aged animals generally had lower distortion product (DP) and first sideband (SB 1) responses evoked by an f1 pure tone and an f2 AM tone, regardless of whether the AM frequency was 45 Hz or 128 Hz. SB 1 thresholds, which corresponds to the smallest stimulus AM depth that can induce cochlear vibrations at the DP generator locus, were higher in aged animals as well. The results suggest that age-related changes in peak f2/f1 ratio and AM detection by basilar membrane vibration are consistent with a reduction in endocochlear

  19. Distortion product otoacoustic emissions and auditory evoked potentials in the hedgehog tenrec, Echinops telfairi.

    PubMed

    Drexl, Markus; Faulstich, Michael; Von Stebut, Boris; Radtke-Schuller, Susanne; Kössl, Manfred

    2003-12-01

    The hedgehog tenrec, Echinops telfairi, has certain basal mammalian features, like a cloaca and a sparsely differentiated brain with smooth cerebral hemispheres. The peripheral auditory capabilities of this species were investigated by means of distortion product otoacoustic emissions (DPOAE). For comparison, we determined auditory evoked potentials (AEP) in the inferior colliculus and the auditory cortex. Both methods show that the auditory range of E. telfairi extends well into ultrasonic frequencies, with a region of highest sensitivity at around 16 kHz. The total auditory range spans about 4 octaves at 40 dB SPL. The low-frequency limit of auditory processing is found at frequencies of about 2-3 kHz. The DPOAE and the AEP thresholds of E. telfairi do not run fully parallel in the high-frequency range. For a threshold value of 40 dB SPL, cochlear mechanical thresholds as measured with DPOAE extend up to 50 kHz, whereas neuronal thresholds reach the high-frequency limit at about 30 kHz. Frequency tuning, as assessed from DPOAE suppression tuning curves, was low to moderate with Q(10 dB) values ranging from 1.7 to 8. The lack of discontinuity in the group delay (derived from DPOAE measurements) reveals that cochlear frequency representation is tonotopic without any region of specialized mechanical tuning.

  20. Evidence for a bipolar change in distortion product otoacoustic emissions during contralateral acoustic stimulation in humans

    NASA Astrophysics Data System (ADS)

    Müller, Jörg; Janssen, Thomas; Heppelmann, Guido; Wagner, Wolfgang

    2005-12-01

    The aim of this study was to investigate the activity of the medial olivocochlear (MOC) efferents during contralateral (CAS) and ipsilateral acoustic stimulation (IAS) by recording distortion product otoacoustic emission (DPOAE) suppression and DPOAE adaptation in humans. The main question was: do large bipolar changes in DPOAE level (transition from enhancement to suppression) also occur in humans when changing the primary tone level within a small range as described by Maison and Liberman for guinea pigs [J. Neurosci. 20, 4701-4707 (2000)]? In the present study, large bipolar changes in DPOAE level (14 dB on average across subjects) were found during CAS predominantly at frequencies where dips in the DPOAE fine structure occurred. Thus, effects of the second DPOAE source might be responsible for the observed bipolar effect. In contrast, comparable effects were not found during IAS as was reported in guinea pigs. Reproducibility of CAS DPOAEs was better than that for IAS DPOAEs. Thus, contralateral DPOAE suppression is suggested to be superior to ipsilateral DPOAE adaptation with regard to measuring the MOC reflex strength and for evaluating the vulnerability of the cochlea to acoustic overexposure in a clinical context.

  1. Influence of sound-conditioning on noise-induced susceptibility of distortion-product otoacoustic emissions.

    PubMed

    Luebke, Anne E; Stagner, Barden B; Martin, Glen K; Lonsbury-Martin, Brenda L

    2015-07-01

    Cochlear damage caused by loud sounds can be attenuated by "sound-conditioning" methods. The amount of adaptation for distortion product otoacoustic emissions (DPOAEs) measured in alert rabbits previously predicted an ear's susceptibility to a subsequent noise exposure. The present study investigated if sound-conditioning influenced the robustness of such DPOAE adaptation, and if such conditioning elicited more protection by increasing the amount of DPOAE adaptation. Toward this end, rabbits were divided into two study groups: (1) experimental animals exposed to a sound-conditioning protocol, and (2) unconditioned control animals. After base-line measures, all rabbits were exposed to an overstimulation paradigm consisting of an octave band noise, and then re-assessed 3 weeks post-exposure to determine permanent changes in DPOAEs. A major result was that prior sound-conditioning protected reductions in DPOAE levels by an average of 10-15 dB. However, DPOAE adaptation decreased with sound-conditioning, so that such conditioning was no longer related to noise-induced reductions in DPOAEs. Together, these findings suggest that sound-conditioning affected neural pathways other than those that likely mediate DPOAE adaptation (e.g., medial olivocochlear efferent and/or middle-ear muscle reflexes).

  2. Optimizing swept-tone protocols for recording distortion-product otoacoustic emissions in adults and newborns.

    PubMed

    Abdala, Carolina; Luo, Ping; Shera, Christopher A

    2015-12-01

    Distortion-product otoacoustic emissions (DPOAEs), which are routinely used in the audiology clinic and research laboratory, are conventionally recorded with discrete tones presented sequentially across frequency. However, a more efficient technique sweeps tones smoothly across frequency and applies a least-squares-fitting (LSF) procedure to compute estimates of otoacoustic emission phase and amplitude. In this study, the optimal parameters (i.e., sweep rate and duration of the LSF analysis window) required to record and analyze swept-tone DPOAEs were tested and defined in 15 adults and 10 newborns. Results indicate that optimal recording of swept-tone DPOAEs requires use of an appropriate analysis bandwidth, defined as the range of frequencies included in each least squares fit model. To achieve this, the rate at which the tones are swept and the length of the LSF analysis window must be carefully considered and changed in concert. Additionally, the optimal analysis bandwidth must be adjusted to accommodate frequency-dependent latency shifts in the reflection-component of the DPOAE. Parametric guidelines established here are equally applicable to adults and newborns. However, elevated noise during newborn swept-tone DPOAE recordings warrants protocol adaptations to improve signal-to-noise ratio and response quality.

  3. Cochlear Gain Control Estimated from Distortion Product Otoacoustic Emissions Evoked by Amplitude Modulated Tones

    NASA Astrophysics Data System (ADS)

    Chen, Shixiong; Bian, Lin

    2011-11-01

    It is known that cochlear outer hair cells (OHCs) can provide dynamic feedback to the basilar membrane vibration. Nonlinearities in OHC activities can generate distortion product otoacoustic emissions (DPOAEs) measurable in the ear canal. If evoked by amplitude modulation (AM) signals, DPOAEs could provide a means to access the dynamic gain control of the cochlea. In this study, one of the primary stimuli was replaced with an AM tone to evoke DPOAEs in human ears. The results showed that the estimated cochlear gain decreased with the increase in stimulus level and the gain functions obtained from different AM tone levels were continuous. However, there was a difference in the gain functions depending on which primary was modulated. The gain showed a stronger compression when f2 was modulated. Considering that DPOAEs are mainly generated at the f2 place, it suggests that the cochlear gain control is more nonlinear for on-frequency signals. Using AM stimulus could provide clues on how dynamic signals are processed in the cochlea.

  4. Risk factors for distortion product otoacoustic emissions in young men with normal hearing.

    PubMed

    Torre, Peter; Dreisbach, Laura E; Kopke, Richard; Jackson, Ron; Balough, Ben

    2007-10-01

    The purpose of this study was to evaluate the possible effects of risk factors on distortion product otoacoustic emissions (DPOAEs) in young adult men with normal hearing. Four hundred thirty-six United States Marine recruit men (mean age = 19.2 years +/- 1.8 years; age range = 17-29 years) participated in this study. Questionnaires were given to each recruit to obtain demographic data and history of noise exposure, solvent exposure, smoking history, and hearing-related histories. Otoscopy, tympanometry, pure-tone air-conduction audiometry (2.0-8.0 kHz) and DPOAEs (2.3-8.0 kHz) were measured. DPOAE levels were lower in Not Hispanic or Latino recruits, in heavy smokers, in recruits who reported loud live music exposure and ringing in their ears after noise exposure. These differences were not statistically significant at all frequencies. Recruits with multiple risk factors had the lowest DPOAEs as compared to recruits with fewer, or no, risk factors; these differences were not statistically significant. Obtaining risk factor data as part of an audiometric evaluation is important even though the individual may have normal hearing.

  5. Unstable distortion-product otoacoustic emission phase in Menière's disease.

    PubMed

    Avan, Paul; Giraudet, Fabrice; Chauveau, Bertrand; Gilain, Laurent; Mom, Thierry

    2011-07-01

    The presence of endolymphatic hydrops as a marker of Menière's disease (MD) suggests abnormal pressure in the intralabyrinthine compartments of patients and excessive stiffness of sound-sensitive structures. Otoacoustic emissions (OAEs) have been reported to respond to changes in the ear's stiffness, including those produced by intracranial pressure steps, by a characteristic phase shift around 1 kHz, thereby suggesting a noninvasive means of monitoring MD. Here, body tilt was used for modulating intracranial pressure in forty-one patients with definite MD who were tentatively measured at two stages, with and without active symptoms. Their distortion-product OAEs (DPOAEs) were dynamically monitored around 1 kHz every few seconds in response to body tilt. In a control sample of thirty normal ears, the maximum phase rotation of DPOAEs produced by body tilt was between -18° and +37°. In MD ears with the complete set of symptoms, the posture-induced phase shifts in 32 out of 35 tests fell outside the normative interval, and in 10 tests, although DPOAEs were well above noise floor, their phase was always so abnormally erratic that body tilt produced hardly any additional effect. When MD ears were asymptomatic, nine out of 32 posture tests were abnormal. The excessive DPOAE phase shift is consistent with either a too stiff cochlear partition or a displacement of the operating point of outer hair cells by endolymphatic hydrops.

  6. Vasospasm of labyrinthine artery in cerebellopontine angle surgery: evidence brought by distortion-product otoacoustic emissions.

    PubMed

    Mom, Thierry; Montalban, Audrey; Khalil, Toufic; Gabrillargues, Jean; Chazal, Jean; Gilain, Laurent; Avan, Paul

    2014-10-01

    In cerebellopontine angle (CPA) surgery, postoperative deafness can be due to alteration of cochlear blood flow that is supplied by the labyrinthine artery (LA). In particular, vasospasm is likely to occur and, if so, can be reversed. This work attempted to track down vascular events occurring during CPA surgery. Twenty consecutive patients with vestibular schwannoma were tested with useful preoperative hearing and presence of otoacoustic emissions (OAEs). Distortion-product otoacoustic emissions (DPOAEs), well-known to react within seconds to cochlear ischemia, were used intraoperatively to indirectly monitor cochlear blood flow. Continuous intraoperative monitoring of DPOAEs revealed three different time patterns associated with distinct auditory outcomes. Pattern P1-acute (n = 4) happened when the LA was severed: DPOAEs immediately and irreversibly foundered and led to postoperative deafness. Pattern P2-protracted (n = 7) revealed a progressive deterioration of DPOAEs from the beginning of tumor debulking, likely due to a steady decrease of cochlear blood flow, with postoperative deafness. Pattern P3-unstable (n = 5) corresponded to large DPOAE oscillations between their normal level and noise floor. It was due to acute LA vasospasm that could be reversed in three cases by topical nimodipin. Last, four patients had uneventful cochlear monitoring. In conclusion, cochlear ischemia can occur in vestibular schwannoma surgery, giving three different patterns among which vasospasm can be reversed if detected early.

  7. Cochlear compression: effects of low-frequency biasing on quadratic distortion product otoacoustic emission.

    PubMed

    Bian, Lin

    2004-12-01

    Distortion product otoacoustic emissions (DPOAEs) are generated from the nonlinear transduction n cochlear outer hair cells. The transducer function demonstrating a compressive nonlinearity can be estimated from low-frequency modulation of DPOAEs. Experimental results from the gerbils showed that the magnitude of quadratic difference tone (QDT, f2-f1) was either enhanced or suppressed depending on the phase of the low-frequency bias tone. Within one period of the bias tone, QDT magnitudes exhibited two similar modulation patterns, each resembling the absolute value of the second derivative of the transducer function. In the time domain, the center notches of the modulation patterns occurred around the zero crossings of the bias pressure, whereas peaks corresponded to the increase or decrease in bias pressure. Evaluated with respect to the bias pressure, modulated QDT magnitude displayed a double-modulation pattern marked by a separation of the center notches. Loading/unloading of the cochlear transducer or rise/fall in bias pressure shifted the center notch to positive or negative sound pressures, indicating a mechanical hysteresis. These results suggest that QDT arises from the compression that coexists with the active hysteresis in cochlear transduction. Modulation of QDT magnitude reflects the dynamic regulation of cochlear transducer gain and compression.

  8. Development of distortion product otoacoustic emissions in C57BL/6J mice.

    PubMed

    Narui, Yuya; Minekawa, Akira; Iizuka, Takashi; Furukawa, Masayuki; Kusunoki, Takeshi; Koike, Takuji; Ikeda, Katsuhisa

    2009-08-01

    Distortion product otoacoustic emissions (DPOAEs) have been used to examine the development of hearing in the rat and gerbil. However, no reports of DPOAE measurement from the onset of hearing in mice are available. Commercially-available components were assembled and adapted to provide a suitable probe microphone and sound delivery system for measuring DPOAE in developing C57BL/6J mice. Furthermore, DPOAE data were compared with the findings of the auditory brainstem response (ABR). DPOAEs were obtained at 8 kHz from 11 days after birth, 20 kHz from 12 days, and 30 kHz from 13 days. Adult-like patterns of DPOAE were obtained 21 days at 8 and 20 kHz, and 28 days at 30 kHz. On the other hand, the ABR thresholds at 12 to 36 kHz appeared between 11 and 12 days and were saturated at 14 days. Based on these data, the onset of measureable DPOAEs in the mouse were earlier than in the rat and gerbil. The maturation of DPOAE in the mouse begins at a lower frequency in the high frequency range. In addition, the ABR threshold reached maturation earlier than DPOAE.

  9. Optimizing swept-tone protocols for recording distortion-product otoacoustic emissions in adults and newborns

    PubMed Central

    Abdala, Carolina; Luo, Ping; Shera, Christopher A.

    2015-01-01

    Distortion-product otoacoustic emissions (DPOAEs), which are routinely used in the audiology clinic and research laboratory, are conventionally recorded with discrete tones presented sequentially across frequency. However, a more efficient technique sweeps tones smoothly across frequency and applies a least-squares-fitting (LSF) procedure to compute estimates of otoacoustic emission phase and amplitude. In this study, the optimal parameters (i.e., sweep rate and duration of the LSF analysis window) required to record and analyze swept-tone DPOAEs were tested and defined in 15 adults and 10 newborns. Results indicate that optimal recording of swept-tone DPOAEs requires use of an appropriate analysis bandwidth, defined as the range of frequencies included in each least squares fit model. To achieve this, the rate at which the tones are swept and the length of the LSF analysis window must be carefully considered and changed in concert. Additionally, the optimal analysis bandwidth must be adjusted to accommodate frequency-dependent latency shifts in the reflection-component of the DPOAE. Parametric guidelines established here are equally applicable to adults and newborns. However, elevated noise during newborn swept-tone DPOAE recordings warrants protocol adaptations to improve signal-to-noise ratio and response quality. PMID:26723333

  10. Physiological vulnerability of distortion product otoacoustic emissions from the amphibian ear

    NASA Astrophysics Data System (ADS)

    van Dijk, Pim; Narins, Peter M.; Mason, Matthew J.

    2003-10-01

    The physiological vulnerability of distortion product otoacoustic emissions (DPOAEs) was investigated in the leopard frog, Rana pipiens pipiens. For each frog, DPOAEs were recorded from the amphibian and the basilar papillae. Measurements were taken before and after either the arrest of oxygen supply due to cardioectomy, or the destruction of the central nervous system (CNS). DPOAEs in response to high-level stimuli (>75 dB SPL) were rather robust to these insults during the first two hours post surgery. In contrast, DPOAE amplitudes in response to low-level stimuli (<75 dB SPL) decreased significantly. On average, low-level emissions from the amphibian papilla disappeared within 6 min for cardioectomy, and after 13 min for CNS destruction. In the basilar papilla, low-level DPOAEs disappeared more slowly: on average after 34 min following cardioectomy, and after 58 min for CNS destruction. The difference in physiological vulnerability between low- and high-level emissions is similar to that in mammals and a lizard. The difference between the DPOAE decay rate of the frog's amphibian and basilar papillae suggests important differences between the hearing mechanisms of the papillae.

  11. Distortion product otoacoustic emissions in college music majors and nonmusic majors.

    PubMed

    Henning, Rebecca L Warner; Bobholz, Kate

    2016-01-01

    The presence and absence of distortion product otoacoustic emissions (DPOAEs) as well as DPOAE amplitudes were compared between college music majors and a control group of nonmusic majors. Participants included 28 music majors and 35 nonmusic majors enrolled at a university with ages ranging from 18-25 years. DPOAEs and hearing thresholds were measured bilaterally on all the participants. DPOAE amplitudes were analyzed at the following f2 frequencies: 1,187 Hz, 1,500 Hz, 1,906 Hz, 2,531 Hz, 3,031 Hz, 3812 Hz, 4,812 Hz, and 6,031 Hz. Significantly more music majors (7/28) than nonmusic majors (0/35) exhibited absent DPOAEs for at least one frequency in at least one ear. Both groups of students reported similar histories of recreational and occupational noise exposures that were unrelated to studying music, and none of the students reported high levels of noise exposure within the previous 48 h. There were no differences in audiometric thresholds between the groups at any frequency. At DPOAE f2 frequencies from 3,031 Hz to 6,031 Hz, nonsignificantly lower amplitudes of 2-4 dB were seen in the right ears of music majors versus nonmajors, and in the right ears of music majors playing brass instruments compared to music majors playing nonbrass instruments. Given the greater prevalence of absent DPOAEs in university music majors compared to nonmusic majors, it appears that early stages of cochlear damage may be occurring in this population. Additional research, preferably longitudinal and across multiple colleges/universities, would be beneficial to more definitively determine when the music students begin to show signs of cochlear damage, and to identify whether any particular subgroups of music majors are at a greater risk of cochlear damage.

  12. Distortion product otoacoustic emissions in college music majors and nonmusic majors

    PubMed Central

    Henning, Rebecca L. Warner; Bobholz, Kate

    2016-01-01

    The presence and absence of distortion product otoacoustic emissions (DPOAEs) as well as DPOAE amplitudes were compared between college music majors and a control group of nonmusic majors. Participants included 28 music majors and 35 nonmusic majors enrolled at a university with ages ranging from 18-25 years. DPOAEs and hearing thresholds were measured bilaterally on all the participants. DPOAE amplitudes were analyzed at the following f2 frequencies: 1,187 Hz, 1,500 Hz, 1,906 Hz, 2,531 Hz, 3,031 Hz, 3812 Hz, 4,812 Hz, and 6,031 Hz. Significantly more music majors (7/28) than nonmusic majors (0/35) exhibited absent DPOAEs for at least one frequency in at least one ear. Both groups of students reported similar histories of recreational and occupational noise exposures that were unrelated to studying music, and none of the students reported high levels of noise exposure within the previous 48 h. There were no differences in audiometric thresholds between the groups at any frequency. At DPOAE f2 frequencies from 3,031 Hz to 6,031 Hz, nonsignificantly lower amplitudes of 2-4 dB were seen in the right ears of music majors versus nonmajors, and in the right ears of music majors playing brass instruments compared to music majors playing nonbrass instruments. Given the greater prevalence of absent DPOAEs in university music majors compared to nonmusic majors, it appears that early stages of cochlear damage may be occurring in this population. Additional research, preferably longitudinal and across multiple colleges/universities, would be beneficial to more definitively determine when the music students begin to show signs of cochlear damage, and to identify whether any particular subgroups of music majors are at a greater risk of cochlear damage. PMID:26780957

  13. Distortion product otoacoustic emission and auditory brainstem responses in the echidna (Tachyglossus aculeatus).

    PubMed

    Mills, D M; Shepherd, R K

    2001-06-01

    The auditory function of four wild-caught echidnas was measured using distortion product otoacoustic emissions (DPOAEs) and auditory brainstem responses (ABRs). Emission audiograms were constructed by finding the stimulus levels required to produce a criterion emission amplitude at a given stimulus frequency. For an emission amplitude of -10 dB SPL, the median "best threshold" was 28 dB SPL, and this minimum threshold occurred between 4 and 8 kHz for all animals. The relative effective range of auditory function was defined by the frequencies at which the audiogram was 30 dB above its best threshold. For the emission audiograms, the median lower-frequency limit was 2.3 kHz, the upper limit was 18.4 kHz, and the effective range was 2.7 octaves. The audiogram as measured by ABR was also found to be strongly "U" shaped with similar low- and high-frequency limits, i.e., from 1.6 to 13.9 kHz, with an effective range of 3.1 octaves. These results suggest that the echidna has a behavioral hearing sensitivity comparable to that of typical therian mammals (e.g., rabbits and gerbils) but with a significantly narrower frequency range. DPOAE responses were also measured in selected animals as a function of the variation of all four stimulus parameters (frequencies and intensities of both stimulus tones). Overall, the measured emission responses establish that the echidna does have a cochlear amplifier, and that it could be the same type as in therian mammals. The amplification mechanism in the echidna, currently unidentified, clearly operates to frequencies above 20 kHz, higher than the hearing function observed in any birds or reptiles but lower than for typical therian mammals. This raises the possibility that at least some aspects of the mammalian cochlear amplifier developed early in evolution, before the divergence of the monotremes (echidna and platypus) from the mainstream therian mammals (marsupials and placentals). In this respect, the presence or absence of outer

  14. Neanderthal paintings? Production of prototypical human (Homo sapiens) faces shows systematic distortions.

    PubMed

    Carbon, Claus-Christian; Wirth, Benedikt Emanuel

    2014-01-01

    People's sketches of human faces seem to be systematically distorted: the eye position is always higher than in reality. This bias was experimentally analyzed by a series of experiments varying drawing conditions. Participants either drew prototypical faces from memory (studies 1 and 2: free reconstruction; study 3: cued reconstruction) or directly copied average faces (study 4). Participants consistently showed this positioning bias, which is even in accord with facial depictions published in influential research articles by famous face researchers (study 5). We discuss plausible explanations for this reliable and stable bias, which is coincidentally similar to the morphology of Neanderthals.

  15. Distortion product otoacoustic emissions: an objective technique for the screening of hearing loss in children treated with platin derivatives.

    PubMed

    Dhooge, Ingeborg; Dhooge, Catharina; Geukens, Sven; De Clerck, Bieke; De Vel, Eddy; Vinck, Bart M

    2006-06-01

    In order to develop a sensitive audiometric protocol for identifying ototoxicity in children, a retrospective study of 16 children treated with cisplatin and/or carboplatin was performed. Audiometric testing was done by means of pure-tone threshold audiometry (PTA), high-frequency audiometry (HFA), and distortion product otoacoustic emissions (DPOAEs). Cisplatin caused a sensorineural high-frequency hearing loss in the study group compared to the controls (p < 0.01). Sixty-six percent of the cisplatin patients had a grade 2 or 3 ototoxicity. However, ototoxicity was not found in the patients treated with carboplatin. An excellent correlation was found between DPOAE levels and results obtained by audiometry (r = 0.82). Patients exposed to cisplatin are at significant risk for the development of drug-induced sensorineural hearing loss. Because of the several advantages of DPOAEs (noninvasive, objective, rapid, easy to use, sensitive) this method should be added in the audiological follow-up in infants and toddlers.

  16. Effects of 900 MHz electromagnetic fields exposure on cochlear cells' functionality in rats: evaluation of distortion product otoacoustic emissions.

    PubMed

    Galloni, Paolo; Lovisolo, Giorgio Alfonso; Mancini, Sergio; Parazzini, Marta; Pinto, Rosanna; Piscitelli, Marta; Ravazzani, Paolo; Marino, Carmela

    2005-10-01

    In recent years, the widespread use of mobile phones has been accompanied by public debate about possible adverse consequences on human health. The auditory system is a major target of exposure to electromagnetic fields (EMF) emitted by cellular telephones; the aim of this study was the evaluation of possible effects of cellular phone-like emissions on the functionality of rat's cochlea. Distortion Products OtoAcoustic Emission (DPOAE) amplitude was selected as cochlea's outer hair cells (OHC) status indicator. A number of protocols, including different frequencies (the lower ones in rat's cochlea sensitivity spectrum), intensities and periods of exposure, were used; tests were carried out before, during and after the period of treatment. No significant variation due to exposure to microwaves has been evidenced.

  17. Is there an ototoxicity risk from Cortisporin and comparable otic suspensions? Distortion-product otoacoustic emission findings.

    PubMed

    Berenholz, Leonard P; Rossi, Dyana L; Lippy, William H; Burkey, John M

    2012-03-01

    The purpose of this investigation was to use distortion-product otoacoustic emission (DPOAE) testing to address the issue of possible ototoxicity from the use of neomycin/polymyxin B/hydrocortisone otic suspension following tympanostomy tube placement. We retrospectively reviewed our clinical records and identified 36 children (52 ears) who had met our three study criteria: (1) unilateral or bilateral placement of transtympanic ventilation tubes, (2) treatment for 3 to 5 days with neomycin/polymyxin B/hydrocortisone drops, and (3) postoperative evaluation by DPOAE testing. We identified another set of 36 children (52 ears) who had not received these drops and who had not undergone tube placement but who had been evaluated by DPOAE testing to serve as a control group. We found no significant differences in DPOAE amplitudes between the treatment and control groups. These findings are consistent with decades of clinical experience indicating that neomycin/polymyxin B/hydrocortisone otic suspension is safe when used responsibly.

  18. A ring-distortion strategy to construct stereochemically complex and structurally diverse compounds from natural products

    NASA Astrophysics Data System (ADS)

    Huigens, Robert W., III; Morrison, Karen C.; Hicklin, Robert W.; Flood, Timothy A., Jr.; Richter, Michelle F.; Hergenrother, Paul J.

    2013-03-01

    High-throughput screening is the dominant method used to identify lead compounds in drug discovery. As such, the makeup of screening libraries largely dictates the biological targets that can be modulated and the therapeutics that can be developed. Unfortunately, most compound-screening collections consist principally of planar molecules with little structural or stereochemical complexity, compounds that do not offer the arrangement of chemical functionality necessary for the modulation of many drug targets. Here we describe a novel, general and facile strategy for the creation of diverse compounds with high structural and stereochemical complexity using readily available natural products as synthetic starting points. We show through the evaluation of chemical properties (which include fraction of sp3 carbons, ClogP and the number of stereogenic centres) that these compounds are significantly more complex and diverse than those in standard screening collections, and we give guidelines for the application of this strategy to any suitable natural product.

  19. A comparative study of distortion-product-otoacoustic-emission fine structure in human newborns and adults with normal hearing.

    PubMed

    Dhar, Sumitrajit; Abdala, Carolina

    2007-10-01

    Distortion product otoacoustic emissions (DPOAE) measured in human newborns are not adult-like. More than a decade of work from various investigators has created a well-developed body of evidence describing these differences but the putative anatomy or physiology has only been partially explained. Recently, Abdala and Keefe [J. Acoust. Soc. Am. 120, 3832-3842 (2006)] have identified outer and middle ear immaturities that at least partially describe the differences observed between newborn and adult input-output functions and suppression tuning curves. DPOAE fine structure characteristics and their maturation have not been examined to any extent in the literature. Fine structure characteristics in two groups of ten newborns and young adults with normal hearing sensitivity are compared here. Consistent with previous reports, the newborns show higher DPOAE levels; greater fine structure depth and wider fine structure spacing is also observed in the newborns. Differences in fine structure morphology are also observed between the two age groups. While some of these findings are attributable to an immature outer and middle ear system in the newborns, it is argued that some observed differences in fine structure characteristics might be due to remnant immaturities in passive motion of the basilar membrane in the newborn cochlea.

  20. Distortion-product otoacoustic emission reflection-component delays and cochlear tuning: Estimates from across the human lifespan

    PubMed Central

    Abdala, Carolina; Guérit, François; Luo, Ping; Shera, Christopher A.

    2014-01-01

    A consistent relationship between reflection-emission delay and cochlear tuning has been demonstrated in a variety of mammalian species, as predicted by filter theory and models of otoacoustic emission (OAE) generation. As a step toward the goal of studying cochlear tuning throughout the human lifespan, this paper exploits the relationship and explores two strategies for estimating delay trends—energy weighting and peak picking—both of which emphasize data at the peaks of the magnitude fine structure. Distortion product otoacoustic emissions (DPOAEs) at 2f1−f2 were recorded, and their reflection components were extracted in 184 subjects ranging in age from prematurely born neonates to elderly adults. DPOAEs were measured from 0.5–4 kHz in all age groups and extended to 8 kHz in young adults. Delay trends were effectively estimated using either energy weighting or peak picking, with the former method yielding slightly shorter delays and the latter somewhat smaller confidence intervals. Delay and tuning estimates from young adults roughly match those obtained from SFOAEs. Although the match is imperfect, reflection-component delays showed the expected bend (apical-basal transition) near 1 kHz, consistent with a break in cochlear scaling. Consistent with other measures of tuning, the term newborn group showed the longest delays and sharpest tuning over much of the frequency range. PMID:25234993

  1. 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.

  2. Contralateral suppression of distortion-product otoacoustic emissions: a potential diagnostic tool to evaluate the vestibular nerve.

    PubMed

    Chang, Mun Young; Song, Jae-Jin; Kim, Ji Soo; Koo, Ja-Won

    2013-11-01

    The amplitude of distortion-product otoacoustic emission (DPOAE) is suppressed in one ear when the contralateral ear is subjected to sound stimulation. Contralateral suppression of DPOAE is the phenomenon resulted by the efferent cochlear innervation on the outer hair cells via medial olivocochlear bundle (MOCB) and inferior vestibular nerve. We assumed that DPOAE would not be suppressed by contralateral sound stimulation in patients with vestibular nerve lesion as long as the specific pathway conveying that efferent innervation is affected. To test this hypothesis, we compared the amount of DPOAE contralateral suppression in patients with vestibular neuritis and healthy controls. Twenty healthy volunteers without hearing loss and vestibulopathy, and 13 patients with vestibular neuritis were recruited. DP audiogram was measured without contralateral sound stimulation and then with contralateral sound stimulation (70 dB HL of 2 kHz narrow band noise, NBN). The suppression value of DPOAE was evaluated according to the f2 frequency and was defined as the amount of DPOAE suppression: An-Ao, where An represents the DPOAE amplitude in the presence of contralateral NBN, and Ao represents the DPOAE amplitude in the absence of NBN. Cervical vestibular evoked myogenic potential (cVEMP) was performed in some patients with vestibular neuritis. The suppression values of DPOAE were compared between groups and were analyzed according to the results of cVEMP. The amount of suppression of DPOAE during contralateral sound stimulation was significantly reduced in the patient group compared to control at the f2 frequencies of 1257, 1587, and 2002 Hz (P=0.045, P<0.001, P=0.009, respectively). However, the results of contralateral suppression of DPOAE were not consistent with the results of cVEMP in this study. Efferent cochlear innervation was affected in vestibular neuritis. Evaluation of contralateral suppression of DPOAE can be a potential diagnostic tool to evaluate the functional

  3. Structures and biological activities of cladolosides C3, E1, E2, F1, F2, G, H1 and H2, eight triterpene glycosides from the sea cucumber Cladolabes schmeltzii with one known and four new carbohydrate chains.

    PubMed

    Silchenko, Alexandra S; Kalinovsky, Anatoly I; Avilov, Sergey A; Andryjaschenko, Pelageya V; Dmitrenok, Pavel S; Yurchenko, Ekaterina A; Dolmatov, Igor Yu; Kalinin, Vladimir I

    2015-09-23

    Eight new nonsulfated triterpene glycosides, cladolosides C3(1), E1(2), E2(3), F1(4), F2(5), G(6), H1(7) and H2(8) have been isolated from the tropical Indo-West Pacific sea cucumber Cladolabes schmeltzii (Cladolabinae, Sclerodactylidae, Dendrochirotida) collected in the Vietnamese shallow waters. The structures of the glycosides were elucidated by 2D NMR spectroscopy and mass-spectrometry. Glycosides 2, 3, 4, and 5 have pentasaccharide branched carbohydrate moieties and differ from each other by monosaccharide compositions and aglycone structures. At that, glycosides 2 and 3 contain three xylose, one 3-O-methyl-glucose and one quinovose residues, while glycosides 4 and 5 have two quinovose, two xylose and one 3-O-methyl-glucose residues. Compounds 1 and 6-8 are hexaosides differing from each other by aglycone structures and by the fifth monosaccharide residue, which proved to be glucose in cladoloside C3(1), xylose in cladoloside G(6) and quinovose in cladolosides H1(7) and H2(8). The presence of quinovose residue in the fifth position, as in 4, 5, 7 and 8 has never been earlier found in carbohydrate chains of triterpene glycosides from sea cucumbers. The carbohydrate chains with xylose in the fifth position of pentaosides and hexaosides are also very unusual for holothurious glycosides. All the substances demonstrate strong or moderate cytotoxic and hemolytic effects with hexaosides being more active than the corresponding pentaosides. Peculiarities of the biosynthesis and biochemical evolution of glycosides of this type are discussed.

  4. 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

  5. Reducing the Distortion in Upward Distortion Data.

    ERIC Educational Resources Information Center

    Sussman, Lyle; Krivonos, Paul

    Because information flow is considered essential to an organization and because decision makers are dependent upon accurate information, the distortion of messages as they move upward in an organization has become a central concern of many organizational communication researchers. The purposes of this paper are to critically review the various…

  6. Protein storage vacuoles of Brassica napus zygotic embryos accumulate a BURP domain protein and perturbation of its production distorts the PSV.

    PubMed

    Teerawanichpan, Prapapan; Xia, Qun; Caldwell, Sarah J; Datla, Raju; Selvaraj, Gopalan

    2009-11-01

    BNM2is a prototypical member of the enigmatic BURP domain protein family whose members contain the signature FX6-7GX10-28PX25-31CX11-12X2SX45-56CHX10 CHX25-29CHX2TX15-16PX5CH in the C-terminus. This protein family occurs only in plants, and the cognate genes vary very widely in their expression contexts in vegetative and reproductive tissues. None of theBURP family members has been assigned any biochemical function. BNM2 was originally discovered as a gene expressed in microspore derived embryos (MDE) of Brassica napus but we found that MDE do not contain the corresponding protein. We show that BNM2 protein production is confined to the seeds and localized to the protein storage vacuoles (PSV) even though the transcript is found in vegetative parts and floral buds as well. In developing seeds, transcript accumulation precedes protein appearance by more than 18 days. RNA accumulation peaks at approximately 20 days post anthesis (DPA) whereas protein accumulation reaches its maximum at approximately 40 DPA. Transgenic expression of BNM2 does not abrogate this regulation to yield ectopic protein production or to alter the temporal aspect ofBNM2 accumulation. Overexpression ofBNM2 led to spatial distortion of storage protein accumulation within PSV and to some morphological alterations of PSVs. However, the overall storage protein content was not altered.

  7. L1,L2 maps of distortion-product otoacoustic emissions from a moth ear with only two auditory receptor neurons.

    PubMed

    Kössl, Manfred; Coro, Frank

    2006-12-01

    The tympanal organ of the moth Empyreuma affinis emits physiologically vulnerable distortion-product otoacoustic emissions. To assess the nature of underlying mechanical nonlinearities, we measured L1,L2 maps by varying both stimulus levels. Two types of maps were found: (1) Maps containing dominant islands centered at the L1=L2 diagonal as it is typical for saturating nonlinearities that can be described by Boltzmann functions. In contrast to maps published for mammals and frogs, the shape of such islands includes sharp ridges at L1 or L2 levels close to 70 dB sound pressure level. This could be produced by a strongly asymmetric operating point of the respective transfer functions, consistent with the fact that the auditory sensory cells are not hair cells but primary mechanoreceptors with a single cilium. The saturating map components could be selectively reduced by acoustic suppression. (2) Maps where separated islands were less conspicuous but in which the dominant feature consisted of contour lines which were orthogonal to the L1=2L2 diagonal and could be generated by an expansive nonlinearity. Maps showing strong islands were found for f2 frequencies between 26.7 and 45 kHz, maps without strong islands for f2 between 42 and 57.5 kHz. This suggests a frequency-dependent change regarding the involved mechanical nonlinearities.

  8. Distortion Product Otoacoustic Emission (DPOAE) as an Appropriate Tool in Assessment of Otoprotective Effects of Antioxidants in Noise-Induced Hearing Loss (NIHL).

    PubMed

    Doosti, Afsaneh; Lotfi, Yones; Moosavi, Abdollah; Bakhshi, Enayatollah; Talasaz, Azita Hajhossein

    2014-09-01

    Distortion product otoacoustic emission (DPOAE) appears to be an objective sensitive test of cochlear function. The aim of this study was to investigate whether DPOAE is an appropriate tool for assessment of minute changes in cochlea due to usage of antioxidant material. 48 workers exposed to continuous noise in a textile factory were randomly assigned into three groups: (1) The Control group (n = 16) received no antioxidant drugs, (2) The N-acetyl-cysteine (NAC) group (n = 16) received oral antioxidant NAC (1200 mg/day), (3) The Ginseng group (n = 16) received oral antioxidant Ginseng (200 mg/day). All three groups had a follow-up period of 2 weeks. The cochlear changes were assessed using DPOAE test before starting the daily work shift on first and 15th day. The associations between groups and DPOAE amplitudes after 2 weeks were analyzed using linear regression analysis. Four separate models were fitted by side of ears and frequency. All models were adjusted for baseline amplitude. Reduced (better) amplitude at DPOAE test was found for NAC and Ginseng groups at high frequencies (4 and 6 kHz) in both ears after 2 weeks compared to control group. Moreover, NAC group showed better DPOAE amplitude than Ginseng group. In conclusion, DPOAE seems to be an appropriate tool in assessing minute changes in the cochlea after antioxidant drugs administration.

  9. Time-frequency analyses of transient-evoked stimulus-frequency and distortion-product otoacoustic emissions: Testing cochlear model predictions

    NASA Astrophysics Data System (ADS)

    Konrad-Martin, Dawn; Keefe, Douglas H.

    2003-10-01

    Time-frequency representations (TFRs) of otoacoustic emissions (OAEs) provide information simultaneously in time and frequency that may be obscured in waveform or spectral analyses. TFRs were applied to transient-evoked stimulus-frequency (SF) and distortion-product (DP) OAEs to test cochlear model predictions. SFOAEs and DPOAEs were elicited in 18 normal-hearing subjects using gated tones and tone pips. Synchronous spontaneous (SS) OAEs were measured to assess their contributions to SFOAEs and DPOAEs. A common form of TFR of measured OAEs was a collection of frequency-specific components often aligned with SSOAE sites, with each component characterized by one or more brief segments or a single long-duration segment. The spectral envelope of evoked OAEs differed from that of the evoking stimulus. Strong emission regions or cochlear ``hot spots'' were detected, and sometimes accounted for OAE energy observed outside the stimulus bandwidth. Contributions of hot spots and multiple internal reflections to the OAE, and differences between measured and predicted OAE spectra, increased as stimulus level decreased, consistent with level-dependent changes in the estimated cochlear reflectance. Suppression and frequency-pulling effects between components were observed. A recursive formulation was described for the linear coherent reflection emission theory [Zweig and Shera, J. Acoust. Soc. Am. 98, 2018-2047 (1995)] that is well suited for time-domain calculations.

  10. Cochlear outer hair cells in a dominant-negative connexin26 mutant mouse preserve non-linear capacitance in spite of impaired distortion product otoacoustic emission.

    PubMed

    Minekawa, A; Abe, T; Inoshita, A; Iizuka, T; Kakehata, S; Narui, Y; Koike, T; Kamiya, K; Okamura, H-O; Shinkawa, H; Ikeda, K

    2009-12-15

    Mutations in the connexin26 gene (GJB2) are the most common genetic cause of congenital bilateral non-syndromic sensorineural hearing loss. Transgenic mice were established carrying human Cx26 with the R75W mutation that was identified in a deaf family with autosomal dominant negative inheritance [Kudo T et al. (2003) Hum Mol Genet 12:995-1004]. A dominant-negative Gjb2 R75W transgenic mouse model shows incomplete development of the cochlear supporting cells, resulting in profound deafness from birth [Inoshita A et al. (2008) Neuroscience 156:1039-1047]. The Cx26 defect in the Gjb2 R75W transgenic mouse is restricted to the supporting cells; it is unclear why the auditory response is severely disturbed in spite of the presence of outer hair cells (OHCs). The present study was designed to evaluate developmental changes in the in vivo and in vitro function of the OHC, and the fine structure of the OHC and adjacent supporting cells in the R75W transgenic mouse. No detectable distortion product otoacoustic emissions were observed at any frequencies in R75W transgenic mice throughout development. A characteristic phenotype observed in these mice was the absence of the tunnel of Corti, Nuel's space, and spaces surrounding the OHC; the OHC were compressed and squeezed by the surrounding supporting cells. On the other hand, the OHC developed normally. Structural features of the lateral wall, such as the membrane-bound subsurface cisterna beneath the plasma membrane, were intact. Prestin, the voltage-dependent motor protein, was observed by immunohistochemistry in the OHC basolateral membranes of both transgenic and non-transgenic mice. No significant differences in electromotility of isolated OHCs during development was observed between transgenic and control mice. The present study indicates that normal development of the supporting cells is indispensable for proper cellular function of the OHC.

  11. 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.)

  12. 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.

  13. 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.

  14. Redshift-space distortions.

    PubMed

    Percival, Will J; Samushia, Lado; Ross, Ashley J; Shapiro, Charles; Raccanelli, Alvise

    2011-12-28

    Comparing measurements of redshift-space distortions (RSDs) with geometrical observations of the expansion of the Universe offers tremendous potential for testing general relativity on very large scales. The basic linear theory of RSDs in the distant-observer limit has been known for 25 years and the effect has been conclusively observed in numerous galaxy surveys. The next generation of galaxy survey will observe many millions of galaxies over volumes of many tens of Gpc(3). They will provide RSD measurements of such exquisite precision that we will have to carefully analyse and correct for many systematic deviations from this simple picture in order to fully exploit the statistical precision obtained. We review RSD theory and show how ubiquitous RSDs actually are, and then consider a number of potential systematic effects, shamelessly highlighting recent work in which we have been involved. This review ends by looking ahead to the future surveys that will make the next generation of RSD measurements.

  15. Cognitive Distortions and Suicide Attempts

    PubMed Central

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

    2014-01-01

    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

  16. 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.

  17. Quantum rate-distortion coding

    NASA Astrophysics Data System (ADS)

    Barnum, Howard

    2000-10-01

    I introduce rate-distortion theory for the coding of quantum information, and derive a lower bound, involving the coherent information, on the rate at which qubits must be used to store or compress an entangled quantum source with a given maximum level of distortion per source emission.

  18. 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

  19. Triangulation in Random Refractive Distortions.

    PubMed

    Alterman, Marina; Schechner, Yoav Y; Swirski, Yohay

    2017-03-01

    Random refraction occurs in turbulence and through a wavy water-air interface. It creates distortion that changes in space, time and with viewpoint. Localizing objects in three dimensions (3D) despite this random distortion is important to some predators and also to submariners avoiding the salient use of periscopes. We take a multiview approach to this task. Refracted distortion statistics induce a probabilistic relation between any pixel location and a line of sight in space. Measurements of an object's random projection from multiple views and times lead to a likelihood function of the object's 3D location. The likelihood leads to estimates of the 3D location and its uncertainty. Furthermore, multiview images acquired simultaneously in a wide stereo baseline have uncorrelated distortions. This helps reduce the acquisition time needed for localization. The method is demonstrated in stereoscopic video sequences, both in a lab and a swimming pool.

  20. Minor Distortions with Major Consequences: Correcting Distortions in Imaging Spectrographs

    PubMed Central

    Esmonde-White, Francis W. L.; Esmonde-White, Karen A.; Morris, Michael D.

    2010-01-01

    Projective transformation is a mathematical correction (implemented in software) used in the remote imaging field to produce distortion-free images. We present the application of projective transformation to correct minor alignment and astigmatism distortions that are inherent in dispersive spectrographs. Patterned white-light images and neon emission spectra were used to produce registration points for the transformation. Raman transects collected on microscopy and fiber-optic systems were corrected using established methods and compared with the same transects corrected using the projective transformation. Even minor distortions have a significant effect on reproducibility and apparent fluorescence background complexity. Simulated Raman spectra were used to optimize the projective transformation algorithm. We demonstrate that the projective transformation reduced the apparent fluorescent background complexity and improved reproducibility of measured parameters of Raman spectra. Distortion correction using a projective transformation provides a major advantage in reducing the background fluorescence complexity even in instrumentation where slit-image distortions and camera rotation were minimized using manual or mechanical means. We expect these advantages should be readily applicable to other spectroscopic modalities using dispersive imaging spectrographs. PMID:21211158

  1. 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).

  2. 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.

  3. 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,…

  4. Distorted turbulence in axisymmetric flow

    NASA Technical Reports Server (NTRS)

    Durbin, P. A.

    1981-01-01

    A solution to the rapid-distortion theory for small-scale turbulence in flow round an axisymmetric obstacle is derived. General formulae for velocity covariances and Eulerian time scales are obtained and are evaluated for the particular case of flow round a sphere. The large-scale limit for this flow is also discussed.

  5. Optical distortions by compressible turbulence

    NASA Astrophysics Data System (ADS)

    Mani, Ali

    Optical distortions induced by refractive index fluctuations in turbulent flows are a serious concern in airborne communication and imaging systems. This project focuses on aero-optical flows in which compressible turbulence is the dominant source of optical distortions. These flows include boundary layers, free shear layers, cavity flows, and wakes typically associated with flight conditions. The present study consists of two theoretical analyses and an extensive numerical investigation of optical distortions by separated shear layers and turbulent wakes. We present an analysis of far-field optical statistics in a general aero-optical framework. Based on this analysis, measures of far-field distortion, such as tilt, spread, and loss of focus-depth, are linked to key flow statistics. By employing these measures, we quantify distortion effects through a set of norms that have provable scaling properties with key optical parameters. The second analysis presents a theoretical estimate of the range of optically important flow scales in an arbitrary aero-optical flowfield. We show that in the limit of high Reynolds numbers, the smallest optically important scale does not depend on the Kolmogorov scale. For a given geometry this length scale depends only on the flow Mach number, freestream refractive index, and the optical wavelength. The provided formula can be used to estimate grid resolution requirements for numerical simulations of aero-optical phenomena. A rough estimate indicates that resolution requirements for accurate prediction of aero-optics is not much higher than typical LES requirements. As a model problem, compressible turbulent flows over a circular cylinder is considered to study the fundamental physics of aero-optical effects. Large-eddy simulation with a high-resolution numerical scheme is employed to compute variations of the refractive index field in the separated shear layers and turbulent wakes in a range of flow Mach numbers (0.2--0.85) and

  6. 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.

  7. Distortions of posterior visual space.

    PubMed

    Phillips, Flip; Voshell, Martin G

    2009-01-01

    The study of spatial vision is a long and well traveled road (which, of course, converges to a vanishing point at the horizon). Its various distortions have been widely investigated empirically, and most concentrate, pragmatically, on the space anterior to the observer. The visual world behind the observer has received relatively less attention and it is this perspective the current experiments address. Our results show systematic perceptual distortions in the posterior visual world when viewed statically. Under static viewing conditions, observer's perceptual representation was consistently 'spread' in a hyperbolic fashion. Directions to distant, peripheral locations were consistently overestimated by about 11 degrees from the ground truth and this variability increased as the target was moved toward the center of the observer's back. The perceptual representation of posterior visual space is, no doubt, secondary to the more immediate needs of the anterior visual world. Still, it is important in some domains including certain sports, such as rowing, and in vehicular navigation.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. Biological motion distorts size perception

    NASA Astrophysics Data System (ADS)

    Veto, Peter; Einhäuser, Wolfgang; Troje, Nikolaus F.

    2017-02-01

    Visual illusions explore the limits of sensory processing and provide an ideal testbed to study perception. Size illusions – stimuli whose size is consistently misperceived – do not only result from sensory cues, but can also be induced by cognitive factors, such as social status. Here we investigate, whether the ecological relevance of biological motion can also distort perceived size. We asked observers to judge the size of point-light walkers (PLWs), configurations of dots whose movements induce the perception of human movement, and visually matched control stimuli (inverted PLWs). We find that upright PLWs are consistently judged as larger than inverted PLWs, while static point-light figures do not elicit the same effect. We also show the phenomenon using an indirect paradigm: observers judged the relative size of a disc that followed an inverted PLW larger than a disc following an upright PLW. We interpret this as a contrast effect: The upright PLW is perceived larger and thus the subsequent disc is judged smaller. Together, these results demonstrate that ecologically relevant biological-motion stimuli are perceived larger than visually matched control stimuli. Our findings present a novel case of illusory size perception, where ecological importance leads to a distorted perception of size.

  13. Biological motion distorts size perception

    PubMed Central

    Veto, Peter; Einhäuser, Wolfgang; Troje, Nikolaus F.

    2017-01-01

    Visual illusions explore the limits of sensory processing and provide an ideal testbed to study perception. Size illusions – stimuli whose size is consistently misperceived – do not only result from sensory cues, but can also be induced by cognitive factors, such as social status. Here we investigate, whether the ecological relevance of biological motion can also distort perceived size. We asked observers to judge the size of point-light walkers (PLWs), configurations of dots whose movements induce the perception of human movement, and visually matched control stimuli (inverted PLWs). We find that upright PLWs are consistently judged as larger than inverted PLWs, while static point-light figures do not elicit the same effect. We also show the phenomenon using an indirect paradigm: observers judged the relative size of a disc that followed an inverted PLW larger than a disc following an upright PLW. We interpret this as a contrast effect: The upright PLW is perceived larger and thus the subsequent disc is judged smaller. Together, these results demonstrate that ecologically relevant biological-motion stimuli are perceived larger than visually matched control stimuli. Our findings present a novel case of illusory size perception, where ecological importance leads to a distorted perception of size. PMID:28205639

  14. Market distortions and technological progress in agriculture

    SciTech Connect

    Alston, J.M.; Pardey, P.G.

    1993-05-01

    It is widely believed that price policies have contributed to low rates of productivity growth in agriculture, but there has been little progress to date in work on the relationship between price distortions and agricultural productivity or agricultural research. Given the importance of technological change in agriculture, it is important to know whether price policies impede investments in R&D and productivity growth. In this article, a theoretical analysis indicates that the effects of commodity price policies on incentives of government and industry to invest in agricultural research are ambiguous. While the results suggest a general tendency of policies that protect producers to encourage greater research investments, the opposite result cannot be ruled out. A statistical model using international, cross-sectional, time-series data shows that agricultural research investments are significantly correlated, but negatively, with rates of producer protection. The implication is that some factor other than price policy is responsible for both the low rates of public-sector investments in agricultural research worldwide, and the low rates of productivity growth in less-developed countries. Research administrators in more- and less-developed countries alike typically consider a multiplicity of goals when setting research priorities and research budgets. Therefore, an alternative explanation of low agricultural productivity and underinvestment in agricultural research may be that public-sector research policy has been misguided. 24 refs., 6 figs., 1 tab.

  15. 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.

  16. a Reevaluation of Distortional Isomerism

    NASA Astrophysics Data System (ADS)

    Desrochers, Patrick John

    The blue and green forms of MoOCl_2 (PMe_2Ph)_3 and (LWOCl_2) PF _6 (L = 1,4,7-trimethyltriazacyclononane) are not examples of distortional isomerism. For both systems, the blue form is pure and the green form is a mixture of the blue complex and other components. Characterizations of the green material of each indicates that green "MoOCl _2(PMe_2Ph) _3" is a mixture of MoOCl _2(PMe_2Ph) _3 and MoCl_3(PMe _2Ph)_3 and that green "(LWOCl_2) PF _6" is a mixture of (LWOCl_2 ) PF_6 and two other species; one is a W(IV) and the other a W(VI) compound. Both solid state (XPS, Raman, infrared, powder X-ray diffraction) and solution phase (^1H NMR, UV -visible, EPR, cyclic voltammetry) measurements were applied to the respective green materials, presenting a consistent description of their composite nature. A single crystal X-ray structure determination of a crystal of green "MoOCl _2(PMe_2Ph) _3" allowed the compositional disorder to be partially resolved in this case, due to the high composition of MoOCl_3(PMe _2Ph)_3 in the sample (ca. 0.30 mole percent by XPS and visible spectroscopies). The single crystal X-ray diffraction data from the original single crystal study of green "(LWOCl_2 ) PF_6" were reinvestigated to ascertain whether compositional disorder could also be implicated in this system. Several composite models were applied to these data, resulting in improved fits to the observed data. This indicated that the original data collected for the crystal of green "(LWOCl _2) PF_6" could not support distortional isomerism in green "(LWOCl _2) PF_6". X-ray structure calculations on models of the compositional disorder in both systems illustrated the pronounced effect of disordering chlorine electron density on the derived metal-oxo bond lengths. A calibration curve of Mo-Cl bond length versus composition calculated from these models resulted in a favorable comparison of this present theoretical work with other experimental X-ray studies of the MoOCl_2 (PMe_2Ph)_3

  17. 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

  18. Frequency modulation television analysis: Distortion analysis

    NASA Technical Reports Server (NTRS)

    Hodge, W. H.; Wong, W. H.

    1973-01-01

    Computer simulation is used to calculate the time-domain waveform of standard T-pulse-and-bar test signal distorted in passing through an FM television system. The simulator includes flat or preemphasized systems and requires specification of the RF predetection filter characteristics. The predetection filters are modeled with frequency-symmetric Chebyshev (0.1-db ripple) and Butterworth filters. The computer was used to calculate distorted output signals for sixty-four different specified systems, and the output waveforms are plotted for all sixty-four. Comparison of the plotted graphs indicates that a Chebyshev predetection filter of four poles causes slightly more signal distortion than a corresponding Butterworth filter and the signal distortion increases as the number of poles increases. An increase in the peak deviation also increases signal distortion. Distortion also increases with the addition of preemphasis.

  19. 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.

  20. Prostate Diffusion Imaging with Distortion Correction

    PubMed Central

    Rakow-Penner, Rebecca A.; White, Nathan S.; Margolis, Daniel J. A.; Parsons, J. Kellogg; Schenker-Ahmed, Natalie; Kuperman, Joshua M.; Bartsch, Hauke; Choi, Hyung W.; Bradley, William G.; Shabaik, Ahmed; Huang, Jiaoti; Liss, Michael A.; Marks, Leonard; Kane, Christopher J.; Reiter, Robert E.; Raman, Steven S.; Karow, David S.; Dale, Anders M.

    2015-01-01

    Purpose Diffusion imaging in the prostate is susceptible to distortion from B0 inhomogeneity. Distortion correction in prostate imaging is not routinely performed, resulting in diffusion images without accurate localization of tumors. We performed and evaluated distortion correction for diffusion imaging in the prostate. Materials and Methods 28 patients underwent pre-operative MRI (T2, Gadolinium perfusion, diffusion at b = 800 s/mm2). The restriction spectrum protocol parameters included b-values of 0, 800, 1500, and 4000 s/mm2 in 30 directions for each nonzero b-value. To correct for distortion, forward and reverse trajectories were collected at b = 0 s/mm2. Distortion maps were generated to reflect the offset of the collected data versus the corrected data. Whole-mount histology, was available for correlation. Results: Across the 27 patients evaluated (excluding one patient due to data collection error), the average root mean square distortion distance of the prostate was 3.1 mm (standard deviation, 2.2 mm; and maximum distortion, 12 mm). Conclusion Improved localization of prostate cancer by MRI will allow better surgical planning, targeted biopsies and image-guided treatment therapies. Distortion distances of up to 12 mm due to standard diffusion imaging may grossly misdirect treatment decisions. Distortion correction for diffusion imaging in the prostate improves tumor localization. PMID:26220859

  1. 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

  2. Child molesters' cognitive distortions. Conceptualizations of the term.

    PubMed

    Szumski, Filip; Zielona-Jenek, Monika

    2016-10-31

    The concept of cognitive distortion was created by A. T. Beck and it is one of the key-concepts of cognitive psychotherapy. In the 80s of the twentieth century, researchers began to use it in studies of sexual offending, but with reference to the social learning theory rather than to the theory of cognitive psychotherapy. Subsequent authors continued the use of this term in the determinants of child molestation and defined them as products emerging from specific implicit theory of the offender, the judgements resulting from his beliefs, values and actions, dysfunctional cognitive schemas, deviant cognitive practices undertaken in the interaction of internal and external components of perpetrator's cognitive system and his social practices. The primary theoretical background in the description of the concept of cognitive distortions of child molesters was the social cognition theory, but it was complemented with the assumptions of the theory of cognitive psychotherapy, extended theory of mind and discursive psychology perspective. Particular concepts describe the cognitive distortions relating them to different classes of cognitive phenomena: products, processes and structures, and the only thing they have in common is their incompatibility of their content to the social norms. Giving this concept a normative nature leads to internal contradictions within the conceptions that concern it. Moreover, using it to explain the various processes oversimplifies the picture of this phenomenon and leads to contradictions between theories. It is, therefore, necessary to consider replacing the term cognitive distortions with alternative and more precise concepts.

  3. 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.

  4. Distortion Of Pressure Signals In Pneumatic Tubes

    NASA Technical Reports Server (NTRS)

    Whitmore, Stephen A.; Gilyard, Glenn B.; Curry, Robert; Lindsey, William

    1993-01-01

    NASA technical memorandum describes experimental investigation of distorting effects of propagation of pressure signals along narrow pneumatic tubes from pressure-sensing orifices on surfaces of models or aircraft to pressure sensors distant from orifices. Pressure signals distorted principally by frictional damping along walls of tubes and by reflections at orifice and sensor ends.

  5. 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…

  6. Hybrid distortion function for JPEG steganography

    NASA Astrophysics Data System (ADS)

    Wang, Zichi; Zhang, Xinpeng; Yin, Zhaoxia

    2016-09-01

    A hybrid distortion function for JPEG steganography exploiting block fluctuation and quantization steps is proposed. To resist multidomain steganalysis, both spatial domain and discrete cosine transformation (DCT) domain are involved in the proposed distortion function. In spatial domain, a distortion value is allotted for each 8×8 block according to block fluctuation. In DCT domain, quantization steps are employed to allot distortion values for DCT coefficients in a block. The two elements, block distortion and quantization steps, are combined together to measure the embedding risk. By employing the syndrome trellis coding to embed secret data, the embedding changes are constrained in complex regions, where modifications are hard to be detected. When compared to current state-of-the-art steganographic methods for JPEG images, the proposed method presents less detectable artifacts.

  7. 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.

  8. 'Distorteidolias' - fantastic perceptive distortion. A new, pure dorsomedial thalamic syndrome.

    PubMed

    Delgado, Montserrat G; Bogousslavsky, Julien

    2013-01-01

    The role of the thalamus in the pathogenesis of the visual and auditory hallucinations has been reported under the name of peduncular hallucinosis, usually with coexisting midbrain involvement. These hallucinations typically take the form of dreamy de novo productions (phanteidolias), less often that of transformations of perceptions into new items (such as seeing faces in clouds) called pareidolias. However, hallucinations taking the form of a complex distortion of perception is a different phenomenon, which to our knowledge has not been reported. We studied 2 patients with complex, 'fantastic', perceptive distortion involving the visual and auditory systems after thalamic stroke limited to the region of the dorsomedial nucleus, sparing the intralaminar nuclei and the midbrain (explaining the lack of disorders of consciousness and confusional state). Our patients reported the modification of usual stimuli (face, body, voices) into unreal, fantastically distorted perceptions (monstrous change of shapes or sounds without appearance of new items). While the exact mechanism leading to such perceptive distortions remains unknown, a release phenomenon due to damage to the dorsomedial thalamus (probably affecting cholinergic system) responsible for a disinhibition of cortical function involved in familiarity of perception seems likely. We suggest that these hallucinations should be called 'distorteidolias'.

  9. 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

  10. Distortions in the visual perception of shape.

    PubMed

    Henriques, Denise Y P; Flanders, Martha; Soechting, John F

    2005-01-01

    It is known that visual illusions lead to a distorted perception of the length and orientation of lines, but it is not clear how these illusions affect the appreciation of the shape of closed forms. In this study two experiments were performed to characterize distortions in the visual perception of the shape of quadrilaterals and the extent to which these distortions were similar to the distortions of haptically sensed shapes. In the first experiment human subjects were presented with two quadrilaterals side by side on a computer monitor. One was a reference shape; the other was rotated and distorted relative to the first. The subjects used the computer mouse to adjust the corners of the distorted quadrilateral to match the shape of the target quadrilateral. They made consistent errors on this task: the adjusted quadrilateral was about 2% wider and about 2% shorter than the veridical shape. Furthermore, subjects adjusted the inner angles of the quadrilateral to make them closer to 90 degrees . The first type of error was also present in a second experiment in which, in a two-alternative forced-choice paradigm, subjects viewed a reference shape and were asked to indicate which of two transiently presented quadrilaterals was closest to the target shape. The width/height errors and the inner angle errors were comparable to those described previously when subjects felt the outline of a quadrilateral and then drew its reproduction in the absence of vision, suggesting that the distortion occurs in the process of remembering the shape.

  11. 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.

  12. Distortion component analysis of outer hair cell motility-related gating charge.

    PubMed

    Takahashi, S; Santos-Sacchi, J

    1999-06-01

    The underlying Boltzmann characteristics of motility-related gating currents of the outer hair cell (OHC) are predicted to generate distortion components in response to sinusoidal transmembrane voltages. We studied this distortion since it reflects the mechanical activity of the cell that may contribute to peripheral auditory system distortion. Distortion components in the OHC electrical response were analyzed using the whole-cell voltage clamp technique, under conditions where ionic conductances were blocked. Single or double-sinusoidal transmembrane voltage stimulation was delivered at various holding voltages, and distortion components of the current responses were detected by Fourier analysis. Current response magnitude and phase of each distortion component as a function of membrane potential were compared with characteristics of the voltage-dependent capacitance, obtained by voltage stair-step transient analysis or dual-frequency admittance analysis. The sum distortion was most prominent among the distortion components at all holding voltages. Notches in the sum (f1+f2), difference (f2-f1) and second harmonic (2f) components occur at the voltage where peak voltage-dependent capacitance resides (VpkCm). Rapid phase reversals also occurred at VpkCm, but phase remained fairly stable at more depolarized and hyperpolarized potentials. Thus, it is possible to extract Boltzmann parameters of the motility-related charge movement from these distortion components. In fact, we have developed a technique to follow changes in the voltage dependence of OHC motility and charge movement by tracking the voltage at phase reversal of the f2-f1 product. When intracellular turgor pressure was changed, VpkCm and distortion notch voltages shifted in the same direction. These data have important implications for understanding cochlear nonlinearity, and more generally, indicate the usefulness of distortion analysis to study displacement currents.

  13. Bending Distortion Analysis of a Steel Shaft Manufacturing Chain from Cold Drawing to Grinding

    NASA Astrophysics Data System (ADS)

    Dias, Vinicius Waechter; da Silva Rocha, Alexandre; Zottis, Juliana; Dong, Juan; Epp, Jérémy; Zoch, Hans Werner

    2017-01-01

    Shafts are usually manufactured from bars that are cold drawn, cut machined, induction hardened, straightened, and finally ground. The main distortion is characterized by bending that appears after induction hardening and is corrected by straightening and/or grinding. In this work, the consequence of the variation of manufacturing parameters on the distortion was analyzed for a complete manufacturing route for production of induction hardened shafts made of Grade 1045 steel. A DoE plan was implemented varying the drawing angle, cutting method, induction hardening layer depth, and grinding penetration depth. The distortion was determined by calculating curvature vectors from dimensional analysis by 3D coordinate measurements. Optical microscopy, microhardness testing, residual stress analysis, and FEM process simulation were used to evaluate and understand effects of the main carriers of distortion potential. The drawing process was identified as the most significant influence on the final distortion of the shafts.

  14. Bending Distortion Analysis of a Steel Shaft Manufacturing Chain from Cold Drawing to Grinding

    NASA Astrophysics Data System (ADS)

    Dias, Vinicius Waechter; da Silva Rocha, Alexandre; Zottis, Juliana; Dong, Juan; Epp, Jérémy; Zoch, Hans Werner

    2017-04-01

    Shafts are usually manufactured from bars that are cold drawn, cut machined, induction hardened, straightened, and finally ground. The main distortion is characterized by bending that appears after induction hardening and is corrected by straightening and/or grinding. In this work, the consequence of the variation of manufacturing parameters on the distortion was analyzed for a complete manufacturing route for production of induction hardened shafts made of Grade 1045 steel. A DoE plan was implemented varying the drawing angle, cutting method, induction hardening layer depth, and grinding penetration depth. The distortion was determined by calculating curvature vectors from dimensional analysis by 3D coordinate measurements. Optical microscopy, microhardness testing, residual stress analysis, and FEM process simulation were used to evaluate and understand effects of the main carriers of distortion potential. The drawing process was identified as the most significant influence on the final distortion of the shafts.

  15. Microwave background distortions from domain walls

    NASA Technical Reports Server (NTRS)

    Goetz, Guenter; Noetzold, Dirk

    1990-01-01

    Domain walls arising in a cosmic phase transition after decoupling were recently proposed as seeds for the formation of large scale structure. The distortion induced in the microwave background radiation is calculated in dependence of the wall thickness, surface density, scalar field potential, cosmic redshift and the velocity of the wall. It was found that the maximal redshift distortion for both spherical and planar walls is of the order pi G sigma H(sup -1)(sub 0), where sigma is the surface energy density and H(sup -1)(sub 0) the Hubble parameter. It was also found that, for a wall thickness smaller than the horizon, walls can be treated as infinitely thin, i.e., the redshift distortion is independent of the wall thickness and the specific form of the scalar potential. For planar walls moving with a Lorentz-factor gamma the redshift distortion is enhanced by gamma cubed.

  16. Microwave background distortions from domain walls

    NASA Astrophysics Data System (ADS)

    Goetz, Guenter; Noetzold, Dirk

    1990-08-01

    Domain walls arising in a cosmic phase transition after decoupling were recently proposed as seeds for the formation of large scale structure. The distortion induced in the microwave background radiation is calculated in dependence of the wall thickness, surface density, scalar field potential, cosmic redshift and the velocity of the wall. It was found that the maximal redshift distortion for both spherical and planar walls is of the order pi G sigma H(sup -1)(sub 0), where sigma is the surface energy density and H(sup -1)(sub 0) the Hubble parameter. It was also found that, for a wall thickness smaller than the horizon, walls can be treated as infinitely thin, i.e., the redshift distortion is independent of the wall thickness and the specific form of the scalar potential. For planar walls moving with a Lorentz-factor gamma the redshift distortion is enhanced by gamma cubed.

  17. Microwave background distortions from domain walls.

    NASA Astrophysics Data System (ADS)

    Goetz, G.; Nötzold, D.

    1991-03-01

    Domain walls arising in a cosmic phase transition after decoupling were recently proposed as seeds for the formation of large-scale structure. The distortion induced in the microwave background radiation is calculated in dependence of the wall thickness, surface density, scalar field potential, cosmic redshift and the velocity of the wall. The authors find that the maximal redshift distortion for both spherical and planar walls is of the order πGσH0-1, where σ is the surface energy density and H0 the Hubble parameter. They also find that, for a wall thickness smaller than the horizon, walls can be treated as infinitely thin, i.e. the redshift distortion is independent of the wall thickness and the specific form of the scalar potential. For planar walls moving with a Lorentz-factor γ the redshift distortion is enhanced by γ3.

  18. Interior of a charged distorted black hole

    SciTech Connect

    Abdolrahimi, Shohreh; Frolov, Valeri P.; Shoom, Andrey A.

    2009-07-15

    We study the interior of a charged, nonrotating distorted black hole. We consider static and axisymmetric black holes, and focus on a special case when an electrically charged distorted solution is obtained by the Harrison-Ernst transformation from an uncharged one. We demonstrate that the Cauchy horizon of such a black hole remains regular, provided the distortion is regular at the event horizon. The shape and the inner geometry of both the outer and inner (Cauchy) horizons are studied. We demonstrate that there exists a duality between the properties of the horizons. Proper time of a free fall of a test particle moving in the interior of the distorted black hole along the symmetry axis is calculated. We also study the property of the curvature in the inner domain between the horizons. Simple relations between the 4D curvature invariants and the Gaussian curvature of the outer and inner horizon surfaces are found.

  19. Harmonic distortion in microwave photonic filters.

    PubMed

    Rius, Manuel; Mora, José; Bolea, Mario; Capmany, José

    2012-04-09

    We present a theoretical and experimental analysis of nonlinear microwave photonic filters. Far from the conventional condition of low modulation index commonly used to neglect high-order terms, we have analyzed the harmonic distortion involved in microwave photonic structures with periodic and non-periodic frequency responses. We show that it is possible to design microwave photonic filters with reduced harmonic distortion and high linearity even under large signal operation.

  20. 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.

  1. Distortion Estimates for Negative Schwarzian Maps.

    DTIC Science & Technology

    1988-02-29

    continuous with respect to Lebesgue measure. If Q(E) > 0. then since ’T generates. Ve > 0. 3n. 3.1 E J, such that e and hence ((f "(E)) > t -,a() < n ecegf...Estimates on Distortion The distortion dis(f) is invariant under changes of scale in the domain and is multi- plied by the inverse of a scaling factor

  2. Reconstructing the distortion function for nonlocal cosmology

    SciTech Connect

    Deffayet, C.; Woodard, R.P. E-mail: woodard@phys.ufl.edu

    2009-08-01

    We consider the cosmology of modified gravity models in which Newton's constant is distorted by a function of the inverse d'Alembertian acting on the Ricci scalar. We derive a technique for choosing the distortion function so as to fit an arbitrary expansion history. This technique is applied numerically to the case of ΛCDM cosmology, and the result agrees well with a simple hyperbolic tangent.

  3. Low distortion laser welding of cylindrical components

    NASA Astrophysics Data System (ADS)

    Kittel, Sonja

    2011-02-01

    Automotive components are for the most part cylindrical and thus the weld seams are of radial shape. Radial weld seams are usually produced by starting at a point on the component's surface rotating the component resulting in an overlap zone at the start/end of the weld. In this research, it is shown that the component's distortion strongly depends on the overlap of weld start and end. A correlation between overlap zone and distortion is verified by an experimental study. In order to reduce distortion generated by the overlap zone a special optics is used which allows shaping the laser beam into a ring shape which is then focused on the cylindrical surface and produces a radial ring weld seam simultaneously by one laser pulse. In doing this, the overlap zone is eliminated and distortion can be reduced. Radial weld seams are applied on precision samples and distortion is measured after welding. The distortion of the precision samples is measured by a tactile measuring method and a comparison of the results of welding with the ring optics to reference welds is done.

  4. Low distortion laser welding of cylindrical components

    NASA Astrophysics Data System (ADS)

    Kittel, Sonja

    2010-09-01

    Automotive components are for the most part cylindrical and thus the weld seams are of radial shape. Radial weld seams are usually produced by starting at a point on the component's surface rotating the component resulting in an overlap zone at the start/end of the weld. In this research, it is shown that the component's distortion strongly depends on the overlap of weld start and end. A correlation between overlap zone and distortion is verified by an experimental study. In order to reduce distortion generated by the overlap zone a special optics is used which allows shaping the laser beam into a ring shape which is then focused on the cylindrical surface and produces a radial ring weld seam simultaneously by one laser pulse. In doing this, the overlap zone is eliminated and distortion can be reduced. Radial weld seams are applied on precision samples and distortion is measured after welding. The distortion of the precision samples is measured by a tactile measuring method and a comparison of the results of welding with the ring optics to reference welds is done.

  5. Model of intermodulation distortion in non-linear multicarrier systems

    NASA Astrophysics Data System (ADS)

    Frigo, Nicholas J.

    1994-02-01

    A heuristic model is proposed which allows calculation of the individual spectral components of the intermodulation distortion present in a non-linear system with a multicarrier input. Noting that any given intermodulation product (IMP) can only be created by a subset of the input carriers, we partition them into 'signal' carriers (which create the IMP) and 'noise' carriers, modeled as a Gaussian process. The relationship between an input signal and the statistical average of its output (averaged over the Gaussian noise) is considered to be an effective transfer function. By summing all possible combinations of signal carriers which create power at the IMP frequencies, the distortion power can be calculated exactly as a function of frequency. An analysis of clipping in lightwave CATV links for AM-VSB signals is used to introduce the model, and is compared to a series of experiments.

  6. Intragenomic conflict produces sex ratio dynamics that favor maternal sex ratio distorters.

    PubMed

    Rood, Elaine S; Freedberg, Steven

    2016-11-01

    Maternal sex ratio distorters (MSDs) are selfish elements that enhance their transmission by biasing their host's sex allocation in favor of females. While previous models have predicted that the female-biased populations resulting from sex ratio distortion can benefit from enhanced productivity, these models neglect Fisherian selection for nuclear suppressors, an unrealistic assumption in most systems. We used individual-based computer simulation modeling to explore the intragenomic conflict between sex ratio distorters and their suppressors and explored the impacts of these dynamics on population-level competition between species characterized by MSDs and those lacking them. The conflict between distorters and suppressors was capable of producing large cyclical fluctuations in the population sex ratio and reproductive rate. Despite fitness costs associated with the distorters and suppressors, MSD populations often exhibited enhanced productivity and outcompeted non-MSD populations in single and multiple-population competition simulations. Notably, the conflict itself is beneficial to the success of populations, as sex ratio oscillations limit the competitive deficits associated with prolonged periods of male rarity. Although intragenomic conflict has been historically viewed as deleterious to populations, our results suggest that distorter-suppressor conflict can provide population-level advantages, potentially helping to explain the persistence of sex ratio distorters in a range of taxa.

  7. 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. PMID:27630779

  8. The Thermal Distortion of a Funnel Mold

    NASA Astrophysics Data System (ADS)

    Hibbeler, Lance C.; Thomas, Brian G.; Schimmel, Ronald C.; Abbel, Gert

    2012-10-01

    This article investigates the thermal distortion of a funnel mold for continuous casting of thin slabs and explores the implications on taper and solidification of the steel shell. The three-dimensional mold temperatures are calculated using shell-mold heat flux and cooling water profiles that were calibrated with plant measurements. The thermal stresses and distorted shape of the mold are calculated with a detailed finite-element model of a symmetric fourth of the entire mold and waterbox assembly, and they are validated with plant thermocouple data and measurements of the wear of the narrow-face copper mold plates. The narrow-face mold distorts into the typical parabolic arc, and the wide face distorts into a "W" shape owing to the large variation in bolt stiffnesses. The thermal expansion of the wide face works against the applied narrow-face taper and funnel effects, so the effect of thermal distortion must be considered to accurately predict the ideal mold taper.

  9. A helically distorted MHD flux rope model

    NASA Technical Reports Server (NTRS)

    Theobald, Michael L.; Montgomery, David

    1990-01-01

    A flux rope model is proposed which has a variable degree of helical distortion from axisymmetry. The basis for this suggestion is a series of numerical and analytical investigations of magnetohydrodynamic states which result when an axial electric current is directed down on dc magnetic field. The helically distorted states involve a flow velocity and seem to be favored because of their lower rate of energy dissipation. Emphasis is on the magnetometer and particle energy analyzer traces that might be characteristic of such flux ropes. It is shown that even a fractionally small helical distortion may considerably alter the traces in minimum-variance coordinates. In short, what may be fairly common MHD processes can render a flux rope almost unrecognizable under standard diagnostics, even if the departures from axisymmetry are not great.

  10. Aberrations of diffracted wave fields: distortion.

    PubMed

    Harvey, James E; Bogunovic, Dijana; Krywonos, Andrey

    2003-03-01

    Near-field diffraction patterns are merely aberrated Fraunhofer diffraction patterns. These aberrations, inherent to the diffraction process, provide insight and understanding into wide-angle diffraction phenomena. Nonparaxial patterns of diffracted orders produced by a laser beam passing through a grating and projected upon a plane screen exhibit severe distortion (W311). This distortion is an artifact of the configuration chosen to observe diffraction patterns. Grating behavior expressed in terms of the direction cosines of the propagation vectors of the incident and diffracted orders exhibits no distortion. Use of a simple direction cosine diagram provides an elegant way to deal with nonparaxial diffraction patterns, particularly when large obliquely incident beams produce conical diffraction.

  11. 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.

  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. On Distortion in Digital Microwave Power Amplifiers

    NASA Astrophysics Data System (ADS)

    Al-Mozani, Dhamia; Wentzel, Andreas; Heinrich, Wolfgang

    2017-01-01

    In this paper, a first study of distortion in digital power amplifiers (PA) is presented. The work is based on a voltage mode class-S PA with a GaN MMIC for the 900 MHz frequency band. The investigation focuses on the quasi-static amplitude-to-amplitude (AM-AM) and amplitude-to-phase (AM-PM) distortions. Different digital modulation schemes are applied and studied versus output power back-off. This includes two pulse-width modulation (PWM) versions as well as band-pass delta-sigma (BPDS) modulation. The results are verified by measurement data.

  17. Properties of the distorted Kerr black hole

    SciTech Connect

    Abdolrahimi, Shohreh; Tzounis, Christos; Kunz, Jutta; Nedkova, Petya E-mail: jutta.kunz@uni-oldenburg.de E-mail: tzounis@ualberta.ca

    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 J{sup 2}/M{sup 4} > 1 and yet avoid a naked singularity.

  18. Distortion compensation techniques for large reflector antennas

    NASA Technical Reports Server (NTRS)

    Imbriale, W. A.

    2001-01-01

    The high-frequency limit of reflector antennas is usually governed by the magnitude of the surface error. Whereas little can be done for the high-spatial frequency portion of this error, there are various techniques that can be employed to compensate for large-scale surface errors due to gravity induced distortions for spacecraft antennas.

  19. 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.

  20. Vowel distortion in traumatic dysarthria: lip rounding versus tongue advancement.

    PubMed

    Ziegler, W; von Cramon, D

    1983-01-01

    Formant analysis of tense, high, German vowels was performed to the end of obtaining information about the role of insufficient lip rounding in distorted vowel production of 8 traumatic dysarthrics. A comparison was made between two allophones of /y/ in different consonantal contexts. Noticeable undershoot in lip rounding or protrusion proved to occur in a context of conflicting labial gestures. Where the articulatory realization of a CVC sequence required gross tongue movements, a lingual undershoot resulted as the prevailing deficit. No evidence for dyscoordinative defects was obtained from the results.

  1. 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

  2. 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

  3. Radiotherapy planning of the pelvis using distortion corrected MR images: the removal of system distortions

    NASA Astrophysics Data System (ADS)

    Tanner, S. F.; Finnigan, D. J.; Khoo, V. S.; Mayles, P.; Dearnaley, D. P.; Leach, M. O.

    2000-08-01

    Image distortion is an important consideration in the use of magnetic resonance (MR) images for radiotherapy planning. The distortion is a consequence of system distortion (arising from main magnetic field inhomogeneity and nonlinearities in the applied magnetic field gradients) and of effects arising from the object/patient being imaged. A two-stage protocol has been developed to correct both system- and object-induced distortion in pelvic images which incorporates measures to maintain the quality, accuracy and consistency of the imaging and correction procedures. The first stage of the correction procedure is described here and involves the removal of system distortion. Object- (patient-) induced effects will be described in a subsequent work. Images are acquired with the patient lying on a flat rigid bed, which reproduces treatment conditions. A frame of marker tubes surrounding the patient and attached to the bed provides quality assurance data in each image. System distortions in the three orthogonal planes are mapped using a separate phantom, which fits closely within the quality control frame. Software has been written which automates the measurement and checking of the many marker positions which the test objects generate and which ensures that patient data are acquired using a consistent imaging protocol. Results are presented which show that the scanner and the phantoms used in measuring distortion give highly reproducible results with mean changes of the order of 0.1 mm between repeated measurements of marker positions in the same imaging session. Effective correction for in-plane components of system distortion is demonstrated.

  4. Maternal transmission, sex ratio distortion, and mitochondria.

    PubMed

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

    2015-08-18

    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.

  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.

  6. 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.

  7. Deformations of Annuli with Smallest Mean Distortion

    NASA Astrophysics Data System (ADS)

    Astala, K.; Iwaniec, T.; Martin, G.

    2010-03-01

    We determine the extremal mappings with smallest mean distortion for mappings of annuli. As a corollary, we find that the Nitsche harmonic maps are Dirichlet energy minimizers among all homeomorphisms {h:{{mathbb A}}(r, R) to {{mathbb A}}(r', R')} . However, outside the Nitsche range of the modulus of the annuli, within the class of homeomorphisms, no such energy minimizers exist. In this case we identify the BV-limits of minimizers.

  8. 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.

  9. 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.

  10. Anisotropic lattice distortions in biogenic aragonite

    NASA Astrophysics Data System (ADS)

    Pokroy, Boaz; Quintana, John P.; Caspi, El'ad N.; Berner, Alex; Zolotoyabko, Emil

    2004-12-01

    Composite biogenic materials produced by organisms have a complicated design on a nanometre scale. An outstanding example of organic-inorganic composites is provided by mollusc seashells, whose superior mechanical properties are due to their multi-level crystalline hierarchy and the presence of a small amount (0.1-5 wt%) of organic molecules. The presence of organic molecules, among other characteristics, can influence the coherence length for X-ray scattering in biogenic crystals. Here we show the results of synchrotron high-resolution X-ray powder diffraction measurements in biogenic and non-biogenic (geological) aragonite crystals. On applying the Rietveld refinement procedure to the high-resolution diffraction spectra, we were able to extract the aragonite lattice parameters with an accuracy of 10 p.p.m. As a result, we found anisotropic lattice distortions in biogenic aragonite relative to the geological sample, maximum distortion being 0.1% along the c axis of the orthorhombic unit cell. The organic molecules could be a source of these structural distortions in biogenic crystals. This finding may be important to the general understanding of the biomineralization process and the development of bio-inspired 'smart' materials.

  11. Summary of investigations of engine response to distorted inlet conditions

    NASA Technical Reports Server (NTRS)

    Biesiadny, T. J.; Braithwaite, W. M.; Soeder, R. H.; Abdelwahab, M.

    1986-01-01

    A survey is presented of experimental and analytical experience of the NASA Lewis Research Center in engine response to inlet temperature and pressure distortions. This includes a description of the hardware and techniques employed, and a summary of the highlights of experimental investigations and analytical modeling. Distortion devices successfully simulated inlet distortion, and knowledge was gained about compression system response to different types of distortion. A list of NASA research references is included.

  12. Appraisal Distortions and Intimate Partner Violence: Gender, Power, and Interaction

    ERIC Educational Resources Information Center

    Whiting, Jason B.; Oka, Megan; Fife, Stephen T.

    2012-01-01

    In relationships characterized by control, abuse, or violence, many appraisal distortions occur including denial and minimization. However, the nature of the distortion varies depending on the individual's role in the relationship (i.e., abuser or victim). Reducing these distortions is an important component in treatment success and involves…

  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…

  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. Optimum distortion-invariant filter for detecting a noisy distorted target in nonoverlapping background noise

    NASA Astrophysics Data System (ADS)

    Javidi, Bahram; Wang, Jun

    1995-12-01

    An optimal distortion-invariant filter for detecting a distorted target in input noise is designed. The input noise consists of two kinds of noise, overlapping additive noise and nonoverlapping background noise. We obtain the filter function by statistically maximizing the peak-to-output-energy ratio criterion, which is defined as the ratio of the square of the expected value of the output signal at the target location to the expected value of the average output energy. The results in a filter output with a well-defined output peak at the target location and a low output-noise floor. This filter is designed to take into account the effects of both overlapping additive noise and nonoverlapping background noise, the finite size of the input data, and the target distortion. The special cases of detecting a distorted target in nonoverlapping background noise and detecting a distorted target in overlapping additive noise are discussed. Computer simulation results are provided to show the performance of the filter. Copyright (c) 1995 Optical Society of America

  16. Filter based phase distortions in extracellular spikes

    PubMed Central

    Yael, Dorin

    2017-01-01

    Extracellular recordings are the primary tool for extracting neuronal spike trains in-vivo. One of the crucial pre-processing stages of this signal is the high-pass filtration used to isolate neuronal spiking activity. Filters are characterized by changes in the magnitude and phase of different frequencies. While filters are typically chosen for their effect on magnitudes, little attention has been paid to the impact of these filters on the phase of each frequency. In this study we show that in the case of nonlinear phase shifts generated by most online and offline filters, the signal is severely distorted, resulting in an alteration of the spike waveform. This distortion leads to a shape that deviates from the original waveform as a function of its constituent frequencies, and a dramatic reduction in the SNR of the waveform that disrupts spike detectability. Currently, the vast majority of articles utilizing extracellular data are subject to these distortions since most commercial and academic hardware and software utilize nonlinear phase filters. We show that this severe problem can be avoided by recording wide-band signals followed by zero phase filtering, or alternatively corrected by reversed filtering of a narrow-band filtered, and in some cases even segmented signals. Implementation of either zero phase filtering or phase correction of the nonlinear phase filtering reproduces the original spike waveforms and increases the spike detection rates while reducing the number of false negative and positive errors. This process, in turn, helps eliminate subsequent errors in downstream analyses and misinterpretations of the results. PMID:28358895

  17. Discovery of two distorted interstellar bubbles

    NASA Technical Reports Server (NTRS)

    Gull, T. R.; Sofia, S.

    1978-01-01

    During an extensive program of direct imagery of emission nebulae, arcuate structures were found around two stars. A well-defined shock-like structure was found about the T-Orionis variable LL Orionis, located to the side of the Orion Nebula. A less extensive shock-like structure was also found about the runaway star zeta Ophiuchus. These structures can best be described in terms of distorted interstellar bubbles. A direct consequence of this interpretation is an independent estimate of the rates of mass loss for these stars.

  18. Redshift distortions of galaxy correlation functions

    NASA Astrophysics Data System (ADS)

    Fry, J. N.; Gaztanaga, Enrique

    1994-04-01

    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 r0 and power index gamma of the two-point correlations, bar-xi0 = (r0/r)gamma, and as the hierarchical amplitudes of the three- and four-point functions, S3 = bar-xi3/bar-xi22 and S4 = bar-xi4/bar-xi32. We find a characteristic distortion for bar-xi2, 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 Omega4/7/b approximately equal to 1. We estimate Omega4/7/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-xi3 and bar-xi4 suffer similar redshift distortions but in such a way that, within the accuracy of our analysis, the normalized amplitudes S3 and S4 are insensitive to this effect. The hierarchical amplitudes S3 and S4 are constant as a function of scale between 1 and 12 Mpc and have similar values in all samples and catalogs, S3 approximately equal to 2 and S4 approximately equal to 6, despite the fact that bar-xi2, bar-xi3, and bar-xi4 differ from one sample to another by large factors (up to a factor of 4 in bar-xi2, 8 for bar-xi3, and 12 for bar-xi4). The agreement between the independent estimations of S3 and S4 is remarkable given the different criteria in the selection of galaxies and also the difference in the resulting range of densities, luminosities, and locations between samples.

  19. Redshift distortions of galaxy correlation functions

    NASA Astrophysics Data System (ADS)

    Fry, J. N.; Gaztanaga, E.

    1993-05-01

    To examine how peculiar velocities can affect the 2-, 3-, and 4-point correlation functions, we evaluate volume-average correlations for configurations that emphasize and minimize 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 r0 and power index gamma of the 2-point correlation, bar-xi2 = (r0/r)gamma), and as the hierarchical amplitudes of the 3- and 4-point functions, S3 = bar-xi3/bar-xi22 and S4 = bar-xi/bar-xi)23. We find a characteristic distortion for bar-xi2: 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, extra power in the redshift distribution is compatible with Omega4/7/b approx. 1; we find 0.53 plus/minus 0.15, 1.10 plus/minus 0.16 and 0.84 plus/minus 0.45 for the CfA, SSRS and IRAS catalogs. Higher order correlations bar-xi3 and bar-xi4 suffer similar redshift distortions, but in such a way that, within the accuracy of our analysis, the normalized amplitudes S3 and S4 are insensitive to this effect. The hierarchical amplitudes S3 and S4 are constant as a function of scale between 1-12 h-1 Mpc and have similar values in all samples and catalogues, S3 approx. 2 and S4 approx. 6, despite the fact that bar-xi2, bar-xi3, and bar-xi4 differ from one sample to another by large factors. The agreement between the independent estimations of S3 and S4 is remarkable given the different criteria in the selection of galaxies and also the difference in the resulting range of densities, luminosities and locations between samples.

  20. Electric current generation in distorted graphene

    NASA Astrophysics Data System (ADS)

    Mizher, Ana Julia; Raya, Alfredo; Villavicencio, Cristián

    2016-12-01

    Graphene-like materials can be effectively described by quantum electrodynamics in (2+1) dimensions, QED3. In a pristine state, these systems exhibit a symmetry between the nonequivalent Dirac points in the honeycomb lattice. Realistic samples which include distortions and crystalline anisotropies are considered through mass gaps of topological and dynamical nature. In this work, we show that the incorporation of an in-plane uniform external magnetic field on this pseudochiral asymmetric configuration generates a nondissipative electric current aligned with the magnetic field: The pseudochiral magnetic effect (PCME). This scenario resembles the chiral magnetic effect in quantum chromodynamics (QCD).

  1. Dual Cauchy rate-distortion model for video coding

    NASA Astrophysics Data System (ADS)

    Zeng, Huanqiang; Chen, Jing; Cai, Canhui

    2014-07-01

    A dual Cauchy rate-distortion model is proposed for video coding. In our approach, the coefficient distribution of the integer transform is first studied. Then, based on the observation that the rate-distortion model of the luminance and that of the chrominance can be well expressed by separate Cauchy functions, a dual Cauchy rate-distortion model is presented. Furthermore, the simplified rate-distortion formulas are deduced to reduce the computational complexity of the proposed model without losing the accuracy. Experimental results have shown that the proposed model is better able to approximate the actual rate-distortion curve for various sequences with different motion activities.

  2. 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

  3. Diborane release and structure distortion in borohydrides.

    PubMed

    Callini, Elsa; Borgschulte, Andreas; Ramirez-Cuesta, Anibal Javier; Züttel, Andreas

    2013-01-21

    Hydrogen desorption from borohydrides is often accompanied by the release of diborane. The amount of diborane released as a byproduct during the decomposition of borohydrides scales inversely with the borohydride stability, which in turn depends on the electronegativity of the corresponding cation. We present a model based on the difference between the symmetric and asymmetric assembly of B(2)H(6) units at the surface. The origin of this reaction is the degree of distortion of the BH(4)(-) anions in the bulk, hitherto depending on the degree of ionization of the cation. A practical measure of the distortion is the range in which the stretching vibration modes appear, which is the difference in the energy of the stretching vibrations of hydrogen atoms with maximum different bonding lengths (Badger's rule). We propose from this relation that the diborane released from the surface of the relatively unstable LiZn(2)(BH(4))(5) is formed from a recombination of BH(2)(δ+) and BH(4)(δ-) units. Ultra high vacuum mass spectroscopy measurements support the presented model and clarify the decomposition of stable borohydrides, such as LiBH(4). The sublimation of borohydrides in UHV competes with their decomposition.

  4. Rate-distortion optimized adaptive transform coding

    NASA Astrophysics Data System (ADS)

    Lim, Sung-Chang; Kim, Dae-Yeon; Jeong, Seyoon; Choi, Jin Soo; Choi, Haechul; Lee, Yung-Lyul

    2009-08-01

    We propose a rate-distortion optimized transform coding method that adaptively employs either integer cosine transform that is an integer-approximated version of discrete cosine transform (DCT) or integer sine transform (IST) in a rate-distortion sense. The DCT that has been adopted in most video-coding standards is known as a suboptimal substitute for the Karhunen-Loève transform. However, according to the correlation of a signal, an alternative transform can achieve higher coding efficiency. We introduce a discrete sine transform (DST) that achieves the high-energy compactness in a correlation coefficient range of -0.5 to 0.5 and is applied to the current design of H.264/AVC (advanced video coding). Moreover, to avoid the encoder and decoder mismatch and make the implementation simple, an IST that is an integer-approximated version of the DST is developed. The experimental results show that the proposed method achieves a Bjøntegaard Delta-RATE gain up to 5.49% compared to Joint model 11.0.

  5. 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.

  6. 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.

  7. The Independent Distorting Ability of the Enhancer of Segregation Distortion, E(sd), in Drosophila Melanogaster

    PubMed Central

    Temin, R. G.

    1991-01-01

    Segregation distortion is a meiotic drive system, discovered in wild populations, in which males heterozygous for an SD chromosome and a sensitive SD(+) homolog transmit the SD chromosome almost exclusively. SD represents a complex of three closely linked loci in the centromeric region of chromosome 2: Sd, the Segregation distorter gene; E(SD), the Enhancer of Segregation Distortion, required for full expression of drive; and Rsp, the target for the action of Sd, existing in a continuum of states classifiable into sensitive (Rsp(s)) and insensitive (Rsp(i)). In an SD/SD(+) male which is Sd E(SD) Rsp(i)/Sd(+) E(SD)(+) Rsp(s), the Sd and E(SD) elements act jointly to induce the dysfunction of those spermatids receiving the Rsp(s) chromosome. By manipulating the number of copies and the position of the Enhancer region, I demonstrated that: (1) E(SD), whether in its normal position or translocated to the Y chromosome, is able to enhance the degree of Sd-caused distortion in a dosage-dependent manner; (2) even in the absence of Sd, the E(SD) allele in two doses can cause significant distortion, in Sd(+) or Df(Sd)-bearing genotypes; (3) quantitative differences among Enhancers of different sources suggest allelic variation at E(SD), which could account at least in part for differences among wild SD chromosomes in strength of distortion; (4) E(SD)/E(SD)-mediated distortion, like that of Sd, is directed at the Rsp target, whether Rsp is on the second or the Y chromosome; (5) E(SD), like Sd, is suppressed by an unlinked dominant suppressor of SD action. These results show that E(SD) is independently capable of acting on Rsp and is not a simple modifier of the action of Sd. E(SD) provides an example of a trans-acting gene embedded in heterochromatin that can interact with another heterochromatic gene, Rsp, as well as parallel the effect of a euchromatic gene, Sd. PMID:1906417

  8. Approximate Coulomb distortion effects in (e,e{sup {prime}}p) reactions

    SciTech Connect

    Kim, K.S.; Wright, L.E.

    1997-07-01

    In this paper we apply a well-tested approximation of electron Coulomb distortion effects to the exclusive reaction (e,e{sup {prime}}p) in the quasielastic region. We compare the approximate treatment of Coulomb distortion effects to the exact distorted wave Born approximation evaluated by means of partial wave analysis to gauge the quality of our approximate treatment. We show that the approximate Mo/ller potential has a plane-wave-like structure and hence permits the separation of the cross section into five terms which depend on bilinear products of transforms of the transition four current elements. These transforms reduce to Fourier transforms when Coulomb distortion is not present, but become modified with the inclusion of Coulomb distortion. We investigate the application of the approximate formalism to a model of {sup 208}Pb(e,e{sup {prime}}p) using Dirac-Hartree single particle wave functions for the ground state and relativistic optical model wave functions for the continuum proton. We show that it is still possible to extract, albeit with some approximation, the various structure functions from the experimentally measured data even for heavy nuclei. {copyright} {ital 1997} {ital The American Physical Society}

  9. A hydrodynamical approach to CMB μ-distortion from primordial perturbations

    SciTech Connect

    Pajer, Enrico; Zaldarriaga, Matias E-mail: matiasz@ias.edu

    2013-02-01

    Spectral distortion of the cosmic microwave background provides a unique opportunity to probe primordial perturbations on very small scales by performing large-scale measurements. We discuss in a systematic and pedagogic way all the relevant physical phenomena involved in the production and evolution of the μ-type spectral distortion. Our main results agree with previous estimates (in particular we show that a recently found factor of 3/4 arises from relativistic corrections to the wave energy). We also discuss several subleading corrections such as adiabatic cooling and the effects of bulk viscosity, baryon loading and photon heat conduction. Finally we provide formulae for the spatial dependence of μ-distortions and its transfer function between the end of the μ-era and now.

  10. 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.

  11. Appraisal distortions and intimate partner violence: gender, power, and interaction.

    PubMed

    Whiting, Jason B; Oka, Megan; Fife, Stephen T

    2012-06-01

    In relationships characterized by control, abuse, or violence, many appraisal distortions occur including denial and minimization. However, the nature of the distortion varies depending on the individual's role in the relationship (i.e., abuser or victim). Reducing these distortions is an important component in treatment success and involves accepting responsibility for actions and attributions. This study used constructivist grounded theory methods to explore the following questions: (1) What are the types of distortions that are used by individuals who have been in violent or abusive relationships? (2) What are the gender and power differences in the appraisal distortions used? (3) What are the functions and interactions of the distortions in the relationship dynamics? Qualitative analysis of interviews with 29 individuals who had been in abusive relationships found that there were several types of distortions used by participants, but there were differences in the function of the distortion, depending on the individual's role in the abuse. These generally corresponded to power and gender, where the male as perpetrator used different distortions (or used similar distortions for different reasons) than did the female as victim. Suggestions for research as well as treatment implications for both offenders and survivors of abuse are given.

  12. 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.

  13. Horizon dynamics of distorted rotating black holes

    SciTech Connect

    Chu, Tony; Cohen, Michael I.; Pfeiffer, Harald P.

    2011-05-15

    We present numerical simulations of a rotating black hole distorted by a pulse of ingoing gravitational radiation. For strong pulses, we find up to five concentric marginally outer trapped surfaces. These trapped surfaces appear and disappear in pairs, so that the total number of such surfaces at any given time is odd. The world tubes traced out by the marginally outer trapped surfaces are found to be spacelike during the highly dynamical regime, approaching a null hypersurface at early and late times. We analyze the structure of these marginally trapped tubes in the context of the dynamical horizon formalism, computing the expansion of outgoing and incoming null geodesics, as well as evaluating the dynamical horizon flux law and the angular momentum flux law. Finally, we compute the event horizon. The event horizon is well-behaved and approaches the apparent horizon before and after the highly dynamical regime. No new generators enter the event horizon during the simulation.

  14. 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.

  15. Distance distortions in memory for spatial locations.

    PubMed

    Anooshian, L J; Wilson, K L

    1977-12-01

    The present study examined developmental differences in the effect of route extensity on the memory for the locations of objects in a spatial array. Kindergarten and adult subjects were trained to remember the locations of 4 objects. During this training, objects were either connected by a combination of indirect, looped train tracks and direct train tracks (experimental subjects) or connected by entirely direct train-track routes (control subjects). Analyses of actual interobject distances, from subjects' reproductions of object locations on a response board (without train tracks), revealed that children, but not adults, distort distance in terms of the nature of travel observed between objects. Further testing revealed that differences in the amount of time taken for travel could not account for the results obtained with children.

  16. 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.

  17. Wave front distortion based fluid flow imaging

    NASA Astrophysics Data System (ADS)

    Iffa, Emishaw; Heidrich, Wolfgang

    2013-03-01

    In this paper, a transparent flow surface reconstruction based on wave front distortion is investigated. A camera lens is used to focus the image formed by the micro-lens array to the camera imaging plane. The irradiance of the captured image is transformed to frequency spectrum and then the x and y spatial components are separated. A rigid spatial translation followed by low pass filtering yields a single frequency component of the image intensity. Index of refraction is estimated from the inverse Fourier transform of the spatial frequency spectrum of the irradiance. The proposed method is evaluated with synthetic data of a randomly generated index of refraction value and used to visualize a fuel injection volumetric data.

  18. 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.

  19. Pellicle-induced reticle distortion: an experimental investigation

    NASA Astrophysics Data System (ADS)

    Chen, Wen; Carroll, James A.; Storm, Glenn; Ivancich, Ronald G.; Maloney, John P.; Maurin, Olivier; Souleillet, Eric

    1999-04-01

    As semiconductor design rules decrease in size, total overlay performance requires a higher standard of the stepper and the photomask which affords a smaller error budget to each. Currently, photomask overlay assessment is done prior to pellicle attachment. However, the physical act of attaching a pellicle to a photomask imparts mechanical stress that distorts the reticle plane and changes the actual pattern placement from the design intent. With the advent of metrology tools capable of through-pellicle registration measurement, we are now able to assess and better characterize the effect pellicalization has on reticle distortion. The focus of this experimental investigation has been to quantify the incremental reticle distortion attributed to attaching the pellicle. To assess pellicle-induced distortion, both pattern registration and reticle flatness were evaluated. Two pellicle gasket materials were evaluated and one of the two materials was found to produce less reticle distortion. Relaxation of pellicle-induced reticle distortion after the pellicle is attached is also discussed.

  20. Pellicle-induced reticle distortion: an experimental investigation

    NASA Astrophysics Data System (ADS)

    Chen, Wen; Carroll, James A.; Storm, Glenn; Ivancich, Ronald G.; Maloney, John P.; Maurin, Olivier; Souleillet, Eric

    1998-12-01

    As semiconductor design rules decrease in size, total overlay performance requires a higher standard of the stepper and the photomask which affords a smaller error budget to each. Currently, photomask overlay assessment is done prior to pellicle attachment. However, the physical act of attaching a pellicle to a photomask imparts mechanical stress that distorts the reticle plane and changes the actual pattern placement from the design intent. With the advent of metrology tools capable of through-pellicle registration measurement, we are now able to assess and better characterize the effect pelliclization has on reticle distortion. The focus of this experimental investigation has been to quantify the incremental reticle distortion attributed to attaching the pellicle. To assess pellicle-induced distortion, both pattern registration and reticle flatness were evaluated. Two pellicle gasket materials were evaluated and one of the two materials was found to produce less reticle distortion. Relaxation of pellicle-induced reticle distortion after the pellicle is attached is also discussed.

  1. 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.

  2. Numerical and Test Investigation on an Aircraft Inlet Distortion

    NASA Astrophysics Data System (ADS)

    Zhang, Zhang; Hou, Anping; Chen, Yinxiu; Tuo, Wei; Xia, Aiguo

    2013-09-01

    Subscale wind tunnel test of an aircraft vehicle is performed at different Mach number, mass-flow and angle of attack. CFD model, corrected by test results, is also presented to predict inlet performance and total pressure distortion. The result shows total pressure recovery decreases and distortion level rises when Mach number increases from subsonic to supersonic speed, AOA is negative and mass-flow value is too large or too small. Compared linear interpolation based on test result of discrete probes, numerical simulation has advantages in showing inlet flow field predicting actual surface distortion level in AIP plane. Swirl distortion is induced by vortex near the fuselage and adjustable ramp and can strengthen total pressure distortion in AIP at negative AOA. And appropriate suction mass-flow coefficient (1.7% to 3%) is beneficial for inlet performance and total pressure distortion control.

  3. 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.

  4. Measuring ultracomplex supercontinuum pulses and spatio-temporal distortions

    NASA Astrophysics Data System (ADS)

    Gu, Xun

    This thesis contains two components of research: studies of supercontinuum pulses generated in the novel microstructure fiber, and research on spatio-temporal coupling in ultrafast laser beams. One of the most exciting developments in optics in recent years has been the invention of the microstructure optical fiber. By controlling the structural parameters of these novel fibers in design and manufacturing, their dispersion profile can be freely tailored, opening up a huge application base. One particularly interesting effect in the microstructure fiber is the generation of ultrabroadband supercontinuum with only nJ-level Ti:sapphire oscillator pulse pump. This supercontinuum is arguably the most complicated ultrafast pulse ever generated, with its huge time-bandwidth product (>1000 from a 16-cm-long fiber). Although many applications have been demonstrated or envisioned with this continuum, its generation is a very complicated process that is poorly understood, and the characteristics of the continuum pulses are not clearly known. In this work, we make a full-intensity-and-phase measurement of the continuum pulses using cross-correlation frequency-resolved optical gating (XFROG). The results reveal surprising unstable fine spectral structure in the continuum pulses, which is confirmed by single-shot measurements. Our study on the coherence of the continuum, on the other hand, shows that the spectral phase of the supercontinuum is fairly stable. Numerical simulations are carried out whose results are in good agreement with experiments. The second component of this thesis is the study of spatio-temporal coupling in ultrafast beams. We propose two definitions of spatial chirp, point out their respective physical meanings, and derive their relationship. On the common perception of the equivalence between pulse-front tilt and angular dispersion, we show that the equivalence only holds for plane waves. We establish a generalized theory of ultrafast laser beams with first

  5. Novel array-feed distortion compensation techniques for reflector antennas

    NASA Technical Reports Server (NTRS)

    Rahmat-Samii, Yahya

    1991-01-01

    Degradation of antenna performance by reflector surface distortion, which lowers gain and increases sidelobe levels, is addressed. Distortion compensation concepts based on the applications of properly matched array feeds are presented. Results of conceptual developments, numerical simulations, and measurement verifications are presented in support of this approach, with particular attention to the measurement technique. It is shown that the concept is most useful for overcoming the deterioration effects of slowly varying surface distortions, which would make the method very useful for future large space and ground antennas. It is further shown that for a typical, slowly varying thermal or gravitational surface distortion, a 19-element array feed can improve the reflector performance considerably.

  6. 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.

  7. 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.

  8. 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.

  9. Expecting the unexpected: applying the Develop-Distort Dilemma to maximize positive market impacts in health.

    PubMed

    Peters, David H; Paina, Ligia; Bennett, Sara

    2012-10-01

    Although health interventions start with good intentions to develop services for disadvantaged populations, they often distort the health market, making the delivery or financing of services difficult once the intervention is over: a condition called the 'Develop-Distort Dilemma' (DDD). In this paper, we describe how to examine whether a proposed intervention may develop or distort the health market. Our goal is to produce a tool that facilitates meaningful and systematic dialogue for practitioners and researchers to ensure that well-intentioned health interventions lead to productive health systems while reducing the undesirable distortions of such efforts. We apply the DDD tool to plan for development rather than distortions in health markets, using intervention research being conducted under the Future Health Systems consortium in Bangladesh, China and Uganda. Through a review of research proposals and interviews with principal investigators, we use the DDD tool to systematically understand how a project fits within the broader health market system, and to identify gaps in planning for sustainability. We found that while current stakeholders and funding sources for activities were easily identified, future ones were not. The implication is that the projects could raise community expectations that future services will be available and paid for, despite this actually being uncertain. Each project addressed the 'rules' of the health market system differently. The China research assesses changes in the formal financing rules, whereas Bangladesh and Uganda's projects involve influencing community level providers, where informal rules are more important. In each case, we recognize the importance of building trust between providers, communities and government officials. Each project could both develop and distort local health markets. Anyone intervening in the health market must recognize the main market perturbations, whether positive or negative, and manage them so

  10. Seeing the body distorts tactile size perception.

    PubMed

    Longo, Matthew R; Sadibolova, Renata

    2013-03-01

    Vision of the body modulates somatosensation, even when entirely non-informative about stimulation. For example, seeing the body increases tactile spatial acuity, but reduces acute pain. While previous results demonstrate that vision of the body modulates somatosensory sensitivity, it is unknown whether vision also affects metric properties of touch, and if so how. This study investigated how non-informative vision of the body modulates tactile size perception. We used the mirror box illusion to induce the illusion that participants were directly seeing their stimulated left hand, though they actually saw their reflected right hand. We manipulated whether participants: (a) had the illusion of directly seeing their stimulated left hand, (b) had the illusion of seeing a non-body object at the same location, or (c) looked directly at their non-stimulated right-hand. Participants made verbal estimates of the perceived distance between two tactile stimuli presented simultaneously to the dorsum of the left hand, either 20, 30, or 40mm apart. Vision of the body significantly reduced the perceived size of touch, compared to vision of the object or of the contralateral hand. In contrast, no apparent changes of perceived hand size were found. These results show that seeing the body distorts tactile size perception.

  11. Is space representation distorted in neglect?

    PubMed

    Karnath, H O; Ferber, S

    1999-01-01

    It has been argued that neglect of contralateral stimuli following brain damage might be associated with either a compressed or an anisometric neural representation of space along the earth-horizontal axis. Two different models have been put forward. One model proposes a uniform compression of subjective space, while the other envisages an expansion on one side of space and a compression on the other. We tested these models by determining neglect patients' perception of spatial distances in the horizontal plane. The models differ concerning the expected degree of under- vs overestimation of distances in the left and right hemispace. In the first experiment, patients were asked to position ten red LEDs equidistantly along a semicircle, which was located horizontally in front of them at eye level. A second experiment compared the patients' subjective perception of short, medium and long distances extending into left and right hemispace. We found no evidence for any compression or expansion, nor for anisometry along the earth-horizontal axis. These findings argue against a distortion of subjective space along the horizontal axis in patients with neglect which could account for their failure to orient towards and to explore the contralesional parts of space.

  12. Distorting limb design for dynamically similar locomotion.

    PubMed Central

    Bullimore, Sharon R.; Burn, Jeremy F.

    2004-01-01

    Terrestrial mammals of different sizes tend to move in a dynamically similar manner when travelling at speeds corresponding to equal values of the Froude number. This means that certain dimensionless locomotor parameters, including peak vertical ground reaction force relative to body weight, stride length relative to leg length and duty factor, are independent of animal size. The Froude number is consequently used to define equivalent speeds for mammals of different sizes. However, most musculoskeletal-tissue properties, including tendon elastic modulus, do not scale in a dynamically similar manner. Therefore, mammals could not be completely dynamically similar, even if perfectly geometrically similar. We argue that, for mammals to move in a dynamically similar manner, they must exhibit systematic 'distortions' of limb structure with size that compensate for the size independence of the tendon elastic modulus. An implication of this is that comparing mammals at equal Froude numbers cannot remove all size-dependent effects. We show that the previously published allometry of limb moment arms is sufficient to compensate for size-independent tendon properties. This suggests that it is an important factor in allowing mammals of different sizes to move in a dynamically similar manner. PMID:15058440

  13. Primordial trispectra and CMB spectral distortions

    SciTech Connect

    Bartolo, Nicola; Liguori, Michele; Shiraishi, Maresuke E-mail: michele.liguori@pd.infn.it

    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 g{sub NL} and τ{sub NL}. 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 g{sub NL} and τ{sub NL}-parts of the primordial trispectrum source a non-vanishing TTμ signal, contrary to the μμ auto-correlation function, which is sensitive only to the τ{sub NL}-component. A simple Fisher matrix-based forecast shows that a futuristic, cosmic-variance dominated experiment could in principle detect g{sub NL} ∼ 0.4 and τ{sub NL} ∼ 40 using TTμ.

  14. 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,…

  15. 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…

  16. 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…

  17. Compact fluorescent lamps, LED lamps and harmonic distortion

    NASA Astrophysics Data System (ADS)

    Franco, A. M. R.; Debatin, R. M.; Cotia, F. C. G.; Silva, M. V. M.; Ribeiro, R. S.; Zampilis, R. R. N.

    2015-01-01

    The aim of this paper is to evaluate the harmonic distortion in the current waveform of Compact Fluorescent Lamps (CFL) and Lamps Lighting Emitting Diode (LED). For this, we analysed the power factor, voltage waveform, current waveform, total harmonic distortion (THD) and active power consumed.

  18. Mass spectral peak distortion due to Fourier transform signal processing.

    PubMed

    Rockwood, Alan L; Erve, John C L

    2014-12-01

    Distortions of peaks can occur when one uses the standard method of signal processing of data from the Orbitrap and other FT-based methods of mass spectrometry. These distortions arise because the standard method of signal processing is not a linear process. If one adds two or more functions, such as time-dependent signals from a Fourier transform mass spectrometer and performs a linear operation on the sum, the result is the same as if the operation was performed on separate functions and the results added. If this relationship is not valid, the operation is non-linear and can produce unexpected and/or distorted results. Although the Fourier transform itself is a linear operator, the standard algorithm for processing spectra in Fourier transform-based methods include non-linear mathematical operators such that spectra processed by the standard algorithm may become distorted. The most serious consequence is that apparent abundances of the peaks in the spectrum may be incorrect. In light of these considerations, we performed theoretical modeling studies to illustrate several distortion effects that can be observed, including abundance distortions. In addition, we discuss experimental systems where these effects may manifest, including suggested systems for study that should demonstrate these peak distortions. Finally, we point to several examples in the literature where peak distortions may be rationalized by the phenomena presented here.

  19. 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"),…

  20. 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…

  1. 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…

  2. 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

  3. Estimation of the level and phase of the simple distortion tone in the modulation domain

    NASA Astrophysics Data System (ADS)

    Sek, Aleksander; Moore, Brian C. J.

    2004-11-01

    These experiments were designed to test the idea that nonlinearities in the auditory system can introduce a distortion component into the internal representation of the envelope of a sound, and to estimate the phase of the hypothetical distortion component. In experiment 1, a two-alternative forced-choice (2AFC) task with feedback was used to measure psychometric functions for detecting 5-Hz probe modulation of a 4-kHz sinusoidal carrier in the presence of a masker modulator with components at 50 and 55 Hz (m=0.3 for each component). Performance was measured as a function of the relative phase, ΔΦ, of the probe relative to the ``venelope'' (envelope of the envelope) of the masker. Performance was poorest for ΔJ=135°. In experiment 2, Δφ was fixed at 135°, m was set to 0.48 for each masker component, and psychometric functions for detecting probe modulation were measured using a 2AFC task without feedback. For small probe modulation depths (m~0.03), the detectability index, d', was consistently negative, consistent with the existence of a weak distortion product which can ``cancel'' the probe modulation. The distortion component for the conditions of the experiment was estimated to have a phase of about -25° relative to the venelope. .

  4. Joint source-channel distortion modeling for MPEG-4 video.

    PubMed

    Sabir, Muhammad Farooq; Heath, Robert W; Bovik, Alan Conrad

    2009-01-01

    Multimedia communication has become one of the main applications in commercial wireless systems. Multimedia sources, mainly consisting of digital images and videos, have high bandwidth requirements. Since bandwidth is a valuable resource, it is important that its use should be optimized for image and video communication. Therefore, interest in developing new joint source-channel coding (JSCC) methods for image and video communication is increasing. Design of any JSCC scheme requires an estimate of the distortion at different source coding rates and under different channel conditions. The common approach to obtain this estimate is via simulations or operational rate-distortion curves. These approaches, however, are computationally intensive and, hence, not feasible for real-time coding and transmission applications. A more feasible approach to estimate distortion is to develop models that predict distortion at different source coding rates and under different channel conditions. Based on this idea, we present a distortion model for estimating the distortion due to quantization and channel errors in MPEG-4 compressed video streams at different source coding rates and channel bit error rates. This model takes into account important aspects of video compression such as transform coding, motion compensation, and variable length coding. Results show that our model estimates distortion within 1.5 dB of actual simulation values in terms of peak-signal-to-noise ratio.

  5. Bilateral Symmetry of Distortions of Tactile Size Perception.

    PubMed

    Longo, Matthew R; Ghosh, Arko; Yahya, Tasneem

    2015-01-01

    The perceived distance between touches on the limbs is generally bigger for distances oriented across the width of the limb than for distances oriented along the length of the limb. The present study aimed to investigate the coherence of such distortions of tactile size perception across different skin surfaces. We investigated distortions of tactile size perception on the dorsal and palmar surfaces of both the left and right hands as well as the forehead. Participants judged which of two tactile distances felt larger. One distance was aligned with the proximodistal axis (along the body), the other with the mediolateral axis (across the body). Clear distortions were found on all five skin surfaces, with stimuli oriented across the width of the body being perceived as farther apart than those oriented along the length of the body. Consistent with previous results, distortions were smaller on the palmar than on the dorsal hand surface. Distortion on the forehead was intermediate between the dorsal and palmar surfaces. There were clear correlations between distortion on the left and right hands, for both the dorsal and palmar skin surfaces. In contrast, within each hand, there was no significant correlation between the two skin surfaces. Distortion on the forehead was not significantly correlated with that on any of the other skin surfaces. These results provide evidence for bilaterally symmetric representations underlying tactile size perception.

  6. 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.

  7. A survey of inlet/engine distortion compatibility

    NASA Technical Reports Server (NTRS)

    Bowditch, D. N.; Coltrin, R. E.

    1983-01-01

    The history of distortion analysis is traced back to its origin in parallel compressor theory which was initially proposed in the late fifties. The development of this theory is reviewed up to its inclusion in the complex computer codes of today. It is found to be a very useful tool to guide development but not quantitative enough to predict compatibility. Dynamic or instantaneous distortion methodology is also reviewed from its origins in the sixties, to its current application in the eighties. Many of the requirements for interpreting instantaneous distortion are considered and illustrated. Statistical methods for predicting the peak distortion are described, and their limitations and advantages discussed. Finally, some Reynolds number and scaling considerations for inlet testing are considered. It is concluded that the deterministic instantaneous distortion methodology combined with distortion testing of engines with screens will remain the primary method of predicting compatibility for the near future. However, parallel compressor analysis and statistical peak distortion prediction will be important tools employed during the development of inlet/engine compatibility.

  8. CMB spectral distortions as solutions to the Boltzmann equations

    NASA Astrophysics Data System (ADS)

    Ota, Atsuhisa

    2017-01-01

    We propose to re-interpret the cosmic microwave background spectral distortions as solutions to the Boltzmann equation. This approach makes it possible to solve the second order Boltzmann equation explicitly, with the spectral y distortion and the momentum independent second order temperature perturbation, while generation of μ distortion cannot be explained even at second order in this framework. We also extend our method to higher order Boltzmann equations systematically and find new type spectral distortions, assuming that the collision term is linear in the photon distribution functions, namely, in the Thomson scattering limit. As an example, we concretely construct solutions to the cubic order Boltzmann equation and show that the equations are closed with additional three parameters composed of a cubic order temperature perturbation and two cubic order spectral distortions. The linear Sunyaev-Zel'dovich effect whose momentum dependence is different from the usual y distortion is also discussed in the presence of the next leading order Kompaneets terms, and we show that higher order spectral distortions are also generated as a result of the diffusion process in a framework of higher order Boltzmann equations. The method may be applicable to a wider class of problems and has potential to give a general prescription to non-equilibrium physics.

  9. 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

  10. Solar shape distortions and Earth climate changes

    NASA Astrophysics Data System (ADS)

    Lefebvre, S.; Rozelot, J.

    The starting point of this presentation consists of an unexpected result obtained when comparing the temporal solar diameter variations obtained at Santiago de Chile by means of a solar astrolabe, with these of the global Earth's temperature gathered at the University of East Anglia. The plot shows unexpected strong analogous variations that can be only explained, if a causal dependence exits, through variations of the irradiance itself, mainly caused by variations of the global shape. Up to now such a relationship was hint but not put in evidence neither through observations or theoretically. Indeed it has been shown these last few years that the Sun's shape is not a perfect spheroid. The complex shape of the surface is due to gravitational perturbations induced mainly by a non constant velocity rate both at the surface and in depth. At its turn, such a distorted surface provoks changes in the luminosity that can be modelized taking into account the thermal wind. We proposed here for the first time such an approach that permits to understand the observed shape of the Sun from space (SOHO) or from the ground (by means of the scanning heliometer at the Pic du Midi Observatory and by solar astrolabes located at different places). These observations show an equatorial bulge followed by a depressed zone at higher latitudes. If the diameter of the Sun's vary in time as it is observed for instance at Santiago de Chile, it results faint changes in the irradiance that could explain some additional fluctuations that cannot be modelized through the classical flux balance between spots and faculae. In such conditions, a dedicated space satellite which will be capable to measure at a very high level of accuracy the solar shape (i.e. the measurements of the solar diameter at any heliographic latitude, at a better than 1 mas precision) simultaneously with the solar irradiance would render possible the determination of the so-called parameter w, which is known as one of the best

  11. 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.

  12. 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.

  13. Measuring source-pull free nonlinear distortions: a multisine approach

    NASA Astrophysics Data System (ADS)

    Van Moer, Wendy; Pintelon, Rik; Rolain, Yves

    2009-12-01

    This paper presents a method to measure the nonlinear distortions generated by a device-under-test (DUT) out of the frequency band where the device operates. The method compensates for the nonlinear distortions present in the input signal of the DUT and, hence, results in a source-pull free level of the output nonlinear distortions. This is important when determining an accurate adjacent co-channel power ratio (ACPR). The proposed measurement technique is based on a vectorial network analyzer (PNA-X) combined with a broadband multisine excitation of the DUT. Results obtained from a microwave amplifier are reported.

  14. Simulation of Distortion and Residual Stress Development During Heat Treatment of Steel Castings

    SciTech Connect

    Beckermann, Christoph; Carlson, Kent

    2011-07-22

    Heat treatment and associated processing, such as quenching, are critical during high strength steel casting production. These processes must be managed closely to prevent thermal and residual stresses that may result in distortion, cracking (particularly after machining), re-work, and weld repair. The risk of casting distortion limits aggressive quenching that can be beneficial to the process and yield an improved outcome. As a result of these distortions, adjustments must be made to the casting or pattern design, or tie bars must be added. Straightening castings after heat treatments can be both time-consuming and expensive. Residual stresses may reduce a casting's overall service performance, possibly resulting in catastrophic failure. Stress relieving may help, but expends additional energy in the process. Casting software is very limited in predicting distortions during heat treatment, so corrective measures most often involve a tedious trial-and-error procedure. An extensive review of existing heat treatment residual stress and distortion modeling revealed that it is vital to predict the phase transformations and microstructure of the steel along with the thermal stress development during heat treatment. After reviewing the state-of-the-art in heat treatment residual stress and distortion modeling, an existing commercial code was selected because of its advanced capabilities in predicting phase transformations, the evolving microstructure and related properties along with thermal stress development during heat treatment. However, this software was developed for small parts created from forgings or machined stock, and not for steel castings. Therefore, its predictive capabilities for heat treatment of steel castings were investigated. Available experimental steel casting heat treatment data was determined to be of insufficient detail and breadth, and so new heat treatment experiments were designed and performed, casting and heat treating modified versions of

  15. 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 .

  16. 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.

  17. 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.

  18. 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.

  19. Distorted Plane Waves on Manifolds of Nonpositive Curvature

    NASA Astrophysics Data System (ADS)

    Ingremeau, Maxime

    2017-03-01

    We will consider the high frequency behaviour of distorted plane waves on manifolds of nonpositive curvature which are Euclidean or hyperbolic near infinity, under the assumption that the curvature is negative close to the trapped set of the geodesic flow and that the topological pressure associated to half the unstable Jacobian is negative. We obtain a precise expression for distorted plane waves in the high frequency limit, similar to the one in Guillarmou and Naud (Am J Math 136:445-479, 2014) in the case of convex co-compact manifolds. In particular, we will show {L_{loc}^∞} bounds on distorted plane waves that are uniform with frequency. We will also show a small-scale equidistribution result for the real part of distorted plane waves, which implies sharp bounds for the volume of their nodal sets.

  20. 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.

  1. Harmonic distortions measured on board of a maritime vessel

    NASA Astrophysics Data System (ADS)

    Zburlea, Elena; Dordea, Stefan

    2016-12-01

    Measurements where performed on four channels by means of an autonomous equipment (galvanic separated and not supplied from the ship's mains) performed on board of some maritime transport vessels, inside the Port of Constanţa aquatorium. Distorted voltages where state in the distribution panels. The sources of those distortions are the switching power supplies of the electric drives. The novelty of our work states in performing those measurements during the inside port maneuvers, when the operating time of each electric equipment is non definable. Harmonic distortions caused by the switching power converters lower the Power Factor. There is no better manner to find out the main distortions sources on board of a maritime transport vessel than to perform the measurements directly, on each location.

  2. 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

  3. Predictors of child molestation: adult attachment, cognitive distortions, and empathy.

    PubMed

    Wood, Eric; Riggs, Shelley

    2008-02-01

    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 victim empathy significantly increased the odds of child molester status. Findings supported theoretically based hypotheses, suggesting that attachment theory may be useful in the conceptualization and treatment of child molesters.

  4. Study on distortion correction for image mosaic of surface defects

    NASA Astrophysics Data System (ADS)

    Wang, Shitong; Liu, Dong; Chen, Xiaoyu; Cao, Pin; Yang, Yongying

    2012-10-01

    It is hard to quantitate the micron-scale defects on large aperture (102mm×102mm) optical components by the conventional optical testing methods. This paper proposes a super-smooth surface defects measurement and evaluation system, achieved by using microscopic dark-field scattering imaging device, two-dimensional sub-image scanning mechanism and multi-cycle image mosaic algorithm. The defects detecting system, with a lateral resolution of 0.5μm, applies a large field of view design (largest FOV: 15mm×15mm). In order to test the largest element (430mm×430mm), however, over 1000 sub-pictures are captured. It takes more than 30 minutes to process these sub-pictures by multi-cycle image mosaic algorithm. This paper also presents a distortion correction method to revise the image mosaic mismatch caused by the optical distortion in the defects testing system on the platform of MATLAB. A binary optical grid plate (BOE) is fabricated as standard board to evaluate distortion. The proposed method applies image division multi-steps to build a look-up matrix of distortion parameters. According to the look-up matrix, all pixels on a sub-image are repositioned from the distortion Cartesian coordinates to the ideal Cartesian coordinates. Finally, feasibility of the distortion correction method is demonstrated by comparing the mosaic results of defect images before and after this process. The full field view distortion is reduced from more than 4% to less than 0.1%. After distortion correction, subimages can be directly mosaicked without using multi-cycle image mosaic algorithm, which improves test efficiency significantly. The method mentioned in this paper may also apply to other optical testing systems for image mosaic.

  5. 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.

  6. Quantum Spin Fluctuations for a Distorted Incommensurate Spiral

    SciTech Connect

    Fishman, Randy Scott

    2012-01-01

    Quantum spin fluctuations are investigated for the incommensurate state of a geometrically- frustrated triangular-lattice antiferromagnet. With increasing anisotropy, the average suppression of the spin by quantum fluctuations is reduced but the distorted spiral becomes more elliptical. Quan- tum fluctuations also increase the wavevector of the spin state and enhance the critical anisotropy above which a collinear spin state is stabilized. An experimental technique is proposed to isolate the effect of quantum fluctuations from the classical distortion of the spiral.

  7. 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.

  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. 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.

  10. 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.

  11. Visual feedback distortion in a robotic environment for hand rehabilitation.

    PubMed

    Brewer, Bambi Roberts; Klatzky, Roberta; Matsuoka, Yoky

    2008-04-15

    Robotic therapy offers a means of enhancing rehabilitation for individuals with chronic stroke or traumatic brain injury. The present research targets members of this population who demonstrate learned nonuse, a tendency to use affected limbs below the level of the individual's true capability. These individuals may not strive for difficult goals in therapy, which ultimately hampers their progress and the outcome of rehabilitation. Our research uses a paradigm called visual feedback distortion in which the visual feedback corresponding to force or distance is gradually changed by an imperceptible amount to encourage improved performance. Our first set of experiments was designed to assess the limits of imperceptible distortion for visual feedback concerning the force exerted or the distance moved by the index finger. A second set of experiments used these limits to gradually distort visual feedback in order to manipulate a subject's force or distance response. Based on this work, we designed a paradigm applying visual feedback distortion to the rehabilitation of individuals with chronic stroke and traumatic brain injury. Initial tests are reported for two subjects who participated in a six-week rehabilitation protocol. Each patient followed visual feedback distortion to levels of performance above that predicted by her performance during an initial assessment. Both patients showed functional improvements after participating in the study. Visual feedback distortion may provide a way to help a patient move beyond his or her self-assessed "best" performance, improving the outcome of robotic rehabilitation.

  12. Pelvic architectural distortion is associated with pelvic organ prolapse.

    PubMed

    Huebner, Markus; Margulies, Rebecca U; DeLancey, John O L

    2008-06-01

    The aim of this study was to determine whether there is an association between architectural distortion seen on magnetic resonance (MR) scans (lateral "spill" of the vagina and posterior extension of the space of Retzius) and pelvic organ prolapse. Secondary analysis of MR imaging scans from a case-control study of women with prolapse (maximum point > or = + 1 cm; N = 144) and normal controls (maximum point < or = -1 cm; N= 126) was done. Two independent investigators, blinded to prolapse status and previously established levator-defect scores, determined the presence of architectural distortion on axial MR scans. Women were categorized into three groups based on levator defects and architectural distortion. Among the three groups, women with levator defects and architectural distortion have the highest proportion of prolapse (78%; p < 0.001). Among women with levator defects, those with prolapse had an odds ratio of 2.2 for the presence of architectural distortion (95% CI = 1.1-4.6). Pelvic organ prolapse is associated with the presence of visible architectural distortion on MR scans.

  13. 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.

  14. Economic choices reveal probability distortion in macaque monkeys.

    PubMed

    Stauffer, William R; Lak, Armin; Bossaerts, Peter; Schultz, Wolfram

    2015-02-18

    Economic choices are largely determined by two principal elements, reward value (utility) and probability. Although nonlinear utility functions have been acknowledged for centuries, nonlinear probability weighting (probability distortion) was only recently recognized as a ubiquitous aspect of real-world choice behavior. Even when outcome probabilities are known and acknowledged, human decision makers often overweight low probability outcomes and underweight high probability outcomes. Whereas recent studies measured utility functions and their corresponding neural correlates in monkeys, it is not known whether monkeys distort probability in a manner similar to humans. Therefore, we investigated economic choices in macaque monkeys for evidence of probability distortion. We trained two monkeys to predict reward from probabilistic gambles with constant outcome values (0.5 ml or nothing). The probability of winning was conveyed using explicit visual cues (sector stimuli). Choices between the gambles revealed that the monkeys used the explicit probability information to make meaningful decisions. Using these cues, we measured probability distortion from choices between the gambles and safe rewards. Parametric modeling of the choices revealed classic probability weighting functions with inverted-S shape. Therefore, the animals overweighted low probability rewards and underweighted high probability rewards. Empirical investigation of the behavior verified that the choices were best explained by a combination of nonlinear value and nonlinear probability distortion. Together, these results suggest that probability distortion may reflect evolutionarily preserved neuronal processing.

  15. On the Components of Segregation Distortion in Drosophila Melanogaster. IV. Construction and Analysis of Free Duplications for the Responder Locus

    PubMed Central

    Brittnacher, J. G.; Ganetzky, B.

    1989-01-01

    Male Drosophila heterozygous for an SD-bearing second chromosome and a normal homolog preferentially transmit the SD chromosome to their offspring. The distorted transmission involves the induced dysfunction of the sperm that receive the SD(+) chromosome. The loci on the SD chromosome responsible for causing distortion are the Sd locus the the E(SD) locus. Their target of action on the SD(+) chromosome is the Rsp(s) locus. Previous studies of Rsp(s) indicated that deletion of this locus rendered a chromosome insensitive to the action of SD and mapped Rsp(s) physically within the centric heterochromatin of 2R. In this study we have constructed a collection of marked free duplications for the centromeric region of a second chromosome that carried Rsp(s). The heterochromatic extent of each duplication as well as its sensitivity to distortion was determined. We found that Rsp(s) is the most proximal known locus within the 2R heterochromatin. Furthermore, our results demonstrate that the presence of Rsp(s) is not only necessary but sufficient to confer sensitivity to distortion irrespective of its association with an intact second chromosome or one that pairs meiotically with an SD chromosome. By use of these duplications we increased the usual dosage of Rsp(s) relative to SD to determine whether there was any competition for limited amounts of SD [and/or E(SD)] product. When two Rsp(s)-bearing chromosomes are present within the same spermatocyte nucleus an SD chromosome is capable of causing efficient distortion of both. However, at least in some cases the degree of distortion against a given Rsp(s) was reduced by the presence of an extra dose of Rsp(s) indicating that there was some competition between them. The bearing of these results on present models of segregation distortion are discussed. PMID:2498160

  16. Nanostructure-Induced Distortion in Single-Emitter Microscopy

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

    Single-emitter microscopy has emerged as a promising method of imaging nanostructures with nanoscale resolution. This technique uses the centroid position of an emitters 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. 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, in contradiction to the conventional wisdom that the nanoparticle is a scattering object that will pull in the diffraction spot of the emitter towards 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, sub-diffraction spatial imaging. These results provide a better understanding of the complex near-field coupling between emitters and nanostructures, and open up new opportunities to perform super-resolution microscopy with higher accuracy.

  17. Unexpected dynamic up-tuning of auditory organs in day-flying moths.

    PubMed

    Mora, Emanuel C; Cobo-Cuan, Ariadna; Macías-Escrivá, Frank; Kössl, Manfred

    2015-07-01

    In certain nocturnal moth species the frequency range of best hearing shifts to higher frequencies during repeated sound stimulation. This could provide the moths with a mechanism to better detect approaching echolocating bats. However, such a dynamic up-tuning would be of little value for day-flying moths that use intra-specific acoustic communication. Here we examined if the ears of day-flying moths provide stable tuning during longer sound stimulation. Contrary to our expectations, dynamic up-tuning was found in the ear of the day-flying species Urania boisduvalii and Empyreuma pugione. Audiograms were measured with distortion-product otoacoustic emissions (DPOAEs). The level of the dominant distortion product (i.e. 2f1-f2) varied as a function of time by as much as 45 dB during ongoing acoustic stimulation, showing a systematic decrease at low frequencies and an increase at high frequencies. As a consequence, within about 2 s of acoustic stimulation, the DPOAEs audiogram shifted from low to high frequencies. Despite the up-tuning, the range of best audition still fell within the frequency band of the species-specific communication signals, suggesting that intra-specific communication should not be affected adversely. Up-tuning could be an ancestral condition in moth ears that in day-flying moths does not underlie larger selection pressure.

  18. Noise Shaping Filter Compensating PWM Distortion for Fully Digital Amplifier

    NASA Astrophysics Data System (ADS)

    Yoneya, Akihiko

    The full-digital audio amplifiers have several merits such as a high power enabling a small size of the amplifier and digital implementation of the signal processing which allows desired precision of the processing except for the final stage switching amplifiers. Unfortunately, the pulse width modulation (PWM) causes signal distortions because of the non-linearity of the modulation from the viewpoint of the transient response. This paper proposes a compensation method of the PWM distortion with feedback approach. In the noise-shaping filter of the delta-sigma modulator to calculate the pulse codes for the PWM, the distortion caused by the PWM is evaluated and fed it back to compensate the distortion. Eventually the filter is implemented as a state-variable filter with non-linear feedback from the quantizer. The calculation of the filter elements is also described. By using proposed filters, PWM signals with small distortions and small floor noise can be obtained to realize high-fidelity audio amplifiers.

  19. Pneumatic distortion compensation for aircraft surface pressure sensing devices

    NASA Technical Reports Server (NTRS)

    Whitmore, Stephen A.; Leondes, Cornelius T.

    1991-01-01

    In this paper a technique of compensating for pneumatic distortion in aircraft surface pressure sensing devices is developed. The 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. Typically, most of the distortion occurs within the pneumatic tubing used to transmit pressure impulses from the surface of the aircraft to the measurement transducer. This paper develops a second-order distortion model that accurately describes the behavior of the primary wave harmonic of the pneumatic tubing. The model is expressed in state-variable form and is coupled with standard 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. Covariance selection and filter-tuning examples are presented. Results presented verify that, given appropriate covariance magnitudes, the algorithms accurately reconstruct surface pressure values from remotely sensed pressure measurements.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. Short-Term Changes in Light Distortion in Orthokeratology Subjects

    PubMed Central

    Santolaria Sanz, Elena; Villa-Collar, Cesar; González-Méijome, Jose Manuel

    2015-01-01

    Purpose. Quantifying adaptation to light distortion of subjects undergoing orthokeratology (OK) for myopia during the first month of treatment. Methods. Twenty-nine healthy volunteers (age: 22.34 ± 8.08 years) with mean spherical equivalent refractive error −2.10 ± 0.93D were evaluated at baseline and days 1, 7, 15, and 30 of OK treatment. Light distortion was determined using an experimental prototype. Corneal aberrations were derived from corneal topography for different pupil sizes. Contrast sensitivity function (CSF) was analyzed for frequencies of 1.50, 2.12, 3.00, 4.24, 6.00, 8.49, 12.00, 16.97, and 24.00 cpd under photopic conditions. Results. Average monocular values of all light distortion parameters measured increased significantly on day 1, returning to baseline after 1 week (P < 0.05 in all cases). Spherical-like aberration stabilized on day 7 for all pupil diameters, while coma-like for smaller pupils only. CSF was significantly reduced on day 1 for all spatial frequencies except for 1.5 cpd, returning to baseline afterwards. Significant correlation was found between light distortion and contrast sensitivity for middle and high frequencies (P < 0.05) after 15 days. Conclusion. Despite consistently increased levels of corneal aberrations, light distortion tends to return to baseline after one week of treatment, suggesting that neural adaptation is capable of overcoming optical quality degradation. PMID:25699265

  5. 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.

  6. Satellite measurement of ionospheric-induced VHF distortion

    NASA Astrophysics Data System (ADS)

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

    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 deg inclination, low earth orbit in late 1992.

  7. Geometric distortion of area in medical ultrasound images

    NASA Astrophysics Data System (ADS)

    Bland, T.; Tong, J.; Ward, B.; Parker, N. G.

    2017-01-01

    Medical ultrasound scanners are typically calibrated to a speed of sound corresponding to the soft tissue average of 1540 m s-1. In regions of different sound speed, for example, organs and tumours, the B-mode image becomes geometrically distorted from the true tissue cross-section, due to refraction and the misrepresentation of length. A ray model is developed to predict this distortion for a generalized two-dimensional object with atypical speed of sound, and verified against ultrasound images of a test object. We quantify the areal image distortion as a function of the key dependencies, including the speed of sound mismatch, the scanning format, the object size and its elongation. Our findings show that the distortion of area can be significant, even for relatively small speed of sound mismatches. For example, a 5% speed mismatch typically leads to a 10 - 20% distortion in area. These findings have implications for the accuracy of ultrasound-based evaluation of area and volume.

  8. Distortion of digital panoramic radiographs used for implant site assessment

    PubMed Central

    Kayal, Rayyan Abdulhamid

    2016-01-01

    Aims: This study is conducted to determine the amount of distortion of digital panoramic radiographs. Materials and Methods: Panoramic radiographs of all patients who received dental implants in the years 2012 and 2013 were selected from the records at the faculty of dentistry, King Abdulaziz University. Radiographs were analyzed using the R4 Kodak Software for linear measurements of implants length and width. The measurements were compared to the actual size of the implant, and the amount of distortion was calculated. Results: A total of 169 implants were analyzed. Horizontally, there was a statistically significant increase of 0.4 mm in width in the radiographic measurement compared to the actual size in the incisor region. Vertically, the sample overall exhibited a decrease by 0.4 mm compared to the actual size. Incisors had the highest difference with a decrease of 1.7 mm in the radiographic measurements compared to actual size. The highest distortion was found in the incisor region for both diameter and length (1.1 and 0.86), respectively. Conclusion: Digital panoramic radiographs show minimal to no distortion. The highest distortion is found in the anterior area. PMID:27843885

  9. Distortion-Based Link Adaptation for Wireless Video Transmission

    NASA Astrophysics Data System (ADS)

    Ferré, Pierre; Chung-How, James; Bull, David; Nix, Andrew

    2008-12-01

    Wireless local area networks (WLANs) such as IEEE 802.11a/g utilise numerous transmission modes, each providing different throughputs and reliability levels. Most link adaptation algorithms proposed in the literature (i) maximise the error-free data throughput, (ii) do not take into account the content of the data stream, and (iii) rely strongly on the use of ARQ. Low-latency applications, such as real-time video transmission, do not permit large numbers of retransmission. In this paper, a novel link adaptation scheme is presented that improves the quality of service (QoS) for video transmission. Rather than maximising the error-free throughput, our scheme minimises the video distortion of the received sequence. With the use of simple and local rate distortion measures and end-to-end distortion models at the video encoder, the proposed scheme estimates the received video distortion at the current transmission rate, as well as on the adjacent lower and higher rates. This allows the system to select the link-speed which offers the lowest distortion and to adapt to the channel conditions. Simulation results are presented using the MPEG-4/AVC H.264 video compression standard over IEEE 802.11g. The results show that the proposed system closely follows the optimum theoretic solution.

  10. Scalable complexity-distortion model for fast motion estimation

    NASA Astrophysics Data System (ADS)

    Yi, Xiaoquan; Ling, Nam

    2005-07-01

    Recently established international video coding standard H.264/AVC and the upcoming standard on scalable video coding (SVC) bring part of the solution to high compression ratio requirement and heterogeneity requirement. However, these algorithms have unbearable complexities for real-time encoding. Therefore, there is an important challenge to reduce encoding complexity, preferably in a scalable manner. Motion estimation and motion compensation techniques provide significant coding gain but are the most time-intensive parts in an encoder system. They present tremendous research challenges to design a flexible, rate-distortion optimized, yet computationally efficient encoder, especially for various applications. In this paper, we present a scalable motion estimation framework for complexitydistortion consideration. We propose a new progressive initial search (PIS) method to generate an accurate initial search point, followed by a fast search method, which can greatly benefit from the tighter bounds of the PIS. Such approach offers not only significant speedup but also an optimal distortion performance for a given complexity constrain. We analyze the relationship between computational complexity and distortion (C-D) through probabilistic distance measure extending from the complexity and distortion theory. A configurable complexity quantization parameter (Q) is introduced. Simulation results demonstrate that the proposed scalable complexity-distortion framework enables video encoder to conveniently adjust its complexity while providing best possible services.

  11. Constraints on gravitino decay and the scale of inflation using CMB spectral distortions

    NASA Astrophysics Data System (ADS)

    Dimastrogiovanni, Emanuela; Krauss, Lawrence M.; Chluba, Jens

    2016-07-01

    If local supersymmetry is the correct extension of the standard model of particle physics, then following inflation the early Universe would have been populated by gravitinos produced from scatterings in the hot plasma during reheating. Their abundance is directly related to the magnitude of the reheating temperature. The gravitino lifetime is fixed as a function of its mass, and for gravitinos with lifetimes longer than the age of the Universe at redshift z ≃2 ×1 06 (or roughly 6 ×1 06 s ), decay products can produce spectral distortion of the cosmic microwave background. Currently available COBE/FIRAS limits on spectral distortion can, in certain cases, already be competitive with respect to cosmological constraints from primordial nucleosynthesis for some gravitino decay scenarios. We show how the sensitivity limits on μ and y distortions that can be reached with current technology will improve constraints and possibly rule out a significant portion of the parameter space for gravitino masses and inflation reheating temperatures.

  12. 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

  13. Lepton asymmetry, neutrino spectral distortions, and big bang nucleosynthesis

    NASA Astrophysics Data System (ADS)

    Grohs, E.; Fuller, George M.; Kishimoto, C. T.; Paris, Mark W.

    2017-03-01

    We calculate Boltzmann neutrino energy transport with self-consistently coupled nuclear reactions through the weak-decoupling-nucleosynthesis epoch in an early universe with significant lepton numbers. We find that the presence of lepton asymmetry enhances processes which give rise to nonthermal neutrino spectral distortions. Our results reveal how asymmetries in energy and entropy density uniquely evolve for different transport processes and neutrino flavors. The enhanced distortions in the neutrino spectra alter the expected big bang nucleosynthesis light element abundance yields relative to those in the standard Fermi-Dirac neutrino distribution cases. These yields, sensitive to the shapes of the neutrino energy spectra, are also sensitive to the phasing of the growth of distortions and entropy flow with time/scale factor. We analyze these issues and speculate on new sensitivity limits of deuterium and helium to lepton number.

  14. Cosmic Microwave Background spectral distortions from cosmic string loops

    SciTech Connect

    Anthonisen, Madeleine; Brandenberger, Robert; Laguë, Alex; Morrison, Ian A.; Xia, Daixi E-mail: rhb@physics.mcgill.ca E-mail: imorrison@physics.mcgill.ca

    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{sup −15} and G μ ∼ 10{sup −12}, thus ruling out particle physics models yielding these kind of intermediate-scale cosmic strings.

  15. Rise-Time Distortion of Signal without Carrying Signal

    NASA Astrophysics Data System (ADS)

    Bukhman, N. S.

    2016-08-01

    The article deals with one-dimensional problem of rise-time distortion signal without carrying signal, that appears in the starting point intermittently, that is signal distortion at front edge or one of its derivative. The authors show that front edge of signal isn't distorted in case of propagation in unrestricted (including absorbing) area (amplitude of starting signal step or of one of its derivatives doesn't change) and move with the accuracy of vacuum light speed. The paper proves that it is the time interval shortage that causes signal loss with the route extension, but not the reduction of its starting amplitude, during which front edge of signal retains its starting value. The research presents new values for this time interval.

  16. 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.

  17. 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.

  18. Self-induced thermal distortion effects on target image quality.

    PubMed

    Gebhardt, F G

    1972-06-01

    Experimental results are reported that show the effects of the self-induced thermal lens due to a high power laser beam on imaging or tracking systems viewing along the same propagation path. The thermal distortion effects of a wind are simulated with a low power ( less, similar 3-W) CO(2) laser beam propagating through a cell of liquid CS(2) moving across the beam. The resulting image distortion includes a warping effect analogous to the deflection of the CO(2) beam, together with a pronounced demagnification of the central portion of the object. An active optical tracker is simulated with a He-Ne laser beam propagating collinearly with the CO(2) beam. The He-Ne beam pattern returned from a specular target is distorted and sharply confined to the outline of the crescent shaped CO(2) beam. Simple ray optics models are used to provide qualitative explanations for the experimental results.

  19. 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.

  20. Time distortion for expert and novice online game players.

    PubMed

    Rau, Pei-Luen Patrick; Peng, Shu-Yun; Yang, Chin-Chow

    2006-08-01

    Online game addiction is a new mental disorder. This disorder is difficult to describe because of its comprehensive nature. Many online game players have problems controlling their playing time. They cannot stop playing a game that they enjoy. This research surveyed the past literature on "flow" and time disorder theory. A time distortion experiment was conducted. This research invited 64 children, teenagers, and young adults to investigate player skill and playing time effects on online game break-off. The playing experience and degree of time distortion were measured and analyzed. The results showed that both novice and expert online game players were subject to time distortion. The participants had difficulty breaking off from the game without intrusion by others in the real world. This research also suggests eight questions for self-evaluation for online game addiction.

  1. Control of nanoparticle self-assemblies using distorted liquid crystals

    NASA Astrophysics Data System (ADS)

    Lacaze, Emmanuelle; Coursault, Delphine

    This chapter concerns the structure and the optical properties of nanoparticle (NP)/liquid crystal (LC) composites in the presence of LC distortion. After a first description of the general behaviour of NPs at the proximity of distorted LC areas, the first section of the chapter discusses the stabilization of the LC phases, characterized by the presence of topological defects in presence of NPs. The assemblies of NPs induced by distorted LC films is addressed in the second section. The last section then extensively develops the structure and optical properties of NP assemblies created within topological defects. Specific localisation and orientations of the NPs will be discussed, but also possible control of the size and shape of the NP assemblies, together with control of the distances between NPs in the assemblies, leading to original optical properties of the composites as far as uorescent or gold NPs are concerned.

  2. 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.

  3. Evidence for distorted mental representation of the hand in osteoarthritis

    PubMed Central

    Gilpin, Helen R.; Moseley, G. Lorimer; Stanton, Tasha R.

    2015-01-01

    Objectives. Some chronic pain states are associated with a distortion of the perceived size or shape of the painful area, and multisensory illusions that disrupt these dimensions can modulate pain in healthy controls and people with painful disorders. Illusory hand resizing has recently been found to relieve pain in hand OA, raising the possibility that the illusion corrects some underlying perceptual disturbance. We evaluated this possibility by measuring perceived hand size in healthy controls and those with painful hand OA before and after illusory hand resizing. The aim was to investigate whether people with painful hand OA have distorted representations of hand size and whether these representations are malleable. We hypothesized that hand OA is associated with a distorted mental representation of the painful hand and that perceived hand size can be modulated via multisensory illusion. Methods. Twelve volunteers with painful hand OA and 12 healthy age-matched controls performed three tasks (hand stretch, hand shrink and no illusion) in a randomized order then estimated the size of their hand using an adjustable photographic image. Results. Our hypotheses were supported: under normal conditions, perceived hand size was smaller for the OA group than for healthy controls, consistent with a distorted mental representation of the painful hand. Furthermore, illusory stretching increased perceived hand size in both groups, while illusory shrinking decreased perceived hand size in healthy controls but not in the OA group. Conclusion. These results suggest that hand OA is associated with a distorted mental representation of the painful hand and are consistent with the idea that the pain relief offered by multisensory illusions may work via normalization of this distortion. PMID:25246638

  4. Testing inflation and curvaton scenarios with CMB distortions

    SciTech Connect

    Clesse, Sébastien; Garbrecht, Björn; Zhu, Yi E-mail: garbrecht@tum.de

    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.

  5. 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.

  6. A Rapid Distortion Theory modified turbulence spectra for semi-analytical airfoil noise prediction

    NASA Astrophysics Data System (ADS)

    Santana, Leandro D.; Christophe, Julien; Schram, Christophe; Desmet, Wim

    2016-11-01

    This paper proposes an implementation of the Rapid Distortion Theory, for the prediction of the noise resulting from the interaction of an airfoil with incoming turbulence. In the framework of the semi-analytical modeling strategy known as Amiet's theory, this interaction mechanism is treated in a linearized form where the airfoil thickness, camber and angle of attack are assumed negligible, leading to a frozen turbulence description of the incident gust. Important semi-analytical developments have been proposed in the literature to improve the modeling of the gust-airfoil interaction accounting for parallel and skewed gusts, non-rectangular linearized airfoil shapes or blade tip effects. This work is rather focused on the investigation of the distortion of turbulence that occurs in the vicinity of the airfoil leading edge, compared with Rapid Distortion Theory, where main results are briefly reminded in this paper. The main contribution of this work is a detailed experimental investigation of the evolution of turbulent quantities relevant to noise production, performed in the close vicinity of the airfoil leading edge subjected to grid turbulence, by means of stereoscopic Particle Image Velocimetry measurements. The results indicate that the distortion effects are concentrated in a narrow region close to the stagnation point of the leading edge, with dimension of the order of its radius of curvature. Additionally, it is shown that the turbulence intensity grows significantly as the flow approaches the airfoil leading-edge. Based on those results, a modified turbulence spectrum is proposed to describe the incoming turbulence in Amiet's theory. The sound predictions show a significantly better match with acoustic measurements than using the original turbulence model.

  7. 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.

  8. 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.

  9. 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.

  10. Compensating for pneumatic distortion in pressure sensing devices

    NASA Technical Reports Server (NTRS)

    Whitmore, Stephen A.; Leondes, Cornelius T.

    1990-01-01

    A general numerical technique for obtaining unsteady pressure measurements using conventional pressure sensing technology has been developed. A pneumatic distortion model, based on the Navier-Stokes equations of momentum and continuity, was 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 the effects of pneumatic distortion. Both postflight and real-time algorithms were developed and evaluated using simulated and flight data.

  11. Distortion of body image among elite female dancers.

    PubMed

    Pierce, E F; Daleng, M L

    1998-12-01

    To examine body image and possible distortion of body image among elite female dancers 10 members of a professional ballet company rated both current and ideal body shape. In addition, an objective measure of body composition was obtained via skinfold techniques. t tests indicated that the mean rating for current body image was significantly higher than the rating for ideal, despite the fact that body-composition measures for all subjects were in an "ideal" range according to normative standards. Analysis indicated a high distortion of body image among these dancers and support psychophysiological concerns previously raised.

  12. 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.

  13. Overlapping Plate Field Distortion Calibration AST-SV-02

    NASA Astrophysics Data System (ADS)

    Jefferys, William

    1991-07-01

    The goal of these activities is to determine the optical field angle distortions of FGS units #3 to within an arbitrary scale factor, with a level of accuracy sufficient to support an overall astrometry error budget of +/- 0.0027 arcseconds rms. The actual solutions will provide the Project Data Base with the significant terms, their values, and their covariances including errors, which may then be applied to general FGS observations to reduce them for field angle distortions, except scale, alignment, and color corrections. THIS PROPOSAL ASSUMES THAT FGS#3 IS THE PRIME UNIT.

  14. Contrast distortion induced by modulation voltage in scanning capacitance microscopy

    NASA Astrophysics Data System (ADS)

    Chang, M. N.; Hu, C. W.; Chou, T. H.; Lee, Y. J.

    2012-08-01

    With a dark-mode scanning capacitance microscopy (SCM), we directly observed the influence of SCM modulation voltage (MV) on image contrasts. For electrical junctions, an extensive modulated area induced by MV may lead to noticeable changes in the SCM signal phase and intensity, resulting in a narrowed junction image and a broadened carrier concentration profile. This contrast distortion in SCM images may occur even if the peak-to-peak MV is down to 0.3 V. In addition, MV may shift the measured electrical junction depth. The balance of SCM signals components explain these MV-induced contrast distortions.

  15. 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).

  16. 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.

  17. 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.

  18. Harmonic distortion analyzer speeds setup of magnetic tape recorders

    NASA Technical Reports Server (NTRS)

    Tinari, D. F.

    1968-01-01

    Harmonic distortion analyzer effects rapid and accurate setup and calibration of magnetic tape instrumentation recorders. The analyzer is portable, requires no warmup period and need not be calibrated for normal usage. Average setup time with this analyzer is approximately 30 seconds per track.

  19. Centration-distortion error: a criterion of perceptual dysfunction.

    PubMed

    Mecke, V

    This was a study to determine whether centration, as a perceptual process, could be a criterion for differentiating between neurologically impaired and emotionally disturbed children. Centration was defined by Piaget as a prolonged involuntary attachment of a sensory modality to one part of a field, causing perceptual errors of exaggerations and distortions. It is hypothesized that centration would affect motor behavior, producing effects on drawing tasks characterized by separation of designs or their parts, coincident with distortions of the figures drawn. The neurologically impaired children were identified as having primary difficulties with perception whereas the emotionally disturbed children would have primary difficulties with intellection. The centration-distortion error would characterize the drawing of the neurologically impaired but not those of the emotionally disturbed children. A sample of 44 children was selected, each with EEG records, psychological tests and psychiatric interviews used as differential criteria for the groups. Eleven children were diagnosed as having minimal brain damage, 33 as emotionally disturbed. Three psychologists scored the Bender Gestalt tests, blind, for indicators of brain injury and emotional disturbance as defined by Koppitz' criteria, and for the centration-distortion error. The hypothesis was upheld at the .001 level of confidence, validating an earlier pilot study.

  20. 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)

  1. 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…

  2. Bridge 40, detail, the spans are distorted upgrade from years ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Bridge 40, detail, the spans are distorted upgrade from years of loaded westbound traffic traveling downgrade. Located at Milepost 40.31 - Camas Prairie Railroad, Second Subdivision, From Spalding in Nez Perce County, through Lewis County, to Grangeville in Idaho County, Spalding, Nez Perce County, ID

  3. 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.

  4. 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

  5. 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.

  6. Threat Perception Distortions and Psychopathological Symptoms in Typically Developing Children

    ERIC Educational Resources Information Center

    Muris, Peter; Meesters, Cor; Smulders, Lianne; Mayer, Birgit

    2005-01-01

    This study examined relationships between symptoms of anxiety, aggression, and depression, on the one hand, and threat perception distortions, on the other hand. A large sample of typically developing children aged 8-12 years (N = 157) were interviewed with an instrument for assessing the main types of childhood psychopathology, and were then…

  7. Spectral Behavior of Weakly Compressible Aero-Optical Distortions

    NASA Astrophysics Data System (ADS)

    Mathews, Edwin; Wang, Kan; Wang, Meng; Jumper, Eric

    2016-11-01

    In classical theories of optical distortions by atmospheric turbulence, an appropriate and key assumption is that index-of-refraction variations are dominated by fluctuations in temperature and the effects of turbulent pressure fluctuations are negligible. This assumption is, however, not generally valid for aero-optical distortions caused by turbulent flow over an optical aperture, where both temperature and pressures fluctuations may contribute significantly to the index-of-refraction fluctuations. A general expression for weak fluctuations in refractive index is derived using the ideal gas law and Gladstone-Dale relation and applied to describe the spectral behavior of aero-optical distortions. Large-eddy simulations of weakly compressible, temporally evolving shear layers are then used to verify the theoretical results. Computational results support theoretical findings and confirm that if the log slope of the 1-D density spectrum in the inertial range is -mρ , the optical phase distortion spectral slope is given by - (mρ + 1) . The value of mρ is then shown to be dependent on the ratio of shear-layer free-stream densities and bounded by the spectral slopes of temperature and pressure fluctuations. Supported by HEL-JTO through AFOSR Grant FA9550-13-1-0001 and Blue Waters Graduate Fellowship Program.

  8. 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.

  9. 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.

  10. 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…

  11. Epipolar Rectification with Minimum Perspective Distortion for Oblique Images

    PubMed Central

    Liu, Jianchen; Guo, Bingxuan; Jiang, Wanshou; Gong, Weishu; Xiao, Xiongwu

    2016-01-01

    Epipolar rectification is of great importance for 3D modeling by using UAV (Unmanned Aerial Vehicle) images; however, the existing methods seldom consider the perspective distortion relative to surface planes. Therefore, an algorithm for the rectification of oblique images is proposed and implemented in detail. The basic principle is to minimize the rectified images’ perspective distortion relative to the reference planes. First, this minimization problem is formulated as a cost function that is constructed by the tangent value of angle deformation; second, it provides a great deal of flexibility on using different reference planes, such as roofs and the façades of buildings, to generate rectified images. Furthermore, a reasonable scale is acquired according to the dihedral angle between the rectified image plane and the original image plane. The low-quality regions of oblique images are cropped out according to the distortion size. Experimental results revealed that the proposed rectification method can result in improved matching precision (Semi-global dense matching). The matching precision is increased by about 30% for roofs and increased by just 1% for façades, while the façades are not parallel to the baseline. In another designed experiment, the selected façades are parallel to the baseline, the matching precision has a great improvement for façades, by an average of 22%. This fully proves our proposed algorithm that elimination of perspective distortion on rectified images can significantly improve the accuracy of dense matching. PMID:27827991

  12. 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.

  13. 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

  14. 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.…

  15. 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…

  16. Epipolar Rectification with Minimum Perspective Distortion for Oblique Images.

    PubMed

    Liu, Jianchen; Guo, Bingxuan; Jiang, Wanshou; Gong, Weishu; Xiao, Xiongwu

    2016-11-07

    Epipolar rectification is of great importance for 3D modeling by using UAV (Unmanned Aerial Vehicle) images; however, the existing methods seldom consider the perspective distortion relative to surface planes. Therefore, an algorithm for the rectification of oblique images is proposed and implemented in detail. The basic principle is to minimize the rectified images' perspective distortion relative to the reference planes. First, this minimization problem is formulated as a cost function that is constructed by the tangent value of angle deformation; second, it provides a great deal of flexibility on using different reference planes, such as roofs and the façades of buildings, to generate rectified images. Furthermore, a reasonable scale is acquired according to the dihedral angle between the rectified image plane and the original image plane. The low-quality regions of oblique images are cropped out according to the distortion size. Experimental results revealed that the proposed rectification method can result in improved matching precision (Semi-global dense matching). The matching precision is increased by about 30% for roofs and increased by just 1% for façades, while the façades are not parallel to the baseline. In another designed experiment, the selected façades are parallel to the baseline, the matching precision has a great improvement for façades, by an average of 22%. This fully proves our proposed algorithm that elimination of perspective distortion on rectified images can significantly improve the accuracy of dense matching.

  17. 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.

  18. 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.

  19. Generalized linear mixed model for segregation distortion analysis

    PubMed Central

    2011-01-01

    Background Segregation distortion is a phenomenon that the observed genotypic frequencies of a locus fall outside the expected Mendelian segregation ratio. The main cause of segregation distortion is viability selection on linked marker loci. These viability selection loci can be mapped using genome-wide marker information. Results We developed a generalized linear mixed model (GLMM) under the liability model to jointly map all viability selection loci of the genome. Using a hierarchical generalized linear mixed model, we can handle the number of loci several times larger than the sample size. We used a dataset from an F2 mouse family derived from the cross of two inbred lines to test the model and detected a major segregation distortion locus contributing 75% of the variance of the underlying liability. Replicated simulation experiments confirm that the power of viability locus detection is high and the false positive rate is low. Conclusions Not only can the method be used to detect segregation distortion loci, but also used for mapping quantitative trait loci of disease traits using case only data in humans and selected populations in plants and animals. PMID:22078575

  20. Information Distortion in the Evaluation of a Single Option

    ERIC Educational Resources Information Center

    Bond, Samuel D.; Carlson, Kurt A.; Meloy, Margaret G.; Russo, J. Edward; Tanner, Robin J.

    2007-01-01

    Extending previous work on biased predecisional processing, we investigate the distortion of information during the evaluation of a single option. A coherence-based account of the evaluation task suggests that individuals will form an initial assessment of favorability toward the option and then bias their evaluation of subsequent information to…

  1. Large magnetocrystalline anisotropy in tetragonally distorted Heuslers: a systematic study

    NASA Astrophysics Data System (ADS)

    Matsushita, Y.-I.; Madjarova, G.; Dewhurst, J. K.; Shallcross, S.; Felser, C.; Sharma, S.; Gross, E. K. U.

    2017-03-01

    With a view to the design of hard magnets without rare earths we explore the possibility of large magnetocrystalline anisotropy energies in Heusler compounds that are unstable with respect to a tetragonal distortion. We consider the Heusler compounds Fe2YZ with Y  =  (Ni, Co, Pt), and Co2YZ with Y  =  (Ni, Fe, Pt) where, in both cases, Z  =  (Al, Ga, Ge, In, Sn). We find that for the Co2NiZ, Co2PtZ, and Fe2PtZ families the cubic phase is always, at T  =  0, unstable with respect to a tetragonal distortion, while, in contrast, for the Fe2NiZ and Fe2CoZ families this is the case for only 2 compounds—Fe2NiGe and Fe2NiSn. For all compounds in which a tetragonal distortion occurs we calculate the magnetocrystalline anisotropy energy (MAE) finding remarkably large values for the Pt containing Heuslers, but also large values for a number of the other compounds (e.g. Co2NiGa has an MAE of  ‑2.38 MJ m‑3). The tendency to a tetragonal distortion we find to be strongly correlated with a high density of states (DOS) at the Fermi level in the cubic phase. As a corollary to this fact we observe that upon doping compounds for which the cubic structure is stable such that the Fermi level enters a region of high DOS, a tetragonal distortion is induced and a correspondingly large value of the MAE is then observed.

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

    SciTech Connect

    Zotti, G. De; Negrello, M.; Castex, G.; Lapi, A.; Bonato, M. E-mail: NegrelloM@cardiff.ac.uk E-mail: lapi@sissa.it

    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{sup −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 ≅ 30% uncertainty.

  3. Dynamic wake distortion model for helicopter maneuvering flight

    NASA Astrophysics Data System (ADS)

    Zhao, Jinggen

    A new rotor dynamic wake distortion model, which can be used to account for the rotor transient wake distortion effect on inflow across the rotor disk during helicopter maneuvering and transitional flight in both hover and forward flight conditions, is developed. The dynamic growths of the induced inflow perturbation across rotor disk during different transient maneuvers, such as a step pitch or roll rate, a step climb rate and a step change of advance ratio are investigated by using a dynamic vortex tube analysis. Based on the vortex tube results, a rotor dynamic wake distortion model, which is expressed in terms of a set of ordinary differential equations, with rotor longitudinal and lateral wake curvatures, wake skew and wake spacing as states, is developed. Also, both the Pitt-Peters dynamic inflow model and the Peters-He finite state inflow model for axial or forward flight are augmented to account for rotor dynamic wake distortion effect during helicopter maneuvering flight. To model the aerodynamic interaction among main rotor, tail rotor and empennage caused by rotor wake curvature effect during helicopter maneuvering flight, a reduced order model based on a vortex tube analysis is developed. Both the augmented Pitt-Peters dynamic inflow model and the augmented Peters-He finite state inflow model, combined with the developed dynamic wake distortion model, together with the interaction model are implemented in a generic helicopter simulation program of UH-60 Black Hawk helicopter and the simulated vehicle control responses in both time domain and frequency domain are compared with flight test data of a UH-60 Black Hawk helicopter in both hover and low speed forward flight conditions.

  4. Affine Covariant Features for Fisheye Distortion Local Modelling.

    PubMed

    Furnari, Antonino; Farinella, Giovanni; Bruna, Arcangelo; Battiato, Sebastiano

    2016-11-10

    Perspective cameras are the most popular imaging sensors used in Computer Vision. However, many application fields including automotive, surveillance and robotics, require the use of wide angle cameras (e.g., fisheye), which allow to acquire a larger portion of the scene using a single device at the cost of the introduction of noticeable radial distortion in the images. Affine covariant feature detectors have proven successful in a variety of Computer Vision applications including object recognition, image registration and visual search. Moreover, their robustness to a series of variabilities related to both the scene and the image acquisition process has been thoroughly studied in the literature. In this paper, we investigate their effectiveness on fisheye images providing both theoretical and experimental analyses. As theoretical outcome, we show that the inherently non-linear radial distortion can be locally approximated by linear functions with a reasonably small error. The experimental analysis builds on Mikolajczyk's benchmark to assess the robustness of three popular affine region detectors (i.e., Maximally Stable Extremal Regions (MSER), Harris and Hessian affine region detectors), with respect to different variabilities as well as to radial distortion. To support the evaluations, we rely on the Oxford dataset and introduce a novel benchmark dataset comprising 50 images depicting different scene categories. Experiments are carried out on rectilinear images to which radial distortion is artificially added, and on real-world images acquired using fisheye lenses. Our analysis points out that affine region detectors can be effectively employed directly on fisheye images and that the radial distortion is locally modelled as an additional affine variability.

  5. The selfish Segregation Distorter gene complex of Drosophila melanogaster.

    PubMed

    Larracuente, Amanda M; Presgraves, Daven C

    2012-09-01

    Segregation Distorter (SD) is an autosomal meiotic drive gene complex found worldwide in natural populations of Drosophila melanogaster. During spermatogenesis, SD induces dysfunction of SD(+) spermatids so that SD/SD(+) males sire almost exclusively SD-bearing progeny rather than the expected 1:1 Mendelian ratio. SD is thus evolutionarily "selfish," enhancing its own transmission at the expense of its bearers. Here we review the molecular and evolutionary genetics of SD. Genetic analyses show that the SD is a multilocus gene complex involving two key loci--the driver, Segregation distorter (Sd), and the target of drive, Responder (Rsp)--and at least three upward modifiers of distortion. Molecular analyses show that Sd encodes a truncated duplication of the gene RanGAP, whereas Rsp is a large pericentromeric block of satellite DNA. The Sd-RanGAP protein is enzymatically wild type but mislocalized within cells and, for reasons that remain unclear, appears to disrupt the histone-to-protamine transition in drive-sensitive spermatids bearing many Rsp satellite repeats but not drive-insensitive spermatids bearing few or no Rsp satellite repeats. Evolutionary analyses show that the Sd-RanGAP duplication arose recently within the D. melanogaster lineage, exploiting the preexisting and considerably older Rsp satellite locus. Once established, the SD haplotype collected enhancers of distortion and suppressors of recombination. Further dissection of the molecular genetic and cellular basis of SD-mediated distortion seems likely to provide insights into several important areas currently understudied, including the genetic control of spermatogenesis, the maintenance and evolution of satellite DNAs, the possible roles of small interfering RNAs in the germline, and the molecular population genetics of the interaction of genetic linkage and natural selection.

  6. 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.

  7. Shape-assimilation effect: retrospective distortion of visual shapes.

    PubMed

    Ono, Fuminori; Watanabe, Katsumi

    2014-01-01

    A brief visual stimulus distorts the perceived shape of a subsequent visual stimulus as being dissimilar to the shape of a previous stimulus (shape-contrast effect). In this study, we presented a visual stimulus after a to-be-estimated target stimulus and found that the perceived shape of the target stimulus appeared to be similar to the shape of the following stimulus (shape-assimilation effect). The assimilation effect occurred even when the following stimulus was presented at positions different from that of the target stimulus, indicating that the shape-assimilation effect is a nonretinotopic distortion. The results suggest that the preceding and succeeding stimuli differentially modulate the perceived shape of a briefly presented stimulus.

  8. The effect of modern compact fluorescent lights on voltage distortion

    SciTech Connect

    Pileggi, D.J.; Gulachenski, E.M.; Root, C.E. ); Gentile, T.J. ); Emanuel, A.E. )

    1993-07-01

    This paper presents the results of a computer simulation of three real life 13.8kV feeders supplying consumers with non-linear loads which include CFL (Compact Fluorescent Lights) with electronic ballasts. The computer simulations are supported by laboratory testing and in-the-home installation/monitoring of CFL. The results of the laboratory tests and in-the-home monitoring were combined with load research information regarding residential load profiles to produce load models for use in computer simulation of the behavior of the three distribution feeders. The input current to electronically ballasted CFL has unusually high distortion, THD (total harmonic distortion) > 100%. The man conclusion of this work is that for a 15kV class feeder with a maximum 10 MVA load, the total load of electronically ballasted CFL should not exceed 100kW is the voltage THD is to be kept [<=] 5%.

  9. 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.

  10. 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.

  11. 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.

  12. Electrohydrodynamic distortion of sample streams in continuous flow electrophoresis

    NASA Technical Reports Server (NTRS)

    Rhodes, Percy H.; Snyder, Robert S.; Roberts, Glyn O.

    1989-01-01

    Continuous flow electrophoresis experiments were carried out, using an electrolyte and a sample both made of aqueous solutions of phosphate buffer (with polystyrene latex added for visibility), to investigate causes of the sample spreading in this procedure. It is shown theoretically that an electric field perpendicular to a circular filament of conducting fluid surrounded by a fluid of different conductivity produces an electrohydrodynamic flow, which distorts the filament into an ellipse. Experimental results were found to be fully consistent with theretical predictions. It was found that the rate of distortion of the sample stream into a ribbon was proportional to the square of the applied voltage gradient. Furthermore, the orientation of the ribbon depends on the ratios of dielectric constant and electrical conductivity between the buffer and the sample.

  13. Adaptive EZW coding using a rate-distortion criterion

    NASA Astrophysics Data System (ADS)

    Yin, Che-Yi

    2001-07-01

    This work presents a new method that improves on the EZW image coding algorithm. The standard EZW image coder uses a uniform quantizer with a threshold (deadzone) that is identical in all subbands. The quantization step sizes are not optimized under the rate-distortion sense. We modify the EZW by applying the Lagrange multiplier to search for the best step size for each subband and allocate the bit rate for each subband accordingly. Then we implement the adaptive EZW codec to code the wavelet coefficients. Two coding environments, independent and dependent, are considered for the optimization process. The proposed image coder retains all the good features of the EZW, namely, embedded coding, progressive transmission, order of the important bits, and enhances it through the rate-distortion optimization with respect to the step sizes.

  14. Investigating the variability of memory distortion for an analogue trauma.

    PubMed

    Strange, Deryn; Takarangi, Melanie K T

    2015-01-01

    In this paper, we examine whether source monitoring (SM) errors might be one mechanism that accounts for traumatic memory distortion. Participants watched a traumatic film with some critical (crux) and non-critical (non-crux) scenes removed. Twenty-four hours later, they completed a memory test. To increase the likelihood participants would notice the film's gaps, we inserted visual static for the length of each missing scene. We then added manipulations designed to affect people's SM behaviour. To encourage systematic SM, before watching the film, we warned half the participants that we had removed some scenes. To encourage heuristic SM some participants also saw labels describing the missing scenes. Adding static highlighting, the missing scenes did not affect false recognition of those missing scenes. However, a warning decreased, while labels increased, participants' false recognition rates. We conclude that manipulations designed to affect SM behaviour also affect the degree of memory distortion in our paradigm.

  15. Rate-distortion analysis of SP and SI frames

    NASA Astrophysics Data System (ADS)

    Setton, Eric; Girod, Bernd

    2006-01-01

    SP and SI frames in the H.264 video coding standard can be used for error resilience, bitstream switching or random access. Despite a widespread interest in these new types of frames, no work so far has investigated, in a systematic way, their rate-distortion efficiency. In this paper, we propose a model for the rate-distortion performance of SI and SP frames. A comparison to experimental results, obtained with our implementation of an SP encoder, recently adopted by JVT, confirms its validity. The model predicts how the relative sizes of SP and SI frames can be traded off. We analyze, both theoretically and experimentally, how this can be used to minimize the transmitted bit-rate when SP frames are used for video streaming with packet losses.

  16. FPGA Based Compensation Method for Correcting Distortion in Voltage Inverters

    DTIC Science & Technology

    2007-12-01

    inserted to prevent the short circuit that would occur if the two transistors in the same inverter leg are both on at the same time. This delay...occur if the two transistors in the same inverter leg are both on at the same time. This delay produces harmonic distortion and non-linearity when...delay inserted to prevent the short circuit that would occur if the two transistors in a single inverter leg were both on at the same time. This

  17. Dynamic simulation for distortion image with turbulence atmospheric transmission effects

    NASA Astrophysics Data System (ADS)

    Du, Huijie; Fei, Jindong; Qing, Duzheng; Zhao, Hongming; Yu, Hong; Cheng, Chen

    2013-09-01

    The imaging through atmospheric turbulence is an inevitable problem encountered by infrared imaging sensors working in the turbulence atmospheric environment. Before light-rays enter the window of the imaging sensors, the atmospheric turbulence will randomly interfere with the transmission of the light waves came from the objects, causing the distribution of image intensity values on the focal plane to diffuse, the peak value to decrease, the image to get blurred, and the pixels to deviate, and making image identification very difficult. Owing to the fact of the long processing time and that the atmospheric turbulent flow field is unknown and hard to be described by mathematical models, dynamic simulation for distortion Image with turbulence atmospheric transmission effects is much more difficult and challenging in the world. This paper discusses the dynamic simulation for distortion Image of turbulence atmospheric transmission effect. First of all, with the data and the optical transmission model of the turbulence atmospheric, the ray-tracing method is applied to obtain the propagation path of optical ray which propagates through the high-speed turbulent flow field, and then to calculate the OPD from the reference wave to the reconverted wave front and obtain the point spread function (PSF). Secondly, infrared characteristics models of typical scene were established according to the theory of infrared physics and heat conduction, and then the dynamic infrared image was generated by OpenGL. The last step is to obtain the distortion Image with turbulence atmospheric transmission effects .With the data of atmospheric transmission computation, infrared simulation image of every frame was processed according to the theory of image processing and the real-time image simulation, and then the dynamic distortion simulation images with effects of blurring, jitter and shifting were obtained. Above-mentioned simulation method can provide the theoretical bases for recovering

  18. Cognitive Distortions Among Sexual Offenders Against Women in Japan.

    PubMed

    Hazama, Kyoko; Katsuta, Satoshi

    2016-09-15

    Research in Western countries has indicated that the cognitive distortions of sexual offenders play an etiological and maintenance role in offending. The present study examines whether the cognitive distortions hypothesized by previous Western studies can be found in Japanese sexual offenders against women. This study used the questionnaire administered by probation officers in the special cognitive-behavioral treatment programs for sexual offenders, which have been implemented since 2006 in Japan. Participants in the offender group were 80 Japanese male probationers and parolees (more than 19 years old, M age = 34.6, SD = 8.8) convicted of rape (n = 39) or indecent assault (n = 41). All of them attended special treatment programs at probation offices. The non-offender comparison group consisted of 95 Japanese male probation officers and police officers (M age = 35.5, SD = 11.4). A factor analysis of the questionnaire responses extracted three factors: Blaming the Victim, Minimization, and Avoidance of Responsibility. The data analyses showed that sexual offenders scored significantly higher than non-offender participants on the three subscales. No significant differences were found among four sexual offender groups classified as rapists or indecent assaulters and with or without previous convictions for sexual offenses. In conclusion, the results of this study indicate that rapists and indecent assaulters placed on probation or parole in Japan hold cognitive distortions concerning sexual assaults against women than the control group of probation and police officers. The findings of this study also suggest that cognitive distortions exhibited by sexual offenders against women transcend cultural divides.

  19. 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.

  20. 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.

  1. 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

  2. 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

  3. 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.

  4. Damage to insula abolishes cognitive distortions during simulated gambling.

    PubMed

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

    2014-04-22

    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.

  5. 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.

  6. 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.

  7. 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.

  8. Gemini planet imager observational calibrations V: astrometry and distortion

    NASA Astrophysics Data System (ADS)

    Konopacky, Quinn M.; Thomas, Sandrine J.; Macintosh, Bruce A.; Dillon, Daren; Sadakuni, Naru; Maire, Jérôme; Fitzgerald, Michael; Hinkley, Sasha; Kalas, Paul; Esposito, Thomas; Marois, Christian; Ingraham, Patrick J.; Marchis, Franck; Perrin, Marshall D.; Graham, James R.; Wang, Jason J.; De Rosa, Robert J.; Morzinski, Katie; Pueyo, Laurent; Chilcote, Jeffrey K.; Larkin, James E.; Fabrycky, Daniel; Goodsell, Stephen J.; Oppenheimer, Ben R.; Patience, Jenny; Saddlemyer, Leslie; Sivaramakrishnan, Anand

    2014-07-01

    We present the results of both laboratory and on sky astrometric characterization of the Gemini Planet Imager (GPI). This characterization includes measurement of the pixel scale* of the integral field spectrograph (IFS), the position of the detector with respect to north, and optical distortion. Two of these three quantities (pixel scale and distortion) were measured in the laboratory using two transparent grids of spots, one with a square pattern and the other with a random pattern. The pixel scale in the laboratory was also estimate using small movements of the artificial star unit (ASU) in the GPI adaptive optics system. On sky, the pixel scale and the north angle are determined using a number of known binary or multiple systems and Solar System objects, a subsample of which had concurrent measurements at Keck Observatory. Our current estimate of the GPI pixel scale is 14.14 +/- 0.01 millarcseconds/pixel, and the north angle is -1.00 +/- 0.03°. Distortion is shown to be small, with an average positional residual of 0.26 pixels over the field of view, and is corrected using a 5th order polynomial. We also present results from Monte Carlo simulations of the GPI Exoplanet Survey (GPIES) assuming GPI achieves ~1 milliarcsecond relative astrometric precision. We find that with this precision, we will be able to constrain the eccentricities of all detected planets, and possibly determine the underlying eccentricity distribution of widely separated Jovians.

  9. [An improved low spectral distortion PCA fusion method].

    PubMed

    Peng, Shi; Zhang, Ai-Wu; Li, Han-Lun; Hu, Shao-Xing; Meng, Xian-Gang; Sun, Wei-Dong

    2013-10-01

    Aiming at the spectral distortion produced in PCA fusion process, the present paper proposes an improved low spectral distortion PCA fusion method. This method uses NCUT (normalized cut) image segmentation algorithm to make a complex hyperspectral remote sensing image into multiple sub-images for increasing the separability of samples, which can weaken the spectral distortions of traditional PCA fusion; Pixels similarity weighting matrix and masks were produced by using graph theory and clustering theory. These masks are used to cut the hyperspectral image and high-resolution image into some sub-region objects. All corresponding sub-region objects between the hyperspectral image and high-resolution image are fused by using PCA method, and all sub-regional integration results are spliced together to produce a new image. In the experiment, Hyperion hyperspectral data and Rapid Eye data were used. And the experiment result shows that the proposed method has the same ability to enhance spatial resolution and greater ability to improve spectral fidelity performance.

  10. 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.

  11. Tidal distortions in pairs of early-type galaxies

    NASA Technical Reports Server (NTRS)

    Prugniel, Philippe; Davoust, E.

    1990-01-01

    The authors are conducting an imaging survey of pairs of elliptical galaxies which has already produced interesting results. Some pairs present a common pattern of distortion interpreted in terms of tidal effects (Davoust and Prugniel, 1988; Prugniel et al., 1989). Other examples drawn from the literature (Borne and Hoessel, 1988; Colina and Perez-Fournon, 1990) share the same morphology. New cases and lists of the characteristics of 24 such systems. The authors' pairs are drawn from a sample of binary and multiple galaxies which has in turn been extracted from the CGCG, UGC (Nilson, 1973) and VV (Vorontsov-Velyaminov, 1959) catalogues. This sample includes that of Karachentsev (1972). It contains 1800 pairs, among which 700 are S - S or mixed morphology pairs. The authors are working on the remainder to produce a sample of close physical pairs of elliptical galaxies (they also include bulge dominated SO's since the morphological discrimination from ellipticals is often ambiguous, in particular for interacting galaxies). One of the interests of this work is to provide a sample selected on purely optical criteria, at variance with other works (e.g., Valentijn and Casertano, 1988). This will allow statistical studies of non-optical properties of these pairs (in particular radio emission). The authors have so far obtained charge-coupled device (CCD) images of 125 pairs with a 2m telescope and velocities' differences of 78 pairs were obtained using the 1.93 meter telescope of Observatoire de Haute Provence and from the literature. One is an optical pair (VV 190). Eighteen of our pairs present the morphological effect described in Davoust and Prugniel (1988): the external parts of each member are stretched in opposite senses in a direction rougly perpendicular to the pair axis. The proportion of 15 plus or minus 4 percent distorted pairs confirms previous estimates. Except for a few cases involving flattened galaxies with nearly aligned major axes which deserve careful

  12. Broadband distortion modeling in Lyman-α forest BAO fitting

    DOE PAGES

    Blomqvist, Michael; Kirkby, David; Bautista, Julian E.; ...

    2015-11-23

    Recently, the Lyman-α absorption observed in the spectra of high-redshift quasars has been used as a tracer of large-scale structure by means of the three-dimensional Lyman-α forest auto-correlation function at redshift z≃ 2.3, but the need to fit the quasar continuum in every absorption spectrum introduces a broadband distortion that is difficult to correct and causes a systematic error for measuring any broadband properties. Here, we describe a k-space model for this broadband distortion based on a multiplicative correction to the power spectrum of the transmitted flux fraction that suppresses power on scales corresponding to the typical length of amore » Lyman-α forest spectrum. In implementing the distortion model in fits for the baryon acoustic oscillation (BAO) peak position in the Lyman-α forest auto-correlation, we find that the fitting method recovers the input values of the linear bias parameter bF and the redshift-space distortion parameter βF for mock data sets with a systematic error of less than 0.5%. Applied to the auto-correlation measured for BOSS Data Release 11, our method improves on the previous treatment of broadband distortions in BAO fitting by providing a better fit to the data using fewer parameters and reducing the statistical errors on βF and the combination bF(1+βF) by more than a factor of seven. The measured values at redshift z=2.3 are βF=1.39+0.11 +0.24 +0.38-0.10 -0.19 -0.28 and bF(1+βF)=-0.374+0.007 +0.013 +0.020-0.007 -0.014 -0.022 (1σ, 2σ and 3σ statistical errors). Our fitting software and the input files needed to reproduce our main results are publicly available.« less

  13. Broadband distortion modeling in Lyman-α forest BAO fitting

    SciTech Connect

    Blomqvist, Michael; Kirkby, David; Margala, Daniel E-mail: dkirkby@uci.edu; and others

    2015-11-01

    In recent years, the Lyman-α absorption observed in the spectra of high-redshift quasars has been used as a tracer of large-scale structure by means of the three-dimensional Lyman-α forest auto-correlation function at redshift z≅ 2.3, but the need to fit the quasar continuum in every absorption spectrum introduces a broadband distortion that is difficult to correct and causes a systematic error for measuring any broadband properties. We describe a k-space model for this broadband distortion based on a multiplicative correction to the power spectrum of the transmitted flux fraction that suppresses power on scales corresponding to the typical length of a Lyman-α forest spectrum. Implementing the distortion model in fits for the baryon acoustic oscillation (BAO) peak position in the Lyman-α forest auto-correlation, we find that the fitting method recovers the input values of the linear bias parameter b{sub F} and the redshift-space distortion parameter β{sub F} for mock data sets with a systematic error of less than 0.5%. Applied to the auto-correlation measured for BOSS Data Release 11, our method improves on the previous treatment of broadband distortions in BAO fitting by providing a better fit to the data using fewer parameters and reducing the statistical errors on β{sub F} and the combination b{sub F}(1+β{sub F}) by more than a factor of seven. The measured values at redshift z=2.3 are β{sub F}=1.39{sup +0.11 +0.24 +0.38}{sub −0.10 −0.19 −0.28} and b{sub F}(1+β{sub F})=−0.374{sup +0.007 +0.013 +0.020}{sub −0.007 −0.014 −0.022} (1σ, 2σ and 3σ statistical errors). Our fitting software and the input files needed to reproduce our main results are publicly available.

  14. Broadband distortion modeling in Lyman-α forest BAO fitting

    SciTech Connect

    Blomqvist, Michael; Kirkby, David; Bautista, Julian E.; Arinyo-i-Prats, Andreu; Busca, Nicolás G.; Miralda-Escudé, Jordi; Slosar, Anže; Font-Ribera, Andreu; Margala, Daniel; Schneider, Donald P.; Vazquez, Jose A.

    2015-11-23

    Recently, the Lyman-α absorption observed in the spectra of high-redshift quasars has been used as a tracer of large-scale structure by means of the three-dimensional Lyman-α forest auto-correlation function at redshift z≃ 2.3, but the need to fit the quasar continuum in every absorption spectrum introduces a broadband distortion that is difficult to correct and causes a systematic error for measuring any broadband properties. Here, we describe a k-space model for this broadband distortion based on a multiplicative correction to the power spectrum of the transmitted flux fraction that suppresses power on scales corresponding to the typical length of a Lyman-α forest spectrum. In implementing the distortion model in fits for the baryon acoustic oscillation (BAO) peak position in the Lyman-α forest auto-correlation, we find that the fitting method recovers the input values of the linear bias parameter bF and the redshift-space distortion parameter βF for mock data sets with a systematic error of less than 0.5%. Applied to the auto-correlation measured for BOSS Data Release 11, our method improves on the previous treatment of broadband distortions in BAO fitting by providing a better fit to the data using fewer parameters and reducing the statistical errors on βF and the combination bF(1+βF) by more than a factor of seven. The measured values at redshift z=2.3 are βF=1.39+0.11 +0.24 +0.38-0.10 -0.19 -0.28 and bF(1+βF)=-0.374+0.007 +0.013 +0.020-0.007 -0.014 -0.022 (1σ, 2σ and 3σ statistical errors). Our fitting software and the input files needed to reproduce our main results are publicly available.

  15. 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.

  16. Document forgery detection using distortion mutation of geometric parameters in characters

    NASA Astrophysics Data System (ADS)

    Shang, Shize; Kong, Xiangwei; You, Xingang

    2015-03-01

    Tampering related to document forgeries is often accomplished by copy-pasting or add-printing. These tampering methods introduce character distortion mutation in documents. We present a method of exposing document forgeries using distortion mutation of geometric parameters. We estimate distortion parameters, which consist of translation and rotation distortions, through image matching for each character. Detection of tampered characters with distortion mutation occurs based on a distortion probability, which is calculated from character distortion parameters. The introduction of a visualized probability map describes the degree of distortion mutation for a full page. The proposed method exposes the forgeries based on individual characters and applies to English and Chinese document examinations. Experimental results demonstrate the effectiveness of our method on low JPEG compression quality and low resolution.

  17. 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

  18. 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…

  19. 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.

  20. 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.

  1. 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.

  2. Hermite-Gaussian Modes and Mirror Distortions in the Free Electron Laser

    DTIC Science & Technology

    2006-06-01

    Trends for Hyperbolic Distortion for the JLab EM Wiggler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 xi 26. Gain and...Extraction Trends for Hyperbolic Distortion for the JLab STI Wiggler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 27. Gain and...Extraction Trends for Ellipsoidal Distortion for the JLab EM Wiggler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 28. Gain and

  3. Signal distortion from microelectrodes in clinical EEG acquisition systems

    NASA Astrophysics Data System (ADS)

    Stacey, William C.; Kellis, Spencer; Patel, Paras R.; Greger, Bradley; Butson, Christopher R.

    2012-10-01

    Many centers are now using high-density microelectrodes during traditional intracranial electroencephalography (iEEG) both for research and clinical purposes. These microelectrodes are FDA-approved and integrate into clinical EEG acquisition systems. However, the electrical characteristics of these electrodes are poorly described and clinical systems were not designed to use them; thus, it is possible that this shift into clinical practice could have unintended consequences. In this study, we characterized the impedance of over 100 commercial macro- and microelectrodes using electrochemical impedance spectroscopy (EIS) to determine how electrode properties could affect signal acquisition and interpretation. The EIS data were combined with the published specifications of several commercial EEG systems to design digital filters that mimic the behavior of the electrodes and amplifiers. These filters were used to analyze simulated brain signals that contain a mixture of characteristic features commonly observed in iEEG. Each output was then processed with several common quantitative EEG measurements. Our results show that traditional macroelectrodes had low impedances and produced negligible distortion of the original signal. Brain tissue and electrical wiring also had negligible filtering effects. However, microelectrode impedances were much higher and more variable than the macroelectrodes. When connected to clinical amplifiers, higher impedance electrodes produced considerable distortion of the signal at low frequencies (<60 Hz), which caused significant changes in amplitude, phase, variance and spectral band power. In contrast, there were only minimal changes to the signal content for frequencies above 100 Hz. In order to minimize distortion with microelectrodes, we determined that an acquisition system should have an input impedance of at least 1 GΩ, which is much higher than most clinical systems. These results show that it is critical to account for variations

  4. MAXAD distortion minimization for wavelet compression of remote sensing data

    NASA Astrophysics Data System (ADS)

    Alecu, Alin; Munteanu, Adrian; Schelkens, Peter; Cornelis, Jan P.; Dewitte, Steven

    2001-12-01

    In the context of compression of high resolution multi-spectral satellite image data consisting of radiances and top-of-the-atmosphere fluxes, it is vital that image calibration characteristics (luminance, radiance) must be preserved within certain limits in lossy image compression. Though existing compression schemes (SPIHT, JPEG2000, SQP) give good results as far as minimization of the global PSNR error is concerned, they fail to guarantee a maximum local error. With respect to this, we introduce a new image compression scheme, which guarantees a MAXAD distortion, defined as the maximum absolute difference between original pixel values and reconstructed pixel values. In terms of defining the Lagrangian optimization problem, this reflects in minimization of the rate given the MAXAD distortion. Our approach thus uses the l-infinite distortion measure, which is applied to the lifting scheme implementation of the 9-7 floating point Cohen-Daubechies-Feauveau (CDF) filter. Scalar quantizers, optimal in the D-R sense, are derived for every subband, by solving a global optimization problem that guarantees a user-defined MAXAD. The optimization problem has been defined and solved for the case of the 9-7 filter, and we show that our approach is valid and may be applied to any finite wavelet filters synthesized via lifting. The experimental assessment of our codec shows that our technique provides excellent results in applications such as those for remote sensing, in which reconstruction of image calibration characteristics within a tolerable local error (MAXAD) is perceived as being of crucial importance compared to obtaining an acceptable global error (PSNR), as is the case of existing quantizer design techniques.

  5. Segregation distortion and linkage analysis in eggplant (Solanum melongena L.).

    PubMed

    Barchi, Lorenzo; Lanteri, Sergio; Portis, Ezio; Stàgel, Anikò; Valè, Giampiero; Toppino, Laura; Rotino, Giuseppe Leonardo

    2010-10-01

    An anther-derived doubled haploid (DH) population and an F2 mapping population were developed from an intraspecific hybrid between the eggplant breeding lines 305E40 and 67/3. The former incorporates an introgressed segment from Solanum aethiopicum Gilo Group carrying the gene Rfo-sa1, which confers resistance to Fusarium oxysporum; the latter is a selection from an intraspecific cross involving two conventional eggplant varieties and lacks Rfo-sa1. Initially, 28 AFLP primer combinations (PCs) were applied to a sample of 93 F2 individuals and 93 DH individuals, from which 170 polymorphic AFLP fragments were identified. In the DH population, the segregation of 117 of these AFLPs as well as markers closely linked to Rfo-sa1 was substantially distorted, while in the F2 population, segregation distortion was restricted to just 10 markers, and thus the latter was chosen for map development. A set of 141 F2 individuals was genotyped with 73 AFLP PCs (generating 406 informative markers), 32 SSRs, 4 tomato RFLPs, and 3 CAPS markers linked to Rfo-sa1. This resulted in the assignment of 348 markers to 12 major linkage groups. The framework map covered 718.7 cM, comprising 238 markers (212 AFLPs, 22 SSRs, 1 RFLP, and the Rfo-sa1 CAPS). Marker order and inter-marker distances in this eggplant map were largely consistent with those reported in a recently published SSR-based map. From an eggplant breeding perspective, DH populations produced by anther culture appear to be subject to massive segregation distortion and thus may not be very efficient in capturing the full range of genetic variation present in the parental lines.

  6. Transmission ratio distortion results in asymmetric introgression in Louisiana Iris

    PubMed Central

    2010-01-01

    Background Linkage maps are useful tools for examining both the genetic architecture of quantitative traits and the evolution of reproductive incompatibilities. We describe the generation of two genetic maps using reciprocal interspecific backcross 1 (BC1) mapping populations from crosses between Iris brevicaulis and Iris fulva. These maps were constructed using expressed sequence tag (EST)- derived codominant microsatellite markers. Such a codominant marker system allowed for the ability to link the two reciprocal maps, and compare patterns of transmission ratio distortion observed between the two. Results Linkage mapping resulted in markers that coalesced into 21 linkage groups for each of the reciprocal backcross maps, presumably corresponding to the 21 haploid chromosomes of I. brevicaulis and I. fulva. The composite map was 1190.0-cM long, spanned 81% of the I. brevicaulis and I. fulva genomes, and had a mean density of 4.5 cM per locus. Transmission ratio distortion (TRD) was observed in 138 (48.5%) loci distributed in 19 of the 21 LGs in BCIB, BCIF, or both BC1 mapping populations. Of the distorted markers identified, I. fulva alleles were detected at consistently higher-than-expected frequencies in both mapping populations. Conclusions The observation that I. fulva alleles are overrepresented in both mapping populations suggests that I. fulva alleles are favored to introgress into I. brevicaulis genetic backgrounds, while I. brevicaulis alleles would tend to be prevented from introgressing into I. fulva. These data are consistent with the previously observed patterns of introgression in natural hybrid zones, where I. fulva alleles have been consistently shown to introgress across species boundaries. PMID:20298609

  7. Novel scanning method for distortion-free BOTDA measurements.

    PubMed

    Dominguez-Lopez, Alejandro; Yang, Zhisheng; Soto, Marcelo A; Angulo-Vinuesa, Xabier; Martin-Lopez, Sonia; Thevenaz, Luc; Gonzalez-Herraez, Miguel

    2016-05-16

    Systematic errors induced by distortions in the pump pulse of conventional Brillouin distributed fiber sensors are thoroughly investigated. Experimental results, supported by a theoretical analysis, demonstrate that the two probe sidebands in standard Brillouin optical time-domain analyzers provide a non-zero net gain on the pump pulse, inducing severe distortions of the pump when scanning the pump-probe frequency offset, especially at high probe power levels. Compared to the impact of non-local effects reported in the state-of-the-art, measurements here indicate that for probe powers in the mW range (below the onset of amplified spontaneous Brillouin scattering), the obtained gain and loss spectra show two strong side-lobes that lead to significant strain/temperature errors. This phenomenon is not related to the well-known spectral hole burning resulting from pump depletion, but it is strictly related to the temporal and spectral distortions that the pump pulse experiences when scanning the Brillouin gain/loss spectrum. As a solution to this problem, a novel scanning scheme for Brillouin sensing is proposed. The method relies on a fixed frequency separation between the two probe sidebands, so that a flat zero net gain is achieved on the pump pulse when scanning the pump-probe frequency offset. The proposed technique is experimentally validated, demonstrating its ability to completely cancel out non-local effects up to a probe power ultimately limited by the onset of amplified spontaneous Brillouin scattering. The method allows for one order of magnitude improvement in the figure-of-merit of optimized long-range Brillouin distributed fiber sensors, enabling measurements along a 100 km-long sensing fiber with 2 m spatial resolution and with no need of added features for performance enhancement.

  8. Aging of the medial olivocochlear reflex and associations with speech perception

    PubMed Central

    Abdala, Carolina; Dhar, Sumitrajit; Ahmadi, Mahnaz; Luo, Ping

    2014-01-01

    The medial olivocochlear reflex (MOCR) modulates cochlear amplifier gain and is thought to facilitate the detection of signals in noise. High-resolution distortion product otoacoustic emissions (DPOAEs) were recorded in teens, young, middle-aged, and elderly adults at moderate levels using primary tones swept from 0.5 to 4 kHz with and without a contralateral acoustic stimulus (CAS) to elicit medial efferent activation. Aging effects on magnitude and phase of the 2f1-f2 DPOAE and on its components were examined, as was the link between speech-in-noise performance and MOCR strength. Results revealed a mild aging effect on the MOCR through middle age for frequencies below 1.5 kHz. Additionally, positive correlations were observed between strength of the MOCR and performance on select measures of speech perception parsed into features. The elderly group showed unexpected results including relatively large effects of CAS on DPOAE, and CAS-induced increases in DPOAE fine structure as well as increases in the amplitude and phase accumulation of DPOAE reflection components. Contamination of MOCR estimates by middle ear muscle contractions cannot be ruled out in the oldest subjects. The findings reiterate that DPOAE components should be unmixed when measuring medial efferent effects to better consider and understand these potential confounds. PMID:25234884

  9. [Locally weighted least squares estimation of DPOAE evoked by continuously sweeping primaries].

    PubMed

    Han, Xiaoli; Fu, Xinxing; Cui, Jie; Xiao, Ling

    2013-12-01

    Distortion product otoacoustic emission (DPOAE) signal can be used for diagnosis of hearing loss so that it has an important clinical value. Continuously using sweeping primaries to measure DPOAE provides an efficient tool to record DPOAE data rapidly when DPOAE is measured in a large frequency range. In this paper, locally weighted least squares estimation (LWLSE) of 2f1-f2 DPOAE is presented based on least-squares-fit (LSF) algorithm, in which DPOAE is evoked by continuously sweeping tones. In our study, we used a weighted error function as the loss function and the weighting matrixes in the local sense to obtain a smaller estimated variance. Firstly, ordinary least squares estimation of the DPOAE parameters was obtained. Then the error vectors were grouped and the different local weighting matrixes were calculated in each group. And finally, the parameters of the DPOAE signal were estimated based on least squares estimation principle using the local weighting matrixes. The simulation results showed that the estimate variance and fluctuation errors were reduced, so the method estimates DPOAE and stimuli more accurately and stably, which facilitates extraction of clearer DPOAE fine structure.

  10. 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.

  11. Perceptual distortions and deceptions: what computers can teach us

    PubMed Central

    Nour, Matthew M.; Nour, Joseph M.

    2017-01-01

    The nature of perception has fascinated philosophers for centuries, and has more recently been the focus of research in psychology and neuroscience. Many psychiatric disorders are characterised by perceptual abnormalities, ranging from sensory distortions to illusions and hallucinations. The distinction between normal and abnormal perception is, however, hard to articulate. In this article we argue that the distinction between normal perception and abnormal perception is best seen as a quantitative one, resting on the degree to which the observer's prior expectations influence perceptual inference. We illustrate this point with an example taken from researchers at Google working on computer vision. PMID:28184316

  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. Total reduction of distorted echelle spectrograms: an automatic procedure.

    PubMed

    Peterson, R C; Title, A M

    1975-10-01

    We describe a semiautomatic procedure for the reduction of high-dispersion echelle spectra recorded with an image tube. The spectra are traced with a computer-controlled microdensitometer that scans along the curved spectral orders. The curvature of each order is calculated approximately by a FORTRAN program from known grating and distortion parameters. A typical spectrum includes 25 orders (covering 1500 A) and is traced with a slit 0.012 A wide. To produce an atlas of intensity vs wavelength and to determine the equivalent widths of 300 lines currently require a day. We discuss the reduction procedures and time requirements in detail.

  14. Reduction of Residual Stresses and Distortion in Girth Welded Pipes.

    DTIC Science & Technology

    1987-06-01

    M7 26 REP-WTION-OF-RESIDUA-L -STRESSES N D 113 II i m IA WELDED PIPES (U) MASSACHUSETTS INST OF TECH CURIDol DEPT OF WOOE ENGINERING P K DAMS JUN 67... WELDED PIPES bv PANIEL KAY BARNES Ocean Engineering - Course XIIIA NAVAL ENG. & SM(M!E) -- 7fSTUl-O,,CON STT"ne 1987 Aar P b’-i ’w REDUCTION OF RESIDUAL...STRESSES AND DISTORTION IN GIRTH WELDED PIPES by PAMELA KAY BARNES B.S., South Dakota School of Mines and Technology (1977) Submitted to the Department

  15. Distortion-invariant kernel correlation filters for general object recognition

    NASA Astrophysics Data System (ADS)

    Patnaik, Rohit

    General object recognition is a specific application of pattern recognition, in which an object in a background must be classified in the presence of several distortions such as aspect-view differences, scale differences, and depression-angle differences. Since the object can be present at different locations in the test input, a classification algorithm must be applied to all possible object locations in the test input. We emphasize one type of classifier, the distortion-invariant filter (DIF), for fast object recognition, since it can be applied to all possible object locations using a fast Fourier transform (FFT) correlation. We refer to distortion-invariant correlation filters simply as DIFs. DIFs all use a combination of training-set images that are representative of the expected distortions in the test set. In this dissertation, we consider a new approach that combines DIFs and the higher-order kernel technique; these form what we refer to as "kernel DIFs." Our objective is to develop higher-order classifiers that can be applied (efficiently and fast) to all possible locations of the object in the test input. All prior kernel DIFs ignored the issue of efficient filter shifts. We detail which kernel DIF formulations are computational realistic to use and why. We discuss the proper way to synthesize DIFs and kernel DIFs for the wide area search case (i.e., when a small filter must be applied to a much larger test input) and the preferable way to perform wide area search with these filters; this is new. We use computer-aided design (CAD) simulated infrared (IR) object imagery and real IR clutter imagery to obtain test results. Our test results on IR data show that a particular kernel DIF, the kernel SDF filter and its new "preprocessed" version, is promising, in terms of both test-set performance and on-line calculations, and is emphasized in this dissertation. We examine the recognition of object variants. We also quantify the effect of different constant

  16. Distorted black hole initial data using the puncture method

    NASA Astrophysics Data System (ADS)

    Brown, J. David; Lowe, Lisa L.

    2004-12-01

    We solve for single distorted black hole initial data using the puncture method, where the Hamiltonian constraint is written as an elliptic equation in R3 for the nonsingular part of the metric conformal factor. With this approach we can generate isometric and nonisometric black hole data. For the isometric case, our data are directly comparable to those obtained by Bernstein et al., who impose isometry boundary conditions at the black hole throat. Our numerical simulations are performed using a parallel multigrid elliptic equation solver with adaptive mesh refinement. Mesh refinement allows us to use high resolution around the black hole while keeping the grid boundaries far away in the asymptotic region.

  17. Observer Compensation for Projective Distortion of Graphic Displays,

    DTIC Science & Technology

    1980-07-15

    replicate and extend our earlier findings In the second s t of studies, observers made magnitude estimationJudgments of the height width and depth of familiar...Accession ror - " , 3 NTIS GRA&I - S DTIC TAB Unannoune-ed y~ Justlfl C ,r~L 1Distribution/j Availebilitv C ,l 5 IDist SpetC. L IL I Effective use of...have been provided elsewhere (Farber and Rosinski, 1978; Rosinski and Farber, 1980). Inspite of the fact that distortion, in principle , is not specified

  18. 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.

  19. 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.

  20. 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.

  1. 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

  2. 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.

  3. 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.

  4. 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.

  5. Adaptive feed array compensation system for reflector antenna surface distortion

    NASA Technical Reports Server (NTRS)

    Acosta, Roberto J.; Zaman, A.

    1989-01-01

    The feasibility of a closed loop adaptive feed array system for compensating reflector surface deformations has been investigated. The performance characteristics (gain, sidelobe level, pointing, etc.) of large communication antenna systems degrade as the reflector surface distorts mainly due to thermal effects from a varying solar flux. The compensating systems described in this report can be used to maintain the design performance characteristics independent of thermal effects on the reflector surface. The proposed compensating system employs the concept of conjugate field matching to adjust the feed array complex excitation coefficients.

  6. 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.

  7. Analysis of distortion data from TF30-P-3 mixed compression inlet test

    NASA Technical Reports Server (NTRS)

    King, R. W.; Schuerman, J. A.; Muller, R. G.

    1976-01-01

    A program was conducted to reduce and analyze inlet and engine data obtained during testing of a TF30-P-3 engine operating behind a mixed compression inlet. Previously developed distortion analysis techniques were applied to the data to assist in the development of a new distortion methodology. Instantaneous distortion techniques were refined as part of the distortion methodology development. A technique for estimating maximum levels of instantaneous distortion from steady state and average turbulence data was also developed as part of the program.

  8. 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.

  9. 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.

  10. Characterization, prediction, and correction of geometric distortion in 3 T MR images

    SciTech Connect

    Baldwin, Lesley N.; Wachowicz, Keith; Thomas, Steven D.; Rivest, Ryan; Gino Fallone, B.

    2007-02-15

    The work presented herein describes our methods and results for predicting, measuring and correcting geometric distortions in a 3 T clinical magnetic resonance (MR) scanner for the purpose of image guidance in radiation treatment planning. Geometric inaccuracies due to both inhomogeneities in the background field and nonlinearities in the applied gradients were easily visualized on the MR images of a regularly structured three-dimensional (3D) grid phantom. From a computed tomography scan, the locations of just under 10 000 control points within the phantom were accurately determined in three dimensions using a MATLAB-based computer program. MR distortion was then determined by measuring the corresponding locations of the control points when the phantom was imaged using the MR scanner. Using a reversed gradient method, distortions due to gradient nonlinearities were separated from distortions due to inhomogeneities in the background B{sub 0} field. Because the various sources of machine-related distortions can be individually characterized, distortions present in other imaging sequences (for which 3D distortion cannot accurately be measured using phantom methods) can be predicted negating the need for individual distortion calculation for a variety of other imaging sequences. Distortions were found to be primarily caused by gradient nonlinearities and maximum image distortions were reported to be less than those previously found by other researchers at 1.5 T. Finally, the image slices were corrected for distortion in order to provide geometrically accurate phantom images.

  11. 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.

  12. A novel method for correction of temporally- and spatially-variant optical distortion in planar particle image velocimetry

    SciTech Connect

    Zha, Kan; Busch, Stephen; Park, Cheolwoong; Miles, Paul C.

    2016-06-24

    In-cylinder flow measurements are necessary to gain a fundamental understanding of swirl-supported, light-duty Diesel engine processes for high thermal efficiency and low emissions. Planar particle image velocimetry (PIV) can be used for non-intrusive, in situ measurement of swirl-plane velocity fields through a transparent piston. In order to keep the flow unchanged from all-metal engine operation, the geometry of the transparent piston must adapt the production-intent metal piston geometry. As a result, a temporally- and spatially-variant optical distortion is introduced to the particle images. Here, to ensure reliable measurement of particle displacements, this work documents a systematic exploration of optical distortion quantification and a hybrid back-projection procedure that combines ray-tracing-based geometric and in situ manual back-projection approaches.

  13. 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.

  14. The role of numeracy and approximate number system acuity in predicting value and probability distortion.

    PubMed

    Patalano, Andrea L; Saltiel, Jason R; Machlin, Laura; Barth, Hilary

    2015-12-01

    It is well documented that individuals distort outcome values and probabilities when making choices from descriptions, and there is evidence of systematic individual differences in distortion. In the present study, we investigated the relationship between individual differences in such distortions and two measures of numerical competence, numeracy and approximate number system (ANS) acuity. Participants indicated certainty equivalents for a series of simple monetary gambles, and data were used to estimate individual-level value and probability distortion, using a cumulative prospect theory framework. We found moderately strong negative correlations between numeracy and value and probability distortion, but only weak and non-statistically reliable correlations between ANS acuity and distortions. We conclude that low numeracy contributes to number distortion in decision making, but that approximate number system acuity might not underlie this relationship.

  15. Beam-Beam Diagnostics from Closed-Orbit Distortion

    SciTech Connect

    Furman, M.; Chin, Y.-H.; Eden, J.; Kozanecki, W.; Tennyson, J.; Ziemann, V.

    1992-07-01

    The authors study the applicability of beam-beam deflection techniques as a tuning tool for asymmetric B factories, focusing on PEP-II as an example. Assuming that the closed orbits of the two beams are separated vertically at the interaction point by a local orbit bump that is nominally closed, they calculate the residual beam orbit distortions due to the beam-beam interaction. Difference orbit measurements, performed at points conveniently distant from the interaction point (IP), provide distinct signatures that can be used to maintain the beams in collision and perform detailed optical diagnostics at the IP. A proposal to test this method experimentally at the TRISTAN ring is briefly discussed. Because of their two-ring structure, asymmetric B factories are likely to require more diagnostics and feedback mechanisms than single-ring colliders in order to guarantee head-on collisions. In addition to the traditional techniques, however, the independence of the two beams allows one to envisage other kinds of beam diagnostics. In this article they investigate one such possibility, by looking at the closed orbit distortion produced by the beam-beam interaction when the beams do not collide exactly head-on. They base this investigation on an analytic model and strong-strong multiparticle simulations. Although the discussion uses the PEP-II design as an example, the conclusion is that this technique is quite a promising diagnostics tool for asymmetric colliders in general.

  16. Privacy-preserving outlier detection through random nonlinear data distortion.

    PubMed

    Bhaduri, Kanishka; Stefanski, Mark D; Srivastava, Ashok N

    2011-02-01

    Consider a scenario in which the data owner has some private or sensitive data and wants a data miner to access them for studying important patterns without revealing the sensitive information. Privacy-preserving data mining aims to solve this problem by randomly transforming the data prior to their release to the data miners. Previous works only considered the case of linear data perturbations--additive, multiplicative, or a combination of both--for studying the usefulness of the perturbed output. In this paper, we discuss nonlinear data distortion using potentially nonlinear random data transformation and show how it can be useful for privacy-preserving anomaly detection from sensitive data sets. We develop bounds on the expected accuracy of the nonlinear distortion and also quantify privacy by using standard definitions. The highlight of this approach is to allow a user to control the amount of privacy by varying the degree of nonlinearity. We show how our general transformation can be used for anomaly detection in practice for two specific problem instances: a linear model and a popular nonlinear model using the sigmoid function. We also analyze the proposed nonlinear transformation in full generality and then show that, for specific cases, it is distance preserving. A main contribution of this paper is the discussion between the invertibility of a transformation and privacy preservation and the application of these techniques to outlier detection. The experiments conducted on real-life data sets demonstrate the effectiveness of the approach.

  17. Distortion outage minimization in Nakagami fading using limited feedback

    NASA Astrophysics Data System (ADS)

    Wang, Chih-Hong; Dey, Subhrakanti

    2011-12-01

    We focus on a decentralized estimation problem via a clustered wireless sensor network measuring a random Gaussian source where the clusterheads amplify and forward their received signals (from the intra-cluster sensors) over orthogonal independent stationary Nakagami fading channels to a remote fusion center that reconstructs an estimate of the original source. The objective of this paper is to design clusterhead transmit power allocation policies to minimize the distortion outage probability at the fusion center, subject to an expected sum transmit power constraint. In the case when full channel state information (CSI) is available at the clusterhead transmitters, the optimization problem can be shown to be convex and is solved exactly. When only rate-limited channel feedback is available, we design a number of computationally efficient sub-optimal power allocation algorithms to solve the associated non-convex optimization problem. We also derive an approximation for the diversity order of the distortion outage probability in the limit when the average transmission power goes to infinity. Numerical results illustrate that the sub-optimal power allocation algorithms perform very well and can close the outage probability gap between the constant power allocation (no CSI) and full CSI-based optimal power allocation with only 3-4 bits of channel feedback.

  18. [Distorted cognition of bodily sensations in subtypes of social anxiety].

    PubMed

    Kanai, Yoshihiro; Sasaki, Shoko; Iwanaga, Makoto; Seiwa, Hidetoshi

    2010-02-01

    The purpose of this study was to investigate the relationship between subtypes of social anxiety and distorted cognition of bodily sensations. The package of questionnaires including the Social Phobia Scale (SPS) and the Social Interaction Anxiety Scale (SIAS) was administered to 582 undergraduate students. To identify subtypes of social anxiety, cluster analysis was conducted using scores of the SPS and SIAS. Five clusters were identified and labeled as follows: Generalized type characterized by intense anxiety in most social situations, Non-anxious type characterized by low anxiety levels in social situations, Averaged type whose anxiety levels are averaged, Interaction anxiety type who feels anxiety mainly in social interaction situations, and Performance anxiety type who feels anxiety mainly in performance situations. Results of an ANOVA indicated that individuals with interaction type fear the negative evaluation from others regarding their bodily sensations whereas individuals with performance type overestimate the visibility of their bodily sensations to others. Differences in salient aspects of cognitive distortion among social anxiety subtypes may show necessity to select intervention techniques in consideration of subtypes.

  19. Local spatial distortion caused by simple geometrical figures.

    PubMed

    Aksentijevic, Aleksandar; Elliott, Mark A

    2017-08-01

    Dynamic distortion of the visual field has been shown to affect perceptual judgment of visual dimensions such as size, length, and distance. Here, we report four experiments demonstrating that the different aspects of a triangle differently influence judgments of distance. Specifically, when the base of the triangle faces the centre of the display, participants consistently underestimate and overestimate the distance of a small dot from the unmarked centre of the display relative to conditions in which the vertex of the triangle faces the centre. When the dot is close to the figure, the distance of the dot to the centre is underestimated. Conversely, when the dot is close to the figure, the distance to the centre is overestimated. The effect is replicated when the internal distances are equalized and when ellipses are used instead of triangles. These results support a ripple model of spatial distortion in which local curvature acts to attract or repel objects. In conclusion, we suggest some implications of our findings for theories of perceptual organization.

  20. 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.

  1. 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.

  2. An improved solution to geometric distortion using an orthogonal method

    NASA Astrophysics Data System (ADS)

    Peng, Huan-Wen; Peng, Qing-Yu; Wang, Na

    2017-02-01

    The geometric distortion of a CCD field of view has a direct influence on the positional measurements of CCD observations. In order to obtain high precision astrometric results, the geometric distortion should be derived and corrected precisely. As presented in our previous work, a convenient solution has been carried out and has also been applied to observations of Phoebe. In order to further improve the solution, an orthogonal method based on Zernike polynomials is used in this work. Four nights of CCD observations including Himalia, the sixth satellite of Jupiter, and open clusters (NGC 1664 or NGC 2324) on each night have been processed as an application. The observations were obtained from the 2.4 m telescope administered by Yunnan Observatories. The catalog UCAC4 was used to match reference stars in all of the CCD frames. The ephemeris of Himalia is retrieved from the Institut de Mécanique Céleste et de Calcul des Éphémérides (IMCCE). Our results show that the means of observed minus calculated (O-C) positional residuals are -0.034 and -0.026 arcsec in right ascension and declination, respectively. The corresponding standard deviations are {0.031}^{\\prime\\prime } and {0.028}^{\\prime\\prime }. The measurement dispersion is significantly improved compared to that by using our previous solution.

  3. Two-point Spectral Modeling of Anisotropic Rapid Distortion

    NASA Astrophysics Data System (ADS)

    Clark, Timothy; Kurien, Susan; Rubinstein, Robert; Zemach, Charles

    2015-11-01

    We perform simulations of a two-point spectral model for the evolution of the energy tensor as function of wave-vector, for arbitrarily anisotropic turbulence in the limit of rapid distortion. The resulting Reynolds stress tensor for such flow is analysed for the effects of anisotropy during evolution. According to the SO(3) rotation group decomposition of the energy tensor, the leading order isotropic contribution is labelled by rotational mode index j = 0 , while higher order anisotropic contributions in statistically homogeneous flows contain a potentially very large array of rotational modes j = 2 , 3 , 4 , ... . We compare our results to those of the classical Launder, Reece and Rodi class of models in the rapid distortion limit. These models only retain anisotropy in a nominal manner up to j = 2 , due to an a priori angle-averaging procedure on the energy tensor, reducing it to a function of wave-number alone. Although the Reynolds stress itself has maximum j = 2 in the SO(3) representation, the terms that contribute to its evolution generate higher order rotational modes. The contributions from the higher order modes are shown to be responsible for the deviation of the LRR solution from the true solution over time.

  4. 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.

  5. 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.

  6. Effect of distorted illumination waves on coherent diffraction microscopy

    SciTech Connect

    Kohmura, Yoshiki; Nishino, Yoshinori; Ishikawa, Tetsuya; Miao Jianwei

    2005-12-15

    Coherent diffraction microscopy requires a well-defined illumination wave such as a plane wave on a specimen. Experimentally, a small pinhole or a focused beam is often used to reduce the illumination area but they unavoidably distort the waves. The distortion of the illumination wave causes artifacts in the phase retrieval of oversampled diffraction patterns. Using computer simulations, we searched for the conditions where strong artifacts arise by changing the Fresnel number, pinhole size, alignment error and photon statistics. The experimental setup with Fresnel number of around 1 and smaller than 1 realized a small reconstruction error when the pinhole radius is larger than a few times the specimen size. These conditions are suitable for the rotation of specimens for the three-dimensional (3D) observations. Such investigation will have an impact in the design of coherent diffraction microscopes for the 3D characterization of nanoscale materials and biological systems using the third generation synchrotron radiation and future x-ray free-electron lasers.

  7. Study on macroblock level distortion-quantization models

    NASA Astrophysics Data System (ADS)

    Guo, Longsheng; Yin, Haibing; Wang, Jia; Xu, Ning; Tan, Jingjing

    2012-04-01

    In H.264/AVC, rate distortion (R-D) model plays an important role in rate control and mode decision for efficient video compression. In general, R-D model includes rate quantization (R-Q) model and distortion quantization (D-Q) model. We have already had a study on frame-level D-Q model in the past, it is meaningful for frame level rate control optimization. However, basic unit level R-D model is crucial for precise rate control and efficient mode decision. Therefore, it is necessary to make in-depth analysis on D-Q model at MB level. In this paper, we test several existing D-Q models and give fair comparison on these models, and have an in-depth study on D-Q modeling from accuracy, complexity and applications. Finally, we have shown advantages and disadvantages of these models. This work is meaningful for efficient video coding algorithm optimization in the future.

  8. Laboratory simulation of atmospheric turbulence induced optical wavefront distortion

    NASA Astrophysics Data System (ADS)

    Taylor, Travis Shane

    1999-11-01

    Many creative approaches have been taken in the past for simulating the effect that atmospheric turbulence has on optical beams. Most of the experimental architectures have been complicated and consisted of many optical elements as well as moving components. These techniques have shown a modicum of success; however, they are not completely controllable or predictable. A benchtop technique for experimentally producing one important effect that atmospheric turbulence has on optical beams (phase distortion) is presented here. The system is completely controllable and predictable while accurately representing the statistical nature of the problem. Previous experimentation in optical processing through turbulent media has demonstrated that optical wavefront distortions can be produced via spatial light modulating (SLM) devices, and most turbulence models and experimental results indicate that turbulence can be represented as a phase fluctuation. The amplitude distributions in the resulting far field are primarily due to propagation of the phase. Operating a liquid crystal television (LCTV) in the ``phase- mostly'' mode, a phase fluctuation type model for turbulence is utilized in the present investigation, and a real-time experiment for demonstrating the effects was constructed. For an optical system to simulate optical wavefront distortions due to atmospheric turbulence, the following are required: (1)An optical element that modulates the phasefront of an optical beam (2)A model and a technique for generating spatially correlated turbulence simulating distributions (3)Hardware and software for displaying and manipulating the information addressing the optical phase modulation device The LCTV is ideal for this application. When operated in the ``phase-mostly'' mode some LCTVs can modulate the phasefront of an optical beam by as much as 2π and an algorithm for generating spatially correlated phase screens can be constructed via mathematical modeling software such as

  9. Distortion Control of Transmission Components by Optimized High Pressure Gas Quenching

    NASA Astrophysics Data System (ADS)

    Heuer, Volker; Faron, Donald R.; Bolton, David; Lifshits, Mike; Loeser, K.

    2013-07-01

    The paper presents how the "Dynamic Quenching" and "Reversing gas flow" processes are successfully applied on internal ring gears and planetary gears for a 6-speed automatic transmission. The specific challenge was to reduce distortion in such a way that subsequent machining operations are entirely eliminated. As a result of extensive development in the quenching process, it was possible to meet the design metrological requirements. The internal ring gears have been in continuous production since 2006. By utilizing the special CFC fixtures and quench methodology of "Dynamic Quenching," the customer was able to achieve the design intent, while eliminating all machining operations of the ring gears following LPC/HPGQ. Subsequent testing and monitoring over a 2-year period progressively demonstrated that conformance. Therefore, quality inspection was reduced accordingly.

  10. 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.

  11. 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.

  12. 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

  13. Restoration of nonlinear motion-distorted composite frame

    NASA Astrophysics Data System (ADS)

    Yitzhaky, Yitzhak; Stern, Adrian; Kopeika, Norman S.

    2000-12-01

    A composite frame image is an interlaced composition of two sub-image odd and even fields. Such image type is common in many imaging systems that produce video sequences. When relative motion between the camera and the scene occurs during the imaging process, two types of distortion degrade the image: the edge 'staircase effect' due to the shifted appearances of the objects in successive fields, and blur due to the scene motion during each field exposure. This paper deals with restoration of composite frame images degraded by motion. In contrast to other previous works that dealt with only uniform velocity motion, here we consider a more general case of nonlinear motion. Since conventional motion identification techniques used in other works can not be employed in the case of nonlinear motion, a new method for identification of the motion from each field is used. Results of motion identification and image restoration for various motion types are presented.

  14. Converging beams for distortion-free imagery in transfer holograms

    NASA Astrophysics Data System (ADS)

    Waddell, Peter; Saxby, Graham

    1995-02-01

    In order to obtain a distortion-free image when a transfer hologram is replayed by a diverging beam, the original reference beam must be the precise conjugate of the replay beam, i.e., it must converge towards the future location of the replay source. Off-the-shelf collimating mirrors have too long a focal length to achieve this, and suitable custom-built mirrors are heavy and prohibitively expensive. Several methods are suggested for obtaining a suitable beam, including a new type of varifocal pellicular mirror made by stretching a metallized plastic membrane over a circular drumhead and creating a partial vacuum behind it, producing a concave mirror of high optical quality with adjustable focal length.

  15. Increased insulin sensitivity and distorted mitochondrial adaptations during muscle unloading.

    PubMed

    Qi, Zhengtang; Zhang, Yuan; Guo, Wei; Ji, Liu; Ding, Shuzhe

    2012-12-11

    We aimed to further investigate mitochondrial adaptations to muscle disuse and the consequent metabolic disorders. Male rats were submitted to hindlimb unloading (HU) for three weeks. Interestingly, HU increased insulin sensitivity index (ISI) and decreased blood level of triglyceride and insulin. In skeletal muscle, HU decreased expression of pyruvate dehydrogenase kinase 4 (PDK4) and its protein level in mitochondria. HU decreased mtDNA content and mitochondrial biogenesis biomarkers. Dynamin-related protein (Drp1) in mitochondria and Mfn2 mRNA level were decreased significantly by HU. Our findings provide more extensive insight into mitochondrial adaptations to muscle disuse, involving the shift of fuel utilization towards glucose, the decreased mitochondrial biogenesis and the distorted mitochondrial dynamics.

  16. Laboratory simulation of atmospheric turbulence-induced optical wavefront distortion

    NASA Astrophysics Data System (ADS)

    Taylor, Travis S.; Gregory, Don A.

    2002-11-01

    Real-time liquid crystal television-based technique for simulating optical wavefront distortion due to atmospheric turbulence is presented and demonstrated. A liquid crystal television (LCTV) operating in the "phase mostly" mode was used as an array of spatially correlated phase delays. A movie of the arrays in motion was then generated and displayed on the LCTV. The turbulence simulation system was verified by passing a collimated and doubled diode pumped Nd:YVO 4 laser beam (532 nm) through the transparent LCTV screen. The beam was then passed through a lens and the power spectra of the turbulence information carrying beam was detected as a measure of the far-field distribution. The same collimated laser beam, without the LCTV, was also transmitted down an open-air range and the power spectra detected as a measure of a real far-field distribution. Accepted turbulence parameters were measured for both arrangements and then compared.

  17. Conformal Magnifier: A Focus+Context Technique with Minimal Distortion

    PubMed Central

    Zhao, Xin; Zeng, Wei; Gu, Xianfeng; Kaufman, Arie; Xu, Wei; Mueller, Klaus

    2010-01-01

    We present the conformal magnifier, a novel interactive Focus+Context visualization technique to magnify a region of interest (ROI) using conformal mapping. Our framework allows the user to design an arbitrary magnifier to enlarge the features of interest while deforming part of the remaining areas without any cropping. By using conformal mapping, the ROI is magnified with minimal distortion, while the transition region is a smooth and continuous deformation between the focus and context regions. An interactive interface is designed for the user to select important features, design focus models of arbitrary shape and set deformation constraints to satisfy his/her specified requirements. We demonstrate the effectiveness, robustness and efficiency of our method using several applications: texts, maps, geographic images, data structures and multi-media visualization. PMID:26279613

  18. Pressure-induced structural distortions in copper pyrazine dinitrate

    NASA Astrophysics Data System (ADS)

    O'Neal, Kenneth; Cherian, Judy; Landee, Chris; Turnbull, Mark; Liu, Zhenxian; Musfeldt, Janice

    2015-03-01

    The vibrational properties of quasi-one-dimensional Heisenberg antiferromagnet copper pyrazine dinitrate were investigated up to 9 GPa using diamond anvil cell techniques and infrared and Raman spectroscopy. Two structural transitions were discovered, at 0.7 GPa and around 5 GPa. The lower pressure transition involves only the nitrate ligands, revealing enhanced interchain interactions. The higher pressure transition includes modes throughout the spectrum. Importantly, the pyrazine ring-related modes show an overall lowering of symmetry through this transition. Ring buckling under pressure likely reduces the exchange along the chains since the exchange pathway becomes distorted. A smaller J may therefore lower the magnetic field of the quantum critical transition. This tunable exchange interaction could be utilized in other pyrazine bridged molecular systems to bring the quantum critical behavior into experimentally realizable fields. We thank the National Science Foundation and the Petroleum Research Fund for support of this work.

  19. 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.

  20. Optimal redshift weighting for redshift-space distortions

    NASA Astrophysics Data System (ADS)

    Ruggeri, Rossana; Percival, Will J.; Gil-Marín, Héctor; Zhu, Fangzhou; Zhao, Gong-Bo; Wang, Yuting

    2017-01-01

    The low-statistical errors on cosmological parameters promised by future galaxy surveys will only be realized with the development of new, fast, analysis methods that reduce potential systematic problems to low levels. We present an efficient method for measuring the evolution of the growth of structure using redshift-space distortions (RSDs), that removes the need to make measurements in redshift shells. We provide sets of galaxy-weights that cover a wide range in redshift, but are optimized to provide differential information about cosmological evolution. These are derived to optimally measure the coefficients of a parametrization of the redshift-dependent matter density, which provides a framework to measure deviations from the concordance ΛCDM cosmology, allowing for deviations in both geometric and/or growth. We test the robustness of the weights by comparing with alternative schemes and investigate the impact of galaxy bias. We extend the results to measure the combined anisotropic baryon acoustic oscillation and RSD signals.

  1. Analysis of distorted unbalanced waveforms in inverter drives

    NASA Astrophysics Data System (ADS)

    Andria, Gregorio; dell'Aquila, Antonio; Salvatore, Luigi

    1989-04-01

    A technique for determining the degree of unbalance in a three-phase electrical system is developed and demonstrated. Expressions for the distorted and unbalanced waveforms are derived; the effects of such waveforms on the performance of induction motors are estimated; the analysis of a typical system is outlined; and the errors inherent in FFT harmonic analysis are evaluated. A PC-based experimental digital measurement system is implemented, tested, and applied to a commercial three-phase PWM inverter with continuous output power 11 kVA, output voltage 380 V, and output frequency 5-50 Hz. The results are presented in extensive tables and graphs and characterized in detail, demonstrating the effectiveness of the procedure.

  2. Phonon triggered rhombohedral lattice distortion in vanadium at high pressure

    SciTech Connect

    Antonangeli, Daniele; Farber, Daniel L.; Bosak, Alexei; Aracne, Chantel M.; Ruddle, David G.; Krisch, Michael

    2016-08-19

    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. Lastly, 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.

  3. Magnetospheric-field distortions observed by OGO 3 and 5.

    NASA Technical Reports Server (NTRS)

    Sugiura, M.; Ledley, B. G.; Skillman, T. L.; Heppner, J. P.

    1971-01-01

    The rubidium vapor magnetometer data of the scalar magnetic-field intensity obtained by the OGO 3 and 5 satellites are analyzed to study the magnetospheric-field distortions in terms of the observed field magnitude under quiet and slightly disturbed conditions minus the magnitude of the reference geomagnetic field (delta B). Average contours of equal delta Bs are shown in the geomagnetic noon-midnight and dawn-dusk meridian planes for magnetically quiet and slightly disturbed conditions. The equatorial distribution of observed delta Bs as a function of geocentric distance differs substantially from that expected from the well-known models of the quiet-time ring current. Other findings suggest that there must be a population of low-energy particles with substantial total energy near the equator at distances of 2 to 5 earth radii that has not been recognized as having sufficient energy to inflate the magnetic field.

  4. 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

    2016-08-19

    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.

  5. India’s Distorted Sex Ratio: Dire Consequences for Girls

    PubMed Central

    Roberts, Lisa R.; Montgomery, Susanne B.

    2017-01-01

    Female gender discrimination related to cultural preference for males is a common global problem, especially in Asian countries. Numerous laws intended to prevent discrimination on the basis of gender have been passed in India, yet the distorted female-to-male sex ratio seems to show worsening tendencies. Using detailed, two-year longitudinal chart abstraction data about delivery records of a private mission hospital in rural India, we explored if hospital birth ratio data differed in comparison to regional data, and what demographic and contextual variables may have influenced these outcomes. Using quantitative chart abstraction and qualitative contextual data, study results showed the female-to-male ratio was lower than the reported state ratio at birth. In the context of India’s patriarchal structure, with its strong son preference, women are under tremendous pressure or coerced to access community-based, sex-selective identification and female fetus abortion. Nurses may be key to turning the tide.

  6. Closed orbit distortion and the beam-beam interaction

    SciTech Connect

    Furman, M.; Chin, Y.H.; Eden, J.; Kozanecki, W. |; Tennyson, J.; Ziemann, V.

    1992-06-01

    We study the applicability of beam-beam deflection techniques as a tuning tool for the SLAC/LBL/LLNL B factory, PEP-II. Assuming that the closed orbits of the two beams are separated vertically at the interaction point by a local orbit bump that is nominally closed, we calculate the residual beam orbit distortions due to the beam-beam interaction. Difference orbit measurements, performed at points conveniently distant from the IP, provide distinct coordinate- or frequency-space signatures that can be used to maintain the beams in collision and perform detailed optical diagnostics at the IP. A proposal to test this method experimentally at the TRISTAN ring is briefly discussed.

  7. Phonon triggered rhombohedral lattice distortion in vanadium at high pressure

    DOE PAGES

    Antonangeli, Daniele; Farber, Daniel L.; Bosak, Alexei; ...

    2016-08-19

    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. Lastly, ourmore » 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.« less

  8. 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

  9. Biomechanics and functional distortion of the human mandible.

    PubMed

    Choi, Andy H; Conway, Richard C; Taraschi, Valerio; Ben-Nissan, Besim

    2015-11-01

    The reaction to the use of finite element analysis (FEA) in the study of the human body has been particularly enthusiastic. Of equal and challenging complexity is the investigation of load/stress distribution and morphological distortion of the human mandible under functional loads. Furthermore, the mandible also impacts directly on body function and esthetics, playing a vital role, such as mastication and speech. The application of FEA to the biomechanical investigation of the oral systems, such as human teeth and mandibular bone remodeling, began in the early 1970s. The clinical significance of jaw deformation is unknown. The primary concern is that deformation might result in an ill-fitting superstructure or the creation of harmful strains in the patient-implant complex. Although mandibular implant treatment has a high success rate, the possibility of failure caused by these dimensional changes and the related micromotion cannot be ignored.

  10. Closed Orbit Distortion and the Beam-Beam Interaction

    SciTech Connect

    Furman, M.; Chin, Y.; Eden, J.; Kozanecki, W.; Tennyson, J.L.; Ziemann, V.; /SLAC

    2007-02-23

    We study the applicability of beam-beam deflection techniques as a tuning tool for the SLAC/LBL/LLNL B factory, PEP-II. Assuming that the closed orbits of the two beams are separated vertically at the interaction point by a local orbit bump that is nominally closed, we calculate the residual beam orbit distortions due to the beam-beam interaction. Difference orbit measurements, performed at points conveniently distant from the IP, provide distinct coordinate- or frequency-space signatures that can be used to maintain the beams in collision and perform detailed optical diagnostics at the IP. A proposal to test this method experimentally at the TRISTAN ring is briefly discussed.

  11. 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.

  12. 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.

  13. 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.

  14. Selecting Map Projections in Minimizing Area Distortions in GIS Applications.

    PubMed

    Yildirim, Faruk; Kaya, Ahmet

    2008-12-03

    Varioussoftware 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.

  15. A Chlamydomonas Homologue of the Putative Murine t Complex Distorter Tctex-2 Is an Outer Arm Dynein Light Chain

    PubMed Central

    Patel-King, Ramila S.; Benashski, Sharon E.; Harrison, Alistair; King, Stephen M.

    1997-01-01

    Molecular analysis of a 19,000-Mr protein from the Chlamydomonas flagellum reveals that it is homologous to the t complex–encoded protein Tctex-2, which is a candidate for one of the distorter products that cause the extreme transmission ratio distortion (meiotic drive) of the murine t complex. The 19,000-Mr protein is extracted from the axoneme with 0.6 M NaCl and comigrates with the outer dynein arm in sucrose density gradients. This protein also is specifically missing in axonemes prepared from a mutant that does not assemble the outer arm. These data raise the possibility that Tctex-2 is a sperm flagellar dynein component. Combined with the recent identification of Tctex-1 (another distorter candidate) as a light chain of cytoplasmic dynein, these results lead to a biochemical model for how differential defects in spermiogenesis that result in the phenomenon of meiotic drive might be generated in wild-type vs t-bearing sperm. PMID:9166408

  16. Testing scenarios of primordial black holes being the seeds of supermassive black holes by ultracompact minihalos and CMB μ distortions

    NASA Astrophysics Data System (ADS)

    Kohri, Kazunori; Nakama, Tomohiro; Suyama, Teruaki

    2014-10-01

    Supermassive black holes and intermediate mass black holes are believed to exist in the Universe. There is no established astrophysical explanation for their origin, and considerations have been made in the literature that those massive black holes (MBHs) may be primordial black holes (PBHs), black holes which are formed in the early universe (well before the matter-radiation equality) due to the direct collapse of primordial overdensities. This paper aims at discussing the possibility of excluding the PBH scenario as the origin of the MBHs. We first revisit the constraints on PBHs obtained from the cosmic microwave background (CMB) distortion that the seed density perturbation causes. By adopting a recent computation of the CMB distortion sourced by the seed density perturbation and the stronger constraint on the CMB distortion set by the COBE/FIRAS experiment used in the literature, we find that PBHs in the mass range 6×104 M⊙-5×1013 M⊙ are excluded. Since PBHs lighter than 6×104 M⊙ are not excluded from the nonobservation of the CMB distortion, we propose a new method which can potentially exclude smaller PBHs as well. Based on the observation that large density perturbations required to create PBHs also result in the copious production of ultracompact minihalos (UCMHs), compact dark matter halos formed at around the recombination, we show that weakly interacting massive particles (WIMPs) as dark matter annihilate efficiently inside UCMHs to yield cosmic rays far exceeding the observed flux. Our bound gives severe restriction on the compatibility between the particle physics models for WIMPs and the PBH scenario as the explanation of MBHs.

  17. 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.

  18. 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.

  19. 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.

  20. Optical compensation for hologram distortion using wavefront interpolation in angle-multiplexed holograms

    NASA Astrophysics Data System (ADS)

    Muroi, Tetsuhiko; Kinoshita, Nobuhiro; Ishii, Norihiko; Kamijo, Koji; Kawata, Yoshimasa; Kikuchi, Hiroshi

    2014-05-01

    Distortion of the hologram may occur when the photopolymer material used in the medium shrinks or expands. We analyzed interference fringe distortion for plane waves and a reference beam with an angular gap between recording and reproducing for the purpose of compensating for the distortion. We found that the wavefronts that could compensate for the distortion could approximately be obtained by linear interpolation of such angle-multiplexed holograms. We recorded 80 data pages with the angle-multiplexing method and obtained an optimized wavefront to compensate for hologram distortion on the first, fortieth, and eightieth data pages using adaptive optics with genetic algorithms and linear interpolated wavefronts at the other data pages. The calculation time for 80 wavefronts to compensate for distortion fell to 3/80th of that of having to calculate optimizations for all pages. The bit error rates were lower than 1.0 × 10-2 on all data pages reproduced using these wavefronts.

  1. Linearity and Efficiency Performance of GaN HEMTs with Digital Pre-Distortion Correction (Preprint)

    DTIC Science & Technology

    2006-07-01

    AFRL-ML-WP-TP-2007-414 LINEARITY AND EFFICIENCY PERFORMANCE OF GaN HEMTs WITH DIGITAL PRE-DISTORTION CORRECTION (PREPRINT) M.J. Poulton, W.K...EFFICIENCY PERFORMANCE OF GaN HEMTs WITH DIGITAL PRE-DISTORTION CORRECTION (PREPRINT) 5c. PROGRAM ELEMENT NUMBER 62102F 5d. PROJECT NUMBER 4348...device performance using Digital Pre-Distortion (DPD) correction. Additionally, both drain voltage and current were optimized to provide high

  2. NARCISSISTIC DEFENSES IN THE DISTORTION OF FREE ASSOCIATION AND THEIR UNDERLYING ANXIETIES.

    PubMed

    Kernberg, Otto F

    2015-07-01

    This paper examines particular distortions in the process of free association characteristics of patients with narcissistic personality disorders. The author proposes that the dominant narcissistic transference developments typical of the early and middle phases of the analytic treatment of these patients are reflected in these distortions of free association. This paper gathers the various patterns that these defensive distortions present, along with technical interventions geared to deal with them.

  3. 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.

  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. Simulation of Distortion Generation in a Modern Serpentine Diffuser to Improve Experimental Effectiveness (Preprint)

    DTIC Science & Technology

    2012-05-16

    AFRL-RZ-WP-TP-2012-0194 SIMULATION OF DISTORTION GENERATION IN A MODERN SERPENTINE DIFFUSER TO IMPROVE EXPERIMENTAL EFFECTIVENESS (PREPRINT...Technical Paper Preprint 01 October 2010 – 02 April 2012 4. TITLE AND SUBTITLE SIMULATION OF DISTORTION GENERATION IN A MODERN SERPENTINE DIFFUSER...ABSTRACT Modern serpentine diffusers create distorted flowfields which are ingested by embedded propulsion systems. Fundamental research into the

  6. 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.

  7. 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

  8. Characterization of SEM speckle pattern marking and imaging distortion by digital image correlation

    NASA Astrophysics Data System (ADS)

    Guery, Adrien; Latourte, Félix; Hild, François; Roux, Stéphane

    2014-01-01

    Surface patterning by e-beam lithography and scanning electron microscope (SEM) imaging distortions are studied via digital image correlation. The global distortions from the reference pattern, which has been numerically generated, are first quantified from a digital image correlation procedure between the (virtual) reference pattern and the actual SEM image both in secondary and backscattered electron imaging modes. These distortions result from both patterning and imaging techniques. These two contributions can be separated (without resorting to an external caliper) based on the images of the same patterned surface acquired at different orientations. Patterning distortions are much smaller than those due to imaging on wide field images.

  9. 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)

  10. Image distortion correction for single-lens stereo vision system employing a biprism

    NASA Astrophysics Data System (ADS)

    Qian, Beibei; Lim, Kah Bin

    2016-07-01

    A single-lens stereo vision system employing a biprism placed in front of the camera will generate unusual distortion in the captured image. Different from the typical image distortions due to lenses, this distortion is mainly induced by the thick biprism and appears to be incompatible with existing lens distortion models. A fully constrained and model-free distortion correction method is proposed. It employs all the projective invariants of a planar checkerboard template as the correction constraints, including straight lines, cross-ratio, and convergence at vanishing point, along with the distortion-free reference point as an additional constraint from the system. The extracted sample points are corrected by minimizing the total cost function formed by all these constraints. With both sets of distorted and corrected points, and the intermediate points interpolated by a local transformation, the correction maps are determined. Thereafter, all the subsequent images could be distortion corrected by the correction maps. This method performs well on the distorted image data captured by the system and shows improvements in accuracy on the camera calibration and depth recovery compared with other correction methods.

  11. Acceptable distortion and magnification of images on reflective surfaces in an augmented reality system

    NASA Astrophysics Data System (ADS)

    Yamamoto, Shoji; Hosokawa, Natsumi; Yokoya, Mayu; Tsumura, Norimichi

    2016-12-01

    In this paper, we investigated the consistency of visual perception for the change of reflection images in an augmented reality setting. Reflection images with distortion and magnification were generated by changing the capture position of the environment map. Observers evaluated the distortion and magnification in reflection images where the reflected objects were arranged symmetrically or asymmetrically. Our results confirmed that the observers' visual perception was more sensitive to changes in distortion than in magnification in the reflection images. Moreover, the asymmetrical arrangement of reflected objects effectively expands the acceptable range of distortion compared with the symmetrical arrangement.

  12. 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.

  13. Investigations on an axial flow fan stage subjected to circumferential inlet flow distortion and swirl

    NASA Astrophysics Data System (ADS)

    Govardhan, M.; Viswanath, K.

    1997-12-01

    The combined effects of swirl and circumferential inlet flow distortion on the flow field of an axial flow fan stage are reported in this paper. The study involves measurements at the inlet of the rotor and exit of the rotor and stator at design and off design flow conditions. The study indicated that at the design flow condition, swirl had caused deterioration of the performance in addition to that caused by distortion. Pressure rise imparted in the distortion zone is higher than in the free zone. The attenuation of distortion is high in the presence of swirl.

  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. Distorted Froude-scaled Flume Analysis of Large Woody Debris

    NASA Astrophysics Data System (ADS)

    Wallerstein, N. P.; Alonso, C. V.; Bennett, S. J.; Thorne, C. R.

    2001-12-01

    This paper presents the results of a movable-boundary, distorted, Froude-scaled hydraulic model based on Abiaca Creek, a sand-bedded channel in northern Mississippi. The model was used to examine the geomorphic and hydraulic impact of simplified Large Woody Debris (LWD) elements. The theory of physical scale models is discussed and the method used to construct the LWD test channel is developed. The channel model had bed and banks molded from 0.8 mm sand, and flow conditions were just below the threshold of motion so that any sediment transport and channel adjustment were the result of the debris element. Dimensions and positions of LWD elements were determined using a Debris Jam Classification Model (Wallerstein et al., 1997). Elements were attached to a dynamometer to measure element drag forces, and channel adjustment was determined through detailed topographic surveys. The fluid drag force on the element decreased asymptotically over time as the channel boundary eroded around the element due to locally increased boundary shear stress. Total time for geomorphic adjustment computed for the prototype channel at the Q2 discharge (discharge occurring once every two years on average) was as short as 45 hours. The size, depth and position of scour holes, bank erosion and bars created by flow acceleration past the elements were found to be related to element length and position within the channel cross-section. Morphologies created by each debris element in the model channel were comparable with similar jams observed in the prototype channel.

  16. Redshift-space distortions with wide angular separations

    SciTech Connect

    Reimberg, Paulo; Bernardeau, Francis; Pitrou, Cyril E-mail: francis.bernardeau@cea.fr

    2016-01-01

    Redshift-space distortions are generally considered in the plane parallel limit, where the angular separation between the two sources can be neglected. Given that galaxy catalogues now cover large fractions of the sky, it becomes necessary to consider them in a formalism which takes into account the wide angle separations. In this article we derive an operational formula for the matter correlators in the Newtonian limit to be used in actual data sets. In order to describe the geometrical nature of the wide angle RSD effect on Fourier space, we extend the formalism developed in configuration space to Fourier space without relying on a plane-parallel approximation, but under the extra assumption of no bias evolution. We then recover the plane-parallel limit not only in configuration space where the geometry is simpler, but also in Fourier space, and we exhibit the first corrections that should be included in large surveys as a perturbative expansion over the plane-parallel results. We finally compare our results to existing literature, and show explicitly how they are related.

  17. Theoretical Study of Orthorhombic Distortions in High-Temperature Superconductors

    NASA Astrophysics Data System (ADS)

    Schnyder, Andreas; Manske, Dirk; Mudry, Christopher; Sigrist, Manfred

    2006-03-01

    Using a Fermi-liquid-based theory we calculate the response function for various spectroscopic probes in hole-doped high-TC superconductors, and determine the effects of orthorhombic distortions in the crystal lattice and asymmetry in the superconducting gap function. Employing the two-dimensional one-band Hubbard model and a generalized RPA-type theory we consider anisotropic hopping parameters (txty) and a mixing of d- and s-wave symmetry of the superconducting order parameter. Within this model, both the electronic Raman spectra and the dynamical magnetic susceptibility [1] are studied in detail. The relevance of these calculations to electronic Raman scattering measurements and inelastic neutron scattering experiments [2] on untwinned YBa2Cu3O6+x are discussed. [1] A. P. Schnyder, D. Manske, C. Mudry, and M. Sigrist, cond-mat/0510790. [2] V. Hinkov, S. Pailhes, P. Bourges, Y. Sidis, A. Ivanov, A. Kulakov, C. T. Lin, D. P. Chen, C. Bernhard, and B. Keimer, Nature 430, 650 (2004).

  18. Coding of correlated sources with prescribed distortion by separated encoders

    PubMed Central

    Wolfowitz, J.

    1980-01-01

    Let (Xn,Yn) = (X1,Y1),...,(Xn,Yn) be n independent, identically distributed pairs of chance variables. Each of two separated encoders encodes a different sequence of (Xn,Yn) to within given respective distortions z1,z2. Call a region in the plane of the respective rates (R1,R2) M-convex if it is convex, closed, and, to every point (r1,r2), contains all points such that each of their coordinates is larger than or equal to the corresponding coordinate of (r1,r2). This paper determines the (M-convex) region of achievable rates by giving its boundary. For z1 = z2 = 0, the region specializes to that of Slepian and Wolf. For z2 = ∞ and R2 = H(Yi), the minimum R1 is that of Wyner and Ziv; for z2 = ∞ and general given R2, the minimum R1 is that of my generalization of the theorem of Wyner and Ziv. PMID:16592887

  19. Centrifugal Distortion Causes Anderson Localization in Laser Kicked Molecules

    NASA Astrophysics Data System (ADS)

    Floss, Johannes; Averbukh, Ilya Sh.

    2014-05-01

    The periodically kicked 2D rotor is a textbook model in nonlinear dynamics. The classical kicked rotor can exhibit truly chaotic motion, whilst in the quantum regime this chaotic motion is suppressed by a mechanism similar to Anderson Localization. Up to now, these effects have been mainly observed in an atom optics analogue of a quantum rotor: cold atoms in a standing light wave. We demonstrate that common linear molecules (like N2, O2, CO2, ...), kicked by a train of short linearly polarized laser pulses, can exhibit a new mechanism for dynamical Anderson Localization due to their non-rigidity. When the pulses are separated by the rotational revival time trev = πℏ / B , the angular momentum J grows ballistically (Quantum Resonance). We show that, due to the centrifugal distortion of fast spinning molecules, above some critical value J =Jcr the Quantum Resonance is suppressed via the mechanism of Anderson Localization. This leads to a non-sinusoidal oscillation of the angular momentum distribution, which may be experimentally observed even at ambient conditions by using current techniques for laser molecular alignment.

  20. Spectral distortions in the cosmic microwave background polarization

    SciTech Connect

    Renaux-Petel, Sébastien; Fidler, Christian; Pitrou, Cyril; Pettinari, Guido W. E-mail: christian.fidler@port.ac.uk E-mail: g.pettinari@sussex.ac.uk

    2014-03-01

    We compute the spectral distortions of the Cosmic Microwave Background (CMB) polarization induced by non-linear effects in the Compton interactions between CMB photons and the flow of intergalactic electrons. This signal is of the y-type and is dominated by contributions arising from the reionized era. We stress that it is not shadowed by the thermal SZ effect which has no equivalent for polarization. We decompose its angular dependence into E- and B-modes, and we calculate the corresponding power spectra, both exactly and using a suitable Limber approximation that allows a simpler numerical evaluation. We find that B-modes are of the same order of magnitude as E-modes. Both spectra are relatively flat, peaking around ℓ = 280, and their overall amplitude is directly related to the optical depth to reionization. Moreover, we find this effect to be one order of magnitude larger than the non-linear kinetic Sunyaev-Zel'dovich effect in galaxy clusters. Finally, we discuss how to improve the detectability of our signal by cross-correlating it with other quantities sourced by the flow of intergalactic electrons.

  1. Genome Scans for Transmission Ratio Distortion Regions in Mice

    PubMed Central

    Casellas, Joaquim; Gularte, Rodrigo J.; Farber, Charles R.; Varona, Luis; Mehrabian, Margarete; Schadt, Eric E.; Lusis, Aldon J.; Attie, Alan D.; Yandell, Brian S.; Medrano, Juan F.

    2012-01-01

    Transmission ratio distortion (TRD) is the departure from the expected genotypic frequencies under Mendelian inheritance. This departure can be due to multiple physiological mechanisms during gametogenesis, fertilization, fetal and embryonic development, and early neonatal life. Although a few TRD loci have been reported in mouse, inheritance patterns have never been evaluated for TRD. In this article, we developed a Bayesian binomial model accounting for additive and dominant deviation TRD mechanisms. Moreover, this model was used to perform genome-wide scans for TRD quantitative trait loci (QTL) on six F2 mouse crosses involving between 296 and 541 mice and between 72 and 1854 genetic markers. Statistical significance of each model was checked at each genetic marker with Bayes factors. Genome scans revealed overdominance TRD QTL located in mouse chromosomes 1, 2, 12, 13, and 14 and additive TRD QTL in mouse chromosomes 2, 3, and 15, although these results did not replicate across mouse crosses. This research contributes new statistical tools for the analysis of specific genetic patterns involved in TRD in F2 populations, our results suggesting a relevant incidence of TRD phenomena in mouse with important implications for both statistical analyses and biological research. PMID:22367040

  2. A Flexible Bayesian Model for Testing for Transmission Ratio Distortion

    PubMed Central

    Casellas, Joaquim; Manunza, Arianna; Mercader, Anna; Quintanilla, Raquel; Amills, Marcel

    2014-01-01

    Current statistical approaches to investigate the nature and magnitude of transmission ratio distortion (TRD) are scarce and restricted to the most common experimental designs such as F2 populations and backcrosses. In this article, we describe a new Bayesian approach to check TRD within a given biallelic genetic marker in a diploid species, providing a highly flexible framework that can accommodate any kind of population structure. This model relies on the genotype of each offspring and thus integrates all available information from either the parents’ genotypes or population-specific allele frequencies and yields TRD estimates that can be corroborated by the calculation of a Bayes factor (BF). This approach has been evaluated on simulated data sets with appealing statistical performance. As a proof of concept, we have also tested TRD in a porcine population with five half-sib families and 352 offspring. All boars and piglets were genotyped with the Porcine SNP60 BeadChip, whereas genotypes from the sows were not available. The SNP-by-SNP screening of the pig genome revealed 84 SNPs with decisive evidences of TRD (BF > 100) after accounting for multiple testing. Many of these regions contained genes related to biological processes (e.g., nucleosome assembly and co-organization, DNA conformation and packaging, and DNA complex assembly) that are critically associated with embryonic viability. The implementation of this method, which overcomes many of the limitations of previous approaches, should contribute to fostering research on TRD in both model and nonmodel organisms. PMID:25271302

  3. Workload induced spatio-temporal distortions and safety of flight

    SciTech Connect

    Barrett, C.L.; Weisgerber, S.A.; Naval Weapons Center, China Lake, CA )

    1989-01-01

    A theoretical analysis of the relationship between cognitive complexity and the perception of time and distance is presented and experimentally verified. Complex tasks produce high rates of mental representation which affect the subjective sense of duration and, through the subjective time scale, the percept of distance derived from dynamic visual cues (i.e., visual cues requiring rate integration). The analysis of the interrelationship of subjective time and subjective distance yields the prediction that, as a function of cognitive complexity, distance estimates derived from dynamic visual cues will be longer than the actual distance whereas estimates based on perceived temporal duration will be shorter than the actual distance. This prediction was confirmed in an experiment in which subjects (both pilots and non-pilots) estimated distances using either temporal cues or dynamic visual cues. The distance estimation task was also combined with secondary loading tasks in order to vary the overall task complexity. The results indicated that distance estimates based on temporal cues were underestimated while estimates based on visual cues were overestimated. This spatio-temporal distortion effect increased with increases in overall task complexity. 30 refs., 6 figs., 1 tab.

  4. Impacts of satellite galaxies on the redshift-space distortions

    SciTech Connect

    Hikage, Chiaki; Yamamoto, Kazuhiro E-mail: kazuhiro@hiroshima-u.ac.jp

    2013-08-01

    We study the impacts of the satellite galaxies on the redshift-space distortions. In our multipole power spectrum analysis of the luminous red galaxies (LRGs) samples of the Sloan digital sky survey (SDSS), we have clearly detected the non-zero signature of the hexadecapole and tetrahexadecapole spectrum, which almost disappears in the power spectrum with the sample of the brightest LRGs only. We thus demonstrate that the satellite LRGs in multiple systems make a significant contribution to the multipole power spectrum though its fraction is small. The behavior can be understood by a simple halo model, in which the one-halo term, describing the Finger of God (FoG) effect from the satellite galaxies, makes the dominant contribution to the higher multipole spectra. We demonstrate that the small-scale information of higher multipole spectrum is useful for calibrating the satellite FoG effect and improves the measurement of the cosmic growth rate dramatically. We further demonstrate that the fiber collision in the galaxy survey influences the one-halo term and the higher multipole spectra, because the number of satellite galaxies in the halo occupation distribution (HOD) is changed. We also discuss about the impact of satellite galaxies on future high-redshift surveys targeting the H-alpha emitters.

  5. Coupling of stripes to lattice distortions in cuprates and nickelates

    NASA Astrophysics Data System (ADS)

    Hücker, M.; Gu, G. D.; Tranquada, J. M.; Zimmermann, M. v.; Klauss, H.-H.; Curro, N. J.; Braden, M.; Büchner, B.

    2007-09-01

    In recent X-ray diffraction experiments on orthorhombic nickelates, we have observed a significant coupling between the stripe correlations and the lattice distortion. In particular, the diagonal charge stripes of this insulating material exhibit a preferred orientation parallel to the orthorhombic a-axis, similar to the diagonal spin stripes in La2-xSrxCuO4 below the metal-insulator transition. In the light of this finding, we draw a comparison between the lightly doped parts of the phase diagrams of La2-xSrxCuO4 with low-temperature orthorhombic (LTO) structure, and La1.8-xEu0.2SrxCuO4 with low-temperature tetragonal (LTT) structure. In La1.8-xEu0.2SrxCuO4, a local minimum in the Sr dependence of the LTO/LTT transition temperature, as well as reduced spin-glass transition temperatures, may be indicators for the presence of diagonal charge correlations. Above the metal-insulator transition the LTT phase is suited to pin parallel stripes, while below that transition the LTT phase seems instead to compete with the formation of diagonal stripes.

  6. Weaving and bonding method to prevent warp and fill distortion

    NASA Technical Reports Server (NTRS)

    Farley, Gary L. (Inventor)

    1997-01-01

    A method to prevent fiber distortion in textile materials employed in a modified weaving process. In a first embodiment, a tacifier in powder form is applied to the yarn and melted while on the fabric. Cool air is then supplied after the tacifier has melted to expedite the solidification of the tacifier. In a second embodiment, a solution form of a tacifier is used by dissolving the tacifier into a solvent that has a high evaporation rate. The solution is then sprayed onto the fabric or fill yarn as each fill yarn is inserted into a shed of the fabric. A third embodiment applies the tacifier in a liquid form that has not been dissolved in a solvent. That is, the tacifier is melted and is sprayed as a liquid onto the fabric or fill yarn as it is being extracted from a fill yarn spool prior to the fill yarn being inserted into the shed of the fabric. A fourth embodiment employs adhesive yarns contained as an integral part of the warp or fill yarn. Additional tacifier material is not required because a matrix is used as the tacifier. The matrix is then locally melted using heating elements on clamping bars or take-up rollers, is cooled, if necessary, and solidified.

  7. Distortion of upstream disturbances in a Hiemenz boundary layer

    NASA Astrophysics Data System (ADS)

    Xiong, Zhongmin; Lele, Sanjiva K.

    2004-11-01

    A theoretical analysis of the distortion of unsteady three-dimensional disturbances in a Hiemenz boundary layer and its effect on the heat transfer enhancement is presented. It is shown that the disturbance length scale is a critical parameter in determining the amplification ratio of the incoming vorticity. For large disturbance length scales, the amplification ratio increases when the length scale decreases, and a maximum value occurs at a length scale close to five times the boundary-layer thickness. The unsteadiness of the disturbances is found to reduce the vorticity amplification, but the effect is second order when the frequency is low compared to the mean flow strain rate. The impinging disturbances induce large-amplitude vorticity of opposite sign at the wall whose magnitude controls the heat transfer enhancement. As an application of the present analysis, a new scaling correlation is derived for stagnation-point heat transfer in the presence of free-stream turbulence. The theoretical correlation, expressed in terms of turbulence intensity, integral length scale and mean flow Reynolds number, agrees reasonably well with recent experimental data.

  8. Evidence for Extensive Transmission Distortion in the Human Genome

    PubMed Central

    Zöllner, Sebastian; Wen, Xiaoquan; Hanchard, Neil A.; Herbert, Mark A.; Ober, Carole; Pritchard, Jonathan K.

    2004-01-01

    It is a basic principle of genetics that each chromosome is transmitted from parent to offspring with a probability that is given by Mendel’s laws. However, several known biological processes lead to skewed transmission probabilities among surviving offspring and, therefore, to excess genetic sharing among relatives. Examples include in utero selection against deleterious mutations, meiotic drive, and maternal-fetal incompatibility. Although these processes affect our basic understanding of inheritance, little is known about their overall impact in humans or other mammals. In this study, we examined genome screen data from 148 nuclear families, collected without reference to phenotype, to look for departures from Mendelian transmission proportions. Using single-point and multipoint linkage analysis, we detected a modest but significant genomewide shift towards excess genetic sharing among siblings (average sharing of 50.43% for the autosomes; P=.009). Our calculations indicate that many loci with skewed transmission are required to produce a genomewide shift of this magnitude. Since transmission distortion loci are subject to strong selection, this raises interesting questions about the evolutionary forces that keep them polymorphic. Finally, our results also have implications for mapping disease genes and for the genetics of fertility. PMID:14681832

  9. MAPPING GROWTH AND GRAVITY WITH ROBUST REDSHIFT SPACE DISTORTIONS

    SciTech Connect

    Kwan, Juliana; Lewis, Geraint F.; Linder, Eric V.

    2012-04-01

    Redshift space distortions (RSDs) caused by galaxy peculiar velocities provide a window onto the growth rate of large-scale structure and a method for testing general relativity. We investigate through a comparison of N-body simulations to various extensions of perturbation theory beyond the linear regime, the robustness of cosmological parameter extraction, including the gravitational growth index {gamma}. We find that the Kaiser formula and some perturbation theory approaches bias the growth rate by 1{sigma} or more relative to the fiducial at scales as large as k > 0.07 h Mpc{sup -1}. This bias propagates to estimates of the gravitational growth index as well as {Omega}{sub m} and the equation-of-state parameter and presents a significant challenge to modeling RSDs. We also determine an accurate fitting function for a combination of line-of-sight damping and higher order angular dependence that allows robust modeling of the redshift space power spectrum to substantially higher k.

  10. An illusory distortion of moving form driven by motion deblurring.

    PubMed

    Marinovic, Welber; Arnold, Derek H

    2013-08-09

    Many visual processes integrate information over protracted periods, a process known as temporal integration. One consequence of this is that objects that cast images that move across the retinal surfaces can generate blurred form signals, similar to the motion blur that can be captured in photographs taken with slow shutter speeds. Subjectively, retinal motion blur signals are suppressed from awareness, such that moving objects seem sharply defined. One suggestion has been that this subjective impression is due to humans not being able to distinguish between focussed and blurred moving objects. Contrary to this suggestion, here we report a novel illusion, and consequent experiments, that implicate a suppressive mechanism. We find that the apparent shape of circular moving objects can be distorted when their rear edges lag leading edges by ∼60 ms. Moreover, we find that sensitivity for detecting blur, and for discriminating between blur intensities, is uniformly worse for physical blurs added behind moving objects, as opposed to in-front. Also, it was easier to differentiate between slight and slightly greater physical blurs than it was to differentiate between slight blur and the absence of blur, both behind and in-front of moving edges. These 'dipper' functions suggest that blur signals must reach a threshold intensity before they can be detected, and that the relevant threshold is effectively elevated for blur signals trailing behind moving contours. In combination, these data suggest moving objects look sharply defined, at least in part, because of a functional adaptation that actively suppresses motion blur signals from awareness.

  11. A novel method for correction of temporally- and spatially-variant optical distortion in planar particle image velocimetry

    NASA Astrophysics Data System (ADS)

    Zha, Kan; Busch, Stephen; Park, Cheolwoong; Miles, Paul C.

    2016-08-01

    In-cylinder flow measurements are necessary to gain a fundamental understanding of swirl-supported, light-duty Diesel engine processes for high thermal efficiency and low emissions. Planar particle image velocimetry (PIV) can be used for non-intrusive, in situ measurement of swirl-plane velocity fields through a transparent piston. In order to keep the flow unchanged from all-metal engine operation, the geometry of the transparent piston must adapt the production-intent metal piston geometry. As a result, a temporally- and spatially-variant optical distortion is introduced to the particle images. To ensure reliable measurement of particle displacements, this work documents a systematic exploration of optical distortion quantification and a hybrid back-projection procedure that combines ray-tracing-based geometric and in situ manual back-projection approaches. The proposed hybrid back-projection method for the first time provides a time-efficient and robust way to process planar PIV measurements conducted in an optical research engine with temporally- and spatially-varying optical distortion. This method is based upon geometric ray tracing and serves as a universal tool for the correction of optical distortion with an arbitrary but axisymmetric piston crown window geometry. Analytical analysis demonstrates that the ignorance of optical distortion change during the PIV laser temporal interval may induce a significant error in instantaneous velocity measurements. With the proposed digital dewarping method, this piston-motion-induced error can be eliminated. Uncertainty analysis with simulated particle images provides guidance on whether to back-project particle images or back-project velocity fields in order to minimize dewarping-induced uncertainties. The optimal implementation is piston-geometry-dependent. For regions with significant change in nominal magnification factor, it is recommended to apply the proposed back-projection approach to particle images prior to

  12. Increasing Honest Responding on Cognitive Distortions in Child Molesters: The Bogus Pipeline Procedure

    ERIC Educational Resources Information Center

    Gannon, Theresa A.

    2006-01-01

    Professionals conclude that child molesters (CMs) hold offense-supportive beliefs (or cognitive distortions) from CMs' questionnaire responses. Because questionnaires are easily faked, we asked 32 CMs to complete a cognitive distortion scale under standard conditions (Time 1). A week later (Time 2), the same CMs completed the scale again. This…

  13. Cognitive Distortions and Blame Attribution in Sex Offenders against Adults and Children.

    ERIC Educational Resources Information Center

    Blumenthal, Stephen; Gudjonsson, Gisli; Burns, Jan

    1999-01-01

    This study compared sex offenders against children and adults on measures of cognitive distortions relating to sex with children and rape and a measure of blame attribution. Child sexual offenders endorsed more cognitive distortions relating to sex with children and reported more guilt-feeling attributions. (Author/DB)

  14. Image Quality Assessment Based on Local Linear Information and Distortion-Specific Compensation.

    PubMed

    Wang, Hanli; Fu, Jie; Lin, Weisi; Hu, Sudeng; Kuo, C-C Jay; Zuo, Lingxuan

    2016-12-14

    Image Quality Assessment (IQA) is a fundamental yet constantly developing task for computer vision and image processing. Most IQA evaluation mechanisms are based on the pertinence of subjective and objective estimation. Each image distortion type has its own property correlated with human perception. However, this intrinsic property may not be fully exploited by existing IQA methods. In this paper, we make two main contributions to the IQA field. First, a novel IQA method is developed based on a local linear model that examines the distortion between the reference and the distorted images for better alignment with human visual experience. Second, a distortion-specific compensation strategy is proposed to offset the negative effect on IQA modeling caused by different image distortion types. These score offsets are learned from several known distortion types. Furthermore, for an image with an unknown distortion type, a Convolutional Neural Network (CNN) based method is proposed to compute the score offset automatically. Finally, an integrated IQA metric is proposed by combining the aforementioned two ideas. Extensive experiments are performed to verify the proposed IQA metric, which demonstrate that the local linear model is useful in human perception modeling, especially for individual image distortion, and the overall IQA method outperforms several state-of-the-art IQA approaches.

  15. Computer correction of turbulent distortions of image of extended objects on near-Earth paths

    SciTech Connect

    Averin, A P; Morozov, Yu B; Pryanichkov, V S; Tyapin, V V

    2011-05-31

    An algorithm of computer-based correction of images of extended objects distorted by turbulent atmosphere is developed. The method of computer correction is used to correct a distorted image of an extended object on a horizontal 2300-m-long observation path. The angular size of the corrected-image region was 15'. (image processing)

  16. FORTRAN program to generate engine inlet flow contour maps and distortion parameters

    NASA Technical Reports Server (NTRS)

    Dicus, J. H.

    1974-01-01

    A computer program is presented and described that generates jet engine inlet flow contour maps and inlet flow distortion parameters. The program input consists of an array of measurements describing the flow conditions at the engine inlet. User-defined distortion parameters may be calculated.

  17. Perceptual quality prediction on authentically distorted images using a bag of features approach

    PubMed Central

    Ghadiyaram, Deepti; Bovik, Alan C.

    2017-01-01

    Current top-performing blind perceptual image quality prediction models are generally trained on legacy databases of human quality opinion scores on synthetically distorted images. Therefore, they learn image features that effectively predict human visual quality judgments of inauthentic and usually isolated (single) distortions. However, real-world images usually contain complex composite mixtures of multiple distortions. We study the perceptually relevant natural scene statistics of such authentically distorted images in different color spaces and transform domains. We propose a “bag of feature maps” approach that avoids assumptions about the type of distortion(s) contained in an image and instead focuses on capturing consistencies—or departures therefrom—of the statistics of real-world images. Using a large database of authentically distorted images, human opinions of them, and bags of features computed on them, we train a regressor to conduct image quality prediction. We demonstrate the competence of the features toward improving automatic perceptual quality prediction by testing a learned algorithm using them on a benchmark legacy database as well as on a newly introduced distortion-realistic resource called the LIVE In the Wild Image Quality Challenge Database. We extensively evaluate the perceptual quality prediction model and algorithm and show that it is able to achieve good-quality prediction power that is better than other leading models. PMID:28129417

  18. Virtually distortion-free imaging system for large field, high resolution lithography

    DOEpatents

    Hawryluk, Andrew M.; Ceglio, Natale M.

    1993-01-01

    Virtually distortion free large field high resolution imaging is performed using an imaging system which contains large field distortion or field curvature. A reticle is imaged in one direction through the optical system to form an encoded mask. The encoded mask is then imaged back through the imaging system onto a wafer positioned at the reticle position.

  19. Evolution of CMB spectral distortion anisotropies and tests of primordial non-Gaussianity

    NASA Astrophysics Data System (ADS)

    Chluba, Jens; Dimastrogiovanni, Emanuela; Amin, Mustafa A.; Kamionkowski, Marc

    2017-04-01

    Anisotropies in distortions to the frequency spectrum of the cosmic microwave background (CMB) can be created through spatially varying heating processes in the early Universe. For instance, the dissipation of small-scale acoustic modes does create distortion anisotropies, in particular for non-Gaussian primordial perturbations. In this work, we derive approximations that allow describing the associated distortion field. We provide a systematic formulation of the problem using Fourier-space window functions, clarifying and generalizing previous approximations. Our expressions highlight the fact that the amplitudes of the spectral-distortion fluctuations induced by non-Gaussianity depend also on the homogeneous value of those distortions. Absolute measurements are thus required to obtain model-independent distortion constraints on primordial non-Gaussianity. We also include a simple description for the evolution of distortions through photon diffusion, showing that these corrections can usually be neglected. Our formulation provides a systematic framework for computing higher order correlation functions of distortions with CMB temperature anisotropies and can be extended to describe correlations with polarization anisotropies.

  20. Virtually distortion-free imaging system for large field, high resolution lithography

    DOEpatents

    Hawryluk, A.M.; Ceglio, N.M.

    1993-01-05

    Virtually distortion free large field high resolution imaging is performed using an imaging system which contains large field distortion or field curvature. A reticle is imaged in one direction through the optical system to form an encoded mask. The encoded mask is then imaged back through the imaging system onto a wafer positioned at the reticle position.

  1. Do Cognitive Distortions Mediate the Test Anxiety-Examination Performance Relationship?

    ERIC Educational Resources Information Center

    Putwain, David William; Connors, Liz; Symes, Wendy

    2010-01-01

    The aim of this study was to follow up exploratory research suggesting that the inverse relationship between test anxiety and examination performance was mediated by cognitive distortions such as catastrophising. Self-report data for measures of test anxiety and cognitive distortions were collected from students in their final year of compulsory…

  2. Rate Distortion Analysis and Bit Allocation Scheme for Wavelet Lifting-Based Multiview Image Coding

    NASA Astrophysics Data System (ADS)

    Lasang, Pongsak; Kumwilaisak, Wuttipong

    2009-12-01

    This paper studies the distortion and the model-based bit allocation scheme of wavelet lifting-based multiview image coding. Redundancies among image views are removed by disparity-compensated wavelet lifting (DCWL). The distortion prediction of the low-pass and high-pass subbands of each image view from the DCWL process is analyzed. The derived distortion is used with different rate distortion models in the bit allocation of multiview images. Rate distortion models including power model, exponential model, and the proposed combining the power and exponential models are studied. The proposed rate distortion model exploits the accuracy of both power and exponential models in a wide range of target bit rates. Then, low-pass and high-pass subbands are compressed by SPIHT (Set Partitioning in Hierarchical Trees) with a bit allocation solution. We verify the derived distortion and the bit allocation with several sets of multiview images. The results show that the bit allocation solution based on the derived distortion and our bit allocation scheme provide closer results to those of the exhaustive search method in both allocated bits and peak-signal-to-noise ratio (PSNR). It also outperforms the uniform bit allocation and uniform bit allocation with normalized energy in the order of 1.7-2 and 0.3-1.4 dB, respectively.

  3. 2D nearly orthogonal mesh generation with controls on distortion functions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A method to control the distortion function of the Ryskin and Leal (RL) orthogonal mesh generation system is presented. The proposed method considers the effects from not only the local orthogonal condition but also the local smoothness condition (the geometry and the mesh size) on the distortion fu...

  4. Least-Squares Camera Calibration Including Lens Distortion and Automatic Editing of Calibration Points

    NASA Technical Reports Server (NTRS)

    Gennery, D. B.

    1998-01-01

    A method is described for calibrating cameras including radial lens distortion, by using known points such as those measured from a calibration fixture. The distortion terms are relative to the optical axis, which is included in the model so that it does not have to be orthogonal to the image sensor plane.

  5. Application of statistical methods for analyzing the relationship between casting distortion, mold filling, and interfacial heat transfer in sand molds

    SciTech Connect

    Y. A. Owusu

    1999-03-31

    This report presents a statistical method of evaluating geometric tolerances of casting products using point cloud data generated by coordinate measuring machine (CMM) process. The focus of this report is to present a statistical-based approach to evaluate the differences in dimensional and form variations or tolerances of casting products as affected by casting gating system, molding material, casting thickness, and casting orientation at the mold-metal interface. Form parameters such as flatness, parallelism, and other geometric profiles such as angularity, casting length, and height of casting products were obtained and analyzed from CMM point cloud data. In order to relate the dimensional and form errors to the factors under consideration such as flatness and parallelism, a factorial analysis of variance and statistical test means methods were performed to identify the factors that contributed to the casting distortion at the mold-metal interface.

  6. Optimizing the balance between area and orientation distortions for variable-scale maps

    NASA Astrophysics Data System (ADS)

    Ti, Peng; Li, Zhilin; Xu, Zhu; Jia, Hongguo

    2016-07-01

    Applying a variable scale transformation to maps leads to area distortions of the maps, i.e. enlarging interesting areas on maps to larger scales and shrinking other areas. Such area distortions improve the clarity of the interesting areas. However, it may result in the over-distortion of line orientations so as to reduce map recognition. This article developed an optimization method to correct orientation distortions for variable-scale maps generated by any existing variable scale transformations, while preserving the map clarity as much as possible. The proposed method is tested with the variable-scale resultant maps of two real-life datasets and evaluated by statistical analysis and perceptual tests. The experimental results indicate that the proposed method is able to effectively reduce the orientation distortions so as to improve map recognition, while map clarity has been sufficiently achieved.

  7. The effect of circumferential distortion on fan performance at two levels of blade loading

    NASA Technical Reports Server (NTRS)

    Hartmann, M. J.; Sanger, N. L.

    1975-01-01

    Single stage fans designed for two levels of pressure ratio or blade loading were subjected to screen-induced circumferential distortions of 90-degree extent. Both fan rotors were designed for a blade tip speed of 425 m/sec, blade solidity of 1.3 and a hub-to-tip radius ratio of 0.5. Circumferential measurements of total pressure, temperature, static pressure, and flow angle were obtained at the hub, mean and tip radii at five axial stations. Rotor loading level did not appear to have a significant influence on rotor response to distorted flow. Losses in overall pressure ratio due to distortion were most severe in the stator hub region of the more highly loaded stage. At the near stall operating condition tip and hub regions of (either) rotor demonstrated different response characteristics to the distorted flow. No effect of loading was apparent on interactions between rotor and upstream distorted flow fields.

  8. Research on measurement and correction of a fish-eye image distortion

    NASA Astrophysics Data System (ADS)

    Wang, Zefeng; Lei, Yangjie; Zhang, Zhi; Zhang, Zhaohui; Zhang, Hui; Huang, Jijiang; Yi, Bo; Liao, Jiawen

    2014-09-01

    Fisheye lenses have the advantages of short focal length and large field of view. However, by using the "non-similar" imaging principle, they artificially introduce a large barrel distortion. In order to improve the quality of the images correction of distortion is required. This article analyzes the polar distortion correction model, raised a simple distortion coefficient calibration method and the use of bilinear interpolation method for gray level interpolation. Compared to other methods, this method is easier to reinforce and achieves high accuracy, and it can be easily implemented in the hardware system. At the end of the paper we introduced a device correction for a fisheye CCD camera. Based on the original data, a distortion correction model is established. In order to minimize the error, the correction was divided into three sections, and the image is well recovered.

  9. The Relationship Between Religious Orientation, and Gender With a Cognitive Distortion

    PubMed Central

    Amirsardari, Leili; Azari, Shafie; Esmali Kooraneh, Ahmad

    2014-01-01

    Objective: The objective of this study was to determine the relationship between religious orientation (intrinsic–external) and cognitive distortions. Methods: General design of this study considered as a descriptive and correlational method. Universal population in this research consist all students of the Urmia Azad University, which were studying during 2012 and 2013 (n = 250). All respondents filled the Alports religious and cognitive distortions questionnaires. The answers were analyzed with step by step regression and correlation method. Results: The research showed a significant relationship between the religious orientation and cognitive distortions (p < 0.005) (p < 0.001). Conclusion: The results suggest that religious orientation is an important factor in cognitive distortions and individuals with intrinsic religious orientation have less cognitive distortion. PMID:25780380

  10. Functional Identification of the Segregation Distorter Locus of Drosophila Melanogaster by Germline Transformation

    PubMed Central

    McLean, J. R.; Merrill, C. J.; Powers, P. A.; Ganetzky, B.

    1994-01-01

    Segregation Distorter (SD) is a meiotic drive system in D. melanogaster that results in the failure of SD/SD(+) males to transmit SD(+) homologs owing to the induced dysfunction of spermatids carrying the normal chromosome. Segregation distorter (Sd), the gene primarily responsible for this distorted transmission, is associated with a novel 12-kb restriction fragment containing a tandem duplication of a 5-kb wild-type segment of genomic DNA. When introduced into appropriate genetic backgrounds by germline transformation, this 12-kb fragment causes full levels of distortion and directs the expression of an SD-specific 4-kb transcript. Transformants that have lost part of this segment are unable to cause distortion and do not express the 4-kb transcript. These results identify the tandem duplication as Sd. PMID:8056311

  11. Which way is down? Positional distortion in the tilt illusion.

    PubMed

    Tomassini, Alessandro; Solomon, Joshua Adam; Morgan, Michael John

    2014-01-01

    Contextual information can have a huge impact on our sensory experience. The tilt illusion is a classic example of contextual influence exerted by an oriented surround on a target's perceived orientation. Traditionally, the tilt illusion has been described as the outcome of inhibition between cortical neurons with adjacent receptive fields and a similar preference for orientation. An alternative explanation is that tilted contexts could produce a re-calibration of the subjective frame of reference. Although the distinction is subtle, only the latter model makes clear predictions for unoriented stimuli. In the present study, we tested one such prediction by asking four naive subjects to estimate three positions (4, 6, and 8 o'clock) on an imaginary clock face within a tilted surround. To indicate their estimates, they used either an unoriented dot or a line segment, with one endpoint at fixation in the middle of the surround. The surround's tilt was randomly chosen from a set of orientations (± 75°, ± 65°, ± 55°, ± 45°, ± 35°, ± 25°, ± 15°, ± 5° with respect to vertical) across trials. Our results showed systematic biases consistent with the tilt illusion in both conditions. Biases were largest when observers attempted to estimate the 4 and 8 o'clock positions, but there was no significant difference between data gathered with the dot and data gathered with the line segment. A control experiment confirmed that biases were better accounted for by a local coordinate shift than to torsional eye movements induced by the tilted context. This finding supports the idea that tilted contexts distort perceived positions as well as perceived orientations and cannot be readily explained by lateral interactions between orientation selective cells in V1.

  12. Color space distortions in patients with type 2 diabetes mellitus.

    PubMed

    Feitosa-Santana, Claudia; Oiwa, Nestor N; Paramei, Galina V; Bimler, David; Costa, Marcelo F; Lago, Marcos; Nishi, Mauro; Ventura, Dora F

    2006-01-01

    Color vision impairment was examined in patients with type 2 diabetes mellitus (DM2) without retinopathy. We assessed the type and degree of distortions of individual color spaces. DM2 patients (n = 32), and age-matched controls (n = 20) were tested using the Farnsworth D-15 and the Lanthony D-15d tests. In addition, subsets of caps from both tests were employed in a triadic procedure (Bimler & Kirkland, 2004). Matrices of inter-cap subjective dissimilarities were estimated from each subject's "odd-one-out" choices, and processed using non-metric multidimensional scaling. Two-dimensional color spaces, individual and group (DM2 patients; controls), were reconstructed, with the axes interpreted as the R/G and B/Y perceptual opponent systems. Compared to controls, patient results were not significant for the D-15 and D-15d. In contrast, in the triadic procedure the residual distances were significantly different compared to controls: right eye, P = 0.021, and left eye, P = 0.022. Color space configurations for the DM2 patients were compressed along the B/Y and R/G dimensions. The present findings agree with earlier studies demonstrating diffuse losses in early stages of DM2. The proposed method of testing uses color spaces to represent discrimination and provides more differentiated quantitative diagnosis, which may be interpreted as the perceptual color system affected. In addition, it enables the detection of very mild color vision impairment that is not captured by the D-15d test. Along with fundoscopy, individual color spaces may serve for monitoring early functional changes and thereby to support a treatment strategy.

  13. Evaluating the Evidence for Transmission Distortion in Human Pedigrees

    PubMed Central

    Meyer, Wynn K.; Arbeithuber, Barbara; Ober, Carole; Ebner, Thomas; Tiemann-Boege, Irene; Hudson, Richard R.; Przeworski, Molly

    2012-01-01

    Children of a heterozygous parent are expected to carry either allele with equal probability. Exceptions can occur, however, due to meiotic drive, competition among gametes, or viability selection, which we collectively term “transmission distortion” (TD). Although there are several well-characterized examples of these phenomena, their existence in humans remains unknown. We therefore performed a genome-wide scan for TD by applying the transmission disequilibrium test (TDT) genome-wide to three large sets of human pedigrees of European descent: the Framingham Heart Study (FHS), a founder population of European origin (HUTT), and a subset of the Autism Genetic Resource Exchange (AGRE). Genotyping error is an important confounder in this type of analysis. In FHS and HUTT, despite extensive quality control, we did not find sufficient evidence to exclude genotyping error in the strongest signals. In AGRE, however, many signals extended across multiple SNPs, a pattern highly unlikely to arise from genotyping error. We identified several candidate regions in this data set, notably a locus in 10q26.13 displaying a genome-wide significant TDT in combined female and male transmissions and a signature of recent positive selection, as well as a paternal TD signal in 6p21.1, the same region in which a significant TD signal was previously observed in 30 European males. Neither region replicated in FHS, however, and the paternal signal was not visible in sperm competition assays or as allelic imbalance in sperm. In maternal transmissions, we detected no strong signals near centromeres or telomeres, the regions predicted to be most susceptible to female-specific meiotic drive, but we found a significant enrichment of top signals among genes involved in cell junctions. These results illustrate both the potential benefits and the challenges of using the TDT to study transmission distortion and provide candidates for investigation in future studies. PMID:22377632

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

    PubMed

    Javaid, Abdul Qadir; Wiens, Andrew D; Fesmire, Nathaniel Forrest; Weitnauer, Mary Ann; Inan, Omer T

    2015-09-01

    Ballistocardiography is a noninvasive 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 preejection 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 nonideal posture, as well as enabling high-quality seated BCG measurements.

  15. Mw Systematic Study of Alkaloids: the Distorted Tropane of Scopoline

    NASA Astrophysics Data System (ADS)

    Ecija, Patricia; Cocinero, Emilio J.; Basterretxea, Francisco J.; Fernandez, Jose A.; Castano, Fernando; Lesarri, Alberto

    2013-06-01

    Tropane alkaloids have diverse pharmacological uses and are well-known for their neurostimulant activity. Previous structure-activity-relationship established correlations between bioactivity and several aspects of ligand conformation and stereochemistry, including delicate intramolecular effects like nitrogen inversion^{a}. We have initiated a series of structural studies on tropane alkaloids^{b}, aimed to discerning their intrinsic stereochemical properties using rotational spectroscopy in supersonic jets^{c}. Here we extend these studies to the epoxytropanes, initially motivated to interrogate the influence of the epoxy group on nitrogen inversion and ring conformation. The rotational spectrum evidences a single structure in the gas phase, providing a first description of the (three ring) structurally-distorted tropane in scopoline. The determined rotational parameters of scopoline reveal the structural consequences of the intramolecular cyclation of scopine, which breaks the original epoxy group and creates a new ether bridge and a 7β-hydroxytropane configuration. The hydroxyl group further stabilizes the molecule by an O-H \\cdots N intramolecular hydrogen bond, which, in turn, forces the N-methyl group to the less stable axial form^{b}. The experimental work was supported by ab initio and DFT calculations. ^{a} i) S.Singh, Chem. Rev. 100, 925 (2000); ii) A. Krunic, D. Pan, W.J. Dunn III, S.V.S. Miariappan, Bioorg. & Med. Chem. 17, 811 (2009). ^{b} E.J. Cocinero, A. Lesarri, P. écija, J.-U. Grabow, J.A. Fernández, F. Castaño, Phys. Chem. Chem. Phys. 12, 6076 (2010). ^{c} E.J. Cocinero, A. Lesarri, P. écija, J.-U. Grabow, J.A. Fernández, F. Castaño, Phys. Chem. Chem. Phys. 12, 12486 (2010).

  16. Characterizing Architectural Distortion in Mammograms by Linear Saliency.

    PubMed

    Narváez, Fabián; Alvarez, Jorge; Garcia-Arteaga, Juan D; Tarquino, Jonathan; Romero, Eduardo

    2017-02-01

    Architectural distortion (AD) is a common cause of false-negatives in mammograms. This lesion usually consists of a central retraction of the connective tissue and a spiculated pattern radiating from it. This pattern is difficult to detect due the complex superposition of breast tissue. This paper presents a novel AD characterization by representing the linear saliency in mammography Regions of Interest (ROI) as a graph composed of nodes corresponding to locations along the ROI boundary and edges with a weight proportional to the line intensity integrals along the path connecting any pair of nodes. A set of eigenvectors from the adjacency matrix is then used to extract discriminant coefficients that represent those nodes with higher salient lines. A dimensionality reduction is further accomplished by selecting the pair of nodes with major contribution for each of the computed eigenvectors. The set of main salient lines is then assembled as a feature vector that inputs a conventional Support Vector Machine (SVM). Experimental results with two benchmark databases, the mini-MIAS and DDSM databases, demonstrate that the proposed linear saliency domain method (LSD) performs well in terms of accuracy. The approach was evaluated with a set of 246 RoI extracted from the DDSM (123 normal tissues and 123 AD) and a set of 38 ROI from the mini-MIAS collections (19 normal tissues and 19 AD) respectively. The classification results showed respectively for both databases an accuracy rate of 89 % and 87 %, a sensitivity rate of 85 % and 95 %, and a specificity rate of 93 % and 84 %. Likewise, the area under curve (A z ) of the Receiver Operating Characteristic (ROC) curve was 0.93 for both databases.

  17. Implementation theory of distortion-invariant pattern recognition for optical and digital signal processing systems

    NASA Astrophysics Data System (ADS)

    Lhamon, Michael Earl

    A pattern recognition system which uses complex correlation filter banks requires proportionally more computational effort than single-real valued filters. This introduces increased computation burden but also introduces a higher level of parallelism, that common computing platforms fail to identify. As a result, we consider algorithm mapping to both optical and digital processors. For digital implementation, we develop computationally efficient pattern recognition algorithms, referred to as, vector inner product operators that require less computational effort than traditional fast Fourier methods. These algorithms do not need correlation and they map readily onto parallel digital architectures, which imply new architectures for optical processors. These filters exploit circulant-symmetric matrix structures of the training set data representing a variety of distortions. By using the same mathematical basis as with the vector inner product operations, we are able to extend the capabilities of more traditional correlation filtering to what we refer to as "Super Images". These "Super Images" are used to morphologically transform a complicated input scene into a predetermined dot pattern. The orientation of the dot pattern is related to the rotational distortion of the object of interest. The optical implementation of "Super Images" yields feature reduction necessary for using other techniques, such as artificial neural networks. We propose a parallel digital signal processor architecture based on specific pattern recognition algorithms but general enough to be applicable to other similar problems. Such an architecture is classified as a data flow architecture. Instead of mapping an algorithm to an architecture, we propose mapping the DSP architecture to a class of pattern recognition algorithms. Today's optical processing systems have difficulties implementing full complex filter structures. Typically, optical systems (like the 4f correlators) are limited to phase

  18. Sex-Related Cochlear Impairment in Cigarette Smokers

    PubMed Central

    Lisowska, Grażyna; Jochem, Jerzy; Gierlotka, Agata; Misiołek, Maciej; Ścierski, Wojciech

    2017-01-01

    Background A number of studies have documented the influence of cigarette smoking on hearing. However, the association between sex and hearing impairment in smokers as measured by otoacoustic emissions (OAEs) has not been clearly established. The aim of this study was to analyze sex-specific effects of smoking on hearing via conventional and ultra-high-frequency pure tone audiometry (PTA), and OAEs, specifically spontaneous OAEs, click-evoked OAEs, and distortion-product OAEs. Material/Methods The study included 84 healthy volunteers aged 25–45 years (mean 34), among them 46 women (25 non-smokers and 21 smokers) and 38 men (16 non-smokers and 22 smokers). The protocol of the study included otoscopic examination, tympanometry, low-, moderate-, and ultra-high-frequency PTA, evaluation of spontaneous click-evoked (CEAOEs) and distortion-product otoacoustic emissions (DPOAEs), assessment of the DP-grams for 2f1-f2 (f1 from 977 to5 164 Hz), and input/output function at L2 primary tone level of 40–70 dB SPL. Results Smokers and non-smokers did not differ significantly in terms of their hearing thresholds assessed with tone audiometry. Male smokers presented with significantly lower levels of CEAOEs and DPOAEs than both male non-smokers and female smokers. Conclusions Smoking does not modulate a hearing threshold determined with PTA at low, moderate, and ultra-high frequencies, but causes a significant decrease in OAE levels. This effect was observed only in males, which implies that they are more susceptible to smoking-induced hearing impairment. Sex-specific differences in otoacoustic emissions level may reflect influences of genetic, hormonal, behavioral, and/or environmental factors. PMID:28110343

  19. Study Protocol on Intentional Distortion in Personality Assessment: Relationship with Test Format, Culture, and Cognitive Ability

    PubMed Central

    Van Geert, Eline; Orhon, Altan; Cioca, Iulia A.; Mamede, Rui; Golušin, Slobodan; Hubená, Barbora; Morillo, Daniel

    2016-01-01

    Self-report personality questionnaires, traditionally offered in a graded-scale format, are widely used in high-stakes contexts such as job selection. However, job applicants may intentionally distort their answers when filling in these questionnaires, undermining the validity of the test results. Forced-choice questionnaires are allegedly more resistant to intentional distortion compared to graded-scale questionnaires, but they generate ipsative data. Ipsativity violates the assumptions of classical test theory, distorting the reliability and construct validity of the scales, and producing interdependencies among the scores. This limitation is overcome in the current study by using the recently developed Thurstonian item response theory model. As online testing in job selection contexts is increasing, the focus will be on the impact of intentional distortion on personality questionnaire data collected online. The present study intends to examine the effect of three different variables on intentional distortion: (a) test format (graded-scale versus forced-choice); (b) culture, as data will be collected in three countries differing in their attitudes toward intentional distortion (the United Kingdom, Serbia, and Turkey); and (c) cognitive ability, as a possible predictor of the ability to choose the more desirable responses. Furthermore, we aim to integrate the findings using a comprehensive model of intentional distortion. In the Anticipated Results section, three main aspects are considered: (a) the limitations of the manipulation, theoretical approach, and analyses employed; (b) practical implications for job selection and for personality assessment in a broader sense; and (c) suggestions for further research. PMID:27445902

  20. Sex-of-offspring-specific transmission ratio distortion on mouse chromosome X.

    PubMed Central

    de la Casa-Esperon, E; Pardo-Manuel de Villena, F; Verner, A E; Briscoe, T L; Malette, J M; Rosa, M; Jin, W H; Sapienza, C

    2000-01-01

    During our study of the DDK syndrome, we observed sex ratio distortion in favor of males among the offspring of F(1) backcrosses between the C57BL/6 and DDK strains. We also observed significant and reproducible transmission ratio distortion in favor of the inheritance of DDK alleles at loci on chromosome X among female offspring but not among male offspring in (C57BL/6 x DDK)F(1) x C57BL/6 and (C57BL/6-Pgk1(a) x DDK)F(1) x C57BL/6 backcrosses. The observed transmission ratio distortion is maximum at DXMit210 in the central region of chromosome X and decreases progressively at proximal and distal loci, in a manner consistent with the predictions of a single distorted locus model. DXMit210 is closely linked to two distortion-controlling loci (Dcsx1 and Dcsx2) described previously in interspecific backcrosses. Our analysis suggests that the female-offspring-specific transmission ratio distortion we observe is likely to be the result of the death of embryos of particular genotypic combinations. In addition, we confirm the previous suggestion that the transmission ratio distortion observed on chromosome X in interspecific backcrosses is also the result of loss of embryos. PMID:10628993

  1. Study Protocol on Intentional Distortion in Personality Assessment: Relationship with Test Format, Culture, and Cognitive Ability.

    PubMed

    Van Geert, Eline; Orhon, Altan; Cioca, Iulia A; Mamede, Rui; Golušin, Slobodan; Hubená, Barbora; Morillo, Daniel

    2016-01-01

    Self-report personality questionnaires, traditionally offered in a graded-scale format, are widely used in high-stakes contexts such as job selection. However, job applicants may intentionally distort their answers when filling in these questionnaires, undermining the validity of the test results. Forced-choice questionnaires are allegedly more resistant to intentional distortion compared to graded-scale questionnaires, but they generate ipsative data. Ipsativity violates the assumptions of classical test theory, distorting the reliability and construct validity of the scales, and producing interdependencies among the scores. This limitation is overcome in the current study by using the recently developed Thurstonian item response theory model. As online testing in job selection contexts is increasing, the focus will be on the impact of intentional distortion on personality questionnaire data collected online. The present study intends to examine the effect of three different variables on intentional distortion: (a) test format (graded-scale versus forced-choice); (b) culture, as data will be collected in three countries differing in their attitudes toward intentional distortion (the United Kingdom, Serbia, and Turkey); and (c) cognitive ability, as a possible predictor of the ability to choose the more desirable responses. Furthermore, we aim to integrate the findings using a comprehensive model of intentional distortion. In the Anticipated Results section, three main aspects are considered: (a) the limitations of the manipulation, theoretical approach, and analyses employed; (b) practical implications for job selection and for personality assessment in a broader sense; and

  2. Performance evaluation of HD camcorders: measuring texture distortions using Gabor filters and spatio-velocity CSF

    NASA Astrophysics Data System (ADS)

    Zhu, Kongfeng; Saupe, Dietmar

    2013-01-01

    This paper presents a new method of measuring physical texture distortions (PhTD) to evaluate the performance of high de_nition (HD) camcorders w.r.t. motion and lossy compression. It is extended to measure perceptual texture distortions (PeTD) by taking into account the spatio-velocity contrast sensitivity function of the human visual system. The PhTD gives an objective (physical) distortion of texture structures, while the PeTD measures the perceptual distortion of textures. The dead leaves chart, invariant to scaling, translation, rotation, and contrast, was selected as a target texture. The PhTD/PeTD metrics of the target distorted by camcorders were measured based on a bank of Gabor _lters with eight orientations and three scales. Experimental results for six HD camcorders from three vendors showed: 1) the PhTD value increases monotonically w.r.t. the motion speed, and decreases monotonically w.r.t. the lossy compression bitrate; 2) the PeTD value decreases monotonically w.r.t. the motion speed, but stays almost constant w.r.t. the lossy compression bitrate. The experiment gives a reasonable result even if the distortions are not radially symmetric. However, some subjective tests should be done in future work to validate the performance of the perceptual texture distortion metric.

  3. Development of the local magnification method for quantitative evaluation of endoscope geometric distortion

    NASA Astrophysics Data System (ADS)

    Wang, Quanzeng; Cheng, Wei-Chung; Suresh, Nitin; Hua, Hong

    2016-05-01

    With improved diagnostic capabilities and complex optical designs, endoscopic technologies are advancing. As one of the several important optical performance characteristics, geometric distortion can negatively affect size estimation and feature identification related diagnosis. Therefore, a quantitative and simple distortion evaluation method is imperative for both the endoscopic industry and the medical device regulatory agent. However, no such method is available yet. While the image correction techniques are rather mature, they heavily depend on computational power to process multidimensional image data based on complex mathematical model, i.e., difficult to understand. Some commonly used distortion evaluation methods, such as the picture height distortion (DPH) or radial distortion (DRAD), are either too simple to accurately describe the distortion or subject to the error of deriving a reference image. We developed the basic local magnification (ML) method to evaluate endoscope distortion. Based on the method, we also developed ways to calculate DPH and DRAD. The method overcomes the aforementioned limitations, has clear physical meaning in the whole field of view, and can facilitate lesion size estimation during diagnosis. Most importantly, the method can facilitate endoscopic technology to market and potentially be adopted in an international endoscope standard.

  4. An Analysis of ISAR Image Distortion Based on the Phase Modulation Effect

    NASA Astrophysics Data System (ADS)

    Wong, S. K.; Riseborough, E.; Duff, G.

    2006-12-01

    Distortion in the ISAR image of a target is a result of nonuniform rotational motion of the target during the imaging period. In many of the measured ISAR images from moving targets, such as those from in-flight aircraft, the distortion can be quite severe. Often, the image integration time is only a few seconds in duration and the target's rotational displacement is only a few degrees. The conventional quadratic phase distortion effect is not adequate in explaining the severe blurring in many of these observations. A numerical model based on a time-varying target rotation rate has been developed to quantify the distortion in the ISAR image. It has successfully modelled the severe distortion observed; the model's simulated results are validated by experimental data. Results from the analysis indicate that the severe distortion is attributed to the phase modulation effect where a time-varying Doppler frequency provides the smearing mechanism. For target identification applications, an efficient method on refocusing distorted ISAR images based on time-frequency analysis has also been developed based on the insights obtained from the results of the numerical modelling and experimental investigation conducted in this study.

  5. Automated detection method for architectural distortion areas on mammograms based on morphological processing and surface analysis

    NASA Astrophysics Data System (ADS)

    Ichikawa, Tetsuko; Matsubara, Tomoko; Hara, Takeshi; Fujita, Hiroshi; Endo, Tokiko; Iwase, Takuji

    2004-05-01

    As well as mass and microcalcification, architectural distortion is a very important finding for the early detection of breast cancer via mammograms, and such distortions can be classified into three typical types: spiculation, retraction, and distortion. The purpose of this work is to develop an automatic method for detecting areas of architectural distortion with spiculation. The suspect areas are detected by concentration indexes of line-structures extracted by using mean curvature. After that, discrimination analysis of nine features is employed for the classifications of true and false positives. The employed features are the size, the mean pixel value, the mean concentration index, the mean isotropic index, the contrast, and four other features based on the power spectrum. As a result of this work, the accuracy of the classification was 76% and the sensitivity was 80% with 0.9 false positives per image in our database in regard to spiculation. It was concluded that our method was effective in detectiong the area of architectural distortion; however, some architectural distortions were not detected accurately because of the size, the density, or the different appearance of the distorted areas.

  6. Distortion correction in EPI using an extended PSF method with a reversed phase gradient approach.

    PubMed

    In, Myung-Ho; Posnansky, Oleg; Beall, Erik B; Lowe, Mark J; Speck, Oliver

    2015-01-01

    In echo-planar imaging (EPI), such as commonly used for functional MRI (fMRI) and diffusion-tensor imaging (DTI), compressed distortion is a more difficult challenge than local stretching as spatial information can be lost in strongly compressed areas. In addition, the effects are more severe at ultra-high field (UHF) such as 7T due to increased field inhomogeneity. To resolve this problem, two EPIs with opposite phase-encoding (PE) polarity were acquired and combined after distortion correction. For distortion correction, a point spread function (PSF) mapping method was chosen due to its high correction accuracy and extended to perform distortion correction of both EPIs with opposite PE polarity thus reducing the PSF reference scan time. Because the amount of spatial information differs between the opposite PE datasets, the method was further extended to incorporate a weighted combination of the two distortion-corrected images to maximize the spatial information content of a final corrected image. The correction accuracy of the proposed method was evaluated in distortion-corrected data using both forward and reverse phase-encoded PSF reference data and compared with the reversed gradient approaches suggested previously. Further we demonstrate that the extended PSF method with an improved weighted combination can recover local distortions and spatial information loss and be applied successfully not only to spin-echo EPI, but also to gradient-echo EPIs acquired with both PE directions to perform geometrically accurate image reconstruction.

  7. Effect of combined pressure and temperature distortion orientation on high-bypass-ratio turbofan engine stability

    NASA Technical Reports Server (NTRS)

    Soeder, R. H.; Mehalic, C. M.

    1984-01-01

    Total-temperature, static-pressure and total-pressure distributions were measured in the inlet duct upstream of the engine inlet and within the fan and compressor of a YTF34 turbofan engine. Free-stream and boundary layer yaw angle variations were measured between a rotable screen assembly and the engine inlet. Total pressure distortions were generated using three 180 deg extent screens and total temperature distortions were generated using a rotatable hydrogen burner. Reynolds number index upstream of the rotatable screen assembly was maintained at 0.5 (based on the undistorted sectors at station 1, the inlet flow measuring station). The engine mechanical fan speed at sea level condition was rated at 7005 rpm. The engine was tested at a corrected fan speed of 90 percent of rated condition. Yaw angle increased between the rotatable screen assembly and the engine inlet. The largest variation in free-stream and boundary layer yaw angle occurs when the combined distortions are 180 deg out-of-phase. Static-pressure distortion increased exponentially as flow approached the engine. Total-pressure distortions were attenuated between the engine inlet and the compressor exit. Total-temperature distortion persisted through the compressor for all four combined distortions investigated.

  8. Body Image Distortions, Weight, and Depression in Adolescent Boys: Longitudinal Trajectories into Adulthood

    PubMed Central

    Blashill, Aaron J.; Wilhelm, Sabine

    2014-01-01

    Depressive symptoms are common among the U.S. population, yet research into prospective risk factors of depression among men is limited. Distorted body image is also prevalent among adolescent boys, and may be linked with elevated depression; however, longitudinal associations have rarely been measured. Thus, the aim of the current study was to assess the prospective relationship between forms of body image distortion and depressive symptoms among adolescent boys, into adulthood. Data were extracted from the National Longitudinal Study of Adolescent Health. Participants were 2,139 U.S. adolescent boys (M age = 16) who were followed prospectively over 13-years (1996 to 2009), into adulthood. Longitudinal mixed-level modeling was employed to assess the temporal prediction of body image distortion on symptoms of depression. Results revealed that boys who were average weight and viewed themselves as either very underweight (very underweight distorted; Cohen's d = .47) or overweight (overweight distorted; Cohen's d = .29) reported significantly higher levels of depressive symptoms compared to boys who accurately viewed their weight as average; this effect remained constant over the 13-year study period. These findings indicated that distortions in body image, particularly extreme distortions, are risk factors for elevated depressive symptoms among adolescent boys, and persist into early adulthood. PMID:25383047

  9. 3-D Coupled FE Analysis and Experimental Validation of Restrained Welding to Control Angular Distortion

    NASA Astrophysics Data System (ADS)

    Damale, A. V.; Nandurkar, K. N.

    2012-10-01

    Welding induced distortion is one of the critical defects in the welded structures. Angular distortion is most pronounced which badly affects the welded structures. Non-uniform heating during welding develops this angular distortion. Various methods are available to control/minimize the welding distortions. One of the methods available to control this distortion is restraining, in which clamping pressure is applied on the deforming edges of the plates. In the present study, a 3-dimensional coupled transient thermal analysis is done for simulating the restraining phenomenon of welding. The developed transient thermal heat source was used to simulate the arc welding phenomenon. The element birth and death technique was used for simulating filler material deposition. Thermal model was verified by comparing the macrograph of Finite Element Analysis (FEA) model and the weld and verification of structural model was done by comparing the measured and predicted angular distortions. Experimental and Finite Element (FE) analysis is done for both conventional welding and welding under restraining pressure. Transient thermal and non-linear structural analyses were carried out in order to predict angular distortions. The Finite Element Method analysis and experimental verification is done for manual metal arc welding process.

  10. Simultaneous measurement of aero-optical distortion and turbulent structure in a heated boundary layer

    NASA Astrophysics Data System (ADS)

    Saxton-Fox, Theresa; McKeon, Beverley; Smith, Adam; Gordeyev, Stanislav

    2014-11-01

    This study examines the relationship between turbulent structures and the aero-optical distortion of a laser beam passing through a turbulent boundary layer. Previous studies by Smith et al. (AIAA, 2014--2491) have found a bulk convection velocity of 0 . 8U∞ for aero-optical distortion in turbulent boundary layers, motivating a comparison of the distortion with the outer boundary layer. In this study, a turbulent boundary layer is developed over a flat plate with a moderately-heated section of length 25 δ . Density variation in the thermal boundary layer leads to aero-optical distortion, which is measured with a Malley probe (Smith et al., AIAA, 2013--3133). Simultaneously, 2D PIV measurements are recorded in a wall-normal, streamwise plane centered on the Malley probe location. Experiments are run at Reθ = 2100 and at a Mach number of 0.03, with the heated wall 10 to 20°C above the free stream temperature. Correlations and conditional averages are carried out between Malley probe distortion angles and flow features in the PIV vector fields. Aero-optical distortion in this study will be compared to distortion in higher Mach number flows studied by Gordeyev et al. (J. Fluid Mech., 2014), with the aim of extending conclusions into compressible flows. This research is made possible by the Department of Defense through the National Defense & Engineering Graduate Fellowship (NDSEG) Program and by the Air Force Office of Scientific Research Grant # FA9550-12-1-0060.

  11. Segregation distortion induced by wild-type RanGAP in Drosophila

    PubMed Central

    Kusano, Ayumi; Staber, Cynthia; Ganetzky, Barry

    2002-01-01

    Segregation Distorter (SD) is a meiotic drive system in Drosophila that causes preferential transmission of the SD chromosome from SD/SD+ males owing to the induced dysfunction of SD+ spermatids. The key distorter locus, Sd, is a dominant neomorphic allele encoding a truncated, but enzymatically active, RanGAP (RanGTPase-activating protein) whose nuclear mislocalization underlies distortion by disrupting the Ran signaling pathway. Here, we show that even wild-type RanGAP can cause segregation distortion when it is overexpressed in the male germ line or when the gene dosage of a particular modifier locus is increased. Both manipulations result in substantial nuclear accumulation of RanGAP. Distortion can be suppressed by overexpression of Ran or Ran guanine nucleotide exchange factor (RanGEF) in the male germ line, indicating that the primary consequence of nuclear mislocalization of RanGAP is reduction of intranuclear RanGTP levels. These results prove that segregation distortion does not depend on any unique properties of the mutant RanGAP encoded by Sd and provide a unifying explanation for the occurrence of distortion in a variety of experimental situations. PMID:11997467

  12. 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.

  13. Characterization of system-related geometric distortions in MR images employed in Gamma Knife radiosurgery applications

    NASA Astrophysics Data System (ADS)

    Pappas, E. P.; Seimenis, I.; Moutsatsos, A.; Georgiou, E.; Nomikos, P.; Karaiskos, P.

    2016-10-01

    This work provides characterization of system-related geometric distortions present in MRIs used in Gamma Knife (GK) stereotactic radiosurgery (SRS) treatment planning. A custom-made phantom, compatible with the Leksell stereotactic frame model G and encompassing 947 control points (CPs), was utilized. MR images were obtained with and without the frame, thus allowing discrimination of frame-induced distortions. In the absence of the frame and following compensation for field inhomogeneities, measured average CP disposition owing to gradient nonlinearities was 0.53 mm. In presence of the frame, contrarily, detected distortion was greatly increased (up to about 5 mm) in the vicinity of the frame base due to eddy currents induced in the closed loop of its aluminum material. Frame-related distortion was obliterated at approximately 90 mm from the frame base. Although the region with the maximum observed distortion may not lie within the GK treatable volume, the presence of the frame results in distortion of the order of 1.5 mm at a 7 cm distance from the center of the Leksell space. Additionally, severe distortions observed outside the treatable volume could possibly impinge on the delivery accuracy mainly by adversely affecting the registration process (e.g. the position of the lower part of the N-shaped fiducials used to define the stereotactic space may be miss-registered). Images acquired with a modified version of the frame developed by replacing its front side with an acrylic bar, thus interrupting the closed aluminum loop and reducing the induced eddy currents, were shown to benefit from relatively reduced distortion. System-related distortion was also identified in patient MR images. Using corresponding CT angiography images as a reference, an offset of 1.1 mm was detected for two vessels lying in close proximity to the frame base, while excellent spatial agreement was observed for a vessel far apart from the frame base.

  14. Correcting distorted paleosecular variation in late glacial lacustrine clay

    NASA Astrophysics Data System (ADS)

    Borradaile, G. J.; Almqvist, B. S.

    2008-01-01

    An undisturbed, horizontal chronostratigraphic marker horizon of laminated red glacio-lacustrine clay crops out over ˜25,000 km 2 in northern Ontario, Canada. The primary, clastic hematite laminae possess two stable vector components of magnetization. We sampled a 1.6 m vertical section at overlapping 2 cm intervals in cubic specimens (8 cm 3, n = 106), precisely oriented in geographic coordinates which permitted measurement of inclination and declination. Alternating field demagnetization (12-17 steps per specimen) isolated a characteristic (ChRM), primary component (coercivity ≥40 mT) approximately 30° shallower than the mean geomagnetic field inclination at this latitude, with distorted paleosecular secular variation (PSV). A lower coercivity overprint (20-40 mT) is 6° shallower than the present geomagnetic field and similarly inclined to the depositional-remanence deflection when the clay was re-sedimented in the laboratory. We believe this angle to be representative of the inclination of the deflected primary remanence inclination during deposition, caused by the magnetic anisotropy of the clay. Using this as a proxy for the initial inclination, the ChRM (hard-component) inclinations were restored to their original values assuming vertical compaction, which averages to 51%. The restored inclinations are compatible with site-latitude and the restored secular-variation loops centre reasonably on the geographic North Pole. The structural correction based on homogeneous vertical shortening over-simplifies the reality of heterogeneous particulate flow in which grain rotations depend on shape, size and packing and effectively combines influences of compaction and depositional settlement. Nevertheless, this correction makes the PSV data more useful and interpretable in terms of paleopole migration. The more logical correction technique using anisotropy of anhysteretic remanence (AARM; Jackson, M.J., Banerjee, S.K., Marvin, J.A., Lu, R., Gruber, W., 1991

  15. F-15 inlet/engine test techniques and distortion methodologies studies. Volume 2: Time variant data quality analysis plots

    NASA Technical Reports Server (NTRS)

    Stevens, C. H.; Spong, E. D.; Hammock, M. S.

    1978-01-01

    Time variant data quality analysis plots were used to determine if peak distortion data taken from a subscale inlet model can be used to predict peak distortion levels for a full scale flight test vehicle.

  16. 2D nearly orthogonal mesh generation with controls on distortion function

    NASA Astrophysics Data System (ADS)

    Zhang, Yaoxin; Jia, Yafei; Wang, Sam S. Y.

    2006-11-01

    A method to control the distortion function of the Ryskin and Leal (RL) orthogonal mesh generation system is presented. The proposed method considers the effects from not only the local orthogonal condition but also the local smoothness condition (the geometry and the mesh size) on the distortion function. The distortion function is determined by both the scale factors and the averaged scale factors of the constant mesh lines. Two adjustable parameters are used to control the local balance of the orthogonality and the smoothness. The proposed method is successfully applied to several benchmark examples and the natural river channels with complex geometries.

  17. GRAIN SIZING AND CALIBRATING OF DISTORTION BY IMAGE PROCESSING WITH INCLINED PHOTOGRAPH

    NASA Astrophysics Data System (ADS)

    Yasuda, Shingo; Ohashi, Keisuke; Ihara, Kazuki

    River bed material is normally heterogeneous, and the grain size distribution shows some features of each rivers. The information of distribution is, therefore, important factor in river engineering, and several traditional methods is practically used. Image processing method with digital photograph is modern analysis by using computer and replaced traditional analog photograph method. In image processing, however, optical distortion brings measurement error. We present a calibration of the distortion with optical theorem. In laboratory experiment with balls supposed river bed gravel, the theoretical calibration is considered to be appropriate. In field experiment, actual coefficient to calibrate distortion is estimated. In consequence of the investigation, it makes image processing method more accurate.

  18. Formulation of a minimum variance deconvolution technique for compensation of pneumatic distortion in pressure sensing devices

    NASA Technical Reports Server (NTRS)

    Whitmore, Stephen A.

    1990-01-01

    Increasingly, aircraft system designs require that aerodynamic parameters derived from pneumatic measurements be employed as control-system feedbacks. Such high frequency pressure measurements' accuracy is compromised by pressure distortion due to frictional attenuation and pneumatic resonance within the sensing system. A pneumatic distortion model is here formulated and reduced to a low-order state-variable model which retains most of the full model's dynamic characteristics. This reduced-order model is coupled with standard results from minimum variance estimation theory to develop an algorithm to compensate for pneumatic-distortion effects.

  19. Radial lens distortion correction with sub-pixel accuracy for X-ray micro-tomography.

    PubMed

    Vo, Nghia T; Atwood, Robert C; Drakopoulos, Michael

    2015-12-14

    Distortion correction or camera calibration for an imaging system which is highly configurable and requires frequent disassembly for maintenance or replacement of parts needs a speedy method for recalibration. Here we present direct techniques for calculating distortion parameters of a non-linear model based on the correct determination of the center of distortion. These techniques are fast, very easy to implement, and accurate at sub-pixel level. The implementation at the X-ray tomography system of the I12 beamline, Diamond Light Source, which strictly requires sub-pixel accuracy, shows excellent performance in the calibration image and in the reconstructed images.

  20. Study of x-ray lithography mask distortion during electron-beam writing

    NASA Astrophysics Data System (ADS)

    Shang, Hongyan; Wang, Yongkun

    2008-10-01

    Three-dimensional finite element model was developed to simulate the X-ray lithography mask distortion during electron-beam writing (EBW). Equivalent heat flux density method was proposed and the transient thermal stress simulation was done. The results show that the in-plane distortion (IPD) of the mask fluctuates with the time. The maximum value is 8.24 nm, and the direction is deviated from the electron beam center. The maximum out-of-plane distortion (OPD) is 9.75μm. The direction is normal to the pattern window, and occurred in the center of the beam center.