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Sample records for optimum tilt angle

  1. Behavior of Tilted Angle Shear Connectors

    PubMed Central

    Khorramian, Koosha; Maleki, Shervin; Shariati, Mahdi; Ramli Sulong, N. H.

    2015-01-01

    According to recent researches, angle shear connectors are appropriate to transfer longitudinal shear forces across the steel-concrete interface. Angle steel profile has been used in different positions as L-shaped or C-shaped shear connectors. The application of angle shear connectors in tilted positions is of interest in this study. This study investigates the behaviour of tilted-shaped angle shear connectors under monotonic loading using experimental push out tests. Eight push-out specimens are tested to investigate the effects of different angle parameters on the ultimate load capacity of connectors. Two different tilted angles of 112.5 and 135 degrees between the angle leg and steel beam are considered. In addition, angle sizes and lengths are varied. Two different failure modes were observed consisting of concrete crushing-splitting and connector fracture. By increasing the size of connector, the maximum load increased for most cases. In general, the 135 degrees tilted angle shear connectors have a higher strength and stiffness than the 112.5 degrees type. PMID:26642193

  2. Rotation Angle for the Optimum Tracking of One-Axis Trackers

    SciTech Connect

    Marion, W. F.; Dobos, A. P.

    2013-07-01

    An equation for the rotation angle for optimum tracking of one-axis trackers is derived along with equations giving the relationships between the rotation angle and the surface tilt and azimuth angles. These equations are useful for improved modeling of the solar radiation available to a collector with tracking constraints and for determining the appropriate motor revolutions for optimum tracking.

  3. Perceptions of tilt angles of an agricultural tractor.

    PubMed

    Görücü, Serap; Cavallo, Eugenio; Murphy, Dennis

    2014-01-01

    A tractor stability simulator has been developed to help study tractor operators' perceptions of angles when the simulator is tilted to the side. The simulator is a trailer-mounted tractor cab equipped with hydraulic lift that can tilt the tractor cabin up to 30 degrees. This paper summarizes data from 82 participants who sat in the simulator while it was tilted. Demographic variables, estimates of tilt angles, and measured tilt angles were collected. The effects of age, gender, tractor driving experience, and frequency of operation on the estimated and measured tilt angles were analyzed. The results showed that about 50% of the participants reported estimations of side tilt angles within ±5 degrees of the actual angles, and nearly the same percentage overestimated the actual side tilt angles. Only a small percentage underestimated the angles. Older, more experienced, and male participants set higher limits on the actual angle at which they felt uncomfortable and would not drive. PMID:24417527

  4. Tilt angles and positive response of head-up tilt test in children with orthostatic intolerance.

    PubMed

    Lin, Jing; Wang, Yuli; Ochs, Todd; Tang, Chaoshu; Du, Junbao; Jin, Hongfang

    2015-01-01

    This study aimed at examining three tilt angle-based positive responses and the time to positive response in a head-up tilt test for children with orthostatic intolerance, and the psychological fear experienced at the three angles during head-up tilt test. A total of 174 children, including 76 boys and 98 girls, aged from 4 to 18 years old (mean 11.3±2.8 years old), with unexplained syncope, were randomly divided into three groups, to undergo head-up tilt test at the angles of 60°, 70° and 80°, respectively. The diagnostic rates and times were analysed, and Wong-Baker face pain rating scale was used to access the children's psychological fear. There were no significant differences in diagnostic rates of postural orthostatic tachycardia syndrome and vasovagal syncope at different tilt angles during the head-up tilt test (p>0.05). There was a significant difference, however, in the psychological fear at different tilt angles utilising the Kruskal-Wallis test (χ2=36.398, p<0.01). It was mildest at tilt angle 60° utilising the Kolmogorov-Smirnov test (p<0.01). A positive rank correlation was found between the psychological fear and the degree of tilt angle (r(s)=0.445, p<0.01). Positive response appearance time was 15.1±14.0 minutes at 60° for vasovagal syncope children. There was no significant difference in the time to positive response, at different tilt angles during the head-up tilt test for vasovagal syncope or for postural orthostatic tachycardia syndrome. Hence, it is suggested that a tilt angle of 60° and head-up tilt test time of 45 minutes should be suitable for children with vasovagal syncope. PMID:24124665

  5. Tilt Angles of Quiescent Filaments and Filaments of Active Regions

    NASA Astrophysics Data System (ADS)

    Tlatov, A. G.; Kuzanyan, K. M.; Vasil'yeva, V. V.

    2016-04-01

    We carry out study of tilt angles of solar filaments using the data from the two observatories: Meudon Observatory and Kislovodsk Mountain Astronomical Station for the century-long period 1919-2014. We developed special software for digitization of the filaments structures on Hα synoptic maps. The filaments were vectorized in semi-automatic mode. The tilt angles of filaments with respect to the equator (τ) were analyzed. Approximately 2/3 of the filaments have positive angles τ >0, which is defined as when the eastern end of the filaments are closer to the poles than the western ones. We have separated tilts for the filaments which are close to the active region structures and those of quiescent filaments. We found that long quiescent filaments mainly have negative tilts. The filaments which are close to active regions mainly have positive tilt angles.

  6. LONG-TERM MEASUREMENTS OF SUNSPOT MAGNETIC TILT ANGLES

    SciTech Connect

    Li Jing; Ulrich, Roger K.

    2012-10-20

    Tilt angles of close to 30,600 sunspots are determined using Mount Wilson daily averaged magnetograms taken from 1974 to 2012, and SOHO/MDI magnetograms taken from 1996 to 2010. Within a cycle, more than 90% of sunspots have a normal polarity alignment along the east-west direction following Hale's law. The median tilts increase with increasing latitude (Joy's law) at a rate of {approx}0.{sup 0}5 per degree of latitude. Tilt angles of spots appear largely invariant with respect to time at a given latitude, but they decrease by {approx}0.{sup 0}9 per year on average, a trend that largely reflects Joy's law following the butterfly diagram. We find an asymmetry between the hemispheres in the mean tilt angles. On average, the tilts are greater in the Southern than in the Northern Hemisphere for all latitude zones, and the differences increase with increasing latitude.

  7. Solar subsurface magnetic and velocity fields from tilt angle patterns

    NASA Astrophysics Data System (ADS)

    Baranyi, Tünde; Muraközy, Judit; Ludmány, András

    2015-08-01

    ABSTRACT A refined form of the well known Joy's law has been formulated by using the new Debrecen tilt angle datasets. These data are intercalibrated with the traditional datasets and several determination methods help to make the material reliable. It has been found that the latitudinal distribution of the tilt angles is not merely a monotonously increasing function, but it has a plateau between the latitudes of about 15-25 degrees, where the toroidal field is the strongest. This may provide new constraints for the theoretical investigations about the mechanisms contributing to the observable tilt angles. The new data also allow to demonstrate that the tilts are primarily caused by the Coriolis impact, no signature has been found for the winding up of the global magnetic field. This work has received funding from the European Community's Seventh Framework Programme (FP7/2012-2015) under grant agreement No. 284461 (eHEROES).

  8. Automated small tilt-angle measurement using Lau interferometry

    SciTech Connect

    Prakash, Shashi; Singh, Sumitra; Rana, Santosh

    2005-10-01

    A technique for a tilt-angle measurement of reflecting objects based on the Lau interferometry coupled with the moire readout has been proposed. A white-light incoherent source illuminates a set of two gratings, resulting in the generation of the Fresnel image due to the Lau effect. The Fresnel image is projected onto a reflecting object. The image reflected from the object is superimposed onto an identical grating, which results in the formation of a moire fringe pattern. The inclination angle of moire fringes is a function of tilt angle of the object. Theory and experimental arrangement of the proposed technique is presented and results of the investigation are reported.

  9. Rotating Shaft Tilt Angle Measurement Using an Inclinometer

    NASA Astrophysics Data System (ADS)

    Luo, Jun; Wang, Zhiqian; Shen, Chengwu; Wen, Zhuoman; Liu, Shaojin; Cai, Sheng; Li, Jianrong

    2015-10-01

    This paper describes a novel measurement method to accurately measure the rotating shaft tilt angle of rotating machine for alignment or compensation using a dual-axis inclinometer. A model of the rotating shaft tilt angle measurement is established using a dual-axis inclinometer based on the designed mechanical structure, and the calculation equation between the rotating shaft tilt angle and the inclinometer axes outputs is derived under the condition that the inclinometer axes are perpendicular to the rotating shaft. The reversal measurement method is applied to decrease the effect of inclinometer drifts caused by temperature, to eliminate inclinometer and rotating shaft mechanical error and inclinometer systematic error to attain high measurement accuracy. The uncertainty estimation shows that the accuracy of rotating shaft tilt angle measurement depends mainly on the inclinometer uncertainty and its uncertainty is almost the same as the inclinometer uncertainty in the simulation. The experimental results indicate that measurement time is 4 seconds; the range of rotating shaft tilt angle is 0.002° and its standard deviation is 0.0006° using NS-5/P2 inclinometer, whose precision and resolution are ±0.01° and 0.0005°, respectively.

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

    PubMed

    Ahn, Sinyeob; Hu, Xiaoping P

    2012-10-01

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

  11. Tilt angle control of nanocolumns grown by glancing angle sputtering at variable argon pressures

    SciTech Connect

    Garcia-Martin, J. M.; Cebollada, A.; Alvarez, R.; Romero-Gomez, P.; Palmero, A.

    2010-10-25

    We show that the tilt angle of nanostructures obtained by glancing angle sputtering is finely tuned by selecting the adequate argon pressure. At low pressures, a ballistic deposition regime dominates, yielding high directional atoms that form tilted nanocolumns. High pressures lead to a diffusive regime which gives rise to vertical columnar growth. Monte Carlo simulations reproduce the experimental results indicating that the loss of directionality of the sputtered particles in the gas phase, together with the self-shadowing mechanism at the surface, are the main processes responsible for the development of the columns.

  12. Optimum design of 2D micro-angle sensor

    NASA Astrophysics Data System (ADS)

    Liu, Qinggang; Zhao, Heng; Lou, Xiaona; Jiang, Ningchuan; Hu, Xiaotang

    2008-12-01

    To improve dynamic measurement performance and resolution, an optimum design on two-dimensional (2D) micro-angle sensor based on optical internal-reflection method via critical-angle refractive index measurement is presented in the paper. The noise signals were filtered effectively by modulating laser-driven and demodulating in signal proceeding. The system's accuracy and response speed are improved further by using 16-bit high-precision AD converter and MSP430 CPU which present with a high-speed performance during signals processes such as fitting angle-voltage curve through specific arithmetic, full range and zero point calibration, filter, scaling transformation etc. The experiment results indicated that, dynamic signal measurement range can be up to +/-600arcsec, the measurement resolution can be better than 0.1arcsec, and the repeatability could be better than +/-0.5arcsec.

  13. Sunspot Tilt Angles Measured with MDI/SOHO and HMI/SDO

    NASA Astrophysics Data System (ADS)

    Li, J.; Ulrich, R. K.

    2015-12-01

    We present sunspot magnetic tilt angles measured from 1996 to the present time, spanning almost two solar cycles. Full disk magnetograms from MDI/SoHO and HMI/SDO are used in our study. The data cadence in our analyses is 96 minutes per day giving about 90 measurements of the tilt angles for each sunspot during the disk passage between -40 to +40 longitudinal degree. In addition to an automated computation, we use a scheme to visually examine each sunspot efficiently to check the tilt angle determinations. Such measurements not only confirm Joy's and Hale's laws, but also reveal the tilt angle variations during the sunspot lifetime, the effect of Coriolis force on the magnetic flux tubes, and the tilt angle dependence of the cycle progress. The measurements also provide uncertainties on the tilt angle measurements.

  14. Controlling pre-tilt angles of liquid crystal using mixed polyimide alignment layer.

    PubMed

    Wu, Wei-Yen; Wang, Chen-Chen; Fuh, Andy Y

    2008-10-13

    Three approaches to controlling liquid crystal (LC) pre-tilt angle in a cell are demonstrated using a polyimide (PI) alignment layer on substrates, in the form of a mixture of horizontal (H) and vertical (V) polyimides. The concentration ratio of H- to V-PI, baking temperature, and rubbing strength influence the pre-tilt angle, and highlight parameters for controlling the pre-tilt angle of an LC cell. Finally, a variable polarization converter is demonstrated using this approach. PMID:18852824

  15. Cell separation using tilted-angle standing surface acoustic waves

    PubMed Central

    Ding, Xiaoyun; Peng, Zhangli; Lin, Sz-Chin Steven; Geri, Michela; Li, Sixing; Li, Peng; Chen, Yuchao; Dao, Ming; Suresh, Subra; Huang, Tony Jun

    2014-01-01

    Separation of cells is a critical process for studying cell properties, disease diagnostics, and therapeutics. Cell sorting by acoustic waves offers a means to separate cells on the basis of their size and physical properties in a label-free, contactless, and biocompatible manner. The separation sensitivity and efficiency of currently available acoustic-based approaches, however, are limited, thereby restricting their widespread application in research and health diagnostics. In this work, we introduce a unique configuration of tilted-angle standing surface acoustic waves (taSSAW), which are oriented at an optimally designed inclination to the flow direction in the microfluidic channel. We demonstrate that this design significantly improves the efficiency and sensitivity of acoustic separation techniques. To optimize our device design, we carried out systematic simulations of cell trajectories, matching closely with experimental results. Using numerically optimized design of taSSAW, we successfully separated 2- and 10-µm-diameter polystyrene beads with a separation efficiency of ∼99%, and separated 7.3- and 9.9-µm-polystyrene beads with an efficiency of ∼97%. We illustrate that taSSAW is capable of effectively separating particles–cells of approximately the same size and density but different compressibility. Finally, we demonstrate the effectiveness of the present technique for biological–biomedical applications by sorting MCF-7 human breast cancer cells from nonmalignant leukocytes, while preserving the integrity of the separated cells. The method introduced here thus offers a unique route for separating circulating tumor cells, and for label-free cell separation with potential applications in biological research, disease diagnostics, and clinical practice. PMID:25157150

  16. RE-EXAMINING SUNSPOT TILT ANGLE TO INCLUDE ANTI-HALE STATISTICS

    SciTech Connect

    McClintock, B. H.; Norton, A. A.; Li, J. E-mail: aanorton@stanford.edu

    2014-12-20

    Sunspot groups and bipolar magnetic regions (BMRs) serve as an observational diagnostic of the solar cycle. We use Debrecen Photohelographic Data (DPD) from 1974-2014 that determined sunspot tilt angles from daily white light observations, and data provided by Li and Ulrich that determined sunspot magnetic tilt angle using Mount Wilson magnetograms from 1974-2012. The magnetograms allowed for BMR tilt angles that were anti-Hale in configuration, so tilt values ranged from 0 to 360° rather than the more common ±90°. We explore the visual representation of magnetic tilt angles on a traditional butterfly diagram by plotting the mean area-weighted latitude of umbral activity in each bipolar sunspot group, including tilt information. The large scatter of tilt angles over the course of a single cycle and hemisphere prevents Joy's law from being visually identified in the tilt-butterfly diagram without further binning. The average latitude of anti-Hale regions does not differ from the average latitude of all regions in both hemispheres. The distribution of anti-Hale sunspot tilt angles are broadly distributed between 0 and 360° with a weak preference for east-west alignment 180° from their expected Joy's law angle. The anti-Hale sunspots display a log-normal size distribution similar to that of all sunspots, indicating no preferred size for anti-Hale sunspots. We report that 8.4% ± 0.8% of all bipolar sunspot regions are misclassified as Hale in traditional catalogs. This percentage is slightly higher for groups within 5° of the equator due to the misalignment of the magnetic and heliographic equators.

  17. Re-examining Sunspot Tilt Angle to Include Anti-Hale Statistics

    NASA Astrophysics Data System (ADS)

    McClintock, B. H.; Norton, A. A.; Li, J.

    2014-12-01

    Sunspot groups and bipolar magnetic regions (BMRs) serve as an observational diagnostic of the solar cycle. We use Debrecen Photohelographic Data (DPD) from 1974-2014 that determined sunspot tilt angles from daily white light observations, and data provided by Li & Ulrich that determined sunspot magnetic tilt angle using Mount Wilson magnetograms from 1974-2012. The magnetograms allowed for BMR tilt angles that were anti-Hale in configuration, so tilt values ranged from 0 to 360° rather than the more common ±90°. We explore the visual representation of magnetic tilt angles on a traditional butterfly diagram by plotting the mean area-weighted latitude of umbral activity in each bipolar sunspot group, including tilt information. The large scatter of tilt angles over the course of a single cycle and hemisphere prevents Joy's law from being visually identified in the tilt-butterfly diagram without further binning. The average latitude of anti-Hale regions does not differ from the average latitude of all regions in both hemispheres. The distribution of anti-Hale sunspot tilt angles are broadly distributed between 0 and 360° with a weak preference for east-west alignment 180° from their expected Joy's law angle. The anti-Hale sunspots display a log-normal size distribution similar to that of all sunspots, indicating no preferred size for anti-Hale sunspots. We report that 8.4% ± 0.8% of all bipolar sunspot regions are misclassified as Hale in traditional catalogs. This percentage is slightly higher for groups within 5° of the equator due to the misalignment of the magnetic and heliographic equators.

  18. Measurements of sunspot group tilt angles for solar cycles 19-24

    NASA Astrophysics Data System (ADS)

    Isik, Seda; Isik, Emre

    2016-07-01

    The tilt angle of a sunspot group is a critical quantity in the surface transport magnetic flux on global scales, playing a role in the solar dynamo. To investigate Joy's law for four cycles, we measured the tilt angles of sunspot groups for solar cycles 19-24. We have developed an IDL routine, which allows the user to interactively select and measure sunspot positions and areas on the solar disc, using the sunspot drawing database of Kandilli Observatory. The method is similar to that used by others in the literature, with the exception that sunspot groups were identified manually, which has improved the accuracy of the tilt angles. We present cycle averages of the tilt angle and compare the results with the existing data in the literature.

  19. Optimum projection angle for attaining maximum distance in a soccer punt kick.

    PubMed

    Linthorne, Nicholas P; Patel, Dipesh S

    2011-01-01

    To produce the greatest horizontal distance in a punt kick the ball must be projected at an appropriate angle. Here, we investigated the optimum projection angle that maximises the distance attained in a punt kick by a soccer goalkeeper. Two male players performed many maximum-effort kicks using projection angles of between 10° and 90°. The kicks were recorded by a video camera at 100 Hz and a 2 D biomechanical analysis was conducted to obtain measures of the projection velocity, projection angle, projection height, ball spin rate, and foot velocity at impact. The player's optimum projection angle was calculated by substituting mathematical equations for the relationships between the projection variables into the equations for the aerodynamic flight of a soccer ball. The calculated optimum projection angles were in agreement with the player's preferred projection angles (40° and 44°). In projectile sports even a small dependence of projection velocity on projection angle is sufficient to produce a substantial shift in the optimum projection angle away from 45°. In the punt kicks studied here, the optimum projection angle was close to 45° because the projection velocity of the ball remained almost constant across all projection angles. This result is in contrast to throwing and jumping for maximum distance, where the projection velocity the athlete is able to achieve decreases substantially with increasing projection angle and so the optimum projection angle is well below 45°. Key pointsThe optimum projection angle that maximizes the distance of a punt kick by a soccer goalkeeper is about 45°.The optimum projection angle is close to 45° because the projection velocity of the ball is almost the same at all projection angles.This result is in contrast to throwing and jumping for maximum distance, where the optimum projection angle is well below 45° because the projection velocity the athlete is able to achieve decreases substantially with increasing

  20. Sunspot areas and tilt angles for solar cycles 7-10

    NASA Astrophysics Data System (ADS)

    Senthamizh Pavai, V.; Arlt, R.; Dasi-Espuig, M.; Krivova, N. A.; Solanki, S. K.

    2015-12-01

    Aims: Extending the knowledge about the properties of solar cycles into the past is essential for understanding the solar dynamo. This paper aims to estimate areas of sunspots observed by Schwabe in 1825-1867 and to calculate the tilt angles of sunspot groups. Methods: The sunspot sizes in Schwabe's drawings are not to scale and need to be converted into physical sunspot areas. We employed a statistical approach assuming that the area distribution of sunspots was the same in the 19th century as it was in the 20th century. Results: Umbral areas for about 130 000 sunspots observed by Schwabe were obtained, as well as the tilt angles of sunspot groups assuming them to be bipolar. There is, of course, no polarity information in the observations. The annually averaged sunspot areas correlate reasonably with sunspot number. We derived an average tilt angle by attempting to exclude unipolar groups with a minimum separation of the two alleged polarities and an outlier rejection method which follows the evolution of each group and detects the moment it turns unipolar at its decay. As a result, the tilt angles, although displaying considerable scatter, average to 5̊.85 ± 0, with the leading polarity located closer to the equator, in good agreement with tilt angles obtained from 20th century data sets. Sources of uncertainties in the tilt angle determination are discussed and need to be addressed whenever different data sets are combined. The sunspot area and tilt angle data are provided at the CDS. The sunspot area and tilt angle data are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/584/A73

  1. Uniform tilt-angle micromirror array for multi-object spectroscopy

    NASA Astrophysics Data System (ADS)

    Waldis, Severin; Clerc, Pierre-Andre; Zamkotsian, Frederic; Zickar, Michael; Noell, Wilfried; de Rooij, Nico

    2007-01-01

    We report on micromirror arrays being developed for the use as reflective slit mask in Multi Object Spectrographs for astronomical applications. The micromirrors are etched in bulk single crystal silicon whereas the cantilever type suspension is realized by surface micromachining. One micromirror element is 100μm x 200μm in size. The micromirrors are actuated electrostatically by electrodes located on a second chip. The use of silicon on insulator (SOI) wafers for both mirror and electrode chip ensures thermal compatibility for cryogenic operation. A system of multiple landing beams has been developed, which passively locks the mirror at a well defined tilt angle when actuated. The mechanical tilt angle obtained is 20 ° at a pull-in voltage of 90V. Measurements with an optical profiler showed that the tilt angle of the actuated and locked mirror is stable with a precision of one arc minute over a range of 15V. This locking system makes the tilt angle merely independent from process variations across the wafer and thus provides uniform tilt angle over the whole array. The precision on tilt angle from mirror to mirror measured is one arc minute. The surface quality of the mirrors in actuated state is better than 10nm peak-to-valley and the local roughness is around 1nm RMS.

  2. Optimum projection angle for attaining maximum distance in a rugby place kick.

    PubMed

    Linthorne, Nicholas P; Stokes, Thomas G

    2014-01-01

    This study investigated the effect of projection angle on the distance attained in a rugby place kick. A male rugby player performed 49 maximum-effort kicks using projection angles of between 20 and 50°. The kicks were recorded by a video camera at 50 Hz and a 2 D biomechanical analysis was conducted to obtain measures of the projection velocity and projection angle of the ball. The player's optimum projection angle was calculated by substituting a mathematical expression for the relationship between projection velocity and projection angle into the equations for the aerodynamic flight of a rugby ball. We found that the player's calculated optimum projection angle (30.6°, 95% confidence limits ± 1.9°) was in close agreement with his preferred projection angle (mean value 30.8°, 95% confidence limits ± 2.1°). The player's calculated optimum projection angle was also similar to projection angles previously reported for skilled rugby players. The optimum projection angle in a rugby place kick is considerably less than 45° because the projection velocity that a player can produce decreases substantially as projection angle is increased. Aerodynamic forces and the requirement to clear the crossbar have little effect on the optimum projection angle. Key PointsThe optimum projection angle in a rugby place kick is about 30°.The optimum projection angle is considerably less than 45° because the projection velocity that a player can produce decreases substantially as projection angle is increased.Aerodynamic forces and the requirement to clear the crossbar have little effect on the optimum projection angle. PMID:24570626

  3. Optimum subsonic, high-angle-of-attack nacelles

    NASA Technical Reports Server (NTRS)

    Luidens, R. W.; Stockman, N. O.; Diedrich, J. H.

    1979-01-01

    The optimum design of nacelles that operate over a wide range of aerodynamic conditions and their inlets is described. For low speed operation the optimum internal surface velocity distributions and skin friction distributions are described for three categories of inlets: those with BLC, and those with blow in door slots and retractable slats. At cruise speed the effect of factors that reduce the nacelle external surface area and the local skin friction is illustrated. These factors are cruise Mach number, inlet throat size, fan-face Mach number, and nacelle contour. The interrelation of these cruise speed factors with the design requirements for good low speed performance is discussed.

  4. Tilt Angle and Footpoint Separation of Small and Large Bipolar Sunspot Regions Observed with HMI

    NASA Astrophysics Data System (ADS)

    McClintock, B. H.; Norton, A. A.

    2016-02-01

    We investigate bipolar sunspot regions and how tilt angle and footpoint separation vary during emergence and decay. The Helioseismic and Magnetic Imager on board the Solar Dynamic Observatory collects data at a higher cadence than historical records and allows for a detailed analysis of regions over their lifetimes. We sample the umbral tilt angle, footpoint separation, and umbral area of 235 bipolar sunspot regions in Helioseismic and Magnetic Imager—Debrecen Data with an hourly cadence. We use the time when the umbral area peaks as time zero to distinguish between the emergence and decay periods of each region and we limit our analysis of tilt and separation behavior over time to within ±96 hr of time zero. Tilt angle evolution is distinctly different for regions with small (≈30 MSH), midsize (≈50 MSH), and large (≈110 MSH) maximum umbral areas, with 45 and 90 MSH being useful divisions for separating the groups. At the peak umbral area, we determine median tilt angles for small (7.°6), midsize (5.°9), and large (9.°3) regions. Within ±48 hr of the time of peak umbral area, large regions steadily increase in tilt angle, midsize regions are nearly constant, and small regions show evidence of negative tilt during emergence. A period of growth in footpoint separation occurs over a 72-hr period for all of the regions from roughly 40 to 70 Mm. The smallest bipoles (<9 MSH) are outliers in that they do not obey Joy's law and have a much smaller footpoint separation. We confirm the Muñoz-Jaramillo et al. (2015) results that the sunspots appear to be two distinct populations.

  5. Variation of the tilt angle of solar filaments in 1919-2013

    NASA Astrophysics Data System (ADS)

    Kuzanyan, Kirill; Tlatov, Andrey; Vasilieva, Valeria

    Variation of the tilt angle of solar filaments in 1919-2013. A. Tlatov 1), V.Vasil’yeva1), K. Kuzanyan2) 1) Kislovodsk Mountain Observing Station, Main Astronomical Observatory of Russian Academy of Sciences 2) IZMIRAN, Moscow, Russian Academy of Sciences Abstract We present systematic analysis of distribution of solar filaments from the data of Meudon Observatory (1919-2003) and Kislovodsk Mountain Observing Station (1979-2013). We use scans of chromospheric synoptic maps of solar activity from Meudon over 1919-1998 as well as synoptic maps catalogue from Kislovodsk. To digitalise the data we developed pattern recognition software which enables us to isolate filament structures and determine their latitudinal and longitudinal location, length, and other geometric parameters for each filament. We found that the most of filaments have their west tip closer to the equator than the east tip. We present the distribution of the number and length of filaments as a function of time and latitude, and show their latitudinal migration. Furthermore, we study distribution the tilt angles of filaments with respect to the solar equator, and present dependence of the tilt on latitude and phase of the solar cycle. We show that maximum filament tilt angles are attained at the maximum sunspot activity, typically peaking at 10-15 degrees. The maximum levels of filament tilt angles are related to the maximum sunspot number; and the greater the tilt the higher the current sunspot cycle. Remarkable, that at sub-polar solar latitudes 60-70 degrees the average filament tilt angles were found to reverse, opposite to the rest of the hemisphere (low and middle latitudes). We discuss relationship of topological structure of the solar large scale magnetic fields in the sunspot cycle and magnetic fields of solar active regions from theoretical point of view.

  6. Control of the bias tilt angles in nematic liquid crystals

    NASA Astrophysics Data System (ADS)

    Yablonskii, S. V.; Nakayama, K.; Okazaki, S.; Ozaki, M.; Yoshino, K.; Palto, S. P.; Baranovich, M. Yu.; Michailov, A. S.

    1999-03-01

    The pretilt angle controlled by electric field was studied by the modulation ellipsometry technique. The easy direction of compensated nematic liquid crystals was controlled by surface flexoelectric torque created by the linear coupling of the director deformation and electric field. The weak anchoring energy necessary for the occurrence of flexoelectric distortion was produced by unidirectional rubbing of the clean indium-tin-oxide covered glasses with a cotton cloth. The pretilt angle was measured as a function of electric field. Long relaxation times of the optical response (hundreds of seconds) were observed. The rubbed thin polyvinyl alcohol and polyimide aligning layers were seen to promote strong anchoring energy (>0.5 erg/cm2) preventing any deviation of pretilt angle and, consequently, to suppress the optical response. The probable applications of the obtained results are discussed.

  7. The aurora at quite magnetospheric conditions: Repeatability and dipole tilt angle dependence

    SciTech Connect

    Oznovich, I. ); Eastes, R.W.; Huffman, R.E. ); Tur, M.; Glaser, I. )

    1993-03-01

    Is there a magnetospheric ground state Do the position and size of the auroral oval depend on the magnetic dipole tilt angle at quiet magnetospheric conditions In order to address these questions, northern hemisphere images of the aurora at 1356 [Angstrom], obtained by Polar BEAR at solar minimum (beginning of 1987), were related to high temporal resolution IPM 8 measurements of the interplanetary magnetic field, to solar wind velocity, and to the ground-based activity index Kp. The first problem was addressed by a two-dimensional correlation study of the repeatability of auroral emissions in corrected geomagnetic space at conditions of minimum energy transfer from the magnetosphere. The correlation measure of auroral images was 0.6-0.85. Error simulations indicate that given the uncertainties in pixel position and intensity, the maximum expected value of the correlation measure is 0.65-0.9. The notion of a ground state magnetosphere is therefore supported by this data. Repeatability was found at the same level regardless of time or reconfigurations of the magnetosphere between images and independent of magnetic time sector. The second problem was addressed by relating latitudinal shifts of the aurora with dipole tilt angle without resorting to auroral boundary specification. This data indicate that the latitude of the continuous aurora is related to the dipole tilt angle at quiet magnetospheric conditions. In the winter hemisphere a 10[degrees] increase in the dipole tilt angle causes a 1[degree] decrease (increase) in the latitude of auroral emissions at noon (midnight). The magnetic local time distribution of the latitudinal shifts with dipole tilt angle support a simple model in which the dipole tilt angle determines the position of the center of the auroral circle along the magnetic meridian 1320-0120 MLT (for IMF B[sub y] positive) and does not affect its radius. 22 refs., 8 figs.

  8. ACTIVE-REGION TILT ANGLES: MAGNETIC VERSUS WHITE-LIGHT DETERMINATIONS OF JOY'S LAW

    SciTech Connect

    Wang, Y.-M.; Colaninno, R. C.; Baranyi, T.; Li, J. E-mail: robin.colaninno@nrl.navy.mil E-mail: jli@igpp.ucla.edu

    2015-01-01

    The axes of solar active regions are inclined relative to the east-west direction, with the tilt angle tending to increase with latitude ({sup J}oy's law{sup )}. Observational determinations of Joy's law have been based either on white-light images of sunspot groups or on magnetograms, where the latter have the advantage of measuring directly the physically relevant quantity (the photospheric field), but the disadvantage of having been recorded routinely only since the mid-1960s. White-light studies employing the historical Mount Wilson (MW) database have yielded tilt angles that are smaller and that increase less steeply with latitude than those obtained from magnetic data. We confirm this effect by comparing sunspot-group tilt angles from the Debrecen Photoheliographic Database with measurements made by Li and Ulrich using MW magnetograms taken during cycles 21-23. Whether white-light or magnetic data are employed, the median tilt angles significantly exceed the mean values, and provide a better characterization of the observed distributions. The discrepancy between the white-light and magnetic results is found to have two main sources. First, a substantial fraction of the white-light ''tilt angles'' refer to sunspots of the same polarity. Of greater physical significance is that the magnetograph measurements include the contribution of plage areas, which are invisible in white-light images but tend to have greater axial inclinations than the adjacent sunspots. Given the large uncertainties inherent in both the white-light and the magnetic measurements, it remains unclear whether any systematic relationship exists between tilt angle and cycle amplitude during cycles 16-23.

  9. 'Abnormal' angle response curves of TW/Rs for near zero tilt and high tilt channeling implants

    SciTech Connect

    Guo Baonian; Gossmann, Hans-Joachim; Toh, Terry; Colombeau, Benjamin; Todorov, Stan; Sinclair, Frank; Shim, Kyu-Ha; Henry, Todd

    2012-11-06

    Angle control has been widely accepted as the key requirement for ion implantation in semiconductor device processing. From an ion implanter point of view, the incident ion direction should be measured and corrected by suitable techniques, such as XP-VPS for the VIISta implanter platform, to ensure precision ion placement in device structures. So called V-curves have been adopted to generate the wafer-based calibration using channeling effects as the Si lattice steer ions into a channeling direction. Thermal Wave (TW) or sheet resistance (Rs) can be used to determine the minimum of the angle response curve. Normally it is expected that the TW and Rs have their respective minima at identical angles. However, the TW and Rs response to the angle variations does depend on factors such as implant species, dose, and wafer temperature. Implant damage accumulation effects have to be considered for data interpretation especially for some 'abnormal' V-curve data. In this paper we will discuss some observed 'abnormal' angle responses, such as a) TW/Rs reverse trend for Arsenic beam, 2) 'W' shape of Rs Boron, and 3) apparent TW/Rs minimum difference for high tilt characterization, along with experimental data and TCAD simulations.

  10. Aurora at quiet magnetospheric conditions: Repeatability and dipole tilt angle dependence. (Reannouncement with new availability information)

    SciTech Connect

    Oznovich, I.; Eastes, R.W.; Huffman, R.E.; Tur, M.; Glaser, I.

    1993-03-01

    Is there a magnetospheric ground state? Do the position and size of the auroral oval depend on the magnetic dipole tilt angle at quiet magnetospheric conditions? In order to address these questions, northern hemisphere images of the aurora at 1356 A, obtained by Polar BEAR at solar minimum (beginning of 1987), were related to high temporal resolution IMP 8 measurements of the interplanetary magnetic field, to solar wind velocity, and to the ground-based activity index Kp. The first problem was addressed by a two-dimensional correlation study of the repeatability of auroral emissions in corrected geomagnetic space at conditions of minimum energy transfer from the magnetosphere. The correlation measure of auroral images was 0.6--0.85. Error simulations indicate that given the uncertainties in pixel position and intensity, the maximum expected value of the correlation measure is 0.65-0.9. The notion of a ground state magnetosphere is therefore supported by this data. Repeatability was found at the same level regardless of time or reconfigurations of the magnetosphere between images and independent of magnetic time sector. The second problem was addressed by relating latitudinal shifts of the aurora with dipole tilt angle without resorting to auroral boundary specification. The authors data indicate that the latitude of the continuous aurora is related to the dipole tilt angle at quiet magnetospheric conditions. In the winter hemisphere a 10 deg increase in the dipole tilt angle causes a 1 deg decrease (increase) in the latitude of auroral emissions at noon (midnight).

  11. Optimum Strategies for Selecting Descent Flight-Path Angles

    NASA Technical Reports Server (NTRS)

    Wu, Minghong G. (Inventor); Green, Steven M. (Inventor)

    2016-01-01

    An information processing system and method for adaptively selecting an aircraft descent flight path for an aircraft, are provided. The system receives flight adaptation parameters, including aircraft flight descent time period, aircraft flight descent airspace region, and aircraft flight descent flyability constraints. The system queries a plurality of flight data sources and retrieves flight information including any of winds and temperatures aloft data, airspace/navigation constraints, airspace traffic demand, and airspace arrival delay model. The system calculates a set of candidate descent profiles, each defined by at least one of a flight path angle and a descent rate, and each including an aggregated total fuel consumption value for the aircraft following a calculated trajectory, and a flyability constraints metric for the calculated trajectory. The system selects a best candidate descent profile having the least fuel consumption value while the fly ability constraints metric remains within aircraft flight descent flyability constraints.

  12. Evaluation of electrolytic tilt sensors for measuring model angle of attack in wind tunnel tests

    NASA Technical Reports Server (NTRS)

    Wong, Douglas T.

    1992-01-01

    The results of a laboratory evaluation of electrolytic tilt sensors as potential candidates for measuring model attitude or angle of attack in wind tunnel tests are presented. The performance of eight electrolytic tilt sensors was compared with that of typical servo accelerometers used for angle-of-attack measurements. The areas evaluated included linearity, hysteresis, repeatability, temperature characteristics, roll-on-pitch interaction, sensitivity to lead-wire resistance, step response time, and rectification. Among the sensors being evaluated, the Spectron model RG-37 electrolytic tilt sensors have the highest overall accuracy in terms of linearity, hysteresis, repeatability, temperature sensitivity, and roll sensitivity. A comparison of the sensors with the servo accelerometers revealed that the accuracy of the RG-37 sensors was on the average about one order of magnitude worse. Even though a comparison indicates that the cost of each tilt sensor is about one-third the cost of each servo accelerometer, the sensors are considered unsuitable for angle-of-attack measurements. However, the potential exists for other applications such as wind tunnel wall-attitude measurements where the errors resulting from roll interaction, vibration, and response time are less and sensor temperature can be controlled.

  13. Acute angles of head-up tilt do not affect forearm and hand volume.

    PubMed

    Boland, R A; Adams, R D

    2000-01-01

    Physiotherapists utilise the effect of gravity in treatment of conditions associated with increased limb volume. In contrast with knowledge about the relationship between body position and lower limb volume, the effect of body position on arm volume is not well understood. To assess the efficacy of a simple intervention proposed for patients to reduce arm volume during sleep, this study investigated the effects on forearm and hand volume of two hours of head-up tilt in supine at three angles of 8, 11 and 14 degrees. Six asymptomatic subjects were measured at each tilt angle over a three-week period. Data indicated that no angle of head-up lying over a two-hour period was associated with any significant reduction in upper limb volume. PMID:11543301

  14. Unique determination of the -CN group tilt angle in Langmuir monolayers using sum-frequency polarization null angle and phase

    SciTech Connect

    Velarde Ruiz Esparza, Luis A.; Wang, Hongfei

    2013-10-14

    The relative phase and amplitude ratio between the ssp and ppp polarization combinations of the vibrational sum-frequency generation (SFG) response can be uniquely and accurately determined by the polarization null angle (PNA) method. In this report we show that PNA measurements of the -CN vibration in the 4-n pentyl-4'-cyanoterphenyl (5CT) Langmuir monolayer at the air/water interface yields ssp and ppp response of the same phase, while those in the 4-n-octyl-4'cyanobiphenyl (8CB) Langmuir monolayer have the opposite phase. Accordingly, the -CN group in the 5CT monolayer is tilted around 25+/-2 from the interface normal, while that in the 8CB is tilted around 57+/-2, consistent with the significant differences in the phase diagrams and hydrogen bonding SFG spectra of the two Langmuir monolayers as reported in the literature. These results also demonstrate that in SFG studies the relative phase information of the different polarization combinations, especially for the ssp and ppp, is important in the unique determination of the tilt angle and conformation of a molecular group at the interface.

  15. Dipole Tilt Angle Effects on Joule and Particle Heating in the Ionosphere

    NASA Astrophysics Data System (ADS)

    Chun, F. K.; Knipp, D. J.; McHarg, M. G.; Lu, G.; Emery, B. A.

    2002-12-01

    Previous work by Chun et al. [2002] presented spatial distributions of Joule heating as a function of the polar cap (PC) index and the season (summer, equinox, and winter). Noticeable differences in the Joule heating maps were observed with respect to both geomagnetic activity and the season. In this study, we present average patterns of height-integrated Pedersen and Hall conductivity, electric potential, Joule heating, and electron particle heating as a function of PC and dipole tilt angle using 56 days (approximately 12,800 individual patterns) of Assimilative Mapping of Ionospheric Electrodynamics (AMIE) data. We investigate differences in the spatial distributions as well as the hemispheric integrated Joule and particle heating. We also present spatial distributions of the ratios of the Joule to particle heating and the Hall to Pedersen conductance as a function of PC and dipole tilt angle.

  16. A deep-seated mechanism for cycle-dependent sunspot group tilt angles

    NASA Astrophysics Data System (ADS)

    Isik, Emre

    2016-07-01

    The cycle-averaged tilt angle of sunspot groups is an important quantity in determining the magnetic flux diffusing across the equator, which is highly correlated with the strength of the next cycle. This quantity has recently been reported to be anti-correlated with the strength of the solar cycle. I suggest that a deep-seated thermodynamic cycle can be responsible for the observed correlation. Motivated by helioseismic indications, I calculate the effect of cooling of the convective overshoot region on the stability and dynamics of thin, unstable flux tubes. I find that only 5-20 K of cooling in the layer can explain the observed range of tilt angle fluctuations among different cycles. This mechanism can play a role in the nonlinear saturation and amplitude fluctuations of the solar dynamo.

  17. Tilt Angles of Solar Filaments over the Period of 1919 - 2014

    NASA Astrophysics Data System (ADS)

    Tlatov, Andrey G.; Kuzanyan, Kirill M.; Vasil'yeva, Valeria V.

    2016-04-01

    The spatial and temporal distributions of solar filaments were analyzed using data from the Meudon Observatory for the period of 1919 - 2003 and the Kislovodsk Mountain Astronomical Station for the period of 1979 - 2014. We scanned Hα solar synoptic charts on which the filaments were identified and digitized. The data on each filament comprise its location, length, area, and other geometrical characteristics. The temporal distributions of the number and total length of the filaments were obtained. We also found latitudinal migration of filament locations with the solar cycle and analyzed the latitudinal distribution and asymmetry of filaments in the northern and southern hemispheres as well as other properties of their distribution. The tilt angles of filaments with respect to the solar equator (τ) were analyzed. On average, the eastern tips of filaments are closer to the poles than the western ones (τ≈10°). On the other hand, the filaments in the polar regions (latitude |θ|>50°) usually have negative tilts (τ<0°). The tilt angles vary with the phase of the 11-year sunspot cycle and show their highest values in the activity maximum. In the century-long modulation of the solar activity (Gleissberg cycle), the mean tilt angles of filaments in the mid-latitude zone (θ≈±40°) were largest in the middle of the 20th century in Solar Cycles 18 - 19. We hereby propose that these statistical properties of solar filaments can be used as a coherent measure of the solar cycle that covers all latitudes and for which an almost century-long systematically calibrated data series is available.

  18. Evaluation of electrolytic tilt sensors for wind tunnel model angle-of-attack (AOA) measurements

    NASA Technical Reports Server (NTRS)

    Wong, Douglas T.

    1991-01-01

    The results of a laboratory evaluation of three types of electrolytic tilt sensors as potential candidates for model attitude or angle of attack (AOA) measurements in wind tunnel tests are presented. Their performance was also compared with that from typical servo accelerometers used for AOA measurements. Model RG-37 electrolytic tilt sensors were found to have the highest overall accuracy among the three types. Compared with the servo accelerometer, their accuracies are about one order of magnitude worse and each of them cost about two-thirds less. Therefore, the sensors are unsuitable for AOA measurements although they are less expensive. However, the potential for other applications exists where the errors resulting from roll interaction, vibration, and response time are less, and sensor temperature can be controlled.

  19. Effects of the scatter in sunspot group tilt angles on the large-scale magnetic field at the solar surface

    SciTech Connect

    Jiang, J.; Cameron, R. H.; Schüssler, M.

    2014-08-10

    The tilt angles of sunspot groups represent the poloidal field source in Babcock-Leighton-type models of the solar dynamo and are crucial for the build-up and reversals of the polar fields in surface flux transport (SFT) simulations. The evolution of the polar field is a consequence of Hale's polarity rules, together with the tilt angle distribution which has a systematic component (Joy's law) and a random component (tilt-angle scatter). We determine the scatter using the observed tilt angle data and study the effects of this scatter on the evolution of the solar surface field using SFT simulations with flux input based upon the recorded sunspot groups. The tilt angle scatter is described in our simulations by a random component according to the observed distributions for different ranges of sunspot group size (total umbral area). By performing simulations with a number of different realizations of the scatter we study the effect of the tilt angle scatter on the global magnetic field, especially on the evolution of the axial dipole moment. The average axial dipole moment at the end of cycle 17 (a medium-amplitude cycle) from our simulations was 2.73 G. The tilt angle scatter leads to an uncertainty of 0.78 G (standard deviation). We also considered cycle 14 (a weak cycle) and cycle 19 (a strong cycle) and show that the standard deviation of the axial dipole moment is similar for all three cycles. The uncertainty mainly results from the big sunspot groups which emerge near the equator. In the framework of Babcock-Leighton dynamo models, the tilt angle scatter therefore constitutes a significant random factor in the cycle-to-cycle amplitude variability, which strongly limits the predictability of solar activity.

  20. Effects of the Scatter in Sunspot Group Tilt Angles on the Large-scale Magnetic Field at the Solar Surface

    NASA Astrophysics Data System (ADS)

    Jiang, J.; Cameron, R. H.; Schüssler, M.

    2014-08-01

    The tilt angles of sunspot groups represent the poloidal field source in Babcock-Leighton-type models of the solar dynamo and are crucial for the build-up and reversals of the polar fields in surface flux transport (SFT) simulations. The evolution of the polar field is a consequence of Hale's polarity rules, together with the tilt angle distribution which has a systematic component (Joy's law) and a random component (tilt-angle scatter). We determine the scatter using the observed tilt angle data and study the effects of this scatter on the evolution of the solar surface field using SFT simulations with flux input based upon the recorded sunspot groups. The tilt angle scatter is described in our simulations by a random component according to the observed distributions for different ranges of sunspot group size (total umbral area). By performing simulations with a number of different realizations of the scatter we study the effect of the tilt angle scatter on the global magnetic field, especially on the evolution of the axial dipole moment. The average axial dipole moment at the end of cycle 17 (a medium-amplitude cycle) from our simulations was 2.73 G. The tilt angle scatter leads to an uncertainty of 0.78 G (standard deviation). We also considered cycle 14 (a weak cycle) and cycle 19 (a strong cycle) and show that the standard deviation of the axial dipole moment is similar for all three cycles. The uncertainty mainly results from the big sunspot groups which emerge near the equator. In the framework of Babcock-Leighton dynamo models, the tilt angle scatter therefore constitutes a significant random factor in the cycle-to-cycle amplitude variability, which strongly limits the predictability of solar activity.

  1. Optimum angle-cut of collimator for dense objects in high-energy proton radiography

    NASA Astrophysics Data System (ADS)

    Hai-Bo, Xu; Na, Zheng

    2016-02-01

    The use of minus identity lenses with an angle-cut collimator can achieve high contrast images in high-energy proton radiography. This article presents the principles of choosing the angle-cut aperture of the collimator for different energies and objects. Numerical simulation using the Monte Carlo code Geant4 has been implemented to investigate the entire radiography for the French test object. The optimum angle-cut apertures of the collimators are also obtained for different energies. Supported by NSAF (11176001) and Science and Technology Developing Foundation of China Academy of Engineering Physics (2012A0202006)

  2. Solar heat gain coefficient of complex fenestrations with a venetian blind for differing slat tilt angles

    SciTech Connect

    Klems, J.H.; Warner, J.L.

    1996-08-01

    Measured bidirectional transmittances and reflectances of a buff-colored venetian blind together with a layer calculation scheme developed in previous publications are utilized to produce directional-hemispherical properties for the venetian blind layer and solar heat gain coefficients for the blind in combination with clear double glazing. Results are presented for three blind slat tilt angles and for the blind mounted either interior to the double glazing or between the glass panes. Implications of the results for solar heat gain calculations are discussed in the context of sun positions for St. Louis, MO.

  3. VizieR Online Data Catalog: Sunspot areas and tilt angles (Senthamizh Pavai+, 2015)

    NASA Astrophysics Data System (ADS)

    Senthamizh Pavai, V.; Arlt, R.; Dasi-Espuig, M.; Krivova, N.; Solanki, S.

    2015-11-01

    We present sunspot positions and areas from historical observations of sunspots by Samuel Heinrich Schwabe from Dessau, Germany. He has recorded his observations of sunspots from 1825-1867 as drawings in small circles of about 5cm diameter (representing the solar disk). Even though he has used quite a number of telescopes for his observations, the majority of the full-disk drawings were made with a 3-1/2-foot telescope from Fraunhofer. His observing log books are stored in the library of the Royal Astronomical Society in London. Those drawings were digitized photographically with a resolution of 2912x4378 pixels per page. The sizes and positions of the sunspots were measured using a dozen of circular mouse cursor shapes with different diameters. The sunspot sizes in Schwabe's drawings are not to scale and need to be converted into physical sunspot areas. We employed a statistical approach assuming that the area distribution of sunspots was the same in the 19th century as it was in the 20th century. Umbral areas for about 130,000 sunspots observed by Schwabe were obtained, as well as the tilt angles of sunspot groups assuming them to be bipolar (two or more spots). There is, of course, no polarity information in the observations. Both an updated sunspot database and a tilt angle database are available at http://www.aip.de/Members/rarlt/ sunspots for further study. (2 data files).

  4. Correlation between Lamina Cribrosa Tilt Angles, Myopia and Glaucoma Using OCT with a Wide Bandwidth Femtosecond Mode-Locked Laser

    PubMed Central

    Shoji, Takuhei; Kuroda, Hiroto; Suzuki, Masayuki; Baba, Motoyoshi; Hangai, Masanori; Araie, Makoto; Yoneya, Shin

    2014-01-01

    Purpose To measure horizontal and vertical lamina cribrosa (LC) tilt angles and investigate associated factors using prototype optical coherence tomography (OCT) with a broad wavelength laser light source. Design Cross sectional study. Methods Twenty-eight no glaucoma eyes (from 15 subjects) and 25 glaucoma eyes (from 14 patients) were enrolled. A total of 300 optic nerve head B-scans were obtained in 10 µm steps and the inner edge of Bruch's membrane opening (BMO) was identified as the reference plane. The vertical and horizontal angles between BMO line and approximate the best-fitting line for the surface of the LC were measured and potential associated factors were estimated with univariate and multivariate logistic regression analyses. Results The median (interquartile range) horizontal and vertical tilt angles were 7.10 (2.43–11.45) degrees and 4.15 (2.60–6.85) degrees in eyes without glaucoma and 8.50 (4.40–14.10) degrees and 9.30 (6.90–14.15) degrees in glaucoma eyes, respectively. The refractive errors had a statistically significant association with horizontal LC tilt angles (coefficients, −1.53 per diopter) and glaucoma had a significant correlation with vertical tilt angles (coefficients, 6.56) using multiple logistic regression analysis (p<0.001). Conclusions OCT allowed evaluation of the internal tilting of the LC compared with the BMO. The horizontal internal LC tilt angle was correlated with refractive errors, corresponding to myopic physiological changes, and vertical internal LC tilt was correlated with glaucoma, corresponding to glaucomatous pathological changes. These parameters have important implications for investigation of the correlation between myopia, glaucoma and LC morphological features. PMID:25551632

  5. A literature review on optimum and preferred joint angles in automotive sitting posture.

    PubMed

    Schmidt, Susanne; Amereller, Maximilian; Franz, Matthias; Kaiser, Ralf; Schwirtz, Ansgar

    2014-03-01

    In this study, a survey of the scientific literature in the field of optimum and preferred human joint angles in automotive sitting posture was conducted by referring to thirty different sources published between 1940 and today. The strategy was to use only sources with numerical angle data in combination with keywords. The aim of the research was to detect commonly used joint angles in interior car design. The main analysis was on data measurement, usability and comparability of the different studies. In addition, the focus was on the reasons for the differently described results. It was found that there is still a lack of information in methodology and description of background. Due to these reasons published data is not always usable to design a modern ergonomic car environment. As a main result of our literature analysis we suggest undertaking further research in the field of biomechanics and ergonomics to work out scientific based and objectively determined "optimum" joint angles in automotive sitting position. PMID:23664245

  6. The effect of electrode tilt angle on the characteristics of coplanar dielectric barrier discharges with Xe-Ne mixtures

    NASA Astrophysics Data System (ADS)

    Shim, Seung Bo; Song, In Cheol; Lee, Ho-Jun; Lee, Hae June

    2011-07-01

    The results of a two-dimensional fluid simulation of a plasma display panel (PDP) cell show that the discharge characteristics of a coplanar dielectric barrier discharge can be controlled by the electrode tilt angle rather than by the gas mixture ratio or gap distance. The change in the tilt angle results in a significant change in the wall charge distribution and the discharge duration for each pulse. Therefore, the breakdown voltage, plasma density, light brightness, and luminous efficacy can be controlled by the tilt angle. A concave electrode structure allows large wall charge accumulation near the outer edge of two coplanar electrodes, and it results in a long-duration discharge, high luminance, and high luminous efficacy. On the other hand, a convex electrode structure allows high wall charge accumulation near the gap between two coplanar electrodes, and it results in a short-duration discharge with a decreased breakdown voltage.

  7. Response properties of gerbil otolith afferents to small angle pitch and roll tilts

    NASA Technical Reports Server (NTRS)

    Dickman, J. D.; Angelaki, D. E.; Correia, M. J.

    1991-01-01

    The responses from isolated single otolith afferent fibers were obtained to small angle sinusoidal pitch and roll tilts in anesthetized gerbils. The stimulus directions that produced the maximum (response vector) and minimum response sensitivities were determined for each otolith afferent, with response vectors for the units being spread throughout the horizontal plane, similar to those reported for other species. A breadth of tuning measure was derived, with narrowly tuned neurons responding maximally to stimulation in one direction and minimally along an orthogonal ('null') direction. Most (approximately 80%) otolith afferents are narrowly tuned, however, some fibers were broadly tuned responding significantly to stimulations in any direction in the horizontal plane. The number of broadly tuned otolith afferents (approximately 20%) differs significantly from the more substantial number of broadly tuned vestibular nuclei neurons (88%) recently reported in rats.

  8. Finite Temperature Response of a 2D Dipolar Bose Gas at Different Dipolar Tilt Angles

    NASA Astrophysics Data System (ADS)

    Shen, Pengtao; Quader, Khandker

    We calculate finite temperature (T) response of a 2D Bose gas, subject to dipolar interaction, within the random phase approximation (RPA). We evaluate the appropriate 2D finite-T pair bubble diagram needed in RPA, and explore ranges of density and temperature for various dipolar tilt angles. We find the system to exhibit a collapse transition and a finite momentum instability, signaling a density wave or striped phase. We construct phase diagrams depicting these instabilities and resulting phases, including a normal Bose gas phase. We also consider the finite-T response of a quasi-2D dipolar Bose gas. We discuss how our results may apply to ultracold dense Bose gas of polar molecules, such as 41K87Rb, that has been realized experimentally. Acknowledge partial support from Institute for Complex Adaptive Matter (ICAM).

  9. Altitude and airspeed effects on the optimum synchrophase angles for a four-engine propeller aircraft

    NASA Astrophysics Data System (ADS)

    Blunt, David M.

    2014-08-01

    Noise and vibration is a serious problem in all types of aircraft. Any techniques that lower cabin noise and vibration levels by even a few decibels with little or no weight or performance penalties are worth pursuing. Propeller synchrophasing is one such technique that has shown potential in aircraft with two or more propellers; however this technique is not being used to its full potential because the synchrophase angles are typically fixed. This paper provides a detailed examination of how the optimum synchrophase angles in a typical four-engine propeller aircraft vary with different altitudes and airspeeds, and how this information could lead to the design of new adaptive propeller synchrophasing systems and potentially yield improvements to other active noise control measures in propeller aircraft.

  10. Simultaneous piston position and tilt angle sensing for large vertical displacement micromirrors by frequency detection inductive sensing

    NASA Astrophysics Data System (ADS)

    Tseng, V. F.-G.; Xie, H.

    2015-11-01

    This paper presents a frequency detection based inductive eddy current sensing mechanism to simultaneously sense the piston position and tilt angle of the mirror plate of large vertical displacement micromirrors that exhibit piston scan ranges above 100 μm. This is accomplished by sensing the inductance change, and thus resonant frequency shift, of two microfabricated sensing coils packaged underneath the mirror plate. For demonstration purpose, the coils were paired with discrete circuit components to oscillate at 11.9 MHz and 12.5 MHz, respectively. The piston position and tilt angle of the mirror plate could be simultaneously monitored over a 500 μm piston scan range, achieving a maximum piston sensitivity of 4.15 kHz/μm with a piston sensing resolution of 96 nm and a maximum tilt angle sensitivity of 60.5 kHz/° with a tilt angle sensing resolution of 0.0013°. Analytical modeling of the coil inductance change via image theory was also conducted, showing that the sensor sensitivity and resolution could be improved by increasing the coil oscillation frequency and decreasing the coil size.

  11. Development of intelligent model to determine favorable wheelchair tilt and recline angles for people with spinal cord injury.

    PubMed

    Fu, Jicheng; Jan, Yih-Kuen; Jones, Maria

    2011-01-01

    Machine-learning techniques have found widespread applications in bioinformatics. Such techniques provide invaluable insight on understanding the complex biomedical mechanisms and predicting the optimal individualized intervention for patients. In our case, we are particularly interested in developing an individualized clinical guideline on wheelchair tilt and recline usage for people with spinal cord injury (SCI). The current clinical practice suggests uniform settings to all patients. However, our previous study revealed that the response of skin blood flow to wheelchair tilt and recline settings varied largely among patients. Our finding suggests that an individualized setting is needed for people with SCI to maximally utilize the residual neurological function to reduce pressure ulcer risk. In order to achieve this goal, we intend to develop an intelligent model to determine the favorable wheelchair usage to reduce pressure ulcers risk for wheelchair users with SCI. In this study, we use artificial neural networks (ANNs) to construct an intelligent model that can predict whether a given tilt and recline setting will be favorable to people with SCI based on neurological functions and SCI injury history. Our results indicate that the intelligent model significantly outperforms the traditional statistical approach in accurately classifying favorable wheelchair tilt and recline settings. To the best of our knowledge, this is the first study using intelligent models to predict the favorable wheelchair tilt and recline angles. Our methods demonstrate the feasibility of using ANN to develop individualized wheelchair tilt and recline guidance for people with SCI. PMID:22254738

  12. Determination of Optimum Viewing Angles for the Angular Normalization of Land Surface Temperature over Vegetated Surface

    PubMed Central

    Ren, Huazhong; Yan, Guangjian; Liu, Rongyuan; Li, Zhao-Liang; Qin, Qiming; Nerry, Françoise; Liu, Qiang

    2015-01-01

    Multi-angular observation of land surface thermal radiation is considered to be a promising method of performing the angular normalization of land surface temperature (LST) retrieved from remote sensing data. This paper focuses on an investigation of the minimum requirements of viewing angles to perform such normalizations on LST. The normally kernel-driven bi-directional reflectance distribution function (BRDF) is first extended to the thermal infrared (TIR) domain as TIR-BRDF model, and its uncertainty is shown to be less than 0.3 K when used to fit the hemispheric directional thermal radiation. A local optimum three-angle combination is found and verified using the TIR-BRDF model based on two patterns: the single-point pattern and the linear-array pattern. The TIR-BRDF is applied to an airborne multi-angular dataset to retrieve LST at nadir (Te-nadir) from different viewing directions, and the results show that this model can obtain reliable Te-nadir from 3 to 4 directional observations with large angle intervals, thus corresponding to large temperature angular variations. The Te-nadir is generally larger than temperature of the slant direction, with a difference of approximately 0.5~2.0 K for vegetated pixels and up to several Kelvins for non-vegetated pixels. The findings of this paper will facilitate the future development of multi-angular thermal infrared sensors. PMID:25825975

  13. Eye movements and motion perception induced by off-vertical axis rotation (OVAR) at small angles of tilt after spaceflight

    NASA Technical Reports Server (NTRS)

    Clement, G.; Darlot, C.; Petropoulos, A.; Berthoz, A.

    1995-01-01

    The nystagmus and motion perception of two astronauts were recorded during Earth-vertical axis rotation and during off-vertical axis rotation (OVAR) before and after 7 days of spaceflight. Postflight, the peak velocity and duration of per- and postrotatory nystagmus during velocity steps about the Earth-vertical axis were the same as preflight values. During OVAR at constant velocity (45/s, tilt angles successively 5, 10, and 15 degrees), the mean horizontal slow-phase eye velocity (bias), produced by the 'velocity storage mechanism' in the vestibular system, and the peak-to-peak amplitude (modulation) in horizontal eye velocity and position, generated from the output of otolith afferents, were also the same before as after flight. There were, however, changes in the vertical eve position and in the perceived body motion during OVAR. The angle of the perceived body path described as a cone was larger in both astronauts postflight. One astronaut experienced either a large cone angle with its axis upright, or a smaller cone angle with its axis tilted backwards, accompanied by an upward vertical eye drift. These results suggest an increase in the sensitivity of the otolithic system after spaceflight and a longer period of readaptation to Earth's gravity for otolith-induced responses than for canal-induced responses. Our data support the hypothesis that just after spaceflight the CNS generally interprets changes in the otolith signals to be due to translation rather than to tilt.

  14. Theoretical and experimental analysis of scan angle-depending pulse front tilt in optical systems for laser scanners

    NASA Astrophysics Data System (ADS)

    Büsing, Lasse; Bonhoff, Tobias; Behnke, Lars; Stollenwerk, Jochen; Loosen, Peter

    2016-02-01

    For realising fast and highly dynamical laser-based material processing, scanner systems are already utilised for many different industrial applications. Furthermore, ultra-short pulsed (<1 ps) laser sources provide possibilities of processing most different materials with highest accuracy. Owing to the large spectral bandwidth of ultra-short laser pulses, dispersion in optical components becomes relevant. The dispersion in optical systems for laser scanners may lead to scan angle-depending pulse properties as, for example, pulse front tilt. The investigation of these effects is not state of the art today but absolutely necessary to exploit the full potential of laser scanners for ultra-short pulse applications. By means of an exemplary focusing lens, the simulation and experimental analysis of scan angle-depending pulse front tilt is presented for the first time.

  15. Intermediate pre-tilt angle control by a composite alignment thin film structure for liquid crystal displays.

    PubMed

    Wu, G M; Chien, H W; Huang, J W; Zeng, H L

    2010-04-01

    We designed a patterned composite alignment thin film structure using a horizontal alignment polyimide (PI) layer and vertical alignment liquid crystal polymer (LCP) pillars. The LCP polymer precursor concentration was varied at 0-10% and the pillars were introduced by a photolithography process. Both single-sided and double-sided liquid crystal display cells were assembled for a series of electro-optical characterization techniques. The horizontal PI alignment layer alone had a designated control of the pre-tilt angle of 7 degrees after the prescribed mechanical rubbing process. The pre-tilt angle was improved to 24 degrees when the LCP precursor concentration was 5%. It was further increased to 61 degrees at the concentration of 10%. In addition, the study on the electrical response time and gray level variation demonstrated promising results for potential applications. The field-on response time was only 2.79 ms and the field-off response time was 0.35 ms for the double-sided liquid crystal display cells using a ramping voltage of 5.5 V. The effective control of the cell pre-tilt angle suggested that the display power consumption and response time would be greatly improved. PMID:20208122

  16. Investigations on the Effects of the Tool Material, Geometry, and Tilt Angle on Friction Stir Welding of Pure Titanium

    NASA Astrophysics Data System (ADS)

    Reshad Seighalani, K.; Besharati Givi, M. K.; Nasiri, A. M.; Bahemmat, P.

    2010-10-01

    Friction stir welding (FSW) parameters, such as tool material, tool geometry, tilt angle, tool rotational speed, welding speed, and axial force play a major role in the weld quality of titanium alloys. Because of excessive erosion, tool material and geometry play the main roles in FSW of titanium alloys. Therefore, in the present work for the first time, tool material and geometry, tool tilt angle, cooling system and shielding gas effects on macrostructure, microstructure, and mechanical properties of pure titanium weld joint were investigated. Result of this research shows that Ti can be joined by the FSW, using a tool with a shoulder made of tungsten (W) and simple pin made of tungsten carbide (WC). The best conditions for welding were use of compressed air as a cooling system, tool tilt angle of 1°, and a stream of Argon as a shielding medium. Investigation on mechanical properties shows that the tensile strength and the yield strength of the welded joint in the best case could be similar to the corresponding strengths of the base metal.

  17. Effects of tilt angle of mirror-lamp system on shape of solid-liquid interface of silicon melt during floating zone growth using infrared convergent heating

    NASA Astrophysics Data System (ADS)

    Hossain, Md. Mukter; Watauchi, Satoshi; Nagao, Masanori; Tanaka, Isao

    2016-01-01

    The tilt effects of the mirror-lamp (M-L) system on the shape of the interface of the silicon molten zone formed during growth using the infrared convergent heating floating zone method were studied at various positions of the M-L system. The stability and the interfaces of the molten zone formed in the tilted condition were compared with those in the no tilt condition. The molten zone appeared to be more stabilized in the tilted condition than in the no tilt condition. However, the conventional parameters characterizing the interface shape such as convexities (h/r), gap and zone length (L) were almost independent of the tilt angle (θ) of the M-L system and insufficient to discuss the tilting effects on the molten zone shape. The curvature of the solid-liquid interface was affected by the θ. New characterizing parameters such as the growth interface and triple point angles (δ and TPA, respectively) were effective to quantitatively describe the tilting effects on the interface shape. With increase of the θ, the δ was decreased and the TPA was increased in both the feed and crystal sides. A silicon crystal of 45 mm in diameter was grown successfully in the tilted condition.

  18. Grain boundary segregation in {l_angle}110{r_angle} symmetrical tilt bicrystals of an Fe-3%Si alloy

    SciTech Connect

    Yoshitomi, Y.; Suzuki, S.; Tsurekawa, S.; Nakashima, H.; Yoshinaga, H.

    1995-04-01

    Grain oriented silicon steel is characterized by the presence of a sharp {l_brace}110{r_brace} <001> texture, which is produced by secondary recrystallization. It has been pointed out that, in an Fe-3%Si alloy in which there were precipitates, the evolution of {l_brace}110{r_brace}<001> texture is associated with the special grain boundary migration characteristics of {Sigma}9 type coincidence boundaries. It has also been reported that, in Fe-3%Si alloys in which there were precipitates, evolutions of {l_brace}110{r_brace}<111>, {l_brace}110{r_brace}<227>, {l_brace}100{r_brace}<001> textures are associated with the special grain boundary migration characteristics of {Sigma}9, {Sigma}5 and {Sigma}7 type coincidence boundaries, respectively. On the other hand, auger electron spectroscopy has been used to investigate grain boundary segregation in <100> symmetrical tilt bicrystals of Fe-Si alloys containing phosphorus and carbon. The results showed that phosphorus and carbon segregated at grain boundaries. Segregation of silicon was not observed, probably because the segregation of phosphorus and carbon dominated at grain boundaries. In order to make the basic background of the selective grain boundary migration clear, the present authors have investigated the grain boundary segregation in Fe-3%Si alloys with <110> symmetric tilt-boundaries, using Auger electron spectroscopy. In this study, {Sigma}9 coincidence boundaries and general boundaries were prepared for the investigation.

  19. Burner tilting angle effect on velocity profile in 700 MW Utility Boiler

    NASA Astrophysics Data System (ADS)

    Munisamy, K. M.; Yusoff, M. Z.; Thangaraju, S. K.; Hassan, H.; Ahmad, A.

    2015-09-01

    700 MW of utility boiler is investigated with manipulation of inlet burner angle. Manipulation of burner titling angle is an operational methodology in controlling rear pass temperature in utility boilers. The rear pass temperature unbalance between right and left side is a problem caused by fouling and slagging of the ash from the coal fired boilers. This paper presents the CFD investigation on the 0° and -30° of the burner angle of the utility boiler. The results focusing on the velocity profile. The design condition of 0° burner firing angle is compared with the off-design burner angle -30° which would be the burner angle to reduce the rear pass temperature un-balance by boiler operators. It can be concluded that the -30° burner angle reduce the turbulence is fire ball mixing inside the furnace. It also shift the fire ball position in the furnace to reduce the rear pass temperature.

  20. A relaxation of tilt angle in a ferroelectric liquid crystal studied by time-resolved FT-IR

    NASA Astrophysics Data System (ADS)

    Matsumoto, T.; Sakaguchi, K.; Yasuda, A.; Ozaki, Y.

    1998-06-01

    Polarization angle dependences of infrared (IR) and time-resolved IR have been measured for a FLC mixture containing 20% cis-(2R,4R)-γ-butyrolactone 1 (YK230C) as a chiral dopant and 80% 5-octyl-2-(4-nonyloxyphenyl) pyrimidine (ONPP) as a nonchiral smectic base LC. These measurements and the measurements of the dichroic ratios of IR bands show that the apparent tilt angle and dichroic ratio in the dynamic state are larger than those in the static state. It seemed therefore that the order of the orientation is higher in the dynamic state than in the static state. In order to confirm the higher orientation order in the dynamic state, we performed time-resolved IR measurements of the FLC mixture for the delay time ranging from 0 to 500μs, which is much longer than the response time. The relaxation process was clearly observed after the response time.

  1. Precipitation of low energy electrons at high latitudes: Effects of substorms, interplanetary magnetic field and dipole tilt angle

    NASA Technical Reports Server (NTRS)

    Burch, J. L.

    1972-01-01

    Data from the auroral particles experiment on OGO-4 were used to study effects of substorm activity, interplanetary magnetic field latitutde, and dipole tilt angle on high-latitude precipitation of 700 eV electrons. It was found that: (1) The high-latitude zone of 700 eV electron precipitation in late evening and early morning hours moves equatorward by 5 to 10 deg during substorms. (2) The low-latitude boundary of polar cusp electron precipitation at 9 to 15 hours MLT also moves equatorward by several degrees during substorms and, in the absence of significant substorm activity, after a period of southward interplanetary magnetic field. (3) With times containing substorm activity or a southward interplanetary magnetic field eliminated, the low-latitude boundary of polar cusp electron precipitation is found to move by approximately 4 deg over the total yearly range of tilt angles. At maximum winter and summer conditions the invariant latitude of the boundary is shown to shift by approximately -3 deg and +1 deg respectively from its equinox location.

  2. Effect of wearing tight pants on the trunk flexion and pelvic tilting angles in the stand-to-sit movement and a seated posture

    PubMed Central

    Yoo, Won-gyu

    2016-01-01

    [Purpose] The purpose of this study was to evaluate the effect of wearing the tight pants on the trunk flexion and pelvic tilting angles in the stand-to-sit movement and a seated posture. [Subjects] Nine male subjects were recruited. [Methods] The trunk flexion angle and pelvic posterior tilting angle were measured using a motion-capture system during the stand-to-sit movement and in a seated posture. [Results] The trunk flexion and the posterior pelvic tilting angles during the stand-to-sit movement and in the seated posture when wearing tight pants significantly increased compared with those when wearing of general pants. [Conclusion] Therefore, wearing tight pants could produce musculoskeletal disorders via abnormal movement and posture in the lumbar spine and pelvis. So the effects of wearing tight pants need to be investigated in further studies to reveal their direct relationship to musculoskeletal problems. PMID:26957736

  3. Effect of Wheelchair Tilt-In-Space and Recline Angles on Skin Perfusion Over the Ischial Tuberosity in People With Spinal Cord Injury

    PubMed Central

    Jan, Yih-Kuen; Jones, Maria A.; Rabadi, Meheroz H.; Foreman, Robert D.; Thiessen, Amy

    2010-01-01

    Objective To investigate the efficacy of wheelchair tilt-in-space and recline on enhancing skin perfusion over the ischial tuberosity in wheelchair users with spinal cord injury (SCI). Design Repeated measures, intervention and outcomes measure design. Setting A university research laboratory. Participants 11 wheelchair users with SCI (9 men, 2 women; mean age ± standard deviation, 37.7±14.2 years; body mass index 24.7±2.6 kg/m2; and duration of injury 8.1±7.5 years). Interventions 6 protocols of various wheelchair tilt-in-space and recline angles were randomly assigned to the participants. Each protocol consisted of a 5-min sitting-induced ischemic period and a 5-min wheelchair tilt-in-space and recline pressure relieving period. A participant sat in a position without tilt or recline for 5 minutes and then sat in one of 6 wheelchair tiled and reclined positions, including (1) 15° tilt-in-space and 100° recline, (2) 25° tilt-in-space and 100° recline, (3) 35° tilt-in-space and 100° recline, (4) 15° tilt-in-space and 120° recline, (5) 25° tilt-in-space and 120° recline, and (6) 35° tilt-in-space and 120° recline. A 5-min washout period (at 35° tilt-in-space and 120° recline) was allowed between protocols. Main Outcome Measures Laser Doppler flowmetry was used to measure skin perfusion over the ischial tuberosity in response to the changes of body positions caused by performing wheelchair tilt-in-space and recline. Skin perfusion response to wheelchair tilt-in-space and recline was normalized to skin perfusion of the upright seated position (no tilt/recline). Results When combined with 100° recline, wheelchair tilt-in-space at 35° resulted in a significant increase in skin perfusion as compared with upright seated position (no tilt/recline) (p<0.05), while there was no significant increase in skin perfusion at 15° and 25° tilt-in-space( non significance). When combined with 120° recline, wheelchair tilt-in-space at 15°, 25°, and 35° tilt

  4. Ultra-sensitive angle sensor based on laser autocollimation for measurement of stage tilt motions.

    PubMed

    Shimizu, Yuki; Tan, Siew Leng; Murata, Dai; Maruyama, Taiji; Ito, So; Chen, Yuan-Liu; Gao, Wei

    2016-02-01

    An ultra-sensitive angle sensor employing single-cell photodiodes, which allows tighter focusing leading to a higher angular resolution better than 0.001 arc-second, has been designed based on laser autocollimation. Aiming to investigate the influences of spherical aberrations in the optical system on the sensor sensitivity, an optical model has been established based on wave optics. Computer simulation has been carried out by using the model, and its feasibility has been verified in experiments. In addition, a prototype optical angle sensor has been designed in a compact size of 100 mm × 150 mm, and its measurement resolution has been verified in experiments. PMID:26906848

  5. Effect of Tilt Angle on the Morphology of SiC Epitaxial Films Grown on Vicinal (0001) SiC Substrates

    NASA Technical Reports Server (NTRS)

    Powell, J. A.; Larkin, D. J.; Abel, P. B.; Zhou, L.; Pirouz, P.

    1996-01-01

    In this study of 4H-SiC and 6H-SiC epitaxial films we found that film morphology was strongly dependent on the tilt angle of the substrate. Large surface steps (up to 25 nm high) due to step bunching were more prevalent at smaller tilt angles. Also, 4H films were more susceptible than 6H to 3C-SiC inclusions during growth. The lateral growth of steps from screw dislocations in low-tilt-angle substrates demonstrated that step bunching on the atomic scale was anisotropic with respect to growth direction for both 4H-SiC and 6H-SiC. A model explaining this behavior is presented. We observed and directly measured the Burgers vector of a 'super' screw dislocation in a 6H-SiC epilayer.

  6. Deposition temperature mediated tunable tilt angle magnetization in Co-Pt/Ni81Fe19 exchange springs

    NASA Astrophysics Data System (ADS)

    Saravanan, P.; Hsu, Jen-Hwa; Tsai, C. L.; Lee, C.-M.

    2015-05-01

    In this study, we investigate the effect of deposition temperature of Co-Pt fixed layer, Td,CoPt (150, 250 and 350 °C) on the tilt angle magnetization (θM) of Ni81Fe19-layer grown at room temperature (RT) and at different thicknesses (tNiFe=0, 1.0, 2.5 and 4.0 nm) in Co-Pt(Td,CoPt)/NiFe(tNiFe) exchange springs. The magnetic studies demonstrated a strong perpendicular magnetic anisotropy (PMA) for the equi-compositional ordered Co-Pt layer grown on glass substrate using the film sequence: Ta(20 nm)/Pt(20 nm)/CoPt(5 nm), regardless of Td,CoPt. The PMA can be retained with the addition of a 4-nm NiFe layer on the top when Td,CoPt≥250 °C. In contrast, relatively a thin layer of Ni-Fe (2.5 nm) can destroy the perpendicular exchange-spring behavior if the Co-Pt layer is deposited at RT. Using 3-D micromagnetic simulation, the interfacial exchange coupling strength (Aij) between the Co-Pt and NiFe-layers was estimated and the Aij value is found to increase rapidly when Td,CoPt is increased from RT to 300 °C. Besides, the magnetization tilted angle (θM) of NiFe can be easily tuned from completely out-of-plane to almost 60° when tNiFe=4.0 nm. Through this study, it is demonstrated that the θM of NiFe-layer can be tuned by not only altering the tNiFe; but also by varying the Td,CoPt.

  7. Three-dimensional evaluation of gettering ability for oxygen atoms at small-angle tilt boundaries in Czochralski-grown silicon crystals

    SciTech Connect

    Ohno, Yutaka Inoue, Kaihei; Fujiwara, Kozo; Deura, Momoko; Kutsukake, Kentaro; Yonenaga, Ichiro; Shimizu, Yasuo; Inoue, Koji; Ebisawa, Naoki; Nagai, Yasuyoshi

    2015-06-22

    Three-dimensional distribution of oxygen atoms at small-angle tilt boundaries (SATBs) in Czochralski-grown p-type silicon ingots was investigated by atom probe tomography combined with transmission electron microscopy. Oxygen gettering along edge dislocations composing SATBs, post crystal growth, was observed. The gettering ability of SATBs would depend both on the dislocation strain and on the dislocation density. Oxygen atoms would agglomerate in the atomic sites under the tensile hydrostatic stress larger than about 2.0 GPa induced by the dislocations. It was suggested that the density of the atomic sites, depending on the tilt angle of SATBs, determined the gettering ability of SATBs.

  8. Liquid-crystal variable-focus lenses with a spatially-distributed tilt angles.

    PubMed

    Honma, Michinori; Nose, Toshiaki; Yanase, Satoshi; Yamaguchi, Rumiko; Sato, Susumu

    2009-06-22

    A pretilt angle controlling method by the density of rubbings using a tiny stylus is proposed. The control of the surface pretilt angle is achieved by rubbing a side-chain type polyimide film for a homeotropic alignment. Smooth liquid crystal (LC) director distribution in the bulk layer is successfully obtained even though the rough surface orientation. This approach is applied to LC cylindrical and rectangular lenses with a variable-focusing function. The distribution profile of the rubbing pitch (the reciprocal of the rubbing density) for small aberration is determined to be quadratic. The variable focusing function is successfully achieved in the LC rectangular lens, and the voltage dependence of the focal length is tried to be explained by the LC molecular reorientation behavior. PMID:19550499

  9. Influences of solid/liquid boundary layer thickness and tilting angle on zone-refinement of germanium crystals

    NASA Astrophysics Data System (ADS)

    Yang, Gang; Guan, Yutong; Mei, Hao; Wang, Guojian; Mei, Dongming

    In zone-refining of metals, solid/liquid (S/L) boundary layer thickness has an influence on segregation coefficient of impurity atoms. Additionally, the segregation of impurity elements during zone refining can be maximized by adjusting the zone refinement tube with a proper angle. In this paper, we report the influences of S/L boundary layer thickness on the segregation coefficients of boron, phosphor, aluminum and gallium, which have been identified as four main impurities in germanium crystal by Photothermal Ionization Spectroscopy (PTIS). The thickness of S/L boundary layer was found by using a well-known model to fit the experimental data. The optimized segregation coefficients have been used to calculate the impurity distribution along the purified ingot. In addition, we have also optimized the tilting angle of the germanium ingot to investigate the impact on the segregation. This work is supported by DOE grant DE-FG02-10ER46709 and the state of South Dakota.

  10. Vortex flow structures and interactions for the optimum thrust efficiency of a heaving airfoil at different mean angles of attack

    NASA Astrophysics Data System (ADS)

    Martín-Alcántara, A.; Fernandez-Feria, R.; Sanmiguel-Rojas, E.

    2015-07-01

    The thrust efficiency of a two-dimensional heaving airfoil is studied computationally for a low Reynolds number using a vortex force decomposition. The auxiliary potentials that separate the total vortex force into lift and drag (or thrust) are obtained analytically by using an elliptic airfoil. With these auxiliary potentials, the added-mass components of the lift and drag (or thrust) coefficients are also obtained analytically for any heaving motion of the airfoil and for any value of the mean angle of attack α. The contributions of the leading- and trailing-edge vortices to the thrust during their down- and up-stroke evolutions are computed quantitatively with this formulation for different dimensionless frequencies and heave amplitudes (Stc and Sta) and for several values of α. Very different types of flows, periodic, quasi-periodic, and chaotic described as Stc, Sta, and α, are varied. The optimum values of these parameters for maximum thrust efficiency are obtained and explained in terms of the interactions between the vortices and the forces exerted by them on the airfoil. As in previous numerical and experimental studies on flapping flight at low Reynolds numbers, the optimum thrust efficiency is reached for intermediate frequencies (Stc slightly smaller than one) and a heave amplitude corresponding to an advance ratio close to unity. The optimal mean angle of attack found is zero. The corresponding flow is periodic, but it becomes chaotic and with smaller average thrust efficiency as |α| becomes slightly different from zero.

  11. Tilted bulk heterojunction organic photovoltaic cells grown by oblique angle deposition

    NASA Astrophysics Data System (ADS)

    Li, Ning; Forrest, Stephen R.

    2009-09-01

    We demonstrate small molecule bulk heterojunction organic photovoltaic cells using oblique angle vacuum deposition. Obliquely deposited donor chloroaluminum phthalocyanine (ClAlPc) films on indium tin oxide have surface feature sizes of ˜30 nm, resulting in ClAlPc/C60 donor-acceptor heterojunctions (HJs) with approximately twice the interface area of HJs grown at normal incidence. This results in nearly twice the external quantum efficiency in the ClAlPc absorption band compared with analogous, planar HJs. The efficiency increase is attributed to the increased surface area presented by the donor-acceptor junction to the incident illumination by ClAlPc protrusions lying obliquely to the substrate plane formed during deposition. The power conversion efficiency improves from (2.0±0.1)% to (2.8±0.1)% under 1 sun, AM 1.5G simulated solar illumination. Similarly, the power efficiency of copper phthalocyanine/C60 organic photovoltaic cells is increased from (1.3±0.1)% to (1.7±0.1)%.

  12. Electro-optic response of the anticlinic, antiferroelectric liquid-crystal phase of a biaxial bent-core molecule with tilt angle near 45∘.

    PubMed

    Nakata, Michi; Chen, Dong; Shao, Renfan; Korblova, Eva; Maclennan, Joseph E; Walba, David M; Clark, Noel A

    2012-03-01

    We describe the unusual electro-optic response of a biaxial bent-core liquid crystal molecule that exhibits an anticlinic, antiferroelectric smectic phase (Sm-C(A)P(A)) with a molecular tilt angle close to 45°. In the ground state, the sample shows very low birefringence. A weak applied electric field distorts the antiferroelectric ground state, inducing a small azimuthal reorientation of the molecules on the tilt cone. This results in only a modest increase in the birefringence but an anomalously large (∼40°) analog rotation of the extinction direction. This unusual electro-optic response is shown to be a consequence of the molecular biaxiality. PMID:22587111

  13. Bioinspired tilt-angle fabricated structure gradient fibers: micro-drops fast transport in a long-distance

    NASA Astrophysics Data System (ADS)

    Chen, Yuan; Wang, Lin; Xue, Yan; Jiang, Lei; Zheng, Yongmei

    2013-10-01

    Issues of surfaces, e.g., inspired from beetle's back, spider silk, cactus stem, etc., become the active area of research on designing novel materials in need of human beings to acquire fresh water resource from air. However, the design of materials on surface structure is little achieved on controlling of micro-scale drop transport in a long distance. Here, we report the ability of micro-drop transport in a long distance on a bioinspired Fibers with Gradient Spindle-knots (BFGS), which are fabricated by tilt angle dip-coating method. The micro-drop of ~0.25 μL transports in distance of ~5.00 mm, with velocity of 0.10-0.22 m s-1 on BFGS. It is attributed to the multi-level cooperation of the release energy of drop coalescence along the gradient spindle-knots, in addition to capillary adhesion force and continuous difference of Laplace pressure, accordingly, water drops are driven to move fast directionally in a long distance on BFGS.

  14. Dynamics of formation of low-angle tilt boundaries in metals and alloys at high loading rates

    NASA Astrophysics Data System (ADS)

    Gutkin, M. Yu.; Rzhavtsev, E. A.

    2015-12-01

    A computer model has been developed in which the process of formation of low-angle tilt boundaries and fragmentation of initial subgrains during shock loading of metals and alloys is clearly demonstrated by the of two-dimensional discrete dislocation-disclination dynamics method. The formation and evolution of such grains proceeds under the action of an external stress and the stress field of grain boundary disclinations distributed on the subgrain boundaries. With the D16 aluminum alloy as an example, three cases of fragmented structures formed in accordance with the initial configuration of the disclination ensemble have been considered for a dipole, quadrupole, and arbitrary octupole of wedge disclinations. It has been shown that, in all these cases, the formation of a stable fragmented structure requires a stress of ~0.5 GPa and time of 10 ns. The main results of computer simulation (the finite form of a fragmented structure, typical level of applied stress, and small fragmentation time) agree well with known experimental results on shock compression of the D16 aluminum alloy.

  15. Bioinspired tilt-angle fabricated structure gradient fibers: micro-drops fast transport in a long-distance.

    PubMed

    Chen, Yuan; Wang, Lin; Xue, Yan; Jiang, Lei; Zheng, Yongmei

    2013-01-01

    Issues of surfaces, e.g., inspired from beetle's back, spider silk, cactus stem, etc., become the active area of research on designing novel materials in need of human beings to acquire fresh water resource from air. However, the design of materials on surface structure is little achieved on controlling of micro-scale drop transport in a long distance. Here, we report the ability of micro-drop transport in a long distance on a bioinspired Fibers with Gradient Spindle-knots (BFGS), which are fabricated by tilt angle dip-coating method. The micro-drop of ~0.25 μL transports in distance of ~5.00 mm, with velocity of 0.10-0.22 m s⁻¹ on BFGS. It is attributed to the multi-level cooperation of the release energy of drop coalescence along the gradient spindle-knots, in addition to capillary adhesion force and continuous difference of Laplace pressure, accordingly, water drops are driven to move fast directionally in a long distance on BFGS. PMID:24113433

  16. Vortex flow structures and interactions for the optimum thrust efficiency of a heaving airfoil at different mean angles of attack

    SciTech Connect

    Martín-Alcántara, A.; Fernandez-Feria, R.

    2015-07-15

    The thrust efficiency of a two-dimensional heaving airfoil is studied computationally for a low Reynolds number using a vortex force decomposition. The auxiliary potentials that separate the total vortex force into lift and drag (or thrust) are obtained analytically by using an elliptic airfoil. With these auxiliary potentials, the added-mass components of the lift and drag (or thrust) coefficients are also obtained analytically for any heaving motion of the airfoil and for any value of the mean angle of attack α. The contributions of the leading- and trailing-edge vortices to the thrust during their down- and up-stroke evolutions are computed quantitatively with this formulation for different dimensionless frequencies and heave amplitudes (St{sub c} and St{sub a}) and for several values of α. Very different types of flows, periodic, quasi-periodic, and chaotic described as St{sub c}, St{sub a}, and α, are varied. The optimum values of these parameters for maximum thrust efficiency are obtained and explained in terms of the interactions between the vortices and the forces exerted by them on the airfoil. As in previous numerical and experimental studies on flapping flight at low Reynolds numbers, the optimum thrust efficiency is reached for intermediate frequencies (St{sub c} slightly smaller than one) and a heave amplitude corresponding to an advance ratio close to unity. The optimal mean angle of attack found is zero. The corresponding flow is periodic, but it becomes chaotic and with smaller average thrust efficiency as |α| becomes slightly different from zero.

  17. Does matching relation exist between the length and the tilting angle of terminal implants in the all-on-four protocol? stress distributions by 3D finite element analysis

    PubMed Central

    Li, Xiaomei; Cao, Zhizhong; Qiu, Xiaoqian; Tang, Zhen; Gong, Lulu

    2015-01-01

    PURPOSE To explore whether there is matching relation between the length and the tilting angle of terminal implants in the All-on-Four protocol by studying the effects of different implant configurations on stress distributions of implant, bone, and framework. MATERIALS AND METHODS Four implants were employed to support a full-arch fixed prosthesis and five three-dimensional finite element models were established with CT images, based on the length (S and L) and distal tilt angle (0°, 30° and 45°) of terminal implants for an edentulous mandible, which named: Tilt0-S, Tilt30-S, Tilt30-L, Tilt45-S and Tilt45-L. An oblique 240 N was loaded at second molar. The von Mises Stresses were analyzed. The implants were consecutively named #1 to #4 from the loading point. RESULTS 1) Tilt0-S had the greatest stress on the implants, with the other groups exhibiting variable reductions; the four implants of Tilt45-L demonstrated the greatest reduction in stress. 2) Tilt0-S had the greatest stress at bone around #1 implant neck, and Tilt45-L exhibited the least stress, which was a 36.3% reduction compared to Tilt0-S. 3) The greatest stress in the framework was found on the cantilevers distal to #1 implant. Tilt45-S exhibited the least stress. CONCLUSION Matching different length and tilting angle of the terminal implants led to variable stress reductions on implants, bone and the superstructure. By optimizing implant configuration, the reduction of stress on implants and surrounding bone could be maximized. Under the present condition, Tilt45-L was the preferred configuration. Further clinical testings are required. PMID:26140176

  18. Electron-beam transmission through a micrometer-sized tapered-glass capillary: Dependence on incident energy and angular tilt angle

    NASA Astrophysics Data System (ADS)

    Wickramarachchi, S. J.; Ikeda, T.; Dassanayake, B. S.; Keerthisinghe, D.; Tanis, J. A.

    2016-08-01

    An experimental study of 500- and 1000-eV incident electrons transmitted through a micrometer-sized funnel-shaped (tapered) glass capillary with inlet diameter 0.80 mm, outlet diameter 0.10 mm, and a length of 35 mm is reported. The properties of the electron beam transmitted were measured as a function of the emerging angle and the incident energy dependence. The angular profiles were found to be comprised of up to three peaks for both 500 and 1000 eV showing evidence for transmission going straight through the capillary without interacting with the walls (direct), as well as transmission resulting from Coulomb deflection of the electrons from a negative charge patch or by scattering from nuclei close to the surface of the capillary (indirect). The energy spectra show that elastically transmitted electrons dominate at 500 eV for increasing sample tilt angles up to ˜5.0°, while inelastic processes dominate for 1000 eV already at tilt angles of ˜1.0°. The angular width of the emitted electrons was found to constitute a narrow beam for direct (˜0.4°) and indirect (<0.6° for 500 eV and <1.0° for 1000 eV) transmission for both energies with the widths decreasing for the largest tilt angles measured and approaching the inherent resolution (˜0.3°) of the electron analyzer.

  19. Wave Propagation Direction and c-Axis Tilt Angle Influence on the Performance of ScAlN/Sapphire-Based SAW Devices.

    PubMed

    Kochhar, Abhay; Yamamoto, Yasuo; Teshigahara, Akihiko; Hashimoto, Ken-Ya; Tanaka, Shuji; Esashi, Masayoshi

    2016-07-01

    Some previously reported surface acoustic wave (SAW) devices using bulk piezoelectric substrates showed higher acoustic power radiated in either forward or backward wave propagation direction depending on their crystal orientations and are called natural single-phase unidirectional transducers (NSPUDT). While these reports were based on bulk piezoelectric substrates, we report directionality in the c-axis tilted 44% scandium doped aluminum nitride thin piezoelectric film-based SAW devices on sapphire. It is worth noting that our observance of directionality is specifically in Sezawa mode. We produced a c-axis tilt up to 5.5° over the single wafer and examined the directionality by comparing the forward and backward insertion loss utilizing split finger electrodes as a receiver. The wave propagation direction and c-axis tilt angle influence on the performance of SAW devices is evaluated. Furthermore, return loss and insertion loss data are presented for various SAW propagation directions and c-axis tilt angles. Finally, the comparison for both acoustic modes, i.e., Rayleigh and Sezawa, is reported. PMID:26978772

  20. Perception of the upright and susceptibility to motion sickness as functions of angle of tilt and angular velocity in off-vertical rotation. [human tolerance to angular accelerations

    NASA Technical Reports Server (NTRS)

    Miller, E. F., II; Graybiel, A.

    1973-01-01

    Motion sickness susceptibility of four normal subjects was measured in terms of duration of exposure necessary to evoke moderate malaise (MIIA) as a function of velocity in a chair rotated about a central axis tilted 10 deg with respect to gravitational upright. The subjects had little or no susceptibility to this type of rotation at 2.5 and 5.0 rpm, but with further increases in rate, the MIIA endpoint was always reached and with ever shorter test durations. Minimal provocative periods for all subjects were found at 15 or 20 rpm. Higher rotational rates dramatically reversed the vestibular stressor effect, and the subjects as a group tended to reach a plateau of relatively low susceptibility at 40 and 45 rpm. At these higher velocities, furthermore, the subjects essentially lost their sensation of being tilted off vertical. In the second half of the study, the effect of tilt angle was varied while the rotation rate was maintained at a constant 17.5 rpm. Two subjects were completely resistant to symptoms of motion sickness when rotated at 2.5 deg off vertical; with greater off-vertical angles, the susceptibility of all subjects increased sharply at first, then tapered off in a manner reflecting a Fechnerian function.

  1. Tilted Solar Panels

    Atmospheric Science Data Center

    2014-09-25

    ... from the monthly average insolation on a horizontal surface. Tilt angles are 0, latitude - 15, latitude, latitude + 15, 90, and the ... the monthly averaged maximum radiation.   Minimum radiation for equator-pointed tilted surfaces (kWh/m2/day) ...

  2. Tilt and Azimuthal Angles of a Transmembrane Peptide: A Comparison between Molecular Dynamics Calculations and Solid-State NMR Data of Sarcolipin in Lipid Membranes

    PubMed Central

    Shi, Lei; Cembran, Alessandro; Gao, Jiali; Veglia, Gianluigi

    2009-01-01

    We report molecular dynamics simulations in the explicit membrane environment of a small membrane-embedded protein, sarcolipin, which regulates the sarcoplasmic reticulum Ca-ATPase activity in both cardiac and skeletal muscle. In its monomeric form, we found that sarcolipin adopts a helical conformation, with a computed average tilt angle of 28 ± 6° and azymuthal angles of 66 ± 22°, in reasonable accord with angles determined experimentally (23 ± 2° and 50 ± 4°, respectively) using solid-state NMR with separated-local-field experiments. The effects of time and spatial averaging on both 15N chemical shift anisotropy and 1H/15N dipolar couplings have been analyzed using short-time averages of fast amide out-of-plane motions and following principal component dynamic trajectories. We found that it is possible to reproduce the regular oscillatory patterns observed for the anisotropic NMR parameters (i.e., PISA wheels) employing average amide vectors. This work highlights the role of molecular dynamics simulations as a tool for the analysis and interpretation of solid-state NMR data. PMID:19413970

  3. Injector Element which Maintains a Constant Mean Spray Angle and Optimum Pressure Drop During Throttling by Varying the Geometry of Tangential Inlets

    NASA Technical Reports Server (NTRS)

    Trinh, Huu P. (Inventor); Myers, William Neill (Inventor)

    2014-01-01

    A method for determining the optimum inlet geometry of a liquid rocket engine swirl injector includes obtaining a throttleable level phase value, volume flow rate, chamber pressure, liquid propellant density, inlet injector pressure, desired target spray angle and desired target optimum delta pressure value between an inlet and a chamber for a plurality of engine stages. The tangential inlet area for each throttleable stage is calculated. The correlation between the tangential inlet areas and delta pressure values is used to calculate the spring displacement and variable inlet geometry. An injector designed using the method includes a plurality of geometrically calculated tangential inlets in an injection tube; an injection tube cap with a plurality of inlet slots slidably engages the injection tube. A pressure differential across the injector element causes the cap to slide along the injection tube and variably align the inlet slots with the tangential inlets.

  4. Calculating the Optimum Angle of Filament-Wound Pipes in Natural Gas Transmission Pipelines Using Approximation Methods.

    PubMed

    Reza Khoshravan Azar, Mohammad; Emami Satellou, Ali Akbar; Shishesaz, Mohammad; Salavati, Bahram

    2013-04-01

    Given the increasing use of composite materials in various industries, oil and gas industry also requires that more attention should be paid to these materials. Furthermore, due to variation in choice of materials, the materials needed for the mechanical strength, resistance in critical situations such as fire, costs and other priorities of the analysis carried out on them and the most optimal for achieving certain goals, are introduced. In this study, we will try to introduce appropriate choice for use in the natural gas transmission composite pipelines. Following a 4-layered filament-wound (FW) composite pipe will consider an offer our analyses under internal pressure. The analyses' results will be calculated for different combinations of angles 15 deg, 30 deg, 45 deg, 55 deg, 60 deg, 75 deg, and 80 deg. Finally, we will compare the calculated values and the optimal angle will be gained by using the Approximation methods. It is explained that this layering is as the symmetrical. PMID:24891748

  5. Role of polarizer-tilting-angle in zero-field spin-transfer nano-oscillators with perpendicular anisotropy

    SciTech Connect

    Gonzalez-Fuentes, C.; Gallardo, R. A. Landeros, P.

    2015-10-05

    An analytical model for studying the stability of a single domain ferromagnetic layer under the influence of a spin-polarized current is presented. The theory is applied to bias-field-free nano-oscillators with perpendicular anisotropy, which allows to obtain a polarizer-angle vs. current phase diagram that describes the stability of magnetic states. Explicit formulae for the critical current densities unveil the influence of the relative orientation between free and polarizer layers, allowing the emergence of precessional steady-states, and also the possibility to reduce the magnitude of the threshold current density to produce microwave oscillations. It is shown that oscillating steady-states arise in a broad angular region, and the dependence of their boundaries is fully specified by the model. The reliability of the analytical results has been corroborated by comparison to numerical calculations. Such structures are currently under intense research because of remarkable properties offering new prospects for microwave applications in communication technologies.

  6. Permanent magnet assembly producing a strong tilted homogeneous magnetic field: towards magic angle field spinning NMR and MRI.

    PubMed

    Sakellariou, Dimitris; Hugon, Cédric; Guiga, Angelo; Aubert, Guy; Cazaux, Sandrine; Hardy, Philippe

    2010-12-01

    We introduce a cylindrical permanent magnet design that generates a homogeneous and strong magnetic field having an arbitrary inclination with respect to the axis of the cylinder. The analytical theory of 3 D magnetostatics has been applied to this problem, and a hybrid magnet structure has been designed. This structure contains two magnets producing a longitudinal and transverse component for the magnetic field, whose amplitudes and homogeneities can be fully controlled by design. A simple prototype has been constructed using inexpensive small cube magnets, and its magnetic field has been mapped using Hall and NMR probe sensors. This magnet can, in principle, be used for magic angle field spinning NMR and MRI experiments allowing for metabolic chemical shift profiling in small living animals. PMID:20891027

  7. Orthogonally polarized bright-dark pulse pair generation in mode-locked fiber laser with a large-angle tilted fiber grating

    NASA Astrophysics Data System (ADS)

    Zhang, Zuxing; Mou, Chengbo; Yan, Zhijun; Sun, Zhongyuan; Zhang, Lin

    2016-06-01

    We report on the generation of orthogonally polarized bright-dark pulse pair in a passively mode-locked fiber laser with a large-angle tilted fiber grating (LA-TFG). The unique polarization properties of the LA-TFG, i.e., polarization-dependent loss and polarization-mode splitting, enable dual-wavelength mode-locking operation. Besides dual-wavelength bright pulses with uniform polarization at two different wavelengths, the bright-dark pulse pair has also been achieved. It is found that the bright-dark pulse pair is formed due to the nonlinear couplings between lights with two orthogonal polarizations and two different wavelengths. Furthermore, harmonic mode-locking of bright-dark pulse pair has been observed. The obtained bright-dark pulse pair could find potential use in secure communication system. It also paves the way to manipulate the generation of dark pulse in terms of wavelength and polarization, using specially designed fiber grating for mode-locking.

  8. Metal artefact reduction in MRI at both 1.5 and 3.0 T using slice encoding for metal artefact correction and view angle tilting

    PubMed Central

    Reichert, M; Morelli, J N; Nittka, M; Attenberger, U; Runge, V M

    2015-01-01

    Objective: To compare metal artefact reduction in MRI at both 3.0 T and 1.5 T using different sequence strategies. Methods: Metal implants of stainless steel screw and plate within agarose phantoms and tissue specimens as well as three patients with implants were imaged at both 1.5 T and 3.0 T, using view angle tilting (VAT), slice encoding for metal artefact correction with VAT (SEMAC-VAT) and conventional sequence. Artefact reduction in agarose phantoms was quantitatively assessed by artefact volume measurements. Blinded reads were conducted in tissue specimen and human imaging, with respect to artefact size, distortion, blurring and overall image quality. Wilcoxon and Friedman tests for multiple comparisons and intraclass correlation coefficient (ICC) for interobserver agreement were performed with a significant level of p < 0.05. Results: Compared with conventional sequences, SEMAC-VAT significantly reduced metal artefacts by 83% ± 9% for the screw and 89% ± 3% for the plate at 1.5 T; 72% ± 7% for the screw and 38% ± 13% for the plate at 3.0 T (p < 0.05). In qualitative analysis, SEMAC-VAT allowed for better visualization of tissue structures adjacent to the implants and produced better overall image quality with good interobserver agreement for both tissue specimen and human imaging (ICC = 0.80–0.99; p < 0.001). In addition, VAT also markedly reduced metal artefacts compared with conventional sequence, but was inferior to SEMAC-VAT. Conclusion: SEMAC-VAT and VAT techniques effectively reduce artefacts from metal implants relative to conventional imaging at both 1.5 T and 3.0 T. Advances in knowledge: The feasibility of metal artefact reduction with SEMAC-VAT was demonstrated at 3.0-T MR. SEMAC-VAT significantly reduced metal artefacts at both 1.5 and 3.0 T. SEMAC-VAT allowed for better visualization of the tissue structures adjacent to the metal implants. SEMAC-VAT produced consistently better image

  9. View-Angle Tilting and Slice-Encoding Metal Artifact Correction for Artifact Reduction in MRI: Experimental Sequence Optimization for Orthopaedic Tumor Endoprostheses and Clinical Application

    PubMed Central

    Jungmann, Pia M.; Ganter, Carl; Schaeffeler, Christoph J.; Bauer, Jan S.; Baum, Thomas; Meier, Reinhard; Nittka, Mathias; Pohlig, Florian; Rechl, Hans; von Eisenhart-Rothe, Ruediger; Rummeny, Ernst J.; Woertler, Klaus

    2015-01-01

    Background MRI plays a major role in follow-up of patients with malignant bone tumors. However, after limb salvage surgery, orthopaedic tumor endoprostheses might cause significant metal-induced susceptibility artifacts. Purposes To evaluate the benefit of view-angle tilting (VAT) and slice-encoding metal artifact correction (SEMAC) for MRI of large-sized orthopaedic tumor endoprostheses in an experimental model and to demonstrate clinical benefits for assessment of periprosthetic soft tissue abnormalities. Methods In an experimental setting, tumor endoprostheses (n=4) were scanned at 1.5T with three versions of optimized high-bandwidth turbo-spin-echo pulse sequences: (i) standard, (ii) VAT and (iii) combined VAT and SEMAC (VAT&SEMAC). Pulse sequences included coronal short-tau-inversion-recovery (STIR), coronal T1-weighted (w), transverse T1-w and T2-w TSE sequences. For clinical evaluation, VAT&SEMAC was compared to conventional metal artifact-reducing MR sequences (conventional MR) in n=25 patients with metal implants and clinical suspicion of tumor recurrence or infection. Diameters of artifacts were measured quantitatively. Qualitative parameters were assessed on a five-point scale (1=best, 5=worst): “image distortion”, “artificial signal changes at the edges” and “diagnostic confidence”. Imaging findings were correlated with pathology. T-tests and Wilcoxon-signed rank tests were used for statistical analyses. Results The true size of the prostheses was overestimated on MRI (P<0.05). A significant reduction of artifacts was achieved by VAT (P<0.001) and VAT&SEMAC (P=0.003) compared to the standard group. Quantitative scores improved in the VAT and VAT&SEMAC group (P<0.05). On clinical MR images, artifact diameters were significantly reduced in the VAT&SEMAC-group as compared with the conventional-group (P<0.001). Distortion and artificial signal changes were reduced and diagnostic confidence improved (P<0.05). In two cases, tumor-recurrence, in

  10. Effect of lip and centerbody geometry on aerodynamic performance of inlets for tilting-nacelle VTOL aircraft

    NASA Technical Reports Server (NTRS)

    Burley, R. R.

    1979-01-01

    Inlets for tilt-nacelle VTOL aircraft must operate over a wide range of incidence angles and engine weight flows without internal flow separation. Wind tunnel tests of scale model inlets were conducted to evaluate the effectiveness of three geometric variables to provide this capability. Increasing the lip contraction ratio increased the separation angle at all engine weight flows. The optimum axial location of the centerbody occurred when its leading edge was located just downstream of the inlet lip. Compared with a short centerbody, the optimum location of the centerbody resulted in an increase in separation angle at all engine weight flows. Decreasing the lip major-to-minor-axis ratio increased the separation angle at the lower engine weight flows.

  11. Ultraviolet fast-response photoelectric effect in tilted orientation SrTiO{sub 3} single crystals

    SciTech Connect

    Zhao Kun; Jin Kuijuan; Huang Yanhong; Zhao Songqing; Lu Huibin; He Meng; Chen Zhenghao; Zhou Yueliang; Yang Guozhen

    2006-10-23

    Ultraviolet photoelectricity based on the vicinal cut as-supplied SrTiO{sub 3} single crystals has been experimentally studied in the absence of an applied bias at room temperature. An open-circuit photovoltage of 130 ps rise time and 230 ps full width at half maximum was observed under the irradiation of a 355 nm pulsed laser of 25 ps in duration. The dependence of the photoelectric effect on the tilting angles was studied, and the optimum angle is 20.9 deg. . Seebeck effect is proposed to elucidate the tilting angle dependence of laser-induced photovoltage. This work demonstrates the potential of SrTiO{sub 3} single crystals in ultraviolet detection.

  12. Combined Scanning Transmission Electron Microscopy Tilt- and Focal Series

    SciTech Connect

    Dahmen, Tim; Baudoin, Jean-Pierre G; Lupini, Andrew R; Kubel, Christian; Slusallek, Phillip; De Jonge, Niels

    2014-01-01

    In this study, a combined tilt- and focal series is proposed as a new recording scheme for high-angle annular dark-field scanning transmission electron microscopy (STEM) tomography. Three-dimensional (3D) data were acquired by mechanically tilting the specimen, and recording a through-focal series at each tilt direction. The sample was a whole-mount macrophage cell with embedded gold nanoparticles. The tilt focal algebraic reconstruction technique (TF-ART) is introduced as a new algorithm to reconstruct tomograms from such combined tilt- and focal series. The feasibility of TF-ART was demonstrated by 3D reconstruction of the experimental 3D data. The results were compared with a conventional STEM tilt series of a similar sample. The combined tilt- and focal series led to smaller missing wedge artifacts, and a higher axial resolution than obtained for the STEM tilt series, thus improving on one of the main issues of tilt series-based electron tomography.

  13. Rocket rendezvous at preassigned destinations with optimum entry trajectories

    NASA Astrophysics Data System (ADS)

    Nangia, A. K.

    Optimum entry rendezvous trajectories of commuter rockets between initial noncoaxial coplanar elliptic orbits and destination orbits in an inverse square gravitational field have been determined. Results are presented for an optimum entry rendezvous between earth and Mars. For a given interception angle, the results show that the launch angle for optimum entry rendezvous is smaller than that for the optimum exit rendezvous.

  14. A micropower tilt-processing circuit.

    PubMed

    Constandinou, T G; Georgiou, J

    2009-12-01

    This paper describes a novel analog circuit for extracting the tilt angle from the output of a linear microelectromechanical-system accelerometer. The circuit uses the accelerometer signal, together with the gravitational acceleration vector, to generate the tilt signal. Using a current-mode representation with metal-oxide semiconductor devices operating in weak inversion, the appropriate trigonometric function has been realized to compute tilt. Furthermore, implementing a long-time constant filter to extract the mean tilt level provides adaptation to the static tilt level. Specifically, this circuit has been designed as part of an implantable vestibular prosthesis to provide inclination signals for bypassing dysfunctional otolith end organs. The circuit has been fabricated in AustriaMicroSystems 0.35-mum 2P4M complementary metal-oxide semiconductor technology, and this paper presents the theory, implementation, and measured results. PMID:23853283

  15. Tilted fuel cell apparatus

    DOEpatents

    Cooper, John F.; Cherepy, Nerine; Krueger, Roger L.

    2005-04-12

    Bipolar, tilted embodiments of high temperature, molten electrolyte electrochemical cells capable of directly converting carbon fuel to electrical energy are disclosed herein. The bipolar, tilted configurations minimize the electrical resistance between one cell and others connected in electrical series. The tilted configuration also allows continuous refueling of carbon fuel.

  16. Roll tracking effects of G-vector tilt and various types of motion washout

    NASA Technical Reports Server (NTRS)

    Jex, H. R.; Magdaleno, R. E.; Junker, A. M.

    1978-01-01

    In a dogfight scenario, the task was to follow the target's roll angle while suppressing gust disturbances. All subjects adopted the same behavioral strategies in following the target while suppressing the gusts, and the MFP-fitted math model response was generally within one data symbol width. The results include the following: (1) comparisons of full roll motion (both with and without the spurious gravity tilt cue) with the static case. These motion cues help suppress disturbances with little net effect on the visual performance. Tilt cues were clearly used by the pilots but gave only small improvement in tracking errors. (2) The optimum washout (in terms of performance close to real world, similar behavioral parameters, significant motion attenuation (60 percent), and acceptable motion fidelity) was the combined attenuation and first-order washout. (3) Various trends in parameters across the motion conditions were apparent, and are discussed with respect to a comprehensive model for predicting adaptation to various roll motion cues.

  17. Conserved electrostatic fields at the Ras-effector interface measured through vibrational Stark effect spectroscopy explain the difference in tilt angle in the Ras binding domains of Raf and RalGDS.

    PubMed

    Walker, David M; Wang, Ruifei; Webb, Lauren J

    2014-10-01

    Vibrational Stark effect (VSE) spectroscopy was used to measure the electrostatic fields present at the interface of the human guanosine triphosphatase (GTPase) Ras docked with the Ras binding domain (RBD) of the protein kinase Raf. Nine amino acids located on the surface of Raf were selected for labeling with a nitrile vibrational probe. Eight of the probe locations were situated along the interface of Ras and Raf, and one probe was 2 nm away on the opposite side of Raf. Vibrational frequencies of the nine Raf nitrile probes were compared both in the monomeric, solvated protein and when docked with wild-type (WT) Ras to construct a comprehensive VSE map of the Ras-Raf interface. Molecular dynamics (MD) simulations employing an umbrella sampling strategy were used to generate a Boltzmann-weighted ensemble of nitrile positions in both the monomeric and docked complexes to determine the effect that docking has on probe location and orientation and to aid in the interpretation of VSE results. These results were compared to an identical study that was previously conducted on nine nitrile probes on the RBD of Ral guanidine dissociation stimulator (RalGDS) to make comparisons between the docked complexes formed when either of the two effectors bind to WT Ras. This comparison finds that there are three regions of conserved electrostatic fields that are formed upon docking of WT Ras with both downstream effectors. Conservation of this pattern in the docked complex then results in different binding orientations observed in otherwise structurally similar proteins. This work supports an electrostatic cause of the known binding tilt angle between the Ras-Raf and Ras-RalGDS complexes. PMID:25127074

  18. Refractive Index Sensitivity of Tilted Long Period Fibre Gratings Written in Thinned Cladding Fibre

    NASA Astrophysics Data System (ADS)

    Zhao, Yunhe; Liu, Yunqi; Guo, Qiang; Wang, Tingyun

    2016-02-01

    We demonstrated the fabrication of tilted long period fibre gratings written in the thinned cladding fibre by CO2 laser. The refractive index characteristics of the gratings with different tilted angles were investigated experimentally. The experimental results show that the grating with larger tilted angle has higher sensitivity to the surrounding refractive index changes.

  19. Simulation of unidirectional solidification with a tilted crystalline axis

    NASA Astrophysics Data System (ADS)

    Okada, Tomohiro; Saito, Yukio

    1996-07-01

    Tilting of the crystal profile during directional solidification is studied numerically, when the crystalline axis is misoriented from the temperature gradient and the pulling direction. Only with the anisotropy in surface stiffness is the crystal shown to tilt to an angle φ smaller than the misorientation of the crystalline axis ψ. The angle φ approaches ψ on increasing the pulling velocity V, as is often observed in experiments. The V dependence of the tilting φ thus does not necessarily mean that the tilting is caused by the kinetic effect. With ψ=45° we observe tip splitting and double fingers, a constituent of the compact seaweed pattern.

  20. Correcting the vertical component of ocean bottom seismometers for the effects of tilt and compliance

    NASA Astrophysics Data System (ADS)

    Bell, S. W.; Forsyth, D. W.

    2013-12-01

    constant, but we observe significant day-to-day variation in tilt angle, requiring the calculation of a tilt transfer function for each individual day for optimum removal of bottom current noise. In removing the compliance noise, there is some distortion of the signal. We show how to correct for this distortion using theoretical and empirical transfer functions between pressure and displacement records for seismic signals.

  1. Tilted Infall Regions?

    NASA Astrophysics Data System (ADS)

    Praton, Elizabeth A.; Abdullah, M.

    2014-01-01

    Recently, a thin plane of co-orbiting satellite galaxies was discovered around M31 (Ibata et al. 2013). Could there be similar unexpected flows on a larger scale, around galaxy clusters? In redshift space, infall regions with rotational flow distort into tilted artifacts. Transverse motion relative to the observer also causes a tilt. Are there galaxy clusters with structure that looks like this? In a recent exploratory study (Abdullah, Praton, Ali 2013), we show that some galaxy clusters do resemble tilted infall artifacts. The characteristic shape is obscured if the structure is axially convolved but clear when it is sliced, and can be fit by a spherical infall model (SIM) that is tilted by transverse motion or rotational flow. Tilted SIMs could therefore be a useful tool for roughly analyzing possible flows. We present a method for fitting tilted SIM envelopes and show how to use the tilt and width-to-length ratio of the envelope to estimate the possible velocity causing the tilt and also the observer's possible radial motion towards the cluster, if the structure is indeed an infall artifact. It is not clear if current cosmological n-body simulations can explain the galaxy clusters whose structure looks like a tilted infall artifact, since clusters in lambda-cdm simulations usually show little infall distortion. We found one similar shape in the outputs we examined. This n-body structure is not a result of velocity distortion and is mostly real (a pseudo-artifact). However, the velocity field of the nearest tilted galaxy cluster (Virgo) resembles a tilted SIM and not the pseudo-artifact. References Ibata, R.A. et al. 2013, Nature, 493, 62 Abdullah, M.H., Praton, E.A., & Ali, G.B. 2013, MNRAS, 434, 1989

  2. Microwave Brightness Temperatures of Tilted Convective Systems

    NASA Technical Reports Server (NTRS)

    Hong, Ye; Haferman, Jeffrey L.; Olson, William S.; Kummerow, Christian D.

    1998-01-01

    Aircraft and ground-based radar data from the Tropical Ocean and Global Atmosphere Coupled-Ocean Atmosphere Response Experiment (TOGA COARE) show that convective systems are not always vertical. Instead, many are tilted from vertical. Satellite passive microwave radiometers observe the atmosphere at a viewing angle. For example, the Special Sensor Microwave/Imager (SSM/I) on Defense Meteorological Satellite Program (DMSP) satellites and the Tropical Rainfall Measurement Mission (TRMM) Microwave Imager (TMI) on the TRMM satellite have an incident angle of about 50deg. Thus, the brightness temperature measured from one direction of tilt may be different than that viewed from the opposite direction due to the different optical depth. This paper presents the investigation of passive microwave brightness temperatures of tilted convective systems. To account for the effect of tilt, a 3-D backward Monte Carlo radiative transfer model has been applied to a simple tilted cloud model and a dynamically evolving cloud model to derive the brightness temperature. The radiative transfer results indicate that brightness temperature varies when the viewing angle changes because of the different optical depth. The tilt increases the displacements between high 19 GHz brightness temperature (Tb(sub 19)) due to liquid emission from lower level of cloud and the low 85 GHz brightness temperature (Tb(sub 85)) due to ice scattering from upper level of cloud. As the resolution degrades, the difference of brightness temperature due to the change of viewing angle decreases dramatically. The dislocation between Tb(sub 19) and Tb(sub 85), however, remains prominent.

  3. Tilted ghost inflation

    SciTech Connect

    Senatore, Leonardo

    2005-02-15

    In a ghost inflationary scenario, we study the observational consequences of a tilt in the potential of the ghost condensate. We show how the presence of a tilt tends to make contact between the natural predictions of ghost inflation and the ones of slow roll inflation. In the case of positive tilt, we are able to build an inflationary model in which the Hubble constant H is growing with time. We compute the amplitude and the tilt of the two-point function, as well as the three-point function, for both cases of positive and negative tilt. We find that a good fraction of the parameter space of the model is within experimental reach.

  4. Holographic display with tilted spatial light modulator.

    PubMed

    Kozacki, Tomasz

    2011-07-10

    In this paper, we analyze a holographic display system utilizing a phase-only spatial light modulator (SLM) based on liquid crystal on silicon (LCoS). An LCoS SLM works in reflection, and, in some applications, it is convenient to use with an inclined illumination. Even with a highly inclined illumination, the holographic display is capable of good-quality image generation. We show that the key to obtain high-quality reconstructions is the tilt-dependent calibration and algorithms. Typically, an LCoS SLM is illuminated with a plane wave with normal wave vector. We use inclined illumination, which requires development of new algorithms and display characterization. In this paper we introduce two algorithms. The first one is designed to process a digital hologram captured in CCD normal configuration, so it can be displayed in SLM tilted geometry, while the second one is capable of synthetic hologram generation for tilted SLM configuration. The inclined geometry asymmetrically changes the field of view of a holographic display. The presented theoretical analysis of the aliasing effect provides a formula for the field of view as a function of SLM tilt. The incidence angle affects SLM performance. Both elements of SLM calibration, i.e., pixel phase response and wavefront aberrations, strongly depend on SLM tilt angle. The effect is discussed in this paper. All of the discussions are accompanied with experimental results. PMID:21743569

  5. Modelling of the UV Index on vertical and 40° tilted planes for different orientations.

    PubMed

    Serrano, D; Marín, M J; Utrillas, M P; Tena, F; Martínez-Lozano, J A

    2012-02-01

    In this study, estimated data of the UV Index on vertical planes are presented for the latitude of Valencia, Spain. For that purpose, the UVER values have been generated on vertical planes by means of four different geometrical models a) isotropic, b) Perez, c) Gueymard, d) Muneer, based on values of the global horizontal UVER and the diffuse horizontal UVER, measured experimentally. The UVER values, obtained by any model, overestimate the experimental values for all orientations, with the exception of the Perez model for the East plane. The results show statistical values of the MAD parameter (Mean Absolute Deviation) between 10% and 25%, the Perez model being the one that obtained a lower MAD for all levels. As for the statistic RMSD parameter (Root Mean Square Deviation), the results show values between 17% and 32%, and again the Perez model provides the best results in all vertical planes. The difference between the estimated UV Index and the experimental UV Index, for vertical and 40° tilted planes, was also calculated. 40° is an angle close to the latitude of Burjassot, Valencia, (39.5°), which, according to various studies, is the optimum angle to capture maximum radiation on tilted planes. We conclude that the models provide a good estimate of the UV Index, as they coincide or differ in one unit compared to the experimental values in 99% of cases, and this is valid for all orientations. Finally, we examined the relation between the UV Index on vertical and 40° tilted planes, both the experimental and estimated by the Perez model, and the experimental UV Index on a horizontal plane at 12 GMT. Based on the results, we can conclude that it is possible to estimate with a good approximation the UV Index on vertical and 40° tilted planes in different directions on the basis of the experimental horizontal UVI value, thus justifying the interest of this study. PMID:22193984

  6. Head tilt during driving.

    PubMed

    Zikovitz, D C; Harris, L R

    1999-05-01

    In order to distinguish between the use of visual and gravito-inertial force reference frames, the head tilt of drivers and passengers were measured as they went around corners at various speeds. The visual curvature of the corners were thus dissociated from the magnitude of the centripetal forces (0.30-0.77 g). Drivers' head tilts were highly correlated with the visually-available estimate of the curvature of the road (r2=0.86) but not with the centripetal force (r2<0.1). Passengers' head tilts were inversely correlated with the lateral forces (r2=0.3-0.7) and seem to reflect a passive sway. The strong correlation of the tilt of drivers' heads with a visual aspect of the road ahead, supports the use of a predominantly visual reference frame for the driving task. PMID:10722313

  7. Fabrication and Characterization of Tilted Fiber Optic Bragg Grating Filters over Various Wavelengths

    NASA Technical Reports Server (NTRS)

    Grant, Joseph; Jackson, Kurt V.; Wang, Y.; Sharma, A.; Burdine, Robert V. (Technical Monitor)

    2002-01-01

    Fiber Optic Bragg Grating taps are fabricated and characterized at various wavelengths using a modified Talbot interferometric technique. Gratings are fabricated by tilting the photosensitive fiber to angles up to 45 degrees w.r.t. the writing angle. Diffraction characteristics of the tilted grating is monitored in first and second orders.

  8. Tilt sensitivity of the two-grating interferometer

    SciTech Connect

    Anderson, Christopher N.; Naulleau, Patrick P.

    2008-01-30

    Fringe formation in the two-grating interferometer is analyzed in the presence of a small parallelism error between the diffraction gratings assumed in the direction of grating shear. Our analysis shows that with partially coherent illumination, fringe contrast in the interference plane is reduced in the presence of nonzero grating tilt with the effect proportional to the grating tilt angle and the grating spatial frequencies. Our analysis also shows that for a given angle between the gratings there is an angle between the final grating and the interference plane that optimizes fringe contrast across the field.

  9. Tilt rotor hover aeroacoustics

    NASA Technical Reports Server (NTRS)

    Coffen, Charles David

    1992-01-01

    The methodology, results, and conclusions of a study of tilt rotor hover aeroacoustics and aerodynamics are presented. Flow visualization and hot wire velocity measurement were performed on a 1/12-scale model of the XV-15 Tilt Rotor Aircraft in hover. The wing and fuselage below the rotor cause a complex recirculating flow. Results indicate the physical dimensions and details of the flow including the relative unsteadiness and turbulence characteristics of the flow. Discrete frequency harmonic thickness and the loading noise mechanism were predicted using WOPWOP for the standard metal blades and the Advanced Technology Blades. The recirculating flow created by the wing below the rotor is a primary sound mechanism for a hovering tilt rotor. The effects of dynamic blade response should be included for fountain flow conditions which produce impulsive blade loading. Broadband noise mechanisms were studied using Amiet's method with azimuthally varying turbulence characteristics derived from the measurements. The recirculating fountain flow with high turbulence levels in the recirculating zone is the dominant source of broadband noise for a hovering rotor. It is shown that tilt rotor hover aeroacoustic noise mechanisms are now understood. Noise predictions can be made based on reasonably accurate aerodynamic models developed here.

  10. Tilt Rotor Aircraft Aeroacoustics

    NASA Technical Reports Server (NTRS)

    George, Albert R.

    1996-01-01

    A fleet of civil tilt rotor transports offers a means of reducing airport congestion and point-to-point travel time. The speed, range, and fuel economy of these aircraft, along with their efficient use of vertiport area, make them good candidates for short-to-medium range civil transport. However, to be successfully integrated into the civilian community, the tilt rotor must be perceived as a quiet, safe, and economical mode of transportation that does not harm the environment. In particular, noise impact has been identified as a possible barrier to the civil tilt rotor. Along with rotor conversion-mode flight, and blade-vortex interaction noise during descent, hover mode is a noise problem for tilt rotor operations. In the present research, tilt rotor hover aeroacoustics have been studied analytically, experimentally, and computationally. Various papers on the subject were published as noted in the list of publications. More recently, experimental measurements were made on a 1/12.5 scale model of the XV-15 in hover and analyses of this data and extrapolations to full scale were also carried out. A dimensional analysis showed that the model was a good aeroacoustic approximation to the full-scale aircraft, and scale factors were derived to extrapolate the model measurements to the full-scale XV-15. The experimental measurements included helium bubble flow visualization, silk tuft flow visualization, 2-component hot wire anemometry, 7-hole pressure probe measurements, vorticity measurements, and outdoor far field acoustic measurements. The hot wire measurements were used to estimate the turbulence statistics of the flow field into the rotors, such as length scales, velocity scales, dissipation, and turbulence intermittency. Several different configurations of the model were tested: (1) standard configurations (single isolated rotor, two rotors without the aircraft, standard tilt rotor configuration); (2) flow control devices (the 'plate', the 'diagonal fences'); (3

  11. Shear mode coupling and tilted grain growth of A1N thin films in BAW resonators.

    PubMed

    Martin, Fabrice; Jan, Marc-Etienne; Rey-Mermet, Samuel; Belgacem, Brahim; Su, Dong; Cantoni, Marco; Muralt, Paul

    2006-07-01

    Polycrystalline A1N thin films were deposited by RF reactive magnetron sputtering on Pt(111)/Ti electrode films. The substrates were tilted by an angle ranging from 40 degrees to 70 degrees with respect to the target normal. A low deposition temperature and a high sputter gas pressure were found ideal for tilted growth. The resulting grain tilt angle amounts to about half the substrate tilt angle. For coupling evaluation, 5 GHz solidly mounted resonator structures have been realized. The tilted grain A1N films exhibited a permittivity in the 9.5-10.5 range and loss tangent of 0.3%. Two shear modes as well as the longitudinal mode could be clearly identified. The coupling coefficient k2(eff) of the fundamental thickness shear mode (TS0) was found to be about 0.5%, which is compatible with a c-axis tilt of about 6 degrees. PMID:16889341

  12. Zoom lens design for tilted objects

    NASA Astrophysics Data System (ADS)

    Malone, Robert M.; Frayer, Daniel K.; Kaufman, Morris I.; Leffler, Heather R.; McGillivray, Kevin D.; Meidinger, Alfred; Phillips, David H.

    2015-09-01

    When a zoom lens views a tilted finite conjugate object, its image plane is both tilted and distorted depending on magnification. Our camera image plane moves with six degrees of freedom; only one moving doublet lens is required to change magnification. Two lens design models were analyzed. The first required the optical and mechanical axes to be collinear, resulting in a tilted stop. The second allowed the optical axis to be tilted from the lens mechanical axis with an untilted stop moving along the mechanical axis. Both designs produced useful zoom lenses with excellent resolution for a distorted image. For both lens designs, the stop is anchored to the moving doublet and its diameter is unchanged throughout magnification changes. This unusual outcome allows the light level at each camera pixel to remain constant, independent of magnification. As-built tolerance analysis is used to compare both optical models. The design application is for proton radiography. At the end of an accelerator, protons exit an aluminum vacuum window producing a shadowgraph image onto an LYSO (lutetium yttrium orthosilicate) scintillator. The 5″ square scintillator emission reflects off a pellicle and is collected by the zoom lenses located 24″ away. Four zoom lenses will view the same pellicle at different alpha and beta angles. Blue emission from the scintillator is viewed at an alpha angle of -14° or -23° and beta angles of ±9° or ±25°. The pellicle directs the light backwards to a zone where adequate shielding of the cameras can be achieved against radiation scattered from the aluminum window.

  13. Optimum propeller wind turbines

    NASA Astrophysics Data System (ADS)

    Sanderson, R. J.; Archer, R. D.

    1983-12-01

    The Prandtl-Betz-Theodorsen theory of heavily loaded airscrews has been adapted to the design of propeller windmills which are to be optimized for maximum power coefficient. It is shown that the simpler, light-loading, constant-area wake assumption can generate significantly different 'optimum' performance and geometry, and that it is therefore not appropriate to the design of propeller wind turbines when operating in their normal range of high-tip-speed-to-wind-speed ratio. Design curves for optimum power coefficient are presented and an example of the design of a typical two-blade optimum rotor is given.

  14. Paleocene arc-continent collision in southeastern Papua New Guinea was followed in the Neogene by 50 km of extension on low-angle faults, emplacement of intrusive rocks, uplift and tilting and erosion to reveal the PUB ophiolite

    NASA Astrophysics Data System (ADS)

    Davies, H. L.; Jonda, L.

    2012-12-01

    The geology of the Owen Stanley Range in southeastern Papua New Guinea was mapped at reconnaissance scale in 1960-1980. The range comprises a core of mostly felsic greenschist-facies metamorphics (Kagi Metamorphics) that is structurally overlain on the northeast side by a fault-bounded partial carapace of mafic partly-blueschist-facies metamorphics (Emo Metamorphics). Metamorphism was by arc-continent collision in the Paleocene (cooling age 58.3 Ma). Subsequently there has been 50 km or more of NE-SW extension of the crust allowing emergence and uplift of the metamorphic rocks and tilting and erosion of the arc to reveal the PUB ophiolite. In 2010-2011 we reviewed the existing field and petrologic data and more recent satellite imagery, and followed up with several days of reconnaissance mapping. We were particularly interested to find and explanation for the interruption of the Owen Stanley Range at 148.4E to 148.8 E. Our preliminary conclusions include (a) there is evidence of a second metamorphic event (a second collision perhaps) in the Eocene; (b) it is likely that the range developed as a series of sub-horizontal thrust sheets; and (c) the thrust sheets were reactivated in the Late Miocene-to-Quaternary as extensional duplexes. Extension was accompanied by emplacement of diorite-granodiorite and K-rich hypabyssal rocks some of which are localised along the former leading edge (the SW front) of the Emo metamorphic carapace.

  15. Tilt optimization of a building integrated solar concentrating unit

    NASA Astrophysics Data System (ADS)

    Chemisana, D.; Tripanagnostopoulos, Y.; Lamnatou, Chr.; Souliotis, M.; Rosell, J. I.; Barrau, J.

    2012-10-01

    The concept of a static linear Fresnel concentrator with a tracking absorber has been simulated and well understood in the past. This paper bridges the gap between theoretical optical performances and operation in outdoor conditions. The effort focuses on the characterization of weather and tilt angle effects on the solar concentrator annual performance. Useful mathematical expressions are derived to show the dependence of the annual concentrated energy on latitude, global radiation, mean clearness index and tilt angle. An equation for the optimization of the annual yield is also proposed. The results are applied to a PVT generator and the annual production of thermal and electrical output energy is evaluated for an installation in Barcelona (Spain). A performance improvement above 5% is reached when the optimized tilt angle is used.

  16. Inverse solutions for tilting orthogonal double prisms.

    PubMed

    Li, Anhu; Ding, Ye; Bian, Yongming; Liu, Liren

    2014-06-10

    An analytical reverse solution and actual examples are given to show how to direct a laser beam from a pair of orthogonal prisms to given targets in free space. Considering the influences of double-prism structural parameters, a lookup table method to seek the numerical reverse solution of each prism's tilting angle is also proposed for steering the double-prism orientation to track a target position located in the near field. Some case studies, as well as a specified elliptical target trajectory scanned by the cam-based driving double prisms, exhibit the significant application values of the theoretical derivation. The analytic reverse and numerical solutions can be generalized to investigate the synthesis of scanning patterns and the controlling strategy of double-prism tilting motion, the potentials of which can be explored to perform the orientation and position tracking functions in applications of precision engineering fields. PMID:24921137

  17. Tilted brownian ratchet for DNA analysis.

    PubMed

    Huang, Lotien Richard; Cox, Edward C; Austin, Robert H; Sturm, James C

    2003-12-15

    In this paper, we report a factor of 3 improvement in the resolution and a factor of 10 improvement in the speed of fractionation of approximately 100-kb DNA molecules in Brownian ratchet arrays. In our device, the electrophoretic flow is tilted at a small angle relative to the array axis. Tilting accelerates the fractionation speed because a higher fraction of the diffusing molecules is "ratcheted" at each step in the array. Molecules of lengths 48.5 and 164 kb can be separated in approximately 70 min with a resolution of approximately 3.8, using a 12-mm-long array. The Brownian ratchet arrays are not limited to DNA separation, but can, in principle, be used for any particle in this size range. PMID:14670059

  18. Tilted Liquid Crystal Alignment on Asymmetrically Grooved Porous Alumina Film

    NASA Astrophysics Data System (ADS)

    Maeda, Tsuyoshi; Hiroshima, Kohki

    2005-06-01

    This paper reports the achievement of tilted liquid crystal (LC) alignment on an anodic porous alumina (APA) film using microgrooves with asymmetric shapes and dozens of minute pores. The microgrooves with asymmetric shapes were formed by a rubbing technique. The minute pores were then produced by anodization. The LC pretilt angle was controlled by the shapes of the microgrooves and pores. The LC director was orientated in the same inclining direction as that of a rubbed polyimide (PI) film. The pretilt angle was in the range of 20 to 90°. This tilted LC alignment remains very stable against external forces such as thermal shock and intense light.

  19. Tilted string cosmologies

    NASA Astrophysics Data System (ADS)

    Clancy, Dominic; Feinstein, Alexander; Lidsey, James E.; Tavakol, Reza

    1999-04-01

    Global symmetries of the string effective action are employed to generate tilted, homogeneous Bianchi type VIh string cosmologies from a previously known stiff perfect fluid solution to Einstein gravity. The dilaton field is not constant on the surfaces of homogeneity. The future asymptotic state of the models is interpreted as a plane wave and is itself an exact solution to the string equations of motion to all orders in the inverse string tension. An inhomogeneous generalization of the Bianchi type III model is also found.

  20. Perception of self-tilt in a true and illusory vertical plane

    NASA Technical Reports Server (NTRS)

    Groen, Eric L.; Jenkin, Heather L.; Howard, Ian P.; Oman, C. M. (Principal Investigator)

    2002-01-01

    A tilted furnished room can induce strong visual reorientation illusions in stationary subjects. Supine subjects may perceive themselves upright when the room is tilted 90 degrees so that the visual polarity axis is kept aligned with the subject. This 'upright illusion' was used to induce roll tilt in a truly horizontal, but perceptually vertical, plane. A semistatic tilt profile was applied, in which the tilt angle gradually changed from 0 degrees to 90 degrees, and vice versa. This method produced larger illusory self-tilt than usually found with static tilt of a visual scene. Ten subjects indicated self-tilt by setting a tactile rod to perceived vertical. Six of them experienced the upright illusion and indicated illusory self-tilt with an average gain of about 0.5. This value is smaller than with true self-tilt (0.8), but comparable to the gain of visually induced self-tilt in erect subjects. Apparently, the contribution of nonvisual cues to gravity was independent of the subject's orientation to gravity itself. It therefore seems that the gain of visually induced self-tilt is smaller because of lacking, rather than conflicting, nonvisual cues. A vector analysis is used to discuss the results in terms of relative sensory weightings.

  1. Dynamics of tilted cylindrical geometry

    NASA Astrophysics Data System (ADS)

    Sharif, M.; Sadiq, Sobia

    2016-09-01

    In this paper, we study the dynamics of tilted cylindrical model with imperfect matter distribution. We formulate the field equations and develop relations between tilted and non-tilted variables. We evaluate kinematical as well as dynamical quantities and discuss the inhomogeneity factor. We also obtain the Raychaudhuri equation to study evolution of expansion scalar. The solutions of field equations are also investigated for static cylinder under isotropy and conformally flat condition. Finally, we analyze some thermoinertial aspects of the system.

  2. Tilting mode in nuclear reactions

    SciTech Connect

    Dossing, T.; Randrup, J.

    1986-02-01

    The relation between tilting relaxation and the reaction plane dynamics is discussed, providing an intuitive understanding of the expression for the cross section close to the beam direction, which has recently been derived. Second, the tilting relaxation time and the related wriggling relaxation time are discussed, based upon nucleon exchange transport (window friction). Finally, recent experimental information on the tilting mode relaxation is discussed, and the dynamics of the tilting mode is discussed qualitatively for the three different types of nuclear reactions considered, compound nucleus fission, quasifission, and damped nuclear reactions. 9 refs., 3 figs.

  3. Aberration and boresight error correction for conformal aircraft windows using the inner window surface and tilted fixed correctors.

    PubMed

    Zhao, Chunzhu; Cui, Qingfeng; Mao, Shan

    2016-04-01

    A static solution to aberrations and boresight error for tilted conformal aircraft windows at different look angles is reported. The solution uses the inner window surface to correct the window aberrations at a 0° look angle and uses fixed correctors behind the window to correct the residual window aberrations at other look angles. Then, the boresight error for the window at different look angles is corrected by tilting the fixed correctors. The principle of the solution is discussed, and a design example shows that the solution is effective in correcting the aberrations and boresight error for a tilted conformal aircraft window at different look angles. PMID:27139665

  4. Human perceptual overestimation of whole body roll tilt in hypergravity

    PubMed Central

    Newman, Michael C.; Oman, Charles M.; Merfeld, Daniel M.; Young, Laurence R.

    2014-01-01

    Hypergravity provides a unique environment to study human perception of orientation. We utilized a long-radius centrifuge to study perception of both static and dynamic whole body roll tilt in hypergravity, across a range of angles, frequencies, and net gravito-inertial levels (referred to as G levels). While studies of static tilt perception in hypergravity have been published, this is the first to measure dynamic tilt perception (i.e., with time-varying canal stimulation) in hypergravity using a continuous matching task. In complete darkness, subjects reported their orientation perception using a haptic task, whereby they attempted to align a hand-held bar with their perceived horizontal. Static roll tilt was overestimated in hypergravity, with more overestimation at larger angles and higher G levels, across the conditions tested (overestimated by ∼35% per additional G level, P < 0.001). As our primary contribution, we show that dynamic roll tilt was also consistently overestimated in hypergravity (P < 0.001) at all angles and frequencies tested, again with more overestimation at higher G levels. The overestimation was similar to that for static tilts at low angular velocities but decreased at higher angular velocities (P = 0.006), consistent with semicircular canal sensory integration. To match our findings, we propose a modification to a previous Observer-type canal-otolith interaction model. Specifically, our data were better modeled by including the hypothesis that the central nervous system treats otolith stimulation in the utricular plane differently than stimulation out of the utricular plane. This modified model was able to simulate quantitatively both the static and the dynamic roll tilt overestimation in hypergravity measured experimentally. PMID:25540216

  5. An optimum world population.

    PubMed

    Willey, D

    2000-01-01

    The optimum population of the world is the one that is most likely to make the option of a good quality of life available to everyone everywhere, both now and in the future. Establishing a consensus about the size of such a population would be an important step towards achieving it. Estimates of an optimum involve three main steps. First, estimate the maximum (carrying capacity) assuming a specified lifestyle. The main criteria are the maintenance of biodiversity, the availability of freshwater, and the availability of land--for agriculture, forestry and artificial systems but above all for the conversion of energy. (In applying the criteria, there are always two questions to ask: 'What is the maximum amount of consumption that the biosphere can stand?' and 'What is an adequate share of such consumption per person?') Second, convert the maximum (two to three billion) into an optimum by applying a far wider range of criteria, including personal liberty, mobility, recreation and political representation. Third, consider just two criteria (economies of scale and technological innovation) in order to ensure that the optimum (one to two billion) has not fallen below the minimum (half to one billion). The estimates are so low because of the need for a huge increase in median per capita consumption if everyone is to have the option of an adequate material standard of living. Opinion-formers are likely not to take much notice of such estimates, but it is probable that minds will be concentrated by an energy shock some time during the next decade. Achieving an optimum world population will not solve the world's major problems, but it would make them solvable. PMID:10824524

  6. Method for Determining Optimum Injector Inlet Geometry

    NASA Technical Reports Server (NTRS)

    Trinh, Huu P. (Inventor); Myers, W. Neill (Inventor)

    2015-01-01

    A method for determining the optimum inlet geometry of a liquid rocket engine swirl injector includes obtaining a throttleable level phase value, volume flow rate, chamber pressure, liquid propellant density, inlet injector pressure, desired target spray angle and desired target optimum delta pressure value between an inlet and a chamber for a plurality of engine stages. The method calculates the tangential inlet area for each throttleable stage. The method also uses correlation between the tangential inlet areas and delta pressure values to calculate the spring displacement and variable inlet geometry of a liquid rocket engine swirl injector.

  7. Method to fabricate a tilted logpile photonic crystal

    DOEpatents

    Williams, John D.; Sweatt, William C.

    2010-10-26

    A method to fabricate a tilted logpile photonic crystal requires only two lithographic exposures and does not require mask repositioning between exposures. The mask and photoresist-coated substrate are spaced a fixed and constant distance apart using a spacer and the stack is clamped together. The stack is then tilted at a crystallographic symmetry angle (e.g., 45 degrees) relative to the X-ray beam and rotated about the surface normal until the mask is aligned with the X-ray beam. The stack is then rotated in plane by a small stitching angle and exposed to the X-ray beam to pattern the first half of the structure. The stack is then rotated by 180.degree. about the normal and a second exposure patterns the remaining half of the structure. The method can use commercially available DXRL scanner technology and LIGA processes to fabricate large-area, high-quality tilted logpile photonic crystals.

  8. Head-Up Tilt.

    PubMed

    Xu, Jinyi; Yang, Lihong; Zhang, Qiang; Li, Shuaibing; Qiao, Zihao; Fang, Ying; Zhao, Guihua; Wang, Qingyi; Liu, Guanghui

    2015-01-01

    Autonomic dysfunction has been associated with paroxysmal atrial fibrillation (PAF). The head-up tilt test (HUTT) is an important diagnostic tool for autonomic dysfunction. The aim of this study was to examine atrial fibrillation recurrence after RFCA by performing HUTT. A total of 488 consecutive patients with PAF who underwent RFCA were prospectively enrolled. HUTT was positive in 154 (31.6%) patients after a mean follow-up of 22.7 ± 3.5 months, and 163 (33.4%) had a recurrence. HUTT positive was significantly higher in PAF patients with recurrence compared to those without (68 (41.7%) versus 86 (26.5%), P < 0.001). Multivariate Cox regression analysis revealed that HUTT positive (HR: 1.96; 95% CI: 1.49-2.48, P < 0.001), left atrial diameter (HR: 1.77; 95%CI: 1.15-2.11, P = 0.004), AF duration (HR: 1.27; 95%CI: 0.98-1.83, P = 0.014), and sleep apnea (HR: 1.02; 95%CI: 0.81-1.53, P = 0.032) were independent predictors of clinical recurrence after RFCA. The success rate of ablation was 70.4% in patients in the HUTT negative group compared with 58.4% in patients in the HUTT positive group (log-rank P = 0.006). Patients with a positive headup tilt test were at an increased risk of AF recurrence after catheter ablation. Our results suggest that HUTT was a significant predictor for AF recurrence after catheter ablation for PAF. PMID:26370369

  9. Tilted dipole model for bias-dependent photoluminescence pattern

    NASA Astrophysics Data System (ADS)

    Fujieda, Ichiro; Suzuki, Daisuke; Masuda, Taishi

    2014-12-01

    In a guest-host system containing elongated dyes and a nematic liquid crystal, both molecules are aligned to each other. An external bias tilts these molecules and the radiation pattern of the system is altered. A model is proposed to describe this bias-dependent photoluminescence patterns. It divides the liquid crystal/dye layer into sub-layers that contain electric dipoles with specific tilt angles. Each sub-layer emits linearly polarized light. Its radiation pattern is toroidal and is determined by the tilt angle. Its intensity is assumed to be proportional to the power of excitation light absorbed by the sub-layer. This is calculated by the Lambert-Beer's Law. The absorption coefficient is assumed to be proportional to the cross-section of the tilted dipole moment, in analogy to the ellipsoid of refractive index, to evaluate the cross-section for each polarized component of the excitation light. Contributions from all the sub-layers are added to give a final expression for the radiation pattern. Self-absorption is neglected. The model is simplified by reducing the number of sub-layers. Analytical expressions are derived for a simple case that consists of a single layer with tilted dipoles sandwiched by two layers with horizontally-aligned dipoles. All the parameters except for the tilt angle can be determined by measuring transmittance of the excitation light. The model roughly reproduces the bias-dependent photoluminescence patterns of a cell containing 0.5 wt. % coumarin 6. It breaks down at large emission angles. Measured spectral changes suggest that the discrepancy is due to self-absorption and re-emission.

  10. Tilted dipole model for bias-dependent photoluminescence pattern

    SciTech Connect

    Fujieda, Ichiro Suzuki, Daisuke; Masuda, Taishi

    2014-12-14

    In a guest-host system containing elongated dyes and a nematic liquid crystal, both molecules are aligned to each other. An external bias tilts these molecules and the radiation pattern of the system is altered. A model is proposed to describe this bias-dependent photoluminescence patterns. It divides the liquid crystal/dye layer into sub-layers that contain electric dipoles with specific tilt angles. Each sub-layer emits linearly polarized light. Its radiation pattern is toroidal and is determined by the tilt angle. Its intensity is assumed to be proportional to the power of excitation light absorbed by the sub-layer. This is calculated by the Lambert-Beer's Law. The absorption coefficient is assumed to be proportional to the cross-section of the tilted dipole moment, in analogy to the ellipsoid of refractive index, to evaluate the cross-section for each polarized component of the excitation light. Contributions from all the sub-layers are added to give a final expression for the radiation pattern. Self-absorption is neglected. The model is simplified by reducing the number of sub-layers. Analytical expressions are derived for a simple case that consists of a single layer with tilted dipoles sandwiched by two layers with horizontally-aligned dipoles. All the parameters except for the tilt angle can be determined by measuring transmittance of the excitation light. The model roughly reproduces the bias-dependent photoluminescence patterns of a cell containing 0.5 wt. % coumarin 6. It breaks down at large emission angles. Measured spectral changes suggest that the discrepancy is due to self-absorption and re-emission.

  11. Tilt angular anisoplanatism and a full-aperture tilt-measurement technique with a laser guide star.

    PubMed

    Belen'kii, M S

    2000-11-20

    A method is presented for sensing atmospheric wave-front tilt from a laser guide star (LGS) by observing a laser beacon with auxiliary telescopes. The analysis is performed with a LGS scatter model and Zernike polynomial expansion of wave-front distortions. It is shown that integration of the LGS image over its angular extent and the position of the auxiliary telescope in an array reduce the tilt sensing error associated with the contribution from the downward path. This allows us to single out only the wave-front tilt of the transmitted beam on the uplink path that corresponds to the tilt for the scientific object. The tilt angular correlation is analyzed in the atmosphere with a finite turbulence outer scale. The tilt correlation angle depends on the angular size of the telescope and the outer scale of turbulence. The tilt sensing error increases with the auxiliary telescope diameter, suggesting that an auxiliary telescope must be small. The Strehl ratio associated with the contribution from the downward path is in the range from 0.1 to 0.9 when the relative telescope diameter D/r(0) varies from 4 to 93 and the turbulence outer scale is in the 10-150-m range. Tilt correction increases the Strehl ratio compared with the uncorrected image for all the system parameters and seeing conditions considered. The method discussed gives a higher performance than the conventional technique, which uses an off-axis natural guide star. A scheme for measuring tilt with a beam projected from a small aperture is described. This scheme allows us to avoid phosphorescence of the main optical train for a sodium LGS. PMID:18354615

  12. Optimum connection management scheduling

    NASA Astrophysics Data System (ADS)

    Kadar, Ivan

    2000-08-01

    Connection Management plays a key role in both distributed 'local' network-centric and 'globally' connected info- centric systems. The role of Connection Management is to provide seamless demand-based sharing of the information products. For optimum distributed information fusion performance, these systems must minimize communications delays and maximize message throughput, and at the same time take into account relative-sensors-targets geometrical constraints and data pedigree. In order to achieve overall distributed 'network' effectiveness, these systems must be adaptive, and be able to distribute data s needed in real- time. A system concept will be described which provides optimum capacity-based information scheduling. A specific example, based on a satellite channel, is used to illustrate simulated performance results and their effects on fusion systems performance.

  13. Optimum shell design.

    NASA Technical Reports Server (NTRS)

    Salama, A. M.; Ross, R. G., Jr.

    1973-01-01

    Comparison of two methods, namely Nedler and Mead's (1965) simplex method and Davidon's (1959) variable metric method, for achieving optimum design in terms of minimum weight for rotational shells under certain constraints. The superiority of one of the methods over the other is shown to depend, among other things, upon the form of the function to be minimized, and whether or not it is continuous everywhere in values and derivatives.

  14. Exploring a possible origin of a 14 deg y-normal spin tilt at RHIC polarimeter

    SciTech Connect

    Meot, F.; Huang, H.

    2015-06-15

    A possible origin of a 14 deg y-normal spin n0 tilt at the polarimeter is in snake angle defects. This possible cause is investigated by scanning the snake axis angle µ, and the spin rotation angle at the snake, φ, in the vicinity of their nominal values.

  15. The effects of gantry tilt on breast dose and image noise in cardiac CT

    SciTech Connect

    Hoppe, Michael E.; Gandhi, Diksha; Schmidt, Taly Gilat; Stevens, Grant M.; Foley, W. Dennis

    2013-12-15

    Purpose: This study investigated the effects of tilted-gantry acquisition on image noise and glandular breast dose in females during cardiac computed tomography (CT) scans. Reducing the dose to glandular breast tissue is important due to its high radiosensitivity and limited diagnostic significance in cardiac CT scans.Methods: Tilted-gantry acquisition was investigated through computer simulations and experimental measurements. Upon IRB approval, eight voxelized phantoms were constructed from previously acquired cardiac CT datasets. Monte Carlo simulations quantified the dose deposited in glandular breast tissue over a range of tilt angles. The effects of tilted-gantry acquisition on breast dose were measured on a clinical CT scanner (CT750HD, GE Healthcare) using an anthropomorphic phantom with MOSFET dosimeters in the breast regions. In both simulations and experiments, scans were performed at gantry tilt angles of 0°–30°, in 5° increments. The percent change in breast dose was calculated relative to the nontilted scan for all tilt angles. The percent change in noise standard deviation due to gantry tilt was calculated in all reconstructed simulated and experimental images.Results: Tilting the gantry reduced the breast dose in all simulated and experimental phantoms, with generally greater dose reduction at increased gantry tilts. For example, at 30° gantry tilt, the dosimeters located in the superior, middle, and inferior breast regions measured dose reductions of 74%, 61%, and 9%, respectively. The simulations estimated 0%–30% total breast dose reduction across the eight phantoms and range of tilt angles. However, tilted-gantry acquisition also increased the noise standard deviation in the simulated phantoms by 2%–50% due to increased pathlength through the iodine-filled heart. The experimental phantom, which did not contain iodine in the blood, demonstrated decreased breast dose and decreased noise at all gantry tilt angles.Conclusions: Tilting the

  16. Satellite sweeping in offset, tilted dipole fields

    NASA Technical Reports Server (NTRS)

    Paonessa, Mark T.; Cheng, Andrew F.

    1987-01-01

    The paper presents a theory for the longitudinally averaged satellite sweeping rate in an offset, tilted dipole magnetic field. It includes the reductions in the sweeping rate when the moon radius is not large compared to the gyroradius or the azimuthal drift distance during a bounce period. With a large tilt angle between the magnetic and rotation axes, moons make large excursions in dipole L value, and more than one moon can sweep at a given L. The sweeping rate peaks at the minimum L for each moon. If the gyroradius is large, additional peaks can occur when the particle mirrors near the moon latitude. To illustrate the theory, sweeping rates are evaluated for parameters relevant to the observations at Uranus by the Voyager 2 Low Energy Charged Particles Experiment. Calculated sweeping rates for ions and electrons are typically two or three orders of magnitude less than the strong-diffusion loss rate. The observation of sweeping signatures at Uranus would imply that pitch-angle scattering there occurs at a rate far below the strong-diffusion limit, contrasting with the situation for energetic ions in the inner Jovian magnetosphere.

  17. Tilt anisoplanatism in extended turbulence propagation

    NASA Astrophysics Data System (ADS)

    Magee, Eric P.; Whiteley, Matthew R.; Das, Shashikala T.; Welsh, Byron M.

    2003-04-01

    The use of high-energy laser (HEL) weapon systems in tactical air-to-ground target engagements offers great promise for revolutionizing the USAF's war-fighting capabilities. Laser directed-energy systems will enable ultra-precision strike with minimal collateral damage and significant stand-off range for the aerial platform. The tactical directed energy application differs in many crucial ways from the conventional approach used in missile defense. Tactical missions occur at much lower altitudes and involve look-down to low-contrast ground targets instead of a high-contrast boosting missile. At these lower altitudes, the strength of atmospheric turbulence is greatly enhanced. Although the target slant ranges are much shorter, tactical missions may still involve moderate values of the Rytov number (0.1-0.5), and small isoplanatic angles compared to the diffraction angle. With increased density of air in the propagation path, and the potential for slow-moving or stationary ground targets, HEL-induced thermal blooming will certainly be a concern. In order to minimize the errors induced by tracking through thermal blooming, offset aimpoint tracking can be used. However, this will result in significant tilt anisoplanatism, thus degrading beam stabilization on target. In this paper we investigate the effects of extended turbulence on tracking (or tilt) anisoplanatism using theory and wave optics simulations. The simulations show good agreement with geometric optics predictions at angles larger than about 5 micro-radians (asymptotic regime) while at smaller angles the agreement is poor. We present a theoretical basis for this observation.

  18. Motion sickness on tilting trains

    PubMed Central

    Cohen, Bernard; Dai, Mingjia; Ogorodnikov, Dmitri; Laurens, Jean; Raphan, Theodore; Müller, Philippe; Athanasios, Alexiou; Edmaier, Jürgen; Grossenbacher, Thomas; Stadtmüller, Klaus; Brugger, Ueli; Hauser, Gerald; Straumann, Dominik

    2011-01-01

    Trains that tilt on curves can go faster, but passengers complain of motion sickness. We studied the control signals and tilts to determine why this occurs and how to maintain speed while eliminating motion sickness. Accelerometers and gyros monitored train and passenger yaw and roll, and a survey evaluated motion sickness. The experimental train had 3 control configurations: an untilted mode, a reactive mode that detected curves from sensors on the front wheel set, and a predictive mode that determined curves from the train's position on the tracks. No motion sickness was induced in the untilted mode, but the train ran 21% slower than when it tilted 8° in either the reactive or predictive modes (113 vs. 137 km/h). Roll velocities rose and fell faster in the predictive than the reactive mode when entering and leaving turns (0.4 vs. 0.8 s for a 4°/s roll tilt, P<0.001). Concurrently, motion sickness was greater (P<0.001) in the reactive mode. We conclude that the slower rise in roll velocity during yaw rotations on entering and leaving curves had induced the motion sickness. Adequate synchronization of roll tilt with yaw velocity on curves will reduce motion sickness and improve passenger comfort on tilting trains.—Cohen, B., Dai, M., Ogorodnikov, D., Laurens, J., Raphan, T., Müller, P., Athanasios, A., Edmaier, J., Grossenbacher, T., Stadtmüller, K., Brugger, U., Hauser, G., Straumann, D. Motion sickness on tilting trains. PMID:21788449

  19. Optimum hovering wing planform.

    PubMed

    Nabawy, Mostafa R A; Crowther, William J

    2016-10-01

    Theoretical analysis is used to identify the optimum wing planform of a flapping/revolving wing in hover. This solution is of interest as a benchmark to which hovering wing geometries driven by broader multidisciplinary evolutionary or engineering constraints can be compared. Furthermore, useful insights into the aerodynamic performance of untwisted hovering wings are delivered. It is shown that profile power is minimised by using an untwisted elliptical planform whereas induced power is minimised by a more highly tapered planform similar to that of a hummingbird. PMID:27329340

  20. Modeling impurities and tilted plates in the ITER divertor

    SciTech Connect

    Rensink, M.E.; Rognlien, T.D.

    1996-07-29

    The UEDGE 2-D edge transport code is used to model the effect of impurities and tilted divertor plates for the ITER SOL/divertor region. The impurities are modeled as individual charge states using either the FMOMBAL 21-moment description or parallel force balance. Both helium and neon impurities are used together with a majority hydrogenic species. A fluid description of the neutrals is used that includes parallel inertia and neutral-neutral collisions. Effects of geometry are analyzed by using the nonorthogonal mesh capability of UEDGE to obtain solutions with the divertor plate tilted at various angles.

  1. XV-15 tilt rotor

    NASA Technical Reports Server (NTRS)

    1980-01-01

    This photo shows the unique XV-15 Tiltrotor aircraft in vertical flight at the NASA Dryden Flight Research Center. The XV-15s, manufactured by Bell, were involved in limited research at NASA/Dryden in 1980 and 1981. The development of the XV-15 Tiltrotor research aircraft was initiated in 1973 with joint Army/NASA funding as a 'proof of concept', or 'technology demonstrator' program, with two aircraft being built by Bell Helicopter Textron (BHT) in 1977. NASA Ames Research Center, where most of the NASA research is conducted, continues to be in charge of the joint NASA/Army/Bell program. The aircraft are powered by twin Lycoming T-53 turboshaft engines that are connected by a cross-shaft and drive three-bladed, 25 ft diameter metal rotors (the size extensively tested in a wind tunnel). The engines and main transmissions are located in wingtip nacelles to minimize the operational loads on the cross-shaft system and, with the rotors, tilt as a single unit. For takeoff, the proprotors and their engines are used in the straight-up position where the thrust is directed downward. The XV-15 then climbs vertically into the air like a helicopter. In this VTOL mode, the vehicle can lift off and hover for approximately one hour. Once off the ground, the XV-15 has the ability to fly in one of two different modes. It can fly as a helicopter, in the partially converted airplane mode. The XV-15 can also then convert from the helicopter mode to the airplane mode. This is accomplished by continuous rotation of the proprotors from the helicopter rotor position to the conventional airplane propeller position. During the ten to fifteen second conversion period, the aircraft speed increases and lift is transferred from the rotors to the wing. To land, the proprotors are rotated up to the helicopter rotor position and flown as a helicopter to a vertical landing.

  2. Reverse time migration in tilted transversely isotropic media

    SciTech Connect

    Zhang, Linbing; Rector III, James W.; Hoversten, G. Michael

    2004-07-01

    This paper presents a reverse time migration (RTM) method for the migration of shot records in tilted transversely isotropic (TTI) media. It is based on the tilted TI acoustic wave equation that was derived from the dispersion relation. The RTM is a full depth migration allowing for velocity to vary laterally as well as vertically and has no dip limitations. The wave equation is solved by a tenth-order finite difference scheme. Using 2D numerical models, we demonstrate that ignoring the tilt angle will introduce both lateral and vertical shifts in imaging. The shifts can be larger than 0.5 wavelength in the vertical direction and 1.5 wavelength in the lateral direction.

  3. Note: Enhancing the sensitivity of roll-angle measurement with a novel interferometric configuration based on waveplates and folding mirror

    NASA Astrophysics Data System (ADS)

    Qi, J.; Wang, Z.; Huang, J. H.; Yu, B.; Gao, J.; Donati, S.

    2016-03-01

    A novel method for very high resolution measurement of roll angle on a transparent plate is developed theoretically and tested experimentally. The new optical configuration is based on the interferometric readout of phase shift accumulated on the double passage through half wave plate, together with a careful control of polarization state by means of quarter wave plate, and optimizing the tilt of the folding mirror. Sensitivity to roll angle is greatly enhanced and a gain coefficient exceeding 700 is found theoretically, based on Jones' matrix analysis, with a 6-fold increase respect to previous results. In the experimental setup, at the optimum 36° incidence to retroreflector, we measured a gain coefficient of 340. Correspondingly, with an interferometer phase meter resolving 0.01°, a roll-angle resolution 0.1-arc sec is attained.

  4. Angle-specific transparent conducting electrodes with metallic gratings

    SciTech Connect

    Rivolta, N. X. A. Maes, B.

    2014-08-07

    Transparent conducting electrodes, which are not made from indium tin oxide, and which display a strong angular dependence are useful for various technologies. Here, we introduce a tilted silver grating that combines a large conductance with a strong and angle-specific transmittance. When the light incidence angle matches the tilt angle of the grating, transmittance is close to the maximum along a very broadband range. We explain the behavior through simulations that show in detail the plasmonic and interference effects at play.

  5. Improvements to tilt rotor performance through passive blade twist control

    NASA Technical Reports Server (NTRS)

    Nixon, Mark W.

    1988-01-01

    A passive blade twist control is presented in which the twist distribution of a tilt rotor blade is elastically changed as a function of rotor speed. The elastic twist deformation is used to achieve two different blade twist distributions corresponding to the two rotor speeds used on conventional tilt rotors in hover and forward flight. By changing the blade twist distribution, the aerodynamic performance can be improved in both modes of flight. The concept presented obtains a change in twist distribution with extension-twist-coupled composite blade structure. This investigation first determines the linear twists which are optimum for each flight mode. Based on the optimum linear twist distributions, three extension-twist-coupled blade designs are developed using coupled-beam and laminate analyses integrated with an optimization analysis. The designs are optimized for maximum twist deformation subject to material strength limitations. The aerodynamic performances of the final designs are determined which show that the passive blade twist control concept is viable, and can enhance conventional tilt rotor performance.

  6. Conservative GRMHD simulations of moderately thin, tilted accretion disks

    SciTech Connect

    Teixeira, Danilo Morales; Fragile, P. Chris; Zhuravlev, Viacheslav V.; Ivanov, Pavel B.

    2014-12-01

    This paper presents our latest numerical simulations of accretion disks that are misaligned with respect to the rotation axis of a Kerr black hole. In this work, we use a new, fully conservative version of the Cosmos++ general relativistic magnetohydrodynamics (GRMHD) code, coupled with an ad hoc cooling function designed to control the thickness of the disk. Together these allow us to simulate the thinnest tilted accretion disks ever using a GRMHD code. In this way, we are able to probe the regime where the dimensionless stress and scale height of the disk become comparable. We present results for both prograde and retrograde cases. The simulated prograde tilted disk shows no sign of Bardeen-Petterson alignment even in the innermost parts of the disk. The simulated retrograde tilted disk, however, does show modest alignment. The implication of these results is that the parameter space associated with Bardeen-Petterson alignment for prograde disks may be rather small, only including very thin disks. Unlike our previous work, we find no evidence for standing shocks in our simulated tilted disks. We ascribe this to the black hole spin, tilt angle, and disk scale height all being small in these simulations. We also add to the growing body of literature pointing out that the turbulence driven by the magnetorotational instability in global simulations of accretion disks is not isotropic. Finally, we provide a comparison between our moderately thin, untilted reference simulation and other numerical simulations of thin disks in the literature.

  7. High tilt susceptibility of the Scintrex CG-5 relative gravimeters

    NASA Astrophysics Data System (ADS)

    Reudink, R.; Klees, R.; Francis, O.; Kusche, J.; Schlesinger, R.; Shabanloui, A.; Sneeuw, N.; Timmen, L.

    2014-06-01

    We report on the susceptibility of the Scintrex CG-5 relative gravimeters to tilting, that is the tendency of the instrument of providing incorrect readings after being tilted (even by small angles) for a moderate period of time. Tilting of the instrument can occur when in transit between sites usually on the backseat of a car even using the specially designed transport case. Based on a series of experiments with different instruments, we demonstrate that the readings may be offset by tens of Gal. In addition, it may take hours before the first reliable readings can be taken, with the actual time depending on how long the instrument had been tilted. This sensitivity to tilt in combination with the long time required for the instrument to provide reliable readings has not yet been reported in the literature and is not addressed adequately in the Scintrex CG-5 user manual. In particular, the inadequate instrument state cannot easily be detected by checking the readings during the observation or by reviewing the final data before leaving a site, precautions suggested by Scintrex Ltd. In regional surveys with car transportation over periods of tens of minutes to hours, the gravity measurements can be degraded by some 10 Gal. To obtain high-quality results in line with the CG-5 specifications, the gravimeters must remain in upright position to within a few degrees during transits. This requirement may often be unrealistic during field observations, particularly when observing in hilly terrain or when walking with the instrument in a backpack.

  8. The Application of Normal Stress Reduction Function in Tilt Tests for Different Block Shapes

    NASA Astrophysics Data System (ADS)

    Kim, Dong Hyun; Gratchev, Ivan; Hein, Maw; Balasubramaniam, Arumugam

    2016-08-01

    This paper focuses on the influence of the shapes of rock cores, which control the sliding or toppling behaviours in tilt tests for the estimation of rock joint roughness coefficients (JRC). When the JRC values are estimated by performing tilt tests, the values are directly proportional to the basic friction of the rock material and the applied normal stress on the sliding planes. Normal stress obviously varies with the shape of the sliding block, and the basic friction angle is also affected by the sample shapes in tilt tests. In this study, the shapes of core blocks are classified into three representative shapes and those are created using plaster. Using the various shaped artificial cores, a set of tilt tests is carried out to identify the shape influences on the normal stress and the basic friction angle in tilt tests. The test results propose a normal stress reduction function to estimate the normal stress for tilt tests according to the sample shapes based on Barton's empirical equation. The proposed normal stress reduction functions are verified by tilt tests using artificial plaster joints and real rock joint sets. The plaster joint sets are well matched and cast in detailed printed moulds using a 3D printing technique. With the application of the functions, the obtained JRC values from the tilt tests using the plaster samples and the natural rock samples are distributed within a reasonable JRC range when compared with the measured values.

  9. 2D tilting MEMS micro mirror integrating a piezoresistive sensor position feedback

    NASA Astrophysics Data System (ADS)

    Lani, S.; Bayat, D.; Despont, M.

    2015-02-01

    An integrated position sensor for a dual-axis electromagnetic tilting mirror is presented. This tilting mirror is composed of a silicon based mirror directly assembled on a silicon membrane supported by flexible beams. The position sensors are constituted by 4 Wheatstone bridges of piezoresistors which are fabricated by doping locally the flexible beams. A permanent magnet is attached to the membrane and the scanner is mounted above planar coils deposited on a ceramic substrate to achieve electromagnetic actuation. The performances of the piezoresistive sensors are evaluated by measuring the output signal of the piezoresistors as a function of the tilt of the mirror and the temperature. White light interferometry was performed for all measurement to measure the exact tilt angle. The minimum detectable angle with such sensors was 30µrad (around 13bits) in the range of the minimum resolution of the interferometer. The tilt reproducibility was 0.0186%, obtained by measuring the tilt after repeated actuations with a coil current of 50mA during 30 min and the stability over time was 0.05% in 1h without actuation. The maximum measured tilt angle was 6° (mechanical) limited by nonlinearity of the MEMS system.

  10. Effects of external feedback about body tilt: Influence on the Subjective Proprioceptive Horizon.

    PubMed

    Bringoux, L; Bourdin, C; Nougier, V; Raphel, C

    2006-11-01

    The present study investigated a cognitive aspect upon spatial perception, namely the impact of a true or false verbal feedback (FB) about the magnitude of body tilt on Subjective Proprioceptive Horizon (SPH) estimates. Subjects were asked to set their extended arm normal to gravity for different pitch body tilts up to 9 degrees . True FB were provided at all body tilt angles, whereas false FB were provided only at 6 degrees backward and 6 degrees forward body tilts for half of the trials. Our data confirmed previous results about the egocentric influence of body tilt itself upon SPH: estimates were linearly lowered with forward tilts and elevated with backward tilts. In addition, results showed a significant effect of the nature of the external FB provided to the subjects. When subjects received a false FB inducing a 3 degrees forward bias relative to physical body tilt, they set their SPH consequently higher than when they received a false FB inducing a 3 degrees backward bias. These findings clearly indicated that false cognitive information about body tilt might significantly modify the judgement of a geocentric direction of space, such as the SPH. This may have deleterious repercussions in aeronautics when pilots have to localize external objects relative to earth-based directions in darkened environments. PMID:16982145

  11. An approach to optimum subsonic inlet design

    NASA Technical Reports Server (NTRS)

    Luidens, R. W.; Stockman, N. O.; Diedrich, J. H.

    1978-01-01

    Inlet operating requirements are compared with estimated inlet separation characteristics to identify the most critical inlet operating condition. This critical condition is taken to be the design point and is defined by the values of inlet mass flow, free-stream velocity and inlet angle of attack. Optimum flow distributions on the inlet surface were determined to be a high, flat top Mach number distribution on the inlet lip to turn the flow quickly into the inlet and a flat bottom skin-friction distribution on the diffuser wall to diffuse the flow rapidly and efficiently to the velocity required at the fan face. These optimum distributions are then modified to achieve other desirable flow characteristics. Example applications are given.

  12. An approach to optimum subsonic inlet design

    NASA Technical Reports Server (NTRS)

    Luidens, R. W.; Stockman, N. O.; Diedrich, J. H.

    1979-01-01

    The approach consists of comparing inlet operating requirements with estimated inlet separation characteristics to identify the most critical inlet operating condition. This critical condition is taken to be the design point and is defined by the values of inlet mass flow, free stream velocity, and inlet angle of attack. Optimum flow distributions on the inlet surface are determined to be a high, flat top Mach number distribution on the inlet lip to turn the flow quickly into the inlet and a low, flat bottom skin friction distribution on the diffuser wall to diffuse the flow rapidly and efficiently to the velocity required at the fan face. These optimum distributions are then modified to achieve other desirable flow characteristics. Example applications are given. Extension of the method is suggested.

  13. Sinking Satellites and Tilting Disk Galaxies

    NASA Astrophysics Data System (ADS)

    Huang, Siqin

    I perform fully self-consistent disk+halo+satellite N-body simulations to investigate the dynamical interaction between a disk galaxy and an infalling satellite. In particular, I study the following three different dynamical responses of the disk to the infalling satellite: tilting, warping, and thickening, as well as the dynamical effects of the parent galaxy on the infalling satellite: orbital decay and tidal disruption. The model in this thesis is characterized with two cosmologically significant improvements. First, the satellite starts at a distance more than three times of the radius of the optical disk. This ensures a realistic interaction among the satellite, the disk, and the halo in the course of the satellite infall. Secondly, evolution of the structure and velocity ellipsoid of the disk due to internal heating is allowed. I study the commonly arising case of satellites having density profiles comparable to that of the parent galaxy in contrast to that of compact satellites considered in previous work. I find that a disk is mainly tilted rather than heated by infalling satellites. Satellites of 10%, 20%, and 30% of the disk mass tilt the disk by angles of (2.9 ± 0.3)o,/ (6.3 ± 0.1)o, and (10.6 ± 0.2)o, respectively. However, only 3.4%, 6.9%, and 11.1% of the orbital angular momentum is transferred to the parent galaxy. The kinetic energy associated with the vertical motion in the initial coordinate frame of the disk is increased by (6 ± 3)%, (26 ± 3)%, and (51 ± 5)%, respectively, whereas the corresponding thermal energy associated with the vertical random motion in the tilted coordinate frame is only increased by (4 ± 3)%, (6 ± 2)%, and (10 ± 2)%, respectively. I find that satellites are mainly accreted onto the parent halo. Satellites having up to 20% of the disk mass produce no observable thickening, whereas a satellite with 30% of the disk mass produces little observable thickening inside the half-mass radius of the disk but significant

  14. Age of tilted reefs, Hawaii.

    USGS Publications Warehouse

    Moore, J.G.; Campbell, J.F.

    1987-01-01

    Submerged carbonate reefs are preserved as a series of submarine terraces between Molokai and Hawaii along a 200-km span of the SE Hawaiian Ridge. Limestones from 2 of the terraces have been dated at 13 and 120 ka. Recognition that the terraces are tilted permits assignment of about a dozen terraces from 150 to 1300 m depth to 8 general reef platforms. These reefs were drowned by the combined effects of island subsidence and sea level rise at the end of successive glacial stages from 13 to 647 ka. The platforms are tilted 5 m/km SE toward the locus of volcanic centered on the island of Hawaii.-from Authors

  15. Optimum filters for narrow-band frequency modulation.

    NASA Technical Reports Server (NTRS)

    Shelton, R. D.

    1972-01-01

    The results of a computer search for the optimum type of bandpass filter for low-index angle-modulated signals are reported. The bandpass filters are discussed in terms of their low-pass prototypes. Only filter functions with constant numerators are considered. The pole locations for the optimum filters of several cases are shown in a table. The results are fairly independent of modulation index and bandwidth.

  16. Transition from self tilt to object tilt during maintained lateral tilt in parabolic flight

    NASA Astrophysics Data System (ADS)

    Wetzig, Joachim; Reiser, Michaela; von Baumgarten, Rudolf J.

    19 young healthy subjects were subjected to parabolic rollercoaster flight. A horizontal luminous line was seen by the subjects in a headfixed goggle device. During the hypergravic phases of parabolic flight the luminous line seemed to rotate into and during the hypogravic phase against the direction of static head tilt. Ocular counter rotation and activity of the neck position receptors cannot explain these subjective rotations. We conclude that information from the otolith system, converging with visual information within the brain, dislocated the headfixed visual target line. While the retinal image of the luminous line remains unchanged, loading and unloading the otoliths in parabolic flight changes the sensation of self tilt into object tilt, hereby subjectively rotating visual targets such as the luminous line.

  17. Tilt and Translation Motion Perception during Off Vertical Axis Rotation

    NASA Technical Reports Server (NTRS)

    Wood, Scott J.; Reschke, Millard F.; Clement, Gilles

    2006-01-01

    The effect of stimulus frequency on tilt and translation motion perception was studied during constant velocity off-vertical axis rotation (OVAR), and compared to the effect of stimulus frequency on eye movements. Fourteen healthy subjects were rotated in darkness about their longitudinal axis 10deg and 20deg off-vertical at 0.125 Hz, and 20deg offvertical at 0.5 Hz. Oculomotor responses were recorded using videography, and perceived motion was evaluated using verbal reports and a joystick with four degrees of freedom (pitch and roll tilt, mediallateral and anteriorposterior translation). During the lower frequency OVAR, subjects reported the perception of progressing along the edge of a cone. During higher frequency OVAR, subjects reported the perception of progressing along the edge of an upright cylinder. The modulation of both tilt recorded from the joystick and ocular torsion significantly increased as the tilt angle increased from 10deg to 20deg at 0.125 Hz, and then decreased at 0.5 Hz. Both tilt perception and torsion slightly lagged head orientation at 0.125 Hz. The phase lag of torsion increased at 0.5 Hz, while the phase of tilt perception did not change as a function of frequency. The amplitude of both translation perception recorded from the joystick and horizontal eye movements was negligible at 0.125 Hz and increased as a function of stimulus frequency. While the phase lead of horizontal eye movements decreased at 0.5 Hz, the phase of translation perception did not vary with stimulus frequency and was similar to the phase of tilt perception during all conditions. During dynamic linear acceleration in the absence of other sensory input (canal, vision) a change in stimulus frequency alone elicits similar changes in the amplitude of both self motion perception and eye movements. However, in contrast to the eye movements, the phase of both perceived tilt and translation motion is not altered by stimulus frequency. We conclude that the neural processing

  18. Human responses to upright tilt: a window on central autonomic integration

    NASA Technical Reports Server (NTRS)

    Cooke, W. H.; Hoag, J. B.; Crossman, A. A.; Kuusela, T. A.; Tahvanainen, K. U.; Eckberg, D. L.

    1999-01-01

    1. We examined interactions between haemodynamic and autonomic neural oscillations during passive upright tilt, to gain better insight into human autonomic regulatory mechanisms. 2. We recorded the electrocardiogram, finger photoplethysmographic arterial pressure, respiration and peroneal nerve muscle sympathetic activity in nine healthy young adults. Subjects breathed in time with a metronome at 12 breaths min-1 (0.2 Hz) for 5 min each, in supine, and 20, 40, 60, 70 and 80 deg head-up positions. We performed fast Fourier transform (and autoregressive) power spectral analyses and integrated low-frequency (0.05-0.15 Hz) and respiratory-frequency (0. 15-0.5 Hz) spectral powers. 3. Integrated areas of muscle sympathetic bursts and their low- and respiratory-frequency spectral powers increased directly and significantly with the tilt angle. The centre frequency of low-frequency sympathetic oscillations was constant before and during tilt. Sympathetic bursts occurred more commonly during expiration than inspiration at low tilt angles, but occurred equally in expiration and inspiration at high tilt angles. 4. Systolic and diastolic pressures and their low- and respiratory-frequency spectral powers increased, and R-R intervals and their respiratory-frequency spectral power decreased progressively with the tilt angle. Low-frequency R-R interval spectral power did not change. 5. The cross-spectral phase angle between systolic pressures and R-R intervals remained constant and consistently negative at the low frequency, but shifted progressively from positive to negative at the respiratory frequency during tilt. The arterial baroreflex modulus, calculated from low-frequency cross-spectra, decreased at high tilt angles. 6. Our results document changes of baroreflex responses during upright tilt, which may reflect leftward movement of subjects on their arterial pressure sympathetic and vagal response relations. The intensity, but not the centre frequency of low

  19. Welfare support-equipment for character input with head tilting and breathing

    NASA Astrophysics Data System (ADS)

    Nakazawa, Nobuaki; Yamada, Kou; Matsui, Toshikazu; Itoh, Isao

    2005-12-01

    This paper describes support-equipment of operating a personal computer for users who have an obstacle on the regions of upper limb. The user wears a head set device with an angle sensor, and holds a plastic pipe connected to a pressure sensor in his or her mouth. Tilting his or her head and breathing are used for mouse cursor operation and characters input. Considering user's body conditions, the voluntary angle range of head tilting and strength of breathing are memorized to the controller beforehand, and obtained information is reflected for operations without fatigue. The character display board is used to indicate the Japanese characters and input options such as Back Space or Enter. Tilting motions change the indicated character and breathing actions can select and input the illuminated functions on the character display board. In test trial, it is confirmed that Japanese characters including Kanji and Katakana can be input with head tilting and breathing, instead of a general keyboard.

  20. Pseudo-polar tilted smectic phases exhibited by bent-core hockey stick shaped molecules.

    PubMed

    Malkar, Deepshika; Sadashiva, B K; Roy, Arun

    2016-06-14

    We report experimental and theoretical studies on two new achiral fluid lamellar phases exhibited by bent-core hockey stick shaped molecules. The packing of these bent-core hockey stick shaped molecules in the layers leads to a pseudo-polar order in these tilted smectic phases. An anticlinic SmCA type stacking of the pseudo-polar layers is observed in the higher temperature smectic phase, while in the lower temperature phase the difference in the azimuthal angles of the tilt directions in successive layers is between zero and π with a randomized tilt organization between the successive layers. The randomness arises due to the sign degeneracy of the azimuthal angle difference of the tilt directions in successive layers. Both of these smectic phases show a strong electro-optic response which can be exploited for potential applications. PMID:27157895

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

    NASA Technical Reports Server (NTRS)

    Walsh, Edward J.

    1999-01-01

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

  2. Measurement errors induced by axis tilt of biplates in dual-rotating compensator Mueller matrix ellipsometers

    NASA Astrophysics Data System (ADS)

    Gu, Honggang; Zhang, Chuanwei; Jiang, Hao; Chen, Xiuguo; Li, Weiqi; Liu, Shiyuan

    2015-06-01

    Dual-rotating compensator Mueller matrix ellipsometer (DRC-MME) has been designed and applied as a powerful tool for the characterization of thin films and nanostructures. The compensators are indispensable optical components and their performances affect the precision and accuracy of DRC-MME significantly. Biplates made of birefringent crystals are commonly used compensators in the DRC-MME, and their optical axes invariably have tilt errors due to imperfect fabrication and improper installation in practice. The axis tilt error between the rotation axis and the light beam will lead to a continuous vibration in the retardance of the rotating biplate, which further results in significant measurement errors in the Mueller matrix. In this paper, we propose a simple but valid formula for the retardance calculation under arbitrary tilt angle and azimuth angle to analyze the axis tilt errors in biplates. We further study the relations between the measurement errors in the Mueller matrix and the biplate axis tilt through simulations and experiments. We find that the axis tilt errors mainly affect the cross-talk from linear polarization to circular polarization and vice versa. In addition, the measurement errors in Mueller matrix increase acceleratively with the axis tilt errors in biplates, and the optimal retardance for reducing these errors is about 80°. This work can be expected to provide some guidences for the selection, installation and commissioning of the biplate compensator in DRC-MME design.

  3. Tilted Microstrip Phased Arrays With Improved Electromagnetic Decoupling for Ultrahigh-Field Magnetic Resonance Imaging

    PubMed Central

    Pang, Yong; Wu, Bing; Jiang, Xiaohua; Vigneron, Daniel B.; Zhang, Xiaoliang

    2014-01-01

    Abstract One of the technical challenges in designing a dedicated transceiver radio frequency (RF) array for MR imaging in humans at ultrahigh magnetic fields is how to effectively decouple the resonant elements of the array. In this work, we propose a new approach using tilted microstrip array elements for improving the decoupling performance and potentially parallel imaging capability. To investigate and validate the proposed design technique, an 8-channel volume array with tilted straight-type microstrip elements was designed, capable for human imaging at the ultrahigh field of 7 Tesla. In this volume transceiver array, its electromagnetic decoupling behavior among resonant elements, RF field penetration to biological samples, and parallel imaging performance were studied through bench tests and in vivo MR imaging experiments. In this specific tilted element array design, decoupling among array elements changes with the tilted angle of the elements and the best decoupling can be achieved at certain tilted angle. In vivo human knee MR images were acquired using the tilted volume array at 7 Tesla for method validation. Results of this study demonstrated that the electromagnetic decoupling between array elements and the B1 field strength can be improved by using the tilted element method in microstrip RF coil array designs at the ultrahigh field of 7T. PMID:25526481

  4. Introduction to τ-tilting theory

    PubMed Central

    Iyama, Osamu; Reiten, Idun

    2014-01-01

    From the viewpoint of mutation, we will give a brief survey of tilting theory and cluster-tilting theory together with a motivation from cluster algebras. Then we will give an introduction to τ-tilting theory which was recently developed. PMID:24982183

  5. Angle performance on optima MDxt

    SciTech Connect

    David, Jonathan; Kamenitsa, Dennis

    2012-11-06

    Angle control on medium current implanters is important due to the high angle-sensitivity of typical medium current implants, such as halo implants. On the Optima MDxt, beam-to-wafer angles are controlled in both the horizontal and vertical directions. In the horizontal direction, the beam angle is measured through six narrow slits, and any angle adjustment is made by electrostatically steering the beam, while cross-wafer beam parallelism is adjusted by changing the focus of the electrostatic parallelizing lens (P-lens). In the vertical direction, the beam angle is measured through a high aspect ratio mask, and any angle adjustment is made by slightly tilting the wafer platen prior to implant. A variety of tests were run to measure the accuracy and repeatability of Optima MDxt's angle control. SIMS profiles of a high energy, channeling sensitive condition show both the cross-wafer angle uniformity, along with the small-angle resolution of the system. Angle repeatability was quantified by running a channeling sensitive implant as a regular monitor over a seven month period and measuring the sheet resistance-to-angle sensitivity. Even though crystal cut error was not controlled for in this case, when attributing all Rs variation to angle changes, the overall angle repeatability was measured as 0.16 Degree-Sign (1{sigma}). A separate angle repeatability test involved running a series of V-curves tests over a four month period using low crystal cut wafers selected from the same boule. The results of this test showed the angle repeatability to be <0.1 Degree-Sign (1{sigma}).

  6. SYSTEMATIC ERROR REDUCTION: NON-TILTED REFERENCE BEAM METHOD FOR LONG TRACE PROFILER.

    SciTech Connect

    QIAN,S.; QIAN, K.; HONG, Y.; SENG, L.; HO, T.; TAKACS, P.

    2007-08-25

    Systematic error in the Long Trace Profiler (LTP) has become the major error source as measurement accuracy enters the nanoradian and nanometer regime. Great efforts have been made to reduce the systematic error at a number of synchrotron radiation laboratories around the world. Generally, the LTP reference beam has to be tilted away from the optical axis in order to avoid fringe overlap between the sample and reference beams. However, a tilted reference beam will result in considerable systematic error due to optical system imperfections, which is difficult to correct. Six methods of implementing a non-tilted reference beam in the LTP are introduced: (1) application of an external precision angle device to measure and remove slide pitch error without a reference beam, (2) independent slide pitch test by use of not tilted reference beam, (3) non-tilted reference test combined with tilted sample, (4) penta-prism scanning mode without a reference beam correction, (5) non-tilted reference using a second optical head, and (6) alternate switching of data acquisition between the sample and reference beams. With a non-tilted reference method, the measurement accuracy can be improved significantly. Some measurement results are presented. Systematic error in the sample beam arm is not addressed in this paper and should be treated separately.

  7. Comparison of two methods for calculating percent body weight on a tilt table.

    PubMed

    Sheldon, M R

    1994-01-01

    Physical therapists commonly treat patients when knowledge of percent weight bearing is desirable during functional lower extremity exercise. The purpose of this study was to compare two methods for calculating percent body weight at different angles of inclination on a tilt table. Twenty healthy subjects were weighed on a spring scale in standing and on a tilt table at 5 degrees increments between 0 and 90 degrees of tilt. Percent body weight at each angle was compared to a value predicted from a trigonometric equation. Predicted values were significantly greater than measured values at all angles greater than 10 degrees of tilt. Predicted overestimation ranged from 2.8 to 14.2%. Compared to the trigonometric method, physical therapists can more easily and accurately determine percent body weight on a tilt table using a scale if total body weight is known. Partial weight-bearing rehabilitation could be performed on the tilt table by varying the degree of inclination, allowing functional lower extremity exercise for patients with weight-bearing restrictions. Guidelines could be established following a variety of injuries and orthopaedic procedures incorporating functional lower extremity exercises at varying percentages of body weight. PMID:8156058

  8. Experimental determination of optimum gutter brush parameters and road sweeping criteria for different types of waste.

    PubMed

    Abdel-Wahab, Magd M; Wang, Chong; Vanegas-Useche, Libardo V; Parker, Graham A

    2011-06-01

    The removal ability of gutter brushes for road sweeping for various debris types and different sweeping parameters is studied through experimental tests. The brushing test rig used comprises two commercial gutter brushes, a concrete test bed, and an asphalt test road with a gutter of 0.25 cm width and 10° slope. The brush-surface contact area is determined by sweeping sand on the concrete test bed. Sweeping problems are identified and discussed, and sweeping criteria for the different debris types are suggested. Also, optimum sweeping parameters are proposed for each debris type. In addition, debris removal mechanisms are discussed and analysed. The results indicate that for large heavy debris such as stones and gravel, it is not difficult to achieve large removal forces, because the steel bristles are relatively stiff. Conversely, high removal forces are not needed for particles of millimetre or micron sizes, but bristle curvature has to be appropriate to remove particles from road concavities. Finally, it is found that mud, especially dry mud on a rough surface, is the hardest debris to sweep, requiring a brush with a large tilt angle and a very large penetration to produce large removal forces. PMID:21277186

  9. Tilted Thick-Disk Accretion onto a Kerr Black Hole

    SciTech Connect

    Fragile, P C; Anninos, P

    2003-12-12

    We present the first results from fully general relativistic numerical studies of thick-disk accretion onto a rapidly-rotating (Kerr) black hole with a spin axis that is tilted (not aligned) with the angular momentum vector of the disk. We initialize the problem with the solution for an aligned, constant angular momentum, accreting thick disk around a black hole with spin a/M = J/M{sup 2} = +0.9 (prograde disk). The black hole is then instantaneously tilted, through a change in the metric, by an angle {beta}{sub 0}. In this Letter we report results with {beta}{sub 0} = 0, 15, and 30{sup o}. The disk is allowed to respond to the Lense-Thirring precession of the tilted black hole. We find that the disk settles into a quasi-static, twisted, warped configuration with Lense-Thirring precession dominating out to a radius analogous to the Bardeen-Petterson transition in tilted Keplerian disks.

  10. Tilt Correction of High Explosive Test Data with Examples

    NASA Astrophysics Data System (ADS)

    Hill, Larry; Francois, Elizabeth; Morris, John

    2013-06-01

    Many high-explosive experiments view a nominally-axially-symmetric detonation wave breaking through a charge surface. Emerging waves virtually always exhibit a degree of tilt, which one generally wants to excise from the data whilst quantifying its direction and magnitude. In some cases, such as front-curvature rate sticks and Onionskin (OS)-type tests, the diagnostic is a single-slit streak camera (1D correction). In other cases, such as a Plane-Wave Lens characterization test or a Furball test, multiple slits or fibers provide sparse data over a surface (2D correction). We demonstrate both 1D and 2D corrections, the latter of which is the more challenging. In 2D, we represent the breakout time as the sum of a symmetric component and an asymmetric component (a tilted plane). The two tilt angle components are found that minimize the data scatter associated with the symmetric component. The most compelling example is the Furball test, an OS-variant for which the breakout time over the hemispherical observation surface is measured at many points using optical fibers. Unlike the OS test that looks in one (random) direction, we are able to construct OS-type data in the direction of maximum tilt, even though there are generally no fibers at that direction.

  11. Exponential tilting in Bayesian asymptotics

    PubMed Central

    Kharroubi, S. A.; Sweeting, T. J.

    2016-01-01

    We use exponential tilting to obtain versions of asymptotic formulae for Bayesian computation that do not involve conditional maxima of the likelihood function, yielding a more stable computational procedure and significantly reducing computational time. In particular we present an alternative version of the Laplace approximation for a marginal posterior density. Implementation of the asymptotic formulae and a modified signed root based importance sampler are illustrated with an example. PMID:27279661

  12. ''Optimum productivity'': a geneticist's view

    SciTech Connect

    Libby, W.J.

    1980-01-01

    Both ''optimum'' and ''productivity'' are explored in a social context with a long time dimension. Renewability, flexibility, and diversity are important concepts in long-term planning to achieve optimum productivity. Various possible genetic contributions, including complementary clones, quantitative genetic engineering, resistant trees and plantations, elimination of inbreeding, single-gene genetic engineering, and agri-forestry, are suggested for long-term sustained or increased productivity.

  13. Electrothermally actuated tip-tilt-piston micromirror with integrated varifocal capability.

    PubMed

    Morrison, Jessica; Imboden, Matthias; Little, Thomas D C; Bishop, D J

    2015-04-01

    MEMS micromirrors have proven to be very important optical devices with applications ranging from steerable mirrors for switches and cross-connects to spatial light modulators for correcting optical distortions. Usually beam steering and focusing are done with different MEMS devices and tilt angles in excess of 10 degrees are seldom obtained. Here we describe a single MEMS device that combines tip/tilt, piston mode and varifocal capability into a single, low cost device with very large tilt angles. Our device consists of a 400 micron diameter mirror driven with thermal bimorphs. We have demonstrated deflection angles of ± 40 degrees along both axes, a tunable focal length which varies between -0.48 mm to + 20.5 mm and a piston mode range of 300 microns - four separately controllable degrees of freedom in a single device. Potential applications range from smart lighting to optical switches and devices for telecom systems. PMID:25968784

  14. Theoretical Analysis of Interferometer Wave Front Tilt and Fringe Radiant Flux on a Rectangular Photodetector

    PubMed Central

    Smith, Robert; Fuss, Franz Konstantin

    2013-01-01

    This paper is a theoretical analysis of mirror tilt in a Michelson interferometer and its effect on the radiant flux over the active area of a rectangular photodetector or image sensor pixel. It is relevant to sensor applications using homodyne interferometry where these opto-electronic devices are employed for partial fringe counting. Formulas are derived for radiant flux across the detector for variable location within the fringe pattern and with varying wave front angle. The results indicate that the flux is a damped sine function of the wave front angle, with a decay constant of the ratio of wavelength to detector width. The modulation amplitude of the dynamic fringe pattern reduces to zero at wave front angles that are an integer multiple of this ratio and the results show that the polarity of the radiant flux changes exclusively at these multiples. Varying tilt angle causes radiant flux oscillations under an envelope curve, the frequency of which is dependent on the location of the detector with the fringe pattern. It is also shown that a fringe count of zero can be obtained for specific photodetector locations and wave front angles where the combined effect of fringe contraction and fringe tilt can have equal and opposite effects. Fringe tilt as a result of a wave front angle of 0.05° can introduce a phase measurement difference of 16° between a photodetector/pixel located 20 mm and one located 100 mm from the optical origin. PMID:24018954

  15. Defining Optimal Head-Tilt Position of Resuscitation in Neonates and Young Infants Using Magnetic Resonance Imaging Data.

    PubMed

    Bhalala, Utpal S; Hemani, Malvi; Shah, Meehir; Kim, Barbara; Gu, Brian; Cruz, Angelo; Arunachalam, Priya; Tian, Elli; Yu, Christine; Punnoose, Joshua; Chen, Steven; Petrillo, Christopher; Brown, Alisa; Munoz, Karina; Kitchen, Grant; Lam, Taylor; Bosemani, Thangamadhan; Huisman, Thierry A G M; Allen, Robert H; Acharya, Soumyadipta

    2016-01-01

    Head-tilt maneuver assists with achieving airway patency during resuscitation. However, the relationship between angle of head-tilt and airway patency has not been defined. Our objective was to define an optimal head-tilt position for airway patency in neonates (age: 0-28 days) and young infants (age: 29 days-4 months). We performed a retrospective study of head and neck magnetic resonance imaging (MRI) of neonates and infants to define the angle of head-tilt for airway patency. We excluded those with an artificial airway or an airway malformation. We defined head-tilt angle a priori as the angle between occipito-ophisthion line and ophisthion-C7 spinous process line on the sagittal MR images. We evaluated medical records for Hypoxic Ischemic Encephalopathy (HIE) and exposure to sedation during MRI. We analyzed MRI of head and neck regions of 63 children (53 neonates and 10 young infants). Of these 63 children, 17 had evidence of airway obstruction and 46 had a patent airway on MRI. Also, 16/63 had underlying HIE and 47/63 newborn infants had exposure to sedative medications during MRI. In spontaneously breathing and neurologically depressed newborn infants, the head-tilt angle (median ± SD) associated with patent airway (125.3° ± 11.9°) was significantly different from that of blocked airway (108.2° ± 17.1°) (Mann Whitney U-test, p = 0.0045). The logistic regression analysis showed that the proportion of patent airways progressively increased with an increasing head-tilt angle, with > 95% probability of a patent airway at head-tilt angle 144-150°. PMID:27003759

  16. Defining Optimal Head-Tilt Position of Resuscitation in Neonates and Young Infants Using Magnetic Resonance Imaging Data

    PubMed Central

    Bhalala, Utpal S.; Hemani, Malvi; Shah, Meehir; Kim, Barbara; Gu, Brian; Cruz, Angelo; Arunachalam, Priya; Tian, Elli; Yu, Christine; Punnoose, Joshua; Chen, Steven; Petrillo, Christopher; Brown, Alisa; Munoz, Karina; Kitchen, Grant; Lam, Taylor; Bosemani, Thangamadhan; Huisman, Thierry A. G. M.; Allen, Robert H.; Acharya, Soumyadipta

    2016-01-01

    Head-tilt maneuver assists with achieving airway patency during resuscitation. However, the relationship between angle of head-tilt and airway patency has not been defined. Our objective was to define an optimal head-tilt position for airway patency in neonates (age: 0–28 days) and young infants (age: 29 days–4 months). We performed a retrospective study of head and neck magnetic resonance imaging (MRI) of neonates and infants to define the angle of head-tilt for airway patency. We excluded those with an artificial airway or an airway malformation. We defined head-tilt angle a priori as the angle between occipito-ophisthion line and ophisthion-C7 spinous process line on the sagittal MR images. We evaluated medical records for Hypoxic Ischemic Encephalopathy (HIE) and exposure to sedation during MRI. We analyzed MRI of head and neck regions of 63 children (53 neonates and 10 young infants). Of these 63 children, 17 had evidence of airway obstruction and 46 had a patent airway on MRI. Also, 16/63 had underlying HIE and 47/63 newborn infants had exposure to sedative medications during MRI. In spontaneously breathing and neurologically depressed newborn infants, the head-tilt angle (median ± SD) associated with patent airway (125.3° ± 11.9°) was significantly different from that of blocked airway (108.2° ± 17.1°) (Mann Whitney U-test, p = 0.0045). The logistic regression analysis showed that the proportion of patent airways progressively increased with an increasing head-tilt angle, with > 95% probability of a patent airway at head-tilt angle 144–150°. PMID:27003759

  17. Optimum Onager: The Classical Mechanics of a Classical Siege Engine

    ERIC Educational Resources Information Center

    Denny, Mark

    2009-01-01

    The onager is a throwing weapon of classical antiquity, familiar to both the ancient Greeks and Romans. Here we analyze the dynamics of onager operation and derive the optimum angle for launching a projectile to its maximum range. There is plenty of scope for further considerations about increasing onager range, and so by thinking about how this…

  18. Effect of lens tilt on SCE and filamentation characteristics of femtosecond pulses in air

    NASA Astrophysics Data System (ADS)

    Sreeja, S.; Prashant, T. Shuvan; Leela, Ch.; Kumar, V. Rakesh; Tewari, Surya P.; Venugopal Rao, S.; Kiran, P. Prem

    2012-06-01

    We present the evolution of SCE associated with filaments due to the tilt of focusing lens under tight focusing geometries. Transform limited femtosecond (fs) pulses (800 nm, 45 fs, 1 kHz repetition rate) were focused in ambient air using three different focusing geometries f/#6, f/#7.5, and f/#12 corresponding to numerical apertures (NA) of 0.08, 0.06, and 0.04, respectively. The focusing lens was tilted from zero up to 20 degrees. The filaments decayed into two shorter parts through tilting of the lens and the separation between shorter filaments increased with increasing lens tilt, in tune with earlier reports [Kamali et al., Opt. Commun. 282, 950-954 (2009)]. The separation between the filaments matched well with the predicted distances due to astigmatism induced in loose focusing geometries. However the deviation increased as we moved to the tighter focusing geometries. The SCE spectrum demonstrated an anomalous behaviour. The SCE spectrum was suppressed at larger tilt angles of 12 - 20°. However at lower tilt angles, up to 8°, the SCE was observed to be same to that measured without any tilt of the focusing lens. This behaviour is predominant with tighter focusing geometries of f/#6 and f/#7.5, wherein the SCE was observed to be higher at 4° and 8° in comparison with that observed at an angle of 0°. Systematic study of the focusing lens tilt on anomalous SCE spectra and filament characteristics in the tight focusing geometry are presented.

  19. Edge and surface-emitting tilted cavity lasers (Invited Paper)

    NASA Astrophysics Data System (ADS)

    Ledentsov, N. N.; Shchukin, V. A.; Kovsh, A. R.; Mikhrin, S. S.; Krestnikov, I. L.; Kozhukhov, A. V.; Gordeev, N. Y.; Karachinsky, L. Y.; Maximov, M. V.; Novikov, I. I.; Shernyakov, Yu. M.

    2005-04-01

    The Tilted Cavity (TC) concept has been proposed to combine advantages of edge- and surface-emitting lasers (detectors, amplifiers, switches, etc.). Tilted Cavity Lasers (TCL) enable wavelength-stabilized high-power edge and surface emitters (TCSEL) in low-cost single-epitaxial step design. The concept covers numerous applications including mode-locked TCL for light speed control, dispersion and linewidth engineering, GaN-based light-emitters, electrooptic wavelength tunable devices, and other applications. Presently, wavelength stabilized TC operation is realized between -200°C and 70°C in broad TCL diodes with cleaved facets based on quantum dots (QDs). The spectral width is below 0.6 nm in broad area 100 μm-wide-stipe devices. The far fields are: 4° (lateral) and 42° (vertical). Wavelength-stabilized 1.16 μm and 1.27 μm edge-emitting QD TCL lasers are demonstrated. Quantum well TCL demonstrate high-temperature operation up to 240°C with a low threshold, high temperature stability and improved wavelength stability. The tilted cavity approach can also be applied in wavelength-optimized photodetectors, switches, semiconductor optical amplifiers, including multi-channel devices, in optical fibers, in photodetectors, in light-emitting diodes and in many other applications. Moreover, microelectronic devices based on similar tilted angle resonance phenomena in quantum wells and superlattices can be realized in electron- or hole-wavefunction-engineered structures, thus, merging the fields of nanophotonics and nanoelectronics. The tilted cavity concept can be further complimented by lateral patterning and (or) processing of three-dimensional photonic crystal structures further extending horizons of modern optoelectronics.

  20. Resolution enhancement of computed radiography images using two orthogonal tilts

    NASA Astrophysics Data System (ADS)

    Pollmann, Steven I.; Norley, Chris J. D.; Yuan, Xunhua; Holdsworth, David W.

    2012-03-01

    Limitations to the spatial resolution of current digital x-ray systems are bounded by the physical characteristics of the xray detector. However, the need to image smaller structures provides motivation to develop high-resolution x-ray detector systems for use with computed radiographic, and tomographic x-ray systems. We report the implementation of a tilted detector technique (TDT) to attain near isotropic resolution enhancement by combining two orthogonal image views, acquired with existing detector hardware tilted at a fixed angle. Images were acquired using a ceiling-mounted x-ray unit (Proteus XR/a, GE Medical Systems, 50kVp, 250mAs). Images were digitized using a Fujifilm Capsula X CR system, from a 35×43cm detector cassette placed on an angulated stand, featuring a 3520×4280 image matrix with an in-plane pixel spacing of 0.1mm. Three images were acquired: two for use with our TDT; and one for comparison, with no detector tilt. Performance was determined by using two line-pair phantoms (Models 07-521 and 07-533, Nuclear Associates) placed orthogonally to each other in the field of view. Custom software corrected for perspective distortion, co-registered and combined the tilted-detector images into a single higher-resolution image. Following unwarping and co-registration, the limiting spatial resolution of an image obtained via the weighted combination of the two orthogonal views (8 lp/mm) is found to be superior to that of a single view acquired with no detector tilt (5 lp/mm). This novel technique shows significant improvement in the spatial resolution of x-ray image acquisitions, using existing x-ray components and detector hardware.

  1. Electron distribution on a tilted sample in the high pressure SEM.

    PubMed

    Belkorissat, R; Kadoun, A; Khelifa, B; Mathieu, C

    2005-01-01

    The effect of the specimen inclination on the electron distribution at the specimen surface in an HPSEM was investigated by Monte Carlo simulation. A broadening of the electron profile versus the tilt angle was obtained and a relationship between the r(0.9) radius and this tilt angle is proposed. The plot of the electron distribution at the sample surface shows that the classical scattering profile in the standard conditions is modified so that an inclined truncated shape is obtained. This result confirms the difficulty to carry out X-ray microanalysis in low vacuum conditions. PMID:15857773

  2. Atlas based kinematic optimum design of the Stewart parallel manipulator

    NASA Astrophysics Data System (ADS)

    Shao, Zhufeng; Tang, Xiaoqiang; Wang, Liping; Sun, Dengfeng

    2015-01-01

    Optimum design is a key approach to make full use of potential advantages of a parallel manipulator. The optimum design of multi-parameter parallel manipulators(more than three design parameters), such as Stewart manipulator, relies on analysis based and algorithm based optimum design methods, which fall to be accurate or intuitive. To solve this problem and achieve both accurate and intuition, atlas based optimum design of a general Stewart parallel manipulator is established, with rational selection of design parameters. Based on the defined spherical usable workspace(SUW), primary kinematic performance indices of the Stewart manipulator, involving workspace and condition number are introduced and analyzed. Then, corresponding performance atlases are drawn with the established non-dimensional design space, and impact of joint distribution angles on the manipulator performance is analyzed and illustrated. At last, an example on atlas based optimum design of the Stewart manipulator is accomplished to illustrate the optimum design process, considering the end-effector posture. Deduced atlases can be flexibly applied to both quantitative and qualitative analysis to get the desired optimal design for the Stewart manipulator with respect to related performance requirements. Besides, the established optimum design method can be further applied to other multi-parameter parallel manipulators.

  3. Extension-twist coupling of composite circular tubes with application to tilt rotor blade design

    NASA Technical Reports Server (NTRS)

    Nixon, Mark W.

    1987-01-01

    This investigation was conducted to determine if twist deformation required for the design of full-scale extension-twist-coupled tilt-rotor blades can be achieved within material design limit loads, and to demonstrate the accuracy of a coupled-beam analysis in predicting twist deformations. Two extension-twist-coupled tilt-rotor blade designs were developed based on theoretically optimum aerodynamic twist distributions. The designs indicated a twist rate requirement of between .216 and .333 deg/in. Agreement between axial tests and analytical predictions was within 10 percent at design limit loads. Agreement between the torsion tests and predictions was within 11 percent.

  4. Gravito-Inertial Force Resolution in Perception of Synchronized Tilt and Translation

    NASA Technical Reports Server (NTRS)

    Wood, Scott J.; Holly, Jan; Zhang, Guen-Lu

    2011-01-01

    the GIF-resolution hypothesis even when the gravito-inertial force vector remains aligned with the body during periodic motion. Perception is also consistent with GIF-resolution in the opposite condition, when the gravito-inertial force vector angle is enhanced by synchronized tilt and translation.

  5. Interferometer mirror tilt correcting system

    NASA Technical Reports Server (NTRS)

    Schindler, R. A. (Inventor)

    1977-01-01

    An interferometer is described, having several means for automatically adjusting the angular tilt of a reflecting surface in one of two paths to maintain the exit beams from the two paths parallel to each other. Three detectors at the output of the interferometer were disposed on mutually perpendicular axes which define a plane normal to the nominal exit beam axis. One detector at the origin of the axes was used as a reference for separate phase difference comparison with the outputs of the other two detectors on the X and Y axes to develop servo error signals.

  6. What's Your Angle on Angles?

    ERIC Educational Resources Information Center

    Browning, Christine A.; Garza-Kling, Gina; Sundling, Elizabeth Hill

    2007-01-01

    Although the nature of the research varies, as do concepts of angle, research in general supports the supposition that angle is a complex idea, best understood from a variety of perspectives. In fact, the concept of angle tends to be threefold, consisting of: (1) the traditional, static notion of two rays meeting at a common vertex; (2) the idea…

  7. Optimum Solar Conversion Cell Configurations

    NASA Technical Reports Server (NTRS)

    Chen, Bin (Inventor)

    2015-01-01

    Methods for maximizing a fraction of light energy absorbed in each of three classes of light concentrators (rectangular parallelepipeds, paraboloids and prisms) by choice of incident angle of radiation and of one or more geometrical or physical parameters (absorber thickness, paraboloid dimensions, location of paraboloid focus, prism angles, concentrator material, cladding, prism angles, etc.). Alternatively, the light energy absorbed plus the light energy that escapes through non-total internal reflection within the light concentrator can be minimized.

  8. Evaluation of tilted cone-beam CT orbits in the development of a dedicated hybrid mammotomograph

    PubMed Central

    Crotty, D J; McKinley, R L; Tornai, M P

    2010-01-01

    A compact dedicated 3D breast SPECT-CT (mammotomography) system is currently under development. In its initial prototype, the cone-beam CT sub-system is restricted to a fixed-tilt circular rotation around the patient’s pendant breast. This study evaluated stationary-tilt angles for the CT subsystem that will enable maximal volumetric sampling and viewing of the breast and chest wall. Images of geometric/anthropomorphic phantoms were acquired using various fixed-tilt circular and 3D sinusoidal trajectories. The iteratively reconstructed images showed more distortion and attenuation coefficient inaccuracy from tilted cone-beam orbits than from the complex trajectory. Additionally, line profiles illustrated cupping artifacts in planes distal to the central plane of the tilted cone-beam, otherwise not apparent for images acquired with complex trajectories. This indicates that undersampled cone-beam data may be an additional cause of cupping artifacts. High-frequency objects could be distinguished for all trajectories, but their shapes and locations were corrupted by out-of-plane frequency information. Although more acrylic balls were visualized with a fixed-tilt and nearly flat cone-beam at the posterior of the breast, 3D complex trajectories have less distortion and more complete sampling throughout the reconstruction volume. While complex trajectories would ideally be preferred, negatively fixed-tilt source–detector configuration demonstrates minimally distorted patient images. PMID:19478374

  9. Tilting marks: Observations on tool marks resembling trace fossils and their morphological varieties

    NASA Astrophysics Data System (ADS)

    Wetzel, Andreas

    2013-04-01

    Tilting marks, defined here as linear tool marks having transverse ornamentation, are produced in shallow water when the oscillatory action of waves of short wavelength tilt grounded objects rhythmically in such a way that they move and push sediment aside. These tool marks can resemble trace fossils, particularly if they are bilaterally symmetrical. Even asymmetrical objects can produce symmetrical tilting marks because the shape of the mark only depends on the geometry of the ground-touching part of the object, which may be partially floating. Objects of either soft or hard consistency, such as jellyfish or wood, respectively, can produce tilting marks. Tilting marks are normally produced linearly parallel or at an angle to the direction of wave propagation and do not show sharp bends or curves. Tilting marks can be formed on plane beds as well as rippled surfaces. Tilting marks can be distinguished from trace fossils by taking into account the geometry (symmetry), the direction of movement, and the mainly linear course and the internal pattern.

  10. A tilt-compensated Fourier transform spectrometer with an image rotator

    NASA Astrophysics Data System (ADS)

    Wei, Ruyi; Yin, Bangsheng

    2015-07-01

    Due to the moving plane mirror, tilt compensation is crucial and challenging in designing high precision Michelson-type interferometers. In this paper, we propose an optical configuration design using an image rotator and plane mirrors, including a movable double-sided mirror (DSM) to balance out the tilt of the mirror. We analysed the optical path differences (OPD) caused by the tilt of the DSM and their effects on interferogram under different tilt cases. Analyses demonstrate that this design is able to cancel out the offset of the OPD introduced by the tilt pitch angle. For different incident rays in parallel, the position of the tilt centre has no relationship with the change of the OPD, implying that the OPD could be self-compensated, and the modulation of the interferogram will not be degraded due to the tilt. This configuration effectively relaxes the requirements on the control of the precision of the postures of the moving mirror and thus may have broad applications.

  11. Modulation of internal estimates of gravity during and after prolonged roll-tilts.

    PubMed

    Tarnutzer, Alexander A; Bertolini, Giovanni; Bockisch, Christopher J; Straumann, Dominik; Marti, Sarah

    2013-01-01

    Perceived direction of gravity, as assessed by the subjective visual vertical (SVV), shows roll-angle dependent errors that drift over time and a bias upon return to upright. According to Bayesian observer theory, the estimated direction of gravity is derived from the posterior probability distribution by combining sensory input and prior knowledge about earth-vertical in a statistically optimal fashion. Here we aimed to further characterize the stability of SVV during and after prolonged roll-tilts. Specifically we asked whether the post-tilt bias is related to the drift pattern while roll-tilted. Twenty-nine healthy human subjects (23-56 yo) repetitively adjusted a luminous arrow to the SVV over periods of 5 min while upright, roll-tilted (± 45°, ± 90°), and immediately after returning to upright. Significant (p<0.05) drifts (median absolute drift-amplitude: 10°/5 min) were found in 71% (± 45°) and 78% (± 90°) of runs. At ± 90° roll-tilt significant increases in absolute adjustment errors were more likely (76%), whereas significant increases (56%) and decreases (44%) were about equally frequent at ± 45°. When returning to upright, an initial bias towards the previous roll-position followed by significant exponential decay (median time-constant: 71 sec) was noted in 47% of all runs (all subjects pooled). No significant correlations were found between the drift pattern during and immediately after prolonged roll-tilt. We conclude that the SVV is not stable during and after prolonged roll-tilt and that the direction and magnitude of drift are individually distinct and roll-angle-dependent. Likely sensory and central adaptation and random-walk processes contribute to drift while roll-tilted. Lack of correlation between the drift and the post-tilt bias suggests that it is not the inaccuracy of the SVV estimate while tilted that determines post-tilt bias, but rather the previous head-roll orientation relative to gravity. We therefore favor central

  12. The importance of prostate bed tilt during postprostatectomy intensity-modulated radiotherapy

    SciTech Connect

    Bell, Linda J.; Cox, Jennifer; Eade, Thomas; Rinks, Marianne; Kneebone, Andrew

    2014-10-01

    Variations in rectal and bladder filling can create a tilt of the prostate bed, which generates the potential for a geographic miss during postprostatectomy radiotherapy. The aim of this study is to assess the effect that bladder and rectum filling has on planning target volume angle, to determine a method to assess prostate bed tilt leading to potential geographic miss, and to discuss possible implementation issues. The cone-beam computed tomography images (n = 377) of 40 patients who received postprostatectomy radiotherapy with intensity-modulated radiotherapy were reviewed. The amount of tilt in the prostate bed was defined as the angle change between 2 surgical clips, one in the upper prostate bed and another in the lower. A potential geographic miss was defined as movement of any clip of more than 1 cm in any direction or 0.5 cm posteriorly when aligned to bone anatomy. Variations in bladder and rectum size were correlated with the degree of prostate bed tilt, and the rate of potential geographic miss was determined. A possible clinical use of prostate bed tilt was then assessed for different imaging techniques. A tilt of more than 10° was seen in 20.2% of images, which resulted in a 57.9% geographic miss rate of the superior clip. When tilt remained within 10°, there was only a 9% rate of geographic miss. Potential geographic miss of the inferior surgical clip was rare, occurring in only 1.9% of all images reviewed. The most common occurrence when the prostate bed tilt increased by more than 10° was a smaller bladder and larger rectum (6.4% of all images). The most common occurrence when the prostate bed tilt decreased by more than 10° was a larger bladder and smaller rectum (1.3% of all images). Significant prostate bed tilt (>± 10°) occurred in more than 20% of images, creating a 58% rate of geographic miss. Greatest prostate bed tilt occurred when the bladder size increased or reduced by more than 2 cm or the superior rectum size increased by more

  13. Decreasing lateral segregation in cadmium zinc telluride via ampoule tilting during vertical Bridgman growth

    NASA Astrophysics Data System (ADS)

    Lun, Lisa; Yeckel, Andrew; Daoutidis, Prodromos; Derby, Jeffrey J.

    2006-06-01

    We employ a 2D, planar computational model to study the effects of ampoule tilting on zinc segregation during the growth of cadmium zinc telluride in a low-gradient vertical Bridgman process. Tilting the axis of the ampoule away from the direction of gravity strongly affects the structure and strength of melt convection, which, in turn, modifies heat transfer and the shape of the solid-liquid interface. While these effects have relatively little direct effect on axial segregation, the pattern of lateral segregation is significantly changed by tilting. Optimal tilt angles are found that locally flatten lateral compositional profiles and that decrease a measure of overall segregation, compared to the case of growth in a perfectly vertical ampoule.

  14. Tilt perception during dynamic linear acceleration.

    PubMed

    Seidman, S H; Telford, L; Paige, G D

    1998-04-01

    Head tilt is a rotation of the head relative to gravity, as exemplified by head roll or pitch from the natural upright orientation. Tilt stimulates both the otolith organs, owing to shifts in gravitational orientation, and the semicircular canals in response to head rotation, which in turn drive a variety of behavioral and perceptual responses. Studies of tilt perception typically have not adequately isolated otolith and canal inputs or their dynamic contributions. True tilt cannot readily dissociate otolith from canal influences. Alternatively, centrifugation generates centripetal accelerations that simulate tilt, but still entails a rotatory (canal) stimulus during important periods of the stimulus profiles. We reevaluated the perception of head tilt in humans, but limited the stimulus to linear forces alone, thus isolating the influence of otolith inputs. This was accomplished by employing a centrifugation technique with a variable-radius spinning sled. This allowed us to accelerate the sled to a constant angular velocity (128 degrees/s), with the subject centered, and then apply dynamic centripetal accelerations after all rotatory perceptions were extinguished. These stimuli were presented in the subjects' naso-occipital axis by translating the subjects 50 cm eccentrically either forward or backward. Centripetal accelerations were thus induced (0.25 g), which combined with gravity to yield a dynamically shifting gravitoinertial force simulating pitch-tilt, but without actually rotating the head. A magnitude-estimation task was employed to characterize the dynamic perception of pitch-tilt. Tilt perception responded sluggishly to linear acceleration, typically reaching a peak after 10-30 s. Tilt perception also displayed an adaptation phenomenon. Adaptation was manifested as a per-stimulus decline in perceived tilt during prolonged stimulation and a reversal aftereffect upon return to zero acceleration (i.e., recentering the subject). We conclude that otolith

  15. Numerical aperture characteristics of angle-ended plastic optical fiber

    NASA Astrophysics Data System (ADS)

    Gao, Cheng; Farrell, Gerard

    2003-03-01

    With the increasing information rates demanded in consumer, automotive and aeronautical applications, a low cost and high performance physical transmission medium is required. Compared with Silica Optical Fiber, Plastic Optical Fiber (POF) offers an economic solution for a range of high-capacity, short-haul applications in industrial and military environments. Recently, a new type of POF, the perfluorinated graded-index plastic optical fiber (PF GI-POF), has been introduced that has low losses and high bandwidth at the communication wavelengths 850 nm and 1300nm. POF is normally terminated perpendicular to the fiber axis. We propose an angle-ended POF, which is terminated at non-perpendicular angles to the fiber axis. The aim of the research is to investigate the numerical aperture (NA) characteristics of angle-ended POF along the major axis of the elliptical endface. A theoretical model indicates that the NA of the angle-ended POF will increase nonlinearly with tilt-angle and the acceptance cone will be deflected with the angle of the deflection increasing nonlinearly with tilt-angle. We present results for the measured NA and the measured deflection angle using the far-field radiation method. Results are presented for 13 angle-ended SI-POF tilt-angles. We also present results for theoretical value of NA and deflection angle as a function of tilt-angle. The agreement between the measured and theoretical value is good up to tilt-angles of about 15 degrees, beyond which deviation occurs.

  16. Dynamic Curving Simulation of Tilting Train

    NASA Astrophysics Data System (ADS)

    Zeng, Jing; Luo, Ren

    The application of carbody tilting technology is the most efficient way to raise train speed during curve negotiations. This paper mainly deals with the dynamic performance simulation of the tilting train. Through the establishment of the nonlinear mathematical model for the titling train electromechanical coupled system, the carbody tilting control law, bogie radial steering mechanism, and titling train curving performance are investigated. The effect of time delay caused by the sensing and control system on the tilting performance of the train is analyzed, and the compensation methods for the time delay effect are studied.

  17. Geometry dependence of the clogging transition in tilted hoppers

    NASA Astrophysics Data System (ADS)

    Thomas, C. C.; Durian, D. J.

    2013-05-01

    We report the effects of system geometry on the clogging of granular material flowing out of flat-bottomed hoppers with variable aperture size D and with variable angle θ of tilt of the hopper away from horizontal. In general, larger tilt angles make the system more susceptible to clogging. To quantify this effect for a given θ, we measure the distribution of mass discharged between clogging events as a function of aperture size and extrapolate to the critical size at which the average mass diverges. By repeating for different angles, we map out a clogging phase diagram as a function of D and θ that demarcates the regimes of free flow (large D, small θ) and clogging (small D, large θ). We do this for both circular holes and long rectangular slits. Additionally, we measure four types of grain: smooth spheres (glass beads), compact angular grains (beach sand), disklike grains (lentils), and rodlike grains (rice). For circular apertures, the clogging phase diagram is found to be the same for all grain types. For narrow slit apertures and compact grains, the shape is also the same as for circular holes when expressed in terms of projected area of the aperture against the average flow direction. For lentils and rice discharged from slits, the behavior differs and may be due to alignment between grain and slit axes.

  18. OPTIMUM FREQUENCY OF CALIBRATION MONITORING

    EPA Science Inventory

    The paper develops an algorithm by which to compute the optimal frequency of calibration monitoring to minimize the total cost of analyzing a set of samples and the required calibration standards. Optimum calibration monitoring is needed because of the high cost and calibration d...

  19. TILTING TABLE AREA, PDP ROOM, LEVEL +27’, LOOKING NORTHWEST. TILTING ...

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

    TILTING TABLE AREA, PDP ROOM, LEVEL +27’, LOOKING NORTHWEST. TILTING TABLE MARKED BY WHITE ELECTRICAL CORD IN LOWER LEFT CENTER - Physics Assembly Laboratory, Area A/M, Savannah River Site, Aiken, Aiken County, SC

  20. Focus variation microscope: linear theory and surface tilt sensitivity.

    PubMed

    Nikolaev, Nikolay; Petzing, Jon; Coupland, Jeremy

    2016-05-01

    In a recent publication [3rd International Conference on Surface Metrology, Annecy, France, 2012, p. 1] it was shown that surface roughness measurements made using a focus variation microscope (FVM) are influenced by surface tilt. The effect appears to be most significant when the surface has microscale roughness (Ra≈50  nm) that is sufficient to provide a diffusely scattered signal that is comparable in magnitude to the specular component. This paper explores, from first principles, image formation using the focus variation method. With the assumption of incoherent scattering, it is shown that the process is linear and the 3D point spread characteristics and transfer characteristics of the instrument are well defined. It is argued that for the case of microscale roughness and through the objective illumination, the assumption of incoherence cannot be justified and more rigorous analysis is required. Using a foil model of surface scattering, the images that are recorded by a FVM have been calculated. It is shown that for the case of through-the-objective illumination at small tilt angles, the signal quality is degraded in a systematic manner. This is attributed to the mixing of specular and diffusely reflected components and leads to an asymmetry in the k-space representation of the output signals. It is shown that by using extra-aperture illumination or tilt angles greater than the acceptance angle of aperture (such that the specular component is lost), the incoherent assumption can be justified once again. The work highlights the importance of using ring-light illumination and/or polarizing optics, which are often available as options on commercial instruments, as a means to mitigate or prevent these effects. PMID:27140371

  1. Optimum conditions for adsorptive storage.

    PubMed

    Bhatia, Suresh K; Myers, Alan L

    2006-02-14

    The storage of gases in porous adsorbents, such as activated carbon and carbon nanotubes, is examined here thermodynamically from a systems viewpoint, considering the entire adsorption-desorption cycle. The results provide concrete objective criteria to guide the search for the "Holy Grail" adsorbent, for which the adsorptive delivery is maximized. It is shown that, for ambient temperature storage of hydrogen and delivery between 30 and 1.5 bar pressure, for the optimum adsorbent the adsorption enthalpy change is 15.1 kJ/mol. For carbons, for which the average enthalpy change is typically 5.8 kJ/mol, an optimum operating temperature of about 115 K is predicted. For methane, an optimum enthalpy change of 18.8 kJ/mol is found, with the optimum temperature for carbons being 254 K. It is also demonstrated that for maximum delivery of the gas the optimum adsorbent must be homogeneous, and that introduction of heterogeneity, such as by ball milling, irradiation, and other means, can only provide small increases in physisorption-related delivery for hydrogen. For methane, heterogeneity is always detrimental, at any value of average adsorption enthalpy change. These results are confirmed with the help of experimental data from the literature, as well as extensive Monte Carlo simulations conducted here using slit pore models of activated carbons as well as atomistic models of carbon nanotubes. The simulations also demonstrate that carbon nanotubes offer little or no advantage over activated carbons in terms of enhanced delivery, when used as storage media for either hydrogen or methane. PMID:16460092

  2. Tilting pad journal bearings - Measured and predicted stiffness coefficients

    SciTech Connect

    Parkins, D.W.; Horner, D. Michell Bearings, Newcastle-upon-Tyne )

    1993-07-01

    This paper presents measured and calculated characteristics of a tilting pad journal bearing suitable for high speed machinery. Descriptions are given of the experimental techniques used with this variety of bearing and the theoretical model for predicting performance. Measured values of pad temperature, eccentricity, attitude angle, and the four stiffness coefficients are given for a range of loads and rotational speeds. Data are given for both load on pad and between pad configurations, the two principal loading arrangements. Comparisons are made between the measured and predicted bearing temperatures and stiffness coefficients over a wide range of values. 11 refs.

  3. Tilting pad journal bearings - Measured and predicted stiffness coefficients

    NASA Astrophysics Data System (ADS)

    Parkins, D. W.; Horner, D.

    1993-07-01

    This paper presents measured and calculated characteristics of a tilting pad journal bearing suitable for high speed machinery. Descriptions are given of the experimental techniques used with this variety of bearing and the theoretical model for predicting performance. Measured values of pad temperature, eccentricity, attitude angle, and the four stiffness coefficients are given for a range of loads and rotational speeds. Data are given for both load on pad and between pad configurations, the two principal loading arrangements. Comparisons are made between the measured and predicted bearing temperatures and stiffness coefficients over a wide range of values.

  4. An assessment of upper surface blowing for the reduction of tilt rotor download

    NASA Technical Reports Server (NTRS)

    Faye, Robert E.; Felker, Fort F.; Light, Jeffrey S.

    1987-01-01

    A study evaluating the use of upper-surface blowing to reduce the wing download on a V-22 tilt rotor aircraft has been completed. The study assesses the penalties associated with the upper-surface blowing system (compressor weight, compressor power, etc.), and the reduction in wing download, for a wide range of blowing slot heights and blowing pressure ratios. Three wing configurations were investigated: blowing at both leading and trailing edges with no change in wing planform relative to the V-22 tilt rotor aircraft, blowing at both leading and trailing edges with a 25% reduction in wing chord, and blowing at the leading edge only with the flap deflected 75 deg. Predicted download is presented for all of these configurations, and is compared with the download of the baseline V-22 tilt rotor aircraft configuration. The optimum configuration had 15% less net download than the baseline V-22 configuration.

  5. A Cardiovascular Mathematical Model of Graded Head-Up Tilt

    PubMed Central

    Lim, Einly; Chan, Gregory S. H.; Dokos, Socrates; Ng, Siew C.; Latif, Lydia A.; Vandenberghe, Stijn; Karunanithi, Mohan; Lovell, Nigel H.

    2013-01-01

    A lumped parameter model of the cardiovascular system has been developed and optimized using experimental data obtained from 13 healthy subjects during graded head-up tilt (HUT) from the supine position to . The model includes descriptions of the left and right heart, direct ventricular interaction through the septum and pericardium, the systemic and pulmonary circulations, nonlinear pressure volume relationship of the lower body compartment, arterial and cardiopulmonary baroreceptors, as well as autoregulatory mechanisms. A number of important features, including the separate effects of arterial and cardiopulmonary baroreflexes, and autoregulation in the lower body, as well as diastolic ventricular interaction through the pericardium have been included and tested for their significance. Furthermore, the individual effect of parameter associated with heart failure, including LV and RV contractility, baseline systemic vascular resistance, pulmonary vascular resistance, total blood volume, LV diastolic stiffness and reflex gain on HUT response have also been investigated. Our fitted model compares favorably with our experimental measurements and published literature at a range of tilt angles, in terms of both global and regional hemodynamic variables. Compared to the normal condition, a simulated congestive heart failure condition produced a blunted response to HUT with regards to the percentage changes in cardiac output, stroke volume, end diastolic volume and effector response (i.e., heart contractility, venous unstressed volume, systemic vascular resistance and heart rate) with progressive tilting. PMID:24204817

  6. Anisotropic cosmology and inflation from a tilted Bianchi IX model

    NASA Astrophysics Data System (ADS)

    Sundell, P.; Koivisto, T.

    2015-12-01

    The dynamics of the tilted axisymmetric Bianchi IX cosmological models are explored allowing energy flux in the source fluid. The Einstein equations and the continuity equation are presented treating the equation of state w and the tilt angle of the fluid λ as time-dependent functions, but when analyzing the phase space w and λ are considered free parameters and the shear, the vorticity and the curvature of the spacetime span a three-dimensional phase space that contains seven fixed points. One of them is an attractor that inflates the universe anisotropically, thus providing a counterexample to the cosmic no-hair conjecture. Also, examples of realistic though fine-tuned cosmologies are presented wherein the rotation can become significant towards the present epoch but the shear stays within the observational bounds. The examples suggest that the model used here can explain the parity-violating anomalies of the cosmic microwave background. The result significantly differs from an earlier study, where a nonaxisymmetric Bianchi IX type model with a tilted perfect dust source was found to induce too much shear for observationally significant vorticity.

  7. A study of the cornering forces generated by aircraft tires on a tilted, free-swiveling nose gear

    NASA Technical Reports Server (NTRS)

    Daugherty, R. H.; Stubbs, S. M.

    1985-01-01

    An experimental investigation was conducted to study the effect of various parameters on the cornering forces produced by a rolling aircraft tire installed on a tilted, free-swiveling nose gear. The parameters studied included tilt angle, trial, tire inflation pressure, rake angle, vertical load, and whether or not a twin tire configuration corotates. These parameters were evaluated by measuring the cornering force produced by an aircraft tire installed on the nose gear of a modified vehicle as it was towed slowly. Cornering force coefficient increased with increasing tilt angle. Increasing trial or rake angle decreased the magnitude of the cornering force coefficient. Tire inflation pressure had no effect on the cornering force coefficient. Increasing vertical load decreased the cornering force coefficient. When the tires of a twin tire system rotated independently, the cornering force coefficients were the same as those for the single-tire configuration. When the twin tire system was made to corotate, however, the cornering force coefficients increased significantly.

  8. Variable-Tilt Helicopter Rotor Mast

    NASA Technical Reports Server (NTRS)

    Kelley, Henry L.

    1995-01-01

    Variable-tilt helicopter rotor mast proposed to improve helicopter performance and reduce vibration, especially at upper end of forward-speed range of helicopters. Achieved by use of universal coupling in main rotor mast or by tilting entire engine-and-transmission platform. Performance, energy efficiency, and safety enhanced.

  9. Large optics inspection, tilting, and washing stand

    DOEpatents

    Ayers, Marion Jay; Ayers, Shannon Lee

    2012-10-09

    A large optics stand provides a risk free means of safely tilting large optics with ease and a method of safely tilting large optics with ease. The optics are supported in the horizontal position by pads. In the vertical plane the optics are supported by saddles that evenly distribute the optics weight over a large area.

  10. Large optics inspection, tilting, and washing stand

    DOEpatents

    Ayers, Marion Jay; Ayers, Shannon Lee

    2010-08-24

    A large optics stand provides a risk free means of safely tilting large optics with ease and a method of safely tilting large optics with ease. The optics are supported in the horizontal position by pads. In the vertical plane the optics are supported by saddles that evenly distribute the optics weight over a large area.

  11. Strong tilt illusions always reduce orientation acuity.

    PubMed

    Solomon, Joshua A; Morgan, Michael J

    2009-03-01

    The apparent spatial orientation of an object can differ from its physical orientation when differently oriented objects surround it. This is the "tilt illusion". Previously [Solomon, J. A., & Morgan, M. J. (2006). Stochastic re-calibration: Contextual effects on perceived tilt. Proceedings of the Royal Society of London. Series B, Biological Sciences, 273, 2681-2686], we reported a loss of orientation acuity whenever a large physical tilt was required to compensate for the tilt illusion and make a target appear horizontal. Since all of those targets appeared to be at least approximately horizontal, we concluded that orientation acuity was not wholly determined by the target's apparent orientation. In the present study, we used oblique (i.e. neither horizontal nor vertical) reference orientations to more directly examine the effect of perceived orientation on orientation acuity. The results show that when surround and reference were parallel, there was no tilt illusion and acuity was high. Acuity suffered whenever the tilt illusion caused a large discrepancy between the target's physical and perceived tilts. Since this was true even for tilted references, context-induced acuity loss cannot be simply an "oblique effect" of the target's physical orientation. PMID:19268684

  12. Tip--tilt compensation for astronomical imaging

    SciTech Connect

    Olivier, S.S. ); Gavel, D.T. )

    1994-01-01

    We present a performance analysis of tip--tilt-compensation systems that use natural stars as tilt references. Taking into account properties of the atmosphere and of the galactic stellar populations, we optimize operating parameters over the system to determine performance limits for several varieties of tip--tilt-compensation system operating on a 10-m telescope on Mauna Kea, Hawaii. We find that, for systems that use a single tilt reference star, if the image of the star is uncorrected, a one-axis root-mean-square tilt residual of less than 190 nrad can be obtained for at least 99% of all astronomical objects, whereas if the image of the tilt reference star is fully corrected this limit drops to 90 nrad. For systems that use two tilt reference stars the limits drop to 160 nrad if the images of the stars are uncorrected and to 60 nrad if the images of the stars are fully corrected. These residual tilt levels would permit [ital V]-band images with long-exposure resolution of 8.5, 4.2, 7.3, and 2.9 times the diffraction limit, respectively, where the diffraction-limited resolution in the [ital V] band is 0.011 arcsec. These results may be compared with the typical seeing of 0.75 arcsec.

  13. Optimum windmill-site matching

    SciTech Connect

    Salameh, Z.M.; Safari, I. )

    1992-12-01

    In this paper a methodology for the selection of the optimum windmill for a specific site is developed. The selection windmill for a specific site is developed. The selection is based on finding the capacity factors (CF) of the available windmills. This is done by using long term wind speed data recorded at different hours of the day for many years. This data is then used to generate mean wind speeds for a typical day in a month. Probability density functions for the mean wind speeds for the different hours of the day are generated with the manufacturer's specifications on windmills used to calculate the capacity factors for the windmills. The windmill with the highest average capacity factor for the specific site is the optimum one and to be recommended.

  14. Detection and correction of wavefront errors caused by slight reference tilt in two-step phase-shifting digital holography.

    PubMed

    Xu, Xianfeng; Cai, Luzhong; Gao, Fei; Jia, Yulei; Zhang, Hui

    2015-11-10

    A simple and convenient method, without the need for any additional optical devices and measurements, is suggested to improve the quality of the reconstructed object wavefront in two-step phase-shifting digital holography by decreasing the errors caused by reference beam tilt, which often occurs in practice and subsequently introduces phase distortion in the reconstructed wave. The effects of reference beam tilt in two-step generalized interferometry is analyzed theoretically, showing that this tilt incurs no error either on the extracted phase shift or on the retrieved real object wave amplitude on the recording plane, but causes great deformation of the recovered object wavefront. A corresponding error detection and correction approach is proposed, and the formulas to calculate the tilt angle and correct the wavefront are deduced. A series of computer simulations to find and remove the wavefront errors caused by reference beam tilt demonstrate the effectiveness of this method. PMID:26560791

  15. Magnetic-assisted triboelectric nanogenerators as self-powered visualized omnidirectional tilt sensing system

    NASA Astrophysics Data System (ADS)

    Han, Mengdi; Zhang, Xiao-Sheng; Sun, Xuming; Meng, Bo; Liu, Wen; Zhang, Haixia

    2014-04-01

    The triboelectric nanogenerator (TENG) is a promising device in energy harvesting and self-powered sensing. In this work, we demonstrate a magnetic-assisted TENG, utilizing the magnetic force for electric generation. Maximum power density of 541.1 mW/m2 is obtained at 16.67 MΩ for the triboelectric part, while the electromagnetic part can provide power density of 649.4 mW/m2 at 16 Ω. Through theoretical calculation and experimental measurement, linear relationship between the tilt angle and output voltage at large angles is observed. On this basis, a self-powered omnidirectional tilt sensor is realized by two magnetic-assisted TENGs, which can measure the magnitude and direction of the tilt angle at the same time. For visualized sensing of the tilt angle, a sensing system is established, which is portable, intuitive, and self-powered. This visualized system greatly simplifies the measure process, and promotes the development of self-powered systems.

  16. Magnetic-assisted triboelectric nanogenerators as self-powered visualized omnidirectional tilt sensing system

    PubMed Central

    Han, Mengdi; Zhang, Xiao-Sheng; Sun, Xuming; Meng, Bo; Liu, Wen; Zhang, Haixia

    2014-01-01

    The triboelectric nanogenerator (TENG) is a promising device in energy harvesting and self-powered sensing. In this work, we demonstrate a magnetic-assisted TENG, utilizing the magnetic force for electric generation. Maximum power density of 541.1 mW/m2 is obtained at 16.67 MΩ for the triboelectric part, while the electromagnetic part can provide power density of 649.4 mW/m2 at 16 Ω. Through theoretical calculation and experimental measurement, linear relationship between the tilt angle and output voltage at large angles is observed. On this basis, a self-powered omnidirectional tilt sensor is realized by two magnetic-assisted TENGs, which can measure the magnitude and direction of the tilt angle at the same time. For visualized sensing of the tilt angle, a sensing system is established, which is portable, intuitive, and self-powered. This visualized system greatly simplifies the measure process, and promotes the development of self-powered systems. PMID:24770490

  17. Classical and semiclassical mechanics of molecular rotors in tilted fields

    NASA Astrophysics Data System (ADS)

    Arango, Carlos Alberto

    We investigate the classical mechanics of diatomic and symmetric top molecules in tilted fields. These molecules exhibit regular, chaotic or mixed phase space depending on the tilt angle beta, the energy E, and the relative intensity of the fields o/Deltao. In the integrable collinear problem the projection of the angular momentum into the spatial z axis is a constant of motion, m, which allows us to use energy momentum diagrams to classify the motions of the rotor. For beta ≠ 0 the system is non-integrable showing mostly regular dynamics in the high-energy (free-rotor) and low-energy (pendular) limits; for energy near the tilted fields barrier the phase space is highly chaotic with degree of chaos increasing with beta between 0 and pi/2. Periodic orbits and bifurcation diagrams are obtained from symmetry lines and their iterations under the Poincare map. Some quantum eigenstates are localized near stable or unstable periodic orbits showing tori quantization or scarring respectively. For asymmetric top molecules in parallel fields m is a constant of the motion and it is possible to define an effective potential Vm(theta, psi). In an E-m diagram the equilibrium solutions of Vm(theta, psi) are curves that enclose regions of qualitatively different accessible theta-psi configuration space; these regions can be used to classify the quantum eigenstates. For plane rotors several primitive semiclassical methods are used to calculate the rotational excitation caused by laser pulses. In the case of plane rotors in electric fields we calculate energy spectra, orientation (), and alignment (), using the Herman-Kluk propagator in terms of periodic coherent states. For diatomic rotors in tilted fields, the HK propagator was used to calculate energy spectra with good agreement for high-energy and not very dense eigenspectra. Some steps are taken towards the development of HK-type propagator for rotational coherent states.

  18. Blade-Pitch Control for Quieting Tilt-Rotor Aircraft

    NASA Technical Reports Server (NTRS)

    Betzina, Mark D.; Nguyen, Khanh Q.

    2004-01-01

    A method of reducing the noise generated by a tilt-rotor aircraft during descent involves active control of the blade pitch of the rotors. This method is related to prior such noise-reduction methods, of a type denoted generally as higher-harmonic control (HHC), in which the blade pitch is made to oscillate at a harmonic of the frequency of rotation of the rotor. A tilt-rotor aircraft is so named because mounted at its wing tips are motors that can be pivoted to enable the aircraft to take off and land like a helicopter or to fly like a propeller airplane. When the aircraft is operating in its helicopter mode, the rotors generate more thrust per unit rotor-disk area than helicopter rotors do, thus producing more blade-vortex interaction (BVI) noise. BVI is a major source of noise produced by helicopters and tilt-rotor aircraft during descent: When a rotor descends into its own wake, the interaction of each blade with the blade-tip vortices generated previously gives rise to large air-pressure fluctuations. These pressure fluctuations radiate as distinct, impulsive noise. In general, the pitch angle of the rotor blades of a tilt-rotor aircraft is controlled by use of a swash plate connected to the rotor blades by pitch links. In both prior HHC methods and the present method, HHC control signals are fed as input to swash-plate control actuators, causing the rotor-blade pitch to oscillate. The amplitude, frequency, and phase of the control signal can be chosen to minimize BVI noise.

  19. Tilt growth of CdTe epilayers on sapphire substrates by MOCVD

    NASA Astrophysics Data System (ADS)

    Ebe, H.; Sawada, A.; Maruyama, K.; Nishijima, Y.; Shinohara, K.; Takigawa, H.

    1991-12-01

    We studied model lattice matching in the growth direction by tilt growth and found that the ratio of the tilt angle of the epilayer (α) to the offset angle of the substrate (θ) had a maximum at α / θ = 0.73, independent of the offset angle. Experimental plots of the ratio versus the full width at half maximum (FWHM) of (333) CdTe rocking curves in double-crystal X-ray diffraction show that the ratio ranges from 0.05 to 0.6 while the FWHM varies from 1100 to 400 arc sec. This result suggests that the lattice inclination orients the lattice structure perpendicular to the CdTe-sapphire heterointerface and that the tilt angle reduces defects such as dislocations and stacking faults. Most epilayers grown on sapphire substrates with offset angles above 3° were confirmed to have a α / θ ratio below 0.2. This suggests that crystal defects may be generated by shearing stress due to large offset angles. Greater defect density lowers the ratio and degrades crystallinity.

  20. Deformation of a free interface pierced by a tilted cylinder

    NASA Astrophysics Data System (ADS)

    Raufaste, C.; Kirstetter, G.; Celestini, F.; Cox, S. J.

    2012-07-01

    We investigate the interaction between an infinite cylinder and a free fluid-fluid interface governed only by its surface tension. We study the deformation of an initially flat interface when it is deformed by the presence of a cylindrical object, tilted at an arbitrary angle, that the interface “totally wets”. Our simulations predict all significant quantities such as the interface shape, the position of the contact line, and the force exerted by the interface on the cylinder. These results are compared with an experimental study of the penetration of a soap film by a cylindrical liquid jet. This dynamic situation exhibits all the characteristics of a totally wetting interface. We show that whatever the inclination, the force is always perpendicular to the plane of the interface, and its amplitude diverges as the inclination angle increases. Such results should bring new insights in both fluid and solid mechanics, from animal locomotion to surface micro-processing.

  1. From plane to spatial angles: PTB's spatial angle autocollimator calibrator

    NASA Astrophysics Data System (ADS)

    Kranz, Oliver; Geckeler, Ralf D.; Just, Andreas; Krause, Michael; Osten, Wolfgang

    2015-10-01

    Electronic autocollimators are utilised versatilely for non-contact angle measurements in applications like straightness measurements and profilometry. Yet, no calibration of the angle measurement of an autocollimator has been available when both its measurement axes are engaged. Additionally, autocollimators have been calibrated at fixed distances to the reflector, although its distance may vary during the use of an autocollimator. To extend the calibration capabilities of the Physikalisch-Technische Bundesanstalt (PTB) regarding spatial angles and variable distances, a novel calibration device has been set up: the spatial angle autocollimator calibrator (SAAC). In this paper, its concept and its mechanical realisation will be presented. The focus will be on the system's mathematical modelling and its application in spatial angle calibrations. The model considers the misalignments of the SAAC's components, including the non-orthogonalities of the measurement axes of the autocollimators and of the rotational axes of the tilting unit. It allows us to derive specific measurement procedures to determine the misalignments in situ and, in turn, to correct the measurements of the autocollimators. Finally, the realisation and the results of a traceable spatial angle calibration of an autocollimator will be presented. This is the first calibration of this type worldwide.

  2. Tilting double-prism scanner driven by cam-based mechanism.

    PubMed

    Li, Anhu; Yi, Wanli; Sun, Wansong; Liu, Liren

    2015-06-20

    A pair of orthogonal tilting prisms has been explored in our previous work to perform the orientation and position tracking function with tracking accuracy better than submicroradian order. Crucial to the function implementation, however, is the real-time nonlinear control of the tilting angles of double prisms for tracking a given target trajectory. In previous papers [Proc. SPIE5892, 1-5 (2005).PSISDG0277-786X; Appl. Opt.45, 8063 (2006).PSISDG0277-786X; Proc. SPIE6709, 41 (2007).PSISDG0277-786X; Appl. Opt.51, 356 (2011).10.1364/AO.51.000356APOPAI1559-128X; Appl. Opt.53, 3712 (2014).10.1364/AO.53.003712APOPAI1559-128X], a new driving method by a cam-based mechanism, which can transfer the control problem to the design of corresponding cam configuration, is investigated. The design process of a cam-based mechanism is explained from the mapping relation between the tilting angles of a prism and the configuration curve of a corresponding cam. Based on the designed cam-based mechanism, a tracking error less than 0.375% is depicted between the tracking trajectory and the original one. Moreover, the dynamic characteristic of the tracking mechanism is discussed in detail as well as the impacts of different tilting speeds on the tracking trajectory. The proposed tracking mechanism of a tilting double-prism scanner can create a new avenue for passively tracking a given target. PMID:26193031

  3. Sensitivity of off-axis performance of aspheric spectacle lenses to tilt and decentration.

    PubMed

    Atchison, D A; Tame, S A

    1993-10-01

    Apparatus was modified to measure, and theoretical raytracing was used to predict, off-axis powers of spectacle lenses in the presence of tilt or decentration. In response to poor fitting in the form of tilt or decentration, lenses with aspheric front surfaces were found to have greater off-axis power errors than best-form lenses with spherical surfaces. This is attributable to the aspheric lenses having flatter surfaces than the spherical lenses. The errors are up to twice those occurring for the spherical lenses, and can be quite high, e.g. 0.9 D astigmatism for +6D power with 10 degrees tilt in 20 degrees upgaze. Negative lenses are more sensitive to poor fitting than are positive lenses of the same power. The errors for straight ahead vision associated with tilt are approximately proportional to the square of the angle of tilt, and the errors for straight ahead vision associated with decentration are approximately proportional to the square of decentration. It is most important that aspheric lenses be correctly fitted, which means that each 2 degrees of pantascopic tilt should be accompanied by approximately 1 mm decentration. PMID:8278198

  4. All-Polymer Electrolytic Tilt Sensor with Conductive Poly(dimethylsiloxane) Electrodes

    NASA Astrophysics Data System (ADS)

    Kyoo Lee, June; Choi, Ju Chan; Kong, Seong Ho

    2013-06-01

    In this study, an all-polymer electrolytic tilt sensor with conductive and corrosion-resistant poly(dimethylsiloxane) (PDMS) electrodes was designed and its performances were characterized. A PDMS cavity in the sensor for holding an electrolyte was fabricated by soft lithography using an ultraviolet-sensitive polymer. A conductive PDMS composite (gPDMS) with graphite powder was used for the electrode to measure the inclination angle of the electrolyte. A gPDMS composite with a graphite concentration above 40 wt % was able to function as a conductive polymer. The fabricated all-polymer tilt sensor exhibited a detectable inclination range of +/-60° and showed a relatively linear output signal compared with those exhibited by conventional micromachined tilt sensors with axis asymmetrical cavities. The maximum hysteresis of the output signal was approximately 0.1 Vrms when the sensor repeatedly tilted and leveled off. In addition to the fundamental characterization of the sensor, various characteristics of the all-polymer tilt sensor, such as time-dependent and electrolyte-volume-dependent variations in the output signal, were investigated in this study. While the performance of the proposed sensor was comparable to that of conventional silicon-micromachined tilt sensors, the sensor could be produced at a fraction of the cost required to fabricate the conventional sensors.

  5. All-Polymer Electrolytic Tilt Sensor with Conductive Poly(dimethylsiloxane) Electrodes

    NASA Astrophysics Data System (ADS)

    Lee, June Kyoo; Choi, Ju Chan; Kong, Seong Ho

    2013-06-01

    In this study, an all-polymer electrolytic tilt sensor with conductive and corrosion-resistant poly(dimethylsiloxane) (PDMS) electrodes was designed and its performances were characterized. A PDMS cavity in the sensor for holding an electrolyte was fabricated by soft lithography using an ultraviolet-sensitive polymer. A conductive PDMS composite (gPDMS) with graphite powder was used for the electrode to measure the inclination angle of the electrolyte. A gPDMS composite with a graphite concentration above 40 wt % was able to function as a conductive polymer. The fabricated all-polymer tilt sensor exhibited a detectable inclination range of ± 60° and showed a relatively linear output signal compared with those exhibited by conventional micromachined tilt sensors with axis asymmetrical cavities. The maximum hysteresis of the output signal was approximately 0.1 V\\text{rms when the sensor repeatedly tilted and leveled off. In addition to the fundamental characterization of the sensor, various characteristics of the all-polymer tilt sensor, such as time-dependent and electrolyte-volume-dependent variations in the output signal, were investigated in this study. While the performance of the proposed sensor was comparable to that of conventional silicon-micromachined tilt sensors, the sensor could be produced at a fraction of the cost required to fabricate the conventional sensors.

  6. Tilted wheel satellite attitude control with air-bearing table experimental results

    NASA Astrophysics Data System (ADS)

    Inumoh, Lawrence O.; Forshaw, Jason L.; Horri, Nadjim M.

    2015-12-01

    Gyroscopic actuators for satellite control have attracted significant research interest over the years, but their viability for the control of small satellites has only recently started to become clear. Research on variable speed gyroscopic actuators has long been focused on single gimbal actuators; double gimbal actuators typically operate at constant wheel spin rate and allow tilt angle ranges far larger than the ranges needed to operate most satellite missions. This research examines a tilted wheel, a newly proposed type of inertial actuator that can generate torques in all three principal axes of a rigid satellite using a spinning wheel and a double tilt mechanism. The tilt mechanism tilts the angular momentum vector about two axes providing two degree of freedom control, while variation of the wheel speed provides the third. The equations of motion of the system lead to a singularity-free system during nominal operation avoiding the need for complex steering logic. This paper describes the hardware design of the tilted wheel and the experimental setup behind both standalone and spherical air-bearing tables used to test it. Experimental results from the air bearing table are provided with the results depicting the high performance capabilities of the proposed actuator in torque generation.

  7. Implant Angle Monitor System of MC3-II

    SciTech Connect

    Sato, Fumiaki; Sano, Makoto; Nakaoka, Hiroaki; Fujii, Yoshito; Kudo, Tetuya; Nakanishi, Makoto; Koike, Masazumi; Fujino, Yasushi

    2008-11-03

    Precise implant angle control is required for the latest generation of ion implanters to meet further shrink semiconductor device requirements. Especially, the highest angle accuracy is required for Halo implant process of Logic devices. The Halo implant angle affects the device performance, because slight differences of beam divergence change the overlap profile towards the extension. Additionally, twist angle accuracy is demanded in case of channeling angle implant. Therefore monitoring beam angles and wafer twist angles is important. A new monitoring system for the MC3-II, SEN Corp.'s single wafer type medium current implanter has been developed. This paper describes the angle control performance and monitoring system of the MC3-II. For the twist angle control, we developed a wafer notch angle monitor. The system monitors the wafer notch image on the platen. And the notch angle variation is calculated by using image processing method. It is also able to adjust the notch angle according to the angle error. For the tilt angle control, we developed a vertical beam profile monitor. The monitor system can detect beam profile of vertical directions with horizontally scanning beam. It also measures beam angles of a tilt direction to a wafer. The system configuration and sample beam data are presented.

  8. Numerical relativity simulations of thick accretion disks around tilted Kerr black holes

    NASA Astrophysics Data System (ADS)

    Mewes, Vassilios; Font, José A.; Galeazzi, Filippo; Montero, Pedro J.; Stergioulas, Nikolaos

    2016-03-01

    In this paper we present 3D numerical relativity simulations of thick accretion disks around tilted Kerr black holes. We investigate the evolution of three different initial disk models with a range of initial black hole spin magnitudes and tilt angles. For all the disk-to-black hole mass ratios considered (0.044-0.16) we observe significant black hole precession and nutation during the evolution. This indicates that for such mass ratios, neglecting the self-gravity of the disks by evolving them in a fixed background black hole spacetime is not justified. We find that the two more massive models are unstable against the Papaloizou-Pringle (PP) instability and that those PP-unstable models remain unstable for all initial spins and tilt angles considered, showing that the development of the instability is a very robust feature of such PP-unstable disks. Our lightest model, which is the most astrophysically favorable outcome of mergers of binary compact objects, is stable. The tilt between the black hole spin and the disk is strongly modulated during the growth of the PP instability, causing a partial global realignment of black hole spin and disk angular momentum in the most massive model with constant specific angular momentum l . For the model with nonconstant l -profile we observe a long-lived m =1 nonaxisymmetric structure which shows strong oscillations of the tilt angle in the inner regions of the disk. This effect might be connected to the development of Kozai-Lidov oscillations. Our simulations also confirm earlier findings that the development of the PP instability causes the long-term emission of large amplitude gravitational waves, predominantly for the l =m =2 multipole mode. The imprint of the black hole (BH) precession on the gravitational waves from tilted BH-torus systems remains an interesting open issue that would require significantly longer simulations than those presented in this paper.

  9. Spin transport in tilted electron vortex beams

    NASA Astrophysics Data System (ADS)

    Basu, Banasri; Chowdhury, Debashree

    2014-12-01

    In this paper we have enlightened the spin related issues of tilted Electron vortex beams. We have shown that in the skyrmionic model of electron we can have the spin Hall current considering the tilted type of electron vortex beam. We have considered the monopole charge of the tilted vortex as time dependent and through the time variation of the monopole charge we can explain the spin Hall effect of electron vortex beams. Besides, with an external magnetic field we can have a spin filter configuration.

  10. A review of tilt rotor download research

    NASA Technical Reports Server (NTRS)

    Felker, Fort F.

    1988-01-01

    Experimental and theoretical research on the forces on a wing immersed in the wake of a hovering rotor is reviewed, with emphasis on the tilt rotor download problem. The basic features of the rotor/wing flow field on a tilt rotor aircraft are described. The effect of important geometric and operational parameters on the wing download is assessed. The magnitude of the download for typical tilt rotor configurations is reviewed, and advanced concepts for download reduction are described. Recommendations are presented for the direction of future research efforts.

  11. Modeling of magnetization precession in spin-torque nano-oscillators with a tilted polarizer

    SciTech Connect

    Lv, Gang; Zhang, Hong E-mail: yaowen@tongji.edu.cn; Cao, Xuecheng; Qin, Yufeng; Li, Guihua; Wang, Linhui; Liu, Yaowen E-mail: yaowen@tongji.edu.cn; Hou, Zhiwei

    2015-07-15

    The spin-torque induced magnetization precession dynamics are studied in a spin-valve with a tilted spin polarizer. Macrospin simulations demonstrate that the frequency of precession state depends both on the external DC current and the intrinsic parameters of devices such as the tilted angle of spin polarizer, the damping factor and saturation magnetization of the free layer. The dependence role of those parameters is characterized by phase diagrams. An analytical model is presented, which can successfully interpret the features of precession frequency.

  12. Scanning transmission electron microscopy through-focal tilt-series on biological specimens.

    PubMed

    Trepout, Sylvain; Messaoudi, Cédric; Perrot, Sylvie; Bastin, Philippe; Marco, Sergio

    2015-10-01

    Since scanning transmission electron microscopy can produce high signal-to-noise ratio bright-field images of thick (≥500 nm) specimens, this tool is emerging as the method of choice to study thick biological samples via tomographic approaches. However, in a convergent-beam configuration, the depth of field is limited because only a thin portion of the specimen (from a few nanometres to tens of nanometres depending on the convergence angle) can be imaged in focus. A method known as through-focal imaging enables recovery of the full depth of information by combining images acquired at different levels of focus. In this work, we compare tomographic reconstruction with the through-focal tilt-series approach (a multifocal series of images per tilt angle) with reconstruction with the classic tilt-series acquisition scheme (one single-focus image per tilt angle). We visualised the base of the flagellum in the protist Trypanosoma brucei via an acquisition and image-processing method tailored to obtain quantitative and qualitative descriptors of reconstruction volumes. Reconstructions using through-focal imaging contained more contrast and more details for thick (≥500 nm) biological samples. PMID:26093182

  13. Effects of tilt interface boundary on mechanical properties of Cu/Ni nanoscale metallic multilayer composites

    NASA Astrophysics Data System (ADS)

    Yang, Meng; Xu, Jian-Gang; Song, Hai-Yang; Zhang, Yun-Guang

    2015-09-01

    The effect of tilt interfaces and layer thickness of Cu/Ni multilayer nanowires on the deformation mechanism are investigated by molecular dynamics simulations. The results indicate that the plasticity of the sample with a 45° tilt angle is much better than the others. The yield stress is found to decrease with increasing the tilt angle and it reaches its lowest value at 33°. Then as the tilt angle continues to increase, the yield strength increases. Furthermore, the studies show that with the decrease of layer thickness, the yield strength gradually decreases. The study also reveals that these different deformation behaviors are associated with the glide of dislocation. Project supported by the National Natural Science Foundation of China (Grant No. 10902083), the Program for New Century Excellent Talent in University of Ministry of Education of China (Grant No. NCET-12-1046), the Program for New Scientific and Technological Star of Shaanxi Province, China (Grant No. 2012KJXX-39), and the Natural Science Basic Research Plan in Shaanxi Province, China (Grant No. 2014JQ1036).

  14. Evolution of the ν = 1 / 2 Fractional Quantum Hall State in Tilted Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Deng, Hao; Hasdemir, Sukret; Liu, Yang; Shayegan, Mansour; Pfeiffer, Loren; West, Ken; Baldwin, Kirk

    2014-03-01

    We report magneto-transport measurements of two-dimensional electron systems confined to 65-nm-wide GaAs quantum wells with density 1.4 1011 cm-2. We observe a remarkable evolution of the magnetoresistance around filling factor ν=1/2 as we increase the tilting angle. The weak ν=1/2 fractional quantum Hall (FQH) state at fully perpendicular field gets stronger as the sample is tilted, but abruptly disappears at higher tilting angles as an insulating phase moves from low fillings to higher ones near ν=1/2. This insulating phase likely signals a bilayer, pinned Wigner crystal. At higher tilting angles, we observe a disappearance of the ν=1 quantum Hall state and the appearance of even-numerator FQH states around ν=1, which are also consistent with the interpretation that the system becomes bilayer. We acknowledge support through the DOE BES (DE-FG02-00-ER45841) for measurements, and the Gordon and Betty Moore Foundation (Grant GBMF2719), Keck Foundation, and the NSF (DMR-0904117, DMR-1305691 and MRSEC DMR-0819860) for sample fabrication.

  15. Maintenance of postural stability as a function of tilted base of support.

    PubMed

    Dutt-Mazumder, Aviroop; Challis, John; Newell, Karl

    2016-08-01

    The experiment was set-up to investigate the mechanisms of postural control by manipulating the base of support angle, using tilted platform wedges. The primary focus was to analyze the coupling of the motion of the center of mass (CoM) and the center of pressure (CoP), and the motions of the leg joints considered as individual components and synergies. The CoM-CoP coupling (both medio-lateral and anterioposterior) was preserved (∼0°) across all tilted platform angles (35°, 30°, 20°, 10° Down, 0° Flat and 10°, 20°, 25° Up), reflecting an in-phase pattern. There was high coherence (∼1) for CoM-CoP in the lower frequency range, whereas contrarily the hip, knee and ankle pair-wise couplings had values ranging between (0.4 and 0.7) across the different platform angle conditions. These findings are consistent with the view that the local pair-wise coupled variables of Hip, Knee and Ankle motions adaptively self-organized to preserve the CoM-CoP in-phase coupling at equilibrium over the baseline (0° Flat) platform condition and all other tilted platform angles. The findings support the hypothesis of CoM-CoP coupling acting as a collective variable that provides the structural integrity of the system for upright quiet standing across the platform angle conditions. PMID:27155961

  16. Dynamic of charged planar geometry in tilted and non-tilted frames

    SciTech Connect

    Sharif, M. Zaeem Ul Haq Bhatti, M.

    2015-05-15

    We investigate the dynamics of charged planar symmetry with an anisotropic matter field subject to a radially moving observer called a tilted observer. The Einstein-Maxwell field equations are used to obtain a relation between non-tilted and tilted frames and between kinematical and dynamical quantities. Using the Taub mass formalism and conservation laws, two evolution equations are developed to analyze the inhomogeneities in the tilted congruence. It is found that the radial velocity (due to the tilted observer) and the electric charge have a crucial effect on the inhomogeneity factor. Finally, we discuss the stability in the non-tilted frame in the pure diffusion case and examine the effects of the electromagnetic field.

  17. The XV-15 tilt rotor research aircraft

    NASA Technical Reports Server (NTRS)

    Dugan, D. C.; Erhart, R. G.; Schroers, L. G.

    1980-01-01

    The design characteristics of the XV-15 Tilt rotor research aircraft are presented. Particular attention is given to the following: control system; conversion system; and propulsion system. Flight test results are also reported.

  18. Aurelia aurita bio-inspired tilt sensor

    NASA Astrophysics Data System (ADS)

    Smith, Colin; Villanueva, Alex; Priya, Shashank

    2012-10-01

    The quickly expanding field of mobile robots, unmanned underwater vehicles, and micro-air vehicles urgently needs a cheap and effective means for measuring vehicle inclination. Commonly, tilt or inclination has been mathematically derived from accelerometers; however, there is inherent error in any indirect measurement. This paper reports a bio-inspired tilt sensor that mimics the natural balance organ of jellyfish, called the ‘statocyst’. Biological statocysts from the species Aurelia aurita were characterized by scanning electron microscopy to investigate the morphology and size of the natural sensor. An artificial tilt sensor was then developed by using printed electronics that incorporates a novel voltage divider concept in conjunction with small surface mount devices. This sensor was found to have minimum sensitivity of 4.21° with a standard deviation of 1.77°. These results open the possibility of developing elegant tilt sensor architecture for both air and water based platforms.

  19. Tilted lines as complex stimuli1

    PubMed Central

    Touchette, Paul E.

    1969-01-01

    Severely retarded boys were taught to respond differentially to lines tilted at 45° and 135°. While all subjects could perform the discrimination, the aspect of the stimulus that controlled responding was shown to differ among subjects. PMID:5781147

  20. Monitoring of unstable slopes by MEMS tilting sensors and its application to early warning

    NASA Astrophysics Data System (ADS)

    Towhata, I.; Uchimura, T.; Seko, I.; Wang, L.

    2015-09-01

    The present paper addresses the newly developed early warning technology that can help mitigate the slope failure disasters during heavy rains. Many studies have been carried out in the recent times on early warning that is based on rainfall records. Although those rainfall criteria of slope failure tells the probability of disaster on a regional scale, it is difficult for them to judge the risk of particular slopes. This is because the rainfall intensity is spatially too variable to forecast and the early warning based on rainfall alone cannot take into account the effects of local geology, hydrology and topography that vary spatially as well. In this regard, the authors developed an alternative technology in which the slope displacement/deformation is monitored and early warning is issued when a new criterion is satisfied. The new MEMS-based sensor monitors the tilting angle of an instrument that is embedded at a very shallow depth and the record of the tilting angle corresponds to the lateral displacement at the slope surface. Thus, the rate of tilting angle that exceeds a new criterion value implies an imminent slope failure. This technology has been validated against several events of slope failures as well as against a field rainfall test. Those validations have made it possible to determine the criterion value of the rate of tilting angle to be 0.1 degree/hour. The advantage of the MEMS tilting sensor lies in its low cost. Hence, it is possible to install many low-cost sensors over a suspected slope in which the precise range of what is going to fall down during the next rainfall is unknown. In addition to the past validations, this paper also introduces a recent application to a failed slope in the Izu Oshima Island where a heavy rainfall-induced slope failure occurred in October, 2013.

  1. Tilt representation beyond the retinotopic level.

    PubMed

    Parwaga, Sandeep; Buckley, David; Duke, Philip A

    2016-01-01

    We perceive a stable visual world, which enables successful interaction with our environment, despite movements of the eyes, head, and body. How are such perceptions formed? One possibility is that retino-centric visual input is transformed into representations at higher levels, such as head-, body-, or world-centered representations. We investigated this hypothesis using the tilt aftereffect in a balanced adaptation paradigm designed to isolate head-, body-, and world-centered aftereffects. Observers adapted to two oppositely tilted stimuli, each contingent on one of two different gaze, head, or body directions. We found aftereffects contingent on gaze direction, but not head or body direction. This demonstrates that adaptable tilt representations exist in a head-centric frame but not in higher reference frames. These aftereffects may be attributed to adaptation of retinotopic tilt-sensitive neurons whose responses are modulated by gaze direction (gain fields). Such neurons could support functionally head-centric tilt representations and are found as early as V1. On the basis of our results we would not expect activity in tilt-sensitive neurons to be modulated by head or body direction. The balanced adaptation paradigm is a useful tool for examining properties of the process responsible for gaze modulation of activity in visual neurons. PMID:26868889

  2. Swarms: Optimum aggregations of spacecraft

    NASA Technical Reports Server (NTRS)

    Mayer, H. L.

    1980-01-01

    Swarms are aggregations of spacecraft or elements of a space system which are cooperative in function, but physically isolated or only loosely connected. For some missions the swarm configuration may be optimum compared to a group of completely independent spacecraft or a complex rigidly integrated spacecraft or space platform. General features of swarms are induced by considering an ensemble of 26 swarms, examples ranging from Earth centered swarms for commercial application to swarms for exploring minor planets. A concept for a low altitude swarm as a substitute for a space platform is proposed and a preliminary design studied. The salient design feature is the web of tethers holding the 30 km swarm in a rigid two dimensional array in the orbital plane. A mathematical discussion and tutorial in tether technology and in some aspects of the distribution of services (mass, energy, and information to swarm elements) are included.

  3. Optimum constrained image restoration filters

    NASA Technical Reports Server (NTRS)

    Riemer, T. E.; Mcgillem, C. D.

    1974-01-01

    The filter was developed in Hilbert space by minimizing the radius of gyration of the overall or composite system point-spread function subject to constraints on the radius of gyration of the restoration filter point-spread function, the total noise power in the restored image, and the shape of the composite system frequency spectrum. An iterative technique is introduced which alters the shape of the optimum composite system point-spread function, producing a suboptimal restoration filter which suppresses undesirable secondary oscillations. Finally this technique is applied to multispectral scanner data obtained from the Earth Resources Technology Satellite to provide resolution enhancement. An experimental approach to the problems involving estimation of the effective scanner aperture and matching the ERTS data to available restoration functions is presented.

  4. Signatures of the Berry curvature in the frequency dependent interlayer magnetoresistance in tilted magnetic fields.

    PubMed

    Wright, Anthony R; McKenzie, Ross H

    2014-02-26

    We show that in a layered metal, the angle dependent, finite frequency, interlayer magnetoresistance is altered due to the presence of a non-zero Berry curvature at the Fermi surface. At zero frequency, we find a conservation law which demands that the 'magic angle' condition for interlayer magnetoresistance extrema as a function of magnetic field tilt angle is essentially both field and Berry curvature independent. In the finite frequency case, however, we find that surprisingly large signatures of a finite Berry curvature occur in the periodic orbit resonances. We outline a method whereby the presence and magnitude of the Berry curvature at the Fermi surface can be extracted. PMID:24501195

  5. Optimum flight paths of turbojet aircraft

    NASA Technical Reports Server (NTRS)

    Miele, Angelo

    1955-01-01

    The climb of turbojet aircraft is analyzed and discussed including the accelerations. Three particular flight performances are examined: minimum time of climb, climb with minimum fuel consumption, and steepest climb. The theoretical results obtained from a previous study are put in a form that is suitable for application on the following simplifying assumptions: the Mach number is considered an independent variable instead of the velocity; the variations of the airplane mass due to fuel consumption are disregarded; the airplane polar is assumed to be parabolic; the path curvatures and the squares of the path angles are disregarded in the projection of the equation of motion on the normal to the path; lastly, an ideal turbojet with performance independent of the velocity is involved. The optimum Mach number for each flight condition is obtained from the solution of a sixth order equation in which the coefficients are functions of two fundamental parameters: the ratio of minimum drag in level flight to the thrust and the Mach number which represents the flight at constant altitude and maximum lift-drag ratio.

  6. Liquid film dynamics in horizontal and tilted tubes: Dry spots and sliding drops

    NASA Astrophysics Data System (ADS)

    King, A. A.; Cummings, L. J.; Naire, S.; Jensen, O. E.

    2007-04-01

    Using a model derived from lubrication theory, we consider the evolution of a thin viscous film coating the interior or exterior of a cylindrical tube. The flow is driven by surface tension and gravity and the liquid is assumed to wet the cylinder perfectly. When the tube is horizontal, we use large-time simulations to describe the bifurcation structure of the capillary equilibria appearing at low Bond number. We identify a new film configuration in which an isolated dry patch appears at the top of the tube and demonstrate hysteresis in the transition between rivulets and annular collars as the tube length is varied. For a tube tilted to the vertical, we show how a long initially uniform rivulet can break up first into isolated drops and then annular collars, which subsequently merge. We also show that the speed at which a localized drop moves down the base of a tilted tube is nonmonotonic in tilt angle.

  7. General Relativistic Magnetohydrodynamics Simulations of Tilted Black Hole Accretion Flows and Their Radiative Properties

    NASA Astrophysics Data System (ADS)

    Shiokawa, Hotaka; Gammie, C. F.; Dolence, J.; Noble, S. C.

    2013-01-01

    We perform global General Relativistic Magnetohydrodynamics (GRMHD) simulations of non-radiative, magnetized disks that are initially tilted with respect to the black hole's spin axis. We run the simulations with different size and tilt angle of the tori for 2 different resolutions. We also perform radiative transfer using Monte Carlo based code that includes synchrotron emission, absorption and Compton scattering to obtain spectral energy distribution and light curves. Similar work was done by Fragile et al. (2007) and Dexter & Fragile (2012) to model the super massive black hole SgrA* with tilted accretion disks. We compare our results of fully conservative hydrodynamic code and spectra that include X-ray, with their results.

  8. Development of a novel straining holder for transmission electron microscopy compatible with single tilt-axis electron tomography.

    PubMed

    Sato, K; Miyazaki, H; Gondo, T; Miyazaki, S; Murayama, M; Hata, S

    2015-10-01

    We have developed a newly designed straining specimen holder for in situ transmission electron microscopy (TEM) compatible with high-angle single tilt-axis electron tomography. The holder can deform a TEM specimen under tensile stress with the strain rate between 1.5 × 10(-6) and 5.2 × 10(-3) s(-1). We have also confirmed that the maximum tilt angle of the specimen holder reaches ±60° with a rectangular shape aluminum specimen. The new specimen holder, termed as 'straining and tomography holder', will have wide range potential applications in materials science. PMID:25904643

  9. Optimum Design of High-Speed Prop-Rotors

    NASA Technical Reports Server (NTRS)

    Chattopadhyay, Aditi; McCarthy, Thomas Robert

    1993-01-01

    An integrated multidisciplinary optimization procedure is developed for application to rotary wing aircraft design. The necessary disciplines such as dynamics, aerodynamics, aeroelasticity, and structures are coupled within a closed-loop optimization process. The procedure developed is applied to address two different problems. The first problem considers the optimization of a helicopter rotor blade and the second problem addresses the optimum design of a high-speed tilting proprotor. In the helicopter blade problem, the objective is to reduce the critical vibratory shear forces and moments at the blade root, without degrading rotor aerodynamic performance and aeroelastic stability. In the case of the high-speed proprotor, the goal is to maximize the propulsive efficiency in high-speed cruise without deteriorating the aeroelastic stability in cruise and the aerodynamic performance in hover. The problems studied involve multiple design objectives; therefore, the optimization problems are formulated using multiobjective design procedures. A comprehensive helicopter analysis code is used for the rotary wing aerodynamic, dynamic and aeroelastic stability analyses and an algorithm developed specifically for these purposes is used for the structural analysis. A nonlinear programming technique coupled with an approximate analysis procedure is used to perform the optimization. The optimum blade designs obtained in each case are compared to corresponding reference designs.

  10. Angle detector

    NASA Technical Reports Server (NTRS)

    Parra, G. T. (Inventor)

    1978-01-01

    An angle detector for determining a transducer's angular disposition to a capacitive pickup element is described. The transducer comprises a pendulum mounted inductive element moving past the capacitive pickup element. The capacitive pickup element divides the inductive element into two parts L sub 1 and L sub 2 which form the arms of one side of an a-c bridge. Two networks R sub 1 and R sub 2 having a plurality of binary weighted resistors and an equal number of digitally controlled switches for removing resistors from the networks form the arms of the other side of the a-c bridge. A binary counter, controlled by a phase detector, balances the bridge by adjusting the resistance of R sub 1 and R sub 2. The binary output of the counter is representative of the angle.

  11. An Explicit One-Dimensional Time-Dependent Tilting Cloud Model.

    NASA Astrophysics Data System (ADS)

    Chen, Shu-Hua; Sun, Wen-Yih

    2004-12-01

    An explicit one-dimensional time-dependent tilting cloud model has been developed for use in cumulus parameterizations. The tilting axis is not necessarily orthogonal to the (r, θ) plane, making the horizontal axisymmetric assumption more reasonable. This explicit time-dependent tilting model (ETTM) consists of an updraft and a downdraft, which are governed by the same dynamic and thermodynamic equations. The updraft is initiated by a moist thermal bubble, while the downdraft is consequently induced by evaporative cooling and the drag force of precipitation separating from the tilting updraft instead of being arbitrarily initialized.The updraft is capable of reproducing the major features of a deep cloud such as overshooting cooling above the cloud top, evaporative cooling near the surface, and drying in the lower atmosphere at dissipating stages. The entrainment detrainment rate in this model is well defined, and its time variation is quite significant. Moreover, the vertical profile of the air inside the updraft does not follow the moist adiabat after deep convection. For the downdraft, the total precipitation and mass flux at low levels contributed from the downdraft cannot be neglected in this case study. In addition, the downdraft can bring dry air from middle levels to lower levels.Three sensitivity tests—the environmental sounding, the tilting angle, and the radius of the updraft downdraft— have also been conducted. The cooling warming of a downdraft near the surface is sensitive to the environmental sounding, consistent with results from Srivastava. The cloud life span, maximum vertical velocity, precipitation amount, and vertical mass flux are strongly influenced by the tilting angle and the radius of the cloud.The results from the ETTM simulation are quite reasonable and promising. However, some deficiencies of this model still exist, and more research will be conducted to improve its performance. The final goal is to implement this 1D model in a

  12. Reply to "Comment on 'Origin of tilted-phase generation in systems of ellipsoidal molecules with dipolar interactions' "

    NASA Astrophysics Data System (ADS)

    Bose, Tushar Kanti; Saha, Jayashree

    2014-04-01

    In a recent article [T. K. Bose and J. Saha, Phys. Rev. E 86, 050701 (2012), 10.1103/PhysRevE.86.050701], we have presented the results of a Monte Carlo simulation study of the systems of dipolar Gay-Berne ellipsoids where two terminal antiparallel dipoles are placed symmetrically on the long axis of each ellipsoid, and the results revealed the combined contribution of dipolar separation and transverse orientations in controlling the tilt angle in the tilted hexatic smectic phase. The tilt angle changed from zero to a significant value, in the case of transverse dipoles, with a change in the dipolar separation. In the related comment, Madhusudana [preceding Comment, Phys. Rev. E 89, 046501 (2014), 10.1103/PhysRevE.89.046501] has claimed that the physical origin of the molecular tilt in the significantly tilted phases found in the simulations is similar to that proposed by McMillan [Phys. Rev. A 8, 1921 (1973), 10.1103/PhysRevA.8.1921]. Here, we explain that the claim is not correct and make it clear that the two compared pictures are quite different. In the preceding Comment, Madhusudana has also suggested an alternative explanation for tilt generation in the simulations by criticizing the original one proposed by us. We argue here in support of the original explanation and clarify that his explanation does not follow the simulation results.

  13. Reply to "Comment on 'Origin of tilted-phase generation in systems of ellipsoidal molecules with dipolar interactions' ".

    PubMed

    Bose, Tushar Kanti; Saha, Jayashree

    2014-04-01

    In a recent article [T. K. Bose and J. Saha, Phys. Rev. E 86, 050701 (2012)], we have presented the results of a Monte Carlo simulation study of the systems of dipolar Gay-Berne ellipsoids where two terminal antiparallel dipoles are placed symmetrically on the long axis of each ellipsoid, and the results revealed the combined contribution of dipolar separation and transverse orientations in controlling the tilt angle in the tilted hexatic smectic phase. The tilt angle changed from zero to a significant value, in the case of transverse dipoles, with a change in the dipolar separation. In the related comment, Madhusudana [preceding Comment, Phys. Rev. E 89, 046501 (2014)] has claimed that the physical origin of the molecular tilt in the significantly tilted phases found in the simulations is similar to that proposed by McMillan [Phys. Rev. A 8, 1921 (1973)]. Here, we explain that the claim is not correct and make it clear that the two compared pictures are quite different. In the preceding Comment, Madhusudana has also suggested an alternative explanation for tilt generation in the simulations by criticizing the original one proposed by us. We argue here in support of the original explanation and clarify that his explanation does not follow the simulation results. PMID:24827369

  14. Eye Orientation During Static Tilts and Its Relationship to Spontaneous Head Pitch in the Laboratory Mouse

    PubMed Central

    Oommen, Brian S.; Stahl, John S.

    2008-01-01

    Both eye position and head orientation are influenced by the macular (otolith) organs, via the tilt maculo-ocular reflex (tiltMOR) and the vestibulo-collic reflexes, respectively. The mechanisms that control head position also influence the rest position of the eye, because head orientation influences eye position through the tiltMOR. Despite the increasing popularity of mice for studies of vestibular and ocular motor functions, relatively little is known in this species about tiltMOR, spontaneous orientation of the head, and their interrelationship. We used 2D video oculography to determine in C57BL/6 mice the absolute horizontal and vertical positions of the eyes over body orientations spanning 360° about the pitch and roll axes. We also determined head pitch during ambulation in the same animals. Eye elevation varied approximately sinusoidally as functions of pitch or roll angle. Over the central ±30° of pitch, sensitivity and gain in the light were 31.7°/g and 0.53, respectively. The corresponding values for roll were 31.5°/g and 0.52. Absolute positions adopted in light and darkness differed only slightly. During ambulation, mice carried the lambda-bregma plane at a downward pitch of 29°, corresponding to a horizontal eye position of 64° and a vertical eye position of 22°. The vertical position is near the center of the range of eye movements produced by the pitch tiltMOR. The results indicate the tiltMOR is robust in this species, and favor standardizing pitch orientation across laboratories. The robust tiltMOR also has significant methodological implications for the practice of pupil-tracking video oculography in this species. PMID:18178173

  15. Hybrid monitor for both beam position and tilt of pulsed high-current beams

    SciTech Connect

    Pang, J. He, X.; Ma, C.; Zhao, L.; Li, Q.; Dai, Z.

    2014-09-15

    A Hybrid beam monitor, integrated with both azimuthal and axial B-dot probes, was designed for simultaneous measurement of both beam position and beam angle for pulsed high-current beams at the same location in beam pipe. The output signals of axial B-dot probes were found to be mixed with signals caused by transverse position deviation. In order to eliminate the unwanted signals, an elimination method was developed and its feasibility tested on a 50-Ω coaxial line test stand. By this method, a waveform, shape-like to that of input current and proportional to the tilt angle, was simulated and processed by following integration step to achieve the tilt angle. The tests showed that the measurement error of displacement and tilt angle less than 0.3 mm and 1.5 mrad, respectively. The latter error could be reduced with improved probes by reducing the inductance of the axial B-dot probe, but the improvement reached a limit due to some unknown systemic mechanism.

  16. The optimum hypersonic wind tunnel

    NASA Technical Reports Server (NTRS)

    Trimmer, L. L.; Cary, A., Jr.; Voisinet, R. L. P.

    1986-01-01

    The capabilities of existing hypersonic wind tunnels in the U.S. are assessed to form a basis for recommendations for a new, costly facility which would provide data for modeling the hypervelocity aerodynamics envisioned for the new generation of aerospace vehicles now undergoing early studies. Attention is given to the regimes, both entry and aerodynamic, which the new vehicles will encounter, and the shortcomings of data generated for the Orbiter before flight are discussed. The features of foreign-gas, impulse, aeroballistic range, arc-heated and combustion-heated facilities are examined, noting that in any hypersonic wind tunnel the flow must be preheated to prevent liquefaction upon expansion in the test channel. The limitations of the existing facilities and the identification of the regimes which must be studied lead to a description of the characteristics of an optimum hypersonic wind tunnel, including the operations and productivity, the instrumentation, the nozzle design and the flow quality. Three different design approaches are described, each costing at least $100 million to achieve workability.

  17. NICMOS Optimum Coronagraphic Focus Determinaton

    NASA Astrophysics Data System (ADS)

    Schneider, Glenn

    1997-07-01

    This test will ascertain the optimum position of the PAM for maximizing the local contrast ratios in coronagraphic images. Because of the forward motion of the NICMOS optical bench and dewar, the nominal operational position for the PAM is set {for each camera} to achieve diffraction limited focus at the image plane formed at the detector. As a result of the forward motion of the camera 2 detector, hard images are no longer formed coincidentally at the field divider mirror surface {where the coronagraphic hole is located} and at the detector. This will lead to an increase in the diffracted energy in the wings of a PSF from a target placed inside of the coronagraphic hole as the image plane will fall behind the surface of the FDA mirror. The contrast in a coronagraphic image might be enhanced by placing the focus to form an image at either image planes {FDA or detector} or at a place in-between. This is highly dependent on scattering and must be ascertained by direct measurement.

  18. Human Ocular Counter-Rolling and Roll Tilt Perception during Off-Vertical Axis Rotation after Spaceflight

    NASA Technical Reports Server (NTRS)

    Clement, Gilles; Denise, Pierre; Reschke, Millard; Wood, Scott J.

    2007-01-01

    Ocular counter-rolling (OCR) induced by whole body tilt in roll has been explored after spaceflight as an indicator of the adaptation of the otolith function to microgravity. It has been claimed that the overall pattern of OCR responses during static body tilt after spaceflight is indicative of a decreased role of the otolith function, but the results of these studies have not been consistent, mostly due to large variations in the OCR within and across individuals. By contrast with static head tilt, off-vertical axis rotation (OVAR) presents the advantage of generating a sinusoidal modulation of OCR, allowing averaged measurements over several cycles, thus improving measurement accuracy. Accordingly, OCR and the sense of roll tilt were evaluated in seven astronauts before and after spaceflight during OVAR at 45 /s in darkness at two angles of tilt (10 and 20 ). There was no significant difference in OCR during OVAR immediately after landing compared to preflight. However, the amplitude of the perceived roll tilt during OVAR was significantly larger immediately postflight, and then returned to control values in the following days. Since the OCR response is predominantly attributed to the shearing force exerted on the utricular macula, the absence of change in OCR postflight suggests that the peripheral otolith organs function normally after short-term spaceflight. However, the increased sense of roll tilt indicates an adaptation in the central processing of gravitational input, presumably related to a re-weigthing of the internal representation of gravitational vertical as a result of adaptation to microgravity.

  19. Optimum form of posterior chamber intraocular lenses to minimize aberrational astigmatism.

    PubMed

    Takei, K; Hommura, S; Okajima, H

    1995-01-01

    To optically determine the optimum form for a posterior chamber intraocular lens (PC IOL), we calculated the aberrational astigmatism induced by tilt and decentration of the PCIOL using an exact raytracing. First, the position and the radii of curvatures of the IOL were determined to make an emmetropic eye model using a paraxial raytracing. Next, the chief rays originating from the fovea centralis were traced backward through the tilted and/or decentrated PC IOL, the center of the pupil and the cornea, using trigonometric raytracing. Finally, the maximum and minimum aberrational astigmatism were calculated based on the Coddington's Equations for the sagittal and the tangential foci of the ray. All the refractive parameters in Gullstrand's No. 1 schematic eye were adopted. The effect of varying anterior corneal asphericity on the results was also examined. Four forms of polymethylmethacrylate PC IOLs (refractive index: 1.491) were analyzed; a plano-convex IOL with the curved surface facing the cornea, and three bi-convex forms with the ratio of anterior-to-posterior radii of curvatures of 1:4, 1:2 and 1:1, respectively. The 1:4 bi-convex form showed the lowest values for the maximum aberrational astigmatism calculated at every combination of tilt and decentration except 0 degrees tilt and/or 0 mm decentration. The aberrational astigmatism with the 1:4 bi-convex form of PC IOL did not exceed 1.0 D at the maximum tilt and decentration. The variation of anterior corneal asphericity did not influence the results. We conclude that the 1:4 bi-convex form of PC IOL minimizes the postoperative astigmatism induced by tilt and/or decentration of the lens. PMID:8926647

  20. The Transmembrane Helix Tilt May Be Determined by the Balance between Precession Entropy and Lipid Perturbation

    PubMed Central

    2012-01-01

    Hydrophobic helical peptides interact with lipid bilayers in various modes, determined by the match between the length of the helix’s hydrophobic core and the thickness of the hydrocarbon region of the bilayer. For example, long helices may tilt with respect to the membrane normal to bury their hydrophobic cores in the membrane, and the lipid bilayer may stretch to match the helix length. Recent molecular dynamics simulations and potential of mean force calculations have shown that some TM helices whose lengths are equal to, or even shorter than, the bilayer thickness may also tilt. The tilt is driven by a gain in the helix precession entropy, which compensates for the free energy penalty resulting from membrane deformation. Using this free energy balance, we derived theoretically an equation of state, describing the dependence of the tilt on the helix length and membrane thickness. To this end, we conducted coarse-grained Monte Carlo simulations of the interaction of helices of various lengths with lipid bilayers of various thicknesses, reproducing and expanding the previous molecular dynamics simulations. Insight from the simulations facilitated the derivation of the theoretical model. The tilt angles calculated using the theoretical model agree well with our simulations and with previous calculations and measurements. PMID:24932138

  1. Influence of Pelvic Tilt on Polyethylene Wear after Total Hip Arthroplasty

    PubMed Central

    Tezuka, Taro; Inaba, Yutaka; Kobayashi, Naomi; Ike, Hiroyuki; Kubota, So; Kawamura, Masaki; Saito, Tomoyuki

    2015-01-01

    We aimed to evaluate the effects of pelvic tilt on polyethylene wear after total hip arthroplasty (THA). A total of 105 joints treated with primary THA were included; conventional polyethylene (CPE) liners were used in 43 hips and highly cross-linked polyethylene (HXLPE) liners were used in the remaining 62 hips. The pelvis was tilted 6° posteriorly in the standing position as compared to the supine position, which resulted in significant increases of 1.7° and 2.8° in cup inclination in the CPE and HXLPE groups, respectively. Moreover, the change in pelvic tilt resulted in significant increases of 3.6° and 4.9° in cup anteversion in the CPE and HXLPE groups, respectively. For the CPE group, multiple regression analysis showed a significant association between the angle of pelvic tilt (PTA) and cup inclination and the polyethylene wear ratio. The adjusted R2 of the regression model was larger for measures obtained in the standing position as compared to the supine position. For the HXLPE group, there was no significant relationship between radiographic parameters and polyethylene wear. Close observation of polyethylene wear is recommended for patients with severe posterior pelvic tilt who have undergone THA with conventional polyethylene. PMID:26258136

  2. Smectic-C tilt under shear in smectic-A elastomers.

    PubMed

    Stenull, Olaf; Lubensky, T C; Adams, J M; Warner, Mark

    2008-08-01

    Stenull and Lubensky [Phys. Rev. E 76, 011706 (2007)] have argued that shear strain and tilt of the director relative to the layer normal are coupled in smectic elastomers and that the imposition of one necessarily leads to the development of the other. This means, in particular, that a smectic-A elastomer subjected to a simple shear will develop smectic-C-like tilt of the director. Recently, Kramer and Finkelmann [e-print arXiv:0708.2024; Phys. Rev. E 78, 021704 (2008)], performed shear experiments on smectic-A elastomers using two different shear geometries. One of the experiments, which implements simple shear, produces clear evidence for the development of smectic-C-like tilt. Here, we generalize a model for smectic elastomers introduced by Adams and Warner [Phys. Rev. E 71, 021708 (2005)] and use it to study the magnitude of SmC-like tilt under shear for the two geometries investigated by Kramer and Finkelmann. Using reasonable estimates of model parameters, we estimate the tilt angle for both geometries, and we compare our estimates to the experimental results. The other shear geometry is problematic since it introduces additional in-plane compressions in a sheetlike sample, thus inducing instabilities that we discuss. PMID:18850850

  3. [Motor adaptation in the Bielschowsky head-tilt test in cases of superior oblique palsy].

    PubMed

    Ohtsuki, H; Kishimoto, F; Kobashi, R; Watanabe, S; Okano, M; Furuse, H

    1992-08-01

    To elucidate a motor adaptation phenomenon in the Bielschowsky head-tilt test in cases of superior oblique palsy, a gain of the otolith-ocular reflex was studied. The amplitude of ocular counter-rolling (OCR) of the non-paretic eye was measured with a photographic method, using limbal conjunctival marks as landmarks which were marked with indigo carmine. The average preoperative OCR of the non-paretic eye was 10.49 degrees at 30 degrees of head tilt to both sides, but after corrective surgery in the paretic eye the OCR of the non-paretic eye decreased to 8.43 degrees. To clarify the relation between OCR, duration of palsy and vertical deviation of the Bielschowsky head-tilt test (BHP), which was the difference of vertical deviation measured with the head tilted to the left and right shoulders at an angle of 30 degrees, the BHP/OCR ratio was calculated. We found no relation between BHP and OCR, but the BHP/OCR ratio increased proportionally in cases of long-standing palsy, From these results an increased BHP/OCR ratio could be an adaptive phenomenon caused by secondary innervational changes or muscle contracture to minimizing the contralateral head tilt to maintain binocular single vision. PMID:1519508

  4. Improved tilt-depth method for fast estimation of top and bottom depths of magnetic bodies

    NASA Astrophysics Data System (ADS)

    Wang, Yan-Guo; Zhang, Jin; Ge, Kun-Peng; Chen, Xiao; Nie, Feng-Jun

    2016-06-01

    The tilt-depth method can be used to make fast estimation of the top depth of magnetic bodies. However, it is unable to estimate bottom depths and its every inversion point only has a single solution. In order to resolve such weaknesses, this paper presents an improved tilt-depth method based on the magnetic anomaly expression of vertical contact with a finite depth extent, which can simultaneously estimate top and bottom depths of magnetic bodies. In addition, multiple characteristic points are selected on the tilt angle map for joint computation to improve reliability of inversion solutions. Two- and threedimensional model tests show that this improved tilt-depth method is effective in inverting buried depths of top and bottom bodies, and has a higher inversion precision for top depths than the conventional method. The improved method is then used to process aeromagnetic data over the Changling Fault Depression in the Songliao Basin, and inversion results of top depths are found to be more accurate for actual top depths of volcanic rocks in two nearby drilled wells than those using the conventional tilt-depth method.

  5. HRM investigation of the structure of the sigma 5(310)/zone axes (001) symmetric tilt grain boundary in Nb

    NASA Astrophysics Data System (ADS)

    King, W. E.; Coombs, A.; Campbell, G. H.; Mills, M. J.

    1990-11-01

    Recent atomistic simulations using interatomic potentials for Nb developed employing the embedded atom method (EAM) and the model generalized pseudopotential theory (MGPT) have indicated a possible cusp at the Sigma 5(310) orientation in the energy vs. tilt angle curves for zone axes group 001 symmetric tilt grain boundaries. In addition, the most stable structure predicted using EAM exhibits shifts of one crystal relative to the other along the tilt axis and along the direction perpendicular to the tilt axis lying in the boundary plane. The structure predicted using the MGPT was mirror symmetric across the plane of the grain boundary. This boundary was n prepared for experimental study using the ultra high vacuum diffusion bonding methods. A segment of this boundary was studied using high resolution electron microscopy.

  6. Measurement of Transcranial Distance During Head-Down Tilt Using Ultrasound

    NASA Technical Reports Server (NTRS)

    Torikoshi, Shigeyo; Ballard, R. E.; Watenpaugh, D. E.; Murthy, G.; Bowley, S.; Yost, W. T.; Hargens, Alan R.

    1995-01-01

    Exposure to microgravity probably elevates blood pressure and flow in the head which may increase intracranial volume (ICV) and pressure (ICP). Due to the slightly compliant nature of the cranium, any increase of ICP will increase ICV and transcranial distance. We used a noninvasive ultrasound technique to measure transcranial distance (frontal to occipital) during head-down tilt. Seven subjects (ages 26-53) underwent the following tilt angles: 90 deg. upright, 30 deg., 0 deg., -6 deg., -10 deg., -6 deg., 0 deg., 30 deg., and 90 deg. Each angle was maintained for 1 min. Ultrasound wave frequency was collected continuously and transcranial distance was calculated (Delta(x) = x(Delta)f/f, where x is path length and f is frequency of the wave) for each tilt angle. Frequency decreased from 503.687 kHz (90 deg. upright) to 502.619 kHz (-10 deg.). These frequencies translated to an increased transcranial distance of 0.403 mm. Although our data suggest a significant increase in transcranial distance during head-down tilt, this apparent increase may result, in part, from head-down tilt-induced subcutaneous edema or cutaneous blood volume elevation. In three subjects, when the above protocol was repeated with an ace bandage wrapped around the head to minimize such edema, the increased transcranial distance from 90 deg. to -10 deg. was reduced by 0.174 mm. Further development of the technique to quantify bone-to-bone expansion unconfounded by cutaneous fluid is necessary. Therefore, this ultrasound technique may provide measurements of changes in cranial dimensions during microgravity.

  7. Tilt assembly for tracking solar collector assembly

    DOEpatents

    Almy, Charles; Peurach, John; Sandler, Reuben

    2012-01-24

    A tilt assembly is used with a solar collector assembly of the type comprising a frame, supporting a solar collector, for movement about a tilt axis by pivoting a drive element between first and second orientations. The tilt assembly comprises a drive element coupler connected to the drive element and a driver, the driver comprising a drive frame, a drive arm and a drive arm driver. The drive arm is mounted to the drive frame for pivotal movement about a drive arm axis. Movement on the drive arm mimics movement of the drive element. Drive element couplers can extend in opposite directions from the outer portion of the drive arm, whereby the assembly can be used between adjacent solar collector assemblies in a row of solar collector assemblies.

  8. Tilted Gaussian beam propagation in inhomogeneous media.

    PubMed

    Hadad, Yakir; Melamed, Timor

    2010-08-01

    The present work is concerned with applying a ray-centered non-orthogonal coordinate system which is a priori matched to linearly-phased localized aperture field distributions. The resulting beam-waveobjects serve as the building blocks for beam-type spectral expansions of aperture fields in 2D inhomogeneous media that are characterized by a generic wave-velocity profile. By applying a rigorous paraxial-asymptotic analysis, a novel parabolic wave equation is obtained and termed "Non-orthogonal domain parabolic equation"--NoDope. Tilted Gaussian beams, which are exact solutions to this equation, match Gaussian aperture distributions over a plane that is tilted with respect to the beam-axes initial directions. A numerical example, which demonstrates the enhanced accuracy of the tilted Gaussian beams over the conventional ones, is presented as well. PMID:20686589

  9. Optimum Structure of Whipple Shield against Hypervelocity Impact

    NASA Astrophysics Data System (ADS)

    Lee, Minhyung

    2013-06-01

    It has been known that the spacecraft protection issues against space debris or meteoroid impact damage are of great importance. Whipple shield structures (double spaced plates) have been investigated and empirical ballistic limit curve (BLCs) are developed. In this paper, we like to investigate an optimum Whipple Shield structure of fixed areal density and space. To do this, a new in-house SPH code has been used. Last 20 years SPH (Smoothed Particle Hydrodynamics) numerical scheme has been widely applied to the hypervelocity impact problems because of the limited velocity range and cost of test. We first examined the extent of debris spreading which seems to be a key factor to the back plate impact. The debris cloud expansion angle shows a maximum value. Then, a series of hypervelocity impact simulations were conducted to predict the critical impacting sphere diameter. It has been found that there is an optimum thickness ratio of front bumper to real wall.

  10. Microelectromechanical apparatus for elevating and tilting a platform

    SciTech Connect

    Miller, Samuel Lee; McWhorter, Paul Jackson; Rodgers, Murray Steven; Sniegowski, Jeffry J.; Barnes, Stephen M.

    2004-07-06

    A microelectromechanical (MEM) apparatus is disclosed which has a platform that can be elevated above a substrate and tilted at an arbitrary angle using a plurality of flexible members which support the platform and control its movement. Each flexible member is further controlled by one or more MEM actuators which act to bend the flexible member. The MEM actuators can be electrostatic comb actuators or vertical zip actuators, or a combination thereof. The MEM apparatus can include a mirror coating to form a programmable mirror for redirecting or switching one or more light beams for use in a projection display. The MEM apparatus with-the mirror coating also has applications for switching light beams between optical fibers for use in a local area fiber optic network, or for use in fiber optic telecommunications or data communications systems.

  11. Microelectromechanical apparatus for elevating and tilting a platform

    SciTech Connect

    Miller, Samuel Lee; McWhorter, Paul Jackson; Rodgers, Murray Steven; Sniegowski, Jeffry J.; Barnes, Stephen M.

    2003-04-08

    A microelectromechanical (MEM) apparatus is disclosed which has a platform that can be elevated above a substrate and tilted at an arbitrary angle using a plurality of flexible members which support the platform and control its movement. Each flexible member is further controlled by one or more MEM actuators which act to bend the flexible member. The MEM actuators can be electrostatic comb actuators or vertical zip actuators, or a combination thereof. The MEM apparatus can include a mirror coating to form a programmable mirror for redirecting or switching one or more light beams for use in a projection display. The MEM apparatus with the mirror coating also has applications for switching light beams between optical fibers for use in a local area fiber optic network, or for use in fiber optic telecommunications or data communications systems.

  12. Apparatus for raising or tilting a micromechanical structure

    DOEpatents

    Allen, James J.

    2008-09-09

    An active hinge apparatus is disclosed which can be used to raise a micromechanical structure (e.g. a plate or micromirror) on a substrate. The active hinge apparatus utilizes one or more of teeth protruding outward from an axle which also supports the micromechanical structure on one end thereof. A rack is used to engage the teeth and rotate the axle to raise the micromechanical structure and tilt the structure at an angle to the substrate. Motion of the rack is provided by an actuator which can be a mechanically-powered actuator, or alternately an electrostatic comb actuator or a thermal actuator. A latch can be optionally provided in the active hinge apparatus to lock the micromechanical structure in an "erected" position.

  13. Capillary rise in a tilted Taylor-Hauksbee cell

    NASA Astrophysics Data System (ADS)

    Medina, Abraham; Klapp, Jaime; Torres Victoria, Ayax Hernando; Peralta Lopez, Salomon; Jara Hernandez, Aydet

    2015-11-01

    The penetration of a wetting liquid in the narrow gap between two tilted plates making a small angle among them is analyzed in the framework of the lubrication approximation. At the beginning of the process, the liquid rises independently at different distances from the line of intersection of the plates. The maximum height of the liquid initially increases as a power law of time, where the exponent is dependent on the angle of inclination of the plates and is attained at a point that reaches the line of intersection only after a certain time. At later times, the motion of the liquid is confined to a thin layer around the line of intersection whose height increases again as a power law of time and the exponent of the power law is a function of the angle of inclination. The thickness of the film decreases as the inverse of the power law of time. The evolution of the liquid surface is computed numerically and compared with the results of simple experiments.

  14. Octahedral tilting in the tungsten bronzes.

    PubMed

    Whittle, Thomas A; Schmid, Siegbert; Howard, Christopher J

    2015-06-01

    Possibilities for 'simple' octahedral tilting in the hexagonal and tetragonal tungsten bronzes (HTB and TTB) have been examined, making use of group theory as implemented in the computer program ISOTROPY. For HTB, there is one obvious tilting pattern, leading to a structure in space group P6₃/mmc. This differs from the space group P6₃/mcm frequently quoted from X-ray studies – these studies have in effect detected only displacements of the W cations from the centres of the WO6 octahedra. The correct space group, taking account of both W ion displacement and the octahedral tilting, is P6₃22 – structures in this space group and matching this description have been reported. A second acceptable tilting pattern has been found, leading to a structure in P6/mmm but on a larger '2 × 2 × 2' unit cell – however, no observations of this structure have been reported. For TTB, a search at the special points of the Brillouin zones revealed only one comparable tilting pattern, in a structure with space-group symmetry I4/m on a '2(1/2) × 2(1/2) by 2' unit cell. Given several literature reports of larger unit cells for TTB, we conducted a limited search along the lines of symmetry and found structures with acceptable tilt patterns in Bbmm on a '2(1/2)2 × 2(1/2) × 2' unit cell. A non-centrosymmetric version has been reported in niobates, in Bbm2 on the same unit cell. PMID:26027010

  15. Design and Performance of the Keck Angle Tracker

    NASA Technical Reports Server (NTRS)

    Crawford, Samuel L.; Ragland, S.; Booth, A.; Colavita, M. M.; Hovland, E.

    2006-01-01

    The Keck Angle Tracker (KAT) is a key subsystem in the NASA-funded Keck Interferometer at the Keck Observatory on the summit of Mauna Kea in Hawaii. KAT, which has been in operation since the achievement of first fringes in March 2001, senses the tilt of the stellar wavefront for each of the beams from the interferometer telescopes and provides tilt error signals to fast tip/tilt mirrors for high-bandwidth, wavefront tilt correction. In addition, KAT passes low-bandwidth, desaturation offsets to the adaptive optics system of the Keck telescopes to correct for slow pointing drifts. We present an overview of the instrument design and recent performance of KAT in support of the V2 science and nulling observing modes of the Keck Interferometer.

  16. Optimum reentry trajectories of a lifting vehicle

    NASA Technical Reports Server (NTRS)

    Chern, J. S.; Vinh, N. X.

    1980-01-01

    Research results are presented of an investigation of the optimum maneuvers of advanced shuttle type spacecraft during reentry. The equations are formulated by means of modified Chapman variables resulting in a general set of equations for flight analysis which are exact for reentry and for flight in a vacuum. Four planar flight typical optimum manuevers are investigated. For three-dimensional flight the optimum trajectory for maximum cross range is discussed in detail. Techniques for calculating reentry footprints are presented.

  17. Tilt error in cryospheric surface radiation measurements at high latitudes: a model study

    NASA Astrophysics Data System (ADS)

    Bogren, W. S.; Burkhart, J. F.; Kylling, A.

    2015-08-01

    We have evaluated the magnitude and makeup of error in cryospheric radiation observations due to small sensor misalignment in in-situ measurements of solar irradiance. This error is examined through simulation of diffuse and direct irradiance arriving at a detector with a cosine-response foreoptic. Emphasis is placed on assessing total error over the solar shortwave spectrum from 250 to 4500 nm, as well as supporting investigation over other relevant shortwave spectral ranges. The total measurement error introduced by sensor tilt is dominated by the direct component. For a typical high latitude albedo measurement with a solar zenith angle of 60°, a sensor tilted by 1, 3, and 5° can respectively introduce up to 2.6, 7.7, and 12.8 % error into the measured irradiance and similar errors in the derived albedo. Depending on the daily range of solar azimuth and zenith angles, significant measurement error can persist also in integrated daily irradiance and albedo.

  18. Tilt and dislocations in epitaxial laterally overgrown GaAs layers

    NASA Astrophysics Data System (ADS)

    Zytkiewicz, Z. R.; Domagala, J. Z.; Dobosz, D.; Dobaczewski, L.; Rocher, A.; Clement, C.; Crestou, J.

    2007-01-01

    Transmission electron microscopy (TEM) and high-resolution x-ray diffraction were used to study the crystalline quality of GaAs layers grown by liquid phase epitaxial lateral overgrowth (ELO) on SiO2-masked (001) GaAs substrates. A low-angle grain boundary with a well-organized set of dislocations accommodating the misorientation of tilted ELO wings was found at the coalescence front of ELO layers. Similar behavior is often reported for GaN on sapphire ELO structures. Unlike the GaN case, however, no dislocations were found above edges of the mask, which is explained by the much smaller wing tilt angle in our case. The geometry of the dislocation network and analysis of thickness fringes on TEM images were used to measure misorientation of merging ELO wings. The values obtained are in good agreement with those determined by x-ray diffraction.

  19. Dipolar capillary interactions between tilted ellipsoidal particles adsorbed at fluid-fluid interfaces.

    PubMed

    Davies, Gary B; Botto, Lorenzo

    2015-10-28

    Capillary interactions have emerged as a tool for the directed assembly of particles adsorbed at fluid-fluid interfaces, and play a role in controlling the mechanical properties of emulsions and foams. In this paper, following Davies et al. [Adv. Mater., 2014, 26, 6715] investigation into the assembly of ellipsoidal particles at interfaces interacting via dipolar capillary interactions, we numerically investigate the interaction between tilted ellipsoidal particles adsorbed at a fluid-fluid interface as their aspect ratio, tilt angle, bond angle, and separation vary. High-resolution Surface Evolver simulations of ellipsoidal particle pairs in contact reveal an energy barrier between a metastable tip-tip configuration and a stable side-side configuration. The side-side configuration is the global energy minimum for all parameters we investigated. Lattice Boltzmann simulations of clusters of up to 12 ellipsoidal particles show novel highly symmetric flower-like and ring-like arrangements. PMID:26323324

  20. Flip-chip integration of tilted VCSELs onto a silicon photonic integrated circuit.

    PubMed

    Lu, Huihui; Lee, Jun Su; Zhao, Yan; Scarcella, Carmelo; Cardile, Paolo; Daly, Aidan; Ortsiefer, Markus; Carroll, Lee; O'Brien, Peter

    2016-07-25

    In this article we describe a cost-effective approach for hybrid laser integration, in which vertical cavity surface emitting lasers (VCSELs) are passively-aligned and flip-chip bonded to a Si photonic integrated circuit (PIC), with a tilt-angle optimized for optical-insertion into standard grating-couplers. A tilt-angle of 10° is achieved by controlling the reflow of the solder ball deposition used for the electrical-contacting and mechanical-bonding of the VCSEL to the PIC. After flip-chip integration, the VCSEL-to-PIC insertion loss is -11.8 dB, indicating an excess coupling penalty of -5.9 dB, compared to Fibre-to-PIC coupling. Finite difference time domain simulations indicate that the penalty arises from the relatively poor match between the VCSEL mode and the grating-coupler. PMID:27464079

  1. An integrated optimum design approach for high speed prop rotors

    NASA Technical Reports Server (NTRS)

    Chattopadhyay, Aditi; Mccarthy, Thomas R.

    1995-01-01

    The objective is to develop an optimization procedure for high-speed and civil tilt-rotors by coupling all of the necessary disciplines within a closed-loop optimization procedure. Both simplified and comprehensive analysis codes are used for the aerodynamic analyses. The structural properties are calculated using in-house developed algorithms for both isotropic and composite box beam sections. There are four major objectives of this study. (1) Aerodynamic optimization: The effects of blade aerodynamic characteristics on cruise and hover performance of prop-rotor aircraft are investigated using the classical blade element momentum approach with corrections for the high lift capability of rotors/propellers. (2) Coupled aerodynamic/structures optimization: A multilevel hybrid optimization technique is developed for the design of prop-rotor aircraft. The design problem is decomposed into a level for improved aerodynamics with continuous design variables and a level with discrete variables to investigate composite tailoring. The aerodynamic analysis is based on that developed in objective 1 and the structural analysis is performed using an in-house code which models a composite box beam. The results are compared to both a reference rotor and the optimum rotor found in the purely aerodynamic formulation. (3) Multipoint optimization: The multilevel optimization procedure of objective 2 is extended to a multipoint design problem. Hover, cruise, and take-off are the three flight conditions simultaneously maximized. (4) Coupled rotor/wing optimization: Using the comprehensive rotary wing code CAMRAD, an optimization procedure is developed for the coupled rotor/wing performance in high speed tilt-rotor aircraft. The developed procedure contains design variables which define the rotor and wing planforms.

  2. Aero-optimum hovering kinematics.

    PubMed

    Nabawy, Mostafa R A; Crowther, William J

    2015-08-01

    Hovering flight for flapping wing vehicles requires rapid and relatively complex reciprocating movement of a wing relative to a stationary surrounding fluid. This note develops a compact analytical aero-kinematic model that can be used for optimization of flapping wing kinematics against aerodynamic criteria of effectiveness (maximum lift) and efficiency (minimum power for a given amount of lift). It can also be used to make predictions of required flapping frequency for a given geometry and basic aerodynamic parameters. The kinematic treatment is based on a consolidation of an existing formulation that allows explicit derivation of flapping velocity for complex motions whereas the aerodynamic model is based on existing quasi-steady analysis. The combined aero-kinematic model provides novel explicit analytical expressions for both lift and power of a hovering wing in a compact form that enables exploration of a rich kinematic design space. Good agreement is found between model predictions of flapping frequency and observed results for a number of insects and optimal hovering kinematics identified using the model are consistent with results from studies using higher order computational models. For efficient flight, the flapping angle should vary using a triangular profile in time leading to a constant velocity flapping motion, whereas for maximum effectiveness the shape of variation should be sinusoidal. For both cases the wing pitching motion should be rectangular such that pitch change at stroke reversal is as rapid as possible. PMID:26248884

  3. Rotatable prism for pan and tilt

    NASA Technical Reports Server (NTRS)

    Ball, W. B.

    1980-01-01

    Compact, inexpensive, motor-driven prisms change field of view of TV camera. Camera and prism rotate about lens axis to produce pan effect. Rotating prism around axis parallel to lens produces tilt. Size of drive unit and required clearance are little more than size of camera.

  4. The XV-15 tilt rotor research aircraft

    NASA Technical Reports Server (NTRS)

    Dugan, D. C.; Erhart, R. G.; Schroers, L. G.

    1980-01-01

    The XV-15 tilt rotor has shown good handling qualities in all modes of flight; in the helicopter mode it allows precision hover and agility with low pilot workload. Vibration and noise levels are low; the conversion procedure is easy, with satisfactory acceleration or deceleration. The XV-15 handling demonstrated its potential for many civil and military applications.

  5. Tilt/Integral/Derivative Compensators For Controllers

    NASA Technical Reports Server (NTRS)

    Lurie, Boris J.

    1995-01-01

    Tilt/integral/derivative (TID) compensators for tunable feedback control systems offer advantages over proportional/integral/derivative compensators. Designed and adjusted more easily, and made to reject disturbances more strongly and less sensitive to variations in parameters of controlled system.

  6. "Happiness and Education": Tilting at Windmills?

    ERIC Educational Resources Information Center

    Verducci, Susan

    2013-01-01

    This essay explores the question: Is Nel Noddings a visionary who sees past the constraints of contemporary education or is she, like Don Quixote, madly tilting at windmills in her description and defense of happiness as an educational aim? Viewing the educational aim of happiness as an ideal raises substantial challenges for the practicality of…

  7. Ion Implantation Angle Variation to Device Performance and the Control in Production

    SciTech Connect

    Zhao, Z.Y.; Hendrix, D.; Wu, L.Y.; Cusson, B.K.

    2003-08-26

    As the device features get smaller and aspect ratios of photoresist openings get steeper, shadowing effect has more impact on the performance of devices. Many of the traditional 7 deg. tilt implants have progressed to 0 deg. implants. But shadowing may still occur if the tilt angle deviates from normal direction. Some implants, such as halo implants, demand even more stringent angle control to reduce device performance variation. The demand for implant angle control and monitoring thus becomes more obvious and important. However, statistical process control (SPC) cannot be done on shadowing effect without special test structures. Channeling, on the other hand, provides good sensitivity in regard to implant angle changes. It is the authors' intention to introduce channeling implant in different channels to monitor the implant angle variation. The incoming <100> silicon wafers have a cut-angle spec of +/- 1.0 deg. This poses a difficulty if one wants to control the implant angle's accuracy within +/- 0.5 deg. Other measures have to be taken to ensure the consistency of test wafers and to have prompt diagnosis feedback when needed. This paper will discuss the effect of implant tilt angle on device parameters and how to control the angle variation in production. Correlations of implant tilt angle variation to ThermaWave, sheet resistance (Rs), Secondary Ion Mass Spectrometry (SIMS) and device parameters will be covered with certain implant conditions.

  8. Ion Implantation Angle Variation to Device Performance and the Control in Production

    NASA Astrophysics Data System (ADS)

    Zhao, Z. Y.; Hendrix, D.; Wu, L. Y.; Cusson, B. K.

    2003-08-01

    As the device features get smaller and aspect ratios of photoresist openings get steeper, shadowing effect has more impact on the performance of devices. Many of the traditional 7° tilt implants have progressed to 0° implants. But shadowing may still occur if the tilt angle deviates from normal direction. Some implants, such as halo implants, demand even more stringent angle control to reduce device performance variation. The demand for implant angle control and monitoring thus becomes more obvious and important. However, statistical process control (SPC) cannot be done on shadowing effect without special test structures. Channeling, on the other hand, provides good sensitivity in regard to implant angle changes. It is the authors' intention to introduce channeling implant in different channels to monitor the implant angle variation. The incoming <100> silicon wafers have a cut-angle spec of +/- 1.0°. This poses a difficulty if one wants to control the implant angle's accuracy within +/- 0.5°. Other measures have to be taken to ensure the consistency of test wafers and to have prompt diagnosis feedback when needed. This paper will discuss the effect of implant tilt angle on device parameters and how to control the angle variation in production. Correlations of implant tilt angle variation to ThermaWave™, sheet resistance (Rs), Secondary Ion Mass Spectrometry (SIMS) and device parameters will be covered with certain implant conditions.

  9. Angle-dependent magnetotransport in GaAs/InAs core/shell nanowires

    NASA Astrophysics Data System (ADS)

    Haas, Fabian; Wenz, Tobias; Zellekens, Patrick; Demarina, Nataliya; Rieger, Torsten; Lepsa, Mihail; Grützmacher, Detlev; Lüth, Hans; Schäpers, Thomas

    2016-04-01

    We study the impact of the direction of magnetic flux on the electron motion in GaAs/InAs core/shell nanowires. At small tilt angles, when the magnetic field is aligned nearly parallel to the nanowire axis, we observe Aharonov–Bohm type h/e flux periodic magnetoconductance oscillations. These are attributed to transport via angular momentum states, formed by electron waves within the InAs shell. With increasing tilt of the nanowire in the magnetic field, the flux periodic magnetoconductance oscillations disappear. Universal conductance fluctuations are observed for all tilt angles, however with increasing amplitudes for large tilt angles. We record this evolution of the electron propagation from a circling motion around the core to a diffusive transport through scattering loops and give explanations for the observed different transport regimes separated by the magnetic field orientation.

  10. Angle-dependent magnetotransport in GaAs/InAs core/shell nanowires

    PubMed Central

    Haas, Fabian; Wenz, Tobias; Zellekens, Patrick; Demarina, Nataliya; Rieger, Torsten; Lepsa, Mihail; Grützmacher, Detlev; Lüth, Hans; Schäpers, Thomas

    2016-01-01

    We study the impact of the direction of magnetic flux on the electron motion in GaAs/InAs core/shell nanowires. At small tilt angles, when the magnetic field is aligned nearly parallel to the nanowire axis, we observe Aharonov–Bohm type h/e flux periodic magnetoconductance oscillations. These are attributed to transport via angular momentum states, formed by electron waves within the InAs shell. With increasing tilt of the nanowire in the magnetic field, the flux periodic magnetoconductance oscillations disappear. Universal conductance fluctuations are observed for all tilt angles, however with increasing amplitudes for large tilt angles. We record this evolution of the electron propagation from a circling motion around the core to a diffusive transport through scattering loops and give explanations for the observed different transport regimes separated by the magnetic field orientation. PMID:27091000

  11. Angle-dependent magnetotransport in GaAs/InAs core/shell nanowires.

    PubMed

    Haas, Fabian; Wenz, Tobias; Zellekens, Patrick; Demarina, Nataliya; Rieger, Torsten; Lepsa, Mihail; Grützmacher, Detlev; Lüth, Hans; Schäpers, Thomas

    2016-01-01

    We study the impact of the direction of magnetic flux on the electron motion in GaAs/InAs core/shell nanowires. At small tilt angles, when the magnetic field is aligned nearly parallel to the nanowire axis, we observe Aharonov-Bohm type h/e flux periodic magnetoconductance oscillations. These are attributed to transport via angular momentum states, formed by electron waves within the InAs shell. With increasing tilt of the nanowire in the magnetic field, the flux periodic magnetoconductance oscillations disappear. Universal conductance fluctuations are observed for all tilt angles, however with increasing amplitudes for large tilt angles. We record this evolution of the electron propagation from a circling motion around the core to a diffusive transport through scattering loops and give explanations for the observed different transport regimes separated by the magnetic field orientation. PMID:27091000

  12. Design of composite laminates for optimum frequency response

    NASA Astrophysics Data System (ADS)

    Kayikci, Rengin; Sonmez, Fazil O.

    2012-04-01

    In this study, natural frequency response of symmetrically laminated composite plates was optimized. An analytical model accounting for bending-twisting effects was used to determine the laminate natural frequency. Two different problems, fundamental frequency maximization and frequency separation maximization, were considered. Fiber orientation angles were chosen as design variables. Because of the existence of numerous local optimums, a global search algorithm, a variant of simulated annealing, was utilized to find the optimal designs. Results were obtained for different plate aspect ratios. Effects of the number of design variables and the range of values they may take on the optimal frequency were investigated. Problems in which fiber angles showed uncertainty were considered. Optimal frequency response of laminates subjected to static loads was also investigated.

  13. Tilt and Translation Motion Perception during Pitch Tilt with Visual Surround Translation

    NASA Technical Reports Server (NTRS)

    O'Sullivan, Brita M.; Harm, Deborah L.; Reschke, Millard F.; Wood, Scott J.

    2006-01-01

    The central nervous system must resolve the ambiguity of inertial motion sensory cues in order to derive an accurate representation of spatial orientation. Previous studies suggest that multisensory integration is critical for discriminating linear accelerations arising from tilt and translation head motion. Visual input is especially important at low frequencies where canal input is declining. The NASA Tilt Translation Device (TTD) was designed to recreate postflight orientation disturbances by exposing subjects to matching tilt self motion with conflicting visual surround translation. Previous studies have demonstrated that brief exposures to pitch tilt with foreaft visual surround translation produced changes in compensatory vertical eye movement responses, postural equilibrium, and motion sickness symptoms. Adaptation appeared greatest with visual scene motion leading (versus lagging) the tilt motion, and the adaptation time constant appeared to be approximately 30 min. The purpose of this study was to compare motion perception when the visual surround translation was inphase versus outofphase with pitch tilt. The inphase stimulus presented visual surround motion one would experience if the linear acceleration was due to foreaft self translation within a stationary surround, while the outofphase stimulus had the visual scene motion leading the tilt by 90 deg as previously used. The tilt stimuli in these conditions were asymmetrical, ranging from an upright orientation to 10 deg pitch back. Another objective of the study was to compare motion perception with the inphase stimulus when the tilts were asymmetrical relative to upright (0 to 10 deg back) versus symmetrical (10 deg forward to 10 deg back). Twelve subjects (6M, 6F, 22-55 yrs) were tested during 3 sessions separated by at least one week. During each of the three sessions (out-of-phase asymmetrical, in-phase asymmetrical, inphase symmetrical), subjects were exposed to visual surround translation

  14. Tilted bilayer membranes as simple transmission quarter-wave retardation plates.

    PubMed

    Azzam, R M; Mahmoud, F A

    2001-02-01

    A tilted bilayer membrane, which consists of two thin films of transparent optically isotropic materials of different refractive indices, can function as a transmission quarter-wave retarder (QWR) at a high angle of incidence. A specific design using a cryolite-Si membrane in the infrared is presented, and its tolerances to small shifts of wavelength, incidence angle, and film thickness errors are discussed. Some designs provide a dual QWR in transmission and reflection. Such devices provide simple linear-to-circular (and circular-to-linear) polarization transformers. Bilayer eighth-wave retarders without diattenuation are also introduced. PMID:11205989

  15. Internal tilting mode stability of non-sperical spheromak

    SciTech Connect

    Yamazaki, K.

    1980-06-01

    Fixed boundary tilting mode stability is analyzed for spheromak with arbitrarily shaped cross section. A prolate spheromak can be stabilized against tilting mode by adding a conducting shell of triangular or trapesoidal half-cross section.

  16. Investigation of Peak Pressure Index Parameters for People with Spinal Cord Injury Using Wheelchair Tilt-in-Space and Recline: Methodology and Preliminary Report

    PubMed Central

    Lung, Chi-Wen; Yang, Tim D.; Crane, Barbara A.; Elliott, Jeannette; Dicianno, Brad E.; Jan, Yih-Kuen

    2014-01-01

    The purpose of this study was to determine the effect of the sensel window's location and size when calculating the peak pressure index (PPI) of pressure mapping with varying degrees of wheelchair tilt-in-space (tilt) and recline in people with spinal cord injury (SCI). Thirteen power wheelchair users were recruited into this study. Six combinations of wheelchair tilt (15°, 25°, and 35°) and recline (10° and 30°) were used by the participants in random order. Displacements of peak pressure and center of pressure were extracted from the left side of the mapping system. Normalized PPI was computed for three sensel window dimensions (3 sensels × 3 sensels, 5 × 5, and 7 × 7). At least 3.33 cm of Euclidean displacement of peak pressures was observed in the tilt and recline. For every tilt angle, peak pressure displacement was not significantly different between 10° and 30° recline, while center of pressure displacement was significantly different (P < .05). For each recline angle, peak pressure displacement was not significantly different between pairs of 15°, 25°, and 35° tilt, while center of pressure displacement was significantly different between 15° versus 35° and 25° versus 35°. Our study showed that peak pressure displacement occurs in response to wheelchair tilt and recline, suggesting that the selected sensel window locations used to calculate PPI should be adjusted during changes in wheelchair configuration. PMID:25057491

  17. Argon-Assisted Glancing Angle Deposition

    NASA Astrophysics Data System (ADS)

    Sorge, Jason Brian

    Glancing angle deposition (GLAD) is a physical vapour deposition (PVD) technique capable of fabricating highly porous thin films with controllable film morphology on the 10 nm length scale. The GLAD process is flexible and may be used on virtually any PVD-compatible material. This makes GLAD a useful technique in many applications including photovoltaics, humidity sensing, and photonic devices. Conventional, dense films grown at normal incidence concurrent with ion or energetic neutral bombardment have been reported to have higher film density than unbombarded films. In a similar sense, highly porous GLAD films grown with concurrent bombardment should generate films with new interesting properties and extend the versatility of the GLAD process. The research presented in this thesis investigates the use of energetic neutral bombardment during GLAD film growth to produce new film morphologies. Here, with increasing bombardment, the column tilt increases, film density increases, and specific surface area decreases. A film simultaneously exhibiting high column tilt angle and film density is enabled by incorporating bombardment concurrent with GLAD film growth. This in turn results in films with larger principal refractive indices, but a smaller normalized in plane birefringence. Bombarded films were also found to be compatible with the phisweep process which helps decouple the column tilt angle from film density. Characterization of the bombardment-assisted growth process indicates that both sputtering and bombardment-induced diffusion play a role in the modification of film morphology. The film property modifications which arise as a result of bombardment-assisted growth lead to device improvements in a number of applications. Bombardment was used to fabricate square spiral photonic crystal structures with increased column tilt which bear a closer resemblance to optimized simulated structures than conventionally-grown GLAD films. The increase in column tilt angle and

  18. Origin of the c-Axis Tilt Occurring During the Lateral Epitaxial Overgrowth of GaN

    NASA Astrophysics Data System (ADS)

    Kuan, T. S.; Inoki, C. K.; Zhang, R.; Gu, S.; Kuech, T. F.

    2001-03-01

    A large angle c-axis tilt has often been observed in GaN layers grown by lateral epitaxial overgrowth (LEO) through narrow windows defined on a seed layer. The c-axis tilt generates vertical tilt boundaries at the coalescence of growth facets. To investigate the defect mechanisms responsible for the onset of c-axis tilt, a series of GaN LEO samples was grown using the hydride vapor phase epitaxy (HVPE) technique and examined by transmission electron microscopy (TEM). Cross sectional TEM images indicate that as LEO proceeds from triangular-shaped ridges originally grown over the windows, all edge-type threading dislocations propagated from the seed layer bend into screw type and glide on the c plane. Plan-view TEM observations reveal further that to relax the twist/shear strain in the LEO regions, these screw dislocations collectively make another 90^o bend again, forming arrays of edge dislocations parallel to the mask edge. The number of dislocations in the arrays can account for the amount of crystal tilt observed. The c-axis tilt is thus a stress-driven phenomenon dictated by the growth window geometry, and is much less influenced by the growth parameters.

  19. Automated optimum design of wing structures. Deterministic and probabilistic approaches

    NASA Technical Reports Server (NTRS)

    Rao, S. S.

    1982-01-01

    The automated optimum design of airplane wing structures subjected to multiple behavior constraints is described. The structural mass of the wing is considered the objective function. The maximum stress, wing tip deflection, root angle of attack, and flutter velocity during the pull up maneuver (static load), the natural frequencies of the wing structure, and the stresses induced in the wing structure due to landing and gust loads are suitably constrained. Both deterministic and probabilistic approaches are used for finding the stresses induced in the airplane wing structure due to landing and gust loads. A wing design is represented by a uniform beam with a cross section in the form of a hollow symmetric double wedge. The airfoil thickness and chord length are the design variables, and a graphical procedure is used to find the optimum solutions. A supersonic wing design is represented by finite elements. The thicknesses of the skin and the web and the cross sectional areas of the flanges are the design variables, and nonlinear programming techniques are used to find the optimum solution.

  20. Optimum structure of Whipple shield against hypervelocity impact

    NASA Astrophysics Data System (ADS)

    Lee, M.

    2014-05-01

    Hypervelocity impact of a spherical aluminum projectile onto two spaced aluminum plates (Whipple shield) was simulated to estimate an optimum structure. The Smooth Particle Hydrodynamics (SPH) code which has a unique migration scheme from a rectangular coordinate to an axisymmetic coordinate was used. The ratio of the front plate thickness to sphere diameter varied from 0.06 to 0.48. The impact velocities considered here were 6.7 km/s. This is the procedure we explored. To guarantee the early stage simulation, the shapes of debris clouds were first compared with the previous experimental pictures, indicating a good agreement. Next, the debris cloud expansion angle was predicted and it shows a maximum value of 23 degree for thickness ratio of front bumper to sphere diameter of 0.23. A critical sphere diameter causing failure of rear wall was also examined while keeping the total thickness of two plates constant. There exists an optimum thickness ratio of front bumper to rear wall, which is identified as a function of the size combination of the impacting body, front and rear plates. The debris cloud expansion-correlated-optimum thickness ratio study provides a good insight on the hypervelocity impact onto spaced target system.

  1. Design rules for a compact and low-cost optical position sensing of MOEMS tilt mirrors based on a Gaussian-shaped light source

    NASA Astrophysics Data System (ADS)

    Baumgart, Marcus; Tortschanoff, Andreas

    2013-05-01

    A tilt mirror's deflection angle tracking setup is examined from a theoretical point of view. The proposed setup is based on a simple optical approach and easily scalable. Thus, the principle is especially of interest for small and fast oscillating MEMS/MOEMS based tilt mirrors. An experimentally established optical scheme is used as a starting point for accurate and fast mirror angle-position detection. This approach uses an additional layer, positioned under the MOEMS mirror's backside, consisting of a light source in the center and two photodetectors positioned symmetrical around the center. The mirror's back surface is illuminated by the light source and the intensity change due to mirror tilting is tracked via the photodiodes. The challenge of this method is to get a linear relation between the measured intensity and the current mirror tilt angle even for larger angles. State-of-the-art MOEMS mirrors achieve angles up to ±30°, which exceeds the linear angle approximations. The use of an LED, small laser diode or VCSEL as a lightsource is appropriate due to their small size and inexpensive price. Those light sources typically emit light with a Gaussian intensity distribution. This makes an analytical prediction of the expected detector signal quite complicated. In this publication an analytical simulation model is developed to evaluate the influence of the main parameters for this optical mirror tilt-sensor design. An easy and fast to calculate value directly linked to the mirror's tilt-angle is the "relative differential intensity" (RDI = (I1 - I2) / (I1 + I2)). Evaluation of its slope and nonlinear error highlights dependencies between the identified parameters for best SNR and linearity. Also the energy amount covering the detector area is taken into account. Design optimizing rules are proposed and discussed based on theoretical considerations.

  2. Scale effect and optimum relations for sea surface planning

    NASA Technical Reports Server (NTRS)

    Sedov, L.

    1947-01-01

    From the general dimensional and mechanical similarity theory it follows that a condition of steady motion of a given shape\\bottom with constant speed on the surface of water is determined by four nondimensional parameters. By considering the various systems of independent parameters which are applied in theory and practice and special tests, there is determined their mutual relations and their suitability as planning characteristics. In studying the scale effect on the basis of the Prnndtl formula for the friction coefficient for a turbulent condition the order of magnitude is given of the error in applying the model data to full scale in the case of a single-step bottom For a bottom of complicated shape it is shown how from the test data of the hydrodynamic characteristics for one speed with various loads, or one load with various speeds, there may be obtained by simple computation with good approximation the hydrodynamic characteristics for a different speed or for a different load. (These considerations may be of use in solving certain problems on the stability of planning.) This permits extrapolating the curve of resistance against speed for large speeds inaccessible in the tank tests or for other loads which were not tested. The data obtained by computation are in good agreement with the test results. Problems regarding the optimum trim angle or the optimum width in the case of planning of a flat plate are considered from the point of view of the minimum resistance for a given load on the water and planning speeds. Formulas and graphs are given for the optimum value of the planning coefficient and the corresponding values of the trim angle and width of the flat plate.

  3. Correction of broadband snow albedo measurements affected by unknown slope and sensor tilts

    NASA Astrophysics Data System (ADS)

    Weiser, Ursula; Olefs, Marc; Schöner, Wolfgang; Weyss, Gernot; Hynek, Bernhard

    2016-04-01

    Geometric effects induced by the underlying terrain slope or by tilt errors of the radiation sensors lead to an erroneous measurement of snow or ice albedo. Consequently, artificial diurnal albedo variations in the order of 1-20 % are observed. The present paper proposes a general method to correct tilt errors of albedo measurements in cases where tilts of both the sensors and the slopes are not accurately measured or known. We demonstrate that atmospheric parameters for this correction model can either be taken from a nearby well-maintained and horizontally levelled measurement of global radiation or alternatively from a solar radiation model. In a next step the model is fitted to the measured data to determine tilts and directions of sensors and the underlying terrain slope. This then allows us to correct the measured albedo, the radiative balance and the energy balance. Depending on the direction of the slope and the sensors a comparison between measured and corrected albedo values reveals obvious over- or underestimations of albedo. It is also demonstrated that differences between measured and corrected albedo are generally highest for large solar zenith angles.

  4. Poloidal tilting symmetry of high order tokamak flux surface shaping in gyrokinetics

    NASA Astrophysics Data System (ADS)

    Ball, Justin; Parra, Felix I.; Barnes, Michael

    2016-04-01

    A poloidal tilting symmetry of the local nonlinear δ f gyrokinetic model is demonstrated analytically and verified numerically. This symmetry shows that poloidally rotating all the flux surface shaping effects with large poloidal mode number by a single tilt angle has an exponentially small effect on the transport properties of a tokamak. This is shown using a generalization of the Miller local equilibrium model to specify an arbitrary flux surface geometry. With this geometry specification we find that, when performing an expansion in large flux surface shaping mode number, the governing equations of gyrokinetics are symmetric in the poloidal tilt of the high order shaping effects. This allows us to take the fluxes from a single configuration and calculate the fluxes in any configuration that can be produced by tilting the large mode number shaping effects. This creates a distinction between tokamaks with mirror symmetric flux surfaces and tokamaks without mirror symmetry, which is expected to have important consequences for generating toroidal rotation using up-down asymmetry.

  5. Tilting train smooths out the curves

    SciTech Connect

    O'Connor, L.

    1993-02-01

    This article describes a Swedish train that leans into curves and speed around them safely at more than 100 miles per hour and is being tested on a tortuous railroad corridor in the Northeast United States. If the test proves successful, the train--the X2000--could become a fixture in the country's rail system. The train has flexible steering that allows the wheels to hug the rail and permits it to drive around turns faster than most other trains, according to Amtrak. Further, all of the train, expect the locomotive, tilts as it winds its way around the curves. The tilting compensates for the centrifugal force on passengers at high speeds. The X2000 is one of several train systems under consideration by railroads in the United States to improve the rail system in the country. Among the others are Germany's Inter-City Express (ICE) and France's Train a Grande Vitesse (TGV), built by GEC Alshthom (Paris).

  6. Prediction of tilted capillary barrier performance

    SciTech Connect

    Webb, S.W.; McCord, J.T.; Dwyer, S.F.

    1997-04-01

    Capillary barriers, consisting of tilted fine-over-coarse layers under unsaturated conditions, have been suggested as landfill covers to divert water infiltration away from sensitive underground regions, especially for arid and semi-arid regions. The Hydrological Evaluation of Landfill Performance (HELP) computer code is an evaluation tool for landfill covers used by designers and regulators. HELP is a quasi-two-dimensional model that predicts moisture movement into and through the underground soil and waste layers. Processes modeled within HELP include precipitation, runoff, evapotranspiration, unsaturated vertical drainage, saturated lateral drainage, and leakage through liners. Unfortunately, multidimensional unsaturated flow phenomena that are necessary for evaluating tilted capillary barriers are not included in HELP. Differences between the predictions of the HELP and those from a multidimensional unsaturated flow code are presented to assess the two different approaches. Comparisons are presented for the landfill covers including capillary barrier configurations at the Alternative Landfill Cover Demonstration (ALCD) being conducted at Sandia.

  7. A CFD study of tilt rotor flowfields

    NASA Technical Reports Server (NTRS)

    Fejtek, Ian; Roberts, Leonard

    1989-01-01

    The download on the wing produced by the rotor wake of a tilt rotor vehicle in hover is of major concern because of its severe impact on payload-carrying capability. In a concerted effort to understand the fundamental fluid dynamics that cause this download, and to help find ways to reduce it, computational fluid dynamics (CFD) is employed to study this problem. The thin-layer Navier-Stokes equations are used to describe the flow, and an implicit, finite difference numerical algorithm is the method of solution. The methodology is developed to analyze the tilt rotor flowfield. Included are discussions of computations of an airfoil and wing in freestream flows at -90 degrees, a rotor alone, and wing/rotor interaction in two and three dimensions. Preliminary results demonstrate the feasibility and great potential of the present approach. Recommendations are made for both near-term and far-term improvements to the method.

  8. A COLLISIONLESS SCENARIO FOR URANUS TILTING

    SciTech Connect

    Boue, Gwenael; Laskar, Jacques

    2010-03-20

    The origin of the high inclination of Uranus' spin-axis (Uranus' obliquity) is one of the great unanswered questions about the solar system. Giant planets are believed to form with nearly zero obliquity, and it has been shown that the present behavior of Uranus' spin is essentially stable. Several attempts were made in order to solve this problem. Here we report numerical simulations showing that Uranus' axis can be tilted during the planetary migration, without the need of a giant impact, provided that the planet had an additional satellite and a temporary large inclination. This might have happened during the giant planet instability phase described in the Nice model. In our scenario, the satellite is ejected after the tilt by a close encounter at the end of the migration. This model can both explain Uranus' large obliquity and bring new constraints on the planet orbital evolution.

  9. Dry tilt network at Mount Rainier, Washington

    USGS Publications Warehouse

    Dzurisin, Daniel; Johnson, Daniel J.; Symonds, R.B.

    1984-01-01

    In addition to its primary responsibility of monitoring active Mount St. Helens, the David A. Johnston Cascades Volcano Observatory (CVO) has been charged with obtaining baseline geodetic and geochemical information at each of the other potentially active Cascade volcanoes. Dry tilt and/or trilateration networks were established during 1975-82 at Mount Baker, Mount St. Helens, Mount Hood, Mount Shasta, Lassen Peak, Crater Lake, and Long Valley caldera; coverage was extended during September 1982 to include Mount Rainier.

  10. Miniature tilting pad gas lubricated bearing

    SciTech Connect

    Sixsmith, H.; Swift, W.L.

    1983-12-01

    This paper describes the design and development of a miniature tilting pad gas bearing developed for use in very small turbomachines. The bearings have been developed for cryogenic turboexpanders with shaft diameters down to about 0.3 cm and rotational speeds up to one million rpm. Cryogenic expansion turbines incorporating this type of bearing should be suitable for refrigeration rates down to about 10 w.

  11. A tilted cold dark matter cosmological scenario

    NASA Technical Reports Server (NTRS)

    Cen, Renyue; Gnedin, Nickolay Y.; Kofman, Lev A.; Ostriker, Jeremiah P.

    1992-01-01

    A new cosmological scenario based on CDM but with a power spectrum index of about 0.7-0.8 is suggested. This model is predicted by various inflationary models with no fine tuning. This tilted CDM model, if normalized to COBE, alleviates many problems of the standard CDM model related to both small-scale and large-scale power. A physical bias of galaxies over dark matter of about two is required to fit spatial observations.

  12. A miniature tilting pad gas lubricated bearing

    NASA Astrophysics Data System (ADS)

    Sixsmith, H.; Swift, W. L.

    1983-12-01

    This paper describes the design and development of a miniature tilting pad gas bearing developed for use in very small turbomachines. The bearings have been developed for cryogenic turboexpanders with shaft diameters down to about 0.3 cm and rotational speeds up to one million rpm. Cryogenic expansion turbines incorporating this type of bearing should be suitable for refrigeration rates down to about 10 w.

  13. A miniature tilting pad gas lubricated bearing

    NASA Technical Reports Server (NTRS)

    Sixsmith, H.; Swift, W. L.

    1983-01-01

    This paper describes the design and development of a miniature tilting pad gas bearing developed for use in very small turbomachines. The bearings have been developed for cryogenic turboexpanders with shaft diameters down to about 0.3 cm and rotational speeds up to one million rpm. Cryogenic expansion turbines incorporating this type of bearing should be suitable for refrigeration rates down to about 10 w.

  14. Interplay between tilted and principal axis rotation

    SciTech Connect

    Datta, Pradip

    2014-08-14

    At IUAC-INGA, our group has studied four neutron rich nuclei of mass-110 region, namely {sup 109,110}Ag and {sup 108,110}Cd. These nuclei provide the unique platform to study the interplay between Tilted and Principal axis rotation since these are moderately deformed and at the same time, shears structures are present at higher spins. The salient features of the high spin behaviors of these nuclei will be discussed which are the signatures of this interplay.

  15. Glacial isostasy - possible tilting of petroleum reservoirs

    NASA Astrophysics Data System (ADS)

    Fjeldskaar, Willy; Amantov, Aleksey

    2015-04-01

    Scandinavia has experienced major uplift after the last ice age. The rate of uplift along the coasts is so high that its effects have been observed within one generation. Glaciers, sediments and erosion act as loads on the Earth's surface - positive or negative. When a load is applied to the lithosphere covering the asthenosphere, part of the applied load will be supported by the elastic stiffness of the lithosphere, and part by the buoyant forces of the asthenosphere. This process is called isostasy, and the rebound over the last thousands of years has revealed how the Earth reacts to loads. Prior to the last glaciation, northern Europe has experienced more than 30 glaciations. Glacial erosion and repeated ice loading over the last millions of years has significantly influenced the temperature history of sedimentary basins, and associated hydrocarbon maturation in potential source rocks. In addition, repeated loading of glaciers leads to an isostatic response of the lithosphere, which may cause tilting of potential reservoirs, and possible remigration of hydrocarbons. The effects of glaciations are assumed to have caused parts of the accumulation in the Johan Sverdrup field (Utsira High) due to changed migration pathways. Glacial isostasy will lead to tilting of potential reservoirs on the entire Norwegian Continental Shelf. In the western Barents Sea and offshore mid Norway the tilts could exceed 4 m/km, dipping towards east during the glaciations.

  16. Phase transition between two kinds of flux-line lattice in high- Tc superconductors in a tilted field

    NASA Astrophysics Data System (ADS)

    Nonomura, Y.; Hu, X.

    2004-10-01

    Structures of flux-line lattices (FLL) in vortex states of high- Tc superconductors in a tilted field are directly studied by Monte Carlo simulations of the three-dimensional anisotropic XY model, where only Josephson couplings are considered between superconducting layers. A nontrivial structural transition between the Josephson-dominant and Abrikosov-dominant FLL phases occurs as the tilting angle of the external field is increased at low enough temperatures. A similar phase transition is observed by varying the anisotropy parameter with a fixed external field. A finite latent heat at the transition point indicates that this phase transition is of first order.

  17. High-power, low-lateral divergence broad area quantum cascade lasers with a tilted front facet

    SciTech Connect

    Ahn, Sangil Schwarzer, Clemens; Zederbauer, Tobias; MacFarland, Donald C.; Detz, Hermann; Andrews, Aaron M.; Schrenk, Werner; Strasser, Gottfried

    2014-02-03

    We introduce a simple technique to improve the beam quality of broad area quantum cascade lasers. Moderately tilted front facets of the laser provide suppression of higher order lateral waveguide modes. A device with a width of 60 μm and a front facet angle of 17° shows a nearly diffraction limited beam profile. In addition, the peak output power and the slope efficiency of the device are increased since most of the light inside the cavity is emitted through the tilted front facet by an asymmetric light intensity distribution along the cavity.

  18. Ambiguous Tilt and Translation Motion Cues in Astronauts after Space Flight

    NASA Technical Reports Server (NTRS)

    Clement, G.; Harm, D. L.; Rupert, A. H.; Beaton, K. H.; Wood, S. J.

    2008-01-01

    Adaptive changes during space flight in how the brain integrates vestibular cues with visual, proprioceptive, and somatosensory information can lead to impaired movement coordination, vertigo, spatial disorientation, and perceptual illusions following transitions between gravity levels. This joint ESA-NASA pre- and post-flight experiment is designed to examine both the physiological basis and operational implications for disorientation and tilt-translation disturbances in astronauts following short-duration space flights. The first specific aim is to examine the effects of stimulus frequency on adaptive changes in eye movements and motion perception during independent tilt and translation motion profiles. Roll motion is provided by a variable radius centrifuge. Pitch motion is provided by NASA's Tilt-Translation Sled in which the resultant gravitoinertial vector remains aligned with the body longitudinal axis during tilt motion (referred to as the Z-axis gravitoinertial or ZAG paradigm). We hypothesize that the adaptation of otolith-mediated responses to these stimuli will have specific frequency characteristics, being greatest in the mid-frequency range where there is a crossover of tilt and translation. The second specific aim is to employ a closed-loop nulling task in which subjects are tasked to use a joystick to null-out tilt motion disturbances on these two devices. The stimuli consist of random steps or sum-of-sinusoids stimuli, including the ZAG profiles on the Tilt-Translation Sled. We hypothesize that the ability to control tilt orientation will be compromised following space flight, with increased control errors corresponding to changes in self-motion perception. The third specific aim is to evaluate how sensory substitution aids can be used to improve manual control performance. During the closed-loop nulling task on both devices, small tactors placed around the torso vibrate according to the actual body tilt angle relative to gravity. We hypothesize

  19. Optimum PWM waveform synthesis - a filtering approach

    SciTech Connect

    Divan, D.M.

    1985-09-01

    A fundamentally different approach is proposed for the synthesis of optimum pulsewidth modulated (PWM) waveforms for highpower inverter applications. Conventional optimum PWM waveform synthesis techniques which seek to control harmonic levels in the inverter output directly are seen to be equivalent to a filtering operation. Digital filter structures capable of processing PWM waveforms are examined and waveform synthesis strategies are proposed and verified experimentally. Finally, the design of a high-performance PWM waveform generator is detailed.

  20. High brightness angled cavity quantum cascade lasers

    NASA Astrophysics Data System (ADS)

    Heydari, D.; Bai, Y.; Bandyopadhyay, N.; Slivken, S.; Razeghi, M.

    2015-03-01

    A quantum cascade laser (QCL) with an output power of 203 W is demonstrated in pulsed mode at 283 K with an angled cavity. The device has a ridge width of 300 μm, a cavity length of 5.8 mm, and a tilt angle of 12°. The back facet is high reflection coated, and the front facet is anti-reflection coated. The emitting wavelength is around 4.8 μm. In distinct contrast to a straight cavity broad area QCL, the lateral far field is single lobed with a divergence angle of only 3°. An ultrahigh brightness value of 156 MW cm-2 sr-1 is obtained, which marks the brightest QCL to date.

  1. High brightness angled cavity quantum cascade lasers

    SciTech Connect

    Heydari, D.; Bai, Y.; Bandyopadhyay, N.; Slivken, S.; Razeghi, M.

    2015-03-02

    A quantum cascade laser (QCL) with an output power of 203 W is demonstrated in pulsed mode at 283 K with an angled cavity. The device has a ridge width of 300 μm, a cavity length of 5.8 mm, and a tilt angle of 12°. The back facet is high reflection coated, and the front facet is anti-reflection coated. The emitting wavelength is around 4.8 μm. In distinct contrast to a straight cavity broad area QCL, the lateral far field is single lobed with a divergence angle of only 3°. An ultrahigh brightness value of 156 MW cm{sup −2 }sr{sup −1} is obtained, which marks the brightest QCL to date.

  2. Speed benefits of tilt-rotor designs for LHX

    NASA Technical Reports Server (NTRS)

    Mcdaniel, R. L.; Adams, J. V.; Balberde, A.; Dereska, S. P.; Gearin, C. J.; Shaw, D. E.

    1983-01-01

    The merits of an advanced helicopter and a tilt rotor aircraft for light utility, scout, and attack roles in combat missions envisioned for the year 2000 and beyond were compared. It is demonstrated that speed has increasing value for 11 different mission classes broadly encompassing the intended LHX roles. Helicopter speeds beyond 250 knots are judged to have lower military worth. Since the tilt rotor concept offers a different cost speed relationship than that of helicopters, assessment of a tilt rotor LHX variant was warranted. The technical parameters of an advanced tilt rotor are stablished. Parameters of representative missions are identified, computed relative value of the tilt rotor LHX are compared to the baseline helicopter, a first-order life cycle estimate for the tilt rotor LHX is established, military worth of the alternative design is computed and the results are evaluated. It is suggested that the tilt rotor is the solution with the greatest capability for meeting the uncertainties of future needs.

  3. Tilt error in cryospheric surface radiation measurements at high latitudes: a model study

    NASA Astrophysics Data System (ADS)

    Bogren, Wiley Steven; Faulkner Burkhart, John; Kylling, Arve

    2016-03-01

    We have evaluated the magnitude and makeup of error in cryospheric radiation observations due to small sensor misalignment in in situ measurements of solar irradiance. This error is examined through simulation of diffuse and direct irradiance arriving at a detector with a cosine-response fore optic. Emphasis is placed on assessing total error over the solar shortwave spectrum from 250 to 4500 nm, as well as supporting investigation over other relevant shortwave spectral ranges. The total measurement error introduced by sensor tilt is dominated by the direct component. For a typical high-latitude albedo measurement with a solar zenith angle of 60°, a sensor tilted by 1, 3, and 5° can, respectively introduce up to 2.7, 8.1, and 13.5 % error into the measured irradiance and similar errors in the derived albedo. Depending on the daily range of solar azimuth and zenith angles, significant measurement error can persist also in integrated daily irradiance and albedo. Simulations including a cloud layer demonstrate decreasing tilt error with increasing cloud optical depth.

  4. 3D shape measurements of fast moving rough surfaces by two tilted interference fringe systems

    NASA Astrophysics Data System (ADS)

    Kuschmierz, Robert; Günther, Philipp; Czarske, Jürgen W.

    2013-04-01

    Shape measurement of moving, especially rotating objects is an important task in the field of process control. The Laser Doppler Distance Sensor was invented for this purpose. It is realized by two tilted interference fringe systems and enables the simultaneous measurement of the surface velocity and profile. The distance is coded in the phase difference between the generated interference signals of two photo detectors. In order to achieve a distance uncertainty of below 1μm a steep calibration function is necessary. This can be achieved by increasing the tilting angle. However, due to the speckle effect at rough surfaces, random envelopes and phase jumps occur disturbing the phase difference estimation with increasing tilting angle. This problem was overcome recently by employing a receiving optics matching reducing the distance uncertainty by about one magnitude. By evaluating the Doppler frequencies of the two fringe systems the surface velocity and thereby the objects mean diameter can be calculated as well as angular misalignment of the sensor can be detected.

  5. Directional Light Extinction and Emission in a Metasurface of Tilted Plasmonic Nanopillars.

    PubMed

    Verre, R; Svedendahl, M; Odebo Länk, N; Yang, Z J; Zengin, G; Antosiewicz, T J; Käll, M

    2016-01-13

    Plasmonic optical antennas and metamaterials with an ability to boost light-matter interactions for particular incidence or emission angles could find widespread use in solar harvesting, biophotonics, and in improving photon source performance at optical frequencies. However, directional plasmonic structures have generally large footprints or require complicated geometries and costly nanofabrication technologies. Here, we present a directional metasurface realized by breaking the out-of-plane symmetry of its individual elements: tilted subwavelength plasmonic gold nanopillars. Directionality is caused by the complex charge oscillation induced in each individual nanopillar, which essentially acts as a tilted dipole above a dielectric interface. The metasurface is homogeneous over a macroscopic area and it is fabricated by a combination of facile colloidal lithography and off-normal metal deposition. Fluorescence excitation and emission from dye molecules deposited on the metasurface is enhanced in specific directions determined by the tilt angle of the nanopillars. We envisage that these directional metasurfaces can be used as cost-effective substrates for surface-enhanced spectroscopies and a variety of nanophotonic applications. PMID:26625299

  6. Measurement of two-dimensional small angle deviation with a prism interferometer

    SciTech Connect

    Chatterjee, Sanjib; Kumar, Y. Pavan

    2008-09-20

    A new technique for the measurement of two-dimensional small angular deviation is presented. A compound prism, which effectively produces a combination of two right-angled prisms in orthogonal directions, and plane reference surfaces have been utilized for the measurement of the orthogonal components of the angular tilt of an incident plane wavefront. Each orthogonal component of the angular tilt is separately measured from the angular rotation of the resultant wedge fringes between two plane wavefronts generated due to splitting of the incident plane wavefront by the corresponding set of right-angled prism and plane reference surface. The technique is shown to have high sensitivity for the measurement of small angle deviation. A monolithic prism interferometer, which is practically insensitive to vibration, is also proposed. Results obtained for the measurement of a known tilt angle are presented.

  7. Cranial diameter pulsations measured by non-invasive ultrasound decrease with tilt

    NASA Technical Reports Server (NTRS)

    Ueno, Toshiaki; Ballard, Richard E.; Macias, Brandon R.; Yost, William T.; Hargens, Alan R.

    2003-01-01

    INTRODUCTION: Intracranial pressure (ICP) may play a significant role in physiological responses to microgravity by contributing to the nausea associated with microgravity exposure. However, effects of altered gravity on ICP in astronauts have not been investigated, primarily due to the invasiveness of currently available techniques. We have developed an ultrasonic device that monitors changes in cranial diameter pulsation non-invasively so that we can evaluate ICP dynamics in astronauts during spaceflight. This study was designed to demonstrate the feasibility of our ultrasound technique under the physiological condition in which ICP dynamics are changed due to altered gravitational force. METHODS: Six healthy volunteers were placed at 60 degrees head-up, 30 degrees headup, supine, and 15 degrees head-down positions for 3 min at each angle. We measured arterial blood pressure (ABP) with a finger pressure cuff, and cranial diameter pulsation with a pulsed phase lock loop device (PPLL). RESULTS: Analysis of covariance demonstrated that amplitudes of cranial diameter pulsations were significantly altered with the angle of tilt (p < 0.001). The 95% confidence interval for linear regression coefficients of the cranial diameter pulsation amplitudes with tilt angle was 0.862 to 0.968. However, ABP amplitudes did not show this relationship. DISCUSSION: Our noninvasive ultrasonic technique reveals that the amplitude of cranial diameter pulsation decreases as a function of tilt angle, suggesting that ICP pulsation follows the same relationship. It is demonstrated that the PPLL device has a sufficient sensitivity to detect changes non-invasively in ICP pulsation caused by altered gravity.

  8. Modulation of bilayer quantum Hall states by tilted-field-induced subband-Landau-level coupling

    NASA Astrophysics Data System (ADS)

    Kumada, N.; Iwata, K.; Tagashira, K.; Shimoda, Y.; Muraki, K.; Hirayama, Y.; Sawada, A.

    2008-04-01

    We study effects of tilted magnetic fields on energy levels in a double-quantum-well (DQW) system, focusing on the coupling of subbands and Landau levels (LLs). The subband-LL coupling induces anticrossings between LLs directly manifested in the magnetoresistance. The anticrossing gap becomes larger than the spin splitting at the tilting angle θ˜20° and larger than the cyclotron energy at θ˜50° , demonstrating that the subband-LL coupling exerts a strong influence on quantum Hall states even at a relatively small θ and plays a dominant role for larger θ . We also find that when the DQW potential is asymmetric, LL coupling occurs even within a subband. Calculations including higher-order coupling reproduce the experimental results quantitatively well.

  9. On the effect of tilted roof reflectors in Martin-Puplett spectrometers

    NASA Astrophysics Data System (ADS)

    Schillaci, Alessandro; de Bernardis, Paolo

    2012-01-01

    In this paper we analyze theoretically and experimentally the effect of tilt of the roof mirrors in a double pendulum Martin-Puplett Polarizing Interferometer (MPI), focusing on the polarization of the interfering beams. In principle, the tilt affects the efficiency and polarimetric properties of the interferometer. The case of a moderate resolution spectrometer is analysed in detail. Using the Stokes formalism we recover the analytical expressions for the orientation angle and the ellipticity of the beam reflected from a metallic surface, and we compute these quantities for the roof-mirror of a MPI. We find that the polarization rotation and depolarization are small. Using the Jones formalism we propagate their effect on the measured interferogram and spectrum, and demonstrate that the performance degradation is small compared to other systematic effects.

  10. Converted-wave PS arrivals in tilted TI media: Analysis of ray-paths and amplitudes

    NASA Astrophysics Data System (ADS)

    Ramos-Martinez, J.; Calderon-Macias, C.

    2005-05-01

    Converted-waves, i.e., downgoing P-waves that convert upon reflection to S-waves, excited by a compressional source and recorded by horizontal geophones provide a measure of media properties that relate to rock type and fluid saturation. Other uses that have arisen from measuring, analyzing and interpreting PS-waves, include improved structural imaging in formations with occurrence of gas and analysis of seismic anisotropy for estimating fracture density and orientation. Addressing anisotropy in the seismic processing flow is paramount due to the strong influence of this phenomenon in the wave path. Furthermore, analyses of both traveltimes and amplitudes that include anisotropic parameters provide a better picture of the subsurface. Anisotropy types used to describe common geologic scenarios include vertical and horizontal transversely isotropy (VTI and HTI, respectively). Presence of horizontal shale formations is a common cause of the VTI type, while a single vertical fracture system is a typical example of the HTI. Another degree of complexity is to consider a tilted symmetry axis corresponding to a formation with thin layers that are dipping, or the presence of non-vertical fractures. These media, described as tilted TI, have important observable effects on the converted-wave arrivals: i) asymmetry of the wave-path; ii) shear-wave splitting; and iii) non-zero amplitudes at zero offset. Based on numerical modeling, effects of the tilt in the simmetry axis on arrival times, travel path, and amplitudes of the converted waves are analyzed. Ultimate objectives of the work include quantifying these effects on converted-wave data processing, and investigating the reflected wavefield signature for retrieving tilt angle in situations where the stress field induces thin layering or fractures with a tilted symmetry axis.

  11. Fabrication of Fiber-Optic Tilted Bragg Grating Filter in 40 nm Range with A Single Phase Mask

    NASA Technical Reports Server (NTRS)

    Grant, Joseph; Wang, Y.; Sharma, A.; Burdine, Robert V. (Technical Monitor)

    2002-01-01

    Fiber-optic Bragg grating filters are fabricated with a range of Bragg wavelength between 1296 and 1336 nm, using a single phase mask. 30 mW of continuous-wave light at 244 nm is used from a frequency-doubled argon-ion laser having an intracavity etalon. Gratings are fabricated by tilting the photosensitive fiber with respect to the phase mask up to an angle of 15 degrees. The variation of Bragg wavelength with the fiber-tilt is explained with a simple formula. High spatial coherence of 244 nm light makes it possible to displace the fiber as much as 6 mm in front of the phase mask and tilt the fiber by as much as 15 degrees. This results in nearly constant band-width and near 100% reflectively for all gratings throughout the 40 nm range.

  12. Magnetic nanocap arrays with tilted magnetization

    NASA Astrophysics Data System (ADS)

    Albrecht, Manfred

    2009-03-01

    In modern magnetic recording materials the ``superparamagnetic effect'' has become increasingly important as new magnetic hard disk drive products are designed for higher storage densities. In this regard, patterned media [1], where two-dimensional arrays of nanostructures are used, is one of the concepts that might provide the required areal density in future magnetic recording devices. However, also nanostructure arrays will ultimately need high anisotropy material such as L10-FePt to provid enough thermal stability and thus much higher writing fields than currently obtainable from perpendicular magnetic recording heads. One proposed solution to this problem is the use of tilted magnetic recording media [2]. The basic idea is to tilt the easy axis of the magnetic medium from the perpendicular direction to 45 degree. In this case, the switching field will be reduced by a foctor of two in the Stoner-Wohlfarth limit. Recently, this approach was realized by oblique film deposition onto arrays of self-assembled spherical particles [3-5]. In this presentation, recent results on different film systems including Co/Pt multilayers, FePt and CoPtCr-SiO2 alloys which have been deposited onto SiO2 particle monolayers will be presented. It turned out that by tuning the growth conditions single domain nanocaps with enhanced magnetic coercivity and tilted anisostropy axis can be achieved even for particle sizes below 50 nm. [4pt] [1] B. D. Terris and T. Thomson, J. Phys. D: Appl. Phys. 38 (2005) R199 [0pt] [2] J.-P. Wang, Nat. Mater. 4, 191 (2005). [0pt] [3] M. Albrecht et al., Nat. Mater. 4, 203 (2005). [0pt] [4] T. Ulbrich et al., Phys. Rev. Lett. 96 (2006) 077202. [0pt] [5] D. Makarov et al., Appl. Phys. Lett. 93, 153112 (2008).

  13. Can imaginary head tilt shorten postrotatory nystagmus?

    NASA Technical Reports Server (NTRS)

    Gianna-Poulin, C. C.; Voelker, C. C.; Erickson, B.; Black, F. O.

    2001-01-01

    In healthy subjects, head tilt upon cessation of a constant-velocity yaw head rotation shortens the duration of postrotatory nystagmus. The presumed mechanism for this effect is that the velocity storage of horizontal semicircular canal inputs is being discharged by otolith organ inputs which signal a constant yaw head position when the head longitudinal axis is no longer earth-vertical. In the present study, normal subjects were rotated head upright in the dark on a vertical-axis rotational chair at 60 degrees/s for 75 s and were required to perform a specific task as soon as the chair stopped. Horizontal position of the right eye was recorded with an infra-red video camera. The average eye velocity (AEV) was measured over a 30-s interval following chair acceleration/deceleration. The ratios (postrotatory AEV/perrotatory AEV) were 1.1 (SD 0.112) when subjects (N=10) kept their head erect, 0.414 (SD 0.083) when subjects tilted their head forward, 1.003 (SD 0.108) when subjects imagined watching a TV show, 1.012 (SD 0.074) when subjects imagined looking at a painting on a wall, and 0.995 (SD 0.074) when subjects imagined floating in a prone position on a lake. Thus, while actual head tilt reduced postrotatory nystagmus, the imagination tasks did not have a statistically significant effect on postrotatory nystagmus. Therefore, velocity storage does not appear to be under the influence of cortical neural signals when subjects imagine that they are floating in a prone orientation.

  14. Thermal annealing of tilted fiber Bragg gratings

    NASA Astrophysics Data System (ADS)

    González-Vila, Á.; Rodríguez-Cobo, L.; Mégret, P.; Caucheteur, C.; López-Higuera, J. M.

    2016-05-01

    We report a practical study of the thermal decay of cladding mode resonances in tilted fiber Bragg gratings, establishing an analogy with the "power law" evolution previously observed on uniform gratings. We examine how this process contributes to a great thermal stability, even improving it by means of a second cycle slightly increasing the annealing temperature. In addition, we show an improvement of the grating spectrum after annealing, with respect to the one just after inscription, which suggests the application of this method to be employed to improve saturation issues during the photo-inscription process.

  15. Tilted excitation implies odd periodic resonances.

    PubMed

    Depetri, G I; Sartorelli, J C; Marin, B; Baptista, M S

    2016-07-01

    Our aim is to unveil how resonances of parametric systems are affected when symmetry is broken. We showed numerically and experimentally that odd resonances indeed come about when the pendulum is excited along a tilted direction. Applying the Melnikov subharmonic function, we not only determined analytically the loci of saddle-node bifurcations delimiting resonance regions in parameter space but also explained these observations by demonstrating that, under the Melnikov method point of view, odd resonances arise due to an extra torque that appears in the asymmetric case. PMID:27575118

  16. Tilted excitation implies odd periodic resonances

    NASA Astrophysics Data System (ADS)

    Depetri, G. I.; Sartorelli, J. C.; Marin, B.; Baptista, M. S.

    2016-07-01

    Our aim is to unveil how resonances of parametric systems are affected when symmetry is broken. We showed numerically and experimentally that odd resonances indeed come about when the pendulum is excited along a tilted direction. Applying the Melnikov subharmonic function, we not only determined analytically the loci of saddle-node bifurcations delimiting resonance regions in parameter space but also explained these observations by demonstrating that, under the Melnikov method point of view, odd resonances arise due to an extra torque that appears in the asymmetric case.

  17. Optimum Suction Distribution for Transition Control

    NASA Technical Reports Server (NTRS)

    Balakumar, P.; Hall, P.

    1996-01-01

    The optimum suction distribution which gives the longest laminar region for a given total suction is computed. The goal here is to provide the designer with a method to find the best suction distribution subject to some overall constraint applied to the suction. We formulate the problem using the Lagrangian multiplier method with constraints. The resulting non-linear system of equations is solved using the Newton-Raphson technique. The computations are performed for a Blasius boundary layer on a flat-plate and crossflow cases. For the Blasius boundary layer, the optimum suction distribution peaks upstream of the maximum growth rate region and remains flat in the middle before it decreases to zero at the end of the transition point. For the stationary and travelling crossflow instability, the optimum suction peaks upstream of the maximum growth rate region and decreases gradually to zero.

  18. Study of optimum methods of optical communication

    NASA Technical Reports Server (NTRS)

    Harger, R. O.

    1972-01-01

    Optimum methods of optical communication accounting for the effects of the turbulent atmosphere and quantum mechanics, both by the semi-classical method and the full-fledged quantum theoretical model are described. A concerted effort to apply the techniques of communication theory to the novel problems of optical communication by a careful study of realistic models and their statistical descriptions, the finding of appropriate optimum structures and the calculation of their performance and, insofar as possible, comparing them to conventional and other suboptimal systems are discussed. In this unified way the bounds on performance and the structure of optimum communication systems for transmission of information, imaging, tracking, and estimation can be determined for optical channels.

  19. Optimum reentry trajectories of a lifting vehicle

    NASA Technical Reports Server (NTRS)

    Chern, J. S.; Vinh, N. X.

    1978-01-01

    The optimum maneuver of a space shuttle vehicle reentering a spherical, stationary, and locally exponential atmosphere was investigated. The use of Chapman's modified variables and a rescaled lift-drag polar leads to the formulation of a set of dimensionless equations of motion for flight analysis. The resulting equations are exact in the sense that they are also valid for flight in the vacuum. For planar flight several typical optimum maneuvers are investigated at different altitude ranges, low, moderate and very high. For three-dimensional flight, the procedure to solve the optimum trajectory for maximum cross range is discussed. Finally, using the equilibrium glide condition the maximum cross ranges for entry from circular speed, for several values of E*, and the footprint for E* = 1.5 are computed in this reduced problem.

  20. Meridionally tilted ice cloud structures in the tropical upper troposphere as seen by CloudSat

    NASA Astrophysics Data System (ADS)

    Gong, J.; Wu, D. L.; Limpasuvan, V.

    2015-06-01

    It remains challenging to quantify global cloud properties and uncertainties associated with their impacts on climate change because of our poor understanding of cloud three-dimensional (3-D) structures from observations and unrealistic characterization of 3-D cloud effects in global climate models (GCMs). In this study we find cloud 3-D effects can cause significant error in cloud ice and radiation measurements if it is not taken into account appropriately. One of the cloud 3-D complexities, the slantwise tilt structure, has not received much attention in research and even less has been reported considering a global perspective. A novel approach is presented here to analyze the ice cloud water content (IWC) profiles retrieved from CloudSat and a joint radar-lidar product (DARDAR). By integrating IWC profiles along different tilt angles, we find that upper-troposphere (UT) ice cloud mass between 11 and 17 km is tilted poleward from active convection centers in the tropics [30° S, 30° N]. This systematic tilt in cloud mass structure is expected from the mass conservation principle of the Hadley circulation with the divergent flow of each individual convection/convective system from down below, and its existence is further confirmed from cloud-resolving-scale Weather Research and Forecasting (WRF) model simulations. Thus, additive effects of tilted cloud structures can introduce 5-20% variability by its nature or produce errors to satellite cloud/hydrometeor ice retrievals if simply converting it from slant to nadir column. A surprising finding is the equatorward tilt in middle tropospheric (5-11 km) ice clouds, which is also evident in high-resolution model simulations but not in coarse-resolution simulations with cumulus parameterization. The observed cloud tilt structures are intrinsic properties of tropical clouds, producing synoptic distributions around the Intertropical Convergence Zone (ITCZ). These findings imply that current interpretations based on over

  1. Optimum viewing distance for target acquisition

    NASA Astrophysics Data System (ADS)

    Holst, Gerald C.

    2015-05-01

    Human visual system (HVS) "resolution" (a.k.a. visual acuity) varies with illumination level, target characteristics, and target contrast. For signage, computer displays, cell phones, and TVs a viewing distance and display size are selected. Then the number of display pixels is chosen such that each pixel subtends 1 min-1. Resolution of low contrast targets is quite different. It is best described by Barten's contrast sensitivity function. Target acquisition models predict maximum range when the display pixel subtends 3.3 min-1. The optimum viewing distance is nearly independent of magnification. Noise increases the optimum viewing distance.

  2. Zone plate tilt study in transmission x-ray microscope system at 8-11 keV

    NASA Astrophysics Data System (ADS)

    Chao, Fu-Han; Yin, Gung-Chian; Liang, Keng S.; Lai, Yin-Chieh

    2009-08-01

    Zone plate [1] has been used as a focal lens in transmission X-ray microscope (TXM) optical system in recent decades [2, 3]. In TXM of NSRRC[4,5], the thickness of zone plate is about 900nm and the width of its out most zones is 50nm, which has a high aspect ratio 18. When zone plate is tilted, the image quality will be affected by aberration. Since the aspect ratio of zone plate is large, for incident beam, the shape of zone plate's transmission function will look different when zone plate is tilted. The both experimental and simulation result will be shown in this present. A five axes stage is designed and manufactured for the zone plate holder for three dimensional movement, tip and tilt. According to Fourier theory, we can calculate the wave distribution on image plane, if we know the original wave function, the distances between each element, and the transparencies of the sample and zone plate. A parallel simulation process code in MATLAB is developed in workstation cluster with up to 128Gbytes memory. The effects of aberration generated by tilt effect are compared from the experimental data and simulation result. A maximum tilt angle within the acceptable image quality is calculated by simulation and will be verified by experiment.

  3. Tilt-effect of holograms and images displayed on a spatial light modulator.

    PubMed

    Harm, Walter; Roider, Clemens; Bernet, Stefan; Ritsch-Marte, Monika

    2015-11-16

    We show that a liquid crystal spatial light modulator (LCOS-SLM) can be used to display amplitude images, or phase holograms, which change in a pre-determined way when the display is tilted, i.e. observed under different angles. This is similar to the tilt-effect (also called "latent image effect") known from various security elements ("kinegrams") on credit cards or bank notes. The effect is achieved without any specialized optical components, simply by using the large phase shifting capability of a "thick" SLM, which extends over several multiples of 2π, in combination with the angular dependence of the phase shift. For hologram projection one can use the fact that the phase of a monochromatic wave is only defined modulo 2π. Thus one can design a phase pattern extending over several multiples of 2π, which transforms at different readout angles into different 2π-wrapped phase structures, due to the angular dependence of the modulo 2π operation. These different beams then project different holograms at the respective readout angles. In amplitude modulation mode (with inserted polarizer) the intensity of each SLM pixel oscillates over several periods when tuning its control voltage. Since the oscillation period depends on the readout angle, it is possible to find a certain control voltage which produces two (or more) selectable gray levels at a corresponding number of pre-determined readout angles. This is done with all SLM pixels individually, thus constructing different images for the selected angles. We experimentally demonstrate the reconstruction of multiple (Fourier- and Fresnel-) holograms, and of different amplitude images, by readout of static diffractive patterns in a variable angular range between 0° and 60°. PMID:26698528

  4. Expected accuracy of tilt measurements on a novel hexapod-based digital zenith camera system: a Monte-Carlo simulation study

    NASA Astrophysics Data System (ADS)

    Hirt, Christian; Papp, Gábor; Pál, András; Benedek, Judit; Szũcs, Eszter

    2014-08-01

    Digital zenith camera systems (DZCS) are dedicated astronomical-geodetic measurement systems for the observation of the direction of the plumb line. A DZCS key component is a pair of tilt meters for the determination of the instrumental tilt with respect to the plumb line. Highest accuracy (i.e., 0.1 arc-seconds or better) is achieved in practice through observation with precision tilt meters in opposite faces (180° instrumental rotation), and application of rigorous tilt reduction models. A novel concept proposes the development of a hexapod (Stewart platform)-based DZCS. However, hexapod-based total rotations are limited to about 30°-60° in azimuth (equivalent to ±15° to ±30° yaw rotation), which raises the question of the impact of the rotation angle between the two faces on the accuracy of the tilt measurement. The goal of the present study is the investigation of the expected accuracy of tilt measurements to be carried out on future hexapod-based DZCS, with special focus placed on the role of the limited rotation angle. A Monte-Carlo simulation study is carried out in order to derive accuracy estimates for the tilt determination as a function of several input parameters, and the results are validated against analytical error propagation. As the main result of the study, limitation of the instrumental rotation to 60° (30°) deteriorates the tilt accuracy by a factor of about 2 (4) compared to a 180° rotation between the faces. Nonetheless, a tilt accuracy at the 0.1 arc-second level is expected when the rotation is at least 45°, and 0.05 arc-second (about 0.25 microradian) accurate tilt meters are deployed. As such, a hexapod-based DZCS can be expected to allow sufficiently accurate determination of the instrumental tilt. This provides supporting evidence for the feasibility of such a novel instrumentation. The outcomes of our study are not only relevant to the field of DZCS, but also to all other types of instruments where the instrumental tilt

  5. Correction of sample tilt in FIB instruments

    NASA Astrophysics Data System (ADS)

    Oral, M.; Lencová, B.

    2011-07-01

    Many particle optical instruments use ion beams focused onto a tilted sample and the rotationally symmetrical beam creates an elliptical spot. Furthermore, an additional electrostatic field may be present near the titled sample, an extracting field of a detector or a spectrometer or a retarding field on the sample, for example. As a result, the dipole and quadrupole components of the field near the axis of the column cause an additional astigmatic focusing of the beam, which leads to even more elongated shape of the spot. A method of determining a correction has been developed, which allows to compensate for both the ellipticity due to the tilt and the additional astigmatism and to achieve a circular spot on the titled sample. The compensation is provided by a suitable setting of two correcting quadruples and by refocusing the objective lens. The required settings of the quadrupole excitations and objective lens are obtained by a paraxial optimization. The results are checked by computing an intensity distribution and determining the beam shape.

  6. An optimum solar wind coupling function for the AL index

    NASA Astrophysics Data System (ADS)

    McPherron, Robert L.; Hsu, Tung-Shin; Chu, Xiangning

    2015-04-01

    We define a coupling function as a product of solar wind factors that partially linearizes the relation between it and a magnetic index. We consider functions that are a product of factors of solar wind speed V, density N, transverse magnetic field B⊥, and interplanetary magnetic field (IMF) clock angle θc each raised to a different power. The index is the auroral lower (AL index) which monitors the strength of the westward electrojet. Solar wind data 1995-2014 provide hour averages of the factors needed to calculate optimum exponents. Nonlinear inversion determines both the exponents and linear prediction filters of short data segments. The averages of all exponents are taken as optimum exponents and for V, N, B⊥, and sin(θc/2) are [1.92, 0.10, 0.79, 3.67] with errors in the second decimal. Hourly values from 1966 to 2014 are used next to calculate the optimum function (opn) and the functions VBs (eys), epsilon (eps), and universal coupling function (ucf). A yearlong window is advanced by 27 days calculating linear prediction filters for the four functions. The functions eps, eys, ucf, and opn, respectively, predict 43.7, 61.2, 65.6, and 68.3% of AL variance. The opn function is 2.74% better than ucf with a confidence interval 2.60-2.86%. Coupling strength defined as the sum of filter weights (nT/mV/m) is virtually identical for all functions and varies systematically with the solar cycle being strongest (188 nT/mV/m) at solar minimum and weakest (104) at solar maximum. Saturation of the polar cap potential approaching solar maximum may explain the variation.

  7. Rotor stability estimation with competing tilting pad bearing models

    NASA Astrophysics Data System (ADS)

    Cloud, C. Hunter; Maslen, Eric H.; Barrett, Lloyd E.

    2012-05-01

    When predicting the stability of rotors supported by tilting pad journal bearings, it is currently debated whether or not the bearings should be represented with frequency dependent dynamics. Using an experimental apparatus, measurements of pad temperatures, unbalance response and stability are compared with modeling predictions for two tilting pad bearing designs. Predictions based on frequency dependent tilting pad bearing dynamics exhibited significantly better correlation with the stability measurements than those assuming frequency independent dynamics.

  8. Compressor Study to Meet Large Civil Tilt Rotor Engine Requirements

    NASA Technical Reports Server (NTRS)

    Veres, Joseph P.

    2009-01-01

    A vehicle concept study has been made to meet the requirements of the Large Civil Tilt Rotorcraft vehicle mission. A vehicle concept was determined, and a notional turboshaft engine system study was conducted. The engine study defined requirements for the major engine components, including the compressor. The compressor design-point goal was to deliver a pressure ratio of 31:1 at an inlet weight flow of 28.4 lbm/sec. To perform a conceptual design of two potential compressor configurations to meet the design requirement, a mean-line compressor flow analysis and design code were used. The first configuration is an eight-stage axial compressor. Some challenges of the all-axial compressor are the small blade spans of the rear-block stages being 0.28 in., resulting in the last-stage blade tip clearance-to-span ratio of 2.4%. The second configuration is a seven-stage axial compressor, with a centrifugal stage having a 0.28-in. impeller-exit blade span. The compressors conceptual designs helped estimate the flow path dimensions, rotor leading and trailing edge blade angles, flow conditions, and velocity triangles for each stage.

  9. Compressor Study to Meet Large Civil Tilt Rotor Engine Requirements

    NASA Technical Reports Server (NTRS)

    Veres, Joseph P.

    2009-01-01

    A vehicle concept study has been made to meet the requirements of the Large Civil Tilt Rotorcraft vehicle mission. A vehicle concept was determined, and a notional turboshaft engine system study was conducted. The engine study defined requirements for the major engine components, including the compressor. The compressor design-point goal was to deliver a pressure ratio of 31:1 at an inlet weight flow of 28.4 lbm/sec. To perform a conceptual design of two potential compressor configurations to meet the design requirement, a mean-line compressor flow analysis and design code were used. The first configuration is an eight-stage axial compressor. Some challenges of the all-axial compressor are the small blade spans of the rear-block stages being 0.28 in., resulting in the last-stage blade tip clearance-to-span ratio of 2.4 percent. The second configuration is a seven-stage axial compressor, with a centrifugal stage having a 0.28-in. impeller-exit blade span. The compressors conceptual designs helped estimate the flow path dimensions, rotor leading and trailing edge blade angles, flow conditions, and velocity triangles for each stage.

  10. Precision tip-tilt-piston actuator that provides exact constraint

    DOEpatents

    Hale, Layton C.

    1999-01-01

    A precision device which can precisely actuate three degrees of freedom of an optic mount, commonly referred to as tip, tilt, and piston. The device consists of three identical flexure mechanisms, an optic mount to be supported and positioned, a structure that supports the flexure mechanisms, and three commercially available linear actuators. The advantages of the precision device is in the arrangement of the constraints offered by the flexure mechanism and not in the particular design of the flexure mechanisms, as other types of mechanisms could be substituted. Each flexure mechanism constrains two degrees of freedom in the plane of the mechanisms and one direction is actuated. All other degrees of freedom are free to move within the range of flexure mechanisms. Typically, three flexure mechanisms are equally spaced in angle about to optic mount and arranged so that each actuated degree of freedom is perpendicular to the plane formed by the optic mount. This arrangement exactly constrains the optic mount and allows arbitrary actuated movement of the plane within the range of the flexure mechanisms. Each flexure mechanism provides a mechanical advantage, typically on the order of 5:1, between the commercially available actuator and the functional point on the optic mount. This improves resolution by the same ratio and stiffness by the square of the ratio.

  11. Magnetic-field dependence of valley splitting in Si quantum wells grown on tilted SiGe substrates

    NASA Astrophysics Data System (ADS)

    Lee, Seungwon; von Allmen, Paul

    2006-12-01

    The valley splitting of the first few Landau levels is calculated as a function of the magnetic field for electrons confined in a strained silicon quantum well grown on a tilted SiGe substrate, using a parametrized tight-binding method. More specifically, the valley splitting arising from the effect of misorientation between the crystal axis and the confinement direction of the quantum well is investigated. In the absence of misorientation (zero substrate tilt angle), the valley splitting slightly decreases with increasing magnetic field. In contrast, the valley splitting for a finite substrate tilt angle exhibits a strong and nonmonotonic dependence on the magnetic-field strength. The valley splitting of the first Landau level shows an exponential increase followed by a slow saturation as the magnetic-field strength increases. The valley splitting of the second and third Landau levels shows an oscillatory behavior. The nonmonotonic dependence is explained by the phase variation of the Landau-level wave function along the washboardlike interface between the tilted quantum well and the buffer material. The phase variation is a direct consequence of the misorientation. This result suggests that when the misorientation effect is dominant, the magnitude of the valley splitting can be easily tuned by controlling the Landau-level filling factor through the magnetic field and the doping concentration.

  12. Investigation of various essential factors for optimum infrared thermography.

    PubMed

    Okada, Keiji; Takemura, Kei; Sato, Shigeru

    2013-10-01

    We investigated various essential factors for optimum infrared thermography for cattle clinics. The effect of various factors on the detection of surface temperature was investigated in an experimental room with a fixed ambient temperature using a square positioned on a wall. Various factors of animal objects were examined using cattle to determine the relationships among presence of hair, body surface temperature, surface temperature of the eyeball, the highest temperature of the eye circle, rectum temperature and ambient temperature. Also, the surface temperature of the flank at different time points after eating was examined. The best conditions of thermography for cattle clinics were determined and were as follows: (1) The distance between a thermal camera and an object should be fixed, and the camera should be set within a 45-degree angle with respect to the objects using the optimum focal length. (2) Factors that affect the camera temperature, such as extreme cold or heat, direct sunshine, high humidity and wind, should be avoided. (3) For the comparison of thermographs, imaging should be performed under identical conditions. If this is not achievable, hairless parts should be used. PMID:23759714

  13. Optimum pinch grips in the handling of dies.

    PubMed

    Heffernan, C; Freivalds, A

    2000-08-01

    Handling roller-press dies has caused numerous work-related musculoskeletal disorders in the leather industry. The dies are quite large (0.61 x 0.30 m), heavy (3.5 kg) and are difficult to handle because of the large pinch span requirements (up to 16 cm). The purpose of this study was to determine the optimum pinch span and optimum crossbar angulation to minimize die handling forces. Five-finger pulp-pinch forces were measured on five males and five females with a force-sensitive-resistor instrumented glove while handling a simulated adjustable die. Maximum pinch forces occurred at pinch spans between 1.27 and 3.81 cm, with average female strengths being 57% of average male pinch strengths. Minimum pinch forces to hold the die occurred at a 45 degrees angulation and increased linearly as the angle approached 90 degrees or the normal vertical orientation. The simplest solution to redesigning the dies is to: (1) decrease the distance between the braces to less than 4 cm and (2) slant the braces at 45 degrees. PMID:10975667

  14. Investigation of Various Essential Factors for Optimum Infrared Thermography

    PubMed Central

    OKADA, Keiji; TAKEMURA, Kei; SATO, Shigeru

    2013-01-01

    ABSTRACT We investigated various essential factors for optimum infrared thermography for cattle clinics. The effect of various factors on the detection of surface temperature was investigated in an experimental room with a fixed ambient temperature using a square positioned on a wall. Various factors of animal objects were examined using cattle to determine the relationships among presence of hair, body surface temperature, surface temperature of the eyeball, the highest temperature of the eye circle, rectum temperature and ambient temperature. Also, the surface temperature of the flank at different time points after eating was examined. The best conditions of thermography for cattle clinics were determined and were as follows: (1) The distance between a thermal camera and an object should be fixed, and the camera should be set within a 45-degree angle with respect to the objects using the optimum focal length. (2) Factors that affect the camera temperature, such as extreme cold or heat, direct sunshine, high humidity and wind, should be avoided. (3) For the comparison of thermographs, imaging should be performed under identical conditions. If this is not achievable, hairless parts should be used. PMID:23759714

  15. Magnetotransport properties of Co90Fe10/Cu/Ni80Fe20 pseudo-spin-valve with out-of-plane tilted magnetic field

    NASA Astrophysics Data System (ADS)

    Luo, Linqiang; Dao, Nam; Kittiwatanakul, Salinporn; Wolf, Stuart; Lu, Jiwei; UVa NanoStar Team

    The giant magnetoresistance (GMR) effect of a pseudo spin valve made of Co90Fe10/Cu/Ni80Fe20 has been investigated, with a magnetic field applied perpendicularly tilted to the sample plane. Without using a pinning layer, the magnetic separation of the free and fixed layers is uniquely achieved by utilizing perpendicular fields due to different anisotropy energies between Ni80Fe20 and Co90Fe10. The magneto-transport measurements are carried out by Van der Pauw method in current-in-plane geometry at room temperature. By tilting the magnetic field at different angles from out-of-plane, the GMR plateau's width can be tuned. A plateau width of about 2000 Oe is observed at tilted angle 0.5o, which opens a significantly larger window for high-resistance states comparing with a plateau width of 10 Oe for in-plane fields. With the out-of-plane tilted fields, the orientation of the magnetic moments can be tuned continuously out of the sample plane, and the relative orientation between Ni80Fe20 and Co90Fe10 can also be tuned by the tilted angle, enabling us to precisely control the sample's states for current-induced spin dynamics study that is very difficult in the case of in-plane applied magnetic fields.

  16. Common Core: Teaching Optimum Topic Exploration (TOTE)

    ERIC Educational Resources Information Center

    Karge, Belinda Dunnick; Moore, Roxane Kushner

    2015-01-01

    The Common Core has become a household term and yet many educators do not understand what it means. This article explains the historical perspectives of the Common Core and gives guidance to teachers in application of Teaching Optimum Topic Exploration (TOTE) necessary for full implementation of the Common Core State Standards. An effective…

  17. DESIGN GUIDELINES FOR AN OPTIMUM SCRUBBER SYSTEM

    EPA Science Inventory

    The report gives results of a review of the performance and operating experience of existing utility scrubber systems and the state-of-the-art in design of scrubber components. It also gives guidelines for the design of the optimum wet scrubber system, based on this review. The U...

  18. Optimum Building Shapes for Energy Conservation

    ERIC Educational Resources Information Center

    Berkoz, Esher Balkan

    1977-01-01

    An approach to optimum building shape design is summarized that is based on local climate and is especially important for heat control in lower cost construction with temperature-responsive thermal characteristics. The study was supported by Istanbul Technical University. For journal availability see HE 508 931. (Author/LBH)

  19. Transient cardio-respiratory responses to visually induced tilt illusions

    NASA Technical Reports Server (NTRS)

    Wood, S. J.; Ramsdell, C. D.; Mullen, T. J.; Oman, C. M.; Harm, D. L.; Paloski, W. H.

    2000-01-01

    Although the orthostatic cardio-respiratory response is primarily mediated by the baroreflex, studies have shown that vestibular cues also contribute in both humans and animals. We have demonstrated a visually mediated response to illusory tilt in some human subjects. Blood pressure, heart and respiration rate, and lung volume were monitored in 16 supine human subjects during two types of visual stimulation, and compared with responses to real passive whole body tilt from supine to head 80 degrees upright. Visual tilt stimuli consisted of either a static scene from an overhead mirror or constant velocity scene motion along different body axes generated by an ultra-wide dome projection system. Visual vertical cues were initially aligned with the longitudinal body axis. Subjective tilt and self-motion were reported verbally. Although significant changes in cardio-respiratory parameters to illusory tilts could not be demonstrated for the entire group, several subjects showed significant transient decreases in mean blood pressure resembling their initial response to passive head-up tilt. Changes in pulse pressure and a slight elevation in heart rate were noted. These transient responses are consistent with the hypothesis that visual-vestibular input contributes to the initial cardiovascular adjustment to a change in posture in humans. On average the static scene elicited perceived tilt without rotation. Dome scene pitch and yaw elicited perceived tilt and rotation, and dome roll motion elicited perceived rotation without tilt. A significant correlation between the magnitude of physiological and subjective reports could not be demonstrated.

  20. The normal response to prolonged passive head up tilt testing

    PubMed Central

    Petersen, M; Williams, T; Gordon, C; Chamberlain-Webbe..., R; Sutton, R

    2000-01-01

    OBJECTIVE—To define the responses to head up tilt in a large group of normal adult subjects using the most widely employed protocol for tilt testing.
METHODS—127 normal subjects aged 19-88 years (mean (SD), 49 (20) years) without a previous history of syncope underwent tilt testing at 60° for 45 minutes or until syncope intervened. Blood pressure monitoring was performed with digital photoplethysmography, providing continuous, non-invasive, beat to beat heart rate and pressure measurements.
RESULTS—13% of subjects developed vasovagal syncope after a mean (SD) tilt time of 31.7 (12.4) minutes (range 8.5-44.9 minutes). Severe cardioinhibition during syncope was observed less often than is reported in patients investigated for syncope. There were no differences in the age or sex distributions of subjects with positive or negative outcomes, or in the proportions with cardioinhibitory and vasodepressor vasovagal syncope compared with previously reported patient populations. Subjects with negative outcomes showed age related differences in heart rate and blood pressure behaviour throughout tilt.
CONCLUSIONS—False positive results with tilting appear to be common. This has important implications for the use of diagnostic tilt testing. The magnitude of the heart rate and blood pressure changes observed during negative tilts largely invalidates previously suggested criteria for abnormal non-syncopal outcomes.


Keywords: syncope; head up tilt; postural hypotension PMID:11040011

  1. Prediction of the heliospheric current sheet tilt: 1992-1996

    SciTech Connect

    Suess, S.T. ); McComas, D.J. ); Hoeksema, J.T. )

    1993-02-05

    Heliospheric current sheet tilt evolves systematically over the solar cycle. Here the authors show that this evolution is different than the sunspot cycle and that tilt for the period 1992-1996 can be predicted using persistence. That is, the tilt over the coming cycle will be the same as for the past cycle. The Ulysses spacecraft has passed Jupiter and is moving out of the plane of the ecliptic, so they use the prediction of the changing heliospheric current sheet tilt to predict that Ulysses will pass beyond the envelope, or maximum latitude, of the heliospheric current sheet in November 1993. 10 refs., 6 figs.

  2. The HAMP Signal Relay Domain Adopts Multiple Conformational States through Collective Piston and Tilt Motions

    PubMed Central

    Zhu, Lizhe; Bolhuis, Peter G.; Vreede, Jocelyne

    2013-01-01

    The HAMP domain is a linker region in prokaryotic sensor proteins and relays input signals to the transmitter domain and vice versa. Functional as a dimer, the structure of HAMP shows a parallel coiled-coil motif comprising four helices. To date, it is unclear how HAMP can relay signals from one domain to another, although several models exist. In this work, we use molecular simulation to test the hypothesis that HAMP adopts different conformations, one of which represents an active, signal-relaying configuration, and another an inactive, resting state. We first performed molecular dynamics simulation on the prototype HAMP domain Af1503 from Archaeoglobus fulgidus. We explored its conformational space by taking the structure of the A291F mutant disabling HAMP activity as a starting point. These simulations revealed additional conformational states that differ in the tilt angles between the helices as well as the relative piston shifts of the helices relative to each other. By enhancing the sampling in a metadynamics set up, we investigated three mechanistic models for HAMP signal transduction. Our results indicate that HAMP can access additional conformational states characterized by piston motion. Furthermore, the piston motion of the N-terminal helix of one monomer is directly correlated with the opposite piston motion of the C-terminal helix of the other monomer. The change in piston motion is accompanied by a change in tilt angle between the monomers, thus revealing that HAMP exhibits a collective motion, i.e. a combination of changes in tilt angles and a piston-like displacement. Our results provide insights into the conformational changes that underlie the signaling mechanism involving HAMP. PMID:23468603

  3. A mathematical simulation model of a 1985-era tilt-rotor passenger aircraft

    NASA Technical Reports Server (NTRS)

    Mcveigh, M. A.; Widdison, C. A.

    1976-01-01

    A mathematical model for use in real-time piloted simulation of a 1985-era tilt rotor passenger aircraft is presented. The model comprises the basic six degrees-of-freedom equations of motion, and a large angle of attack representation of the airframe and rotor aerodynamics, together with equations and functions used to model turbine engine performance, aircraft control system and stability augmentation system. A complete derivation of the primary equations is given together with a description of the modeling techniques used. Data for the model is included in an appendix.

  4. Theoretical flow characteristics of inlets for tilting-nacelle VTOL aircraft

    NASA Technical Reports Server (NTRS)

    Boles, M. A.; Luidens, R. W.; Stockman, N. O.

    1978-01-01

    The results of a theoretical investigation of geometric variables for lift-cruise-fan, tilting nacelle inlets operating at high incidence angles are presented. These geometric variables are investigated for their effects on surface static to free stream pressure ratio, and the separation parameters of maximum to diffuser exit surface velocity ratio and maximum surface Mach number for low speed operating conditions. The geometric parameters varied were the internal lip contraction ratio, external forebody to diffuser exit diameter ratio external forebody length to diameter ratio and internal lip major to minor axis ratio.

  5. Tunneling Spectroscopy from Magnetization Evolution in a Tilted Rotating Frame of Nuclear Spins

    NASA Astrophysics Data System (ADS)

    Damyanovich, A.; Peternelj, J.; Pintar, M. M.

    2000-07-01

    The time evolution of the proton Zeeman magnetization in the rotating frame at the magic angle θM = cos-1(1/3) is calculated for an isolated tunneling methyl group and its Fourier transform is given. The calculation compares well with the experimental spectra of CH3CD2I and methylmalonic acid. It is shown that Fourier transform spectroscopy of the magnetization evolution in a tilted RF frame represents an excellent alternative to the analogous experiment performed at exact resonance, resulting in improved resolution and a much better signal-to-noise ratio.

  6. Micromagnetic study of spin transfer switching with a spin polarization tilted out of the free layer plane

    SciTech Connect

    Chaves-O'Flynn, Gabriel D. Wolf, Georg; Pinna, Daniele; Kent, Andrew D.

    2015-05-07

    We present the results of zero temperature macrospin and micromagnetic simulations of spin transfer switching of thin film nanomagnets in the shape of an ellipse with a spin-polarization tilted out of the layer plane. The perpendicular component of the spin-polarization is shown to increase the reversal speed, leading to a lower current for switching in a given time. However, for tilt angles larger than a critical angle, the layer magnetization starts to precess about an out-of-plane axis, which leads to a final magnetization state that is very sensitive to simulation conditions. As the ellipse lateral size increases, this out-of-plane precession is suppressed, due to the excitation of spatially non-uniform magnetization modes.

  7. Noncircular skyrmion and its anisotropic response in thin films of chiral magnets under a tilted magnetic field

    SciTech Connect

    Lin, Shi-Zeng; Saxena, Avadh

    2015-11-03

    Here we study the equilibrium and dynamical properties of skyrmions in thin films of chiral magnets with oblique magnetic field. The shape of an individual skyrmion is non-circular and the skyrmion density decreases with the tilt angle from the normal of films. As a result, the interaction between two skyrmions depends on the relative angle between them in addition to their separation. The triangular lattice of skyrmions under a perpendicular magnetic field is distorted into a centered rectangular lattice for a tilted magnetic field. For a low skyrmion density, skyrmions form a chain like structure. Lastly, the dynamical response of the non-circular skyrmions depends on the direction of external currents.

  8. Noncircular skyrmion and its anisotropic response in thin films of chiral magnets under a tilted magnetic field

    DOE PAGESBeta

    Lin, Shi-Zeng; Saxena, Avadh

    2015-11-03

    Here we study the equilibrium and dynamical properties of skyrmions in thin films of chiral magnets with oblique magnetic field. The shape of an individual skyrmion is non-circular and the skyrmion density decreases with the tilt angle from the normal of films. As a result, the interaction between two skyrmions depends on the relative angle between them in addition to their separation. The triangular lattice of skyrmions under a perpendicular magnetic field is distorted into a centered rectangular lattice for a tilted magnetic field. For a low skyrmion density, skyrmions form a chain like structure. Lastly, the dynamical response ofmore » the non-circular skyrmions depends on the direction of external currents.« less

  9. Impact of body tilt on the central aortic pressure pulse.

    PubMed

    Rotaru, Corina; Liaudet, Lucas; Waeber, Bernard; Feihl, François

    2015-04-01

    The present work was undertaken to investigate, in young healthy volunteers, the relationships between the forward propagation times of arterial pressure waves and the timing of reflected waves observable on the aortic pulse, in the course of rapid changes in body position. 20 young healthy subjects, 10 men, and 10 women, were examined on a tilt table at two different tilt angles, -10° (Head-down) and + 45° (Head-up). In each position, carotid-femoral (Tcf) and carotid-tibial forward propagation times (Tct) were measured with the Complior device. In each position also, the central aortic pressure pulse was recorded with radial tonometry, using the SphygmoCor device and a generalized transfer function, so as to evaluate the timing of reflected waves reaching the aorta in systole (onset of systolic reflected wave, sT1r) and diastole (mean transit time of diastolic reflected wave, dMTT). The position shift from Head-up to Head-down caused a massive increase in both Tct (women from 130 ± 10 to 185 ± 18 msec P < 0.001, men from 136 ± 9 to 204 ± 18 msec P < 0.001) and dMTT (women from 364 ± 35 to 499 ± 33 msec P < 0.001, men from 406 ± 22 to 553 ± 21 msec P < 0.001). Mixed model regression showed that the changes in Tct and dMTT observed between Head-up and Head-down were tightly coupled (regression coefficient 2.1, 95% confidence interval 1.9-2.3, P < 0.001). These results strongly suggest that the diastolic waves observed on central aortic pulses reconstructed from radial tonometric correspond at least in part to reflections generated in the lower limbs. PMID:25862096

  10. Sensitivity improvement of reflective tilted FBGs.

    PubMed

    Elzahaby, Eman A; Kandas, Ishac; Aly, Moustafa H; Mahmoud, Kamal

    2016-04-20

    Tilted fiber Bragg gratings are used as energy couplers in which the core mode and cladding modes can be coupled together. Cladding modes have extensive importance in sensing applications due to their sensitive characteristics to the surrounding refractive index. The cladding modes are investigated theoretically by studying a three-layer model of optical fibers, whereas the core mode is investigated by studying a two-layer model of optical fibers. The analysis reveals that to increase the coupling of the energy transferred from the core mode to cladding modes, the cladding radius needs to be decreased. Such behavior is illustrated through studying the change in the electric field distribution and is used to improve the sensitivity of the sensing refractive index of the surrounding medium. PMID:27140103

  11. Hybrid tilted-pulse-front excitation scheme for efficient generation of high-energy terahertz pulses.

    PubMed

    Pálfalvi, L; Ollmann, Z; Tokodi, L; Hebling, J

    2016-04-18

    Conception of a hybrid type tilted-pulse-front pumping scheme for the generation of high-energy terahertz pulses is presented. The proposed setup is the combination of the conventional setup containing imaging optics and the contact grating. The solution was developed for nonlinear materials requiring large pulse-front-tilt angle, like LiNbO3. Due to the creation of the pulse-front-tilt in two steps the limitations of imaging errors can be significantly reduced. Furthermore the necessary grating constant of the contact grating can be larger compared to the simple contact grating scheme making possible the fabrication of the grating profile with significantly higher precision. A detailed optimization procedure with respect to the diffraction efficiency on the contact grating is given for LiNbO3. Instructions are also given how to construct the geometry of the setup in order to minimize imaging errors. Examples are given for LiNbO3 based practically realizable, optimized schemes with reduced imaging errors and high diffraction efficiency on the contact grating. PMID:27137255

  12. Physical properties of the inner shocks in hot, tilted black hole accretion flows

    SciTech Connect

    Generozov, Aleksey; Blaes, Omer; Fragile, P. Chris; Henisey, Ken B.

    2014-01-01

    Simulations of hot, pressure-supported, tilted black hole accretion flows, in which the angular momentum of the flow is misaligned with the black hole spin axis, can exhibit two nonaxisymmetric shock structures in the inner regions of the flow. We analyze the strength and significance of these shock structures in simulations with tilt angles of 10° and 15°. By integrating fluid trajectories in the simulations through the shocks and tracking the variations of fluid quantities along these trajectories, we show that these shocks are strong, with substantial compression ratios, in contrast to earlier claims. However, they are only moderately relativistic. We also show that the two density enhancements resembling flow streams in their shape are in fact merely post-shock compressions, as fluid trajectories cut across, rather than flow along, them. The dissipation associated with the shocks is a substantial fraction (≅ 3%-12%) of the rest mass energy advected into the hole, and therefore comparable to the dissipation expected from turbulence. The shocks should therefore make order unity changes in the observed properties of black hole accretion flows that are tilted.

  13. Direct mapping of Li-enabled octahedral tilt ordering and associated strain in nanostructured perovskites

    NASA Astrophysics Data System (ADS)

    Zhu, Ye; Withers, Ray L.; Bourgeois, Laure; Dwyer, Christian; Etheridge, Joanne

    2015-11-01

    Self-assembled nanostructures with periodic phase separation hold great promise for creating two- and three-dimensional superlattices with extraordinary physical properties. Understanding the mechanism(s) driving the formation of such superlattices demands an understanding of their underlying atomic structure. However, the nanoscale structural fluctuations intrinsic to these superlattices pose a new challenge for structure determination methods. Here we develop an optimized atomic-level imaging condition to measure TiO6 octahedral tilt angles, unit-cell-by-unit-cell, in perovskite-based Li0.5-3xNd0.5+xTiO3, and thereby determine the mathematical formula governing this nanoscale superstructure. We obtain a direct real-space correlation of the octahedral tilt modulation with the superstructure geometry and lattice-parameter variations. This reveals a composition-dependent, self-ordered octahedral superlattice. Amazingly, we observe a reversible annihilation/reconstruction of the octahedral superlattice correlated with the delithiation/lithiation process in this promising Li-ion conductor. This approach to quantify local octahedral tilt and correlate it with strain can be applied to characterize complex octahedral behaviours in other advanced oxide systems.

  14. System analysis of a tilted field-widened Michelson interferometer for high spectral resolution lidar.

    PubMed

    Liu, Dong; Hostetler, Chris; Miller, Ian; Cook, Anthony; Hair, Johnathan

    2012-01-16

    High spectral resolution lidars (HSRLs) have shown great value in aircraft aerosol remote sensing application and are planned for future satellite missions. A compact, robust, quasi-monolithic tilted field-widened Michelson interferometer is being developed as the spectral discrimination filter for an second-generation HSRL(HSRL-2) at NASA Langley Research Center. The Michelson interferometer consists of a cubic beam splitter, a solid arm and an air arm. Piezo stacks connect the air arm mirror to the body of the interferometer and can tune the interferometer within a small range. The whole interferometer is tilted so that the standard Michelson output and the reflected complementary output can both be obtained. In this paper, the transmission ratio is proposed to evaluate the performance of the spectral filter for HSRL. The transmission ratios over different types of system imperfections, such as cumulative wavefront error, locking error, reflectance of the beam splitter and anti-reflection coatings, system tilt, and depolarization angle are analyzed. The requirements of each imperfection for good interferometer performance are obtained. PMID:22274485

  15. Tilted femtosecond pulses for velocity matching in gas-phase ultrafast electron diffraction

    NASA Astrophysics Data System (ADS)

    Zhang, Ping; Yang, Jie; Centurion, Martin

    2014-08-01

    Recent advances in pulsed electron gun technology have resulted in femtosecond electron pulses becoming available for ultrafast electron diffraction experiments. For experiments investigating chemical dynamics in the gas phase, the resolution is still limited to picosecond time scales due to the velocity mismatch between laser and electron pulses. Tilted laser pulses can be used for velocity matching, but thus far this has not been demonstrated over an extended target in a diffraction setting. We demonstrate an optical configuration to deliver high-intensity laser pulses with a tilted pulse front for velocity matching over the typical length of a gas jet. A laser pulse is diffracted from a grating to introduce angular dispersion, and the grating surface is imaged on the target using large demagnification. The laser pulse duration and tilt angle were measured at and near the image plane using two different techniques: second harmonic cross correlation and an interferometric method. We found that a temporal resolution on the order of 100 fs can be achieved over a range of approximately 1 mm around the image plane.

  16. Deceleration parameter in tilted Friedmann universes

    NASA Astrophysics Data System (ADS)

    Tsagas, Christos G.; Kadiltzoglou, Miltiadis I.

    2015-08-01

    Large-scale peculiar motions are believed to reflect the local inhomogeneity and anisotropy of the Universe, triggered by the ongoing process of structure formation. As a result, realistic observers do not follow the smooth Hubble flow but have a peculiar "tilt" velocity relative to it. Our local group of galaxies, in particular, moves with respect to the universal expansion at a speed of roughly 600 km /sec . Relative motion effects are known to interfere with the observations and their interpretation. The strong dipolar anisotropy seen in the cosmic microwave background, for example, is not treated as a sign of real universal anisotropy, but as a mere artifact of our peculiar motion relative to the Hubble flow. With these in mind, we look into the implications of large-scale bulk motions for the kinematics of their associated observers, by adopting a tilted Friedmann model. Our aim is to examine whether the deceleration parameter measured in the rest frame of the bulk flow can differ from that of the actual Universe due to relative-motion effects alone. We find that there is a difference, which depends on the speed as well as the scale of the bulk motion. The faster and the smaller the drifting domain, the larger the difference. In principle, this allows relatively slow peculiar velocities to have a disproportionately strong effect on the value of the deceleration parameter measured by observers within bulk flows of, say, a few hundred megaparsecs. In fact, under certain circumstances, it is even possible to change the sign of the deceleration parameter. It goes without saying that all these effects vanish identically in the Hubble frame, which makes them an illusion and mere artifact of the observers' relative motion.

  17. Tip-tilt compensation: Resolution limits for ground-based telescopes using laser guide star adaptive optics. Revision 2

    SciTech Connect

    Olivier, S.S.; Max, C.E.; Gavel, D.T.; Brase, J.M.

    1992-10-08

    The angular resolution of long-exposure images from ground-based telescopes equipped with laser guide star adaptive optics systems is fundamentally limited by the the accuracy with which the tip-tilt aberrations introduced by the atmosphere can be corrected. Assuming that a natural star is used as the tilt reference, the residual error due to tilt anisoplanatism can significantly degrade the long-exposure resolution even if the tilt reference star is separated from the object being imaged by a small angle. Given the observed distribution of stars in the sky, the need to find a tilt reference star quite close to the object restricts the fraction of the sky over which long-exposure images with diffraction limited resolution can be obtained. In this paper, the authors present a comprehensive performance analysis of tip-tilt compensation systems that use a natural star as a tilt reference, taking into account properties of the atmosphere and of the Galactic stellar populations, and optimizing over the system operating parameters to determine the fundamental limits to the long-exposure resolution. Their results show that for a ten meter telescope on Mauna Kea, if the image of the tilt reference star is uncorrected, about half the sky can be imaged in the V band with long-exposure resolution less than 60 milli-arc-seconds (mas), while if the image of the tilt reference star is fully corrected, about half the sky can be imaged in the V band with long-exposure resolution less than 16 mas. Furthermore, V band images long-exposure resolution of less than 16 mas may be obtained with a ten meter telescope on Mauna Kea for unresolved objects brighter than magnitude 22 that are fully corrected by a laser guide star adaptive optics system. This level of resolution represents about 70% of the diffraction limit of a ten meter telescope in the V band and is more than a factor of 45 better than the median seeing in the V band on Mauna Kea.

  18. Atomistic aspects of crack propagation along high angle grain boundaries

    SciTech Connect

    Farkas, D.

    1997-12-31

    The author presents atomistic simulations of the crack tip configuration near a high angle {Sigma} = 5 [001](210) symmetrical tilt grain boundary in NiAl. The simulations were carried out using molecular statics and embedded atom (EAM) potentials. The cracks are stabilized near a Griffith condition involving the cohesive energy of the grain boundary. The atomistic configurations of the tip region are different in the presence of the high angle grain boundary than in the bulk. Three different configurations of the grain boundary were studied corresponding to different local compositions. It was found that in ordered NiAl, cracks along symmetrical tilt boundaries show a more brittle behavior for Al rich boundaries than for Ni-rich boundaries. Lattice trapping effects in grain boundary fracture were found to be more significant than in the bulk.

  19. Development of scanning micromirror with discrete steering angles

    NASA Astrophysics Data System (ADS)

    Wang, Z. F.; Noell, W.; Zickar, M.; de Rooij, N. F.; Lim, S. P.

    2006-04-01

    This paper describes the development of a new MEMS-based optical mirror, which can perform optical switching (or scanning) function with discrete reflection angles in an outof- plane configuration. The device is fabricated through the Deep Reactive Ion Etching (DRIE) process on silicon-on-insulator (SOI) wafer, followed by wafer dicing and assembly with two metalised glass dies. The MEMS mirror can be tilted under electrostatic force between the opposite electrodes embedded on SOI and glass structures. The most outstanding feature of this MEMS mirror is the discrete and therefore, reliable tilting angles, which generated by its unique mechanical structural design and electrostatic-driven mechanism. In this paper, the concept of the new scanning mirror is presented, followed by the introduction of device design, mechanical simulation, microfabrication process, assembly solution, and some testing results. The potential applications of this new MEMS mirror include optical scanning, optical sensing (or detection), and optical switching.

  20. OPTIMUM PLASMA STATES FOR NEXT STEP TOKAMAKS

    SciTech Connect

    LIN-LIU,YR; STAMBAUGH,RD

    2002-11-01

    OAK A271 OPTIMUM PLASMA STATES FOR NEXT STEP TOKAMAKS. The dependence of the ideal ballooning {beta} limit on aspect ratio, A, and elongation {kappa} is systematically explored for nearly 100% bootstrap current driven tokamak equilibria in a wide range of the shape parameters (A = 1.2-7.0, {kappa} = 1.5-6.0 with triangularity {delta} = 0.5). The critical {beta}{sub N} is shown to be optimal at {kappa} = 3.0-4.0 for all A studied and increases as A decreases with a dependence close to A{sup -0.5}. The results obtained can be used as a theoretical basis for the choice of optimum aspect ratio and elongation of next step burning plasma tokamaks or tokamak reactors.

  1. TILTING ELECTRIC ARC FURNACE USED TO MELT BRONZE IN THE ...

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

    TILTING ELECTRIC ARC FURNACE USED TO MELT BRONZE IN THE BRASS FOUNDRY BY MEANS OF AN ARC CREATED BETWEEN TWO HORIZONTAL ELECTRODES. WHEN MELTED, THE FURNACE TILTS, FILLING MOBILE LADLES FROM THE SPOUT. - Stockham Pipe & Fittings Company, Brass Foundry, 4000 Tenth Avenue North, Birmingham, Jefferson County, AL

  2. Tilt-induced biases in sediment trap functioning

    NASA Astrophysics Data System (ADS)

    Chiswell, Stephen M.; Nodder, Scott D.

    2015-12-01

    We present data from two sediment traps moored 5 km apart ˜150 km off the east coast of New Zealand. Both traps were at 1500 m in 3100 m of water. One trap was attached to a 3038 m tall mooring and exhibited tilts measured by a tilt sensor ranging from 5° to 20°, the other trap was attached to a 1659 m tall mooring and exhibited tilts ranging from 2° to 4°. The computed relative trapping efficiency depends on which flux constituent (mass, particulate organic carbon, biogenic silica, etc.) is used to compute it. We suggest that this physically unrealistic result arises because of relatively high noise in the measurements due to patchiness, sampling and/or measurement errors. On average, the trap exhibiting most tilt collected 30-50% less material than the trap exhibiting least tilt. For the total mass flux, efficiencies appear to be lower at higher trap tilt. However, with only 5 months of data, we do not have enough samples to accurately model the relationship between trap tilt and efficiency, except to show that with even moderate tilt, the sediment trap trapping efficiency can be reduced by a factor of nearly two.

  3. Active magnetic bearings for optimum turbomachinery design

    NASA Technical Reports Server (NTRS)

    Hustak, J.; Kirk, R. G.; Schoeneck, K. A.

    1985-01-01

    The design and shop test results are given for a high speed eight stage centrifugal compressor supported by active magnetic bearings. A brief summary of the rotor dynamics analysis is presented with specific attention given to design considerations for optimum rotor stability. The concerns for retrofit of magnetic bearings in existing machinery are discussed with supporting analysis of a four stage centrifugal compressor. Recommendations are given on design and analysis requirements for successful machinery operation of either retrofit or new design turbomachinery.

  4. Boolean computation of optimum hitting sets

    SciTech Connect

    Hulme, B.L.; Baca, L.S.; Shiver, A.W.; Worrell, R.B.

    1984-04-01

    This report presents the results of computational experience in solving weighted hitting set problems by Boolean algebraic methods. The feasible solutions are obtained by Boolean formula manipulations, and the optimum solutions are obtained by comparing the weight sums of the feasible solutions. Both the algebra and the optimization can be accomplished using the SETS language. One application is to physical protection problems. 8 references, 2 tables.

  5. V/STOL tilt rotor aircraft study. Volume 7: Tilt rotor flight control program feedback studies

    NASA Technical Reports Server (NTRS)

    Alexander, H. R.; Eason, W.; Gillmore, K.; Morris, J.; Spittle, R.

    1973-01-01

    An exploratory study has been made of the use of feedback control in tilt rotor aircraft. This has included the use of swashplate cyclic and collective controls and direct lift control. Various sensor and feedback systems are evaluated in relation to blade loads alleviation, improvement in flying qualities, and modal suppression. Recommendations are made regarding additional analytical and wind tunnel investigations and development of feedback systems in the full scale flight vehicle. Estimated costs and schedules are given.

  6. Constrained optimum trajectories with specified range

    NASA Technical Reports Server (NTRS)

    Erzberger, H.; Lee, H.

    1980-01-01

    The characteristics of optimum fixed-range trajectories whose structure is constrained to climb, steady cruise, and descent segments are derived by application of optimal control theory. The performance function consists of the sum of fuel and time costs, referred to as direct operating costs (DOC). The state variable is range-to-go and the independent variable is energy. In this formulation a cruise segment always occurs at the optimum cruise energy for sufficiently large range. At short ranges (500 n. mi. and less) a cruise segment may also occur below the optimum cruise energy. The existence of such a cruise segment depends primarily on the fuel flow vs thrust characteristics and on thrust constraints. If thrust is a free control variable along with airspeed, it is shown that such cruise segments will not generally occur. If thrust is constrained to some maximum value in climb and to some minimum in descent, such cruise segments generally will occur. The performance difference between free thrust and constrained thrust trajectories has been determined in computer calculations for an example transport aircraft.

  7. Description of a tilt wing mathematical model for piloted simulation

    NASA Technical Reports Server (NTRS)

    Totah, Joseph J.

    1991-01-01

    A tilt-wing mathematical model that was used in a piloted six-deg-of-freedom flight simulation application is presented. Two types of control systems developed for the model - a conventional programmed-flap wing-tilt control system and a geared-flap wing-tilt control system - are discussed. The objective of this effort was to develop the capability to study tilt-wing aircraft. Experienced tilt-wing pilots subjectively evaluated the model using programmed-flap control to assess the quality of the simulation. The objective was met and the model was then applied to study geared-flap control to investigate the possibility of eliminating the need for auxiliary pitch control devices. This was performed in the moving-base simulation environment, and the vehicle responses with programmed-flap and geared-flap control were compared.

  8. Potential Applications of an Integrated Seismic, Tilt, and Temperature Instrument

    NASA Astrophysics Data System (ADS)

    Bainbridge, Geoffrey; Parker, Tim; Karimi, Sepideh; Devanney, Peter

    2016-04-01

    Force feedback seismometers provide mass position outputs which represent the time-averaged feedback force applied to each inertial mass, in order to cancel external forces and keep it balanced at its center point. These external forces are primarily due to tilt and temperature. In a symmetric triaxial seismometer, tilt and temperature effects can be distinguished because temperature affects all 3 axes equally whereas tilt causes a different force on each axis. This study analyzes the resolution of tilt and temperature signals that can be obtained from a force-feedback seismometer, and the potential applicability of this data to applications such as volcano monitoring and cap rock integrity monitoring. Also the synergy of a combined seismic, tilt, and temperature instrument is considered.

  9. Dislocation modeling of creep-related tilt changes

    USGS Publications Warehouse

    McHugh, S.; Johnston, M.J.S.

    1979-01-01

    Tilt changes associated with 1-5 mm of fault creep have been detected at several different locations on the San Andreas fault on tiltmeters within 500 m of the creep observation point. The creep-related tilts have amplitudes of 0??.5 ??rad and durations comparable to the creep events. No changes $ ??10-2 ??rad have been observed on tiltmeters at distances $ ??1 km from the fault at the time of the creep events. Dislocation models capable of replicating the creep-related tilt events have been constructed to examine the relationship of the model parameters to details of the tilt waveforms. The tilt time histories and bounded assumptions of the source-station configurations, and the displacement time history, can be used to infer the type and amount of displacement, the propagation direction and depth of the slip zone. The shallow depth and finite size of the slip zone indicated by these models constrasts with the horizontal extent. ?? 1979.

  10. How the Tilt of the Dipole Could Affect the Rate of Reconnection at the Earth's Magnetopause

    NASA Astrophysics Data System (ADS)

    Russell, C. T.; Raeder, J.; Wang, Y. L.; Luhmann, J. G.

    2002-12-01

    The semiannual variation of geomagnetic activity was attributed by Russell and McPherron (1973) to reconnection modulated by the varying angle of the magnetic field at the nose of the magnetosphere to the statistically Parker-spiral-oriented IMF. The division of the semiannual variation of geomagnetic activity into two annual variations according to the polarity of the IMF clearly demonstrates that reconnection is the cause of the semiannual variation. The so-called Russell-McPherron mechanism does not explain the diurnal variation of geomagnetic indices, albeit it does explain the annual variation of this diurnal variation. O'Brien and McPherron (2002) have recently demonstrated that if the reconnection rate depends on the tilt of the dipole an improved prediction of both the semiannual and diurnal variation results, but they do not provide a credible explanation for tilt dependence. Nevertheless, a very simple explanation does exist based on simple geometric arguments following those of Crooker (1979) and Luhmann et al (1984) who predicted the sites of reconnection for a dipole perpendicular to the solar wind flow. If reconnection is initiated where the IMF is antiparallel to the magnetospheric field and if the rate of reconnection depends on the solar wind pressure normal to the magnetopause, then the rate maximizes for the 0 deg. tilt (0 deg. magnetic latitude of the subsolar point) and lessens as either pole of the dipole tilts toward the Sun. In short, the simple merging law used by Russell and McPherron may need tuning, but the basic mechanism is valid as proposed.

  11. Wavelength switching of picosecond pulses generated from a self-seeded Fabry-Perot laser diode with a tilted fiber Bragg grating formed in a graded-index multimode fiber.

    PubMed

    Liu, Yunqi; Chiang, Kin Seng

    2011-02-20

    We demonstrated the generation of wavelength-switchable picosecond pulses from a self-seeded Fabry-Perot laser diode that used a tilted fiber Bragg grating (FBG) formed in a graded-index multimode fiber as an external optical feedback element, where wavelength switching was achieved by controlling the modal distribution in the FBG. We measured the reflection spectra of multimode FBGs fabricated with different tilt angles and discussed the effects of the tilt angle on wavelength selection. By using a 20 mm long 1.65° tilted FBG and a fiber deformer to control the modal distribution in the FBG, we generated 2 GHz pulses with a wavelength switchable over 14 wavelengths at a spacing of ∼0.8 nm. PMID:21343961

  12. A correlation polarimeter for noise-like signals. [optimum estimation of linearly polarized electromagnetic wave

    NASA Technical Reports Server (NTRS)

    Ohlson, J. E.

    1976-01-01

    Optimum estimation (tracking) of the polarization plane of a linearly polarized electromagnetic wave is determined when the signal is a narrow-band Gaussian random process with a polarization plane angle which is also a Gaussian random process. This model is compared to previous work and is applicable to space communication. The estimator performs a correlation operation similar to an amplitude-comparison monopulse angle tracker, giving the name correlation polarimeter. Under large signal-to-noise ratio (SNR), the estimator is causal. Performance of the causal correlation polarimeter is evaluated for arbitrary SNR. Optimum precorrelation filtering is determined. With low SNR, the performance of this system is far better than that of previously developed systems. Practical implementation is discussed. A scheme is given to reduce the effect of linearly polarized noise.

  13. Optimum design of composite laminates with thermal effects. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Markham, L. R.; Herakovich, C. T.

    1976-01-01

    An analytical approach to determine an optimum laminate for a variety of thermal and mechanical loading combinations is presented. The analysis is performed for a linear elastic material under static mechanical and uniform thermal loadings. The problem is restricted to a unit width and length laminate with angle orientations resulting in an orthotropic, symmetric, and balanced configuration. An objective function defining total strain energy, is formulated and an optimum laminate design determined subject to constraints on stiffness, average coefficient of thermal expansion, and strength. The objective function is formulated in terms of the orientation angles, number of plies, and material properties. The method presented has, in varying degrees, shown that the design of a laminate can be accomplished using strain energy minimization as the primary criteria. The results of various combinations of applied constraints in the optimized design process are presented and discussed.

  14. Low speed tests of a fixed geometry inlet for a tilt nacelle V/STOL airplane

    NASA Technical Reports Server (NTRS)

    Syberg, J.; Koncsek, J. L.

    1977-01-01

    Test data were obtained with a 1/4 scale cold flow model of the inlet at freestream velocities from 0 to 77 m/s (150 knots) and angles of attack from 45 deg to 120 deg. A large scale model was tested with a high bypass ratio turbofan in the NASA/ARC wind tunnel. A fixed geometry inlet is a viable concept for a tilt nacelle V/STOL application. Comparison of data obtained with the two models indicates that flow separation at high angles of attack and low airflow rates is strongly sensitive to Reynolds number and that the large scale model has a significantly improved range of separation-free operation.

  15. Performance of a V/STOL tilt nacelle inlet with blowing boundary layer control

    NASA Technical Reports Server (NTRS)

    Johns, A. L.; Williams, R. C.; Potonides, H. C.

    1979-01-01

    A scale model of a V/STOL tilt nacelle fitted to a 0.508 m single stage fan was tested in the NASA Lewis 9x15 ft low speed wind tunnel to determine the effect of diffuser blowing on the inlet aerodynamics and aeromechanical performance. The test was conducted over a range of freestream speeds (up to 120 knots) and angles of attack (up to 120 deg). Diffuser blowing had a beneficial affect on all performance parameters. The angle of attack range for separation free flow substantially increased, and the fan face distortion significantly reduced with a corresponding increase in total pressure recovery. Discrete narrow band blade stress peaks which were common to the nonblowing (baseline) configuration were eradicated with diffuser blowing.

  16. Performance of a V/STOL tilt nacelle inlet with blowing boundary layer control

    NASA Technical Reports Server (NTRS)

    Johns, A. L.; Williams, R. C.; Potonides, H. C.

    1979-01-01

    A scale model of a V/STOL tilt nacelle fitted to a 0.508 m single stage fan was tested in the NASA Lewis low speed wind tunnel to determine the effect of diffuser blowing on the inlet aerodynamics and aeromechanical performance. The test was conducted over a range of freestream speeds (up to 120 knots) and angles-of attack (up to 120 deg). In general, diffuser blowing had a beneficial affect on all performance parameters. The angle-of-attack range for a separation-free flow substantially increased, and the fan face distortion reduced with a corresponding increase in total pressure recovery. Discrete narrow band blade stress peaks which were common to the nonblowing (baseline) configuration were eradicated with diffuser blowing.

  17. Perception of Perspective Angles.

    PubMed

    Erkelens, Casper J

    2015-06-01

    We perceive perspective angles, that is, angles that have an orientation in depth, differently from what they are in physical space. Extreme examples are angles between rails of a railway line or between lane dividers of a long and straight road. In this study, subjects judged perspective angles between bars lying on the floor of the laboratory. Perspective angles were also estimated from pictures taken from the same point of view. Converging and diverging angles were judged to test three models of visual space. Four subjects evaluated the perspective angles by matching them to nonperspective angles, that is, angles between the legs of a compass oriented in the frontal plane. All subjects judged both converging and diverging angles larger than the physical angle and smaller than the angles in the proximal stimuli. A model of shallow visual space describes the results. According to the model, lines parallel to visual lines, vanishing at infinity in physical space, converge to visual lines in visual space. The perceived shape of perspective angles is incompatible with the perceived length and width of the bars. The results have significance for models of visual perception and practical implications for driving and flying in poor visibility conditions. PMID:27433312

  18. Perception of Perspective Angles

    PubMed Central

    2015-01-01

    We perceive perspective angles, that is, angles that have an orientation in depth, differently from what they are in physical space. Extreme examples are angles between rails of a railway line or between lane dividers of a long and straight road. In this study, subjects judged perspective angles between bars lying on the floor of the laboratory. Perspective angles were also estimated from pictures taken from the same point of view. Converging and diverging angles were judged to test three models of visual space. Four subjects evaluated the perspective angles by matching them to nonperspective angles, that is, angles between the legs of a compass oriented in the frontal plane. All subjects judged both converging and diverging angles larger than the physical angle and smaller than the angles in the proximal stimuli. A model of shallow visual space describes the results. According to the model, lines parallel to visual lines, vanishing at infinity in physical space, converge to visual lines in visual space. The perceived shape of perspective angles is incompatible with the perceived length and width of the bars. The results have significance for models of visual perception and practical implications for driving and flying in poor visibility conditions. PMID:27433312

  19. Multidisciplinary Optimization of Tilt Rotor Blades Using Comprehensive Composite Modeling Technique

    NASA Technical Reports Server (NTRS)

    Chattopadhyay, Aditi; McCarthy, Thomas R.; Rajadas, John N.

    1997-01-01

    An optimization procedure is developed for addressing the design of composite tilt rotor blades. A comprehensive technique, based on a higher-order laminate theory, is developed for the analysis of the thick composite load-carrying sections, modeled as box beams, in the blade. The theory, which is based on a refined displacement field, is a three-dimensional model which approximates the elasticity solution so that the beam cross-sectional properties are not reduced to one-dimensional beam parameters. Both inplane and out-of-plane warping are included automatically in the formulation. The model can accurately capture the transverse shear stresses through the thickness of each wall while satisfying stress free boundary conditions on the inner and outer surfaces of the beam. The aerodynamic loads on the blade are calculated using the classical blade element momentum theory. Analytical expressions for the lift and drag are obtained based on the blade planform with corrections for the high lift capability of rotor blades. The aerodynamic analysis is coupled with the structural model to formulate the complete coupled equations of motion for aeroelastic analyses. Finally, a multidisciplinary optimization procedure is developed to improve the aerodynamic, structural and aeroelastic performance of the tilt rotor aircraft. The objective functions include the figure of merit in hover and the high speed cruise propulsive efficiency. Structural, aerodynamic and aeroelastic stability criteria are imposed as constraints on the problem. The Kreisselmeier-Steinhauser function is used to formulate the multiobjective function problem. The search direction is determined by the Broyden-Fletcher-Goldfarb-Shanno algorithm. The optimum results are compared with the baseline values and show significant improvements in the overall performance of the tilt rotor blade.

  20. Tilt Error in Cryospheric Surface Radiation Measurements at High Latitudes: A Model Study

    NASA Astrophysics Data System (ADS)

    Bogren, W.; Kylling, A.; Burkhart, J. F.

    2015-12-01

    We have evaluated the magnitude and makeup of error in cryospheric radiation observations due to small sensor misalignment in in-situ measurements of solar irradiance. This error is examined through simulation of diffuse and direct irradiance arriving at a detector with a cosine-response foreoptic. Emphasis is placed on assessing total error over the solar shortwave spectrum from 250nm to 4500nm, as well as supporting investigation over other relevant shortwave spectral ranges. The total measurement error introduced by sensor tilt is dominated by the direct component. For a typical high latitude albedo measurement with a solar zenith angle of 60◦, a sensor tilted by 1, 3, and 5◦ can respectively introduce up to 2.6, 7.7, and 12.8% error into the measured irradiance and similar errors in the derived albedo. Depending on the daily range of solar azimuth and zenith angles, significant measurement error can persist also in integrated daily irradiance and albedo.

  1. Orbital effect, subband depopulation, and conductance fluctuations in ballistic quantum dots under a tilted magnetic field

    NASA Astrophysics Data System (ADS)

    Gustin, C.; Faniel, S.; Hackens, B.; Melinte, S.; Shayegan, M.; Bayot, V.

    2005-04-01

    Using two-dimensional electron gases (2DEGs) confined to wide and narrow quantum wells, we study the magnetoconductance of ballistic quantum dots as a function of the well width and the tilt angle of the magnetic field B with respect to the 2DEG. Both the wide and narrow quantum well dots feature magnetoconductance fluctuations (MCFs) at intermediate tilt angles, due to the finite thickness of the electron layer and the field-induced orbital effect. As B approaches a strictly parallel configuration, a saturation of the MCFs’ spectral distribution is observed, combined with the persistence of a limited number of frequency components in the case of the narrow quantum well dot. It is found that the onset of saturation strongly depends on the width of the confining well. Using the results of self-consistent Poisson-Schrödinger simulations, the magnetoconductance is rescaled as a function of the Fermi level in the 2DEG. We perform a power spectrum analysis of the parallel field-induced MCFs in the energy space and find a good agreement with theoretical predictions.

  2. Hover test results of a small-scale twin-tilt nacelle model

    NASA Technical Reports Server (NTRS)

    Schmidt, S. B.

    1985-01-01

    Characteristics in hover of an 11/36%-scale, powered, twin-tilt nacelle model were measured in the NASA Ames Research Center's 40- by 80-Foot Wind Tunnel. The model was powered by two high-pressure air-driven turbofan propulsion simulators. The position of the sting-mounted model was fixed and a movable ground plane was used to vary ground height and orientation. Hover characteristics were investigated in and out of ground effect for roll angles of -2 deg to +14 deg and pitch angles of -15 deg to +10 deg. Results for the basic configurations are compared with data from hover tests of the full-scale tilt nacelle model. Two methods were investigated to increase vertical vane effectiveness: (1) extending the maximum vane deflection from 20 deg to 70 deg, and (2) adding a third vertical vane. The goal was to increase the roll-control capability to significantly reduce or balance the strong, unfavorable rolling moment created by the loss of one engine. Results indicate that the three-vertical-vane configuration is more effective than two vertical vanes and that extended vane deflections significantly reduce the engine-out roll in hover.

  3. Characterizing the Galactic warp with Gaia - I. The tilted ring model with a twist

    NASA Astrophysics Data System (ADS)

    Abedi, Hoda; Mateu, Cecilia; Aguilar, Luis A.; Figueras, Francesca; Romero-Gómez, Mercè

    2014-08-01

    We explore the possibility of detecting and characterizing the warp of the stellar disc of our Galaxy using synthetic Gaia data. The availability of proper motions and, for the brightest stars radial velocities, adds a new dimension to this study. A family of Great Circle Cell Counts methods is used. They are ideally suited to find the tilt and twist of a collection of rings, which allow us to detect and measure the warp parameters. To test them, we use random realizations of test particles which evolve in a realistic Galactic potential warped adiabatically to various final configurations. In some cases a twist is introduced additionally. The Gaia selection function, its errors model and a realistic 3D extinction map are applied to mimic three tracer populations: OB, A and red clump stars. We show how the use of kinematics improves the accuracy in the recovery of the warp parameters. The OB stars are demonstrated to be the best tracers determining the tilt angle with accuracy better than ˜0.5 up to Galactocentric distance of ˜16 kpc. Using data with good astrometric quality, the same accuracy is obtained for A-type stars up to ˜13 kpc and for red clump up to the expected stellar cut-off. Using OB stars the twist angle is recovered to within <3° for all distances.

  4. A strategy for advancing tilt-rotor technology

    NASA Technical Reports Server (NTRS)

    Morlok, Edward K.; Schoendorfer, David L.

    1985-01-01

    Tilt-rotor technology has many features which make it a very promising development in aviation which might have application to a wide variety of transportation and logistics situations. However, aside from military applications and rather specialized industrial applications, little is known regarding the potential of tilt-rotor for commercial transportation and hence it is difficult to plan a development program which would gain support and be likely to produce a stream of significant benefits. The purpose is to attempt to provide some of this information in a manner that would be useful for preparing a strategy for development of tilt-rotor aircraft technology. Specifically, the objectives were: to identify promising paths of development and deployment of tilt-rotor aircraft technology in the air transportation system considering both benefits and disbenefits, and to identify any particular groups that are likely to benefit significantly and propose plans for gaining their support of research and development of this technology. Potential advantages of the tilt-rotor technology in the context of air transportation as a door-to-door system were identified, and then promising paths of development of such tilt-rotor systems were analyzed. These then lead to recommendations for specific studies, information dissemination and development of awareness of the tilt-rotor among specific transport-related groups.

  5. Performance Analysis of a Convection-Based Tilt Sensor

    NASA Astrophysics Data System (ADS)

    Ju Chan Choi,; Seong Ho Kong,

    2010-06-01

    This paper presents fabrication sequence and performance improving methods for convection-based tilt sensor. Also a packaging method to minimize the effect of environmental temperature fluctuation is proposed. Both electrolytic solution-based and air convection-based tilt sensors realized using micro-electro-mechanical-system (MEMS) technology have been previously reported by our research group. Although the MEMS-based electrolytic tilt sensor shows merited characteristics, such as wider operating tilt range, lower cost and compactness, compared to commercialized conventional electrolytic tilt sensors, it still suffers from metal electrode corrosion, electrolyte deterioration, surface tension of the electrolyte, and difficulty in packaging. In order to avoid those demerits, convective tilt sensor using air medium instead of electrolytic solution has been proposed and its fundamental performances has also been demonstrated in the previous works. In this paper, the effect of air medium condition on sensitivity of proposed convective tilt sensor has been investigated. In addition, a packaging method utilizing the Peltier device is presented to minimize environmental thermal effect without additional temperature compensation circuit. It is expected that this technique can be similarly applied to improve the performance and reliability of other sensors using gas media.

  6. Motion perception during tilt and translation after space flight

    NASA Astrophysics Data System (ADS)

    Clément, Gilles; Wood, Scott J.

    2013-11-01

    Preliminary results of an ongoing study examining the effects of space flight on astronauts' motion perception induced by independent tilt and translation motions are presented. This experiment used a sled and a variable radius centrifuge that translated the subjects forward-backward or laterally, and simultaneously tilted them in pitch or roll, respectively. Tests were performed on the ground prior to and immediately after landing. The astronauts were asked to report about their perceived motion in response to different combinations of body tilt and translation in darkness. Their ability to manually control their own orientation was also evaluated using a joystick with which they nulled out the perceived tilt while the sled and centrifuge were in motion. Preliminary results confirm that the magnitude of perceived tilt increased during static tilt in roll after space flight. A deterioration in the crewmember to control tilt using non-visual inertial cues was also observed post-flight. However, the use of a tactile prosthesis indicating the direction of down on the subject's trunk improved manual control performance both before and after space flight.

  7. The effects of dipole tilt on magnetotail structure and dynamics

    NASA Technical Reports Server (NTRS)

    Walker, Raymond J.; Ashour-Abdalla, Maha; Ogino, Tatsuki

    1989-01-01

    A three-dimensional time-dependent global magnetohydrodynamic (MHD) model of the interaction between the solar wind and the earth's magnetosphere has been used to study the effects of dipole tilt on the structure and dynamics of the magnetotail. The location of the tail neutral sheet shifts in the north-south direction following changes in the dipole tilt. When the northern edge of the geomagnetic dipole is tilted toward the sun (positive tilt), it is above the geocentric solar magnetosphere (GSM) equator, while for negative tilt, it is below. The neutral sheet forms an arc across the tail in the y-z plane for nonzero tilt. For positive tilt, the neutral sheet rises above the GSM equatorial plane near the noon-midnight meridian and returns to the equator near the magnetopause. The position and shape of the neutral sheet result from the requirement that the earthward magnetic flux equals the tailward flux and can be well explained by a simple analytical model.

  8. Sensitivity of optimum solutions to problem parameters

    NASA Technical Reports Server (NTRS)

    Sobieszczanski-Sobieski, J.; Barthelemy, J. F.; Ryan, K. M.

    1981-01-01

    Derivation of the sensitivity equations that yield the sensitivity derivatives directly, which avoids the costly and inaccurate perturb-and-reoptimize approach, is discussed and solvability of the equations is examined. The equations apply to optimum solutions obtained by direct search methods as well as those generated by procedures of the sequential unconstrained minimization technique class. Applications are discussed for the use of the sensitivity derivatives in extrapolation of the optimal objective function and design variable values for incremented parameters, optimization with multiple objectives, and decomposition of large optimization problems.

  9. Influence of Vibrotactile Feedback on Controlling Tilt Motion After Spaceflight

    NASA Technical Reports Server (NTRS)

    Wood, S. J.; Rupert, A. H.; Vanya, R. D.; Esteves, J. T.; Clement, G.

    2011-01-01

    We hypothesize that adaptive changes in how inertial cues from the vestibular system are integrated with other sensory information leads to perceptual disturbances and impaired manual control following transitions between gravity environments. The primary goals of this ongoing post-flight investigation are to quantify decrements in manual control of tilt motion following short-duration spaceflight and to evaluate vibrotactile feedback of tilt as a sensorimotor countermeasure. METHODS. Data is currently being collected on 9 astronaut subjects during 3 preflight sessions and during the first 8 days after Shuttle landings. Variable radius centrifugation (216 deg/s, <20 cm radius) in a darkened room is utilized to elicit otolith reflexes in the lateral plane without concordant canal or visual cues. A Tilt-Translation Sled (TTS) is capable of synchronizing pitch tilt with fore-aft translation to align the resultant gravitoinertial vector with the longitudinal body axis, thereby eliciting canal reflexes without concordant otolith or visual cues. A simple 4 tactor system was implemented to provide feedback when tilt position exceeded predetermined levels in either device. Closed-loop nulling tasks are performed during random tilt steps or sum-of-sines (TTS only) with and without vibrotactile feedback of chair position. RESULTS. On landing day the manual control performance without vibrotactile feedback was reduced by >30% based on the gain or the amount of tilt disturbance successfully nulled. Manual control performance tended to return to baseline levels within 1-2 days following landing. Root-mean-square position error and tilt velocity were significantly reduced with vibrotactile feedback. CONCLUSIONS. These preliminary results are consistent with our hypothesis that adaptive changes in vestibular processing corresponds to reduced manual control performance following G-transitions. A simple vibrotactile prosthesis improves the ability to null out tilt motion within a

  10. Strains and tilts on crustal blocks

    NASA Technical Reports Server (NTRS)

    Bilham, R. G.; Beavan, R. J.

    1979-01-01

    Geodetic work done over the past century is examined to investigate block motion in areas of intense tectonic deformation, with special attention to geodetic releveling data obtained for Japan. Problems in interpreting strainmeter and tiltmeter to study the behavior of crustal blocks and block boundaries are discussed. Block dimensions of 5 to 50 km seem to occur frequently in regions of intense tectonic activity. Block boundaries are often considerably weaker than contiguous crustal blocks, resulting in a concentration of strains at boundaries and decrease of strains within blocks. Block to block variations in tilt phase and magnitude are observed. There is some evidence that block boundaries may exhibit strain-dependent elastic properties or respond viscoelastically, possibly accounting for the slow transmission of tectonic deformation reported in Japan. If nonlinear behavior is characteristic of regions fragmented by crustal blocks, it will generally not be possible to apply a site correction factor based on the observed distortion of tidal or seismic strains in interpreting secular strains.

  11. Tilt-Sensitivity Analysis for Space Telescopes

    NASA Technical Reports Server (NTRS)

    Papalexandris, Miltiadis; Waluschka, Eugene

    2003-01-01

    A report discusses a computational-simulation study of phase-front propagation in the Laser Interferometer Space Antenna (LISA), in which space telescopes would transmit and receive metrological laser beams along 5-Gm interferometer arms. The main objective of the study was to determine the sensitivity of the average phase of a beam with respect to fluctuations in pointing of the beam. The simulations account for the effects of obscurations by a secondary mirror and its supporting struts in a telescope, and for the effects of optical imperfections (especially tilt) of a telescope. A significant innovation introduced in this study is a methodology, applicable to space telescopes in general, for predicting the effects of optical imperfections. This methodology involves a Monte Carlo simulation in which one generates many random wavefront distortions and studies their effects through computational simulations of propagation. Then one performs a statistical analysis of the results of the simulations and computes the functional relations among such important design parameters as the sizes of distortions and the mean value and the variance of the loss of performance. These functional relations provide information regarding position and orientation tolerances relevant to design and operation.

  12. Circuitry for Angle Measurements

    NASA Technical Reports Server (NTRS)

    Currie, J. R.; Kissel, R. R.

    1983-01-01

    Angle resolver pulsed and read under microprocessor control. Pulse generator excites resolver windings with dual slope pulse. System sequentially reads sine and cosine windings. Microprocessor determines angle through which resolver shaft turned from reference angle. Suitable applications include rate tables, antenna direction controllers, and machine tools.

  13. Preoperative posterior tilt of at least 20° increased the risk of fixation failure in Garden-I and -II femoral neck fractures

    PubMed Central

    Dolatowski, Filip C; Adampour, Mina; Frihagen, Frede; Stavem, Knut; Erik Utvåg, Stein; Hoelsbrekken, Sigurd Erik

    2016-01-01

    Background and purpose It has been suggested that preoperative posterior tilt of the femoral head may increase the risk of fixation failure in Garden-I and -II femoral neck fractures. To investigate this association, we studied a cohort of 322 such patients. Patients and methods Patients treated with internal fixation between 2005 and 2012 were retrospectively identified using hospital records and the digital image bank. 2 raters measured the preoperative posterior tilt angle and categorized it into 3 groups: < 10°, 10–20°, and ≥ 20°. The inter-rater reliability (IRR) was determined. Patients were observed until September 2013 (with a minimum follow-up of 18 months) or until failure of fixation necessitating salvage arthroplasty. The risk of fixation failure was assessed using competing-risk regression analysis, adjusting for time to surgery. Results Patients with a posterior tilt of ≥ 20° had a higher risk of fixation failure: 19% (8/43) as compared to 11% (14/127) in the 10–20° category and 6% (9/152) in the < 10° category (p = 0.03). Posterior tilt of ≥ 20° increased the risk of fixation failure, with an adjusted hazard ratio of 3.4 (95% CI: 1.3–8.9; p = 0.01). The interclass correlation coefficient for angular measurements of posterior tilt was 0.90 (95% CI: 0.87–0.92), and the IRR for the categorization of posterior tilt into 3 groups was 0.76 (95% CI: 0.69–0.81). Interpretation Preoperative posterior tilt of ≥ 20° in Garden-I and -II femoral neck fractures increased the risk of fixation failure necessitating salvage arthroplasty. The reliability of the methods that we used to measure posterior tilt ranged from good to excellent. PMID:26937557

  14. Preoperative posterior tilt of at least 20° increased the risk of fixation failure in Garden-I and -II femoral neck fractures.

    PubMed

    Dolatowski, Filip C; Adampour, Mina; Frihagen, Frede; Stavem, Knut; Erik Utvåg, Stein; Hoelsbrekken, Sigurd Erik

    2016-06-01

    Background and purpose - It has been suggested that preoperative posterior tilt of the femoral head may increase the risk of fixation failure in Garden-I and -II femoral neck fractures. To investigate this association, we studied a cohort of 322 such patients. Patients and methods - Patients treated with internal fixation between 2005 and 2012 were retrospectively identified using hospital records and the digital image bank. 2 raters measured the preoperative posterior tilt angle and categorized it into 3 groups: < 10°, 10-20°, and ≥ 20°. The inter-rater reliability (IRR) was determined. Patients were observed until September 2013 (with a minimum follow-up of 18 months) or until failure of fixation necessitating salvage arthroplasty. The risk of fixation failure was assessed using competing-risk regression analysis, adjusting for time to surgery. Results - Patients with a posterior tilt of ≥ 20° had a higher risk of fixation failure: 19% (8/43) as compared to 11% (14/127) in the 10-20° category and 6% (9/152) in the < 10° category (p = 0.03). Posterior tilt of ≥ 20° increased the risk of fixation failure, with an adjusted hazard ratio of 3.4 (95% CI: 1.3-8.9; p = 0.01). The interclass correlation coefficient for angular measurements of posterior tilt was 0.90 (95% CI: 0.87-0.92), and the IRR for the categorization of posterior tilt into 3 groups was 0.76 (95% CI: 0.69-0.81). Interpretation - Preoperative posterior tilt of ≥ 20° in Garden-I and -II femoral neck fractures increased the risk of fixation failure necessitating salvage arthroplasty. The reliability of the methods that we used to measure posterior tilt ranged from good to excellent. PMID:26937557

  15. Roll-Tilt Perception Using a Somatosensory Bar Task

    NASA Technical Reports Server (NTRS)

    Black, F. O.; Wade, S. W.; Arshi, A.

    1999-01-01

    Visual estimates of roll-tilt perception during static roll-tilt are confounded by an offset due to the ocular counterroll that simultaneously occurs. An alternative, non-visual ('somatosensory') measure of roll-tilt perception was developed which is not contaminated by this offset. The aims of this study were to determine: 1) inter-subject variability of somatosensory settings across test session in normal subjects and patients with unilateral or bilateral vestibular loss and 2) intra-subject variability of settings across test session in normal subjects.

  16. Fractional quantum Hall effect in a tilted magnetic field

    NASA Astrophysics Data System (ADS)

    Papić, Z.

    2013-06-01

    We discuss the orbital effect of a tilted magnetic field on the quantum Hall effect in parabolic quantum wells. Many-body states realized at the fractional (1)/(3) and (1)/(2) filling of the second electronic subband are studied using finite-size exact diagonalization. In both cases, we obtain the phase diagram consisting of a fractional quantum Hall fluid phase that persists for moderate tilts, and eventually undergoes a direct transition to the stripe phase. It is shown that tilting of the field probes the geometrical degree of freedom of fractional quantum Hall fluids, and can be partly related to the effect of band-mass anisotropy.

  17. Data correction for gantry-tilted local CT.

    PubMed

    Liang, Hongzhu; Zhang, Cishen; Yan, Ming

    2008-06-01

    The gantry-tilted helical cone-beam computed tomography (CT) has an inherent problem that the relative shift of the region of interest (ROI) blurs the reconstructed image. This problem becomes more serious in the gantry-tilted local CT imaging due to the nature of local scanning. This paper proposes a new method to improve the gantry-tilted local imaging by correcting the local scanning data. Computer simulations show that the proposed method can enhance the local imaging performance to a certain extent in terms of the image sharpening and artifacts reduction. PMID:18314308

  18. Compact and stress-released piston tip-tilt mirror

    NASA Astrophysics Data System (ADS)

    Noell, W.; Overstolz, T.; Stanley, R.; de Rooij, N. F.

    2006-04-01

    Devices based on SOI technology are subject to bow due to residual stress induced by the buried oxide. We have designed and fabricated a compact tunable piston tip-tilt mirror device in which the shape and the arrangement of the suspension beams result in both a reduced stress in the suspension beams and an optically flat mirror. The piston tip-tilt mirror is characterized by an accurate vertical displacement of up to 18 μm @ 80 V with good repeatability, and a tip-tilt of up to 2 mrad @ 50 V.

  19. Adaptive phase-locked fiber array with wavefront phase tip-tilt compensation using piezoelectric fiber positioners

    NASA Astrophysics Data System (ADS)

    Liu, Ling; Vorontsov, Mikhail A.; Polnau, Ernst; Weyrauch, Thomas; Beresnev, Leonid A.

    2007-09-01

    In this paper, we present the recent development of a conformal optical system with three adaptive phase-locked fiber elements. The coherent beam combining based on stochastic parallel gradient descent (SPGD) algorithm is investigated. We implement both phase-locking control and wavefront phase tip-tilt control in our conformal optical system. The phase-locking control is performed with fiber-coupled lithium niobate phase shifters which are modulated by an AVR micro-processor based SPGD controller. The perturbation rate of this SPGD controller is ~95,000 iterations per second. Phase-locking compensation bandwidth for phase distortion amplitude of 2π-radian phase shift is >100Hz. The tip-tilt control is realized with piezoelectric fiber positioners which are modulated by a computer-based software SPGD controller. The perturbation rate of the tip-tilt SPGD controller is up to ~950 iterations per second. The tip-tilt compensation bandwidth using fiber positioners is ~10Hz at 60-μrad. jitter swing angle.

  20. Optimum interface properties for metal matrix composites

    NASA Technical Reports Server (NTRS)

    Ghosn, Louis J.; Lerch, Bradley A.

    1989-01-01

    Due to the thermal expansion coefficient mismatch (CTE) between the fiber and the matrix, high residual sresses exist in metal matrix composite systems upon cool down from processing temperature to room temperature. An interface material can be placed between the fiber and the matrix to reduce the high tensile residual stresses in the matrix. A computer program was written to minimize the residual stress in the matrix subject to the interface material properties. The decision variables are the interface modulus, thickness and thermal expansion coefficient. The properties of the interface material are optimized such that the average distortion energy in the matrix and the interface is minimized. As a result, the only active variable is the thermal expansion coefficient. The optimum modulus of the interface is always the minimum allowable value and the interface thickness is always the maximum allowable value, independent of the fiber/matrix system. The optimum interface thermal expansion coefficient is always between the values of the fiber and the matrix. Using this analysis, a survey of materials was conducted for use as fiber coatings in some specific composite systems.

  1. New magic angle bumps and magic translation bumps

    SciTech Connect

    Seeman, J.

    1983-10-28

    SLC beams of opposite charge can be transversely deflected in the same direction by RF fields in the accelerating cavities caused by girder tilts, coupler-asymmetries, or manufacturing errors. A symmetric deflection can be corrected by a magic angle bump if the deflection is located adjacent to one of the linac quadrupoles. However, if the deflection is located between quadrupoles, two magic angle bumps or a magic angle bump and a magic translation bump are needed for the correction. Several examples of translation bumps are included. A new magic angle bump is also presented which is longitudinally compressed and has significantly reduced particle excursions. Finally, if new correctors are added midway along the girders so that the number of correctors are doubled, then the longitudinal extent and the maximum particle excursion of these new magic bumps can be further reduced.

  2. A simple instrument for measuring edge angles using a light sectioning method

    NASA Astrophysics Data System (ADS)

    Takatsuji, Toshiyuki; Kirita, Atsushi; Kurosawa, Tomizo

    1997-07-01

    A simple instrument for measuring edge angles is proposed, in which a light sectioning method is introduced. It has the advantage of simplicity, and consequently provides easy operation and an inexpensive instrument. A specimen is tilted in parallel planar laser beams. V-shaped lines are drawn by the laser beams on both sides of the specimen and are observed through a microscope. The tilt angle of the specimen can also be measured by the parallel planar laser beams. The edge angle can be calculated from the observed apex angle of the V-shaped lines and the tilt angle of the specimen. Measurement error factors are analysed and the measurement result is compensated. The measurement error of the instrument is estimated to be about 0957-0233/8/7/013/img1 an average and 0957-0233/8/7/013/img2 in variance after compensation. Although the instrument is capable of measuring the edge angles of many kinds of object, it is most suitable for measuring the edge angles of knives. The accuracy of this novel instrument may be sufficient for the quality control of knives.

  3. Advance in a nano-accuracy surface profiler with an extended-angle test range

    NASA Astrophysics Data System (ADS)

    Qian, Shinan; Qian, Kun; Idir, Mourad

    2013-05-01

    An advanced design of a nano-accuracy surface profiler (NSP) is introduced wherein we combined a scanning optical head with non-tilted reference system to facilitate measurements over an extended range of angles. The lateral motion of the beam during testing of a strongly curved mirror induces a systematic error. For a pencil-beam scanning profiler, the arm with varying optical-path lengths should be non-tilted so to eliminate the beam's lateral motion, and the arm for testing larger angles should be short and fixed so to reduce the beam's lateral motion. Our new scheme of having a non-tilted reference system offers an effective, simple, and convenient solution. A beam spot of 0.5-1 mm is used for higher spatial frequency tests in surface-figure measurements. Some preliminary studies and test are demonstrated.

  4. NASA Now: Engineering Design: Tilt Rotors, Aircraft of the Future

    NASA Video Gallery

    Meet Carl Russell, a research aerospace engineer who is working on developing new innovations for air travel. Russell discusses how tilt rotors work, including a demonstration on how rotors use Ber...

  5. Tilted pion sources from azimuthally sensitive HBT interferometry

    NASA Astrophysics Data System (ADS)

    Lisa, M. A.; Heinz, U.; Wiedemann, U. A.

    2000-09-01

    Intensity interferometry in noncentral heavy ion collisions provides access to novel information on the geometry of the effective pion-emitting source. We demonstrate analytically that, even for vanishing pair momentum, the cross terms Rol2 and Rsl2 of the HBT correlation function in general show a strong first harmonic in their azimuthal dependence. The strength of this oscillation characterizes the tilt of the major axis of the spatial emission ellipsoid away from the direction of the beam. Event generator studies indicate that this tilt can be large (/>20°) at AGS energies which makes it by far the most significant azimuthally sensitive HBT signal at these energies. Moreover, transport models suggest that for pions this spatial tilt is directed opposite to the tilt of the directed flow ellipsoid in momentum space. A measurement of the azimuthal dependence of the HBT cross terms Rol2 and Rsl2 thus probes directly the physical origin of directed pion flow.

  6. The modified Thomas test is not a valid measure of hip extension unless pelvic tilt is controlled.

    PubMed

    Vigotsky, Andrew D; Lehman, Gregory J; Beardsley, Chris; Contreras, Bret; Chung, Bryan; Feser, Erin H

    2016-01-01

    The modified Thomas test was developed to assess the presence of hip flexion contracture and to measure hip extensibility. Despite its widespread use, to the authors' knowledge, its criterion reference validity has not yet been investigated. The purpose of this study was to assess the criterion reference validity of the modified Thomas test for measuring peak hip extension angle and hip extension deficits, as defined by the hip not being able to extend to 0º, or neutral. Twenty-nine healthy college students (age = 22.00 ± 3.80 years; height = 1.71 ± 0.09 m; body mass = 70.00 ± 15.60 kg) were recruited for this study. Bland-Altman plots revealed poor validity for the modified Thomas test's ability to measure hip extension, which could not be explained by differences in hip flexion ability alone. The modified Thomas test displayed a sensitivity of 31.82% (95% CI [13.86-54.87]) and a specificity of 57.14% (95% CI [18.41-90.10]) for testing hip extension deficits. It appears, however, that by controlling pelvic tilt, much of this variance can be accounted for (r = 0.98). When pelvic tilt is not controlled, the modified Thomas test displays poor criterion reference validity and, as per previous studies, poor reliability. However, when pelvic tilt is controlled, the modified Thomas test appears to be a valid test for evaluating peak hip extension angle. PMID:27602291

  7. Displacement, distance, and shape measurements of fast-rotating rough objects by two mutually tilted interference fringe systems.

    PubMed

    Günther, Philipp; Kuschmierz, Robert; Pfister, Thorsten; Czarske, Jürgen W

    2013-05-01

    The precise distance measurement of fast-moving rough surfaces is important in several applications such as lathe monitoring. A nonincremental interferometer based on two mutually tilted interference fringe systems has been realized for this task. The distance is coded in the phase difference between the generated interference signals corresponding to the fringe systems. Large tilting angles between the interference fringe systems are necessary for a high sensitivity. However, due to the speckle effect at rough surfaces, different envelopes and phase jumps of the interference signals occur. At large tilting angles, these signals become dissimilar, resulting in a small correlation coefficient and a high measurement uncertainty. Based on a matching of illumination and receiving optics, the correlation coefficient and the phase difference estimation have been improved significantly. For axial displacement measurements of recurring rough surfaces, laterally moving with velocities of 5 m/s, an uncertainty of 110 nm has been attained. For nonrecurring surfaces, a distance measurement uncertainty of 830 nm has been achieved. Incorporating the additionally measured lateral velocity and the rotational speed, the two-dimensional shape of rotating objects results. Since the measurement uncertainty of the displacement, distance, and shape is nearly independent of the lateral surface velocity, this technique is predestined for fast-rotating objects, such as crankshafts, camshafts, vacuum pump shafts, or turning parts of lathes. PMID:23695313

  8. The modified Thomas test is not a valid measure of hip extension unless pelvic tilt is controlled

    PubMed Central

    Lehman, Gregory J.; Beardsley, Chris; Contreras, Bret; Chung, Bryan; Feser, Erin H.

    2016-01-01

    The modified Thomas test was developed to assess the presence of hip flexion contracture and to measure hip extensibility. Despite its widespread use, to the authors’ knowledge, its criterion reference validity has not yet been investigated. The purpose of this study was to assess the criterion reference validity of the modified Thomas test for measuring peak hip extension angle and hip extension deficits, as defined by the hip not being able to extend to 0º, or neutral. Twenty-nine healthy college students (age = 22.00 ± 3.80 years; height = 1.71 ± 0.09 m; body mass = 70.00 ± 15.60 kg) were recruited for this study. Bland–Altman plots revealed poor validity for the modified Thomas test’s ability to measure hip extension, which could not be explained by differences in hip flexion ability alone. The modified Thomas test displayed a sensitivity of 31.82% (95% CI [13.86–54.87]) and a specificity of 57.14% (95% CI [18.41–90.10]) for testing hip extension deficits. It appears, however, that by controlling pelvic tilt, much of this variance can be accounted for (r = 0.98). When pelvic tilt is not controlled, the modified Thomas test displays poor criterion reference validity and, as per previous studies, poor reliability. However, when pelvic tilt is controlled, the modified Thomas test appears to be a valid test for evaluating peak hip extension angle. PMID:27602291

  9. A New Higher-Order Composite Theory for Analysis and Design of High Speed Tilt-Rotor Blades

    NASA Technical Reports Server (NTRS)

    McCarthy, Thomas Robert

    1996-01-01

    A higher-order theory is developed to model composite box beams with arbitrary wall thicknesses. The theory, based on a refined displacement field, represents a three-dimensional model which approximates the elasticity solution. Therefore, the cross-sectional properties are not reduced to one-dimensional beam parameters. Both inplane and out-of-plane warping are automatically included in the formulation. The model accurately captures the transverse shear stresses through the thickness of each wall while satisfying all stress-free boundary conditions. Several numerical results are presented to validate the present theory. The developed theory is then used to model the load carrying member of a tilt-rotor blade which has thick-walled sections. The composite structural analysis is coupled with an aerodynamic analysis to compute the aeroelastic stability of the blade. Finally, a multidisciplinary optimization procedure is developed to improve the aerodynamic, structural and aeroelastic performance of the tilt-rotor aircraft. The Kreisselmeier-Steinhauser function is used to formulate the multiobjective function problem and a hybrid approximate analysis is used to reduce the computational effort. The optimum results are compared with the baseline values and show significant improvements in the overall performance of the tilt-rotor blade.

  10. Lens tilting effect on filamentation and filament-induced fluorescence

    NASA Astrophysics Data System (ADS)

    Kamali, Y.; Sun, Q.; Daigle, J.-F.; Azarm, A.; Bernhardt, J.; Chin, S. L.

    2009-03-01

    In filament-induced fluorescence spectroscopy, we experimentally found that if the lens used for the creation and localization of filament is tilted, the signal to noise ratio of spectral measurement increases. Further study shows that with lens tilting, astigmatism occurs and the filament is split into shorter parts. In turn the shortening of filament reduces the generation of white light which is the major 'noise' source of the spectra.

  11. Electrically Tilted Liquid Crystal Display Mode for High Speed Operation

    NASA Astrophysics Data System (ADS)

    Gwag, Jin Seog; Kim, Jae Chang; Yoon, Tae-Hoon

    2006-09-01

    To develop liquid crystal displays suitable for moving picture, a liquid crystal display mode having an electrically tilted phase is proposed. This is realized by initially having a tilted liquid crystal with low bias voltage. We found that its measured response time is in good agreement with numerical calculation obtained using the Erickson-Leslie equation. The falling times were smaller than 10 ms with conventional driving and 6 ms with overdriving.

  12. Littrow angle method to remove alignment errors in grating pulse compressors.

    PubMed

    Guardalben, M J

    2008-09-20

    An alignment method for pulse-compression gratings that obviates the need to place the gratings at normal incidence to remove grating-tip error is proposed. Grating-tip and groove-orientation errors are removed using two alignment wavelengths in a manner analogous to a laser-beam pointing and centering procedure entirely at the respective Littrow angles for the two wavelengths. By choosing wavelengths with Littrow angles close to the use angle of the grating, the residual tip and groove-orientation errors that may be introduced when the grating mount is tilted to its use angle are reduced. This method has greatly facilitated the alignment of the OMEGA Extended Performance (EP) large-aperture pulse compressors, thereby reducing residual pulse-front tilt caused by nonparallel gratings. OMEGA EP is a high-energy, petawatt-class laser at the University of Rochester's Laboratory for Laser Energetics. A numerical simulation of the alignment procedure is presented. PMID:18806858

  13. Littrow Angle Method to Remove Alignment Errors in Grating Pulse Compressors

    SciTech Connect

    Guardalben, M.J.

    2008-09-16

    An alignment method for pulse-compression gratings that obviates the need to place the gratings at normal incidence to remove grating-tip error is proposed. Grating-tip and groove-orientation errors are removed using two alignment wavelengths in a manner analogous to a laser-beam pointing and centering procedure entirely at the respective Littrow angles for the two wavelengths. By choosing wavelengths with Littrow angles close to the use angle of the grating, the residual tip and groove-orientation errors that may be introduced when the grating mount is tilted to its use angle are reduced. This method has greatly facilitated the alignment of the OMEGA Extended Performance (EP) large-aperture pulse compressors, thereby reducing residual pulse-front tilt caused by nonparallel gratings. OMEGA EP is a highenergy, petawatt-class laser at the University of Rochester’s Laboratory for Laser Energetics. A numerical simulation of the alignment procedure is presented.

  14. Littrow angle method to remove alignment errors in grating pulse compressors

    SciTech Connect

    Guardalben, M. J

    2008-09-20

    An alignment method for pulse-compression gratings that obviates the need to place the gratings at normal incidence to remove grating-tip error is proposed. Grating-tip and groove-orientation errors are removed using two alignment wavelengths in a manner analogous to a laser-beam pointing and centering procedure entirely at the respective Littrow angles for the two wavelengths. By choosing wavelengths with Littrow angles close to the use angle of the grating, the residual tip and groove-orientation errors that may be introduced when the grating mount is tilted to its use angle are reduced. This method has greatly facilitated the alignment of the OMEGA Extended Performance (EP) large-aperture pulse compressors, thereby reducing residual pulse-front tilt caused by nonparallel gratings. OMEGA EP is a high-energy, petawatt-class laser at the University of Rochester's Laboratory for Laser Energetics. A numerical simulation of the alignment procedure is presented.

  15. Optimum runway orientation relative to crosswinds

    NASA Technical Reports Server (NTRS)

    Falls, L. W.; Brown, S. C.

    1972-01-01

    Specific magnitudes of crosswinds may exist that could be constraints to the success of an aircraft mission such as the landing of the proposed space shuttle. A method is required to determine the orientation or azimuth of the proposed runway which will minimize the probability of certain critical crosswinds. Two procedures for obtaining the optimum runway orientation relative to minimizing a specified crosswind speed are described and illustrated with examples. The empirical procedure requires only hand calculations on an ordinary wind rose. The theoretical method utilizes wind statistics computed after the bivariate normal elliptical distribution is applied to a data sample of component winds. This method requires only the assumption that the wind components are bivariate normally distributed. This assumption seems to be reasonable. Studies are currently in progress for testing wind components for bivariate normality for various stations. The close agreement between the theoretical and empirical results for the example chosen substantiates the bivariate normal assumption.

  16. Optimum design of geodesically stiffened composite plates

    NASA Technical Reports Server (NTRS)

    Guerdal, Zafer; Phillips, John L.

    1988-01-01

    With the goal of tailorability in mind, the in-plane stiffness characteristics of a particular grid stiffened plate configuration under axial and shear loads have been studied. The contribution of the skin to the stiffener network and the resultant skin/rib interaction is analyzed. For the given plate geometry and loads, it is shown that an optimum configuration does exist. To achieve optimally designed practical plate configurations, buckling constraints need to be included in the design. Due to the complex geometry and loading of the plates, a simplified local buckling analysis of isolated stiffeners and triangular skin elements between the stiffeners is considered. Development of a stiffener buckling analysis represent stiffeners as shear deformable plate elements is presented.

  17. Optimum frequency assignment for satellite SCPC systems

    NASA Astrophysics Data System (ADS)

    Okinaka, H.; Yasuda, Y.; Hirata, Y.

    A technique for deriving a quasi-optimum solution for IM-minimum channel allocation for single-level SCPC systems is presented. Two types of IM products are considered as the dominant components in an RF band. The third order IM product is proportional to the product of the power of concerned carriers, allowing a weighting function to be defined for calculating the IM noise. An IM minimum channel allocation technique can then be used to reduce the IM noise occurring in the carrier slots through frequency assignment. The worst carrier is automatically deleted with an initial channel allocation and the process is iterated until the maximum noise reduction is obtained. The first two or three carriers are assigned to unused frequency slots with low noise. The method is also viable when dealing with a larger number of carriers.

  18. Experimental validation of tilt measurement technique with a laser beacon

    NASA Astrophysics Data System (ADS)

    Belen'kii, Mikhail S.; Karis, Stephen J.; Brown, James M.; Fugate, Robert Q.

    1999-09-01

    We have experimentally demonstrated for the first time a method for sensing wavefront tilt with a laser guide star (LGS). The tilt components of wavefronts were measured synchronously from the LGS using a telescope with 0.75 m effective aperture and from Polaris using a 1.5 m telescope. The Rayleigh guide star was formed at the altitude of 6 km and at a corresponding range of 10.5 km by projecting a focused beam at Polaris from the full aperture at the 1.5 m telescope. Both telescope mounts were unpowered and bottled down in place allowing us to substantially reduce the telescope vibration. The maximum value of the measured cross-correlation coefficient between the tilt for Polaris and the LGS is 0.71. The variations of the measured cross- correlation coefficient in the range from 0.22 to 0.71 are caused by turbulence at altitudes above 6 km, which was not sampled by the laser beacon, but affected the tilt for Polaris. It is also caused by the cone effect for turbulence below 6 km, residual mount jitter of the telescopes, and variations of the S/N. The experimental results support our concept of sensing atmospheric tilt by observing a LGS with an auxiliary telescope and indicate that this method is a possible solution for the tip-tilt problem.

  19. Age, splanchnic vasoconstriction, and heat stress during tilting

    NASA Technical Reports Server (NTRS)

    Minson, C. T.; Wladkowski, S. L.; Pawelczyk, J. A.; Kenney, W. L.

    1999-01-01

    During upright tilting, blood is translocated to the dependent veins of the legs and compensatory circulatory adjustments are necessary to maintain arterial pressure. For examination of the effect of age on these responses, seven young (23 +/- 1 yr) and seven older (70 +/- 3 yr) men were head-up tilted to 60 degrees in a thermoneutral condition and during passive heating with water-perfused suits. Measurements included heart rate (HR), cardiac output (Qc; acetylene rebreathing technique), central venous pressure (CVP), blood pressures, forearm blood flow (venous occlusion plethysmography), splanchnic and renal blood flows (indocyanine green and p-aminohippurate clearance), and esophageal and mean skin temperatures. In response to tilting in the thermoneutral condition, CVP and stroke volume decreased to a greater extent in the young men, but HR increased more, such that the fall in Qc was similar between the two groups in the upright posture. The rise in splanchnic vascular resistance (SVR) was greater in the older men, but the young men increased forearm vascular resistance (FVR) to a greater extent than the older men. The fall in Qc during combined heat stress and tilting was greater in the young compared with older men. Only four of the young men versus six of the older men were able to finish the second tilt without becoming presyncopal. In summary, the older men relied on a greater increase in SVR to compensate for a reduced ability to constrict the skin and muscle circulations (as determined by changes in FVR) during head-up tilting.

  20. Observational Signatures of Tilted Black Hole Accretion Disks from Simulations

    NASA Astrophysics Data System (ADS)

    Dexter, Jason; Fragile, P. Chris

    2011-03-01

    Geometrically thick accretion flows may be present in black hole X-ray binaries observed in the low/hard state and in low-luminosity active galactic nuclei. Unlike in geometrically thin disks, the angular momentum axis in these sources is not expected to align with the black hole spin axis. We compute images from three-dimensional general relativistic magnetohydrodynamic simulations of misaligned (tilted) accretion flows using relativistic radiative transfer and compare the estimated locations of the radiation edge with expectations from their aligned (untilted) counterparts. The radiation edge in the tilted simulations is independent of black hole spin for a tilt of 15°, in stark contrast to the results for untilted simulations, which agree with the monotonic dependence on spin expected from thin accretion disk theory. Synthetic emission line profiles from the tilted simulations depend strongly on the observer's azimuth and exhibit unique features such as broad "blue wings." Coupled with precession, the azimuthal variation could generate time fluctuations in observed emission lines, which would be a clear "signature" of a tilted accretion flow. Finally, we evaluate the possibility that the observed low- and high-frequency quasi-periodic oscillations (QPOs) from black hole binaries could be produced by misaligned accretion flows. Although low-frequency QPOs from precessing, tilted disks remains a viable option, we find little evidence for significant power in our light curves in the frequency range of high-frequency QPOs.

  1. Optimum design of ninety degree bends

    NASA Technical Reports Server (NTRS)

    Modi, Vijay; Cabuk, Hayri; Huan, Jian-Chun; Quadracci, Richard

    1992-01-01

    An algorithm for the optimum design of an internal flow component to obtain the maximum pressure rise is presented. Maximum pressure rise in a duct with simultaneous turning and diffusion is shown to be related to the control of flow separation on the passage walls. Such a flow is usually associated with downstream conditions that are desirable in turbomachinery and propulsion applications to ensure low loss and stable performance. The algorithm requires the solution of an 'adjoint' problem in addition to the 'direct' equations governing the flow in a body, which in the present analysis are assumed to be the laminar Navier-Stokes equations. The theoretical framework and computational algorithms presented in this study are for the steady Navier-Stokes equations. A procedure is developed for the numerical solution of the adjoint equations. This procedure is coupled with a direct solver in a design iteration loop, that provides a new shape with a higher pressure rise. This procedure is first validated for the design of optimum plane diffusers in two-dimensional flow. The direct Navier-Stokes and the 'adjoint' equations are solved using a finite volume formulation for spatial discretization in an artificial compressibility framework. A simplified version of the above approach is then utilized to design ninety degree diffusing bends. Calculations were carried out for a mean radius ratio at inlet of 2.5 and Reynolds numbers varying from 100 to 500. While at this stage laminar flows is assumed, it is shown that a similar approach can be conceived for turbulent flows.

  2. Angled Screw Channel: An Alternative to Cemented Single-Implant Restorations--Three Clinical Examples.

    PubMed

    Gjelvold, Björn; Sohrabi, Majid Melvin; Chrcanovic, Bruno Ramos

    2016-01-01

    This article presents three cases of single labially tilted implants restored with screw-retained single crowns. Individualized abutments with an angled screw channel were used to avoid an unesthetic vestibular access channel. This individualized abutment allows the dentist and dental technician to use the screw-retained restorations where a cemented reconstruction would otherwise have been needed. PMID:26757334

  3. Skin cooling maintains cerebral blood flow velocity and orthostatic tolerance during tilting in heated humans

    NASA Technical Reports Server (NTRS)

    Wilson, Thad E.; Cui, Jian; Zhang, Rong; Witkowski, Sarah; Crandall, Craig G.

    2002-01-01

    Orthostatic tolerance is reduced in the heat-stressed human. The purpose of this project was to identify whether skin-surface cooling improves orthostatic tolerance. Nine subjects were exposed to 10 min of 60 degrees head-up tilting in each of four conditions: normothermia (NT-tilt), heat stress (HT-tilt), normothermia plus skin-surface cooling 1 min before and throughout tilting (NT-tilt(cool)), and heat stress plus skin-surface cooling 1 min before and throughout tilting (HT-tilt(cool)). Heating and cooling were accomplished by perfusing 46 and 15 degrees C water, respectively, though a tube-lined suit worn by each subject. During HT-tilt, four of nine subjects developed presyncopal symptoms resulting in the termination of the tilt test. In contrast, no subject experienced presyncopal symptoms during NT-tilt, NT-tilt(cool), or HT-tilt(cool). During the HT-tilt procedure, mean arterial blood pressure (MAP) and cerebral blood flow velocity (CBFV) decreased. However, during HT-tilt(cool), MAP, total peripheral resistance, and CBFV were significantly greater relative to HT-tilt (all P < 0.01). No differences were observed in calculated cerebral vascular resistance between the four conditions. These data suggest that skin-surface cooling prevents the fall in CBFV during upright tilting and improves orthostatic tolerance, presumably via maintenance of MAP. Hence, skin-surface cooling may be a potent countermeasure to protect against orthostatic intolerance observed in heat-stressed humans.

  4. Expecting ankle tilts and wearing an ankle brace influence joint control in an imitated ankle sprain mechanism during walking.

    PubMed

    Gehring, Dominic; Wissler, Sabrina; Lohrer, Heinz; Nauck, Tanja; Gollhofer, Albert

    2014-03-01

    A thorough understanding of the functional aspects of ankle joint control is essential to developing effective injury prevention. It is of special interest to understand how neuromuscular control mechanisms and mechanical constraints stabilize the ankle joint. Therefore, the aim of the present study was to determine how expecting ankle tilts and the application of an ankle brace influence ankle joint control when imitating the ankle sprain mechanism during walking. Ankle kinematics and muscle activity were assessed in 17 healthy men. During gait rapid perturbations were applied using a trapdoor (tilting with 24° inversion and 15° plantarflexion). The subjects either knew that a perturbation would definitely occur (expected tilts) or there was only the possibility that a perturbation would occur (potential tilts). Both conditions were conducted with and without a semi-rigid ankle brace. Expecting perturbations led to an increased ankle eversion at foot contact, which was mediated by an altered muscle preactivation pattern. Moreover, the maximal inversion angle (-7%) and velocity (-4%), as well as the reactive muscle response were significantly reduced when the perturbation was expected. While wearing an ankle brace did not influence muscle preactivation nor the ankle kinematics before ground contact, it significantly reduced the maximal ankle inversion angle (-14%) and velocity (-11%) as well as reactive neuromuscular responses. The present findings reveal that expecting ankle inversion modifies neuromuscular joint control prior to landing. Although such motor control strategies are weaker in their magnitude compared with braces, they seem to assist ankle joint stabilization in a close-to-injury situation. PMID:24365326

  5. Extremely high resolution tip-tilt-piston mirror mechanism for the VLT-NAOS field selector

    NASA Astrophysics Data System (ADS)

    Spanoudakis, Peter; Zago, Lorenzo; Chetelat, O.; Gentsch, R.; Mato Mira, F.

    2000-07-01

    NAOS (Nasmyth Adaptive Optics System) is the adaptive optics system presently developed for the ESO VLT. The field selectors are to feed the NAOS wavefront sensor with the light coming from an appropriate reference source which can be up to 1 arcmin (on the sky) distant from the center of the field of view. A large input tip-tilt-piston mirror selects the required part of the field of view. A second active mirror redirects the selected field to the wavefront sensor. The displacement of both mirrors are synchronized. The NAOS Field Selector consists of two extremely accurate tip-tilt-piston mirror mechanisms controlled in closed loop. Each mechanism provides a mechanical angle amplitude of +/- 6 degrees with a resolution and mechanical stability of 0.42 arcsec rms over 20 minutes. This implies a dynamic range of 100,000 which requires an extremely accurate, very high resolution closed loop control. Both mirrors are made in SiC for low mass and inertia. The design configuration of the mechanism in based on three electromagnetic actuators 120 degrees apart with the mobile magnets mounted on flexure guides. The mirror is supported by a combination of flex pivots and a membrane for flexibility in tilt and high radial stiffness. All kinematic joints consist of flexure elements so that the mechanism is essentially frictionless. The control system is implemented on a VME bus operated with the VXWorks OS with high electrical resolution (>= 18-bit) AD and DA interface boards. The controller has been carefully designed to achieve the best overall performances, i.e., a very good noise rejection, and a relatively low settling time.

  6. Calf Venous Compliance in Supine Posture Equals that Measured with Head-up Tilt

    NASA Technical Reports Server (NTRS)

    Watenpaugh, Donald E.; Ballard, R. E.; Breit, G. A.; Bernauer, E. M.; Blomqvist, C. G.; Hargens, Alan R.

    1995-01-01

    Calf venous compliance is measured conventionally with venous occlusion, where compliance equals calf volume elevation per mmHg thigh occlusion pressure in relaxed legs of supine subjects. Compliance may also be measured during stepwise head-up tilt (HUT) as calf volume elevation per mmHg gravitational venous pressure elevation produced by HUT. Although HUT on a tilt table with a footplate activates calf muscles which could reduce compliance, this muscle activation is relatively small (less than or = 10% of maximal voluntary levels). Therefore, we hypothesized that calf compliance measured with HUT equals that measured with conventional supine venous occlusion. The venous occlusion protocol consisted of 20, 40, 60 and 80 mmHg thigh cuff inflations held for 1, 2, 3 and 4 min, respectively, in 14 supine subjects. One min of cuff deflation to 0 mmHg separated occlusions. Nine other subjects underwent HUT through the following angles held for 30s each: -12 deg., -6 deg., 0 deg., 12 deg., 30 deg., 54 deg., and 90 deg. HUT calf venous pressure data were interpolated from Katkov and Chestukhin; these data correspond to 70-80% of calculated calf venous pressure changes (pgh). Liquid metal-in-silastic strain gauges measured calf volume for both venous occlusion and HUT compliance. Relaxed calf compliance in supine subjects equaled 4.6 +/- 0.4 ml/mmHg (X +/- SE), as measured with venous occlusion. Calf compliance during HUT equaled 4.6 +/- 1.0 ml/mmHg. Therefore, calf compliance in supine, relaxed subjects equals that measured during head-up tilt. We conclude that the minimal calf muscle activation which occurs during HUT does not importantly affect calf compliance.

  7. Polymeric waveguide array with 45 degree slopes fabricated by bottom side tilted exposure

    NASA Astrophysics Data System (ADS)

    Lin, Xiaohui; Dou, Xinyuan; Wang, Alan X.; Chen, Ray T.

    2011-01-01

    This paper demonstrated a practical fabrication process of polymeric waveguide array (12 channels) with 50μm(W)×50μm(H)×23mm(L) dimension and mirror embedded 45° degree slopes for vertical coupling purpose. The entire process contained three main parts: a SU8 pre-mold with 45° slope, a PDMS mold and the final waveguide array device. The key step of fabricating the pre-mold included a bottom side tilted exposure of SU8 photo resist. By placing the sample upside down, tilting by 58.7° and immersing into DI water, the ultraviolet (UV) beam that shined vertically was directed to go through from the bottom of the glass substrate into top side SU8 resist with 45° angle to form the surface. This method was able to guarantee no-gap contact between the mask pattern and the photo resist when exposing. By comparing the process complexity and achieved structure of the top and bottom side exposure, the later was proved to be a promising method for making high quality tilted structure without any tailing effect. The reversed PDMS mold was then fabricated on the SU8 pre-mold. The PDMS mold was used to imprint the cladding layer of the waveguide array. After metal deposition, core filling and top cladding layer coating, the final polymeric waveguide array device was achieved. For performance evaluation, 850nm laser beam from VCSEL was modulated to 10Gbps signals and vertically coupled into the waveguide array. The eye diagrams revealed high Q factor when transmitting signals along these waveguide array.

  8. Ocean tide, Baltic Sea and atmospheric loading model tilt comparisons with interferometric geodynamic tilt observation - case study at Lohja2 geodynamic station, southern Finland

    NASA Astrophysics Data System (ADS)

    Ruotsalainen, H.; Nordman, M.; Virtanen, J.; Virtanen, H.

    2015-12-01

    Ocean loading models, Baltic Sea loading and atmospheric loading tilt models are compared with the long interferometric water level tilt meter recordings at the Lohja2 geodynamics laboratory in southern Finland. The tilt meter shows a high response to different loading phenomena, and it can be used to study earth dynamics, earth structure modeling, and 2D surface mass loading model validation. Special attention is paid on the Baltic Sea and atmospheric loading tilt oscillations. The four ocean loading models used show deviating values compared to the measured earth tide tilt parameters. The CSR4.0 ocean loading model fits best to analyzed tidal tilt observations at the site. After reductions of earth tides, ocean, the Baltic Sea and atmospheric loading tilt, the largest residual tilt signals are located in frequency bands below 0.5 cycle/day.

  9. Prior head-down tilt does not impair the cerebrovascular response to head-up tilt

    PubMed Central

    Yang, Changbin; Gao, Yuan; Greaves, Danielle K.; Villar, Rodrigo; Beltrame, Thomas; Fraser, Katelyn S.

    2015-01-01

    The hypothesis that cerebrovascular autoregulation was not impaired during head-up tilt (HUT) that followed brief exposures to varying degrees of prior head-down tilt (HDT) was tested in 10 healthy young men and women. Cerebral mean flow velocity (MFV) and cardiovascular responses were measured in transitions to a 60-s period of 75° HUT that followed supine rest (control) or 15 s HDT at −10°, −25°, and −55°. During HDT, heart rate (HR) was reduced for −25° and −55°, and cardiac output was lower at −55° HDT. MFV increased during −10° HDT, but not in the other conditions even though blood pressure at the middle cerebral artery (BPMCA) increased. On the transition to HUT, HR increased only for −55° condition, but stroke volume and cardiac output transiently increased for −25° and −55°. Total peripheral resistance index decreased in proportion to the magnitude of HDT and recovered over the first 20 s of HUT. MFV was significantly less in all HDT conditions compared with the control in the first 5-s period of HUT, but it recovered quickly. An autoregulation correction index derived from MFV recovery relative to BPMCA decline revealed a delay in the first 5 s for prior HDT compared with control but then a rapid increase to briefly exceed control after −55° HDT. This study showed that cerebrovascular autoregulation is modified by but not impaired by brief HDT prior to HUT and that cerebral MFV recovered quickly and more rapidly than arterial blood pressure to protect against cerebral hypoperfusion and potential syncope. PMID:25749443

  10. Solar angle reference manual

    SciTech Connect

    Sibson, R.

    1983-01-01

    The introduction is the only text in the volume; the rest of the book contains easy-to-use graphical methods for building design and construction using solar energy. Isogonic charts and solar angle diagrams are included. Isogonic charts. Solar angle diagrams.

  11. Reading Angles in Maps

    ERIC Educational Resources Information Center

    Izard, Véronique; O'Donnell, Evan; Spelke, Elizabeth S.

    2014-01-01

    Preschool children can navigate by simple geometric maps of the environment, but the nature of the geometric relations they use in map reading remains unclear. Here, children were tested specifically on their sensitivity to angle. Forty-eight children (age 47:15-53:30 months) were presented with fragments of geometric maps, in which angle sections…

  12. Tilt measurement and compensation algorithm for holographic data storage with optimized quadratic windows

    NASA Astrophysics Data System (ADS)

    Son, Kyungchan; Lim, Sung-Yong; Lee, Jae-seong; Jeong, Wooyoung; Yang, Hyunseok

    2016-09-01

    In holographic data storage, tilt is one of the critical disturbances. There are two types of tilt: tangential and radial. In real systems, tangential and radial tilt occur simultaneously. Thus, it is difficult to measure and compensate for tilt. In this study, using a quadratic window, which compares the intensity of a certain area, a tilt error signal was generated and compensated for with the proposed algorithm. The compensated image obtained satisfied a 0.3 dB tolerance.

  13. A high-accuracy roundness measurement for cylindrical components by a morphological filter considering eccentricity, probe offset, tip head radius and tilt error

    NASA Astrophysics Data System (ADS)

    Sun, Chuanzhi; Wang, Lei; Tan, Jiubin; Zhao, Bo; Zhou, Tong; Kuang, Ye

    2016-08-01

    A morphological filter is proposed to obtain a high-accuracy roundness measurement based on the four-parameter roundness measurement model, which takes into account eccentricity, probe offset, probe tip head radius and tilt error. This paper analyses the sample angle deviations caused by the four systematic errors to design a morphological filter based on the distribution of the sample angle. The effectiveness of the proposed method is verified through simulations and experiments performed with a roundness measuring machine. Compared to the morphological filter with the uniform sample angle, the accuracy of the roundness measurement can be increased by approximately 0.09 μm using the morphological filter with a non-uniform sample angle based on the four-parameter roundness measurement model, when eccentricity is above 16 μm, probe offset is approximately 1000 μm, tilt error is approximately 1″, the probe tip head radius is 1 mm and the cylindrical component radius is approximately 37 mm. The accuracy and reliability of roundness measurements are improved by using the proposed method for cylindrical components with a small radius, especially if the eccentricity and probe offset are large, and the tilt error and probe tip head radius are small. The proposed morphological filter method can be used for precision and ultra-precision roundness measurements, especially for functional assessments of roundness profiles.

  14. Designing from minimum to optimum functionality

    NASA Astrophysics Data System (ADS)

    Bannova, Olga; Bell, Larry

    2011-04-01

    This paper discusses a multifaceted strategy to link NASA Minimal Functionality Habitable Element (MFHE) requirements to a compatible growth plan; leading forward to evolutionary, deployable habitats including outpost development stages. The discussion begins by reviewing fundamental geometric features inherent in small scale, vertical and horizontal, pressurized module configuration options to characterize applicability to meet stringent MFHE constraints. A proposed scenario to incorporate a vertical core MFHE concept into an expanded architecture to provide continuity of structural form and a logical path from "minimum" to "optimum" design of a habitable module. The paper describes how habitation and logistics accommodations could be pre-integrated into a common Hab/Log Module that serves both habitation and logistics functions. This is offered as a means to reduce unnecessary redundant development costs and to avoid EVA-intensive on-site adaptation and retrofitting requirements for augmented crew capacity. An evolutionary version of the hard shell Hab/Log design would have an expandable middle section to afford larger living and working accommodations. In conclusion, the paper illustrates that a number of cargo missions referenced for NASA's 4.0.0 Lunar Campaign Scenario could be eliminated altogether to expedite progress and reduce budgets. The plan concludes with a vertical growth geometry that provides versatile and efficient site development opportunities using a combination of hard Hab/Log modules and a hybrid expandable "CLAM" (Crew Lunar Accommodations Module) element.

  15. Optimum nutrition: thiamin, biotin and pantothenate.

    PubMed

    Bender, D A

    1999-05-01

    The metabolism of glucose is deranged in thiamin deficiency, but once any deficiency has been corrected there is no further effect of increased thiamin intake on the ability to metabolize glucose through either pyruvate dehydrogenase (EC 1.2.4.1) and the citric acid cycle, or the pentose phosphate pathway, in which transketolase (EC 2.2.1.1) is the thiamin-dependent step. It has been suggested that the Wernicke-Korsakoff syndrome is associated with a genetic variant of transketolase which requires a higher than normal concentration of thiamin diphosphate for activity. This finding would suggest that there may be a group of the population who have a higher than average requirement for thiamin, but the evidence is not convincing. There are no estimates of biotin requirements, but either coenzyme saturation of erythrocyte pyruvate carboxylase, or the excretion of 3-hydroxy-isovalerate (perhaps after a test dose of leucine) could be used to assess requirements in depletion-repletion studies. Biotin deficiency leads to impaired glucose tolerance, but it is unlikely that glucose tolerance could be used to assess optimum biotin status, since other more common factors affect glucose tolerance to a greater extent. Plasma triacylglycerol and nonesterified fatty acids are moderately elevated in pantothenic acid deficiency. However, this is unlikely to be useful in assessing pantothenate status, since again, other more common factors affect plasma lipids. To date there are no biochemical indices of adequate pantothenate nutrition, and no estimates of requirements. PMID:10466187

  16. Optimum coding techniques for MST radars

    NASA Technical Reports Server (NTRS)

    Sulzer, M. P.; Woodman, R. F.

    1986-01-01

    The optimum coding technique for MST (mesosphere stratosphere troposphere) radars is that which gives the lowest possible sidelobes in practice and can be implemented without too much computing power. Coding techniques are described in Farley (1985). A technique mentioned briefly there but not fully developed and not in general use is discussed here. This is decoding by means of a filter which is not matched to the transmitted waveform, in order to reduce sidelobes below the level obtained with a matched filter. This is the first part of the technique discussed here; the second part consists of measuring the transmitted waveform and using it as the basis for the decoding filter, thus reducing errors due to imperfections in the transmitter. There are two limitations to this technique. The first is a small loss in signal to noise ratio (SNR), which usually is not significant. The second problem is related to incomplete information received at the lowest ranges. An appendix shows a technique for handling this problem. Finally, it is shown that the use of complementary codes on transmission and nonmatched decoding gives the lowest possible sidelobe level and the minimum loss in SNR due to mismatch.

  17. Optimum harvest maturity for Leymus chinensis seed

    PubMed Central

    Lin, Jixiang; Wang, Yingnan; Qi, Mingming; Li, Xiaoyu; Yang, Chunxue; Wang, Yongcui

    2016-01-01

    ABSTRACT Timely harvest is critical to achieve maximum seed viability and vigour in agricultural production. However, little information exists concerning how to reap the best quality seeds of Leymus chinensis, which is the dominant and most promising grass species in the Songnen Grassland of Northern China. The objective of this study was to investigate and evaluate possible quality indices of the seeds at different days after peak anthesis. Seed quality at different development stages was assessed by the colours of the seed and lemmas, seed weight, moisture content, electrical conductivity of seed leachate and germination indices. Two consecutive years of experimental results showed that the maximum seed quality was recorded at 39 days after peak anthesis. At this date, the colours of the seed and lemmas reached heavy brown and yellow, respectively. The seed weight was highest and the moisture content and the electrical conductivity of seed leachate were lowest. In addition, the seed also reached its maximum germination percentage and energy at this stage, determined using a standard germination test (SGT) and accelerated ageing test (AAT). Thus, Leymus chinensis can be harvested at 39 days after peak anthesis based on the changes in parameters. Colour identification can be used as an additional indicator to provide a more rapid and reliable measure of optimum seed maturity; approximately 10 days after the colour of the lemmas reached yellow and the colour of the seed reached heavy brown, the seed of this species was suitable for harvest. PMID:27170257

  18. Improve filtration for optimum equipment reliability

    SciTech Connect

    Cervera, S.M.

    1996-01-01

    The introduction 20 years ago of the American Petroleum Institute Standard API-614 as a purchase specification for lubrication, shaft sealing and control oil systems, had a considerable impact and did much to improve system reliability at that time. Today, however, these recommendations regarding filter rating and flushing cleanliness are outdated. Much research in the tribology field correlates clearance size particulate contamination with accelerated component wear, fatigue and performance degradation. Some of these studies demonstrate that by decreasing the population of clearance size particulate in lubrication oils, component life increases exponentially. Knowing the dynamic clearances of a piece of machinery makes it possible, using the ISO 4406 Cleanliness Code, to determine what cleanliness level will minimize contamination-related component wear/fatigue and thus help optimize machinery performance and reliability. Data obtained by the author through random sampling of rotating equipment lube and seal oil systems indicate that the API-614 standard, as it pertains to filtration and flushing, is insufficient to ensure that particulate contamination is maintained to within the levels necessary to achieve optimum equipment reliability and safety, without increasing operating cost. Adopting and practicing the guidelines presented should result in the following benefits: (1) the frequency of bearing, oil pump, mechanical seal, fluid coupling, gearbox and hydraulic control valve failures would be minimized; (2) the mean time between planned maintenance (MTBPM) would be increased. The result will be a substantial increase in safety and cost savings to the operator.

  19. Optimum deposition conditions of ultrasmooth silver nanolayers

    PubMed Central

    2014-01-01

    Reduction of surface plasmon-polariton losses due to their scattering on metal surface roughness still remains a challenge in the fabrication of plasmonic devices for nanooptics. To achieve smooth silver films, we study the dependence of surface roughness on the evaporation temperature in a physical vapor deposition process. At the deposition temperature range 90 to 500 K, the mismatch of thermal expansion coefficients of Ag, Ge wetting layer, and sapphire substrate does not deteriorate the metal surface. To avoid ice crystal formation on substrates, the working temperature of the whole physical vapor deposition process should exceed that of the sublimation at the evaporation pressure range. At optimum room temperature, the root-mean-square (RMS) surface roughness was successfully reduced to 0.2 nm for a 10-nm Ag layer on sapphire substrate with a 1-nm germanium wetting interlayer. Silver layers of 10- and 30-nm thickness were examined using an atomic force microscope (AFM), X-ray reflectometry (XRR), and two-dimensional X-ray diffraction (XRD2). PACS 63.22.Np Layered systems; 68. Surfaces and interfaces; thin films and nanosystems (structure and nonelectronic properties); 81.07.-b Nanoscale materials and structures: fabrication and characterization PMID:24685115

  20. Optimum harvest maturity for Leymus chinensis seed.

    PubMed

    Lin, Jixiang; Wang, Yingnan; Qi, Mingming; Li, Xiaoyu; Yang, Chunxue; Wang, Yongcui; Mu, Chunsheng

    2016-01-01

    Timely harvest is critical to achieve maximum seed viability and vigour in agricultural production. However, little information exists concerning how to reap the best quality seeds of Leymus chinensis, which is the dominant and most promising grass species in the Songnen Grassland of Northern China. The objective of this study was to investigate and evaluate possible quality indices of the seeds at different days after peak anthesis. Seed quality at different development stages was assessed by the colours of the seed and lemmas, seed weight, moisture content, electrical conductivity of seed leachate and germination indices. Two consecutive years of experimental results showed that the maximum seed quality was recorded at 39 days after peak anthesis. At this date, the colours of the seed and lemmas reached heavy brown and yellow, respectively. The seed weight was highest and the moisture content and the electrical conductivity of seed leachate were lowest. In addition, the seed also reached its maximum germination percentage and energy at this stage, determined using a standard germination test (SGT) and accelerated ageing test (AAT). Thus, Leymus chinensis can be harvested at 39 days after peak anthesis based on the changes in parameters. Colour identification can be used as an additional indicator to provide a more rapid and reliable measure of optimum seed maturity; approximately 10 days after the colour of the lemmas reached yellow and the colour of the seed reached heavy brown, the seed of this species was suitable for harvest. PMID:27170257

  1. Nutations of sunflower seedlings on tilted clinostats

    NASA Technical Reports Server (NTRS)

    Brown, A. H.; Chapman, D. K.

    1977-01-01

    The kinetics of hypocotyl nutations in Helianthus annuus L. were measured on plants which were rotated on clinostats with axes of rotation inclined at various angles, alpha, away from the vertical. The g-force component acting in the direction of the plant axis was taken as g cos alpha. The average period and average amplitude of nutation were constant for all such axially directed g-forces between 1.0 and 0.2 g (vertical to about 80 inclination). On the horizontal clinostat (90 inclination) nutation was neither initiated nor sustained. The g-force just sufficient fully to activate nutational oscillations should be sought for g-force parameter values ranging from 0 to 0.2.

  2. Structural Setting of the Northeastern Biga Peninsula (Turkey) from Tilt Derivatives of Gravity Gradient Tensors and Magnitude of Horizontal Gravity Components

    NASA Astrophysics Data System (ADS)

    Oruç, B.; Keskinsezer, A.

    2008-10-01

    The tilt derivatives (or angles) are determined using the gravity gradient tensors (GGT) from two horizontal components (Gx, Gy) and vertical component (Gz), and the magnitude of the horizontal components (MHC). We show that the tilt derivatives from GGT and MHC are highly suitable for mapping linear geological structures or edges of target geology. The results obtained from theoretical data, with and without random noise, have been analyzed in this study. The tilt derivatives from GGT and MHC allow imaging the horizontal boundaries of gravity sources with a high resolution and show an improvement performance as edge detectors since they are ultra sensitive for detecting source boundaries. The tilt derivatives from GGT and MHC over the northeast of the Biga Peninsula in northwestern, Turkey are interpreted to image the edges of geological structures. Tilt derivatives provide a quick method which works well to obtain a detailed structural image of the complex area, with the most precision. The results indicate that the most predominant structural trends are in a NE-SW direction. Therefore, a good correspondence is recognized between structures well known by surface geology and many other lineaments which are unknown or only partially known.

  3. Adapting Tilt Corrections and the Governing Flow Equations for Steep, Fully Three-Dimensional, Mountainous Terrain

    NASA Astrophysics Data System (ADS)

    Oldroyd, Holly J.; Pardyjak, Eric R.; Huwald, Hendrik; Parlange, Marc B.

    2016-06-01

    In recent studies of atmospheric turbulent surface exchange in complex terrain, questions arise concerning velocity-sensor tilt corrections and the governing flow equations for coordinate systems aligned with steep slopes. The standard planar-fit method, a popular tilt-correction technique, must be modified when applied to complex mountainous terrain. The ramifications of these adaptations have not previously been fully explored. Here, we carefully evaluate the impacts of the selection of sector size (the range of flow angles admitted for analysis) and planar-fit averaging time. We offer a methodology for determining an optimized sector-wise planar fit (SPF), and evaluate the sensitivity of momentum fluxes to varying these SPF input parameters. Additionally, we clarify discrepancies in the governing flow equations for slope-aligned coordinate systems that arise in the buoyancy terms due to the gravitational vector no longer acting along a coordinate axis. New adaptions to the momentum equations and turbulence kinetic energy budget equation allow for the proper treatment of the buoyancy terms for purely upslope or downslope flows, and for slope flows having a cross-slope component. Field data show that new terms in the slope-aligned forms of the governing flow equations can be significant and should not be omitted. Since the optimized SPF and the proper alignment of buoyancy terms in the governing flow equations both affect turbulent fluxes, these results hold implications for similarity theory or budget analyses for which accurate flux estimates are important.

  4. Single-cell diffraction tomography with optofluidic rotation about a tilted axis

    NASA Astrophysics Data System (ADS)

    Müller, Paul; Schürmann, Mirjam; Chan, Chii J.; Guck, Jochen

    2015-08-01

    Optical diffraction tomography (ODT) is a tomographic technique that can be used to measure the three-dimensional (3D) refractive index distribution within living cells without the requirement of any marker. In principle, ODT can be regarded as a generalization of optical projection tomography which is equivalent to computerized tomography (CT). Both optical tomographic techniques require projection-phase images of cells measured at multiple angles. However, the reconstruction of the 3D refractive index distribution post-measurement differs for the two techniques. It is known that ODT yields better results than projection tomography, because it takes into account diffraction of the imaging light due to the refractive index structure of the sample. Here, we apply ODT to biological cells in a microfluidic chip which combines optical trapping and microfluidic flow to achieve an optofluidic single-cell rotation. In particular, we address the problem that arises when the trapped cell is not rotating about an axis perpendicular to the imaging plane, but is instead arbitrarily tilted. In this paper we show that the 3D reconstruction can be improved by taking into account such a tilted rotational axis in the reconstruction process.

  5. THE TRANSIT INGRESS AND THE TILTED ORBIT OF THE EXTRAORDINARILY ECCENTRIC EXOPLANET HD 80606b

    SciTech Connect

    Winn, Joshua N.; Howard, Andrew W.; Marcy, Geoffrey W.; Johnson, John Asher; Gazak, J. Zachary; Starkey, Donn; Ford, Eric B.; Colon, Knicole D.; Reyes, Francisco; Nortmann, Lisa; Dreizler, Stefan; Odewahn, Stephen; Welsh, William F.; Kadakia, Shimonee; Vanderbei, Robert J.; Adams, Elisabeth R.; Lockhart, Matthew; Crossfield, Ian J.; Valenti, Jeff A.; Dantowitz, Ronald

    2009-10-01

    We present the results of a transcontinental campaign to observe the 2009 June 5 transit of the exoplanet HD 80606b. We report the first detection of the transit ingress, revealing the transit duration to be 11.64 +- 0.25 hr and allowing more robust determinations of the system parameters. Keck spectra obtained at midtransit exhibit an anomalous blueshift, giving definitive evidence that the stellar spin axis and planetary orbital axis are misaligned. The Keck data show that the projected spin-orbit angle lambda is between 32 deg. and 87 deg. with 68.3% confidence and between 14 deg. and 142 deg. with 99.73% confidence. Thus, the orbit of this planet is not only highly eccentric (e = 0.93) but is also tilted away from the equatorial plane of its parent star. A large tilt had been predicted, based on the idea that the planet's eccentric orbit was caused by the Kozai mechanism. Independently of the theory, it is worth noting that all three exoplanetary systems with known spin-orbit misalignments have massive planets on eccentric orbits, suggesting that those systems migrate through a different channel than lower mass planets on circular orbits.

  6. Proto-CIRCUS tilted-coil tokamak-torsatron hybrid: design and construction

    NASA Astrophysics Data System (ADS)

    Doumet, M.; Israeli, B. Y.; Hammond, K. C.; Sweeney, R. M.; Volpe, F. A.; Spong, D. A.; Clark, A. W.; Kornbluth, Y.

    2014-10-01

    An innovative magnetic confinement concept is based on a toroidal configuration in which the toroidal field coils are tilted and interlinked with each other. Field line tracing and equilibrium calculations suggest that this configuration can generate rotational transform with lower plasma current and exhibit less effective magnetic ripple than tokamaks of comparable size. These properties may have interesting implications for disruptions and steady-state operation. Proto-CIRCUS is a tabletop device recently constructed at Columbia University to test this concept. It features six interlocked coils with independently adjustable radial positions and tilt angles. Plasmas will have major and minor radii of approximately 16 cm and 5 cm, respectively. Start-up, heating and current drive will initially rely on 2.45 GHz electron cyclotron waves. Here we describe the design and construction of the device and present the results of numerical optimizations aimed at minimizing the required plasma current. Flux surface measurements will confirm whether this relatively simple concept can generate the expected rotational transform.

  7. The two-dimensional array of 2048 tilting micromirrors for astronomical spectroscopy

    NASA Astrophysics Data System (ADS)

    Canonica, M. D.; Zamkotsian, F.; Lanzoni, P.; Noell, W.; de Rooij, N.

    2013-05-01

    In multi-object spectrometers, field selectors, which are located in the focal plane of the telescopes, are required for the selection of astronomical objects, such as stars or faint galaxies. We present a two-dimensional micromirror array as a field selector. Object selection is achieved through the precise tilting of micromirrors, which reflect the light of objects toward the spectrometer. These arrays were composed of 2048 (32 × 64) electrostatically actuated silicon micromirrors that measured 100 × 200 μm2. The micromirrors were addressed either by lines or individually using a line-column addressing scheme. The fabrication process of these devices involved three wafers and two wafer-level bondings. Characterization, by white light interferometry, revealed a tilt angle of 25° at a voltage of 121 V, and a coated micromirror deformation below 10 nm. A fill factor of 82% and a contrast of 1000:1 were also observed. Demonstration of the line-column addressing scheme was achieved through its application to a sub-array of 2 × 2 micromirrors.

  8. A study on difference and importance of sacral slope and pelvic sacral angle that affect lumbar curvature.

    PubMed

    Choi, Seyoung; Lee, Minsun; Kwon, Byongan

    2014-01-01

    Individual pelvic sacral angle was measured, compared and analyzed for the 6 male and female adults who were diagnosed with lumbar spinal stenosis, foraminal stenosis and mild spondylolisthesis in accordance with spinal parameters, pelvic parameters and occlusion state of sacroiliac joint presented by the author of this thesis based on the fact that the degree of lumbar excessive lordosis that was one of the causes for lumbar pain was determined by sacral slope. The measured values were compared with the standard values of the average normal range from 20 s to 40 s of normal Koreans stated in the study on the change in lumbar lordosis angle, lumbosacral angle and sacral slope in accordance with the age by Oh et al. [5] and sacral slope and pelvic sacral slope of each individual of the subjects for measurement were compared. Comparing the difference between the two tilt angles possessed by an individual is a comparison to determine how much the sacroiliac joint connecting pelvis and sacral vertebrae compensated and corrected the sacral vertebrae slope by pelvic tilt under the condition of synarthrodial joint.Under the condition that the location conforming to the line in which the sagittal line of gravity connects with pelvic ASIS and pubic pubic tuberele is the neutral location of pelvic tilt, sacral slope being greater than pelvic sacral slope means pelvic anterior tilting, whereas sacral slope being smaller than pelvic sacral slope means pelvic posterior tilting. On that account, male B, female A and female C had a pelvic posterior tilting of 16 degrees, 1 degree and 5 degrees respectively, whereas male A, male C and female B had a pelvic anterior tilting of 3 degrees, 9 degrees and 4 degrees respectively. In addition, the 6 patients the values of lumbar lordosis angle, lumbosacral angle and sacral slope that were almost twice as much as the normal standard values of Koreans. It is believed that this is because the pelvic sacral slope maintaining an angle that is

  9. Simulation and optimum design of hybrid solar-wind and solar-wind-diesel power generation systems

    NASA Astrophysics Data System (ADS)

    Zhou, Wei

    Solar and wind energy systems are considered as promising power generating sources due to its availability and topological advantages in local power generations. However, a drawback, common to solar and wind options, is their unpredictable nature and dependence on weather changes, both of these energy systems would have to be oversized to make them completely reliable. Fortunately, the problems caused by variable nature of these resources can be partially overcome by integrating these two resources in a proper combination to form a hybrid system. However, with the increased complexity in comparison with single energy systems, optimum design of hybrid system becomes more complicated. In order to efficiently and economically utilize the renewable energy resources, one optimal sizing method is necessary. This thesis developed an optimal sizing method to find the global optimum configuration of stand-alone hybrid (both solar-wind and solar-wind-diesel) power generation systems. By using Genetic Algorithm (GA), the optimal sizing method was developed to calculate the system optimum configuration which offers to guarantee the lowest investment with full use of the PV array, wind turbine and battery bank. For the hybrid solar-wind system, the optimal sizing method is developed based on the Loss of Power Supply Probability (LPSP) and the Annualized Cost of System (ACS) concepts. The optimization procedure aims to find the configuration that yields the best compromise between the two considered objectives: LPSP and ACS. The decision variables, which need to be optimized in the optimization process, are the PV module capacity, wind turbine capacity, battery capacity, PV module slope angle and wind turbine installation height. For the hybrid solar-wind-diesel system, minimization of the system cost is achieved not only by selecting an appropriate system configuration, but also by finding a suitable control strategy (starting and stopping point) of the diesel generator. The

  10. Prediction of noise constrained optimum takeoff procedures

    NASA Technical Reports Server (NTRS)

    Padula, S. L.

    1980-01-01

    An optimization method is used to predict safe, maximum-performance takeoff procedures which satisfy noise constraints at multiple observer locations. The takeoff flight is represented by two-degree-of-freedom dynamical equations with aircraft angle-of-attack and engine power setting as control functions. The engine thrust, mass flow and noise source parameters are assumed to be given functions of the engine power setting and aircraft Mach number. Effective Perceived Noise Levels at the observers are treated as functionals of the control functions. The method is demonstrated by applying it to an Advanced Supersonic Transport aircraft design. The results indicate that automated takeoff procedures (continuously varying controls) can be used to significantly reduce community and certification noise without jeopardizing safety or degrading performance.

  11. Optimum wavelengths for two color ranging

    NASA Technical Reports Server (NTRS)

    Degnan, John J.

    1993-01-01

    The range uncertainties associated with the refractive atmosphere can be mitigated by the technique of two color, or dual wavelength, ranging. The precision of the differential time of flight (DTOF) measurement depends on the atmospheric dispersion between the two wavelengths, the received pulsewidths and photoelectron counts, and on the amount of temporal averaging. In general, the transmitted wavelengths are not independently chosen but instead are generated via nonlinear optics techniques (harmonic crystals, Raman scattering, etc.) which also determine their relative pulsewidths. The mean received photoelectrons at each wavelength are calculated via the familiar radar link equation which contains several wavelength dependent parameters. By collecting the various wavelength dependent terms, one can define a wavelength figure of merit for a two color laser ranging system. In this paper, we apply the wavelength figure of merit to the case of an extremely clear atmosphere and draw several conclusions regarding the relative merits of fundamental-second harmonic, fundamental-third harmonic, second-third harmonic, and Raman two color systems. We find that, in spite of the larger dispersion between wavelengths, fundamental-third harmonic systems have the lowest figure of merit due to a combination of poor detector performance at the fundamental and poor atmospheric transmission at the third harmonic. The fundamental-second harmonic systems (approximately 700 nm and 350 nm) have the highest figure of merit, but second-third harmonic systems, using fundamental transmitters near 1000 nm, are a close second. Raman-shifted transmitters appear to offer no advantage over harmonic systems because of the relatively small wavelength separation that can be achieved in light gases such as hydrogen and the lack of good ultrashort pulse transmitters with an optimum fundamental wavelength near 400 nm.

  12. Implementation of optimum solar electricity generating system

    NASA Astrophysics Data System (ADS)

    Singh, Balbir Singh Mahinder; Sivapalan, Subarna; Najib, Nurul Syafiqah Mohd; Menon, Pradeep; Karim, Samsul Ariffin A.

    2014-10-01

    Under the 10th Malaysian Plan, the government is expecting the renewable energy to contribute approximately 5.5% to the total electricity generation by the year 2015, which amounts to 98MW. One of the initiatives to ensure that the target is achievable was to establish the Sustainable Energy Development Authority of Malaysia. SEDA is given the authority to administer and manage the implementation of the feed-in tariff (FiT) mechanism which is mandated under the Renewable Energy Act 2011. The move to establish SEDA is commendable and the FiT seems to be attractive but there is a need to create awareness on the implementation of the solar electricity generating system (SEGS). In Malaysia, harnessing technologies related to solar energy resources have great potential for implementation. However, the main issue that plagues the implementation of SEGS is the intermittent nature of this source of energy. The availability of sunlight is during the day time, and there is a need for electrical energy storage system, so that there is electricity available during the night time as well. The meteorological condition such as clouds, haze and pollution affects the SEGS as well. The PV based SEGS is seems to be promising electricity generating system that can contribute towards achieving the 5.5% target and will be able to minimize the negative effects of utilizing fossil fuels for electricity generation on the environment. Malaysia is committed to Kyoto Protocol, which emphasizes on fighting global warming by achieving stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system. In this paper, the technical aspects of the implementation of optimum SEGS is discussed, especially pertaining to the positioning of the PV panels.

  13. Implementation of optimum solar electricity generating system

    SciTech Connect

    Singh, Balbir Singh Mahinder Karim, Samsul Ariffin A.; Sivapalan, Subarna; Najib, Nurul Syafiqah Mohd; Menon, Pradeep

    2014-10-24

    Under the 10{sup th} Malaysian Plan, the government is expecting the renewable energy to contribute approximately 5.5% to the total electricity generation by the year 2015, which amounts to 98MW. One of the initiatives to ensure that the target is achievable was to establish the Sustainable Energy Development Authority of Malaysia. SEDA is given the authority to administer and manage the implementation of the feed-in tariff (FiT) mechanism which is mandated under the Renewable Energy Act 2011. The move to establish SEDA is commendable and the FiT seems to be attractive but there is a need to create awareness on the implementation of the solar electricity generating system (SEGS). In Malaysia, harnessing technologies related to solar energy resources have great potential for implementation. However, the main issue that plagues the implementation of SEGS is the intermittent nature of this source of energy. The availability of sunlight is during the day time, and there is a need for electrical energy storage system, so that there is electricity available during the night time as well. The meteorological condition such as clouds, haze and pollution affects the SEGS as well. The PV based SEGS is seems to be promising electricity generating system that can contribute towards achieving the 5.5% target and will be able to minimize the negative effects of utilizing fossil fuels for electricity generation on the environment. Malaysia is committed to Kyoto Protocol, which emphasizes on fighting global warming by achieving stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system. In this paper, the technical aspects of the implementation of optimum SEGS is discussed, especially pertaining to the positioning of the PV panels.

  14. Photoelectric angle converter

    NASA Astrophysics Data System (ADS)

    Podzharenko, Volodymyr A.; Kulakov, Pavlo I.

    2001-06-01

    The photo-electric angle transmitter of rotation is offered, at which the output voltage is linear function of entering magnitude. In a transmitter the linear phototransducer is used on the basis of pair photo diode -- operating amplifier, which output voltage is linear function of the area of an illuminated photosensitive stratum, and modulator of a light stream of the special shape, which ensures a linear dependence of this area from an angle of rotation. The transmitter has good frequent properties and can be used for dynamic measurements of an angular velocity and angle of rotation, in systems of exact drives and systems of autocontrol.

  15. High-speed reference-beam-angle control technique for holographic memory drive

    NASA Astrophysics Data System (ADS)

    Yamada, Ken-ichiro; Ogata, Takeshi; Hosaka, Makoto; Fujita, Koji; Okuyama, Atsushi

    2016-09-01

    We developed a holographic memory drive for next-generation optical memory. In this study, we present the key technology for achieving a high-speed transfer rate for reproduction, that is, a high-speed control technique for the reference beam angle. In reproduction in a holographic memory drive, there is the issue that the optimum reference beam angle during reproduction varies owing to distortion of the medium. The distortion is caused by, for example, temperature variation, beam irradiation, and moisture absorption. Therefore, a reference-beam-angle control technique to position the reference beam at the optimum angle is crucial. We developed a new optical system that generates an angle-error-signal to detect the optimum reference beam angle. To achieve the high-speed control technique using the new optical system, we developed a new control technique called adaptive final-state control (AFSC) that adds a second control input to the first one derived from conventional final-state control (FSC) at the time of angle-error-signal detection. We established an actual experimental system employing AFSC to achieve moving control between each page (Page Seek) within 300 µs. In sequential multiple Page Seeks, we were able to realize positioning to the optimum angles of the reference beam that maximize the diffracted beam intensity. We expect that applying the new control technique to the holographic memory drive will enable a giga-bit/s-class transfer rate.

  16. Anti-windup control of tip-tilt mirror

    NASA Astrophysics Data System (ADS)

    Folcher, Jean-Pierre

    2014-08-01

    In the context of next generation instrumentation for current telescope and future Extremely Large Telescopes (ELT), the requirements on the correction of the tip-tilt modes are stringent. In a strong turbulence situation and in the presence of structural vibration of the telescope, tip-tilt mirror saturation phenomena can occur, which can degrade the performance or even destabilize the feedback system that is denoted the windup" effects. In this paper we investigate a control strategy which aims to mitigate the undesirable windup" effects. The approach gives possibilities to ensure the performance of a relevant anti-windup" control strategy invoking the small gain theorem and using the H∞ optimization framework. The proposed control method, based on H∞ optimization, guarantees the stability and performance of the tip-tilt loop.

  17. Tilt precursors before earthquakes on the San Andreas fault, California

    USGS Publications Warehouse

    Johnston, M.J.S.; Mortensen, C.E.

    1974-01-01

    An array of 14 biaxial shallow-borehole tiltmeters (at 10-7 radian sensitivity) has been installed along 85 kilometers of the San Andreas fault during the past year. Earthquake-related changes in tilt have been simultaneously observed on up to four independent instruments. At earthquake distances greater than 10 earthquake source dimensions, there are few clear indications of tilt change. For the four instruments with the longest records (>10 months), 26 earthquakes have occurred since July 1973 with at least one instrument closer than 10 source dimensions and 8 earthquakes with more than one instrument within that distance. Precursors in tilt direction have been observed before more than 10 earthquakes or groups of earthquakes, and no similar effect has yet been seen without the occurrence of an earthquake.

  18. Cerebrospinal fluid pressure in conscious head-down tilted rats

    NASA Technical Reports Server (NTRS)

    Severs, Walter B.; Morrow, Bret A.; Keil, Lanny C.

    1991-01-01

    The acute effects of a 1-h -45 deg head-down tilt on continouously recorded cerebrospinal fluid pressure (PCSF) of conscious rats are studied in order to investigate the shift of blood volume into the thoracic cavity in microgravity. PCSF, evaluated in 15-min time blocks over a 3-h experiment, increased slightly (less than 0.05) during the first 30 min of a control hour at 0 deg. There was a transient increase for about 5 min immediately after tilt (-45 deg) that may have been due to head movement after the position change. PCSF was statistically unchanged (above 0.05) during the second (-45 deg) hour and the third (0 deg) recovery hour. It is shown that the dynamics of intracranial pressure regulation can accommodate the acute cephalad fluid shift after tilting.

  19. Effect of tilt on strong motion data processing

    USGS Publications Warehouse

    Graizer, V.M.

    2005-01-01

    In the near-field of an earthquake the effects of the rotational components of ground motion may not be negligible compared to the effects of translational motions. Analyses of the equations of motion of horizontal and vertical pendulums show that horizontal sensors are sensitive not only to translational motion but also to tilts. Ignoring this tilt sensitivity may produce unreliable results, especially in calculations of permanent displacements and long-period calculations. In contrast to horizontal sensors, vertical sensors do not have these limitations, since they are less sensitive to tilts. In general, only six-component systems measuring rotations and accelerations, or three-component systems similar to systems used in inertial navigation assuring purely translational motion of accelerometers can be used to calculate residual displacements. ?? 2004 Elsevier Ltd. All rights reserved.

  20. Atomic structure of [110] tilt grain boundaries in FCC materials

    SciTech Connect

    Merkle, K.L.; Thompson, L.J.

    1997-04-01

    High-resolution electron microscopy (HREM) has been used to study the atomic-scale structure and localized relaxations at grain boundaries (GBs) in Au, Al, and MgO. The [110] tilt GBs play an important role in polycrystalline fcc metals since among all of the possible GB geometries this series of misorientations as a whole contains the lowest energies, including among others the two lowest energy GBs, the (111) and (113) twins. Therefore, studies of the atomic-scale structure of [110] tilt GBs in fcc metals and systematic investigations of their dependence on misorientation and GB plane is of considerable importance to materials science. [110] tilt GBs in ceramic oxides of the fcc structure are also of considerable interest, since in this misorientation range polar GBs exist, i.e. GBs in which crystallographic planes that are made up of complete layers of cations or anions can join to form a GB.

  1. Coulomb interaction effect in tilted Weyl fermion in two dimensions

    NASA Astrophysics Data System (ADS)

    Isobe, Hiroki; Nagaosa, Naoto

    Weyl fermions with tilted linear dispersions characterized by several different velocities appear in some systems including the quasi-two-dimensional organic semiconductor α-(BEDT-TTF)2I3 and three-dimensional WTe2. The Coulomb interaction between electrons modifies the velocities in an essential way in the low energy limit, where the logarithmic corrections dominate. Taking into account the coupling to both the transverse and longitudinal electromagnetic fields, we derive the renormalization group equations for the velocities of the tilted Weyl fermions in two dimensions, and found that they increase as the energy decreases and eventually hit the velocity of light c to result in the Cherenkov radiation. Especially, the system restores the isotropic Weyl cone even when the bare Weyl cone is strongly tilted and the velocity of electrons becomes negative in certain directions.

  2. The ischial spine sign: does pelvic tilt and rotation matter?

    PubMed

    Kakaty, Diganta K; Fischer, Andreas F; Hosalkar, Harish S; Siebenrock, Klaus A; Tannast, Moritz

    2010-03-01

    Although the ischial spine sign (ISS) has been advocated to detect acetabular retroversion, it is unknown whether the sign is valid on anteroposterior (AP) pelvic radiographs with tilted or rotated pelves. We therefore evaluated reliability of the ISS as a tool for diagnosing acetabular retroversion in the presence of considerable pelvic tilt and/or malrotation. We obtained radiographs of 20 cadaver pelves in 19 different malorientations resulting in 380 pelvis images (760 hips) for evaluation. In addition, 129 clinical radiographs of patients' hips that had varying pelvis orientations were reviewed. We found an overall sensitivity of 81% (90%), specificity of 70% (71%), positive predictive value of 77% (80.7%), and negative predictive value of 75% (85%) in the cadaver (patient) hips. Our data suggest the ISS is a valid tool for diagnosing acetabular retroversion on plain radiographs taken using a standardized technique regardless of the degree of pelvic tilt and rotation. PMID:19662463

  3. The Ischial Spine Sign: Does Pelvic Tilt and Rotation Matter?

    PubMed Central

    Kakaty, Diganta K.; Fischer, Andreas F.; Hosalkar, Harish S.; Siebenrock, Klaus A.

    2009-01-01

    Although the ischial spine sign (ISS) has been advocated to detect acetabular retroversion, it is unknown whether the sign is valid on anteroposterior (AP) pelvic radiographs with tilted or rotated pelves. We therefore evaluated reliability of the ISS as a tool for diagnosing acetabular retroversion in the presence of considerable pelvic tilt and/or malrotation. We obtained radiographs of 20 cadaver pelves in 19 different malorientations resulting in 380 pelvis images (760 hips) for evaluation. In addition, 129 clinical radiographs of patients’ hips that had varying pelvis orientations were reviewed. We found an overall sensitivity of 81% (90%), specificity of 70% (71%), positive predictive value of 77% (80.7%), and negative predictive value of 75% (85%) in the cadaver (patient) hips. Our data suggest the ISS is a valid tool for diagnosing acetabular retroversion on plain radiographs taken using a standardized technique regardless of the degree of pelvic tilt and rotation. PMID:19662463

  4. Tilt Precursors before Earthquakes on the San Andreas Fault, California.

    PubMed

    Johnston, M J; Mortensen, C E

    1974-12-13

    An array of 14 biaxial shallow-borehole tiltmeters (at 1O(-7) radian sensitivity) has been installed along 85 kilometers of the San Andreas fault during the past year. Earthquake-related changes in tilt have been simultaneously observed on up to four independent instruments. At earthquake distances greater than 10 earthquake source dimensions, there are few clear indications of tilt change. For the four instruments with the longest records (> 10 months), 26 earthquakes have occurred since July 1973 with at least one instrument closer than 10 source dimensions and 8 earthquakes with more than one instrument within that distance. Precursors in tilt direction have been observed before more than 10 earthquakes or groups of earthquakes, and no similar effect has yet been seen without the occurrence of an earthquake. PMID:17843056

  5. State reversals of optically induced tilt and torsional eye movements

    NASA Technical Reports Server (NTRS)

    Finke, R. A.; Held, R.

    1978-01-01

    Alternations of the state of apparent self-motion during observation of a large visual display rotating about the line of sight are associated with alternations in the magnitude of induced tilt and torsional eye rotation. In one experiment, shifts in visually induced tilt during these state alternations are found to be in the opposite direction to corresponding shifts in induced ocular torsion. In a second experiment, the reversals of self-motion perception are shown to be an intravisual phenomenon, independent of competing inputs provided by the vestibular system. These results emphasize the importance of distinguishing between visual and vestibular processes in tilt perception and ocular rotation during human orientation to gravitational vertical.

  6. Sub-2 nm size and density tunable platinum nanoparticles using room temperature tilted-target sputtering.

    PubMed

    Ramalingam, Balavinayagam; Mukherjee, Somik; Mathai, Cherian J; Gangopadhyay, Keshab; Gangopadhyay, Shubhra

    2013-05-24

    This paper describes a tilted-target RF magnetron sputter deposition system to grow nanoparticles in a controlled way. With detailed characterization of ultra-high density (up to 1.1 × 10¹³ cm⁻²) and ultra-small size Pt nanoparticles (0.5-2 nm), it explains their growth and crystalline properties on amorphous Al₂O₃ thin films. It is shown that Pt nanoparticle size and number density can be precisely engineered by varying selected experimental parameters such as target angle, sputtering power and time of deposition to control the energy of the metal atoms in the deposition flux. Based on rate equation modelling of nanoparticle growth, three distinct growth regimes, namely nucleation dependent, coalescence dependent and agglomeration dependent regimes, were observed. The correlation between different nanoparticle growth regimes and the consequent crystal structure transformation, non-crystalline clusters → single crystalline nanoparticles → polycrystalline islands, is also discussed. PMID:23609435

  7. A tilted grating interferometer for full vector field differential x-ray phase contrast tomography.

    PubMed

    Rutishauser, Simon; Donath, Tilman; David, Christian; Pfeiffer, Franz; Marone, Federica; Modregger, Peter; Stampanoni, Marco

    2011-12-01

    We report on a setup for differential x-ray phase-contrast imaging and tomography, that measures the full 2D phase-gradient information. The setup uses a simple one-dimensional x-ray grating interferometer, in which the grating structures of the interferometer are oriented at a tilt angle with respect to the sample rotation axis. In such a configuration, the differential phase images from opposing tomography projections can be combined to yield both components of the gradient vector. We show how the refractive index distribution as well as its x, y, and z gradient components can be reconstructed directly from the recorded projection data. The method can equally well be applied at conventional x-ray tube sources, to analyzer based x-ray imaging or neutron imaging. It is demonstrated with measurements of an x-ray phantom and a rat brain using synchrotron radiation. PMID:22273882

  8. Three-dimensional microelectromechanical tilting platform operated by gear-driven racks

    DOEpatents

    Klody, Kelly A.; Habbit, Jr., Robert D.

    2005-11-01

    A microelectromechanical (MEM) tiltable-platform apparatus is disclosed which utilizes a light-reflective platform (i.e. a micromirror) which is supported above a substrate by flexures which can be bent upwards to tilt the platform in any direction over an angle of generally .+-.10 degrees using a gear-driven rack attached to each flexure. Each rack is driven by a rotary microengine (i.e. a micromotor); and an optional thermal actuator can be used in combination with each microengine for initially an initial uplifting of the platform away from the substrate. The MEM apparatus has applications for optical switching (e.g. between a pair of optical fibers) or for optical beam scanning.

  9. Determination of structure tilting in magnetized plasmas—Time delay estimation in two dimensions

    SciTech Connect

    Guszejnov, Dávid; Bencze, Attila; Zoletnik, Sándor; Krämer-Flecken, Andreas

    2013-06-15

    Time delay estimation (TDE) is a well-known technique to investigate poloidal flows in fusion plasmas. The present work is an extension of the earlier works of Bencze and Zoletnik [Phys. Plasmas 12, 052323 (2005)] and Tal et al.[Phys. Plasmas 18, 122304 (2011)]. From the prospective of the comparison of theory and experiment, it seems to be important to estimate the statistical properties of the TDE based on solid mathematical groundings. This paper provides analytic derivation of the variance of the TDE using a two-dimensional model for coherent turbulent structures in the plasma edge and also gives an explicit method for determination of the tilt angle of structures. As a demonstration, this method is then applied to the results of a quasi-2D Beam Emission Spectroscopy measurement performed at the TEXTOR tokamak.

  10. Direct and Inverse Kinematics of a Novel Tip-Tilt-Piston Parallel Manipulator

    NASA Technical Reports Server (NTRS)

    Tahmasebi, Farhad

    2004-01-01

    Closed-form direct and inverse kinematics of a new three degree-of-freedom (DOF) parallel manipulator with inextensible limbs and base-mounted actuators are presented. The manipulator has higher resolution and precision than the existing three DOF mechanisms with extensible limbs. Since all of the manipulator actuators are base-mounted; higher payload capacity, smaller actuator sizes, and lower power dissipation can be obtained. The manipulator is suitable for alignment applications where only tip, tilt, and piston motions are significant. The direct kinematics of the manipulator is reduced to solving an eighth-degree polynomial in the square of tangent of half-angle between one of the limbs and the base plane. Hence, there are at most 16 assembly configurations for the manipulator. In addition, it is shown that the 16 solutions are eight pairs of reflected configurations with respect to the base plane. Numerical examples for the direct and inverse kinematics of the manipulator are also presented.

  11. [Arthroscopically assisted osteosynthesis of dorsally tilted intraarticular distal radius fractures--technique and results].

    PubMed

    Lutz, M; Wieland, T; Deml, C; Erhart, S; Rudisch, A; Klestil, T

    2014-10-01

    The present paper describes the indication and application of an arthroscopically assisted osteosynthesis for distal radius fractures. Visualisation of articular incongruency is emphasised with special regard to articular fracture fragment reduction. In addition to that, classification of soft tissue injuries and treatment options are discussed. The final clinical and radiological results of 17 patients are presented: DASH and PRWE averaged 4.9 and 6.0 respectively. Active range of motion measured 123° for flexion/extension, 51° for radial and ulnar deviation and 163° for pronosupination, which is 87%, 98% and 97%, respectively, compared with the opposite wrist. Radial inclination at final follow-up was 23°, palmar tilt measured 6° and ulnar variance averaged -1.2 mm. The scapholunate gap at follow-up was 1.6 mm, and the scapholunate angle measured 57°. PMID:25290269

  12. A novel deformable mirror with curvature and tip/tilt control based on the spider actuator concept

    NASA Astrophysics Data System (ADS)

    Rodriguez Sanmartin, Daniel; Button, Tim; Meggs, Carl; Michette, Alan; Pfauntsch, Slawka; James, Ady; Willis, Graham; Dunare, Camelia; Stevenson, Tom; Parkes, William

    2012-06-01

    The Smart X-Ray Optics (SXO) project comprises a UK-based consortium developing active/adaptive micro-structured optical arrays (MOAs). MOA devices are designed to focus X-rays using grazing incidence reflection through consecutive aligned arrays of microscopic channels. Adaptability is achieved using a combination of piezoelectric actuators, which bend the edges of the silicon chip, and a spider structure, which forms a series of levers connecting the edges of the chip with the active area at the centre, effectively amplifying the bend radius. The spider actuation concept, in combination with deep silicon etching stopped close to the surface, can also be used to create deformable mirrors where the curvature and tip/tilt angles of the mirror can be controlled. Finite Element Analysis (FEA) modelling, carried out for the optimization of the spider MOA device, indicates that deformable mirrors with curvature varying from flat to 5cm ROC and control over the tip/tilt angles of the mirror of +/-3mrad could be achieved. Test spider structures, manufactured using a Viscous Plastic Processing Process for the PZT piezoelectric actuators and a single wet etch step using <111> planes in a (110) silicon wafer for both the silicon channels and the spider structure, have been bent to a radius of curvature smaller than 5 cm. This paper evaluates the spider MOA's concept as a means to achieve deformable mirrors with controllable ROC and control over the tip/tilt angles. FEA modelling results are compared with obtained characterization data of prototype structures. Finally, manufacturing and integration methods and design characteristics of the device, such its scalability, are also discussed.

  13. Inversion of Dynamical Scattering from Large-Angle Rocking-Beam Electron Diffraction Patterns

    NASA Astrophysics Data System (ADS)

    Wang, Feng; Pennington, Robert S.; Koch, Christoph T.

    2016-07-01

    A method for ab initio structure factor retrieval from large-angle rocking-beam electron diffraction data of thin crystals is described and tested with experimental and simulated data. No additional information, such as atomicity or information about chemical composition, has been made use of. Our numerical experiments show that the inversion of dynamical scattering works best, if the beam tilt range is large and the specimen not too thick, because for moderate multiple scattering, the large tilt amplitude effectively removes local minima in this global optimization problem.

  14. Inversion of Dynamical Scattering from Large-Angle Rocking-Beam Electron Diffraction Patterns.

    PubMed

    Wang, Feng; Pennington, Robert S; Koch, Christoph T

    2016-07-01

    A method for ab initio structure factor retrieval from large-angle rocking-beam electron diffraction data of thin crystals is described and tested with experimental and simulated data. No additional information, such as atomicity or information about chemical composition, has been made use of. Our numerical experiments show that the inversion of dynamical scattering works best, if the beam tilt range is large and the specimen not too thick, because for moderate multiple scattering, the large tilt amplitude effectively removes local minima in this global optimization problem. PMID:27419576

  15. Age, splanchnic vasoconstriction, and heat stress during tilting.

    PubMed

    Minson, C T; Wladkowski, S L; Pawelczyk, J A; Kenney, W L

    1999-01-01

    During upright tilting, blood is translocated to the dependent veins of the legs and compensatory circulatory adjustments are necessary to maintain arterial pressure. For examination of the effect of age on these responses, seven young (23 +/- 1 yr) and seven older (70 +/- 3 yr) men were head-up tilted to 60 degrees in a thermoneutral condition and during passive heating with water-perfused suits. Measurements included heart rate (HR), cardiac output (Qc; acetylene rebreathing technique), central venous pressure (CVP), blood pressures, forearm blood flow (venous occlusion plethysmography), splanchnic and renal blood flows (indocyanine green and p-aminohippurate clearance), and esophageal and mean skin temperatures. In response to tilting in the thermoneutral condition, CVP and stroke volume decreased to a greater extent in the young men, but HR increased more, such that the fall in Qc was similar between the two groups in the upright posture. The rise in splanchnic vascular resistance (SVR) was greater in the older men, but the young men increased forearm vascular resistance (FVR) to a greater extent than the older men. The fall in Qc during combined heat stress and tilting was greater in the young compared with older men. Only four of the young men versus six of the older men were able to finish the second tilt without becoming presyncopal. In summary, the older men relied on a greater increase in SVR to compensate for a reduced ability to constrict the skin and muscle circulations (as determined by changes in FVR) during head-up tilting. PMID:9887196

  16. Reading Angles in Maps

    PubMed Central

    Izard, Véronique; O'Donnell, Evan; Spelke, Elizabeth S.

    2013-01-01

    Preschool children can navigate by simple geometric maps of the environment, but the nature of the geometric relations they use in map reading remains unclear. Here, children were tested specifically on their sensitivity to angle. Forty-eight children (age 47:15–53:30 months) were presented with fragments of geometric maps, in which angle sections appeared without any relevant length or distance information. Children were able to read these map fragments and compare 2D to 3D angles. However, this ability appeared both variable and fragile among the youngest children of the sample. These findings suggest that 4-year-old children begin to form an abstract concept of angle that applies both to 2D and 3D displays and that serves to interpret novel spatial symbols. PMID:23647223

  17. Angles, Time, and Proportion

    ERIC Educational Resources Information Center

    Pagni, David L.

    2005-01-01

    This article describes an investigation making connections between the time on an analog clock and the angle between the minute hand and the hour hand. It was posed by a middle school mathematics teacher. (Contains 8 tables and 6 figures.)

  18. Reading angles in maps.

    PubMed

    Izard, Véronique; O'Donnell, Evan; Spelke, Elizabeth S

    2014-01-01

    Preschool children can navigate by simple geometric maps of the environment, but the nature of the geometric relations they use in map reading remains unclear. Here, children were tested specifically on their sensitivity to angle. Forty-eight children (age 47:15-53:30 months) were presented with fragments of geometric maps, in which angle sections appeared without any relevant length or distance information. Children were able to read these map fragments and compare two-dimensional to three-dimensional angles. However, this ability appeared both variable and fragile among the youngest children of the sample. These findings suggest that 4-year-old children begin to form an abstract concept of angle that applies both to two-dimensional and three-dimensional displays and that serves to interpret novel spatial symbols. PMID:23647223

  19. The Value of Tilt Testing and Autonomic Nervous System Assessment.

    PubMed

    Sutton, Richard

    2015-08-01

    Tilt testing for the investigation of syncope was introduced in 1986. Since then, it has propagated worldwide as a routine test to determine the cause of transient loss of consciousness when that event has not been diagnosed by history, including that of a witness, physical examination, supine and erect blood pressures, and 12-lead electrocardiogram. Tilt testing allows reproduction of syncope with monitoring of physiologic parameters including electrocardiogram, beat-to-beat blood pressure, electroencephalogram, and middle cerebral artery blood-flow velocity. As a result, much has been learned about syncope. PMID:26115821

  20. Pulse front tilt measurement of femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Dimitrov, Nikolay; Stoyanov, Lyubomir; Stefanov, Ivan; Dreischuh, Alexander; Hansinger, Peter; Paulus, Gerhard G.

    2016-07-01

    In this work we report experimental investigations of an intentionally introduced pulse front tilt on femtosecond laser pulses by using an inverted field correlator/interferometer. A reliable criterion for the precision in aligning (in principle) dispersionless systems for manipulating ultrashort pulses is developed, specifically including cases when the pulse front tilt is a result of a desired spatio-temporal coupling. The results obtained using two low-dispersion diffraction gratings are in good qualitative agreement with the data from a previously developed analytical model and from an independent interferometric measurement.